Photochemistry Volume 30
J-4
A Specialist Periodical Report
Photochemistry
Volume 30
A Review of the Literature Published between July 1997 and June 1998 Sen ior Reporter A. Gilbert, Department of Chemistry, University of Reading, UK Reporters N.S. Allen, Manchester Metropolitan Unversity, UK A. Cox, University of Warwick, UK 1. Dunkin, University of Strathclyde, Glasgow, UK A. Harriman, Ecole Europeenne Chimie Pdymeres Ma teriaux, Strasbo u rg, France W.M. Horspool, University of Dundee, UK A.C. Pratt, Dublin City University, Ireland
RSK
ROYAL SOCIETY OF CHEMiSTRY
ISBN 0-85404-420-5 ISSN 0556-3860 Copyright 0The Royal Society of Chemistry 1999 All rights reserved Apart from any fair dealing for the purposes of research or private study, or criticism or review as permitted under the terms of the UK Copyright, Designs and Patents Act, 1988, this publication may not be reproduced, storedor transmitted, in any form or by any means, without the prior permission in writing of The Royal Society of Chemistry, or in the case of reprographic reproduction only in accordance with the terms of the licences issued by the appropriate Reproduction Rights Orgunizution outside the UK.Enquiries concerning reproduction outside the terms stated here should be sent to The Royal Society of Chemistry at the addressprinted on this page.
Published by The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 OWF, UK Typeset by Computape (Pickering) Ltd, Pickering, North Yorkshire, UK Printed and bound by Athenaeum Press Ltd, Gateshead, Tyne and Wear, UK
Contents
Introduction and Review of the Year By Andrew Gilbert Part I
1
Physical Aspects of Photochemistry Photophysical Processes in Condensed Phases By Anthony Harriman
13
1
Introduction
13
2
General Aspects of Photophysical Processes
13
3
Theoretical and Kinetic Considerations
15
4
Photophysical Processes in Liquid or Solid Media 4.1 Detection of Single Molecules 4.2 Radiative and Nonradiative Decay Processes 4.3 Amplitude or Torsional Motion 4.4 Photophysics of Fullerenes 4.5 Quenching of Excited States 4.5.1 Energy-transfer Reactions 4.5.2 Electron-transfer Reactions
18 18 18 22 23 25 26 21
5
Applications of Photophysics
29
6
Advances in Instrument Design and Utilization 6.1 Instrumentation 6.2 Data Analysis
30 30 32
References
33
Part I1
Organic Aspects of Photochemistry
Chapter 1
Photolysis of Carbonyl Compounds By William M. Horspool
59
1
Norrish Type I Reactions
59
2
Norrish Type I1 Reactions 2.1 1,5-Hydrogen Transfer 2.2 Other Hydrogen Transfers
61 61 62
3
Oxetane Formation
64
Photochemistry, Volume 30 0The Royal Society of Chemistry, 1999 V
Contents
vi
4
Chapter 2
Miscellaneous Reactions 4.1 Decarbonylation and Decarboxylation 4.2. Reactions of Miscellaneous Haloketones 4.3. Photo Reactions of Esters and Photodeprotection 4.4. Other Fission Processes
65 65 70 71 74
References
75
Enone Cycloadditionsand Rearrangements: Photoreactions of Dienones and Quinones By William M. Horspool
78
Cycloaddition Reactions 1.1 Intermolecular Cycloaddition 1.1. I Open-chain Systems 1.1.2 Additions to Cyclopentenones and Related System s 1.1.3 Additions to Cyclohexenones and Related Systems 1.2 Intramolecular Additions 1.2.1 Intramolecular Additions to Cyclopentenones 1.2.2 Additions to Cyclohexenones and Related Systems
78 78 78
Rearrangement Reactions 2.1 m,P-Unsaturated Systems 2.1. I Hydrogen Abstraction Reactions 2.1.2 Radical Addition Reactions 2.1.3 Miscellaneous Processes 2.2 P,y-Unsaturated Systems 2.2.1 The Oxa Di-n-methane Reaction and Related Processes 2.2.2 Miscellaneous Processes
88 88 88 89 92 94
3
Photoreactions of Thymines and Related Compounds 3.1 Photoreactions of Pyridones 3.2 Photoreactions of Thymines etc.
97 97 98
4
Photochemistry of Dienones 4.1 Cross-conjugated Dienones 4.2 Linearly Conjugated Dienones
101 101 101
5
1,2-, 1,3- and I ,4-Diketones 5.1 Reactions of 1,2-Diketones 5.2 Reactions of 1,3-Diketones 5.3 Reactions of 1,4-Diketones 5.3.1 Phthalimides and Related Compounds 5.3.2 Fulgides and Fulgimides
103 103 105 106 107 109
1
2
82 83 84 84 85
94 95
vii
Contents
6
Chapter 3
Chapter 4
Quinones 6.1 o-Quinones 6.2 p-Quinones
110 110 110
References
114
Photochemistry of Alkenes, Alkynes and Related Compounds By Williurn M. Horspool
119
1
Reactions of Alkenes 1.1 cis,trans-Isomerization 1.1.1 Stilbenes and Related Compounds 1.2 Miscellaneous Reactions 1.2.1 Addition Reactions 1.2.2 Electron Transfer Processes 1.2.3 Other Processes
119 119 120 122 122 123 124
2
Reactions Involving Cyclopropane Rings 2.1 The Di-n-methane Rearrangement and Related Processes 2.2 Other Reactions Involving Cyclopropane Rings 2.2.1 SET Induced Reactions 2.2.2 Miscellaneous Reactions Involving Three-membered Ring Compounds
126 126 128 128 129
3 Reactions of Dienes and Trienes 3.1 Vitamin D Analogues
130 135
4
(2+2)-Intramolecular Additions
137
5
Dimerization and Intermolecular Additions
138
6
Miscellaneous Reactions 6.1 Miscellaneous Rearrangements and Bond Fission Processes
141 141
References
144
Photochemistry of Aromatic Compounds By Alan Cox
149
1
Introduction
149
2
Isomerisation Reactions
149
3
Addition Reactions
157
4
Substitution Reactions
163
5
Cyclisation Reactions
166
6
Dimerisation Reactions
171
... Vlll
Chapter 5
Contents
7
Lateral Nuclear Shifts
173
8
Miscellaneous Photochemistry
174
References
178
Photo-reduction and exidation By Alan Cox
188
1
Introduction
188
2
Reduction of the Carbonyl Group
188
3
Reduction of Nitrogen-containing Compounds
198
4
Miscellaneous Reductions
202
5
Singlet Oxygen
206
6
Oxidation of Aliphatic Compounds
207
7
Oxidation of Aromatic Compounds
209
8
Oxidation of Nitrogen-containing Compounds
213
9
Miscellaneous Oxidations
219
References
Chapter 6
Photoreactions of Compounds Containing Heteroatoms Other
than Oxygen
220
230
By Albert C. Pratt
Chapter 7
1 Introduction
230
2
Nitrogen-containing Compounds 2.1 E,Z-Isomerisations 2.2 Photocyclisations 2.3 Photoadditions 2.4 Rearrangements 2.5 Other Processes
230 230 232 24 1 249 251
3
Sulfur-containing Compounds
265
4
Compounds Containing Other Heteroatoms 4.1 Silicon and Germanium 4.2 Phosphorus 4.3 Other Elements
277 277 282 284
References
285
Photoelimination By Ian R. Dunkin
296
1
296
Introduction
Contents
Part 111
ix
2
Elimination of Nitrogen from Azo Compounds and Analogues
296
3
Elimination of Nitrogen from Diazo Compounds and Diazirines 3.1 Generation of Alkyl and Alicyclic Carbenes 3.2 Generation of Aryl Carbenes 3.3 Photolysis of a-Diazo Carbonyl Compounds
298 298 300 302
4
Elimination of Nitrogen from Azides and Related Compounds 4.1 Aryl Azides 4.2 Heteroaryl Azides
302 303 305
5
Photoelimination of Carbon Monoxide and Carbon Dioxide 5.1 Photoelimination of CO and C02 from Organometallic Compounds
305 306
6
Photoelimination of NO and NO2
310
7
Miscellaneous Photoeliminations and Photofragmentations 7.1 Photoelimination from Hydrocarbons 7.2 Photoeliminations from Organohalogen Compounds 7.3 Photofragmentations of Organosilicon and Organogermanium Compounds 7.4 Photofragmentations of Organosulfur and Organoselenium Compounds 7.5 Photolysis of o-Nitrobenzyl Derivatives 7.6 Other Photofragmentations
312 312 313 316 317 318 320
References
322
Polymer Photochemistry By Norman S.Allen
33 1
1 Introduction
33 1
2 Photopolymerisation 2.1 Photoinitiated Addition Polymerisation 2.2 Photocrosslinking 2.3 Photografting
33 1 332 336 34 1
3 Luminescence and Optical Properties
342
4 Photodegradation and Photooxidation Processes in Polymers 4.1 Polyolefins 4.2 Poly(viny1 halides) 4.3 Poly(acry1ates) and (alkyl acrylates) 4.4 Polyamides and Polyimides 4.5 Poly(alky1and aromatic ethers)
354 354 355 355 355 356
Contents
X
4.6 4.7 4.8 4.9 4.10 4.1 1 4.12
Part IV
Polyesters Silicone Polymers Polystyrenes and Copolymers Polyurethanes and Rubbers Photoablation of Polymers Natural Polymers Miscellaneous Polymers
358 358 358 359 360 361 361
5
Photostabilisation of Polymers
362
6
Photochemistry of Dyed and Pigmented Polymers
363
Rejerences
363
Photochemical Aspects of Solar Energy Conversion By Alan Cox
389
1
Introduction
389
2
Homogeneous Photosystems
389
3
Heterogeneous Photosystems
39 1
4
Photoelectrochemical Cells
393
5
Biological Systems
394
Rejkrences
395
Author Index
398
Introduction and Review of the Year BY ANDREW GILBERT
As usual, the chapter and references of the papers cited in this Introduction and Review can be found by using the Author Index. The tremendous activity directed towards the synthesis and photochemistry of fullerenes noted in previous years is possibly abating. Nonetheless, interesting accounts of the photoinduced behaviour of these fascinating molecules continue to appear. Areas of current importance appear to be the synthesis of water soluble materials (see inter alia Bourdelande et al.; and Crooks et al.) and the incorporation of fullerenes into multicomponent arrays. In the latter context, Guldi et al. have reported on the competition between through-bond and through-space interactions for various fullerenes - ferrocene dyads. More generally, photoelectron transfer to C60 continues to be a major area attracting considerable attention (Sasaki et al.; and Fukuzuh et al. inter alia) Non-resonant two-photon fluorescence spectroscopy is a new field of laser spectroscopy which has particular relevance to the in situ study of biomolecules. The technique can be readily adapted for the investigation of two-photon anisotropy of large molecules dispersed in membranes and has been reviewed by Callis. The application of fluorescence to monitor chiral resolution of enantiomers (Grady et al.; Stockman et al.), and the possible discrimination between enantiomers from the electron transfer quenching of excited states continue to attract attention (Tsukahara et al.). Xie et al. and Takeuchi et al. report on the development of new systems for chiral recognition of targeted substrates. There has been a considerable increase in the interest in design of fluorescent sensors for the recognition of molecules in solution and da Silva et af. have reviewed this rapidly expanding area. In the past, there has been surprisingly little concern regarding the possibility of fast energy migration amongst the chromophores of supramolecular assemblies but Muller and Stock have now reported on this subject and have formulated an expression for the temporal dependence of the distribution of the excited states of structurally identical chromophores in bichromophoric compounds. Dovinchi and Chen have reviewed recent advances in photophysical processes of single and isolated molecules with particular reference to applications in analytical chemistry and to the combination of single molecule detection with capillary electrophoresis. Despite the enormous volume of literature which has appeared over the years concerned with the photoreduction of benzophenone in solution, interesting observations and comments continue to be reported for this system, and the importance of exciplex-type intermediates in the reaction has been stressed Photochemistry, Volume 30 0The Royal Society of Chemistry, 1999 1
2
Photochemistry
(Marciniak et al.; and Shizuka). Kotani et af. and Miyasaka et af have reported the important finding that similar rate versus energy gap profiles to those described earlier for systems in solution are observed for charge-transfer complexes adsorbed onto porous glass. These data indicate that high frequency vibrational modes control the rate of charge recombination in such complexes, a situation which questions the validity of applying Marcus-type theory to intimate donor-acceptor complexes. Singlet singlet energy transfer to a porphyrin from a covalently-bound carotenoid has been described by Debreczney et al. and surprisingly, this transfer occurs from the very short lifetime Sz state in at least one example. Striplin et al. in a departure from the usual theme, have described energy transfer from porous silicon to adsorbed metal polypyridine complexes, and the photochemistry of a number of rigidly linked dyads which allow the study of geometry effects to be studied has been described (Sumida et al.; and Dieks et af.).A new triad in which naphtho- 1,4-quinone and tyrosine units are linked to a central porphyrin chromophore is reported by Evstigneeva and Grihkov, and a two-colour laser has been used in a novel approach to control the rates of electron transfer in multicomponent molecular systems (Gosztola et af.). Three-photon excitation combined with single photon counting fluorimetry gives a powerful approach to the selective study of fluorescent molecules, and the technique has been applied to the investigation of several scintillators (Hatrick et al.). Publications of the more organic aspects of photochemistry are now considered. A two-photon process for a-cleavage has been suggested from a laser flash study of the photochemistry of acetone (Markaryan), and irradiation of (1) is reported to yield the alkene (2) both in benzene solution and in the solid state (Kim et af.).The site of &-hydrogenabstraction from the amides (3) (Lindemann et af.) and of the regiochemistry of the keto ester (4) (Hasegawa et al.) are considered to be controlled to some extent by the heteroatom, and for the first time the regiochemistry of the addition of triplet carbonyl compounds to alkenes has been interpreted in terms of hard and soft acid-base systems (Sengupta et al,).
Me
CN (1)
Me
CN
(2)
As in previous years, there have been a number of accounts published describing the use of the photochemistry of enones as a key step in the synthesis of target systems. For example, the adduct ( 5 ) from the addition of ethene to the lactam (6) has been elaborated by Tsujishima et al. to provide a route to ~-2-(2carboxycyclobuty1)glycine derivatives, and the popular target molecule, ( & )-
Introduction and Review of the Year
3
grandisol(7) has been obtained using (-)-quinic acid as the starting material in a photochemical procedure (Matsuo et ul.). In contrast to many enone systems, the principal reaction of the esters (8) is one of dimerisation rather than intramolecular (2n + 271) photocycloaddition (Piva-Le Blanc et ui.) but the latter process does occur with (9) and the product (10) provides a key intermediate towards the natural product (+)-ligudentatol (1 1) (Haddad and Salmon).
c>SU
(9)
Diastereoselective photoinduced electron transfer initiated cyclisation of unsaturated esters such as (12) and (13) gives the cyclic alkanols (14) and (15) respectively (Pandey et ul.),and the intramolecular cycloaddition of (16) produces the complex enone (17) which undergoes photorearrangement to the pentacyclic compound (18) on prolonged irradiation (Kalena et uZ.). Ito et uZ. report a novel coupling reaction from studies into the photochemistry of mixed crystals of 1,2,4,5tetracyanobenzeneand benzyl cyanide, and the pyridones (19) which crystallise to give a chiral space group are photochemically converted in the solid state into j3-lactams (20) in good yield and with reasonable ee's (Wuet d.). A
Photochemistry
4
two-laser technique for irradiating reaction intermediates has been used to provide yet further evidence for the mechanistic steps in the photo-Fries reaction (Jimenez et ul.), and the bisaryne (21) is reported to be formed from the dianhydride (22) photochemically in an argon matrix by using a KrF laser (Moriyama and Yabe).
p';
0
I H (19) R = Me, MeO, Br or CI
&o
A+
0
N\
H
(20)
0
0
(22)
Irradiation of (23) yields the isomer (24) by a concerted 1,3-alkyl migration on an ally1 moiety which Rodriguez and Shi claim to be the first example of a rearrangement from a cembrane to a pseudoterane skeleton. In solution, the dibenzonorbornadiene (25) gives the cyclo-octatetraene (26) while in the solid phase only the pyrrole derivative (27) is formed which is suggested by Scheffer and Ihmels to result from steric effects within the crystal. The Dewar paracyclophanes (28) ring open to their benzenoid isomers on irradiation in a glass at 77 K but, interestingly, for (28) with R' = CN and R2 = H, the aromatic compound undergoes the first reported thermal cyclisation back to (28) on warming to room temperature (Okoyuma et d ) . Irradiation in the charge-transfer band of the
NH2
H2N)
H
Introduction and Review of the Year
5
complex of acenaphthylene and tetracyanoethene in solution yields no products, but co-crystallised samples with the same wavelength light form the (27t + 27t) cycloadduct (29) exclusively (Haga et al.), and mixed crystals of acridine and phenothiazine (3:4 ratio respectively) give (30) photochemically but in solution the dihydrodimer (3 1) is also formed (Koshima et al.). H
H
Gade and Porada have described a new procedure for the determination of quantum yields of a reversible photoisomerisation, and a novel adiabatic pathway has been suggested for the trans-cis photoisomerisation of di-(anaphthy1)ethene (Budyka et d.). Scavarda et al. report that irradiation of 4hydroxybenzonitrile in deoxygenated water isomerises from the triplet state to 4hydroxyisobenzonitrile by way of an intermediate which may possibly be the azirine and this yields the product in a secondary photochemical rearrangement. The anti-Bredt ( 2 + ~ 2 ~ tricyclic ) adducts (32) are formed from the sensitised irradiation of the bichromophoric compounds (33), and the first report has appeared of the formation of a 11.11 paracyclophane (34) (Tsuji et al.). The efficient conversion of the ubiquinol-benzoin adduct into (36) and (37) is considered by Stowell et al. to be significant for the study of rapid electrontransfer events in ubiquinol oxidising enzymes. Chiang et al. have described the photoconversion of the cyclopropanone (38) into N-(pentafluoropheny1)phenylethynamine and (39) for which there is no precedent, and a new photosensitive amine protecting group based on o-hydroxy-trans-cinnamic acid has been reported by Wang and Zheng. The first fluorescence and fluorescence quantum yields from the excited state of the radical anion of 1,4-benzoquinone have been reported by Cook et al., and electron transfer from aromatic donors to the S, state of chloranil giving the singlet radical ion pair has been observed on the fs/ps time scale (Hubig et al.). A series of porphyrin quinones having variable acceptor strengths of the quinone moiety has been synthesised by Dieks et al. and may be considered to be wellsuited as biomimetic model compounds for studying photochemically-induced electron transfer in photosynthesis. The usual number of publications have appeared within the review year concerning the reactions of singlet oxygen, and Huang et al. have published an order of effectiveness of metal phthalocyanines for the generation of this species. The ethenyl hydrogens of the twisted 1,3-diene (40) have unusually high reactivity towards O,('A,) (Mori et al.),and Maras et al. have described a convenient route
Photochemistry
6
%OM.
M Me0 (35)
e
I I O
OMe
0
0
\
(36)
Ph
\ QN,
OMe
(37)
H Ph \ / /c=C, C02H F5 H (39)
to ( k )-talo-quercitol and ( f)-ribo-quercitol from the reaction of cyclo-l,4-diene with singlet oxygen. Irradiation of the norbornadiene (41) produces the expected quadricyclane which undergoes a secondary photoreaction to give (42) by a (2 + 2 + 2) cyclisation followed by a [ 1.51-hydrogen shift (Ivakhnenko et d).The efficient photodimerisation of the sterically hindered 1,4-dihydropyridine (43) in the solid CMe3
Introduction and Review of the Year
7
state is considered to result from a disordered packing region (“buffer zone”) which maintains the crystal structure in the monomer but allows conformational change in the pyridine ring to avoid steric effects in the photoreaction (Marubayashi et al.). A sequence of (2x + 2x) photocycloadditiodretro-Mannich fragmentation/Mannich closure in the vinylogous amide (44)provides the key procedure in the synthesis of the pentacyclic ring system of the anti-leukaemia marine alkaloid, manazamine A (Winkler et al.). CO(CH2)3CS(CH&,COzEt
If
A general method for producing highly efficient photoreactions initiated by electron-transfer quenching of excited states has been described by Chen et al. and it has been report by Engel et al. that the y-perester radical (45) produced cyclises to from irradiation of t-butyl-4-methyl-4-(t-butylazo)peroxypentanoate, give the y-lactone sufficiently slowly to allow the azoperester precursor to be used as a photochemical bifunctional initiator. Donati et al. have described an access to the new isoxazolo-[4,5-dJ- and -[4,5-e]-diazepines (46) and (47) respectively by irradiation of the diazide (48) in methanol, and a nitrobenzyl linker incorporated at different positions in a fraction of the oligomers during the split synthesis combinatorial approach has been used to initiate photochemical cleavage of the oligomers on a bead (Burgess et al. ). 2,3,4,5-Tetraphenylsilacyclopentadienylidene, the first silylene incorporated into a silole ring, has been generated by irradiation of 7-silanorbornadiene and norbornene precursors at 77 K (Kato et al.). Me Me+OLOCMe3
0
A comprehensive theoretical study has been made of the potential energy surfaces and reaction pathways of the singlet and triplet states associated with the photolysis of 2,3-diazabicyclo[2.2.l]hept-2-ene(Yamamoto et al.). All possible
8
Photochemistry
processes have seemingly been considered and the reactions are proposed to evolve through a network of 18 ground and excited state species, 17 intermediates and 10 “funnels” where internal conversion or intersystem crossing may occur, but for the transimt triplet intermediate observed experimentally, the best candidate is considered to be the 3(nn*) - 3(~n*)species. The first triplet diazatrimethylenemethane (49) has been observed from the photolysis of (50) (Quast et d), and in agreement with much experimental evidence and theoretical data, it is proposed from studies of (51), that diazirines open by C-N cleavage and the resulting diazirinyl diradicals may recombine, form diazo compounds, cleave to give carbene (+N2), or rearrange to cyclobutenes (+N2) (Platz et a/.). 1,2’-Biazulene derivatives, which are difficult to obtain, can be formed in yields around 90% from the irradiation of (52) in the presence of azulene or its alkyl and photolysis of 9-diazo-1-fluorenylmethanol (53) gives derivatives (Lin et d), yields of the aldehyde (54) in excess of 95% (Kirmse and Krzossa).
Shimizu et al. report that while [2.2] paracyclophane (55) undergoes twophoton dissociation in low temperature matrices by way of the triplet state, in the gas phase, the efficient two-photon process proceeds via a hot molecule formed by internal conversion from the initially formed singlet excited state. The photocleavage of 2-nitrobenzyl ethers and ester has been widely reported and has now been evaluated as a deprotection methodology for indoles, benzimidazole, and 6-ch1orourdcil (Voelker et al.). The mechanism of the cleavage of such compounds is considered to involve the o-quinonoid intermediate, but previously these had only been deduced from transient electronic spectra produced in flash photolysis experiments. Infrared spectral data from photochemical studies of 2nitrobenzyl methyl ether in argon and nitrogen matrices have now been published which confirm that the intermediate does indeed have the o-quinonoid structure
introduction and Review of the Year
9 OMe
OH OH
M e 2 N e ( ! I+ A I e N M e 2 Me Me
OH OH
Me-+N>t-tGN+-Me Me Me
(56) (Dunkin et a!.). Interestingly, the irradiation of a mixture of the two pinacols (57) and (58) in acetonitrile induces efficient fragmentation of the central carboncarbon bond in both compounds in a chain process (+ = 9 & 1) initiated by single electron transfer quenching of (57) by (58) (Caen et al.). Again this year, the tremendous interest in “polymer photochemistry” is reflected in the considerable number of publications reviewed in Part I11 of this Volume. Eklund et al. report on the photopolymerisation of C6o-fullerene (see also Burger et al.), and polymeric fullerene hydrides have been synthesised which have the potential for storage of hydrogen (Lawson et al.). Konno et al. have observed that compared to thermally polymerised acrylate monomers (room temperature), the photoinduced free radical process gives high yields of stereoregular syndiotactic polymers, and a new light emitting polynorborene has been synthesised by a ring-opening metathesis of coumarin-containing derivatives (Tlenkopatchev et al.). In the presence of N, N-dimethyl-4-toluidine, a series of novel N-phenylmaleimides are found to undergo rapid photopolymerisation (Xu et a/.), and the first report of the curing of polydimethylsiloxanes having epoxynorbornyl units has appeared (Lecamp et al.). A novel method of molecular switching through surface photochromism has been described by Seki et al. from their studies into systems having polyacetylene monolayers cast onto an azobenzene monolayer. Konigstein and Bauer have discussed pathways for hydrogen production based on electron transfer using new homogeneous catalysts and with ascorbic acid as the sacrificial donor, and a range of new dithiolene complexes have been investigated for their abilities to promote the photo-oxidation of water (Lyris at al.). In heterogeneous photosystems, a new photochemical catalyst has been described for the production of hydrogen from water using visible light (Park and Lim), and a new three-layered structure also capable of splitting water comprises a monolithic polypyromellitimide film, a second layer of this polymer incorporating [Ru(bpy)3I2’ and the third layer is [Ru(bpy)J2+ with EDTA.2Na and dispersed ultrafine platinum (Swarnkar et al.). A new type of photocell based upon the dye sensitisation of thin films of Ti02 nanoparticles in contact with a non-aqueous liquid electrolyte has been described (Frank et a/.), and in a further new solar cell, a UV filtering photocatalyst layer (preferably anatase) is situated on the light incident side of the cell (Oka).
Part I Physical Aspects of Photochemistry By Anthony Harriman
Photophysical Processes in Condensed Phases BY ANTHONY HARRIMAN
1
Introduction
The format of this chapter follows that adopted last year. The first section deals with the general aspects of photophysical properties of molecules in condensed phase, with particular emphasis being given to supramolecular systems. This is followed by a review of progress made in the theoretical description of photophysical events and of the kinetic models used to describe photophysical processes taking place in solution. The third section reviews the many different types of photophysical event that might accompany deactivation of an excited state while a separate section is concerned with possible applications for molecular photophysics. The final section describes advances made with instrumentation and data analysis. Regretably, shortage of space prohibits a full listing of all the relevant literature that has appeared during the review period. 2
General Aspects of Photophysical Processes
The complementary features of laser flash photolysis and pulse radiolysis have been reviewed'*2while the application of electron spin polarization techniques to the measurement of molecular photophysics in solution has been highlighted.3 have been The fundamental aspects of luminescence and chemiluminescen~e~~~ considered in detail and particular attention has been given to the theory of spontaneous emission.697A comprehensive review of the dynamics of the fluorescence Stokes shift has appeared' and the underlying theory for radiative migration of electronic excitation energy has been considered by special reference to the fluorescence of Rhodamine 101 in ethanol.' Attention has been paid to the possibility of extracting a statistical temporal signature of quantum chaos from time-resolved fluorescence decay curves" while other studies have concentrated on the implications of gelatin fluorescence for photography.' The technique of non-resonant two-photon fluorescence spectroscopy has been reviewed.12 This is a new field of laser spectroscopy, having particular relevance to the in situ study of biological molecules, that can be readily adapted for examination of twophoton anisotropy of large molecules dispersed in membranes. The mechanism for light-induced hydrogen atom abstraction by n,n* excited states has been ~o ns i der ed'~while . '~ separate studies have addressed the issue of Photochemistry, Volume 30 0The Royal Society of Chemistry, 1999 13
14
Photochemistry
ultrafast proton-transfer reactions. '',I6 Application of femtosecond spectroscopy to solvation and electron-transfer dynamics continues to be an attractive subject.l7,I8 Recent attention has focussed on the dynamics of geminate recombination in charge-transfer complexe~'~ and in geminate radical pairs2' and of nonergodic reactions2' Theoretical models have been presented to account for the selectivity of organic singlet and triplet photoreactions.22 Other studies23have considered the implications of vibronic coupling for light-induced electrontransfer processes occurring in multicomponent supramolecular systems. Marcus theory has been applied to electrochemiluminescence24and quantum beats have been reported25in the recombination of radical ion pairs, as caused by hyperfine interaction in the radical anions. Interest has been shown in the development of protecting groups that can be cleaved by photochemical electron-transfer reactions26and in the use of polarized light to attain stereocontrol of reactive encounter^.^^ The possible discrimination between enantiomers by way of electron-transfer quenching of excited states continues to attract attention,28 as does the application of fluorescence spectroscopy to monitor chiral resolution of e n a n t i o m e r ~ .Several ~ ~ ' ~ ~ new systems have been developed for chiral recognition of targeted substrate^.^"^^ The interconversion of enantiomers has been monitored by time-resolved chiroptical luminescence s p e ctr o ~c o p y~ while ~ a theory has been proposed to account for the special case of circularly polarized fluorescence emanating from chiral nematic liquid crystals.34Circularly polarized luminescence has also been reported from rigid complexes of chiral macrocyclic tetranaphthylamide~.~~ Considerable attention has been given to the study of those systems in which light is used to engineer a conformational change in a large molecule. Such effects are important in certain biological systems and the effect of solvent on the conformational equilibrium of previtamin D has been described.36 Related studies have been devoted to following the a-helix-to-coil transformation for a series of photochromic polypeptide^.^^ Several artificial phototropic systems have been d e ~ e l o p e d ~in ~ -which ~' light is used to drive a largescale conformational change. The mechanism and dynamics of the transformation have been followed for the photoejection of a guest from a macrocyclic host and of its subsequent reentry into the cavity.38The photochemistry of many supramolecular assemblies has been considered in terms of energy or electron transfer between the reactive s ~ b u n i t s .A ~ ~strategy - ~ ~ has been proposed for the construction of extended 2D and 3D arrays that display long-range magnetic ordering and for which there are interesting photophysical properties." During the past year there has been a tremendous upsurge in interest in the design of fluorescent sensors for the recognition of target molecules in solution and the field has been comprehensively reviewed. 51 Because of its great biomedical significance, attention has focussed on the detection of nitric oxide by fluorescence t e c h n i q ~ e s The . ~ ~ development of photozymes for water purification has been reviewed.53 Attempts to better understand natural photosynthesis and to construct artificial models54955 continue to be important areas of modern photochemistry. The photophysical properties of certain bacteriochlorophylls56and carotenes57 have been reported while the mechanisms of electron58and energy59transfer in natural
i: Photophysical Processes in Condensed Phases
15
photosynthetic systems have been reviewed. Particular attention has been given to the design of artificial photosystems that mimic the manganese-containing enzyme of PS2 that is responsible for water oxidation in green plant^.^-^^ Most of these photosystems use a powerful oxidant to photo-oxidize a simple manganese complex but they lack the ability to store oxidizing equivalents that is an inherent feature of the natural organism. Progress is being made in this area, however, and many of the important spectroscopic features of the natural manganese cluster can now be duplicated in model systems.67
3
Theoretical and Kinetic Considerations
One of the great strengths of photochemistry is the close interplay between experimental work and theoretical analysis and there has been a constant evolution of the theoretical framework for many types of photochemical processes. A model has been proposed6* for the specific case where proton transfer is coupled to light-induced electron transfer in a polar solvent, with proton transfer being sequential or concerted to the electron-transfer event. Semiclassical and quantum mechanical treatments have been given for nonadiabatic photodissociation dynamics, with particular reference to interference effects.69A complete thermodynamic classification has been presented that describes orientational relaxation in both excited and ground states following Franck-Condon transition^.^' The photophysical properties of styrene and indene have been explained in terms of a combined molecular mechanics and valence bond meth~dology,~' wherein the geometry of the excited state is fully optimized before calculation of the various potential energy surfaces. Quantum mechanical approaches, based on the LCAO MO SCF method, have also been used to calculate the photophysical properties of complex heteroaromatic corn pound^.^^ Electron-transfer processes continue to play a central role in molecular photophysics and there remains much fundamental information to be learned before we have a complete understanding of the mechanism of such reactions. Although it has been known for many years that intramolecular charge recombination can lead to population of both the ground state and the triplet excited state of the chromophore little is known about the mechanism of this latter process. It has now been found that the two recombination steps possess quite disparate attenuation factors for through-bond electron t ~ n n e l l i n g .An ~ ~ evaluation has been made of the electronic coupling matrix elements for electron exchange in mixed-valence complexes74while an expression has been derived for the dependence of the rate of self-exchange on the extent of electron delocalization in the corresponding mixed-valence ~omplex.~'Path integral calculations have been used to follow the charge-transfer events that follow from laser excitation of these mixed-valence complexes.76 The calculations indicate that the strong electronic interaction between the metal centres gives rise to very fast oscillations in the electronic state population as the wave function oscillates coherently between donor and acceptor, It is suggested that the Fermi golden rule might not be applicable to such systems. Other theoretical evaluations of charge-transfer
16
Photochemistry
effects in solution77 and in weakly coupled conjugated polymers78 have been described. Detailed information about the nuclear79 and solvent8' re-organization energies that accompany electron transfer is critical for a deeper insight into the reaction mechanism and evaluation of these parameters is an important subject. Replacing the solvent bath with a protein scaffold, as in photosynthetic bacterial reaction centres, introduces additional complications for understanding the dynamics of electron-transfer events. Attention has been given to modelling the non-linear dynamics of photosynthetic reaction centres8' and to estimating the importance of protein relaxation dynamics on the rate of electron transfer from the bacteriochlorophyll special pairsB2 Increasing attention is being paid to the possibility of calculating the fluorescence properties of large molecules, especially for those cases where chargetransfer interactions are likely to be important.83 Calculations have also been made to gauge the significance of incorporating vibronic transitions into the expression for ultrafast solvation of excited state dye molecules in polar solvents.84385Experimental studies have addressed the mechanisms by which rapid re-orientations6 and ~ o l v a t i o n ~ ~ of- ~dye ' molecules occur in organized media and in polar solution. Particular attention has been given to seeking a better understanding of the transient dynamics of the solvatochromic shift in binary solvents.90 The role of the excitation lifetime in controlling the initial distribution of electron-transfer products has been considered." Given the widespread interest in the photophysics of supramolecular assemblies wherein numerous identical chromophores are built into a large array it is surprising to find that little concern has been shown about the possibility of fast energy migration amongst the chromophores. This subject has now been examined9*and an expression has been formulated for the temporal dependence of the distribution of the excited states of structurally identical chromophores in bichromophoric molecules. The expression describes the temporal dependence of emission anisotropy in cases where dissipative iriteractions between the chromophores can take place, A combined quantum mechanical and classical description of non-adiabatic photoprocesses, such as internal conversion, has been given.93 The model might be useful for looking at interconversion between high-lying excited states. Advances in kinetic theory, with particular reference to fluorescence quenching in fluid solution, have been while the advantages of monitoring fluorescence quenching by way of stimulated emission have been stressed. lo' A theoretical expression has been given for resonance energy transfer occurring in dense dispersive media"* and separate calculations have been concerned with the possibility of energy transfer taking place via higher-energy excited states. lo3 Limitations to the analysis of fluorescence quenching techniques have been raisedIo4 while a kinetic model has been presented for the photomodulated transport of species across liquid membranes. ' 0 5 Quenching of excited singlet and triplet states by molecular oxygen has been examined for systems where the second-excited triplet states lies close in energy to the first-excited singlet state. Io6 Other studies have reported anomalously high rates of bimolecular fluorescence quenching that could be ascribed to the effects of static q~enching."~A kinetic model has been proposed for the slow photo-
1: Photophysical Processes in Condensed Phases
17
tautomerization of free-base porphyrins. '08 Numerous studies lo9-' l 5 have considered the kinetics of fluorescence quenching in terms of structural or environelectrolyte mental effects, such as temperature,"6i' l7 solvent,' 18-12' composition,'22 or viscosity.123 Additional studies have addressed the issue of non-diffusional formation of e ~ c i m e r sand ' ~ ~the relaxation behaviour of excitedstate complexes.125y126 The influence of secondary structure on the decay properties of fluorescent donor-acceptor labelled peptides has been c o n ~ i d e r e dwhile '~~ the fluorescence of chlorophyll in concentrated solution has been re-examined.128 Particular attention has been given to the kinetics of triplet-triplet annihilation in fluid ~ o l u t i o n ' ~and ~ - 'to ~ ~the various factors that influence the rate of reverse electron transfer in charge-transfer complexes133or radical ion pairs. 134 Diffusional processes available to transient species formed during photochemical processes, especially hydrogen-atom abstraction reactions, have been reviewed'35 and it has been shown that the diffusion coefficients depend markedly on the nature of the surrounding solvent. 13' Photophysical processes involved in the formation of twisted intramolecular charge-transfer (ICT) states continue to be of considerable interest and to receive intense investigation. Theoretical studies have addressed the structure of the ICT state in amino-substituted benzenes'37.'38 while the dual fluorescence of dialkylaminobenzonitrile has been examined in different solvents and as a function of t e m p e r a t ~ r e . ' ~ ~Coupling -'~' between the close-lying S1 and S2 energy levels in dimethylaminobenzonitrile has been detected by picosecond emission anisotropy and related to internal twisting of the amino group.'42 Numerous derivatives of dimethyaminobenzonitrile have been s t ~ d i e d ' ~ in ~ -order ' ~ ~ to determine the structural requisites for dual fluorescence. Similar ICT state formation occurs in diphenylamino-substituted biphenyl'49 and in N,N-dimethyladen~sine~~' while triple fluorescence has been found for certain benzonitriles substituted with tetraazacyclotetradecyl rings. 5 1 y 1 52 The dynamics of ICT state formation have been monitored for amino-substituted oxadiazoles and ketones'53 while the effects of pressure-tuning of the solvent relaxation time on the rate of internal rotation of the ICT state have been At high viscosity, it appears that the rate of ICT state formation greatly exceeds the solvent relaxation time. The importance of hydrogen bonding in controlling ICT state formation has been ~ t r e s s e d ' ~while ~ . ' ~ the ~ involvement of the excited triplet state has been 15* noted for ICT states formed from 4-amino-N-methylphthalimide. Ultrafast intramolecular charge transfer occurs in the excited singlet state of trans-4-dimethylamino-4'-cyanostilbene,followed by trans-to-cis isomerization by way of a highly polar ICT state.'59 The activation barrier for isomerization increases with increasing solvent viscosity in nonpolar solvents but the specific effect of viscosity cannot be separated from polarity effects in alcohols or polar nitriles. Competing photoisomerization also occurs in 4-dialkylamino-9-styrylacridines. 6o Several reports have addressed the photoprocesses occurring in the push-pull polyenes 1617162where both one- and two-photon effects have been observed and where complex formation has been noted at high concentration. The absence of dual fluorescence from 4-dimethylaminophenylacetylenehas been a t t r i b ~ t e d 'to ~ ~a large energy gap between S1 and S2 levels but ICT state
'
18
Photochemistry
formation has been detected for N,N-dimethylaminophenyI-4'-cyanophenylacetylene by virtue of picosecond laser spectroscopy measurements. 9,9'-Dianthrylmethanol shows complicated fluorescence behaviour that depends markedly on temperature and solvent polarity due to the co-existence of local n,n*, excimer, and ICT states.'65 The results have been considered in terms of different molecular conformations for which the degree of orbital overlap between the aryl rings can vary over a wide range. Internal conversion in 1aminonaphthalene derivatives has been linked to twisting of the amino group, even in nonpolar solvents, and the activation energy has been measured.'66 In polar solvents, ICT state formation begins to compete with internal conversion but there are interesting effects caused by pre-twisting of the donor group. Formation of an ICT state has also been invoked to explain the photophysical properties of 4-( 1H-pyrrol-1-yl)benzoic acid. 167 4
Photophysical Processes in Liquid or Solid Media
4.1 Detection of Single Molecules - The most elegant photophysical processes are undoubtedly those associated with single or isolated molecules and such studies have become possible over the past few years by way of selective laser excitation and ultrasensitive fluorescence detection. Recent advances in this field have been reviewed,'68 with particular reference to applications in analytical chemistry and to the combination of single-molecule detection with capillary electrophoresis. Detection of single molecules, such as r h ~ d a r n i n e 'or ~ ~cowmarin'70 dyes in water has been described under conditions that permit measurement of the fluorescence lifetime by way of one-photon laser excitation. A mechanism for the two-step photolysis of coumarin dyes has been proposed on the basis of fluorescence correlation spectroscopy and transient absorption. I7O Fluorescence anisotropy has been applied at the single-molecule levelI7' in order to elicit information about the rotational diffusion of isolated molecules and about their interaction with specific solutes. Counting of single molecules on microchip devices,'72 fused silica,'73 and nan~ part i cl es'~~ has been described while the fluorescence decay characteristics of single molecules near to a surface have been monitored under conditions of variable interaction with the surface.'75 Methods for improving the spatial resolution of the technique have been d e ~ c r i b e d ' ~while ~ - ' ~ related ~ studies have indicated the advantages of dispersing the fluorophore in a m i ~ r o d r o p l e tor ' ~ flowing ~ sample stream. I8O Single-molecule detection by way of two-photon absorption spectroscopy has been reported. 1 8 * 4.2 Radiative and Nonradiative Decay Processes - The use of cyclodextrins or surfactant dispersions to promote room-temperature phosphorescence from organic molecules is a particularly simple but elegant way in which to characterise triplet excited state^.'^^-'^^ This field has been greatly extended by the synthesis of modified cyclodextrins bearing chromophoric groups that can be included into the cavity.190-'92Additional studies have reported binding constants for the
1: Photophysicul Processes in Condensed Phases
19
inclusion complex formed with various small organic molecule^,'^^-'^^ including a r ~ t a x a n e ,and ' ~ ~described how the host modifies the photophysical properties of the included guest .200-202 Diffuse-reflectance laser flash spectroscopic studies have been performed with the solid-state complex.196i200 Because of their relevance to natural photosynthetic organisms, there is a long and well-established history associated with the photophysics and photochemistry of tetrapyrrolic pigments. Such interest has been stimulated in recent years by the application of these pigments as sensitizers for photodynamic therapy of tumours. The mechanism for the singlet oxygen sensitized delayed fluorescence from certain phthalocyanines has been re-examined203while the photophysical properties of many new phthalocyanines have been reported.204-2'0Most attention has been given to improving the optical properties of the pigment, notably by moving the absorption bands to longer wavelength, or in solubilizing the chromophore in such a way as to improve its biocompatibility. The origin of the violet emission observed from some phthalocyanines has been discussed.2' Similar studies have been made with the corresponding metallop~rphyrins~'~-~'~ Many different laser dyes have been and with their protonated studied by flash photolysis studies, partly because of the increased use of such compounds as fluorescent labels in biochemistry. The photophysical properties of several rhodamine dyes have been reported2199220 and the characteristics of the SI-S, absorption spectra have been discussed in terms of the lasing characteristics of the dye. Several new members of the rhodamine family have been synthesized and fully characterized in solution2*' and in the presence of amines.222 In polymeric media, the importance of two-photon excitation has been stressed and its pressure dependence measured.223 A new class of acridine-1,&dione-based laser dyes224has been introduced and their photophysical properties have been recorded. Coumarin dyes have often been used as probes for dynamical Stokes shift measurements and several amino-substituted coumarins have been examined by ultrafast upconversion fluorescence spectroscopy.225Extremely fast intramolecular relaxations take place following laser excitation and it has been possible to monitor breaking and reformation of various hydrogen bonds formed with the surrounding solvent. Related studies have described an excitation energydependent spectral relaxation in coumarin 153 in selected solvents226and the effects of solvent on the spontaneous emission characteristics of 7-diethylamino4-methylcoumarin have been reported.227The lasing properties of several new coumarin dyes have been described.228 The photophysical properties of polyacene molecules depend markedly on the number of rings and the fluorescence behaviour of hexacene has now been compared with that of earlier members of the series.229A similar comparison has been made of the photophysical properties of catacondensed aromatic polycycles.230Fluorescence from an upper-excited singlet state has been described for benz[a]azulene derivative^^^' while the fluorescence properties of some antiaromatic molecules have been described in Several t h i o p y r y l i ~ mand ~~~ p y r y l i ~ r nsalts ~ ~ ~ have been studied and the effects of various substituents attached to the heterocycle have been examined in terms of the triplet yield. A full evaluation of the photophysical properties of 4-aminonaphthalimide, and its
'
20
Photochemistry
alkylated derivatives, has appeared235that includes the effects of solvent polarity and viscosity. The fluorescence properties of several amines have been dewhile laser flash photolysis techniques have been used to study the photoreactions of 4-tolyltrifluoromethyI~arbene.~~~ 4-Nitroaniline has potential applications as a photoinitiator and its photophysical properties have been recorded in the presence of a tertiary amine.239Separate reports have addressed the photophysical properties of coelenteramide analogs,240methyl red,241benzylP-naphthyl ~ u l f o x i d eacyl , ~ ~ phosphine ~ and triphenylphosphines.2a It has been reported245that the phosphorescence spectrum of 4-hydroxy-3-methoxybenzaldehyde exhibits a temperature-dependent hysteresis due to the co-existence of different molecular conformations. The transient intermediate observed during laser flash photolysis of ketoprofen shows the combined properties of a ketyl radical and a ~ a r b a n i o n Photophysical .~~~ properties have been reported for 3 -a~a f lu o r e n o n edinaphthyl ,~~~ ketone,248b i a n t h r ~ n eand , ~ ~pyridimethi~nes.~~' ~ There have been several interesting reports concerning the photophysical properties of biologically-relevant molecules recorded in fluid solution. Thus, the fluorescence properties of the nucleic acid bases have been recorded251and the excited singlet state lifetimes of purines and pyrimidines in aqueous solution have been found to be ca. 7 and 2 ps, respectively. A theoretical explanation has been provided for the vastly different fluorescence properties displayed by the isomers adenine and 2 - a m i n o p ~ r i n e .The ~ ~ ~ fluorescence properties of cysteine and cystine have been measured and compared with theoretical calculations253while the photophysics of p-carotene and related compounds have been reviewed.254A quantitative evaluation has been made of the triplet absorption spectra of several carotenoid pigments on the basis of triplet sensitization with a n t h r a ~ n eThe .~~~ photophysical properties of several N-substituted 1,8-naphthalimides and 1,4,5,8naphthaldimides have been recorded256and used as a basis by which to better understand the biological applications for such chromophores. An examination of dipolar relaxation around indole has revealed257both a slow fluorescence component and a fast relaxation process that depends on excitation wavelength. Flash photolysis studies of 4',7-dihydroxyflavylium perchlorate have shown that cis-trans isomerization is not the determining step in conversion of the molecule into trans-~halcone.~~' The photochemistry of 1- and 9-naphthyl glyoxylic acids has been interpreted in terms of an ionic mechanism for photodecarb~nylation~~~ while the triplet state properties of flavone and flavanone have been compared.260 Since the availability of ultrafast laser spectroscopic techniques, increasing attention has been given to characterizing upper-lying excited singlet states. Using fluorescence upconversion spectroscopy, the lifetime of the S2 state of zinc tetraphenylporphyrin has been measured at 2.35 ps in ethanol.261 Similar measurements262made with malachite green in water place the lifetime of S2 at 0.27 ps but the lifetime is longer in more viscous solvents. Internal conversion from S2 into S1 in coumarin 481 in cyclohexane is reported263to occur with a lifetime of 220-280 fs while the origin of the second-excited singlet state in dimethyldiazirine has been examined by high-resolution fluorescence spectrocopy.^^ Emission has been observed265from unrelaxed vibrational levels in the S2 state of thiocoumarin, where the S2 lifetime is ca. 1 ps, while the application of
I : Photophysical Processes in Condensed Phases
21
two-colour (two-laser) spectroscopy to probe the photochemistry of upper-lying excited states has been recommended.266The temperature dependence267of the photophysical properties of 3-chloro-7-methoxy-4-methylcoumarinhas been related to the energy gap between the two lowest-lying excited singlet states. Related studies have addressed the issue of reversible triplet energy transfer between excited states of comparable triplet energy268and the importance of upper-lying triplet states in controlling the photophysical properties of fluorenone derivatives has been noted.269 Photoinduced intramolecular proton transfer makes a major contribution towards nonradiative deactivation of the excited singlet state of salicylic acid and its derivative^.^^'-^^^ Similar photoreactions, leading to transient formation of an enol, have been reported for 5-methyl-1,4-na~hthoquinone,~~~ h~pericin,*~~ 2-(2’-aminophenyl)ben~irnidazole,2~~ ortho-hydroxy deriva2’-hydro~ychacone,2~~ tives of 2,5-diarylo~azole,2~~ and anthralin.280 Proton transfer tautomerism in 3-hydroxyisoquinone is promoted by dual hydrogen bonding to suitable substrates, in both ground and excited states.281 The involvement of rotational processes in the intramolecular proton-transfer cycle of 2-(2-hydroxyphenyl)imidazo[1,Za]pyridine has been monitored by picosecond transient absorption measurements.282Photoinduced proton transfer is responsible for the lack of fluorescence from 8-hydro~yquinoline~~~ while the effects of organized media on excited-state proton transfer in 2-(2’-pyridy1)benzimidazole have been deDeuterium isotope effects have been noted for the fluorescence properties of phenylpyridines and interpreted in terms of protonation of the excited state.285 The phototropic behaviour of l’-(purin-6-yl)-3-methylimidazolium chloride in water has been described in terms of the Forster cycle.286Hydrogen bonding between the fluorophore and solvent can promote nonradiative decay of the excited state and the mechanisms of such processes have been explored for aminoanthraquinone~,~~~ aminofluorenones,2886,ll -dihydroxynaphthacene-5,12d i ~ n e , ~acridine’~ 1,8-di0ne,~” and mono-functionalized hydroxybenzophenones.29’ 5,5’-Dimethyl-[2,2’-bipyridyl]-3,3’-diol undergoes single and double proton transfer on very fast time scales.292The rate of proton transfer is independent of the nature of the solvent for aprotic solvents but the proton transfer rate depends on viscosity for protic solvents.293A direct measurement of the rate of bimolecular acid-base reactions has been made for several pairs of naphthol photoacids and carboxylate bases.294A full kinetic analysis has been made of proton-base recombination processes.295Interaction between 7-hydroxycoumarin and tertiary amines leads to highly selective proton transfer296while hydrogen bonding of tyrosine to amide-like ligands is reported297to affect the fluorescence properties of the amino acid. Similarly, binding to serum proteins can perturb the photophysical properties of triarylmethane dyes due to restricted rotation.298 Extremely fast double proton transfer has been described for the 7-azaindole dimer in benzene.299Other studies have noted unusual photophysical properties for closely-spaced pairs of p ~ r e n or e ~anthracene ~ m o l e ~ u l e s and ~ ~ for ’~~ self~~ Photodissociation of assembled complexes containing metaIlop~rphyrins.~~-~~~ ~ ~ ~ the importance of methoxybenzenes occurs under UV laser p h o t o l y ~ i swhile
22
Photochemistry
internal rotation in controlling the photophysical properties of tyrosine model compounds has been stressed.309 Three reports have described the solvent dependence for the (blZg+) + (a'A& emission of molecular oxygen in solution,310-312 Quenching of the emission of singlet molecular oxygen by diary1 telluride^,^'^ dialkyl di ~ ul f i des , ~and '~ naphthal~cyanines~'~ has been described. Simultaneous quenching of both triplet and singlet states of naphthalene derivatives by oxygen has been observed during separation of geminate Lightinduced generation of superoxide ions in solution has been r e p ~ r t e d . ~ ' ~ . ~ ' '
4.3 Amplitude or Torsional Motion - Many molecules undergo a light-induced change in conformation that provides a facile means for nonrddiative deactivation of the first-excited singlet state, Such geometry changes might be small, as in the slight twisting around a connecting bond that optimizes ICT state formation, or large-scale, leading to the formation of an isomer. In either case, the process tends to be extremely fast and competitive with other forms of excited-state decay. Various aspects of the photoisomerization process have been r e ~ i e w e d , ~ ' ~ - ~ ~ although a unified theory for large-scale torsional motion in a viscous medium is still lacking. Photoisomerization of the rhodopsin chromophore has been considered in terms of a transient electric field associated with a change in local charge that accompanies geometrical displacement.323A crucial feature of this model concerns the coupling of torsional motion, vibrational interactions, and electronic effects associated with the surrounding amino acids into a single theoretical description. The effects of temperature and local viscosity on the rotational diffusion of simple organic molecules have been examined by way of molecular-mechanics simulations and time-resolved fluorescence spectroscopy.324 A comprehensive study of the solvent dependence of the photophysical properties of 9,9'-bianthryl shows that the fluorescence lifetime is essentially constant in low polarity solvents.325In more polar solvents, light-induced electron transfer occurs to form a perpendicular ICT state having D2d symmetry and which is weakly fluorescent. Reports have appeared that describe the photoisomerization of 4nitr~benzaldehyde,~~~ 5 - h y d r o ~ y t r o p o l o n e4-hydro~ybenzonitrile,~~* ~~~~ methylbenzonitrile, 329 and cinnamaldehyde.330 Because of their structural relevance to the retinal pigments, considerable attention has been given to the photoisomerization of polyenes in solution. Ab initio calculations have been made for isomerization of a Schiff base having five conjugated double bonds in the polyene backbone331 while the dynamics for light-induced and thermal isomerization of hexatriene have been measured in cyclohexane solution.332The lifetime of the first-excited singlet state of the cisisomer is believed to be ca. 200 fs and this species decays to form a mixture of vibrationally-excited ground-state rotamers that rapidly converts into the stable distribution of isomers. Photoisomerization of the corresponding I ,6-diphenyl1,3,5-hexatriene has been considered for both the excited singlet333and triplet334 states; in this latter case there are indications for a quantum chain reaction at high concentration. The alkali metal salts of the a,o-diphenylpolyenylic carbanions exist in ether solution as mixtures of tight and loose ion pairs.335The loose ion pairs undergo isomerization from the first-excited singlet state by way of an
I : Photophysicul Processes in Condensed Phuses
23
activated process for which the Arrhenius parameters have been measured by time-resolved fluorescence spectroscopy using the Daresbury synchrotron source. Despite its short lifetime, the excited singlet state of 1,6-diphenyl-l,3,5-hexatriene reacts by way of light-induced electron transfer in the presence of suitable electron acceptors336 while its photophysical properties are affected by the presence of substituents in the phenyl rings.337The fluorescence properties of hexamethylsexithiophene have been interpreted in terms of increased conjugation in the excited state caused by ultrafast planarization of the molecule.338 Extremely rapid ring-opening reactions are known to occur for certain cycloa l k e n e ~ . ~ ~ ~ ~ ~ ~ Quantum yields for the reversible photoisomerization of donor-acceptor substituted 1,2-diet hyn ylethenes and tetraet hynyle t henes have been reported. 341 Several studies have described the photoisomerization of m e r ~ c y a n i n e s , ~ ~ ~ . ~ o x a car b o ~y an in e s ,and ~ ~ ~c a r b ~ c y a n i n e s . ~ There ~ ~ , ~is~growing ~ evidence that isomerization of such molecules can take place via higher excited states.346 Photoisomerization of azobenzene is very fast;347photolysis of cis-azobenzene leading to product formation on time scales of 170 fs and 2 ps whereas the corresponding trans-isomer reacts on time scales of 320 fs and 2.1 ps.348These latter results are interpreted in terms of the Si n-n* excited state undergoing rapid inversion at one of the N atoms. In fact, the early time dynamics of isomerization of trans-azobenzene have been investigated by resonance Raman spectroscopy349 and it appears that, within 30 fs of excitation, the major geometrical changes are localized on N=N and C-N stretching vibrations. Substituted azobenzenes also undergo reversible photoisomerization, both in solution350 and in LangmuirBlodgett films,35’and provide a facile means for the construction of photoresponsive chelating macro cycle^.^^^^^^^ The photoisomerization of cis-stilbene continues to attract attention and the importance of both vibrational coherence354and solvent polarity355in controlling the dynamics of the process has been stressed. The photophysical properties of numerous derivatives of stilbene have been recorded in solution in order to better define the nature of the isomerization step.356-36’Additional studies have considered the effects of attaching freely-rotating or rigid substituents to the isomerizing bond362and the effects of mixing between S1 and S2 levels are known to be important.363Many other aryl-substituted ethenes undergo photoisomerization, with the rate depending on the nature of the terminal g r o ~ p s . ~A~ ” ~ ~ detailed examination366of the photoisomerization dynamics has been made for cis- 1-(2-anthryl)-2-phenylethene at different temperatures and the importance of triplet state formation has been explained. Involvement in an upper-lying singlet excited state has been invoked to explain the unusual fluorescence properties of aryl-substituted styrenes.368
Photophysics of Fullerenes - Interest in the synthesis, derivatization, and photochemistry of the various fullerenes continues but perhaps the fervour of earlier years is passing. These materials display important photophysical properties and it is clear that they can serve as unique components in supramolecular assemblies. A special has been devoted to the photophysics and photo-
4.4
24
Photochemistry
chemistry of fullerenes while recent advances in the field have been reviewed.374A critical comparison of the properties of parent and substituted fullerenes has appeared375and the various photoreactions leading to structural modification of fullerenes have been reviewed.376A theoretical examination of the triplet state characteristics of the higher fullerenes, including excited state geometries, excitation energies and Jahn-Teller splitting energies, has been presented.377Photoinduced electron-transfer reactions of carbon clusters have been reviewed378and compared to similar reactions undertaken by aromatic carbonyl compounds.379 Photophysical properties have been reported for the higher f ~ l l e r e n e s and ~~~~~~' for several hydrogenated f ~ l l e r e n e sTriplet-triplet .~~~ annihilation takes place for fine particles of c60 but is suppressed in favour of light-induced electron transfer when electron donors are present.383 Formation of c60 radical ions can be monitored by EPR spectroscopy under conditions that show reaction between the radical cations and solvent molecules.3s4Transient oxidation of fullerenes has also been followed by laser flash photolysis techniques.385 Numerous studies have been concerned with the luminescence properties of fullerenes in solution or solid phase.386-393 An important issue yet to be solved for the various fullerenes concerns the need to prepare samples that are genuinely soluble in water. Several approaches continue to be advocated, including coating the particle with a polymer wrapping,394but progress in this area is slow. Other methods for solubilizing the fullerene particles include forming inclusion comp l e ~ e or s ~using ~ ~ surfactant dispersion^.^'^ Functionalization of fullerenes with hydrophilic groups increases solubility but can lead to irreversible formation of clusters.397Capping the hydrophilic groups with surfactant residues restricts selfassociation. Fullerenes are susceptible to attack by many different types of r a d i ~ a l ' ~ ~while ' ~ ~ ' the excited triplet state readily enters into electron-transfer reaction^.^^^-^'^ Likewise, fullerenes function as efficient quenchers for many other excited states formed in fluid solution.409"' The photophysical properties of many different adducts of c60 have been recorded and compared with those of the parent c ~ m p o u n d .2-42 ~ ' Particular attention has been given to the ability of these derivatives to sensitize formation of singlet molecular oxygen and to enter into light-induced electron-transfer processes. One of the more interesting aspects of fullerene photochemistry concerns the incorporation of such units into multicomponent arrays that display intercompartment energy or electron transfer. Competition between through-bond and through-space interactions has been reported for various fullerene-ferrocene with the importance of intramolecular reactions depending on the nature of the connecting bridge. Bimolecular electron transfer from fullerene to ferrocene also occurs for fullerene derivatives containing a nitroxido Photoactive dyads have been synthesized in which a fullerene is linked to ruthenium(I1) tris(2,2'-bipyridyl) c ~ m p l e x e s . Laser ~ ~ ~ flash * ~ ~ photolysis ~ studies indicate that light-induced charge separation takes place when the metal complex is illuminated, with the lifetime of the redox pair depending on the length and type of bridging unit used to connect the reactants. Intramolecular electron transfer also occurs from an appended porphyrin to Cm and several such dyads have been With zinc porphyrin-fullerene dyads, a variety of
'
I : Photophysical Processes in Condensed Phases
25
processes follow from selective excitation of the porphyrin moiety. Thus, rapid singlet-singlet energy transfer occurs from the porphyrin to populate the lowestenergy singlet excited state localized on the fullerene. The fate of this latter excited state depends on the energetics of the system. Thus, fast intramolecular electron abstraction from the nearby porphyrin occurs in polar solvents but intersystem crossing to the triplet manifold dominates in nonpolar media. The triplet state localized on the fullerene unit can participate in reversible energytransfer processes with the excited triplet state of the porphyrin. These latter studies have been extended to include photoactive triads comprising fullerenep~rphyrin-carotene~~”~~~ or fullerene-porphyrin-pyromellitimideunits.433 Both triads display sequential electron-transfer events that lead to long-range charge separation across the molecule. 4.5 Quenching of Excited States - Photobleaching of dyes during illumination in chlorinated solvents results in transient formation of free Intramolecular photoaddition reactions have been observed for a family of styrene-spacer-amine compounds, where the spacer is a rigid amide interspersed between flexible alkane chains.436Several reports have addressed the mechanism of the photoreduction of benzophenone in and the importance of exciplex-type intermediates has been stressed. Certain halogenated naphtho- 1,4quinones abstract a hydrogen atom from phenolM0 and the reaction has been monitored by laser flash photolysis and CIDEP techniques. The mechanism by which azoalkanes are photoreduced by amines has been investigateda1 and, as found earlier for benzophenone, hydrogen-atom abstraction and charge-transfer compete as modes for deactivation of the excited triplet state. Exciplex formation, involving amino donors, has been described for numerous systems,M2-446including reagents bound on the surface of silica gel.447 Interaction between thiacyanine and acridine orange also leads to exciplex formation in premicellar surfactant medium, but once the critical micelle concentration is reached exciplex formation is suppressed in favour of intermolecular energy transfer.M8 The dynamics of charge recombination in charge-transfer complexes represents an extremely important and general area of photophysics and there is still doubt about how the rate varies with thermodynamic driving force. Charge separation and recombination have now been monitored for several types of charge-transfer complex adsorbed onto porous glassM9~450 under conditions where no solvent is present. Similar rate vs energy-gap profiles are observed to those found earlier in polar solvents, indicating that high frequency vibrational modes control the rate of charge recombination in such complexes. This is an extemely important finding since it calls into question the validity of applying Marcus-type theory to intimate donor-acceptor complexes. Other studies have addressed the photoprocesses occurring in closely-spaced, donor-acceptor c ~ m p l e x e s . ~ Related ~’-~~~ work has been concerned with the effects of ion pairing on the efficiency of lightinduced electron-transfer reactions455and specific cation effects have been noted. Electron-transfer quenching has been reported for donor-acceptor pairs in l i q ~ i d ~ ’ ~and - ~ solid ’ ~ states.459 In many cases, energy- and electron-transfer processes compete as the major
26
Photochemistry
route for deactivation of excited states and resolving the overall reaction mechanism can be hazardous. Often, the two processes can be distinguished by virtue of their different response to solvent polarity460or to structural facets.461 For photoactive dyads having the terminals tethered by a flexible chain, there is the additional need to distinguish between intramolecular and intermolecular quenching.462Such realizations allow construction of systems capable of displaying tandem energy-transfer and electron-transfer processes.463 4.5.I Energy-transfer Reactions - Many elaborate multicomponent molecular arrays have been engineered over the past few years in an effort to mimic the light-harvesting complexes found in natural photosynthetic organisms. Such artificial systems can also be considered as prototypes for molecular-scale photoelectronic devices in which selective excitation causes vectorial energy transfer along the molecular axis. Although the available mechanisms for excitation energy transfer between closely-spaced chromophores are well established there remains considerable uncertainty as to how best to assemble these artificial arrays. Most synthetic arrays are built from porphyrin-based modules and it is known that varying the nature of the cation housed in the porphyrin ring can modulate the energy-transfer process.464The rate of energy transfer also depends on the type of porphyrin nucleus465and on any substituents attached to the connecting bridge.466In the latter case, it appears that the rate of through-bond energy transfer is remarkably sensitive to the orientation of bridging phenyl rings and this can be affected by the presence of bulky substituents. Several hydrid porphyrin dimers have been s y n t h e ~ i z e d and ~~~'~~~ used to study both singlet and triplet energy-transfer processes. A cascade of triplet energy-transfer steps has been established for a carotenoid-porphyrinpyropheophorbide triad molecule.470 Highly efficient intramolecular singletsinglet energy transfer from a covalently-linked carotenoid to a porphyrin chromophore has been described for a series of dyads.47' It is suggested that energy transfer occurs predominantly via the Forster-type Coulombic mechanism involving the first-excited singlet state of the carotenoid as energy donor. Surprisingly, in view of its very short lifetime, energy transfer occurs from the S2 level of the carotenoid in at least one case.471Intermolecular energy transfer has been reported for porphyrin-based systems in s o l ~ t i o n and ~ ~ in~ Langmuir-~~~ Blodgett layers.475 Flexible arrays of porphyrinic chromophores have been constructed as simple models of natural light-harvesting c ~ m p l e x e s . ~ ~ ~ Intramolecular energy transfer has been reported for dyads built from 1,8naphthalimide and 1,3,4-0xadiazole Reversible energy transfer between monomeric and dimeric forms of rhodamine 6G in ethylene glycol has been observed479and the concentration dependence of the overall fluorescence quantum yield has been modelled by MonteCarlo simulations. Triplet energy transfer in disordered polymers has been analyzed on the basis of Bawler's model in which the trap energies have a Gaussian di~tribution.~~' Energy transfer has also been observed in monolayers48' and for photoswitchable molecular triads.482The structural requirements for efficient energy transfer from a carotenoid to chlorophyll have been
I : Photophysical Processes in Condensed Phases
27
elucidated483 while the solvent dependence of energy transfer from triplet benzophenone to naphthols and methoxynaphthalene has been investigated.484It was observed that the rate of intermolecular triplet energy transfer depends on both viscosity and polarity of the solvent, with the latter effect being due to perturbation of the relative energy levels of x,n* and n,x* excited states. Intramolecular energy transfer has also been reported for dyads based on ruthenium(I1) polypyridine With covalently-linked arenes, localization of the triplet energy depends on the nature of the arene. Thus, with naphthalene the triplet state remains on the ruthenium(I1) polypyridine but efficient intramolecular triplet energy transfer occurs when the arene is a n t h r a ~ e n eWith . ~ ~ ~a covalently-bound pyrene fragment, the two triplet states are almost isoenergetic and reversible triplet energy transfer takes so that the triplet lifetime of the metal complex is prolonged. In a marked variation on the usual theme, energy transfer has been observed from porous silicon to adsorbed metal polypyridine complexes.488
4.5.2 Electron-transfer Reactions - Quenching of fluorescence from organic dyes in solution by inorganic anions is known to proceed by way of bimolecular electron-transfer Electron transfer has also been implicated in many other bimolecular quenching reaction^,^^'-^^^ including the quenching of naphthalene fluorescence by nucleic acid components.495An interesting effect of how the relative size of the reactants can affect the outcome of fluorescence quenching in solution has been described498with respect to the quenching of fluorescence of aryl hydrocarbons by thiocyanate. The Marcus inverted region has been observed for a bimolecular electron-transfer reaction in which emission from ruthenium(I1) polypyridine complexes is quenched by phenolate ions.499 The effects of both internal and external heavy atoms on the efficiency of bimolecular electron-transfer reactions have been explored500by reference to the fluorescence quenching of thiopyrylium salts by halogenated benzenes. A popular method for distinguishing between electron- and energy-transfer quenching is to freeze the solution into a solid glass where energy transfer is likely to Intermolecular electron transfer can occur on very fast time scales at high concentrations of quencher or when the quencher is also the solvent.503 More useful mechanistic information is obtained from intramolecular electrontransfer reactions if the kinetics for the electron-transfer step can be isolated from the effects of diffusion. The main stimulus for making such studies is the urge to design systems that mimic some of the essential features of the photosynthetic reaction centre complex and much attention has focussed on the study of porphyrin-based photoactive dyads. Thus, a series of N-alkylporphyrins linked to a quinolinium cation has been synthesized and found to display a rich variety of photo reaction^.^^ The singlet excited state of the quinolinium cation operates in both intramolecular energy- and electron-transfer reactions while the excited singlet state of the porphyrin transfers an electron to the appended quinolinium cation. Several new porphyrin-quinone dyads have been s t ~ d i e d , ~ ' ~including -~' cyclophane-derived systems where the reactants are held in a face-to-face orienta-
28
Photochemistry
tion506,507 Particularly important examples are provided by the rigidly-linked dyads509,5'0where the effects of geometry can be studied. Certain closely-spaced dyads undergo fast charge separation for which the rate is essentially activationless509 whereas slight separation of the reactants renders the electron-transfer event sensitive to temperature and solvent polarity. A series of rigidly-linked porphyrin-quinone dyads built around cis- or trans- 1,4-disubstituted cyclohexylene bridges has been synthesized for which exact geometries are a~ailable.~" Structural information has also been obtained for the folded conformations of some zinc(I1) pyropheophytin-anthraquinonedyads in solution from 2D N M R studies.512Light-induced electron transfer has been observed with porphyrinferrocene dyads assembled onto a gold Building photoactive porphyrin-based dyads by way of non-covalent linkages continues to be an attractive 5 14-5 17
This work has been extended to include the study of porphyrin-based triads and higher-order analogues by the attachment of additional redox-active groups. A new triad has been introduced in which the central porphyrin chromophore is equipped with naphthoquinone and tyrosine The dynamics of successive electron-transfer steps occurring in a carotenoid-porphyrin-dinitronaphthalenedicarboximide (C-P-Nim) triad have been elucidated5I9 and compared with those of the corresponding P-Nim dyad. In benzonitrile, the final charge-separated state of the triad survives for 430 ns and is formed with a quantum yield of 0.33. It is noted that light-induced electron transfer does not occur from the firstexcited singlet state of the carotenoid moiety. The effect of an internal hydrogen bond on the dynamics of electron transfer in carotenoid-porphyrin-naphthoquinone (C-P-NQ) triads, and the corresponding P-NQ dyads, has been evaluated520and the importance of sequential electron and proton transfers has been stressed. Stepwise electron transfer has been described for a ZnC-ZnP-ZnP-I tetrad comprising zinc chlorin (ZnC), zinc porphyrin (ZnP), and pyromellitimide (I) units.52' The lifetime of the fully-separated state is ca. 230 ps in tetrahydrofuran at room temperature. A novel approach to controlling the rates of electron transfer in these multicomponent molecular systems involves the use of twocolour laser excitation spectroscopy.522This technique has been applied to the selective excitation of tetrads comprising two donor-acceptor pairs and it is shown that the photogenerated electric field associated with formation of a transient ion-pair inhibits formation of the second ion pair. Numerous studies have been concerned with further evaluation of how the environment affects the rate of electron transfer. It has been shown that the rate of electron transfer through a donor-(amidinium-carboxy1ate)-acceptor salt bridge is about 100-fold slower than electron transfer in the corresponding donor-(carboxylate-amidinium)-acceptor system.523 The .effects of temperatUre524,525 and selective d e ~ t e r a t i o n ~ on* ~the rates of charge separation and/or charge recombination have been explored while electron-transfer reactions occurring along helical or oligonucleotides528 have been monitored. Similarly, the dynamics of electron-transfer reactions have been studied for reactants adsorbed onto micelle surfaces,529incorporated in porous glasses,530 bound to silica gel,S3' or interspersed into dry gelatin.532 This latter study has
I : Photophysicul Processes in Condensed ?%uses
29
revealed a marked difference in reactivity between gelatin in the random coil and a-helical forms. Light-induced electron transfer has also been reported in organic-inorganic multilayer composites533 and across liquid-liquid junctions.534.535 Electron transfer along conjugated polyenes is extremely fast536but the rate can depend on the nature of the solvent for through-space electron tunnelling.537 Intramolecular electron transfer has been observed in several non-porphyrinic dyads and triads.538-543Thus, intramolecular electron transfer involving an anilido group as electron donor has been described540while the effects of chain length on exciplex formation and electron-transfer rates have been described for some styrene-spacer-amine dyads.54' An unusual effect of bidirectionality has been observed for I-(4-~yanopheny1)-4-(cyanomethylene)piperidinein different solvents538caused by competitive electron transfer occurring through the CTor 71: bonds of the organic framework. Two charge-transfer states are formed, corresponding to electron donation to either acceptor, before electron exchange occurs to form the thermodynamic distribution. Photoinduced electron transfer in a constrained bicyclic structure has been d e ~ c r i b e d . ~ ~ There have been several reports describing intramolecular electron transfer in dyads formed from transition metal complexes. The effect of hybridization of the bridge on the rate of through-bond electron exchange, hole transfer and electron delocalization has been described for ethanylene, ethenylene, and ethynylene bridges separating terminal metal terpyridine complexes.545 Electron transfer proceeds through a salt bridge separating two different ruthenium(i1) polypyridine complexes546while certain r h e n i ~ m ( 1 )or ~ ~~~o p p e r ( 1 )complexes ~~~ have been found to effect unusually long-lived charge-separated states. Electrontransfer events that follow excitation of ruthenium(I1)-rhodium(II1) terpyridylbased dyads have been described.549 Other studies have concerned electron transfer in triads constructed from transition metal c ~ m p l e x e s . ~ ~ ' - ~ ~ ~
5
Applications of Photophysics
The study of photophysical processes, especially time-resolved luminescence spectroscopy, provides unique opportunities to explore elaborate molecular systems, to selectively transfer information at the molecular level, to label biological materials, and to design analytical protocols. A great number of molecular systems have been proposed as luminescence sensors for species dissolved in solution but most systems have poor sensitivity and little, if any, selectivity for particular substrates. The most popular design feature involves complexation of a cation to a luminophore in such a way as to switch on or to extinguish emission, usually by perturbing an intramolecular electron-transfer reaction. Such systems have been reviewed in detai1554-559 while alternate design protocols have been p r o p o ~ e d . ~Many ~ . ~ ~new ' sensors have been reported that respond, with varying levels of success, to and/or In several cases, the mechanism for sensory action has been established by laser flash photolysis studies and binding constants have been determined. Related lumines-
30
Photochemistry
cence sensors are available for the in situ determination of oxygen concentrations,573-580 although the operating principle of the device requires only that molecular oxygen quenches a long-lived excited triplet state. Other types of environmental sensors have been designed to detect volatile organic compounds,58' aryl hydrocarbons,582petroleum,5833584 sugars,585and water.5867587 Photophysical processes have been adapted to provide systems for the measuremen t of temperature, 588-590 critical micellar concentrations, 591*592 micropolarity and microviscosity of organized media,593and sol-gel transition points.594-s98 Other systems have been used to probe the mobility of materials in monolayer assembles599and the microenvironmental pH in highly-charged polymers.600 Several systems are available for in situ monitoring of free radical-induced polymerization6013602 and changes in refractive index603or mobility604of polymer films. A simple system has been developed that allows monitoring of stress induced in polymer films upon exposure to light.605Models have been proposed for photofacilitated transport across liquid membranesm6and for imaging liquid drops and jets.607 Methods for establishing dipole moments of ground and excited states have been considered 608 and a fluorescence probe for lipid organization has been described.609A fluorescence method has been used to measure the thickness of the water layer formed when a hydrophobic plastic slides across ice6'' and the results have been used to better understanding the physics of skiing. The methodology used for luminescence dating of rock art has been described.61' Applications of fluorescenceprobes in cellular biology have been r e ~ i e w e d ~ ' ~ - ~ ' ~ while labelled polypeptides6I5and proteins6I6 have been described. Detection of DNA fragments has been considered by several a ~ t h o r s , ~including ' ~ - ~ ~ ~the quantitative estimation of low concentrations of DNA in drinking water. A phosphorescence-based method623has been used to study refolding of disulfide reduced RNase TI. 6
Advances in Instrument Design and Utilization
Photophysics depends critically on the availability of appropriate instrumentation and adequate computational protocols, as well as a ready supply of suitable molecular systems. As the systems become more complex it becomes necessary to design new instruments and to improve procedures for data analysis. A necessary part of this improvement concerns increasing the reliability and precision of existing facilities. 6.1. Instrumentation - A methodology has been devised for comparing the features of fluorescence spectrometer^.^^^ The technique of fluorescence recovery after photobleaching has been applied to the special case of transport across an interface625 while gain spectroscopy has been used to study solute-solvent exciplexes.626A strategy for replacing the excitation monochromator from commercial spectrofluorimeters with an acousto-optic device has been proposed627and tested by studying the fluorescence properties of merocyanine dyes.
I : Photophysical Processes in Condensed Phases
31
The main advantage of this technique relates to the improved optical purity of the excitation source. The concept of continuous measurement of resonance fluorescence has been discussed and improvements in the experimental methodology have been suggested.628Several reports have focussed on ways to increase the spatial resolution of near-field scanning optical microscopes, with special reference to measurements made at interface^.^^^-^^' A methodology has been developed that permits detection and manipulation of individual microdroplets with a fluorescence microscope.632Two-photon fluorescence spectroscopy is now an established technique, especially in biophysics, and several developments have been r e p ~ r t e d . This ~ ~ ~technique - ~ ~ ~ has been applied to the study of DNA-dye and resonance energy transfer in labelled b i ~ m a t e r i a l s Three.~~~ photon excitation has been combined with single-photon counting fluorometry to give a very powerful approach to the selective study of fluorescent molecules.639 The technique has been applied to the study of several scintillators and makes use of a 120 fs excitation pulse from a Ti-sapphire laser.@’ Two new microchannel plate photomultipliers have been described for spaceand time-correlated, single-photon counting that possess temporal resolution around 75 psa’ An apparatus for making double-pulse fluorescence lifetime measurements has been reported.642 A workstation for fluorescence imaging microscopy has been designeda3 that is completely automated and constructed from readily available parts. Several 2D fluorescence lifetime imaging spectrometers have been d e s ~ r i b e d and ~ - ~applied ~ ~ to various problems. Time and wavelength fluorescence detectors have been designed for use with capillary zone electrophoresisa8 and high-performance liquid chromatography.6497650 It is now possible to record an entire fluorescence decay profile during HPLC elution. Several designs have been given for the construction of inexpensive frequencydomain f l u ~ r o m e t e r s . ~ ”Such - ~ ~instruments ~ have been used for making fluorescence-lifetime imaging measurements652and for flow cyt0rnet1-y.~~~ Magnetic field effects continue to provide important information about the dynamics and mechanisms of charge-recombination reactions. Several experimental setups have been improved and described in detai1,654-663 including the application of ultrahigh magnetic fields655and phase-locked detection.656Techniques for recording absorption and fluorescence spectra under an applied electric field have been The technique of photochemically-induced dynamic nuclear polarization has been comprehensively reviewed666and its potential application to many different problems in organic photochemistry has been stressed. The corresponding CIDEP technique has been been applied to quenching One of the most important experimental techniques to appear in the last few years has been transient grating spectroscopy and this methodology has numerous important applications. The technique has been used to measure the quantum yield for photodissociation of diphenyl disulfide,668and compared to photoacoustic and transient absorption spectoscopic methods. Additional studies have used transient grating spectroscopy to monitor the energetics and dynamics of charge separation of an ion pair into free ions.669The approach permits direct measurement of the enthalpy change accompanying formation of the free ions
32
Photochemistry
and, consequently, the mechanism can be addressed in great detail. Translational diffusion processes can be followed by the transient grating method, allowing determination of diffusion coefficients for numerous radicals670 and unstable photo isomer^.^^' Time-dependent anisotropy measurements have also been made for several photoexcited f u l l e r e n e ~A. ~double-pulse ~~ fluorescence technique has been described that permits facile measurement of rotational diffusion times in solution.67' The main advantage of this technique, apart from its simplicity of operation, is that it does not require fast-time response detectors. A thermal lens spectrometery has been constructed that is highly sensitive to the presence of low concentrations of aggregated dye in equilibrium with monomer.674 Lateral diffusion of cell surface proteins can be monitored by interferometric fringe patterns during photobleaching recovery.67s This technique seems to be more reproducible than the more commonly used method of spot fluorescence recovery. A common problem in photophysics concerns the inner-filter effect that prevents the study of optically dense materials. A way round this problem might be to use the total internal reflectance technique of evanescent wave fluorescence spectroscopy.676 The technique of stimulated nuclear polarization has been applied to light-induced electron-transfer reactions.677 Laser-induced photoacoustic calorimetry has been used to measure enthalpy and volume changes during photolysis of methylcobalamin in neutral aqueous solution.67s Diffuse-reflectance laser-flash photolysis techniques have been used to monitor solid-state photo reaction^^^^^^^^ while an experimental approach for the use of high pressures in quenching studies has been described.68' This latter setup might have particular applications to the study of enantioselective quenching. A two-colour spectral hole-burning technique has been developed and applied to zinc tetrdphenylchlorin.682 Several new far-red absorbing dyes have The technique of femtosebeen proposed for spectral hole burning cond hole-burning spectroscopy has been used to monitor nonradiative decay between exciton states that occurs on a time scale of cu. 120 fs.685
Data Analysis - The basis of molecular fluorescence and phosphorescence spectrometry has been reviewed with special emphasis on the detection of trace constituents in biological and chemical systems.686A detailed analytical procedure has been formulated687 that evaluates fluorescence quenching in micellar media where the fluorophore can migrate between micelles. A method has been devised for the multicomponent analysis of absorption and emission spectra that allows extraction of spectra for pure components from complex mixtures.688 Attention has been given to the procedures used to calibrate modern fluorescence s p e c t r o p h o t ~ m e t e r sand ~ ~ ~to the simultaneous recording of spectral, temporal and polarized emission spectra.690 Analysis of time-resolved fluorescence decay records, using computer simulation, has been considered69' while various methods used for deconvolution of the instrument response function have been critically compared and evaluated.692 An analytical procedure for frequencydomain multidimensional fluorescence spectroscopy has been provided693and a treatment has been given694 for measuring fluorescence lifetimes using noisemodulated light. A directly modulated CCD imaging device has been developed 6.2.
I : Photophysical Processes in Condensed Phases
33
which is suitable for frequency-domain phosphorescence measurements up to ca. 400 kHz.695 A general kinetic scheme has been proposed for intermolecular two-state photoreactions that covers such processes as excimer formation, acid-base equilibria, fluorescence indicators and sensors, and quenching phenomena.696 The time dependence of fluorescence anisotropy in the region of pure electronic transitions from the molecular ground state has been examined697and a system has been outlined that allows the rapid acquisition of lifetime-resolved fluorescence images.698Software for controlling a time-resolved fluorescence instrument, as well as for data storage and analysis, has been presented.699An improved system for fluorescence anisotropy measurements has been described7" while a model for the statistical analysis of single-molecule detection has been given.701 Methods used for the analysis of time-resolved delayed emission and transient Raman spectra have been reviewed.702A theoretical model has been advanced that permits estimation of two-photon absorption cross-sections for photochromic molecules703while fast Fourier transformations have been applied to pyrene f l u o r e s c e n ~ eTheories .~~ have been developed for studying the size effect in fluorescence correlation spectroscopy705and for the measurement of diffusion coefficients by this t e~ hni que. ~Total '~ internal reflection fluorescence has been applied to the problem of counting molecules at solid/liquid interfaces707and adsorbed onto cellular surfaces.708Analytical routines have been devised for determining the distribution of fluorophores in mixed mono layer^^^^ and in A protocol has been established that permits evaluation of the mi~elles .~~' microviscosity of micellar media on the basis of measuring the rotational and transitional diffusion coefficients of included dyes as a function of temperature." Techniques for measuring diffusion coefficients by conventional recovery of dye photofading have been reviewed712 while the use of reaction-induced birefringence provides an interesting alternative approach to obtaining the same informat i ~ n .A ~ ' new ~ family of xdnthene dyes that fluoresce strongly in the far red region of the spectrum has been introduced714and their potential application as biological probes has been stressed.
'
7
References
1.
J. F. Wishart, A h . Chem. Ser., 1998,254 (Photochemistry und Radiution Chemistry),
2.
J. R . Miller, K . Penfield, M. Johnson, G . Closs, and N. Green, Adv. Chem. Ser., 1998,254 (Photochemistry and Radiation Chemistry), 161. K. A. McLauchlan, J. Chem. SOC.,Perkin Trans. 2, 1997,2465. S . W. S. McKeever and R. Chen, Radiat. Meus., 1998,27,625. S. A. Soper, I. M. Warner, and L. B. McGown, Anal. Chem., 1998,70,4778. L. P. Knight, Phys. Scr., T, 1997, T70,94. D. T. Pegg, Phys. Scr., T, 1997, 770, 106. L. W. Ungar and J. A. Cina, Adv. Chem. Phys., 1997,100, 171. M. N. Berberan-Santos, E. J. N. Perreira, and J. M. G. Martinho, J. Fluoresc., 1997, 7, 119s.
1.
3. 4. 5. 6. 7. 8. 9.
34 10. 11. 12. 13. 14.
15. 16. 17. 18.
19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43.
Photochemistry
J. Wilkie and P. Brumer, J. Chem. Phys., 1997,107,4893. C. G. B. Cole and J. J. Roberts, Imaging Sci. J . , 1997,45, 145. P. R. Callis, Annu. Rev. Phys. Chem., 1997, 48,271. W. M. Nau, Ber. Bunsenges-Ges., 1998,102,476. W. M. Nau, G. Greiner, J. Wall, H. Rau, M. Olivucci, and M. A. Robb, Angew. Chem., Int. Ed. Engl., 1998,37, 98. A. Douhal, Science, 1997,276, 22 1. L. G. Arnaut and S. J. Formosinho, Wiley Ser. Photosci. Photoeng., 1997, 2 (Homogeneous Photocatalysis), 55. M. Glasbeek, Czech. J, Phys., 1998,48,417. Y. Gauduel and H. Gelabert, Adv. Chem. Ser., 1998, 254 (Photochemistry and Radiation Chemistry), 33 1. F. P. X. Everdij and D. A. Wiersma, Femtochem. Femtobiol.: Ultrafast React. Dynamics. Nobel Symp., 1997,101,488, V. Sundstroem, Imperial College Press, London. E. Gershgoren, U. Banin, and S . Ruhman, J. Phys. Chem. A , 1998,102,9. E. W.-G. Diau, J. Herek, Z. H. Kim, and A. H. Zewail, Science, 1998,279,847. M. Klessinger, Pure Appl. Chem., 1997,69,773. J. F. Endicott, M. A. Watzky, X. Song, and T. Buranda, Coord. Chem. Rev., 1997, 159,295. A. Kapturkiewicz, Adv. Electrochem. Sci. Eng., 1997,5, 1 . V. A. Bagryansky, V. I. Borovkov, Y. N. Molin, M. P. Egorov, and 0. M. Nefedov, Mendeleev Commun., 1997, 132. A. Banerjee and D. E. Falvey, J. Org. Chem., 1997,62,6245. K.-H. Gericke, C. Kreber, and J. L. Rinmenthal, J. Phys. Chern. A, 1997,101,7530. K. Tsukahara, C. Kimura, J . Kaneko, K. Abe, M. Matsui, and T. Hara, Inorg. Chem., 1997,36,3520. T. Grady, T. Joyce, M. R. Smyth, D. Diamond, and S . J. Harris, Anal. Commun., 1998,35, 123. T. G. Stockman, C. A. Klevickis, C. M. Grisham, and F. S. Richardson, J. Mol. Recognit., 1996, 9, 595. J.-W. Xie, Y.-Q. Zhai, Z.-P. Yang, and J.-X. Huan, Huaxue Xuebao, 1997,18,1447. M. Takeuchi, S. Yoda, T. Imada, and S. Shinkai, Tetrahedron, 1997,53, 8335. D. P. Glover-Fischer, D. H. Metcalf, T. A. Hopkins, V. J. Pugh, S. J. Chisdes, J. Kankare, and F. S . Richardson, Inorg. Chem., I998,37,3026. H. Shi, B. M. Conger, D. Katsis, and S. H. Chen, Liq. Cryst., 1998,24, 163. R. S. Dickens, J. A. K. Howard, J. M. Moloney, D. Parker, R. D. Peacock, and G. Siligardi, Chem. Commun., 1997, 1747. 0 . G. Dmitrenko, 1. P. Terenetskaya, and W. Reischl, J. Photochem. Photohiol. A , 1997,104, 113. L. V. Natarajan, T. M. Cooper, and D. Stilzel, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A , 1997,298, 205. ‘4. C. Benniston, A. Harriman, and D. S. Yufit, ,4ngw. Chem., Int. Ed. Engl., 1997, 36,2356. J.-P. Collin, P. Gavina, V. Heitz, and J.-P. Sauvage, Eur. J. Inorg. Chem., 1998, 1. T. Shikata, S. Imai, and Y. Morishima, Langmuir, 1997, 13, 5229. N. Armaroli, F. Diederich, C. 0. Dietrich-Buchecker, L. Flamigni, G. Marconi, J.-F. Nierengarten, and J.-P. Sauvage, Chem.- Eur. J., 1998,4,406. M. Tamura and A. Ueno, Chem. Lett., 1998,369. D. G. Hamilton, J. E. Davies, L. Prodi, and J. K. M . Sanders, Chem.-Eur. J., 1998, 4,608.
I : Photophysiwl Processes in Condensed Phases 44. 45. 46. 47. 48. 49. 50. 51.
52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78.
35
L. Moggi and M. F. Manfrin, Suprumol. Chem. Anions, I997,32 1. M. D. Ward, Chem. SOC.Rev., 1997,26,365. I. Yamazaki, N. Ohta, A. Osuka, and M. Mimura, Hyomen, 1997,35,418. K. Mizuno and Y. Inoue, Kohuguhu, 1997,25,36. V. Balzani, A. Credi, and M. Venturi, Coord Chem. Rev., 1998,171,3. A. Bar-Haim and J. Klafter, J. Phys. Chem. B, 1998,102, 1662. S. Decurtins, H. W. Schmaile, R. Pellaux, A. Hauser, M. E. van Arx, and P. Fischer, Synth. Met., 1997,85, 1689. A. P. da Silva, H. Q. N. Gunaratne, T. Gunniaugsson, A. J. M. Huxley, C. P. McCoy, J. T. Rademacher, and T. E. Rice, Chem. Rev., 1997,97, 1515. T. Rieth and K. Sasamoto, Anal. Cummun., 1998,35, 195. J. E. Guillet, N. A. Burke, and M. Nowakowska, Mucrornol. Symp., 1997,118, 527. A. Osuka, N. Mataga, and T. Okada, Pure Appl. Chem., 1997,69,797. A. Osuka, Kihan Kagaka Sosetsu, 1997,31, 120. K. Teuchner, H. Steel, D. Leupold, A. Scherz, D. Noy, I. Simonin, G. Hartwich, and H. Scheer, J. Lumin., 1997, 72-74,612. S . L. Cardoso, Quim. Nova, 1997,20,535. L. G. Arnaut and S. J. Formosinho, J, Photochem. Photobiol, A , 1997, I 1 1, 11 1. J. T. M. Kennis, A. M. Streltsov, S. I. E. Vulto, T. J. Aartsma, T. Nozawa, and J.Amesz, J. Phys. Chem. B, 1997,101,7828. A. Magnuson, H. Berglund, P. Karall, L. Hammarstroem, B. Aakermark, S. Styring, and L. Sun, J. Am. Chem. SOC.,1997,119, 10720. T. K. La1 and R. Mukherjee, Znorg. Chem., 1998,37,2373. S . M. Gorun, R. T. Stilbrany, and A. Lillo, Znorg. Chem., 1998,37,836. H. Berglund-Baudin, L. Sun, R. Davydov, M. Sundahl, S. Styring, B. Aakermark, M. Almgren, and L. Hammarstroem, J. Phys. Chem. A , 1998,102,2512. L. Sun, H. Berglund, R. Davydov, T. Norrby, L. Hammarstroem, P. Korall, A. Boerje, C. Philouze, K. Berg, A. Tran, M. Andersson, G. Stenhagen, J. Maartensson, M. Almgren, S. Styring, and B. Aakermark, J, Am. Chem. SOC., 1997,119,6996. C. E. Dube, D. W. Wright, P. J. Bonitatebus Jr., S. Pal, and W. H. Armstrong, J. Am. Chem. SOC.,1998,120,3704. L. Sun, L. Hammarstroem, T. Norrby, H. Berglund, R. Davydov, M. Andersson, A. Boerje, P. Korall, C. Philouze, M. Almgren, S. Styring, and B. Aakermark, Chem. Commun., 1997,607. M. T. Caudle, J. W. Kampf, M. L. Kirk, P. G. Rasmussen, and V. L. Peoraro, J. Am. Chem. SOC.,1997,119,9297. J.-Y. Fang and S. Hammes-Schiffer, J. Chem. Phys., 1997,107,5727. D. Romstad, G. Granucci, and M. Persico, Chem. Phys., 1997,219,21. V. S . Pavlovich, J. Appl. Spectrosc., 1997,64,764. F. Bernardi, M.Olivucci, and M. A. Robb, J. Phys. Chem. A , 1997,101,8395. A. E. Obukhov, Laser Phys., 1997, 7, I 102. M. R. Roest, A. M. Oliver, M. N. Paddon-Row, and J. W. Verhoeven, J. Phys. Chem. A, 1997,101,4867. B. Gholamkhass, K. Nozaki, and T. Ohno, J. Phys. Chem. B, 1997,101,9010. E. L. Bominaer, C. Achun, S. A. Borshch, J.-J. Girerd, and E. Muenck, Znorg. Chem., 1997,36,3689. D. G . Evans, A. Nitzao, and M. A. Ratner, J. Chem. Phys., 1998,108,6387. P. L. Nordio, A. Polimeno, and G. Saielli, J. Photochem. Photobiol. A , 1997, 105, 269. M. W. Wu and E. M. Conwell, Chem. Phys., 1998,227, 11.
36 79. 80. 81. 82. 83. 84. 85. 86. 87 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 99. 100. 101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112. 113. 114. 115. 116.
Photochemistry A. Yoshimura, K. Nozaki, andT. Ohno, Coord. Chem. Rev., 1997,159,375. J. Najbar, Bull. Pol. Acad. Sci.. Chem., 1997,45, 79. A. Goushcha, M. Kapoustina, and V. Kharkyanen, J. Tech. Phys. (Warsaw), 1997, 38,283. A. J. A. Aquino, P. Beroza, J. Reagan, and J. N. Onuchic, Chem. Phys. Lett., 1997, 275, 181. A. B. J. Parusel, R. Schamschule, and G. Koekler, Ber. Bunsenges-Ges., 1997, 101, 1836. Y. Ho, Y. Xiong, Z. Wang, Q. Zhu, and F. Kong, J. Phys. Chem. A , 1998, 102, 4266. C.-P. Hsu, Y. Georgievskii, and R. A. Marcus, J. Phys. Chem. A, 1998,102,2658. M. Choi, D. Jin, H. Kim, T. J. Kang, S. C. Jeoung, and D. Kim, J. Phys. Chem. B, 1997,101,8090. P. van der Meulen, A. M. Jonkman, and M. Glasbeek, J. Phys. Chem. A , 1998,102, 1906. G . Saielli, A. Polimeno, P. L. Nordio, P. Bartolini, M. Ricci, and R. Righini, J. Chem. Soc., Faruduy Trans., 1998, 94, 121. N. K. Petrov, A. Wiessner, and H. Staerk, J. Chem. Phys., 1998,108,2326. A. I. Burschtein and A. Y. Sivachenko, J. Photochem. Photobiol. A , 1997,109, 1. V. A. Morozov, Zh. Fiz. Khim., 1998, 72, 119. U. Muller and G. Stock, J. Chem. Phys., 1997,107,6230. M. Yang, S. Lee, and K. J. Shin, J. Chem. Phys., 1998,108, 1 17. V. V. Sapunov, Opt. Spektrosk., 1997,83, 749. A. V. Barzykin and M.Tachiya, J. Phys. Chem. B, 1998,102, 1296. G. Cosa and C . A. Chesta, J. Phys. Chem. A, 1997,101,4922. A. I. Burschtein and P. A. Frantsuzov, J. Chem. Phys., 1997, 107,2872. S. Taen, J. Chem. Phys., 1998,108,6857. I. Frank, J. Hutter, D. Marx, and M. Parrinello, J. Chem. Phys., 1998, 108,4060. F. Tanaka, J. Chem. Phys., 1998, 109, 1084. J. R. Lakowicz and I. Gryczynski, Top. Fluoresc. Spectrosc., 1997,5, 305. A. Y. Sechin, A. N. Starostin, Y. K. Zemtsov, D. I. Chekhov, and A. G. Leonov, J. Quant. Spectrosc. Raciiut. Trurufer, 1997,58,887. M. N. Berberan-Santos, E. N. Bodunov, and J. M. G. Martingo, Opt. Spektrosk., 1997,83, 378. Y . Rakicioglu, M. Young, and S . G. Schulman, Anal. Chim. Acta, 1998,359, 269. T. L. Longin, C. A. Koval, and R. D. Noble, J. Phys. Chem. B, 1998,102, 1036. C. Wirp, J. Bendig, and H. D. Brauer, Ber. Bunsen-Ges., 1997,101,961. S. Icli, H. Icil, and I. Gurol, Turk. J. Chem., 1997,21, 363. V. A. Kuz’mitskii, Khim. Fiz., 1996, 15,61. Y.-H.Zhang, B. Jiang, andX.-K. Jiang, Chin. J. Chem., 1997, 15, 395. A. I. Burschtein and E. Krisinel, J. Phys. Chem. A , 1998, 102, 816. E. Szajdzinska-Pietek and M. Wolszczak, J. Photochem. Photobiol. A, 1998, 112, 245. C. E. Bunker, Y.-P. Sun, and J. R. Gord, J. Phys. Chem. A , 1997,101,9233. K. Weidemaier, H. L. Tavernier, and M. D. Fayer, J. Phys. Chem. B, 1997, 101, 9352. F. Caruso, E, Donath, and H. Moehwald, J. Phys. Chem. B, 1998,102,201 1. H. Rosenbluth, B. Weiss-Lopez, and A. F. Olea, Photochem. Photobiol., 1997, 66, 802. S. Sinha, R. De, T. Ganguly, A. K. De, and S. K. Nandy, J. Lumin., 1987, 75,99.
I : Photophysicul Processes in Condensed Phases
37
125. 126. 127.
T. P. Giraddi, J. S. Kadadevarmath, G. C. Chikkur, M. C. Rath, and T. Mukherjee, J. Photosci., 1997,4,97. G. P. Zanini, H. A. Montejano, J. J. Cosa, and C. M. Previtali, J. Photochem. Photobiol. A, 1997, 109, 9. P. Chen and T. J. Meyer, Chem. Rev., 1998,98, 1439. C. G. Clark and M. Z. Hoffman, Coord. Chem. Rev., 1997,159,359. S. V. Kuznetov, M. Bazin, and R. Santus, J. Photochem. PhotobiuI. A , 1997,103, 57. P. Piotrowiak, A h . Chem. Ser., 1998, 254 (Photochemistry and Radiation Chemistry), 219. W. Jaeger, S. Schneider, and J. W. Verhoeven, Chem. Phys. Lett., 1997,270,50. V. M. Reyes, C. S. Renamayer, I. Pierola, J. C. Lima, E. C. Melo, and A. L. Macanita, Chem. Phys. Lett., 1998,287, 379. I. V. Rubtsov and K. Yoshihara, J. Phys. Chem. A, 1997,101,6138. J. Prochorov, J. Mol. Struct., 1997,404, 199. G. Hungerford, F. Donald, D. J. S. Birch, and B. D. Moore, Biosens. Bioelectron.,
128.
R. S. Knox, P. D. Laible, D. A. Sawicki, and M. F. J. Talbot, J. Lumin., 1997, 72-74,
129.
L. V. Levshin, G. A. Ketsle, G. V. Mel’nikov, and Y. D. Lantukh, J. Appl. Spectrosc., 1997,64, 639. E. A. Ermilov, 0. L. Markovskii, and I. M. Gulis, J. Appl. Spectrosc., 1997,64, 642. I. M. Gulis, E. A. Ermilov, and S. A. Sakharuk, J. Appl. Spectrosc., 1997,64,354. B. Nickel, H. E. Wilhelm, and C. P. Janesch, Opt. Spektrosk., 1997,83,584. Y. Kimura, Y. Takebayashi, and N. Hirota. J. Chem. Phys., 1998,108, 1485. S. Sekiguchi, Y. Kobori, K. Akiyama, and S . Tero-Kubota, J. Am. Chem. Soc.,
117. 118. 119. 120. 121. 122. 123. 124.
1997,12, 1183. 580.
130. 131. 132. 133. 134.
1998,120, 1325.
138. 139.
M. Terazima, Kokugaku, 1997,24, 12. K. Okamoto, N. Hirota, and M. Terazima, J. Phys. Chem. A, 1998,102, 3447. A. L. Sobolewski, L. Andrzej, and W. Domcke, J. Photochem. Photobiol. A, 1997, 105, 325. R. Schamschule, A. B. J. Parusel, and G. Kohler, Internet J. Chem., 1998, I , 5. A. Mordzinski, A. Sobolewski, L. Andrzej, and D. H. Levy, J. Phys. Chem. A, 1997,
140. 141.
A. Kawski and G. Piszcek, Z. Nuturforsch., A: Phys. Sci., 1997,52,409. A. Polimeno, P. L. Nordio, P. Bartolini, M. Ricci, and R. Riggini, Chem. Phys.,
142. 143.
J. J. Fisz and A. van Hoek, Chem. Phys. Lett., 1997,27,432. K. A. Zachariasse, M. Grobys, Th. Van der Haar, A. Hebecker, Y. V. Tl’ichev, 0.Morawski, I. Roeckert, and W. Kuehnle, J. Photochem. Photobiol. A, 1997,105,373. Y. V. Il’ichev, W. Kuehnle, and K. A. Zachariasse, J. Phys. Chem. A, 1998, 102,
135. 136. 137.
101,8221.
1997,223, 51.
144.
5670.
145. 146. 147. 148. 149.
G. Koehler, K. Rechthaler, G. Grabner, R. Luboradzki, K. Suwinska, and K. Rotkiewicz, J. Phys. Chem. A , 1997, 101,8518. S. Delmond, J.-F. Letard, R. Lapouyade, and W. Rettig, J. Photochem. Photobiol. A , 1997,105, 135. D. Braun, W. Rettig, S. Delmond, J.-F. Letard, and R. Lapouyade, J. Phys. Chem. A, 1997,101,6836. F. D. Lewis and T. M. Long, J. Phys. Chem. A, 1998,102,5327. W. Verbouwe, L. Viaene, M. Van der Auweraer, F. C. De Schryver, H. Masuhara, R. Pansu, and J. Faure, J. Phys. Chem. A , 1997,101,8157.
38 150. 151. 152. 153. 154. 155. 156. 157. 158. 159. 160. 161. 162. 163. 164. 165. 166. 167. 168. 169. 170. 171. 172. 173. 174. 175. 176. 177. 178. 179. 180. 181.
Photochemistry
B. Albinsson, J. Am. Chem. Soc., 1997, I 19,6369. L.-S. Choi, Chem. Commun., 1998,893. G. E. Collins, L.-S. Choi, and J. H. Callahan, J. Am. Chem. Soc., 1998, 120, 1474. A. P. Klishchenko, M. A. Senyuk, S. A. Tikhomirov, and G. B. Tolstorozhev, Opt. Spektrosk., 1997,83,664. N . Kometani, 0. Kajimoto, and K. Hara, J. Phys. Chem. A , 1997,101,4916. K. Hara, D. Bulgarevich, S. Dmitry, and 0. Kajimoto, Ber. Bunsenges-Ges., 1997, 101,1443. Y. H. Kim, D. W. Cho, N. W. Song, D. Kim, and M. Yoon, J. Photochem. Phorobiol. A , 1997, 106, 161. Y. Kim, B. I. Lee, and M. Yoon, Chem. Phys. Lett., 1998,286,466. S . Aich, C. Raha, and S. Basu, J. Chem. Soc., Faraday Trans., 1997, 93,2991. Y. V. Il’ichev and K. A. Zachariasse, Ber. Bunsenges-Ges., 1997, 101,625. U.-W. Grummt, E. Birckner, H. Lindauer, B. Beck, and R. Rotomskis, J. Photochem. Photobiol. A, 1997, 104, 69. A. P. Klishchenko and I. N. Koziov, J. Appl. Spectosc., 1997,64, 126. E . Abraham, J. Oberle, G. Jonusauskas, R. Lapouyade, K. Minoshima, and C. Rulliere, Chem. Phys., 1997,219, 73. K. A. Zachariasse, M. Grobys, and E. Tauer, Chem. Phys. Lett., 1997,274,372. Y . Hirata, Chem. Phys. Lett., 1997,278, 133. C. Cornelissen-Gude and W. Rettig, Chem. Phys., 1998,229, 325. K. Susuki, H. Tanabe, and H. Shruka, J. Phys. Chem. A , 1997,101,4496. P. R. Bangal, S. Chakravorti, and G. Mustafa, J. Photochem. Photobiol. A , 1998, 113, 35. N. J. Dovinchi and D. D. Chen, Single-Mol. Opt. Detect., Imaging Spectrosc., 1997, 223. C. Zander, M. Sauer, K. H. Drexhage, J. Wolfrum, L. Brand, C. Eggeling, and C. A. M. Seidel, Proc. SPIE-Int. Soc. Opt. Eng., 1997, 2980 (Advances in Fluorescence Sensing Technology III), 107. C. Eggeling, L. Brand, and C. A. M. Seidel, Bioimuging, 1997,5, 105. T . Ha, J. Glass, Th. Enderle, D. S. Chemla, and S. Weiss, Phys. Res. Lett., 1998,80, 2093. J. C. Fister 111, S. C. Jacobson, L. M. Davis, and J. M. Ramsey, Anal. Chem., 1998, 70,43 I . W. P. Ambrose, P. M. Goodwin, J. Enderlein, D. J. Semin, and R. A. Keller, Proc. SPIE-Int. Soc. Opt. Eng., 1998,3270 (Methodsfor Ultrasensiiive Detection), 190. T. Basche, J. Lumin., 1998, 76,263. M . Xiao and X. Chen, J. Phys. Soc. Jpn., 1998,67,351. C. Zander and K. H. Drexhage, Proc. SPIE-Int. SOC. Opt. Eng., 1997, 2980 (Advunces in Fluorescence Sensing Technology III), 546. M. A. Bopp, G. Tarrach, M. A. Lieb, and A. J. Meixner, J. Vuc. Sci. Technol. A , 1997,15, 1423. S. C. Hill, M. D. Barnes, W. B. Whitten, and J. M. Ramsey, Appl. Opt., 1997,36,4425. M . D. Barnes, N. Lerner, C.-Y. Kung, W. B. Whitten, J. M. Ramsey, and S. C. Hill, Opt. Lett. , 1997,22, 1265. A. Van Orden, M. P. Machara, P. M. Goodwin, and R. A. Keller, Anal. Chem., 1998, 70, 1444. C. Zander, L. Brand, C. Eggeling, K. H. Drexhage, and C. A. M. Seidel, Proc. SPIE-Int. SOC.Opt. Eng., 1997,2980 (Advances in Fluorescence Sensing Technology III), 552.
I: Photophysiml Processes in Condensed Phases 182. 183. 184. 185. 186. 187. 188. 189. 190. 191. 192. 193. 194. 195. 196. 197. 198. 199. 200. 201. 202. 203. 204. 205. 206. 207. 208. 209. 210. 21 1. 212.
39
C. Eggeling, J. Widnegren, R. Rigler, and C. A. M. Siedel, Anal. Chem., 1998, 70, 265 I. W.-Y. Lin, Huuxue, 1997,55, 59. X.-Z. Du, Y. Zhang, Y.-B. Jiang, L. R. Lin, X.-Z. Huang, and G.-Z. Chen, J. Photochem. Photobiol. A, 1998,112, 53. J. Xie, D. Huang, J. Xu, and G. Chen, Chin. Sci. Buff.,1997,42, 1468. X.-Z. Du, Y.B. Jiang, X.-Z. Huang, and G.-Z. Chen, Chin. Chem. Lett., 1997, 8, 431. X.-Z. Du, Y. B. Jiang, X.-Z. Huang, and G.-Z. Chen, Spectrochim. Acta, Part A, 1997,53,671. K. Nakashima and S. Yasuda, J, Photochem. Photobiol. A, 1997,111,249. A. S . Carretero, C. C. Blanco, A. F. Gutierrez, and A. M. De La Pena, Appf. Spectrosc., 1998,52,420. A. Ueno, Kikun Kagaku Sosetsu, 1997,31,44. J. W. Park, S. E. Park, B. A. Lee, and S.-Y. Lee, Chem. Lett., 1997, 1043. T. Aoyagi, A. Ueno, M. Fukushima, and T. Osa, Macromol. Rapid Commun., 1998, 19, 103. X. Shen, M. Belletele, and G. Durocher, J. Phys. Chem. B, 1998,102, 1877. S. Mitra, R. Das, and S. Mukherjee, J. Phys. Chem. B, 1998,102,3730. S . Monti, S. Sortino, G. De Guidi, and G. Marconi, New J. Chem., 1998,22, 599. M. Milewski, M. Sikorski, A. Maciejewski, M. Mir, and F. Wilkinson, J. Chem. Soc., Faraduy Trans., 1997,93,3029. B. D. Wagner and P. J. MacDonald, J. Photochem. Photobiol. A , 1998,114, 151. E. L. Roberts, J. Dey, and I. M. Warner, J. Phys. Chem. A, 1997,101,5296. R. De, S. Sinha, and T. Gunguly, Nuovo Cimento SOC.Itul. Fis. D, 1997,19,955. M. Mir, F. Wilkinson, D. R. Worrall, J. L. Bourdelande, and J. Marquet, J. Photochem. Photobiol. A , 1997,II, 241. S. De Feyter, J. van Stam, F. Imans, L. Viaene, F. C. De Schryver, and C. H. Evans, Chem. Phys. Lett,, l997,277,44. S . Akimoto, €3. Nishizawa, T. Yamazuki, I. Yamazaki, Y. Hayashi, M. Fujimaki, and K. Ichimura, Chem. Phys. Lett., 1997,276,405. A. A. Krasnovskii Jr., Y. Fu, M. E. Bashtanov, S. Murphy, and C. S. Foote, Opt. Spektrosk., 1997,83,616. R. A. Kipp, J. Simon, M. Beggs, H. E. Ensley, and R. H. Schmehl, J. Phys. Chem. A, 1998,102,9659. N. Kobayashi, N. Sasaki, and H. Konami, Inorg. Chem., 1997,36,5674. E. Liu, J. Huang, Z. Dai, S.Yang, Y. Wu, N. Chen, J. Huang, Z. Huang, J. Sun, and J. Xu, WujiHuaxue Xuebuo, 1997,13,411. M. Aoudia, G. Chang, V. 0. Kennedy, M. E. Kenney, and M. A. J. Rodgers, J. Am. Chem. SOC., 1997,119,6029. G. X. Xiong, S. Y. Shen, J. P. Ya, Q. F. Zhou, and H. J. Xu, Chin. J. Chem., 1997, 15,443. S . Foley, G. Jones, R. Liuzzi, D. J. McGarvey, M. H. Perry, and T. G. Truscott, J. Chem. Soc., Perkin Trans 2, 1997,1725. N. Kobayashi, Y. Yoshikawa, 0. Ito, H. B. Goodbrand, and J. Mayo, Chem. Lett., 1998,423. Y. Kaneko, Y. Nishimura, N. Takane, T. Arai, H. Sakurago, N. Kobayashi, D. Matsunaga, C. Pac, and K. Tokumaru, J. Photochem. Photobiol. A, 1997,106,177. A. V. Savitskaja, E. A. Lukjanetz, S. N. Dashkevich, and E. A. Markarova, Proc. SPZEInt. SOC.Opt. Eng., 1997,2980 (Advances in Fluorescence Sensing Technology), 352.
40 213. 214. 21 5. 216. 217. 218. 219. 220. 221. 222. 223. 224. 225. 226. 227. 228. 229. 230. 231. 232. 233. 234. 235. 236. 237. 238. 239. 240. 241. 242.
Photochemistry
M. Li, J. Zou, Z. Xu, and X. You, Spectrochim. Acta, Part A, 1997,53,2109. E. Vogel, M. Broring, S. J. Weghorn, P. Scholz, R. Deponte, J. Lex, H. Schmickler, K. Schaffner, S. E. Braslavsky, M. Muller, S. Porting, C. J. Fowler, and J. L. Sessler, Angew. Chem., Inl. Ed. Engl., 1997,36, 1651. W. Freyer, H. Stiel, M. Hild, K. Tauchner, and D. Leopold, Photochem. Photobiol., 1997,66, 596. E. Balasubramaniam and P. Natarajan, J. Photochem. Photobiol. A, 1997,103,201. P. Lopez-Cornejo and S. M. B. Costa, Langmuir, 1998,14,2042. V. N. Knyukshto, K. N. Solovyov, and G. D. Egorova, Biospectroscopy, 1998, 4, 121. P. C. Beaumont, D. G. Johnson, and B. J. Parsons, J. Chem. Soc., Furaduy Trans., 1998, 94, 195. P. C. Beaumont, D. G. Johnson, and B. J. Parsons, J. Photochem. Photobiol. A , 1997,107, 175. T. Lopez Arbeloa, F. Lopez Arbeloa, 1. Lopez Arbeloa, A. Costela, L. GarciaMoreno, and J. M. Figuera, J. Lumin., 1997, 75, 309. S. Becker, I. Gregor, and E. Thiel, Chem. Phys. Lett., 1998,283,350. Z . A. Dreger, G. Yang, J. 0. White, Y. Li, and H. G. Drickamer, J. Phys. Chem. B, 1998,102,4380. N. Srividya, P. Ramamurthy, and V. T. Ramakrishnan, Spectrochim. Acta, Part A , 1998,54,245. T. Gustavsson, L. Cassara, V. Gulbinas, G. Gurzadyan, and J.-C. Mialocq, J. Phys. Chem. A , 1998,102,4229. W. C. Flory and G. J. Blanchard, Appl. Spectrosc., 1998,52,82. D. Sastikumar and V. Masilamani, Proc-Indian Acad. Sci., Chem. Sci., 1997, 109, 325. M. K . Desai, S. K. Manon, and Y. K. Agrawal, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. C, 1997,8, 329. N. Nijegorodov, V. Ramachandram, and D. F. Winkoun, Spectrochim. Actu, Part A, 1997,53,1813. N. Nijegorodov and D. F. Winkoun, Spectrochim. Actu, Part A, 1997,53,2013. H. Yamaguchi, S. Sato, M. Yasunam, T. Sato, and M. Yoshinobu, Spectrochim. Actu, Part A , 1997,53, 2471. A. Falchi, C. Gellini, P. R. Salvi, and K. Hafner, J. Phys. Chem. A, 1998,102, 5006. F. Morlet-Savary, S. Parret, J. P. Fouassier, K. Inomata, and T. Matsumoto, J. Chem. Soc., Faraday Trans., 1998,94,745. Y. Chen and S.-K. Wu, J. Photochem. Photobiol. A, 1997,102,203. S . L. Dmitruk, S. L. Druzhinin, R. A. Minakova, A. I. Bedrik, and B. M. Uzhinov, Russ. Chem. Bull., 1997,46,2027. J. M. Zwier, P. G. Waring, A. M. Brouwer, D. Bebelaar, and W. J. Buma, J. Am. Chem. SOC.,1997, I19, 11525. S. Yamamoto and H. Habara, Chem. Lett., 1997,757. A. Admasu, A. D. Gudmundsdottir, M. W. Platz, D. S. Waqtt, S. Kwaitkowski, and P. J. Crocker, J. Chem. Soc., Perkin Trans 2, 1998, 1093. A. Costela, I. Garcia-Moreno, J. Dubrin, and R. Sastre, J. Photochem. Photobiol. A, 1997, 109, 77. R. Saito, T. Hirano, H. Niwa, and M. Ohashi, J. Chem. Soc., Perkin Trans. 2, 1997, 1711. S. Mukherjee and C. B. Subbash, J. Chem. Soc., Faraday Tram., 1998,94,67. Y. Guo, A. Darmanyan, and W. S. Jenks, Tetrahedron Lett., 1997,38, 8619.
1: Photophysical Processes in Condensed Phases
243.
41
S. Jockusch, I. V. Koptyug, P. F. McGarry, G. W. Sluggert, N. J. Turro, and D. M. Watkins, J. Am. Chem. SOC.,1997,119, 11495. 244. P. Changenet, P. Plaza, M. M. Martin, Y. H. Meyer, and W. Rettig, Chem. Phys., 1997,221,311. 245. A. Nishigaki, U. Nagashima, A. Uchida, I. Ohnishi, and S. Ohshima, J, Phys. Chem. A , 1998,102, 1108. 246. L. J. Martinez and J. C. Scaiano, J. Am. Chem. Soc., 1998,119, 11066. 247. L. Biczok, Reuct. Kinet. Catal. Lett., 1997,61,57. 248. S . V. Jovanovic, D. G. Morris, C. N. Pliva, and J. C. Scaiano, J. Photochem. Photobiol. A, 1997,107, 153. 249. D. E. Nicodem and M. F. V. da Cunha, J. Photochem. Photobiol. A , 1997,107, 169. 250. M. M. Alam, M. Fujitsuka, A. Watanabe, and 0. Ito, J. Chem. Sac., Perkin Trans. 2, 1998,817. 251. T. Haupl, C. Windolph, T. Jochum, 0. Brede, and H. Hermann, Chem. Phys. Lett., 1997,280,520. 252. A. Broo, J. Phys. Chem. A, 1998,102, 526. 253. H. F. Hameka, J. 0. Jensen, K. K. Ong, A. C. Samuels, and C. P. Vlahacos, J. Phys. Chem. A, 1998,102, 361. 254. S . L. Bondarev, J. Appl. Spectrosc., 1997,64, 1. 255. B. 0. Neilsen, K. Jorgensen, and L. H. Skibsted, J. Photochem. Photobiol. A , 1998, 112, 127. 256. B. M. Aveline, S. Matsugo, and R. W. Redmond, J. Am. Chem. SOC.,1997, 119, 11785. 257. M. Vincent, J. Gallay, and A. P. Demchenko, J. Fluoresc., 1997, 7, 107. 258. F. Pina, M. J. Melo, R. Ballardini, L. Flamigni, and M. Maestri, New J. Chem., 1997,21,696. 259. C . Laurich, H. Gorner, and H. J. Kuhn, J. Photochem. Photobiol. A , 1998, 112, 29. 260. T. Nakayama, T. Shimizu, Y. Torii, S. Miki, and K. Hamanoue, J. Photochem. Photobiol. A , 1997, I I I, 35. 261. G. G. Gurzadyan, T.-H. Tran-Thi, and T. Gustavsson, J. Chem. Phys., 1998, 108, 385. 262. M. Yoshizawa, K. Suzuki, A. Kubo, and S. Saikan, Chem. Phys. Lett., 1998,290,43. 263. J. T. Kang, K. Ohta, K. Tominaga, and K. Yoshihara, Chem. Phys. Lett., 1998,287, 29. 264. T.-S. Kim, K. Kyu, C. Sang, S. Young, and I. Kwak, J. Chem. Phys., 1997, 107, 8719. 265. M. Szymanski, A. Maciejewski, J. Kozlowski, and J. Koput, J. Phys. Chem. A , 1998, 102,677. 266. W. G. Megimpsey, Trends Org. Chem., 1997,6,233. 267. J. Seixas de Melo, R. S. Becker, F. Elisei, and A. L. Macanita, J. Chem. Phys., 1997, 107,6062. 268. M. Yamaji, K. Okada, B. Marcinisk, and H. Shizuka, Chem. Phys. Lett., 1997,277, 375. 269. R. S. Murphy, C. P. Moorlag, W. H. Green, and C. Bohne, J. Photochem. Photobiol. A, 1997,110, 123. 270. H. C. Joshi, H. Mishra, and H. B. Tripathi, J. Photochem. Photobiol. A , 1997, 105, 15. 271. F. Lahmani and A. Zehnacker-Rentien, J. Phys. Chem. A , 1997,IOI,6141. 272. J. Catalan and C. Diaz, J. Phys. Chem. A , 1998, 102,323.
42 273, 274. 275. 276. 277. 278. 279. 280. 281. 282. 283. 284.
285. 286. 287. 288. 289. 290. 291. 292. 293. 294. 295. 296. 297. 298. 299. 300. 301. 302. 303. 304.
Photochemistry
P. B. Bisht, M. Okamoto, and S. Hirayama, J. Phys. Chem. B, 1997,101,8850. G . S . Denisov, N. S. Golubev, V. M. Schreiber, S. S. Shajakhmedov, and A. V. Shurakhina, J. Mol. Struct., 1997,436, 153. Y. Chiang, J. A. Kresge, B. Ht."iung, P. Schunemann, and J. Wirz, Helv. Chim. Actu, 1997,80, 1 106. D. S. English, K. Das, K. D. Ashby, J. Park, J. W. Petrich, and E. W. Castner Jr., J. Am. Chem. Soc., 1997,119, 11585. T. Arai and Y. Norikano, Chem. Lert., 1997, 339. S. Santra and S. K. Degra, Chem. Phys., 1998,226,285. A. 0. Doroshenko, E. A. Posokhov, V. M. Shershukov, V. G. Mitina, and 0. A. Ponomarev, High Energy Chem., 1997,31, 388. S. Moller, K. B. Andersen, J. Spanger-Larsen, and J. Waluk, Chem. Phys. Lett., 1998,291,51. C.-Y. Wei, W.-S. Yu, P.-T. Chou, P.-T. Hung, C.-P. Chang, and T.-C. Lin, J. Phys. Chem. B, 1998,102, 1053. A. Douhal, Ber. Bunsenges-Ges., 1988,102,448. E. Bardez, I. Devol, B. Larry, and B. Valeur, J. Phys. Chem. B, 1997,101,7786. M. C. Rath, D. K. Palit, and T. Mukherjee, J. Chem. Soc., Furaday Trans., 1998,94, 1189. F. Deng, J. Kubin, and A. C. Testa, J. Photochem. Photobiol. A , 1997,104,65. G. Wenska, B. Skalski, M. Insinka, S Paszyc, and R. E. Verrall, J. Photochem. Photobiol. A , 1997,108, 135. T. Yatsuhashi and H. Inoue, J. Phys. Chem. A , 1997,101,8166. T. Yatsuhashi, Y. Nakajima, T. Shimaoa, and H. Inoue, J. Phyx Chem. A , 1998, 102,3018. M. C. Rath and T. Mukherjee, J. Chem. Soc., Furuduy Trans., 1997,3331. B. Venkatachalapathy, P. Ramamurthy, and V. T. Ramakrishnan, J. Photochem. Photobiol. A , 1997,111, 163. A. C. Bhasikuttan, A. K. Singh, D. K. Palit, A. Y. Sapre, and J. P. Mittal, J. Phys. Chem. A, 1998,102,3470. D. Marks, H. Zhang, and M. Glasbeek, J. Luminesc., 1998, 76, 52. D. Marks, H. Zhang, M. Glasbeek, P. Borowicz, and A. Grabowska, Chem. Phys. Lett., 1997,275, 370. E. Pines, B.-Z. Magnes, M. J. Lang, and G. R. Fleming, Chem. Phys. Lett., 1997, 281,413. E. Pines, D. Tepper, B.-Z. Magnes, D. Pines, and T. Barzek, Ber. Bunsenges-Ges., 1998,102,504. H. Mizoguchi, K. Kubo, T. Sakurai, and €I. Inoue, Ber. Bunsenges-Ges., 1997, 101, 1914. J. K. Lee and R. T. Ross, J. Phys. Chem. B, 1998,102,4612. M. S. Baptista and G. I. Indig, J. Phys. Chem. B, 1998,102,4678. S . Takeuchi and T. Tahara, Chem. Phys. Lett., 1997,277,340. 0.Oishi, S. Yamashita, M. Ohno, S. Lee, G. Sugihara, andN. Nishino, Chem. Phys. Lett., 1997,269, 530. K. Nishiyama, T. Honda, H. Reis, U. Muelier, K. Muellen, W. Baumann, and T. Okada, J. Phys. Chem. A , 1998,102,2934. A. Schuetz and T. Wolff, J. Photochem. Photobiol. A , 1997,109,251. Z. Lin, S. Priyadarshy, A. Bartko, and D. H. Waldeck, J. Photochem. Photobiol. A , 1997,110, 131. M . Aoudia and M. A. J. Rodgers, J. Am. Chem. Soc., 1997,119, 12859,
I : Photophysical Processes in Condensed Phases 305. 306. 307. 308. 309. 310. 31 1 . 312. 313. 314. 315. 316. 317. 318. 319. 320. 321. 322. 323. 324. 325. 326. 327. 328. 329. 330. 331. 332. 333. 334. 335. 336. 337. 338. 339. 340.
43
J. M. Kroon, R. B. M. Koehorst, M. van Dijk, G. M. Sanders, and E. J. R. Sundholter, J. Muter. Chem., 1997, 7,615. N. C. Maiti, S. Mazumdar, and N. Periasamy, J. Phys, Chem. B, 1998,102, 1528. M. Kimura, K. Nakada, Y. Yamaguchi, K. Hanabusa, H. Shirai, and N. Kobayashi, Chem. Commun., 1997, 1215. M. Fujiwara and K. Toyami, J. Chem. Phys., 1997,107,9354. W. Wieslaw, S. Krystyna, C. Cezary, L. Leszek, and M. Alicja, J. Photochem. Photobiol. A, 1997,102, 189. A. P. Losev, S. M. Bachilo, and I. N. Nichiporovich, J. Appl. Spectrosc., 1998,65, 1 . D. Weldon, B. Wang, T. D. Poulsen, K. V. Mikkelsen, and P. R. Ogilby, J. Phys. Chem. A , 1998,102, 1498. P.-T. Chou, Y.-C. Chen, C.-Y. Wei, S.-J. Chen, H.-L. Lu, and T.-H. Wei, J. Phys. Chem. A, 1997,101,8581. P. Serguievski and M. R. Detty, Organometallics, 1997,16,4386. E. L. Clennan, D. Wang, C. Clifton, and M.-F. Chen, J. Am, Chem. Soc., 1997,119, 9081. M. E. Bashtanov and A. A. Krasnovskii Jr., High Energy Chem., 1997,31,338. A. L. Mamaev, V. V, Korolev, N. M. Bazhin, and S. V. Morozov, Chem. Phys. Lett., 1998,289,247. M. Weng, M.-H. Zhang, and T. Shen, J. Chem. Soc., Perkin Trans. 2, 1997,2393. M. Weng, M.-H. Zhang, and T. Shen, J. Photochem. Photobiol. A , 1997,108, 159. M. Ikegami and T. Arai, Kokagaku, 1997,26,42. J. Troe, Pure Appl. Chem., 1997,69,841. M. S . Kurdoglyan, Opt. Spektrosk., 1997,82,581. M. R. V. Sahyun and J. T. Blair, J. Photochem. Photobiol. A , 1997,104,179. H. Kikuchi and H. Suzuki, J. Phys. Chem. B, 1997,101,6050. G. S. Jas, Y. Wang, S. W. Pauls, C. K. Johnson, and K. Kuczera, J. Chem. Phys., 1997,107,8800. G. Grabner, K. Rechthaler, and G. Koehler, J. Phys. Chem. A , 1998,102,689. H. Gorner, J. Photochem. Photobiol. A , 1998,212, 155. J. J. Paz, M. Moreno, and J. M. Lluch, J. Chem. Phys., 1997,107,6275. F. Scavarda, F. Bonnichon, C. Richard, and G. Grabner, New J. Chem., 1997,21,1119. P. J. MacLeod, A. L. Pincock, J. A. Pincock, and K. A. Thompson, J. Am. Chem. Soc., 1998, 120,6443. R. J. Olsen, J. Photochem. Photobiol. A, 1997,103,91. M. Garavelli, T. Vreven, P. Celani, F. Bernardi, and M. A. Robb, J. Am. Chem. Soc., 1998,120, 1285. S. H. Pullen, N. A. Anderson, L. A. Walker 11, and R. J. Sension, J. Chem. Phys., 1997,107,4985. Y. Sonada, H. Morii, M. Sakuragi, and Y. Suzuki, Chem. Lett., 1998,349. J. Saltiel, S. Wang, D.-H. KO,and D. A. Gormin, J. Phys. Chem. A , 1998,102,5383. R. N. Young, B. Brocklehurst, and C. E. Oliver, J. Photochem. Photobiol. A , 1997, 102, 163. F. Schael, J. Kuester, and H.-G. Loehmannroeben, Chem. Phys., 1997,218, 175. G . Pistolis and A. Malliaris, Chem. Phys., 1998,226, 83. K. S. Wong, H. Wang, and G. Lanzani, Chem. Phys. Lett., 1998,288,59. A. M. Muller, S. Lochbrunner, W. E. Schmid, and W. Fuss, Angew. Chem., Int. Ed. Engl., 1998,37, 505. S . H. Pullen, N. A. Anderson, L. A. H. Walker, and R. J. Sension, J. Chem. Phys., 1998,108,556.
44
341. 342. 343. 344. 345, 346. 347. 348. 349. 350. 351. 352. 353. 354. 355. 356. 357. 358. 359. 360. 361. 362. 363. 364. 365. 366. 367. 368. 369. 370. 371.
Photochemistry
R. E. Martin, J. Bartek, F. Diederich, R. R. Tykwinski, E. C. Meister, A. Hilger, and H.-P. Luthi, J. Chem. SOC.,Perkin Trans. 2, 1998,233. A. K. Chibisov and H. Goerner, J. Photochem. Photobiol. A, 1997,105,261. A. I. Tolmachev, Y . L. Slominski, and M. A. Kudinova, Zh. Nauchn. Prikl. Fotogr., 1997,42, 54. D. Pevenage, D. Corens, W. Dehaen, M. Van der Auweraer, and F. C. De Schryver, Bull. Soc. Chim. Belg., 1997, 106, 565. E. S. Voropai and M. P. Samtsov, Opt. Spektrosk., 1997,82, 577. S. Reindl and A. Penzkofer, Chem. Phys., 1998,230,83. J. Wachtveitl, T. Naegele, B. Puell, W. Zinth, M. Krueger, S. Rudolph-Boehner, D. Osterhelt, and L. Moroder, J. Photochem. Photobiol. A, 1997,105,283. T. Nagele, R. Hoche, W. Zinth, and J. Wachtveitl, Chem. Phys. Lett., 1997,272,489. N. Biswas and S . Umapathy, J. Chem. Phys., 1997,107,7849. S. Mukherjee and S. C. Bera, J. Photochem. Photobiol. A, 1998,113,23. E. Markava, D. Gustina, G . Matisova, I. Kaula, I. Muzikanto, M. Rutkis, and L. Gerca, Suprumol. Sci., 1997,4, 369. R. Tahara, T. Morozumi, H. Nakamura, and M. Shimomura, J. Phys. Chem. B, 1997,101,7736. M. V. Alfinov, A. 1. Vedernikov, S. P. Gromov, Y . V. Fedorov, and 0. A. Fedorova, Russ. Chem. Bull., 1997,46,2099, D. K. Palit, A. Z. Szarka, N. Pagliano, and R. M. Hochstrasser, Ultrufust Processes Spectrosc. [Proc. Int. ConJ], 1996, 9,75. N. R. King, E. A. Whale, F. J. Davis, A. Gilbert, and G. R. Mitchell, J. Muter. Chem., 1997,7,625. S . Dobrin, A. Starakhin, P. Kaszynski, and J. Waluk, Opt. Spektrosk., 1997,83,669. H. E. Wilhelm, H. Gebert, and W. Regenstein, 2. Nuturforsch., A: Phys. Sci., 1997, 52, 837. V. Papper, D. Pines, G. Likhtenshtein, and E. Pines, J. Photochem. Photobiol. A , 1997, I l l , 87. V. Strehmel, C. W. Frank, and B. Strehmel, J. Photochem. Photobiol. A , 1997, 105, 353. W. J. Oldham Jr., Y. J. Miao, R. Lachicotte, and G. C. Bazan, J. Am. Chem. Soc., 1998,120,419. S. Dobrin, P. Kaszynski, and J. Waluk, J. Photochem. Photobiol. A , 1997,105, 149. G. Strati and P. Piotrowiak, J. Photochem. Photobiol. A, 1997,105,255. S. M. Bachilo, E. V. Bachilo, and T. Gillbro, Chem. Phys., 1998,229,75. E. J. Shin, E. Y . Bae, S. H. Kim, H. K. Kang, and S. C. Shin, J. Photochem. Photobiol. A, 1997,107, 137. V. Raj Gopal, V. Jayathritha, G. Saroja, and A. Samanta, Chem. Phys. Lett., 1997, 270, 592. J. Saltiel, Y . Zhang, and D. F. Sears Jr., J. Am. Chem. SOC.,1997, 119, 11202. L. Latterini, F. Elisei, G. G. Aloisi, and M. A. J. Rodgers, J. Phys. Chem. A, 1997, 101,9870. G . G . Aloisi, F. Elisei, L. Latterini, G. Marconi, and U. Mazzucato, J. Photochem. Photobiol. A , 1997,105,289. M. F. Budyka, 0. D. Laukhina, and V. F. Razumov, Chem. Phys. Lett., 1997,279, 327. T. Arai, Y . Hozumi, 0. Takahashi, and K. Fujimori, J. Photochem. Photobiol. A , 1997,104, 85. E. J. Shin and S. W. Choi, J. Photochem. Photobiol. A , 1998,114,23.
I: Photophysical Processes in Condensed Phases
45
Z. Li and S. Wu, J. Lumin., 1997, 7,237. Special Issue: Fullerenes, Photoexcited States and Reactive Intermediates, Part I . ed. D. M. Guldi, P. V. Kamat, and K.-D. Asmus, Res. Chem. Intermed., 1997,23. 374. Y.-P. Sun, Mol. Suprumol. Photochem., 1997, I , 325. 375. L. Juha, V. Hamplova, Z. Pokorna, J. Kodymova, 0. Spaiek, J. Krasa, K. Lang, P. Kubat, F. P. Boody, E. Koudoumas, S. Couris, I. Stibor, T. Gareis, 0. Kothe, and J. Daub, Proc.-Electrochem. Soc., 1997, 97, 56. 376. J. Mattay, C. Siedschlag, G. Torres-Garcia, L. Ulmer, C. Wolff, M. Fujisuka, A. Watanabe, 0. Ito, and H. Luftmano, Proc.-Electrochem. Soc., 1997,97,326. 377. M. Kallny, K. Nemeth, and P. R. Surjan, J. Phys. Chem. A , 1998,102, 1261. 378. 0.Ito, Reza Kenkyu, 1997,25,776. 379. S . Fukuzumi, Res. Chem. Intermed., 1997,23, 519. 380. P. V. Kamat and D. M. Guldi, Proc.-Electrochem. SOC.,1997, 97,203. 381. R. V. Bensasson, E. Bienvenue, J.-M. Janot, E. J. Land, and P. Seta, Chem. Phys. Lett., 1998,283,221. 382. D. K. Palit, H. Mohan, and J. P. Mittal, J. Phys. Chem. A, 1998, 102,4456. 383. M. Fujitsuka, H. Kasai, A. Masuhara, S. Okada, H. Oikawa, H. Nakanishi, A. Watanabe, and 0. Ito, Chem. Lett., 1997, 121 1 . 384. Y. L. Hwang and K. C. Hwang, Huaxue, 1997,55,53. 385. M. Fujitsuka, A. Watanabe, 0. Ito, K. Yamamoto, and H. Funasaka, J. Phys. Chem. A, 1997,101,7960. 386. M. Ichida, M. Sakai, T. Yajima, and A. Nakamura, J. Lumin., 1997, 72,499. 387. J . S. Ahn, K. Suzuki, Y. Iwasa, and T. Mitani, J. Lumin., 1997, 72,464. 388. V. V. Kveder, V. D. Negrii, E. A. Steinman, A. N. Izotov, Y. A. Ossip’yan, and E. K. Nikolaev, Zh. Eksp. Teor. Fiz., 1998,113, 734. 389. I. Akimoto, J. Azuma, M. Ashida, and K. Kan’no, J. Lumin., 1998, 76,206. 390. T. Ohno, K. Matsuishi, and S. Onari, J. Appl. Phys., 1998,83,4939. 391. Y. Wang, Y. Yang, Y. Guo, R. Gan, J. Wang, Y. Sun, and G. Chen, Proc. SPIE-Int. SOC.Opt. Eng., 1998,3175 (Thin Film Physicsand Applications), 104. 392. J. Qian, J. Song, C. Xu, S. Qian, and W. Peng, Zhongguo Jiguang, 1997, A24,251. 393. V. A. Gaisin, B. S. Kulinkin, and B. V. Novikov, Vestri. St.-Petersbg. Univ., Ser. 4. Fiz. Khim., 1997, 113. 394. Y.-P. Sun, B. Kiu, and G. E. Lawson, Photochem. Photobiol., 1997,66, 301. 395. J. L. Bourdelande, J. Font, R. Gonzalez-Moreno, and S. Nonell, J. Photochem. Photobiol. A , 1998,115,69. 396. E. R. Crooks, J. Eastoe, and A. Beeby, J. Chem. Soc., Faraday Trans., 1997, 93, 4131. 397. D. M. Guldi and K.-D. Asmus, Proc. Electrochem. Soc., 1997,97,82. 398. C . Wang and S. Yao, Huaxue Wuli Xuebuo, 1998,II, 146. 399. L. Juha, V. Hamplova, Z. Pokorna, K. Lang, P. Kubat, I. Stilbor, and F. P. Brody, Proc. Electrochem. SOC.,1997,97, 256. 400. Z. R. Lian, S. D. Yao, W. Z. Lin, W. F. Wang, and N. Y. Lin, Radiut. Phys. Chem., 1997,50,245. 401. S. D. Yao, W. Z. Lin, Z. R. Lian, W. F. Wang, and N. Y. Lin, Rudiat. Phys. Chem., 1997,50,249. 402. S . Michaeli, V. Meiklyar, B. Endeward, K. Mobius, and €3. Levanon, Res. Chem. Intermed., 1997,23, 505. 403. V. A. Nadtochenko and E. F. Brazgun, Russ. Chem. Bull., 1997,46, 1074. 404. S. Fukuzumi, M. Patz, T. Suenobu, A. Ishida, and K. Mikami, Proc.-Electrochem. SOC.,1997, 97,45.
372. 373.
46 405. 406. 407. 408. 409. 410. 41 1. 412. 41 3. 414. 415. 41 6. 41 7 41 8. 419. 420. 421. 422. 423. 424. 425. 426. 427. 428. 429. 430. 431. 432. 433.
Photochemistry
L. Biczok, N. Gupta, and H. Linschitz, J. Am. Chem. SOC.,1997,119, 12601. J. Qiao, X. Yuan, and W. Jin, Shanzi Daxue Xuebao, Ziran Kexuebuo, 1998,21,147. D. M. Guldi, J. Phys. Chem. B, 1997,101,9600. M. Alam, A. Watanabe, and 0. Tto, J. Photochem. Photobiol. A, 1997,104, 59. T. Nojiri, M. Alam, H. Konami, A. Watanabe, and 0. Ito, J. Phys. Chem. A, 1997, 101,7943. Y . Sasaki, M. Fujitsuka, A. Watanabe, and 0. Ito, J. Chem. SOC.,Faruday Trans., 1997,93,4275. M. I. Sluch, I. D. W. Samuel, and M. C. Petty, Chem. Phys. Lett., 1997,280,215. R. V. Bensasson, E. Bienvenue, C. Fabre, J.-M. Janot, E. J. Land, S. Leach, V. Leboulaire, A. Rassat, S. Roux, and P. Seta, Chem.-Eur. J., 1998,4,270. H. Mohan, L. Y. Chiang, and J. P. Mittal, Res. Chem. Intermed., 1997,23,403. H. Mohan, D. K. Palit, J. P. Mittal, L. Y. Chiang, K.-D. Asmus, and D. M. Guldi, J. Chem. Soc., Faraday Trans., 1998,94,359. C. Carvaja, M. Maggini, M. Rossi, G. Scorrano, and A. Toffoletti, Appl. Magn. Reson., 1997,12,477. P. V. Kamat, D. M. Guldi, D. Liu, K. G. Thomas, Y. Biju, S. Das, and M. V. George, Proc.-Electrochem. Soc., 1997, 97, 122. D. K. Palit, H. Mohan, P. R. Birkett, and J. P. Mittal, J. Phys. Chem. A, 1997, ZOI, 5418. M. Moggini, S. Mondini, G. Scorrano, M. Prato, F. Paolucci, P. Ceroni, S. Roffia, and D. M. Guldi, Proc.-Electrochem. SOC.,1997,97, 325. C. Luo, M. Fujitsuka, A. Watanabe, 0. Tto, L. Gan, Y. Huang, and C.-H. Huang, J. Chem. Soc., Faraday Trans., 1998,94,527. A. W. Jansen, A. Khong, M. Saunders, S. R. Wilson, and D. I. Schuster, J. Am. Chem. SOC.,1997,119,7303. M. Ohno, N. Koide, H. Sato, and S. Eguchi, Tetrahedron, 1997,53,9075. D. M. Guldi, M. Maggini, G. Scorrano, and M. Prato, Res. Chem. Intermed., 1997, 23,561. D. M. Guldi, M. Maggini, G. Scorrano, and M. Prato, Fullerenes, Fullerene Nunostruct., Proc. Int. Wintersch. Electron. Prop. Novel Muter., loth, ed. H. Kuzmany, World Scientific, Singapore, 1996, pp 487-491. F. Conti, C. Corvaja, M. Maggini, F. Piu, G. Scorrano, and A. Toffoletti, Appl. Magn. Reson., 1997, 13, 337. D. M. Guldi, M. Maggini, S. Mondini, G. Scorrano, and M. Prato, ProcElectrochem. Soc., 1997,97,89. D. M. Guldi, M. Maggini, S. Mondini, G. Scorrano, and M. Prato, Proc. SPIE-Int SOC.Opt. Eng., 1997,3142 (Fullerenes and Photonics I V ) , 96. I. G. Sahonov, P. S. Baran, and D. 1. Schuster, Tetrahedron Lett., 1997,38, 8132. T. D. M. Bell, T. A. Smith, K. P. Ghiggino, M. Ranasinghe, M. J. Shepard, and M. N. Paddon-Row, Chem. Phys. Lett., 1997,268,223. H. Imahori and Y. Sakata, Mv. Muter., 1997,9, 537. D. Gust, T. A. Moore, and A. L. Moore, Res. Chem. Intermed., 1997,23,621. D. Gust, T. A. Moore, A. L. Moore, P. A. Liddell, D. Kuciauskas, J. P. Sumida, B. Nash, and D. Nguyen, Proc.-Electrochem. SOC.,1997,97,9. D. Carbonera, M. Di Valentin, C. Corvaja, G. Agostino, G. Giacometti, P. A. Liddell, D. Kuciauskas, A. L. Moore, T. A. Moore, and D. Gust, J. Am. Chem. Soc., 1998,120,4398. H. Imahori, K. Yamada, M. Hasegawa, and S. Taniguchi, Angew. Chem., Int. Ed. Engl., I997,36, 2626.
I : Photophysical Processes in Condensed Phases 434. 435. 436. 437. 438. 439. 440. 441. 442. 443. 444. 445. 446. 447. 448. 449. 450. 451. 452. 453. 454. 455. 456. 457. 458. 459. 460. 461. 462. 463. 464. 465. 466.
47
A. Mortensen and L. H. Skibsted, Free Radical Rex, 1997,26,549. K. Iwata and H. Hamaguchi, Bull. Chem. Soc. Jpn., 1997, 70,2677. F. D. Lewis, J. M. Wagner-Brennan, and J. M. Denari, J. Photochem. Photobiol. A , 1998,112, 139. B. Marciniak, E. Andrzejewska, and G. L. Hug, J. Photochem. Photobiol, A , 1998, 112,21. H. Shizuka, Pure Appl. Chem., 1997,69,825. K. Okada, M. Yamaji, and H. Shizuka, J. Chem. Soc.. Furaday Trans., 1998, 94, 861. I. Amada, M. Yamaji, M. Sase, H. Shizuka, and T. Shimokage, Res. Chem. Intermed., 1998,24, 8 1 . W. Adam, J. N. Moorthy, W. M. Nau, and J. C. Scaiano, J. Am. Chem. SOC.,1997, I 19,6749. A. I. Novaira, C. D. Borsarelli, J. J. Cosa, and C. M. Previtali, J. Photochem. Photobiol. A , 1998, I15,43. T. Nakayama, S. Akimoto, I. Yamazaki, and K. Hamanoue, J. Photochem. Photobid. A, 1997,104, 77. D. Burget and P. Jacques, Chem. Phys. Lett., 1998,291,207. Y. H. Lee and M Lee, Bull. Korean Chem. Soc., 1997,18, 1054. P. Bortolus, S. Monti, G. Galiazzo, and G. Gennari, Chem. Phys., 1997,223,99. G. Zhang, J. K. Thomas, A. Eremenko, T. Kikieva, and F. Wilkinson, J. Phys. Chem. B, 1997, IOI, 8569. A. Goswami and M. Kanta Pal, Collids Surf., 1998,138, 123. S . Kotani, H. Miyasaka, A. Itaya, Y. Hamanaka, N. Mataga, S. Nakajima, and A. Osuka, Chem. Phys. Lett., 1997,269,274. H. Miyasaka, S. Kotani, A. Itaya, G. Schweitzer, F. C. De Schryver, and N. Mataga, J. Phys. Chem. B, 1997,101,7978. H. A. Staab, D. Q. Zhang, and C. Krieger, Liebigs Ann. I Reel., 1997,1551. T. Fiebig, W. Kuhnle, and H. Staerk, Chem. Phys. Lett., 1998,282,7. F. Schael and H. G. Loehmannsroeben, J. Photochem. Photobiol. A , 1997,105,317. G . Jones I1 and X. Qian, J. Phys. Chem. A, 1998,102,2555. C. D. Clark and M. Z. Hoffman, J. Photochem. Photobiol. A , 1997,111,9. S . Icli, H. Icil, D. G. Whitten, C. Sayil, and I. Dityapak, J. Lumin., 1997, 75, 353. A. 0. Doroshenko, V. T. Skripkina, V. M. Schershukov, and 0. A. Ponomaryov, J. Fluoresc., 1997, 7 , 10I . N. A. Bayri and 0. Kocsk, Turk. J. Chem., 1997,21, 172 E. Bosch, S. M. Hubig, S. V. Linderman, and J. K. Kochi, J. Org. Chem., 1998,63, 592. T. Fournier, S. M. Tavender, A. W. Parker, G. D. Scholes, and D. Phillips, J. Phys. Chem. A , 1997,101,5320. Y. L. Chow, Y.-H. Zhang, M. X. Zheng, and A. Rassat, Chem. Phys. Lett., 1997, 2?2,47 1 . X. Yan, M. Weng, M. Zhang, and T. Shen, Dyes Pigm., 1997,35,87. M. Fagnoni, M. Melia, and A. Albini, J. Phys. Org. Chem., 1997, 10, 777. F. Li, S. Gentemann, W. A. Karlsbeck, J. Seth, J. S. Lindsey, D. Holten, and D. F. Bocian, J. Mater. Chem., 1997, 7 , 1245. J.-P. Strachan, S. Gentemann, W. A. Karlsbeck, J. Seth, J. S. Lindsey, D. Holten, and D. F. Bocian, J. Am. Chem. Soc., 1997,119,11191. J.-P. Strachan, S. Gentemann, W. A. Karlsbeck, J. Seth, J. S. Lindsey, D. Holten, and D. F. Bocian, Inorg. Chem., 1998,37, 1191.
48 467. 468. 469. 470. 471. 472. 473. 474. 475. 476. 477. 478. 479. 480. 481. 482. 483. 484. 485. 486. 487. 488. 489. 490. 491. 492. 493, 494. 495. 496. 497. 498.
Photochemistry
E. I. Zenkevich, V. N. Koyukshto, A. M. Shulga, V. A. Kuzmitsky, V. I. Gael, E. G. Levinson, and A. E. Mironov, J. Lumin., 1997, 75, 229. S. Kawahata, I. Yamazaki, Y. Nishimura, and A. Osuka, J. Chetn. Soc., Perkin Trans. 2 , 1997,479. K. M. Kadish, N. Guo, E. Van Caemelbecke, A. Froijo, R. Paolesse, D. Monti, P. Tagliatesta, T. Boschi, L. Prodi, F. Bolletta, and N. Zaccheroni, Inorg. Chem., 1998,37,2858. A. A. Krasnovskii Jr., M. E. Bashtanov, N. N. Drozdova, P. A. Liddell, A. L. Moore, T. A. Moore, and D. Gust, J. Photochem. Photobiol. A , 1997,102, 167. M. P. Debreczney, M. R. Wasielewski, S. Shinoda, and A. Osuka, J. Am. Chem. Soc., 1997,119,6407. J. Ho, M. Zhang, and T. Shen, Sci. Chinu, Ser. B: Chem., 1997,40,380. W. Zhao, Y.-J. Hou, W.4. Wang, B.-W. Zhang, and Y. Co, Chin. J. Chem., 1998, 16, 7. J. Delaire, C. Giannotti, and J. Zakrzewski, J. Photochem. Photobiol. A , 1998,112,205. Z. Zhang, A. L. Verma, K. Nakashima, M. Yoneyama, K. Iriyama, and Y. Ozaki, Lungmuir, 1997, 13, 5726. G. Vaijayanthimala and V. Krishnan, J. Porphyrins Phthulocyunines, 1997, I , 17. M. R. Shortreed, S. F. Swallen, Z.-Y. Shi, W. Tan, Z. Xu, C. Davadoss, J. S. Moore, and R. Kopefman, J. Phys. Chem. B, 1997,101,6318. H. Tian, W. Ni, J. Su, and K. Chen, J. Photochem. Photobiol. A , 1997,109,213. P. Bojarski and L. Kulak, Asiun J. Spectrosc., 1997, I , 107. K. Hisada, S. Ito, and M. Yamamoto, J. Phys. Chem. B, 1998,102,4075. T. Morita, S. Kimura, and Y. Tmanishi, Langmuir, 1998,14, 171. H. Tian, K. Yang, andX. Luo, J. Photochem. Photobiol. A , 1997,110,253. Y .Yamano, M. Mimuro, and M. Ito, J. Chem. Soc., Perkin Truns I , 1997,2713. T. Tanaka, M. Yamaji, and H. Shizuka, J. Chem. Soc., Faraduy Truns., 1998, 94, 1179. L. Flamigni, N. Armaroli, F. Barigelletti, V. Balzani, J.-P. Collin, J.-0. Dalbavia, V. Heitz, and J.-P. Sauvage, J. Phys. Chem. B, 1997,101,5935. G . J. Wilson, A. Launikonis, W. H. F. Sasse, and A. W.-H. Mau, J. Phys. Chem. A , 1997,101,4860. J. A. Simon, S. L. Curry, R. H. Schmehi, T. R. Schatz, P. Piotrowiak, X. Jin, and R. P. Thummel, J. Am. Chem. SOC.,1997,119, 11012. D. R. Striplin, C. G. Wall, B. W. Erickson, and T. J. Meyer, J. Phys. Chem. B, 1998, 102,2383. M. Mac, Bull. Pol. Acad. Sci., Chem., 1997,45, 53. P. Ray, S. C. Bhattacharya, and S. P. Moufik, J. Photochem. Phtobiol. A , 1997, f0.5, 69. L. A. Al-Hassan and F. S. Al-Amro, J. Photochem. Photobiol. A , 1998,112, 165. S . G. Bertolotti and C. M. Previtali, J. Photochem. Photobiol. A , 1997, 103, 1 15. D. K. Palit, A. V. Sapre, and J. P. Mittal, Chem. Phys. Lett., 1997,269, 286. N. Manoj, K. Ajit, and K. R. Gopidas, J. Photochem. Photobiol. A, 1997,109, 109. G . Wanaska, Pol. J. Chem., 1997, 71, 797. W. Bergmark, S. Hector, G. Jones 111, C. Oh, T. Kumagai, S. Hara, T. Segawa, N. Tanaka, and T. Mukai, J. Photochem. Photobiol. A , 1997,109, 119. M. Suzuki, T. Ikeno, K. Osoda, K. Narasaka, T. Suenobu, S. Fukuzumi, and A. Ishida, Bull. Chem. Soc. Jpn., 1997, 70,2269. C. Sato, K. Kikuchi, H. Ishikawa, M. Iwahashi, H. Ikeda, Y. Takahashi, and T. Miyashi, Chem. Phys. Lett., 1997,276,210.
I : Photophysical Processes in Condensed Phases
49
P. Thanasekaren, T. Rajendren, S. Rajagopal, C. Srinivasan, R. Ramaraj, P. Ramamurthy, and B. Venkatachalapathy, J. Phys. Chem. A , 1997,101,8195. 500. S. S. Jayanthi and P. Ramamurthy, J. Phys. Chem. A, 1998,102,51 I . 501. S . Sinha, R. De, and T. Ganguly, Spectrochim. Actu, Part A, 1998, M A , 145. 502. S. Sinha, R. De, and T. Ganguly, J. Photochem. Photobiol. A, 1998,112, 13. 503. H. Shirota, H. Pal, K. Tominaga, and K. Yoshihara, J. Phys. Chem. A, 1998, 102, 3089. 504. K. Tsukahara, K. Ito, M. Matsui, M. Subo, and 0. Yoshaki, Chem. Phys. Lett., 1997,281,261. 505. P. K. Malnen, A. Y. Tauber, J. Helnja, and P. H. Hynninen, Liebigs Ann. I Recl., 1997, 1801. 506. H. A. Staab, A. Feurer, C. Krieger, and A. S. Kumar, Liebigs Ann. I R e d , 1997, 2321. 507. H. A. Staab, R. Hauck, and B. Popp, Eur. J. Chem., 1998,631. 508. A. P. Losev, S. M. Bachilo, D. I. Volkovich, Y. S. Avlasevich, and K. N. Solov’yov, J. Appl. Spectrosc., 1997,64, 62. 509. J . P. Sumida, P. A. Liddell, S. Lin, A. N. Macpherson, G. R. Seely, A. L. Moore, T. A. Moore, and D. Gust, J. Phys. Chem. A , 1998,102,5512. 510. H. Dieks, M. 0. Senge, B. Kirste, and H. Kurreck, J. Org. Chem., 1997,62, 8666. 51 1. G. Elger, H. Mossler, P. Tian, E. Johnen, M. Fuhs, H. Kurreck, and K. Mobius, Nukleonika, 1997,42,293. 512. J. Helaja, A. Y. Tauber, I. Kilpelainen, and P. H. Hynninen, Mugn. Reson. Chem., 1997,35,619. 513. K. Unsaki, T. Kondo, Z.-Q. Zhang, and M. Yamagida, J. Am. Chem. SOC., 1997, I 1 9,8367. 514. M. H. Wall Jr., P. Basu, T. Buranda, B. S. Wicks, E. W. Findsen, M. Ondrias, J. H. Enemark, and M. L. Kirk, Inorg. Chem., 1997,36,5676. 515. H. Imahori, K. Yamada, K. Yoshizawa, K. Higawara, T. Okada, and Y. Sakata, J. Porphyrins Phthalocyanines, 1997, I , 55. 516. E. Kaganer, E. Joselevich, I. Willner, Z. Chen, M. J. Gunter, T. P. Gayness, and M. R. Johnson, J. Phys. Chem. B, 1998,102, 1159. 517. M. C. Feiters, M. C. T. Fyfe, M. V. Martinez-Diaz, S. Menzer, R. J. M. Nolte, J. F. Stoddart, J. M. van Kan, and D. J. Williams, J. Am. Chem. SOC.,1997,119,8119. 518. R. P. Evstigneeva and A. A. Grihkov, Dokl. Akud. Muuk, 1997,357,779. 519. Q . Tan, D. Kuciauskas, S. Lin, S. Stone, A. L. Moore, T. A. Moore, and D. Gust, J. Phys. Chem. B, 1997,101,5214. 520. S.-C. Hung, A. N. Macpherson, S. Lin, P. A. Liddell, G. R. Seely, A. L. Moore, T. A. Moore, and D. Gust, A h . Chem. Ser., 1998, 254 (Photochemistry and Radiation Chemistry), 177. 521. A. Osuka, S. Marumo, T. Okada, S. Taniguchi, N. Mataga, T. Ohno, K. Nozaki, I. Yamazaki, and Y. Nishimura, J. Photosci., 1997,4, 113. 522. D. Gosztola, M. P. Niemczyk, and M. R. Wasielewski, J. Am. Chem. SOC.,1998, 120,5118. 523. J. P. Kirby, J. A. Roberts, and D. G. Nocera, J. Am. Chem. Soc., 1997,119,9230. 524. N. A. Sadovskii, M. G. Kuzmin, H. Gorner, and K. Schaffner, Chem. Phys. Lett., 1998,282,456. 525. D. Wiedenfeld, M. Bachrach, T. M. McCleskey, M. G. Hall, H. B. Gray, and J. R. Winkler, J. Phys. Chem. B, 1997, 101,8823. 526. C. A. Slate, D. R. Striplin, J. A. Moss, P. Chen, B. W.Erickson, and T. J. Meyer, J. Am. Chem. SOC.,1998,120,4885.
499.
50 527. 528. 529. 530. 531. 532. 533. 534. 535. 536. 537. 538. 539. 540. 54 I 542. 543. 544. 545. 546. 547. 548. 549. 550. 551. 552. 553. 554. 555.
Photochemistry A. Knorr, E. Galoppini, and M. A. Fox, J. Phys. Org. Chem., 1997,10,484. K. Fujimoto, H. Sugiyama, and I. Saito, Tetrahedron Lett., 1998,39,2137. K, Weidemaier, H. L. Tavernier, K. T. Chu, and M. D. Fayer, Chem. Phys. Lett.,
1997,276, 309. D. Wang, M. Hu, L. Hu, L. Zhao, Y. Hamanaka, N. Mataga, S. Nakajima, and A. Osuka, Chem. Phys. Lett., 1997,269,274. D. R. Worrall, S. L. Williams, and F. Wilkinson, J. Phys. Chem. B, 1997,101,4709. G. J. Smith, A. Harriman, A. D. Woolhouse, T. C. Haskell, and T. H. Barnes, Photochem. Photobiol., 1998,67, 101. S . W. Keller, S. A. Johnson, E. H. Yonemoto, E. S. Brigham, G. B. Saupe, and T. E. Mallouk, Adv. Chem. Ser., 1998,254 (Photochemistry and Radiation Chemistry), 359. X.-Z. Song, S.-L. Jia, M. Miura, J.-G. Ma, and J. A. Shelnutt, J. Photochem. Photobiol. A, 1998,113,283. S . V. Lymar, R. F. Khairutdinov, V. A. Sukova, and J. R. Hurst, J. Phys. Chem. B, 1998,102,281. H. Port, A. Hartschuh, T. Hirsch, and H. C. Wolf, J. Luminesc., 1997, 72,75. M. B. Zimmt, Chimia, 1997,SI, 82. S . Depaemelaere, F. C. De Schryver, and J. W. Verhoeven, J. Phys. Chem. A , 1998, 102,2109. H. Zhang, M. Zhang, and T. Shen, Sci. China, Ser. B: Chem., 1997,40,449. S. R. Greenfield, D. J. Gosztola, and M. R. Wasielewski, J. Phys. Chem. A , 1997, 101,4939. F. D. Lewis, J. M. Wagner-Brennan, and J. M. Denari, J. Phys. Chem. A, 1998,102, 519. B.-W. Zhang, Y. Cao, J.-W. Bai, and J.-R. Chen, J, Photochem. Photobiol. A , 1997, 106, 169. S. Li, H. Tian, Q. Zhou, Z. Li, and H. Su, Chin. Sci. Bull., 1997,42, 1619. Y.-S. Chen, J. W. Kampf, and R. G. Lawton, Tetrahedron Lett., 1997,38, 7815. A. C. Benniston, A. Harriman, V. Grosshenny, and R. Ziessel, New J. Chem., 1997, 21,405. J. A. Roberts, J. P. Kirby, S. T. Wall, and D. G. Nocera, Inorg. Chim. Acta, 1997, 263, 395. R. Ziessel, A. Juris, and M. Venturi, Chem. Commun., 1997, 1593. M. Ruthkosky, C. A. Kelly, M. C. Zaros, and G. J. Meyer, J. Am. Chem. Soc., 1997, 119, 12004. M. T. Indelli, F. Scandola, L. Flamigni, J.-P. Collin, J,-P. Sauvage, and A. Sour, Inorg. Chem., 1997,36,4247. M. D. Hossain, M. Wage, H. Monjushiro, B. Gholamkhass, and K. Nozaki, Chem. Lett., 1997,573. J. A. Treadwey, P. Chen, T. J. Rutherford, F. R. Keene, and T. J. Meyer, J. Phys. Chem. A , 1997,101,6824. S . E. Ronco, D. W. Thompson, S. L. Gahan, and J. D. Petersen, Inorg. Chem., 1998, 37,2020. B. W. Pfennig, J. K.Goertz, D. W. Wolff, and J. L. Cohen, Inorg. Chem., 1998, 37, 2608. A. P. da Silva, H. Q. N. Gunaratne, T. Gunnlaugsson, A. J. M. Huxley, and J. T. Rademacher, NATO ASI Ser., Ser. C , 1997,492 (Chemosensors of Ion and Molecule Recognition), 143. A. P. da Silva, H. Q. N. Gunaratne, T. Gunnlaugsson, A. J. M. Huxley, C. P. Mccoy, J. T. Rademacher, and T. E. Rice, Adv. Suprumol. Chem., 1997,4, I .
I: Photophysical Processes in Condensed Phases 556. 557. 558. 559. 560. 561. 562. 563. 564. 565. 566. 567. 568. 569. 570. 571. 572. 573. 574. 575. 576. 577. 578. 579. 580. 581. 582. 583. 584. 585. 586. 587.
51
J. N. Demas and B. A. DeGraff, J. Chem. Educ., 1997,74,690. Y. Shen and B. P. Sullivan, J. Chem. Educ., 1997, 74,685. L. Fabbrizzi, G. Francese, M. Liorhelli, P. Pallavicini, A. Perotil, A. Poggi, D. Succhi, and A. Taglietti, NATO ASI Ser., Ser. C, 1997, 492 (Chemosensorsof Ion and Molecule Recognition), 75. B. Valeur, F. Badaoui, E. Bardez, J. P. Lefevre, and A. Soulet, NATO ASI Ser., Ser. C, 1997,492 (Chemosensorsof Ion and Molecule Recognition), 195. J. D. Winkler, C. M. Bowen, and V. Michelet, J. Am. Chem. SOC.,1998, 120, 3237. I. K. Lednev. T.-Q. Ye, R. E. Hester, and J. N. Moore, J. Phys. Chem. A, 1997,101, 4966. K . Meuwis, N. Boens, F. C. De Schryver, M. Ameloot, J. Gallay, and M. Vincent, J. Phys. Chem. B, 1998,102,641. S. Sasaki, Y. Ando, M. Dejima, Y.Arikawa, and I. Korube, Anal. Chem., 1998,31, 555. G. J. Mohr, S. Drawler, K. Tranasel, F. Lehmann, and M. E. Lippitsch, And. Chim. Acta, 1998,360, 119. J . Yoon, N. E. Ohler, D. H. Vance, W. D. Aumiller, and A. W. Czernik, NATO ASI Ser., Ser. C, 1997,492 (Chemosensorsof Ion and Molecule Recognition), 189. J. Yoon, N. E. Ohler, D. H. Vance, W. D. Aumiller, and A. W. Czernik, Tetrahedron Lett., 1997,38, 3845. F. Unob, Z. Asfari, and J. Vicens, Tetrahedron Lett., 1998,39,2951. J. M. Price, W. Xu, J. N. Demas, and B. A. DeGraff, Anal. Chem., 1998, 70,265. A. P. da Silva, H. Q. N. Gunaratne, T. E. Rice, and S. Stewart, Chem. Commun., 1997,1891. P. D. Beer, F. Szemes, V. Balzani, C. M. Sala, M. G. Drew, S. W. Denti, and M. Maestri, J. Am. Chem. SOC.,1997,119, 11864. D. Parker, K. Senanayake, and J. A. G. Williams, Chem. Commun., 1997,1777. L. Fabbrizzi and I. Faravelli, Chem. Commun., 1998,971. K. A. Kneas, W. Xu, J. N. Demas, and B. A. DeGraff, Appl. Spectroscop., 1997,51, 1346. N . E. Azoz and J. J. Birmingham, J. Fluoresc., 1997, 7,227. K . P. McNamara, X. Li, A. D. Stull, and Z. Rosenweig, Anal. Chim. Acta, 1998,36, 73. F. Alava-Moreno, M. J. Valencia-Gonzalez, A. Sanz-Medel, and M. E. Diaz-Garcia, Analyst, 1997,122,807. A. Mills and F. C. Williams, Thin Solid Films, 1997,306, 163. N. Valesco-Garcia, M. J. Valencia-Gonzdez, and M. E. Diaz-Garcia, Analyst, 1997, 122, 1405. S.-K. Lee and 1. Okura, Anal. Sci., 1997,13,535. H. Chuang and M. A. Arnold, Anal. Chim. Acta, 1998,368,83. M. A. Mansour, W. B. Connick, R. J. Lachioette, H. J. Gysling, and R. Eisenberg, J. Am. Chem. SOC.,1998, 220, 1329. W. K. Hartmann, M. A. Mortellaro, D. G. Nocera, and Z. Pikramenou, NATO AS1 Ser., Ser. C, 1997,492 (Chemosensorsof Ion and Molecule Recognition), 159. S. H. Lieberman, Field Anal. Chem. Technol., 1998,2,63. G. Ellingsen and S. Fery-Forgues, Rev. Inst. Fr. Pet., 1998,53,201. H. Shinmori, M. Takeuchi, and S. Shinkai, J. Chem. SOC.,Perkin Trans 2, 1998,847. Q. Chang, Z. Murtaza, J. R. Lakowicz, and G. Rao, Anal. Chim. Acta, 1997,350,97. J . M. Costa-Fernandez, M. E. Diaz-Garcia, and A. Sanz-Medel, Sens. Actuators, B, 1997, B38,103.
52 588.
589. 590. 591. 592. 593. 594. 595. 596. 597. 598. 599. 600. 601. 602. 603. 604. 605. 606. 607. 608. 609. 610. 61 I. 612. 613. 614. 61 5. 616. 617. 618. 619. 620. 621. 622. 623. 624. 625.
Photochemistry
C. Parigger, D. H. Plemmons, R. J. Litchford, and S.-M. Jeng, Opt. Lett., 1998, 23, 76. A. Kawaski, Asian J. Spectrosc., 1997, I , 27. K. B. Migler and A. J. Bur, Polym. Eng. Sci., 1998,38,213. J. van Stam, S. Depaemelaere, and F. C. De Schryver, J. Chem. Educ., 1998, 75,93. K.-Y. Wong and W. W.-S. Lee, J. Photochem. Photobiol. A , 1997,102,231. R. Zana, L. In, H. Levy, and G. Duportail, Langmuir, 1997,13,5552. T. A. Kikteva, B. V. Zhmud, N. P. Smirnova, A. M. Eremenko, Y. Polevaya, and M. Ottolenghi, J. Collid InterJace Sci., 1997,193, 163. L. Zheng, W. R. Reid, and J. D. Brennan, Anal. Chem., 1997,69,3940. I. Black, D. J. S. Birch, D. Ward, and M. J. Leach, J. Fluoresc., 1997, 7, I 11. C. M. Marchi, S. A. Bilmes, and R. M. Negri, Lungmuir, 1997,13,3665. A. N. Diaz, J. Lovillo, and M. C. R. Peinado, Chem. Muter., 1997, 9,2647. N. Kimura and T. Araiso, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A, 1997, 294, 149. Y. Agi and D. R. Walt, J. Polym. Sci., Part A; Polym. Chem., 1997,35,2105. S . Hu, R. Popielarz, and D. C. Neckers, Macromolecules, 1998,31, 4107. G. Moad, D. A. Shipp, T. A. Smith, and D. H. Solomon, Macromolecules, 1997,30, 7627. S. Morino and K. Horie, ACS Symp. Ser., 1997, 672 (Photonic and Optoelectronic Polymers), 260. M. H. Klopffer, L. Bokobza, and L. Monnerie, Macromol. Symp., 1997,119, 119. T. Shiga, T. Narita, T. Ikawa, and A. Okada, Polym. Eng. Sci., 1998,38,693. T. L. Longin, C. A. Koval, and R. D. Noble, Polym. Muter. Sci.Eng., 1997, 77,278. K. T. Chojnacki and D. A. Feikema, Appl. Opt., 1998,37,4034. N. Srividya, P. Ramamurthy, and V. T. Ramakrishnan, Spectrochim. Acta, Part A , 1997,53, 1743. M. Viard, J. Gallay, M. Vincent, 0. Meyer, B. Robert, and M. Paternostre, Biophys. J., 1997, 73, 222 1. H. Strausky, J. R. Krenn, A. Leitner, and F. R. Aussenegg, Appl. Phys. B: Lasers Opt., 1998,66, 599. R. Roberts, G. Walsh, A. Murray, J. Olley, R. Jones, M. Morwood, C. Tuniz, E. Lawson, M. Macphail, D. Bowdery, and I. Naumann, Nature, 1997,387,696. A. Bafter, J. Fluoresc., 1997, 7,99. J. Slavik, J. Lumin., 1997, 72, 575. G. Bendas, K. Schubert, and P. Nuhn, Pharmazie, 1998,53,43. M. Sisido, A h . Photochem., 1997,22, 197. K. A. Giuliano and D. L. Taylor, Trends Biotechnol., 1998,16, 135. M. Collini, G. Chirico, M. E. Bianchi, and G. Baldini, J. Lumin., 1997, 72,585. R . Sjoeback, C. M. Gustafsson, and M. Kubista, J. Lumin., 1997, 72, 610. J. Dapprich, N. G. Walter, F. Salingue, and R. Staerk, J. Fluoresc., 1997, 7, 87. D. Boturyn, A. Boudali, J.-F. Constant, E. Defranoq, and J. Lhomme, Telrahedron, 1997,53,5485. Y. Hamaguchi, M. Iwai, T. Uchida, H. Shimada, and M. Mitsuhashi, J. Environ. Health, 1997,60, 14. K. Yamana, S. Kumamoto, and H. Nakano, Chem. Lett., 1997, 1 173. Y. Kai and T. Maeda, J. Phys. Soc. Jpn., 1998,67, 1486. Instrumentation for Molecular Fluorescence Spectrometry, Anulyst, 1998,123, 1649. E. P. Browne and T. A. Hatbridge, NASA Con$ Publ., 1996, (Third Microgruvity Fluid Physics Conference), 667.
1: Photophysical Processes in Condensed Phases 626. 627. 628. 629. 630. 631. 632. 633. 634. 635. 636. 637. 638. 639. 640. 641. 642. 643. 644.
645.
646. 647. 648. 649. 650. 651. 652. 653.
53
L. Vetrivel and B. M. Sivaram, Proc. SPIE-Int. Soc. Opt. Eng., 1997,2980 (Advances in Fluorescence Sensing Technology III) , 360. A. George and G. Patonay, Talanta, 1997,45,285. G. N . Jones and C. T. Lee, J. Mol. Opt., 1998,45,283. S. A. Safvi, J. Liu, and T. F. Kuech, J. Appl. Phys., 1997,82, 5252. A. Kramer, T. Hartmann, and R. Eschrich, Ultramicroscopy, 1998, 71, 123. H. Monobe, A. Koike, H. Muramatsu, N. Chiba, N. Yamamoto, T. Ataka, and M. Fujihira, Ultramicroscopy, 1998, 71,287. S. Arnold, S. Holler, and G. L. Goddard, Muter. Sci. Eng. B, 1997,48, 139. Z. Zhang, G. J. Sonek, X. Wei, M. W. Berns, and B. J. Tromberg, Jpn. J. Appl. Phys., Part 2, 1997,36, L1598. L. Avanessian and V. Hovanessian, Proc. SPIE-Int. Soc. Opt. Eng., 1997, 2980 (Advances in Fluorescence Sensing Technology III), 42. J. R. Lakowicz, I. Gryczynski, H. Malak, and Z. Gryczynski, Proc. SPIE-Int. Sor. Opt. Eng., 1997,2980 (Advances in Fluorescence Sensing Technology III), 368. P. Allcock and D. L. Andrews, J. Chem. Phys., 1998,108,3089. W . G. Fisher, E. A. Wachter, F. E. Lytle, M. Armas, and C. Seaton, Appl. Spectrosc., 1998,52, 536. J. D. Bhawalkar, J. Swiatkiewicz, S. J. Pan, J. K. Sumarahundu, W. S. Liou, G. S. He, R. Berezney, P. C. Cheng, and P. N. Prasad, Scanning, 1996,18,562. D. A. Hatrick, A. Volkmer, Y. Bai, and D. J. S. Birch, Proc. SPIE-Int. Soc. Opt. Eng., 1997,2980 (Advances in Fluorescence Sensing Technology III), 48. A. Volkmer, D. A. Hatrick, and D. J. S. Birch, Meas. Sci. Technol., 1997,8, 1339 K . Kemnitz, L. Pfeifer, R. Paul, and M. Coppey-Moisan, J. Fluoresc., 1997, 7, 93. A. H. Buist, M. Muller, E. J. Gijsbers, G. J. Brackenhoff, T. S. Sosnowski, T. B. Norris, and J. Squier, J. Microsc., 1997, 186,212. F. R. Boddeke, L. K. Van Geest, and I. T. Young, Proc. SPIE-Int. Soc. Opt. Eng., 1997,2980 (Advances in Fluorescence Sensing Technology III), 35. K . Dowling, S. C. W. Hyde, N. P. Barry, J. C. Dainty, P. M. W. French, A. J. Hughes, M. J. Lever, A. K. L. Dymoke-Bradshaw, and P. A. Kellett, Proc. SPIEInt. Soc. Opt. Eng., 1997, 2980 (Advances in Fluorescence Sensing Technology I I I ) , 20. H. Itoh, A. Evenzahev, K. Kinoshita, Y. Inaguki, M. Toshimori, T. Hiroshi, F.Akira, H. Tadashi, T. Hayakawa, and A. Kusumi, Proc. SPIE-Int. SOC.Opt. Eng., 1997,2980 (Advances in Fluorescence Sensing Technology III), 12. D. McInskey, K. Suhling, and D. J. S. Birch, Proc. SPIE-Int. Soc. Opt. Eng., 1997, 2980 (Advances in Fluorescence Sensing Technology III) ,400. M . E. Lippitsch, S. Draxler, and D. Kieslinger, Sens. Actuators, B, 1997,38,96. A. Fultz, T. M. Branch, and V. Majidi, Microchem. J., 1997,57,231. E. Moutiez, P. Prognon, G, Mahuzier, P. Bourrinet, S. Zehaf, and A. Dencausse, Analyst, 1997,122, 1347. M . A. Dvorak, G. A. Oswald, M. H. Van Benthem, and G. D. Gillispie, Anal. Chem., 1997,69,3458. R. Levy, E. F. Guignon, S. Cobane, E. St. Louis, and S. M. Salvador, Proc. SPIEInt. Soc. Opt. Eng., 1997, 2980 (Advances in Fluorescence Sensing Technology III), 81. T . W. J. Gadella Jr., A. Van Hoek, and A. J. W. G. Visser, J. Fluoresc., 1997, 7, 35. J. A. Steinkamp, H. A. Crissman, B. E. Lehnert, N. M. Lehnert, and C. Deka, Proc. SPIE-Int. Soc. Opt. Eng., 1997, 2980 (Advances in Fluorescence Sensing Technology III), 96.
54 654. 655. 656. 657. 658. 659. 660. 661. 662. 663. 664. 665. 666. 667. 668. 669. 670. 671. 672. 673. 674. 675. 676. 677. 678. 679. 680. 681. 682. 683. 684. 685. 686. 687. 688.
Photochemistry
S. Aich and S. Basu, J. Phys. Chem. A , 1998,102,722. K. Nisizawa, Y. Sakaguchi, H. Hayashi, H. Abe, and G. Kido, RIKEN Rev., 1997, 15,49. S. Aich, S. Basu, and D. N. Nath, J. Photochem. Photobid. A , 1997, 109,95. J. C. Scaiano, S. V. Jovanovic, and D. G. Morris, J. Photochem. Photobiol. A , 1998, 113, 197. S. Aich and S. Basu, Chem. Phys. Lett., 1997,28,247. T. Nakai, M. Tani, S. Nishio, A. Matsuzaki, andH. Sato, Chem. Lett., 1997,795. N. K. Petrov, W. Kuehale, T. Fiebig, and H. Staerk, J. Phys. Chem. A, 1997, 101, 7043. T. Fiebig, W. Kuehnle, and H. Staerk, J. Fluoresc., 1997, 7,29S. M. H. Kleinman, T. Shevchenko, and C. Bohne, Photochem. Photobiol., 1998, 67, 198. M. Sacher and G. Grampp, Ber. Bundsenges-Ges., 1997,101,971. N. Ohta, T. Ito, S. Okazaki, and I. Yamazaki, J. Phys. Chem. B, 1997,101, 10213. S. Umeuchi, Y. Nishimura, I. Yamazaki, H. Murakami, M. Yamashita, and N. Ohta, Thin SolidFilms, 1997,31,239. M . Goez, Adv. Photochem., 1997,23,63. A. N. Savitsky, S. N. Batchelor, and H. Paul, Appl. Magn. Resun., 1997,13,285. Y. Kimura, K. Sugihara, M. Terazima, and N. Hirota, Bull, Chem. Sue. Jpn., 1997, 70,2657. E . Vauthey and A. Henseler, J. Photochem. Photobiol. A, 1998,112, 103. K. Okamoto, N. Hirota, and M. Terazima, J. Phys. Chem. A , 1997,101,5269. M . Terazima, J. Phys. Chem. A, 1998,102,545. D. V . Khodyakov, I. V. Rubtsov, and V. A. Nadtochenko, Res. Chem. Intermed., 1997,23,479. J. R. Torga, J. L. Etcheverry, and M. C. Marconi, Opt. Commun., 1997,143,230. M . Fischer and J. Georges, Spectrochim. Acta, Part A , 1997,53, 1419. B. G. Barisas, H. M. Munnelly, and D. A. Roess, Proc. SPIE-Int. SOC.Opt. Eng., 1997,2980 (Advances in Fluorescence Sensing Technology III), 523. J. A. Elliott, G. Rumbles, A. J. De Mello, and H. L. Anderson, Muter. Res. SOC. Symp. Pruc., 1997,464 (Dynamics in Small Confining Systems III), 295. Y. Yamakage, T. Nagashima, K. Mineda, H. Murai, and T. Azumi, Appl. Magn. Reson., 1997,12,441. L, B. Luo, G. Li, H. L. Chen, S. W. Fu, and S. Y. Zhang, J. Chem. Soc., Dulton Trans., 1998,2103. M. Barra and K. A. Agha, J. Photochem. Photobiol. A, 1997,109,293. S. Hishimoto, J. Chem. Soc., Faruday Trans., 1997,93,4401. C . L. Maupin, S. C. J. Meskers, H. P. J. Dekkers, and J. P. Riehl, J. Phys. Chem. A, 1998,102,4450. S. Salhi, S. G. Koulikov, C. Bied-Charreton, and J.-F. Galaup, J. Lumin., 1998, 78, 187. I. Renge, H. Wolleb, H. Spahni, and U. P. Wild, J. Phys. Chem. A , 1997,101,6202. B. Plagemann, I. Renge, A. Renn, and I. P. Wild, J. Phys. Chem. A, 1998,102, 1725 M. D. Edington, R. E. Riter, and W. F. Beck, J. Phys. Chem. B, 1997,101,4473. E. L. Wehry, Molecular Fluorescence and Phosphorescence Spectrometry, in Hundbook Instrum. Tech. Anal. Chem,. ed. F.A. Settle, Prentice Hall, Upper Saddle River, NJ, 1997, pp 507-539. M. R. Gehlen, Chem. Phys., 1997,224,275. M. Dalibart, Talanta, 1997,44,223 1 .
I : Photophysical Processes in Condensed Phases
55
D. H. Leaback, J. Fluoresc., 1997, 7,55. L. A. Kelly, J. G. Trunk, and J. C. Sutherland, Proc. SPIE-Int. Soc. Opt. Eng., 1997, 2980 (Advances in Fluorescence Sensing Technology I I I ) , 2. 691. V . Apanasovich, E. G. Novokov, and N. N. Yatskov, Proc. SPIE-Int. Suc. Opt. Eng., 1997,2980 (Advances in Fluorescence Sensing Technology III), 516. 692. Z. Y. Zhang, T. Sun, K. T. V. Grattan, and A. W. Palmer, Proc. SPIE-Int. Soc. Opt. Eng., 1997,2980 (Advances in Fluorescence Sensing Technology III), 90. 693. S. L. Neal, Anal. Chem., 1997,69,5109. 694. V . M. E. Schenkeveld and I. T. Young, J. Fluoresc., 1997,7,55. 695. C. G. Morgan, A. C. Mitchell, J. G. Murray, and E. J. Wall, J. Fluoresc., 1997, 7,65. 696. A. Molski and N. Boens, J. Phys. Chem. A, 1997, 101, 5124. 697. V. A. Morozov, Opt. Spektrosk., 1997,83,227. 698. P. C. Schneider and R. M. Clegg, Rev. Sci. Instrum., 1997,68,4107. 699. C. Dusan Jr., C. Dusan, and S. Libusa, J. Fluoresc., 1997, 7,45. 700. I. Gryczynski, Z. Gryczynski, and J. R. Lakowicz, Proc. SPIE-Int. Soc. Opt. Eng., 1998,2256 (Advances in Optical Biophysics), 40. 701. J. Enderlein, D. L. Robbins, W. P. Ambrose, P. M. Goodwin, and R. A. Keller, Proc. SPIE-Int. SOC. Opt. Eng., 1997, 2980 (Advances in Fluorescence Sensing Technology III) , 4 6 1. 702. J. C. Fister I11 and J. M. Harris, Anal. Chim. Acta, 1997,348, 31 1. 703. A. A. Angeluts, N. IL. Koreteev, S. A. Magnitskii, 1. A. Ozheredov, and A. P. Shukuronov, Proc. SPIE-Int. Soc. Opt. Eng., 1998, 3347 (Optical Recording Mechanisms and Media), 228. 704. M. Itaguki, M. Hosono, and K. Watanabe, Anal. Sci., 1997,13, 891. 705. K . Starchov, J. Zhang, and J. Buffie, J. Collid. Interface Sci., 1998,203,289. 706. R. L. Hansen, N. R. Zhu, and J. M. Harris, Anal. Chem., 1998, 70, 1281. 707. R. L. Hansen and J. M. Harris, Anal. Chem., 1998, 70,2565. 708. J. S. Burmeister, L. A. Olivier, W. M. Boitchert, and G. A. Truskey, Biomaterials, 1998, 19,307. 709. M. T. Martin and D. Mobius, Supramol. Sci., 1997,4,381. 710. T. Asakawa, A. Sareta, and K. Miyagishi, Colloid. Polym. Sci., 1997,275,958. 71 1. N. C . Maiti, M. M. G, Krishna, P. J. Britto, and N. Periasamy, J. Phys. Chem. B, 1997,101, 11051. 712. J . M. Kavaleski and M. J. Wirth, Anal. Chem., 1997,69,600. 713. A. Morita and Q. Tran-Cong, Physica A (Amsterdam), 1997,242,377. 714. J. Arden-Jacob and K. H. Drexhage, J. Fluoresc., 1998,7,91. 689. 690.
Part II Organic Aspects of Photochemistry
1
Photolysis of Carbonyl Compounds BY WILLIAM M. HORSPOOL
As in previous years there is a continued swing away from the more traditional areas of study. This feature is obvious not oniy in this chapter but also in the other two compiled by this reviewer. Interest in organic photochemistry is clearly not on the wane, however, and there are still as many publications as in past years. Some topics of general interest have been addressed during the past year. Thus the results from a study of exchange interactions between donors such as triphenylamine and N,N,N',N'-tetramethylbenzidine and ketonic acceptors (xanthone, duroquinone and 2,3-dimethoxy-5-methylbenzoquinone) have been published.' The influence of so-called spectator molecules (e.g. pyridine) upon the intrazeolite chemistry of ketones such as benzophenone, xanthone and p methoxy-Pphenylpropiophenonehas been studied.2 The results of the irradiation of the radical cation of dimethylformamide in a matrix at 77 K have been publi~hed.~ A laser-flash examination of the ketones (1-3) has been carried out? The photochemical reactions of some a-aryloxyacetophenones have been studied and the results obtained compared and contrasted with those obtained from thermolysis experiment^.^ Many products were obtained from these reactions. aPhenoxyacetophenone undergoes photochemical changes when it is irradiated as a complex with fkyclodextrin either in the solid state or in aqueous solution.6 In the solid state a-fission occurs and products of recombination are formed. In solution hydrogen abstraction is the principal reaction.
1
Norrish Type I Reactions
A laser flash study of the photochemistry of acetone has examined the polarization induced by irradiati~n.~ The author suggests that this study shows the
Photochemistry, Volume 30 0The Royal Society of Chemistry, 1999
60
Photochemistry
possibility of a two photon process for a-cleavage. Ketones such as (4) are often used as initiators in industrial polymerization processes under high light intensity irradiation conditions. Faria and Steenken have examined the photoreactivity of such compounds in polar solvents using laser light sources.* They have observed that on irradiation of (4) at 248 nm Norrish Type I fission occurs to yield the radical ( 5 ) . Second photon irradiation at 308 nm brings about the formation of the cation (6) by oxidation of the radical. The authors suggest that such a step might also be involved in industrial photocuring. 0 OMe II I Ph-C-C-Ph I OMe (4)
OMe I Ph-CI OMe
(5)
OMe I PhC' I OMe (6)
A CIDNP study of the irradiation of (7) has shown that a-fission occurs on irradiation.' The resultant radical (8) eliminates diethyl phosphoric acid and yields the radical cation (9). When irradiation is carried out in methanol this species is trapped as the ether (10). Other products are methyl benzoate and the acetal(l1). A laser irradiation study of the reaction of acetophenone with amines constrained in NaY zeolites has been carried out and evidence has been collected that shows that ketyl and amino radicals are formed by hydrogen abstraction pathways. lo
The photochemical reactions of the ketones (12) which are used as sunscreens in cosmetics has shown that degradation is considerable when they are irradiated as thin films. Norrish Type I reactions dominate affording benzoic acid derivatives.' I A study of the biradicals formed on flash photolysis of the ketone (1 3) has been reported.12 The reaction involves a Norrjsh Type I process and yields an acyl-ketyl biradicai that transforms into an alkyl-ketyl biradical by decarbonylation.
R*
'
(12) R' = R2 = Pr' R' = But, R2 = Me0
a 0 Me R'
(13)
OH
IIII: Photolysis of Carbonyl Compounds
2
61
Norrish Type I1 Reactions
2.1 1,SHydrogen Transfer - The Norrish Type I and Type I1 photochemical behaviour of pentan-2-one constrained in zeolite cavities has been studied.13 The series of ketones (14) all undergo Norrish Type I1 elimination of acetophenone when irradiated.14 A study of intramolecular energy transfer was carried out using these compounds. Wessig and co-workers have examined the photochemical reactivity of the bridged ketones (15).15 Ring-size was found to be one of the controlling factors on the outcome of the reactions. The ketone (16) undergoes Norrish Type I1 hydrogen abstraction. However, a cyclobutanol is not formed in this case but instead the resultant l,.l-biradical (17) fragments to yield the alkene (18).16 The reaction is reasonably efficient and a quantum yield of 0.2 was measured for the reaction in benzene as solvent. The same reaction is observed when (16) is irradiated in the solid state. H 0
(14) Ar = Ph, n = 3,4,5, 7, 10 or 11 Ar = 2-naphthyl, n = 3, 4, 5 6 , 7, 9, 10, 11 or 14 Ar = 4-biphenyly1, n = 3-7, S 1 1 or 14
Me
CN
CN
OH
Me NC
Me
Considerable interest continues to be shown in photoenolization reactions. Results from the study of reaction volume changes in the photoenolization of 2methyl benzophenone have been reported. l7 o-Benzylbenzophenone (1 9) is photochemical reactive and undergoes a Norrish Type I1 transformation into an enol.'* Cyclization of this intermediate affords the cyclobutenol (20) quantitatively. A detailed study of the factors that control the formation of o-xylylenes (the photoenols) by the photoenolization of alkylphenyl ketones such as (19) and (21) has been reported. The product selectivity appears to correlate with the geometries of the twisted xylylene triplet state. l9 The photoenolization of the aldehyde (22, R = H) and ketone (22, R = CH3) has been reported.*' The photoenol (23, R = H) can be obtained from the aldehyde and cycloaddition of acrolein yields the dihydronaphthalene derivative (24). The photoenol of the ketone (23, R = CH3) undergoes ring closure to the cyclobutenol (25). The cyclobutenol is thermally reactive and can be ring opened to reform the enol that can also undergo thermal cycloaddition reactions with suitable dienophiles. The synthetic utility of such photoenolization reactions continues to be of interest. Thus, the photochemistry of the aldehydes (26) has been examined using
Photochemistry
62 Me
Ph
Ph
OMe 0
Ph
OMe
OMe OH
OMe
Pyrex-filtered irradiation in de-aerated acetonitrile solution. The resultant enols can be trapped by dimethyl maleate to yield the adducts (27) and (28) in the ratios and yields shown.21Trapping of the enols can also be acomplished using dimethyl acetylenedicarboxylate or ethyl propiolate as the dienophile. A study of the phototautomerism of methyl salicylate (29) into (30) at 77 K has been carried out and this again involves a 1$-hydrogen transfer.22 Interestingly, the authors report that triplet state emission occurs from the transient keto form (30). The influence of aryl substituents (p-Me and p-MeO) upon the photochemically induced intramolecular proton transfer in salicylic acid has also been studied in
(26) n=1,2or3
(27)
Ratio Yield (YO)
06Me
12: 1 15: 1 3:l OYoMe
(28)
10 70 40
2.2 Other Hydrogen Transfers - Irradiation (h =- 300 nm) of the ketoamines (31) in methanol solution results in the formation of the cyclopropanols (32) via the triplet excited state of the arylketo function.24 The reactions involve 1,4hydrogen transfer processes and the yields range from modest to good. The
MI: Photolysis of Carbonyl Compounds
63 HO R2 R3
NR2'
R2
R3
R4 Yield (YO)
Morpholino
H H H H H
H H H
H CN F Ci Br
H
H
46
75
43 42 20
authors reason that the regioselectivity involved, where hydrogen abstraction occurs from the site next to the amino function, must be due to preferred chargetransfer interaction between the benzoyl and the amino groups. The hydrogen abstraction reactivity of the benzophenone derivatives (33) involves a 1,6-transfer and has been studied in various solvents.25The key step on irradiation is the formation of the corresponding 1,5-biradical produced on hydrogen abstraction from the 8-methylene group of the ether function. When the irradiations are carried out in benzene the furanols (34) are formed in 80-94% by ring closure of the 1,5-biradical. The ratio of cis:trans-isomers ranged from 12:1 to 1:O dependent upon the substituent R. The yields of products were poorer in acetonitrile than in methanol and a decreased selectivity was also observed. A further study of the photochemical cyclization of the arylketones (35) has sought to evaluate the effects of solvents and substituents on the outcome of the reactions.26The cyclizations follow the normal &hydrogen abstraction path that leads to the benzofuranols (36). 0
(33) R = H, Me, Et, Pri, Ph, CH=CH2, CN
(34)
(35) (36) R' = H, Me, Et or Pri, R2 = CH2Phor CH2CQEt
&-Hydrogen abstraction is the outcome of irradiation of the amides (37) in methylene chloride solution.27The site of the hydrogen abstraction is controlled to some extent by the presence of hetero atom. The resultant 1,6-biradical undergoes cyclization to afford (38) and (39) with high diastereoselectivity as
Photochemistry
64
ph
$:: Q::
N'R2 R1
0
HO Ph
HO Ph
0
0
(37)
HO Ph
Ph
0
0
:;
H 61 Me 75 H CH2C02Me 63
shown by the yields under the appropriate structures. Cyclization also takes place in good yield with the derivatives (40) which yield compounds (41). The keto ester (42) undergoes photochemical hydrogen abstraction reactions to afford a l,S-biradical.** Again, in this case, the regiochemistry is controlled by the presence of the hetero atom. The resultant biradical cyclizes to yield the azalactone (43), the structure of which was determined by X-ray crystallography. The cyclization process is not stereoselective.
(42)
3
(43)a: R1 = Ph, R2 = H
b: R' = H, R2 = Ph
Oxetane Formation
Doubt has been cast on the stereochemical assignments within oxetanes obtained from the addition of benzaldehyde to alkenes. The authors of a recent report were unconvinced by earlier assignments of stereochemistry to the adducts (44) and (45) formed from the addition of benzaldehyde to styrene.29The previous study has been repeated and a 3:l ratio of the trunxcis-oxetanes has been reported. Re-investigation of the effect of methyl substituents was also carried
IIII: Photolysis of Curbonyl Compounds
65
out in the present study and the results of this are shown in Scheme 1. These results allowed the assignment of the structure of the oxetanes formed from the addition of benzaldehyde to the trans-alkene (46). The results suggest that while (nx-overlap is involved in the addition of benzaldehyde to styrene this is not the case in the addition to the silyl substituted alkene (47) which yields the oxetane (48), exclusively.
$+
Ph
PhCHO
h Pyrex
benzene
(46)
Me. Ph
'Ph 25% Scheme 1
Ph
Ph
Ph 'Ph < 3% (ratio 5 : 1)
Further work has been carried out to study the facial diastereoselectivity of the addition of benzaldehyde to alkene~.~' In this study the three enamines (49)-(51) were used as the substrates to which benzaldehyde was added photochemically. The results show that addition does occur to all three enamines but with varying degrees of success as far as diastereoselectivity is concerned. Thus addition to (49) gives the two oxetanes (52) and (53) but with only 32% de. Poorer selectivity is observed with (50) when (54) and (55) are obtained. The best de of 62% is achieved from (51) where the products are (56) and (57). The photochemical addition of the aldehydoester (58) to the enamine (59) results in the formation of the oxetane (60).3' This product is obtained in around 30% yield and it can be transformed into racemic oxetin (61). Bach has reviewed the stereocontrol that can be exercised on the formation of oxetane~.~* The regioselectivity of the addition of triplet carbonyl compounds to alkenes has been interpreted for the first time in terms of hard and soft acid-base systems.33The authors of this report suggest that there is overall good agreement between HSAB prediction and experimental fact.
4
Miscellaneous Reactions
4.1 Decarbonylation and Decarboxylation- The kinetics of the decarbonylation of benzaldehyde into benzene and carbon monoxide has been reported in The cis-di-t-butylcyclopropanone(62, R = H) has been synthesised and photochemically this readily undergoes decarbonylation to yield the corresponding cis-
Photochemistry
66
di-t-butyl alkene.35Interestingly, the cyclopropanone (62, R = Me) is unstable at room temperature but can be irradiated at low temperature to yield the strained alkene (63). Decarbonylation is also the result of irradiation of the ketone (64) through Pyrex.36The product (65) is obtained in 48% yield and can be readily transformed by thermal means into the diketone (66).
(62) R = H
R=Me
Photochemical decarbonylation has also been used as a route to enols. Thus irradiation of the indanone (67) leads to the formation of the two enols (68) and (69).37The lifetime of the enols and their reactivities were assessed. Maier and coworkers have demonstrated that irradiation at 254 nm of CO and CS in a low temperature matrix leads to the formation of the thioxoetheneone (70).38 Decarboxylation is also a common photochemical reaction. The results of a
Wo Ph
I
I
%OH
Ph OH
Ph
Ph
q Ph
P
h
OH
IIIl: Phorolysis of Curbonyl Compounds
67
study of the photochemical decomposition of malonic acid in the presence of sodium tungstate as sensitizer have been rep~rted.~' The photoreactivity of p phenylenediacrylic acid amide derivatives has been de~cribed.~' Koshima and his co-workers have studied the reactivity of co-crystals of acridine and 1-phenylpropionic acid.4' This work is analogous to that described last year for the reactivity of acridine with diphenylacetic acid.42 The present study is summarized in Scheme 2.41Again irradiation brings about decarboxylation of the propionic acid and the resulting radical bonds to the acridine. The yields of the compounds and their optical activities are shown below the appropriate structures. When acridine and the acid are irradiated in acetonitrile solution racemic (71) is formed along with the dimer (72). A review of the photochemistry in two-component and mixed crystals systems has been publi~hed.~~
hv
I
+m
crystallinephase
H
/
\
H CHMePh crystal R (71) 16%(+2.0) 12% S 17% 19% (-15) Scheme 2
[+38]
[-2*2]
CHMePh 5Y0[+47.8] 4%[-45.4]
H
The degradation, by decarboxylation, of a-naphthaleneacetic acid has been shown to be wavelength dependent.@ Short wavelengths are the more destructive and the decarboxylation follows pseudo-first order kinetics. The photodegradation of 2,4-dihydroxybenzoic acid in water catalysed by titanium dioxide has been reported in some detail.45 A laser-flash examination of the photochemical behaviour of ketoprofen (73) in water has shown that deprotonation occurs with decarboxylation following as a second step to yield the benzylic anion (74).46 Interestingly this anion exhibits both anionic and radical characteristics. In another study of compound (73)
68
Photochemistry
photochemical decarboxylation has also been observed.47The reactions of the compound occur from the lowest excited triplet state and involve intramolecular single electron transfer (SET) processes. The photodegradation of (2S)-2-[4-(3S)1-acetimidoyl-3-pyrroIidinyl]-3-(7-amidino-2-naphthyI)propanoic acid follows first order kinetics in the pH range of 1.1-8.0.48A study of the decarboxylation of 1 - and 2-naphthyl glyoxylic acids has been carried Photodecarboxylation occurs in acetonitrile or water and yields the corresponding naphthaldehydes.
The use of the carbazole derivative (75) has been made in some SET reactions of benzoate derivative^.^' The reaction depends on electron transfer from the carbazole to the benzoate to afford the corresponding radical anion and it is suggested that the removal of the benzoate group occurs most efficiently with the rn-trifluorophenyl benzoate derivatives. Typically the yields are high; for example the conversion of (76) into (77) which takes place in 84% yield.
(76) Ar = mCF3C6H4
A full account of the methodology of the addition of alkyl radicals to acrylamide using the photochemical decomposition of (78) has been published.51 The yields of products (79) are good to excellent. The method has been developed as a synthetic approach to 3-deoxy-D-arabino-2-heptulosonicacid and its 4epimer. This synthesis has already been reported in note form.52 The cyclopropene (80) undergoes smooth decarboxylation on sensitized (N-phenylcarbazole) irradiation with wavelengths > 350 nm.53 In the presence of t-butylthiol the products formed were identified as the cyclopropane derivatives (81) and (82). With different hydrogen donors such as tri-n-butyltin hydride the products obtained are cyclopropenes (83) and (84). The cyclopropane (85) is also photoreactive and in THF/water yields the cyclopropane (86). The authors suggest that the cyclopropene double bond in (80) is particularly prone to undergo addition reactions and that the thiol adds prior to the photochemical decarboxylation. Iminocarbene (87) are formed by the loss of carbon dioxide on irradiation of the dihydroisoxazoles (S8).54 The irradiation can be effected by either 254 or 300 nm but the best conditions involve the latter wavelength with (88) in acetone or acetonitrile solution. The yields for some of the compounds studied are shown in Scheme 3. Some level of substituent dependency is obvious from the variation in
Mi:Photolysis of Carbonyl Compounds
69
the yields of the oxazoles obtained. The thio analogues (89) are similarly reactive and yield the thiazoles (90), again in reasonable yields.55The path to the thiazoles occurs in competition with a reaction mode leading to the formation of the oxazines (91).55
Me PhCH2 Ph Me Ph
H H Me Ph Me
C02Et C02Et CGEt H H
Scheme 3
65 88 30 29 24
70
Photochemistry
A study of matrix isolated 1,2,3,4-benzenetetracarboxylicdianhydride has provided evidence for the formation of 1,3,5-he~atriyne.~~ The possibility of the formation of C6H2 by photochemical extrusion of carbon dioxide and carbon monoxide was discussed.
4.2 Reactions of Miscellaneous Haloketones - Acetyl chloride undergoes photochemical loss of HCl when irradiated either neat or in a matrix.57 Irradiation of 3-chloropropanoyl chloride in a matrix using wavelengths greater than 230 nm yields 3-chloro- I ,2-propenone and acryloyl chloride as the principal photochemical products.58 Further studies on the photochemical reactivity of a-haloacetophenone derivatives have been reported. The results in the present publication have shown that the acetophenone derivatives (92)undergo a variety of reactions but the one of interest is the Favorskii type rearrangement where by a 1,2-aryl migration occurs to yield an acyl cation that can form a carboxylic acid d e r i ~ a t i v e .The ~~ investigation examined the influence of media on the outcome of the reaction and some of the results are illustrated in Scheme 4.The best yields of carboxylic acids, the products formed via the acyl cation path, are obtained in aqueous acetonitrile. The singlet states of the ketones (93) and (94) are reactive and undergo elimination of halide to form aroylmethyl radicals.60 These then rearrange to arylacetyl radicals by a 1,2-aryl migration. Subsequent decarbonylation yields the arylinethyl radicals (95)and these have been detected spectroscopically. 0 Ar
Ar
Ar-CQR
aq. acetone (i) (ii)(R=H) (iii) 37 24 16 10
24 47
43 14
29 23 14 31
aq. CH3CN (i) (ii)(R=H) (iii) 14 14 9 6
47 70 54 35
18 11 8 18
Scheme 4 Br
The ester (96) undergoes electron transfer photochemistry on irradiation in acetonitrile solution in the presence of the amine (97).61The SET process brings about the expulsion of bromide and produces the radical (98). This radical undergoes ring expansion by the path illustrated in Scheme 5 to yield the final product (99). This product can be accompanied by varying amounts of the
IIl I : Photolysis of Carbonyl Compounds
71
t COz Et
(104)
Yield
2
TMS
2 2 1 1
Et H TMS TMS TMS
CH;!
coH20 0
NHBoc
(YO) Ratio E : Z
74 61 72 68 64 51
3:l 1:l
-
5:3 3:l
-
reduced ester (100) and the dimer (101). However, these reaction paths can be suppressed by the addition of water to the reaction system with the best yields of (99) being obtained by radiation in 30% aqueous acetonitrile. Irradiation of the iodoketones (102) under electron transfer conditions (with triethylamine as the donor and acetonitrile as solvent) brings about C-I bond fission and the formation of the radical (103).62 These radicals undergo cyclization with the alkyne moiety in the side chain to yield ultimately the products (104) in the yields shown. 4.3 Photo Reactions of Esters and Photodeprotection - Laser irradiation at 183 nm of a series of alkyl acetates has been reported.63The aryl phenylacetates (105) undergo photo-Fries reactions when irradiated in acetonitrile solution.@ The reactivity is appreciably more selective when they are irradiated within the cavities in NaY zeolites. Under these conditions only the ortho photo-Fries product is formed. The oxime derivative (106) undergoes N-O bond fission when the compound is irradiated on a micellar surface.65Such bond fission results in
72
Photochemistry
both 1,3- and 1,5-benzoyloxy migration to afford products such as (107) from the former process. These products are also accompanied by the decarboxylation product (108). A detailed analysis of the influence of benzyl alcohol and of the presence of bromide ion (a heavy atom) on this fission were also described. The outcome of the photolyses of the esters (109) and (110) in pentasil or faujasite zeolites has been shown to be extremely sensitive to the zeolite structure.66 A mechanistic study of the single electron transfer reactivity of the esters (1 1 1) has been reported.67
(105) A r = Ph Ar = pMeC6H4 Ar = oMeC6H4
(108) R = l-naphthyl
(106)
0
Considerable interest has been shown in derivatives of esters that can be photodeprotected. One of the more common of these is the 3’,5’-dimethoxybenzoin ester system. A reinvestigation of the photochemistry of this system has suggested that the reaction does not involve attack by the carbonyl oxygen on the dimethoxy substituted benzene ring.68Instead from the detailed examination, it is proposed that a charge transfer, or perhaps an electron transfer, occurs between the electron-rich dimethoxy substituted ring and the carbonyl group within (1 12), for example. This results in the formation of the cation (1 13) with the release of the acid group. Deprotonation of (1 13) affords the furan byproduct. A new method has been described for the protection of amino acids with a photoremovable This procedure involves the conversim of the amino acid into the phenacyl derivative (1 14). Irradiation of (1 14) in a buffered aqueous
+ CH3CO2-
R (112) R = Me, PhCH2, Ph or But
(1 13)
73
IIil: Photolysis of Carbonyl Compounds
solution results in the release of the amino acid and the transformation of the phenacyl group into a phenylacetic acid. The reaction proceeds by way of the triplet state from which there is intramolecular displacement of the amino acid moiety as represented in (1 15). The resultant intermediate (1 16) undergoes ring opening by attack of water to afford thep-hydroxyphenyl acetic acid as the byproduct of the deprotection. The use of single electron transfer activation has been applied to this area of study and in particular to the phenacyl esters (1 17).70 These undergo cleavage with the release of the acid by a path in which an electron is transferred on irradiation from amines such as (1 18) to yield the radical anion
&
HO (114) R = - C H ~ C H Z C H ~ ) ; ~ H ~ R = -CH&HCO2I NH3+ R = -CHNHCOCHCH3
LOGoMeI
I
NH3+
CH3
0 PhCMe II +
Ph
Me0
0
Scheme 6
0
0
OH
(117) R =
A,,,.,, H
I OMe
NMe2
0
OH
74
Photochemistry
intermediate (1 19). This undergoes fission to yield the anion radical pair (120) from which acetophenone and the carboxylic acids are formed in excellent yield. One example of this process is shown in Scheme 6 where the yield of 3methoxycyclohexane carboxylic acid is quantitative. Related to this work is the report dealing with the photochemistry of phenacyl protecting group^.^' These simple systems such as (121) undergo cleavage to phenylacetic acid and acetophenone. The efficiency of the reaction is solvent dependent and irradiation in benzene, for example, fails to yield products. However, when a hydrogen donating reagent, such as 2-propanol or tri-n-butyltin hydride, is present the irradiations are very efficient. The authors suggest that a hydrogen abstraction rather than a C-0 bond cleavage is involved as the primary photochemical step. Thus irradiation affords the radical (122) which is trapped by, for example, an isopropoxy radical. The intermediate (123) then collapses to the observed products.
Other Fission Processes - Considerable use is being made of radical reactions in organic synthesis. For example, Deng and Kutateladze have described a novel method for the synthesis of esters.72This involves the irradiation of the ester (124) in the presence of terminal alkenes. Unfiltered light from a medium pressure mercury arc lamp results in the fission of the S-methylene bond and the formation of a radical which adds to the alkenes. The yields obtained are reasonable with acetonitrile as the solvent. Other solvents such as methanol or ethanouwater can also be used. Yields of the products obtained are shown in Scheme 7. 4.4
Yield (YO) 70 0
n=l
84
n = 3 90
0
21
45
Scheme 7
The acetone-sensitized decarbonylation of E-( 1S),2(S) (125a) has been studied. The principal reaction is the formation of the 2(S),3(R)-cyclopropane (126a).73 Other products (127a), (128a) and (129a) are also formed in low yield. The reaction arises from the triplet state and this was confirmed by using Michler's ketone as the sensitizer and by quenching experiments. A similar selectivity is
75
IIII: Photolysis of Carbonyl Compounh
k2
R’ (125) a: R’ = R2 = CH20Bz b: R’ = CH~OBZ,R2 = H
(126)
a: 53
b: 86
(127) 17
-
R’ (128) 19 10
R’
R2
(129) 5 Yield (YO) Yield (YO)
-
reported for the 2(S)-ketone (1 25b) which affords the cyclopropane (126b) as the principal product. This reaction is more selective and only one by-product (128b) is formed. The photochemical aromatization of the bicyclodienones (1 30) has been reported.74 The major products obtained were identified as (131) and arose by extrusion of ketene.
References
5
1. 2.
3. 4.
5. 6. 7. 8. 9. 10. 11. 12. 13.
14. 15.
S. Sekiguchi, Y. Kobori, K. Akiyama and S. Tero Kubota, J. Am. Chem. Soc., 1998, 120, 1325. J. C. Scaiano, M. Kaila and S. Corrent, J. Phys. Chem., 1997,101, 8564. M. Ya. Mel’nikov, V. N. Belevskii, S. I. Belopushkin and 0. L. Mel’nikova, Russ. Chem. Bull., 1997,46, 1245 (Chem. Abstr., 1997,713770). S . V. Jovanovic, D. G. Morris, C. N. Pliva and J. C. Scaiano, J. Photochem. Photobiol. A , 1997,103, 153 (Chem. Abstr., 1997,127,240808). A. E.-A. M. Gaber, Bull. Pol. Acad Sci., Chem., 1997,44,235 (Chem. Abstr., 1997, 437582). N. C. De Lucas and J. C. Netto-Ferreira, J. Photochem. Phorobiol. A, 1997, 103, 137 (Chem. Abstr., 1997,127,72894). Sh. A. Markaryan, Arm. Khim. Zh., 1996,49,71 (Chem. Abstr., 1998,256773). J. L. Faria and S. Steenken, J. Chem. Soc., Perkin Trans. I , 1997, I 153. A. Gugger, B. Batra, P. Rzadek, G. Rist and B. Giese, J. Am. Chem. Soc., 1997, 119, 8740. J. C. Scaiano, S. Garcia and H. Garcia, Tetrahedron Lett., 1997,38, 5929. W . Schwack and T. Rudolf, GIT Lab. J., 1997, 17 (Chem. Abstr., 1997,595520). 0. B. Morozova, A. V. Yurovakaya, V. Alexandra, Y. P. Tsentalovich, R. Z. Sagdeev, T. Wu and M. D. E. Forbes, J. Phys. Chem. A, 1997,101,8803. H. Yamashita, N. Sato, M. Anpo, T. Nakajima, M. Hada and H. Nakatsuji, Stud. SurJ Sci. Catal., l997,105B, 1141 (Chem. Abstr., 1998,128, 183387). P. Klan and P. J. Wagner, J. Am. Chem. SOC.,1998,120,2198. P. Wessig, J. Schwarz, D. Wulff-Molder and G. Reck, Monatsh. Chem., 1997, 128, 849 (Chem. Abstr., 1997,127,331378).
76 16. 17. 18. 19. 20. 21. 22 23. 24. 25. *
26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 45. 46. 47. 48. 49.
Photochemistry
T. Y. Kim, E. S. KO, B. S. Park, H. Yoon and W. K. Chae, Bull. Korean Chem. Soc., 1997,18,439 (Chem. Abstr., 1997,127,65424). M. Terazima, J. Phys. Chem. A , 1998,102,545. M. Sobczak and P. J. Wagner, Tetrahedron Lett., 1998,39,2523. P. J . Wagner, M. Sobczak and B.4. Park, J. Am. Chem. SOC.,1998,120,2488. G. A. Krauss and G. Zhao, Synlett, 1995,541. T. J . Connolly and T. Durst, Tetrahedron, 1997,53, 15969. J . Catalan and C. Diaz, J. Phys. Chem. A, 1998,102,323. F. Lahmani and A. Zehnacker-Rentien, J. Phys. Chem., 1997,101,6141. W. Weigel, S. Schiller and H.-G. Henning, Tetrahedron, 1997,53,7855. E. Sharshira, M. Essam, M. Okamura, E. Hasegawa and T. Horaguchi, J. Heterocycl. Chem., 1997,34,861 (Chem. Abstr., 1997,127, 161648). E. M. Sharshira and T. Horaguchi, J. Heterocycl. Chem., 1997, 34, 1837 (Chem. Abstr., 1998, 128, 180290). U. Lindemann, G. Reck, D. Wulff-Molder and P. Wessig, Tetrahedron, 1998, 54, 2529. T. Hasegawa, Y. Yamazaki and M. Yoshioka, J. Photosci., 1997,4,7 (Chem. Abstr., 1997,127, 121403). S. A. Fleming and J. J. Gao, Tetrahedron Lett., 1997,38, 5407. T . Bach, J. Schroder, T. Brandl, J. Hecht and K. Harms, Tetrahedron, 1998, 54, 4507. T. Bach and J. Schroder, Liebigs AndRecueil, 1997,2265. T . Bach, , Liebigs AmlRecl., 1997, 1627. D. Sengupta, A. K. Chandra and M. T. Nguyen, J. Org. Chem., 1997,62,6404. C. R. Silva and J. P. Reilly, J. Phys. Chem. A , 1997,101, 7934. T. S. Sorensen and F. Sun, Can. J. Chem., 1997,75, 1030. D. Leinweber and H. Butenschon, Tetrahedron Lett., 1997,38,6385. J. C. Netto-Ferreira, V. Wintgens and J. C. Scaiano, J. Braz. Chem. SOC.,1997, 8, 427 (Chem. Abstr., 1997,620850). G. Maier, H. P. Reisenauer and R. Ruppel, Angew. Chem., Znt. Ed. Engl., 1997, 36, 1862. N. Sahoo, Orient J. Chem., 1997,13,53 (Chem. Abstr., 1997,428330). F . Nakashini, J. Nagasawa, M. Yoshida and H. Abdedaal, J. Photopolym. Sci. Technol., 1997,10,25 (Chem. Abstr., 1997,127,227215). H. Koshima, H. Nakagawa and T. Matsuura, Tetrahedron Lett., 1997,38,6063. H. Koshima, K. L. Ding, Y. Chisaka and T. Matsuura, J. Am. Chem. Soc., 1996, 118, 12059. Y. Ito, Synthesis, 1998, 1. Z . Zhou, W. Jiang and W. Liu, Huanjing Kexue, 1997, 18, 35 (Chem. Abstr., 1997, 683592). F. Benoit-Marquie, E. Puech-Costes, A. M. Braun, E. Oliveros and M.-T. Maurette, J. Photochem. Photobiol., A, 1997,108,73 (Chem. Abstr., 1997,127,285784). J . Cossy, S. BouzBouz and A. Hakiki, Tetrahedron Lett., 1997,38,8853. L. J . Martinez and J. C. Scaiano, J. Am. Chem. Soc.. 1997,119,11066. S. Monti, S. Sortino, G. De Guido and G. Marconi, J. Chem. SOC.,Faraday Trans., 1997,93,2269. Y. Kawai and K. Matsubayashi, Chem. Pharm. Bull., 1998, 46,131 (Chem. Abstr., 1998,128, 184585). C. Laurich, H. Gorner and H. J. Kuhn, J. Photochem. Photobiol. A, 1998, 112, 29 (Chem. Abstr., 1998, 128, 160840).
IIII: Photolysis of Carbonyl Compounds 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66.
67. 68. 69. 70. 71. 72. 73. 74.
77
D. R. Prudhomme, Z. Wang and C. J. Rizzo, J. Org. Chem, 1997,62,8257. D. H. R. Barton and W. S. Liu, Tetrahedron, 1997,53, 12067. D. H. R. Barton and W.-S. Liu, Tetrahedron Lett., 1997,38,367. M . Cano, G. Fabrias, F. Camps and J. Joglar, Tetrahedron Lett., 1998,39, 1079. R. H. Prager, J. A. Smith, B. Weber and C. M. Williams, J. Chem. Soc., Perkin Trans. I , 1997,2665. R. H. Prager, M. R. Taylor and C. M. Williams, J. Chem. Soc., Perkin Trans. I , 1997,2673. M. Moriyama and A. Yabe, Chem. Lett., 1998,337. B. Rowland and W. P. Hess, J. Phys. Chem. A , 1997,101,8049. N. Pietri, J. Piot and J.-P. Aycard, J. Mol. Strucf., 1998, 443, 163 (Chem. Abstr., 1998, 198458). D. D. Dhavale, V. P. Mail, S. G. Sudrik and H. R. Sonawane, Tetrahedron, 1997,53, 16789. M. Hall, L. Chen, C. R.Pandit and W. G. McGimpsey, J. Photochem. Photobiol. A , 1997,111,27 (Chem. Abstr., 1998,128, 121513). E. Hasegawa, Y. Tamura and E. Tosaka, J. Chem. Soc., Chem. Commun., 1997, 1895. C.-K. Sha, K. C. Santhosh, C.-T. Tseng and C.-T. Lin, J. Chem. Soc., Chem. Commun., 1998,397. M. Wasche, U. Bruckner and E. Linke, Laser Med., Vortr. 10. Tag. Dtsch, Ges. Lmermed 12. Int. Kongr., 1995,645 (Chem. Abstr., 1997,127, 168900). C. H. Tung and Y. M. Ying, J. Chem. Soc.. Perkin Trans. 2, 1997, 1319, T. Kaneko, K. Kubo and T. Sakurai, Tetruhedron Lett., 1997,38,4779. C.-H. Tung and Y.-M. Ying, Res. Chem. Intermed., 1998,24, 15 (Chem. Abstr., 1998, 78146). M. P. D. De Costa, P. K. Cumaranatunga and K. A. D. Sriyanimallika, J. Natl. Sci. Counc. Sri Lanka, 1997,25, 127 (Chem. Abstr., 1998,128,47936). Y. Shi, J. E. T. Corrie and P. Wan, J. Org. Chem., 1997,62,8278. R. S. Givens, A. Jung, C. H. Park, J. Weber and W. Barlett, J. Am. Chem. Soc., 1997,119,8369. A. Banerjee and D. E. Falvey, J. Org. Chem., 1997,62,6245. A. Banerjee and D. E. Falvey, J. Am. Chem. SOC.,1998,120,2965. L. X. Deng and A. G. Kutateladze, Tetrahedron Lett., 1997,38,7829. J. Ramnauth and E. Lee-Ruff, Can. J. Chem., 1997,75, 518. A. A. Bogachev and L. S. Kobrina, Russ. J. Org. Chem., 1997, 33, 681 (Chem. Abstr., 169148).
2
Enone Cycloadditions and Rearrangements: Photoreactions of Dienones and Quinones BY WILLIAM M. HORSPOOL
1
Cycloaddition Reactions
1.1 Intermolecular Cycloaddition - Cycloaddition reactions continue to be a valued route to compounds that are key intermediates in the synthesis of natural products or other compounds of general interest.
I. 1. I Open-chain Systems - Several reports over the last few years have made use of the pentenoate (1) in photochemical cycloaddition reactions. Typical of these
4 CGMe Me02C Me (5) 43%
C02Me
+
Me
3.5%
8%
9 3%
1.5%
Scheme 1
/
' Me
he
Me
C@Me
Me Me
(2)
Photochemistry, Volume 30 0The Royal Society of Chemistry, 1999 78
Me
/
(3)
OMe
MeQ-Me
(6)
CMe20H
M2: Enone Cycloadditions and Rearrangements
79
studies is a description of a route to Sollasin a (2) and Sollasin d (3).' This utilized the cycloaddition reaction of (1) to the butenoate (4) as shown in Scheme 1. Several compounds were obtained from this reaction, all of which arise by (2+2)photocycloaddition to yield a cyclobutane intermediate. Ring-opening then affords the products isolated as illustrated in Scheme 1. The subsequent transformation of the major adduct ( 5 ) results in the completion of the synthetic approach to the targeted natural products. The cycloaddition of the same 2,4dioxopentanoate (1) as its enol to terpinolene has been described and has been used as a route to a total synthesis of racemic a-chamigren-3-0ne.~ Another report describes the addition of methyl 2,4-dioxopentanoate (1) to alkenes and the adduct obtained from 1,5-dirnethyI-6-methylene cyclohexene has been transformed into Hinesol(6) and related compound^.^ Interest in the control that environment can exert on (2+2)-cycloaddition reactions is still being shown. A recent study has examined the dimerization of the cinnamic acid derivatives (7) in the presence of surfactant vesicles in water.4 The surfactants used are the N-oxides (8) with varying alkyl chain lengths. The dimerization affords p- and 8-truxinic and y-truxillic acids. The yields of the adducts as shown are reasonable with a preponderance of the truxillic acid type. These results are illustrated in Scheme 2. The yields of cyclodimers decrease with decreasing molar ratio of the acid to the surfactant. The irradiation of monolayers of 4-octadecyloxy-E-cinnamic acid and 4-octadecyloxy-E-cinnamideon a water surface has been ~ t u d i e dThe . ~ cycloaddition reactions that occur reflect the packing within the monolayers. The cinnamic acid derivative yields p-truxinic acids while the cinnamides undergo only cis-trans isomerization. Other workers have reported the dimerization of cinnamic acid in mixed crystals composed of cinnamic acid and the pentafluoro derivative (9).6 The orientation within the crystal is such that the phenyl group interacts with the pentafluorophenyl group
pcQH C02H
H 0 2 C bCO2H +A+ (7) ArArxC02H = Ph or pMeOCsH4
Ar
14
16
5 5 6
Scheme 2
L
C4H Yield (YO)
n (in 8) 12
C02H +
12 16 17
Ar Ar = Ph 25 38 31
80
Photochemistry
thus ensuring the orientation within the crystal. Irradiation for several hours affords an 87% yield of the truxinic acid (10). D'Auria and Racioppi have reported that the arylacrylonitriles (1 1) undergo facile (2+2)-cycloaddition when subjected to benzophenone-sensitized irradiation in acetonitrile s ~ l u t i o n .The ~ products obtained from this treatment and the yields obtained are shown under the appropriate structures in Scheme 3. Again a mixture of addition types is encountered in line with results obtained from the cycloaddition reactions with the cinnamic acids. Dimerization of the nitrile (12) was also studied and yielded the two adducts (13) and (14). Irradiation of 3(estran- 16-y1)acrylates and 2-(estran- 16-y1)vinyl ketones brings about the formation of dimers and also isomerization of the unsaturated side chains.'
18% 24%
Ar = MeO
Photochemical cycloaddition of dimethyl fumarate and dimethyl maleate to the psoralen (1 5) has been reported.' The adducts formed are presumed to be of the (2+2)-type illustrated by (16) where addition to the furan ring has occurred. The photodimerization of a,w-bis(4-methylcoumarin)tetraethylene glycol is regiospecific and only the syn head-to-tail dimer is formed."
Further examples of the photoaddition of alkenes to the diketonatoboron difluoride (17) have been published." The irradiations are carried out in 1,4dioxane or acetonitrile as solvent and use 350 nm light. Irradiation times are relatively long (20 h) but result in the formation of the expected adducts. Thus addition of the alkenes (18) affords the 1,Sdiketones (19). These arise by ring opening of the initially formed cyclobutane adducts [e.g. (20)]. Similar results are
IIl2: Enone Cycloudditionsand ReurrangemenIS
F\
7
Ph O
81
q
P
h
PhQPh
R (18) R
= HorMe
R CN (19) R = H or CH3
(21) X-CH2, R = M e X=O, R = H
obtained with the enones (21) which give (22) and (23). Margaretha and coworkers have reported that irradiation of angelicin in benzene with 2,3dimethylbut-2-ene results in the formation of a cyclobutane adduct. l 2 The solid state dimerization of three polymorphic forms of (24) has been reported.I3 From these irradiations, the dimer (25) is obtained when light in the range 320400 nm is used. The principal product (25) is obtained in 58% yield and is accompanied by several minor products. Another report of the photochemical reactivity of (24) has shown that irradiation in solution brings about aromatization quantitatively. l4 In the crystal, however, irradiation of the (4R",1'RS)-(24) affords the dimer (25). Apparently this dimerization in the crystalline phase is possible because of extra space within the crystal, but this is not so with crystals
/-\
H
(24) X = CH or N
gN
Me02C Me
C02Me
H
Me
82
Photochemistry
of (26) and this fails to dimerize. The photochemical addition of ethyl 2,2dimethyl-5-0~0-5,6-dihydro-2H-pyridine1-carboxylate to 2,3-dimethylbut-2-ene has been investigated. Ethyl 5-0x0- 1a,2,5,5a,6,6a-hexahydro-2,6-methano-2aHindeno[5,6-b]oxirene-2a carboxylate undergoes photochemical dimerization on irradiation in solution.'6
'
1.1.2 Additions to Cyclopentenones and Related Systems. - A report has given details of the photochemical (2+2)-cycloaddition reactions of cyclopentenone with dichloroethylene.l7 The stereochemistry of the principal adducts was established as cis,anti,cis and cis,syn,cis. The acetone-sensitized addition of ethene to the lactam (27) can be brought in good yield by irradiation at O"C.'* Two products are obtained from this reaction and were identified as a mixture of the 1R,5S- adduct (28) and the lS,SR-isomer in a ratio of 11:l. Addition also occurs to the lactam (29) where the two products isolated were identified as (30) and (31). The addition to (29) occurs with lower stereoselectivity to give a 3:l ratio of products. The major product (28) from the initial addition to (27) was used as a starting material in a synthesis of ~-2-(2-carboxycyclobutyl)glycinederivatives.
A series of (2+2) photocycloaddition reactions have been carried out using (5R)5-menthyloxy-2(5H)-furanone (32) as the substrate." Photoaddition of cyciopentenone to this substrate gives the four products (33)-(36) with some level of regioselectivity but no facial selectivity. Interestingly, cyclohexenone, cycloheptenone and cyclooctenone fail to undergo the mixed addition. High facial selectivity is observed when more complex enones such as the 3,5,5-trimethylcyclohexenone and isophorone, (37) are used. The reaction affords adducts of the type illustrated
0
H
oow oow
RO
0
RO
83
I112: Enone Cycdoadditions and Rearrangements
in (38). (2+2)-Photocycloaddition reactions have been carried out between 4hydroxy-2,5-dimethyl-3(2H)-furanone and chloroethylenes.20 1.1.3 Additions to Cyclohexenones and Related Systems - A re-investigation of the photodimerization of isophorone (37) has been reported.21 The study examined the influence of solvent and of the concentration of the enone. Some of the results and the yields of dimers obtained are shown in Scheme 4. From this detailed study the authors suggest that supramolecular structures are involved in the dimerization. These apparently take part even at low concentrations of enone. The photocycloaddition of enones such as (39) to buckminsterfullerene(C,) has been studied.22The outcome of the addition is the formation of low yields of furanylfullerenes. This addition occurs to the exclusion of de Mayo type of addition. Photocycloaddition of the cyanocyciohexenone derivative (40) to alkenes has been reported.23 0
-K
(37)
0
divers (%) conversion (YO) HH : HT
[MI Cyclohexane Butanol H20 H20 H20 (under argon)
0.1 0.1
40 5 95 90 100
25 70
0.02 0.06
90
85 100 0.02 Scheme 4
R
30 : 70 70 : 30 95: 5 90: 10 99: 1
M cN *:
R
OH
(39) R = MeorH
(40)
Over the years (+)-grandis01 (41) has been a popular target molecule for photochemical syntheses. Another approach to this molecule using (-)-quinic acid as the starting material has been described.24The cycloaddition provided a route to the key intermediate (42). Further chemical transformation of this afforded the final product. 0
Photochemistry
84
1.2 Intramolecular Additions - A synthesis of modhephene (43) has been reported using a sequence of reactions based on the enone (44).25Irradiation of this in benzene solution through Corex resulted in an 89% yield of the adduct (45) which was used as the key intermediate for elaboration into the final product.
1.2.1 intramolecular Additions to Cyclopentenones - Irradiation (h > 350 nm in THF) of the enone (46) affords a single diastereoisomer identified as (47, The outcome of the reaction does not seem to be solvent dependent and the same degree of success is obtained with methylene chloride, acetonitrile or methanol as solvents. The corresponding amide also cyclizes efficiently. Crimmins and coworkers have demonstrated that irradiation ( h > 350 nm) of the eiione (48) results in cycloaddition and the formation of the diastereoisomeric adducts (49) and (50) in a ratio of 83:17.27A single product (51) is obtained on irradiation of the related enone (52). These adducts are key intermediates in a synthesis of some spirovetivanes. 0
C02Et Me
(%?=Me I,
I,
Et3Si07\/
OSiEt3
(47)
bmH C02Me
(50)
(51)
(49)
0
(52)
The photochemical reactivity of the diastereoisomeric compounds (53) and (54) has been studied.28The irradiation of the individual compounds, using perdeuterated acetone as the sensitizer, results in the conversion into the cycloadducts ( 5 5 ) and (56), respectively. Direct irradiation of (54), however, affords a mixture of the two cycloadducts while direct irradiation of (53) affords only the cycloadduct
IIl2: Enone Cycloadditionsand Rearrangements
85
(55). The authors reason that direct irradiation of (54) must induce bond fission to yield the radical pair (57) as well as yielding the cycioadduct. Rebonding within the radical pair (57) can yield (53) which would then undergo the photocycloaddition to yield the cycloadduct (55). Intramolecular cycioaddition is observed on irradiation of the enones (58).29 The reaction is both wavelength and temperature dependent. Irradiation through Pyrex brings about the formation of a cisltrans mixture of the alkene moiety as the main reaction. Low yields of the two adducts (59a) and (59b) are also formed under these conditions. When a quartz vessel is used the cycloaddition assumes major importance. From the results obtained it is clear that there is a preference for the formation of isomer (59a). Both the isomeric products arise from the biradical intermediate (60) which is formed by addition at the p carbon of the enone moiety and affords the more stable biradical.
Bo0 8 N - R
I
R
R
(59)
a: R1 = Ph, R2 = H b: R'
= H,
R2 = Ph
1.2.2 Additions to Cyclohexenones and Related Systems - Interest is still being shown in the minutiae of the mechanism of the photochemical addition of alkenes to cyclic enones. Recently reported work has examined the intramolecular addition observed on the irradiation of (61) in solution.30 Apparently both Ca and Cp bond formation can occur. The principal products formed from the reaction are the two (2+2)-photo-adducts (62) and (63) and the ene-product (64). An analysis of the reaction has shown for the E-isomer of (61) that there is no cleavage of the 1,4-biradical (65) or of the endo-biradicals (66) and (67). Intramolecular (2+2)-cycloaddition occurs when the enones (68) and (69) are irradiated in hexane solution with wavelengths > 350 nm (using a uranium glass filter).31The authors reason that bond formation can either arise by 2,7 or 1,8 closure. Good yields of products are obtained and it is interesting to note that with the irradiation of (68c and d) only one product is formed in each case. The exclusive formation of the products (7Oc and d) must arise by a path involving diastereoisomeric transition states. Changes in the substitution pattern close to the alkene moiety have an adverse effect on the yield of product. Thus,
86
Photochemistry
&,&
(65)
H
H
(67)
OBu'
0 R' R2 (68) a: R' = R2 = H b: R' = H, R2 = Me c: R' = Me, R2 = H d: R' = OSiBu'Ph2, R2 = H
0
Me (69)
(71) a: X = CH2, R ' = R2 = H b: X = 0, R' = Me, R2 = H (72) a: X = CH2, R' = H, R2 = Me c: 70% R' = Me, R2 = R3 = H b: X = 0, R' = R2 = Me d: 75% R' = OSiBu'Ph2, R2 = R3 = H e: 50% R' = Me, R2 = H, R3 = 061.1'
(70)a: 65% R' b: 78%
R'
= R2 = R3 = H
=
R3 = H, R2 = Me
(73)a: 52% b: 62%
the irradiation of (69) gives (70e) but only in 50% yield. Contrary to the foregoing, the main photochemical reaction of the esters (71) was dimerization of the enone system and no intramolecular cycloaddition was detected.32 This failure was attributed to conformational problems that can be overcome by the introduction of alkyl substituents into the side chain as in (72). These derivatives
IIl2: Enone Cycloadditions unci Reurrungements
87
smoothly undergo cycloaddition to yield the adducts (73) in the yields shown. Conformational problems were also reduced by the use of a longer side chain as in (74) when cycloaddition also occurred with reasonable yield. The yield of products in this system was temperature dependent with poor yields obtained at -55 "C. The products of intramolecular cycloaddition from this enone (74) were accompanied by a mixture of cyclodimers of the general structures (75) and (76). A study of the intramolecular (2+2)-addition in the enones (77) has been reported.33 The outcome of the addition is both temperature and substituent dependent. Thus irradiation of the enone (77a) at 0°C in acetonitrile with benzophenone as the sensitizer yields a single adduct (78) in 900/0yield after only 35 min. irradiation. The photocycloaddition of the enone (77b) at lower temperatures yields a mixture of (78) and (79) in a ratio of 1.8:l. The other derivatives (77c,d) afford only one product identified as (79). The products obtained from the cycloaddition can be cleaved to spiroacetals. The synthetic potential of the intramolecular (2+2)-cycloaddition reaction of enones continues to be exploited. In a recent example example the cycloaddition of the enone (80) affords the product (81) which is then subjected to ring-opening and further transformation to provide a path to the natural product (+)-ligudentatol (82).34
(78)
R1 a: Me b: H c: Me d: Me
OBn
E = CO2Et
(79)
R2 Yield I%) Me 90
Bu.' Prl Ph
90 80 73
9"
Intramolecular (2+2)-cycloaddition within the dioxenones (83) results in the formation of the adducts (84) and (85) in the ratios shown.35The adducts can be opened by thermal means to provide routes to tetrahydrofuran-3-ones and tetrahydropyran-4-ones. Intramolecular cycloaddition of the dioxenone (86) results in the formation of the diastereoisomeric mixture of (87) and (88) in a
Photochemistry
88 Me
Me
Me Me
(83)R
R
= Ph = PhCH2CH2
0
4%
fq0"&! H
H
(84)
(85)
77 : 23 73 : 27
I
Md
,
Me' 0
Me
Md
ci 0
0
OH
OMe
(89)
ratio of 2.5:1.36 These compounds are important in an approach to the total synthesis of Saudin. The regio- and stereo-selective (2+2)-photocycloadditions have been reviewed.37 2
Rearrangement Reactions
2.1 a,fi-Unsaturated Systems. 2.1.1 Hydrogen Abstraction Reactions - The photochemical behaviour of the unsaturated enone (89) has been investigated." Irradiation of (89) yields the demethylated ketone (90) by way of a Norrish Type I1 hydrogen abstraction reaction from the Me0 substituent by the excited carbonyl group. This product is accompanied by the aldehyde (91) which arises by a Norrish Type I fission. The fission of this bond affords both an acyl radical and a stabilized ally1 radical. The ketone (89) is also reactive in the di-x-methane mode and affords a bicyclopentene product. The enone (92) is reactive in its triplet state and when irradiated in methylene chloride solution is converted into the tetracyclic compound (93).39The reaction involves a step-wise process in which the biradical(94) is involved. This process is reminiscent of (2+2)-cycloaddition reactions where bonding occurs at the p-atom of the enone, and rather than completing the cyclization, hydrogen (or deuterium) abstraction occurs. A detailed stereochemical analysis of the system was carried out and proof of the stereochemistry of the final product (93) has been presented.
IIl2: Enone Cycloadditions and Rearrangements
89
Photoreduction of steroids ( 9 9 , (96) and (97) in zeolites has been studied. The results indicate that hydrogen abstraction by the enone system is enhanced in NaY zeolite^.^' 2.1.2 Radical Addition Reactions - The photochemistry of enones such as (98) has been reported!' Generally these enones are inert on irradiation in benzene, but in alcohol solution addition to the enone double bond results. Addition of In radicals is also a key feature in the reactivity of the enones (99) and this case, the radicals are generated from propan-2-01 by hydrogen abstraction using excited state benzophenone. The carbon centred radicals formed by this process undergo facile addition to the terminal carbon of the double bond of the enones resulting in the formation of a-keto radicals. intramolecular cyclization of these onto the pendant alkenyl groups results in the formation of cyclic products such as (101, 5oy0)from (99) and (102, 8Oy0) from (100). The intramolecular cyclizations of the furanone derivative (103) have been studied.43The outcome of the reaction is dependent upon the conditions under which the irradiations are carried out. Thus, with acetone sensitization or on irradiation at 254 nm in acetonitrile, cyclization affords the two spiro derivatives (1 04) and (105). This reaction path presumably involves the triplet state of the enone. Transfer of the aldehyde hydrogen to the P-carbon of the enone double bond results in a biradical that cyclizes to yield the products. With chemical sensitization using
90
Photochemistry
3°
TBDMSO
OH
TBDMSO
T B D M s : ~ :
TBDMSO%
0
*’
Scheme 6
O
0
(1 14) R = Bu’MepSi
91
1112: Enone Cycloudditions und Rearrangements
benzophenone the product obtained is (106). This route involves abstraction of the aldehyde hydrogen by the benzophenone to yield an acyl radical. This cyclizes by addition to the P-carbon of the enone double bond to yield ultimately (106). A further example of this type of cyclization has been published which involves the cyclization of the enone (107).44 Again irradiation uses benzophenone as the hydrogen abstracting agent. The resultant radical, with the radical centre adjacent to the nitrogen, again adds to the P-carbon of the enone. The reaction is carried out at -50°C in acetonitrile and the process affords the two products, (108) and (109), in an overall yield of 21% and a ratio of 1.6:l. Better yields are obtained using dicyanonaphthalene as the sensitizer. Use of single electron transfer photochemistry has been made in the synthesis of cyclic alkanols from the unsaturated esters (1 lo)-( 1 12).45Thus irradiation of the aldehydo or keto esters (Scheme 5 ) with DCA and a sacrificial electron donor such as triphenylphosphine or 1,5-dimethoxynaphthaleneleads to the formation of the cyclized products. As can be seen from Scheme 5, the method is diastereoselective and the yields are high. The method was extended to the cyclization of the ester (1 13) as a route to the optically pure C-furanoside (1 14) as outlined in Scheme 6. Single electron transfer-induced cyclizations of the esters (1 15) have also been described.46This process is readily brought about by the use of the DCA/Ph3P/ DMF/2-propanol/H20 system. The incident light is filtered through a copper solution to achieve incident wavelengths >380 nm. Some of the systems studied are shown for the conversion of (1 15) into (1 16). Again the yields are high. R
R
1 1
2
H
CH20TBDMS H
90
80
85
Some years ago Sat0 and his colleagues reported the use of silver trifluoromethanesulfonate (silver triflate) in the photochemical synthesis of cyclic ket0nes.4~~ A further study from the same group has shown that the chloroenones (1 17) and (1 18) also undergo photoreactions with alkenes in the presence of the silver salt.47b The yields and identities of the products range from low to good as can be seen in the samples cited in Scheme 7. The irradiations are carried out through Pyrex in benzene solution and, while the mechanism of the reaction is not completely understood, the possibility of electron transfer cannot be ruled out. The authors suggest that a radical intermediate (1 19) is involved and the best yields are obtained when thiophenol is added to the reaction mixture to suppress the formation of unwanted by-products. The search for different or specific electron transfer sensitizers continues. Tetramethyl pyromellitate has been shown to be a useful sensitizer for the photochemical reactions of a$-unsaturated ketones with tetraalkylstannanes?*
92
Photochemistry
a CI
+
R' R2 Yield !YO) Me Me H Me H H
45 77 21
Me Me H Me
77 22
(1 18)
-
Scheme 7
The triplet state of the mellitate brings about the cleavage to the stannanes by electron transfer and the resultant alkyl radicals add readily to the enones. Fission of a 0 - C ether linkage is the prime photochemical event on irradiation of pseudo-saccharin ethers.49 2.1.3 Miscellaneous Processes
- The results of a study of the rearrangement of flavanone and 3-chloroflavanone on irradiation in an alkaline medium have been rep~rted.~' The enone (120) is formed by a photochemical (2+2)-cycloaddition reaction within the benzene derivative (121) in benzene ~olution.~'Such cycloadditions have become of considerable interest as paths to molecules with complex skeleta. The intramolecular adduct (120) is also photochemically active and on further irradiation is converted into the pentacyclic derivative (122). This product is also formed directly if the irradiation of (121) is carried out in methanol. The rearrangement of (120) involves, in the first instance, the fission of the bond marked "a" in (120). Subsequent rearrangement within the resultant biradical affords the final product. Irradiation of the a$-unsaturated compounds (123) with a high pressure mercury lamp in benzene solution results in their efficient conversion into the 1,4-diketones ( 124).52The quantum yield of around 0.1 for the processes shows that the reactions are reasonably efficient. Cross-over experiments have demonstrated that the rearrangement is truly intramolecular and proof of the mechanism of the rearrangement was obtained by the conversion of (125) into (126). This cyclopropane derivative can be converted thermally into the final 1,4-dicarbonyl compound (127). This transformation suggests that the reaction path involves an unusual 1,4-hydrogen abstraction to yield an intermediate biradical such as (128). Cyclization of this species affords a cyclopropane and in the case of the keto alcohols (123) the cyclopropanol intermediates (129) are unstable to the reaction conditions readily undergoing ring opening to afford the 1,4-diketones (124). The cyclopropenone (130) undergoes decarbonylation on flash photolysis in water.s3 The resultant ynamine (13 1) is accompanied by the enamine (1 32). The enamine is formed from the carbene (133) and its trapping with water. The ynamine (13 1) is unstable and transforms into the ketenimine (134). The photo-
1112: Enone Cycloudditions und Rearrangements
93
Me H‘ @o Me
Me
( 123)
R’
( 124)
R2
Yield (YO)
dissociation of acrylonitrile brought about by irradiation at 193 nm has been studied.% A novel coupling reaction has been reported following the irradiation at h > 280 nm of mixed crystals of 1,2,4,5-tetracyanobenzene and benzyl cyanide.55The product isolated from this reaction was identified as the adduct (135). This compound is formed by a path that involves electron transfer and an intermolecular hydrogen abstraction process.
Photochemistry
94
P,y-Unsaturated Systems - As was mentioned earlier in this Chapter, Norrish Type I processes can occur with P,y-unsaturated enones. This process is also observed in the formation of a ketene on irradiation at h > 230 nm of cyclopenten-3-one in an argon matrix.56 The presence of the ketene intermediate was detected by IR spectroscopy, Irradiation at 300 nm of the enones (136) results in decarbonylation again by a Norrish Type I process.57 The resultant biradical undergoes ring closure and yields the cyclopropylpropenes (137). The propenonitrile product (137b) is formed as mixtures of 2 and E-isomers. The enones (138) and (139) undergo efficient conversion into (140) and (141), respectively, on direct irradiation through Pyrex in a benzene solution.58 The reaction is a good example of a 1,3-acyl migration in a P,y-unsaturated enone and is a route to the protoilludanoid skeleton. Irradiation using quartz filtered light affords a complex mixture of products.
2.2
LR
Me Me
Me (136) a: R = Me b:R=CN
(138)
(137) a: R = Me
b:R=CN
(139) R = H or OH
2.2.1 The Oxa Di-x-methane Reaction and Related Processes - Interest in the control of reactions in the constrained environment of zeolites continues to grow. A recent report describes the control exercised on the outcome of the photochemical reactions of the enones (142).59The conditions used involve the enones included in some M Y zeolites where M was Cs or T1. The usual acetonesensitized irradiation of (142, n = 1) and (142, n = 2) brings about the oxa-di-nmethane conversion to yield (143a) and (143b) in 41?4 and 37.3%, respectively. The zeolite/enone irradiations were carried out either as slurries in hexane or as dry powders. The best yields were obtained from the dry powder irradiations when up to a twofold enhancement in product formation was observed. TI+ Zeolites gave better results than the Cs materials and, for example, (143a) was formed in 61.1% from (142, n = 1) and (143b) from (142, n = 2) in 44.7% from the former systems. Clearly the presence of heavy atom cations enhances the intersystem crossing within the enones. The dienone (144a) undergoes the oxa-dix-methane rearrangement on irradiation in benzene solution using a tungsten
IIl2: Enone Cycloadditions and Reurrangements
95 OTBS
,
(142) n = 1 o r 2
(143) a: n = 1 b:n=2
(144) a: R = H b: R = OMe
OTBS
f\ I
0
H
(149)
R’ = R2 = H R1 = R2 = Me R’ = CH&H=CH2,
R2 = Me
lamp as the light source.6oThis treatment gives the tricyclic product (145) in 50% yield. The related compound (144b) does not follow this reaction path either on direct irradiation or on acetone-sensitized irradiation and under either of these conditions, only the 1,3-acyl migrated product (1 46) is formed in 52% yield. The oxa-di-n-methane reactivity of the tricyclic enones (147) and (148) has been described.6’ The reactions are carried out by irradiation in acetone as the solvent and sensitizer and this transforms the compounds (147) into the rearranged products (149) in the good yield. The reactions can be dependent upon the nature of the substituents on the skeleton and for example (148) also undergoes the oxadi-n-methane rearrangement but rather than forming a diketone it is transformed into the acetal (150) by reaction of the second carbonyl group with the hydroxymethyl substituent .
2.2.2 Miscellaneous Processes - Triplet sensitization by benzophenone of solutions of the lactone (151a) in benzene using a Pyrex filter brings about bond fission.62The product obtained from this reaction was identified as (152a) and was formed in 83% yield. The formation of this product occurs via the specific bond rupture of “a” in (151). This specific reactivity is to be contrasted with the direct irradiation of (151a) when (153) and (154) are formed in low yield. Specificity in the sensitized reactions is also displayed by the substituted derivatives (151b - d) when (152b - d) are formed in the yields shown.
96
Photochemistry
Phenylacetonitrile undergoes photochemical addition of amines via an electron transfer process.63 Such reactivity is typical for many systems and the SET process yields the radical anion/radical cation pair (155). Loss of cyanide from (1 55) affords a benzylic radical from which the products (1 56 - 158) are formed.
(151) X Yield ("0) 83 96 c: CI 80 d: Me0 40 e: Ph 69
a: H b: Me
I-\
DPSO' V (159) Z = R' = Me, R 2 = H E = R' = H, R2 = Me DPS = Me2PhSi
DPS0'(160) a: R'
b: R'
= Me, R2 = H = H, R2 = Me
Further interest has been shown in the transfer of energy along the rigid backbone of steroidal fystems. The steroidal system (159) has been chosen from among the many systems reported as an example of the processes encountered. The irradiation of (1 59) at 254 or 308 nm results in the isomerism of the alkene moiety from the 2 to the E isomer.@ The conditions chosen mean that the phenyldimethylsiloxy group is the initial absorber. Singlet energy is transferred from this moiety to give the ketone singlet which then undergoes ISC to afford the triplet keto group. Triplet energy is then transferred to the alkene that undergoes the isomerism. The keto group has clearly been shown to be involved. Thus, prolonged irradiation affords the Norrish Type I1 products (160) by hydrogen abstraction from the adjacent methyl group followed by bond formation in the l ,4-biradical.
IIl2: Enone Cycloudditions and Rearrangements
3
97
Photoreactions of Thymines and Related Compounds
3.1 Photoreactions of Pyridones - Irradiation of 1-benzyl-1,4-dihydronicotinamide (161) with the malonate derivative (162) affords a variety of products resulting from debromination and dirnerisati~n.~’ The dihydropyridine derivatives (163) are photochemically reactive in the solid phase.66The formation of the products by irradiation has been shown to be a two step process affording the (2+2)-cycloaddition product (164)in the first step. Secondary irradiation of (164) then gives the cage compounds (165) in yields greater than 900/.
(163)
(1 64) Yield (YO)
R’
R2
Ar
H H
Me Et Et Me Et
pMeOC6H4
CHZPh Me Me
65 40 60 60 52
( 165)
Yield (YO) 91
92 96 96 90
The photochemical addition of the pyridones (166) to the pentadienoate (167) does not occur on sensitized i r r a d i a t i ~ nDirect . ~ ~ irradiation is effective, however, and many cycloadducts, (1 68)-(173, were obtained. The results from these cycloadditions were compared with those obtained from the addition of the same pyridone (166) to methylpropenoate. Single crystals of the pyridones (176) were grown and examined by X-ray diffraction.68 Some of the systems crystallized to give a chiral space group which was particularly evident for the derivatives (1 76ac). Irradiation of these crystals resulted in the formation of the f3-lactams (1 77) in high yield with reasonably high ees. The study of the photodegradation of some antimicrobial quinolones has been reported.69 Irradiation of the enantiomerically pure bis-pyridone (178) in acetone solution results in almost quantitative conversion into the single cycloadduct (1 79).70 Several years ago Sieburth and co-workers reported that irradiation of (180) gave the adduct (181).7’aThis unstable cycloadduct could be reduced to the saturated derivative (182). Further study has shown that the derivative (182) can be ring opened using lithium in liquid ammonia and that this provides a reasonable synthetic route to the large ring compound (1 83).7’b
98
Photochemistry
(166) R’ = H or Me
(168) R’ = H or Me R2 = H or Me R3 = C02Me R2
---/
4
(167) R2 = H or Me
R2
H
0
R3\ R’/
0 (172)
(173)
&
0
H
(176) R =a: mCI b: mMe c: mMeO, d: mBr, H. CFCI,pCI, pBu’
p’
0
0 (174)
(175)
k
0
+NH 0 (177) a: ee 78% b:ee 71% c: ee 100%
3.2 Photoreactions of Thymines etc. - The uracil derivative (184) undergoes photochemical transformation when it is irradiated in frozen benzene with added triff uoroacetic acid.72 Cyclodimerization occurs yielding derivatives of diazapentacyclo[6.4.0.0’~3.02y6.04~8]dodecane derivatives such as (185). Other addition products (186) and (187) were also identified. The photoreduction of 5-bromouracil (1 88) has been studied.73 De Keukeleire and co-workers have reported a further example of the intramolecular addition of a pyrimidone to a pendant benzene ring.74 In this example. the cyclobutane adduct (189) formed from (190) on irradiation could not be isolated. Instead it underwent rearrangement on attempted isolation. Cyclodextrin is often used as a template upon which specific photochemical reactions
99
IIf2: Enone Cycloariditions and Rearrangements
b..,.
Ph
Me
Me0
(180)
Ph
'Ph
0
NCOPh Me0
\ H Me (189)
0
(191)
100
Photochemistry
F
HO (192) ( 193) R' = ribosyl, R2 = deoxyribosyl
(195)
0 (196) 0
0 (197) S
can be carried out. Another such example has been studied recently which involves the irradiation at 280 nm of the modified cyclodextrin (191).75 This procedure brings about reversible dimerization of the thymine moieties and the kinetic details of the forward and back reactions have been analysed. Irradiation at 366 nm in aqueous solution of the thiothymine (192) in the
IIl2: Enone Cycloadditions and Reurrangemenfs
101
presence of the adenine derivative (193) results in the formation of the adduct (194).76 Further studies on the photochemistry of the pyridone adducts (195) have been reported.77 Interest in photochemical reactions in constrained environments or on backbones has continued in the present year. The study by Clivio et al. has examined the photochemical reactions between the thymine units shown in (196).78 Irradiation at 366 nm in water results in the formation of the product (197) and similar treatment of related peptide nucleic acid dimers such as (198) leads to intramolecular hydrogen abstraction reactions yielding the three new products (199) - (201).79 The photochemical dimerization of some esters of urocanic acid has been described." 4
Photochemistry of Dienones
4.1 Cross-conjugated Dienones - The photochemical behaviour of several derivatives of the cyclohexadieneone (202) has been studied. The irradiation of these compounds in methanol follows the conventional ring contraction path to yield cyclopentenone derivatives.8' A study of intermolecular electron transfer in the dyads of the type illustrated in (203) has been examined.82
4.2 Linearly Conjugated Dienones - An extremely detailed study of the reactions of a variety of 6,6-disubstituted cyclohexa-2,4-dienones has been published.83Spectroscopic analysis of the intermediates at low temperatures was also carried out. The ketene intermediates obtained by the ring opening processes can be trapped by a variety of reagents. In this case methanol was favoured and, for example, ring opening and trapping of the ketene from (204) affords the large ring ester (205). Many other examples including the ring opening and trapping of the ketene from (206) affording (207) were also described. Further interest has been shown in the mechanistic steps of the photo-Fries reaction. Recent work has used the two-laser technique of irradiating intermediate^.^^ Thus the irradiation of the ether or the acetate (208) at h = 266 nm brings about the formation of the linearly conjugated cyclohexadienone derivatives (209). Irradiation of these
Photochemistry
102
OAc (204)
(209)R = Bn or COCH3
(210)
OR2
0r2
R20
/
~. -0.. . R’
&- I
R’
R’ H Me H H H
H H Me Ac Ts
11 19
-
46 74
5 7
-
22 17
5
-
39 7
-
8 10 12 6
-
Scheme 8
b i v
species at 308 nm causes ring opening to give the ketenes (210). Calculations relating to the photochemical isomerism of 5hydroxytropolone have been carried The irradiation of the pyranone derivatives (21 1) results in the products shown in Scheme 8.86 The reaction is of use for the synthesis of eight-membered rings and is the result of a (4+4)-cycloaddition. The best conditions for the reactions
IIl2: Enone Cycloadditionsand Rearrangements
103
are low temperature and aqueous methanol. The synthesis of the exdendo products (212)/(213) was studied further with the cyclization of (214) to yield the two adducts (215) and (216) in 20% and 58%, respectively. These compounds are of value as starting materials for the synthesis of the fusicoccane/ophiobolane skeleton. A review has highlighted the photochemical cycloaddition reactions and photocyclization reactions of 2- and 4-pyrone derivative^.'^ 5
1,2-, 1 , s and 1,4-Diketones
5.1 Reactions of 1,2-Diketones - A study of the ketoamides (217) has shown that their direct irradiation in benzene solution brings about efficient cycloaddition to give the bicyclic oxetanes (218).*' In the solid state, irradiation of (217) also affords these products. However, the syn:anti ratio is higher in the solid state than in solution. Furthermore, there is a temperature effect and the syn:anti ratio is greater at lower temperatures. The ee is also affected by changes of temperature.
Ph '0 (217) R' R2
(218) Yield (%) syn : anti Me Pr' 100 2.1 : 1 100 2.1 : 1 Me PhCH2 76 2.1 : 1 Ph Me 100 2.1 : 1 Me etolyl Me 2,6diMe& 100 2.1 : 1 H Pr' 96 H CH2Ph 99 H Ph 100 H 2,6diM&&i3 100 H 2.6diCICeH3 100
Studies aimed at measuring the lifetimes of the biradicals formed on irradiation of the keto esters (219) have been carried Particular interest was directed towards the 1,4-biradicals formed by Norrish Type I1 reactivity. Apparently the triplet reactivity is not influenced to any great extent by the presence of the halogen substituent. The alkenylphenyl glyoxalates (220) have been shown to be photochemically reactive.g0The outcome of the reactions is dependent upon the substitution pattern of the alkenyl moiety; hydrogen abstraction, oxetane formation [e.g. formation of (221)] and large-ring lactones result. A detailed study of the mechanism of the processes was also reported. Neckers and co-workers have also described the photochemical behaviour of the keto esters (222).91 Irradiation of (222d) and (222g) leads to the formation of the large ring lactones (223a) and (223b) in moderate yield. The path to these products involves long range hydrogen transfer at either the 1,lO-positions for (222d) or the 1,ll-positions for
104
Photochemistry
0 Ph+OMo\
0
(219) n R 2 CI 2 Br 2 1 2 PhS 2 PhS=O 3 Br 3 PhS
R
0
= R2 = H n= 1 R' = H, R2 = Pr" n- 1 R 1 = R 2 = M e n=l R1=R2=Me n=2
(220)R'
a
b
c d
e f g h
2 2 3 4 5 6
3 5
Me
Et
Et Me Me Me PhCH2 PhCH2
(223)a: R = H, n = 1 (25%) b: R = Ph, n = 2 (20%)
(222g). The resulting biradicals cyclize but the main reaction of all the compounds studied is either intermolecular hydrogen abstraction that leads to the pinacols (224), or Norrish Type I1 hydrogen abstraction to yield benzaldehyde via the biradical (225). The photochemical hydrogen transfer reactions of ethyl phenylglyoxalate derivatives attached to a polymer backbone have also been studied.92 The photochemical ring opening of the series of cyclobutene-1 ,2-diones (226)
R' But B u b Me3Si Ph Ph Ph Ph Ph Me But C1 CI But B u b PhS Me3Si Me3Si R2 Bu' B u b EtO H Ph Me CN Br Me But CI Me0 Pr'O Bu'O PhS EtO Me
H CHO
IIl2: Enone Cycloadditions and Rearrangements
105
to yield the corresponding bisketenes (227) has been reported.93 The diketone (228) affords the two cyclobutane derivatives (229) and (230) in a ratio of 7:l on irradiation in benzene solution using wavelengths > 340 nm.94 This cyclization involves a typical Norrish Type I1 process and the cis-cyclobutane (229) is also formed when crystals of (228) are irradiated. However, under these latter conditions the trans-isomer (230) is not formed and the other product from the irradiation in the solid state was identified as the keto-aldehyde (231). The formation of (231) is thought to involve a-fission of the bond between the two keto groups followed by carbene-type insertion into a C-H bond. The study showed that the cis-cyclobutane is formed by a Norrish Type I1 hydrogel, abstraction within the conformer (232). In this species either bowsprit hydrogen can be abstracted to afford the 1,3-biradical that is the precursor of the final product. High chemical but low quantum yields of the two products (233) and (234) are obtained on irradiation ( h > 500 nm) of the tetraketones (235).95 The primary photochemical step is the conversion of the tetraketones into carbon monoxide and the ketenes (236). The reaction process occurs from the singlet state and is thought to be concerted. The final products are formed by the addition of these ketenes (236) to ground state tetraketone. The ketene (236b) was studied in a little more detail and it was shown that irradiation in benzene or toluene at room temperature results in the formation of the dimer (237). Addition of the same ketene to diketones such as biacetyl was also reported.
'OAr
Ar&Ar
0
(233)a:Ar=Ph
b: Ar = 4-BrC6H4 c: Ar = 4-MeOCsH4
(236)
(234)
0
(235)
(237)Ar = 4-BrC6H4
5.2 Reactions of 1,3-Diketones - Irradiation of the 1,3-diketone (238) in ethanol or benzene results in the formation of 1-hydro~y-2-naphthaIdehyde.~~ The site of photochemical hydrogen abstraction reactions within the keto esters (239, X = S) is controlled by SET transfer reactions from the thio substituent to the excited carbonyl The usual reaction train following this event yields the biradical (240) which undergoes cyclization to yield (241) in modest to good yields. The involvement of an SET process is proven by the failure of the sulfone derivative (239, X = SO*) to undergo the same reaction.
Pho tuchemistry
106 0
(2411 R1 R2 X
Yield(%)
a: Ph
H S 65 b: Me Me S 44 c: Me H S 29 26 d: H H S 35 8: Ph H SO2 0
Reactions of I&Diketones - A photo electrodhole transfer process is involved in the alkylation of maleic acid catalysed by titanium dioxide in acetonitrile solution.98The reaction involves the silyl derivatives (242) or the corresponding arylacetic acids. The electron transfer leads to the corresponding benzyl radical either by fission of the C-Si bond in (242) or decarboxylation of the carboxylic acid. This benzylic radical adds to maleic acid to yield either the monoalkylation products (243) or the di-adduct (244). Rivas and co-workers have reported the photochemical (2+2)-cycloaddition of maleic anhydride to selenophene and tellurophene derivatives using benzophenone sensitization.w Irradiation of the dianhydride (245) in an argon matrix using a XeCI laser results in conversion into the aryne (246) by decarbonylation and decarboxylation.Iw Further irradiation at this wavelength brings about little change in the observed spectra but if (245) is irradiated using a KrF laser the bis aryne (247) is formed and further decomposition results in the formation of hexa-1,3,5triyne.
5.3
107
IIl2: Enone CycloacWitionsand Rearrangements
The triplet state of the 1,4-diketones (248) has been shown to undergo electron transfer in polar solvents.lo' Irradiation of the Diels-Alder adduct (249) results in the formation of the cage dione (250) by intramolecular (2+2)-cycloaddition.lo*
f--ygx
Me
X
0
Me%Br
(248) X = Br or CI
Br'
H0 (249)
5.3.I Phthafimides and Related Compounds - 4-Amino-N-methylphthalimide has been studied by laser flash photoly~is.'~~ The photophysical parameters have been established by this approach and this study has supported the results obtained from steady state irradiations. Intramolecular photoelectron transfer photochemistry of the N-[(N-acetyl-N-trimethylsilyl-methyl)amidoalkylJphthalimides has been demonstrated.'04The yields obtained on irradiation in methanol range from low to medium. 0
qL:g--J II
0
& 0
HO>
H
H H O x P h
Ph
A
HO
R' R2 (257) R' = CH20H. R2 = H R' = H, R2 = CH20H
I08
Photochemistry
The tetrahydrophthalimide derivative (25 1) undergoes intramolecular (2+2)photocycloaddition on irradiation in acetonitrile solution using Pyrex-filtered light.Io5This process gives reasonable yields of the cyclobutane adduct (252). The system was extended to use silicon tethers for the alkene (253) or the alkyne (254) side chains to the tetrahydrophthalimide. In addition a chiral group was incorporated adjacent to the nitrogen of the phthalimide. When these molecules are irradiated the diastereoisomeric diols (255) and (256) were obtained from (253), after ring opening of the initially formed photoadducts. A similar result was observed with (254) which gave (257). The yields in all the examples are in the range of good to excellent. Lactams such as (258) can be synthesized from the phthalimides (259) by irradiation.'06 Again the reactions are controlled by single electron transfer processes that are usually encountered in the photochemical reactions of phthalimides. The outcome of the reaction is a conventional proton transfer from the benzylic site within the zwitterionic biradical formed on irradiation. Cyclization within the resultant 1,5-biradicaI affords the final product. Griesbeck and his coworkers have studied the photochemical reactivity of the phthalimide derivatives (260).'07 These compounds on irradiation under triplet sensitized conditions undergo decarboxylation and cyclization. The reaction involves SET and the key intermediates are shown as (261) and (262). The biradical anion (262) is the species that either cyclizes to afford (263) or abstracts hydrogen to yield (264). The reaction is controlled by a variety of factors that have been reported in some detail. Some photochemical reactions of phthaloylcysteine derivatives have been described."' Typical of the processes are the decarboxylations of the derivative 0
(260)/I= 1-5, 10, 11
(259)
(263) n Yield (YO) 1
2 3 4 5
10 11
-
5 75 61 71 72 78
(264) n Yield (YO) 1
2 3
95
45 4
4 4 5 5 8 10 <5 11 4
109
IIl2: Enone Cycloadditionsand Rearrangements
(265) which yields (266) and (267). The outcome of the process is solvent dependent. In acetonitrile the path yielding (266) is dominant while in acetone/ water (267) is the major product. With protected thiol derivatives such as (268) electron transfer reactions in acetonitrile lead to (269, R = H, < 3%), (269, R= COOH, 66%) and (270,22%0).In acetone, however, the path followed favours the formation of (269, R = H, 39%) and (269, R= COOH, 6lY0). Cyclization is not observed under these conditions. The photophysics of naphthalimides such as (27 1) have been reported. log
(267) 3% >97% C
5.3.2 Fulgides and Fulgimides - A b initio calculations have been carried out to assess the photochemical properties of 3-furylfulgide. l o Photochromism of fulgides continues to be an area of considerable interest. The photochromic behaviour of fulgides with chiral properties has also attracted interest." The effects of constraining environments are also important and photochromic properties of the indolylfulgide (272) have been examined where the compound has been trapped in a hybrid matrix prepared by a sol gel process.I12 More complex systems continue to be devised within this family of molecules and (273) is a good example of further developments.'13 The photochromism of ( a - 2 isopropylidene-3-[ 1-(3,4-dimethoxyphenyl)ethylidene]-3-isopropylidene succinic anhydride has been reported.'14 Fulgides have also been studied as potentials for optical switches.' l 5
'
I10
Photochemistry
The influence of chiral substituents attached to the trienes (274) on the cyclization of these molecules has been examined.'I6 Irradiation at 450 nm leads to diastereoisomeric pairs in the closed form. The outcome of the reaction is solvent dependent and one of the best results is obtained on irradiation at low temperature in toluene. Under these conditions the diastereoenantiomeric excess was 86.6%.
(CN
(274) R = Cmenthyl or &menthy1
6
Quinones
6.1 o-Quinones - Quinone methides can be formed by the irradiation of 0benzoquinones in the presence of diphenylacetylene. This reaction is quite normal behaviour for quinones and involves (2+2)-cycloaddition to the carbonyl function to yield an oxetene. In this instance elimination of benzaldehyde affords the quinone methide. 6.2 p-Quinones - The 1,3-diketone (275) in its enol form undergoes cycloaddition to p-benzoquinone derivatives.I l 8 The cycloaddition is a typical (2+2)process of the de Mayo type to afford a cyclobutane. Ring opening of the fourmembered ring yields the 1,Sdiketo (276). Duroquinone also undergoes (2+2)cycloaddition to yield cyclobutane derivatives.'" This photochemical addition to stilbene yields the unstable adduct (277). The final product from the reaction is the cyclooctatriene (278) which is formed by oxidation and ring opening of (277). A study of the photochemical addition of diarylalkynes (279) to the quinone (280) has shown that the quinone methides (281) are formed.'20 As is well known, the addition involves the formation of an oxetene (282) that ring opens. There is some degree of selectivity when non-symmetric alkynes are used as indicated by results shown beside the appropriate structures. The photochemical reaction can be brought about either by irradiation at wavelengths > 410 nm or by irradiation into the charge transfer band at wavelengths > 530 nm. The outcome is the same P h q o
Ph
0
P
Ph
Ph
Ph
0
h
a
H Me
M
e
;
;
G
M
Me
Me 0
e
Me
0
111
IIl2: Enone Cycloadditionsand Rearrangements
YtC' 0
A?-Arl
cPc'cT 0
:'
o A? /
0
A?
(281) a: 60% yield b: Ar' = 3,5diMeCsH3, A? = Ph Ar' = Ph, A? = 3,5diMeC6H3 80% (ratio 10 : 1) c: Ar' = 3,5diMeC6H3, A? = pMeC6H4 Ar' = pMBCsH4, A? = 3,5diMeC6H3 82% (ratio 3 : 2)
0 0
Me Me
/
Me Me
M*
Me0
112
Photochemistry
under both conditions. The authors state that the reaction probably involves a single electron transfer process with the formation of radical catiodradical anion pair. Indeed, irradiation of the crystalline complexes of the same alkynes with the same quinone also gives adducts.I2l One example is shown when irradiation at h > 410 nm of the quinone with the alkyne (283) gives a 90% yield of the adducts (284a) and (284b) in a ratio of 4:l. Irradiation of the benzoin derivative (285) readily affords the free alcohol, 2-ubiquinol. 122 The photoenolization of the quinone (286) can be carried by irradiation at 3 13 or 365 nm in acid solution.'23The steady state irradiation has identified the product as the unstable hydroxylated compound (287) which is formed via the enol(288). The presence of this intermediate was detected in a laser flash study of the reaction. The quinones (289) undergo cyclization when irradiated with visible light.124The mechanism by which the compounds (289) are transformed into the derivatives (290) involves the production of an excited state that is either a zwitterion or a biradical. After the transfer of a hydrogen the intermediate (291) is formed. It is within this species that cyclization occurs to give the final products. (2+2)-Cycloadducts such as (292) and oxetanes can be obtained by the photochemical addition of quinones to homobenzvalene. Interest in the photo-SET in quinone systems has led to the synthesis of the pyropheophytin substituted ndphthoquinone dyads (293). 126 A pulse radiolysis study of vitamin K in solution has been reported. 127
@ 0
@ Me
OH
0
R'
yJ$J
O*
0
(290) R2 Yield (Yo) H 27 H Me 38 Me Me 83 PhCH2 H 80
R1 H
0
1112: Enone Cycloadditionsand Rearrangements
113
1-Alkylanthraquinones undergo Norrish Type I1 hydrogen transfer on irradiation. 12' The photochromism exhibited by anthraquinones (294) has been examined. 129 With the corresponding phenoxyquinones the reactions involve a phenyl migration which is a non-adiabatic process and yields a triplet biradical. A study of the photochemical electron transfer systems of the substituted anthraquinone derivatives (295) has been carried out.'30 The influence of the binding mode of quinones such as (296) and (297) to DNA has an effect on the light-induced cleavage of duplex DNA.13' 0
II
NH-(CH2),-O-P-O-[5'-OLI-3'] I 0-
Q \ y-$lfJ$ry 0
0
(294)R =aryl or alkyl
(295)n = 2 or5
QypR 0 (296)R = S02NH(CH2)4NH&I R = CONH(CH&NH&I
(297)
Crystal structures of triptycene-l,4-quinone and its photoproduct have been determined. 132A full account of the photochemical reactivity of azulene quinones has been pub1i~hed.I~~ This study has already been published in note form.134The authors note that the methoxy substituted azulene quinone (298) undergoes
Me0
Ll
O
g
$
l
0
OMe (301)
qo
0
114
Photochemistry
photochemical dimerization on irradiation using a 400 W mercury arc lamp in methylene chloride. Three main products were isolated from this and were identified as (299), (300) and (301) in 6, 10 and 24%, respectively. The head-tohead adducts are predominant when the reactions are carried out in polar solvents, The bromo derivative (302), in contrast, yields only the single dimer (303).
7 1. 2.
3. 4. 5. 6.
7. 8. 9. 10. 11. 12. 13. 14.
15.
16. 17. 18. 19. 20. 21. 22.
References T. Hatsui, M. Taga, A. Mori and H. Takeshita, Chem. Lett., 1998, 1 13. J. J. Wang, C. J. Yao, B. Z. Chen and G. J. Jiang, Chin. Chem. Lett., 1997, 8, 781 (Chem. Abstr., 1997,127,307501). J. J. Wang, C. J. Yue, J. Qiu and C. Y. Qian, Chin. Chem. Lett., 1997, 8, 957 (Chem. Abstr., 1998, 128, 89025). T. Nakamura, K. Takagi, M. Itoh, K. Fujita, H. Katsu, Y. Imae and Y. Sawaki, J. Chem. SOC.,Perkin Trans. 2, 1997,2751, I. Weissbuch, W. Bouwman, K. Kjaer, J. Als-Nielsen, M. Lahav and L. Leiserowitz, Chiraltiy, 1998,10,60 (Chem. Abstr. 1998, 128,85139). G . W. Coates, A. R. Dunn, L. M. Henling, J. W. Ziller, E. B. Lobovsky and R. H. Grubbs, J. Am. Chem. Soc., 1998,120,3641. M. D’Auria and R. Racioppi, Tetrahedron, 1997,51, 17307. T. Thiemann, C. Thiemann, S. Sasaki, V. Vill, S. Mataka and M. Tashiro, J. Chem. Res., Synop., 1997,248. G . S . Han and S. C. Shim, Photochem. Photobiol., 1998,67, 84 (Chem. Abstr., 1998, 128,217353). A. Zhu and S. Wu,Ganguang Kexue Yu Guang Huaxue, 1997,15, 15 1 (Chem. Abstr., 1997,127,480026). Y. L. Chow, X. N. Cheng, S. S. Wang and S. P. Wu,Ccm. J. Chem., 1997,75,720. J. Bethke, A. Jakobs and P. Margaretha, J. Photochem. Photobiol., A , 1997, 104, 83 (Chem. Abstr., 1997,127, 128589). N. Marubayahsi, T. Ogawa and N. Hirayama, Bull. Chem. SOC.Jpn., 1998,71,321. N. Marubayashi, T. Ogawa, T. Hamasaki and N. Hirayama, J. Chem. Soc., Perkin Trans. 2, 1997, 1309. C. Jeandon, R. Constien, V. Sinnwell and P. Margaretha, Helv. Chim. Acta, 1998, 81,303. A. A. Pinkerton, A. Martin, A. P. Marchand and A. Devasagayaraj, J. Chem. Crystallogr., 1997,27,701 (Chem. A bstr., 1998,128,243970). A. B. Brown, S. E. McKay and D. E. Meeroff, Synth. Commun., 1997, 27, 1989 (Chem. Abstr., 1997,127,33899). H. Tsujishima, K. Nakatani, K. Shimamoto, Y. Shigeri, N. Yumoto and Y. Ohfune, Tetrahedron Lett., 1998,39, 1 193. S. Bertrand, N. Hoffmann and J. P. Pete, Tetrahedron, 1998,54,4873. T. Shimo, H. Minamishin and K. Somekawa, J. Heterocycl. Chem., 1997, 34, 533 (Chem. Abstr., 1997, 127,34076). H. Goncalves, G. Robinet, M. Barthelat and A. Lattes, J. Phys. Chem. A , 1998,102, 1279. A. W. Jensen, A, Khong, M. Saunders, S. R. Wilson and D. I. Schuster, J. Am. Chem. Soc., 1997,119,7303.
IIf2: Enone Cycloadditions and Rearrangements 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39.
40. 41. 42. 43. 44. 45. 46. 47.
48. 49. 50. 51. 52. 53. 54.
55.
115
S. Andresen and P. Margaretha, J. Photochem. Photobiol. A , 1998, 112, 135 (Chem. Absfr., 1998, 128,25051 7). K. Matsuo, M.Morita and K.4. Kawashima, Chem. Pharm. Bull., 1997,45, 1734. C. A. Dvorak and V. H. Rawal, J. Chem. SOC.,Chem. Commun., 1997,2381. M. T. Crimmins and A. L. Choy, J. Am. Chem. SOC.,1997,119,10237. M. T. Crimmins, Z. Wang and L. A. McKerlie, J. Am. Chem. SOC.,1998,120, 1747. M. N. Wrobel and P. Margaretha, J. Chem. SOC.,Chem. Commun.,1998,541. N. Braussaud, N. Hoffmann and H.-D. Scharf, Tetrahedron, 1997,53, 14701. N. Haddad and N. Galili, TetrahedronLett., 1997,38,6083. M.T. Crimmins, B. W.King, P. G. Watson and L. E. Guise, Tetrahedron, 1997,53,
8963. S . Piva-Le Blanc, J.-P. Pete and 0. Piva, J. Chem. SOC.,Chem. Commun., 1998,235. N. Haddad, I. Rukhman and Z. Abramovich, J. Org. Chem., 1997,62,7629. N. Haddad and H. Salman, TetrahedronLett., 1997,38,6087. J. H. Dritz and E. M. Carreira, TetrahedronLett., 1997,38, 5579. J. D. Winkler and E. M.Doherty, TetrahedronLett., 1998,39,2253. S . A. Fleming, C. L. Bradford and J. J. Gao, Mol. Supramol. Photochem., 1997, 1 (Organic Photochemistry), 187 (Chem. Abstr., 1998,128,204464). J. T. Moon, Y.-C. Kong, D. S. Ryu and D. J. Choo, Bull Korean Chem. SOC.,1997, 18,1236 (Chem. Abstr., 1998,128, 167076). C. A. Hastings, J. D. Riggenberg and E. M. Carreira, Tetrahedron Lett., 1997, 38, 8789. V. J. Rao, S. R. Uppili, D. R. Corbin, S. Schwarz, S. R. Lustig and V. Ramamurthy, J. Am. Chem. SOC.,1998,120,2480. R. A. Bunce, R. S. Childress and E. M.Holt, J. Photochem Photobiol., A , 1997,109, 125 (Chem. Abstr., 1997,126,3 12965). A. M. Gomez, S. Mantecon, S. Valverde and J. C. Lopez, J. Org. Chem., 1997, 62, 6612. D. Brown, M. G. B. Frew and J. Mann, J. Chem. SOC.,Perkin Trans. I , 1997,3651. E. Farrant and J. Mann, J. Chem. SOC.,Perkin Trans. I , 1997,1083. G. Pandey, S. Hajra, M. K. Ghorai and K. R. Kumar, J. Org. Chem., 1997, 62, 5966. G. Pandey, M. K. Ghorai and S. Hajra, TetrahedronLett., 1998,39, 1831 (a) S. H. Oh, K. Tamura and T. Sato, Tetrahedron, 1992, 48, 9687; T. Sat0 and K. Tamura, Tetrahedron Lett., 1984,25, 1821; S.-H. Oh and T. Sato, J. Org. Chem., 59,3744 (1994); (b) Y.Sawayanagi, T. Sat0 and I. Shimizu, Chem. Lett., 1997,843. M. Fagnoni, M. Mella and A. Albini, J. Phys. Org. Chem., 1997, 10, 777 (Chem. Absrr., 1998,128, 74996). U. C. Yoon, J. H. Kim, S. J. Lee, H. J. Kim, S. W. Oh and W. W. Park, J. Korean Chem. SOC.,1997,41,666 (Chem. Abstr., 1998,128,60093). S. Jain, Natl, Acad. Sci. Lett. (India), 1997, 20, 130 (Chem. Abstr., 1998, 128, 238053). G. P. Kalena, P. P. Pradhan, Y. Swaranlatha, T. P. Singh and A. Banerji, Tetrahedron Lett., 1997,38,555 1. S. Matsumoto, Y. Okubo and K. Mikami, J. Am. Chem. SOC.,1998,120,4015. Y . Chiang, A. S. Grant, H.-X. Guo, A. J. Kresge and S. W. Paine, J. Org. Chem., 1997,62,5363. D. A. Blank, A. G. Suits, Y. T. Lee, S.W. North and G. E. Hall, J. Chem. Phys., 1998,108,5784. Y. Ito, S. Endo and S. Ohba, J. Am. Chem. SOC.,1997,119,5974.
116 56. 57. 58. 59. 60. 61. 62. 63.
64. 65. 66. 67. 68. 69, 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80. 81. 82. 83.
Photochemistry
J.-P. Aycard, D. Synaly and H. Bodot, Spectroscop. Lett., 1997, 30, 1325 (Chem. Abstr., 1997, 127, 749591). S. Andresen and P. Margaretha, J. Chem. Res., Synop., 1997,345. V. Singh and U. Sharma, J. Chem. Soc., Perkin Trans. I , 1998, 305. R. Sadeghpoor, M. Ghandi, H. M. Najafi and F. Faraneh, J. Chem. Suc., Chem. Commun., 1998,329. R. M. Corbett, C.-S. Lee, M. M. Sulikowski, J. Reibenspies and G. A. Sulikowski, Tetrahedron, 1997,53,11099. V. Singh and B. Thomas, J. Org. Chem., 1997,62,5310. S . Kohmoto, H. Yajima, S. Takami, K. Kishikawa, M. Yamamoto and K. Yamada, J. Chem. Soc., Chem. Commun., 1997, 1973. K. Homma and S. Yamada, Chem. Pharm. Bull., 1997,45,1198 (Chem. Abstr., 1997, 127,240777). J. K. Agyin, L. D. Timberlake and H. Morrison, J. Am. Chem. Soc., 1997,119,7945. B. Li, Y.-C. Liu and Q.-X. Guo, J. Photochem. Photobiol. A , 1997, 103, 101 (Chem. Abstr., 1997, 127, 72888). A. Hilgeroth, Chem. Lett., 1997, 1269. T. Suishi, S. Tsuru, T. Simo and K. Somekawa, J. Heterocycl. Chem., 1997,34, 1005 (Chem. Abstr., 1997, 127, 161382). L.-C. Wu, C. J. Cheer, G. Olovsson, J. R. Scheffer, J. Trotter, S.-L. Wang and F.-L. Liao, Tetrahedron Lett. , 1997,38, 3 135. K. Thoma and N. Kubler, Pharmuzie, 1997, 52, 519 (Chem. Abstr., 1997, 127, 499813). D. L. Comins, Y.S. Lee and P. D. Boyle, Tetrahedron Lett., 1998,39, 187. (a) S. McN. Sieburth and C.-H. Lin, J. Org. Chem., 1994, 59, 3597; (b) S. McN. Sieburth, T. H. Ai-Tel and D. Rucando, Tetrahedron Lett., 1997,38,8433. K. Ohkura, Y. Noguchi and K. Seki, Heterocycles, 1998, 47, 429 (Chem. Abstr., 1998,187271). K. Fujimoto, H. Sugiyama and I. Saito, Tetrahedron Lett., 1998,39,2137. W. Saeyens, D. De Keukeleire, P. Herdewijn and A. De Bruyn, Biomed. Chromutogr., 1997,11,79 (Chem. Abstr., 1997,126, 343426). T. Nozaki, M. Maeda, Y. Maeda and H. Kitano, J. Chem. Soc., Perkin Trans. 2, 1997, 1217. C. Saintome, P. Clivio, A. Favre and J. L. Fourrey, J. Org. Chem., 1997,62, 8125. P . Clivio and J. L. Fourrey, Tetrahedron Lett., 1998,39,275. P. Clivio, D. Guillaume, M. T. Adeline and J. L. Fourrey, J. Am. Chem. Soc., 1997, 119,5255. P. Clivio, D. Guillaume, M.-T. Adeline, J. Hamon, C. Riche and J.-L. Fourrey, J. Am. Chem. Soc., 1998,120,1157. M. D’Auria and R. Racioppi, J. Photochem. Photobiol. A , 1998, 112, 145 (Chem. Abstr., 1998,128,237102). F.-T. Hong, K . 3 . Lee, Y.-F. Tsai and C.-C. Liao, J. Chin. Chem. SOC.(Taipei), 1998,45, 1 (Chem. Abstr., 1998, 190888). H. Zhang, M.Zhang and T. Shen, Sci. China, Ser. B: Chem, 1997,40, 192 (Chern. Abstr., 1997, 126, 330394). G. Quinkert, S. Scherer, D. Reichert, H.-P. Nessler, H. Wennemers, A. Ebel, K. Urbahns, K. Wagner, K.-P. Michaelis, G. Wiech, G. Prescher, B. Bronstert, B.-J. Freitag, I. Wicke, D. Lisch, P. Belik, T. Crecelius, D. Hoerstermann, G. Zimmermann, J. W. Bats, G. Duerner and D. Rehm, Helv. Chim. Acta, 1997, 80, 1683.
IIl2: Enone Cycloudditions and Rearrangements 84. 85. 86. 87. 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 99. 100. 101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111.
112. 113. 114.
117
M. C. Jimenez, M. A. Miranda, J. C. Scaiano and R. Tormos, J. Chem. Soc., Chem. Commun., 1997,1487. J. J. Paz, M. Moreno and J. M. Lluch, J. Chem. Phys., 1997,107,6275. C. E. Chase, J. A. Bender and F. G. West, Synlett, 1996, 1 173. F. G. West, Adv. Cycloaddit., 1997, 1 (Chem. Abstr., 1997,127, 148738). M. Sakamoto, M. Takahashi, T. Fujita, S. Watanabe, T. Nishio, I. Iida and H. Aoyama, J. Org. Chem., 1997,62,6298. S . K. Hu and D. C. Neckers, J. Org. Chem., 1997,62,7827. S . Hu and D. C. Neckers, J. Org. Chem., 1997,62,6820. S . K. Hu and D. C. Neckers, J. Chem. Soc., Perkin Trans. 2, 1997, 1751. S. Hu and D C. Neckers, Macromolecules, 1998, 31, 322 (Chem. Abstr., 1998, 128, 22129). A. D. Allen, J. D. Colomvakos, F. Diederich, I. Egle, X. K. Hao, R. H. Liu, J. Lusztyk, J, H. Ma, M. A. McAllister, Y. Rubin, K. Sung, T. T. Tidwell and B. D. Wagner, J. Am. Chem. Soc., 1997,119,12125. G. Olovsson, J. R. Scheffer, J. Trotter and C. H. Wu, Tetrahedron Lett., 1997,38,6549, M. B. Rubin, M. Etinger, M. Kapon, E. C. Krochmal, R. Monosov, S. Wieriacher and W. Sander, J. Org. Chem., 1998,63,480. S . Garg and J. C. Kohli, Asian J. Chem., 1997, 9, 845 (Chem. Abstr., 1998, 128, 88649). Y. Yamazaki, T. Miyagawa and T. Hasegawa, J. Chem. Soc., Perkin Trans. 1, 1997, 2979. L. Cermenati, M. Mella and A. Albini, Tetrahedron, 1998,54,2575. C. Rivas, F. Vargas, G. Aguiar, A. Torrealba and R. Machado, J. Photochem. Photobiol., A , 1997,104, 59(Chem. Abstr., 1997,127, 128585). M. Moriyama and A. Yabe, Chem. Lett., 1998,337. 1. Amada, M. Yamaji, M. Sase, H. Shizuka, T. Shimokage and S. Tero-Kabata, Res. Chem. Intermed, 1998,24,81 (Chem. Abstr., 1998,128,78152). X.-P. Guan, Z. Su, J.-G. Sun and Y.-Z. Yu, Molecules, 1996, 1, 46 (Chem. Abstr., 1997,127, 50315). S . Aich, C. Raha and S. Basu, J. Chem. Soc., Faraday Trans., 1997,93,2991. U. C. Yoon, J. W. Kim, J. Y. Ryu, S. J. Cho, S. W. Oh and P. S. Mariano, J. Photochem. Photobiol. A , 1997,106,45 (Chem. Abstr., 1997,127,197606). K. I. Booker-Milburn, S. Gulten and A. Sharpe, J. Chem. Soc., Chem. Commun., 1997,1385. M. Close, J. D. Coyle, E. J. Haws and C. J. Perry, J. Chem. Res. Synop., 1997, 1 1 5 (Chem. Abstr., 1997, 126, 330576). A. G. Griesbeck, A. Henz, W. Kramer, J. Lex, F. Nerowski, M. Oelgemoller, K. Peters and E. M. Peters, Helv. Chim. Acta,, 1997, 80, 912 (Chem. Abstr., 1997, 3662 14). A. G. Griesbeck, J. Hirt, W. Kramer and P. Dallakian, Tetrahedron, 1998,54, 3169. B. M. Aveline, S. Matsugo and R. W. Redmond, J. ,4m. Chem. Soc.. 1997,119,11785. Y. Yoshioka and M. Irie, Electron. J. Theor. Chem., 1996, 1, I (Chem. Abstr., 1997, 35 9890). L. Yu, D. Zhu and M. Fan, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A , 1997,2W, 107 (Chem. Abstr., 1997,461738). J . Biteau, F. Chaput, Y.Yokoyama and J. P. Boilot, Chem. Lett., 1998,359. 2. X. Guo, G. J. Wang, Y. W. Tang and X. Q. Song, Liebigs AnnJRecl., 1997,941. 2. Gou, Y. Tang, F. Zhang, F. Zhao and X. Song, J. Photochem. Photobiol., A , 1997,110, 29 (Chem. Abstr., 1998, 128,8653).
Photochemistry
118
Y. Yokoyama, S. Uchida, Y. Shimizu and Y. Yokoyama, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A, 1997,297,85 (Chem. Abstr., 1997,461730). 116. T. Yamaguchi, K. Uchida and M. Irie, J. Am. Chem. SOC.,1997,119,6066. 117. A. R. Kim, Y. J. Mah, S. C. Shim and S. S. Kim, J. Photosci., 1997,4, 49 (Chem. Abstr., 1997,644665). 118. A. R.Kim, K. J. Kim, S. C. Shim and S . S. Kim, Bull. Korean Chem. SOC., 1997,18, 1125 (Chem. Abstr., 1998,128,22683). 119. A. R. Kim, S. S. Kim, D. J. Yo0 and S. C. Shim, Bull. Korean Chem. SOC.,,1997,18, 665 (Chem. Abstr., 1997,127, 176240). 120. E. Bosch, S. M. Hubig and J. K. Kochi, J. Am. Chem. SOC.,1998,120,386. 121. E. Bosch, S . M. Hubig, S. V. Lindeman and J. K. Kochi, J. Am. Chem. SOC., 1998, 115.
120, 592. 122.
M. H. B. Stowell, G. Y. Wang, M. W. Day and S. I. Chan, J. Am. Chem. SOC.,1998,
123.
Y. Chiang, A. J. Krege, B. Hellrung, P. Schunemann and J. Wirz, Helv. Chim. Acta,
124.
T. J. Onofrey, D. Gomez, M. Winters and H. W. Moore, J. Org. Chem., 1997, 62,
120, 1657.
1997,80,1106.
5658. 125. 126.
M. Christ1 and M. Braun, Liebigs Ann./ R e d , 1997, 1135. P. K. Malinen, A. Y. Tauber, J. Helaja and P. H. Hynninen, Liebigs Ann.lRecl.,
127.
J.-F. Chen, S.-D. Yao, G.-S. Chu, Z.-C. Zhang, M.-W. Zhang, W.-F. Wang and N.-Y. Lin, Gaodeng Xuexiao Huaxue Xuebao, 1997, 18, 2004 (Chem. Abstr., 1998,
1997, 1801.
128,22259).
Z. Leonenko, L. Klimenko and N. Gritsan, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A , 1997,297, 1 75 (Chem. Abstr., 1997,46 1767). 129. N. Gritsan, Mol. Crysf. Liq. Cryst. Sci. Technol., Sect. A, 1997, 297, 167 (Chem. Abstr., 1997,461766). 130. S. M . Gasper and G. B. Schuster, J. Am. Chem. SOC., 1997,119,12762. 131. D. T. Breslin, J. E. Coury, J. R. Anderson, L. McFaillsom, Y. Z. Kan, L. D. Williams, L. A. Bottomley and G. B. Schuster, J. Am. Chem. SOC.,1997,119,5043. 132. T . Y. Fu, J. N. Gamlin, G. Olovsson, J. R. Scheffer, J. Trotter and D. T. Young, Acta Crystallogr., Sect. C: Cryst. Struct. Commun., 1998, C54B, 1 16 (Chem. Abstr., 128.
1998,128, 86234). 133. 134.
H. Kawakami, Y. Z. Yan, N. Kato, A. Mori, H. Takeshita and T. Nozoe, Bull. Chem. SOC.Jpn., 1998,71,711. A. Mori, H. Kawakami, H. Takeshita and T. Nozoe, Chem. Lett., 1996,985.
Photochemistry of Alkenes, Alkynes and Related Compounds BY WILLIAM M. HORSPOOL
1
Reactions of Alkenes
1.1 &,trans-Isomerization - Considerable interest has been shown over the years in the cis-trans-isomerism of cyclo-octene. Much of this work has focused on the sensitized process in routes to obtain optically active forms. A recent account is concerned with the cyclo-octene derivative ( I ) where the sensitizer is linked to the alkene by means of an optically active side chain.' Irradiation of this (a-cyclo-octene results in diastereoisomeric excesses of 33% and a ZIE ratio of
MeYYMe
RaN c) ) onononoAo
\\//
0
wOwOwOP Photochemistry, Volume 30 0The Royal Society of Chemistry, 1999 119
120
Photochemistry
up to 0.8. Further studies have shown that better des are obtained using the terephthalate analogue of (1). The solvent, temperature and wavelength dependency of reversible cis,trans-isomerism of the donor acceptor alkenes (2), (3) and (4) has been studied in great detail.2 Irradiation of the coronand (5) using benzoquinone as the sensitizer brings about trans,cis-isomerism of the double bond. Both the cis- and the trans-compounds of (5) have been synthesized independently and their photochemical behaviour ~ t u d i e d .The ~ irradiation, however, does not give pure cis- or trans- but yields a photostationary state with cis:trans ratio of 2:3. The photochemical cis,trans isomerism of the crotonate ester (6) using 313 nm radiation has been ~ t u d i e d Isomerism .~ in poly(methacryloyloxyethyl-3N-n-butylaminocrotonate) was also examined under the same conditions.
1.1.I Stifbenes and Related Compounds - The photoisomerization of stilbene has been studied under collisional gas-phase condition^.^ The photophysical characteristics of a series of 4,4'-disubstituted stilbenes have been measured.6 The control exercised by the dextrins on photochemical processes within the cavities continues to produce interesting results. Thus irradiation ( h = 312 nm) of the Interest in the synthesis stilbene (7) in P-cyclodextrin results in E,Z-is~merism.~ of polyrotaxanes has grown considerably over the years. Recently reported work has examined the trans,cis-isomerism of the model stilbene (8) and of polymers based on the more complex derivative (9).* The isomerism within the polymer system occurs smoothly and without degradation of the polymer chain. Saltiel
1113: Photochemistry of Alkenes, A Ikynes and Related Compounds
121
and his co-workers have studied the photochemical processes encountered with the stilbene analogue (lo).' Among many features studied the temperature dependence of the isomerism was evaluated. The photoisomerization of the stilbene analogues, e.g. 1-(9-anthryl)-2-(pyridyl)ethenes has been examined in various solvents." Upper excited singlet states are proposed to be implicated in the fluorescent decay of some trans- 1,2-diarylethenes bearing naphthyl, phenanthryl, anthryl, pyrenyl and pyridyl groups." Arai et al. have studied the photochemical isomerization of 2-styrylazulene and 1,2-di(azulenyl)ethene.l 2 Both of these compounds undergo one-way cis, trans-isomerism on direct and sensitized irradiation. A further study on the photochemical rearrangement of alkenes of the type represented by (1 1) has demonstrated that in the open form the system can complex Cs+ specifically.'3 Irradiation at 313 nm brings about ring closure (a six electron cyclization) into a form where Cs+ is not complexed. Thus the authors suggest that the thienylalkene behaves as a pair of molecular tweezers. Other studies by the same group have examined photocyclizations of such molecules as the dithienylperfluorocyclopentene (12 ) in the crystalline phase.14" The quantum yield for the photocyclization of (12) is enhanced when it is irradiated in the cavity
R
R (12) R = S03Na
F2(3F2
NC
"
(13) n = 0 , 1 or2
CN
122
Photochemistry
of p- or y-cyclodextrin. Applications of such systems for liquid crystal displays have also been noted.’4b A review has highlighted the advances made in the study of photochemistry in organized or constrained systems.l 5 More data concerning the photochemical behaviour of alkenes such as (13) has been reported.16 In this case the photochromic compound has thiophene oligomers as the aryl groups. Photochromism of some iodothienylethenes in a sol-gel matrix has been reported. l7 The photochromic properties of 2-(1,2-dimethyl-3-indoly1)-3-(2,4,5-trimethyl3-thieny1)maleic anhydride in poly(vinylbutyra1) film have been examined.l 8 1.2 Miscellaneous Reactions. 2.2.2 Addition Reactions - A novel photochemical reaction of stilbene in carbon tetrachloride solution has been described.’’ Irradiation of this system populates the first excited singlet state of stilbene which then abstracts a halogen from the solvent. The resulting radical pair composed of a trichloromethyl radical and (14) yields the products.
CI
(14)
H
Fischer and Wan report that the phenol derivatives (19,(16) and (1 7) undergo addition of water to the double bond when they are irradiated in acetonitrile/water solution.20 The study has shown that the hydrogen transfer occurs with the participation of a so-called water trimer. This process yields the zwitterion (18) that is responsible for the formation of the products [e.g.(19) from (15)]. The reactions are efficient withquantum yieldsin the0.1-0.24 region. Thephotohydrationofthediynes (20)has been examined indetail. Quenchingstudiesindicatethat the photohydration occurs from the excited singlet state of the alkyne in preference to the triplet. Four products, (21), (22), (23) and (24), are obtained from these hydrations. The ratio of C4:Cl hydration appears to besubstituentdependent and thevaluesobtainedareO.84 from (20, X=p-C02Me), 3.6 from(20, X =p-OMe), 0.12 from(20, X =rn-CF3)and0.73 from (20, X = p-CF3). A review has highlighted the photochemical reactions of conjugated polyalkynes. 22 As well as cis, trans-isomerism, irradiation of the cinnamylnaphthols (25) brings about photochemical cyclisation to afford the two products (26) and (27).23 Cyclization also occurs with phenyl derivatives such as (28).24Again the cyclizations follow two paths to yield a mixture of the cyclized derivatives (29) and (30). The influence on the photochemistry of substituent groups attached to the styryl moiety has been evaluated and it is evident that a charge transfer (CT) is involved and that the outcome of the reactions is solvent dependent. The CT in the excited state brings about a proton transfer followed by cyclization to yield the products (29) and (30) where the latter is predominant. When acetone is used as sensitizer no reaction is observed. The competition between dehalogenation and cyclization within the derivatives (31) has been studied.25 With the chloro and bromo derivatives fission of the halogen bond occurs and addition of solvent to the aromatic ring takes place.
IIl3: Photochemistry of Alkenes, Alkynes and Related Compounds
123
Yh
Ph
OH
HO
Wh@ II CH=C=CHC--BU'
@CH2C=C-But
x -
(22)
W \
OH
(23)
/ P
h
\
(24)
\
/
,.: R (26) R = H (55%) R = COCH3
R (25) R = H or CH3CO
/
R
(27)R = H (44%)
R = COCH3 (92%)
UR flR \
\
\
(28) R = Ph, Me, OMe
R
(29)
\ (31) R = CI or Br
(30)
Ph
1.2.2 Electron Transfer Processes - The use of photochemical single electron transfer processes has been made in an approach to the synthesis of naphthalones. The reaction involves irradiation of the en01 ether of a ketone such as (32) which yields the radical cation (33) that cyclizes onto the aryl ring.26
Photochemistry
124
(35)
0-TBDMS
(36)
'0
Elimination of the silyl group affords the final products (34). The reaction has been extended to provide a path to larger ring ketones such as the cyclization of (35) to yield (36) and also to the synthesis of spiro ketones (37) from (38). Other studies have sought to establish the scope and limitations of the photoNOCAS process. Thus Arnold and co-workers have examined the reactions of alkenes with 1,4-dicyanobenzene (DCB).27 A typical result from this reaction is shown in Scheme 1. All of the products arise from the attack of the radical cation of the alkene on the DCB sensitizer with loss of the cyano function. A further study of photo-NOCAS reactivity has demonstrated that the radical cation of 2,3-dimethylbut-2-ene, formed by irradiation in the presence of DCB/biphenyl, can be trapped by fluoride ion.**The resultant radical (39) reacts with the radical anion of DCB to yield the adduct (40). The radical cation of methylenecyclopropane (41) can be formed by irradiation in the presence of DCB as the ~ensi t i zer. ~~ The products are illustrated in Scheme 2 and, as shown, in all cases the cyclopropane ring remains intact. The diene (42) undergoes SET to dicyanobenzene as the sensitizer with biphenyl as the co-~ensitizer.~'In the absence of nucleophiles many products are formed such as (43) and (44)by reaction with the solvent acetonitrile or the sensitizer, respectively. In the presence of alcohols low yields of (45) and (46) are formed by reaction of the alcohol with the radical cation of the diene (42). A study of the cyclization of (aminoa1kyl)styrylamides has been rep~rt ed. ~' Medium sized-ring lactams can be prepared by irradiation of some N-(aminoalkyl)-2-stilbenecarboxamides.32A review has discussed the use of immobilized photosensitizers in organic photo~hemistry.~~ 1.2.3 Other Processes - The unfiltered irradiation of (47) in acetonitrile solution results in isomerization into (48) in reasonable yield.34The reaction is an example of a concerted 1,3-alkyl migration on an ally1 moiety. The authors claim this to be the first example of a rearrangement from a cembrane to the pseudoterdne
Ul3: Photochemistry of Aikenes, Alkynes und Reluted Compounds
CN
CN
CN
42%
23%
125
CN trace
Scheme 1
(41)
CN 5%
1 1Yo
13% Scheme 2
21%
8%
12%
-5' 6Me CN
0 (42)
(43) 2Yo
(44) 2%
CN
/
(45) 3%
(46) 2%
skeleton. Bentrude and co-workers previously reported the 1,3-allylic rearrangement of phosphites under electron transfer conditions3' and they have used this methodology in a further study.36Thus irradiation of (49) in acetonitrile solution using DCN as the sensitizer brings about conversion, via the radical cation, into the isomeric product (50). The study of the photochemical reactions of 1,3-diaryl-1,2-dihydropentalenes (5 1) has shown that irradiation transforms them into the isomers (52).37 It is proposed that this process occurs by a photochemical 1,5-hydrogen shift but concerted 1,Shydrogen migrations are
Photochemistry
126
(47)
OP(OEt)* (49)
@ A?
A?
required to be antarafacial on the skeleton and this is unlikely in this system. The same outcome could arise from two suprafacial 1,3-hydrogen migrations. A study of the photodissociation of chloroethene on irradiation at 193 and 210 nm has been reported.38 The photochemical decomposition of 1,l- and 1,2difluoroethene has also been studied using 193 nm light.39 Two studies have examined the photochemical decomposition of tri~hloroethene.~'One of these has utilized in situ NMR studies for the analysis of the system.40b 2
Reactions Involving Cyclopropane Rings
2.1 The Di-lt-methane Rearrangement and Related Processes - The di-nmethane reactivity of the 1,4-dienes (53) has been reported.41 The rearrangement occurs in either methanol or acetone and affords the cyclopropane derivative (54) as the major product. Other products include (55) and (56) from both (53a) and (53b). Another minor product (57) is forrned from (53b). While the reaction of (53) is fairly selective the photorearrangement of (58) affords many products. The authors reason that the preference for the formation of (54) is a result of the orientation of the phenyl moiety. The axial orientation is the one in which the 1,2-phenyl migration occurs most readily. The cyclopropane derivatives (55) could well be formed by a second photochemical step involving the rearrangement of the principal product (54). Other studies on the rearrangement of such systems have been described.42 Thus both the dienolactones (59) and (60)
127
IIl3: Photochemistry of Alkenes, Alkynes und Related Compounds
R 0
Ph
(54) a: 43% b: 48%
(53) a : R = R = H
b: R-R = (CH&
0
(55) a: 4% b: 80/0
Ph
(56) a: 5% b: 9%
Ph
k0k0 I
Ph
(611
Ph 0
(62)
6h
&o
Ph
(63)
undergo the di-x-methane conversion on irradiation in methanol to yield the rearrangement products (61), as a 1:l mixture of the 6a and the 6p isomers, from (59) and (62) and (63) from (60). The question of conformational control was discussed. Some enantioselectivity in the product (64)has been reported following the irradiation of the norbornadiene (65) in a TIY zeolite.43(-)-Ephedrine was used as the chiral inductor and sensitisation brought about the reaction in 30 min. An ee of about 14% was achieved. A study of the influence of electron-donating and electron-withdrawing substituents on the outcome of the di-x-methane reaction of some benzobarrelenes has been evaluated.4 George and co-workers have been studying the photochemical reactivity of systems such as (66) for a number of years?’ Irradiation of these dibenzobarrelenes yields the corresponding semibullvalenes and the structures of these photo-products have now been determined by X-ray crystallographic analysis. Other studies by the same group have examined the photoreactivity of (67).46 Direct irradiation in acetonitrile, benzene or p-xylene solution of the dibenzonorbornadiene derivative (68) affords the cyclooctatetraene (69) in 48% yield.47The reaction only arises from the singlet state and sensitized irradiation fails to yield a clean product. When the bis hydrochloride salt of (68) is irradiated in methanol using xanthene as the sensitizer the semibullvalene (70) is obtained. The photochemistry of (68) in the solid phase is completely different and irradiation yields only the pyrrole derivative (71). The authors suggest that steric effects within the crystal direct the reaction along this path. The barrelene (72a) undergoes efficient photorearrangement to the semibullvalene (73a).48 The reaction is best carried out in cyclohexane with 254 nm radiation. The yield of product (73a) is 94% and the isomeric barrelene (72b) is
Photochemistry
I28 COPh
COPh
But
(72) a: R'
= H, R2 = Ph b: R' = Ph, R2 = H
(73)a: R ' = But, R2 = H
b: R' = H, R2 = Bu'
also photoreactive by the same di-x-methane rearrangement path and yields (73b). A detailed review of the family of reactions related to and including the di-rcmethane rearrangement has been published.49
2.2 Other Reactions Involving Cyclopropane Rings. 2.2.I SET Induced Reactions The radical cation of phenylcyclopropane can be obtained by irradiation in the presence of chloranil as the electron accepting ~ensitizer.~' Armesto and his co-workers have studied the photochemical reactivity of the Sensitized imine (74) under both sensitized and electron transfer conditi~ns.~' irradiation using acetophenone in methylene chloride brings about conversion to the three products shown in Scheme 3. The reaction is proposed to take place by energy transfer to the 1,l -diphenyl alkenyl moiety followed by bridging to yield
M3: Photochemistry of Alkenes, Alkynes and Related Compounds
129
the biradical (75). This radical is the source of the primary photoproduct (76) which is converted during chromatography into the isolated products (77) and (78). A further product (79) survives the isolation procedures. Direct irradiation follows the same path and yields (77) and (78) as the isolable products. Single electron transfer with DCA yields the zwitterion (80) that has two possible forms. Reaction within this radical cation gives the products (77), (79) and another compound identified as (81). This last compound arises from hydrolysis of the structurally rearranged imine (82). Several other examples of this novel photochemical behaviour were reported.
(77) 82%
(74)
Ph Ph$ N Ph
-
Ph
Ph
" PhA
N
Ph
Ph
(79) 3%
(78) 11%
Scheme 3 Ph Ph Ph/$NyPfh9Lph "Ph
Ph
Ph
Ph
(75)
PhPh X
P NH2h
ex
P Phh
x
L
II
2.2.2 Miscellaneous Reactions Involving Three-membered Ring Compounds - The dichlorocyclopropylarenes (83) undergo photochemical ring opening via the corresponding radical cation.52 The intermediate is formed by irradiation of (83) at 300 nm in the presence of DCB as the sensitizer. When methanol is used as a co-solvent, addition occurs at the benzylic site to yield the adducts (84). The outcome of the reaction is somewhat substituent dependent as can be seen from the isolated yields shown below (84). The regiochemistry observed within this system is different from that reported from the irradiation of phenylcyclopropane under similar conditions when 1-phenyl-3-methoxypropanewas formed.53 The authors suggest that the controlling feature is the dichloro substituents. A review lecture has focused on the electron transfer photochemistry of strained-ring and unsaturated systems.54 The cyclopropane derivative (85) undergoes photochemical reduction when
rcl Photochemistry
130
Me0
Q
I&"
A
(83) R = OMe, Pr', Me, H, F, CI or CN
A
(84) R Yield (%)
Me0 Pr' Me H F
CI
CN
18 21 71 85
22 88 17
irradiated in a mixture of ethanol and a~etone.~' The reduction proceeds by way of the cyclopropyl radical intermediate (86) which cyclizes to yield a diastereoisomeric mixture of (87). The irradiation through Pyrex of solutions of (88) in cyclohexane affords the two products (89, 29%) and (90, 10Y0).The formation of (89) is clearly a result of radical attack on the solvent and involves hydrogen abstraction and bonding. An analogous reaction is observed when (88) is irradiated in pentane. A low temperature study has identified the biradical(91) as the key intermediate in the photochemical reaction.56
3
Reactions of Dienes and Trienes
Laser irradiation at 266 nm of the 2,5-dimethylhexa-2,4-dienein aerated acetonitrile affords the corresponding radical cation.57 Other less heavily substituted dienes do not undergo this process on direct irradiation and electron transfer sensitization has to be used. Typical of this process is the generation of the radical cation of piperylene by irradiation with dicyanobenzene as the sensitizer and biphenyl as the co-sensitizer. The presence of the co-sensitizer permits cage escape of the radical cation of the diene. A study of the photochemical ring
131
IIl3: Photochemistry of Alkenes. Alkynes und Reluted Compounds
opening of cyclohexa-1,3-diene has shown that the process is very rapid and occurs within 250 fs.'* The azepines (92) undergo photoisomerization, a typical reaction of such trienes, into the bicyclic derivatives (93).'9 Substitution dependent reactivity has been observed on irradiation of the differently substituted dienes (94) and (9S).60 The diester (94) undergoes the more usual isomerization, as observed for (92), to yield the cyclobutene derivative (96). The mono-ester, as the optically active compound (+)-(99, however, affords a good yield (77%) of the bicyciobutane (+)-(97). In this case crossed addition occurs within the diene.
(92) (93) R = OEt, NH2 or NMQ
(94) R=C@Me (95) R = H
(96) R=C@Me
(97)
Okoyuma et al. have reported that the strained Dewar paracyclophanes (98) can be converted into the benzenoid parent compounds (99) by irradiation of the compounds in a diethylether-isopentane glass at 77 K using 365 nm light.6' Interestingly when (99, R' = CN, R2 = H) is allowed to thaw to room temperature there is a thermal reaction that converts it back into the Dewar form which provides the first observation of such a thermal cyclization. Irradiation at 254 nm of the tetraene (loo), a bis-Dewar benzene, at 77 K in a matrix results in its conversion into the paracyclophane (10 1).62Continued irradiation transforms (101) into the (4+4)-adduct (102). The products from this low temperature
(98) R'
= CN,
R2= H
R1 =CN, R2=Me
I32
Photochemistry
irradiation were not isolable. A theoretical study of the phototransformations of the radical cation of cyclooctatetraene has been published.63ab initio Calculations have been used to study the photochemical reactivity of the protonated Schiff's base, 4-cis-y-methyl-nona-2,4,6,8-tet raeniminium ion.64 The photocycloreversion of the cage compounds (103) and (104) affords the corresponding naphthalenes q~antitatively.~~ Noh et al. have described the photochemical dissociation of the adducts (105)? Benzophenone-sensitized irradiation of the cyclobutene derivative (106) in acetonitrile solution results in the formation of a diene.67The reaction mixture is subsequently heated in xylene at 150 "C whereby the dimer (107) was obtained. Irradiation of the silacyclobutene (108) at 193 nm brings about ring opening with the formation of the silene ( 109).68 Various studies were carried out including the effects of solvent on the lifetime of the siladiene (109) and also its reactivity with alcohols. Leigh and coworkers have also reported that the irradiation of the disilacyclobutane derivative (1 10) at -196 "C in methylcyclohexane affords the silene (1 11) as the principal product.69 The silene can be trapped when the irradiations are carried out in the presence of buta-l,3-diene when (1 12) and (1 13) can be isolated. 2,2'-Biadamantylidene is also formed under these conditions. Similar behaviour was observed for the analogous 1,2-digermacyclobutanederivative.
(104) R = H or CN
(105) R = C02Me or CN
C02R2 C02R2 (106) R' = CHMe2, R2 = Me
(Me3Si)2Si-SicSiMe&
(110)
(111)
(112)
(113)
A study of the photochemical behaviour of the diene (114) using DCA as the sensitizer has shown that a degenerate Cope process is ~perative.~' This treatment affords a mixture (52:48) of the two dienes (1 14) and (1 1 9 , and a detailed study of this reaction has been carried out. 1 , l -Diphenylhepta-l,6-diene(1 16) undergoes photocyclization to give the radical cation (1 17) which cyclizes via the sixmembered transition state shown in (1 18).7' This intermediate is trapped by attack of acetonitrile to yield ultimately the adduct (1 19) which is formed in
133
IIl3: Photochemistry of Alkenes, Alkynes and Reluted Compounds
competition with (120) formed by the addition of water. Nitriles other than acetonitrile can be used effectively as traps for the cyclized radical cation (I 18). The reaction fails when the chain linking the two alkene moieties is shortened. Thus with (121) only the alcohol (122) is formed. Further examples of the intramolecular electron transfer photochemistry of compounds sucF as (1 23) have been reported.72 The first examples of this type of reaction were described by Armesto, Horspool and co-workers some years The present report gives further examples of the conversion of (123) into the cyclobutene (124), the principal photochemical product, and the fragmentation products (125) and ( 126).72 Ph
-f>
Ph /
/
Ph
Ph$
Ph& Ph
NHCOMe
Ph
NC
CONH2 (124)
R' R2 R3 Pri Pr' Ph Ph Ph Ph
H H H H H H
(126) (yield YO) (124) (125) (126)
(125)
Ph Me Ph Me Ph H
X C02Et C02Et C02Et C02Et COPh CN
26 49 29 29 21 23
-
-
11 20 17 17
-
-
10 8 13 22
Yoon and Chae have examined the photochemical reactivity of the cyclopentadiene derivatives (127) under DCA sensitized condition^.^^ Irradiation brings about the formation of several products but only the anti-Bredt adduct (128) is different from those obtained by thermal reactions. The data suggest that the
I34
Photochemistry
(127) n = 2 O f 3
(128) n=2(12%) n = 3 (13%)
(132) Ar = pMeOC6H4
adducts (1 28) are formed via a triplex intermediate, such as that shown in (129), with interaction between the diene, the alkene and the sensitizer. While the irradiation involves a mixture of the cyclopentadienes it is likely that the anti-Bredt products are formed exclusively from the 2-isomer (130). Irradiation of the vinylbenzofuran (13 1) in the presence of I ,3-dienes such as cyclohexa-l,3-diene and the pyrilium salt (132) results in the formation of adducts such as (1 33).75As well as the formation of the Diels-Alder product, cycloaddition to afford cyclobutane derivatives is observed. The authors propose that the reactions involve electron transfer processes resulting in radical cations that undergo the addition to the dienes. Calculations have been carried out that support these findings. The deactivation of the excited singlet state of the triene (134) by charge transfer processes has been studied in The influence of substituents on the spectroscopic properties of the triene (134) has also been studied.77 Other workers have demonstrated substituent effects on the cis-trans isomerism of (1 35) to give (136).78The quantum yield for this isomerism was enhanced when the substituents were polar. Contrary to this effect the isomerism to (137) was
(134)
(135) R = CN, Me02C, CHO, CI, CH3, OCH3
IIl3: Photochemistry of Alkenes, Alkynes and Related Compounds
135
enhanced when the substituents were electron donating. Tsujimoto and coworkers have observed that 11-methylretinochrome can be photochemically converted into 1 1-cis-1 1-methylretinochrome in 90% yield.79 This product is accompanied by the 13-&isomer and the all-trans-isomer. Other accounts have reported calculations dealing with the photoisomerism of retinals and protonated Schiff's bases8' Evenzahav and Turro have studied in considerable detail the photochemical cyclizations encountered with the diynes (1 38) and (139) in propan-2-01.~' This work was originally published in note form.82Direct irradiation of the diyne (138) results in the formation of the products shown in Scheme 4. These products are obtained in ratios of 2:4:2: 1. Irradiation of (139) gives the cyclized product (140) exclusively. From a series of investigations using triplet sensitization and laser flash studies it was concluded that a biradical mechanism was involved.
PiOH
+
__c
Scheme 4
The distyrylbenzene derivative (1 4 1) is photochemically reactive on irradiation in solution.83The solvent of choice is acetonitrile/benzene/water(7:2: 1) saturated with ammonia. The reactions encountered with this system are derived from electron transfer initiated by pdicyanobenzene as the electron accepting sensitizer. This process yields the radical cation (142) of the starting material and also the cyclized radical cation (143). These species are trapped by ammonia to yield the final products (144) and (145) in the yields shown. The naphthyl system [141, R-R = (CH=CH)z] is also reactive and affords the analogous products (146) and (147). A study has examined the photochemically-induced cyclization of tetraenes such as (148) under SET conditions in aqueous acetonitrile solution.84 A variety of electron accepting sensitizers was used. In the example cited the sensitizer (149) was effective and the cascade cyclization yielded the product (150). 3.1 Vitamin D Analogues - The analogues (1 5 1) of pre-vitamin D3 have been synthesised and their irradiation in THF solution at wavelengths around 300 nm brings about cis,trans-is~merism.~~ Cyclization to (152) is also observed and in this process there is a wavelength and excited state dependence. Thus with
136
Photochemistry
Ph
Ph
[q--'] lTph -
(142)
-
:
Ph (143)
(144) (146)
Ph
R = H (37%) R-R = (CH=CH)z (31%)
(151) R = H or
Me
q
-
-
p
h
Ph (145) R = H 30% (147 R-R = (CHSH);! (23%)
(152)
irradiation using h > 309 nm the first singlet state is involved while with h < 306 nm the second excited singlet state is involved. Photochemical transformations of previtamin D at low temperatures (90 K) has shown that there are slight differences in the rate of ring opening of (153) into (1 54) dependent upon the wavelength used.86 Further irradiation of the triene (1 54) leads to the formation of the more stable conformer (1 55). A detailed study of this isomerization has shown that the methyl group and the hydroxyl function
@ HO
p
1113: Photochemistry of Alkenes, Alkynes und Related Compounds
137
reorient themselves without leaving the plane of the system. A study of the wavelength dependence of the photochemical processes of previtamin D has been published.87The effect of solvents on the outcome of previtamin D photoreactions has been studied.88The quantum efficiency of the formation of previtamin D3 has been determined following irradiation of provitamin D3 in THF solutions of some copolymer^.^^ The study included an examination of the influence that polymers have on excimer formation and energy migration within the system. 4
(2+2)-Intramolecular Additions
The propellaprismane (156) has been synthesized by the intramolecular (2+2)photocycloaddition of the diene (157).90 Interest in the synthesis of cage compounds such as (158) continues. This particular example is produced on irradiation of the triene (159) through quartz in a mixture of acetone and benzene.” The reaction is chemically efficient and the product is formed in 80% yield.
The copper(1) catalysed photo-cycloaddition reactions of the dienes (160) have been studied.92This process provides an efficient route to the (2+2) cycloadducts (160a) in the ratios and yields shown under the appropriate structures. These adducts are key components in an approach to the synthesis of A9(’*)-capnellene. Copper triflate controlled photocycloadditions have also been used as a key step in the synthesis of some cy~lopentanes.~~ The reaction involves the cyclization of the dienes (161) under the copper(1) controlled conditions into the adducts (162) and this is followed by thermal reactions that bring about rearrangement and ring opening. The radical cation of (163) can be formed by electron transfer photochemistry and in methanol addition products are formed.94 A study of the photochemical reactivity of some novel 3-phenylnorbornadienes has been reported.” Bichromophoric norbornadiene derivatives have also been synthesized and studied photoA study of the photoisomerization of some norbornadienes has ~h emic ally .~~ been carried out within the constrained environment of P-cy~lodextrin.~~ The bichromophoric system (1 64) undergoes intramolecular electron transfer by a through-bond mechanism on i r r a d i a t i ~ n .The ~ ~ transfer is from the benzidine
138
Photochemistry Me,, R’OEt
(160) R’ R2 Me Me
Me
Me
Me
(1 60a)
Yield (%I 41
53
p~~52
PhCH2 4%e
52
8x0:
endo
2.5: 1 0 : 100 2.2: 1 3: 1
0 H
(162) R’ R2 n n = l n=2 a: Me Me 1 or2 50 46 b: Me CH2CH2Ph 1 or2 59 45 C: Me CH2Ph 1 or2 70 40 d: -(CH2)41 or2 45 58 e: -(CH2)5l o r 2 60 57
moiety to the norbornadiene and occurs with 12% efficiency. The ultimate intermediate is the triplet radical ion pair. Several copper(1) based photosensitizers have been synthesized in an attempt to improve the norbornadiendquadricyclane solar energy storage system.*
Me
5
Me
Dimerization and Intermolecular Additions
Interest in reactions within constrained environments continues apace. A report has described the results of irradiating complexes of the stilbene (7) with ycy~lodextrin.~ Rather than cis, trans-isomerization, dimerization occurs to afford (165) and (166) in 79% and 19% yield, respectively. These results are different
1113: Photochemistry of Alkenes, Alkynes and Related Compounds
139
from those obtained by irradiation in aqueous solution when the isomerization occurs as the major process. Only low yields the dimers (165) and (166) are obtained under these conditions. Other workers studying the photoreactions of terpenes have demonstrated that the type of cyclodextrin used can also affect the outcome of these processes.'00
The synthesis of so-called paddlanes has been reported following the irradiation of the divinylbenzene derivative (1 67).1°' The product isolated from this reaction was identified as the cycloadduct (1 68), and interestingly this intermolecular cycloaddition only occurs with the o-divinyl moiety: the corresponding pderivative fails to yield the excepted product. The intermolecular photocycloaddition, brought about by irradiation through Pyrex of a benzene solution, of the diene (169) results in the formation of the adducts (1 70) and (17 1) in 15 and 13% yield, respectively.lo*
(170)
The photochemical dimerization of acenaphthylene (172) at 435.8 nm has been studied.lo3 The reaction generally affords both the cis,syn,cis-dimer and the cis,anti,cis-dimer. Intersystem crossing from the S1 state occurs with low efficiency and the ratio of the dimers produced is solvent dependent. If the reaction is carried out in concentrated solution the singlet state adds to ground state acenaphthylene and yields the cis,syn,cis-dimer exclusively. Irradiation at wavelengths > 500 nm of a 1:1 mixture of acenapthylene and tetracyanoethylene in acetonitrile or dichloromethane fails to yield a product.'04 This failure is interesting since it is clear that a CT complex is formed with an absorption extending to 700 nm. The authors report that acenapthylene and the tetracyanoethylene can be cocrystallized and that irradiation of such crystals at
140
Photochemistry
wavelengths > 500 nm results in the exclusive formation of the (2+2)-cycloadduct identified as (173). The quantum yield for the formation of this adduct is 4 x The reaction in the crystal is thought to involve an electron transfer process with the generation of a radical ion pair. Irradiation of acenaphthene on silica gel at the gel air interface results in the formation of l-a~enaphthenol.'~~
Photochemical cycloadditions of the alkyne (174) to the dienedione (175) occurs sequentially and affords the two adducts (1 76) and (1 77).Io6 The latter was chemically transformed into the [ 1 . 1 Jparacyclophane (1 78) which was then studied photochemically. The photochemical cycloaddition of ethyne to the dehydrodoanthracene (1 79) results in the formation of the (2+2)-cycloadduct (1 80). Io7 A study of unti-o,o'-dibenzene (1 81 a) has shown that on irradiation bond cleavage occurs with the formation of excited state benzene.'" The related compound (1 8 1 b) is also photoreactive and on irradiation through a Vycor filter gives benzene and phenyl acetate. 0
gR 4 gR "
(174)
R
R
(175)
/
/
0
R
0
X
Ul3: Photochemistry of Alkenes, Alkynes and Related Compounds
141
(181) a : R = H
b: R = AcO
6
Miscellaneous Reactions
6.1 Miscellaneous Rearrangements and Bond Fission Processes - Full details of the photochemical reactivity of 1,3-dichloro-1,3-diphenylpropane have been p~blished.'~'Nagahara et al. have reported several examples of the photochemical conversion of alkyl iodides into esters."' This reaction is achieved by irradiation for 15 hours through Pyrex of an alkyl iodide in an alcohol under a pressure of 20 atm of carbon monoxide. If the reaction is carried out in the presence of a base such as potassium carbonate then good yields of product are obtained. The conversion of 2-iodooctane, for example, gives the ester (182) in 72% yield. In the absence of a base the reaction fails. Several alcohols were used such as benzyl alcohol, cyclohexanol and chloroalcohols. An acyl radical is the key intermediate and is formed by the trapping of the alkyl radical by carbon monoxide. Sonoda and Yanagi have patented this process.'I The patent reports that the irradiation for 16 hours of 5-iodononane in ethanol under a pressure of 40 atmospheres of carbon monoxide affords ethyl 2-butylhexanoate. The photochemical dissociation at 304 nm of methylene iodide has been studied.'I2
'
The product (183) is formed on irradiation of acridine (184):phenothiazine (185) crystals in which the ratio of the reactants is 3:4.'13 This reactivity is different from the solution phase (in acetonitrile) process which affords both (183) and the dihydro dimer (186). The photoinduced electron transfer reactions of some a-silyl ethers has been investigated. I4 The sensitizing system uses DCA/ biphenyl and irradiation at h > 345 nm in acetonitrilelmethanol. The irradiation brings about the formation of the radical cation (187) of the ether which undergoes cleavage to yield the radical (1 88), a hydroxymethyl equivalent. When these are generated in the presence of a$-unsaturated esters such as (189) addition takes place affording the adducts (190). Additions to dimethyl maleate were also carried out successfully. l4 High yields of alcohols can be obtained on irradiation of the ether derivatives (19 l).' l 5 The ethers in acetonitrile/water solution are photo-cleavable on irradiation at 254 nm or 300 nm and the yields obtained are good to excellent. The multi-photon chemistry of the naphthalene derivative (192) has been studied
'
'
Photochemistry
142
R.oATMs
-
-
+* [.-,ATMS] R.
(1 87) R = Me, PhCH2, TIPS or TBDMS
HH::3
00. (1 88)
Me
(1 89)
= Me (46%), R = TIPS (25%) R = PhCHP (64%), R = TBDMS (42%)
(190) R
using laser-jet irradiation at 333, 351 and 364 nm.'I6 The naphthalene (193) is obtained in 26% in a two-photon process when (192) is irradiated in carbon tetrachloride. Irradiation of Mannich bases such as (193) in acetonitrile/water solution using h c 300 nm induces the formation of the o-quinomethide intermediate (195) which is then readily trapped in a Diels-Alder reaction by ethoxyethene to give the adduct (196) in 71% yield.Il7 The use of wavelengths ca. 300 nm is less aggressive than the 254 nm irradiation of diols such as (197) that has been reported in past by Wan and his co-workers. The influence of the position of the aryl substituent in (194) was also investigated and it was shown that the best yields were obtained when the phenyl group was in the meta-position to the hydroxyl substituent. Other systems such as (198) and (199) were also studied. Wan and co-workers have previousIy shown that it is possible to generate o-quinone methides photochemically. Their recent account described such a reaction where the resultant quinone methide has a suitable electron rich dienophile substituent and this leads to Diels-Alder trapping. ** Photosolvolysis, using irradiation from a ruby laser or a flashed xenon lamp, of the cycloheptatrienes (200) results in the formation of the aryltropylium ions (2Ol).Il9 The lifetime of these species is dependent upon the substituent in the aryl ring. A study of the reactivity induced by irradiation at 254 nm of the epoxides (202) has been carried out.'*' The aim was to study the formation of the ylides (203). The reactions were carried out in acetonitrile solution with ethyl vinyl ether as the addend and are reported to be dependent to some extent on the substitution pattern. Thus, irradiation of (202a) fails to yield an adduct and only the enone (204, 33"/0) is formed. Epoxides (202b) and (202c) do produce ylides that add to the alkene to yield mixtures of the adducts (205) regiospecifically with a preponderance of the exo-adduct. The epoxide (202d) is also reactive and gives a low yield of the adduct (206, 2%). In general the overall yields are moderate. The
IIl3: Photochemistry of Alkenes, Alkynes and Related Compounds
143
photochemical reactivity of the 3-( 1 -naphthyl)-2-(1 -naphthalenemethyl)oxaziridine has been studied by benzophenone sensitized irradiation in acetonitrile or benzene.12' Ph O-R
(191) R = PhCH2CH2, Ph,-
gMe2 H:&
\
OH
\
\
R'
(202) R2
Q 0
R3QR1
R2
/
Ar
(204) 33%
n
a:H H b: CN H c: CN Me d: CN H
1 1 1
2
NC
CN
R'
(205) R' = H, R2 = OEt, R3 = H 36% R' = H, R2 = H, R3 = OEt 8% R' = Me, R2 = OEt, R3 = H 25% R' = Me, R2 = H, R3 = OEt 7%
OEt
N&
(206)2%
144
Photochemistry
Suzuki and co-workers have examined the influence of substituents on the outcome of some photochemical ring opening reactions involving SET sensitiOne of the reactions studied is the photochemical ring opening of the acetal (207). Following the photochemical reaction the mixture is treated with HCVMeOH and separated to yield the two products shown in Scheme 5. The relative quantum yields shown under the reaction sequence illustrates the influence of increasing substitution by methyl groups of the viability of 1,4dicyanobenzene and derivatives as SET sensitizers in this reaction.
relative 6 l,.Q-DCB 1 2-MeDCB 2 2,CidiMeDCB 2.3 0.8 2,3,5-triMeDCB 2,3,5,6-tetraMeDCB 0
Scheme 5
7 1.
2. 3.
4. 5. 6.
7. 8.
9. 10. 11.
12. 13. 14.
References T. Sugimura, H. Shimizu, S. Umemoto, H. Tsuneishi, T. Hakushi, Y. Inoue and A. Tai, Chem. Lett., 1998, 323. R. E. Martin, J. Bartek, F. Diederich, R. R. Tykwinski, E. C. Meister, A. Hilger and H. P. Luthi, J. Chem. Soc., Perkin Trans. 2, 1998,233. D. Marquis, B. Henze, H. Bouas-Laurent and J. P. Desvergne, Tetrahedron Lett., 1998,39, 35. I. Lukac, Cs. Kosa, U. Salz and N. Moszner, J. Photochem. Photobiol., A , 1997,110, 23 (Chem. Abstr., 1998,128, 8652). A. Meyer, J. Schroeder, J. Troe and M. Votsmeier, J. Photochem. Photobiol. A, 1997, 105,345 (Chem. Abstr., 1997,127, 197600). V. Papper, D. Pines, G. Likhtenshtein and E. Pines, J. Photochem. Photobiol., A , 1997,111,87 (Chem. Abstr., 1998,128, 108252). W. Herrmann, S. Wehrle and G . Wenz, J. Chem. SOC.,Chem. Commun., 1997, 1709. W. Hermann, M. Schneider and G. Wenz, Angew. Chem. Int. Ed. Engl., 1997, 36, 2511. J. Saltief, Y. Zhang and D. F. Sears, Jr., J. Am. Chem. Suc., 1997, 119, 1 1202. E. J. Shin, E. Y. Bae, S. H. Kim, H. K. Kang and S. C. Shim, J. Photochem. Photobiol. A , 1997,103, 137 (Chem. Abstr., 1997,127,255092). G . G. Aloisi, F. Elisei, L. Latterini, G. Marconi and U. Mazzucato, J. Photochem. Photobiol., A, 1997,105,289 (Chem. Abstr., 1997,127,212339). T . Arai, Y. Hozumi, 0. Takahashi and K. Fujimori, J. Photochem. Photobiol., A , 1997, 104, 85 (Chem. Abstr., 1997, 127, 128590). M. Takeshita and M. Irie, Tetrahedron Letl., 1998,39,613. (a) M. Takeshita, C. N. Choi and M. Irie, J. Chem. Soc., Chem. Commun., 1997,
1113: Photochemistry of Alkenes, Alkynes and Reluted Compounds
15. 16. 17.
18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33.
34. 35. 36. 37. 38. 39. 40 41. 42. 43. 44. 45.
I45
2265; (b) M. Irie, T. Lifka and K. Uchida, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A, 1997,297,81 (Chem. Abstr., 1997,461728). S. Wu, Huaxue Jinzhan, 1997,9, 160 (Chem. Abstr., 1997,501188). M. hie, T. Eriguchi, T. Takada and K. Uchida, Tetrahedron, 1997,53, 12263. J. Biteau, G. Tsivgoulis, F. Chaput, J.-P. Boilot, S. Gilat, S. Kawai, J.-M. Lehn, B. Darracq, F. Martin and Y. Levy, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A , 1997,297,65 (Chem. Abstr., 1997,461725). T. Tsujioka, M. Kume and M. hie, J. Photochem. Photobiol., A , 1997, 104, 203 (Chem. Abstr., 1997,127, 142664). K. Twata and H. 0. Hamaguchi, Bull. Chem. SOC.Jpn., 1997,70,2677. M. Fischer and P. Wan, J. Am. Chem. SOC.,1998,120,2680. S. C. Shim, Y. S. Chae and E. K. Baek, Bull. Korean Chem. SOC., 1997, 18, 364 (Chem. Abstr., 1997,127,63358). S. C. Shim, Mol. Supramol. Photochem., 1997, l(0rganic Photochemistry), 1 1 1 (Chem. Abstr., 1998, 128,204462). M. C. Jiminez, P. Leal, M.A. Miranda, J. C. Scaiano and R. Tormos, Tetrahedron, 1998,54,4337. M. C. Jimenez, M. A. Miranda and R. Tormos, Tetrahedron, 1997,53, 14729. M. C. Jiminez, M. A. Miranda and R. Tormos, J. Org. Chem., 1998,63,1323. G. Pandey, M. Karthikeyan and A. Murugan, J. Org. Chem., 1998,63,2867. D. R. Arnold, K. A. McManus and M. S. W. Chan, Can. J. Chem., 1997,75,1055. M. S. W. Chan and D. R. Arnold, Can. J. Chem., 1997,75,1810. H . J . P. De Lijser, T. S. Cameron and D. R. Arnold, Can. J. Chem., 1997,75, 1795. H. J. P. De Lijser and D. R. Arnold, J. Chem. SOC.,Perkin Trans. 2, 1997,1369. F . D. Lewis, J. Wagner-Brennan and J. M. Denari, J. Photochem. Photobiol. A , 1998,112, 139 (Chem. Abstr., 1998,128,237101). F. D. Lewis and S. G. Kultgen, J. Photochem. Photobiol. A , 1998, 112, 159 (Chem. Abstr., 1998,128,250519). M. Julliard, Photosci. Photoeng., 1997, 2 (Homogeneous ), 22 1 (Chem. Abstr., 1998, 128,167004). A. D. Rodriguez and J.-G. Shi, J. Org. Chem., 1998,63,420. S. Ganapathy, K. P. Dockery, A. E. Sopchik and W. G. Bentrude, J. Am. Chem. SOC.,1993, 115,8863. G. S. Jeon and W. G. Bentrude, Tetrahedron Lett., 1998,39,927. V . Nair, G. Anilkumar, C. N. Jayan and P. N. Rath, Tetrahedron Lett., 1998, 39, 2437, K. Tonokura, L. B. Daniels, T. Suzuki and K. Yamashita, J. Phys. Chem. A,, 1997, 101,7754. B. A. Balko, J. Zhang and Y. T. Lee, J. Phys. Chem., 1997,101,661. (a) K.-H. Wang, H.-H. Tsai and Y.-H. Hsieh, Chemosphere, 1998, 36, 2763 (Chem. Abstr., 1998, 238326); (b) S. J. Hwang, C. Petucci and D. Raferty, J. Am. Chem. SOC.,1997, 119,7877. 0.Muraoka, G. Tanabe and Y. Igaki, J. Chem. Soc., Perkin Trans. 1,1997,1669. 0. Muraoka, G. Tanabe, E. Yamamoto, M. Ono, T. Minematsu and T. Kimura, J. Chem. SOC.,Perkin Truns. 1, 1997,2879. A. Joy, R. J. Robbins, K. Pitchumani and V. Ramamurthy, Tetrahedron Lett., 1997, 38,8825. R. Altundas and M. Balci, Aust. J. Chem., 1997,50,787. M. Muneer, N. P. Rath and M. V. George, Acta Crystallogr., Sect. C: Cryst. Struct. Commun., 1997, C53, 1475 (Chem. Abstr., 1997,127,324685).
146 46. 47. 48. 49. 50. 51. 52. 53. 54. 55.
56. 57. 58. 59. 60. 61. 62. 63.
64. 65.
66. 67. 68. 69. 70.
71. 72. 73. 74.
Photochemistry
S. A. Kumar, D. Ramaiah, N. V. Eldho, S. Das, N. P. Rath and M. V. George, J. Photochem Photobiol. A, 1997,103,69 (Chem. Abstr., 1997,127,72886). J. R. Scheffer and H. Ihmels, Liebigs Ann.lRecl., 1997, 1925. V. Nair, G. Anilkumar, J. Prabhakaran, D. Maliakal, G. K. Eigendorfand P. G. Williard, J. Photochem. Photobiol. A, 1997, 111, 57 (Chem. Abstr., 1998, 128, 121515). H. E. Zimmerman and D. Armesto, Chem. Rev., 1996,96,3065. W. Bergmark, S. Hector, G. Jones, 11, C. Oh, T. Kumagi, S. Hara, T. Segawa, N. Tanaka and T. Mukai, J, Photochem. Photobiol., A , 1997,109, 119 (Chem. Abstr., 1997,312964). D. Armesto, 0.Caballero and U. Amador, J. Am. Chem. Soc., 1997,119,12659. J. Y. Wu, J, C. Mai, K. Pan and T. I. Ho, Tetrahedron Lett., 1998,39,647. V. R. Rao and S. S. Hixson, J. Am. Chem. SOC.,1979,101,4658. H. D. Roth, H. Weng, D. Zhou and T. Herbertz, Pure Appl. Chem., 1997, 69, 809 (Chem. Abstr., 1997,430018). L. V. Sydnes and H. H. Ovrebo, Acta Chem. Scand., 1997, 51, 889 (Chem. Abstr., 1997,127,247789). W. T. Pan, M. Jones, B.Esat and P. M. Lahti, Tetrahedron Lett., 1998,39, 1505. C . S. Q. Lew, J. R. Brisson and L. J. Johnston, J. Org. Chem., 1997,62,4047. S . H. Pullen, N. A. Anderson, L. A. Walker, I1 and R.J. Sension, J. Chem. Phys., 1998,108,556. R. A. Odum and B. Schmall. J. Chem. Res., Synop., 1997,276 (Chem. Absfr., 1997, 127,220537). W. Tochtermann, T. Panitzsch, M. Peschanel, C. Wolff, E. M. Peters, K. Peters and H. G. Von Schnering, Liebigs AnnJRecl., 1997, 1125. M. Okoyuma, M. Ohkita and T. Tusji, J. Chem. SOC.,Chem. Commun., 1997,1277. T. Tsuji, M. Ohkita, T. Konno and S. Nishida, J. Am. Chem. SOC.,1997,119,8425. T. Bally, L. Truttmann and F. Williams, THEOCHEM, 1997, 398-399,255 (Chem. Abstr., 1997, 127,292776). M. Garavelli, T. Vreven, P.Celani, F. Bernardi and M. A. Robb, J. Am. Chem. Soc., 1998,120, 1285. T. Noh, D. Kim and S. Jang, Bull. Korean Chem. SOC.,1997,18, 357 (Chem. Abstr., 1997,127,65371). T. Noh, H. Lim and D. Kim, Bull. Korean Chem. SOC.,1997,18,247 (Chem. Abstr., 1997,126,330354). Y. Nakajima, H. Watanabe, T. Adachi and H. Hotta, Jpn. Kokai Tokkyo Koho, JP 09,278,711 (Chem. Abstr., 1998,128,3483). C . Kerst, M. Byloos and W. J. Leigh, Can.J. Chem., 1997,75,975. Y . Apeloig, D. Bravo-Zhivotovskii, I. Zharov, V. Panov, W. J. Leigh and G. W. Sluggett, J. Am. Chem. Soc., 1998,120,1398. H. Ikeda, T. Minegishi, H. Abe, A. Konno, J. L. Goodman and T. Miyashi, J. Am. Chem. SOC.,1998,120,87. H. Ishii, T. Hirano, S. Maki, H. Niwa and M. Ohashi, Tetruhedron Lett., 1998, 39,2791 . D. Armesto, A. Albert, F. H. Cano, N. Martin, A. Ramos, M. Rodriguez, J. L. Segura and C. Seoane, J. Chem. SOC.,Perkin Trans. 1, 1997,3401. D. Armesto, W. M. Horspool, N. Martin, A. Ramos and C. Seoane, J. Chem. SOC., Chem. Commun., 1987, 1231; D. Armesto, W. M. Horspool, N. Martin, A. Ramos, C. Seoane, J. Org. Chem., 1989,54,3069. H. Yoon and W. Chae, Tetrahedron Lett., 1997,38,5169.
1113: Photochemistry of Alkenes, Alkynes and Related Compounds
147
77.
J. Botzem, U. Haberl, E. Steckhan and S. Blechert, Acta Chem. Scand, 1998,52, 175 (Chem. Abstr., 1998,128, 180292). F. Schael, J. Kuester and H.-G. Loehmannsroebben, Chem. Phys., 1997, 218, 175 (Chem. Abstr., 1997, 127, 101641). G. Pistolis and A. Malliaris, Chem. Phys., 1998, 226, 83 (Chem. Abstr., 1998, 128,
78. 79. 80.
Y. Sonada, H. Morii, M. Sakuragi and Y.Suzuki, Chem. Lett., 1998,349. K. Tsujimoto. Y. Shirasaka, T. Mizukami and M. Ohahsi, Chem. Lett., 1997,813. M. Garavelli, T. Vreven, P. Celani, F. Bernardi and M. A. Robb, J. Am. Chem. SOC.,
75. 76.
167113).
1998,120,1285. A. Evenzahav and N. J. TUKO,J. Am. Chem. SOC.,1998,120,1835. N. J. Turro and A. Evenzahav, TetrahedronLett., 1994,358089. R. Kojima, T. Shiragami, K. Shima, M. Yasuda and T. Majima, Chem. Lett., 1997, 1241. 84. H. Goerner, K.-D. Warzecha and M. Demuth, J. Phys. Chem. A , 1997,101,9964. 85. W. G . Dauben, B. L. Zhou and J. Y.L. Lam, J. Org. Chem., 1997,62,9005. 86. A. M. Muller, S. Lochbrunner, W. E. Schmid and W. Fuss, Angew. Chem. Int. Ed. Engl., 1998,37,505. 87. W. Fuss and S. Lochbrunner, J. Photochem. Photobiol., A , 1997, 105, 159 (Chem. Abstr., 1997,127,212325). 88. 0. G. Dmitrenko, I. P. Terenetskaya and W . Reischl, J. Photochem. Photobiol., A, 1997,104, 113 (Chem. Abstr., 1997,127, 128594). 89. M. Nowakovska and J. E. Guillet, J. Photochem. Photobiol. A, 1997, 103, 189 (Chem. Abstr., 1997,127,240810). 90. S. Brand and R. Gleiter, TetrahedronLett., 1997,38,2939. 91. C.-T. Lin, N.-J. Wang, H.-Z. Twng and T.-C. Chou, J. Org. Chem., 1997,62,4857. 92. S. Samajdar, D. Patra and S. Ghosh, Tetrahedron, 1998,54,1789. 93. A. Haque, A. Ghatak, S. Ghosh and N. Ghoshal, J. Org. Chem., 1997,62,5211. 94. S. McIlroy, H. Weng and H. D. Roth, J. Phys. Org. Chem., 1997, 10, 607 (Chem, Abstr., 1997,645863). 95. V. A. Chernoivanov, A. D. Dubonosov, V. A. Bren, V. I. Minkin, A. N. Suslov and G. S. Gennadii, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A , 1997,297,239 (Chem. Abstr., 1997,127, 212365). 96. V. A. Bren, V. I. Minkin, A. D. Dubonosov, V. A. Chernoivanov, V. P. Rybalkin and G. S. Gennadii, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A , 1997, 297, 247 (Chem. Abstr., 1997,127, 212366). 97. M. Maafi, J.-J. Aaron and C. Lion, J. faclusion Phenom. Mol. Recognit. Chem., 1998,30,227 (Chem. Abstr., 1998,166730). 98. C.-H. Tung, L.-P. Zhang, Y. Li, H. Cao and Y. Tanimoto, J. Am. Chem. SOC.,1997, 119,5348. 99. F. Franceschi, M. Guardigli, E. Solari, C. Floriani, A. Chiesi-Villa and C. Rizzoli, Inorg. Chem., 1997,36,4099. 100. 0.A. Luzina, L. E. Tatarova, D. V. Korchagina, N. F. Salakhutdinov and V. A. Barkhash, Russ. J. Org. Chem., 1997,33, 183 (Chem. Abstr., 1998,72521). 101. Y. Nakamura, Y. Hayashida, Y. Wada and J. Nishimura, Tetrahedron, 1997, 53, 4593. 102. Y. Okada, M. Hagihara, M. Mineo and J. Nishimura, Synlett, 1998,269. 103. N. Haga, H. Takayanagi and K. Tokumaru, J. Org. Chem., 1997,62,3734. 104. N. Haga, H. Nakajima, H. Takayanagi and K.Tokumaru, J. Chem. SOC.,Chem. Commun., 1997, I 17 1. 81. 82. 83.
148
Photochemistry
C. Reyes, M. E. Sigman, R. Arce, J. T. Barbas and R. Dabestani, J. Photochem. Photobiol. A , 1998,112,277 (Chem. Abstr., 1998,128,250534). 106. H. Kawai, T. Suzuki, M. OhkitaandT. Tsuji, Angew. Chem. Znt. Ed. Engl., 1998,37, 817. 107. S. Kammermeier, P. G. Jones and R. Herges, Angew. Chem. Int. Ed. Engl., 1997,36, 1757. 108. T. Noh, H. Gan, S. Halfon, B. Hrnjez and N. C. Yang, J. Am. Chem. SOC.,1997, 119,7470. 109. M. A. Miranda, J. Perez-Prieto, E. Font-Sanchis, K. Konya and J. C. Scaiano, J. Org. Chem., 1997,62, 5713. 110. K. Nagahara, I. Ryu, M. Komatsu and N. Sonoda, J. Am. Chem. SOC.,1997, 119, 5465. 111. N. Sonoda and N. Yanagi, Jpn. Kokai, Tokkyo Koho, JP 09,241,181 (Chem. Abstr., 1997,127,277815). 112. K.-W. Woo, T. S. Ahmadi and M. A. El-Sayed, Bull, Korean Chem. Soc.,, 1997, 18, 1274 (Chem. Abstr., 1998,47434). 113. H. Koshima, Y. Wang, T. Matsuura, I. Miyahara, H. Mizutani, K. Hirotsu, T. Asahi and H. Masuhara, J. Chem. SOC.,Perkin Trans. 2, 1997,2033. 114. G. Gutenberger, E. Steckhan and S. Blechert, Angew. Chem. Znt. Ed. Engl., 1998,37, 660. 115. A. Misetic and M.K. Boyd, Tetrahedron Lett., 1998,39,1653. 116. W. Adam, K. Schneider and S. Steenken, J. Org. Chem., 1997,62,3727. 117. K. Nakatani, N. Higashida and I. Saito, Tetrahedron Lett., 1997,38,5005. 118. B. Barker, L. Diao and P. Wan, J. Photochem. Photobiol., A , 1997, 104, 91 (Chem. Abstr., 1997, 127, 128591). 119. U. Pischel, W. Abraham, W. Schnabel and U. Mueller, J. Chem. Soc., Chem. Commun., 1997,1383. 120. M. Kotera, K. Ishii, 0. Tamura and M. Sakamoto, J. Chem. SOC.,Perkin Trans. I, 1998,313. 121. Y. Ohba, K. Kubo and T. Sakurai, J. Photochem. Photobiol. A , 1998,113,45 (Chem. Abstr., 1998,128,250541). 122. M. Suzuki, T. Ikeno, K. Osoda, K. Narasaka, T. Suenobu, S. Fukuzumi and A. Ishida, Bull. Chem. SOC.Jpn., 1997,70,2269. 105.
4
Photochemistry of Aromatic Compounds BYALAN COX
1
Introduction
Topics which have formed the subjects of reviews this year include photoinduced organic synthesis, photoisomerisations involving super-cyclophanes,2regioselective and stereoselective [2+2] photocy~loadditions,~ position- and stereoselective photocyclisation? the photochemistry of indoles,' five-membered heterocyclic compounds of the indigo group,6 pyrazoles and i~othiazoles,~ and heterocyclic Noxides,*photochromic reactions of naphthopyran derivatives,' photodegradation reactions of photochromic spirooxazines and 2H-chromenes,lo and chiral photochromic compounds. Fluorescent calix[4]arenes which respond to alkali metal ions have also been discussed. l 2
''
2
Isomerisation Reactions
A new procedure has been described which enables the quantum yields of a reversible photoisomerisation to be determined.I3 Wave packet motion on the cis-stilbene reactive surface has been detected by ultrafast time re~olution.'~ Kamers theory in its original form has been found to fail in the case of the photoisomerisation of trans-stilbene and the error has been traced to modifications of the excited state potential energy surface by the solvent.I5 This explanation is applicable over a wide range of physical conditions from jet-cooled isolated molecules to compressed liquid solution at very high viscosities. An assessment of the effects of substituents and media polarity on the photoinduced E -+ Z isomerisation in stilbene, azobenzene, and N-benzylideneaniline shows that both electron-donor and -acceptor substituents in the 4- and 4'-positions have a powerful influence on the efficiency of the reaction and are discussed in terms of the relaxation of the E-excited singlet state.16 Singlet (1) induces ultrafast intramoexcitation of trans-4-Me2NC6H4CH:CHC6H4CN-4 lecular charge transfer followed by photoisomerisation to the cis isomer.'7 A study of this photoisomerisation in various solvent classes as a function of temperature indicates that the process does not depend on solvent viscosity and that the Stokes-Einstein-Debye equation holds for overall rotation of (1). Examination of the aminostilbenes (2), (3), and (4) reveals that in their excited ~~~~
~
~~
~~
~
~
Photochemistry, Volume 30 0The Royal Society of Chemistry, 1999 149
150
Photochemistry
singlet state the mderivatives have greater charge-transfer character, longer lifetimes, and higher fluorescence quantum yields than the corresponding pderivatives, and that only the meta derivatives are subject to quenching by methanol. Is These observations have been attributed to the charge transfer states of the rn-derivatives being twisted, and those of the para derivatives being planar. Photoisomerisation of a stilbenesulfonate-containing amphiphile in which the chromophore is present in the hydrophilic head group is reported to be capable of control by complexation with alkaline earth metals, under which conditions the transformation apparently proceeds faster. l9 A study of the sensitized
photoisomerisation of cis-stilbazolium by [Ru(bpy)3I2' in saponite clay layers has revealed that the reaction occurs by static quenching, and it has been concluded that substrate and sensitizer are suitably arranged for effective photoelectron transfer and subsequent relay action.20 It has been reported that the result of irradiating (E)-4,4'-bis(dimethylamrnoniummethyl)stilbene in the presence of P-cyclodextrin is to induce photoisomerisation to the (Z)-isomer, whereas in the presence of y-cyclodextrin, [2+2]-cycloaddition products are obtained.21 These products are a molecular imprint of the cyclodextrin cavity. Diphenylamine seems to accelerate the photoisomerisation of trans-di(a-naphthy1)ethyleneand to retard the photocyclisation of the corresponding The same workers have also measured the kinetics and determined the effect of excitation intensity on the photocyclisation of di(a-naphthylbthylene to dihydropicene, and have suggested a novel adiabatic pathway for the trans-cis photoisomerisation of the same substrate.23 Novel photoresponsive molecular tweezers ( 5 ) having two 18crown-6 groups as recognition sites for Cs' and based upon dithienylethene have been described,24and an investigation of the reversible trans-cis photoisomerisation of (E)-hex-3-ene-l,5-diynesand 3,4-diethynylhex-3-ene-1,Sdiynes substituted with electron donating p-dialkylaminophenyl or electron accepting pnitrophenyl groups shows that the partial quantum yields of isomerisation are greatly influenced by the type and degree of f~nctionalisation.~~ It has been reported that on triplet sensitization and even on direct irradiation, the azulenylethenes, 2-styrylazulene and 1,2-di(azuIenyl)ethene, undergo one-way cis -+trans isomerisation as a quantum chain process in the excited triplet state after intersystem crossing.26Measurements of the quantum yields of photoisomerisation of trans- 1-(9-anthryl)-2-(n-pyridyl)ethenes(n = 2,3,4) and the corresponding cis-isomers in various solvents reveal that as the solvent polarity is increased, the fluorescence intensity falls and isomerisation to the cis isomer becomes efficient.*7
1114: Photochemistry of Aromutic Compounh
151
An intramolecular charge transfer excited state may be involved, and the inverse relationship between fluorescence and photoisomerisation suggests a singlet state mechanism. Irradiation of (2)-urocanic acid, 3 4 1H-imidazol-4-yl)prop-2-enoic acid, in the presence of nitro blue tetrazolium and sodium azide promotes its photoisomerisation in a process which involves reversible addition of the azidyl radical to the double bond.28
A study of the photoisomerisation of the E,E and E,Z-isomers of benzalcyclohexanone oxime shows that direct irradiation of the E, E-isomer primarily induces C=N photoisomerisation whereas sensitized irradiation causes isomerisation about the C=C bond.29 The E,Z-isomer undergoes C=C isomerisation under both sets of conditions. These results have been rationalised in terms of steric effects on the relative energies of the intermediates. The minimum energy path for photoisomerisation of the minimal retinal protonated Schiff base model tZtpenta-3,5-dieniminium cation (c~s-CSH~NH~+) has been computed using MCSCF and multi-reference Moller-Plesset methods.30 The results reveal that cisC&NH2+ is a satisfactory “ab initio” model for the sub-picosecond isomerisation dynamics of the retinal chromophore in rhodopsin. Counter ions may greatly affect the rate, specificity, and quantum yield of the photoisomerisation. A time-resolved investigation of the photoisomerisation of cis-azobenzene on the fs timescale suggests that excitation to the Sl(nn*) state induces inversion at one of the N atoms,31 and reversible cisltrans photoisomerisation of the newly reported amphiphilic f3-alanine derivatives of the type 4-RNMeC6H4N:NC6H4-4CONHCH2CH2C02H [R = H, Me(CH2)loCO, Me(CH2)&0] has been studied.32 trans-cis-Photoisomerisation of aqueous solutions of an azobenzene 4,4‘-disubstituted with two f3-cyclodextrinsunits has been described.33Anomalously large increases have been observed in the quantum yields of cis-trans photoisomerisation of (6; n = 1 , 2) when complexed by alkaline earth metal ions, and these have been attributed to interaction between the coordinated metal ions and the oxygen atoms on the 2,2’-positions andor nitrogen atoms of the azobenzene moiety.34 The same authors also describe the photoisomerisation of (7) and report that the cis-isomer shows complexation selectivity towards Cs+ and Rb+.35The cationic double azobenzene-chain lipid (8) is reported to undergo an efficient trans-cis photoisomerisation in MeCN, but in co-aggregates with bis ether lipid (9) of certain compositions, or in pure liposomes, the degree of photoisomerisation is very sensitive to t e m p e r a t ~ r e . ~ ~
152
Photochemistry
A study of the photochemical behaviour of calix[4]resorcinarenes and 0octaacetylated derivatives with 4-azobenzene residues at their lower rim has been carried out in solution and mono layer^,^^ and the crystal structures of some calix[4]crowns including a photoisomerisable azobenzene unit in the ether bridge has appeared, and the diazo cisltrans geometry seems to be dependent on both the bridge-length and the calixarene c o n f ~ r m a t i o nPhotoisomerisation .~~ of p,p’bis(ch1oromethy1)azobenzene in poly-(N, N-dimethyl-4-vin y lphene t hylamineblock-styrene) block polymer has been observed not to proceed by first order kinetics,39and the novel biphotochromic systems 2-[N-(3-phenylnorbornadiene2-carbonyl)]-N-arylaminomethylene-(2H)benzo[b]thiophenones undergo Z1E photoisomerisation, N - + Oacyl rearrangement, and also valence isomerisation in the norbornadiene fragment.40 The E/Z photoisomerisation of phosphaethenyl-
M4: Photochemistry of Aromatic Compounds
153
CMe3
I
benzenes possessing more than one phosphorus-carbon double bond have been prepared, and the structure of 1,2-bis[2-(2,4,6-tri-t-butylphenyl)-2-phosphaethenyllbenzene (10) has been determined ~rystallographically.~' irradiation of deoxygenated solutions of trans-lob, 1Oc-dimethyl-lob,l0c-dihydropyrene gives anti-8,16-dimethy1[2.2]metacyclophane1,9-diene (1 l), whereas in non-degassed solutions, there is successive formation of (1 1) and 5,8-epidioxyanti-8,16-dimethy1[2.2]metacyclophane-1,9-diene.42 A series of potassium sulfonate derivatives of (11) has also been reported and in some cases epidioxybridged products are formed. The kinetics of the photoisomerisation of some to 2-aryl-4-methyltetrasubstituted 4-aryl-4-methyl-2,6-diphenyl-4H-thiopyrans 3,6-diphenyl-2H-thiopyransvia 6-aryl-5-methyl- 1,3-diphenyl-2-thiabicyclo[3.1 .O]hex-3-enes have been measured.43The results along with the effects of substituents and consideration of solvent polarity have enabled a mechanism for the interconversion to be proposed. Among some 4-alkyl or 4-phenyl substituted 2,3dihydro-6H-l,3-thiazine-5-carboxylates investigated, the 4-methyl derivative rearranges to a thiazolidine, and the 4-ethyl derivative gives an acyclic thioamidodiene.44 The 4-phenyl derivative gives a 2,3-dihydro-6H-1,3-thiazine. Photochemical isomerisation of some 4H-imidazole N-oxides and N,N-dioxides to yield oxaziridines has been studied.45 Photolysis of a-chloroacetophenones induces an electron transfer process to give (12) followed by a medium-sensitive 1,2-phenyl migration to produce phenylacetic acids; the effects of substituents on this process have been investigated.46 Irradiation of N-(2-phenylprop-2-enyl)thiobenzamides induces double bond migration to give N-(2-phenylprop- 1-enyl)thiobenzamides by consecutive 1,4- and 1,&hydrogen and benzene solutions of 4-methoxy-ONNazoxybenzene containing trichloroacetic acid have been photoisomerised to 4methoxy-NNO-azoxybenzene.48However, in the absence of the acid catalyst the
154
Photochemistry
products are 5-methoxy-2-(phenylazo)phenol(2) and 2-(4-methoxyphenylazo)phenol(3). The major photorearrangement products of 1-phenylbenzo[b]thiophenium salts are reported to be 2-phenylbenzo[b]thiophenes and 3phenylbenzo[b]thiophenes together with some dephenylated products; by contrast thermal rearrangement induces ring opening.49 PM3-RHF-CI semiempirical calculations have been performed on derivatives of furan, thiophene and pyrr~le.~' These show that isomerisation products of furans and thiophene can arise from the excited singlet state derived from the Dewar form, and that the only pyrrole known to be capable of giving this intermediate is 2-cyanopyrrole. 1-one and 7Both 9-phenyl-1,3,4,5,6,7,8,9-0ctahydronaphtho[2,3-c]furanphenyl- 1,3,4,7-tetrahydroisobenzofuran-l -one undergo di-n-methane rearrangement in processes whose chemoselectivity can be rationalised in terms of the configuration of the phenyl group.51 The same authors also report that di-xmethane rearrangement of cis- and trans-4,7-diphenyl-l,3,4,7-tetrahydroisobenzofuran-1-one, cis- and trans-( 13) and the 4-methyl analogues cis- and trans-(14) give (15), (16) and (1 7), and MM2 calculations suggest that rearrangement of (1 3) and (14) occurs by a boat conformation having a pseudo phenyl substituent.s2 The photoproducts arising from the di-n-methane rearrangement of the benzobarrelenes (1 8;X = CN, CHO) are (19) and (20), indicating that vinyl-vinyl nitrile bridging does not occur.53These observations have been accounted for in terms of the stabilising effect of the substituents on the intermediate radical, and their destabilising effect on the formation of the cyclopropane ring. Di-n-methane rearrangement of the quinoxalinobarrelenes (21) and (22) gives the quinoxalinosemibullvalenes (23) and (24) re~pectively,'~and direct irradiation of (25) produces the singlet state product (26), whereas irradiation in the presence of xanthen-9-one as triplet sensitizer gives the dihydrochloride salt of the semibullvalene (27).55In the solid state, the outcome is influenced by steric interactions, and the pyrrole (28) is produced. Under triplet sensitized conditions which promote single electron transfer, the py-unsaturated oximes (29; R' = Ph, R2 = H) and hydrazones (30; R = Me, X = Ts) cyclise to the corresponding dihydroisoxazoles (31; R' = Ph, R2 = H) and dihydropyrazoles (32; R = Me) re~pectively.~~ However, oxime and hydrazine derivatives from aldehydes undergo an aza di-n-methane rearrangement. Photochemical isomerisation of [6]( 1,4)naphthalenophane (33) and [6](1,4)anthracenophane (34) produces the corresponding Dewar valence isomers (35) and (36) re~pectively,~~ and the efficiency of excited product formation in the adiabatic photocycloreversion of the bridged biplanemer (37) has been determined by the size of its side-chain substituents which influence the interchromophore distance in photoproduct (38).58 Irradiation of 4-hydroxybenzonitrile in deoxygenated water and other hydroxylic solvents causes isomerisation to 4-hydroxyisobenzonitrile and subsequent hydrolysis to 4-hydro~yformanilide.~~ Kinetic analysis reveals the involvement of a two-stage photoprocess, the first step of which occurs on the triplet manifold to give an intermediate which may be an azirine, and which following absorption of a second photon is transformed into the product. In the presence of DCA, 2,5diaryl-3,3,4,4-tetradeuteriohexa1,5-diene undergoes a photosensitized electron
155
M4: Photochemistry of Aromatic Compounds
Me Ph
Me
n
Ph CMe3
(23)
CMe3
transfer Cope rearrangement to generate the 1,1,6,6-tetradeuterioanalogue of the starting material via the 1,4-diaryl-2,2,3,3-tetradeuteriocyclohexane1,&diyI cation radical which has been captured.60If cerium(1V) ammonium nitrate is used, degenerate Cope rearrangement does not occur, and this change is ascribed
Photochemistry
156
(H2c0-$ Ph (34)
(33)
(35)
Ph
RCON
to the absence of a back electron transfer in the ground state process. Solutions of either trans- or cis-9,10-di-tert-butyl-9,lO-dihydro-9,lO-disilaanthracenes will undergo photointerconversion in the presence of di-tert-butyl peroxide to give a photostationary state comprised of 81% cis and 19% trans isomer.61 These observations indicate that the rare inversion of silyl radicals is occurring. Irradiation of the sulfide (39) in benzene gives the thiaphosphirane derivative (40).62
An investigation of the influence of methyl and methoxy substituents situated para relative to the hydroxyl group in salicylic acid has appeared.63 The results show the existence of an excited tautomer arising from intramolecular H+ transfer, and the observations are further taken to imply the existence of a modification of the excited potential energy surface along the tautomerisation coordinate without introducing an energy barrier in the proton-transfer reaction. The proton transfer rates in some crystalline N-salicylideneanilines have been examined by fs time-resolved spectroscopy and other methods, and it has been concluded that in the excited state photoinduced transfer occurs by quantum mechanical tunnelling.64In aqueous media and alkanes, the lack of fluorescence
IIl4: Photochemistry of Aromatic Compounh
157
from 8-hydroxyquinoline (8-HQ) has been attributed to the existence of the substrate in the tautomeric form, 8-HQ(T*).65 Intermolecular proton transfer may occur with the surrounding medium under these conditions, along with the possibility of intramolecular proton transfer betwGsn the hydroxyl and N functions, but in organic media a stable dimer is formed in the ground state within which biprotonic concerted proton transfers may occur upon excitation. A study of excited state intramolecular proton transfer in 2-(2'-hydoxypheny1)benzimidazole has been made using steady state and time-resolved emission spectroas well scopy in cyclodextrins such as p-, y-, and 2,6-di-O-methyl-~-cyclodextrins, as in solvents.66 These media weaken the 2-(2'-hydoxyphenyl)benzimidazole intramolecular H-bonds and promote strong intermolecular H-bond formation with the various cyclodextrins and solvent molecules, suggesting that in the presence of cyclodextrins, 2-(2'-hydoxyphenyl)benzimidazole adopts a zwitterionic structure. Molecular packing is observed to be a crucial factor in photoinduced proton-transfer in crystals of 2-(2,4-dinitrobenzyl)pyridine and some of its derivative^.^^ Experimental results suggest that the absence of nstacking between the chromophore and other aromatic rings leads to photoactive systems, and that it is an 0 atom of the nitro group which systematically interacts with the abstracted proton and results in photoinduced proton abstraction of the benzylic H atom. The role of the pyridine N atom is mainly inductive. Quantum mechanical calculations on the structure of the triplet intermediates in the photochromic reactions of phenoxy quinones show that photochemically induced phenyl migration occurs non-adiabatically with generation of the spiro form of the triplet biradical.68 Details of a range of new photochromic compounds have appeared in both the scientific and patent l i t e r a t ~ r e . ~ ~ - ' * ~
3
Addition Reactions
Photoaddition of methanol to 1-aryl-2,2-dichlorocyclopropanesusing 1,4-dicyanobenzene as sensitizer occurs with reverse regioselectivity to give 1-aryl- I-methoxy3,3-dichloropropanes. '27 Analogous results are found with both ethanol and ammonia, and a cation-radical mechanism may be involved. Irradiation of pentafluoroiodobenzene and alkenes produces adducts, but in the presence of electron scavengers the reaction is suppressed suggesting the participation of an electron transfer mechanism. Quenching studies indicate that the dominant state in the photohydration of XC6H4CCCCBut (X = p COzMe, p-OMe, rn-CF3,p-CF3) to XC6H4CCCOCH2Bu',XC6H4CHzCOCCBu', XC6f&CHCCHCOBut and XC6H4COCHCCHBu' is a singlet,129and the same authors also report that photohydration of 1-aryl-5,5-dimethyIhexa- 1,3-diynes in aqueous sulfuric acid gives two types of alkynyl and allenyl ketones through both S1 and TI excited states for substituents other than a nitro group.I3* Electronwithdrawing substituents promote C1 protonation leading to one type of allenyl ketone, but by contrast electron donating groups cause C4 protonation and give the second type of allenyl ketone; nitro-substituted diynes form only allenyl ketones via TI excited states.
158
Photochemistry
Irradiation of a mixture of tetracyanobenzene and benzyl cyanide in the solid state leads to the coupling product (41) which subsequently cyclises to the isoindole (42). 13' In alcoholic media, irradiation of (+)-3,4,4a,5,6,7-hexahydro4a-methyl-7,7-diphenyl-1(2H)-naph thalenone and ( & )-3,4,4a,5,6,7-hexahydro4a,7,7-trimethyl-l(2H)-naphthalenone,both of which incorporate a rigid s-cis enone, leads to solvent addition to the enone double bond with formation of hydrogen-bonded enols. * 32 However, in aqueous dioxan P-hydroxy ketones are produced. The mechanism of the transformation is thought to be stepwise addition of the solvent to a triplet-derived ground state trans enone. Formation of 1,5-diketones by photochemical addition of benzophenone derivatives to 1,3diphenylpropan- 1,3-dione has been reported, 133 and irradiation of 9-aryloxyI , 10-anthraquinones in the presence of nucleophiles such as water, alcohols, and primary amines induces 1,4-addition. This and other observations are in good agreement with the results of AM 1 calculation^.'^^ Irradiation of phenanthrenequinone in the presence of various cyclic organosilanes such as (43), (44), and (45) leads to silylene adducts (46; R = Me, 'Pr) which arise by attack of the triplet state of the ketone on the organosilane to give radical insertion products, and which themselves subsequently undergo a displacement reaction. 35 Me. Me
Ph'
(45)
A photoaddition-fragmentation-aromatic annulation sequence Las been used in the first synthesis of (+)-ligudentatol (47),'36 and a study of the photoaddition of amines to styrylthiophenes and its derivatives shows that the addition o f tertiary and secondary amines to 2-styrylthiophenes is non-regioselective; the addition of ammonia sensitized by dicyanobenzene is, by contrast, regioselective. '37 Examination of the photochemical reaction between CC14 and anthracene using time-resolved IR spectroscopy suggests that the trichloromethyl radical is
1114: Photochemistryof Aromatic Compounds
159
involved and that the final product is the 9-chloro-l0-trichloro adduct of anthracene.13*Photoaddition of pyrroles to give 1:l and 2:l adducts occurs with phenylethenes and phenylethynes in a process which proceeds with formation of an exciplex. 39 The ortho photocycloadducts formed on irradiating 3-tert-butyl-4-phenoxybut1-ene and 3-acetoxy-4-(4-methoxyphenoxy)but-l -ene are reported to be further photorearranged to tricyclic species.l4O Irradiation of the pyrazinopsoralen (48) in the presence of ethenes such as dimethyl fumarate, dimethyl maleate, and dimethyl ethylidenemalonate gives the corresponding C4-cycloadducts in a process which occurs by a singlet exciplex.14' The 1 ,haphthylene-bridged syncyclophanes (49) and (50) have been synthesised by intramolecular [2+2] photocycloaddition of 1,8-bis(4-vinylphenyl)naphthalene and 1,8-(3-~inylphenyl)naphthalenes re~pectively,'~~ and irradiation of a variety of ketones in the presence of homobenzvalene promotes the formation of Paterno-Buchi products which contain the tricyclo[4.I .0.02.7]heptane fragment. '43 Use of naphtho-l,4quinone leads to (51). Irradiation of 5-cinnamyloxy-4-methyl-2(5H)-furanonein acetone as sensitizer induces a [2+2] intramolecular photocycloaddition by a process whose photostationary state composition has been determined, 144 and it has been reported that irradiation of the photochromic percinnamoylated cyclomaltoheptaose (P-cyclodextrin) solid inclusion complexes with N-salicylideneaniline and N-5-chlorosalicylideneaniline as guests causes formation of cyclobutane bridges, effectively restraining the guests to a specific geometry.145
So far the reverse reaction has not been achieved. Photolysis of (52; R = H) produces the alkyne (53; R = H), and evidence is also provided to support the view that the mechanism is an enantioselective [2+2] photocycloaddition involving a 1,4-biradical intermediate. 146 Intramolecular photocycloaddition of the enantiopure bis-dihydropyridone (54) gives a high yield of a single cycloa d d ~ c t . ' ~The ' photocycloaddition of arylalkenes to c60 has been shown to occur by a two-step mechanism and to involve formation of a dipolar or diradical intermediate in the rate determining step.'48 These authors also report that photocycloaddition of cis- and trans- 1-(p-methoxypheny1)prop- 1-ene to C a gives the trans [2+2] adducts only, and present evidence to suggest that a two-step mechanism again operates. 14' 1,2- and 1,2,4,5-Paddlanes have been prepared by [2+2]photocycloaddition of o-divinylbenzene and 1,2,4,5-tetravinyIbenzene,and in particular, cyclisation of 1,2,4,5-tetravinylbenzene( 5 5 ) gives 1,2,4,5-paddlane
I60
Photochemislry
(56).lS0 Sensitized irradiation of the alkenylcyclopentadiene (57; n = 2,3) using 9,lO-dicyanoanthracene gives the anti-Bredt [2+4] tricyclic adducts (58).15' Such adducts are not obtained thermally and this observation may indicate the involvement of a triplex intermediate in the photochemical reaction.
y e 3 I
2-Methoxy-5-[3-(trifluoromethyl)phenyl]pent-l -ene will undergo 2,6- and 1,3meta-photocycloaddition to give products having the methoxy group endo, whereas by contrast, the analogous trifluoro ortho- and para-substituted substrates form products derived from ortho photocycloaddition. 152 These observations have been rationalised in terms of the free enthalpy of electron transfer. Photoaddition of duroquinone to trans-stilbene gives the eight-membered ring 2,3,5,8-tetramethyl-6,7-diphenyl-2,5,7-cyclooctatrien1,4-dione,I s3 compound, and irradiation of 4-(4-methoxyphenoxy)-3-(N3-benzoylthymin1-yl)but-1-ene induces a chemo-, regio-, and stereo-selective intramolecular 1,2-ortho photocycloaddition to the phenyl ring to give (59).lS4 Intramolecular meta photocycloaddition of 3-benzyl(dimethylsila)prop-1-enes is reported to be controlled by the presence of an electron donor substituent on the phenyl ring and also by the silicon atom in the tether.155 Benzene 1,4-endoperoxide (60) is formed by irradiating the monoperoxide (61) at low temperature and following a concerted and intramolecular photorearretrocycloaddition gives benzene and 02( to the rangement of 7-hydroxy-2-methyl-2-(4-methylpent-3-enyl)chroman-4-one 1,3-arene-aIkenephotocycloadduct, rel-( 1R,2S,5S, 7S,10R,13S)-6,6,10-trimethyl-
I114: Photochemistry of Aromatic Compounh
161
14-oxapentacyclo[8.3.1.0'97.023'3.057'3]tetradeca-3, 12-dione, is reported to occur by secondary photorearrangement of the 1,2-arene-aIkene photocycloadduct. '57 The photocycloaddition of 2-morpholinoacrylonitrile to substituted 1-acetonaphthone (62) has been found to be substituent-dependent. '51 For example, (62; R = MeO, R' = H) gives only the [4+2] cycloadduct whereas (62; R = H, R' = CN; R = H, R' = MeO) lead to the [2+2] cycloadduct. The calix[4]arene-based 2naphthoate (63) is reported to be photoconverted into the dimer and photocycloreversion of the cyclodimers (65 - 69) gives quantitative yields of the corresponding naphthalenes. 16*
(63) Np = naphthalene
CMe3 Me& CMe3 (64)
CMe3
Quenching of the exciplex formed in acetonitrile solution between the lowest excited state of 9,lO-dichloroanthracene ('DCA*) and the ground state of 2,sdimethylhexa-2,4-diene gives the DCA radical anion intermediate which suffers mono-dechlorination.'61 In heptane solution no exciplex is formed, but by contrast a [4+2] adduct of a dibenzobicyclo[2.2.2]octadiene-type is produced. A detailed study of the photodissociation of (70; X = C02Me, CN), the [4+4] cyclodimer of furan with 9-cyanoanthracene, has appeared, 162 and the same authors also report that irradiation of tert-butyl 9-anthroate and furan gives a mixture of the [4+4] (70; X = C02Bu-tert), 1,4-10,9 (71; same X), and 9,lO-10,Y (72; same X) c y c l~di m er s . Upon '~ ~ excitation, the [4+4] cyclodimers of tert-butyl 9-anthroate and the [4+4] cyclodimers of methyl 9-anthroate are quantitatively dissociated, but no adiabatic photoreversion of any of the cyclodimers is
162
Photochemistry
observed. 9-Anthrylmethyl phosphite gives the corresponding phosphonate by a photo-Arbusov rearrangement but prolonged irradiation produces the centrosymmetric head-to-tail, [4+4] pho tocycloadduct. X
Mono- and disubstituted N-alkyl and N-arylaziridines are reported to undergo a photoinduced electron transfer [3+2] cycloaddition to dipolarophiles to produce five-membered heterocycles, and it is suggested that in this process the radical cation intermediate behaves differently from the corresponding classical azomethine ylide. Intramolecular [4+4] photocycloaddition of the dipyridylpropane (73) followed by Li/NH3 reduction is a useful route to the elevenmembered ring system (74),16' and on irradiation of benzene solutions of 2,3dicyano-5,6-dimethylpyrazinein the presence of allylic silanes a [2+2] cyclisation is induced followed by rearrangement to give 2,8-diazatricyclo[3.2.1.0498]oct-2-ene (75; R = H, Me).'67
q Me
(73)
0
h-NMe
O
(74)
[4+2] Cycloaddition of heteroaromatic analogues of o-quinonedimethanes such as furan, thiophene, oxazole, thiazole, indole, and quinoxaline to [60]fullerenes gives the corresponding heterocyclic-linked [60]fullerenes which undergo selfsensitized photooxygenation to epoxy-y-lactones. 2-Vinylbenzofuran and 2isopropenylbenzofuran will participate in photoelectron transfer cycloaddition reactions with alkenes such as cyclohexa-l,3-dienes, styrenes, and acyclic 1,3dienes to form a range of products including [2+2]-cycloadducts such as (76),'69 and irradiation of solutions of methyl 1-naphthoate in the presence of furan leads to three products, a syn-[2+2] cycloadduct, an endo-[4+4] cyclodimer, and a cage cy~lodirner.'~~ 2,3-Dimethylmaleic anhydride and 2,3-dimethylmaleimide will undergo a [2+2] benzophenone sensitized photocycloaddition to selenophene and to a range of substituted selenophenes, as well as to tellurophene and benzo[bJtellurophene. I 7 l Irradiation of indoline-2-thiones in the presence of alkenes promotes [2+2] cycloaddition followed by cleavage of the intermediate spirocyclic thietane to give 2-alkylindoles.17* Under similar conditions but in the presence of
1114: Photochemistry of Aromatic Compounh
I63
the tertiary amines R3N (R = Me, Et, Pr, Bu, PhCH*), 3-alkylindoles are formed. Diarylfuroxans (77; Ar = Ph, 2-ClCsH4, 2,6-C12CsH3) can be photolysed in the presence of alkenes such as tetramethylethylene to give cyclobutaphenanthrenes (78) in a process which occurs by loss of (NO)z from a diazete-N,N-dioxide intermediate. '73
Solid state excitation of electron donor-acceptor complexes of various diarylacetylenes and dichlorobenzoquinone in either the acceptor or the 1:2 complex absorption bands induces [2+2] cycloaddition and produces identical mixtures of the quinone methides.'74 Evidence is presented for the participation of an ionradical pair as the reactive intermediate in both cases. Irradiation of an appropriately substituted o-hydroxybenzyl alcohol precursor generates the corresponding o-quinone methide which is reported to undergo an efficient [4+2] cycloaddition to form the hexahydrocannabinol system.175Time-resolved studies confirm the intermediacy of the o-quinone methide and show its lifetime to be > 2 ms. Laser photolysis of 1,2-bis(phenoxymethyl)benzene, 1,2-bis[(phenylthio)methyllbenzene, and 1,2-bis[(phenylseleno)methyl]benzene occurs by a twophoton process to produce o-quinodimethane which will cycloadd to various dienophiles including maleic anhydride, dimethyl maleate, dimethyl fumarate, fumaronitrile and dimethyl acetylenedicarboxylate. 76
'
4
SubstitutionReactions
In the presence of methanol as solvent and 1,4-dicyanobenzene as acceptor, photoinduced electron transfer from 1,4-bis(methylene)cyclohexane gives 4(methoxymethy1)-1-methylenecyclohexane and 4-(4-~yanophenyl)-4-(methoxymethyl)- 1-methylenecyclohexanewhich arise by nucleophilic attack of the solvent on the radical cations, followed either by reduction and protonation, or by combination with the radical anion of the electron acceptor.'77 These observations are in accordance with the proposed mechanism of the nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reaction. The same group has also investigated the use of cyanide ion as nucleophile and report that irradiation of a mixture of 1,4-dicyanobenzene in the presence of biphenyl as donor, KCN, and 18-crown-6 gives a mixture of (79) and (80).'78 These workers have also extended the scope of NOCAS to fluoride ion.'79 In particular, use of 2,3-dimethylbut-2-ene and 2-methylbut-2-ene gives 4-cyanophenyl substituted
Photochemistry
164
CN
(79)
fluoroalkanes in a process whose selectivity has been explained in terms of the HSAB principle, and whose regiochemistry is anti-Markownikov. The relative stability of the intermediate P-fluoroalkyl radicals has been determined by ab initio calculations and the addition step is kinetically controlled. Irradiation of chlorobenzene solutions of [Pd(PPh&] produces trans[PdC12(PPh&] and a mixture of chlorobiphenyls, 180 and irradiation of 2-amino5-iodo-3-(N-methyl-N-tosylarnino)pyridine in benzene solution gives 2-amino-3methylamino-5-phenylpyridine by simultaneous phenylation and tosyl removal.'*' This reaction is a key step in the synthesis of the food-borne carcinogen 2-amino- I -methyl-6-phenylimidazo[4,5-b]pyridine.Substituted 1,2'biazulenes have been prepared by photolysis of 2-diazo- I ,3-dicyanoazulen-6(2H)one in the presence of azulene derivatives.'82 Calculations performed on transient radical intermediates derived from cleavage of the C-X bond following irradiation of halogenoheterocycles have been found to be useful tools with which to rationalise the behaviour of these substrates towards arylation and deha10genation.I~~ Irradiation of acetonitrile solutions of 4(5)-nitro-2-iodoimidazole containing benzene leads to phenyl substitution in the 2-position, and similar reactions are observed for rn-xylene and thienyl derivatives.184A study of the chain photosubstitution of the chlorine atom in 4-chloro-1-hydroxynaphthalene by sulfite using aqueous sodium sulfite has appeared. 185 Two mechanisms of photoinitiation are involved and two intermediates have been observed, namely a radical anion of 4-chloro- 1-hydroxynaphthoxide and the sulfite radical anion. The conclusions are drawn that there are two other competitive mechanisms, an SRNlmechanism and a mechanism which involves the participation of sulfite radical anions, and secondly that these are independent of the initiation processes. A range of 6-iodo derivatives of 2,3-diphenylbenzo[b]furans has been prepared and on irradiation in benzene solution these give the corresponding 6-phenylated products; on further irradiaIOtion, photocyclisation to the corresponding 1 1-phenylbenzo[b]phenanthro[9, dlfurans occurs.186 From an examination of the photoreactions of 4-fluorophenol, 4-bromophenol, and 4-iodophenol using both steady state and timeresolved photolysis it appears that, as in the case of 4-chlorophenol, the carbene 4-oxocyclohexa-2,5-dienylideneis formed by loss of HX, and that this species reacts with molecular oxygen to produce benzo- 1,4-quinone O-oxide followed by its rearrangement to benzo- 1,4-quinone.187 Time-resolved photolysis of 9,l O-dibromoanthracene (DBA) in cyclohexane-amine gives the (' DBA-amine) exciplex but this is not observed to decay by electron transfer even though the
IIl4: Photochemistry of Aromatic Compounds
165
presence of DBA'- is apparent from absorption measurements in acetonitrile solution.'88 It is concluded that DBA'- is the intermediate in the amine-assisted monodebromination of DBA to give 9-bromoanthracene, and that the dielectric constant of the solvent plays a n important role in the transformation. The photochemistry of some iodo substituted pyrroles has been d e ~ c r i b e d . 'Ethyl ~~ 3,4-dimethyl-5-iodopyrrole-2-carboxylategives a 1:1 mixture of ethyl 3,4-dirnethyl-5-phenylpyrrole-2-carboxylate and ethyl 3,4-dimethylpyrrole-2-carboxylate quantitatively, and in acetonitrile as solvent the single product is ethyl 3,4dimethylpyrrole-2-carboxylate.Under similar conditions, 4,5-diiodopyrrole-2carbaldehyde in benzene gives the corresponding 5-phenyl derivative. The effects of adding ethanol to a range of solvents used in the photolysis of some alkoxy- and dialkoxyarenes in the presence tetranitromethane have been shown to include a reduction in the tendency of the trinitromethyl derivative to form the ring-substituted nitroarene, a reduction in the nucleophilicity of the trinitromethanide ion, and a reduction in attack ips0 to the alkoxy substituent.I9' Irradiation of the charge transfer complex formed between 1,4-dimethoxynaphthalene and tetranitromethane is reported to give mainly 1,4-dimethoxy-2nitronaph thalene, 1,4-dimethoxy -2-t rini trometh y lnapht halene and 4-met hoxy-2(dinitromethylene)-l(2H)-naphthalenone, together with small amounts of other materials.'" Reaction has been shown to occur by attack of the trinitromethanide ion or nitrogen dioxide ips0 to a methoxy group. Charge transfer complexes formed by irradiating benzofuran and tetranitromethane give the epimeric pairs of adducts 3-nitro-2-trinitromethyl-2,3-dihydrobenzofurans, 2-nitro-3-trinitromethyl-2,3-dihydrobenzofurans, and 3-hydroxy-2-trinitromethyl-2,3-dihydrofurans, together with other products.'92 These adducts seem to arise by attack of the trinitromethanide ion on the benzofuran radical cation. The use of lower temperatures in the bromate-induced monobromopentahydroxylation of benzene by catalytic photoinduced charge transfer osmylation favours formation of the neo diastereoisomer of the deoxybromoinositol. 193 Photolysis of N-(diphenylamino)-2,4,6-trimethylpyridinium tetrafluoroborate salts induces nuand N-[bis(4-methylphenyI)amino]-2,4,6-trimethylpyridinium cleophilic addition of various n-nucleophiles such as electron rich alkenes to the 0-and p-positions of one of the phenyl rings.'94 These observations are thought to imply the presence of the diarylnitrenium ion (Ar2N+) as intermediate, but evidence is also presented for the involvement of radical species, as well as for the formation of indoles and indolinones. Some MO calculations are also reported. Irradiation of aqueous solutions of 4-thiothymin- 1-ylacetic acid (8 1) and adenosine (82), 4-thiothymidine (83) and adenin-9-ylacetic acid (84), or (81) and (84) gives 4,5-diamino-6-formamidopyrimidinederivatives as observed after irradiating a mixture of (82) and (83).'95 From these observations it has been concluded that replacement of the nucleoside sugar residues by a carboxymethyl group does not affect the regioselectivity of the reaction, Photolysis of methanolic 5-amino-3-phenyl- and 3,5-diphenyl-1,2,4-oxadiazole in the presence of sodium hydrogen sulfide or thiols causes a redox reaction of the ring 0 - N bond, and formation of the corresponding N-substituted ben~amidines.'~~ However, in the presence of thioureas or thiocarbonates 3-phenyl-substituted 1,2,4-thiadiazoles
166
Photochemistry
are produced suggesting N-S bond formation between the ring-photolytic species and the sulfur nucleophile. 5
Cyclisation Reactions
[ 1 . l]Paracyclophane and its bis(methoxycarbony1) derivative have been success-
fully generated for the first time by photoisomerisation of the corresponding bis(Dewar benzene) precursors (Scheme l),I9’ and in some related work by the same authors the [4]paracyclophane (85; R’ = H, CN; R2 = Me,H) has been thermally isomerised to the Dewar valence tautomer (86; same R’, R2) and subsequently reconverted photochemically to (85). ‘98 Irradiation of the 7-silanorbornadiene (87) produces the silacyclopentadienylidene (88) which has been trapped in a hydrocarbon matrix at 77 K.’99 Similarly, photolysis of benzene solutions of (87) in the presence of MeZSiEtH as trapping agent gives dole (89). The photocyclisation quantum yield of 2,2’-dimethyl-3,3’-(perfluorocyclopentene- 1,2-diyl)-bis(benzo[b]thiophene-6-sulfonate) is enhanced on irradiation within the cavity of 0- or y-cyclodextrin, in which the favourable photoreactive antiparallel conformation is preferentially included.2m Irradiation of substituted a-carbonylstyrenes promotes either cyclisation or dimer formation depending upon the substitution pattern of the Solvent and substituent effects on the photocyclisation of a-(2-acylphenoxy)toluenes and ethyl 2-acylphenoxyacetates in the synthesis of dihydrobenzofuranols R
g
R
R
Scheme 1
R’ R\‘
R’
\didMe
Me Et
IIl4: Photochemistry of Aromutic Compound
167
have been examined, and conformational, solvent, and substituent effects on the cyclisation of the 1,5-biradicals and reaction pathways have been discussed.202 The naphthoic acid component of kedarcidin has been synthesised by a route which includes a photochemical electrocyclisation as a key feature.203A theoretical analysis of the conformational stereoisomerism in the sterically hindered 4a,4b-dihydrophenanthrenesof C2 symmetry which arise as photointermediates, suggests the presence of two low energy structures C and T.*04The C conformation has been assigned to the primary photocyclisation product from which the T conformation arises spontaneously. S-Aryl 2-benzoylbenzothioates undergo photoinduced cyclisation to 3-aryl-3-arylthioisobenzofuranonesin a process which is followed by homolytic cleavage of the isobenzofuranone product to give the dihydroisobenzofuranone dimer.*” A study of the consequences of attaching substituents to the styrene ring of trans-2-cinnamylphenol (90) shows that a lowering of the singlet state energy occurs, and this is reflected in the marked regioselectivity towards 6-membered ring products (91) which occurs in excited state proton transfer.206Annulated quinones of the type (92; R’ = R2 = H; R’= Me, R2 = H; R’ = R2 = Me; R’ = CH2Ph, R2 = H) are reported to be obtained when alkoxynaphthoquinones (93; same R’, R2) are irradiated, and the stability of the radical or carbocation intermediate is thought to be important for the efficiency of the reaction.207
Diarylethenes having an optically active 1- or d-menthyl group at the 2-position of a benzo[b]thiophene ring such as (94; R = I-menthyl, d-menthyl) can be photocyclised to give diastereomeric pairs whose product ratio is both solvent polarity and temperature dependent, and under suitable conditions a diastereomeric excess of 86% has been obtained.208The regioselectivity of the intramolecular photocyclisation of macrocyclic stilbenes is strongly influenced by the length of the connecting alkanediyl chain.209In the presence of p-dicyanobenzene, photoamination of 1,2-distyrylbenzene proceeds with nucleophiiic addition of NH3 to the 1,2-distyrylbenzene radical cation and results in intramolecular and 1-aminocyclisation to give l-benzyl-3-phenyl-l,2,3,4-tetrahydroisoquinoline 3-benzyl-2-phenylindane.”’ Irradiation of the enediyne (95) in propan-2-01 leads to (96) in an analogue of the thermal Bergman cyclisation, together with addition
168
Photochemistry
It is suggested that a substituted 1,4-dehydronaphthalene biradical is the most likely intermediate. The photochemical behaviour of the bridged 4-benzoylcyclohexanones (97; X = (CH& NZCH2, NZ(CH2)2, CH2NZCHz; Z = PhCH202C; n = 2-4) depends upon both ring size and the possible presence of the nitrogen atom.212In compounds capable of forming 1,6-biradicals, the reactions are unselective, but the remaining substrates afford tricyclic hydroxyketones with high diastereoselectivity if a protected nitrogen atom is present. Regiocontrolled photocyclisation of the aryl enamide (98; R = 4-MeOC6H4CH2)gives the phenanthridone (99), and may be important in the synthesis of the antineoplastic alkaloid pancratistatin; it is suggested that the regioselectivity may arise from hydrogen bonding between the A-ring phenolic hydrogen and the enamide carbonyl Photocyclisation of dicarboxamide Mannich bases of the type (100) gives o-hydroxylactams (101) which on treatment with HCl form the imidazole derivatives (102),214and a study of the photocyclisation of 2-halopyridinium salts tethered to an arene shows that pyrido[2,1-a]-3H,4H-isoquinolinium salts are formed, and that transient intermediates such as the 2,3-dihydrocyclohexadienylradical and dibromide radical are produced.215The transformation appears to occur by a photohomolytic radical mechanism. Photolysis of the azidopyrimidine (103) gives a mixture of the isoxazolopyrimidine (104) and the azo compound (105),216and diastereoselectivephotocyclisation of some N-arylenaminolactams and esters to spiroindoline lactams and imides has been reported; such transformations may be of significance for the synthesis of ( k )-vindorosine and Aspidosperma alkaloid^.^'^ Single electron transfer induced photocyclisation of N-[(N-acetyl-N-trimethylsilylmethyl)amidoalkyl]phthalimide (alkyl = ethyl, Pr, n-pentyl, n-hexyl) and N[(N-mesyl-N-trimethylsilylmethyl)amidoethyl]phthalimideleads to the formation of products in which the phthalimide carbonyl carbon has become bonded to the carbon of the side chain in place of the trimethylsilyl group.*l* It is suggested that these transformations occur by intramolecular single electron transfer from the nitrogen of the a-silylamido group to the singlet excited state of the phthalimide, followed by de-silylation of the intermediate a-silylamido cation radical and cyclisation by radical coupling. One-electron photoinduced cycloreversion of stereoisomeric stilbazolium cyclodimers has been achieved by irradiating their iodide salts and occurs by a process which is highly sensitive to structure.219 Evidence has been presented to show that the structural dependence of the quantum efficiency is attributable to through-bond interaction of the two pyridinium rings. 2-Alkylbenzimidazoles have been produced in high yield by
IIl4: Photochemistry of Aromatic Compounrtr
169
OEt
photolysis of suitable dinitrobenzenes or nitroanilines in the presence of Ti.22oIn aqueous alcohol or in a polymer matrix, 4,4-bis(2-pyridylamino)-3,3'-dichlorobiphenyl photocyclises regioselectively at the nitrogen atom of the heterocycle into 8-[4-(2-pyridylamino)-3-chlorophenyl]pyrido[1,2-a]benzimidazole, and in alcoholic solution 2-(2-pyridylamino)-3-chloroanthracene cyclises by forming C-C and C-N bonds to pyrido[ 1,2-a]anthra[2',3'-d]imidazoleand naphtho[3,2-h]-acarboline.221Irradiation of the 4,5-disubstituted 1,2,4-triazole-3-thione(106; X = halo; R' = H, Me; R2 = H or R'R2 = CH:CHCH:CH; R3 = H, Me, MeO; R4 = H, Me) gives s-triazolo[3,4-b]benzothiazoles(107; same R', R2, R3,R4)in what is a general route to these compounds.222The transformation may proceed by an electron transfer mechanism. Solutions of methyl 3-cyano-2-diazo-6-0~0-2,6dihydroazulene-1-carboxylate in THF are reported to undergo photolysis to 1,3-dioligomeric crown ethers .223 Dimethy 1 2-diazo-6-0~0-2,6-dihydroazulenecarboxylate, however, is observed to give only small quantities of the crown ether, and this is regarded as evidence of a significant steric factor in the cyclisation process. Irradiation of spiro[fluorene-9,1'-pyrrol0[2,1 -a]quinolines]
I70
Photochemistry
(108; R' = R2 = H) and their styryl homologues (109; R2 of 108 replaced by CH:CHR', where R2 = (un)substituted Ph) under time-resolved conditions indicates the presence of transients in the ps and ms domains.224 These are thought to possess slightly tilted educt or product-like geometries, and an energy diagram has been proposed for reaction of (108) to give (I 10).
A study of solvent and substituent effects on the cyclisation of 1,Sbiradical intermediates generated on photolysis of 2-RCH20C6H4COPh (1 11; R = H, Me, Et, CHMe2, Ph, CH:CH2, CN) and 2-PhCOC6H40CHRC02Et (112) has appeared.225 For (1 1 l), decreases in stereoselectivity in some solvents are attributed to intermolecular H-bonding between the hydroxyl group of the 1,5biradicals and the solvents, whereas in the case of (112) photolysis leads to a mixture of cis- and trans-dihydrobenzofuranolsas a consequence of intermolecular hydrogen bonding between the hydroxyl group of the 1,5-biradicals and the solvents. Irradiation of the ubiquinol-benzoin adduct (1 13) cleanly produces (1 15).226 ubiquinol-2 (1 14) and the expected 5,7-dimethoxy-2-phenylbenzofuran
Q
1114: Photochemistry of Aromatic Compounds
171
This observation is significant for the study of rapid electron-transfer events in ubiquinol oxidising enzymes. Photodecarboxylation of N-acylisoxazol-5-ones affords iminocarbenes which give oxazoles following intramolecular cyclisation through the oxygen of the acyl group.227The same authors also report that N-thioacylisoxazol-5(2H)-ones will photoextrude carbon dioxide, and, after subsequent intramolecular cyclisation of the iminocarbene, produce thiazoles.228Photocyclisation of 3-chloro-N-(3-phenanthryl)thieno[2,3-b]thiophene-2-carboxamide gives thieno[3’,2’:4,5]thieno[2,3c]naphtho[1,2-f ]q~inoIin-6(5H)-one.~~~ 6
Dimensation Reactions
In non-polar solvents, phenyl- and 2,6-diphenyl-p-benzoquinonegive the corresponding cyclobutane-type dimers, but polar solvents promote intramolecular photocyclisation to the corresponding 2-hydroxydibenzof~rans.~~~ In the case of alkoxy-substituted 2,6-diphenyl-p-benzoquinone,cyclisation to the 6H-dibenzo[b,d]pyran system occurs. Arylacrylonitriles in which the aromatic group may be homo- or heterocyclic undergo regiochemically controlled photodimerisation in the presence of benzophenone as sensitizer, and this has been rationalised in terms of overlap of the frontier orbitals participating in the reaction.231The products show structural similarities to some antimicrobially active sponges. Irradiation of cinnamic acids involving a complex with surfactant amine N-oxides (C,DAO, n = 12, 14 and 16) as vesicles in water gives cyclodimers, and studies have shown that the dimerisation is controlled by a range of molecular assemblies such as rod-like micelles and homogeneous or heterogeneous vesicles,232 Solid state irradiation of 1H-[2]benzothiopyran-l-one (1 16) selectively gives 6au,6ba, 12ba,l2cu-tetrahydrocyclobuta[l,2-c:4,3-c’)bis([2]benzothiopyran)-5,8dione (1 17), the head-to-head cis-cisoid-cis-cyclodimer of (1 16); the same dimer is obtained in low yields in solution.233In the presence of tetrachloroethene, the [2+2] photocycloadduct is (1 18) formed.
A study of the photodimerisation of anthracene in supercritical C02 at different densities has revealed that the reaction is about an order of magnitude more efficient in C02 than in normal liquid solvents,234This is rationalised in terms of a reaction whose mechanism is diffusion-controlled even for those rate constants which are of the order of 10” M-’ 6’. An investigation of the influence
172
Photochemistry
of ester chain length (C4-CI2) on the photodimerisation of n-alkyl esters of 9anthracenecarboxylic acid to the head-to-tail and head-to-head products has been carried out in micellar and vesicular solution.235Increasing the chain length promotes formation of the head-to-head dimer in organic solvents as do temperature decreases. Photodimerisation of 6,7-benz[c]acephenanthrylene(1 19), an overlapping and repeating CZ0 subunit of [60]fullerene, produces the ciscyclobutane (120) which can be thought of as a simple molecular tweezer.236 Irradiation of azulenequinones in polar solvents gives mainly head-to-head dimers whereas in less polar solvents head-to-tail dimers are formed in greater abundance.237The results of related reactions are also reported.
18 /
In contrast to most bulky olefins, irradiation of (4RS, 1'RS)-methyl l-phenyl-2piperidinoethyl- 1,4-dihydro-2,6-dimethyl-4 - (2-thienyl)pyridine-3,5-dicarboxylate (121) in the crystalline state has been found to give the corresponding dimer, (4RS,8SR)-4a,8a-dimethoxycarbonyl-2,4b,6,8b-tetramethyl-3-[( 1RS)- 1-phenyl-2piperidinoethoxycarbonyl]-7-[(1SR)- 1-phenyl-2-pipidinoethoxycarbonyl]-4,8-di(2- thieny1)- 1,4,4a,4b,5,8,8a,8b-octahydro-truns-cyclobuta[ 1,2-b:3,4-b']dipyridine Inspection of the crystal structure of (122) quantitatively as a single (121) reveals a space between the reacting molecules, designated a buffer zone, which may be capable of modulating the steric hindrance from which the reacting molecules suffer on close approach, and whose presence may be a prerequisite before solid state dimerisation can occur. In some closely related work, the same authors show that in the solid state photodimerisation of the three polymorphic crystal forms of the bulky olefin methyl (RS)- 1-phenyl-2-piperidinoethyl (RS)1,4dihydro-2,6-dimethyl-4-(2-thiazolyl)pyridine-3,5-dicarboxylatehydrochloride, the buffer zone is an essential controlling factor.239 Irradiation of 3-amino-2-oxo-4-hydroxyquinoline leads to its photochemical condensation to a dimer,240and photodimerisation of acridizinium bromide in both solution and in the solid state forms four photodimers, two of which may be In anionic micelles, a different regioselectivity is observed as enanti~meric.~~' reflected in a higher yield of those dimers showing higher dipole moments. Radiative lifetimes, quantum yields, and substituent and solvent effects have been examined for the photodimerisation of trans- 1,2-bis[2-(5-phenyloxazolyI)]ethene, and it has been found that increases in solvent polarity promote photodimerisation, whereas heavy atom solvents cause its suppression.242These observations are thought to suggest that the dimerisation occurs by a singlet mechanism.
173
1114: Photochemistry of Aromatic Compouncis
7
Lateral Nuclear Shifts
ZSM-5 is a member of the pentasil family whose internal surface possesses two pore systems, one of which is sinusoidal and the other straight and perpendicular to the sinusoidal channels.243Organic molecules such as arylmethyl esters can be occluded within these ordered media, and under such conditions their photochemistry has been examined. The same group has also investigated the photoFries reaction of various aryl phenylacetates such as p-tolyl phenylacetate, o-tolyl phenylacetate, and phenyl o-tolylacetate in homogeneous solution and adsorbed on ZSM-5 and NaY zeolites.2a Different products are reported for the two catalysts, and these are accounted for in terms of their size and shape sorption selectivity on the zeolite, and by the restriction of their diffusional and rotational mobility. The photo-Fries reaction of 1- and 2-naphthyl acetates has been investigated using a range of techniques including steady state and time-resolved photolysis, and CIDNP.245Confirmation that the primary radical pair is a singlet has been obtained (triplet radical pairs are shown to proceed to disproportionation products) and a general kinetic scheme for the rearrangement has been proposed. The photochemical behaviour of N-acetyl- and N-benzoylcarbazole is reported to be dependent on the properties of the medium and may give photoFries or photoinduced single electron transfer.246 AGoEThas been determined using the Weller equation. Two photon chemistry has been successfully promoted using the two-laser two-colour technique in the cases of benzyl phenyl ether and phenyl acetate, and is based upon the photoconversion of transient cyclohexa2,4-dienone intermediates which occur in the photo-Claisen and photo-Fries rearrangements, to the dienic ketenes (Scheme 2).247
0 6OR
0-
hv )1=266
R = Benzyl, Ac
\
0
H@ /
& !dR -
Scheme 2
The photo-Claisen rearrangement of ally1 phenyl ether in water and in the presence of P-cyclodextrin gives a mixture of o- and p-ally1 phenols and Product quantum yields are modified by addition of P-cyclodextrin, and the total yields are reduced by molecular oxygen with inhibition being less marked when P-cyclodextrin is present. An investigation of the benzophenonesensitized rearrangement of N-( 1-naphthoy1)-N-phenyl-O-benzoylhydroxylamine in micelles suggests that the benzoyloxy migrated products arise from the amidylbenzoyloxy radical pair present at the micellar surface, and that the amidylphenyl radical pair which is located more deeply within the micelle, leads to the phenyl rearranged products.249
I74
8
Photochemistry
Miscellaneous Photochemistry
A laser flash photolysis and time-resolved resonance Raman study of competitive energy and electron transfer processes in 1-nitronaphthalene has shown that in polar solvents the substrate can act as an electron acceptor with nitrite ions and trans-stilbene, but that in non-polar solvents energy transfer is the dominant process.250It has been suggested that the transition between these processes is governed by electronic and nuclear factors. A study of the influence of cyclodextrins on the photophysics of 4H-1-benzopyran-4-thionein solution and in the solid state has revealed that complexes with the cyclodextrins may be involved.25' An examination of the influence of molecular structure on the light sensitivity of 1,2- and 2,l -naphthoquinonediazide-4-sulfonicacid shows that the position of the diazide group is Flash photolysis of lO-diazo-9( 10H)-phenanthrenone in aqueous media gives fluorenylideneketene and subsequently its hydrated product fluorene-9-carboxylic acid enol as transients.253This has enabled the rate of enolisation of fluorene-9-carboxylic acid to be determined. Photolysis of the diazaquinone (1 23) gives the corresponding fluorenylideneketene which has been detected using laser photolysis techniques, and which reacts with amines such as diethylamine to give ylides (124) and subsequently amides as final products.254
A temperature-dependent photodecomposition has been established for 1-(2azidophenyl)-3,5-dimethylpyrazole, which at temperatures >200 K gives 1,3dimethylpyrazolobenzotriazole by electrophilic cyclisation of the singlet nitrene, but which at lower temperatures leads to products derived from the dimerisation of the triplet nitrene along with products arising from intramolecular radical c y c l i s a t i ~ n Recent . ~ ~ ~ advances in the photochemistry of 2-pyridylazides (tetrazolo[1,5-a]pyridines) have appeared.2s6 On photolysis, these compounds form 2pyridylnitrenes which rearrange to 1,3-diazacycloheptatetraenes,and the initially formed nitrenes have now been observed. Some new chemistry involving the Wolff rearrangement of pyridine diazoketones and in which ketene-nucleophile ylid intermediates are thought to participate has been described. Photolysis of methanolic 4,6-diazido-3-methylisoxazolo-[4,5-c]pyridinepromotes loss of nitrogen and subsequent solvent addition to give 3-methylisoxazolo-I ,3-diazepine derivatives,257and the triplet states of 4-nitrophenylnitrene and 4-nitrene-4'nitrostilbene have been generated at low temperature by photolysis of the corresponding azides, and have been ~ h a r a c t e r i s e d .Their ~ ~ ~ photoinduced hydrogen abstraction reactions may be accounted for either in terms of a hot ground state or alternatively as an excited state process. The experimental observations are correlated with the results of quantum mechanical calculations.
IIt4: Photochemistry of Aromatic Compounh
175
Irradiation of the charge transfer band of [ArN2+,Ar’H] initiates a homolytic chain arylation whose kinetics have been determined and which have been now been verified by computer ~imulation.~’~ In an inert matrix, 2- and 3-(diazomethy1)furan can be photolysed to (Z)-pent-2-en-4-yn- 1-a1 and (s-2)-(a-formy1)methylenecyclopropene in transformations which respectively proceed through a carbene and an oxabicyclopropene species.260 Irradiation of solutions of p-chloroaniline produces both benzidine and aniline as secondary products, and this is taken to indicate the formation of 4-iminocyclohexa-2,5-dienylidene as a transient.26’ N-Propyl-o-sulfobenzoic imide (125) has been photolysed in ethanol and various monocyclic aromatic solvents, and although the S1 and TI states participate in both cases, the ensuing transformations are different.262In ethanol, the diradical produced following extrusion of sulfur dioxide abstracts hydrogen from the solvent to give (126) as the final product, whereas in aromatic solvents energy transfer occurs from the solvent to the substrate triggering addition of the resulting radicals to the aromatics with formation of (127). The photoactivatable dolichol analogue (128; R = H, P03H2,; R’ = (102,142,182,222,262,302, 34E,38E)-Me2C:CHCH2(CH2CMe:CHCH2)2(CH2CMe:CHCH2)6) has been prepared and is a substrate for dolichol kinase from yeast membranes, an essential enzyme involved in the N-linked glycosylation p a t h ~ a y . 2 ~ ~ 0
RO-,
,-,
,CH~R’
Irradiation of 2-[N-(pentafluorophenyl)amino]-3-phenylcyclopropenone promotes decarbonylation to give N-(pentafluoropheny1)phenylethynamine and 2-phenyl-3-[N-(pentafluorophenyl)amino]acrylic acid by a process for which there is no known precedent,264and the photoextrusion of carbon monoxide from 1,3-bis(ethylenedioxy)indan-2-0ne has been used as the first step in a new synthesis of 1,2-dioxobenzocyclobutene.265This represents an unusual example of the decarbonylation of a five-membered cyclic ketone in the preparation of a highly strained and functionalised cyclobutane derivative. The photolysis of a-naphthaleneacetic acid in aqueous solution proceeds by decarboxylation and oxidation of the aromatic ring, and has been carried out at a variety of different wavelengths.266The primary step occurs by pseudo-first order kinetics and the optimum photolysis rate has been observed using Ti02 as photocatalyst. Within the cavity of P-cyclodextrin, naproxene (129) has been photodecarboxylated to
176
Photochemistry
give products having ethyl, 1-hydroxyethyl, and acetyl side chains.267Irradiation of 2-( 1-naphthyl)ethyl 3-anilinoalkanoates produces tricyclic lactones containing the 2-azabicyclo[3.3.llnonane skeleton,268and photodecomposition of the fluorescent system (130; T = thymidine) is reported to give the N,-deprotected cyclised precursor (1 3 1) together with (132).269These observations may be of relevance to photolabile fluorescent protecting groups. Photosensitive fatty acid esters which may serve as useful biological precursors of several model &unsaturated fatty acids, including arachidonic acid, have been prepared using 1-(2'-nitropheny1)ethanedi01.~~'Photocleavage of some carboxylic acid esters of 3',5'-dimethoxybenzoin (133; R = CH3, CH2Ph, Ph, C(CH3)3) in acetonitrile and aqueous acetonitrile gives the corresponding benzofuran (134; same R) and the corresponding carboxylic acid.271 The primary photochemical step is heterolytic cleavage of the C-OCOR bond a to the acetophenone carbonyl in a process which is assisted by electronic interaction between the electron-rich dimethoxybenzene ring and the n,x* excited carbonyl group of the acetophenone fragment; in this latter process the cyclohexadienyl cation is formed. The sulfimides, TosN-S(R')CH2R2 (135; R' = Ph, 2-pyridinyl, Me; R2 = naphthyl, Ph; Tos = p-toluenesulfonyl) are reported to undergo the photoStevens rearrangement, and for example (1 35; R = 2-pyridinyl; R2 = naphthyl) is
'
0
OMe
IIl4: Photochemistry of Aromatic Compounds
177
converted into R I S N ( T O S ) C H ~ RIt~is. ~ also ~ ~claimed that photolysis of the 2,13dithia[3.3](1,3)naphthalenophanes (136) in trimethyl phosphite gives the corresponding tetrahydro-3,4:8,9-dibenzopyrene(1 37) and tetrahydro-3,4:9,1O-dibenzopyrene (138).273
Photoprotecting groups continue to be an active field of interest. A mechanistic investigation of the photolytic transformation of various phenacyl esters (PhCOCH2-OCOR) in the presence of electron donating sensitizers, and which leads to the formation of acetophenone and the corresponding carboxylic acid, has appeared.274These reactions, which occur in high yield, seem to be triggered by photoinduced electron transfer to the phenacyl ester to give an anion radical which suffers C - 0 bond scission forming the phenacyl radical and the corresponding carboxylate anion. The authors have also shown that photolysis of phenacyl phenylacetate gives acetophenone and phenylacetic acid in a triplet state process whose quantum yield is increased by the presence of H-atom donors.275The p-hydroxyphenacyl protecting group has been used as a phototrigger for excitatory amino acids such as L-Glu and y-aminobutyric Irradiation of buffered solutions of the esters brings about release of the amino acid or peptide and this is accompanied by rearrangement of the phenacyl group to p-hydroxyphenylacetic acid in a process which occurs through the phenacyl triplet state, A new photosensitive protecting group for amines incorporating o-hydroxy-trans-cinnamicacid has been described, and which is based upon High overall yields the facile lactonisation of o-hydroxy-cis-cinnamic have been obtained for the range of amines, HNRR’ (R = H, Et, R’ = n-Pr, CHZCH~OH, CH*Ph, cyclohexyl). o-Nitrobenzyloxycarbonyl and related groups have been examined as photolabile protecting groups for nucleoside 5’-hydroxyl functions.278Photodeprotection rates for a series of 5’-0-protected thymidine derivatives irradiated at 365 nm vary by a factor of 17, and rates are also found to be affected by substitutions on both the phenyl ring and the a-carbon atom. Nucleoside derivatives have been prepared using a photolabile protecting group for oligonucleoside synthesis.279For example, N6-[02N-4-C6H4CH2CH20CO-]5’-0-[2-(O2N-2-C6H4)CH2CH2SO2-]-2’-deoxyadenosine has been prepared from N6-protected adenosine and 2-(2-chloro-6-nitrophenyl)ethylsulfonyl chloride. Irradiation of polymer supports containing the new o-nitrobenzyl photocleavable linker (139) gives amino acid and sugar products in high yields, and its utility has been demonstrated by the synthesis and photocleavage of a branched trimannan from a polymer support.28o The caged L-leucyl-L-leucine methyl ester ( 140) will release L-leucyl-L-leucine
Photochemistry
178
Hovc methyl ester on irradiation in methanol and in liposomes suspended in PBS.28' These observations may have significance for investigating the mechanism of the induction of an apoptosis to NK cells and macrophage. The o-nitrobenzyl group appears to be a useful photosensitive protecting group for indoles, benzimidazoles and 6 - c h l o r o ~ r a c i lphotocleavable ;~~~ cyclic oligonucleotides (141; X' = X2 = 5'oligonucleotide-3' or 3'-oligonucleotide-5') having a base sequence capable of hybridising with a target DNA or RNA and a structure cyclised with a photocleavable linkage have been prepared,283and substituted desyl (2-0x0- 1,2diphenylethyl) groups have been explored as potential photolabile protecting groups to mask primary and secondary amines as photosensitive a-keto carbamates such as (142; R' = H, OMe, SMe; R2 = H, OMe; R3 = H, Me, Ph).284
References 1.
2. 3. 4.
5. 6.
B. Ohtani, Yuki Gosei Kagaku Kyokaishi, 1997,55,460. T. Inazu and H. Takemura, Kagaku (Kyoto), 1998,53,68. S. A. Fleming, C. L. Bradford, and J. J. Gao, Mol. Supramol. Photochem., 1997, 1, 187. A. Sugimoto and K. Mizuno, Kokagaku, 1997,2444. A. Weedon, Adv. Photochem., 1997,22,229. M. Sainsbury, RoMs Chem. Carbon Compd (2nd E d ) , 1997,4(Pt. B), 361.
1114: Photochemistryof Aromatic Compounds
7. 8. 9. 10. 11. 12. 13. 14.
15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27.
28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40.
179
3. W.Pavlik, Mol. Supramol. Photochem., 1997, I, 57. H. Ciurla, Pr. Nauk Akad. Ekon. im. Oskara Langego Wroclawiu,1996,728,83. M. Uchida and M. Irie, Senryo to Yakuhin, 1997,42, 155. R. Guglielmetti, Opt. Spektrosk., 1997,83,682. Y.Yokoyama, Gendai Kagaku, 1997,321,46. T. Jin, Senryo to Yakuhin, 1997,42,187. R. Gade and Th. Porada, J. Photochem. Photobiol., A, 1997,107,27. D. K. Palit, A. Z. Szarka, N. Pugliano, and R. B. Hochstrasser, Ultrufast Processes Spectrosc., [Proc. Int. ConJ], 9th, 1996,75. J. Schroeder, Ber. Bunsen-Ges., 1997,101,643. N. R. King, E. A. Whale, F. J. Davis, A. Gilbert, and G. R. Mitchell, J. Mater. Chem., 1997,7,625. Y. V. Il’ichev and K. A. Zachariasse, Ber. Bunsen-Ges., 1997,101,625. F. D. Lewis and J.-S. Yang, J. Am. Chem. Soc,, 1997,119,3834. 0.Karthaus, H. Hioki, and M. Shimomura, Colloids SurJ, A, 1997,126, 181. H . Usami, T. Nakamura, T. Makino, H. Fujimatsu, and 0. Shinji, J. Chem. SOC., Faraday Trans., 1998,94,83. W. Herrmann, S. Wehrle, and G. Wenz, Chem. Commun. (Cambridge), 1997,1709. M . F. Budyka, 0.D. Laukhina, and D. N. Dogadkin, Mendeleev Commun., 1997,107. M. F. Budyka, 0. D. Laukhina, and V. F. Razumov, Chem. Phys. Lett., 1997,279, 327. M. Takeshita and M. Irie, Tetrahedron Lett., 1998,39,613. R. E. Martin, J. Bartek, F. Diederich, R. R. Tykwinski, E. C. Meister, A. Hilger, and H.P. Luthi, J. Chem. SOC.,Perkin Trans. 2, 1998,233. T. Arai, Y. Hozumi, 0. Takahashi, and K. Fujimori, J. Photochem. Photobiol., A , 1997,104,85. E. J. Shin, E. Y.Bae, S. H. Kim, H. K. Kang, and S. C. Shim, J. Photochem. Photobiol., A, 1997,107, 137. A. Kpissay, C. N. Kuhl, T. Mohammad, K. Haber, and H. Morrison, Tetrahedron Lett., 1997,38, 8435. R. J. Olsen, J. Photochem. Photobiol., A, 1997,103,91. M. Garavelli, P. Celani, F. Bernardi, M. A. Robb, and M. Olivucci, J. Am. Chem. SOC.,1997,119,6891. T . Naegele, R. Hoche, W. Zinth, and J. Wachtveitl, Chem. Phys, Lett., 1997, 272, 489. E. Markava, G. Matisova, andI. Muzikante, Latv. Kim. Z., 1997,65. T . Aoyagi, A. Ueno, M. Fukushima, and T. Osa, Macromol. Rapid Commun., 1998, 19, 103. R. Tahara, T. Morozumi, H. Nakamura, and M. Shimomura, J. Phys. Chem. B, 1997,101,7736. M. Saadioui, N. Reynier, J.-F. Dozol, Z. Asfari, and J. Vicens, J. Inclusion Phenom. Mol. Recognit. Chem., 1997,29, 153. R. A. Moss and W. Jiang, Langmuir, 1997,13,4498. K. Ichimura, N. Fukushima, M. Fujimaki, S.Kawahara, Y. Matsuzawa, Y.Hayashi, and K. Kudo, tangmuir, 1997,13,6780. P. Thuery, M. Lance, M.Nierlich, N. Reynier, V. Lamare, J.-F.Dozol, M.Saadioui, 2. Asfari, and J. Vicens, An. Quim. Int. Ed., 1997,93, 324. K. Se, M. Kijima, and T. Fujimoto, Polymer, 1997,38,5755. V. A. Bren, V. I. Minkin, A. D. Dubonosov, V. A. Chernoivanov, V. P. Rybalkin, and G. S. Borodkin, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A , 1997,297,247.
180 41.
42. 43. 44. 45.
46. 47. 48. 49. 50. 51. 52. 53. 54. 55.
56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74.
Photochemistry
H. Kawanami, K. Toyota, M. Yoshifuji, J. Organomet. Chem., 1997,535, 1. H. Cerfontain, A. Koeberg-Telder, B. H. Bakker, R. H. Mitchell, and M. Tashiro, Liebigs AnnSRecl., 1997, 873. H. Rahmani and H. Pirelahi, J. Pholochem. Photobiol., A, 1997,111, 15. S . H. Bhatia, D. M. Buckley, R. W. McCabe, A. Avent, R. G. Brown, and P. B. Hitchcock, J. Chem. Soc., Perkin Trans. 1,1998,569. I. V. Nechepurenko, 0. P. Petrenko, I. A. Grigor’ev, and L. B. Volodarskii, Russ. J. Org. Chem., 1997,33, 705. D. P. Dhavale, V. P. Mali, S. G. Sudrik, and H. R. Sonawane, Tetrahedron, 1997, 53, 16789. H. Aoyama, J. Chem. Soc., Perkin Trans. I , 1997, 1851. T. Isshiki, H. Miyagawa, H. Sasaki, and J. Yamamoto, Nippon Kagaku Kaishi, 1997, 532. T. Kitamura, K. Morizane, H. Taniguchi, and Y. Fujiwara, Tetrahedron Lett., 1997, 38, 5157. M. D. Auria, Internet J. Sci.: Biol. Chem., 1997,4. 0. Muraoko, G. Tanabe, and Y. Igaki, J. Chem. Soc., Perkin Trans. I , 1997,1669. 0. Muraoka, G. Tanabe, E. Yamamoto, M. Ono, T. Minematsu, and T. Kimura, J. Chem. Soc., Perkin Trans. I , 1997, 2879. R. Altundas and M. Balci, Aust. J. Chem., 1997,50,787. V. Nair, G. Anilkumar, J. Prabhakaran, D. Maliakal, G. K. Eigendorf, and P. G. Williard, J. Photochem. Photobiol., A, 1997,111, 57. J . R. Scheffer and H. Ihmels, Liebigs Ann. /Red., 1997,1925. D. Armesto, A. Ramos, M. J. Ortiz, W. M. Horspool, M.J. Mancheno, 0.Caballero, and E. P. Mayoral, J. Chem. SOC.,Perkin Trans. I , 1997,1535. Y. Tobe, S. Saiki, H. Minami, and K. Naemura, Bull. Chem. SOC.Jpn., 1997, 70, 1935. H. Okamoto, K. Satake, and M. Kimura, Chem. Lett., 1997,873. F. Scavarda, F. Bonnichon, C. Richard, and G. Grabner, New J. Chem., 1997, 21, 1119. H. Ikeda, T. Minegishi, H. Abe, A. Konno, J. L. Goodman, and T. Miyashi, J. Am. Chem. SOC.,1998,120,87. S . Kyushin, T. Shinnai, T. Kubota, and H. Matsumoto, Organometallics, 1997, 16, 3800. M. Yoshifuji, H. Takahashi, K. Shimura, K. Toyota, K. Hirotsu, and K. Okada, Heteroat. Chem., 1997,8,375. F. Lahmani and A. Zehnacker-Rentien, J. Phys. Chem. A , 1997,101,6141. T. Sekikawa, T. Kobayashi, andT. Inabe, J. Phys. Chem. B, 1997,101,10645. E. Bardez, I. Devol, B. Larry, and B. Valeur, J. Phys. Chem. B, 1997,101,7786. E. L. Roberts, J. Dey, and I. M. Warner, J. Phys. Chem. A, 1997,101,5296. S . Khatib, M. Botoshansky, and Y. Eichen, Acta Cystallogr., Sect, B: Struct. Sci., 1997,53, 306. N. Gritsan, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A., 1997,297, 167. T. Schirmeister, Liebigs Ann.lRecl., 1997, 1895. S. P. Gromov and M.V. Alfimov, Russ. Chem. Bull., 1997,46,611. Z . X.Guo, G. J. Wang, Y. W. Tang, and X. Q. Song, Liebigs Ann. IRecl., 1997,941. V. P. Tsybyshev, V. A. Livshits, B. B. Meshkov, 0.A. Fedorova, S. P. Gromov, and M. V. Alfimov, Russ.Chem. Bull., 1997,46,1239. T. Nakai, M. Tani, S. Nishio, A. Matsuzaki, and H. Sato, Chem. Lett., 1997,795. T. Nagasaki, S. Tamagaki, and K. Ogino, Chem. Lett., 1997,717.
IIl4: Photochemistry of Aromatic Compounds
75. 76. 77. 78. 79. 80.
81. 82. 83. 84.
85. 86. 87.
88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 99. 100. 101. 102. 103. 104. 105.
181
M. Irie, T. Eriguchi, T. Takada, and K. Uchida, Tetrahedron, 1997,53, 12263. P. Y. Wang and C. J. Wu, Dyes Pigm., 1997,35,279. H. Laatsch, A. J. Schmidt, A. Kral, N. Heine, and G. Haucke, Indian J. Chem., Sect. A: Znorg., Bio-inorg., Phys., Theor. Anal. Chem., 1997,36A, 476. V. I. Minkin and V. N. Komisarov, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A , 1997,297, 205. 0.Brede, L. Goebel, and T. Zimmermann, J. Phys. Chem., A , 1997,101,4103. A. C. Benniston, A. Harriman, and C. McAvoy, J. Chem. SOC.,Faraday Trans., 1997,93,3653. Yu. K. Mihailovskii, V. E. Agabekov, I. V. Astapovich, and V. A. Azarko, Vestsi Akad Navuk Belarusi, Ser. Khim. Navuk, 1996,30. K. Chamontin, V. Lokshin, A. Samat, and R. Guglielmetti, PCT Int. Appl. WO 98 04,563. M. Campredon, B. Luccioni-Houze, G. Giusti, R. Lauricella, A. Alberti, and D. Macciantelli, J. Chem. Soc., Perkin Trans. 2, 1997,2559. Z.-N. Huang, S. Jin, Y. Ming, and M. Fan, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A, 1997,2!97,99. J.-W. Kim, K.-H. Ahn, H. Kim, and T. Chang, Pollimo, 1997,21,512. E. P. Ivakhnenko, N. I. Makarova, M. I. Knyazhansky, V. A. Bren, V. A. Chernoivanov, A. I. Shiff, and G. S. Borodkin, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A, 1997,297,233. A. T. Hu and H.-J. Lee, Proc. Natl. Sci. Counc., Repub. China, Part A: Phys. Sci. Eng., 1997,21, 185. V. Lokshin, A. Samat, and R. Guglielmetti, Tetrahedron, 1997,53,9669. Y.-P. Chan, PCT Int. Appl. WO 97 10,241. V. S. Marevtsev and N. L. Zaichenko, J. Photochem. Photobiol., A , 1997, 104, 197. A. V. Metelitsa, 0. A. Kozina, S. M. Aldoshin, B. S. Lukyanov, M. I. Knyazhansky, and V. I. Minkin, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A , 1997,297,227. S . Delbaere, C. Bochu, N. Azaroual, G. Buntinx, and G. Vermeersch, J. Chem. SOC., Perkin Trans. 2,1997, 1499. T. Horii, Y. Miyake, R. Nakao, and Y. Abe, Chem. Lett., 1997,655. P. Celani, F. Bernardi, M. Olivucci, and M. A. Robb, J. Am. Chem. SOC.,1997, 119, 10815. Y. Kawanishi, K. Seki, T. Tamaki, M. Sakuragi, and Y. Suzuki, J. Photochem,. Photobiol., A , 1997, 109,237. H. Goerner, Chem. Phys., 1997,222,315. J. Momoda, S. Imura, and T. Kobayakawa, U.S. US 5,693,830. T. Hori, H. Tagaya, T. Nagaoka, J. Kadokawa, and K. Chiba, Appl. Su$ Sci., 1997,121,530. S . Yoshimoto and Y. Onishi, Jpn. Kokai Tokkyo Koho JP 09,323,990. Y. Dong, G. Fan, J. Shi, Q. Gao, and Y. Jia, Xibei Daxue Xuebao Ziran Kexueban, 1997,27, 103. L. Zhijie, H. Yi, and J. Zhang, IS&Ts Annu. ConJ, Final Program. Proc., 49th, 1996, 529. J.-Q. Bai, X.-C. Han, Y.-M. Wang, and J.-B. Meng, Chin. J. Chem., 1997, 15, 553. K. Fukunaga and M. Fujimoto, Jpn. Kokai Tokkyo Koho JP 10 36,354 [98 36,3541. H. G. Heller, J. R. Levell, D. E. Hibbs, D. S. Hughes, and M. B. Hursthouse, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A , 1997,297, 123. J. Momoda and T. Hara, Eur. Pat. Appl. EP 778,276.
182
Photochemistry
106.
J. L. Pozzo, A. Samat, R. Guglielmetti, R. Dubest, and J. Aubard, Helv. Chim. Acta, 1997,80, 725.
A. Kumar, D. B. Knowles, and B. Van Gemert, PCT Int. Appl. WO 97 21,698. A Kumar, U.S. US 5698141 A. H. G. Heller and J. R. Levell, PCT Int. Appl. WO 9748762. M. Melzig and H. Zinner, Ger. Offen. DE 19,65 1,286. M. Melzig and H. Zinner, Ger. Offen. DE 19540185 Al. J. J. Luthern, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A , 1997,297, 155. F. J. Hughes, U.S. US 5679805A. H. Pirelahi, H. Rahmani, A. Mouradzadegun, A. Fathhi, and A. Moudjoodi, Phosphorus, Sulphur, Silicon Relat. Elem., 1997,120,403. 115. H. Nakashima and M. hie, Macromol. Rapid Commun., 1997, 18,625. 116. T. Tsujioka, M. Kume, and M. Irie, J. Photochem Photobiol., A, 1997,104,203. 117. F. J. Hughes and E. A. Travnicek, U.S. US 5628935 A 13 May 1997. 118. Y. Yoshioka and M. Irie, Electron J. Theor. Chem., 1996,1, 1. 119. L. Yu, D. Zhu, and M. Fan, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A, 1997,297, 107. 108. 109. 110. 111. 112. 113. 114.
120. 121. 122. 123. 124.
107. Z. Gou, Y. Tang, F. Zhang, F. Zhao, and X . Song, J. Photochem. Photobiol., A , 1997, 110, 29. Y. Yokoyama, S. Uchida, Y.Shimizu, and Y. Yokoyama, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A, 1997,2W, 85.
H. G. Heller, K. Koh, M. Kose, and N. Rowles, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A , 1997,297,73. T. Watanabe, G. Yamakawa, S. Tokita. and H. Nakahara, J. Photopolym. Sci. Technol., 1997,10,255. J. Biteau, G. M. Tsivgoulis, F. Chaput, J.-P. Boilot, S. Gilat, S. Kawai, J.-M. Lehn, B. Darracq, F. Martin, and Y. Levy, Mol. Cryst. Liq. Cryst. Sci. Technol. Sect. A, 1997,297,65.
125.
M. Irie, T. Lifka, and K. Uchida, Mol. Cr-yst.Liq. Cryst. Sci. Technol. Sect. A , 1997, 297,81.
126.
F. Pina, M. J. Melo, M. Maestri, R. Ballardini, and V. Balzani, J. Am. Chem. Sue.,
127. 128. 129. 130.
J.-Y. Wu, J.-C. Mai, K. Pan, and T.4, Ho, Tetrahedron Lett., 1998,39, 647. P. Cao, Z.-Y. Long, and Q.-Y. Chen, Molecules, 1997,2, 11. S . C. Shim, Y. S. Chae, and E. K. Baek, Bull. Korean Chem. SOC.,1997,18,364. S. C. Shim, Y. S. Chae, E. K. Baek, and S. K. Park, J. Photochem. Photobiol., A ,
131. 132.
Y. Ito, S. Edo, and S. Ohba, J. Am. Chem. SOC.,1997,119,5974. R. A. Bunce, C. R. Shawn, and E. M. Holt, J. Photochem. Photobiul., A , 1997, 109,
133.
A. R. Kim, K. J. Kim, S. C. Sim, and S. S. Kim, Bull. Korean Chem. SOC.,1997,18,
134.
L. Klimenko, Z. Leonenko, and N. Gritsan, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A, 1997,297, 181. M. Kako, M. Ninomiya, and Y. Nakadaira, Chem. Commun. (Cambridge), 1997,
1997,119,5556.
1997,106, 155. 125.
1125. 135. 136. 137. 138.
1373. N . Haddad and H. Salman, Tetrahedron Lett., 1997,38,6087. T. I. Ho, C. S. Ho, S. M. Shin, and K. Pa, Electron. Con$ Heterocycl. Chem., (Proc.], 1997, Eds, H. S. Rzepa, J. P.Snyder, and C. Leach. K. Iwata and H. Hamaguchi, J. Mol. Struct., 1997,413, 101.
IIl4: Photochemistry of Aromatic Compounds
139. 140. 141. 142. 143. 144. 145. 146. 147. 148. 149. 150.
151. 152. 153.
154. 155. 156.
157. 158. 159. 160. 161. 162. 163. 164. 165. 166. 167.
168. 169. 170. 171. 172.
183
M. Austin, C. Covell, A. Gilbert, and R. Hendricks, Liebigs Ann./Recl., 1997, 943. R. Busson, J. Schraml, W. Saeyens, E. Van der Eycken, P. Herdewijn, and D. De Keukeleire, Bull. SOC.Chim. Belg., 1997, 106,671. G. S. Han and S. C. Shim, Photochem. Photobiol., 1998,67,84. Y. Nakamura, M. Matsumoto, Y. Hayashida, and J. Nishimura, Tetrahedron Lett., 1997,38,1983. M. Christ1 and M. Braun, Liebigs AnnJRecl., 1997, 1135. N. Braussaud, N. Hoffmann, and H.-D. Scharf, Tetruhetiron, 1997,53, 14701. E. Hadjoudis, A. Botsi, G. Pistolis, and H. Galons, J. Carbohycir. Chem., 1997, 16, 549. C. A. Hastings, J. D. Riggenberg, and E. M. Carreira, Tetruhedron Lett., 1997, 38, 8789. D. L. Comins, Y. S. Lee, and P. D. Boyle, Tetrahedron Lett., 1998,39, 187. G. Vassilikogiannakis and M. Orfanopoulos, J. Am. Chem. Suc., 1997,119, 7394. G. Vassilikogiannakis and M. Orfanopoulos, Tetrahedron Lett., 1997,38,4323. Y. Nakamura, Y. Hayashida, Y. Wada, and J. Nishimura, Tetrahedron, 1997, 53, 4593. H. Yoon and W. Chae, Tetrahedron Lett., 1997,38,5169. R. de Haan, E. W. de Zwart, and J. Cornelisse, J. Photochem. Photobiol., A, 1997, 102, 179. A. R. Kim, S. S. Kim, D. J. Yoo, and S . C. Shim, Bull. Korean Chem. SOC.,1997,18, 665. W. Saeyens, R. Busson, J. Van der Eycken, P. Herdewijn, and D. De Keukeleire, Chem. Commun. {Cambridge), 1997,8 17. D. M. Amey, D. C. Blakemore, M. G. B. Drew, A. Gilbert, and P. Heath, J. Photochem. Photobiol., A, 1997,102, 173. H. Gan, S. Halfon, B. J. Hrnjez, and N. C. Yang, J. Am. Chem. SOC.,1997, 119, 7470. G. P. Kalena, P. P. Pradhan, Y. Swaranlatha, T. P. Singh, and A. Banerji, Tetrahedron Lett., 1997,38,555 1 . H. R. Memarian, M. Nasr-Esfahani, R. Boese, and D. Dopp, Liebigs Ann./Recl., 1997,1023. H. Ji, Z. Tong, and C. Tung, Ganguang Kexue Yu Guung Huaxue, 1996,14,289. T. Noh, D. Kim, and S. Jang, Bull. Korean Chem. SOC.,1997,18,357. T. Nakayama, Y. Amijima, S. Miki, and K. Hamanoue, Chem. Lett., 1997,223. T. Noh, H. Lim, and D. Kim, Bull. Korean Chem. Soc., 1997,18,247. T. Noh, H. Lim, D. Kim, and K. Jeon, Buff.Koreun Chem. Soc., 1997,18, 1002. W. Bhanthumnavin, S . Ganapathy, A. M. Arif, and W. G. Bentrude, Heteroat. Chem., 1998,9,155. C . Gaebert and J. Mattay, Tetrahedron, 1997,53, 14297. S . M. Sieburth, T. H. Ai-Tel, and D. Rucando, Tetrahedron Lett., 1997,38,8433. G. Konishi, K. Chiyonobu, A. Sugimoto, and K. Mizuno, Tetrahedron Lett., 1997, 38,5313. M. Ohno, N. Koide, H. Sato, and S. Eguchi, Tetrahedron, 1997,53,9075. J. Botzem, U. Haberl, E. Steckhan, and S. Blechert, Acta Chem. Scund., 1998, 52, 175. T. Noh, C. Kim, and D. Kim, Bull. Korean Chem. Soc., 1997,18,781. C . Rivas, F. Vargas, G. Aguiar, A. Torrealba, and R. Machado, J. Photochem. Photobiol., A, 1997, 104, 53. T. Nishio and M. Oka, Helv. Chim. Acta, 1997,80,388.
184
Photochemistry
173. 174.
S. Auricchio, A. Selva, and A. M. Truscello, Tetrahedron, 1997,53, 17407. E. Bosch, S. M. Hubig, S. V. Lindeman, and J. K. Kochi, J. Org. Chem., 1998, 63, 592. B. Barker, L. Diao, and P. Wan, J. Photochem. Photobiol., A , 1997, 104,91. A. Ouchi and Y. Koga, J. Org. Chem., 1997,62,7376. H. J. P. de Lijser and D. R. Arnold, J. Chem. Soc., Perkin Trans. 2 , 1997, 1369. D. R. Arnold, K. A. Mcmanus, and M. S . W. Chan, Can. J. Chem., 1997,75,1055. M. S. W. Chan and D. R. Arnold, Can. J. Chem., 1997,75,1810. T. Tsubomura, A. Ishikura, K. Hoshino, H. Narita, and K. Sakai, Chem. Lett., 1997, 1171. F. S. Bavetta, T. Caronna, M. Pregnolato, and M. Terreni, Tetrahedron Lett., 1997, 38, 7793. S.-J. Lin, S.-Y. Jiang, T.-C. Huang, C.3. Dai, P.-F. Tsai, H. Takeshita, Y.-S. Lin, and T. Nozoe, Bull. Chem. Soc. Jpn., 1997,70,3071. M. D’Auria, Heterocycles, 1997,45, 1775. M. D’Auria, E. De Luca, G. Mauriello, and R. Racioppi, J. Chem. Soc., Perkin Trans. I, 1998,271. V. L. Ivanov, S. Yu. Lyashkevich, and H. Lemmetyinen, J. Photochem. Photobiol., A , 1997,109,21. H. Ofenberg, L. Cires, A. Vlahovici, and A. Lablache-Combier, Rev. Roum. Chim., 1997,42, 137. A.-P. Durand, R. G. Brown, D. Worrall, and F. Wilkinson, J. Chem. Soc., Perkin Trans. 2,1998, 365. T. Nakayama, S. Akimoto, 1. Yamazaki, and K. Hamanoue, J. Photochem. Photob i d , A, 1997,104, 77. M. D’auria, E. De Luca, G. Mauriello, R. Racioppi, and G. Sleiter, J. Chem. Soc., Perkin Trans. I , 1997,2369. C. P. Butts, L. Eberson, M. P. Hartshorn, and 0. Peterson, Acta Chem. Scand., 1997, 51, 718. C. P. Butts, L. Eberson, M. P. Hartshorn, 0. Persson, R. S. Thompson, and W. T. Robinson, Acta Chem. Scand., 1997,51, 1066. C. P. Butts, L. Eberson, R. Gonzales-Luque, C. M. Hartshorn, M. P. Hartshorn, M. Merchan, W. T. Robinson, B. 0. Roos, C . Vallance, and B. R. Wood, Acta Chem. Scand., 1997,51,984. P. M. J. Jung, W. B. Motherwell, and A. S . Williams, Chem. Commun. (Cambridge), 1997, 1283. R . J. Moran, C. Cramer, and D. E. Falvey, J. Org. Chem., 1997,62,2742. C. Saintome, P. Clivio, A. Favre, and J.-L. Fourrey, J. Org. Chem., 1997,62, 8125. N. Vivona, S. Buscemi, S. Asta, and T. Caronna, Tetrahedron, 1997,53, 12629. T. Tsuji, M. Ohkita, T. Konno, and S . Nishida, J. Am. Chem. Sue., 1997,119, 8425. M. Okuyama, M. Ohkita, and T. Tsuji, Chem. Commun. (Cambridge), 1997, 1277. M. Kako, S. Oba, R. Uesugi, S. Sumiishi, Y, Nakadaira, K. Tanaka, and T. Takada, J. Chem. Soc., Perkin Trans. 2 , 1997, 125 1. M. Takeshita and M. Irie, Chem. Commun (Cambridge), 1997,2265. J. Buddrus, S. Boeckstegers, H. Hemetsberger, H. Mayer-Figge, A. Nowienski, K. F. Rammert, and W. S . Sheldrick, J. Photochem. Photobiol., A , 1997, 105, 39. E. M. Sharshira and T. Horaguchi, J. Heterocycl. Chem., 1997,34, 1837. A. G. Myers and Y. Horiguchi, Tetrahedron Lett., 1997,38,4363. K. A. Muszkat, M. Eisenstein, E. Fischer, A. Wagner, Y. Ittah, and W. Luettke, J. Am. Chem. Soc., 1997,119,9351.
175. 176. 177. 178. 179. 180. 181. 182. 183. 184. 185. 186. 187. 188. 189. 190. 191. 192. 193. 194. 195. 196. 197. 198. 199. 200. 201. 202. 203. 204.
IIl4: Photochemistry of Aromatic Compounds
185
M. Takahashi, T. Fujita, S. Watanabe, and M. Sakamoto, J. Chem. Soc., Perkin Trans. 2,1998,487. 206. M. C. Jimenez, M. A. Miranda, and R. Tormos, Tetrahedron, 1997,53, 14729. 207. T. J. Onofrey, D. Gomez, M. Winters, and H. W. Moore, J. Urg. Chem., 1997, 62, 5658. 208. T. Yamaguchi, K. Uchida, and M. Irie, J. Am. Chem. SOC.,1997,119,6066. 209. G. Dyker, J. Koerning, and W. Stirner, Eur. J. Org. Chem., 1998, 149. 210. R. Kojima, T. Shiragami, K. Shima, M. Yasuda, and T. Majima, Chem. Lett., 1997, 1241. 21 1. A. Evenzahav and N. J. Turro, J. Am. Chem. Soc., 1998,120, 1835. 212. P. Wessig, J. Schwarz, D. Wulff-Molder, and G. Reck, Monatsh. Chem., 1997, 128, 849. 213. J. H. Rigby and V. Gupta, Synlett, 1995, 547. 214. M. Close, J. D. Coyle, E. J. Haws, and C. J. Perry, J. Chem. Res. Synop., 1997, 1 15. 215. Y.-T. Park, C.-G. Hwang, K.-W. Kim, N. W. Song, and D. Kim, J. Am. Chem. SOC., 1997,119, 10677. 216. V. P. Vetchinov, E. B. Nikolaenkova, V. 1. Mamatyuk, and V. P. Krivopalov, Russ. Chem. Bull., 1997,46,607. 217. M. Ibrahim-Ouali, M.-E. Sinibaldi, Y. Troin, D. Guillaume, and J.-C. Gramain, Tetrahedron, 1997,53, 16083. 21 8. U. C. Yoon, J. W. Kim, J. Y. Ryu, S. J. Cho, S. W. Oh, and P. S. Mariano, J. Photochem. Photobiol., A , 1997,106, 145. 219. T. Nakamura, K. Takagi, and Y. Sawaki, Bull. Chem. SOC.Jpn., 1998,71,419. 220. H. Wang, R. E. Partch, and Y. Li, J. Org. Chem., 1997,62,5222. 221. A. N. Frolov and N. I. Rtishchev, Rum. J. Urg. Chem., 1997,33,246. 222. G. Jayanthi, S. Muthusamy, R. Paramasivam, V. T. Ramakrishnan, N. K. Ramasamy, and P. Ramamurthy, J. Org. Chem., 1997,62, 5766. 223. S.-J. Lin, S.-Y. Jiang, T.-C. Huang, P. Kao, P.-F. Tsai, H. Takeshita, Y-S. Lin, and T. Nozoe, Heterocycles, 1997,45, 1879. 224. C. Andreis, H. Durr, V. Wintgens, P. Valat, and J. Kossanyi, Chem. Eur. J., 1997, 3, 509. 225. E. M. Sharshira, M. Okamura, E. Hasegawa, and T. Horaguchi, J. Heterocycl. Chem., 1997,34,861. 226. M. H. B. Stowell, G. Wang, M. W. Day, and S. I. Sunney, J. Am. Chem. SOC.,1998, 120, 1657. 227. R. H. Prager, J. A. Smith, B. Weber, and C. M. WilIiams, J. Chem. Suc., Perkin Truns. I , 1997,2665. 228. R. H. Prager, M. R. Taylor, and C. M. Williams, J. Chem. Soc., Perkin Trans. I, 1997,2673. 229. J.-K. Luo, R. F. Federspiel, and R. N. Castle, J. Heterocycl. Chem., 1997, 34, 1597. 230. H. J. Hageman and J. W. Verhoeven, J. Photochem. Photobiol., A , 1997,103,75. 231. M. D’auria and R. Racioppi, Tetrahedron, 1997,53, 17307. 232. T. Nakamura, K. Takagi, M. Itoh, K. Fujita, H. Katsu, T. Tmae, and Y. Sawaki, J. Chem. Soc., Perkin Trans. 2,1997,275 I . 233. J. Bethke, J. Kopf, P. Margaretha, B. Pignon, L. Dupont, and L. E. Christiaens, Helv. Chim. Acta, 1997,80, 1865. 234. P. Ya, J. Org. Chem., 1997,62,7324. 235. A. Schuetz and T. Wolff, J. Photochem. Photobiol., A, 1997,109, 251. 236. P. Magnus, J. C. Morris, and V. Lynch, Synthesis, 1997,506. 205.
186 237. 238. 239. 240. 241. 242. 243. 244. 245. 246. 247. 248. 249. 250. 251.
252. 253. 254. 255. 256. 257. 258. 259. 260. 261. 262. 263. 264. 265. 266. 267. 268. 269.
Photochemistry
H. Kawakami, Y. Z. Yan, N. Kato, A. Mori, H. Takeshita, and T. Nozoe, Bull. Chem. SOC.Jpn., 1998,71,711. N. Marubayashi, T. Ogawa, T. Hamasaki, and N. Hirayama, J. Chem. SOC.,Perkin Truns. 2 , 1997, 1309. N. Marubayashi, T. Ogawa, and N. Hirayama, Bull. Chem. SOC.Jpn., 1998,71,321. I. V. Ukrainets, S. G. Taran, L. V. Sidorenko, 0. V. Gorokhova, A. V. Turov, and A. A. Ogirenko, Chem. Heterucycl. Cumpci. ( N . Y),1997,33,815. C. Lehnberger, D. Scheller, and T. Wolff, Heterocycles, 1997,45, 2033. W. Zhang and M. Wang, Ganguang Kexue Yu h a n g Huaxue, 1997,15,19. Z. Tong, Y.-M. Ying, and L. Yuan, Gunguung Kexue Yu Guung Huaxue, 1997, 15, 104. C.-H. Tung and Y .-M. Ying, J. Chem. Soc., Perkin Truns. 2, 1997, 1319. I. F. Molokov, Yu. P. Tsentalovich, A. V. Yurkovskaya, and R. Z. Sagdeev, J. Photochem. Photobiol., A , 1997,110, 159. S. M. Bonesi and R. Erra-Balsells, J. Phorochem. Photobiol. A, 1997, 110,271. M. C. Jimenez, M. A. Miranda, J. C. Scaiano, and R. Tormos, Chem. Cummun. (Cumbridge), 1997, 1487. A. M. Sanchez, A. V. Veglia, and R. H. De Rossi, Can. J. Chem., 1997,75, 1 151. T. Kaneko, K. Kubo, and T. Sakurai, Tetrahedron Lett., 1997,38,4779. T. Fournier, S. M. Tavender, A. W. Parker, G. D. Scholes, and D. Phillips, J. Phys. Chem., A , 1997,101,5320. M. Milewski, M. Sikorski, A. Maciejewski, M. Mir, and F. Wilkinson, J. Chem. Sac., Furaday Trans., 1997,93, 3029. T. H. Nguyen and N. B. Tran, Tup Chi Hoa Hoe, 1996,34,34. J. Andraos, Y. Chiang, A. J. Kresge, and V. V. Popik, J. Am. Chem. SOC.,1997, 119, 8417. N. C. de Lucas, J. C. Netto-Ferreira, A. J. Lusztyk, B. D. Wagner, and J. C. Scaiano, Tetrahedron Lett., 1997,38, 5147. A. Albini, G. Bettinetti, and G. Minoli, J. Am. Chem. SOC.,1997, 119, 7308. C. Wentrup, A. Reisinger, G. G. Qiao, and P. Visser, Pure Appl. Chem., 1997, 69, 847. D. Donati, S. Fusi, and F. Ponticelli, J. Chem. Rex, Synop., 1997, 170. T. Harder, R. Stosser, P. Wessig, and J. Bendig, J. Photochem. Photobiol., A , 1997, 103, 105. D. Kosynkin, T. M. Bockman, and J. K. Kochi, J. Am. Chem. Soc., 1997,119,4846. R . Albers and W. Sander, Liebigs Ann.lRecl., 1997,897. B. Szczepanik and T. Latowski, Pol, J. Chem., 1997,71,807. I. Ono, S. Sato, K. Fukuda, and T. Inayoshi, Bull. Chem. SOC.Jpn., 1997,70,2051. D. Grassi, V. Lippuner, M. Aebi, J. Brunner, and A. Vasella, J. Am. Chem. SOC., 1997,119, 10992. Y. Chiang, A. S. Grant, H.-X. Guo, A. J. Kresge, and S. W. Paine, J. Org. Chem., 199?, 62,5363. D. Leinweber, Tetrahedron Lett., 1997,38,6385. Z . Zhou, W. Jiang, and W. Liu, Huanjing Kexue, 1997,18, 35. M . C. Jimenez, M. A. Miranda, and R. Tormos, J. Photochem. Photobiol., A , 1997, 104,119. A. Sugimoto, C. Hayashi, Y. Omoto, and K. Mizuno, Tetrahedron Lett., 1997, 38, 3239. K. Burgess, S. E. Jacutin, D. Lim, and A. Shitangkoon, J. Org. Chem., 1997, 62, 5165.
IIl4: Photochemistry of Aromatic Compounds
187
J. Xia, X. Huang, R. Sreekumar, and J. W. Walker, Bioorg. hied Chem. Lett., 1997, 7 , 1243. 271. Y. Shi, J. E. T. Corrie, and P. Wan, J, Org. Chem., 1997,62, 8278. 272. H. Morita, H. Kamiyama, M. Kyotani, T. Fujii, T. Yoshimura, S. Ono, and C. Shimasaki, Chem. Commun. (Cambridge), 1997, 1347. 273. M. Ashram, D. 0. Miller, J. N. Bridson, and P. E. Georghiou, J. Org. Chem. 1997, 62,6476. 274. A. Banerjee and D. E. Falvey, J. Org. Chem., 1997,62,6245. 275. A. Banerjee and D. E. Falvey, J. Am. Chem. Soc., 1998,120,2965. 276. R. S . Givens, A. Jung, C.-H. Park, J. Weber, and W. Bartlett, J. Am. Chem. Soc., 1997,119,8369. 277. B. Wang and A. Zheng, Chem. Pharm. Bull., 1997,45,715. 278. A. Hasan, K.-P. Stengele, H. Giegrich, P.Cornwell, K. R. Isham, R. A. Sachleben, W. Pfleiderer, and R. S. Foote, Tetrahedron, 1997,53,4247. 279. W. Pfleiderer and S. Eisele, Ger. Offen. DE 19,620,170. 280. R. Rodebaugh, B. Fraser-Reid, and €1. M. Geysen, Tetrahedron Lett., 1997, 38, 7653. 281. S. Watanabe and M. Iwamura, J. Org. Chem., 1997,62,8616. 282. T. Voelker, T. Ewell, J. Joo, and E. D. Edstrom, Tetrahedron Lett., 1998,39,359. 283. H. Shiono, H. Kodama, and M. Kojima, PCT Int. Appl. WO 97 47,639. 284. J. F. Cameron, C. G. Willson, and J. M. J. Frechet, J. Chem. Soc., Perkin Trans. 1 , 1997,2429. 270.
5
Photo-reduction and -oxidation BYALAN COX
1
Introduction
Topics which have formed the subjects of reviews this year include excited state chemistry within zeolites, photoredox reactions in organic synthesis,2 selectivity control in one-electron r e d ~ c t i o n ,the ~ photochemistry of f~llerenes,~ photochemical P-450 oxygenation of cyclohexene with water sensitized by dihydroxybiocoordinated (tetraphenylporphyrinato)antimony(V) hexafl~orophosphate,~ mimetic radical polycyclisations of isoprenoid polyalkenes initiated by photoinduced electron transfer,6 photoinduced electron transfer involving C6dC70,~" comparisons between the photoinduced electron transfer reactions of C ~ and O aromatic carbonyl compound^,^ recent advances in the chemistry of pyrrolidinofullerenes, l o photoinduced electron transfer in donor-linked fullerenes, I supraphotoinduced molecular model systems, I 2 , l 3 and within dendrimer architect~re,'~ electron transfer reactions of homoquinones, amines, l 6 and azo compounds,l 7 photoinduced reactions of five-membered monoheterocyclic compounds of the indigo group," photochemical and polymerisation reactions in solid C60,19 photo- and redox-active [2]rotaxanes and [ 2 ] ~ a t e n a n e sreactions ,~~ of sulfides and photoprocesses of sulfoxides and related sulfenic acid derivatives with 0 2 ( compounds,22 semiconductor photo catalyst^,^^ chemical fixation and photoreduction of carbon dioxide by metal p h t h a l ~ c y a n i n e sand , ~ ~ multiporphyrins as photosynthetic models.25 The role of excitation lifetime in electron transfer reactions,26 and photoinduced electron transfer in isolated jet-cooled molecular have also been discussed.
'
'
2
Reduction of the Carbonyl Group
Some general rules for photochemical hydrogen abstractions by n,x*-excited states have appeared.28 Computer simulation of intramolecular hydrogen atom transfer to carbonyl oxygen has been achieved by a Monte Carlo method.29 In particular, the model has been found to give good agreement when applied to intramolecular p-, y-, 6-, E-, and <-hydrogen atom abstraction in ketones as well as q- and 0-proton transfer in oxoesters, and it has also been used to predict the reactivities of Photochemistry, Volume 30 0The Royal Society of Chemistry, 1999
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III.5: Photo-reduction und - oxiriution
I89
2-(N ,N-dibenzy1amino)ethyl 2-, 3-, and 4-benzoylbenzoate. The first fluorescence and fluorescence quantum yield measurements from the excited state of the radical anion of benzo- 1,4-quinone have appeared, and since these species are powerful reducing agents generally, such parameters are of considerable importan~e.~' Zeolites have been found to be capable of promoting facially selective photoreduction of steroidal ketone^.^' In particular, androstenedione is reduced at the j3-face, and testosterone acetate and cholestenone are reduced at the enone double bond from the same face. Pentan-2-one has been irradiated within various zeolites having cavities whose sizes have been increased by changing the cation from Li+ to C S + . ~The * observed relative yields of the Norrish Type I and Norrish Type I1 products are found to be dependent upon the cavity sizes. Photoelectron transfer in flexible dyads consisting of 9-aminoacridine benzoyl ester moieties linked by a hydrophilic tetraethylene glycol chain has been examined, and the results suggest that these structures exist preferentially in folded conformations in which the donor and acceptor stand in close enough proximity to allow efficient intramolecular fluorescence quenching to occur.33 The quenching of triplet benzophenone by alkylbenzenes and anisole derivatives has been studied in aqueous acetonitrile and benzene solutions.34 In both solvent systems, quenching by alkylbenzenes produces ketyl radicals, but quenching by anisole derivatives occurs by electron transfer in acetonitrile, and in benzene no chemical species are observed. In polar media, triplet exciplexes formed between benzophenone and various naphthalene derivatives (ArX) may undergo hydrogen atom transfer, protoninduced electron transfer, and hydrogen-bonding-induced electron transfer, depending upon the nature of X.35 A study of the photoreduction of benzophenone by 2,4,6-trimethyl-1,3,5-trithiane has established a correlation between the kinetic results and the known ability of 2,4,6-trimethyl-1,3,5-trithiane to accelerate benzophenone-induced polymer is at ion^,^^ and in the photoreduction of benzophenone-3,3',4,4-tetracarboxylicacid using triethylamine in aqueous solution, the primary electron transfer process gives solvent-separated radical ionpairs.37A Coulomb-coupled solvent-separated ion pair has also been detected. A range of tertiary amines has been used to show that in the photoreduction of triplet benzophenone no correlation exists between the ketyl radical yields and either the quenching rate constants or the electron donicity of the a m i n e ~The .~~ currently available evidence seems to suggest that the photoreduction yields are determined by the individual structural features of the amines. 4-Carboxybenzophenone (CB) has been photoreduced by the various hydroxyalkyl sulfides, 2(methylthio)ethanol, 2,2'-dihydroxydiethyl sulfide, 3-(methylthio)propanol, 3,3'dihydroxydipropyl sulfide, 3-(methylthio)propanol, and 4-(methylthio)b~tanol.~~ The ketyl radical anion (CB)*-,the ketyl radical (CBH)', and intermolecularly (S-S)-bonded radical cations were also observed, and a detailed mechanism for the sensitized photooxidation of these sulfur-containing alcohols by CB has been proposed. Investigation of the decay kinetics of intermediates produced in the photolysis of 4,4'-bis-dimethylaminobenzophenone, 4,4'-diethylaminobenzophenone, and 4-dimethylaminobenzophenone in various polar solvents has estab-
190
Photochemistry
lished that, in addition to alkylamine or ketyl radicals, a further intermediate absorbing at about 470 nm is formed.40 In contrast to the behaviour of acetophenone/amine mixtures in acetonitrile/water mixtures, laser flash photolysis reveals that in the cavities of NaY zeolites there exist acetophenone triplets, ketyl radicals and dimers of amine radical cation^.^' Observations suggest that in the cavities, the amine radical cations react with neutral amine to give the dimerised radical cation, and in the particular case of the acetophenone/triethylamine system, hydrazines are formed. Photolysis of neat a-(ary1oxy)acetophenonesgives a mixture of biphenyl, benzil, benzoic acid, acetophenone, and the corresponding phenol, benzaldehyde, benzyl alcohol, benzofuran, and styrene; similar results are obtained following t her m ~ l ys i s .A~ ~laser flash photolysis examination of 1,1'-, 1,2'-, and 2,2'-dinaphthyl ketones and the structurally related 2,3,5,6-dibenzofluorenone suggests that these compounds are not photoreduced by propan-20 1 . ~ Reactions ~ of their triplets with 1,4-diazabicyclo[2.2.2]octane,triethylamine, cyclohexa-1,4-dienone, and 2,4,6-trimethylphenol show that there is a strong preference for electron transfer. Irradiation of 2'-hydroxychalcone (1) promotes an intramolecular photoinduced hydrogen atom transfer to the corresponding tautomer whose triplet state has been observed.44
CIDEP spectra obtained in the photoinduced electron transfer between acceptors such as 2,3-dimethoxy-5-methylbenzoquinoneand related quinones and electron donors such as triphenylamine and N,N,N,N-tetramethylbenzidine suggest that charge recombination free energy determines the sign of J: this observation has lead to a new mechanism for the sign of J based upon Marcus theory.45 Solutions of benzoquinone are reported to react with the hydrideterminated surface of luminescent porous silicon to form a surface-bound p hydroquinone species.46 The rate of derivatisation is reported to increase on irradiation with 435 nm light. Electron transfer from aromatic donars to excited singlet state chloranil (CA) to give singlet radical-ion pairs, [D'+,CA'-] has been demonstrated on the fs/ps time scale and is a process which is in competition with intersystem crossing.47 These observations imply that both singlet and triplet manifolds should now be considered as possible pathways among quinone acceptors. Stimulated nuclear polarisation measurements of the photoinduced electron transfer to tetrafluoro-p-benzoquinone from quadricyclane indicate that the cation radical of quadricyclane is produced, and that its conversion into the norbornadiene cation radical occurs mainly outside the cage of the radical ion pair.48 An investigation of the photoreduction of chloranil to the hydroquinone by benzhydrols has established the participation of three distinct mechanism^.^^ Quenching of the triplet state of the quinone gives the semiquinone radical, triplet quenching by bis(4-methoxypheny1)methanol gives the chloranil radical anion,
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IIl.5: Pholo-reduction and -oxidation
191
and quenching by 1-naphthylmethanol and acenaphthenol gives the chloranil radical anion together with the naphthalene radical cation. These observations have been accounted for in terms of hydrogen atom transfer with benzhydrol, and by electron transfer followed by proton transfer between geminate radical ions for the powerful electron donors. The encounter complex [Q*-ArH] formed between photoexcited quinones such as chloranil and 2,5-dichloroxyloquinone (Q*) and aromatic donors such as hexamethylbenzene has been observed before it undergoes electron transfer to the radical ion pair [Qo--ArH*'].50The temporal evolution of the encounter complex was established by kinetic analysis, and its structure accounted for in terms of cofacial juxtaposition of the donor and acceptor moieties for maximum overlap of their n-orbitals. Excited Safranine T will photoreduce benzoquinone by electron transfer in polar solvents such as methanol and acetonitrile." In the latter solvent, electron transfer follows a Rehm-Weller correlation, but in MeOH the rates for triplet quenching are significantly larger. A study of the CIDEP spectra of p-benzosemiquinone radicals from photolysis of p-benzoquinone (PBQ) in ethylene glycol using timeresolved ESR spectroscopy in homogeneous solvents and in Triton-X- 100 micellar solutions has been described.52Since polarisation of PBQ'- is transferred from PBQH' through its dissociation reaction, it is suggested that special properties of the bound water in the PG shell of TX-100 micelles can be used to explain the results. The photoexcited triplet states of 2,3-dibromonaphtho- 1,4-quinone and 2,3-dichloronaphtho- 1,Cquinone in polar media are capable of abstracting a hydrogen atom from phenol in a process which is sterically indifferent, and At room temperature involves an electron from 1,2,4,5-tetrametho~ybenzene.~~ both triplet states are of mixed '(n,n), 3(n,7t) character. A FT-ESR study of the photoreduction of 9,lO-anthraquinone- 1,5-disulfonate and 9,lO-anthraquinone2,6-disulfonate with triethylamine in aqueous solution shows that the lifetimes of a variety of intermediates, such as the semiquinone radical anion, the triethylamine radical cation, and the a-aminoalkyl radical, are pH dependent.54 Photoinduced intramolecular electron transfer in an anthraquinone-fluoresceincarbazole triad involves competing electron transfer between the fluoresceincarbazole and anthraquinone-fluorescein pairs, with the initiating process being dominated by transfer between fluorescein and ~ a r b a z o l e An . ~ ~investigation of the solution structures of the P-4-epimers of the anthraquinone-Zn(I1)-pyropheophytin dyads has revealed that the mutual orientations of the rings of the components are distinct.56In both dyads the anthraquinone ring is located below that of the phorbin macrocycle, but in ZnPQl the anthraquinone ring is sloping below subrings B, C, and E of the phorbin, whereas in ZnPQ2 the two n-systems are almost parallel. The photoinduced intramolecular hydrogen atom transfer from the substituted methyl group in 1-alkylanthraquinone to the peri-quinoid oxygen atom giving the corresponding 9-hydroxy-l , 10-anthraquinone occurs via the ~n-biradical.~' Quantum chemical calculations on the nature of the transition state in the back thermal reaction have been reported. A study of the photoinduced intramolecular electron transfer reactions of porphyrin-anthraquinones using a fluorescence procedure has been described,58 and an ESR study has
192
Photochemistry
appeared of the formation of ionic free radicals by electron transfer between porphyrins and anthraquinones as a function of the porphyrin ligands, metalporphyrin, axially coordinated organic base, and solvent.59The signal intensities are greater for metalloporphyrins, dipolar aprotic solvents, and axial groups such as piperidine and imidazole. p-Carotene may further enhance charge separation. The same workers have also showed that photoinduced electron transfer involving a Pd-porphyrin-quinone complex (Pd-P-Q) proceeds by efficient quenching of the excited triplet state by unexcited molecules in a process which is related to intermolecular charge transfer between the Pd-P portion of the excited molecule and the quinone portion of an unexcited molecule.60On the basis of a structural analysis of the porphyrin-quinone cyclophane (2) and some related compounds, an assessment of the distance dependencies of photoinduced electron transfer from porphyrin to quinone has been made.61Excitation of cyclohexylene-bridged chlorin-quinones in frozen ethanol promotes electron transfer, and time resolved ESR studies indicate the presence of both the transient spin-polarised chlorin triplet state and the spin-polarised triplet state of the charge separated radical pair.62
An examination of the photophysics of hypericin (3) and its fully methylated analogue, hexamethoxyhypericin: has shown the presence of an intramolecular excited-state proton transfer for the former compound, but that the hexamethylated analogue is incapable of protonating its own carbonyl groups.63 The same authors have confirmed these conclusions using fluorescence upconversion meas u r e m e n t ~Visible . ~ ~ light illumination of the mercapto-substituted hypocrellin B (4) derivatives 5,8-RS-HB or 5-RS-HB gives the semiquinone radical anion, superoxide anion radical, singlet oxygen, and the hydroxyl radical.65 In aerobic solution the semiquinone radical anion arises by self-electron transfer between ground and excited state species, and in aerobic solution singlet oxygen is
IIIS: Photo- reduction and -oxidutiorz
193
generated. The results imply that both electron transfer (Type I) and O2('Ag) (Type 11) are involved but to different extents depending on the substrate. These authors have also examined the relative yields of 02('Ag), 0 2 ' - , and the anion radical produced during photosensitization of hypocrellin B and its 5- and 5,8brominated derivatives, and it has been shown that although monobromination does not increase the yield of 02(lAg), dibromination enhances the yield by about 200/P*~~
A laser flash photolysis study of the behaviour of the lowest excited triplet state and semiquinone radical anion of hypocrellin A (HA'-) suggests that, in the presence of substrates such as ascorbic acid and cysteine, formation and decay of (HA'-) occurs by electron transfer.68 The production of superoxide radical anion (02") was also confirmed, and the conclusion is drawn from the experimental results that an electron transfer (Type I) mechanism may be important in the photodynamic interaction between HA and some biological substrates. Photoelectron transfer and hydrogen abstraction in the phenothiazinelp-benzoquinone system proceeds ~ o m p e t i t i v e l yand , ~ ~ a series of porphyrin quinones (5; R7 = H, R8 = trans-PQ; R8 = H, R7 = cis-PQ; Q = 6 , 7, 8,9) rigidly and covalently linked by a cis- or trans-l,4-disubstituted cyclohexylene bridge has been prepared in which the acceptor strength of the quinone is ~ a r i a b l e . ~The ' conformation of the cyclohexane ring was determined in all cases. These compounds may be wellsuited as biomimetic model compounds for the study of photoinduced electron transfer reactions in photosynthesis. Various hydroxylactams, for example (lo), have been synthesised from o-phthalimidoalkanoates (1 1) by triplet-sensitized photodecarboxylation in a process whose crucial step in this macrocyclisation is protonation of the intermediate ketyl radical^.^' P-Aminopropiophenones (12) can be regioselectively photolysed to 2-aminocyclopropanols (1 3) which can subsequently undergo photooxidative ring opening to the enaminones ( 14).72 The regioselectivity is controlled by the preferred charge transfer interaction between the photoexcited benzoyl chromophore and the amino group. ~-2,2,2-(Trifluoroethoxy)benzophenone can be photocyclised to give the cisand trans-benzofurans (15; R = CF3) in a process which is best rationalised in terms of the captodative effect of the biradical intermediate,73 and the 9,lO-
194
Photochemistry
R*
*
Me
0
0
*Me
MeQMe 0
0 (7) 0
0
dicyanoanthracene radical anion (DCA'-), generated by photoelectron transfer using triphenylphosphine, has been used to promote efficient cyclisation of aldehydes and ketones tethered with activated 01efins.~~ This latter transformation is a one electron reductive activation to give diastereoselective cycloalkanols in high yield. The cyclisation probably involves a ketyl radical intermediate and has been used to prepare optically pure C-furanoside (16) from L-tartaric acid. Irradiation of the eight-membered ring compound (17; NV = 2-nitro-4,5dimethyloxybenzyloxy) gives the ring-opened mitosene (1 8) as a 1 : 1 mixture of secondary alcohol diastereoi~omers.~~ Photocyclisation of 2-(N,N-dibenzyl-
M.5: Photo-reductionand -oxidation
195
amino)ethyl benzoylacetate proceeds through a 1,8-biradical to form the cis- and trans-isomers of an azalactone (19) and (20) respectively, but does not do so stereo~electively.~~ This has been rationalised by the suggestion that in the transition state for cyclisation, the 1,8-biradicals may have almost identical boatchair like conformations with the dihedral angles between the C5- and C6-Ph groups being about 45" in both isomers. The same group also report that irradiation of 2-(a1kylthio)ethyl benzoylacetates induces their photocyclisation to the eight-membered ring thialactone (21) via a 1,9-proton transfer following intramolecular charge-transfer interaction between the sulfur and the excited carbonyl
mR
MeO-0
H O C H 2 . . q .CH2C02Me
\
HO (15)
Ph
N
C
O
z
M
e
I
OH
HO'
OHCa
NVCO
(16)
(17)
ph,
/-
.Ph
In benzene solution cyclodeca-l,2-dione, already known to undergo a Norrish Type I1 reaction to form a mixture of (22) and (23), has now been reported to produce a mixture of (22) and (24) on photolysis in the crystalline state.78
The results of an AM 1 semi-empirical MO examination of y-hydrogen abstractions by the triplet states of pentan-2-one and 2-methylpent-l-ene show that the carbonyl oxygen atom and the terminal carbon atom of the ethylenic moiety It is also suggested that acquire high free valence and spin density re~pectively.~~ room temperature tunnelling of hydrogen is significant. Using ab initio MO methods, the same authors have also examined two-dimensional tunnelling of hydrogen in a Norrish Type I1 process of pentan-2-one, and claim that these calculations indicate a lowering of the tunnelling probability obtained by the conventional one-dimensional calculation in those cases in which the barrier is anharmonic.80 Photolysis of 5-(o-tolyl)-5-cyano-4,4-dimethylpentan-2-one
196
Photochemistry
produces Norrish Type I1 products in a 1 : 1 ratio without formation of any products of cyclisation.8' This same reaction is observed in the solid state and factors influencing abstraction of the tertiary hydrogen atom have been examined. Flash photolysis of benzoylformate esters promotes a Norrish Type I1 reaction to give phenylhydroxyketene which undergoes hydration to give the enol of mandelic acid (PhC(OH):(C(OH)2).82 An identical enol is formed by hydration of the phenylcarboxycarbene generated when phenyldiazoacetic acid is irradiated. Rates of enolisation have been determined and compared with other keto-enol systems. Alkoxy-containing alkyl phenyl glyoxalates have been studied, and in particular 4-methoxybutyl phenylglyoxalate and 5'-benzyloxypentyl phenylglyoxylate are found to lead to the products of 1,lO- and 1,ll-hydrogen abstraction, as well as to products derived from Norrish Type I1 and intermolecular hydrogen abstract i ~ nThe . ~ same ~ authors have also made an assessment of the photochemistry of some halo/aryl sulfide-substituted alkyl phenylgly~xalates.'~ For example, it has been shown that for 2'-bromo-, 2'-iodo-, 2'-(pheny1thio)-, and 2'-(phenylsulfiny1)ethyl phenylglyoxalate, vinyl phenylglyoxalate is suggested to be the result of p-elimination from the 1,4-biradical which arises by triplet state y-hydrogen abstraction. Aromatic ketocarboxylate anions of the type p CH&bH&O(CH2),C02- (n = 4 -10) adsorbed into the anion exchange clay hydrotalcite in aqueous suspension yield the Type I1 photoproducts p-methylacetophenone and alkenecarboxylates, together with cyclobutanols, the yields of which are dependent upon the alkyl chain length (n).85The proportion of Type I1 products is found to increase with increasing n, and the presence of the coadsorbates promotes a significant acceleration of the Type I1 reaction. These observations can be rationalised in terms of the conformational flexibility of the substrate imposed by the interlayer space of the clays. Laser flash photolysis studies of various N-substituted 1,8-naphthalimides (25) and 1,4,5&naphthaldiimides (26) have shown that S1 of,(25) is KIT* and S1 of (26) is n7c*, a consequence of which is that only (26) is capable of y-hydrogen abstraction.86 Triplet states will sensitize production of 02('A,) efficiently, and in the absence of quenchers they will undergo electron transfer with their ground state. These observations are discussed with special reference to the photobiological effects of the compounds. Reaction enthalpy and reaction volume changes in the photoenolisation of 2methylbenzophenone have been rneas~red,'~ and the geometries, and formation enthalpies of reagents, products, and triplet state intermediates in the photoenolisation of 2-methylacetophenone and 1-methylanthraquinone have been calculated by semiempirical quantum chemical methods." Two cyclic peroxides are formed by Diels-Alder addition of molecular oxygen to the o-xylylenol photoenol produced from o-benzyla~etophenone.~~ Irradiation of o-benzylbenzophenone gives cis- 1,2-diphenyl-1-benzocyclobutenol, and the results have been interpreted in terms of a twisted triplet model of xylylenol conformers. The photoenol of 5methylnaphtho-l,4-quinonehas been shown to be formed with a quantum yield of unity in the ground state by a conical intersection of the So and S1 hypersurfaces within 2 ps of excitation, and these observations may be important for the study of hydrogen and proton transfer reaction^.'^ Irradiation of
111.5: Photo-reduction and -oxidation
197
1 -hydroxy-l,3-diphenylindan-2-one gives a mixture of the ( E , Q and (Z,E) enols of which the latter is short-lived and decays to give o-benzylben~ophenone.~’ The (E,E) enol (T > 100 ps in methanol) forms a mixture of products including 10phenylanthrone and 10-hydroxy-10-phenylanthrone. Studies have also been reported on 1 -hydroxy- 1,3,3-triphenyIindan-2-onewhich also gives two photoenols. Details of a route to bicyclic o-quinodimethanes, which starts by irradiation of indan-1-01, a-tetralol, and 1-benzosuberone, and gives the E-photoenols, have appeared.92 The photoenols from benzosuberan-9-carboxaldehyde and dimethyl fumarate are observed to proceed with much lower selectivity in comparison with the other substrates investigated, and this has been accounted for in terms of distortion of a diene consequential upon the geometry of the 7membered ring. Diarylacetylenes and 2,6-dichlorobenzoquinonewill undergo a regioselective Paterno-Buchi reaction to yield a single quinone methide adduct both on direct photoactivation of the quinone, and on photoactivation of the 1 : 1 electron donor-acceptor complex which subsequently decays to the corresponding radical ion pair.93 This is strong evidence that the Paterno-Buchi reaction proceeds by the same sequence of reactive intermediates in these cases. Irradiation of benzaldehyde and styrene gives the 2,3-trans- and 2,3-cis-isomers of diphenyloxetane in a ratio of 3: 1, but it has now been reported that under similar conditions phenylprop- 1 -ene and trimethylsilyl cinnamyl ether generate the corresponding oxetanes with high ~tereoselectivity.~~ 1 ’,5’-Dimethylhe~-4’-enyl phenylglyoxalate undergoes an intramolecular Paterno-Biichi reaction, but increasing the distance between the excited carbonyl group and same alkenyl function as in 3’,7’-dimethyloct-6-enyl phenylglyoxalate induces a Norrish Type I1 reaction as well as intramolecular cy~loaddition.~~ This is attributed to a competitive distance-dependent electron transfer process. Shortening of the distance as for example in 4’-methylpent-3’-enyl phenylglyoxalate induces cyclol formation along with a Paterno-Biichi reaction. A variety of N-(a, P-unsaturated carbony1)benzoylformamides (27) undergo a [2+2] photoconversion in both solution and the solid state to produce bicyclic oxetanes (28).96Substrates which crystallise in a chiral space group form optically active oxetanes.
A time-resolved study of the photochemistry of aqueous 2-(3-benzoylphenyl)propionic acid reveals that the main pathway for decarboxylation is intramolecular electron transfer through triplet b i r a d i ~ a l sand , ~ ~ similar examination of the photoreactions of 6H-purine-6-thione (29) shows that (329*) acts as an electron acceptor for tetramethylbenzidine and as an electron donor for p-dinitroben~ e n e Rate . ~ ~constants for H-atom abstraction from benzenethiols, tocopherol,
198
Photochemistry
and cyclohexa-l,4-diene have also been measured. Irradiation of ethyl 2-bromo(30) and related commethyl- 1-oxo- 1,2,3,4-tetrahydronaphthalene-2-~arboxylate pounds in the presence of Me3SiCH2NEt2 in aqueous acetonitrile gives the ring expansion product ethyl 5-oxo-6,7,8,9-tetrahydrobenzocycloheptene-7-carboxylate (3 1) in a single electron transfer process.99
C02Et
3 Reduction of Nitrogen-containing Compounds Alkylviologen photoreduction in anionic SDS and cationic DTAB micelles has been studied as a function of alkyl chain length, the number of alkyl chains on the viologens, and the interface charge on the micelles.’OO The results show that the electron transfer process across the micellar interfaces is determined by the energy barrier, the electron transfer distance, and by the relative orientations of the donor and acceptor. Continuous photoreduction of methylviologen by 5,5’bis(aminomethyl)-2,2’:5‘,2’-terthiophene(32) and 2,2’:5’,2’-terthiophene-5,5’-dicarboxylic acid using EDTA as a sacrificial electron donor occurs in aqueous media at various pH, and the highest conversion efficiency was shown by (32) at pH 7.7. lo’ The quenching of photoexcited [Ru(bpy)3I2’ by viologen-carbazole linked compounds in aqueous solution is more efficient than by the simple viologen alone, and this has been ascribed to an enhanced electron transfer to the partially dehydrated viologen.Io2 A preliminary study of long range intramolecular electron and energy transfer has been made in the rigid bichromophoric systems (33a).2BF4 and (33b).2BF4 comprising either a dimethoxybenzene (a) or a dimethoxynaphthalene (b) moiety linked through a six-bond norbornylogous bridge to a methylviologen unit, and it is suggested that an additional rapid nonradiative process in (33b).2BF4 participates compared with a model dimethoxynaphthalene unit.Io3 n-Donor-polyoxyethylene-capped Zn(I1)-porphyrins such as (34) which form supramolecular complexes with methylviologen have been found to be quenched within the complexes by internal electron transfer, and in the case of the free chromophore by diffusional electron transfer. lo4 Copolymers based upon chloromethylstyrene and divinylbenzene and containing viologen moieties have been photoreduced to form radical monocations and biradicals in both pure water and salt solutions.105 The transport numbers of various ions through the membrane have been investigated before (oxidised form) and after (reduced form) irradiation of the membrane, and have been found to be reversible. These changes have been attributed to photoinduced shrinkage of the polymer network caused by a decrease in the charge density of the anion-exchange membranes.
IIf.5: Photo-reduction und -0xidution
199
it
(34)
Et
The new dyads [Ru(tpy)(Metpp)13' and [Ru(bpy)(Metpp)(CH$N)l3+ (tpp = 2,3,5,6-tetrakis(2-pyridyl)pyrazinebound in tridentate fashion, Me = methylated N) in which the methylated nitrogen functions as an electron acceptor as in a viologen, have been prepared.lo6 Studies have been made of the photochemistry of this light absorber-electron acceptor molecular dyad along with the unmethylated analogues. Intramolecular electron transfer rate constants have been measured for electron transfer in the water soluble viologen-linked trisulfonatophenylporphyrins (TPPSC,V) having different methylene chain lengths (n = 3-6).'07 These compounds have been applied to photoinduced hydrogen evolution in a system containing nicotinamide-adenine dinucleotide phosphate and hydrogenase under steady state conditions. The same authors have also examined the photochemistry of the water-soluble viologen-linked Zn porphyrin ZnP(C4VC4), and bisviologenlinked Zn porphyrin, ZnP(C4VAC4V&, in which the viologens, butylviotogen and 1-benzyl-1'-butylviologen are connected with the tetrakis-(4-pyridyI)-Zn porphyrin by a C4 methylene chain.lo8 In the latter case the photoexcited triplet state of the porphyrin is not quenched by the bonded viologen although quenching does occur in the former case. Stereoselective photoinduced electron transfer has been observed between zinc-substituted myoglobin and optically active viologens and bisviologens containing naphthyl-, phenyl-, and cyclohexylethyl-carbamoyl-methyl groups, and the triplet state of the myoglobin is reported to be preferentially quenched by (S,S)-isomers of the optically active v i o l o g e n ~ . ' ~ ~ It is suggested that the naphthyl groups on the viologens may be responsible for inducing steric repulsion with the polypeptide chain of the zinc myoglobin. The photoelectrochemical characteristics of PCgFcCl lSHSAM (35; P = porphyrin; Cs = chain comprising eight carbon atoms; Fc = ferrocene; SAM a self assembled monolayer of alkanethiols on gold in which S is a photoactive group) have revealed that after prolonged irradiation of the electrode, MV2+ is reduced to MV."' Photoelectron transfer from the excited singlet state of zinc(I1) tetraphenylporphyrin (ZnTPP) to MV2+ in a compartmentalised system in which the ZnTPP moieties are covalently attached to amphiphilic sodium polysulfonates carrying lauryl2-(naphthyl)methyl, or cyclododecyl groups, is reported to be much slower
Photochemistry
200
Q
than analogous systems having no hydrophobic groups." Such compartmentalisation promotes accumulation of ZnTPP'+, and the naphthyl and cyclohexyl groups provide effective assistance. Silver clusters stabilised on zeolite-Y (Ag-Y) will photoreduce intrazeolitic methylviologen (MV2') to its x-cation radicals and the photoinduced electron transfer process has been considered in terms of the oxidative quenching mechanism of the excited silver plasmon resonance.' * Linear Langmuir plots have been obtained for the steady state photocatalytic reduction of methylviologen and a range of monosubstituted nitrobenzenes using Ti02 in the presence of propan-2-01 as sacrificial electron donor.'I3 From this information rate constants for reduction of the nitroaromatics have been obtained assuming a bimolecular model. The fluorescence of aromatic guests such as 3-(2-naphthoxyl)-1-aminopropane, 3-( 1-naphthoxyl)-1-aminopropane, and 3-(2-dibenzofuranoxyl)-1-aminopropane by P-cyclodextrin-bound viologens is more efficient than by dimethylviologen itself, and it has been suggested that this is due to static quenching within the inclusion c~mplexes."~ Photoinduced electron transfer has been investigated by FT-EPR at the surface of Ti02 nanoparticles by means of three systems, namely the coumarin 343 dye and methylviologen in ethanol, a colloidal solution of Ti02 in ethanol containing methylviologen, and a colloidal solution of Ti02 in ethanol containing both the coumarin dye and methylviologen. l 5 The kinetics suggest that reduction of the methylviologen proceeds by photoelectron transfer from the Ti02 particles by interfacial charge transfer as opposed to occurring by diffusive encounters. The fluorescence quenching dynamics of excited state electron donors by various pyrimidine and 5,6-dihydropyrimidine substrates have been examined and found to obey the Rehm-Weller relationship.' l 6 In addition, an unexpected difference was observed between the reduction potentials for the trans-syn and cis-syn diastereoisomers of dimethylthymine cyclobutane dimers, and this has been ascribed to a stereoelectronic effect in the cis-syn dimer anion radical resulting from an unfavourable charge-dipole interaction between the added electron and the O4 carbonyl group of the pyrimidine ring Irradiation of acidic aqueous solutions of Fe(1II) tetrakis(2-N-methylpyridy1)porphyrin in the presence of mono- or dibasic amino acids or the corresponding
'
'
IIIS: Photo-reductionand -oxidation
20 1
N-acetylated derivatives leads to the formation of Fe(I1) porphyrins together with the acyloxy radical which undergoes decarboxylation to give ammonio-alkyl or amidoalkyl radi~a1s.l'~Large differences in the observed rates of Fe(I1) porphyrin formation can be accounted for in terms of two factors, the binding affinity of the carboxyl to form a photoactive complex, and competitive reactions of acyloxy radicals following photolysis. The 3 ( n ~* state ) of the azo chromophore present in azoalkanes such as 2,3diazobicyclo[2.2.l]heptene (36; R', R2 = CH3, Ph) is efficiently quenched by amines with concomitant reduction to the corresponding hydrazine (37).' l 8 The same authors have also discussed this photoreduction in the presence of alcohols, cyclohexa-1,4-diene, tributylstannane, and tris(trimethylsily1)silane as hydrogen donor, and find that azoalkanes of this type having a lowest triplet state are also converted into the corresponding hydrazines.' I 9 However, in sharp contrast, those azoalkanes having lower triplet yields and shorter triplet lifetimes also produce lower yields of hydrazines even at high donor concentrations. Following intramolecular photoinduced electron transfer of N-alkylcyclopropyl phthalimides (38; n = 1,2) and (39; n = 1,2), attack of the resulting radical anion on the radical cation of the phenylcyclopropane fragment and radical-radical coupling, a range of products is formed including (40), (41), and (42).l2'
Photoinduced electron transfer has been observed in mixed p-quinodimethane analogues of tetrathiafulvalene and tetracyano-p-quinodimethane,12' irradiation of Mannich bases derived from phenols in aqueous acetonitrile generates 0-quinone methides,122and online electrospray mass spectrometry has been used to show the presence of a reductive allylation product of 1,4-dicyanobenzeneas a key intermediate in the photoinduced electron transfer reaction of 1,4-dicyanobenzene with allyltrimethylsilane.123The mechanism of the photodegradation of spiroxazines has been studied in the case of the model compound 1,3,3,4,5pentamethylspiro[indoline-2,3'-[3H]naphthoxazine]with particular reference to the effects of solvent, molecular oxygen, and 1,4-diazabicyclo[2.2.2]octane (DABC0).'24Degradation occurs almost exclusively by a radical mechanism and the effect of DABCO on the photodegradation is best interpreted in terms of an electron transfer process. The photocatalytic reduction of nitrite and nitrate using
202
Photochemistry
Ti02 as catalyst doped with Fe3+, Cr3+,Co2+,or Mg2+has been described, and the role of the dopant may be to improve charge separation by means of a permanent electric 4
Miscellaneous Reductions
A laser flash photolysis examination of the behaviour of fine particles of c60 when irradiated in the presence of an electron donor has shown that photoinduced electron transfer occurs.126The photoexcited triplet state of 3C60 is reported to be capable of abstracting both an electron and energy from 0carotene, and the partitioning of the two routes is dependent on solvent polarity. '27 Photoinduced electron transfer from NADH and its dimeric analogues to Cm yields Cm'-.'28However, if 10-methyl-9,lO-dihydroacridine is used as H- donor in trifluoracetic acid, CW is reduced to l,2-C60H2.These observations are taken to suggest that photoreduction proceeds by electron transfer from donor to the triplet excited state of c60. Flash photolysis of Cm or C70 in solvents of various polarities containing tetraethoxyethene (TEOE) shows that electron transfer occurs from TEOE to 3C6~*or to 3C7~*followed by back electron transfer from the c60'- and C70'- formed, and that the efficiencies of electron transfer are dependent upon the polarities of the solvents.129An investigation of c6{' stabilised within Triton-X 100 micelles has appeared including a mechanism for its formation and decay,13' and generation of Cm triplets in the presence of 10-methyl-9,lO-dihydroacridineand trifluoroacetic acid using visible light leads to their two-electron reduction to 1,2-dihydr0[60]fullerene.3 1 The quenching mechanism of the photoexcited triplet state of c60 by N,N,N',N'-tetramethylbenzidine (NTMB) has been studied in benzonitrile. 132 Following electron transfer to give NTMB'+, this species reacts with 3C60 causing photoinduced electron polarization of the amine radical cation. Photoinduced reaction of [6O]fullerenes with tertiary amines leads to the formation of [60]fulleropyrrolidines.133 A timeresolved study has been made of photoinduced electron transfer to C a from tetrathiafulvalene and bis(ethy1enedithio)tetrathiafulvalene in a range of solvents ~ ~ group has also and a transient ascribed to C*- has been 0 b ~ e r v e d . lThis demonstrated photoinduced electron transfer from phthalocyanines such as tetratert-butylphthalocyanine (H2TBPc) and the corresponding zinc derivative (ZnTBPc) to c60 and C70.135Nanosecond flash photolysis has indicated the presence of transients such as phthalocyanine cation radicals and fullerene anion radicals; and the occurrence of electron transfer from the phthalocyanines to 3C6~*and 3C7~*has been proved. Energy transfer from 3C6~* and 3C7~* occurs in nonpolar solvents. In another study by the same group, intramolecular electrod energy transfer within the supramolecular fullerene donor-bridge-acceptor dyads (Ru = [R~(bipyridyl)~]~+) is revealed as an C60-Fc (Fc = ferrocene) and C 6 0 - R ~ important deactivation mechanism, and time resolved studies suggest that the photoexcited dyads *Cso-Fc and Cbo-Ru* are rapidly converted into the corresponding charge-separated species. 36 The nature of the bridging spacer is important for both the lifetime and stabilisation of the charge-separated states.
1115: Photo-reduction and -oxidation
203
Relative quenching of some irradiated Ru(II)-C60 donor-bridge-acceptor dyads is significantly greater than in the model complex Ru(II)(bpy)z(bpy-R), suggesting an intramolecular electron or energy transfer quenching process. 137 This has been confirmed by ps resolved photolysis which indicates that the MLCT state of the Ru(II)-Cm dyad undergoes rapid conversion into the charge-separated state [Ru(III)-Cm'-]. In non-polar solvents, irradiating the dyad comprising c60 separated by a saturated norbornylogous bridge nine sigma bonds in length from a tetraarylporphyrin (Pzn), (PZ,&-c6~), leads to singlet-singlet energy transfer to the Cm.138However, in benzonitrile efficient charge separation occurs to give a long lived charge-separated state. The synthesis of the hybrid Q10(CH2CH20)32-C&O(CH2CH 2 ) 3 0 Q 2 (Q' = [6,6]-clo~edC~~met hanocarbon yl, Q2 = mesotriphenylporphyrin-4-phenylcarbonyl)has appeared and is reported to give a high quantum yield of 02('Ag) formation. 139 Details of the porphyrin-pyromellitimideCSo triad have also been published, and acceleration of the sequential photoinduced electron relay by Cm discussed.140A time resolved investigation of the photoinduced electron transfer dynamics of poly(N-vinylcarbazole) films doped with c60 has shown that the initial charge-separated state decays by three channels. 14' These are charge-recombination, hole-migration to the neighbouring carbazolyl chromophores, and formation of the local triplet state (3C6~*),and it appears that it is the hole-migration process which is effective in the initial charge separated state of &-,-doped PVCz films. Irradiation of benzonitrile solutions of c 7 6 in the presence of tetramethyl-p-phenylenediamine promotes electron transfer to 3c76*,142and the triplet excited states of C76(D2) and C78(c&') have been generated and found to undergo one-electron reduction and oxidation by reaction with the radiolytically generated species (CH3)2'C(OH) and (CH2C12)". 143 Complementary reduction experiments with photoirradiated Ti02 nanoparticles have been used to characterise these radical anions. Irradiation of the 1,l -dibromo-2-phenylcyclopropane(43)gives two diastereoisomers of 5-bromo-4-methyl-1-phenylbicyclo[3.1.O]hexan-2-01 (44)proving the intermediacy of a cyclopropyl radical, and olefins have been photohydrogenated using dihydrogen at a pressure of 6 kg cm-2 together with [CoH(PPh(OEt)2)4] (CoHL4) by a process in which the unsaturated transient species CoHL3 is thought to play a key role.145 EHMO calculations suggest that equatorial photodissociation of the phosphonite ligand occurs, and that this is followed by incorporation of the ethene at the newly unoccupied position. Ethenes are also reported to undergo an efficient tin-free reductive photochemical carboxymethylation using a-alkylthioacetates in a reaction whose mechanism depends upon the absence of short-lived MeS-group-transfer, and which allows hydrogen abstraction from the medium to occur.146
204
Photochemistry
Strong electron acceptors such as 1,2,4,5tetracyanobenzene undergo single electron reduction when irradiated within the cavity of a zeolite framework like faujasite, and give the anion radical of the guest.'47 This transformation proceeds mainly in the singlet state of the aromatic, but some electron transfer to the triplet state is also observed. Photoinduced electron transfer from N,N-dimethylaniline to pyrene adsorbed on to porous silica occurs by an exciplex mechanism which has been described quantitatively using a two-dimensional kinetics m0de1.I~~ Photoassisted electron-transfer theory has been used to rationalise deactivation of the complex via charge recombination. A study of the electron transfer quenching of pyrene singlets by indole and 3-cyanopyridine, and of a,hdi benzanthracene singlets by o-dicyanobenzene in solvents of different polarity has shown that the trends in rate constants can be accounted for in terms of' semiclassical theory provided that the solvent is aprotic and a continuum model is used.'49 In protic solvents, however, this model fails. Photoinduced electron transfer has been observed to occur to the singlet and triplet excited state of 2,6dimethyl-4-(alkylphenyl)pyrylium and thiapyrylium derivatives from biphenyl and 4,4'-dimethoxystilbene to give separated radical pairs derived from the corresponding pyranyl and thiopyranyl radicals. lS0 High radical yields are obtained suggesting that these compounds may find use as efficient photosensitizers in photoinduced electron transfer reactions. Photolysis of solutions of C60(OH)18 at low solute concentration leads to [C~O(OH)I~].by electron transfer from Me2C(OH) radicals or from hydrated electrons, and this has enabled the reduction potential of the C60(OH)18/ [C60(0H)18]'- couple to be estimated."' The kinetics of the photoreduction of hexanal using RhCl(PMe3)2CO as catalyst have been measured and the feasibility of a photocatalytic synthesis of hexanol from pentane, CO, and H2 in the presence of rhodium complexes has been demonstrated. Irradiation of a chiral bimolecular crystal of acridine and R-(-)- or S-(+)-2-phenylpropionic acid induces photodecarboxylation followed by stereoselective condensation to give a mixture of three optically active products, 153 and the 3-0-S-methyl dithiocarbonate derivatives of oleanolic and ursolic methyl esters have been used as models for the photodeoxygenation of alcohols.'s4 Complexes of the type [Re(4,4'-X~bpy)(CO)3PR3]+ (X = H, Me; PR3 = P(OEt),, P(O'Pr),) are reported to photoreduce C02 to CO by a transformation in which the one-electron reduced complex which arises by electron abstraction from triethanolamine reacts with C02 in a dark process.'5s Carbon dioxide has been photoreduced to carbon monoxide using methane at room temperature over zirconium oxide,lS6 in aqueous suspensions of SiC/Zn0,157and on hexagonal CdS nanocrystallites prepared in N,N-dimethylformamide by using visible radiation.Is8 It is suggested that in this last case, the surface structures of CdS/DMF play an important role in the transformation. Photoreduction of carbon dioxide to formate has been achieved by 2,5-dihydrofuran using ZnS or CdS on large surface area Si02, in a transformation which probably occurs by a two-electron process. lS9 Over potassium ferrocyanide-coated Ti02 powder in aqueous media, the photoreduction gives a mixture of formic acid and formaldehyde for which a tentative mechanism has been proposed. 160 An investigation of solvent effects on
205
W 5 : Photo-reduction and -oxiddon
the photoreduction of carbon dioxide on Ti02 nanocrystals in Si02 matrices shows that the ratio of formate to carbon monoxide rises with increasing dielectric constant of the solvent.I6' This effect has been interpreted in terms of solvent stabilisation of the reaction intermediates. The same authors also report that semiconductor nanoparticles (Q-Sc) possess higher activities as photocatalysts for the reduction of carbon dioxide than the corresponding bulk photocatalysts, and this has been attributed to several factors including the size of the Q-Sc, the charged condition of the stabilisers, and the polarity of the solvents.162 Photocatalytic reduction of C 0 2 on Ti02 in a liquid C 0 2 medium followed by addition of water gives formic acid exclusively, and it is suggested that the water protonates the reaction intermediates present on the Ti02 powders. 163Saturated solutions of carbon dioxide containing triethanolamine have been photoreduced to formic acid by irradiating a metal porphyrin and phthalocyanine adsorbed on to a Nafion membrane suspended in the solution.Iw Carbon dioxide has been photoreduced with water over the highly reactive mesoporous zeolites Ti-MCM41 and Ti-MCM-48 to give methan01,'~' and on a Ti02 surface in the presence of water photoreduction of carbon dioxide leads to the formation of CO, CH4, H2, and some higher hydrocarbons.166 A model of the transformation has been constructed and this has enabled the activation energy for methane formation to be calculated. Carbon dioxide has been photoreduced using CdS nanocrystallites, and a large increase in the reactivity has been achieved by adding Cd2+which is ' ~ ~ conclusion believed to result in the formation of sulfur surface v a ~ a n c i e s . This is supported by MO calculations which indicate the preferential bidentate-type absorption of C02 with the Cd atom proximate to the sulfur vacancy. Irradiation of a solution of hydrogen carbonate in aqueous dimethyl sulfoxide containing triethanolamine in the presence of trisodium trisulfonatophthalocyaninezincate(II), dimethylviologen, and a ruthenium colloid brings about its reduction to methane. Under similar conditions, ethylene is photoreduced to ethane. Direct irradiation of variously substituted 2-amino-4H-pyrans (45; R' = 'Pr, Ph; R2 = H, Me; R3 = Ph, Me, H; G = COzEt, CN) gives the corresponding cyclobutenes (46; same R', R2,R3, G) with high stereochemical control,'69 and an examination of the photocatalytic reduction of nitrite and nitrate ions to ammonia on M/Ti02 catalysts has shown that the yield of ammonia depends on the nature and amount of metal, and the method of metali~ation.'~~ Ethyl (Z)-acyano-P-bromomethylcinnamate has been photoreduced by the coenzyme N AD(P)H model compound 1-benzyl- 1,4-dihydronicotinamide to give the (E)and (2)-isomers of ethyl a-cyano-P-methylcinnamate in a process which has been rationalised in terms of an electron transfer-debromination-hydrogen abstraction mechanism.17' R' R2
R'
G
206
5
Photochemistry
Singlet Oxygen
Quantum yields of formation of 02('A& obtained by irradiation of benzene solutions of various f l a v o n o i d ~ ,and ' ~ ~ by irradiation of oxodiperoxo-molybdenum(V1) complexes of the type (L-L)Mo0(02)2 (L-L = 2-( 1-alkyl-3-pyrazolyl)pyridine, alkyl = Bu, n-octyl, n-octadecyl; L-L = 2-(3-n-octyl-2imidazoly1)pyridine) have been reported. 73 Production of 02( 'A& from the tetrasodium salt of meso-tetrakis(4-sulfonatopheny1)porphine and its water soluble metal complexes with the divalent metals Ag(II), Cd(II), Co(II), Cu(II), Mg(II), Ni(II), Pd(II), Pt(II), and Zn(I1) has been accomplished, and it appears that reactions utilising those complexes having full or empty d-orbitals are characterised by high quantum ~ i e 1 d s . IAn ~ ~ order of effectiveness of metal phthalocyanines for the generation of O2('Ag) has appeared.175Metallotetracarboxyphthalocyanines (MTCPc, M = Cu, Al) attached to the amino groups of Amberlite IRA-93 by amide bonding have been prepared.'76 These materials have been used to generate 02('Ag) and the process monitored using diphenylisobenzofuran. In organic media, the quantum yields of Oz(IAg) production are less than in water and appear to be dependent upon the polarity of the medium. This has been rationaiised in terms of self-quenching. Irradiation of porphyrin-like rare earth metal complexes ([R-APPC)RE]C12) in oxygenated solvents leads to the formation of OZ(IAg) which can be detected by production of the 2,2,6,6tetramethylpiperidine-N-oxideradical using ESR spectroscopy.177 The rate of generation of 02('Ag) is determined by the concentration of the sensitizer, the metal, the nature of the substituents, and by the oxygen content of the reaction mixture. 02('Ag) yields and photopysical properties of a range of polyether substituted metallo- and free-base phthalocyanines have been reported and their possible use in the photodynamic therapy of cancer d i ~ c u s s e d ,and ' ~ ~ asymmetric tripyrrole-containing macrocycles and their metal complexes have been found to be highly effective for the production of 02('Ag). In the particular case of the photooxygenation of A3-carene,yields of 02('A& reach about 68%. 179 A kinetic study has shown that disulfides are capable of deactivating 02('Ag) by two different physical quenching mechanisms.18* Of these, the more important is in part influenced by the RSSR dihedral angle and also by substituent steric requirements on the disulfide. A quenching study of 02('A& by various substituted diary1 tellurides suggests that although the participation of a charge-transfer intermediate cannot be completely eliminated, there is probably a strong contribution from the heavy atom effect of the tellurium, an element which appears to be relatively insensitive to inductive electronic substituent effects.I8' Quenching rate constants of 0 2('A by derivatised nucleosides in non-aqueous solutions have been determined,18'and the efficiencies with which 02('Ag) is generated on quenching aromatic cations such as acridizinium, protonated heterocyclic compounds, and protonated 6-aminochrysene have been measured. The results suggest that there is a competition between energy transfer and a process involving the second excited triplet state.'83
'
IIl.5: Photo-reduction and -oxidation
6
207
Oxidation of Aliphatic Compounds
The photofunctionalisation of alkanes may proceed by a variety of mechanisms and results have been obtained which allow mechanistic probes to be proposed.184 Photoactivated nitropyridinium salts are effective in the oxidation of such hydrocarbons as indane, tetralin, 2-ethylnaphthalene, and cyclohexane,185 and visible light irradiation of propane-oxygen mixtures in solvent-free BaY and CaY zeolites leads to the highly selective formation of isopropyl hydroperoxide as intermediate; analogously, ethane is oxidised to acetaldehyde completely selectively in CaY zeolite using blue light. 2-Methylpropane will undergo partial oxidation when irradiated in the presence of V205/Si02 modified with alkali ions, and mainly forms propanone and 2-methylpropan-2-01,'~~The role of the alkali metal is to generate an active site which can be excited using visible light. The catalytic activity of ultrafine Ti02 in the photooxidation of cyclohexane is found to increase with decrease in particle size, and occurs with a selectivity for cyclohexanol production of 85Y0.l~~ Irradiation of (n-Bu4N)4W 10032 in the presence of oxygen gives radicals which are capable of transforming cyclohexane into a mixture of cyclohexanone and cyclohexanol in a high quantum yield process whose composition is dependent upon oxygen pressure. 189 Photocatalytic C-H bond activation has been achieved by irradiating a mixture of Co(acac), and cyclohexane to give cyclohexanecarboxaldehyde. Alkanes are reported to be oxidised by irradiation in the presence of the Co(II1) alkylperoxy complexes [(RBPI)Co(OAc)(00CMe3)] [R-BPI = 1,3-bis(R-substituted 2'-pyridylimino)isoindoline; R = H, 3'-Me, 4'-C1].'91 Following photohomolysis of the Co-0 bond of the Co-0-0-CMe3 group, Me3COO' radicals are formed which along with Me3C0 oxidise the C-H bonds of the alkane. Electron transfer photosensitized photolysis of methanolic 7-(spirocyclopropane)quadricyclane produces two rearranged mono-methanol adducts and a bis-methanol adduct. 192 The structures of these products suggest that reaction on the trisubstituted cyclopropane ring occurs stereospecifically and regiospecifically to give a free radical which rapidly undergoes a cyclopropylcarbinyYbuteny1 rearrangement. Solar energy has been used for the production of f~1lerenes.l~~ At submonolayer coverages, c6()adsorbed on to Ti02 particles undergoes irreversible photooxidation and evidence is presented which suggests that direct interaction with the oxide surface is essential for the photooxidation to pro~eed.''~Irradiation of c 6 0 in the presence of 9,lO-dicyanoanthracene and biphenyl as co-sensitizer gives which will react with H-donors to give the 1 : 1 adducts, 1-substituted 1,2-dihydr0[60]fullerenes,lg5 and irradiation of c 6 0 in the presence of piperidinoacetic acid and morpholinoacetic acid gives the 1,2-dihydrofullerenes C~O(H)[CH~N(CH&] and C~O(H)[CH~N(CH~CH~)~O]; under the same conditions the corresponding methyl esters give the fulleropyrrolidine derivatives C ~ O [ ~ ( C H ~ ) ~ N ~ Cand O ~ C,[ C HCH(CH20CH2CH2)NCHCO*CH3]. ~] 196 c 6 0 radical cations have been generated by photosensitized electron transfer from the substrate to N-methylacridinium hexafluorophosphate in a suitable solvent containing biphenyl, and their addition to methanol examined.197A laser flash photolysis investigation of c60, C70, and c76 in the presence of tetracyanoethylene
208
Photochemistry
as electron acceptor shows the presence of the radical cations of the hydrocarbons, but if tetracyanoquinodimethane or chloranil is used as acceptors, no corresponding transient is seen. 19* These observations are rationalised in terms of the free energy changes for the reaction. The use of co-sensitizers has also been examined. The radical cation of c 6 0 has been generated and occurs by hole transfer from the radical cation of polar chlorinated methane to Cb0, or by electron transfer from k 6 0 to electrophilic chlorinated methane. 199 The same authors have also reported the rate constant for addition of the trichloromethyl radical to C70.200 In order to demonstrate the generality of photooxidation in zeolite cavities, detailed studies have been undertaken of the photoconversion of propylene to acrolein, and of toluene to benzaldehyde using zeolites X and Y, and ZSM-5.20' In some related work, it has been shown that photooxidation of trans,trans-1,4diphenylbuta- 1,3-diene in zeolite ZSM-5 using dicyanoanthracene as sensitizer gives only the products of 02('AB) oxidation.202 This is a consequence of the substrates being isolated from the sensitizer within the zeolite, and has the effect of inhibiting electron transfer. Gas phase photooxidation of trichloroethylene on Ti02 and ZnO has been studied as a function of substrate pressure, oxygen pressure, and photocatalyst surface.203The photohydroperoxidation of stereoisomers of pinenes and limonene using anthracene or Rose Bengal on a polystyrene support as sensitizers, proceeds with accumulation of hydroperoxides in the first stages of the sensitized oxidation.204 However, when ZnO is used, associated alcohols and carbonyl products are produced. Photooxidation of methoxy, siloxy, and acetoxy substituted adamantylideneacridanes leads to the formation of dioxetane~.~'~ In the new linear twisted 1,3-diene (47; R = H, Me, iPr, t-Bu, Me2C(OH)) the vinyl hydrogens show unusually high reactivity towards 0 2 ( ' A g ) as compared with the ally1 hydrogen,*06 and under similar conditions cyclohexa-1,4-diene gives the hydroperoxyendoperoxides (48; R = H, OOH; R I = OOH, H) the second of which following its reduction, acetylation of the hydroxyl group and oxidation of the double bond produces proto-quercitol; gala-quercitol can be obtained similarly.207The same authors also report a convenient synthesis of ( f)-talo-quercitol and ( +)-ribo-quercitol from cyclohexa- 1,4-diene by an ene reaction with 02('A,).208 Irradiation of trisubstituted cyclic ethenes under an atmosphere of 0 2 in the presence of sodium azide and Cu(O$CF& gives good yields of keto nit rile^.^'^ Using similar conditions 1,5-diniethylcycloocta-1,5diene and 1,5,9-trimethylcyclododeca1,5,9-triene are converted into the corresponding unsaturated keto nitriles. Aryl-substituted sulfines (49; R = Ph, pC6H4Cl, p-C6H4-OMe)undergo photolysis in the presence of strained alkenes such as norbornene and cis- and trans-cyclooctene to produce thiiranes (50; same R).2'o A high stereoselectivity is observed and this suggests that the reaction proceeds by a concerted mechanism rather than by diradical or dipolar intermediates. Dehydrogenation of cyclohexa- 1,4-diene has been achieved in a cryogenic Ar matrix with visible light through a process which involves photoexcited NO2 as the first step, followed by hydrogen atom transfer to give a complex of cyclohexadienyl radical and nitrous acid, and finally by photodissociation of the complex.21 Oxidation of 2,3-bis(bromomethyl)-buta-l,3-diene using O2(IAg)
IIl.5: Photo-reduction and -oxidation
209
leads to the formation of a peroxide which on treatment with CoTPP produces bis(bromomethyl)furan,2’2 and photosensitized oxygenation of guaiol gives an allylic hydroperoxide in a process which shows a preference for attack at the 01face to give (51).213
The isothermal photooxidation of ethanol on TiOz occurs by preferential attack at the a-carbon atom which is oxidised to C02,214and salt has been shown to be useful in the DCA-BP co-sensitised electron transfer photooxidation of c h ~ l e s t e r o l .The ~ ’ ~ effects of UV irradiation and photocatalysis of Ti02 on the autoxidation rate of linoleic acid have been studied, and acceleration by UV irradiation and also by the photocatalytic effect of Ti02 was observed.216 Conformationally fixed chiral allylic alcohols bearing an electron withdrawing group such as (52) can be photooxygenated using 0 2 ( l A & in high threo diastereoselectivity to (53) and (54) in a process whose steering effect arises from synergistic interplay between conformational ( 1,3-allylic strain) and stereoelectronic factors.217
7
Oxidation of Aromatic Compounds
Quenching of the excited state of *UO:+ by naphthalene can occur along two parallel pathways, exciplex formation and electron transfer to give the naphthaIn the presence of molecular oxygen, ~ 6 ~ 8 is* lene radical cation oxidised to 2-formylcinnamaldehyde and other products. Photooxygenation of 1,2-dihydronaphthalene gives diendoperoxides and hydroperoxides from [4+2] cycloadditions and ene reactions respectively, and the structures as well as the stereochemistry of these products have been reported.219 From a study of photoinduced electron transfer in the donor-acceptor molecules comprised of dimethoxyanthracene and various bisphenol A derivatives (55; R = 56, 57, 58, 59), the rate constants ket and the free energy changes AGet have been determined.22oThis has enabled the dependence of theoretically obtained transfer rates on exothermicity to be confirmed with those of experimentally obtained results. Photoinduced intramolecular electron transfer in the donor acceptor
+
210
Photochemistry
binary compounds pyrene-dicyanovinylbenzene and anthracene-dicyanovinylbenzene having differing chain lengths has been studied as a function of the dynamics of chain conformation and of the size of the electron donor unit by varying the solvent polarity, viscosity, temperature, and salt content.22' Irradiation of pyrene and perylene in methanolic solutions of the surfactant hexadecylpyridinium chloride promotes electron transfer to give Py" and Pee+ but in aqueous micellar 'solution only Py" is formed.222 Decay kinetics have been obtained using ps laser flash photolysis and these can been interpreted in terms of electron transfer and geminate recombination processes. The new electron donor [3](N,N')- 1,8;4,5-naphthalenetetracarboxdiimido-[3](2,7)-pyrenocompounds phane and its [4,4]cyclophane homologue (60; n = 1-2) have been synthesised, and their intramolecular charge transfer interactions compared with those of the related excimer models [3,3]- and [4,4]-pyrenophane~.~~~ Tetrabenzo[a,cdj,lm]perylene undergoes photooxidation by visible light, but under the same conditions the closely related tribenzo[a,h,rst]phenanthra[10,1,2-~de]pentapheneis inert, and the experimental results have been accounted for in terms of the relative stabilisation energy of their respective en doper oxide^.^^^
Photooxidation of cumene in liquid acetonitrile containing dispersions of Ti02 produces acetophenone and carbon dioxide, and occurs by a mechanism involving methyl migration.225Irradiation of a mixture of phenylcyclopropane and chloranil in various solvents gives products which are derived from nucleophilic attack on the radical cation of the cyclopropane ringzz6 Under similar conditions, however, although 1,2-diphenylcyclobutenealso generates a radical cation, the result is a product which formally occurs from addition of the quinone across the allylic C-H bond. All of the products arise from participation of a radical ion consisting of quinone radical anions and radical cations derived from the small
IIl.5: Photo-reduction and -oxidation
21 1
ring structures. Photolysis of 1,2-bis(2-nitrophenyl)ethaneoccurs by an intermolecular redox reaction to give a range of products including 2-nitrobenzoic acid, 2-nitrobenzyl 2'-nitrophenyl ketone, 2,2'-dinitrobenzil, and dibenzo[c,g][ I ,2]diazocin-5,6-dione-N,N'-dioxide, whereas the lower homologue bis(2-nitropheny1)methane photoreacts mainly intram~lecularly.~~~ Photosensitized oxidation of (61; X = H; R' = H; R2 = Me) using tetraphenylporphyrin gives a mixture of (62) and (63) in the ratio 85: 15, but if the hydroxy group is protected little diastereoselectivity is observed.228The results of some investigations on the Schenck reaction are also reported.
P-Methylstyrene has been photooxidised to cinnamaldehyde by irradiating in the presence of 2-iod0-5-nitrothiophene,~~~ and a time-resolved study of the irradiation of a series of substituted styrenes embedded in acidic and non-acidic zeolites has appeared.230 In this latter case, the corresponding radical cation is produced for which the zeolite framework provides a stabilising effect whose strength is dependent upon the nature of the substituents. An MCSCF study of the addition of 02('Ag) to ethenol has been reported, and this has been used as a model for the photooxidation reactions of unsaturated and aromatic compounds bearing hydroxyl groups.23' A kinetic model for the photooxidative degradation of phenol by hydrogen peroxide has been derived and reveals the presence of two phases.232 in the first of these the peroxide concentration is the controlling factor, whereas the controlling factor in the second phase is phenol concentration. The photooxidation of 2,6-dimethylphenol and 0-, m-,and p-phenylphenols by *U022+ has been investigated, and it is shown that the initial step is phenoxyl radical formation.233However, whereas 2,6-dimethylphenol gives both quinone and dimer, o-phenylphenol yields two dimers and a quinone, and in degassed solutions only the dimers are formed. The mechanistic origins of this selectivity are discussed. A study of the photoinduced oxidation of hydroquinone by the cobalt azide complex in aqueous acidic solution has shown it to proceed by electron transfer to generate the semiquinone radical; an overall mechanism has been established.234 An examination of the electron transfer dynamics of 9-anthracenecarboxylic acid bound to nanometre-sized Ti02 particles has shown that transfer occurs with a time constant of 350 fs.235Evidence is also presented which indicates that the back electron transfer is an example of a reaction in the Marcus inverted region. Excitation of donor-acceptor salts derived from methylviologen and carboxylate donors (RC02-), including benzilates (Ar2C(OH)CO;) and arylacetates (ArCH2C02'), leads to [MV" RC02.1 radical pairs which rapidly decarboxy-
212
Photochemistry
late.236 Rate constants have been determined for these processes, and it is. concluded that in the case of the benziloxy radicals real-time monitoring provides a direct observation of the transition state for C-C bond scission. A highly selective photodecarboxylation of aralkyl carboxylic acids such as 3-indolepropionic acid and 1-naphthylacetic acid has been achieved by irradiating the twocomponent crystals formed with acridine or phenanthridine as electron acceptor at -70 0C.237Electron transfer followed by proton transfer produces a carboxylate radical and either a hydroacridine or hydrophenanthridine radical which decays by decarboxylation. DL-a-acetamido-P-hydroxy-p-nitropropiophenone has been prepared from L(+)-threo-(p-nitrophenyl)-2-aminopropan-l,3-dioland acetic anhydride followed by photooxidation in the presence of acidic KBr03 and HBr.238Photosensitized electron transfer reactions of tri- 1-naphthyl phosphate and di-1-naphthyl methyl phosphate using 9,lO-dicyanoanthracene are reported to lead to the formation of 1,l'-binaphthyl, but no reaction occurs for mono-1-naphthyl and di- or tri-phenyl esters.239Irradiation of bis(3,4-methylenedioxyphenyl)methylphosphonate in the presence of DCA induces single electron oxidation followed by intramolecular rearrangement and gives 2-(3,4-methylenedioxyphenyl)-3,4-methylenedioxyphenyl methylphosponate.240 2-Methylbenzene- 1,6dicarbonitrile (2-methyl-BDC) and 2,5-dimethylbenzene1,4-dicarbonitrile (2,5-dimethyl-BDC) are reported to increase the quantum yield of the photosensitized electron transfer reaction of methanolic 6,6-diphenyl-1,4dioxaspiro[4S]decane more than benzene-l,4-dicarbonitrile (BDC).24' This has been attributed to the occurrence of electron transfer between MeOH and excited BDC, a process which is suppressed in the methylated BDCs. Photooxygenation of the angular furonaphthopyrones (64) and (65) produces the hydroperoxide (66),242and irradiation of solutions of some naphthofurans in the presence of tetraphenylporphine and molecular oxygen at low temperature is reported to give the corresponding d i o x e t a n e ~ . ~ ~ ~
(64)
Me
ESR parameters for the products of the photoinduced oxidation of aromatic azides in polymeric matrices and crystals have been reported.244
21 3
IIl.5: Photo-reductionand -oxidation
8
Oxidation of Nitrogen-containing Compounds
A study has appeared in which the fate of the nitrogen atom in a range of compounds such as amines, amino acids, amides, and related model systems is examined when irradiated on a Ti02 surface, and in which the nature and quality of the product ions NH4+ and N03- are addressed.245Photochemical formation of hydrazine from aqueous ammonia (pH > 8) has been achieved using short wavelength radiation,246and photoexcitation of some tert- aminocyclopropanes in the presence of an electron acceptor is reported to give the corresponding amine radical cation which subsequently undergoes ring opening.247 For example, in the presence of 1,4-dicyanobenzene, cyclopropylamine (67) gives an 85% yield of PrCO(CH2)40TIPS in a transformation which occurs by rearrangement of the cyclopropylamine cation radical and subsequent 1,Shydrogen transfer. In oxygenated solution containing 9,lO-dicyanoanthracene or triphenylpyrylium tetrafluoroborate, 2-morpholinocyclopropanols undergo an electron transfer photooxidation to give the amino enone derivatives (E)-PhC0CH:CPhR and (E)-PhC0CR:CHPh (R = m o r p h ~ l i n o ) Photoinduced .~~~ electron transfer
'CH2CH20TIPS
(67)
between N,N-dimethylaniline and octadecylrhodamine B on the surfaces of dodecyltrimethylammonium bromide and Triton X- 100 micelles has been investigated, and diffusion of the chromophores over the micelle surface models the reaction rate by a distance-dependent Marcus form.249The same authors have extended this work to a range of micelles, which although structured similarly, show significant differences in electron transfer kinetics.250It is observed that the overall amount of electron transfer increases with chain length, and this has been attributed to differences in solvent reorganisation energy. Irradiation of ethanolic solutions of N-aryl-N-nitrosohydroxylammoniumsalts leads to the azoxy comp o u n d ~ , and ~ ~ ' an investigation of the triplet state of 4-amino-N-methylphthalimide using time-resolved techniques shows that in aprotic solvents an intramolecular charge transfer state predominates, whereas in protic media a twisted intramolecular charge transfer state becomes important.252 It also appears that in protic media, formation of the semiquinone radical occurs through hydrogen abstraction from the medium by the triplet state of the substrate. Sensitized photooxidation of boldine (68) and glaucine, its permethylated derivative, occurs by a charge-transfer quenching mechanism, and evidence is advanced suggesting that the transition leading to products is more polar than that corresponding to the initial step.253 Excitation of the bichromophoric 3~-{[2-(methoxycarbonyl)bicyclo[2.2.1]hepta-2,5-diene-3-yl]carboxy} androst-5-en- 17 p-yl-2,2',6,6',N, N, N',N'-heptamethylbenzidine induces electron transfer to the norbornadiene chromophore to give a
214
Photochemistry
HO
(68)
Me
singlet radical ion pair which following intersystem crossing and reverse electron transfer yields triplet n ~ r b o r n a d i e n e .Selective ~~~ excitation of the benzidine chromophore promotes isomerisation to quadricyclane via either intramolecular triplet sensitization or a radical-ion pair combination mechanism. Irradiation of 9-endo-p-dirnethylaminophenyl-8,9,10,11 -tetrahydro-7,11 -methano- 12-keto-7Hcycloocta[de]naphthalene, a molecule in which the dimethylamino group is constrained to lie over the naphthalene ring, induces intramolecular electron transfer, and this process has been studied in solvents having a variety of different polarities.255Semiempirical calculations have been performed on 4-[4-(dimethylamino)phenyl]-3,5-dimethyl-1,7-diphenylbispyrazo10[3,4-b;4‘,3’e]pyridine, a bulky electron donor-acceptor compound consisting of several subunits of differing redox properties, and these have been used to validate an intramolecular chargetransfer model of the molecule.256 Irradiation of diphenylamino substituted triphenylbenzene (69; pEFTP), biphenyl (70; pEFBP), and fluorene (7 I; pEFF) derivatives induces formation of a polar excited state in which the excitation is located in one branch of the P E F T P . ~Relaxation ~~ occurs to give a more planar geometry and the observations are rationalised in terms of a model based upon the photophysics of substituted biphenyl. CNDO/S-CI calculations have been carried out on 4-N,N-dibutylamino-4”-cyanoterphenyl and analogues, some of which are conformationally more planar and some less planar.258These suggest that in certain instances the twisted intramolecular charge transfer states become the lowest excited states in polar solvents because of their high dipole moments, and such conclusions have found experimental support. Photooxygenation of 2amino-3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophene in the presence of urea leads to 3-cyano-7-hydroxy-2-thio-2,4,5,6,7,7a-he~ahydroindole,~~~ and photoexcited p-(N,N-didecy1amino)benzonitrilein a water-dioxan mixture exists in a twisted intramolecular charge-transfer state.260 An examination of photoinduced intramolecular charge-transfer (ICT) in (72; x = 2 - 7) indicates that for decreasing ring size there is a corresponding decrease in the efficiency of ICT, and this has been attributed to an increased barrier for configurational change of the amino nitrogen atom from pyramidal to planar.26’ These observations are consistent with the effects of pressure increases in the case of 4-(dimethylamino)benzonitnle and 4-(didecylamino)benzonitrile, and suggest that a large amplitude of motion does not occur during the ICT. An investigation of the photocatalytic bleaching of p-nitrosodimethylaniline in aqueous suspensions of Ti02 indicates that both the hole and electron charge carriers are active in the bleaching process.262A reaction mechanism has been proposed and has
III.5: Photo-reductionand -oxidation
215
been supported by the results of a kinetic investigation. Photooxidation of 8amino- 1,2,3,4-tetrahydro-2-methyl-4-phenylisoquinoline (nomifensine) (73) gives (74),263and a comparative study of the activity of different homogeneous photochemical and heterogeneous photocatalytic systems in the oxidation of rnethylviologenin aqueous solutions has been reported.264
216
Photochemistry
The order of their effectiveness as photosensitizers for the oxidation of glycyltryptophan in aqueous solution is nicotinic acid > nicotinamide > nicotinehydroxymethylamide; these reactions seems to involve the superoxide radical anion.265 In the presence of quinones, the photoinitiated oxidation of N-acetyl-3,5dicarbomethox y-4-phenyl- 1,4-dihydroquinone to 3,5-dicarbomethoxy-4-phenylpyridine in polar solvents involves both radical ions and neutral radicals and may occur by a [ 1,3]-sigmatropic rearrangement of N-centred dihydropyridine radicals.266Photooxygenation of natural piperine (75) has been reported to give 1Npiperidino- 1-oxo-5-(3’-formatyl-4-hydroperoxyphenyl)penta-2,4-dieneand 1Npiperidino- 1-oxo-5-(4’-formatyl-3’-hydroperoxyphenyl)pen ta-2,4-diene.267 In tramolecular electron transfer and exciplex formation have been investigated for a family of styrene-spacer-amine molecules, and the dependence of the electron transfer kinetics and exciplex formation studied as a function of length of the spacer, orientation of the amide, and amine oxidation 0
Sensitized and self-sensitized photooxidation of N-benzylidene-N-tert-butylimine is a facile reaction, but under analogous conditions, N-phenyl-N-diphenylmethyleneimine has by contrast been shown to be largely inert.269A study of the photooxidation mechanism of cyanine dyes suggests that some protection can be afforded by the incorporation of heterocyclic groups such as benzoxazole, benzothiazole, and benzoselena~ole.~~~ Both the 02( ‘Ad and superoxide anion mechanisms may be involved in the autosensitized process. Dye-sensitized photooxygenation of 2-methoxyfuran in the presence of RR’C:NOH gives the hydroperoxynitrone (E,Z)-HOOCRR’N+(O-):CHCH:CHCO*Me ( R R = (CH2)4; R = Me, PhCH2, Me3C, Ph; R’ = H, Me, Et) which on further irradiation forms the corresponding trans-oxaziridine (76; same R, R’).27’
A time-resolved study of the decay kinetics of transient radicals produced from 2,2,4,64etramethyl- 1,2-dihydroquinoline in both aqueous and micellar solution has appeared,272and sanguinarine, a benzophenanthridine plant alkaloid, has been photooxidised to oxysanguinarine in an irreversible singlet state process.273 Pyrro10-[2,3-b]indole (77) has been produced with some enantioselectivity by photosensitized oxygenation of Nb-(methoxycarbony1)tryptamine in the presence of (-)-nicotine,274and irradiation of 3-methylindole on a CdS surface and under
III.5: Photo-reductionand -oxidution
217 OH
QLXJ I H I
H
CO2Me
an oxygen atmosphere gives 2-acetylformanilide and 2-aminoacetophenone by a process which involves scavenging of an electron and the associated hole by molecular oxygen.275 Dyads of the type (78) and (79) have been synthesised and show negligible interaction between the components in the ground state.276The rate constants for electron transfer in the excited state have been determined and found to be larger for (78) than for (79), presumably because of the more favourable face-to-face mutual orientation between donor and acceptor present in (78). The same authors also report that fluorescence quenching of fluorescein by viologen occurs mainly by a static process through a non-emission complex, whereas quenching by carbazole is mainly a dynamic electron transfer process.277Investigations on the related viologen-fluorescein-carbazole triads have also been carried out. Substitution influences the initial spin state in the exciplex systems, N-ethylcarbazole/ 1,4-dicyanobenzene, 1,4,5,8,9-pentamethylcarbazole/ 1,6dicyanobenzene, ethylcarbazole/l,2,4,5-tetracyanobenzene,and 1,4,5,8,9-pentamethylcarbazole/ 1,2,4,S-tetracyanobenzene,and has been monitored using a low magnetic field.278 Major roles are played by the contact ion pairs (A-D+)and the solvent-separated ;on pairs (A-(S)D’+),and a correlation has been established between the observed magnetic field effects and the Marcus relation between free energy changes and redox potentials.
The photoinduced intramolecular electron transfer reactions of some poly(ethylene glycol)-linked 9-aminoacridine-benzoate electron donor-acceptor systems have been described.279Photosensitized oxidation of S-rnethyl-2’-deoxygives 5,6-dihydroxycytidine using menadione (2-methylnaphthalene-1,4-dione) 5,6-dihydro-S-rnethyl-2’-deoxycytidine in what is thought to be an electron transfer process which first forms the radical cation of the substrate?’’ A mechanistic study of the photooxidation of thymidine using menadione as
218
Photochemistry
sensitizer gives 5-carboxy-2’-deoxyuridinewhich itself arises by autoxidation of the aldehydic group of 5-formyI-2’-deoxyuridineproduced by substrate photooxidation.28’ Reaction of photolytically generated HO’ with adenine in aqueous solution leads to an adduct at the 8-position which can be oxidised to 8hydroxyadenine,282and use of ferricyanide as oxidant induces oxidation by electron transfer, whereas oxidation by molecular oxygen occurs by formation of a peroxyl radical, Ade-8-OH-O2*. The excited state behaviour of the fullerophenylpyrrolidines, Cdo-fused 1,2,5triphenylpyrrolidine, bis( 1,2,5-triphenylpyrrolidine),and bis( 1-phenylpyrrolidine) have been presented.283Anhydro-1,1’-diethyl-3,3’-disulfobutyl-5,5’-dicyanimidazolocarbocyanine hydroxide is reported to be strongly adsorbed on to the surface of colloidal Ti02, and irradiation promotes electron ejection into the conduction ~~~ of the substituted 3,3-dimethyl-3Hband of the s e m i c o n d ~ c t o r .Excitation pyrazole (80; R’, R2 = Ph, CO2Me; p-ClC6H4, C02Me; p-MeCsH4, CO2Me; H, C02Me) in the presence of 2,4,6-triphenylpyrylium tetrafluoroborate as sensitizer gives cyclopropenes together with 2H-pyrroles which arise by solvent addition to the 1,3-radical cation intermediate.285Phenylmercaptotetrazole has been photocatalytically oxidised on aerated Ti02 dispersions (hi, >330 nm) and a mechanism suggested which involves the formation of C02, S04’-, NOY, and NH4+.286Photooxidation of phenothiazine in either benzene or cyclohexane in the presence of molecular oxygen has been shown by EPR experiments to give the phenothiazine nitroxyl radical rather than the radical cation.287These observations are supported by the results of AM1 calculations. The photooxidation of Azure A (81) as well as its fluorescence properties have been studied in the presence of P-cyclodextrin, and this has enabled an induced fluorimetric method to be developed for the determination of (81).288
The photoinduced processes in a dyad consisting of a porphyrin module (PH2) covalently linked to a Ru(1I) complex comprising a tridentate 4-p-tolyl2,2’,6’,2”-terpyridine (ttpy) and a tridentate 2,6-bis(4-phenyl-2’-quinolyl)pyridine (bpqpy) have been studied at room temperature, and electron transfer from the porphyrin moiety to the Ru-based moiety observed.289Measurements of the ps intramolecular charge transfer dynamics of 2,8,12,1 8-tetrakis(9-anthryl) substituted porphyrin adsorbed on porous glass show that the first process is protonation to form a dication which subsequently accepts an electron from the anthryl group.29oThis latter step occurs within 7 ps of excitation. Photoelectron transfer from meso-phenyltetrabenzoporphyrinato zinc as donor to dicyanobenzene as acceptor in a poly(methy1 methacrylate) dispersion has been investigated at low t e m p e r a t ~ r e , ~and ~ ’ fluorescence emission from (82) appears to be effectively quenched relative to the analogous structure lacking the naphthoquinonepropio-
III5: Photo-reduction and -0xida tion
219
nate residue, strongly suggesting that intramolecular electron transfer from the excited donor occurs readily in the former dyad.292Dyads consisting of eosin and a porphyrin linked with a semi-rigid (-CH2-C&-CH2-) or flexible ((-CH2)4-) bridge have been synthesised, and excitation of the porphyrin component is shown to be capable of inducing electron transfer to the porphyrin moiety from the eosin as donor.293Excitation of a molecular triad comprising a porphyrin (P) bonded to a fullerene (c6()) and a carotenoid polyene (C) gives its singlet state which decays by electron transfer to c'P'+-c60'-, followed by a second electron transfer to give C'+-P-Cm'-, and which after charge recombination yields the triplet state of the ~ a r o t e n o i d Deactivation .~~~ of the porphyrin S1 state in the covalently linked porphyrin systems { 5,10,15-tri-p-tolyl-20-[2,3-[((hydrotris(3,5dimethylpyrazolyl)borato)oxomolybdenio)dioxy]phenyl]porphyrinato)-zinc(I I), and { 5,10,15-tri-p-tolyl-20-[3,4-[((hydrotris(3,5-dimethylpyrazolyl)borato)oxomolybdenio)dioxy]phenyl]porphyrinato) -zinc(II) has been found to be consistent an ultrafast electron transfer.295These complexes may be of use as catalysts in photoelectron transfer processes. 9
Miscellaneous Oxidations
Irradiation of benzils (83; R' = R2 = Ph; R' = R2 = p-MeC6H4)having a lowest n,n* excited state on silica gel gives benzoic acids (84;same R2)and bibenzofurans (85;same R', R2), whereas l-phenylpropan-l,2-dione(83;R' = Me, R2 = Ph) and biacetyl give acetaldehyde and/or benzoic acid.296By contrast, 4,4'dimethoxybenzil(83; R' = R2 = p-MeOCsH4), a ketone which may have a lowest x,x* excited state, shows no reaction. Various reactions of sulfur-containing compounds have been studied including
220
Photochemistry
the photooxidation of 2-mercaptoethanol and sodium thiosulfate using Co(11) and Zn(I1) phthalocyanine immobilised on silica or intercalated in the galleries and cavities of layered double hydroxides and NaX zeolites.297Enhanced sample activity is observed and seems to have its origin in improved diffusion of the reactants towards the phthalocyanines within the bulk of the supports. Photooxidative polymerisation of diary1 disulfides to poly(thioary1enes) has been achieved using [Ru(bpy)3I2' in oxygenated media, and occurs by electrophilic reaction of the sulfonium cation.298 A study of the photoinduced reactions of benzyl phenyl sulfides under oxygenated conditions and in the presence of 9,lOdihydroanthracene as sensitizer leads to reaction by one of three main pathways, namely C-S bond cleavage, C-H bond cleavage, and S - ~ x i d a t i o n Not . ~ ~ ~all pathways are available to every substrate and the influence of structure on the relative partitioning of the pathways as well as the role of Oy are discussed. Sensitized photooxidation of aromatic sulfides such as benzyl phenyl sulfide, 4methoxybenzyl phenyl sulfide, and phenethyl phenyl sulfide in the presence of Ti02 gives mainly the corresponding aldehydic products, suggesting that the principal reaction pathway is a-C-H depr~tonation.~"Oxygenated basic sites on the Ti02 surface are also envisaged as playing an important role. Experimental support has been obtained for the results of an ab initio study of the structures and energetics of persulfoxides and thiadioxiranes derived from sulfenic acid substrates, and this suggests that hydroperoxysulfonium ylides are formed.30' In particular the photooxidations of N-methyl-, N-n-butyl-, and N-tert-butylbenzenesulfenamides have been examined. References I. 2. 3. 4. 5. 6.
7. 8. 9. 10. 11. 12. 13. 14. 15.
16. 17.
V. Ramamurthy, Wiley Ser. Photosci. Photoeng., 1996, 1, 65. G. Pandey, Mol. Supramol. Photochem., 1997,1,245. A. Ogawa, Kagaku (Kyoto), 1997,52,70. M. N. B. E. Santos, Rev. Port. Quim., 1996,3,3. S. Takagi, M. Suzuki, T. Shiragami, and H. Inoue, J. Am. Chem. Soc., 1997, 119, 8712. C . Heinemann, K. D. Waarzecha, X. Xing, and M. Demuth, Indian J. Chem., Sect. A: Inorg., Bio-inorg., Phys., Theor. Anal. Chem., 1997,36,494. 0 .Ito, Hyomen, 1997,35, 361. 0.Ito, Reza Kenkyu, 1997,25,776. S . Fukuzumi, Res. Chem. Intermed., 1997,23, 519. M. Maggini, S. Mondini, G. Scorrano, M. Prato, F. Paolucci, P. Ceroni, S. Roffia, and D. M. Guldi, Proc. - Electrochem. SOC.,1997,97,318. H. Imahori and Y. Sakata, Adv. Muter. (Weinheim, Ger.), 1997,9, 537. T. Arimura, Yuki Gosei Kagaku Kyokaishi, 1997,55,557. M. D. Ward, Chem. Soc. Rev., 1997,26,365. D. Takasu and T. Aida, Reza Kenkyu, 1997,25,770. H. Moriwaki, Seikatsu Eisei, 1996,40,373. J. S. D. Kumar and S. Das, Res. Chem. Intermed., 1997,23,755. A. Kitamura, N. Miyagawa, and T. Karatsu, Yuki Gosei Kagaku Kyokaishi, 1997, 55,678.
III.5: Photo-reduction and -oxidution 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45.
46. 47. 48. 49. 50. 51. 52. 53. 54.
22 I
M. Sainsbury, Rodn’s Chem. Carbon Compd (2nd Ed.), 1997,qPt. B), 361. P. C. Eklund, J. M. Holden, and A. M. Rao, Springer Ser. Solid-Stale Sci., 1996, 124,256. A. C. Benniston, Chem. SOC.Rev., 1996,25,427. E. L. Clennan, Sulphur Rep., 1996,19, 171. W . S. Jenks, D. D. Gregory, Y. Guo, W. Lee, and T. Tetzlaff, Mol. Supramol. Photochem., 1997,l 1. P. Zhang, G. Yu, and Z. Jiang, Huanjing Kexue Jinzhun, 1997,5, I . K. Kasuga, Phthulocyanines, 1996,4, 199. A. Osuka, Kikan Kugaku Sosetsu, 1997,31, 120. A. 1. Burshtein and A. Yu. Sivachenko, J. Photochem. Photobiol., A, 1997, 109, 1. V. Brenner, Ph. Millie, F. Piuzzi, and A. Tramer, J. Chem. SOC.,Faraduy Trans., 1997,93,3277. W . M. Nau, Ber. Bunsen-Ges., 1998, 102,476. T. Hasegawa, Y. Yamazaki, and M. Yoshioka, J. Photosci, 1997,4,61. A. R. Cook, L. A. Curtiss, and J. R. Miller, J. Am. Chem. SOC.,1997, 119, 5729. V. J. Rao, S. R. Uppili, D. R. Corbin, S. Schwarz, S. R. Lustig, andV. Ramamurthy, J. Am. Chem. SOC.,1998,120,2480. H. Yamashita, N. Sato, M. Anpo, T. Nakajima, M. Hada, and H. Nakatsuji, Stud. Surf: Sci. Cutal. B, 1997, 105, 1141. S. Li, H. Tian, Q. Zhou, Z. Li, and H. Xu, Chin. Sci. Bull., 1997,42, 1619. K. Okada, M. Yamaji, and H. Shizuka, J. Chem. Soc., Faraday Trans., 1998, 94, 861. H. Shizuka, Pure Appl. Chem., 1997,69,825. B. Marciniak, E. Andrzejewska, and G. L. Hug, J. Photochem. Photobiol., A, 1998, 112,21. J. Saeuberlich, 0. Brede, and D. Beckert, Acta Chem. Scand., 1997,51,602. M. Von Raumer, P. Suppan, and E. Haselbach, Helv. Chim. Acta, 1997,80, 719. K. Bobrowski, G. L. Hug, B. Marciniak, B. Miller, and C. Schoeneich, J. Am. Chem. Soc., 1997, 119, 8000. T. S. Kotsyuba, V. M. Granchak, and I. I. Dilung, Theor. Exp. Chem., 1997,33,26. J. C. Scaiano, S. Garcia, and H. Garcia, Tetrahedron Lett., 1997,38, 5929. A. E.-A. M. Gaber, Bull. Pol. Acad Sci.,Chem., 1997,44,235. S. V . Jovanovic, D. G. Morris, C. N. Pliva, and J. C. Scaiano, J. Photochem. Photobiol., A, 1997, 107, 153. T. Arai and Y. Norikane, Chem. Lett., 1997, 339. S. Sekiguchi, Y. Kobori, K. Akiyama, and S. Tero-Kubota, J. Am. Chem. SOC., 1998,120, 1325. T. F. Harper and M. J. Sailor, J. Am. Chem. Soc., 1997,119,6943. S. M. Hubig, T. M. Bockman, and J. K. Kochi, J. Am. Chem. SOC.,1997, 119,2926. Y . Yamakage, T. Nagashima, K. Maeda, H. Murai, and T. Azumi, Appl. Mugn. Reson., 1997, 12,441. G. Jones, N. Mouli, W. A. Haney, and W. R. Bergmark, J. Am. Chem. SOC.,1997, 119,8788. R. Rathore, S. M. Hubig, and J. K. Kochi, J. Am. Chem. Soc., 1997,119, 11468. S. G. Bertolotti and C. M. Previtali, J. Photochem. Photobiol., A , 1997,103, 115. H. Su, G. Li, L. Zheng, T. Lu, and W. Zhang, Colloids Surf.’,A, 1997,123,107. I . Amada, M. Yamaji, M. Sase, H. Shizuka, T. Shimokage, and S. Tero-Kubota, Res. Chem. Intermed., 1998,24, 81. J . Saeuberlich, 0. Brede, and D. Beckert, J. Phys. Chem., A , 1997,101,5659.
222
Photochemistry
55. 56.
H. Zhang, M. Zhang, and T. Shen, J. Photochem. Photobiol., A , 1997,103,63. J. Helaja, A. Y. Tauber, I. Kilpelainen, and P. H. Paavo, Magn. Reson. Chem., 1997,
57.
35,6 19. Z. Leonenko, L. Klimenko, and N, Gritsan, Mol. Cryst. Liq Cryst. Sci. Technol., Sect. A, 1997,297, 175.
58. 59.
60. 61. 62. 63.
64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80. 81. 82. 83. 84. 85. 86.
X.-Q. Wang, C.-X. Wang, Q.-M. Wang, L.-X. Yu, X.-Z. Cao, C.-Z. Min, and L.-P. Wang, Gaodeng Xuexiuo Huuxue Xuebao, 1997,18,834. X.-Q. Wang, C.-X. Wang, Q.-M. Wang, L.-X. Yu, X.-Z. Cao, C.-Z. Min, and L.-P. Wang, Gaodeng Xuexiao Huuxue Xuebao, 1997,18,1241. A. P. Losev, S. M. Bachilo, D. 1. Volkovich, Yu. S. Avlasevich, and K. N. Solov’yov, J. Appl. Spectrosc., 1997,64,62. H. A. Staab, A. Feurer, C. Krieger, and A. S. Kumar, Liebigs AnnJRecl., 1997,
2321. G. Elger, H. Mossler, P. Tian, E. Johnen, M.Fuhs, H. Kurreck, and K. Mobius, Nukleoniku, 1997,42, 293. D. S. English, W. Zang, G. A. Kraus, and J. W. Petrich, J. Am. Chem. Soc., 1997, 119,2980. D. S. English, K. Das, K. D. Ashby, J. Park, J. W. Petrich, and E. W. Castner, J. Am. Chem. Soc., 1997,119, 11585. M.Weng, M.-H. Zhang, and T. Shen, J. Photochem. Photobiol., A , 1997,108, 159. H. Zhang, Z. Zhang, Q. Wan, and D. Wang, Fushe Yunjiu Yu Fushe Gongyi Xuebao, 1997, 15, 75. M. Weng, M.-H. Zhang, and T. Shen, J. Chem. Soc., Perkin Trans. 2,1997,2393. M. Weng, M.-H. Zhang, and T. Shen, J. Photochem. Photobiol., A , 1997,108, 169. G. He, X. Li, C. Chen, and G. Xu, Bopuxue Zazhi, 1997,14,205. H. Dieks, M. 0. Senge, B. Kirste, and H. Kurreck, J. Org. Chem., 1997,62,8666. A. G. Griesbeck, A. Henz, W. Kramer, J. Lex, F. Nerowski, M. Oelgelmoller, K. Peters, and E. M. Peters, Helv. Chim. Acta, 1997,80,912. W. Weigel, S. Schiller, and H.-G. Henning, Tetrahedron, 1997,53, 7855. T. Y. Kim and B. S. Park, Bull. Korean Chem. Soc., 1997,18,141. G. Pandey, S. Hajra, M. K. Ghorai, and K. R. Kumar, J. Org. Chem., 1997, 62, 5966. S. B. Rollins and R. M. Williams, Tetrahedron Lett., 1997,38,4033. T. Hasegawa, Y. Yamazaki, and M. Yoshioka, J. Photosci., 1997,4,7. Y. Yamazaki, T. Miyagawa, and T. Hasegawa, J. Chem. SOC.,Perkin Truns. I , 1997, 2979. G. Olovsson, J. R. Scheffer, J. Trotter, and C,-H. Wu, Tetrahedrori Lett., 1997, 38, 6549. V. S. Rao and A. K. Chandra, J. Photochem. Photobiol., A , 1996,101, 189. A. K. Chandra and V. S. Rao, Chem. Phys. Lett., 1997,270,87. T. Y. Kim, E. S. KO, B. S. Park, H. Yoon, and W. K. Chae, Bull. Korean Chem. Soc., 1997,18,439. Y. Chiang, A. J. Kresge, V. V. Popik, and N. P. Schepp, J. Am. Chem. Soc., 1997, 119, 10203. S. Hu and D. C. Neckers, J. Chem. Soc. Perkin Truns. 2, 1997, 1751. S. Hu and D. C. Neckers, J. Org. Chem., 1997,62,7827. K. Takagi, E. Harata, T. Shichi, T. Kanoh, and Y. Sawaki, J. Photochem. Photobiol., A, 1997,105,47. B. M. Aveline, S. Matsugo, and R. W. Redmond, J. Am. Chem. Soc., 1997, 119, 11785.
IIl.5: Pho to-reduction and -oxidation 87. 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 99. 100. 101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112. 113. 114. 115. 116. 117. 118.
223
M. Terazima, J. Phys. Chem. A, 1998,102, 545. Z. V. Leonenko and N. P. Gritsan, J. Struct. Chem., 1997,38,536. P. J. Wagner, M. Sobczak, and B.4. Park, J. Am. Chem. SOC.,1998,120,2488. Y. Chiang, J. A. Kresge, B. Hellrung, P. Schunemann, and J. Wirz, Helv. Chim. Acta, 1997,80, I 106. J. C. Netto-Ferreira, V. Wintgens, and J. C. Scaiano, J. Braz. Chem. Suc., 1997, 8, 427. T. J. Connolly and T. Durst, Tetrahedron, 1997,53, 15969. E. Bosch, S. M.Hubig, and J. K. Kochi, J. Am. Chem. SOC.,1998,120, 386. S. A. Fleming and J. J. Gao, Tetrahedron Lett., 1997,38,5407. S . Hu and D. C. Neckers, J. Org. Chem., 1997,62,6820. M. Sakamoto, M. Takahashi, T. Fujita, S. Watanabe, T. Nishio, 1. Iida, and H. Aoyama, J. Org. Chem., 1997,62,6298. S. Monti, S. Sortino, G. De Guida, and G Marconi, J. Chem. SOC.,Faradcry Trans., 1997,93,2269. M. M. Alam, M. Fujitsuka, A. Watanabe, and 0. Tto, J. Phys. Chem. A , 1998,102, 1338. E. Hasegawa, Y. Tamura, and E. Tosaka, Chem. Commun. (Cambridge), 1997, 1895. D. K. Lee, Y. I. Kim, Y. S. Kwon, Y. S. Kang, and L. Kevan, J. Phys. Chem. B, 1997,101,5319. Y.-S. Kim, S. McNiven, K. Ikebukuro, and I. Karube, Phutochem. Photobiol., 1997, 66,180. K. Yamada, H. Yonemura, Y. Kuwahara, S. Iida, and T. Matsuo, Chem. Lett., 1997,261. D. C. Craig, K. P. Ghiggino, K. A. Jolliffe, S. J. Langford, and M. N. Paddon-Row, J. Org. Chem., 1997,62,2381. E. Kaganer, E. Joselevich, I. Willner, Z. Chen, M. J. Gunter, T. P. Gayness, and M. R. Johnson, J. Phys. Chem. B, 1998,102, 1159. T. Sata, Y. Matsuo, T. Yamaguchi, and K. Matsusaki, J. Chem. SOC.,Faraday Trans., 1997,93,2553. L. M. Vrana and K. J. Brewer, J. Photochem. Photobiul., A , 1997,109,201. Y. Amao, T. Hiraishi, and I. Okura, J. Mul. Catal. A: Chem., 1997,126,21. Y. Amao, T. Kamachi, and I. Okura, Inorg. Chim. Acta, 1998,267,257. K. Tsukahara, C. Kimura, J. Kaneko, K. Abe, M. Matsui, and T. Hara, Inorg. Chem., 1997,36,3520. K. Oosaki, T. Kondo, X.-Q. Zhang, and M. Yanagida, J. Am. Chem. Suc., 1997, 119,8367. H. Aota, S.4. Araki, Y. Morishima, and M. Kamachi, Macromolecules, 1997, 30, 4090. W. S. Szulbinski, Inorg. Chim. Acta, 1998,269,253. J. L. Ferry and W. H. Glaze, J. Phys. Chem. B, 1998,102,2239. J. W. Park, S. H. Park, B. A. Lee, and S.-Y. Lee, Chem. Lett., 1997, 1043. D. M. Martino, H. van Willigen, and M. T. Spitler, J. Phys. Chem. B, 1997, 101, 89 14. M. P. Scannell, G. Prakash, and D. E. Falvey, J. Phys. Chem. A , 1997,101,4332. B. C. Gilbert, J. R. L. Smith, A. F. Parsons, and P. K. Setchell, J. Chem. SOC., Perkin Trans. 2, 1997, 1065. W. Adam, J. N. Moorthy, W. M. Nau, and J. C. Scaiano, J. Am. Chem. Soc., 1997, 119,6749.
224 119. 120. 121. 122. 123. 124. 125. 126. 127. 128. 129. 130. 131.
132. 133. 134. 135. 136. 137. 138. 139. 140. 141. 142.
143. 144. 145.
146. 147. 148.
Photochemistry
W. Adam, J. N. Moorthy, W. M. Nau, and J. C. Scaiano, J. Org. Chem., 1997, 62, 8082. M. A. Weidner-Wells, K. Oda, and P. H. Mazzocchi, Tetrahedron, 1997,53, 3475. M. R . Bryce, E. Chinarro, A. Green, N . Martin, A. J. Moore, L. Sanchez, and C. Seoane, Synth. Met. 1997,86, 1857. K. Nakatani, N. Higashida, and I. Saito, Tetrahedron Lett., 1997, 38. 5005. R . Arakawa, J. Lu, K. Mizuno, H. Inoue, €-I. Doe, and T. Matsuo, Int. J. Mass Spectrum. Ion Processes, 1997, 160, 371. D. Eloy, C. Gay, and P. Jardon, J. Chim. Phys. Phys.-Chim. Biol., 1997,94,683. K. T. Ranjit and B. Viswanathan, J. Photochem. Photobiol., A, 1997,107,215. M. Fujitsuka, H. Kasai, A. Masuhara, S. Okada, H. Oikawa, H. Nakanishi, A. Watanabe, and 0. Ito, Chem. Lett., 1997, 121 1. Y. Sasaki, M. Fujitsuka, A. Watanabe, I. Osamu, and A. Katahira, J. Chem. Soc., Furaday Trans., 1997,93,4275. S. Fukuzumi, M. Patz, T. Suenobu, A. Ishida, and K. Mikami, Proc. - Electrochem. Soc., 1997,97,45. 0 .Ito, Y. Sasaki, A. Watanabe, R. Hoffmann, C. Siedshlag, and J. Mattay, J. Chem. Soc., Perkin Trans. 2 , 1997, 1007. E. R. Crooks, J. Eastoe, and A. Beeby, J. Chem. Soc., Faraduy Trans., 1997, 93, 4131. S. Fukuzumi, T. Suenobu, S. Kawamura, A. Ishida, and K. Mikami, Chem. Commun., (Cumbridge), 1997, 29 1 . S. Michaeli, V. Meiklyar, B. Endeward, K. Mobius, and H. Levanon, Res. Chem. Intermed., 1997,23, 505. S.-H. Wu, D.-W. Zhang, G.-W. Wang, L.-H. Shu, H.-M. Wu, J.-F. Xu, and X.-F. Lao, Synth. Commun., 1927,27,2289. M. M. Alam, A. Watanabe, and 0. Ito, J. Photochem. Photobiol., A, 1997, 104, 59. T. Nojiri, M. M. Alam, H. Konami, A. Watanabe, and 0. Ito, J. Phys. Chem. A, 1997,101, 7943. D. M. Guldi, M. Maggini, S. Mondini, G. Scorrano, and M. Prato, Proc. SPIE-Int. Soc. Opt. Eng., 1997,3142,96. D. M. Guldi, M. Maggini, S. Mondini, G. Scorrano, and M. Prato, Proc. Electrochem. Soc., 1997,97, 89. T. D. M. Bell, T. A. Smith, K. P. Ghiggino, M. G. Ranasinghe, M. J. Shepard, and M. Paddon-Row, Chem. Phys. Lett., 1997,268,223. I. G. Safonov, P. S. Baran, and D. 1. Schuster, Tetrahedron Lett., 1997,383, 8133. H. Imahori, K. Yamada, M. Hasegawa, S. Taniguchi, T. Okada, and Y. Sakata, Angew. Chem., Int. Ed. Engl., 1997,36, 2626. A. Itaya, I. Suzuki, Y. Tsuboi, and H. Miyasaka, J. Phys. Chem. B, 1997,101,5118. M. Fujitsuka, A. Watanabe, 0. Ito, K. Yamamoto, and H. Funasaka, J. Phys. Chem. ‘4, 1997,101,4840. D. M. Guldi, D. Liu, and P. V. Kamat, J. Phys. Chem. A, 1997,101,6195. L. K. Sydnes and H. H. Ovrebo, Acta Chem. Scund., 1997,51,889. M. Onishi, M. Yonekura, K. Hiraki, M. Shugyo, H. Kawano, and H. Kobayashi, J. Mol. Catul. A: Chem., 1997, 121,9. L. X. Deng and A. G. Kutateladze, Tetrahedron Lett., 1997,38, 7829. S . Hashimoto, J. Chem. Soc., Furaday Trans., 1997,93,4401. G . Zhang, J. K. Thomas, A. Eremenko, T. Kikteva, and F. Wilkinson, J. Phys. Chem. B, 1997,101,8569.
IIt.5: Photo-reduction und -oxiclution 149. 150.
225
G. P. Zanini, H. A. Montejano, J. J. Cosa, and C. M. Previtali, J. Photochern. Photobiol., A , 1997, 109, 9. N. Manoj, K. R. Ajit, and K. R. Gopidas, J. Photochem. Photobiol., A , 1997, 109, 109.
151.
H. Mohan, D. K. Palit, J. P. Mittal, L. Y. Chiang, K.-D. Asmus, and D. M. Guldi, J. Chem. Soc., Furaduy Truns., 1998,94,359. 152. N. K . Khannanov, G. N. Menchikova, and E. A. Grigoryan, Kinet. Cutal., 1997,38, 801.
153. 154. 155. 156. 157. 158. 159. 160.
H. Koshima, T. Nakagawa, and T. Matsuura, Tetruheciron Lett., 1997,38,6063. L. Rodriguez-Hahn, M. E. Manriquez, B. A. Frontana, and J. Cardenas, An. Quim. Int. Ed., 1997,93,291. K. Koike, H. Hori, M. Ishizuka, J. R. Westwell, K. Takeuchi, T. Ibusuki, K. Enjouji, H. Konno, K. Sakamoto, and 0. Ishitani, Organometallics, 1997,16,5724. Y. Kohno, T. Tanaka, T. Funabiki, and S. Yoshida, Chem. Lett., 1997, 993. T. S. Dzhabiev, Kinet. Cutul., 1997,38, 795. S. Yanagida, M. Kanemoto, K.4. Ishihara, Y. Wada, T. Sakata, and H. Mori, Bull. Chem. SOC.Jpn., 1997,70,2063. P. Johne and H. Kisch, J. Photochem. Photobiol., A , 1997,111,223. B. K. Sharma, R. Ameta, J. Kaur, and S. C. Ameta, int. J. Energy Rex, 1997, 21, 923.
161. 162. 163. 164. 165. 166. 167. 168. 169. 170. 171. 172. 173. 174. 175. 176. 177 178.
B.-J. Liu, T. Torimoto, H. Matsumoto, and H. Yoneyama, J. Photochem. Photobiol., A , 1997,108, 187. H. Yoneyama, Catul. Tocluy,1997,39, 169. S. Kaneco, H. Kurimoto, K. Ohta, T. Mizumo, and A. Saji, J. Photochem. Photobiol., A , 1997, 109, 59. J. Premkumar and R. Ramaraj, J. Photochem. Photobiol., A , 1997,110,53. S. G. Zhang, Y. Fujii, H. Yamashita, K. Koyano, T. Tatsumi, and M. Anpo, Chem. Lett., 1997,659. F . Saladin and I. Alxneit, J. Chem. SOC.,Furuduy Trans., 1997,93,4159. H. Fujiwara, H. Hosokawa, K. Murakoshi, Y. Wada, S. Yanagida, T. Okada, and H. Kobayashi, J. Phys. Chem. B, 1997,101,8268. K. Kasuga, M. Terauchi, M. Hara, K. Nishie, T. Sugimori, and M. Handa, Bull. Chem. Soc. Jpn., 1997,70,2107. D. Armesto, A. Albert, F. H. Cano, N. Martin, A. Ramos, M. Rodriguez, J. L. Segura, and C. Seoane, J. Chem. Soc., Perkin Truns. I , 1997,3401. K. T. Ranjit and B. Viswanathan, J. Photochem. Photobiol., A , 1997,108,73. X.-Q. Zhu, Y.-C. Liu, J. Li, and H.-Y. Wang, J. Chem. Soc., Perkin Truns. 2, 1997, 2191. E. A. Venedictoy and 0. G. Tokareva, Mendeleev Commun., 1997,84. 1. Hatzopoulos, W. R. Thiel, and H.-D. Brauer, J. Photochem. Photobiol., A , 1997, 102,151. J. Mosinger and Z. Micka, J. Photochem. Photobiol., A , 1997, 107,77. J. Huang, E. Liu, S. Yang, D. Wu, N. Chen, J. Huang, and R. Ouyang, Xiumen Duxue Xuebao Ziran Kexuebun, 1997,36,399. J. L. Bourdelande, M. Karzazi, L. E. Dicelio, M. I. Litter, G. M. Tura, E. San Roman, and V. Vincent, J. Photochem. Photobiol., A, 1997,108,273. W.-F. Sun, S.-M. Dong, D.-Y. Wang, J.-C. Yue, Q. Wan, M.-F. Li, and S.-Z. Pang, Huaxue Xuebao, 1997,55665. S. Foley, G. Jones, R. Liuzzi, D. J. McGarvey, M. H. Perry, and T. G. Truscott, J. Chem. Soc.. Perkin Truns. 2, 1997, 1725.
226 179. 180.
181. 182. 183. 184. 185.
186. 187. 188. 189. 190. 191. 192. 193. 194. 195. 196. 197. 198. 199. 200. 201. 202. 203. 204. 205. 206. 207. 208. 209. 210. 21 1. 212. 21 3.
Photochemistry
J. Xie and H. He, Ganguang Kexue Yu Guung Huaxue, 1996,14,212. E. L. Clennan, D. Wang, C. Clifton, and M.-F. Chen, J. Am. Chem. SOC.,1997,119, 9081. P. Serguievski and M. R. Detty, Organometallics, 1997,16,4386. F. Prat, C.-C. Hou, and C. S. Foote, J. Am. Chem. Soc., 1997,119,5051. C. Wirp, J. Bendig, and H. D. Brauer, Ber. Bunsen-Ges., 1997,101,961. M. Mella, M. Freccero, M. Fagnoni, E. Fasani, and A. Albini, NATO ASI Ser., Ser. 3, 1997,27, 161. S. Negele, K. Wieser, and T. Severin, J. Org. Chem., 1998,63, 1138. H. Sun, F. Blatter, and H. Frei, Catal. Lett., 1997,44,247. S. Takenaka, T. Tanaka, T. Funabiki, and S. Yoshida, Catal. Lett., 1997,44,67. B. Su, Y. He, X. Li, E. Lin, and Q. Li, Indian J. Chem., Sect. A: Inorg., Bio-inorg., Phys., Theor. Anal. Chem., 1997,36,785. A. Maldotti, R. Amadelli, V. Carassiti, and A. Molinari, Inorg. Chim. Acta, 1997, 256, 309. D. B. Gao, J. M. Yin, M. Guo, Y. Yu, and Y. A. Ma, Chin. Chem. Lett., 1997, 8, 763. E. T. Farinas, C. V. Nguyen, and P. K. Mascharak, Inorg. Chim. Acta, 1997,263, 17. S . Mcilroy, H. Weng, and H. D. Roth, J. Phys. Org. Chem., 1997,10,607. D. Laplaze, P. Bernier, C. Journet, J. L. Sauvajol, D. Bormann, G. Flamant, and M. Lebrun, J. Phys. III, 1997,7,463. P. V. Kamat, M. Gevaert, and K. Vinodgopal, J. Phys. Chem. B, 1997,101,4422. C. Siedschlag, H. Luftmann, C. Wolff, and J. Mattay, Tetrahedron, 1997,53,3587. W. Zhang, Y. Su, L. Gan, J. Jiang, and C. Huang, Chem. Lett., 1997, 1007. I. G. Safonov, S. H. Courtney, and D. 1. Schuster, Res. Chem. Intermed., 1997, 23, 541. M. Fujitsuka, A. Watanabe, 0. Ito, K. Yamamoto, and H. Funasaka, J. Phys. Chem. A , 1997,101,7960. Z. R. Lian, S. D. Yao, W. Z. Lin, W. F. Wang, and N. Y. Lin, Radiat. Phys. Chem., 1997,50,245. S . D. Yao, W. Z. Lin, Z. R. Lian, W. F. Wang, and N. Y. Lin, Radiat. Phys. Chem., 1997,50,249. K. B. Myli, S. C. Larsen, and V. H. Grassian, Cutal. Lett., 1997,48, 199. Z. Tong, C.-h. Tung, and H. Wang, Ganguang Kexue Yu Guang Huaxue, 1997,15, 289. M. D. Driessen, A. L. Goodman, T. M. Miller, G. A. Zaharias, and V. H. Grassian, J. Phys. Chem. B, 1998,102,549. F. Chiron, J. C. Chalchat, R. P. Garry, J. F. Pilichowski, and J. Lacoste, J. Photochem. Photobiol. A , 1997,111,75. W. Adam and D. Reinhardt, J. Chem. Soc., Perkin Trans. 2, 1997, 1453. H. Mori, K . Ikoma, and S. Katsumura, Chem. Commun. (Cambridge), 1997,2243. E. Salamci, H. Secen, Y. Suetbeyaz, and M. Balci, J. Org. Chem., 1997,62,2453. A. Maras, H. Secen, Y. Suetbeyaz, and M. Balci, J. Org. Chem., 1998,63,2039. 1. Shimizu, M. Fujita, T. Nakajima, and T. Sato, Synlett, 1997, 887. W. Adam, 0. Deeg, and S. Weinkoetz, J. Org. Chem., 1997,62,7084. N. Tanaka, M. Nakata, and K. Shibuya, J. Photochem. Photobiol., A , 1997, 106, 113. B. Atasoy and R. Ozen, Tetrahedron, 1997,53, 13867. R. E. K . Winter, J. A. Baker, B. V. Lam, A. G. Breite, and N. Rath, Nut. Prod. Lett., 1997,10, 105.
IZIS: Photo-reduction and -oxidation
214. 215. 216. 217. 218. 219. 220. 221. 222. 223. 224. 225. 226. 227. 228. 229. 230. 231. 232. 233. 234. 235. 236. 237. 238. 239. 240. 241. 242. 243. 244. 245. 246. 247. 248.
227
D. S. Muggli, J. T. McCue, and J. L. Falconer, J. Catal., 1998,173,470. C.-G. Yang, Y. Wan, and Z.-Q. Jiang, Chem. Res. Chin. Univ., 1997,13,392. K. Shiomori, Y. Kawano, Y. Baba, H. Mitani, and Y. Hatate, Kagaku Kogaku Ronbunshu, 1997,23,694. W. Adam, J. Renze, and T. Wirth, J. Org. Chem., 1998,63,226. Y. Mao and A. Bakac, J. Phys. Chem. A , 1997,101,7929. G . Toth, T. Linker, and F. Rebien, Mugn. Reson. Chem., 1997,35,367. S. Li, X. Dong, and H. Xu, Wuli Huaxue Xuebao, 1997,13,680. B.-W. Zhang, Y. Cao, J.-W. Bail and J.-R. Chen., J. Photochem. Photobiol., A , 1997, 106,169. D. K. Palit, A. V. Sapre, and J. P. Mittal, Chem. Phys. Lett., 1997,269,286. H. A. Staab, D. Q. Zhang, and C. Krieger, Liebigs Ann.lRecl., 1997, 1551. A. Uchida, S. Shimizu, A. Saitou, S. Ohshima, I. Oonishi, and S. Fujisawa, Polycyclic Aromat. Compd., 1996, 11, 305. R. Wittenberg, M. A. Pradera, and J. A. Navio, Langmuir, 1997,13, 2373. W. Bergmark, S. Hector, G. Jones, C. Oh, T. Kumagai, S.4. Hara, T. Segawa, N. Tanaka, and T. Mukai, J. Photochem Phorobiol., A , 1997,109, 119. K. N. Rajasekharan and A. Sulekha, Indian J. Chem., Sect. B: Org. Chem. Incl. Med. Chem., 1997,36,697. K. Kohiro and Y . Inoue, Kokagaku, 1997,26,44. M. D’Auria and V. Esposito, Gazz. Chim. Ital., 1997,127,471. F. L. Cozens, R. Bogdanova, M. Regimbald, H. Garcia, V. Marti, and J. C. Scaiano, J. Phys. Chem. B, 1997,101,6921. A. Liwo, D. Dyl, D. Jeziorek, M. Nowacka, T. Ossowski, and W. Woznicki, J. Comput. Chem, 1997,18,1668. A. De, S. Bhattacharjee, and B. K. Dutta, Inn Eng. Chem. Res., 1997,36,3607. M. Sarakha, M. Bolte, and H. D. Burrows, J. Photochem. Photobiol., A, 1997, 107, 101. F. Bonnichon, M. Sarakha, and M. Bolte, J. Photochem. Photobiol., A , 1997, 109, 217. I. Martini, J. H. Hodak, and G. V. Hartland, J. Phys. Chem. B, 1998,102,607. T. M. Bockman, S. M. Hubig, and J. K. Kochi, J. Org. Chem., 1997,62, 2210. H. Koshima, K. Ding, Y. Chisaka, T. Matsuura, I. Miyahara, and K. Hirotsu, J. Am., Chem. SOC.,1997,119, 10317. C. Li, Q. Wang, and Y. Cheng, Xiangtan Daxue Ziran Kexue Xuebao, 1997,19,65. M. Nakamura, R. Dohno, and T. Majima, Chem. Commun. (Cambridge), 1997, 1291. Y. Okamoto, T. Tatsuno, and S. Takamuku, Phosphorus, Sulfur, Silicon, Relat. Elem., 1996,117, 129. M . Suzuki, T. Tkeno, K. Osoda, K. Narasaka, T. Suenobu, S. Fukuzumi, and A. Ishida, Bull. Chem. Soc. Jpn., 1997,70,2269. Z.-F. Tao, X. Qian, and M. Fan, Tetrahedron, 1997,53, 13329. X.-H. Qian and Y.-L. Zhang, Youji Huaxue, 1997,17,329. S . V. Zelentsov, A. V. Eryutov, A. A. Ezhevskii, and A. V. Oleinik, High Energy Chem., 1997,31, 193. N. Serpone, P. Calza, A. Salinaro, L. Cai, A. Emeline, H. Hidaka, S. Horikoshi, and E. Pelizzetti, Proc. - Electrochem. SOC.,1997,97,301. H.-R. Park, H.-J. Kim, and H.-C. Lee, Bull. Korean Chem. Soc., 1997,18,226. J . Lee, J. S. U, S. C. Blackstock, and J. K. Cha, J. Am. Chem. Soc., 1997,119, 10241. W. Weigel and H.-G. Henning, Chem. Commun. (Cambridge), 1997, 1893.
Phot ochemis tr.y
228 249. 250.
251. 252. 253. 254. 255. 256. 257. 258. 259. 260. 261. 262. 263. 264. 265. 266. 267. 268. 269. 270. 271. 272. 273. 274. 275. 276. 277. 278. 279.
K. Weidemaier, H. L. Tavernier, K. T. Chu, and M. D. Fayer, Chem. Phys. Lett., 1997,276,309. K . Weidemaier, H. L. Tavernier, and M. D. Fayer, J. Phys. Chem. B, 1997, 101, 9352. J. R. Hwu, C. S. Yau, S.-C. Tsay, and T.-I. Ho, Tetruhedron Lett., 1997,38,9001. S. Aich, C. Raha, and S. Basu, J. Chem. Soc., Furuday Trans., 1997,93,2991. A. L. Zanocco, E. Lemp, and G. Gunther, J. Chem. Soc., Perkin Trans. 2, 1997, 1299. C.-H. Tung, L.-P. Zhang, Y. Li, H. Cao, and Y. Tanimoto, J. Am. Chem. Soc., 1997, 119,5348. Y . 3 . Chen, J. W. Kampf, and R. G. Lawton, Tetruhedron Lett., 1997,38,7815. A. B. J. Parusel, R. Schamschule, and G. Koehler, Ber. Bunsen-Ges., 1997,101, 1836. W . Verbouwe, L. Viaene, M. Van der Auweraer, F. C. De Schryver, H. Masuhara, R. Pansu, and J. Faure, J. Phys. Chem., A, 1997,101,8157. S. Delmond, J.-F. Letard, R. Lapouyade, and W. Rettig, J. Photochem. Photobiol., A , 1997,105,135. R. Altundas, M. Krawiec, W. H. Watson, and M. Balci, J. Chem. Crystallogr., 1997, 27, 645. Y. Jiang, Gunguung Kexue Yu Guung Huuxue, 1996,14,207. K. A. Zachariasse, M. Grobys, Th. von der Haar, A. Hebecker, Yu. V. Il’ichev, 0. Morawski, I. Rueckert, and W. Kuehnle, J. Photochem. Photobiol., A , 1997, 105, 373. L. Zang, P. Qu, J. Zhao, T. Shen, and H. Hidaka, J. Mol, Cutal. A: Chem., 1997, 120, 235. E. Popova, E. Iskrenova, and Z. Mardirosjan, Dokl. Bulg. Akad Nuuk, 1996,49,63. I. N. Martyanov and E. N. Savinov, Catal. Toduy, 1997,39, 197. E. N. Makareyeva, Yu. V. Makedonov, and E. L. Lozovskaya, Russ. Chem. Bull., 1997,46,902. N . E . Polyakov, A. I. Kruppa, T. V. Leshina, V. Lusis, D. Muceniece, and G. Duburs, J. Photochem. Photobiol. A, 1997,111,61. S . N . Ayyad and E. M. Elgendy, Mansouru Sci. Bull., A: Chem., 1997,24207. F. D. Lewis, J. M. Wagner-Brennan, and J. M. Denari, J. Phys. Chem. A, 1998,102, 519. S. Wu, Z. Jiang, and F. Jia, Gunguung Kexue Yu Guang Huaxue, 1996,14,351. J. Li, P. Chen, J. Zhao, D. Zheng, 0. Tsuneki, and H. Masaaki, Gunguung Kexue Yu Guang Huuxue, 1996,14,314. M. R. Iesce, F. Cermola, and A. Guitto, Synthesis, 1997, 657. T. D. Nekipelova and N. 0.Pirogov, Russ. Chem. Bull., 1997,46,672. K. G. Suresh, A. Das, and M. Maiti, J. Photochem. Photobiol., A, 1997,111,51. A. Sakai, H. Tani, T. Aoyama, and T. Shioiri, Synlett, 1998,257. D. P. S. Negi, J. Chem. Res. Synop., 1998,54. H . Zhang, M. Zhang, and T. Shen, Sci. China, Ser. B: Chem., 1997,40, 192. H. Zhang, M. Zhang, and T. Shen, Sci. China, Ser. B: Chem., 1997,40,449. S. Aich and S. Basu, J. Phys. Chem. A, 1998, 102,722. S. Li, H. Tian, Q. Zhou, and H. Xu, Ganguung Kexue Yu Guung Huaxue, 1997, 15, 138.
280. 281. 282.
C. Bienvenu, C. Lebrun, and J. Cadet, J. Chim. Phys. Phys.-Chim. Biol.,1997, 94, 300. T. Berthod, J. Cadet, and D. Molko, J. Photochem. Photobiol., A , 1997,104,97. R. M. B. Dias and A. J. S. C. Vieira, J. Photochem. Photobiol., A, 1997,109.133.
IIl.5: Photo-reduction and -oxidation
229
P. V. Kamat, D. Guldi, D. Liu, K. G. Thomas, V. Biju, S. Das, and M. V. George, Proc. - Electrochem. Soc., 1997,97, 122. 284. C. Chen, X. Qi, and B. Zhou, J. Photochem. Photobiol., A , 1997,109, 155. 285. N. Miyagawa, T. Karatsu, and A. Kitamura, Chem. Lett., 1997, 1005. 286. C.-y. Wang, C.-y. Liu, and T. Shen, J. Phorochem. Photobiol., A, 1997, 109,65. 287. S. Wang, D. Chen, J. Gou, and H. Wang, Chin. Sci. Bull., 1997,42,998. 288. M. Maafi, B. Laassis, J.-J. Aaron, M. C. Mahedero, M. De La Pena, and F. Salinas, J. Fluoresc., 1997,7,25S. 289. L. Flamigni, N. Armaroli, F. Barigelletti, V. Balzani, J.-P. Collin, J . - 0 . Dalbavie, V. Heitz, and J. P. Sauvage, J. Phys. Chem. B, 1997, 101, 5936. 290. S. Kotani, H. Miyasaka, A. Ttaya, Y. Hamanaka, N. Mataga, S. Nakajirna, and A. Osuka, Chem. Phys. Lett., 1997,269,274. 291. D. Wang, M. Hu, L. Hu, L. Zhao, Z. Lu, and Y. Nie, Sci. China, Ser. B: Chem., 1997,40, 183. 292. P. K. Malinen, A. Y. Tauber, J. Helaja, and P. H. Hynninen, Liebigs Ann. Reel., 1997, 1801. 293. J. He, M. Zhang, and T. Shen, Sci. China, Ser. B: Chem., 1997,40,380. 294. D. Gust, T. A. Moore, A. L. Moore, P. A. Liddell, D. Kuciauskas, J. P. Sumida, B. Nash, and D. Nguyen, Proc. - Electrochem. Soc., 1997,97,9. 295. M. H. Wall, P. Basu, T. Buranda, B. S. Wicks, E. W. Findsen, M. Ondrias, J. H. Enemark, and M. L. Kirk, Inorg. Chem., 1997,36,5676. 296. H. Hasegawa, M. Imada, Y. Imase, Y. Yamazaki, and M. Yoshioka, J. Chem. Soc., Perkin Trans. I , 1997, 127 1 . 297. V. Iliev, A. Ileva, and L. Bilyarska, J. Mol. Cutal. A : Chem., 1997, 126,99. 298. K. Yamamoto, K. Oyaizu, S. Kobayashi, and E. Tscuhida, Phosphorus, Sulfur Silicon Relat. Elem., 1997, 120 & 121,407. 299. E. Baciocchi, C. Crescenzi, and 0. Lanzalunga, Tetruhedron, 1997,53,4469. 300. E. Baciocchi, T. Del Giacco, M. I. Ferrero, C. Rol, and G. V. Sebastiani, J. Org. Chem., 1997,62,4015. 301. A. Greer, M.-F. Chen, F. Jensen, and E. L. Clennan, J. Am. Chem. Soc., 1997, 119, 4380. 283.
6
Photoreactions of Compounds Containing Heteroatoms other than Oxygen BY ALBERT C. PRATT
1
Introduction
Topics reviewed during the year include the photochemistry of indoles,' sulfoxides,* pyrazoles and isothia~oles,~ (S-hetero)cyclic unsaturated carbonyl c o m p o ~ n d sphotoinduced ,~ single electron transfer (SET) reactions of amines5 and of azo compounds,6 SET reactions of organmilanes and organostannanes with C60 and ketone^,^ photochromic polypeptides' and di(heter~)arylethenes,~ processes in chromophore sequences on a-helical polypeptides, l o aryl-aryl coupling in furans, thiophenes and pyrroles, [3+2]cycloaddition of aromatic nitriles (and esters) with alkenes,12and reactions of benzylsilane derivative^.'^
''
2
Nitrogen-containing Compounds
2.1 E,Z-Isomerisations - Photoeffects arising from the influence of heteroatoms on systems containing carbon-carbon double bonds have been reported. Studies with benzothiazolium styryl azacrown ether dyes show that an azacrown ether unit linked to an electron acceptor is potentially a photocontrolled ion-release system, with photoinduced charge transfer away from nitrogen reducing the stability constant of the complex.14 2-(2-(2-Pyrrolyl)ethenyl)phenanthroline exhibits one-way Z- to E-isomerisation; intramolecular hydrogen bonding in the E-isomer results only in singlet excited state intramolecular hydrogen transfer. However, complexation of the E-isomer with nickel cations disrupts the hydrogen bonding and E- to Z-photoisomerisation then occurs. l 5 The photoisomerisation and photophysical properties of a series of 1-(9-anthryl)-2-(2-,3-, or 4-pyridy1)ethenesi6and of 1-(9-anthryl)-2-(2-pyra~inyl)ethene'~are solvent dependent. Of significance to the development of diagnostic and therapeutic strategies in earlystage leukaemia, the isomerisation, fluorescence and triplet excited state quantum yields have been examined for some merocyanine dyes. The isomerisation behaviour of a series of (4-hydroxycinnamoy1)spermidines has been reported. l 9 Donor/acceptor-substituted 1,2-diethynylethenes and tetraethynylethenes undergo photoisomerisation that is strongly dependent on the type and degree of substitution, on solvent polarity and on excitation wavelength.*' In the presence
''
Photochemistry, Volume 30 0The Royal Society of Chemistry, 1999 230
1116: Photoreactions of Compounds Containing Heteroaioms other than Oxygen
23 1
of nitro blue tetrazolium and sodium azide, only the 2-isomer of 3-[1H-imidazol4(5)-yl]-2-propenoic acid (urocanic acid) undergoes photoisomerisation, involving reversible addition of the azidyl radical to the double bond.21 The effects of intramolecular charge transfer in excited 4-nitrostilbenes and 2,4-dinitrostilbenes have been investigated?2 Ab initio computations have been used to investigate the minimum energy paths for isomerisation of a series of polyeniminium cations, for example (l), which are models for the 11-cis retinal protonated Schiff base of the human retina visual pigment rhodopsin .23-25 One-way Z- to E-photoisomerisation of Nmethoxy-l-(9-anthryl) methanimine (2) occurs from the excited triplet state whereas the singlet excited state results in two-way isomerisation.26 0-Acyl-2oximinoketones undergo reversible E,Z-isomerisation and/or N-0 bond cleavage on irradiation, depending on the nature of the substituent at the imino carbon. Photoisomerisation is the major process observed for aryl-substituted compounds (3) whereas, for alkyl-substituted compounds (4), formation of radicals (7)and (8) is the exclusive process, occurring in all cases from a short-lived triplet excited state.27E,Z-Benzylidenecyclohexanoneoxime (5) gives primarily C = C isomerisation on both direct and sensitised irradiation, whereas the corresponding E,Eisomer results primarily in C = N isomerisation on direct irradiation but C=C isomerisation on sensitisation. In acidified methanol direct irradiation causes isomerisation about both double bonds in addition to formation of tetrahydroacridine, involving dehydration of the electrocyclisation intermediate (6).28 CH=NOMe
1
PhCOC=NOCOR2 I 3 R' = aryl,R'R2 = aryl, alkyl 4 R' = alkyl, R2 = awl, alkyl
PhCOC=N' I R' 7
Jh
+
'OCOR2
8 2
H9,
/
5
\ 6
8
Geometrical isomerisations involving the azobenzene chromophore continue to attract attention. Low temperature flash photolysis studies of 4-aminoazobenzene and 4-(N,N-dimethylamino)azobenzene in an ethanol glass on the microsecond timescale indicate that for both compounds the photoexcited 2-isomer produces two species. One of these is the E-isomer; the other is a short-lived intermediate, tentatively identified as a zwitterionic species, which decays to form the Eisomer.29The donor-acceptor substituted azobenzene sodium 4-(4'-aminophenylazo)benzoate has been reported to complete the E- to 2-photoisomerisation
232
Photochemistry
process within 200 PS.~’ In aqueous solution at pH 10.5 the Z-azobenzene (9), bearing two boronic acid units, recognises glucose and allose by formation of cyclic 1 :1 complexes and shows promise as a selective light-gated saccharide acceptor. Visible light irradiation results in the formation of the corresponding Eazobenzene in which the boronic acid groups are too far apart for complexation to The effects of complexation by metal cations on the E,Z-photoisomerisations of two crown ethers3* and a calix[4]~rown,~~ each incorporating an azobenzene chromophore, have been reported. The photochromic and electrochemical behaviour of crown-ether-derived azobenzene monolayer assemblies has been reported,34735as have further studies of lipids containing the azobenzene chromophore and of the photoresponsive properties of their aggregates.36937 The particle size of photoresponsive dendrimers which involve a 1,3-alternate conformer of calix[4]arene as a core and azobenzene skeletons as branches may be controlled by exposure to variable levels of UV or visible light and darkness.38
9
2.2 Photocyclisations - The preservation of amidine or imidate resonance in a dipolar excited state accounts for the contrasting selectivities observed in the photocyclisations of 3H-azepines (10) to 3-substituted derivatives (12), and of cycloheptatrienes (11) to 5-substituted derivatives (13).39An 18~-electronphotocyclisation has been used as a key step in the synthesis of a reduced macrocycle of haem d1.40Interest continues in the photochromism of systems such as (14), capable of undergoing reversible 6n-electron conrotatory ring closure and having potential applications in a wide range of technological devices. The influences of cycloalkene ring strain and alkyl substituents on the thermal stability and fatigue resistance of 1,2-bis(N-alkyl-2-methylindol-3-yl)cyclopentenesand cyclohexenes have been in~estigated.~’ Solid phase studies on a series of dithienylperfluorocy~lopentenes~~ and solution phase investigations of 1,2-bis(thiazolyl)perfluorocy~lopentenes~~ have been reported. The addition of cyclodextrins (CDs) to 1,2-diyl)bis(benaqueous solutions of 2,2’-dimethyl-3,3’-(perfluorocyclopentenezo[b]thiophene-6-sulfonate)results in the preferential inclusion of a favourable antiparallel conformation in the CDs cavities and leads to increased cyclisation quantum yields.@ Photoirradiation changes the affinity for caesium ions of a dithienyl perfluorocyclopentene with two attached 18-crown-6
UI4: Photoreactions of Compouncis Containing Heteroatoms other than Oxygen
233
whereas related systems carrying two aza- 18-crown-6 groups exhibit significantly smaller complexation differences between the ring-opened and ring-closed forms.46Semi-empirical molecular orbital calculations have been applied to an investigation of conformational and other factors involved in the photochromism of 2,3-bis(2,4,5-trimethyl-3-thieny1)maleic anhydride.47
10 X = N; Y = OR, NR2 11 X = CH; Y = OR, NR2
a=& 12
13
H H
14 CYC = cycloalkyl, HET = heterocycle
The related 67c-electron systems (15)-(26) have also been the subject of continuing interest. Indolyl anhydride (15) does not photocyclise, undergoing only Z- to E-isomerisation, whereas (16),with an additional methyl group on the exocyclic double bond, photocyclises with low efficiency.& The photochromism of chiral indolyl anhydride (17) and of its diastereomeric 2,2’-binaphthol ketal (18), and the consequential changes in their chiral properties, have been examined.49 The previously reported” structure (19) for a photochromic dicyanomethylenetetrahydrofuran-Zone has been revised to (21).5’ Authentic (21) also undergoes cyclisation as do isoimides (22)-(25). Pyrryl derivative (20)52 and benzofuranones (26) cyclise with 366 nm light to give coloured products. Exposure to visible or near-IR radiation reverses the cyclisation, bleaching the
line 15 R’ = R3 = H; R2,R2 = 2-adamantylidene 16 R1 = Me; R2,R2= 2-adamantylidene; R3 = H 17 R’ = CHMe2; R2 = = Me
234
Photochemistry
I Me
18
19 X = O , R = M e 20 X = 4-MeOC6H4N, R = Ph
21
NNMePh
Med
$
N Me R
NMePh
Me
22 R = M e 23 R = cyclopropyl
Me R 24 R = M e 25 R = cyclopropyl
R2
R3
26 X = 0, S; R' = Me, Ph; R2 = Ph, NH2; R3 = H, CN; R4 = alkyl
colour. The photochromic behaviour of spiropyran-type systems also continues to attract attention both in the patent53 and in the research literature. A 6-nitro group strongly enhances the intersystem crossing quantum yield, changing the singlet pathway for photocolouration of (27) via C-0 bond cleavage into a triplet pathway for (28). However, &'&isomerisation of the resulting openchain merocyanines (34)and (35) appears to be a singlet excited state process.54 Incorporation of cationic or anionic moieties in (29) and (30) has little effect on the photocolouration process but has a large influence, significantly greater than that arising from solvent polarity changes, on the reverse thermal ring closure process for the merocyanine form due to its ionic recombinant nature.55 The
I I h : Photoreactions of Compoundv Containing Heteroatoms other than Oxygen
235
photochromism of spirooxazines is pH-dependent. The addition of hydrochloric acid to alcoholic solutions of (31) gives rise to a new longer wavelength absorption band. Irradiation results in formation of the corresponding protonated openchain merocyanine form, which exhibits a hypsochromic shift of 75 nm compared to the non-protonated form.56Solutions of the isomeric spironaphthoxazines(31) and (32) become blue on exposure to UV light. At ambient temperature the colour disappears rapidly when irradiation ceases, due to rapid thermal reconversion of the merocyanine forms into the oxazines. In hexane at 183 K the coloured forms are long-lived. Exposure of that from naphthoE2,l-b]oxazine (31) to visible light rapidly converts it photochemically into the colourless oxazine. In contrast, that from the naphtho[1,2-b]oxazine (32) undergoes interconversion to another merocyanine isomer and the two open-chain forms are in thermal e q ~ i l i b r i u m . ~ ~ Pulsed laser irradiation of naphtho[2,l-b]oxazine (31) in the cavity of an NMR spectrometer at low temperatures permits one- and two-dimensional 'H and I3CNMR studies to be conducted. These confirm that two coloured merocyanines are formed and NOE experiments have been used to support structural assignment^.^' A comparative analysis of nitrosubstituted spirobenzopyrans, for example (28), suggests that the same trans isomer of the merocyanine is formed over a wide range of temperatures (77-300 K) whereas for related naphthoxazines, for example (31), the merocyanine formed is temperature dependent. The different behaviour is linked to the lower energy barriers to rotation around the carbonnitrogen double bond than around the carbon-carbon double bond.59Substituents at the lO'-position of naphthoxazines (33) have no significant influence on their absorption spectra. However, following irradiation, the fading rate constants for thermal reversion of the merocyanine isomers are considerably increased, probably as a consequence of unfavourable steric interaction between the 10-substituent and the N-methyl group in the open-chain merocyanine form.60 The spiropyrans (36), on irradiation at 365 nm, undergo pyran ring opening with formation of an isomeric coloured merocyanine.6' Half-lives of the order of 90 seconds have been found for the reversible light-driven coil to a-helical conformational changes in poly(L-glutamates) to which spiropyrans have been Me Me R2
Me 27 R1,R3,R4= H, OMe; R2 = H, OMe; X = CH 28 R',R3,R4 = H, OMe, allyl; R2 = NQ; X = CH 29 R' = = H; R2 = NO2; R4 = CH$lAlk&t, CH2fiCsH5Cr; X = CH 30 R' = R3 = H; R2 = NO2; R4 = CH2S03-Na+; X = CH 31 R1,R2= benzo; R3 = R4 = H; X = N 32 R' = R2 = H; R3,R4 = benzo; X = N 33 R1,R2= lU-substituted benzo; R3 = R4 = H; X = N
&R3
'
'N I Me 34 R',R3,R4 = H, OMe; R2 = H, OMe; X = CH 35 R1,R3,R4= H, OMe, allyl; R2=NQ; X = C H
236
Photochemistry
covalently attached.62 The influences of the nature and positions of substituents and heteroatoms on heterocyclo-annulated spirooxazines and 2H-chromenes in modulating their photochromic properties have been ~ u m m a r i s e d . ~ ~
36 X = 0,S; R = 6-OMe, 5,6-benzo
37
The P-vinyl-a-naphthol (37) is photochromic, presumably as a result of photoinduced enol-keto t aut om er i ~ r n.Fused ~ ~ benzothiophene derivatives (38) are photochromic on exposure to 366 nm radiation, and they bleach thermally. On prolonged irradiation, (39) is ultimately converted quantitatively into (42), probably by photocycloadditionhearrangement of the ring-opened form. Further examples of photochromism arising from interconversion of spirocyclohexadienone systems (40) to the ring-opened forms (43) have been reported. Thermal reversion is slow but may be accelerated by longer wavelength i r r a d i a t i ~ nThe .~~ related bis-spirocycles (41) undergo a related conversion into the corresponding bis-quinoneimines (44)with the reverse reaction occurring on irradiation with longer wavelengths.
R'
a
/
e
3
Ar R2
38 X
= 0;Y = S; R = Me, Ar = Ph, 4-MeOC6H4
Ph;
39 X = O ; Y = S ; R = A r = P h
I
(7-Y f Q-J
M
CMe3
40 X = CH, N; Y = NH, Nalkyl, 0; R',R2 = H, Me, Br; R3 = H; R4 = But; R3,R4= benzo
41
I
CMe3 I
?Me3
Ph
7-N R-N
Ph
/
YH
42 k2
v:e3 CMe3
44
IIi4: Photoreactions of Compounds Containing Heteroatoms other than Oxygen
231
The photochromism of a series of new b e n ~ o p y r a n sand ~ ~ ferrocenylnaphthop y r a d 8 has been reported. Factors contributing to the photodegradability of spiro[fluorene]benzopyrans have been i n~ es t i gated.The ~~ photochromism of dihydroindolizines has been kinetically modelled:' and emission spectroscopy and laser flash photolysis have been applied to a detailed study of the ringopening pro~ess.~'Isomerisation processes in styryl cyanine dyes have been investigated by absorption and emission ~ pect r os co py~~ and in merocyanine dyes by 'H-NMR spectroscopy and CS INDO CI calculation^.^^ Irradiation of the 2benzoxazolyl-3-phenylnorbornadiene(45) results in reversible formation of the corresponding benzoxazolyl-phenyl quadricyclane. Prolonged irradiation leads to (46),involving [2+2+2] photocyclisation followed by a [ 1,5]-hydrogen shift.74
45
46
Excited state intramolecular proton transfer is an integral part of the photocyclisatiodoxidation of the N,N-diphenyldiimine (47) to the acridine (49), whereas compounds (48) which lack a hydroxyl group are unreactive on prolonged i r r a d i a t i ~ n .Hydrogen ~~ bond directed arylenamide photocyclisation of (50) in benzene gives the trans-fused phenanthridone (51) with the requisite A/ B/C ring substitution pattern for subsequent elaboration to (+)-narciclosine. In methanol disruption of the intramolecular hydrogen bonding results in preferred cyclisation at the phenolic carbon.76 3-Chloro-N-(3-phenanthryl)thieno[2,3blthiophene-2-carboxamide (52) yields a single photodehydrochlorination product with cyclisation occurring exclusively at the 4-phenanthryl position.77 Photoisomerisation of E-2-[2-(2-chlorophenyl)vinyl]pyridinesforms the corresponding 2-stilbazoles which undergo subsequent photoinduced intramolecular quaternization to yield the azonia aromatics (53) incorporating a benzo[c]quinolizinium ring system.78 Photodehydrochlorination of the biaryl (54) occurs regioselectively, resulting in the displacement of chlorine by the pyridyl nitrogen. The regioselectivity of the process is much reduced for 2-(2-pyridylamino)-3chloroanthracene from which the products of competing displacement of chlorine by the pyridyl nitrogen and by the pyridyl 3-carbon are obtained.79 The Narylenamino esters (55) and lactams (56) photocyclise to a mixture of the corresponding cis- and trans-indolines, which are useful as intermediates in alkaloid synthesis.80 Photocyclisatioddehydrohalogenation occurs more efficiently for 2-halo-N-benzylpyridinium cations (57) than for 2-halo-N-(2-phenylethy1)pyridinium cations (58) (4 x 0.2 vs. 0.03-0.06, respectively), probably because of the preferred unfavourable staggered conformation of the two-carbon connector group in the latter.'' Photocyclisation of the quinone conjugate of
238
47 X = O H 48 X = H , O M e
Photochemistry
49
50
51
L-alanine (59) gives (60)via a biradical zwitterion that results from intramolecular trapping of an aminoquinone charge-transfer excited state.**
55 X = CN, Y = OEt 56 X,Y = CH2N-alkyl
57 n = 1; X = Br, CI 58 n = 2; X = Br, CI
59 X = L-alanyl
60
&-Hydrogenabstraction by 4-0x0-4-butanoyl amines affords the corresponding 6-lactams (61) with steric interactions in the intermediate 1,4-biradicals leading to high diastereosele~tivities.~~ The normally favoured y-hydrogen abstraction by a benzoyl group is blocked by the conformational rigidity of heterocyclic ketones (62). &Hydrogen abstraction occurs on irradiation and hydrogen bonding between the resulting hydroxyl group and the benzyloxycarbonyl functional group results in stereoselective 1,5-biradical cyclisation to yield the corresponding endo tricyclic alcohols.84 X-Ray structure analysis of the cis- and trans-8membered azalactones previously reported from irradiation of 2-(N,N-dibenzylamino)ethyl benzoylacetate has led to the suggestion that the stereochemical outcome is the result of ring-closure from a boat-chair conformation of the intermediate 1,8-biradi~al.~~ Photodeprotection of (63), which is of interest as a model phototriggered precursor to reactive mitosenes with potential antitumour activity, occurs on irradiation in aqueous acetonitrile. The ring-opened mitosene
IIl6: Photoreactions of Compounds Containing Heteroatoms other than Oxygen
239
(68) is obtained following subsequent cyclisation and aziridine ring-opening.86A
series of 4-benzyloxy-2-pyridones,whose benzyl groups are meta-substituted, has been found to crystallise in the chiral space group P212121. Optically active plactams are obtained via allowed disrotatory 4~-electrocyclisationby irradiation of single crystals of these compounds.87 Photolysis of the Barton esters from condensation of N-hydroxy-2-thiopyridonewith substituted 4-alkenoic acids gives, in the presence of 1,l -dichloro-2,2-difluoroethene, adduct radicals which yield mixtures of cyclised and noncyclised products. For example the Barton ester from 2-cyclohexenylaceticacid gives (64)-(67) in 14-25% yields.88
H
61
62 n = o , 1
63
-
P = 6-nitroveratryl, R CH20Me OR
I
64 R = S-2-P 65 R = CF2C6I2S-2-Py
66 R = S-2-P 67 R = CF2C61$3-2-Py
68
Further examples of cyclisations involving compounds containing an alkene or arene chromophores separated by an a l k y l a m i d ~ *or ~ *alkanoate” ~~ spacer from a secondary or tertiary amino group have been reported. Intramolecular electron transfer, followed by proton transfer from the nitrogen or a-carbon of the radical cation to the alkene/arene radical anion and subsequent carbon-nitrogen or carbon-carbon bond formation, leads to formation of medium-sized lactams or lactones in modest yields. For example, the 3-anilinopropylamide of transstilbene-2-carboxylic acid is converted regioselectively into the 1O-ring azalactam (69) (43% yield). Singlet excited state cyclisation of (N-trimethylsilylmethy1)aminoalkyl phthalimides (70)occurs efficiently in methanol. Desilylation of the a-silylamino radical cation formed by intramolecular SET, followed by biradical coupling, results in regioselective formation of the observed product (71).92The phototransformations of the N-phthaloylcysteine derivatives (72)-(75)may be rationalised in terms of Scheme 1. Singlet excited state decarboxylative elimination yields the corresponding N-vinylphthalimides (77)by thiolate elimination from the singlet biradical (76). Triplet biradical (78) cannot eliminate an ionic leaving group prior to intersystem crossing and hydrogen transfer occurs preferentially to give (79)which can be isolated in the case of (72). However, for (73)-(75) much faster secondary photolysis of (79) intervenes and thiazinoisoindoles (82)-(84)are formed respectively, and are accompanied by the y-hydrogen abstraction product (B)in the case of (79;R = X = H). Intramolecular electron
240
Photochemistry
transfer also occurs on excitation of (72)-(75) to give intramolecular radical ion pairs (RIPs). The singlet RIPs decay by preferential back electron transfer whereas triplet RIPs (80) undergo a-deprotonation and cyclisation to the corresponding thiazinoisoindole carboxylic acids (81)-93 The lowest singlet excited states of a series of biologically significant N-substituted 1&naphthalimides are mainly n,n* in nature whereas n,n* character tends to predominate for the corresponding 1,4,5,8-naphthaldiirnide~.~~ Time-resolved spectroscopy and conductivity have been applied to a detailed study of the intermediates involved
69
71
70 0
72 73 74 75
R=X=H, n=O R=X=H, n = l R=H, n = l , X=C02H R=Me, n=1, X = H
R
-PN2R --s
-COZ
1 I
'(A)*
-XCH2S-
0
isc
3(A)'
-2
0-
I
e-tr
t
0-
80
77
81
Scheme 1
X 82 R = X = H 83 R = H , X = C @ H 84 R=Me, X = H
1116: Photoreactions of Compounds Containing Heteroatoms other than Oxygen
24 1
in the cyclisation of terpenoid dicarbonitrile polyalkenes to the corresponding polycyclic products following electron transfer to a range of cyanoarenes. For example (85) yields (86). The role of solvent, the presence of water and the influence of biphenyl as cosensitiser have been investigated. A detailed reaction scheme is proposed and optimised reaction conditions for synthetic applications discussed.95 In methanol, electron transfer from the solvent to excited 1,4benzenedicarbonitrile (BDC) occurs to some extent and this is suppressed when methylated-BDCs are used. Some typical photoinduced electron transfer reactions in methanol proceed more efficiently when 2-methyl-BDC or 2,5-dimethylBDC are used instead of BDC.96A laser flash photolysis study of the cosensitisation ability of polyphenylenes such as biphenyl and terphenyls in the 9,lOdicyanoanthracene (DCA) sensitised cis-trans photoisomerisation of 1,2-bis(4methoxypheny1)cyclopropane has been reported.97
Cyclisation of (87) occurs on irradiation in the presence of triethylamine. The process involves SET, loss of iodide and attack by the resulting cr-enone radical on the acetylenic bond. The unprotected compound (88) does not cycli~e.~* Irradiation of N-(chloropyridy1)enaminones (89) and (90) in the presence of triethylamine yields the tetrahydrocarbazolones (91) and (92), with the regioselectivity being dependent on the solvent system used. Additionally the N-ethylenaminone (90) gives solvent incorporated products (93) or (94) in methanol or benzene re~pectively.~~
I X 87 X = C02CMe3 88 X = H
I
R 89 R = H 90 R = Et
I R 91 R = H , E t
92 R' = H, R2 = H, Et 93 R' = OMe, R2 = Et 94 R' = Ph, R2 = Et
2.3 Photoadditions - Although 1 5-crown-5 ethers of benzothiazolium styryl dyes carrying a sulfonated N-benzyl group undergo only E,Z-photoisomerisation in dilute solution, the addition of magnesium salts to the system results in the formation of dimeric complexes that undergo anti-head-to-head (HH) [2+2]photocycloaddition.'O0 E-4,4-Bis(dimethy1ammoniomethyl)stilbene undergoes 1:l inclusion in P-cyclodextrin but 2:l inclusion in y-cyclodextrin. In aqueous solution the former undergoes exclusive E- to Z-photoisomerisation whereas prolonged irradiation of the latter leads to complete [2+2]photodimerisa-
242
Photochemistry
tion.'" Syn-head-to-tail (HT), syn-HH and anti-HH [2+2]photodimers are obtained from cinnamic acids in alkyldimethylamine N-oxide aggregates in water. The ratios of the dimers are determined by the nature of the aggregation, which can be controlled by choice of surfactant, pH and additives.''* In a cast film of dimethyldioctadecylammonium bromide, highly selective formation of the syn-HH dimer occur^.''^ The [2+2] photocycloaddition of singlet 2-pyridone to methyl 2,4-hexadienoate occurs stereospecifically to yield all eight possible adducts. Irradiation of N-acetyl-2-azetine in acetone results in dimerisation with formation of approximately equal amounts of syn- (95) and anti-diazatricyclooctanes (diaza-3-ladderanes) (%).Io5 The exclusive formation of HH dimers (97) and (98) from benzophenone sensitisation of esters of urocanic acid can be explained on the basis of frontier orbital interactions. The observed stereochemistries may be rationalised on the basis of the relative heats of formation of all possible HH dimers, with the most stable dimer(s) being obtained.Io6 Direct irradiation of diethyl N,2,6-trimethyl-l,4-dihydropyridine-3,5-dicarboxylate yields a photodimer.Io7 In spite of the presence of bulky groups, 1,4-dihydropyridine (99) undergoes quantitative solid state photodimerisation, involving the carbomethoxy-substituted double bond, to give the centrosymmetric HT photodimer. H H AcN
NAc H H 95 synisomer 96 anti-isomer
Im' 'C aR 97 98 R = Me, Et; Im = 1H-imidazol-4-yl
qN02
m Dl
""cyJ
C02Me
Me
99 X = C H 100 X = +NHCi-
H
Me
101
In contrast crystalline (101), with less bulky substituents and with the relative orientation of double bonds practically identical to that in (W), is completely unreactive. For (99) there is a 'buffer zone' (i.e. a disordered packing region), which maintains the crystal structure in the monomer state but permits sufficient conformational change of the piperidine rings to occur to avoid steric hindrance as the reaction centres approach at the initiation of dimerisation. For (101), however, there is no such buffer zone available to permit the conformational changes and molecular movements necessary for dimerisation,"* in addition to the geometrical requirements previously identified by Schmidt.'Og The buffer zone concept has been used to rationalise the different photodimerisation behaviour of
I M : Photoreactions of Compound Containing Heteroatoms other than Oxygen
243
'
closely-related crystalline forms of thiazolyl analogue (100). l o Substitution of the primary hydroxyls of P-cyclodextrin with thymine groups, followed by photoirradiation at 280 nm, causes intramolecular [2+2] photodimerisation of the attached thymines and the catalytic efficiency of the modified cyclodextrin in hydrolyses of p - and rn-nitrophenyl acetates is increased. Further irrradiation at 240 nm results in photocleavage of the thymine dimers and the catalytic efficiency decreases to that of the unirradiated modified cyclodextrin. I ' 3,4,5,6-Tetrahydrophthalimidesderived from L-(+)-valinol and containing carbonate or silicon tethered alkenol or alkynol groups undergo efficient diastereoselective intramolecular [2+2]photocycloadditions;for example (102) is converted into a mixture of (103) and (104)."* Ph, ,Ph
103 R' = H, R2 = CHMe 104 R' = CHMe2, R2 = H
102
Diastereomer-differentiating intramolecular [2+2] photocycloaddition has been reported for the diastereomeric 2,6-dienones (105) and (106). Both direct and sensitised irradiation of (105) yields (107) whereas (108) is formed from (lM).'13 Reinvestigation, at -78 "C, of the photocycloadditions of 1-cyanonaphthalene (1 -CN) and 2-cyanonaphthalene (2-CN) with 1,3-~yclohexadienehas suggested that the primary major singlet-derived products are the corresponding exo[4+4]adducts, (109) and (110) respectively, and the syn-[2+2]adducts, (111) and (112) respectively. Consideration of primary and secondary orbital interactions has been used to interpret these observations."4
107
109 X = CN, Y = H. major from 1GN 110 X = H, Y = CN, minor from 2-CN
I C02CMe3 108
111 X = CN, Y = H, minor from 1 C N 112 X = H, Y = CN, major from 2 C N
244
Photochemistry
A [2+2] cycloadditiodretro-Mannich fragmentatiodMannich closure cascade, conceptualised in Scheme 2, has been applied to the vinylogous amide (113) as a key step in the synthesis of the pentacyclic ring system found in the antileukaemia marine alkaloid manzamine A. l 5
'
Scheme 2
Allyltrimethylsilanes react with triplet excited 2,3-dicyano-5,6-dimethylpyrazine to give diazatricyclooctenes (119, possibly via intermediate (114) formed from ring-opening of an initially-formed [2+2]adduct. l6 Intramolecular [2+2]cycloaddition yields the pentacyclic compound (116) on irradiation of the corresponding tethered enantiopure bis-2,3-dihydro-4-pyridone. l 7 Addition of ethylene to the corresponding a$-unsaturated-y-lactams in acetone yields (117) and (118) as the major photoproducts."* Direct irradiation of N-acyl- 1H-pyrrol-2(5H)-ones (119) results predominantly in cleavage of the exocyclic nitrogen-carbon bond and disproportionation to the
'
Mexly Me
SiMe3
CN
Mee
S
CN 114
i
M
e
3
115
H 116
117 R' = C&CMe3, R2 = CH20TBS 118 R' ,R2 = CMe20CH2
IIl6: Photoreactions of Compounh Containing Heteroatorns other than Oxygen
245
parent lactam (120). Sensitised irradiation in acetone gives low yields of the HH and HT cis-transoid-cis [2+2]dimers, accompanied by substantial amounts of hydrogen abstraction products. In contrast, in hexadeuterioacetone the pyrrolones (119) are cleanly converted into 1:l mixtures of the dimers, since hydrogen abstraction in this solvent is significantly less competitive due to the much lower rates of deuterium atom abstraction from the deuterated ~olvent."~ 3,9-Diazatetraasteranes (121) are obtained in almost quantitative yield from the corresponding 1,4-dihydropyridines by consecutive [2+2]photocycloadditions in the solid state.12' Photosensitisation effects on the photocycloreversion of stilbazolium,121 1,3-dimethylthymine and 1,3-dimethyl~racil'~~ [2+2]cyclodimers have been reported. Steric hindrance, due to the gem-dimethyl and carbamate groups in the enone and alkyl groups in the alkene, is suggested to account for the main products (123) and (124) from direct irradiation of enone (122) in the presence of excess 2,3-dimethyl-2-butene. This directs reaction to the enone oxygen and acarbon atoms, and subsequent ring closures and an intramolecular 1,2-acyl shift account for the products formed.123
Me
I
R 119 R = COMe, COCH2Me, COCHM%, COCMe3 120 R = H
123
121 Ar = 4-MeOCeH4, R' = H, Me, CH2Ph, R2 = C02Me, CQEt
124
Irradiation of imides (125)-(129) in solution gives oxetanes (130) in high yield. In the crystalline state the outcome is controlled by the conformations adopted about the imide unit in the crystal lattice. Compound (125) crystallises in a chiral space group and forms the oxetane in high enantiomeric excess. In addition to solid state oxetane formation, (126) and (127) also yield (131) and (132)
246
Photochemistry
respectively. Azetidinone (131) is obtained by a sequence involving or-cleavage, 1$migration of the benzoyl radical and ring closure, whereas formation of (132) involves hydrogen abstraction from the N-benzyl group by the alkenyl terminal carbon and cyclisation of the resulting 1,4-biradical. Crystalline (128) and (129) do not cyclise. 124 Irradiation of pyrazinopsoralen in dichloromethane in the presence of either dimethyl maleate or dimethyl fumarate gives the same major cis-endo [2+2] adduct (133), involving a common 1,Cbiradical intermediate, from reaction at the furan double bond. Dimethyl ethylidenemalonate similarly gives Irradiation of chiral N-(a-phenylethy1)aldimines in photoadduct (134).'21 methanol in the presence of titanium(1V) chloride gives 1,2-aminoalcohols (135) with moderate diastereoselectivities. 26
125 126 127 128 129
R1 = Me; R2 = CHMe2, CH2Ph R1 = H; R2 = CHMe2 R' = H; R2 = CH2Ph A' = Me; R2= Ph R' = H; R2 = Ph
130
131 R' = Me, R2 = CH2COPh, R3,R4 = 0, R5 = CHMe 132 R' = R2 = Me, R3 = Ph, R4 = H, R5 = COCOPh
133 134
Acridine and R-(-)-2-phenylpropionic acid associate in a 3:2 ratio respectively to form a chiral crystalline bimolecular material. Irradiation of the crystals leads to electron and proton transfer followed by decarboxylation to produce the hydroacridine and a-phenylethyl radicals. With their relative orientations controlled by the crystal lattice, coupling yields a mixture of three chiral products. 127 Acridine also co-crystallises with phenothiazine to give a yellow solid (3:4 ratio) and a red solid (1:1 ratio). Irradiation of the yellow solid yields the coupled product 9-(N-phenothiazinyl)acridine,following electron and proton transfer, coupling and dehydrogenation. In contrast the red solid is photoinert, apparently due to inhibition of radical coupling by the rigidity of molecular packing in the crystal lattice.'28 The bis-anthracenes (136)-(138) exhibit low photoreactivity towards intramolecular [4+4]cycloaddition, due to intramolecular SET from the amino groups to the excited anthracene and to poor flexibility of the chains linking the ch r o moph~ r es . '~ Irradiation ~ of the bisanthracenyl azacrown ether (139) converts it reversibly into the intramolecular cycloadduct, a cryptand. The efficiency of the photoreaction and the rate of the thermal reverse reaction are
IIf6: Photoreactionsof Compounds Containing Heteroutoms other than Oxygen
247
strongly affected by the presence of cationic substrate^.'^^ 2,4-Dichloro-l,3diazaanthracene and 2,4-dimethoxy-l,3-diazaanthracene yield the anti-€-IT dimers, (140) and (141) respectively, and the corresponding anti-HH dimers on irradiation in benzene. In the solid state only the anti-HT dimers are formed. In the presence of 1,3-~yclopentadiene,irradiation yields single [4+4]cycloadducts (142) and (143) respectively.'3'
3
R
-X
\ /
140 R = C I 141 R=OMe
AN
136 X = (CH2NHCH2)z 137 X = CH*N(CH2Ph)CH2 138 X = CH2NMeCH2
139 X
coAo7
-O(CH&-N ~o
oJcHz)20-
\
N=( 142 R - C I 143 R=OMe
U
Contrary to previous reports, acridizinium bromide yields all four isomeric [4+4]photodimerisation products both in solution and in the solid state.I3* 2-Cyano-6,6-dimethyl-2-cyclohexenone undergoes photoaddition to 2,3-dimethyl2-butene to give tricyclic[c,d]fused isoxazole (146) in 92% yield, possibly involving the triplet biradical (144) and the nitrene (145). With 2-methyt-2-butene and 2methylpropene, isoxazoles (147) and (148) respectively are formed, though products from competitive formation of triplet biradical (149) are also found.'33 The crystalline 1:2 adducts of 1,2,4,Stetracyanobenzenewith benzyl cyanide yield the coupling product (150) on irradiation: this involves electron and proton transfer, radical coupling and tautomerisation steps. In solution (150) is not formed. 134
'aNLn
144 R 1 = R 2 = M e
Me
Me Me 149 R = M e , H
146 R1 = R2 = Me 147 R1 = H, R2 = Me 148 R ' = R ~ = H
145
N
C
NC
'
C
CN 150
L
L
248
Photochemistry
Single stranded aminoethylglycine dimers carrying a thymine and a 4-thiothymine unit differ in their photobehaviour depending on the separation between the bases and which is at the C-terminal end.I3' A DNA-photocleaving amino acid derivative, methyl 64N- 1,8-naphthalimid0)-2-aminohexanoate, induces GG specific cleavage via SET from electron rich GG sites, with the most readily oxidisable in B-DNA being the 5'-G sites. A "guanine-guanine stacking rule" has been proposed for prediction of the most electron-donating sites in B-DNA.'36 The 193 nm photodecomposition of four aliphatic dipeptides containing valine and methionine has been reported. 37 In frozen benzene containing trifluoroacetic acid, the cyclobutene (151) is formed by ortho-cycloaddition of 6-chloro-1,3dimethyluracil (CDU) to benzene followed by elimination of hydrogen chloride. Further irradiation converts (151) consecutively into (152) and (153). Addition of hydrogen chloride to (153) yields (154). Subsequent intramolecular [2+2] photocycloaddition converts (154) into the major chlorine-containing product from CDU under these conditions. 13'
151
152
153
154
Carbonyl ylides (155), generated photochemically from the corresponding a$unsaturated, y,&epoxy dinitriles, undergo regioselective 1,3-dipolar cycloaddition with ethyl vinyl ether, leading predominantly to the em-adduct. The very low reactivity of seven-membered ring ylides (155) is rationalised by AM 1 calculations which show the ylide reactivity to depend on the LUMO energy and on the c,-c& separation.139 CN
155
156
Although direct irradiation of aziridines generates the corresponding azomethine ylides which react stereospecifically with reactive dipolorophiles, photoinduced SET generates the corresponding radical cations that undergo isomerisation with consequent loss of stereospecificity in the cycloaddition. 140 Photolysis of 2H-arylazirines with 248 nm laser light yields substituted benzonitrile ylides by heterolytic cleavage of the azirine carbon-carbon bond. In alcohols the nitrile ylides are protonated to yield azaallenium cations (156): the kinetic isotope effect is consistent with a linear O..H..C arrangement in the transition state for protonation. 14' Attempted alkylation of a,&unsaturated ketones by radicals generated from tetraalkylstannanes by photoinduced SET was unsuccessful due to the endothermicity of SET from stannanes to enone triplets. However, the inclusion of an additive (tetramethyl pyromellitate) with a
IIl6: Photoreactionsof Compounds Containing Heteroatoms other than Oxygen
249
sufficiently low triplet energy to be sensitised by energy transfer from the enone, and which would be a stronger oxidant (Erd = -1.31 V) than the enone (Ered M 2.0 V), facilitates the alkylation. For example irradiation of 2-cyclohexenone and tetrabutylstannane in acetonitrile in the presence of tetramethyl pyromellitate gives 3-butylcyclohexanone in 62% yield. 142 Rearrangements - The photochromism of N-salicylideneanilines involves excited state intramolecular proton transfer (ESIPT) within the hydroxyimino isomer (157) to form the keto-amine tautomer (158). The involvement of shortlived intermediates in solution has been investigated for N,N-bis(2-hydroxy-1naphthy1idene)-l,4-phenylenediamine'43and for N-salicylidene-(4-N,N-dimethylamino)aniline,IM as have aspects of the solid state photochromism of N~alicylideneaniline'~~ and N-sali~ylidene-(2-methyl-5-chloro)aniline.'~ESIPT processes have also been studied for o-hydroxy derivatives of 2,5-diaryloxazoles,'41 2,4-dimethoxy-6-(1-hydroxy-2-naphthyl)-s-triazine,14* and 2-(2'-aminophenyl)ben~imidazole.'~~ Semiempirical PM3 calculations have been applied to a study of the mechanisms of light-induced transformations in salicylideneanilines. The So,S1 and TI potential energy hypersurfaces were explored and the structwreenergy scheme compared with the experimental findings."' Photophysical studies in aqueous solution over a wide pH range have been used to determine the acidbase properties of 1-(purin-6-yl)-3-methylimidazoliumch10ride.l~' 2.4
The ethenoanthracene (159) undergoes singlet excited state rearrangement to 5,12-bis(aminomethyl)di~nzo{a,e]cycloocteneon direct irradiation in solution whereas, on triplet excitation by xanthone, the dihydrochloride (160) forms the corresponding dibenzosemibullvalene via a Zimmerman (di-n-methane) rearrangement. In contrast crystalline (159) results in solid-state intramolecular elimination of ammonia to form dihydropyrrole (161), which is oxidised to the corresponding pyrrole on work-up. 52 Two quinoxalinobarrelenes have also been reported to undergo the Zimmerman rearrangement.'53 The first examples of the 2-am-di-lr-methane photorearrangement have been reported. Triplet excited 2aza-l,4-pentadiene (162) is converted into the cyclopropylimine (168) and the vinylaziridine (169) via cleavage of bridged biradical (165). SET sensitisation by 9,lO-DCA yields the alkene-localised cation radical (163). Carbon-nitrogen bridging to give the cation radical (166), followed by C-C bond cleavage, back electron transfer from DCA-' and ring closure leads to (169). A competing route involving phenyl migration leads, via the radical cation (164), to a different CyclopropyIimine (167). 2-Amino-3-cyano-4H-pyrans undergo photochemical ring contraction to cyclobutenes, possibly via intramolecular SET, 2,5-bridging and ring-opening. 55 4Hyroxybenzonitrileis converted in deoxygenated water, methanol or ethanol into
'
Photochemistry
250 R
159 R = NH2 160 R = +NH3C r 161 R,R=NH
162 hv
1
163
I
DirectorSens
y&
Ph
Ph
164
Bridging
Ph
I
‘
BET/cyclisation
H
P h A P h
Ph
PhF
Ph b
p
h
Ph 167
165
i “a”cleavage ii cyclisation
Ph
Ph 168
169
4-hydroxybenzoisonitrile in high chemical yield by a two-photon process involving a strongly absorbing intermediate, which is probably the azirine (170).’56 Oxadiaziridine (174) is formed from the bisdiazene oxide (171). The mixture of dioxides (172) and (173) isomerises into (175) and subsequently into the corresponding bisoxadiaziridine. 57 Photolysis of 4H-imidazole 3-oxides and 1,3dioxides yields the corresponding 6-oxa- 1,4-diazabicycl0[3.1 .O]hex-3-enes and their 4-oxides, respectively, Further photolysis of the 4-oxides results in isomerisation of the second N-oxide group, yielding mixtures of the cis- and trans-3,7dioxa- 1,4-diazatricyclo[4.1.O.O**?heptanes. 58 5-Nitroquinoxaline derivatives (176) isomerise in aqueous ethanol to the corresponding nitrites (177) respectively. 59 N-Substituted aroyl-a-dehydrophenylalanines(178) give 1-azetine derivatives (179) via an excited state 1,3-aroyl shift, reduction and cyclisatiod dehydration sequence.160 Reinvestigation of the photochemistries of N-acetyl and N-benzoyl carbazoles has confirmed that only the photo-Fries rearrangement products (carbazole and
’
’
’
IIl4: Photoreactions of Compounds Containing Heteroatoms other than Oxygen
170
171 n - 0 , m - 0 172 n = 1 , m=O 173 n = 0 , m = l
174 n = O 175 n = l
25 1
176 R1,R2= H, Me; Y = N, hMe; X = NO2 177 R1,# = H, Me; Y = N, h e ; X = ON0
NHCOAr
RCH+ CONHBu CONHBu 178 179 R 4cIc&4, Ar Ph, 4-M8CgH4,2-, 3- OT 4-CICeH4,4-F&C6H4
the 1- and 3-acyl carbazoles) are observed in non-halocarbon solvents. In contrast N-benzoyl carbazole in dichloromethane, chloroform or carbon tetrachloride yields only 3-chloro-N-benzoyl carbazole by an SET process, whereas for Nacetyl carbazole the two processes compete in these solvents.16' Isonitriles have been confirmed as important intermediates in the P4 permutation pathway for phototransposition of pyrazoles. For example, 1-methyl-4-phenylpyrazole(180) yields imidazole (188), mainly via the intermediacy of isonitriles (187), with isomeric nitriles (186) also formed as primary products. Initial N-N bond fragmentation yields the g-iminovinyl nitrene (la), possibly via the iminoazirine (183) and the nitrile ylide (184). 1-Methyl-5-phenylpyrazole (181), in addition to the P4 pathway transformation to give 1-methyl-5-phenylimidazoleand formation of analogous nitriles and isonitriles, undergoes Ps and P7 permutation transpositions to 1-methyl-2-phenylimidazoleand 1-methy14phenylimidazole respectively. These pathways have been proposed to involve initial electrocyclic closure to 175-diazabicyclopentene(185) and this intermediate can be trapped as the Diels-Alder adduct when 1-methyl-5-phenylpyrazole (181) is irradiated in furan.16* Photolysis of N-methanesulfonyloxy-4-aza-5a-cholestan-3-onegives derivatives of 4-azacholestan-3-one, 4-aza-A-nor-B-homocholestan-3-one, 3-azaA-norcholestane and bis(3-aza-A-norcholestan-3-yl)urea.The corresponding 5a derivative gives the 5fl (coprostane) analogues. A mechanism involving N-0 bond homolysis and SET to form an N-acylnitrenium ion, from which product formation originates, has been ~uggested.'~~ 2.5 Other Processes - The benzophenone sensitised reaction of the N,O-diacyl N-phenylhydroxylamine(189) in hexadecyltrimethylammonium chloride micelles yields benzoyloxy-migrated products (190) and (191) derived from amidylbenzoyloxyl radical pairs located at the micellar surface, whereas amidyl-phenyl radical pairs that penetrate more deeply into the micelle are responsible for phenyl-migrated products (192) and (193). Irradiation of ethanolic solutions of N-aryl-N-nitrosohydroxylamineammonium salts produces azoxy compounds.
Photochemistry
252
h
R2b
z i z
N
Me 180 R' = Ph, R2 = H 181 R' = H, R2 = Ph
I
R' =H, R 2 - Ph
P h q N
d
Me 185
186
187
188
Bifunctional systems form heterocyclic rings; for example (194) yields (195).'65 Photolysis of N-(triphenylmethy1)aniline.sresults exclusively in C-N bond homolysis to give the trityl (+ = 0.6-0.8) and anilino radicals.'66 Reduction of the N-0 bond cleaved intermediate (1%) (formed on irradiation of 5-amino or 5-phenyl1,2,4-0xadiazoles) by sodium hydrogen sulfide, thiols or thioamides yields the corresponding benzamidines (197). In contrast, in the presence of nucleophilic thioureas (199) or thiocarbamates (200), N-S bond formation occurs and subsequent elimination from the possible intermediate (201) yields the thiadiazoles (1%) or (202) respective~y.'~~ The scope of the photochemical nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reaction has been extended to include cyanide, 0
bR2 FyJ-JJF
II 1-NP-C-~R'
R3
X-(l-
N+
0 196 X = NH2, Ph
-
Ph
XCONH?,
/
NH 197
v'
198
201
202
IIl6: Photoreactions of Compounch Containing Heteroatoms other than Oxygen
253
fluoride or acetonitrile as the nucleophile in reactions involving displacement of a cyano group from 1,Idicyanobenzene (DCB). Thus irradiation of 1,4-DCB and 2-methylpropene in acetonitrile results in SET to yield the corresponding radical ion pair. Addition of acetonitrile to the radical cation of 2-methylpropeneyields a distonic radical cation that couples with the I,4-DCB radical anion to yield the zwitterion (203). Subsequent reactions lead to the observed product, 7-cyano1,4,4-trimethy1-2-benazine(204).
203
204
With cyanide as the nucleophile, 1,4-DCB yields 4-cyanophenylsubstituted cyanoalkanes from a variety of alkenes and dienes. Highest yields are obtained when the alkene or diene has an oxidation potential c 1.5 V vs. SCE. Both nitriles and isonitriles are obtained from the alkenes studied whereas only nitriles were detected from conjugated d i e n e ~ . With ' ~ ~ fluoride ion, 4-cyanophenylsubstituted A uoroalkanes were obtained from alkenes but not from conjugated d i e n e ~ . ' ~ ~ ~ ' ~ For both fluoride and cyanide, the anion adds preferentially to the less alkylsubstituted end of an unsymmetrical radical cation to yield the more heavily alkyl-substituted p-fluoro-, P-cyano- or P-isocyano alkyl radical. The addition is kinetically controlled and the regiochemistry of addition is determined before the relative stabilities of the resulting radicals become important.' The photoinduced SET reaction of tncyclo[4.3.1 .O1*7deca-2,4dienewith 1,I-DCB/phenanthrene in acetonitrile/methanol yields the photo-NOCAS trans-products (205) and (206), involving regiospecific capture of the diene radical cation by methanol at the 2-position and subsequent aromatic substitution at the @so-carbonof the DCB radical anion. Relief of cyclopropane ring strain in the radical cation by attack of methanol at a cyclopropyl carbon does not occur. It does, however, occur at C-2 where both SOMO and LUMO orbital coefficients are significant.17' Irradiation of 1,l-diphenyl-1,Bheptadiene in wet acetonitrile, butyronitrile or benzonitrile in the presence of I,4-DCB yields the photo-Ritter products (208) with high cisstereoselectivity. SET to 1,6DCB yields the corresponding radical cation which cyclises through a chair-like transition state (207) in which the developing distonic cationic centre is attacked by the nitrile group from the equatorial direction leading to (208). 17*
P h 2 C H - a \
Y = OMe X = OMe
207 R = Me, Et, Pr, Ph
208
NHCOR
254
Photochemistry
Photoinduced SET from triethylamine to the phenylacetonitrile derivatives
(B) gives the corresponding radical anions which eliminate cyanide ion. The resulting benzylic radicals react further to yield a-(benzylated)triethylamine, bibenzyl and toluene derivative^.'^^
Strong hydrogen bonding between the 5-bromourad carbonyl and a complementary base in a duplex oligonucleotide is an important factor in a highly efficient sequence-dependent photodebromination process involving intramolecular SET from an adjacent 5'-adenine via a fluorescent exciplex. Subsequent loss of bromide ion and hydrogen abstraction by the uracil-5-yl radical centre occur. 74 SET debromination also occurs on irradiation of 2-bromo-1-phenylethylidenemalonic ester in the presence of N-benzyl-1,4-dihydronicotinamide (BNAH). Comparable amounts of three products are produced from the resulting radical (210); these are a dimer, an ct,P-unsaturated diester resulting from hydrogen abstraction from BNAH, and a B,y-unsaturated diester resulting from SET from BNAH to (210) with subsequent protonation of the stabilised carbanion. The presence of MgZCcomplexation of (210) facilitates the second SET step and the P,y-unsaturated diester is the sole product.'7' Encounter complexes between photoexcited 1-cyanonaphthalene and norbornadiene lead to products of several structural types. In polar solvents containing methanol, adducts are formed from em-attack by methanol on the norbornadiene radical cation. In less polar solvents l-cyanonaphthalene and norbornadiene form [2+2]adducts,exclusively on the norbornadiene em-face. In non-polar solvents an endo-encounter complex between 1-cyanonaphthaleneand norbornadiene is attacked by methanol from the em-face to yield 1:l:l adducts.176SET to 1,4-DCB from readily accessible tertiary aminocyclopropanes yields cation radicals which undergo facile ring opening. A subsequent 1$hydrogen shift and hydrolytic workup provides ring-opened ketones; for example E- or 24211) yields (212) in 85% yield.177
211
212
The cation radical of the electron-rich pinacol (213) generates p-dimethylaminoacetophenone (215) and the relatively strongly reducing ketyl radical (217). Analogously, the electron-deficient pinacol (214) undergoes fragmentation on one-electron reduction to generate (216) and the moderately strongly oxidising ketyl radical (218). Irradiation of (213) in a 1:1 mixture with (214) in acetonitrile solution leads to stoichiometric fragmentation of both pinacols by an SET-
ZZl6: Photoreactions of Compounh Containing Heteroatoms other than Oxygen
255
induced radical chain process with a quantum yield of 9.0. The key chain-carrying steps are reactions involving oxidation of the pinacol (213) by the radical (218) and reduction of the pinacol(214) by the radical (217). Analogous processes may provide a general method of producing highly efficient photoreactions initiated by electron-transfer quenching of excited states. The 2-morpholinocyclopropanols (219) and (220), on irradiation in aerated solution with triphenylpyrilium perchlorate or 9,10-DCA, are converted by a chain process into the c1- and pmorpholinoenones (221) and (222) respectively; the regioselectivity of radical cation ring opening is determined by the positions of the phenyl groups. Capture by molecular oxygen yields a proxy species, (223) from (220), and subsequent back electron transfer from the reduced sensitiser, proton transfer and elimination of hydrogen peroxide yield the final product.179o-Quinone methides are generated efficiently by photolysis of phenolic Mannich bases in aqueous acetonitrile at neutral pH. 4-Phenyl-2-(N,N-dimethylaminomethyl)phenol,for example, yields 4-phenyl-6-methylene-2,4-cyclohexadienone, trappable as the Diels-Alder adduct (71%) with ethyl vinyl ether.'"
215
MqNC6H4CMeOH 217
Me-kC5H4~MeOH 218
0
219 R' = H, R2 = Ph, NR2 = morpholino 220 R'sPh, R2=H, NR2= morpholino
210
Ph
R' 221 R1 H, R3 = morpholino 222 R1 = morpholino, R3 = H =I
HO&Ph
Ph 00 223 N& = morpholino
Photolysis of 3-phenyl-5(4H)-isoxazolone yields 2,5-diphenylpyrazine in 67% yield.'" Singlet excited isoxazol-S-one (224) undergoes both decarbonylation and decarboxylation to carbene intermediates, both of which are captured by alcohol or amine solvents. With triplet sensitisers an oxaziridine intermediate reacts with the solvent. N-Acylisoxazol-5-ones decarboxylate to yield singlet carbenes (225) which cyclise at the acyl oxygen to yield the isoxazoles (227),lS3and the isothiazoles (228) are obtained via thioacyl carbenes (226) from N-thioacylisazol5-0nes."~ The isolation of (229) as the main product from irradiation of benzophenone/N,N-dimethylanilinein the presence of the non-polymerising
Photochemistry
256
224
225 X = O 226 X = S
227 x = o 228 X = S
229
substrate 1,l -di(p-toly1)ethyleneconfirms the (N-methylani1ino)methyl radical as the main initiating species in Type I1 photoinitiating systems. Similar conclusions were reached for systems involving N,N-dimethylaniline with dimethyl or diethyl benzoylphosphonate, benzil or thioxanthone.'85 The azoperester, t-butyl 4-methyl-4-(t-butylazo)peroxypentanoate, cleaves at the azo group on excitation to yield the y-perester radical (231). Cyclisation of (231) by attack on the peroxy linkage to yield the corresponding y-lactone occurs sufficiently slowly (1.5 x lo4 s-' at 22 "C) that the azoperester precursor may be used as a photochemical bifunctional initiator. In contrast thermolysis occurs at the peroxy linkage. Decarboxylation and cyclisation of y-azo radical (230) occur so rapidly that an azo-containing polymer would not be produced.'86 Diarylfuroxans (232) yield 1 ,Zdiarylacetylenes in low yield on i r r a d i a t i ~ n . ' ~ ~ An experimental and theoretical investigation of the solvent-induced quenching of n,n* singlet excited azoalkanes supports a hydrogen abstraction mechanism in which a transition state is followed by a conical intersection. The mechanism should be general for n,x* singlet excited chromophores.'88 The triplet n,n* excited states of azoalkanes (236) react with primary, secondary and tertiary aliphatic amines to give high chemical yields of the corresponding hydrazines. A mechanism involving hydrogen atom transfer from the amine a-carbon within an azoalkane-amine exciplex is proposed.'89 Facile photoreduction of (236) also
230
233 R' = C02Me, R2 = H,Ar
231
*
232
1
234
R 236 R = H , M e
235 MeCN
R'
eR i2*
-N Me'
237
W6: Photoreactions of Compounris Containing Heteroutoms other than Oxygen
257
occurs in the presence of other hydrogen donors which include 2-propanol, benzhydrol, 1,4-~yclohexadiene, tributylstannane and tris(trimethylsily1)silane. In contrast to photoreduction by amines, charge transfer does not appear to be involved with these donors and a dependence of the rate for hydrogen abstraction on the donor bond dissociation energies is found.lgOA theoretical study of the photolysis of 2,3-diazabicyclo[2.2.l]hept-2-ene has been carried out using a 631G* basis set. The S1 (n,a*), TI (n,n*) and T2 (x,n*)pathways for deazetization via a-carbon-nitrogen bond cleavage and rearrangement to the azirane 1,2diazabicyclo[4.1.O]hept-2-ene via P-carbon-carbon bond cleavage have been investigatd.I9' 2,4,6-Triphenylpyrilium perchlorate sensitisation of 3,3-dimethyl3H-pyrazoles (233) in acetonitrile yields the cyclopropenes (234) via SET, loss of nitrogen and cyclisation steps. The accompanying 2H-pyrroles (237) are secondary products and involve SET from (234) to TPP. Ring opening to radical cation (235), trapping by acetonitrile and cyclisation results in formation of (237). 192
Methyl 3-cyano-2-diazo-6-oxo-2,6-dihydroazulene1-carboxylate gives high yields of azulenic crown ether derivatives (241) when irradiated in tetrahydrofuran. The initially formed carbene is highly polar, with electrophilic and nucleophilic centres as shown in (238). Reaction with THF involves intermediates such as (239) on the pathway to products (241). The corresponding diester gives cyclic oligomers in very low yield because of the much greater steric interactions in intermediates such as (240).193 The corresponding 2-diazo-4-0x0 precursors form analogous polyether bridged derivatives in high yield when irradiated in THF, tetrahydropyran or 1,4-dioxan.'94
CN
238
239 X = C N 240 X = C02Me
Irradiation into the charge transfer band of the intermolecular complexes of arenes with aryldiazonium salts in anhydrous acetonitrile gives good yields of the corresponding biaryls. For example pentafluorobenzenediazonium tetrafluoroborate and p-xylene give 1,4dimethyl-2-(pentafluoropheny1)benzenein 62% yield. SET to the diazonium cation, followed by loss of nitrogen from the transient diazenyl radical, yields an aryl radical that propagates reaction via a radical chain mechanism. Photolysis of 1-(2-azidophenyl)-3,5-dimethylpyrazole above 200 K gives pyrazolobenzotriazole (248)by electrophiliccyclisation of the singlet nitrene (242). In the presence of diethylamine, a diethylaminoazepineis formed, possibly involving prior ring enlargement of the singlet nitrene to a didehydroazepine (243); however, this intermediate, if formed, has no inherent stability and is
258
Photochemistry
in equilibrium with the singlet nitrene. Below 100 K, only azobenzene formation and intramolecular cyclisation onto the pyrazole 5-methyl group, reactions of the triplet nitrene, are observed. 1962-Fluorophenylazidessuch as (M), on irradiation in cyclohexane containing diethylamine, yield %-(diethylamino)-3-fluoro-3Hazepines via the intermediacy of a didehydroazepine such as (244) by ring closure of the singlet nitrene on the side away from the 2-fluorine substituent, which imposes a barrier to cyclisation in the alternative direction to didehydroazepine (245). 2,6-Difluorophenylazides such as (247) yield nitrenes in which there is an even higher barrier to ring expansion and N,N-diethyl-2,6-difluorophenyl hydrazines are formed by singlet aryl nitrene insertion into the N-H bond ofdiethylamine. In the absence of 2- and 6-fluoro substituents both modes of cyclisation occur and products from both of the isomeric didehydroazepines are obtained. 197
243 R = 2,5diMepyrazolyl, X = H 244 R = H , X - F 245 R = F , X = H
242
246 R = H 247 R = F
248
Irradiation of the N-(2-cyclopropenylcarbonyloxy)phthalimide (249) in the presence of N-phenylcarbazole and a radical donor such as tributylstannane results in smooth decarboxylation to yield N-(2-~yclopropenyl)phthalimide (250) in high yield. In contrast the N-(cyclopropylcarbony1oxy)phthalimide (251) underwent complete decarboxylation to the corresponding cyclopropane (252).19’ Irradiation of the diazide (253) in methanol provides access to the new isoxazolo[4,5-d]- and -[4,5-e]-diazepinesystems, (254) and (255) re~pective1y.l~~ Photolysis of N-(methylphenylamino)-2,4,6-trimethylpyrid~nium tetrafluoroborate yields the singlet N-methyl-N-phenylnitreniumion which reacts with methanol and tetra-
251 R = COONPhth 252 R e H
249 n = 1 250 n = O
N ‘0
’
253
NH N3
254
MeO
255
1116: Photoreactionsof Compounctr Contuining Heteroatoms other than Oxygen
259
butylammonium chloride to give N-methyl-p-anisidine and 4- (and 2-) chloro-Nmethylaniline. A hydride shift from the N-methyl group to the nitrogen followed by hydrolysis of the resulting iminium ion yields aniline as a product. Another product, N-methylaniline, is believed to be formed, at least in part, by hydrogen abstractions of the triplet nitrenium ion.200 Pregnan-20-01 derived radicals (256) and (257) are formed by intramolecular hydrogen abstraction by alkoxy radicals generated by photolysis of the corresponding 1 la-nitrites. Radical (256), substituted at C-20 by a phenyl group, yields the benzo-fused derivative (258) as major product. In contrast the 4-methoxy substituent on the aromatic ring in (257) reduces its electrophiiicity and therefore the tendency of the nucleophilic C-18 radical centre to attack it. The alternative pathway, involving y-hydrogen abstraction from the 2 1-methyl group and trapping of the resulting C-21 radical, gives the nitroso intermediate (259). Air oxidation and elimination of water during workup yield the 20-nitromethylene derivative as the major product.20'
11
--OH
21
256 Ar=Ph 257 Ar = 4-MeOC,3H4
The photoreactions
(L >435 nm in dichloromethane) of tetranitromethane
(261) with styrenes (260) to yield nitro-trinitromethyl adducts (269), diastereomeric oxazolidines nitro ketones (271) and nitronic esters (272) may be
(no),
rationalised in terms of the interlinked pathways in Scheme 3. SET yields nitrogen dioxide (262), the styrene radical cation (263) and the trinitromethanide ion (264). Addition of nitrogen dioxide (262) to the styrene (260)initiates a radical chain process. Benzylic radical (266) is oxidised by tetranitromethane (261) to the benzylic cation (265). Nitro-trinitromethyl adducts (269) result from coupling of the cation (265) with the anion (264). A competing pathway involves reaction of radical cation (263) with anion (264).Cyclisation of the resulting radical (268) yields the aminoxyl(267), from which loss of nitrogen dioxide yields the nitronic ester (272), whereas coupling of (26'7) with the radical (266) forms oxazolidine diastereomers (270). The nitroketones (271) may arise, at least in part, from secondary photolysis of the oxazolidines (270).202-204 The main products from irradiation (A >435 nm) into the 1,4-dimethoxybenzendtetranitromethane charge-transfer band in dichloromethane are 2-nitro-l,4dimethoxybenzene, 2-trinitromethyl-1,4-dimethoxybenzene and the naphthalenone (273). Smaller amounts of labile adducts are also formed.2o5Similar irradiation with benzofuran gives adducts arising from initial attack by trinitromethanide anion at C-2, C-3 or C-4 of the benzofuran radical cation.
Photochemistry
260 ArCR’=CHR2 + C(NQ)4 260 Ar = Ph, 4-MeoCsH4,
hv
+ -C(N02)3
NQ + [AtCR1=CHR2]t
R1,R2= H, Me
NO2 c265
Ar
268 A~CR’-CHR~N@ I C(No2)3 269
0-
AreR2 R1=H
R’ H 270
TI-
0
271
R’ H 272
Scheme 3
Products formed include the cis- and trans-isomers of 2-trinitromethyl-3-nitro2,3-dihydrobenzofuran, 2-trinitromethyl-3-hydroxy-2,3-dihydrobenzofuran (from hydrolysis of the nitrite ester), 2-nitro-3-t rinit romet hyl-2,3-dihydrobenzofuran, 4-trinitromethyl-7-nitro-4,7-dihydrobenzofuran and nitronic ester (274).206 OMe
273
274
The inclusion of ethanol (8% v/v) in the reaction solvent (dichloromethane or acetonitrile) used for photolysis of the charge transfer complexes of tetranitromethane with alkoxy or dialkoxyarenes leads to stabilisation of alkoxytrinitromethylarenes. Reduction in the nucleophilicity of the trinitromethanide ion as well as changes in the regioselectivity of trinitromethanide ion attack on the arene radical cations and stabilisation of the adducts also result.207 Strong interest continues in the use of the 2-nitrobenzyl group as a convenient and versatile photoremovable protecting group and a variety of systems have been patented.208 The steroid derivative (275) releases cytotoxic L-leucyl-Lleucine methyl ester on photolysis in liposomes, leaving the undesired by-product, 2-nitrosobenzaldehyde, attached to the liposome-soluble steroid nucleus.209The photoactive mustards (276) and (277) are potential prodrug candidates, releasing a phosphoric acid derivative which has been identified as an intermediate in cyclophosphamide cancer therapy.210The 2-nitrobenzyl quaternary ammonium derivative (278) photodecomposes with rapid release of nor-butyryl choline and is
M6: Photoreactions of Compounds Containing Heteroatoms other than Oxygen
26 1
a promising probe for mechanistic studies on butyrylcholinesterase activity.21 The a-carboxyl-2-nitrobenzylderivatives (279) degrade thermally within several hours and are therefore unsuitable for use in biological studies. The a-(hydroxymethyl)-2-nitrobenzyl derivatives (280), however, are chemically stable, undergo clean photolytic release of the fatty acids and suggest 1-(2'-nitropheny1)1,2-ethanediolas a useful derivatising agent for fatty acids.212
275 276 277 278 279 280
R' = OSteroid, R2 = H, X = Leu-Leu OMeR' = OCH2C@Na, R2 = allyl, X = OP(O)(NHP)N(CH~CH~CI)~ R' = OCH2CH2NH3C1, R2 = (CH2)30HI X = OP(O)(NH2)N(CH2CH2CI)2 R' = H, R2 = Me, X = +NMe&H2CH20COCH2Et R' H, R2 = C02H, X = arachidonate, deate, linoleate or linolenate R' = H, = CHzOH, X = arachidonate, oleate, linoleate or linolenate
-
A photolabile fluorescent 2-nitrobenzyl derivative that releases a 5'-silylated thymidine has been developed.213A series of N-(2-nitrobenzyl)substituted indoles, benzimidazoles, indolones and 6-chlorouracilundergo clean deprotection on i r r a d i a t i ~ n . ~A' ~nitrobenzyl linker which can be incorporated at different positions in a fraction of the oligomers during the split syntheses combinatorial approach has been used to permit photolytic cleavage of the oligomers on a bead at these positions. Subsequent MALDI-MS analysis can then be used for efficient sequence determination of the peptides generated.21 Amino-derivatised polymer supports incorporating 2-nitrobenzyl linkers have been prepared and used for the synthesis of reducing oligosaccharides2I6and oligonucleotides:217cleavage from the solid support is being cleanly achieved by photolysis. Derivatives of EGTA, a calcium selective chelator, have been synthesised, each having a 2-nitrophenyl group attached to a backbone carbon. Cleavage of a benzylic bond on irradiation disrupts the coordination sphere and concentrationjumps in intracellular calcium can be achieved.218On irradiation in benzene 1,2-bis(2-nitrophenyl)ethaneyields 2-nitrobenzoic acid, 2-nitrobenzyl 2'-nitrophenyl ketone, 2,2'-dinitrobenzil and dibenzo[c,g][ 1,2]diazocin-5,6-dione N,N'dio~ide.~I'The photochromism of 2(2',4'-dinitrobenzyl)pyridine arises from intramolecular proton transfer involving three different tautomeric species. In the presence of a macrobicyclic cryptand proton transfer occurs from two of the tautomers and back transfer is slow as the proton is shielded within the cryptate cavity.22oIn propan-2-01, triplet excited 4nitroacetophenone is reduced to 4-hydroxylaminoacetophenone which in turn is further photoreduced to 4-aminoacetophenone and 4,4'-diacetyla~obenzene.~~' The stable triplet species generated by irradiation of crystalline 2-nitrobiphenyl below 120 K may be formed by intramolecular abstraction of the 2'-hydrogen by the nitro group?22 Nanosecond laser photolysis and conductimetric detection have been used to show that the photoisomerisation of 4-nitrobenzaldehyde to 4-nitrosobenzoic acid in aqueous solution occurs via the mechanism in Scheme 4.223 The
Photochemistry
262
photogeneration of 1-nitroso-2-naphthoic acid from 1-nitro-2-naphthaldehyde using 355 nm light provides the proton source for transformation of colourless non-fluorescent Rhodamine B base to the coloured and strongly fluorescing dye Rhodamine B. In solid PMMA matrices the process has been used as the basis for a ROM memory Aminopolycarboxylic esters react with [60]fullerene on photolysis to produce fulleropyrrolidine multicarboxylates. For example, tetramethyl ethylenediaminetetraacetate (EDTA) gives (281) as well as the more symmetrical fulleropyrrolidine C60(CHC02Me)2NCH2CH2N(CH2C02Me)2. Analogous reactions occur for the methyl esters of (N-morpho1ino)acetic acid and (N-piperidino)acetic acid whereas the free carboxylic acids photoreact with C a by decarboxylation and formation of the 1,2-dihydrofullerenes Cm(H)[CH2N(CH2CH2)20] and C60(H)[CH2N(CH2),] respectively.225y226 The one-pot formation of (282) by photolysis of (283)in benzene/trifluoroaceticacid is the key step in the synthesis of a food-borne carcinogen.227Excitation of the isoindoline nitroxide (284) results in abstraction of primary, secondary and tertiary hydrogens from unactivated hydrocarbons such as cyclohexane, 2-methylpropane and butane. The resulting carbon-centred radicals are trapped by ground state nitroxide as the adducts (28S).228
281
282 R - P h , X - H 283 R = I , X=tOSyl
284
x=o’
285 X-Oalkyl
Triplet excited 3-( 1-naphthyl)-2-(1-naphthylmethyl)oxaziridine (286) gives N(1-naphthoxy)-1-(aminomethyl)naphthalene (289) by N-O bond cleavage and a hydrogen shift, and 1-naphthaldehyde(287)by N - 0 and C-N bond fissions in the three-membered ring with naphthylmethylnitrene (288) as an intermediate. The oxaziridine radical cation (290), obtained by 9,lO-DCA sensitisation, is proposed to form the ring-opened nitrone radical cation (291).This species is believed to be a source of oxygen atoms for oxidation of naphthylmethylnitrene (288) to 1(nitromethy1)naphthalene(292) and also to be a precursor to naphthaldehyde (287)and 1 -(aminomethyl)naphthalene (293).229 1,3-Diarylpyrazolinesfluoresce efficiently and are used as optical brighteners. Studies with a series of derivatives (294) has concluded that the presence of a
1116: Photoreactionsof Compounds Containing Heteroatoms other than Oxygen
0
/ \
ArCH-NCH2Ar
286
h
PkCO
hlDCA
0'
/ \
ArCHZCH2Ar 290
ArCH=r;?CHzAr 291
-
0'
I Ar-CH-kH2Ar
-
I
ArCHO 287
+
+
ArCH&
HN='CHAr
DCA'
288
t
:NCH2Ar ps8
ArCONHCH2Ar 289
ArCHO 287
263
ArCHO +ArCH$H2 287
ArCH2N 288
DCA:
AICH2N&
293
4'4ialkylamino group makes them good electron transfer quenchers of excited ketones and singlet oxygen, resulting in physical decay rather than photoreaction. They are liable to radical attack, which leads to aromatisation of the heterocyclic ring, though this process is operative only under particular conditions.230 Irradiation of a titanium dioxide suspension in ethanol containing o-dinitrobenzene gives 2-methylbenzimidazole in 96% yield. Reduction to 2-nitroaniline, formation of the corresponding imine by reaction with the acetaldehyde formed by oxidation of the solvent and subsequent reduction of the second nitro group to the corresponding hydroxylamine, intramolecular cyclisation and dehydration lead to the observed product. The synthesis is tolerant of methyl, ethoxy, chloro and ester substituents on the aromatic ring and propan-1-01 may replace ethanol in the reaction.231The kinetics of photoreduction of nitroaromatics and methyl viologen by titanium dioxide have been investigated,232and mechanistic details of the cadmium sulfide mediated oxidative carbon-carbon bond cleavage of the pyrrole ring in 2- and 3-methylindoles have been e l ~ d i c a t e d . ~ ~ ~ ~ ~ ~ Iodopyrrole (2wwand 4-nitro-2-iodoimidazole (297),236 when irradiated in the presence of aromatic compounds such as benzene, rn-xylene, thiophene, 2chlorothiophene or 2-methylthiophene, yield the corresponding arylpyrroles (2%) and the 4-nitro-2-arylimidles (298). Reaction appears to require population of a higher triplet excited state (A,o*, n,n* or qn*)mainly lacalised in the Me
294 X = H, NEt2, N(CH2CH&O
295 x-I 296 X = Avl
297 X = I 298 X=Ar
264
Photochemistry
carbon-iodine bond, followed by C-I homolysis and reaction between the resulting radical and the aromatic substrate. In certain cases, for example ethyl 3,4-dimethyl-5-iodopyrrole-2-carboxylate, dehalogenation rather than arylation is observed. Semiempirical calculations show that, where the difference between the heats of formation of the radical intermediate and its parent halogenoheterocycle is ~ 5 kcal 5 mol-I, arylation occurs. Where this difference is >55 kcal mol- dehalogenation is observed.237 The pseudosaccharin 2-,3- and 4-pyridylmethyl ethers (2W)undergo facile singlet excited state reaction in methanol. Homolysis of the 0-CH2 bond and radical recoupling yield the corresponding N-(pyridylmethy1)saccharin derivatives and hydrogen abstraction from the solvent yields saccharin. The nucleophilic photosubstitution product, pseudosaccharin methyl ether, is also formed as a minor product.238 Photoinduced SET from the electron-donatingtetraphenylborate counteranion to a series of electron-accepting chromophores in benzylic trialkylammonium cations in acetonitrile results in efficient cleavage of the benzylic C-N bond and generation of the corresponding trialkyamines. Laser flash photolysis and product studies have shown that, for N-(4-benzoylbenzyl)-N,N,N-tributylammonium and N-(4-acetylbenzyl)-N,N,N-trimethylammoniumtetraphenylborates, SET occurs to their triplet excited states. The resulting reduced quaternary ammonium cations cleave to release the tertiary amine and a benzylic radical, coupling of which results in formation of the corresponding dimers. For N,N,Ntributyl-N-(2-naphthyl)methylammonium and N,N,N-tributyl-N-(7-methoxycoumariny1)methylammoniumtetraphenylborates SET occurs to their singlet excited states. The C-N bond breaking process in each case seems to be coupled to the primary SET step and to occur so rapidly that back electron transfer to regenerate the salt cannot compete.239 The photochemical reduction of Methylene Blue by triethylamine in methanol has been investigated.240Photolysis of 3-(3,4-dichlorophenyl)-l,1-dimethylurea (diuron) in aqueous solution containing methanol gives 3-(3-chlorophenyl)-1,ldimethyl~rea.~~' The photostabilities of chloroquine d i p h ~ s p h a t eand ~ ~ meflo~ quine hydrochloride243have been reported and a commentary published on the
299
300
301
302 R
I
Ar
I M : Photoreactions of Compounds Containing Heteroatoms other than Oxygen
265
suitability of the quinine actinometry system for use in drug stability testing.244 Further aspects of the photodegradation of the herbicides metribuzin (4-amino-6t-butyl-3-methylthio-1,2,4-triazin-5-0ne)~~’ and metamitron (4-amino-6-phenyl3-methylthio-1,2,4-triazin-5-0ne)~~~ have been reported. The pH dependence of the photoreactivity of the antimalarial chloroquine [4-(4-N,Ndiethylamino-lmethylbutyl)amino-7-chloroquinoline]247 and the influence of oxygen on the light-induced reactions of the antimalarial primaquine [8-(4-amino-1-methylbutyl)amino-6-methoxyquinoline]248 have been investigated. The carboxylate form of the factor Xa inhibitor, (2S)-2-[4-[(3S)-l -acetimidoyl-3-pyrrolidinyl]phenyl]-3-(7-amidino-2-naphthyl)propanoic acid, undergoes essentially quantitative decarboxylation whereas the free carboxylic acid is p h ~ t o s t a b l e .The ~~~ primary photoproduct from the synthetic 7-piperazinyl fluoroquinoline antibiotic ciprofloxacin is the corresponding 7-[(2-aminoethyl)amino-1-cyclopropyl-6fluoro-l,4-dihydro-4-oxo-3-quinoline carboxylic acid.2M Conditions for the photosensitised preparation of green-yellow fluorescent 7-(fl-D-ribofuranosylamino)pyrido[2,1-h]pteridin-1 1-ium-5-olate, luminarosine, and its 2’-deoxy- and 2’0-methyl analogues, from N-[9-(2,3,5-tri-O-acetyl-~-D-ribofuranosyl)purin-6-y1]pyridinium chloride, have been ~ptimised.~’’ Further diverse systems have been developed and used in the investigation of intramolecular SET processes. These include styrene/amide-spacerlamine diad~?’~ 9-aminoacridindpolyether-spacer/benzoateester d i a d ~ , ~1-(4-cyano’~ phenyl)-4-(cyanomethylene)piperidine,2” n-donor/polyoxyethylene/Zn(II)porphyrin/N,N’-dimethyl4,4’-bipyridinium sy~tems,~’’ naphthalene/porphyrin/ quinone cy~lophanes~’~ and their anthracene analogues,257pyropheophytinnaphthoquinone d i a d ~ , ~rigid ’ ~ donor/bridge/acceptor systems,259anilide-substituted 10-methylacridinium ions,2M)viologerdfluoresceirdcarbazole triads,261an anthraquinone/fluorescein/carbazoletriad,262 a carotenoid/porphyrin/dinitronaphthalenedicarboximide triad?63 pyrene/peptide/dimethylaniline systems?64 9-dicyanomethylene-10-( 1,3-dithiol-2-ylidene)ant h r a c e n e ~ * ~ and ’ * ~ ~9-N-cyanoimine-lo-( 1,3-dithi01-2-ylidene)anthracenes.
3
sulfurcontaining compounds
Singlet excited cis- 1,2-di(2-thienyl)ethylene cyclises to give benzo[ 1,2-b:4,3bldithiophene as a reaction product.267Irradiation of a series of bicyclic and monocyclic thioketones, for example 3,3dimethylthiocamphor, in pentane with 254 nm light leads primarily to &insertion via excitation to the S2 manifold: this is in agreement with earlier findings for related systems and in contrast to the preferred 6-insertion for aryl alkyl thioketones. For the more flexible bicyclic thione (300), and for 2,2-diet hy1-5,5-dimethylcyclopentanethione and 242thy12,6,6-trimethylcyclohexanethione,though B-insertion dominates some y-insertion is also observed. In contrast, endo-5,6-trimethylene-2-norbornanethionegives only the 6-insertion product (301). Vapour phase photolysis (254 nm) of these thiones on the other hand yields equivalent amounts of thioenol products resulting from Norrish type I1 fragmentation. For example, the thione (300)
266
Photochemistry
yields the thioenol (302) as the major product, in addition to the fb and yinsertion products observed in the solution phase photolysis. This process constitutes a potentially useful synthetic method for preparation of alicyclic thioenols (tautomerically stable isomers of thioketones) uncontaminated by the corresponding thioketones. Photophysical studies suggest that a vibrationally excited 52 state leads to the Norrish type I1 fragmentation via intramolecular yhydrogen abstraction and cleavage of the intermediate 1,4-biradical whereas the f3-insertion products originate from the vibrationally relaxed S2 state.268When the thioketones (303) are irradiated into the n,n* absorption band (Lax 320 nm), either in the solid state or in benzene solution, y-insertion is observed and the cyclobutanes (304)are N-Allylthioamides on irradiation yield the corresponding N-vinylthioamides and pyrroles. For example (305)yields (307)and (309)by &hydrogen abstraction and the intermediate biradical (306). Irradiation of the N-vinylthioamides, for example the enethioamide (308), results in formation of the corresponding isoquinolinethione derivative (310).270 mt
S
CHM~ 305
310
Irradiation of the monothioimides (311) in moist benzene yields the thiobenzanilides (314) and 3-phenylpropanoic acid (315), whereas in anhydrous benzene no reaction occurs. The same photoconversion is found in the solid state in the presence of moisture, whereas when moisture is rigorously excluded no reaction occurs. The monothioimides adopt conformation (311) in the solid state and M M X calculations indicate thi! to be the most stable. The short intramolecular OC(S)distances observed (2.8 A) suggest that excited state nucleophilic attack on the C=S group by the carbonyl oxygen results in (312) and that subsequent reaction with moisture forms (313) which decomposes to (315) and the thioenol Ar'
A? 311
-
Arl
R
OH
Ar'C-NHA? II S
+ RC02H
312 313 314 315 Ar' = Ph, 4-MeOC6H4; A6 = Ph, 4-BrC6H4,443r-2,6-M%GH2; R = CH2CH2Ph
267
1116: Photoreactionsof Compounh Containing Heteroatoms other than Oxygen
of the thiobenzanilide (314). An alternative mechanism, involving y-hydrogen abstraction by the thione group from the carbon u to the carbonyl group, has been eliminated by studies with deuterated precursor^.^^' The 4-(2-haloaryl)-5-aryl-1,2,4-triazole-3-thiones (316) are converted into the s-triazolo[3,4-b]benzothiazoles(317) on irradiation. SET from sulfur to the aryl ring, followed by sulfur-aryl bond formation and loss of hydrogen halide, is proposed.272
P?
--
Ar \
RJ @ J X N Y H
316 X CI, BI; R = H,Me; Ar Ph, 4-MG3H4,2-MeC6H4,4-MeOGjH4,2-naphthyl
317
The ethylthioalkyl phenylglyoxylates (322) undergo regioselectivephotocyclisation to produce up to 13-membered ring thiacyclols (324) involving bonding between the benzoyl carbon and the carbon u to sulfur on the remote side. SET from sulfur to the excited carbonyl, followed by proton transfer and subsequent cyciisation of the resulting biradical, yields the thiacyclols. Rate constants for electron transfer increase as the chain connecting the donor and acceptor becomes longer and more flexible. This also favours back electron transfer and results in lower yields of cyclisation products (324) as competition from Norrish type I1 and reductive dimerisation processes becomes important.273In the cases of the 1,3-dithiolaneand 1,3dithiane derivatives (323) back electron transfer is so efficient that thiacyclol formation does not occur and only Norrish type I1 and reductive dimerisation products are reported.274 Vinyl phenylglyoxylate, the result of p-elimination from the 1,4-biradicals (318) formed by triplet excited state y-hydrogen abstraction, is the dominant photoproduct from the corresponding iodoethyl or phenylsulfinylethyl phenylglyoxylates. For the bromoethyl or phenylthioethyl substituted radicals (319), both p-elimination and Norrish type I1 products are observed, whereas for the chloroethyl, bromopropyl and phenylthiopropyl analogues (320) and (321) only Norrish type 11 processes result.275Photocyclisation of 2-(alky1thio)ethyl benzoylacetatesgives 8-membered thialactones (325), involving 1,9-proton transfer following SET from sulfur to the excited benzoyl group. Lack of donor electrons on the sulfur in 2-(benzylsulfony1)ethyl benzoylacetate results in loss of p h o t ~ r e a c t i v i t y . ~ ~ ~ Dithia[3.3]metacyclophanes (326) containing at least one intra-annular methoxy group, when photolysed in trimethyl or triethyl phosphite, form the corresponding tetrahydropyrenes (329) in a one-pot procedure. The mechanism in Scheme 5 is supported by the isolation of intermediates corresponding to (327) and (328) from interrupted photolyses. Intra-annularly substituted methoxydithia[3.3](1,3)-naphthalenophanes similarly produce the corresponding tetrahydrodibenzopyrenesin a single synthetic step?77 Solid state photodimerisation has been reported for a series of unsymmetrical
268
Photochemistry
Ph
0
318 319 320 321
n = 1, n = 1, n = 1, n = 2,
X = I, S(0)Ph X = Br, SPh X=CI X = Br, S f h
322 n=2-8, X=SEt
1
S
324 n = 2-8
323 n=3,4, X =Hx, rn=1,2
s
)m
325 R1,R2 = H,Me Ph
trans- 1,Zdiheteroaryl e t h y l e n e ~ .Phosphatidylcholine ~~~ derivatives (330) containing the trans-styrylthiophene chromophore aggregate in aqueous dispersions. Irradiation of these aggregates results in formation of the syn HH-dimer, suggestive of a topologically controlled reaction from a translational structure in which nearest-neighbur chromophores are aligned parallel. Codispersion of styrylthiophene- and saturated-phospholipids results in bilayer vesicles which entrap water-soluble carboxyfluorescein.Irradiation results in photodimerisation
269
IIl6: Pholoreactions of Compounds Containing Heteroatoms other than Oxygen
M~sN(CH~)~-P-O-
330
8‘c
of the styrylthiophenes and release of the entrapped carboxfluorescein in a manner suggestive of “catastrophic” destruction of the vesicles.279 Irradiation of 3-thioxoandrosta-l,4-dien-l7-one (331) with 589 nm light in the presence of dimethyl acetylenedicarboxylateyields the 1:2 adduct (334), possibly involving intermediates such as (332) and (333). The reaction also occurs thermally.280
331
332
333
334
Alkyl thiopheneglyoxylates have a lowest triplet x,n* state which exhibits low photoreactivity in benzene: only traces of Norrish type I1 products are detected on prolonged irradiation. However, the upper triplet n,x* state is reactive and, in the presence of electron-rich 2,3-dimethylbut-2-ene, [2+2] cycloaddition occurs to give the oxetane (335) in high yield from the methyl ester. The corresponding alkyl furanylglyoxylates behave analogously.281The photophysics of the thiocoumarin Sz state has been investigated.282Irradiation (>350 nm) of solid isothiocoumarin affords the [2+2] dimer (336), which is also obtained in low yields in ethanol or acetonitrile but not in benzene. In acetonitrile in the presence of tetrachloroethylene, the adduct (337) is obtained from the triplet excited state. No photoreaction occurs between isothiocoumarin and 2.3dimethylb~t-2-ene.~’~ In contrast thiocoumarin gives a [2+2] photoadduct with 2,3-dimethylbut-2ene,284and the [2+2]photoadduct (341) with tetrachlorocthylene. Similar irradiation of thioangelicin in benzene containing 2,3-dimethylbut-Zene gives a mixture of the trans-adduct (338) and the cis-adduct (339) in 25% and 75% yields respectively. Angelicin gives only the corresponding cis-adduct (340)under these conditions.28s Thiopsoralen photobinds to DNA via a triplet mechanism, following intercalation inside duplex DNA. The furan side monoadduct with thymine, isolated from
270
Photochemistry
335 Me
336
@
CI
\
0 H CI CI
0 4
339 340
338
% 337
x-s
341
x=o
DNA photomodified by thiopsoralen, has the cis-syn structure (342). Thiopsoralen may also exert photobiological activity by damaging membrane components such as unsaturated fatty acids. In ethanol solution addition of linolenic acid to thiopsoralen occurs at the enone double bond to give an adduct of the type (343).286
342
343
The repair mechanisms of UV-induced DNA damage, caused by DNA crosslinking resulting from excited state product formation, are of major interest. The sulfur analogue of a (6-4)-pyrimidine/pyrimidone“dimeric” photoproduct undergoes efficient conversion to its Dewar valence bond isomer (344)?87 Irradiation of (344)in water has yielded a new “tetramer” (349). Previously pyrimidinone (347) was isolated, presumably via the Dewar isomer (346). The tetramer (349) has been suggested to arise from (344) via the mechanism in Scheme 6. Disproportionation of radical (345) yields (M), the precursor to (347), and the enamide (348).Michael addition of (344)to (348)yields the tetramer (349).288 Irradiation (366 nm) of aqueous solutions of the 4-thiothymines (352) in the presence of the N-9-substituted adenines (351) yields the N-6-formamidopyrimidines (354), which have potential use in the field of DNA lesion studies. Similarly N-3-methyl-4-thiothymidine(353) in the presence of adenosine gives the N-3methylcytidine (350), involving attack by the adenine 6-amino group at the electrophilic C-4 position of the excited thiocarbonyl group with subsequent elimination of hydrogen sulfide. In the formation of the N-6-formamidopyrimidines (354), analogous nucleophilic attack by the adenine N-7 centre in (351) at C-4 of the excited thiocarbonyl group of (352), followed by elimination of
I M : Photoreactions of Compounds Containing Heteroatoms other than Oxygen
tiN
27 1
0
344
346
346
tiN o&
348 0
hydrogen sulfide and hydrolytic imidazole ring opening, results in the observed
transformation^.^^^
hvl H20
350
A3
352 R' = H, R2 = CH2C02H, deoxyribosyl 353 R1= Me, R2= deoxyribosyl
A3
3s
Irradiation of the benzothiazinyl vinylcyclopropanes (355) in the presence of one equivalent of thiophenol gives good to excellent yields of the corresponding thiyl adducts. Regioselectivity is determined by captodative stabilisation of the intermediate radicals (356)which subsequently abstract hydrogen to yield the adducts. Substituent control of the conformations of the vinylcyclopropanes (355) determines the stereochemistriesof the radicals (356) and hence that of the product ally1 sulfides.29o Singlet excited state cyclisation of S-aryl-2-benzoylbenzothioates occurs by bond formation between the thioester oxygen and the
272
Photochemistry
benzoyl carbon to yield the zwitterionic intermediates (357). Subsequent aryl migration from the benzoyl carbon to the thioester carbon results in the formation of the 3-aryl-3-(arylthio)isobenzofuranoneproduct. Irradiation of the isobenzofuranone causes homolytic loss of the thioaryl group and subsequent dimerisation of the resulting isobenzofuranone radical occurs.29' Me
Me
355 a; R1 = R2 = Me
b; R1 = R2 = H C; R ' = Ph, R 2 = H d; R'= H, R 2 = Ph
356 a; E : Z = 9 : 1 b; E : Z = 1 : 9
357 R - H, Me; At-' = Ph, 4-MeCsH4,4-CIC6H4; AP = Ph, 2-,3-,4-MeC&Id
E : Z = 1 :4 d; E : Z = 1 :2 C;
Photoreaction of the N-acylbenzoxazole-2-thiones(358) with alkenes yields iminothietanes (362) and 2-substituted benzoxazoles (363) by intramolecular trapping of the zwitterionic intermediates (361) and (360), respectively, derived from the spirocyclic aminothietanes (359) whose regiochemistry is in accord with formation of the more stable biradical intermediate in the [2+2] cycloaddition process.292
I
I COR
COR
COR 360
358
aN+ OCOR
362
'
S-
I
ROC4 363
361
When ethyl a-(methy1thio)acetate (MeSCH2C02Et) is irradiated in the presence of an alkene (RCH=CH2), the corresponding carboethoxymethylated product (RCH2CH2CH2C02Et)is obtained in moderate to good yields via sulfurmethylene bond homolysis and attack by 'CH2C02Et on the alkene. Hydrogen abstraction by the adduct radical completes the addition. The success of this tinfree radical addition to alkenes, which is compatible with the presence of polar/ protic functional groups and solvents, relies on the inefficiency of thiomethyl group transfer. The major by-products are those from addition of the thiomethyl
I M : Photoreactions of Compounds Containing Heteroatoms other than Oxygen
273
radical to the alkene: this wastage may be reduced by inclusion of trimethylphosphite as a radical scavenger. N,N-Dimethyl a-(methy1thio)acetamide (MeSCH2CONMe2) may be used in the analogous process to yield RCH2CH2CH2CONMe2.293 Naphtho[ 1,8de]-1,3-dithiin-1-N-tolylsulfilimines (364) undergo consecutive photoreactions to give quantitatively the corresponding N-tosylaldimines (368) and naphtho[1,8-cd]-1,Zdithiole (369). The intermediate (367)can be isolated. That the conversion of (364)into (367) is intramolecular is confirmed by the absence of crossover products when a mixture of (365) and (366)is irradiated.294 In an analogous reaction, S-naphthylmethyl-N-p-tosylsulfimides(370) undergo photoinduced Stevens rearrangement in dichloromethane or acetonitrile to give (371). Separate irradiation of (371) results in S-Nbond cleavage and formation of R'SSR' and R'CH~NHTS.~~' H
sxs' R H
Rj-yswr
&
NS02Ar
s
s
L&
364 Ar = 4-WG3H4, R = aryl, akyl 365 Ar = Ph, R = 4-MeC6H4 366 Ar = 4-MGH4, R = Ph
+
NqAr
+& s-s
,RKH NSQAr
368
367
369
S02Ar
I
R'SCH2R2 R'SNCH2R2 370 371 R' = Me, Ph, Ppyridyl; R2 = Ph, 1-naphthyl, 2-naphthyl
The photochromic properties of a series of 4-aryl- and 4-methyl-2,3,4,5,6pentaphenyl4H-thiopyrans and of 4-aryl- and 4-methyl-3,5-dimethyl-2,4,6-triphenyl4H-thiopyrans have been reported.296'H-NMR spectroscopy has been used to investigate the photoconversion of a series of 4-aryM-methyl-2,6diphenyl-4H-thiopyrans into the corresponding 6-aryl-5-methyl-l,3-diphenyl-2thiabicyclo[3.I .O]hex-3-enes and subsequently to the thermodynamically more stable 2-aryl-4-methyl-3,6-diphenyl-2H-thiopyrans in quantitative yield. Electron-donating or electron-withdrawing groups at the 4-position of the migrating aryl group increase the relative rates of migration in methanol and, for each migrating aryl group, the rearrangement is faster in methanol than in benzene. A Zimmerman di-n-methane rearrangement mechanism, involving aryl-vinyl bridging via polarised transition states (372) or (373), is proposed for the aryl migration step.2974-Alkyl-2,3-dihydro-6H-1,3-thiazine-5-carboxylateson irradiation in toluene undergo carbon-sulfur bond homolysis to form the diradicals (374)-(376). Diradical(374), from the 4methyldihydrothiazine derivative, results in the formation of the enamine (377) and the corresponding imino tautomer whereas the 4-ethyldihydrothiazine derived diradical (375) results in a single product, Z,Z-(378). In contrast, the 4-benzyldihydrothiazine precursor yields a
Photochemistry
274
372 XsEWG,
*=a+,
*'=r
373 X=EDG, *=&, * ' = S +
374 R = Me 375 R = Et 376 R=CH2Ph
377
378 R1 = I? = Me 379 R1 = Me, R2 = Ph
mixture of all four geometrical isomers of (379) via the intermediacy of diradical (376)?98 Singlet excited benzyl P-naphthyl sulfoxide undergoes a-cleavage to give the isomeric sulfenic ester (np-S-0-benzyl) as major product, in addition to deoxygenation to benzyl P-naphthyl sulfide. Acetone sensitisation leads to the "escape" dimers, np-S02-S-np and bibenzyl, which are absent from the direct irradiation. Benzyl P-naphthyl sulfide is not formed from the sensitised reaction, confirming sulfoxide deoxygenation to be a singlet-derived process.2wPhotolysis of unsymmetrical dibenzylsulfones results in loss of sulfur dioxide and formation of a radical pair which, in solution, normally results in combination to form all three possible products. The corresponding processes in zeolites are highly sensitive to zeolite structure. In NaZSM-5 zeolite, benzoyl p-tolyl sulfone yields 1-phenyl-2-ptolylethane as the main product whereas benzyl a-naphthylmethyl sulfone gives only bibenzyl and 1,2-dinaphthylethane. The differences can be understood in terms of the size and shape selectivity of the absorbed substrate molecules on the zeolite surfaces and restrictions imposed by the surfaces on the diffusional motion of the radicals.300The effects of reaction conditions on the photodegradation of dibenzylsulfone catalysed by Ti02 semiconductor particles have been inve~tigated.~"Photolysis of S-phenylbenzo[b]thiophenium triflates results in phenyl migration to the thiophene 2- or 3-positions. Homolytic cleavage of the Sphenyl bond to give (381), followed by recombination within the solvent cage to form (380) or (382) and subsequent deprotonation, may be the route leading to the products.302 Ph* Ph
H 386
R1=H 2-recombinatm
381
382
The radical EtOCOCMe,COO', generated by photolysis of the corresponding Barton (N-hydroxy-2-thiopyridone) ester, decarboxylates inefficiently unless generated in benzene under reflux. Under these conditions 2-pyridyl-SCMe2C02Et is obtained in 80% yield. Investigation of the reaction of the decarboxy-
IIl4: Photoreactions of Compounh Containing Heteroatoms other than Oxygen
275
lated radical with methyl acrylate shows that its nucleophilicity is less than that of a simple alkyl radical.303The nonsteroidal antiinflammatory drug tiaprofenic acid, 2-(5-benzoyl-2-thienyl)propionicacid, has an unusually high energy gap between the Tl('rr,n*)and T2(n,'rr*)excited states and has been associated with phototoxic and photoallergic side effects. The T2 state decarboxylates to give 2benzoyl-5-ethylthiophene.The T2 state of this photoproduct abstracts hydrogen from propan-2-01 to give the corresponding pinacol, whereas the TI state can act as an electron acceptor.304Direct thioepoxidation of strained cyclic alkenes such as norbornene and trans-cyclooctene occurs by concerted sulfur atom transfer from the labile three-membered heterocyclic oxathiiranes generated by photolysis of sulfines Ar2C=S=0.30SThe irradiation of 2-iodo-5-nitrothiophene in the presence of B-methylstyrenes in acetonitrile gives the corresponding cinnamaldehyde (72-76%) and benzaldehyde (15-23Y0) derivatives. Formation of the cinnamaldehyde derivatives may involve hydrogen abstraction from the P-methylstyrenes by the excited nitroarene, followed by radical coupling and elimination, whereas benzaldehyde formation may involve an SET process.3o6 The major primary photoprocess for 2-phenylthiobenzothiazole involves rupture of the sulfur-thiazole bond whereas for 2-alkylthiobenzothiales product formation results from both sulfur-alkyl and sulfur-benzothiazolebond cleavages.3o7 S-Benzoyl2-mercaptoimidazol-2-ene(383),on irradiation in the presence of an aliphatic or aromatic m i n e (RNH2), yields the corresponding benzamide derivative (PhCONHR) in high yield. The reaction does not occur thermally and provides a mild method for amide formation.308
SCOPh
383
The charge-transfer complex of dibenzothiophene and tetranitromethane in dichloromethane gives the dibenzothiophene radical cation, the trinitromethanide ion and NO2 on photolysis and subsequent conversions result in formation of dibenzothiophene sulfoxide (56%), with minor amounts of 2-nitrodibenzothiophene, r- 1-hydroxy-c4trinitrornethyl-1,44ihydrodibenzothiophene, t-2-nitro-r1-trinitromethyl-1,2-dihydrodibenzothiophene and c- 1-nitro-r-4-trinitromethyl1,4dihydrodiben~othiophene.~~ Oxidation andor fragmentation products are observed in the photoreactions of alkyl phenyl sulfides with tetranitromethane; the product distribution is dependent on the substrate structure. For methyl phenyl sulfide or benzyl phenyl sulfide (384)only the corresponding sulfoxides are formed and are produced by geminate coupling between the sulfide radical cations and NO2 followed by loss of nitroxyl cation. Diphenylmethyl phenyl sulfide (385) gives some sulfoxide but fragmentation of the sulfide radical cation and subsequent conversions of Phs' and Ph2CH+ gave the main products. For triphenylmethyl phenyl sulfide (386)only products from PhS' and Ph&+ are formed. "he ease of C-S bond scission in these sulfur-centred radical cations follows the ease of carbocation formation: Ph3C+> Ph2CH+ > PhCH2' > CH3+.310
276
Photochemistry
PhSR
384 R = Me,CH2Ph 385 R=CHPh2 386 R=CPh3
387 R = carbohydrate moiety
388
The photodissociation of sulfonate esters has been widely used for photoacid generation in chemically amplified photoresists. Product and laser flash photolysis studies with three phenolic sulfonate esters are consistent with s-0 bond homolysis yielding phenoxy and sulfonyl radicals. Those that escape from the solvent cage are converted into phenol and a sulfonic acid. Alternatively sulfur dioxide lost from the sulfonyl radicals undergoes oxidative and hydration processes to form sulfuric and sulfurous acids. Phenyl benzylsulfonate undergoes essentially quantitative sulfur dioxide extrusion whereas, in addition to formation of a large excess of phenol and the corresponding sulfonic acid, phenyl methanesulfonate and phenyl p-toluenesulfonate undergo photo-Fries reax~angement.~' Sulfonic esters of a-hydroxymethylbenzoin ethers PhCOCPh(OR)CH20SO*R' undergo a-cleavage on irradiation to give benzoyl and a-alkoxy-a-sulfonyloxymethylbenzyl radicals from a short-lived triplet excited state. The a,a-disubstituted benzyl radicals subsequently fragment to generate benzoylmethyl radicals and sulfonic The imidazyl (imidazole-1-sulfonyl) group is a useful and readily photoremovable protecting group for carbohydrates. For example, irradiation of a series of carbohydrate imidazylates (387) in methanol in the presence of added triethylamine gives essentially quantitative yields of the precursor carbohydrates. SET forms the imidazylate radical anion which fragments to give the imidazolesulfonyl radical and an alkoxide which, on protonation by the solvent, yields the deprotected ~arbohydrate.~'~ The photochemistry of N-propyl2-sulfobenzoic imide involves both S-N and S-Ar bond cleavages and results in loss of sulfur dioxide to yield the diradical(388). In ethanol N-propylbenzamide is subsequently formed whereas in benzene the product is N-propyl-2-phenylbenzamide. A Stern-Volmer plot, using biacetyl as triplet quencher, shows that product formation in ethanol involves both singlet and triplet pathways. In contrast, quenching and sensitisation studies in benzene show that in this solvent reaction occurs almost exclusively from the singlet excited state. In the presence of toluene or anisole irradiation results in formation of 2-(2-tolyl)-N-propylbenzamide and 2-(p-tolyl)-N-propylbenzamidefrom the former and 2-(2-anisyl)-Npropylbenzamide and 2-(p-anisyl)-N-propylbenzamidefrom the latter. Analogous products are obtained from p-xylene and mesitylene whereas no reaction occurs with benzonitrile or acet~phenone.~'~ Arylazo sulfides (389)behave as arylating agents in an SRN' photostimulated process involving the conjugate bases (390) of malononitrile, ethyl cyanoacetate, diethyl malonate and ethyl acetoacetate and provide access to synthetically strategic substrates (391). The effectiveness of the arylation depends on the electrophilicity of the aryl radicals (392) and on the HOMO energy of the
'
277
IIf6: Photoreactions of Compoundr Containing Heteroatoms other than Oxygen
stabilised carbanions (390) participating in the propagation cycle (eqs. 2-4). A complicating factor in the use of arylazo sulfides is competition from sulfide anions (393) generated from the radical anion of (389)(eq. 2). In many cases the formation of significant quantities of aryl sulfides (394) (eqs. 5, 6) may be suppressed by the use of a large excess of the stabilised ~ a r b a n i o n . ~ ' ~
i Z X Y Z 990 hv I DMSO
Ar-N=N-SR
389
-
ii HsO+
Ar-N=N-SR
-
3 :
P
Malononitrile Ethyl cyanoacetate Diethyl rnalonate Diethyl methylmalonate Ethyl acetoacetate
-389
Ar-NrN-SR'
hv
+e
48 75 72 59 70
Ar-N=N--SR'
Ar' 392
+
N2
+
(eq.1) R S 393
Ar' + -CXYZ 390 ArCXYZ-' ArCXYZ-' Ar-N=N-SR ArCXYZ 391 Ar' + A S ArSR-'
ArSFt' + Ar-N=N-SR
I % Yield of 391
HCXYZ
Ar = 2-NCGH4, R Ph Ar 3-NCGH4, R CMe3 Ar = 4-PhCGH4, R = CMe3 Ar = 4-(2-thien0yl)C6H4, R CM% Ar = 2-NCGH4, R = Ph Ar-N=N-SR
Ar-CXYZ 391
-
+
(eq.2) (eq.3) Ar-N=N-SR'
A6R 394 + Ar-N=N-SR-'
(eq.4)
(eq.5) (eq.6)
Further studies of the deoxygenation of alcohols by triplet sensitisation and SET to their S-methyl dithioearbonates under a variety of conditions have been reported.316The properties of 2,4,6-triphenylthiapyrilium tetrafluoroborate as an SET sensitiser have been disc~ssed.~"The triplet excited state of 6H-purine-6thione acts as an electron donor for pdinitrobenzene and as an electron acceptor for tetramethylben~idine.~'~ Photolysis of sulfuryl chloride in the presence of tetramethylsilane yields exclusively Me3SiCH2S02Cl. In the presence of added yttrium(II1) chloride or sulfur, the reaction is less selective and Me3SiCH2Cl is also obtained. In contrast the presence of these photocatalysts in the photoreaction of sulfuryl chloride with hexamethyldisiloxane yields solely Me3SiOSiMe2CH2S02C1, whereas in their absence Me3SiOSiMezCHzCl is also 4
Compounds Containing Other Heteroatoms
Silicon and Germanium - Tris(trimethylsily1)silyl (sisyl) ethers are readily prepared from primary and secondary alcohols and are stable to many of the reagents used in organic synthesis. When irradiated through Pyrex in methanol/ dichloromethane the deprotected alcohols can be recovered in high yield and are readily separated from the silicon-based products by flash chr~matography.~~' A series of a-silyl ethers (RO-CH2TMS) have been used as hydroxymethyl anion equivalents. Photoinduced SET to 9,lO-DCAhiphenyl yields the corresponding radical cation which fragments with loss of the electrofugal trimethylsilyl group. 4.1
278
Photochemistry
The resulting nucleophilic alkoxymethyl radical may be trapped by an electrondeficient alkene. Reduction of the adduct radical (395) by DCA radical anion and protonation of the resulting anion, confirmed by deuterium incorporation from methanol-OD, gives the final product (3%). The diastereoselectivity shown has its origin in a preference for protonation, under kinetic control, from the less hindered side. For acyclic alkenes such as methyl 2-cyanocrotonate or dimethyl maleate, free rotation within (3%) results in a low cis:truns ratio of 1.8-2.5:l whereas for cyclic alkenes such as N,3-dimethylmaleimide or 3-methylmaleimide the cis:trans ratio is considerably higher at 86:14.32'
EWG 'EWG
395
EWG 'EWG
396
A detailed study of the competition between C-C, C-H and C-Si bond fragmentation in a series of 4-methoxy-a-substituted toluene radical cations in acetonitrile has confirmed the trimethylsilyl cation as an excellent electrofugal group. The 2-methyl-I ,3-dioxolan-2-yl cation may also be an effective alternat i ~ e Solar . ~ ~light ~ irradiation has been used to drive titanium dioxide photocatalysis of the reaction between maleic anhydride and (4-methoxybenzy1)trimethylsilane to give 2-(4-methoxybenzyl)succinic anhydride. Electrodhole transfer from the semiconductor produces a pair of radical ions. The silane radical cation fragments to give the 4-methoxybenzyl radical which is trapped by maleic anhydride. Reduction of this adduct radical by the persistent maleic anhydride radical anion, or by SET to the semiconductor, and protonation by water present in the solvent, yield the product.323 Excitation of 3-(t-butyldimethylsilyloxy)phenylmethylenemalonodinitrile (397) in acetonitrile leads to C-Si bond homolysis via a polarised singlet excited state which involves internal charge transfer. The phenoxydimethylsilyl radical (398) loses dimethylsilylene and is subsequently converted into the phenol (399). The accompanying t-butyl radicals diffuse out of the solvent cage and react with (397) to form the photolkylated derivative (401). In contrast the analogous photoalkylation of benzylidenemalononitrile (400)by t-butyldimethylsilyloxybenzenedoes not occur on direct irradiation. Rather, phenanthrene sensitisation is required and formation of (402) involves prior generation of the t-butyldimethylsilyloxybenzene radical cation. In apolar cyclohexane, (397) undergoes slow [2+2] dimerisation to give predominantly a single cyclobutane product.324 BU'
I
X 3S7 X = OSiMe@u' 398 X=OSiM+' 399 X = O H 400 X = H
X 401 X=OSiMe&' 402 X = H
IIl6: Photoreactionsof Compounh Containing Heteroatoms other than Oxygen
279
403 R = H
404 R = 2’-Me, 2’-OM9,4’-F, 3’-F, 2‘-F
The regiochemistry of intramolecular rneru-photocycloaddition of 3-(benzyldimethylsila)propl-ene (403)is controlled by the silicon in the tether. However the capacity of silicon to stabilise a positive charge at the P-carbon does not compete with the 1’,3’-directing influence of 2-electron-donating substituents in the aromatic ring. Only the products from 1’,3’-addition are found, which is the result of asymmetry in the benzene-ethene orientation in the bichromophore conformation (404)preceding addition. For the rn-fluoro bichromophore, both 1’,S-and 2’,6‘-additions occur, the P-silicon effect competing to some extent with fluorine stabilisation of an adjacent negative charge.325Laser flash photolysis and trapping experiments with the 1,Zdisilacyclobutane (405) suggest that the sole primary photoproduct is the disilene (Me3Si)2Si=Si(SiMe3)2, together with 2,2’biadamantylidene, and that the disilene dissociates to the silylene (Me3Si)zSi: on further photolysis. The 1,2-digemacyclobutane (406) undergoes analogous photwonversions. The disilenebutadiene adduct (407)is converted into (408)on irradiation. Thermolysis of disilacyclobutane (405)results in the alternative [2+2] cycloreversion process and formation of bis(trimethylsilyl)adamantylidenesilene, whereas the digermacyclobutane(406)cleaves thermally to give (Me3Si)2Ge= Ge(SiMe3)2.326
Si(SiMe& 405 X = S i 406 X = G e
407 n = l 408 n = O
Absolute rate constants have been reported for the reaction of Me2Si=CHCH=CH2, generated from 1,l-dimethyl-(1-sila)cyclobut-Zene by irradiation with 193 nm light, with alcohols and oxygen and the potential and limitations of the use of far-UV radiation in such solution phase flash photolysis studies have been discussed.327 The method has also been applied to similar reactions of Me2Si=CH2,similarly generated from 1,l -dimethyl~iletane.~~~ 2,3,4,5-Tetraphenylsilacyclopentadienylidene,the first silylene incorporated in a silole ring, has been generated by photolysis of 7-silanorbornadiene and norbornene precursors, for example (409),and has been observed in a frozen 3-methylpentane matrix at 77 K and trapped as the adducts with efficient silylene traps, EtMe2SiH and 2,3dimethylbuta-1,3-diene.329 Photolysis (254 nm) of substituted phenylpolysilanes (RL3SiSiR22Ph)in the presence of [60]fullerenein benzene results in 1,16-addition to Cm to give (410) by
280
Photochemistry
Ph Ph
Ph
409
411
410
silyl radical addition and/or 1,Zaddition to give (411) (and the corresponding cisand trans-1,6cyclohexadiene isomers) involving attachment of the phenylsilyl radical to Cso via the silicon and 2-carbon atoms.330 Irradiation of the disilanylethyne (412)in methanol yields the adduct E-(416), formed by methanolysis of silacyclopropene(414),which is the product of singlet excited state rearrangement of (412).In dichloromethane containing acetone as the trapping agent, cyclopropene (414)is converted into adduct (417).Intramolecular trapping by the 2-allyloxy substituent was not observed. Under these conditions an additional product (421)is also obtained, which is believed to be In formed via the intermediacy of silaallene (415)and the acetone adduct (418).331 a complementary laser flash photolysis study of phenylethynylpentamethyldisilane (413)in hexane, dimethylsilylene, the corresponding silacyclopropene (414) and silaallene (415)were detected and characterised. Absolute rate constants for reaction of the silaallene with methanol, acetic acid and oxygen have been determined.332Photolysis of hexa-t-butylcyclotrisilane in the presence of Nmethylpyrrole results in formation of (419),possibly via rearrangement of the adduct formed by addition of di-t-butylsilylene across the 2,3-double bond. Cophotolysis of (419)with hexa-t-butylcyclotrisilanegives the seven-membered ring compound (420), which is the product of addition of di-t-butylsilylene to (419)followed by cleavage of the central four-membered ring in the initially-
Ar--8-SiMe
Me Me 1. I
I
t
SiMe3 ACH+ SiMe2 I OMe
416
419
-ArMSiMe3
z'r-
Me Me 412 Ar = 2-(CH2=CHCH20)C6H4 413 Ar= Ph
Si Me2
SiMe3
MeZ S i M e 2 Me
417
420
+
Me3si)=C=SiMe2 Ar
415
J Me2CO
Me&i
A rMe % r eMe 2
418 Me Ar*O-Si-SiM%
Me I
Me
I Me
421
IIi4: Photoreactions of Compounds Containing Heteroatoms other than Oxygen
28 1
formed a d d ~ c t .(Trimethylsilylmethy1)trimethyldisilene ~~~ (Me2Si = SiMeCH2SiMe3) has been generated photochemically from 1-phenyl-7-trimethylsilylmethyl-7,8,8-trimethyl-7,8-disilabicyclo[2.2.2]octa-2,5-diene and the regioselectivity of the addition of phenols to the disilene investigated.334 1,2-Disila-3,5-cyclohexadienes(422) have been reported to give 2,6-disilabicycl0[3.1.O]hex-3-enes and 5,6-disilabicyclo[2.l.l]hex-2-eneson direct irradiation, possibly via ring-opened 1,6-disila-l,3,5-hexatrienes(425), by analogy with 1,3cyclohexadienes and 1-sila-2,4-cyclohexadienes.335 In contrast SET sensit isation of 1,2-disila-3,5-cyclohexadienes(422) by methylene blue yields the corresponding five-membered siloles (428). Silicon-silicon bond cleavage within the radical cation of (422) is proposed to yield an open intermediate and subsequent cyclisation, elimination and back electron transfer steps lead to the observed 1,ZDigermacyclohexa-3,5-dienes (423) on irradiation in benzene yield germoles (429) quantitatively by extrusion of a dialkylgermylene, which may be trapped by 2,3-dimethylbuta-l,3-dieneas the corresponding 1,l -dialkyl-3,4dimethyl-1-germacyclopent-3-enes. Irradiation of a 1-germa-2-silacyclohexa-3,5diene (424) yields mainly silole (428) along with a small amount of germole (429). These ring contractions may possibly proceed via labile dimetallotrienes (425) and the biradicals (426) and (427); the regioselectivity in the case of (424) is consistent with the C-Si bond being stronger than the C-Ge bond and with germylenes being more thermodynamically stable then ~ i l y l e n e sIrradiation .~~~ of the tetraphenyl-1,2-disila- (422) and 1,2-digermacyclohexa-3,5-dienes(423) in benzenelbenzonitrile in the presence of Cm as electron acceptor similarly yields the corresponding siloles (428) and germoles (429), respectively, via the intermediacy of the corresponding radical cations. That from 1-germa-2-silacyclohexa-3,5-diene(424) yields only the silole (428).-
422 X = Y = S i 423 X - Y = G e 424 X=Si, Y = G e
425 X,Y
= Si, Ge
426 X Y P Si, Ge 427 X=Si, Y = G e P
428 X = Si 429 X = G e
1,l -Dimethyl-2,5-diphenylgermoleyields anti,trans-, anti@-, and syn,cis-[2+2] photodimers, whereas the more sterically crowded 1,l-dimethyl-2,3,4,5-tetraphenyl or lf1,2,3,4,5-hexamethyl derivatives do not photodimerise. Triplet excited 9,lO-phenanthraquinone reacts with cyclic organosilanes to give silylene insertion products via radical displacement at the silicon of the organosilanes. For example reaction with dodecamethylcyclohexasilane or 1-phenyl-7-trimethylsilylmethyl-7,8,8-trimethyl-7,8-disilabicyclo[2.2.2.]octa-2,5-diene yields the adduct (430), in the latter case YMthe intermediacy of the biradical (431).339 Substituent labelling has been employed to confirm that the photoisomerkdtion of hexakis(t-butyldimethy1silyl)tetrasilacyclobutene to the corresponding tetrasilabicyclo[1.1 .O]butane (or the reverse thermal transformation) proceeds by
Photochemistry
282
431
1,Zmigration of a I-butyldimethylsilyl group with formation (or cleavage) of the central Si-Si bond, rather than skeletal isomerisation requiring cleavage or formation of two Si-Si bonds.340Irradiation of the 1-(pentamethyldigermanyl)naphthalenes (432) yields mainly the isomeric rearranged compounds (433), accompanied by small amounts of the 1-trimethylgermyl compounds (434). Homoiysis of the Ge-Ge bond, recombination of the resulting trimethylgermyl 1naphthyldimethylgermyl radical pair at the 8-position of the latter and an intramolecular 1,4-hydrogen shift to give (433) is consistent with deuterium labelling studies. Extrusion of dimethylgermylene from (432) results in formation of (434). In contrast the corresponding 2-(pentamethy1digermanyl)naphthalenes are converted into high molecular weight polymers under similar conditions of irradiati~n.~~'
432 R1 = H, R2 = GeMq, R3 = H, Me 433 R1 +i GeMe3, R2 = H, R3 = H, Me 434 R1 = H, R2 = Me, R3 = H, Me
Photoinitbated SET from an electron rich aromatic such as 1,S-dimethoxynaphthalene (DMN) to t-butyldiphenyl(phenylse1eno)silane yields the corresponding radical anion (439, mesolysis of which generates the phenylselenyl anion (436) and the t-butyldiphenylsilyl radical (437).This Se-Si system has been utilised syntheticallyin bimolecular group transfer radical processes. For example irradiation of a solution containing t-butyldiphenyl(phenylseleno)silane, the bromo ester (439, DMN and ascorbic acid (added as sacrificial electron donor to regenerate DMN from its radical cation) results in formation of the cyclisation product (441) in 75% yield via the intermediacy of radicals (439) and (4U2)?42 4.2
Phosphorus - Photochemical SET from singlet excited 1,Cdicyanonaphthalene converts the nucleoside analogue-based ally1 phosphites (443) into the allylphosphonates (444).343The relative quantum efficiencies of the triplet sensitised photorearrangement of allylphosphites to allylphosphonates have been qualitatively correlated using the 1,2-biradical model for n,n* excited states and consideration of the effect on excited state eneregies and lifetimes of placing the
I M : Photoreactions of Compounds Containing Heteroatoms other than Oxygen
PhSe-SiPh2But-'
435
-
283
Br
PhSe- + Ph&iBut 436 437 I
439
PhSeSePh
ii
I
LSePh 441
c
442
=
n-bond in a small ring.344Irradiation of dimethyl 9-anthrylmethyl phosphite in benzene yields the corresponding dimethyl 9-anthrylmethylphosphonate which, on further irradiation either in solution or in the solid state, undergoes HT 9,lOanthracene-type ph~todimerisation.~~~ P
443
444
445 R = Me, OAr; Ar = Inaphthyl
9,lO-DCA sensitisation of tri- I-naphthyl phosphate or di- 1-naphthyl methylphosphonate results in formation of 1,l'-binaphthyl. The reaction occurs only in compounds with at least two naphthyl substituents linked by an 0-P(0)-0chain. Reaction involves intramolecular face-to-face dimerisation of the two naphthyl units within the radical cation (445), followed by elimination of the 1,l'binaphthyl radical cation, which is subsequently reduced by the DCA radical anion.346 In a related reaction DCA-sensitisation of bis(3,4-methylenedioxyphenyl) methylphosphonate in acetonitrile gives 2-(3,4methylenedioxyphenyl)4,5-methylenedioxyphenyl methylphosphonate whereas direct irradiation in methanol gives bis(3,4-methylenedioxy)biphenyl as an additional product.347 In contrast to product formation by thermal extrusion of molecular nitrogen from the 4-phosphapyrazolines (446),photoproduct formation results in deepseated skeletal rearrangements. Irradiation of the 5-alkylidene derivatives yields the azomethineimines (447),which are spectroscopicallydetectable and thermally stable in solution. Continued irradiation converts (447)into (449) which opens to give (451). In the case of the 5-arylidene derivative, the ring-contracted product (448)is converted to primary photoproduct (450) which aromatises on standing to give (452).348 31P NMR has been used to observe the E,Z-photoisomerisation of phosphaethenes having more than one C=P group attached to a benzene ring.
284
Photochemistry Ar
Ar
Ar Ph
-
Ph
OSiR3
N=N
,
O-
I SiR3 449
R3Si 447 R' = CMe3,l-adamantyl 448 Ri = 4-MeOC6H4
446 Ar = 2,4,6-Me3CsH2, R = CHMe2
I
Ph
I Ph
Ar
At'
I
Ph R&iO
Ar
0 450
1
R1
451
H-shift
Ph R3Si0 452
E,E- 1,4- (453) and E,E-1,3(454) disubstituted benzenes appear to isomerise directly to the Z,Z-isomers to yield a photostationary state with an E,E-: Z,Zratio of 1:2 in each case. In contrast the E,E- 1,2-isomer (455) appears to reach a photostationary state involving only the E,E- and E , Z - i s ~ m e r sBoth . ~ ~ ~(2,4,6trimethylbenzoy1)diphenylphosphine oxide and bis(2,6-dimethoxybenzoyl)-2,4,4trimethyl-pentylphosphine oxide undergo a-cleavage to produce benzoyl and P-centred radicals mainly from their triplet excited states. Investigations on the nanosecond and picosecond timescales reveal that the rate of a-cleavage is of the same order or faster than the rate of intersystem crossing, analogous to the well investigated photochemistry of dibenzyl ketone.350 I
HYp
Me I
Other Elements - Further investigations of the benzophenone sensitised reactions of methyl-substituted selenophenes and tellurophenes with a range of maleic anhydride derivatives have been reported.351Cleavage of the acyl-tellurium 4.3
IIl6: Photoreactions of Compounh Containing Heteroatoms other than Oxygen
285
bond on photolysis of PhTeCOOCH(C8H 17)CH2CH2SeCH2Ph followed by cyclisation of the resulting oxyacyl radical yields the 3-oxaselenan-2-one derivative (456) in high yield. Attempted cyclisations to form larger rings have been unsuccessful.352Cycloalkyl radicals, generated by photolysis of cycloalkyl aryl tellurides in the presence of N-acetoxy-2-thiopyridone, react with protonated electron-deficient heteroaromatic bases to give the corresponding cycloalkylated heteroaromatic derivatives. For example 3-(benzyloxymethyl)cyclobutyl 4-methoxyphenyltelluride and 4-methyquinolinium trifluoroacetate yield a 1:1 mixture of cis- and trans-(457) in 68% yield.353The 1,3-stannyl photorearrangements of E-cinnamyl(tripheny1)stannane and E-cinnamyl(trialky1)stannanes to the corresponding branched allylstannanes occur intramolecularly via cinnamyl n,n* excitation in competition with homolysis of the (cinnamy1)C-Sn bond. But-2enyl(tripheny1)stannane and but-2-enyl(dibutyl)phenylstannane undergo the 1,3rearrangement via excitation of a phenyl group on the tin.354 References 1. 2. 3. 4. 5. 6 7. 8. 9. 10. 11. 12. 13. 14.
A. Weedon, Adv. Photochem., 1997,22,229. W. S . Jencks, D. D. Gregory, Y. Guo, W. Lee and T. Tetzlaff, Mol. Supramol. Photochem , 1997, I, 1. J. W. Pavlik, Mol. Supramol. Photochem., 1997,1, 57. P. Margaretha, Mol. Supramol. Photochem., 1997,1,85. J. S . D. Kumar and S. Das, Res. Chem. Zntermed, 1997,23,755. A. Kitamura, N. Miyagawa and T. Karatsu, Yuki Gosei Kugaku Kyokaishi, 1997,55, 678 (Chem. Abstr., 1997,127,205 184a). S. Fukuzumi, Res. Chem. Intermed, 1997,23,519. 0.Pieroni, A. Fissi and G. Popova, Prog. Polym. Sci., 1998,23,81. M. Irie and K. Uchida, Bull. Chem. SOC.Jpn., 1998,71,985. M. Sisido, A h . Photochem, 1997,22, 197. M. D’Auria, Targets Heterocycl. Syst., 1997, I, 277. Y. Kubo, Kokagaku, 1998,27,10 (Chem. Abstr., 1998,128,3082482). H. Hiratsuka, Bunko Kenkyu, 1997,46,167 (Chem. Abstr., 1997,127,248138f). I. K. Lednev, T.-Q. Ye, R. E.Hester and J. N. Moore, J, Phys. Chem. A , 1997, 101,
4966.
15. 16. 17. 18. 19. 20. 21. 22. 23.
Y. Yang and T. Arai, Tetrahedron Lett., 1998,39,2617. E. J. Shin, E. Y.Bae, S. H. Kim, H. K. Kang and S. C. Shim, J. Photochem.
Photobiol. A: Chem., 1997,107, 137. E. J. Shin and S. W .Choi, J. Photochem. Photobiol. A: Chem., 1998,114,23. A. C . Benniston, A. Harriman and C. McAvoy, J. Chem. SOC.,Faraday Trans., 1997, 93,3653. W . Hu, C. Werner and M.Hesse, Helv. Chim. Acta, 1998,81,342.
R. E. Martin, J. Bartek, F. Diederich, R. R.Tykwinski, E. C. Meister, A. Hilger and H. P. Liithi, J. Chem. SOC.,Perkin Trans. 2,1998,233. A. Kpissay, C. N. Kuhl, T. Mohammad, K. Haber and H. Morrison, Tetrahedron
Lett., 1997,38,8435. H. Goerner, Ber. Bunsen-Ges,, 1998,102,726. M. Garavelli, P. Celani, F. Bernardi, M. A. Robb and M. Olivucci, J. Am. Chem. Soc., 1997,119,6891.
286
Photochemistry
24.
M. Garavelli, F. Bernardi, P. Celani, M.A. Robb and M. Olivucci, J. Photochem. Photobiol. A: Chem., 1998,114, 109. M. Garavelli, T. Vreven, P. Celani, F. Bernardi, M, A. Robb and M. Olivucci, J. Am. Chem. SOC.,1998,120,1285. T. Arai, Y. Furuya, H. Kawashima and K. Tokumaru, J. Photochem. Photobiol. A: Chem., 1997,103,85. C . J. Groenenboom, H. J. Hageman, P. Oosterhoff, T. Overeem and J. Verbeek, J. Photochem. Photobiol. A: Chem., 1997,107,26 1. R. J. Olsen, J. Photochem. Photobiol. A: Chem., 1997,103,91. S. Mukherjee and S. C. b r a , J. Photochem. Photobiol. A: Chem, 1998,113,23. J. Wachtveitl, T. NPgele, B. Puell, W. Zinth, M. Kruger, S. Rudolph-Whner, D. Oesterhelt and L. Moroder, J. Photochem. Photobiol. A: Chem., 1997,105,283. H. Shinmori, M. Takeuchi and S. Shinkai, J. Chem. SOC.,Perkin Trans. 2,1998,847. R. Tahara, T. Morozumi, H. Nakamura and M. Shimomura, J. Phys. Chem. B, 1997,101,7736. M . Saadioui, N. Reynier, J.-F. Dozol, Z. Asfari and J. Vicens, J. Inclusion Phenom. Mol. Recognit. Chem., 1997,29. 153. Y. Q. Wang, H. Z. Yu, Y. Luo, C. X. Zhao and Z. F. Liu, J. Electroanal. Chem., 1997,438, 127. L. M. Goldenberg, J. F. Biernat and M. C. Petty, Langmuir, 1998, 14, 1236. X. Song, J. Perlstein and D. G. Whitten, J. Am. Chem. SOC.,1997,119,9144. R. A. Moss and W. Jiang, Langmuir, 1997,13,4498. T. Nagasaki, A, Noguchi, T. Matsumoto, S. Tamagaki and K. Ogino, An. Quim. Int. Ed., 1997,93, 341. R. A. Odum and B. Schmall, J. Chem. Res. (S), 1997,276. C. J. Aucken, F. J. Leeper and A. R. Battersby, J. Chem. SOC.,Perkin Trans. I , 1997, 2099. Z.-N. Huang, S. Jin, Y. Ming and M. Fan, Mol. Cryst. Liq. Cryst., 1997,297,99. M. Irie, T. Lifia and K. Uchida, MoZ. Cryst. Liq. Cryst., 1997,297,81. K. Uchida, T. Ishikawa, M. Takeshita and M. hie, Tetrahedron, 1998,54,6627. M. Takeshita, C. N. Choi and M. Irie, Chem. Commun., 1997,2265. M. Takeshita and M. Irie, TetrahedronLett., 1998,39,613. S. H. Kawai, TetrahedronLett., 1998,39,4445. H.-G. Cho and B . 4 . Cheong, Bull. Korean Chem. SOC.,1998,19,308. A. V. Metelitsa, M. I. Knyazhansky, E. A. Medyantseva, 0. T. Liashik, S. M. Aldoshin and V. I. Minkin, Mol. Cryst. Liq. Cryst., 1997,297,93. Y. Yokoyama, S. Uchida, Y. Shimin! and Y. Yokoyama, Mol. C r y t . Liq. Cryst., 1997,297,85. H. G. Heller, D. Hughes, M. B. Hursthouse and K. S. V. Koh, Chem. Commun., 1994,27 13. H. G. Heller, K. Koh, M. Kose and N. Rowles, Mol. Cryst. Liq. Cryst., 1997, 297, 73. L. Yu, D. Zhiu and M. Fan, Mol. Cryst. Liq. Cryst., 1997,297, 107. F. J. Hughes, U. S. Patent, 1997, US 5679805 A; M. Melzig and H. Zinner, U. S. Patent, 1997, US 5645768 A; A. Kumar, D. B. Knowles and B. Van Gemert, 1997, PCT Int. Appl., WO 97 21,689; S. Yoshimoto and Y. Onishi, Jpn. Kokai Tokkyo Koho, 1997, JP 09,323,990; A. Kumar, U. S. Patent, 1997, US 5698141 A; M. Tanaka, T. Aono, M. Satomura and Y. Ichijima, Jpn. Kokai Tokkyo Koho, 1997, JP 09,241,263; K. Chamontin, V. Lokshin, A. Samat and R. Guglielmetti, PCT Int. Appl., WO 98 04,563.
25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48.
49. 50.
51. 52. 53.
1116: Photoreactionsof Compoundr Containing Heteroatoms other than Oxygen
54. 55. 56. 57. 58. 59. 60.
61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80. 81. 82.
287
(a) H. Gorner, Chem. Phys., 1997, 222, 315; (6) A. K. Chibisov and H. Gorner, J. Photochem. Photobiol, A: Chem., 1997,105,261; (c) A. K. Chibisov and H. Gorner, J. Phys. Chem. A , 1997,101,4305; (4 H. Giirner, Chem. Phys. Lett., 1998,282,381. Y. Kawanishi, K. Seki, T. Tamaki, M. Sakuragi and Y. Suzuki, J. Photochem. Photobiol. A: Chem., 1997,109,237. X . D. Sun, M. G. Fan, X.J. Meng and E. T. Knobbe, J. Photochem. Photobiol. A: Chem., 1997,102,213. T. Horii, Y. Miyake, R. Nakao and Y. Abe, Chem. Lett., 1997,655. S. Delbaere, C. Bochu, N.Azaroual, G. Buntinx and G. Vermeersch, J. Chem. Soc., Perkin Trans. 2, 1997, 1499. V. Marevtsev and N. L. Zaichenko, J. Photochem. Photobiol. A: Chem., 1997, 104, 197. K. Chamontin, V. Lokshin, G. Garros, A. Samat and R. Guglielmetti, Mol. Cryst. Liq. Cryst., 1997,298, 7. A. V. Metelitsa, 0.A. Kozina, S. M.Aldoshin, B. S. Lukyanov, M. I. Knyazhansky andV. I. Minkin, Mol. Cryst. Liq. Cryst., 1997,297,227. L. V. Natarajan, T. M. Cooper and D. Stitzel, Mol. Cryst. Liq. Cryst., 1997, 298, 205. R. Guglielmetti, Mol. Cryst. Liq. Cryst., 1997,298, 13. H. Heller, J. R. Levell, D. E. Hibbs, D. S. Hughes and M. B. Hursthouse, Mol. Cryst. Liq. Cryst., 1997,297, 123. V. I. Minkin and V. N. Komissarov, Mol. Cryst. Liq. Cryst., 1997,2W, 205. A. V. Metelitsa, V. N. Komissarov M. I. Knyazhansky, and V. I. Minkin, Mol. Cryst. Liq. Cryst., 1997,297,219. A. V. Metelitsa, M. I. Knyazhansky, A. V. Koblik, L. A. Muradyan, S. M. Lukyanov and V. I. Minkin, Mol. Cryst. Liq. Cryst., 1997,297,227. S. Anguille, P. Brun and R. Guglielmetti, Heterocycl. Commun.,4,63. C. Salemi-Delvaux, G. Giwti and R. Guglielmetti, Mol. Cryst. Liq. Cryst., 1997, 2w, 53. M. H. Deniel, J. Tixier, D. Lavabre, J. C. Micheau and H. Durr, Mol. Cryst. Liq. Cryst., 1997,298, 129. H. Blesinger, P. Scheidhauer, H. DOrr, V. Wintgens, P. Valat and J. Kossanyi, J. Org. Chem., 1998,63,990. N. Sertova, J.-M Nunzi, I. Petkov and T. Deligeorgiev, J. Photochem. Photobiol. A: Chem, 1998,112,187. I. Baraldi, S. Ghelli, Z. A. Krasnaya, F. Momicchioli, A. S. Tatikolov, D. Vanossi and G. Ponterini, J. Photochem. Photobiol. A: Chem., 1997,105,297. E. Ivakhnenko, N. I. Makarova, M. I. Knyazhansky, V. A. Bren, V. A. Chernoivanov, A. I. Shiff and G. S. Borodkin, Mol. Cryst. Liq. Cryst., 1997,297,233. K. Kobayashi, M. Iguchi, T. Imakubo, K. Iwata and H. Hamaguchi, Chem. Commun., 1998,763. J. H. Rigby and M. E. Mateo, J. Am. Chem. Soc., 1997,119, 12655. J.-K. Luo,R. F. Federspiel and R. N. Castle, J. Heterocycl. Chem., 1997,34, 1597. S . Arai, M. Ishikura and T. Yamagishi, J. Chem. Soc., Perkin Trans. I , 1998,1561. A. N. Frolov and N. I. Rtishchev, Russ. J. Org. Chem., 1997,33,246. M. Ibrahim-Ouali, M.-E. Sinbaldi, Y. Troin, D. Guillaume and J.-C. Gramain, Tetrahedron,1997,53, 16083, Y.-T. Park, N. W. Song, C.-G. Hwang, K.-W. Kim and D. Kim, J. Am. Gem. SOC., 1997,119,10677. G. Jones and X . Qian, J. Phys. Chem. A , 1998,102,2555.
288
Photochemistry
83.
U. Lindemann, G. Reck, D. Wulff-Molder and P. Wessig, Tetrahedron, 1998, 54,
84.
P. Wessig, J. Schwarz, D. Wulff-Molder and G. Reck, Monatsh. Chem., 1997, 128,
2529. 849.
85.
86. 87. 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 99. 100.
(a) T. Hasegawa, Y. Yamazaki and M. Yoshioka, J. Photosci., 1997, 4, 7; (b) T. Hasegawa, T. Ogawa, K. Miyata, A. Karakizawa, M. Komiyama, K. Nishizawa and M. Yoshioka, J. Chem. Soc., Perkin Trans. I , 1990,901. S. B. Rollins and R. M. Williams, Tetrahedron Lett., 1997,38,4033. L.-C. Wu, C. J. Cheer, G. Olovsson, J. R. Scheffer, J. Trotter, S.-L. Wang and F.-L. Liao, Tetruhedron Lett., 1997,38, 3135. T. Okano, H. Ishihara, N. Takakura, H. Tsuge, S. Eguchi and H. Kimoto, J. Urg. Chem., 1997,62,7192. F. D. Lewis, J. M. Wagner-Brennan and J. M. Denari, J. Photochem. Photobiol. A: Chem., 1998,112, 139. F. D. Lewis and S. G. Kultgen, J. Photochem. Photobiol. A: Chem., 1998,112,159. A. Sugimoto, C. Hayashi, Y. Omoto and K. Mizuno, Tetrahedron Lett., 1997, 38, 3239. U. C. Yoon, J. W. Kim, J. Y. Ryu, S. J. Cho, S. W. Oh and P. S. Mariano, J. Photochem. Photobiol. A: Chem., 1997,106,145. A. G. Griesbeck, J. Hirt, W. Kramer and P. Dallakian, Tetrahedron, 1998,54, 3169. B. M. Aveline, S. Matsugo and R. W. Redmond, J. Am. Chem. Soc., 1997, 119, 1 1785. H. Gorner, K.-D. Warzecha and M. Demuth, J. Phys. Chem. A , 1997,101,9964.
M. Suzuki, T. Ikeno, K. Osoda, K. Narasaka, T. Suenobu, S. Fukuzumi and A. Ishida, Bull. Chem. Soc. Jpn., 1997,70,2269. T. Tamai, N. Ichinose, T. Tanaka, T. Sasuga, I. Hashida and K. Mizuno, J. Urg. Chem., 1998,63,3204. C.-K. Sha, K. C. Santhosh, C.-T. Tseng and C.-T. Lin, Chem. Commun., 1998,397. Y. Blache, M.-E. Sinbaldi-Troin, A. Voldoire, 0. Chavignon, J.-C. Gramain, J.-C. Teulade and J.-P. Chapat, J. Org. Chem., 1997,62,8553. S. P. Gromov, 0. A. Federova, E. N. Ushakov, I. I. Baskin, A. V. Lindeman, E. V. Malysheva, T. A. Balashova, A. S. Arsen’ev and M. V. Alfimov, Russ. Chem. Bull., 1998,47,97.
W. Herrmann, S. Wehrle and G. Wenz, Chem. Commun., 1997,1709. T. Nakamura, K. Takagi, M. Itoh, K. Fujita, H. Katsu, T. Imae and Y. Sawaki, J. Chem. Soc.. Perkin Trans. 2, 1997,2751. 103. T. Nakamura, K. Takagi and Y. Sawaki, Bull. Chem. SOC,Jpn., 1998,71,909. 104. T. Suishu, S. Tsuru, T. Shimo and K. Somekawa, J. Heterocycl. Chem., 1997, 34, 101. 102.
1005.
105. 106. 107. 108. 109. 110.
111.
P. R.Dave, R. Duddu, J. Li, R. Surapaneni and R. Gilardi, Tetrahedron Lett., 1998, 39,548 1. M. D’Auria and R. Racioppi, J. Photochcm. Photobiol. A: Chem., 1998,112, 145. H. R. Memarian, M. M. Sadeghi and H. Aliyan, Indian J. Chem., 1998,37B, 219. N. Marubayashi, T. Ogawa, T. Hamasaki and N. Hirayama, J. Chem. Soc., Perkin Trans. 2, 1997, 1309. G. M. J. Schmidt, Pure Appl. Chem., 1971,27,647. N. Marubayashi, T. Ogawa, T. Hamasaki and N. Hirayama, Bull. Chem. Soc. Jpn., 1998,71, 321. T. Nozaki, M. Maeda, Y. Maeda and H. Kitano, J. Chem. Soc., Perkin Trans. 2, 1997,1217.
IIl4: Photoreactions of Compouncls Contuining Heteroatoms other than Oxygen
289
112. K. I. Booker-Milburn, S. Gulten and A. Sharp, Chem. Commun., 1997, 1385. 113. M. N. Wrobel and P. Margaretha, Chem. Commun., 1998,541. 114. T. Noh, D. Kim and Y.-J. Kim, J. Org. Chem., 1998,63, 1212. 115. J. D. Winkler, J. E. Stelmach, M. G. Siegel, N. Haddad, J. Axten and W. P. Dailey, Israel J. Chem., 1997,37,47. 116. G. Konishi, K. Chiyonobu, A. Sugimoto and K. Mizuno, Tetrahedron Lett., 1997, 38,5313. 117. D. L. Comins, Y. S. Lee and P. D. Boyle, TetrahedronLett., 1998,39,187. 118. H. Tsujishima, K.Nakatani, K. Shimamoto, Y. Shigeri, N. Yumoto and Y. Ohfune, Tetrahedron Lett., 1998,39, 1 193. 119. M. N. Wrobel and P. Margaretha, J. Photochem. Photobiol. A: Chem., 1997,105,35. 120. A. Hilgeroth, Chem. Lett., 1997, 1269. 121. T. Nakamura, K. Takagi and Y.Sawaki, Bull. Chem. SOC.Jpn., 1998,71,419. 122. M. Yasuda, Y. Nishinaka, T. Nakazono, T. Hamasaki, N. Nakamura, T. Shiragami, C. Pac and K. Shima, Photochem. Photobiol., 1998,67,192. 123. C. Jeandon, R. Constien, V. Sinnwell and P. Margaretha, Helv. Chim. Actu, 1998, 81, 303. 124. M. Sakamoto, M. Takahashi, T. Fujita, S. Watanabe, T. Nishio, I. Iida and H. Aoyama, J. Org. Chem., 1997,62,6298. 125. G. S. Han and S . C. Shim, Photochem. Photobiol,, 1998,67,84. 126. A. G. Griesbeck, S. Buhr and J. Lex, TetrahedronLett., 1998,39,2535. 127. H. Koshima, T. Nakagawa and T. Matsuura, TetrahedronLett., 1997,38,6063. 128. H. Koshima, Y. Wang, T. Matsuura, I. Miyahara, H. Mizutani, K. Hirotsu, T. Asahi and H. Masuhara, J. Chem. Soc., Perkin Trans.2,1997,1217. 129. S . Lahlou, N. Bitit and J.-P.Desvergne, J. Chem. Res. ( S ) , 1998,302. 130. J. H. R. Tucker, H.Bouas-Laurent, P. Marsau, S. W.Riley and J.-P. Desvergne, Chem. Commun., 1997,1165. 131. R . N. Warrener, M.Golic and D. N. Butler, TetrahedronLett., 1998,39,4717. 132. C. Lehnberger, D. Scheller and T. Wolff, Heferocycles, 1997,45,2033. 133. S. Andresen and P. Margaretha, J. Photochem. Photobiol. A: Chem., 1998,112, 135. 134. Y. Ito and S. Endo, J. Am. Chem. Soc., 1997,119,5974. 135. P. Clivio, D. Guillaume, M.-T. Adeline, J. Hamon, C. Riche and J.-L. Fourrey, J. Am. Chem. Soc., 1998,120, 1 157. 136. I. Saito, M. Takayama, H. Sugiyama and T. Nakamura, J. Photochem. Photobiol. A: Chem., 1997,106,141. 137. D. N. Nikogosyan and H. Gorner, Biol. Chem., 1997,378,1349. 138. (a) K. Ohkura, Y. Noguchi and K.-I. Seki, Heterocycles, 1997, 45, 141; (6) K. Ohkura, Y. Noguchi and K.-I. Seki, Heterocycles, 1998,47,429. 139. M. Kotera, K. Ishii, 0. Tamura and M. Sakamoto, J. Chem. Soc., Perkin Trans. I , 1998,313. 140. C. Gaebert and J. Mattay, Tetrahedron, 1997,53, 14297. 141. E. Albrecht, J. Mattay and S . Steenken, J. Am. Chem. Soc., 1997,119, 11605. 142. M. Fagnoni, M. Mella and A. Albini, J. Phys. Org. Chem., 1997,10, 777. 143. Y. Ming, Z. Huang, M. Fan, B. Xu, S. Jin and S . Yao, Sci. in China (Ser. B ) , 1997, 40,373. 144. F. Wang, Y. Li, X.Li and J. Zhang, Res. Chem. Intermed, 1998,2467. 145. T. Goto and Y.Tashiro, J. Luminescence, 1997,72-74,921. 146. A. Elmali and Y. Elerman, J. Mol. Struct., 1998,442,31. 147. A. 0. Doroshenko, E. A. Posokhov, V. M. Shershukov, V. G. Mitina and 0 . A. Ponomarev, High Energy Chem., 1997,31,388.
290
Photochemistry
148. M. Moriyama, Y. Kawakami, S. Tobita and H. Shizuka, Chem. Phys., 1998,231,205. 149. S . Santra and S. K. Dogra, Chem. Phys., 1998,231,285. 150. M. E. Kletskii, A. A. Millov, A. V. Metelitsa and M. I. Knyazhansky, J. Photochem Photobiol. A: Chem., 1997,110,267. 151. G. Wenska, B. Skalski, M. Insinska, S. Paszyc and R. E. Verrall, J. Photochem. Photobiol. A: Chem., 1997,108, 135. 152. J . R. Scheffer and H. Ihmels, Liebigs AnnJRecueil, 1997, 1925. 153. V. Nair, G. Anilkumar, J. Prabhakaran, D. Maliakal, G. E. Eigendorf and P. G. Willard, J. Photochem. Photobiol. A: Chem., 1997,111,57. 154. D. Armesto, 0.Caballero and U. Amador, J. Am. Chem Soc., 1997,119,12659. 155. D. Armesto, A. Albert, F. H. Cano, N. Martin, A. Ramos, M. Rodriguez, J. L. Segura and C. Seoane, J. Chem. Soc., Perkin Trans. I , 1997,3401. 156. F. Scavarda, F. Bonnichon, C. Richard and G. Grabner, New J. Chem., 1997, 21, 1119. 157. 0. Cullmann, M. Vogtle, F, Stelzer and H. Prinzbach, Tetrahedron Lett., 1998, 39, 2303. 158. I. V. Nechepurenko, 0. P. Petrenko, I. A. Grigor'ev and L. B. Volodarskii, Russ. J. Org. Chem., 1997,33,705. 159. A. V. El'tsov, A. V. Selitrenikov and N. I. Rtishchev, Russ. J. Gen. Chem., 1997,67, 285. 160. K . Kubo, M. Koshiba, H. Hoshina and T. Sakurai, Heterocycles, 1998,48,25. 161. S. M. Bonesi and R. Erra-Balsells, J. Photochem. Photobiol. A: Chem., 1997, 110, 271. 162. J. W. Pavlik and N. Kebede, J. Org. Chem., 1997,62,8325. 163. 0.E. Edwards, G. Grue-Serensen and B. A. Blackwell, Can. J. Chem., 1997,75,857. 164. T. Kaneko, K. Kubo and T. Sakurai, TetrahedronLett., 1997,38,4779. 165. J. H. Hwu, C. S. Yau, S.-C. Tsay and T.4. Ho, TetrahedronLett., 1997,38,9001. 166. M. G. Siskos, A. K. Zarkadis, S. Steenken, N. Karakostas and S. K. Garas, J. Org. Chem., 1998,63,325 1. 167. N. Vivona, S. Buscemi, S. Asta and T. Caronna, Tetrahedron, 1997,53, 12629. 168. H. J. P. de Lijser and D. R.Arnold, J. Org. Chem., 1997,62,8432. 169. D. R. Arnold, K. A. McManus and M. S. W. Chan, Can.J. Chem., 1997,75,1055. 170. M. S . W. Chan and D. R. Arnold, Can. J. Chem., 1997,75,1810. 171. T. Herbertz, F. Blume and H. D. Roth, J. Am. Chem. SOC.,1998,120,4591. 172. H. Ishii, T. Hirano, S. Maki, H. Niwa and M. Ohashi, Tetrahedron Lett., 1998, 39, 2791. 173. K. Homma and S. Yamada, Chem. Pharm. Bull., 1997,45,1198. 174. K. Fujimoto, H. Sugiyama and I. Saito, TetrahedronLett., 1998,39,2137. 175. B. Li, Y.-C. Liu and Q.-X. Guo, J. Photochem. Photobiol. A: Chem., 1997,103, 101. 176. H. Weng and H. D. Roth, J. Phys. Org. Chem., 1998,11, 101. 177. J . Lee, J. S. U, S. C.Blackstock and J. K . Cha, J. Am. Chem. SOC.,1997,119, 10241. 178. L. Chen, L. Lucia and D. G. Whitten, J. Am. Chem. SOC.,1998,120,439. 179. W. Weigel and H.-G, Henning, Chem. Commun., 1997,1893. 180. K. Nakatani, N. Higashida and A. Saito, TetrahedronLett., 1997,38,5005. 181. G. Venkateshwarlu and A. K. Murthy, J. Indian Chem. SOC.,1997,74,648. 182. K. H. Ang and R. H. Prager, Aust. J. Chem., 1998,51,483. 183. R. H. Prager, J. A. Smith, B. Weber and C. M. Williams, J. Chem. Soc., Perkin Truns. I , 1997,2665. 184. R. H. Prager, M. R. Taylor and C. M. Williams, J. Chem. Soc., Perkin Trans. I , 1997,2673.
M6: Photoreactions of CompounciS Containing Heteroatoms other than Oxygen
29 1
H. J. Hageman, Macromol. Rapid Commun., 1997,18,442. P. S. Engel, S. L. He and W. B. Smith, J. Am. Chem SOC.,1997,119,6059. S. Auricchio, A. Selva and A. M. Truscello, Tetrahedron, 1997,53, 17407. W. M. Nau, G. Greiner, J. Wall, H. Rau, M. Olivucci and M. A. Robb, Angew. Chem., Int. Ed Engl., 1998,37,98. 189. W . Adam, J. N. Moorthy, W. M. Nau and J. C. Scaiano, J. Am. Chem. SOC.,1997, 185. 186. 187. 188.
119,6749.
W . Adam, J. Moorthy, W.M.Nau and J. C. Scaiano, J. Org. Chem., 1997,62,8082. N. Yamamoto, M.Olivucci, P. Celani, F. Bernardi and M. A. Robb, J. Am. Chem. SOC.,1998,120,239 1. 192, N. Miyagawa, T. Karatsu and A. Kitamura, Chem. Lert., 1997, 1005. 193. S.-J. Lin, S.-Y. Jiang, T.-C. Huang, P. Kao, P.-F. Tsai, H. Takeshita, Y . 4 . Lin and T. Nozoe, Heterocycles, 1997,45, 1879. 194. Y.-S. Lin, S.-Y. Jiang, T.-C. Huang, S.-J. Lin and Y.L. Chow, J. Org. Chem., 1998, 190. 191.
195. 196. 197. 198. 199. 200. 201. 202. 203. 204. 205. 206. 207.
63,3364.
D. Kosynkin, T. M. Bockman and J. K.Kochi, J. Am. Chem SOC.,1997,119,4846. A. Albini, G. Bettinetti and G. Minoli, J. Am. Chem. SOC.,1997, 119,7308. E. Leyva and R. Sagredo, Tetrahedron, 1998,54,7367. M. Cano, G. FabriAs, F. Camps and J. Joglar, TetrahedronLett., 1998,39, 1079. D. Donati, S. Fusi and F. Ponticelli, J. Chem. Research ( S ) , 1997, 170. D. Chiapperino and D. E. Falvey, J. Phys. Org. Chem., 1997,10,917. J. Kalvoda, J. Grob, M. BjelakoviC, L. Lorenc and M. Lj. MihailoviC, Helv. Chim. Acta, 1997,80, 1221. L. Eberson, M. P. Hartshorn and 0.Persson, Acta Chem Scand., 1998,52,745. L. Eberson, M. P. Hartshorn and 0.Persson, Acta Chem. Scand., 1998,52,751. U. Berg, C. P. Butts, L. Eberson, M. P. Hartshorn and 0. Persson, Acta Chem. Scand, 1998,52,761. C. P.Butts, L. Eberson, M. P. Hattshorn, 0. Persson, R. S. Thompson and W. T. Robinson, Acta Chem. Scand, 1997,51,1066. C. P. Butts, L. Eberson, R. Gonzhles-Luque, C. M. Hartshorn, M. P. Hartshorn, M. Merchan, W. T. Robinson, B. 0. Roos, C. Vallance and B. R. Wood, Acta Chem Scand., 1997,51,984. C. P. Butts, L. Eberson, M. P. Hartshorn and 0. Persson, Acta Chem. Scad., 1997, 51,718.
208.
209. 210. 21 1. 212.
W . Meiderer and S.Eisele, Ger. Offen., 1997, DE 19,620,170; R. P. Haugland and K. R. Gee, U. S. Patent, 1997, US 5,635,608; F. Yagihashi, A. Kiyomori, T. Iwasaki and J. Hatakeyama, Jpn. Kokai Tokkyo Koho, 1998, JP 10 77,264, C. P. Holmes, U. S. Patent, 1998, US 5,739,386; S. Watanabe and M. Iwamura, J. Org. Chem., 1997,62,8616. R. Reinhard and B. F. Schmidt, J. Org. Chem., 1998,63,2434. L. Peng, J. Win and M. Goeldner, TetrahedronLett., 1997,38,2961. J. Xia, X.Huang, R. Sreekumar and J. W. Walker, Bioorg. Med Chem. Lett., 1997,
213. 214. 215.
7, 1243. K.Burgess, S. E. Jacutin, D. Lim and A, Shitan, J. Org. Chem., 1997,62,5165. T. Voelker, T. Ewell, J. Joo and E. D. Edstrom, TetrahedronLett., 1998,39,359. K.Burgess, C. I. Martinez, D. H. Russell, H. Shin and A. J. Zhang, J. Org. Chem.,
216. 217. 218.
R. Rodebaugh, B. Fraser-Reid and H. M. Geysen, TetrahedronLett., 1997,38,7653. C. Dell’Aquila, J.-L. Imbach and B. Rayner, Tetrahedron Left.,1997,38,5289. G. C . R.Ellis-Davies, TetrahedronLett., 1998,39,953.
1997,62,5662.
292 219. 220. 221. 222. 223. 224. 225. 226. 227. 228. 229. 230. 231. 232. 233. 234. 235. 236. 237. 238. 239. 240. 241. 242. 243. 244. 245. 246. 247. 248. 249. 250. 251. 252. 253.
Photochemistry
K. N. Rajasekharan and A. Sulekha, Indian J. Chem., 1997,36B, 697. K. Kuldovk, A. Corval, H. P. Trommsdorff and J. M. Lehn, J. Phys. Chem. A, 1997, 101,6850. Y.-N. Lin, G.-Y. Jeng, T.-T. Chan, G.-F. Yen and Y.-G. Wong, J. Chin. Chem. SOC., 1998,45,313. A. Yoshida, K. Sato, T. Takui, K. Itoh, M. Fujisawa, M. Yagi and J. Higuchi, Mol. Cryst. Liq. Cryst., 1997,306, 373. H. Gorner, J. Photochem. Photobiol. A: Chem., 1998,112, 155. A. S. Dvornikov, I. V. Tomov, P. Chen and P. M. Rentzepis, Mol. Cryst. Liq. Cryst., 1997,298, 251. W. Zhang, Y. Su, L. Gan, J. Jiang and C. Huang, Chem. Lett., 1997,1007. L. Gan, J. Jiang, W. Zhang, Y. Su, Y. Shi, C. Huang, J. Pan, M. Lii and Y. Wu, J. Org. Chem., 1998,63,4240. F. S. Bavetta, T. Caronna, M. Pregnolato and M. Terreni, Tetrahedron Lett., 1997, 38,7793. S. E. Bottle, U. Chand and A. S. Micallef, Chem. Lett., 1997, 857. Y. Ohba, K. Kubo and T. Sakurai, J. Phorochem. Photobiol. A: Chem., 1998, 113, 45. M. Mella, M. Fagnoni, G. Viscardi, P. Savarino, E. Elisei and A. Albini, J. Photochem. Photobiol. A: Chem., 1997, 108, 143. H. Wang, R. E. Partch and Y. Li, J. Org. Chem., 1997,62,5222. J. L. Ferry and W. H. Glaze, J. Phys. Chem. B, 1998,102,2239. A. Kumar, S. Kumar and D. P. S. Negi, J. Chem. Res. ( S ) , 1998,54. A. Kumar and S. Kumar, J. Phys. Org. Chem., 1998,11,277. M. D’Auria, E. De Luca, G. Mauriello, R. Racioppi and G. Sleiter, J. Chem. Soc., Perkin Trans. I , 1997,2369. M. D’Auria, E. De Luca, G. Mauriello and R. Racioppi, J. Chem. SOC.,Perkin Trans. I , 1998,271. M. D’Auria, Heterocycles, 1997,45, 1775. U. C. Yoon, J. H. Kim, S. J. Lee, H. J. Kim, S. W. Oh and W. W. Park, J. Korean Chem. Soc., 1997,41,666. A. M. Sarker, Y. Kaneko, A. V. Nikolaitchik and D. C. Neckers, J. Phys. Chem. A, 1998,102,5375. F. Uddin, I. M. Adhami and M. A. Yousufzai, J. Saudi Chem. SOC.,1998,2,47. V. Faure and P. Boule, Toxicol. Environ. Chem., 1997,63, 171. K. Nord, H. Andersen and H. Hanne, Drug Stab., 1997,1,243. H. H. Tonneswen, G. Skrede and B. K. Martinsen, Drug Stab., 1997,1,249. S . W. Baertschi, Drug Stab., 1997, 1, 193. U. Raschke, G. Werner, H. Wilde and U. Stottmeister, Chemosphere, 1998,36,1745. W.-U. Palm, M. Millet and C. Zetzsch, Chemosphere, 1997,35, 11 17. K. Nord, A.-L. Orsteen, J. Karlsen and H. H. Tsnnesen, Pharmazie, 1997,52,598. S. Kristensen, K. Nord, A.-L. Orsteen and H. H. Tsnnesen, Pharmazie, 1998,53,98. Y. Kawai and K. Matsubayashi, Chem. Pharm. Bull., 1998,46, 13 1 . K. Torniainen, C.-P. Askolin and J. Mattinen, J. Pharm. Biomed. Anal., 1997, 16, 439. A. Burdzy, B. Skalski, S. Paszyc, Z. Gdaniec and R. W . Adamiak, Nucleosides and Nucleotides, 1998, 17, 143. F. D. Lewis, J. M. Wagner-Brennan and J. M. Denari, J. Phys. Chem. A , 1998,102, 519. S. Li,. H. Tian, Q. Zhou, Z. Li and H. Xu, Chin. Sci. Bull., 1997,42, 1619.
IIl4: Photoreactions of Compound Containing Heteroatoms other than Oxygen 254. 255. 256. 257. 258. 259. 260. 261. 262. 263. 264. 265. 266. 267. 268. 269. 270. 271. 272. 273. 274. 275. 276. 277. 278. 279. 280. 281. 282. 283. 284.
293
S. Depaemelaere, F. C. de Schryver and J. W. Verhoeven, J. Phys. Chem. A, 1998, 102,2109. E. Kaganer, E. Joselevich, I. Willner, Z. Chen, M. J. Gunter, T. P. Gayness and M. R . Johnson, J. Phys. Chem. B, 1998,102,1159. H. A. Staab, A. Feurer, C. Krieger and A. S. Kurnar, Liebigs AndRecueil, 1997, 232 1. H. A. Staab, R. Hauck and B. Popp, Eur. J. Org. Chem., 1998,631. P. K. Malinen, A. Y. Tauber, J. Helaja and P. H. Hynninen, Liebigs Ann.lRecuei1, 1997,1801. M. R. Roest, A. M. Oliver, M. N. Paddon-Row and J. W. Verhoeven, J. Phys. Chem. A, 1997,101,4867. G. Jones, D.-X. Yan, S. R. Greenfield, D. J. Gosztola and M. R. Wasielewski, J. Phys. Chem. A, 1997,101,4939. H. Zhang, M. Zhang, and T. Shen, Science in China (Ser. B), 1997,40,449. H. Zhang, M. Zhang and T. Shen, J. Photochem. Photobiol. A: Chem., 1997,103,63. Q. Tan, D. Kuciauskas, S. Lin, S. Stone, A. L. Moore, T. A. Moore and D. Gust, J. Phys. Chem. B, 1997,101,5214. A. Knorr, E. Galoppini and M. A. Fox, J. Phys. Org. Chem., 1997,10,484. M. R . Bryce, E. Chinarro, A. Green, N. Martin, A. J. Moore, L. Sanchez and C. Seoane, Synth. Met., 1997,86, 1857. A. S. Batsanov, M. R. Bryce, M. A. Coffin, A, Green, R. E. Hester, J. A. K. Howard, I. K. Lednev, N. Martin, A. J. Moore, J. N. Moore, E. Orti, L. Sinchez M. Saviron, P. M. Viruela, R. Viruela and T.-Q. Ye, Chem. Eur. J., 1998,4,2580. Y. Yamashita, M. Maehara and S. Hayashi, Kenkyu Kiyo - Nihon Duiguku Bunrigakubu Shizen Kagaku Kenkyusho, 1998, 33, 237 (Chem. Abstr., 1998, 129, 4345w). H. Morrison, Y. Lu and D. Carlson, J. Phys. Chem. A , 1998,102,5421. T . Y. Fu, J. R. Scheffer and J. Trotter, Acta Cryst., 1997, C53,1257. H. Aoyama, J. Chem Soc., Perkin Trans. I , 1997, 1851. T. Y.Fu, J. R. Scheffer and J. Trotter, Acta Cryst., 1998, C54, 103. G. Jayanthi, S. Muthusamy, R. Paramasivan, V. T. Ramakrishnan, N. K. Ramasamy and P. Ramamurthy, J. Org. Chem., 1997,62,5766. S . Hu and D. C. Neckers, Tetrahedron, 1997,53,7165. S. Hu and D. C. Neckers, J. Photochem. Photobiol. A: Chem., 1998,114,103. S. Hu and D. C. Neckers, J. Org. Chem., 1997,62,7827. Y. Yamazaki, T.Miyagawa and T. Hasegawa, J. Chem. Soc., Perkin Trans. 1, 1997, 2979. M. Ashram, D. 0. Miller, J. N. Bridson and P. E. Georghiou, J. Org. Chem., 1997, 62,6476. V. Baret, A. Gandini and E. Rousset, J. Photochem Photobiol. A: Chem., 1997,103, 169. X . Song, J. Perlstein and D. G. Whitten, J. Phys. Chem. A, 1998, 102,5440. S. Moller, D. WeiD and R. Beckert, Liebigs AnnJRecueil, 1997,2347. Y. Kaneko, S. Hu and D. C . Neckers, J. Photochem. Photobiol. A: Chem., 1998,114, 173. M. Szymanski, A. Maciejewski, J. Kozlowski and J. Koput, J. Phys. Chem. A, 1998, 102,677. J. Bethke, J. Kopf, P. Margaretha, B. Pignon, L. Dupont and L. E. Christiaens, Helv. Chim. Acta, 1997,80, 1865. C. P. Klaus and P. Margaretha, Liebigs Ann., 1996,291.
294
Photochemistry
285.
J. Bethke, A. Jakobs and P. Margaretha, J. Photochem. Photobiol. A: Chem., 1997, 104,83. D. Vedaldi, G. Piazza, S. Moro, S. Caffieri, G. Miolo, G. G. Aloisi, F. Elisei and F. Dall’Acqua, I! Farmaco, 1997,52,645. P. Clivio, J.-L. Fourrey and A. Favre, J. Am. Chem. Soc., 1991,113,5481. P. Clivio and J.-L. Fourrey, Tetrahedron Lett., 1998,39,275. C. Saintomk, P. Clivio, A. Favre and J.-L. Fourrey, J. Org. Chem., 1997,62,8125. T. Kataoka, T. Iwama and H. Matsumoto, Chem. Pharm. Bull., 1998,46, 151. M. Takahashi, T. Fujita, S. Watanabe and M. Sakamoto, J. Chem. Soc., Perkin Trans. 2,1998,487. T. Nishio, J. Chem. Soc., Perkin Trans. I , 1998,1007. L. X. Deng and A. G. Kutateladze, Tetrahedron Lett., 1997,38,7829. T. Fujii, E. Horn and N. Furukawa, Heteroatom Chem., 1998,9,29. H. Morita, H. Kamiyama, M. Kyotani, T. Fujii, T. Yoshimura, S. Ono and C. Shimasaki, Chem. Commun., 1997, 1347. H. Pirelahi, H. Rahmani, A. Mouradzadegun, A. Fathi and A. Moudjoodi, Phosphorus, Sulfur and Silicon, 1997,120 &121,403. H. Rahmani and H. Pirelahi, J. Photochem. Photobiol. A: Chem., 1997,111, 15. S. H. Bhatia, D. M. Buckley, R. W. McCabe, A. Avent, R. G. Brown and P. B. Hitchcock, J. Chem. Soc., Perkin Trans. I, 1998,569. Y . Guo, A. P. Darmanyan and W. S. Jenks, Tetrahedron Lett., 1997,38, 8619. C.-H. Tung and Y.-M. Ying, Res. Chem. Intermed, 1998,24,15. Z . Chi and Y. Wang, Jilin Daxue Ziran Kexue Xuebao, 1998, 100 (Chem. Abstr., 1998,12s,208451s). T. Kitamura, K. Morizane, H. Taniguchi and Y. Fujiwara, Tetrahedron Lett., 1997, 38,5157. R. Borah and J. C. Sarma, Indian J. Chem., 1997,36A&B, 533. S . Encinas, M. A. Miranda, G. Marconi and S. Monti, Photochem. Photobiol., 1998, 67,420. W. Adam, 0. Deeg and S. Weinkotz, J. Org. Chem., 1997,62,7084. M. D’Auria and V. Esposito, Gazz. Chim. Ital., 1997,127,471. A. Gaplovskjl, R. Hercek and P. Kurt%, Toxicol. Environ. Chem., 1997,64, 155. E. Purushothaman, Ind. J. Heterocyclic Chem., 1997,7,93. C. P. Butts, L. Eberson, M. P. Hartshorn, F. Radner, W. T. Robinson and B. R. Wood, Acta Chem. Scand., 1997,51,839. W. Adam, J. E. Argiiello and A. B. Pefiefiory, J. Org. Chem., 1998,63,3905. J. Andraos, G. G. Barclay, D. R. Medeiros, M. V. Baldovi, J. C. Scaiano and R. Sinta, Chem. Muter., 1998,10, 1694. H. A. Gaur, H. J. Hageman, P. Oosterhoff, T. Overeem, J. Verbeek and S. van der Werf, J. Photochem. Photobiol. A: Chem., 1997,104,53. S . Duan, E. R. Binkley and R. W. Binkley, J. Carbohydr. Chem., 1998,17, 391. I. Ono, S. Sato, K. Fukuda and T. Inayoshi, Bull. Chem. SOC.Jpn., 1997,70,2051. C. Dell’Erba, M. Novi, G. Petrillo and C. Tavani, Gazz. Chim. Ital., 1997,127,361. L. Rodriguez-Hahn, M. E. Manriquez, B. A. Frontana and J. Cardenas, An. Quim. Int. Ed., 1997,93,29 1. R. Akaba, M. Kamata, A. Koike, K.4. Mogi, Y. Kuriyama and H. Sakuragi, J. Phys. Org. Chem., 1997,10,861. M. Alam, M. Fujitsuka, A. Watanabe and 0. Ito, J. Phys. Chem. A , 1998,102, 1338. S. A. Bol’shakova, N. N. Vlasove, Y. N. Pozhidaev and M. G. Voronkov, Russ. J. Gen. Chem., 1997,67,712.
286. 287. 288. 289. 290. 291. 292. 293. 294. 295. 296. 297. 298. 299. 300. 301. 302. 303. 304. 305. 306. 307. 308. 309. 310. 31 1. 312. 313. 314. 315. 316. 317. 318. 319.
M6: Photoreactions of Compounds Containing Heteroatoms other than Oxygen
320. 321. 322. 323. 324. 325. 326. 327. 328. 329. 330. 331. 332. 333. 334. 335. 336. 337. 338. 339. 340. 341. 342. 343. 344. 345.
346. 347. 348. 349. 350. 351. 352. 353. 354.
295
M. A. Brook, C. Gottardo, S. Baldazzi and M. Mohamed, Tetrahedron Lett., 1997, 38,6997. G. Gutenberger, E. Steckhan and S. Blechert, Angew. Chem., Int. Ed. Engl., 1998,37, 660. M. Freccero, A. Pratt, A. Albini and C. Long, J. Am. Chem. SOC.,1998,120,284. L. Cermenati, C. Richter and A. Albini, Chem. Commun., 1998,805. M. C . Courtney, M. Mella and A. Albini, J. Chem. SOC.,Perkin Trans. 2,1997,1105. D. M. Amey, D. C. Blakemore, M. B. Drew, A. Gilbert and P. Heath, J. Photochem. Photobiol. A: Chem., 1997,102, 173. Y. Apeloig, D. Bravo-Zhivotovskii, H. Zharov, V. Panov, W. J. Leigh and G. W. Sluggett, J. Am. Chem. SOC.,1998, 120, 1398. C. Kerst, M. Byloos and W. J. Leigh, Can J. Chem., 1997,75,975. C. Kerst, R. Boukherroub and W. J. Leigh, J. Photochem Photobiol. A: Chem., 1997,110,243. M. Kato, S. Oba, R.Uesugi, S. Sumiishi, Y. Nakadaira, K. Tanaka and T. Takada, J. Chem. SOC.,Perkin Trans. 2,1997,1251. T. Kusukawa and W. Ando, J. Organometal. Chem., 1998,559,ll. S . C. Shim and S. K. Park, Bull. Korean Chem. SOC.,1998,19,686. C. Herst, R. Ruff010 and W.J. Leigh, Organometallics, 1997,16,5804. M. Weidenbruch, L. Kirmaier, H. Marsmann and P. G. Jones, Organometallics, 1997,16,3080. T. Hoshi, R. Shimada, C.Kabuto, T.Sanji and H. Sakurai, Chem. Lett., 1998,427. Y. Nakadaira, S. Kanouchi and H. Sakurai, J. Am. Chem. SOC.,1974,%, 5622. M. Kako, H. Takada and Y. Nakadaira, TetrahedronLett., 1997,38,3525. K. Mochida, M. Akazawa, M. Goto, A. Sekine, Y. Ohashi and Y. Nakadaira, Organometallics, 1998,17, 1782. K. Mochida, M. Akazawa, M.Goto, A. Sekine, Y. Ohashi and Y . Nakadaira, Bull. Chem SOC.Jpn., 1997,70,2249. M. Kako, M. Ninomiya and Y. Nakadaira, Chem. Commun., 1997,1373. T. Iwamoto and M. Kira, Chem. Lett., 1998,277. K . Mochida, H. Ginyama, M. Takahashi and M. Kira, J. Organometal. Chem., 1998,553, 163. G. Pandey, K. S. S. P.Rao, D. K. Palit and J. P. Mittal, J. Org. Chem, 1998,63,3968. G. S . Jeon and W.G. Bentrude, TetrahedronLett., 1998,39,927. Y. Huang and W.G. Bentrude, TetrahedronLett., 1997,38,6989. W. Bhanthumnavin, S. Ganapsthy, A. M. Arif and W . G. Bebtrude, Heteroatom Chem, 1998,9,155. M. Nakamura, R. Dohno and T. Majima, Chem. Commun., 1997,1291. Y . Okamoto, T. Tatsuno and S. Takamuku, Phosphorus, Sulfur and Silicon, 1996, 117, 129. B. Manz, J. Kerth and G. Maas, Chem. Eur. J. , 1998,4,903. H. Kawanami, K. Toyota and M. Yoshifuji, J, Organometal. Chem., 1997,535, 1. S. Jockusch, I. V. Koptyug, P. F. McGarry, G. W. Sluggett, N. J. Turro and D. M. Watkins, J. Am. Chem. Soc., 1997,119,11495. C . Rivas, F. Vargas, G. Aguiar, A. Torrealba and R. Machado, J. Photochem. Photobiol. A: Chem., 1997,104,53. M. A. Lucas and C.H. Schiesser, J. Org. Chem, 1998,63,3032. W . He, H. Togo, H. Ogawa and M.Yokoyama, Heteroatom Chem., 1997,8,411. A. Takuwa, T. Kanaue, K. Yamashita and Y. Nishigaichi, J. Chem. Soc., Perkin Trans. I , 1998, 1309.
7
Photoelimination BY IAN R. DUNKIN
1
Introduction
This chapter deals with photoinduced fragmentations of organic and selected organometallic compounds, in particular reactions accompanied by loss of small molecules such as nitrogen, carbon monoxide or carbon dioxide. Photodecompositions which produce two or more larger fragments and other miscellaneous photoeliminations are reviewed in the final section. Photofragmentations of carbonyl compounds, taking place by Norrish Type I and I1 processes, are discussed in Part 11, Chapter 1. A number of papers have appeared which are of general relevance to photoelimination chemistry. These include discussions of spin-orbit coupling in diradicals,' and theoretical models for the selectivity of triplet and singlet photoreactions.* 2
Elimination of Nitrogen from Azo Compounds and Analogues
The photofragmentation of azomethane has been studied theoretically by classical trajectories and surface hopping on ub initio potential energy surface^.^ There were two main conclusions. Firstly, internal conversion, SI+SO, is so efficient that fragmentation takes place almost exclusively on the ground state potential energy surface. It seems unlikely that intersystem crossing could compete with such fast internal conversion; thus there is probably no significant role for triplet states. Secondly, both C-N bonds are broken within a short time, of the order of 1 ps. The majority of trajectories show almost simultaneous bond breaking, but, even when the CH3NN' radical is formed, its lifetime is too short to permit experimental detection. This result is consistent with a concerted mechanism, which has already been deduced from molecular beam experiments. A comprehensive theoretical study has been made of the potential energy surfaces and reaction pathways of the singlet (SO, S1) and triplet (TI, T2) states associated with the photolysis of 2,3-diazabicyclo[2.2.l]hept-2-ene(1) (Scheme 1): The S1 (nn*), TI (nx*), and T2 (RX*) reaction paths for N2 elimination via CN cleavage to a diazenyl diradical(2), and for rearrangement to an azirane ( 5 ) by way of CC cleavage to a hydrazonyl diradical(4), have been investigated, as well as reaction pathways for cyclization and rearrangement of the I ,3cyclopentadienyldiradical Photochemistry, Volume 30 0The Royal Society of Chemistry, 1999
296
297
IIi7: Photoelimination
(3). The reactions evolve through a network of 18 ground and excited state intermediates, 17 transition structures and 10 'funnels', where internal conversion or intersystem crossing may occur. A stable excited state 3(n7t*)3(7m*) intermediate is proposed as the best candidate for the transient triplet intermediate observed experimentally.
0-@
(4)
Scheme 1
(5)
Photolysis of (E)-perfluoroazooctane with 185 nm light provides an efficient method for the perfluorooctylation of aromatic and heteroaromatic compounds, such as benzene, toluene, anisole, furan, thiophene and pyrr01e.~Reported yields are in the range 50-75%. Mechanistic studies based on measurements of quantum yield, dependence on light intensity and UV-visible absorption showed that (E)perfluoroazooctane is isomerized to the (&)-isomer by absorption of one photon, with subsequent extrusion of N2 on absorption of a second photon. Thermolysis of the y-azoperester, tBuN=NCMe2CH2CHzCO+Bu, produces the y-azoradical, t-BuN=NCMe2CH2CH2',which undergoes cyclization by attack of the radical centre on the azo linkage.6 In contrast, photolysis of this y-azoperester selectively cleaves the azo group, yielding the y-perester radical, * C M ~ ~ C H ~ C H ~ C O + B U , which undergoes intramolecular attack on the peroxide linkage to give tetrahydro-5,5-dimethyl-2-furanone. A number of annulated 5-alkylidene-4,5-dihydro1H-tetrazoles, such as (6, (R=H, Me) (Scheme 2), have been synthesized and a study made of their ph~tolyses.~ For example, photolysis of (6) in d8-toluene at -60°Cresults in extrusion of N2, giving annulated iminoaziridines (E- and 2-7)with exocyclic C=N- bonds. On thermolysis, the iminoaziridines undergo [2 + 11 cycloreversion into methyl isocyanide and cyclic imines (8, R = H, Me). Irradiation of the tricylic analogue (9) (Scheme 3) in 2-methyltetrahydrofuran or butyronitrile matrices at 77 K yields a triplet diradical, with a four-line ESR spectrum, which is assigned the structure (1 0), the first triplet diazatrimethylenemethaneto be reported. The chemistry of the photoactive diazosulfonate group (-N*SO<) and its applications in polymer chemistry have been reviewed by Nuyken and Voit in an article which also contains some experimental details.8 Polymer applications include photoresins, test stripes for assays of phenolic compounds, and photolabile surfactants. Novel polyesters with photosensitive backbones based on the
298
Photochemistry
(8)
+
,Me \
N=N
CN-Me
I
(6) (2-7) Scheme 2
Me
Jy&+-Jy& . . \
I
triazene unit (-N=N-N-) have been synthesized and shown to undergo fast and irreversible photocleavage? Radical intermediates in the photochemical and redox initiated decomposition of thioazo compounds (Ar-N2-SAr') have been studied by ESR and cyclovoltammetry;lo while a poly(alkylaryldiazosu1fide) has also been synthesized and its thermal and photochemical decomposition investigated by IR and UV-visible spectroscopy.'' Similar arylazo sulfides have been shown to act as arylating agents for the anions derived from active methylene compounds such as malononitrile and ethyl acetoacetate.12 Moderate to good yields are reported for this photochemically initiated SRN1 reaction.
3
Elimination of Nitrogen from D i m Compoundsand Diazirines
The photolysis of diazo compounds and the isomeric diazirines continues to attract a great deal of interest, ranging from fundamental theoretical studies to applications such as photoaffinity labelling.
3.1 Generation of Alkyl and Alicyclic Carbenes - A prompt, long-lived, red fluorescence has been observed in the photodissociation of jet-cooled diazirine, excited at the origin of the S0+SI transition (323 nm).13 This emission is attributed to electronically excited singlet methylene, CH2 ( ~ ' B I ) which , is also highly vibrationally excited, and which appears to be formed directly from the SI state of diazirine. Products from the photolysis (350 nm, 25°C) and pyrolysis (100 "C) of trans-3-(2-tert-butylcyclopropyl)-3H-diazirine(1 1) (Scheme 4) in CF2CICFCl2 (Freon-113) and in the presence of added tetramethylethylene (TME) have been compared for a range of concentrations of TME.14 In the absence of TME, the major product is the cyclobutene (12,44-64%), with smaller
IIl7: Photoelimination
299
amounts of (14) and halogenated products of solvent trapping also being formed. In the presence of TME, the adduct (13) is produced in yields up to 2637%. The yield of (13) increases smoothly with increasing concentration of TME, but, at the same time, the yield of the cyclobutene (12) is depressed by only a small amount (less than 7%). Clearly there are at least two reaction-pathways. In accord with a growing body of theoretical and experimental evidence, the authors postulate that diazirines open by C-N bond cleavage when activated, to give diazirinyl diradicals, which can then undergo ( i ) ring closure to reform the diazirines, (ii) formation of diazo compounds, (iii) cleavage to form carbenes and N2, or (iv) rearrangement to cyclobutenes in concert with nitrogen extrusion. Dimethylcarbene and its perdeuteriated isotopomer have been generated by laser flash photolysis and trapped as ylides by reaction with pyridine.I5 Values were obtained for the rate constants of reaction of the carbenes with pyridine and for the lifetimes of the carbenes in the absence of pyridine, and their associated Arrhenius parameters. The experimentally determined barrier to carbene rearrangement (10.7k0.2 kJ mol-’) is much less than that obtained from ab initio calculations ( 3 1rf: 8 kJ mol- I), suggesting that this process has a large component of quantum mechanical tunnelling.
Photolysis of the diazoazulenone (15) in the presence of azulene (16, R’= R2 = R3 = R4 = R5 = H) or azulene derivatives (16; R’ = R2 = R3 = R4 = R5 = Me; R’= R3 = H,R2 = R4 = R5= Me; R2= R4 = H, R’ = R5 = Me, R3 = CHMe2) affords 1,T-biazulene derivatives, which are otherwise difficult to obtain, in yields of nearly 90% or more.16 The analogous azulen-4-ones (17) R’ = R2 = CN; R’ = R2 = CO2Me; R’ = COZMe, R2 = CN) have been photolysed in cyclic ethers, such as THF and dioxane,” to give good yields of 2,4-polyetherbridged azulenes, e.g. (1 8). The reactions are initiated by electrophilic attack of the singlet state carbenes on the oxygen atoms of the solvent ethers, followed by one or two propagation steps and ring closure by phenolate attack. Photolysis of some related azulene-6-ones revealed a steric effect in the formation of the polyether-bridged products: a methoxycarbonyl substituent inhibited the ring forming reaction to a marked extent compared with a cyano group at the same position. The photolyses of three pbenzoquinone diazide carboxylic acids (19, R = H, Me, t-Bu) have been studied in low temperature matrices.” The general reaction pathway involves primary carbene formation, followed by secondary photodecarboxylation to yield 2,4-didehydrophenols (20), which could be observed directly by IR spectroscopy.
300
Photochemistry
R'
3.2 Generation of Aryl Carknes - Phenylcarbene, o-tolylcarbene and mesitylcarbene have been studied in laser flash photolysis experiments of the corresponding diazo precursors.20 Rates of reaction of the carbenes with pyridine and carbene lifetimes in the absence of pyridine were determined, while transient spectra were observed for both mesitylcarbene and its co-product, 3,5-dimethyl1,2-benzoquinodimethane.The latter does not seem to be formed from the carbene, but rather from hydrogen atom transfer in the excited state of the diazo precursor. 2-Hydroxyphenylcarbene (23) (Scheme 5) has been generated in argon matrices at 10 K from the masked precursor (21) by way of 2-hydroxyphenyldiazomethane (22), and the reactions monitored by IR spectroscopy.*' The carbene itself was not observed under these conditions, but underwent immediate ring closure to benzoxetene (26), which was found to exist in photoequilibrium with the quinonoid isomer (25). The identities of (25) and (26)were confirmed by their independent generation from the photolysis of benzofuranone (24). Ab initio calculations indicated that both (25) and (26) are true minima on the potential energy surface, and that the quinonoid isomer is more stable than benzoxetene by
CH=N' OH
Ph
h,>300nm ~
-Ph F
0:
CH=N;,
OH
h.>300nm, -N2
[UG OH
IIl7: Photoelimination
30 1
21 kJ mol-’. A brief review of this and related work with 2-aminophenylcarbene has been published.22 Fluorenylidene, generated by UV-irradiation of diazofluorene in benzene solution containing di-p-tolyl or di-p-anisyl disulfide, undergoes di-insertion into the S-S bonds of the disulfides to yield the corresponding 9,9’-bis(arylmercapto)bifluorenyls in moderate to good yields, accompanied by formation of 9,9’bi~(ary1mercapto)fluorenes.~~ Photolysis of 9-diazo-1-fluorenylmethanol (27) in benzene or acetonitrile gives the aldehyde (28) in yields of 95% or greater.24In methanol, trapping by the solvent of the intermediate carbene competes with formation of (28). Intramolecular hydrogen transfer in the triplet carbene derived from (27), leading initially to enol (29), is proposed as the mechanism for formation of the aldehyde.
Diazo(2-fury1)methaneand diazo(3-fury1)methanehave been photolysed in low temperature matrices, and rearrangements of the corresponding carbenes studied.25The carbene derived from diazo(2-fury1)methane ring opens to give (Z)-pent-2-en-4-yn-l-a1(30, R = H) (Scheme 6) in a clean reaction, while that derived from diazo(3-fury1)methane (31) (Scheme 6) yields (s-2)-(a-formy1)methylenecyclopropene (33) as the only detectable product, in a reaction which is proposed to involve cyclopropene (32) as an intermediate. 2-Furylchlorocarbene has been generated in low temperature matrices by photolysis of chloro-2furyldiazirine and observed directly by IR and UV-visible spectroscopy.26On secondary photolysis, the carbene ring opens to give the aldehyde acetylene (30) (R = C1) and its (E)-isomer.
Photolysis of a 1 : 1 complex of copper(I1) with 5-trimethylsilyl-l,3-phenylenebis[diazo(4-pyridyl)methane] produces a ferromagnetic chain with an alternating array of the 3d spins of Cu(I1) and the 2p spins of the quintet dicarbene~.~’ The diazirine radioligand (34) has been synthesized as a photoaffinity probe for NADHxbiquinone oxidoreductase, to help define the structure of the pyridabeninhibition site.28
Photochemistry
302
3.3 Photolysis of a-Diazo Carbonyl Compounds - Some recent advances in the matrix photochemistry of diazoketones, including some heterocyclic species, have been reviewed.29 Flash photolysis of 10-diazo-9(1OH)-phenanthrenone (35) in aqueous solution led to the detection of two transient species on the pathway to the final product, fluorene-9-carboxylic acid.30 These were identified, from solvent isotope effects and the nature of the observed acid-base catalysis, as fluorenylideneketene (36,X = CO) and the enol of fluorene-9-carboxylic acid (36, X = C(OH)2), formed by hydration of the ketene. In related studies, fluorenylideneketene was found to react with amines to give ylides as intermediates on the route to the amide final product^.^' The product distribution from the photochemical reactions of 2-diaz0-3-0~0-5,10,15,20-tetraphenylchlorins with alcohols strongly depends on the central metal ion of the irradiated diaz~ketones.~~
A guanine specific DNA cleavage by irradiation of dibenzoyldiazomethaneoligonucleotide conjugates has been reported.33 A selective photoaffinity ligand for the kainate class of amino acid receptors has been developed by replacing the isopropenyl side-chain of kainic acid with the CF3C(:N2)CO group, and this was shown to give efficient photo-induced crosslinking to the active site of the kainate class of glutamate receptor.34A tritium labelled 2 1-diazoprogesterone has been synthesized as a photoaffinity reagent for the mineralocortoid recept~r.~’ Diazoketones are incorporated in photosensitive compositions for fluorescent patterns, which are claimed to give vivid images without containing chromium cornand in photosensitive polymer compositions for manufacturing relief
pattern^.^'
4
Elimination of Nitrogen from Azides and Related Compounds
Compared with studies of aryl and heteroaryl azides, work on aliphatic azides remains uncommon. No doubt one reason for this is the generally lower stability of aliphatic azides. Perfiuoro(2-methyl-2-pentene) reacts with sodium azide at
303
IIl7: Photoelim inat ion
-10 "C to give perAuoro(3-azido-2-methyl-2-pentene) which is stable only at low temperature^.^^ Thermolysis at 0°C or photolysis of this azide in non-reactive solvents, such as CCl, or benzene, results in extrusion of N2 and formation of 3pentafluoroethyl-2,2-bis(trifluoromethyl)-2H-azirine, by ring closure of the corresponding nitrene. Photolysis at 248 nm of dimethylsilylazide (37) (Scheme 7) in argon matrices at 10 K produces 1,l-dimethylsilanimine (39) and 1-(methylsilyl)methaninime (4 l), as indicated by IR spectro~copy.~~ Neither the nitrene (38) nor the proposed silanimine intermediate (40) were observed directly, but the nitrene could be chemically trapped by CO or 0 2 . Thermal reaction of silanimine (39) at 50 K gives the head-to-tail cyclic dimer. Upon photolysis at 193 nm, (39) undergoes extrusion of CH4, giving silyl isocyanide (H3Si-NC), presumably by rearrangement of the initially formed methylnitrilosilane (H3CSi I N), which was not, however, detected directly. Me\
- ] hv, 248 nm
M~/S~-N~ I Ar, 10 K H (37)
Me\ MeASi-l!l* I H (38)
I
1,2-H shift
Me\ ,Si=N, Me
H
(39)
1,2-Me shift
scheme7
4.1 Aryl Azides - A number of papers have appeared dealing with some of the finer points of phenyl azide photochemistry. Measurements have been made of the relative rates of formation of azacyclohepta-1,2,4,6-tetraene and the disappearance of starting material in the photolysis of phenyl azide in argon, methane and 3-methylpentane matrices.40With narrow band light (280k 5 nm), chosen to coincide with a minimum in the UV absorption spectrum of phenylnitrene, formation of the ring expanded product lagged behind the decomposition of the azide in the early stages of the photolyses in methane and 3-methylpentane, but not in argon. Full arc photolysis resulted in a linear relationship between growth of product and disappearance of the azide in all three matrices. This observation provides evidence that the photolysis in hydrocarbon matrices proceeds in part to triplet phenylnitrene, which can subsequently absorb a second photon to give the final product, azacycloheptatetraene. Vibrational coupling between the initially formed singlet nitrene and the host material, which should be more efficient in methane and 3-methylpentane than in argon, is proposed to account for this medium eflect. At temperatures above 200 K, photolysis of 1-(2-azidophenyl)3,5-dimethylpyrazole (42) gives 1,3-dirnethylpyrazolobenzotriazole (43), by
304
Photochemistry
cyclization of the corresponding singlet r~itrene.~’ At lower temperatures, the yield of this product decreases and the azo product derived from dimerization of the triplet nitrene is obtained, as well as products from intramolecular radical cyclization. The triplet nitrene was observed directly by matrix-isolation UVvisible spectroscopy. Irradiation of 4-nitrophenyl azide in the presence of diphenylamine does not result in dissociation of the azide group, but leads instead to formation of the azide radical anion by electron transfer within the charge transfer complex of the two starting rnateriak4* In contrast, photolysis of 4-azidoacetophenone is accelerated by diphenylamine, owing to an increase in the efficiency of light absorption and possibly also to photosensitization by way of an electron-transfer mechanism. Molecular orbital calculations have indicated that there are two accessible states for the radical anions of aromatic azides (ArN,), the structure of one of which favours cleavage of the ArN-N2 bond, while that of the other does not.43ESR studies of the photoinduced oxidation of aryl azides in polymeric matrices and crystals have also been reported.u345 Triplet 44trophenylnitrene and 4-nitrene-4’-nitrostilbene have been characterized by low temperature UV-visible and ESR spectroscopy in 2-methyltetra. ~ 77~ hydrofuran matrices, following photolysis of the corresponding a z i d e ~At 90 K, the two nitrenes undergo a stepwise, twofold hydrogen abstraction from the solvent, leading to the corresponding primary amines. The photolyses of 2 7 diazidoazobenzene and 2-azidoazobenzene have been investigated in argon and 2-methyltetrahydrofuran matrices, and the resulting nitrenes observed by ESR, UV-visible and IR spectro~copy.~~ 4H-Azepin-4-ones such as (44,R = C1, Br) have been trapped in N2 matrices following photolysis or vacuum pyrolysis of 4azidophenols such (45, R = C1, Br), and were characterized by IR spectroscopy?’ In some conditions, intermediate hydroxyazacyclohepta-1,2,4,6-tetraenes(e.g. 46, R = Cl, Br) were also observed. The azepinones did not survive warming to room temperature, and attempts to isolate them on a preparative scale were unsuccessful. There has been a brief review of the matrix photolysis of phenyl azides
305
III 7: Pho toelimination EtO
(47)
Me
3!
Me
(48) NH
having o-hydroxy and o-amino groups, from which reactive o-quinonoid species can be generated.22 A number of photoaffinity reagents incorporating aryl azide groups have been developed. These include photoactive analogues of ATP:9*50 arylazido oligonucleotide derivative^,^"^^ derivatives of 6-azidohexafluoro-2-naphthoicacid for directed modification of biopolymers,Ma photoaffinic hepoxilin anal~gue,~’ and photoaffinity labels for mammalian squalene ep~xidase.’~
4.2 Heteroaryl Azides - Some recent matrix-isolation studies of the photolysis of pyridyl azides have been reviewed.= The isoxazolopyrimidine (47, R = 2HOC6H4) was the main product (57%), obtained from photolysis of the azidopyrimidine (48,R = 2HOC6H4),but the azo compound formed by dimerization of the nitrene derived from (47) was also produced in significant quantities (47Y0).~’ Photolysis of 4,6-diazido-3-methylisoxazolo[4,5-c]pyridine(49) in methanol gave two main products (50 and 51), arising from loss of one or two molecules of nitrogen.58 This reaction provides a convenient route to 3-methylisoxazolo[1,3]diazepinesystems. Oligonucleotides containing the photoreactive nucleosides, 2-azido-2’-deoxyinosine and 8-azido-2’-deoxyadenosine, have been prepared.59 5
Photoelimination of Carbon Monoxide and Carbon Dioxide
The research on photoelimination of CO and C02 covered by this review consists mainly of studies of photodecarbonylationsof small molecules, such as ketene, or of metal carbonyls. Detailed ab initio calculations have been carried out for the potential energy surfaces of the photodissociation of ketene in the SO, S1, TI and T2 states.60The triplet state, which produces the ground state products, is likely to be formed from the process Sl+So+Tn. The way in which a transition state tightens as energy increases above the dissociation threshold has been studied for the dissociation of singlet ketene.61 The triplet and singlet states of ketenylidene (CCO) have been investigated using fast radical beam photofragment transla-
306
Photochemistry
tional spectroscopy, in which CCO is generated from CCO- and subsequently photodissociated.62In argon matrices at 10-20 K, carbon suboxide (C3O2) forms a ‘T complex’ of C2, symmetry (52), which has been characterized by IR spectro~copy.~~ On broad-band UV irradiation (>230 nm), the complex preferentially decomposes to chloroketene and CO, the latter probably formed by reaction of HCl with the carbene CCO, arising from photodissociation of C302.
The spin-forbidden channel to give NH(g ’Z-) + CO has been observed directly in the photodissociation of jet-cooled HNCO, following S o 4 1 excitation.64 The competition between triplet and singlet channels was discussed in terms of the different timescales for intersystem crossing and dissociation. Ab initio studies have been made of both N-H and C-N bond photodissociation of HNCO in the S1 state.65i66 There is only a very small barrier to C-N cleavage, but a much larger one to N-H cleavage. Dissociation dynamics of HNCO (to H + CO) and DNCO (to D + CO), after photoexcitation in the vacuum UV, have been investigated using the laser photolysis-laser-inducedfluorescence ‘pumpprobe’ technique.67 Vacuum UV photodissociation of jet-cooled OCS has also been studied:* as has the photodesorption and photodissociation of OCS on GaAs(100) surfaces.69 Two examples of the generation of highly reactive organic species by photoelimination of CO or C02 have been included in previous sections of this review. These are the formation of 2,4-didehydrophenols (20) by photoextrusion of both N2 and C02 from benzoquinone diazides (19), and the photolysis of benzofuranone (24)(Scheme 5). In a similar manner, argon-matrix laser photolysis of 1,4bis(trifluoromethyl)-2,3,5,6-benzenetetracarboxylicdianhydride (53) resulted in stepwise elimination of COz and CO, allowing detection by IR spectroscopy of I ,4-bis(trifluoromethyl)benzdiyne (54). Subsequent irradiation of (54) led to products from ring opening. Matrix photolysis of 1,2,3,4-benzenetetracarboxylic dianhydride (59, using a careful choice of successively shorter wavelengths, was also shown to proceed by stepwise loss of C02 and CO, but the proposed intermediate, l,a-benzdiyne, was not detected directly.70 The final observed product was hexatriyne. A convenient three-stage preparation of 1,2-dioxobenzocyclobutene from ninhydrin has been reported, which involves a photodecarbonylation of a five-membered cyclic ketone.” It is unusual for such a decarbonylation to give a highly strained product.
Photoelimination of CO and COz from Organometallic Compounds - There have been several reviews covering various aspects of the photodissociation of metal carbonyls. These include quantum chemistry and photodynarnics,’* photo-
5.1
IIl7: Photoelimination
307
chemistry as a tool for elucidating organometallic reaction mechani~ms?~ solvent effects as probes for sub-nanosecond processes,74 photochemical reactions of Group 6 metal carbonyls in catalytic transformations of alkenes and alkyne~?~ and pressure effects in mechanistic studies of the photochemistry of metal complexes.76 Photochemical reactions of simple metal carbonyls have been studied by a variety of experimental techniques. The photodissociation dynamics of of Fe(CO)S in a molecular beam have been investigated with femtosecond time resol~tion.~'It is proposed that after absorption of two 400 nm photons, Fe(CO)s loses four CO molecules in about 100 fs, while the subsequent dissociation of the Fe(C0) fragment takes about 230 fs. Jet-cooled Fe(C0) and Fe(C0)2, produced by UV photolysis of Fe(CO)5, have been studied by time-resolved IR diode laser ~pectroscopy.~~ It was confirmed by alternately missing spin components in one of the IR bands of Fe(C0)2 that this radical is linear with Dmh symmetry. Controlled low-temperature photolysis of Fe(C0)s in the presence of excess alkynes gave the hitherto elusive Fe(C0),(q2-RC =C R ) complexes (R = R = H,Me, CF3; R = H,R' = Me, CF3), which had been proposed as intermediates in the iron carbonyl mediated coupling of alkynes and C0.79 Density functional calculations on the excited states of Cr(CO), are in agreement with other recent calculations in re-assigning the low intensity absorption on the low energy side of the first charge-transfer band, to symmetry forbidden chargetransfer excitation rather than to ligand-field excited states.8o The calculations further show that two states arising from the low energy charge-transfer excitation have dissociative potential, in accord with experimentaily observed photodissociation of Cr(C0)6 upon low energy absorption. Twelve different ions have been observed in the dissociative photoionization of Mo(CO)~,using a synchrotron radiation source with photons in the 8-40 eV range." Kinetic studies of the photooxidation of Mo(CO)~and W(CO)6 adsorbed on Ti02 suggest that decarbonylation is strongly enhanced by photoinduced band holes.82 Flash photolysis of W(CO)6 in the presence of 1-fluorohexane generates a complex, (l-C6H13F)W(C0)s, containing a W-F b0nd.8~The initial steps in the formation of certain heterogeneous olefin metathesis catalysts have been studied by flash photolysis of mixtures of CCl, and M(CO)6 (M = Mo, W),with IR and visible detection.84 In each case, (C13CCl)M(CO)s, with the CCG datively bonded through a single C1 atom, is produced immediately after the flash. The mechanism of ligand exchange between photogenerated (q '-bromobenzene)Cr(CO)s, which contains a weak dative Cr-Br bond, and more strongly bonding alkenes has been
308
Photochemistry
investigated in laser flash photolysis experiments with IR and visible d e t e ~ t i o n . ~ ~ In this study it was noted that activation parameters for complexes with weak CT or R bonding are diagnostic for each type of linkage. Broad-band UV photolysis of THF solutions of M(C0)6 (M = Cr, Mo, W) containing Fe(C0)2(PR3)(q2CS2) (R = Et, Ph) leads to the formation of heterobimetallic complexes via initial loss of C0.86 Photochemical reactions of Ru(C0)S with a series of nitrogen heterocycles have been investigated, leading to the identification of a novel, highly unstable monosubstituted complex, R~(Co)~(py), amongst others.*’ Transients generated by photolysis of CpFe(C0)2CH3 (Cp = q5C5H5) have been studied by IR spectroscopy in methylcyclohexane at 77 K and by timeresolved IR detection at ambient temperature in cyclohexane and THF.88These species were identified as monocarbonyl complexes with the solvent. The photolytic exchange of ethylene and H2 for CO in cymantrene, CpMn(C0)3, and methylcymantrenehas been observed by high-pressure NMR in supercriticalCOZ, and ethylene.89 Substitution of ethylene for CO goes to completion under all conditions studied, but only one ethylene molecule is incorporated, even in neat ethylene under extreme conditions of pressure and temperature. Only small amounts of H2 are substituted for CO on cymantrene. Photochemical Si-H bond activation in Et3SiH by CpMn(C0h has been studied by femtosecond IR methods.g0The results suggest that c~Mn(cO)~(H)(siEt,) may be formed by the two pathways of (i) formation through a new intermediate - possibly a ringslipped species - which decays to product on a timescale of about 71 ps, and (ii) formation through an ethyl-solvated dicarbonyl species, CpMn(CO),(Et,SiH), which dissociatively rearranges to the product on a timescale greater than 1 ns. This observation emphasizes the low reaction barrier for Si-H bond activation compared with the isoelectronic C-H bond. Various mononuclear and dinuclear hydrido disilanyl complexes are obtained in the photochemical reactions of (MeCp)Mn(CO)3(MeCp = qS-MeC5H4)and Fe(CO).+PPh3 with HPh2Si-SiPhzH and HMe2SiSiMe2H.” Thermal and photochemical decompositions of the complexes proceed by reductive elimination of the disilane. Photolysis of ironally1 complexes (q5:q1-C5H4CH2CH2PPh2)Fe(CO)(q’-CH2CR:CH2) (R = H, Me) gives a mixture of products derived from Fe-CO and Fe-ally1 bond cleavages?2 An alkyne-carbene chelate (56), a model complex for the first intermediate of the Dotz benzannulation reaction, has been generated by photodecarbonylation of pentacarbonyl[(o-tert-butylethynylphenyl)methoxycar~ne]chromium.93 A matrix-isolation study revealed that the chromium carbene complex (CO)&r[C(OMe)(Me)] undergoes CO loss upon UV irradiation more readily than its tungsten analogue, but gave no direct evidence for a metal-ketene complex, which is proposed as a likely intermediate in p-lactone formation in the solution photochemistry of the chromium complex.” A quantitative study of ligand substitution and C-H and Si-H bond activation in the photochemistry of CpRh(CO)2 has been carried out, leading to a complete mechanistic description of the various competing pathways?’ In the absence of an entering ligand, a CO-bridged complex, trans-Cp2Rh2(C0)3, is formed as the major photochemical product. A comparison has been made of the intermolecular C-H bond activating properties of CpRh(CO)z, CpIr(CO)2 and some
iIl7: Photoelimination
309 OMe
related c o m p l e x e ~while ; ~ ~ the effect of added CO on the kinetics of photochemical alkane dehydrogenation by Rh(PMe3)(CO)C1 has also been in~estigated.~' Calculations on H ~ F e ( c 0 have ) ~ yielded a theoretical absorption spectrum with bands at 246 and 272 nm?8 From these results it is predicted that 254 nm irradiation will lead mainly to elimination of H2, that loss of CO will be a minor and slower reaction channel, and that triplet states will have only a minor role in the early stages of photodissociation. Photolysis of thin amorphous films of Fe(C0)4PPh3 on Si(ll1) surfaces leads, after initial CO loss, to a thermally unstable intermediate, Fe(C0)3PPh3, which decomposes further with the production of iron.99 In CH2C12 solution, photolysis of the gold complex Au(C0)Cl gives AuC13 and metallic gold, presumably after CO loss as the primary photochemical step.loo There have been several reports of the photochemistry of dinuclear metal carbonyl compounds, amongst which is a matrix-isolation study of the mechanism of the photochemical Pauson-Khand reaction, in which hexacarbonylcobalt complexes of acetylenes react with alkenes to give cyclopentenones.lo' The first step of the process is thought to involve loss of a CO ligand followed by complexation of the alkene. UV irradiation of (phenylacetylene)Co2(C0)6(57) at 254 nm in argon matrices leads to loss of CO to give (phenylacetylene)C02(CO)~, which was characterized by UV-visible and IR spectroscopy. Reversal of the CO loss takes place at longer wavelengths. In N2 or N2-doped Ar matrices, a dinitrogen complex (phenylacetylene)Co2(CO)s(N2)is formed. The photolysis of bis-[chloro(dicarbonyl)rhodium] has also been investigated in frozen gas matrices at 12 K and Nujol mulls at 77 K, under which conditions facile loss of the terminal CO ligands occurs, while the [(Cl)Rh]2 bridging unit is retained.'02 Photolysis of (58, M = Fe) in the presence of phosphines or phosphites results in the formation of simple monocarbonyl-substitution prod~cts,"~ while acetylenes react photochemically with the diiron compound to give vinylketone-bridged derivatives (59, R = Ph, COzMe). In contrast, photolysis
0 (59)
..
310
Photochemistry
of (58, M = Ru) in the presence of triphenylphosphine leads to loss of two CO ligands, followed by P-C insertion by ruthenium to yield Ru2(CO)(o-Ph)(p CO)(Cr-PPhz)(CL-rlS,r15-C~H4CH2C~H4). Photochemical reactions of R u ~ ( C O and ) ~ ~ Os3(CO)12 with nitrogen heterocycles have been studied, with substitution products being formed in most cases.'04 For example, with pyridine the ruthenium compound forms the orthometallated complex RU~H(CO)~ 1(C5H4N), while the osmium compound gives the simple substitution product O S ~ ( C O'(py). ) ~ The novel dihydrido triruthenium cluster H~Ru~(CO)~O can be synthesized by photolysis of Ru3(C0)12 under an atmosphere of dihydrogen.lo' 6
Photoelimination of NO and NO2
Elimination of NO and NO2 is observed in the photochemistry of a range of nitro and nitroso compounds, nitrites and nitrates. The photodisscociations of 1-propyl, 2-propyl, 1-butyl and 1-pentyl nitrates at 308 nm has been investigated.IM The exclusive fragmentation pathway is cleavage of the RO-NO2 bond to yield NO2 and alkoxy radicals. From the results, rates of tropospheric photolysis of these alkyl nitrates were calculated. The photoelimination (355 nm) of NO from tert-butyl nitrite adsorbed on Ag(ll1) surfaces has been studied for a range of coverages.'" At high coverages the outermost layers dissociate normally, but reflection absorption IR spectroscopy (RAIRS) reveals that in the more inward layers caging prevents dissociation, and only isomerization of the nitrite occurs. An IR study of the photolysis of trifluoronitromethane (CF3N02) adsorbed on alkali halide films and isolated in argon and nitrogen matrices has been carried out."* As in the gas phase, carbonyl fluoride (CF20) was observed as one product, but the other gas-phase product, FNO, was not observed, presumably owing to secondary photolysis to F atoms and NO. Quantum efficiencies for adsorbed CF3N02 are lower than those for the matrix isolated species, suggesting that the interactions of the adsorbed molecules with the halide films enhance the relaxation rates of the excited state. This result illustrates the effects that seemingly inert substrates may have on the photochemistry of adsorbed species. A long-term, comprehensive investigation of photochemical nitrations with tetranitromethane has produced several new papers in the period under review. l 4 The basic mechanism of the reactions involves electron transfer within a charge transfer (CT) complex between the aromatic substrate (ArH) and tetranitromethane, resulting in formation of a radical cation (ArH'+), NO2 and the trinitromethanide anion. Photolysis of the CT complex of benzofuran and tetranitromethane at 435 nm in CH2C12 gives the epimeric pairs of adducts (60 - 63), the nitronic ester (M),and smaller amounts of dimeric products.'@ There is, however, a marked solvent effect. In acetonitrile similar photolysis gives the same group of products with the addition of epimeric dinitro (65) and hydroxynitro (66) adducts, together with 3-nitrobenzofuran; while in 1,1,1,3,3,3-hexafluoropropan-2-0lmainly dimeric
'@-'
M7: Photoelimination
31 1
products are obtained, with small amounts of 3-, 4- and 6-nitrobenzofuran. Clearly these reactions show considerable mechanistic complexity. Photolysis of the CT complex of 1,4-dimethoxynaphthaIeneand tetranitromethane in CHZC12 results mainly in nitration and trinitromethylation at the 2position and formation of the dinitromethylene compound (67), together with smaller amounts of addition products.' lo A mechanism involving initial attack of trinitromethanide anion ips0 to a methoxy group, followed by rearrangement or elimination, is proposed to account for the observed products. The photochemical reactions of tetranitromethane with 4-methoxystyrene and its trans$methyl derivative give mainly products of addition across the alkene double bond (68, R = H, Me), apparently by a radical chain mechanism.'" In similar reactions with styrene, 4-methylstyrene, 3- and 4-chlorostyrene, and 4-acetoxystyrene, stereoisomeric isoxazolidines (69, R = H, 4-Me, 3-C1, 4-C1, 4-AcO) are produced, often as the major products.'I2 The radical (70) is proposed as the key intermediate in this reaction. Analogous formation of isoxazolidines has been observed with 2-phenylpropene, but not with 2,4,6-trimethylstyrene.
312
Photochemistry
In a study of the effects of added ethanol on the photolysis of alkoxy- and dialkoxyarenes in the presence of tetranitromethane, enhancements of adduct formation and trinitromethyl substitution have been found.'I4 Amongst the effects of added ethanol that have been identified are ( i ) stabilization of alkoxytrinitromethylarenes, thus reducing their tendency to decompose, (ii) a reduction in the nucleophilicity of the trinitromethanide anion, and (iii) changes in the regioselectivity of trinitromethanide anion attack.
7
MiscellaneousPhotoeliminationsand Photofragmentations
Photoelimination from Hydrocarbons - A number of theoretical studies of the photodissociation of small hydrocarbons and hydrocarbon fragments have been published. These include photodissociation of CH4 on Pt(ll1) surface^,"^ and photodissociation of CH2 through the coupled 2Af and 3Af states.I16 The electronic excited states of C2H have been explored in ab initio MO calculations and the results compared with previously obtained experimental data.' l7 Ab initio approaches have also been adopted to help understand the photodissociation dynamics of allene, *J l9 propyne' l9 and vinylidenecarbene (CH2C2). l 8 Data from the laser-induced fluorescence of C2 radicals obtained in the laboratory during 193 nm photolysis of C2H2 have been used to explain band profiles of C2 in the nucleus of comet Hyakutake, observed by the Hubble Space Telescope.120 In conjunction with ab initiu computations, the data have led to the proposal that photolysis of CzH2, in the laboratory and in comets, proceeds by a sequential mechanism, first producing C2H and then C2. Two excited electronic states of C2H have been identified (22Z+ and 2211) through which photodissociation in the second step occurs. Measurements of the kinetics and translational energy release in the near-UV photodissociation of the ally1 radical have indicated that allene formation is the dominant H-loss reaction channel.12' The formation of the benzyl radical by photolysis of toluene in benzene at 4.2 and 77 K has been investigated as a function of light intensity and shown to be unimolecular and biphotonic, and to occur via the lowest excited triplet state.'22 The gas-phase photodissociation of [2,2]paracyclophane(71) into two molecules of p-quinodimethane and analogous dissociations of two methyl-substituted derivatives have been shown to be efficient two-photon processes.'23 A hot molecule formed by internal conversion from the initially formed singlet electronic excited state is proposed as an intermediate, a mechanism which is completely different from that of the two-photon dissociation of (71) in lowtemperature matrices, which involves a triplet state. The photolyses of [2,2]paracylcophane and [2,2]paracyclophane-1-ene have also been studied in THF and hexane matrices at 77 K,using detection by both luminescence and absorption spectro~copy.'~~ The products from both these compounds in THF matrices included alkyl derivatives of trans-stilbene, and in hexane matrices alkylphenanthrenes. Cycloreversion of so-called 'cyclodimers' of naphthalene derivativeswith benzene or furan, e.g. (72), occurs efficiently upon UV i r r a d i a t i ~ n . ' ~ ~ 7.1
'
'
Ml7: Photoelimination
313
7.2 Photoeliminationsfrom Organohalogen Compounds - Velocity distributions of both bromine atoms and methyl radicals have been measured for the photolysis of CH3Br in the first continuum (A band), and the results suggest that vibrational energy distribution in the nascent CH3 is non-statistical, with appreciable excitation of the v2 umbrella mode.'26 The photodissociations of CH31, CH2ICl and CH212,127l-iodopropane,'28 and 1,1,1,3,3,3-d6-2-iOdOprOpaneand dg-tert-butyl iodide,'29excited in their A band absorptions, have been studied by resonance Raman scattering. In the case of 1-iodopropane, the trans and gauche conformers display significantly different Franck-Condon region dissociation dynamics, indicating that the C-I bond cleavage is dependent on conformation. Vibrationally excited CH3Cl has been prepared by laser excitation of the fourth C-H stretch overtone, and then photodissociated at wavelengths near 238 nm.I3O Such vibrational excitation greatly enhances the yield of Cl fragments, and produces markedly different spin-orbit branching ratios. Thus the photodissociation dynamics can be significantly altered, even when the bond being broken is not directly involved in the initial vibrational excitation. The dynamics of Hatom formation in the photodissociations of CH3C1, CH2C12 and CHC13 at 193 nm have been in~estigated.'~' Only in the cases of CH3CI and CH2C12 are the H atoms formed in a primary photodissociation step; the H atoms detectable after laser irradiation of CHC13 arise from secondary photodissociation of the CHCl2 radical. Similar studies of H-atom formation in the photolysis of CH3CF2Cl have also been r e ~ 0 r t e d . IBoth ~ ~ C-Cl and C-H bond cleavage in the 193 nm photodissociation of CH3CF2Cl and CH3CFC12 have been examined by a laser pump-and-probe technique.133 Only atomic products were observed; no HCl was formed. The 193 nm photodissociations of 1,l- and 1,Zdifluoroethylene were studied by measuring product translational energy distributions.134 Both three-centred elimination of HF to produce :C=CHF and four-centred elimination of HF to give HC=CF were observed, and both channels were shown to have small exit barriers. Additionally, the energy distributions for F-atom elimination indicate that 'CH=CF is more stable than 'CF=CHZ. Photodissociation studies of vinyl and propargyl bromide and propargyl chloride137have also been reported. The photochemical reactions of CHC13 in neat and aqueous chloroform, in both the presence and absence of 0 2 , have been investigated with 185 nm light.I3* In deoxygenated neat chloroform hexachloroethane and 1,1,2,2-tetrachloroethane are formed, while in aqueous chloroform chloride ion is also produced. The presence of oxygen reduces the yields of products. A time-resolved IR study of the photochemical reaction between anthracene and carbon tetrachloride led
314
Photochemistry
to the detection of a strong transient band at 896 cm-', assigned to the trichloromethyl radical. 39 Other transient bands showing the same temporal behaviour as that of CC13 were assigned to the anthracene-Cl adduct. These two intermediates react with each other, following second-order kinetics, to yield the final product, the 9-chloro-10-trichloromethyl adduct of anthracene. An ester synthesis from alkyl iodides, involving irradiation (>300 nm) of the iodides with CO and alcohols in the presence of K2CO3, has been reported. '40 For example, 2iodooctane with ethanol gives Me(CH2)5CH(Me)C02Et.The proposed mechanism of this reaction involves as key steps the carbonylation of an alkyl radical, generated by photolysis of the iodide, and subsequent iodine transfer from the alkyl iodide to form an acyl iodide. Low intensity irradiation of 1,3dichloro-1,3-diphenylpropane in cyclohexane gives the 3-chloro-l,3,-diphenyl radical through homolytic C-Cl bond cleavage.14' At high intensities secondary photolysis of this radical leads to the 1,3-diphenylpropenyl radical, detected by nanosecond techniques. Irradiation (>265 nm) of the dibromocyclopropane derivative (73) in ethanol-acetone afforded diastereomeric bicyclohexanols (74) by way of a cyclopropyl radical intermediate generated by C-Br bond cleavage.142
'
The photodissociation of chlorobenzene at 266 nm has been investigated by use of the crossed laser-molecular beam technique.143A 6 initio calculations predict that the first excited singlet state of chlorobenzene has large geometry changes compared with the ground state, and these probably enhance internal conversion from S1 to a highly vibrationally excited ground state. It was therefore concluded that dissociation probably occurs from hot chlorobenzene molecules to give vibrationally hot phenyl radicals. Time-of-flight spectra of the C1 fragments have been measured for molecular beams of 0-, rn- and p-chlorotoluene and 0-,m- and pdichlorobenzene irradiated by a 193 nm laser pulse.'4q The results revealed three dissociation channels: ( i ) very fast predissociation or direct dissociation, (ii) predissociation through a triplet state, and (iii) predissociation via a highly vibrationally excited electronic ground state. The three channels for dichlorobenzenes have similar probabilities, but the methyl substituent in the chlorotoluenes enhances dissociation through triplet states, probably owing to enhancement of instersystem crossing. Photolyses of 2,4- and 2,6-difluorobromobenzene at 254 nm in acetonitrile give isomenzed and brominated products in addition to 1,3-difluorobenzene produced by debromination.145 Comparison of the reactions with those of the corresponding difluorochloro and difluoroiodo analogues showed that, in general, cleavage of the C-X bond (X = Cl, Br, I) in the 2,6-difluoro compounds proceeds more easily than in the 2,4-difluoro isomers.
IIl7: Photoelimination
315
Laser flash photolysis of dibromo compounds (75 and 76, X = Br) generates dibromocarbene, while bromochlorocarbene can be obtained from (76, X = Cl).'& The carbenes can be trapped as ylides by reaction with pyridine, and the lifetimes of CBr2 and CBrCl and their absolute reactivities towards pyridine and alkenes have been determined. Yields of pyridine ylides from alkylchlorocarbenes, similarly generated by flash photolysis of a series of cyclopropaphenanthridenes, have been compared with yields of the same ylides generated from diazirine prec~rsors.'~'In the studies with diazirines, the yields of trappable carbenes were found to be sensitive to the alkylcarbene structure. This feature was attributed to ring opening of the diazirines to diradicals, which could either rearrange or fragment to the carbenes, but might alternatively have been due to formation of carbene-pyridine complexes, which could either rearrange or collapse to the ylides. The new results show that, if such carbene-pyridine complexes are intermediates, they do not rearrange to chloroalkenes at rates competitive with ylide formation. Triplet fluorenyl-substituted rn-xylylene diradicals such as (77)have been prepared from the corresponding dichloro precursors by photolysis in 2-methyltetrahydrofuran glasses, and observed by ESR.14*
The photodissociations of CH31 on LiF(OO1) and NaCl(OO1) surfaces at 248 nm have been studied by probing the CH3 fragments by angularly resolved resonantly enhanced multiphoton ionization (REMPI) and time-of-flight mass ~pectrometry.'~~ The adsorption and photodissociation of CHzI2 on Cu( 100) surfaces at 90-250 K were investigated, with the aim of generating CH2 on the Cu(100) surface. I5O The processes were monitored using a variety of spectroscopic techniques and work-function measurements. The primary products detected were adsorbed CH2 and I, showing that self-hydrogenation of CH2, observed on platinum metals, does not occur on Cu(100). Photodecomposition studies of 1,1,2-trichloroethane on Pt( 1OO), utilizing high-resolution electron-energy loss spectroscopy (HREELS) and temperature-programmed desorption, have provided evidence for vinyl formation.' * Multiphoton IR dissociations of various organohalogen compounds have been investigated. Photofragment translational spectroscopy revealed that IR multiphoton dissociations of perfluoro-1-butene and perfluoro-2-butene proceed by
31 6
Photochemistry
predominant cleavage of a carbon-carbon single bond, to give CF3 and C3F5 as products.'52 Two other reactions that take place are CF2 elimination and the formation of two isomeric C2F4 fragments, both reactions taking place by way of a diradical intermediate. Strong visible luminescence has been observed in the multiphoton IR dissociation of 1,2-dichloro-l ,1-difluoroethane. '53 This emission is attributed to the electronically excited carbene CF2Cl-CH. Effects due to added argon on the gas-phase multiphoton IR dissociation of hexafluoropropene have been associated with the induction of an anharmonic barrier, which is principally vibrational. 54 7.3 Photofragmentations of Organosilicon and Organogermanium Compounds Flash photolysis of 1,l-dimethylsiletane at 193 nm has allowed the direct -255 nm) of 1,I-dimethylsilene detection by transient UV absorption (A, (MezSi=CH2).155The silene reacts rapidly with methanol and oxygen, and Arrhenius activation parameters have been determined for the reaction with methanol. Ring-substituted 1,l-diphenylsilenes (78, X = H, Me, F, Cl, CF3) have been generated by flash photolysis of the corresponding 1,l -diphenylsiletanes, and the absolute rate constants for their reactions with methanol, tert-butanol and acetic acid measured. 156 These three reactions exhibit small positive Hammett p-values, consistent with a mechanism in which initial, reversible nucleophilic attack at silicon, to form a o-bonded complex, is followed by collapse to product by a rate-limiting proton transfer. Upon heating, the sterically congested disilacyclobutane (79, X = Si) undergoes [2+2] cycloreversion to give the adamantylidenesilene (go), which can be trapped chemically by reagents such as 1,3-butadienes, styrene, phenylacetylene and methanol.157In contrast, photolysis of (79, X = Si) at 77 K in methylcyclohexane produces 1,1,2,2-tetrakis(trimethylsilyl)disilene (8 1) and 2,2'-biadamantylidene by a [2+2] cycloreversion in the opposite sense to that of the thermal cleavage. Disilene (81) can dissociate to the silylene, (Me3Si)2Si:, in a secondary photolysis step. Upon photolysis, the digermacyclobutane (79, X = Ge) behaves similarly to its silicon analogue, giving the digermene (Me3Si)2Ge=Ge(Me3Si)z and the germylene, (MeJSi)zGe:, together with 2,T-biadamant~lene.'~' Heating (79, X = Ge), however, does not produce the germanium analogue of (80), but instead gives a quantitative yield of 2,2'-biadamantylene and germaniumcontaining oligomers. Irradiation of the disilabicyclo compound (82) (Scheme 8) at 254 nm in 3-methylpentane glasses at 77 K led to the observation of a new UV absorption at 360 nm, which was attributed to the disilene (83).'58 The disilene could be trapped by reaction with added phenols. A direct MO dynamics study has indicated that photoextrusion of dimethylsilylene, MezSi:, from permethylcyclohexasilane,(MezSi)6, is possible on the triplet energy surface (TI) as well as on the S1 surface.'59 IR multiphoton dissociation of 2-chloroethenylsilane generates silylene vibrationally excited in the bending mode.'60 Silacyclopentadienylidene (84) has been generated from 7-silanorbomadiene and 7-silanorbomene precursors, e.g. (85), by pho tolysis in hydrocarbon matrices at 77 K.16' The silylene has a 500 nm absorption band, and can be trapped chemically by reaction with MeSiEtH. Di-tert-butylsilylene, generated by
III7: Photoelimination
317
X
Si(SiMe3)p (MesSi)nSi= Si(SiMe& (78)
(79)
(80)
(811
photolysis of hexa-tert-butylcyclotrisilane,( t - B ~ ~ s ireacts ) ~ , with N-methylpyrrole to give the azasilabicyclo[2.2.0]hexene (86), possibly via an intermediate [2+ 11 cycloadduct. The bicyclic product (86) rearranges to the 1-aza-2-silacyclohexa3,s-diene (87) when heated. Several 1,2-digermacyclohexa-3,5dieneshave been synthesized and photolysed, yielding dialkyl germylenes (R2Ge:) and the corresponding germacyclopentadienes. In the same study, an analogous 1-germa-2silacyclohexa-3,5-diene yielded preferentially the silacyclopentadiene via extrusion of a dialkylgermylene. Co-photolyses of cyclic organosilanes with phenanthraquinone are reported to give silylene insertion products via radical displacement at the Si atoms by excited phenanthraquinone.la Photolyses of tert-butyl-substituted disilanes in the presence of Cm yield mainly 1,16-adducts, and a free silyl radical process has been suggested for these reactions.'65Photolysis of (88) in a polar solvent leads to C-Si cleavage, generating tert-butyl radicals, via a polarized singlet excited state, but in an apolar solvent only a slow dimerization occurs.166The sisyl (tris(trimethy1sily1)silyl) group has been shown to be a convenient photolabile protecting group for alcohols, which is stable to many synthetic procedure^.'^^ 7.4 Photofragmentations of Organosulfur and Organoselenium Compounds Transient grating spectroscopy, photoacoustic spectroscopy and transient
318
Photochemistry
absorption spectroscopy have been applied to a study of the photodissociation of diphenyl disulfide, including measurement of the quantum yield for dissociation.168A new model to describe the polarized fluorescence of polyatomic fragments from photodissociation reactions has been developed and tested, with encouraging results, on preliminary data from the photolysis of bis(p-aminophenyl) disulfide and bis(p-acetylaminophenyl) disulfide.169 Transient absorption spectra have been obtained for 1- and 2-naphthylseleno radicals, generated by flash photolysis of the corresponding diselenides.170 The reactions of these radicals with 2-methyl-1,3-butadiene and a-methylstyrene were investigated by monitoring decay rates for the radicals, and it was concluded that they add to alkenes in a reversible manner. Both 2-dl-thiirane-1-oxide and 2,2-&thiirane- 1-oxide have been synthesized, the monodeuterated species existing in two diastereomeric forms with the D atom either cis or trans to the 0 atorn.l7' IR multiphoton excitation with a C02 laser leads to dissociation of the thiiranes into deuteriated ethylene and SO, and the monodeuteriated isotopomer shows a small but significant diastereoselectivity, based on the small frequency difference of the v4 (SO stretching) vibration in the two diastereomers. The photodissociation dynamics of trimethylene sulfoxide (C3H6SO) have been studied by monitoring the SO fragment following 193 and 248 nm irradiation, using laser-induced fluorescence spectroscopy.17* When arylsubstituted sulfines (thiocarbonyl S-oxides) are photolysed in the presence of the strained cyclic alkenes, norbornene and trans-cyclooctene, thiiranes are produced by S-atom transfer in moderate to good ~ i e 1 d s . l ~ ~ The photochemistry of N-propyl-o-sulfobenzoic imide (89) has been investigated in ethanol and monocylic aromatic solvents, such as benzene, anisole, toluene and benzonitrile.'74 It appears that in ethanol direct photoextrusion of SO2 generates the diradical (90), which yields the final product, Ac "propylbenzamide, by H-atom abstraction form the solvent. In aromatic solvents, the mechanism seems to involve energy transfer from the singlet excited aromatic molecules, and the addition of the resulting diradicals to the partner aromatics, to give arylated benzamides. The thermolyses and photolyses of two epimeric steroidal hydroxamic acid methanesulfonates (9 1) have been re~0rted.I~'The numerous products include those from a Favorskii-like ring contraction of the heterocyclic ring, and mechanisms are proposed involving heterolytic N-0 bond cleavage to give ion pairs. 7.5 Pbotolysis of o-Nitrobenzyl Derivatives - The photocleavage reactions of onitrobenzyl ethers, esters and other derivatives continue to find applications in a number of areas. Two mechanistic studies of this type of photocleavage have
IIi7: Photoelimination
319
been published in the period under review. In one of these, the IR and UV-visible absorption spectra of the o-quinonoid intermediate (92) were observed in argon and nitrogen matrices at 12 K, following photolysis of 2-nitrobenzyl methyl ether.'76 The matrix IR spectrum helped to confirm the identity of this intermediate, an analogue of which had previously been detected in flash photolysis studies, but only by its transient electronic absorption. The other mechanistic study was an investigation of the release of adenosine 5'-triphosphate (ATP) from its P3-[1-(2-nitrophenyl)ethyl] ester, utilizing rapid scan FTIR and time-resolved single wavelength IR ~pectroscopy.'~~ Transient IR bands due to the o-quinonoid, aci-nitro anion intermediate (93) were assigned with the aid of 13C, "N and l80labelling, and time-resolved monitoring confirmed that the release of ATP occurs in a single exponential process synchronous with the decay of (93). The reactions of the by-product, 2-nitrosoacetophenone, with thiols were also investigated.
The potential utility of o-nitrobenzyl as a photocleavable nitrogen protecting group for indoles, benzimidazole and 6chlorouracil has been evaluated.178 Simple photolyses of the protected molecules at 300 nm afford good yields of the starting materials. Nitrobenzyl-based phosphoramide mustards (94) with various substituents (R',R2,R3)have been developed as potential prodrugs for cancer therapy.'79 UV and 31PNMR spectroscopy showed that the phosphoramide mustard was quickly liberated upon irradiation with mercury arc lamps. 2-Nitrobenzyl quaternary ammonium derivatives of norbutyrylcholine (N, N-dimethylaminoethyl butyrate) have been synthesized and assessed as photolabile inhibitors
320
Photochemistry
of butyrylcholinesterase. 8o Compounds with photoremovable a-carboxy-substituted o-nitrobenzyl groups have been prepared for the study of biological processes, and a steroidal compound which releases L-leucyl-L-leucine methyl ester by o-nitrobenzyl photocleavage has been reported. 182 A number of nucleoside derivatives with photolabile o-nitrobenzyl protecting groups, for use in oligonucleosidesynthesis, have been the subject of a patent.183 Photocleavable cyclic oligonucleotides, exploiting o-nitrobenzyl photochemistry and having base sequences capable of hybridizing with a target DNA or RNA, have been prepared.ls4 These are not decomposed by nucleases in the living cell, owing to their cyclic structures, so they can diffuse to predetermined positions and then be ringcleaved by irradiation, thus acting as antisense oligonucleotides. Novel photocleavable, o-nitrobenzyl based linkers for solid-phase synthesis have been developed;1859186and N-(2-nitrobenzyloxycarbonyl)cyclic amines have been synthesized as photobase generating agents for resists.I8' 7.6 Other Photofragmentations- In studies of the 193 nm photodissociation of acrylonitrile by photofragment translational spectroscopy, four primary reaction channels have been identified: elimination of atomic and molecular hydrogen, and elimination of HCN and CN radicals.'88 There is evidence that all four dissociation channels occur on the ground electronic surface, following internal conversion from the initial excited state. UV-laser photolysis at 193 and 337 nm and IR-laser SF6-photosensitized decomposition of secondary but-Zene ozonide (95) in the gas phase follow different reaction pathways.189At 193 nm, a range of products is obtained, including C02, methanol, acetaldehyde, methane and ketene, but 337 nm photolysis is a much slower process than oligomerization of the ozonide on the walls of the reactor. IR photosensitized decomposition of the ozonide affords acetaldehyde as the main product, along with acetic acid and minor amounts of other products. Trifluoromethoxy radicals (CF3O') have been generated in the presence of CO in N2 or air at 296 K, by photolysis of CF302CF3 at 254 nm.lW In N2, the products, CF30C(O)C(O)CF, and CF3OC(O)O,C(O)OCF3, were detected by IR spectroscopy. In air, the only observed products were CF20 and C02. A chain process initiated by CF30' radicals was proposed for the oxidation of CO to C02.
Two methods for the photolytic generation of p-methoxybenzyl radicals, by CH cleavage in p-methoxytoluene and C-0 cleavage in p-methoxybenzyl alcohol,
have been studied in n-heptane solution by nanosecond fluorescence and absorption spectroscopy.l9I The results indicate two distinct dissociation channels. p-Methoxytoluene dissociates from thermally equilibrated levels of the S1 state after vibrational relaxation, whereas p-methoxybenzyl alcohol dissociates from vibrationally excited levels of the S1 state in competition with vibrational
32 I
IID: Photoelimination
relaxation. A series of N-(triphenylmethy1)anilines have been photolysed in acetonitrile and hexane solutions, and found to undergo exclusively C-N bond homolysis to give the triphenylmethyl radical in a single-photon process.'92 This observation contrasts with the dominance of heterolytic cleavage in, for example, the photolysis of Ph3C-Cl in acetonitrile under the same conditions. The singletborn spin-correlated radical pair generated in the photolysis of tetraphenylhydrazine in a micelle has been observed, and the time-evolution of its spectrum analysed in terms of the time-dependence of the individual spin states of the radical pair and the rate of geminate re~ombinati0n.l~~ Evidence has been provided for the intermediacy of N-methyl-N-phenylnitrenium ion in the photolysis of N-(methylphenylamino)-2,4,6-trimethylpyridinium tetrafluoroborate.'94 Substituted aryltropylium ions have been generated by photolysis of a series of 7-methoxycycloheptatrienes,and found to have lifetimes strongly dependent on the donor capacity of the aryl substituent.'95Photolysis of a mixture of the two pinacols (96 and 97) in acetonitrile resulted in efficient fragmentation of both compounds, by cleavage of the central C-C bonds.'96This reaction has a quantum yield of 9+ 1, which suggest a chain process initiated by single electron-transfer quenching of excited (96) by (97).
(96)
(97)
o-Quninone methides and o-quinodimethanes have been generated in several photofragmentation reactions. The hexahydrocannabinol derivative (I 00) (Scheme 9) is formed in an efficient intramolecular Diels-Alder reaction from the o-quinone methide (99), which can be generated from the substituted benzyl alcohol (98) by photoelimination of water.19' The tethered dienophile must have at least three alkyl groups to be sufficiently electron rich. The intermediate o-quinone methide (99) was detected in flash photolysis studies (A,, -400 nm) and found to have a lifetime of less than 2 ms. It has been shown that o-quinone methides can be efficiently produced by photolysis of phenolic Mannich bases in aqueous a~etonitrile;'~~ and a synthesis of tetra- and di-hydrophthalene derivatives has been reported, which involves laser photolysis of 1,2-bis(phenoxymethyl)-, 1,2-[bis(phenylthio)methyl]- or 1,2-bis[(phenylseleno)methyl)]benzene, followed by addition of dienophiles to the resulting o-quinodimethane.
Scheme 9
322
Photochemistry
There have been several studies of photoreactions in which metal-carbon bonds are broken. Photodissociation of dimethylmercury at 193 and 248 nm has been investigated in argon matrices.200At 193 nm the main product is a complex between mercury and ethane (Hg-C2H6), but this is decomposed by 248 nm irradiation, giving HHgC2H5, which is further photolysed to HgH2 and ethylene. Photodecompositions of methylmercury complexes, MeHgL (L = Me, H20+, OH, C1, SH), which are related to the sunlight-induced decompositions of mercury pollutants in the environment, have been studied theoretically.*" Photolysis of dialkylthallium halides in cyclohexane results in cleavage of the carbonthallium bond and formation of radicals, which yield products by reaction with cyclohexane or with themselves.202Irradiation of Ru(q6-mes):+ (mes = mesitylene) in acetonitrile results in substitution of one mesitylene ring by solvent to yield the half-sandwich complex, Ru(q6-mes)(CH3CN);+, which on further photolysis undergoes either substitution of the second mesitylene ring or exchange of coordinated CH3CN.203 8 1. 2. 3. 4.
5. 6. 7. 8. 9. 10. 11.
12. 13. 14. 15.
16. 17. 18. 19. 20.
References J. Michl and Z. Havlas, Pure Appl. Chem., 1997,69,785. M. Klessinger, Pure Appl. Chem., 1997,69,773. P. Cattaneo and M. Persico, Chem. Phys. Lett., 1998,289, 160. N. Yamamoto, M. Olivucci, P. Celani, F. Bernardi and M. A. Robb, J. Am. Chem. Suc., 1998,120,2391. T . Nakamura and Y. Koga, J. Chem. SOC.,Perkin Trans. 2,1998,659. P. S . Engel, S. L. He and W. B. Smith, J. Am. Chem. SOC.,1997,119,6059. H. Quast, A. Fuss and W. Nudling, Eur. J. Org. Chem., 1998,317 0.Nuyken and B. Voit, Macromol. Chem. Phys., 1997,198,2337. 0.Nuyken and U. Dahn, J. Polym. Sci., Part A: Polym. Chem., 1997,35,3017. K. Erentova, V. Adamcik, A. Stasko, 0. Nuyken, A. Lang and M. B. Leitner, Collect. Czech. Chem. Commun., 1997,62,855, J. Kritzenberger, D. Franzke, T. Kunz, A. Lang, 0.Nuyken and A. Wokaun, Angew. Makrumol. Chem., 1998,254,17. C . Dell'Erba, M. Novi, G. Petri110 and C . Tavani, Gazz. Chim. Ital., 1997,127,361. S.-M. Lim, T.-S. Kim, G.-I. Lim, S. K. Kim and Y . S. Choi, Chem. Phys. Lett., 1998,288,828. M. S. Platz, H. Huang, F. Ford and J. Toscano, Pure Appl. Chem., 1997,69,803. F. Ford, T. Yuzawa, M. S. Platz, S. Matzinger and M . Fiilscher, J. Am. Chem. SOC., 1998,120,4430. S.-J. Lin, S.-Y.Jiang, T.-C. Huang, C.-S. Dai, P.-F. Tsai, H. Takeshita, Y,-S. Lin and T. Nozoe, Bull. Chem. SOC.Jpn., 1997,70, 3071. Y.-S. Lin, S.-Y. Jiang, T.-C. Huang, S.-J. Lin and Y.L. Chow, J. Org. Chem., 1998, 63,3364. S.-J. Lin, S.-Y. Jiang, T.-C. Huang, P. Kao, P.-F. Tsai, H. Takeshita, Y.3. Lin and T. Nozoe, Heterocycles, 1997,45, 1879. W. Sander, G. Bucher, H. Wandel, E. Kraka, D. Cremer and W. S. Sheldrick,J. Am. Chem. Suc., 1997,119,10660. A. Admasu, M. S. Platz, A. Marcinek, J. Michalak, A. D. Gudmundsdottir and J. Gebicki, J. Phys. Org. Chem., 1997, 10,207.
IIl7: Photoelimination
21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31.
32. 33. 34.
35.
36. 37. 38. 39. 40. 41. 42. 43. 44. 45.
46. 47. 48. 49. 50. 51.
323
H. Tomioka and T. Matsushita, Chem. Lett., 1997,399. H.Tomioka, Pure Appl. Chem., 1997,69,837. Y.Kawamura, K. Akitomo, M.Oe, T. Horie and M. Tsukayama, TetrahedronLett., 1997,38,8989. W. Kirmse and B. Krzossa, TetrahedronLett., 1998,39,799. R. Albers and W.Sander, Liebigs Ann. I Recueil, 1997,897. T.Khasanova and R.S. Sheridan, J. Am. Chem. SOC.,1998,120,233, S . Karasawa, M. Tanaka, N. Koga and H. Iwamura, J. Chem Soc., Chem. Commun., 1997,1359. B. Latli, H. Morimoto, P, G. Williams and J. E. Casida, J. Labelled Compd Radiopharm., 1998,41,191. C. Wentrup, A. Reisinger, G. C. Qiao and P. Visser, Pure Appl. Chem., 1997,69, 847. J. Andraos, Y.Chiang, A. J. Kresge and V.V. Popik, J. Am. Chem. SOC.,1997,119, 8417. N.C.de Lucas, J. C. Netto-Ferreira, A. J. Lusztyk, B. D. Wagner and J. C. Scaiano, TetrahedronLett., 1997,38,5147. H.K. Hombrecher, V. M. Gerdan, J. A. S. Cavaleiero and M. G. P. M. S . Neves, Heterocycl. Commun., 1997,3,453. K. Nakatani, J. Shirai, S.Sando and I. Saito, J. Am Chem. Soc., 1997,119,7626. D.A. Wacker, F. E. Lovering, R. J. Bridges, C. Willis, R. Bartlett and A. R. Chamberlin, Synlett, 1997,503. J. Fagart, F. Sobrio and A. Marquet, J. Labelled Compd. Radiopharm., 1997, 39, 791. T. Tochizawa, M. Miyazaki and H. Kikuchi (Toyo Gosei, Kogyo K. K.,Japan), Japanese Patent JP 09 319 079,12Dec.1997;Chem. Abstr., 1998,128,108193r. M. Nunomura and S. Uchimura (Hitachi Chemmical Co., Ltd., Japan), Japanese Patent JP 10 07 796,13Jan.1998; Chem. Abstr., 1998,128,174145~. E. L. Zhuzhgov and G. G. Furin, Rurs. J. Org. Chem., 1997, 33, 710; Zh. Org. Khim., 1997,33,772. A. Kuhn and W.Sander, Organometallics, 1998,17,248. I. R.Dunkin, M.A. Lynch, F. McAlpine and D. Sweeney, J. Photochem Photobiol. A: Chem., 1997,102,207. A. Albini, G. BettinettiandG. Minoli, J. Am. Chem. SOC.,1997,119,7308. M. F. Budyka, M. M. Kantor and R.M.Fatkulbayanov, Russ. Chem. Bull., 1997, 46,265. M.F. Budyka, M. M.Kantor and T. S. Zyubina, High Energy Chem., 1998,32,26. S. V. Zelentsov, A. V. Eryutov, A. A. Ezhevskii and A. V . Oleinik, High Energy Chem., 1997,31,193. S . V. Zelentsov, E. A. Bykova, A. A. Ezhevskii and A. V. Oleinik, High Energy Chem, 1997,31,397. T. Harder, R. Stosser, P. Wessig and J. Bendig, J. Photochem. Photobiol. A: Chem., 1997,103,105. T. Ohana and Y.Koga, Spectrochim. Actu, Part A, 1998,54,411. I. R.Dunkin, A. A. El Ayeb, S.L. Gallivan and M. A. Lynch, J. Chem SOC.,Perkin Trans.2, 1997,1419. S. Shin, W. Lee and J.-S. Park, J. Biochem. Mol. Biol., 1997,30,211. A. S . Phadke and J. F. W. Keana, New J. Chem., 1997,21,517. V. V. Koval, G. A. Maksakova and 0. S . Fedorova, Bioorg. Khim., 1997,23, 266; Chem. Abstr., 1997,127,293530~.
324 52. 53. 54. 55. 56. 57. 58. 59.
60. 61. 62. 63. 64. 65. 66.
67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80. 81. 82. 83. 84.
Photochemistry
T. S. Godovikova, M. V. Berezovskii and D. G. Knorre, Bioorg. Khim., 1995, 21, 858; Chem. Abstr., 1997,127,248375f. D. G. Knorre, P. V. Alekseyev, Y. V. Gerassimova, V. N. Silnikov, G. A. Maksakova and T. S. Godovikova, Nucleosides Nucleotides, 1998,17, 397. E. D. Tenetova, M.I. Dobrikov, G. V. Shishkin and V. D. Shteingartz, Russ. Chem. Bull., I998,47, 32 1. P. M. Demin, D. M. Kochev, H. Perrier, C. R. Pace-Asciak and K. R. Pivnitsky, Mendeleev Commun., 1997,90. J.-P. Gotteland, C. Dax and S. Halazy, Bioorg. Med Chem. Lett., 1997,7, 1153. V. P. Vetchinov, E. B. Nikolaenkova, V. I. Mamatyuk and V. P. Krivopalov, Russ. Chem. Bull., 1997,46,607. D. Donati, S. Fusi and F. Ponticelli, J. Chem. Res. ( S ) , 1997, 170. C. Fabrega, R. Gueimil Garcia, A. R. Diaz and R. Eritja, Biol. Chem., 1998,379,527. Q. Cui and K.Morokuma, J. Chem. Phys., 1997,107,4951. E. A. Wade, A. Mellinger, M. A. Hall and C. B. Moore, J. Phys. Chem. A , 1997, 101,6568. H. Choi, D. H. Mordaunt, R. T. Bise, T. R. Taylor and D. M. Neumark, J. Chem. Phys., 1998,108,4070. N. Pibtri, 1. Tamburelli, J. P. Aycard and T. Chiavassa, J. Mol. Struct., 1997, 416, 187. M. Zyrianov, T. Droz-Georget and H. Reisler, J. Chem. Phys., 1997,106,7454.. J. E. Stevens, Q. Cui and K.Morokuma, J. Chem. Phys., 1998,108, 1452. J.-J. Klossika, H. Flothmann, C. Beck, R. Schinke and K. Yamashita, Chem. Phys. Lett., 1997,276,325. R. A. Brownsword, T. Laurent, M. Hillenkamp, R. K. Vatsa and H.-R. Volpp, J. Chem. Phys., 1997,106,9563. K. Yamanouchi, K. Ohde and A. Hishikawa, Adv. Chem. Phys., 1997,101,789. H. H. Huang, Z. Zou, X.Jiang, W. Y. Chan and G. Q. Xu, J. Phys. Chem. B, 1997, 101,8 162. M. Moriyama and A. Yabe, Chem. Lett., 1998,337. D. Leinweber and H. Butenschon, Tetrahedron Lett., 1997,38,6385. M. C. Heitz, K.Finger and C. Daniel, Coord Chem. Rev., 1997,159,171. W. Boese, K. McFarlane, B. Lee, J. Rabor and P. C. Ford, Coord Chem. Rev., 1997, 159, 135. C. H. Langford and L. E. Shaw, Coord. Chem. Rev., 1997,159,221. T. Szymanska-Buzar, Coord. Chem. Rev., 1997,159,205. G. Stochel and R. van Eldik, Coord. Chem. Rev., 1997,159,153. L. Banares, T. Baumert, M. Bergt, B. Kiefer and G. Gerber, J. Chem. Phys, 1998, 108,5799. K . Tanaka, Y. Tachikawa and T. Tanaka, Chem. Phys. Lett,, 1997,281,285. J. Cooke and J. Takats, J. Am. Chem. SOC.,1997,119, 11088. C. Pollak, A. Rosa and E. J. Baerends, . I Am. . Chem. Soc., 1997,119,7324. F. Qi, S. Yang, L. Sheng, W.Ye, H. Gao, Y. Zhang and S. Yu, J. Phys. Chem. A , 1997,101,7194. Y. Okamoto, Y. Kobayashi, Y. Teraoka, S. Shobu and S. Kagawa, J. Chem. SOC., Faraday Trans., 1997,93,2561. G. R. Dobson, J. P.Smit, S. Ladogana and W. B. Walton, Organometallics, 1997, 16,2858. G. R. Dobson, J. P. Smit, W. Purcell and S. Ladogana, J. Organomet. Chem., 1997, 535,63.
IID: Photoelimination 85. 86.
87. 88. 89.
90. 91. 92. 93. 94. 95. 96. 97. 98. 99. 100. 101. 102. 103. 104. 105. 106. 107. 108. 109. 110.
111. 112, 113. 114. 115.
325
S. Ladogana, S. K. Nayak, J. P. Smit and G. R. Dobson, Znorg. Chim. Ada, 1998, 267,49. P. V. Broadhurst, N. E. Leadbeater, J. Lewis and P. R. Raithby, J. Chem. SOC., Dalton Trans., 1997,4579. G. R. Haire, N. E. Leadbeater, J. Lewis, P. R. Raithly, A. J. Edwards and E. C. Constable, J. Chem. SOC.,Dalton Tram., 1997,2997. K. L. McFarlane and P. C. Ford, Organometallics, 1998,17,1166. J. C . Linehan, S. L. Wallen, C. R. Yonker, T. E. Bitterwolf and J. T. Bays, J. Am. Chem. SOC.,1997,119,10170. H. Yang, K. T. Kotz, M. C. Asplund and C. B. Harris, J. Am. Chem. SOC.,1997, 119,9564. R. Karch and U.Schubert, Inorg. Chim Acta, 1997,259,151. T.-F. Wang and C.-Y. Lai, J. Organomet. Chem., 1997,5451546,179. K. H. Dotz, S. Siemoneit, F. Hohmann and M.Nieger, J. Urgunomet. Chem., 1997, 541,285. M. L. Gallagher, J. B. Greene and A. D. Rooney, Organometallics, 1997, 16, 5260. N. Dunwoody and A. J. Lees, Organometallics, 1997, 16,5770. A. J. Lees, J. Organornet. Chem., 1998,554,l. G. P . Rosini, S. Soubra, M. Vixamar, S. Wang and A. S. Goldman, J. Organomet. Chem., 1998,554,41. M.-C. Heitz and C . Daniel, J. Am. Chem. SOC.,1997,119,8269. S . L. Blair and R. H. Hill, J. Organomet. Chem., 1998,554,63. H. Kunkely and A. Vogler, J. Organomet. Chem., 1997,541, 177. C. M. Gordon, M. Kiszka, I. R. Dunkin, W. J. Kerr, J. S. Scott and J. Gebicki, J. Organomet. Chem., 1998,554,147. J. T . Bays, T. E. Bitterwolf, K.A. Lott, M.A. Ollino, A. J. Rest and L. M.Smith, J. Organomet. Chem., 1998,554,75. T . E. Bitterwolf, J. L. Haener, J. E. Shade, A. L. Rheingold and G. P. A. Yap, J. Organomet. Chem., 1997,547,23. N. E. Leadbetter, J. Lewis, P. R. Raithby and G. N. Ward, J. Chem. Soc., Dalton Trans., 1997,2511. N. E. Leadbeater, J. Lewis and P.R. Raithby, J. Organomer. Chem., 1997,543,251. L. Zhu and D. Kellis, Chem. Phys. Lett., 19!47,278,41. H. G. Jenniskens, L. Philippe, W. van Essenberg, M. Kadodwala and A. W. Kleyn, J. Chem. Phys., 1998,108, 1688. M. Galie, J. M. Rusnock, M. E. Yevich and C. A. Baumann, J. Phys. Chem. B, 1997,101,8304. C. P. Butts, L. Eberson, R. Gondles-Luque, C. M.Hartshorn, M.P. Hartshorn, M. Merchan, W.T. Robinson, B. 0. Roos, C. Vallance and B. R. Wood, Acra Chem Scand., 1997,51,984. C. P. Butts, L. Eberson, M. P. Hartsorn, 0. Persson, R. S. Thompson and W. T. Robinson, Acta Chem. Scand., 1997,51,1066. L. Eberson, M. P. Hartshorn and 0. Persson, Acra Chem. Scand, 1998,52,745. L. Eberson, M. P. Hartshorn and 0.Persson, Acta Chem. Scand., 1998,52,751. U. Berg, C. P. Butts, L. Eberson, M. P. Hartshorn and 0. Person, Acta Chem. Scand, 1998,52,761. C. P. Butts, L. Eberson, M.P.Hartshorn and 0. Persson, Acta Chem. Scund., 1997, 51, 718. Y. Akinaga, T. Taketsugu and K. Hirao, J. Chem. Phys., 1997,107,415.
326
Photochemistry
116.
G.-J. Kroes, M.C. van Hemert, G. D. Billing and D. Neuhauser, J. Chem. Phys.,
1997,107,5757. Q. Cui and K. Morokuma, J. Chem. Phys., 1998,108,626. W. M. Jackson, A. M. Mebel, S. H. Lin and Y. T. Lee, J. Phys. Chem. A , 1997,101, 6638. 119. A. M. Mebel, W. M. Jackson, A. H. H. Chang and S. H. Lin, J. Am. Chem. Soc., 1998,120,5751. 120. 0.Sorkhabi, V. M. Blunt, H. Lin, M. F. A’hearn, H. A. Weaver, C. Arpigny and W. M. Jackson, Planet. Space Sci,, 1997,4572 1. 121. H.-J. Deyerl, T. Gilbert, I. Fischer and P. Chen, J. Chem. Phys., 1997,107,3329. 122. M. Koyanagi and K. Uejoh, J. Lumin., 1997,72#4,5 11. 123. S . Shimizu, N. Nakashima and Y. Sakata, Chem. Phys. Lett., 1998,284,396. 124. R . N. Nurmukhametov, N. V. Ryzhakov, A. V. Gromov, A. V. Pebalk and I. E. Kardash, Zh. Fiz. Khim., 1997,71, 1122; Chem. Abstr., 1998,128, 160847~. 125. T. Noh, D. Kim and S. Jang, Bull. Korean Chem. Soc., 1997,18, 357; Chem. Abstr., 1997,127,65371g. 126. T . Gougousi, P. C. Samartzis and T. N. Kitsopoulos, J. Chem. Phys., 1998, 108, 5742. 127. F. Duschek, M. Schmitt, P. Vogt, A. Materny and W. Kiefer, J, Raman Spectrosc., 1997,28,445. 128. X. ZhengandD. L. Phillips, J. Chem Phys., 1998,108,5772. 129. D. L. Phillips and A. B. Myers, J. Raman Spectrosc., 1997,28,839. 130. H. M. Lambert and P. J. Dagdigian, Chem. Phys. Lett., 1997,275,499. 131. R. A. Brownsword, M. Hillenkamp, T. Laurent, R. K. Vatsa, H.-R. Volpp and J. Wolfrum, J. Phys. Chem. A, 1997,101,5222. 132. R. A. Brownsword, M. Hillenkamp, T. Laurent, H.-R. Volpp, J. Wolfrum, R. K. Vatsa and H.-S. Yoo, J. Chem. Phys., 1997,107,779. 133. A. Melchior, I. Bar and S. Rosenwaks, J. Chem. Phys., 1997,107,8476. 134. B. A. Balko, J. Zhang and Y. T. Lee, J. Phys. Chem A , 1997,101,661 1. 135. K. Tonokura, L. B. Daniels, T. Suzuki and K. Yamashita, J. Phys. Chem. A , 1997, 101,7754. 136. D. A. Blank, W. Sun, A. G. Suits, Y.T. Lee, S. W. North and G. E. Hall, J. Chem. Phys., 1998,108,5414. Lin, J. Chem. Phys., 1998,108,134. 137. Y.-R. Lee and S.-M. 138. H.-R. Park, Y.-T. Jeong, S.-K. KO, J. Oh and H.-S. Ham, J. Photosci., 1997,4, 17. 139. K. Iwata and H. Hamaguchi, J. Mol. Struct., 1997,4131414,101. 140. K. Nagahara, I. Ryu, M. Komatsu and N. Sonoda, J. Am. Chem. Soc., 1997, 119, 5465. 141. M. A. Miranda, J. Perez-Prieto, E. Font-Sanchis, K. Konya and J. C. Scaiano, J. Org. Chem., 1997,62,5713. 142. L. K. Sydnes and H. H. Ovrebo, Acta Chem Scand., 1997,51,889. 143. G.-J. Wang, R.-S. Zhu, H. Zhang, K.-L. Han, G.-Z. He and N.-Q. Lou, Chem. Phys. Lett., 1998,288,429. 144. T. Ichimura, Y. Mori, H. Shinohara and N. Nishi, J. Chem. Phys., 1997,107,835. 145. Y.-Q. Song, T. Yuzuri, H. Suezawa, K. Sakakibara, M. Hirota and M.Nakada, Bull. Chem. Soc. Jpn., 1997,70, 1875. 146. M. Robert, J. R. Snoonian, M. S. Platz, G. Wu, H. Hong, D. M. Thamattoor and M. Jones, Jr., J. Phys. Chem. A , 1998,102, 587. 147. M. Robert, I. Likhotvorik, M. S. Platz, S. C. Abbot, M. M. Kirchoff and R. Johnson, J. Phys. Chem. A , 1998,102, 1507. 117. 118.
IIl7: Photoelimination 148. 149. 150. 151. 152. 153. 154. 155. 156. 157. 158. 159. 160. 161. 162. 163. 164. 165. 166. 167. 168. 169. 170. 171. 172. 173. 174. 175. 176. 177. 178. 179. 180. 181. 182.
327
J. J. Gajewski and G. C. Paul, TetrahedronLett., 1998,39,351. J. C . Polanyi, N. S.-K. Sze and J.-X. Wang, J. Phys. Chem. A , 1997,101,6679. I. Kovacs and F. Solymosi,J. Phys. Chem. B, 1997,101,5397. G. S. Hsiao, W. Erley and H. Ibach, Surf: Sci., 1998,396,422. C . A. Longfellow, C. L. Berrie, A. G. Suits and Y. T. Lee, J. Chem. Phys., 1997,107, 7202. K. K. Pushpa, A. Kumar, P. D. Naik, K. Annaji Rao, V. Parthasarathy, S. K. Sarkar and J. P. Mittal, Chem. Phys. Lett., 1997,279, 172. J. A. Torresano and M. Santos, Chem. Phys. Lett., 1997,277,39. C . Kerst, R. Boukherroub and W. J. Leigh, J. Photochem. Photobiol. A: Chem., 1997,110,243. C. J. Bradaric and W. J. Leigh, Can. J. Chem., 1997,75, 1393. Y . Apeloig, D. Bravo-Zhivotovskii, I. Zharov, V. Panov, W. J. Leigh and G. W. Sluggett, J. Am. Chem. Soc., 1998,120,1398. T. Hoshi, R. Shimada, C. Kabuto, T. Sanji and H. Sakurai, Chem. Lett., 1998,427. H. Tachikawa, J. Organomet. Chem., 1998,555,161. M. Castillejo, R. de Nalda, M. Ouija, L. Diaz and M. Santos, J. Photochem. Photobiol. A: Chem., 1997,110, 107. M. Kako, S.Oba, R.Uesugi, S. Sumiishi, Y. Nakadaira, K. Tanaka and T. Takada, J. Chem. SOC.,Perkin Trans. 2, 1997,1251. M. Weidenbruch, L. Kirmaier, H. Marsmann and P. G. Jones, Orgunometullics, 1997,16,3080. K. Mochida, M. Akazawa, M. Goto, A. Sekine, Y. Ohashi and Y. Nakadaira, Organometallics,1998,17,1782. M.Kako, M.Ninomiya and Y. Nakadaira, J. Chem. SOC.,Chem. Commun.,1997, 1373. T. Kusukawa and W. Ando, Organometallics, 1997,16,4027. M. C . Courtney, M.Mella and A. Albini, J. Chem. SOC.,Perkin Truns. 2, 1997, 1105. M. A. Brook, C. Gottardo, S.Balduzzi and M. Mohamed, Tetrahehon Lett., 1997, 38,6997. Y.Kimura, K.Sugihara, M. Terazima and N. Hirota, Bull. Chem. SOC.J p n , 1997, 70,2657. A. P. Blokhin, M. F. Gelin, S. A. Polubisok, V. A. Tolkachev and A. A. Blokhin, J. Mol. Struct., 1997,408/409, 569. M. M. Alam, 0.Ito, Y. Koga and A. Ouchi, Int. J. Chem. Kinet., 1998,30,193. H. Gross, G. Grassi and M . Quack, Chem., Eur. J., 1998,4,441. F. Wu, X.Chen and B. R. Weiner, J. Phys. Chem. A , 1998,102, 1450. W. Adam, 0.Deeg and S . Weinkotz, J. Org. Chem., 1997,62,7084. I. Ono, S.Sato, K. Fukuda and T. Inayoshi, Bull. Chem. SOC.Jpn., 1997,70,2051. 0.E. Edwards, G. Grue-Ssrensen and B. A. Blackwell, Can. J. Chem., 1997,75,857. I. R. Dunkin, J. Gqbicki, M. Kiszka and D. Sanin-Leira, Spectrochim. Acta, Part A , 1997,53,2553. A. Barth, J. E. T. Corrie, M. J. Gradwell, Y. Maeda, W. Mantele, T. Meier and D. R. Trentham, J. Am. Chem. SOC.,1997,119,4149. T. Voelker, T.Ewell, J. Joo and E. D. Edstrom, TetrahedronLett., 1998,39,359. R. Reinhard and B. F.Schmidt,J. Org. Chem., 1998,63,2434. L.Peng, J. Wirz and M. Goeldner, TetrahedronLett., 1997,38,2961. R. P. Haugland and K. R.Gee (Molecular Probes, Inc., USA), US Patent US 5 635 608,3 Jun.1997; Chem. Abstr., 1997,127,817842. S . Watanabe and M. Iwamura, J. Org. Chem., 1997,62,8616.
328
Photochemistry
183. W. Pfleiderer and S. Eisele, German Patent DE 19 620 170, 27 Nov. 1997; Chem. Abstr., 1998,128,13405~. 184. H. Shiono, H. Kodama and M. Kojima (Laboratory of Molecular Biophotonics, Japan), PCT Int. Appl. Patent W O 97 47 639, 18 Dec. 1997; Chem. Absrr., 1998,128, 102344~. 185. R. Rodebaugh, B. Fraser-Reid and H. M. Geysen, Tetrahedron Lett., 1997,38,7653. 186. C . P. Holmes (Affymax TechnologiesN. V., UK), US Patent US 5 739 386, 14 Apr. 1998; Chem. Abstr., 1998,128,295056h. 187. F. Yagihashi, A. Kiyomori, T. Iwasaki and J. Hatakeyama (Shin-Etsu Chemical Industry Co., Ltd. Japan), Japanese Patent JP 10 77 264, 24 Mar. 1998; Chem. Abstr., 1998,128,243959k. 188. D. A. Blank, A. G. Suits, Y. T. Lee,S. W. North and G. E . Hall, J. Chem. Phys., 1998,108,5784. 189. L. Khachatryan, Y. Haas and J. Pola, J. Chem. Soc., Perkin Trans. 2,1997,1147. 190. R. Meller and G. K. Moortgat, Int. J. Chem. Kinet., 1997,29,579. 191. M. Fujiwara and K. Toyomi, J. Chem. Phys., 1997,107,9354. 192. M. G. Siskos, A. K. Zarkadis, S. Steenken, N. Karakostas and S. K.Garas, J. Org. Chem., 1998,63,3251. 193. T. Fukuju, H. Yashiro, K. Maeda, H. Murai and T. Azumi, J. Phys. Chem. A, 1997, 101,7783. 194. F. Chiapperinoand D. E.Falvey, J. Phys. Org. Chem., 1997,10,917. 195. U. Pischel, W. Abraham, W. Schnabel and U. Miiller, J. Chem. SOC.,Chem. Commun., 1997,1383. 196. L. Chen, L. Lucia and D. G. Whitten, J. Am. Chem. Soc., 1998,120,439. 197. B. Barker, L. Diao and P. Wan, J. Photochem. Photobiol. A: Chem., 1997,104,91. 198. K. Nakatani, N. Higashida and I. Saito, Tetrahedron Lett., 1997,38, 5005. 199. A. Ouchi and Y.Koga, J. Org. Chem.,1997,62,7376. 200. C. Crepin, N. Legay-Sommaire, J. G. McCaffrey and A. Tramer, J. Phys. Chem. A , 1998,102,4014. 201. J. A. Tossell, J. P h p . Chem. A, 1998,102,3587. 202. 1. F . Gun’kin and E . F. Finaenova, Rum. J. Gen. Chem., 1997,67, 19. 203. R. J. Lavallee and C. Kutal, J. Photochem. Phorobiol. A: Chem., 1997,103,213.
Part 111 Polymer Photochemistry By Norman S. Allen
Polymer Photochemistry BY NORMAN S. ALLEN
1
Introduction
The field of polymer photochemistry continues to expand in to many new areas of academic interest and industrial development. Photolithography is still being developed particularly with regard toward designing systems for molecular devices. There continues to be a very marked increase in interest in active ionic initiators and radicaYionic processes while the photocrosslinking of polymers is attractive in terms of enhancing the physical and mechanical properties of materials. The luminescence of polymers, particularly the use of probes and excher formation, continues to be an active area as a means of studying their macromolecular structure, energy migration and molecular mobility. Polymer interactions and behavioural features in micellar media provide a valuable probe for determining molecular sizes and forces in surfactant systems. In terms of growth, interest in polymeric light emitting diodes has markedly increased since there are obvious commercial implications. On a more commercial front, the photooxidation of polymers continues to attract attention with a sustained special interest in natural cellulosic-based materials. Bio- and photodegradable plastics are important for agricultural usage although interest in this area appears to be in decline. The same applies to polymer stabilisation where commercial applications dominate very much with much emphasis on the practical use of stabilisers. The stability of dyes and pigments continues to be of major concern. 2
wotopolymerisation
Interest and activity in a field is often a reflection of the number and variety of papers that have appeared of a topical or review nature. This last year has seen over twenty articles to date. An extensive review has appeared on the function of different types of photoinitiators and their future development' as well as a large number of overviews* and advances in terms of developments in the different types of application system^?^ A number of articles have targeted interest in photosensitive emulsion polymers, lo novel highly catalytic systems,' I anaerobic adhesives' and liquid crystalline materials."" Photocuring reactions for 3D moulds is an area of significant industrial intered6 as is smart card production for security." Recent trends in radiation Photochemistry, Volume 30 0The Royal Society of Chemistry, 1999 331
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Photochemistry
grafting onto polymer surfaces for compatibility processes have also been discussed" while the conditions for protection of metal substrates by water based coatings have been described in detail." Pulsed lasers have been found to be especially useful for obtaining propagation rate constants20while the photopolymerisation of Cm-fullerene has extensive interest.*l Extensive applications of the diazonium sulfonate group have been covered in as have tagged poly(viny1 alcohols).23
2.1 Photoinitiated Addition Polymerisation - New photoinitiator systems continue to be developed. Several carboxylic amide derivatives of thioxanthone have been synthesised and their photoactivity in curing has been related to their absorption spectra in the region of optical Derivatives based on 1chloro-4-acyloxythioxanthonehave also been synthesised and found to exhibit enhanced triplet nn* activity through the electron withdrawing effect of the 4acyloxy High photocuring activity was also observed in the presence of oxygen and under visible light due to photodehalogenation of the 1-chloro group to produce active chlorine radicals. An extensive range of novel 4'-(4-methylpheny1thio)benzophenone photoinitiators has been synthesised and their photochemical properties establishedF8 The bistolylthio groups were found to exhibit the highest activity using RTIR for monitoring photocuring whereas a 4-nitro group exhibited a marked deactivating effect. The substitution of long alkyl groups also gave increasing photoactivity. Triplet states with a strong n d m * mixing were found to be responsible for the observed photoactivity. In the case of a benzophenone amine system the amine N,N-dimethylaniline has been found to be the initiator of p~lymerisation~~ while a series of 2,Gdihalogen derivatives of p-nitroaniline have been found to be more photoactive than a range of aromatic ketone initiator^.^' A series of silane photoinitiators with 2-benzoylbenzoic acid ester side groups has been made and found to be markedly photoactive, especially when used in conjunction with an amine ~o-synergist.~' In a recent assessment of such initiator types the benzoyl radical is considered to be the effective initiator while the alkoxybenzyl radicals are essentially terminator^.^^ Aromatic amines continue to be examined as oxygen scavengers during p h o t ~ c u r i n gin~ ~ order to enhance cure rates while pyrazoline compounds are effective photoinitiators for the photopolymerisation of methyl methacrylate and effectively become part of the polymer structure.34 Iron-arene complexes are known to exhibit extremely high photoactivity as initiators. Quantum efficiencies have been found to be greater than 1 in the photopolymerisation of dicyanate esters.35 Phenylglycine derivatives have been found to be excellent co-synergists for the iron-arene complexes36when used in conjunction with dyes and amines. Complexes of various types have also been proposed. Maleic anhydride-THF complexes have been used for the photopolymerisation of oligourethane a ~ r y l a t e while s ~ ~ metal-ion complexes of spiropyran copolymers undergo reversible polymer precipitation.38 Azo and polyazo initiators have been used to make butadiene-isoprene block copolymers39 while charge-transfer complexes of morpholine-chlorine induce the radical polymerisation of methyl metha~rylate."~' The presence of zinc chloride enhances the
HI: Polymer Photochemistry
333
polymerisation of the same monomer by benzoin ether initiators.42 The zinc chloride forms a complex with the vinyl groups. Telechelic polystyrenes have been made using diphenyl diselenide as initiator43and AIBN has been used to copolymerise dibutyl tin maleate with vinyl acetate.44 Photoiniferters based on N,N-dialkyldithiocarbamylacetateshave been used to make block copolymers of styrene with methyl m e t h a ~ r y l a t eand ~ ~a~ photosensitive ~ poly(ary1ene ether) with pendant benzoyl groups has been made?’ Photoinduced free radical polymerisation of acrylate monomers has been found to give high yields of stereoregular syndiotactic polymers4’ when compared with that of a room temperature thermally polymerised material. The use of bulky amines such as dicyclohexylamine enhances the stereospecificity of the polymers. The geometry of the excited state of the photoinitiator appears to be important in the control of the orientation of addition of monomer to the propagating macroradicals. A number of novel monomers have been synthesised and their properties studied. Ionic polymerisation of 4-vinylbenzene afforded high yields of a photochromic polymer material5* where the cis-trans isomerism is independent of molecular weight. Polymeric fullerene hydrides have been synthesised that have the potential for storage of hydrogen gas51while methacrylate monomers with azobenzene side groups have been polymerised and found to exhibit deviations from normal polymerisation kinetics due to monomer a g g r e g a t i ~ nThe . ~ ~ laser induced decomposition of silacyclobutanes yielded silenes that subsequently polymerise to give polycarbo~ilanes~~ while the photopolymerisation of oligoorganosilaoxanes is inhibited by oxygen.54Two different template processes have been observed in the photoinduced polymerisation of methacrylic acid with macroaz~initiators~~ and a new light emitting polynorbornene has been synthesised by a ring opening metathesis of coumarin-containing derivative^.^^ Novel photopolymers based on 4-(2-hydroxymethylpropanoyl)phenoxyethyl-2-(2-propenylamino)-2-methylpropanoate have been made and their microstructure det e m ~ i n e dwhile ~ ~ copolymers with amidic arylsulfonate groups are water soluble.58Photopolymerised C a has been found to exhibit a zig-zag conformation5’ and, using a pulsed laser, the excited state characteristics of photopolymerised Cm have been examined on a Cu substrate.60 Polyethers containing coumarin dimers photopolymerise to give coumarin dimer based polymers in the main chain.61The configurations of the dimeric units were found to be highly dependent upon the substitution in the units. Under 254 nm irradiation these polymers cleave to give dioxycoumarins which, on subsequent irradiation with longer wavelength light (>300 nm), polymerise to give dimeric products.62 Substitution of a methyl group in the coumarin units enhances the rate of photopolymerisation due to electron donation increasing the absorption of the chromophores. Noncovalent interactions between diphenylbutadienes and 2,3,4,5,6-pentafluorodiphenyldiacetylene have been used to align diyne molecules for polymerisation in the solid ~ t a t e . 6Irradiation ~ of the stacks resulted in initial crystal formation followed by shattering to give dark-red powders that consisted of low molecular weight alternating head-to-tail homo and copolymers. Cationic triarylsulfonium initiators have been doped into poly(3-alkylthiophene) to enhance its electrical conductivityMand a range of spectrally tuned photoinitiators
334
Photochemistry
have been examined in clear coatings.65 Photopolymerised poly(viny1 pivalate) has been found to yield highly syndiotactic poly(viny1 alcohol) upon subsequent hydrolysis.66 High conversions were obtained using AIBN as initiator and the thermal stability of the polymer was significantly greater than that obtained by conventional hydrolysis of poly(viny1 acetate). Acrylamide is reported to be useful for the production of highly diffractive hologram^.^^ A number of papers have appeared dealing with the use of maleimides. N-[5[[2-(vinyloxy)ethoxy~arbonyl]pentyl]maleimide undergoes rapid photocuring without the requirement of a photoinitiator.68The monomer itself is also an effective photointiator for the curing of acrylic systems. A series of novel Nphenyl maleimides have been synthesised and found to undergo rapid polymerisation in the presence of N,N-dimethyl-4-t0luidine.~~ The imide was found to form an exciplex with the amine through which proton transfer was highly effective. Other workers have found that N-substituted maleimides can abstract hydrogen atoms from their e n ~ i r o n m e n tand ~ ~ can copolymerise effectively with vinyl ethers in the absence of an i n i t i a t ~ r . ~Maleimides ”~~ with carbonate groups are highly effective73374 as are bi~maleimides.~~ Donor monomers are found to be highly effective with maleimides, confirming the role of hydrogen atom transfer.76 Rates of photopolymerisation were found to be significantly faster than acrylate polymerisationsand had the additional advantage of being oxygen in~ensitive.~~ The rates and kinetics of photopolymerisation have been monitored in various ways. In this regard the photopolymerisation kinetics of the monomer 2-hydroxyethyl methacrylate are important in order to optimise the properties of the material for contact lens p r o d ~ c t i o nFor . ~ ~the same monomer 2,2-dimethoxy-2phenylacetophenone has been found to be the most effective ph~toinitiator.~~ Here the rate of polymerisation was found to influence the mechanical properties of the hydrogels produced. Interestingly low temperature methods have been developed for producing unimolecular nitroxide initiators for “living” free radical polymerisations.” Oxidation methods were used such as lead dioxide to generate carbon centred radicals in the presence of TEMPO. Macroiniferters have been found useful for producing block copolymers of vinyl monomers” while in the free radical polymerisation of HEMA the increasing concentration of N,N,N,N-tetraethylthiuram disulfide as co-initiator suppressed the rate of reaction.82The reactivity ratios have been measured for the photocopolymerisation of 1-(N,N-dimethy1amino)thylene-2- derivatives with butyl a ~ r y l a t eHere .~~ radical reactivity was found to increase with the electron withdrawing character of the substituents attached to the pposition of the nitrogen atom. Quantum mechanical models were developed to predict the activities of the radicals next to the hetero-atom. In the photopolymerisation of methyl methacrylate using p-nitroacetanilide as initiator high rates were achieved only in polar solvents.84 ESR spectroscopy showed the formation of both nitro and amine free radicals, with the latter being implicated in initiation. High photopolymerisation efficiencies have also been observed using p-nitroaniline as initiator together with N,Ndimethylanilinee5(DMA). Using photo-DSC the rate of polymerisation was found to be proportional to the square root of the DMA concentration and was significantly higher than that achieved by conventional aromatic ketone initia-
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tors. The use of poly(styrene peroxide) as a photoinitiator for methyl methacrylate has been found to exhibit unusual kinetic behaviour.86Here primary radical termination due to alkoxy radical decomposition was found to compete with primary radical initiation. Segments of the polymeric initiator were identified in the polymer formed. Thermal and laser induced polymerisations of styrene were found to exhibit the same rate constants while photoinduced polymerisation was twice as fast.87 The latter was associated with the use of broad wavelengths capable of photoexciting the propagating styrene radicals. A new mathematical model has been developed to determine the propagation rate coefficients for pulsed laser induced polymerisations.88 A number studies continue to show the value of fluorescence emission as a probe for polymerisation kinetics and conversions. Particle nucleation in emulsion polymerisation of styrene and methyl methacrylate has been investigated through the use of pyrene as a fluorescent For styrene, polymerisation was found to occur within the droplets whereas for the methacrylate monomer a homogeneous nucleation mechanism was in operation. In the microemulsion polymerisation of butyl acrylate, particle size increased with both monomer concentration and conversion time.g0 The photolysis of the monomer swollen emulsifier micelles generated the initiating radicals. Pyrene has also been used as a fluorescent probe in the photopolymerisation of methyl methacrylate to measure the gel effectg1whereas 4-maleimido fluoroprobe has been found to be the most effective fluorescent system for measuring polymerisation rates?2 In unpolymerised systems this probe is non-fluorescent while during polymerisation the loss of the maleimide C=C double bond results in saturated bond formation to give a succinimide. Even at low conversions the rate of fluorescence enhancement is very high and is coupled with the usual blue spectral shift in the emission wavelength associated with microscopic changes in the probe’s environment. Cationic photopolymerisation of vinyl ethers continues to attract interest. Using real-time infrared spectroscopy the rate of photopolymerisation of the vinyl ether of triethylene glycol proceeds rapidly with chain lengths of the order of 10,000?3 In the presence of an acrylic comonomer the acrylate was found to have twice the reactivity toward itself as that of the vinyl ether. The presence of a cationic initiator eliminated the content of unreacted double bonds. A novel visible photosensitiser based on a diphenyliodonium salt of an esterified eosine dye has been synthesised and found to be highly effkctive.94 Electron transfer from the anion to the cation takes place producing initiating phenyl and eosine radicals. A novel class of metal carbonyl pyridine complexes has also been prepared for visible sensiti~ation.~~ Here photoreleased pyridine radicals act as the initiator species. Cation species produced in the laser photolysis of onium salt systems have been measuredg6and found to accelerate the rate of photopolymerisation of acrylic monomers by thioxanthone photo initiator^.'^ The same cationic photoinitiators will induce the ring opening polymerisation of hexamethylcyclotri~iloxane~~ and the molecular weight has been found to increase with increasing light intensity. Onium butyltriphenylborates behave as donor-acceptor initiatorsw while silyl radicals generated from the photolysis of poly(methylpheny1silane) can be oxidised by N-ethoxy-2-methylpyridiniumiodide to give silyl radical
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cations.'00 In the presence of iodide ions Si-I groups are formed that can then initiate the polymerisation of butyl vinyl ether. Using an iron tris(2,2'-bipyridine) complex the rate of photopolymerisation of methyl methacrylate (MMA) shows a linear dependence on the MMA concentration.'" At high concentrations of this initiator the termination rate is high. Phenyliodonium hexafluoroantimonates have been found to induce the ring opening polymerisation of 4-methylene-2phenyl-1,3-dio~olane.'~~ Copolymers could be produced in this reaction with thermal characteristics being dependent upon the copolymer ratios. Other workers claim this reaction also results in the formation of terminal oxyallyl cationslo3 while a novel allyloxy-picolinium hexafluoroantimonate salt can photoinduce the polymerisation of cyclohexene oxide.'" In the latter case the use of benzoin ethers as coinitiators can markedly extend the spectral response of the system. Cyclohexene oxide has also been photopolymerised in the presence of noveI 2-methyl-l-(2-phenyl-2-propenyloxy)-pyridiniumhexafl~oroantimonate'~~ in conjunction with a free radical source. It is claimed that this co-initiator system can be effectively tuned to meet a number of cationically polymerisable monomer systems.
Photocrosslinking - A number of novel initiator systems have been developed for photocuring. Polymer based amine synergists derived from 4-aminobenzoic acid on a polyether chain exhibit high synergistic activity in the photocuring of acrylate monomers.'06 Here the advantages of low migration coupled with enhanced photoactivity were illustrated. Several substitution reactions have been undertaken on the commercial initiator 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyll-2-methylpropane-1-one by way of the hydroxyl group.107~108Water soluble amine groups have been found to be particularly useful for water based systems. A series of Schiff bases have been found useful for the curing of epoxy acrylates'@and 2-alkylanthraquinones are reported to be more effective initiators than many acetophenone and thioxanthone types. lo Polysiloxanes with pendant benzophenone groups have been studied in 2-ethylhexylacrylate by photoDSC' while a fluorone initiator has been found to be extremely effective in the curing of white pigmented coatings.' l 2 In the latter case synergism is observed when an iodonium salt is added to the system. Polytetrahydrofuran undergoes rapid crosslinking when sensitised by anthra~ene"~ as does a polymer with furan units on the backbone.'14 Thick films are claimed to be cured morz efficiently at low levels of photoinitiators' and highly effective organic-inorganic hybrid matrixes have been made by reacting silica using sol-gel techniques with epoxy and vinyl ether groups. l6 Photosensitive polymers based on 1,3-bis(3-ally1-4-hydroxybenzy1idene)acetone have been prepared via interfacial polycondensation' " as have thin film membranes with diazoketone groups."* Copolymers with both side chain thioxanthones and aminoacetophenone groups have been prepared' l9 and found to be highly synergistic in white pigmented coatings and squarylium dyes are effective photosensitisers in their region of optical absorption.'20 Layers of organic dyes and pigments in poly(viny1 butyral) have been found to be effective sensitisers for the photocuring of triacrylates.12' Phthalocyanine pigments are reported to be highly effective in this regard and dependent upon their photo2.2
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emf. Cyanine dyes when tagged to a triazine nucleus have been found to exhibit high photosensitivity when irradiated with a laser diode.'22 Osmium and ruthenium complexes of cymene are effective for the ring opening of norbornene and dicyclopentadiene.123 Here the Ru complexes were the more effective. Cationic photocuring has maintained a steady interest. Polydimethylsiloxanes bearing epoxy norbornyl groups have been prepared and cured for the first time with triaryl hexaflu~roantimonate.'~~ Maximum curing was observed at 50-60 '(2. Propenyl ether functional siloxanes have also been ~ynthesised.'~'-'~~ In one the crosslinking rate was found to be influenced by the type of a,oterminated disiloxane with a difference of ten orders of magnitude in rate between the aliphatic epoxy to the vinyl ether derivatives. Sulfonium salts are reported to be much less active than the lipophilic ionium salts. A random copolymer has been obtained in the copolymerisation of cyclopentene oxide with cyclohexene oxide using a phenyldiphenylsulfonium hexafluorophosphate initiator.I3' Cumene hydroperoxide enhances the cationic curing efficiency of epoxy resins by the cyclopentadienylferrocinium ~a1t.I~' In the same study benzophenone was found to operate in the same manner although no explanation was given. Here, sensitised photolysis of the cationic curing may be operative. Polymers bearing both epoxy and cationic units have been synthesised that can generate sulfonic acid groups on i r r a d i a t i ~ n . 'Using ~ ~ these polymers for CVD, alkylsiloxanes could be deposited as polysiloxane layers on irradiation. Allyloxystyrene monomers have been found useful for the production of thermally stable UV curable adhesives133while ruthenium complexes find applications for the photooxidative polymerisation of diary1 sulfide to give poly(thioarylenes).'34 Various dioxolanes have been copolymerised by a cationic initiator'35 and the reactivity of biscycloaliphatic epoxides has been e~a1uated.l~~ In the latter case the presence of an ester group plays a major role by interacting with the growing oxonium cation to give dioxacarbenium ions. Such species are less reactive and slow down the rate process as do ether groups. Different materials have been intercompared for commercial cationic photocuring' 37 as have the advantages of different hexafluoroantimonates. 38 Multifunctional silicon containing vinyl ethers have been made and photocured with hybrid mixtures of diphenylphosphines and sulfonium salts.'39 Similar hybrid systems have been found to be effective for pigmented coatings.'@ A number of new techniques in UV curing have been developed and studied. The spectral sensitivity of coatings is based on the technique of Internal Reflection spectroscopy and does not require the use of selective monochromatic sources.141Xenon chloride lamps are claimed to give very fast rates of photocuring when compared with medium pressure mercury lamps142and new photomoulding techniques have been developed for structurised surfaces.143 Raman spectroscopy has been found to be a valuable technique for the monitoring of the kinetics of photopolymerisation of vinyl ethers'44 as has photo-DSC equipped with a photodiode for monitoring turbidity changes.'45High aspect ratio microparts have been been developed using a sensitive photopolymer'46 and different polymers have been surface modified using argon p1a~mas.I~'Higher intensity UV lamps are claimed to give greater performance at lower initiator levels thus
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Photochemistry
achieving better co~t-efficiency'~~ and conductivity measurements are claimed to be useful for monitoring the photocuring of ink films. 149 Only a few studies have appeared on the photocrosslinking of thermoplastics. The nature of photocrosslinked structures in polyethylene has been determined by 13C-NMRspectroscopy.*50~15' Well-resolvedlines related to both a and P-CH2 groups from H-crosslinks were observed below the gel dose. Resonance lines due to Y-type long branches were also found at up to 21.6 per 10,000 carbon atoms. Using X-ray diffraction spectroscopy the crystallinity in these polymers was also found to be much reduced after phot~crosslinking.'~~ Four distinct types of ordering processes have been identified in the photocrosslinking of polymer blends'53 while polystyrenes ring substituted with thiocyanate groups undergo rapid photocrosslinking The main reactions appear to be cleavage of cyano and phenylthio radicals giving highly sensitive photoresist materials. The rates of photopolymerisation of styrene using an azo tagged polydimethylsiloxane have been been found to be less than that of the equivalent AIBN systemlS6and reaction rate exponents in the photocuring of various dimethacrylate monomers have been measured and modelled at different temperatures and pressures. 57 The photocuring of commercial acrylate prepolymers has been found to increase in terms of depth at lower initiator concentrat i o n ~ ' ~ ~while " ' ~ large monomer structures are reported to form more crosslinked structures.'60 Using DSC, photoconversions achieve a maximum at 90"C16'while other factors such as pigment levels and light intensity also play a Potassium persufate and hydrogen peroxide have been found to yield high concentrations of gels in the aqueous photopolymerisation of N-iso-propylacrylamidela with light below 290 nm. Hydrogen atom abstracting initiators were found to be less effective in this system. Diffusion appears to be the only reaction mechanism controlling the termination rate of acrylate monomers in an SBS c ~ p o l y m e r 'while ~ ~ in the photocuring of dicyanate esters cyclotrimerisation predominates.'66 Different techniques have been utilised to investigate photocuring kinetics. Fluorescence is a highly sensitive method and has been used to measure the photosensitisation of anthracene on the efficiency of diaryliodonium salts.167 Here photosensitisation was found to decrease with increasing viscosity of the resin. In the photocuring of 7,7'-coumarinyl polyethylene dicarboxylates fluorescence intensities of the polymers were found to match their curing rates.'68 In the presence of the benzophenone triplet sensitisation occurs to give anti-configuration products. Fibre-optic sensors have also been used to measure the curing of epoxy resins in composities'@ while complexes of europium with aminophosphazine tagged styrenes exhibit strong fluorescence properties,170 In the latter case hydrogen bonding interactions with the solvents were found to markedly control viscosity effects on the fluorescence. Different phase substrates were found to influence the photocuring of epoxy resins"' while in the photocuring of bis(maleimide)-diallylbisphenol resins the maleimide component quenched the fluorescence.'729173 During cure the phenolic portions of the resins gave enhanced fluorescence while the succinimide derivatives were weak emitters. RTIR continues be a widely used technique where rates of diacrylate curing have been
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found to be dependent upon light and this is in turn dependent upon the temperature increase as a consequence of the exotherm produced. This is also reported to be the case in the photocuring of thiol-ene ~ y s t e m s . ' ~ ~The *''~ photocuring of solid acrylates has also been examined'78 as have oligodimethacrylates. 79 For fibre reinforced resins photodynamic mechanical analysis has been found useful'8o as has dielectric spectroscopy'" and 13C NMR.182 PhotoDSc has been used to measure the viscosity effects on polymerisation rates. 183 Various new materials have been developed. Water soluble copolyamides have been made from hexamethylene adipate and piperazine-2,2'-0xybis(acetatate)'~~ where crystallinity was found to be unaffkcted by the polymerisation. Azoxyaromatic polyethers undergo photocrosslinking only at high temperature^'^^ while crosslinked ethylene-vinylsilanes are useful for electrical insulation. New materials based on copolysiloxaneimides have been synthesised and charact e r i ~ e dwhereas '~~ the dielectic characteristics of UV cured vinylsilane rubbers are controlled by the initiator concentration.188 A tetra-functional cyclotetrasiloxane has been prepared which undergoes photocycloaddition by way of the ethenyl groups to form a thermally reversible crosslinked network. Polydimethylsiloxanes with oxetane groups have also been made'w and found to undergo maximum curing at 8OoC.Epoxy resins have been cured using a range of novel imidazole derivative^'^' as have epoxy resins and vinyl siloxanes in the presence of partially photocured vinyl The latter are claimed to produce materials with good optical characteristics. Photothermoplastic layers have been prepared from novel monomers of carbazole tagged ~inylsilanes'~~ as have inclusion compounds that give polyrotaxanes.lg4 Polymerisable acrylated gelling agents have been developed for organic solvents,'g5the thermal stability of which increases with subsequent light exposure in the presence of an initiator. The role of curable composites in industry has been discussed'96 while in photoemulsion polymerisation initiation occurs at the interface of the oil and water phases.197In the latter case particle size increases with increasing polymerisation time. Poly(vinyl alcoho1)s with pendant acrylic and acrylamide groups have been synthesised and are useful for making contact lenses.'98 Polymers with pendant ethyl phenylglyoxylate undergo hydrogen atom abstraction by an intramolecular process'w while photoreactive diimides have been made and are useful negative type resists.200Polyimides with chalcone moieties are highly thermally stable resistsm' while the thermal stability of other resists requires improvement?o2 Polymers with triazeno groups are also useful photo resist^^^^ while a new type of diacrylate of propylene glycol has been synthesised for photocuring.20q Multifunctional Eketoesters with vinyl groups and acrylates have been found to undergo photocuring to give two distinct highly crosslinked phases with interpenetrating networks.2o5Polystyrene block copolymers with cinnamoylethyl methacrylate groups undergo photocrosslinking to yield star type po1ymers2O6in micelles in solution. The aggregation numbers of these star micelles were found to follow theoretical scaling laws. Dienes and bismaleixnides have been photocuredm and the microstructure'of N-substituted polyacrylamides has been determined by 13C NMR.208 The properties of vinyl esters for glass
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Photochemistry
composites,209coatings for leathe?" and epoxy functionalised materials2'19212 have been examined while irradiated polyesters with norbornadiene units yield large amounts of energy upon conversion into quadricyclane Photoreactive polymers have been made by the polycondensation of diacrboxymethoxy1,4-oligobutadiene with a hydroxy terminated oligomers with acrylic acid:15 pentaerythritol and 1,2,4-benzenetricarboxylicanhydride216and polycarboxylic acids with p o l y ~ l s . ~ ' ~ Diphenylacetylene polymers containing acrylate groups are reported to cure at different temperatures218while the quenching effect of oxygen on photocuring has been found to be highly monomer dependent.219A model system has been developed for the preparation of macroporous monolithic sorbents from glycidyl methacrylate and trimethylolpropane trimethacrylate.220The porous properties of the monoliths depend upon the quality of the porogenic solvent, the percentage of crosslinkable monomer and the ratio of monomer to the porogen phases. The gas selectivitiesof polyimide membranes are enhanced with irradiation time22'as is the thermal stability of pentacosa-lO,12-diynoicacid.222Crosslinked heterocyclic structures have been produced from copolymers of 2-(4-ethenyl)phenyl-5phenyl-2H-tetra~ole~~~ while gel formation in mixed methacrylate oligomers depends upon the reactivity of pendant vinyl Photocrosslinkable starch was made by acrylating the carbohydrate structure225while photosensitive polymers have been characterised based on oligocarbonate methacrylates:26 p ~ l y i m i d e s ,poly(L-lactic ~~~ acid-co-L-aspartic acid):28 poly(urethane acrylates),229y230 glycol a ~ r y l a t e s and ~ ~ ' pigmented coatings.232Some low temperature anomalies have been observed in poly(viny1 alcohol) photo polymer^^^^ while polymerisable double bonds have been introduced into silica fillers by crosslinking in epoxy acrylate resins.234Spherical microcapsules have been made by p h o t o c ~ r i n gand ~ ~ in ~ asymmetrically photocrosslinked polymers positive feedback loops are driven by concentration fl~ctuations?~~ Microfabrication techniques have been developed through the use of titanium-sapphire lasers237while centrifugal force influences the gelation of polya~rylamide.~~~ Micromoulding has been developed239as have polyimide membrane? whereas ancient Japanese varnishes have been found to give gold coloured coatings on exposure to light.24' A number of articles deal with polymers undergoing a (271 + 2n) cycloaddition reaction. Vinylamine polymers functionalised with cinnamoyl groups are one such class exhibiting high h y d r ~ p h i l i c i t yand ~ ~ ~ hydroxyethyl methacrylate copolymers behave ~imilarly."~In the latter case no evidence was found for cistrans isomerism. Polymers based on diarylidene-cycloalkanonealso undergo cycloaddition to give flame retardant materials244 as do a new class of poly(benzy1idene p h o s p h ~ r a m i d e s ) . The ~ ~ ~ extent ~ ~ ~ of cycloaddition of poly(methacry1amides) with chalcone groups is influenced by the presence of the spacer whereas furan derivatives in the presence of Csoundergo a 2+4 cycloaddition reaction where singlet oxygen appears to be implicated in an initial step involving oxidation of the Poly(viny1 cinnamate) is claimed to undergo marked refractive index changes on cy~loaddition~~' while polyp-(phydroxypheny1)maleimide with cinnamoyl groups gives good negative resist materials.252
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A number of studies have appeared on photopolymerisable liquid crystalline polymers. Both mesogenic and non-mesogenic p-phenylene diacrylate and 1,6hexanediol diacrylate have been photopolymerised in order to examine the influence of monomer and order on the physical and optical properties of the Polymerisation rates increased with increasing order while in isotropic solution rates were slower. Differences in rates of termination were found to be responsible for the rate variations with a high degree of termination in ordered systems. Various block copolyetheresters produce thermotropic liquid crystals258as do methacrylate copolymers with alkenyloxy-biphenyl m e ~ o g e n s . ~ ~ ~ Anisotropic properties of crosslinked polymers are important in many structural applications.260This orientation is frozen-in the network after crosslinking26' giving high glass transition temperatures. A number of other studies have also dealt with monomer composition and temperature effects on liquid crystalline Both these factors were found to influence switching voltage, luminance and response times. Metal complexes of 3,4-bis( 11-acryloylundecanoxy)benzoate based on Zn(I1) or Mg(1I) gave photopolymerisable liquid crystalline products with a high residual metal content.264Gravity effects have also been examined on polymer dispersed liquid crystals265to determine phase separations in space craft. Polycarbonates containing 4,4'dihydroxychalcone groups have been found to be non-mesogenic while those with isosorbide and biphenyl groups were thermotropic.266All these polymers crosslinked on irradiation. Diacrylate liquid crystalline systems are reported to phase separate due to unreacted while alignment in liquid crystalline polymers with cinnamoyl groups depends upon the time of exposure?@ In another study it has been shown that although a diacrylate monomer prefers to diffuse to areas with high light intensity monoacrylates prefer low intensity light.269 Using mixed systems, holograms could be produced. Analysis of liquid crystalline materials by ionisation mass spectrometry has been found to be effective for large ions when using hexadecane as a solvent270and a general overview on producing ordered photopolymerised films has appeared.271
2.3 Photografting - The photografting of monomers onto polymer substrates continues to attract interest for property modifications. N,N-Dimethylacrylamide has been successfully photografted onto the surface of poly(ethy1eneterephthalate) using an excimer lase?72 as has acrylamide onto the surface of PTFE to reduce the Methyl methacrylate has been photografted onto 0-acetyl chitin2" and acrylic acid onto c e l l ~ l o s with e ~ ~the~ presence ~ ~ ~ ~ of aromatic ketone initiators enhancing the rate of grafting. Superacidic sites such as SO:- have been photografted onto the surface of fluorinated polymers278as has styrene onto polypropylene.279In the latter case benzophenone gave good graft yields whereas other initiators tended to produce high yields of unwanted homopolymer on the surface. Acrolein has been photografted onto gold surfaces2**and vinyl monomers onto glass plates.281In the latter case azo groups had to be first attached to the glass surface using 4,4'-azobis-(cycloptanoic acid) with isocyanate groups. Organic liquids have been separated by a novel method involving surface grafted hydrophilic membranes of poly(acrylonitri1e)
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Photochemistry
with methacrylate-glycol mixtures.282Here variations in the membrane composition could be targeted toward specific solvent mixtures. Fluorescence depolarisation has been used to monitor the local mobility of polymer chain grafts onto polyethylene membranes.283In general polymer surface modification can produce marked property changes in materials for a host of applications, including the attachment of antibodies for diagnostic applications and purifaction methods?84
3
Luminescence and Optical Properties
The field of polymer luminescence and general optical properties continues to grow at an alarming rate with particular interest centring on polymers for LED applications. This last year has seen an exponential growth in papers in this area with the emphasis being on the poly(pheny1ene vinylenes). A number of specific reviews of interest have appeared. Pulp and cellulose are materials where fluorescence and degradation are of particular concern.285New generations of efficient fluorescent polymers have been reviewed286as have new electrosensor devices.287Reviews have been published on LED liquid crystalline materials,289 polymer stereochemistry,290 fluorescence depolari~ation~~' and stimuli-responsive polymers.292 A number of articles have appeared on photochromic polymers. Living free radical systems have been synthesised based on 4-vinylpyridine followed by reaction with spiro[cycloprene-l,9'-fl~orenes].~~~ The photochromic properties of Bisphenol-A coatings with spirooxazine are dependent upon the prior thermal treatment of the polymer.294The addition of fluorosilanes to the polymer enhances both the abrasion and photostability of the system. The applications of spiropyranic based polymers are widespread295with a number of copolymers having been made based on and water soluble met ha cry late^.^^^ In the latter case evidence was obtained for photoinduced associations in water which can be suppressed by the addition of co-ions. A new bicyclic (spiro) bindon derivative has been made which exhibits second order NLO properties showing visible changes from red to green298while spironaphthoxazine tagged to methyl cellulose showed significant fatigue.299Spirobenzopyrans with ~alicylaldehyde~~ and silyoxy groups'*' have been synthesised as have silsesquioxanes with 1-(2methylbenzo[b]thien-3-y1)-2-[5-(butylphenyl)-2,4-dimethylthien-3-yl]-pe~uorocy~lopentenes.~'~ In the latter case although there was no effect of Tg on the photoconversion rates, the polymer itself reduced the efficiency when compared with the non-bonded chromophore. Polymers with azo chromophores are also attractive and have rates of isomerism considered to be higher than those in liquid ~ysterns.''~cis Isomers of azobenzene chromophores tagged onto poly(Llysine) are perpendicular to the surface304while in a polyester environment the same chromophore exhibits a biexponential decay.305Dielectric spectroscopy is useful for studying phot~chromisrn~'~ and alkylammonium silicates are excellent reaction media for the immobilisation and isomerism of azobenzene The trans-cis isomerism of azobenzene groups in styrene-diblock copolymers has been found to be dependent upon the thermal motion above and below the
III: Polymer Photochemistry
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polymer while in methacrylate copolymers the mobility of the azobenzene chromophore increases with increasing butyl methacrylate content.309 In the latter case thermal and photoisomerism processes are involved, as are in-plane inversion and an out-of-plane rotation of one of the phenyl rings of the azobenzene chromophore. Novel photochromic amphiphiles of 4-(4'-alkylpheny1azo)benzoic acids have been developed3" as Langmuir-Blodgett films in the trans form only. Attempts to synthesise the cis isomer failed. The colour of polyacetylene monolayers cast onto an azobenzene monolayer has been found to depend upon the trans-cis form of the latter.311It is claimed that this is a novel method of molecular switching through surface photochromism. The length of alkoxy tail groups on photochromic poly(g1utamates)has been found to influence the crystallinity of the and this in turn influences the extent of the photochromism. Highly stable cis isomers have been produced from crown ether styryl dyes with am- 15-crown-ether moieties314 while packing azobenzene moieties into polysilaoxanes alters the phase transition temperature of switching.315 Raman spectroscopy has been used to study the surface activity of benzodithiacrown ether styryl dyes316while colour transformations have been measured for polymeric phenoxyanthraquinone dyes.317*318 Norbornadiene based copolymers exhibit high refractive changes as well as high yields of isomerism319J20 whereas photochromism in poly(diacety1enes) is associated with excitation excitonic relaxation p r o c e ~ s e s . Chiral ~ ~ ~ *t h~ i~~~x a n t h e n eand ~ ~ polycyan~rate~" ~ copolymers have also been made as have copolycarbonates with isosorbide The latter were found to exhibit NLO properties. Keto-enol tautomers are responsible for photochromism in N,N-bis-Schiff bases.326 General opt-electronic properties of polymers have shown that two types of polypropylene crystal play an important role as traps for excited electrons which on release give thermolumine~cence?~~ Increasing irradiation time reduced the thennoluminescence intensity. In polyethylene the electroluminescence varies with the excitation source used.328Carbonyl doping indicated that the chromophores were similar. Variations in emission spectra from polyethylene have also been observed after oxidation.329However, when electrically stressed, the observed emission is not due to impurities.330In the case of poly(acetylene), lattice dimerisation has been observed331which supports solitons while polymer tagged with azobenzene groups exhibits NLO properties.332Photoinduced phase transitions in poly(acety1ene) have been found to occur within 50 ns333while vibrations around a soliton can be described by the Hiickel A theoretical analysis has been made of the photoinduced IR absorption spectra of p~ly(diacetylene)~~~ whereas poly(ani1ine) and poly(pyrro1e) coatings have been photosensitised by a polaron mechanism.336 Two a-carbonyl biphenyl lignin models have been characterised by phosphorescence spectroscopy337while treeing luminescence has been characterised in poly(methy1 m e t h a ~ r y l a t e )In .~~ the ~ same polymer thermoluminescence has been used to measure the recombination processes of photoejected electrons and cations formed through a two photon ionisation process.339 The electrons were found to form stable anions with a motional relaxation of the polymer. Scanning near field optical images of doped polystyrene have been obtained.340Attempts have been made to determine the groundstate structure of
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Photochemistry
dimers of C60341while oxygen diffusion rates in poly(methy1 methacrylate) have been measured through the quenching of the phosphorescence of probes.342Time resolved fluorescence can be used to measure internal stresses in polymers343 whereas the fluorescence of polymethine dyes is reduced on heating.344 Soluble poly(ary1 ketone) polymers have been synthesised that exhibit green fluores~ e n c while e ~ ~the ~ fluorescence of perylene dyes is dominated by self absorpt i ~ nPolar . ~ ~order in a polymer has been demonstrated through dual-frequency interferences using appropriate combinations of circular writing beam polarisati on^.^^^ For the case of a fundamental beam with linear polarisation, second harmonic generation was found to be independent of the polarisation direction. A 1,l’-binaphthol based optically active oligomer with a 3,3’-acetylene spacer has been made348 which exhibits reduced delocalisation on twisting. The local polarity in poly(ethy1ene terephthalate) has been measured using the positions of solvatochromatic dyes349while distyrylbenzene fragments have been identified in p~ly(p-xylylene).~~~ Intermolecular interactions have been examined on the luminescent properties of conjugated polymers35’ and liquid phase thermometers have been developed for use at high temperatures.352 The fluorescence from polyesters of coumarin has been found to disappear on heating353while that from c 6 0 red shifts with increasing applied pre~sure.~” A fluorescence based thermal imaging system has been developed for identifying regions of thermal damage in a polymer matrix.355An obvious application here is in the aerospace industry. Steric effects play an important role in the luminescence of l - m e t h y l p y r r ~ l e ~ ~ ~ while surface transformations can influence the luminescence of polymers.357 Photocarrier generation has been observed in poly(dimethy1silane~)~~~ whereas increasing imidisation in polyamic acids and polyimides enhances the degree of charge-transfer fluorescence.359Poly(3-alkylthiophenes) exhibit low fluorescence quantum yields360while poly(dimethylsi1ane) films cast onto PTFE exhibit high fluorescence intensities due to an increased number of delocali~ations.~~~ The effect of lattice fluctuations on the photoexcited relaxation processes in transpolyacetylene has been examined.362 Earlier studies are claimed to have overlooked these fluctuations on relaxation processes. The luminescence spectra of poly(4,4‘-dialkyl-2,2’-bithiazole-5,5’-diyls) demostrate stacking of the chains363 while poly(carbazoly1 oxiranes) only show monomer f l ~ o r e s c e n c ePolyamides .~~ have been synthesised with coumarin groups365that exhibit green fluorescence emission and confocal microscopy has been used to measure the surface and fracture properties of polymers.366 The red phase of polydiacetylene which is observed in the dark transforms to a blue phase on irradiati~n.~~’ This process occurs at low light intensities and is due to the transformation of excitation energy from the main chains to side chains giving rise to conformation reconstruction into an ordered phase. Polysilane copolymers have been found to exhibit luminescence368while those with stilbene units undergo cis-trans isom e r i ~ m Fluorescent .~~~ copper and silver complexes based on 1,8-diisocyano para-methane have been ~ynthesised,~~’ and ancient green coloured cloths,have been identified by fluorescence analy~is.~” As mentioned earlier one of the most active areas of polymer photochemistry with growing interest is that dealing with polymeric light emitting diodes. This
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last year has seen the appearance of over 80 research papers on the subject. Two extensive reviews on this subject have appeared with emphasis on methods used to enhance the quantum yield of Some quantum mechanical theory is also presented on these materials.374Ternary and binary rod-coiled systems have been explored to determine the effects of structure on emission quantum yields.375Enhanced emission was observed from the ternary rod-coiled system with two rod-like segments having different excitation energies. It was suggested that these polymers could be used for electrically induced lasering. Time-resolved studies on poly(p-phenylene vinylene) (PPV) and its cyano derivatives has shown that the PPV emission is consistent with ultrafast intrachain excitons whereas the cyan0 derivative formed inter-chain e x ~ i t o n s . ~ ~ ~ , Using femtosecond spectroscopy the excitons decay with a dual exponential in The fast decay component is essentially associated with nonradiative deactivation processes and migration. The emissions from various PPVs have been found to be dependent upon the supramolecular structure of the polymer with single crystals exhibiting the highest yield."' Oriented oligomers, however, exhibit reduced emission quantum yields.381*382 In another study, oligomers have allowed predictions regarding emission quantum yields and polymer structure.383The design of white light emitting diodes has been i n v e ~ t i g a t e d .Here ~ ~ substitution of PPV with phenylanthracene units gave a polymer material with no change in emission spectral characteristics whereas the use of spacer groups produced polymers with broad emitting spectra. The fluorescence spectra from oligomeric PPVs has been shown to be due to traps below the exciton bands385while ESR has shown the presence of three types of A number of resonance signals due to Coulomb bound polaron pairs.386*387 theories continue to be developed to understand photocarrier generation in PPVs. The mobility of carriers is important3" with spacer side-groups on the main chains enhancing emission quantum yields.389 An analytical model has also been developed to understand migration and trapping processes39oand the distribution of conjugated chain lengths is important.391Photoluminescence quantum yields of PPVs are dependent upon the excitation wavelength392with bimodal emission dominating the decay kinetics as discussed above.3933394 In fact excitation of PPV above the absorption edge is expected to result in the formation of long-lived excitation rather than the expected ex~itons.~~' The blue emission from PPV has a second order hyperlinear blue emission associated with a characteristic excitonic depopulation of 2 ps3% and alkyl substituted PPVs exhibit electroluminescence efficiencies of 3%.397 Excimer maxima from various PPV's have been used to determine the interchain distances398in the polymer while irradiated PPV exhibits different optical properties to that of a thermally aged material.399 The application of an external electrical field quenches the photoluminescence of PPVs by a field dissociation process of the emitting species.400*40'This alters the binding energies of the excitons and thus causes spectral shifts in the emission. Temperature effects on the luminescence of PPV has shown the presence of an extrinsic chromophore which emits at 600 nm.4029403 In this work the normal emission at 492 nm exhibits a hyperlinear dependence with excitation intensity and is not limited by saturation effects. The
346
Photochemistry
existence of excimers in PPVs has been discusseda as well as the luminescence efficiencies of these polymers for LED applications.m5im6 Enhancing or changing the emission characteristics of PPVs have been studied in different ways. Conversion of the polymer films under ultra-high vacuum conditions enhances the luminescence efficiencym7as do layers of the polymer formed between sputtered layers of aluminium.408The distance of the metal films to the polymer has been optimised in order to achieve non-radiative decay channels whereby the intensity of the luminescence can be m a ~ i m i s e dDoping .~~ of PPVs with pristine can alter the exciton decay dynamics4" while doping the PPV with a red emitting aluminium dye complex shifts the emission maxima to the red:' The photoluminescence of PPV is reduced after photo~xidation~'~ while in conjugated PPV/cadmium selenide nanocrystals short circuit quantum efficiencies of up to 12% are When the surface of the nanocrystals is treated to remove the surface ligand the photoluminescenceis quenched which is consistent with rapid charge separation at the polymer/nanocrystal interface. Electron transfer processes have been evaluated from PPVs to tetracyanoquinone deri~atives.4'~ The efficiency correlates with the reduction potential of the acceptors. Several modified PPVs have been made. Qligophenylene vinylene units have been linked to porphyrin units4" and found to exhibit strong electronic coupling and energy transfer in the solid state. PPVs have been made with distyrylnaphthalene and anthracene units where the photoluminescence is associated with localised molecular interaction^.^'^ Alkoxy, and octylsilyl substituted PPVs are luminescent417i418 while electrical fields are shown not to influence the emission from PPVs provided their chain lengths are Cyanobiphenyl groups give rise to NLO properties in PPV420and stilbenoid dyes enhance the electroluminesc e r ~ c e . Substitution ~~' of pyridine groups alters the excitation dependence of the emission from PPV422-424 as do thiophene and polymer blends?26The incorporation of ethynylene groups in PPV gives rise to weaker electroluminescence due to improved exciton confinement efficiency427whereas water soluble PPVs with 2,3-dicarboxybarrelenes are highly luminescent but blue shifted.428 Diphenyl PPV shows lower electroluminescence and higher photoluminescence than PPV while naphthalene groups cause blue shifts43o9431 in the emission maxima. Zirconocene PPVs are shown to be very versatile in terms of their emission characteristics432and polysiloxane based PPVs are chemically stable.433Substitution effects in PPV can alter the interchain aggregation434and coatable PPVs may be obtained by copolymerisation with methacrylate monom e r ~ F1uoro,436 . ~ ~ ~ 2 , 6 - n a ~ h t h y k n eand ~ ~ ~2,5-thien~lene~~~ groups enhance the fluorescence emission of PPVs. Several other highly photoluminescent LEDs have been made, including polyacetylene-polythiophenestar polymers,439distyrylpyrazines,440poly(benzoy1- 14enylene),"' poly(ppheny1ene-1,3-butadieneml ,4ylene),442poly(3,6-N-ethylhexylcarbazolyl ~yanoterephthalidene),~~ distyrylbenzene copolymers,4e4polyaromatic ether^,"^ poly(p-pyridine),w poly(pyridy1vinylene)447-"g poly(diphenylsily1enemethylene),450 p l y (bisthiazoles),45 poly(2,7fl~orene):~~ poly(dia~aphenylenes)~~~ and poly(diphenylacetylene)!M A number of articles have appeared on polythiophenes. The incorporation of
'
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347
oligothiophene structures into polyesters results in the production of tunable emissive and electroactive p0lymers.4~~"'~~ The quaterthiophene moieties give rise to a reversible redox process leading to the formation of radical cations. Poly(3alkylthiophenes) doped with 1,2,3,4,5-pentaphenyl-l,3cycIopentadiene exhibit high electroluminescence efficiency458while sensors have been developed from ply(3-he~ylthiophene)?~~ The fluorescence decay time from poly(3-alkylthiophene) with PMMA increases linearly with applied stress.460This effect was associated with an increase in nconjugation which also redshifted the fluorescence emission maxima. Chain length influences the fluorescence emission maxima from regiocontrolled poly(3-hexylthiophene-ylene)ethynylene46'~462 while doping with oxadiazole derivatives enhances the emi~sion.4~~ Annealing of Cm doped poly(3-octadecylthiophene) broadens the emission spectraw whereas copolymers of 3- and 4-butylthiophene exhibit tunable emission ~ p e c t r a . 4 ~ ~ Polycation layers of poly(dihexyldipropargy1ammonium bromide) with polyanions of poly(thiophene-3-acetic acid) exhibit an enhanced photovoltaic effectM6 while the fluorescenceemission from thiophene-2,5diyl into palladium poly-ynes is significantly enhanced especially with phosphine l i g a n d ~Single . ~ ~ crystals of a-sexithiophene give only broad emission spectra indicating the presence of a thermally activated defect Studies on micellisation structure are extensive. Ethyl(hydroxy)ethylcellulose (EHEC) and sodium dodecyl sulfate (SDS) display different properties in hydrophobicity in the presence of salt.Mg Excimer formation for pyrene was found to be high for low numbers of polymer bound clusters (Np). It is suggested that the maximum in bulk viscosity is due to a three-dimensional network of polymer and cluster tie points while the maximum in microviscosity is related to a high content of hydrophobic polymer segments which actually stabilises the surfactant c l ~ s t e r s . 4Riboflavin ~~ has been found to bind to cyclodextrins in different ways giving rise to different emission spectra47' while the assembly properties of Triton X-100/phosphatidylcholine derivatives are measured from the release of 5-carboxylfluorescein as a molecular pr0be.4'~ Here, a direct dependence was established between the bilayer and aqueous phase surfactant partition coefficients, the growth rate of vesicles and the leakage of the carboxyfluorescein in the initial interaction steps. Such changes are due to the increasing presence of surfactant molecules in the outer monolayer of vesicles. Non-ionic surfactants have been found to form a 1 : 1 complex with Safranine T?73 In the presence of poly(ethy1ene glycols) (PEG) the equilibrium constant of dye-micelle complex was found to be proportional to the PEG molecular weight. Using 1bromonaphthalene as a phosphorescent probe the hydrocarbon chain of surfactants has been found to be partly included in the cavity of c y ~ l o d e x t r i n . ~ ~ ~ Safranin 0,Rose Bengal and Eosin Y have also been used as molecular probes for micellar s t r u ~ t u r e . 4 ~Rose ~*~'~ Bengal has been found to complex with amylose, the interaction being enhanced by the addition of a cationic detergent. Using dansyl labels an n-octyl modified copolymer of sodium maleate-altethyl vinyl ether has been found to exist as compact globules at pH values less than 6.7.477 Under these conditions fluorescence anisotropy shows two rotational correlation times corresponding to two distinct molecular motions; one due to
348
Photochemistry
the motion of the chromophore within the polymer backbone and the other associated with rotational motion of the chromophore. At higher pH the chains stretch and only rotational motions of the labels are observed. Poly(N-acryloxyphenoxazine) has been synthesised and found to undergo structural self quenching478while in acidic media the fluorescence of poly(pyridines) is enhanced especially in the presence of poly(viny1 Excimer formation from a naphthyl tagged zwitterionic sulfbetaine copolymer is greater in the absence of a salt such as KCI.480The presence of salt enhances the hydrodynamic diameter of the polymeric labels thus expanding the chains. Naphthylene and pyrene end chain tagged acrylic copolymers have been made where the presence of salt strongly influenced energy transfer and polymer Luminescence analysis of phenyldibenzophosphole in poly(styrene) and poly(n-butyl methacrylate) has showed the presence of several species giving rise to monomer, excimer and delayed fluorescence.482 Long wavelength van der Waals excited state complexes are also observed. A new fluorescent probe has been developed483as have transition metal complexes of Schiff bases.484 Fluorescence has shown the presence of an interphase between the core and shell of acrylic latex particles485 and an amphiphilic crown ether styryl dye exhibits changes at monolayers.486 Energy transfer has been found to occur on the surface of a micelle sphere with a narrow interfacial region when using phenanthrene-anthracene as the donor acceptor system.487In this system the poly(isoprene)-PMMA diblock coplymer showed evidence of strong segregation of the isoprene-PMMA components in the micelle. Fluorescence has shown that poly(styrene) ionomers form stable colloidal nanoparticles in THF/water mixtures!88 The hydrophobic poly(styrene) backbone core is stabilised by the surface sulfonate ionic groups. Hydroxyl and hydrogen ions have been partitioned in poly(hydroxyethy1 methacrylate) at a given pH489 while interactions of a negatively charged 1,2-dipaImitoylphosphatidic layer have been balanced by a positively charged electrolyte at a film interface?90 Poly(viny1pyridinium and vinylimidazolium) bromides form compact coils in aqueous media.491In the former case hydrophobic domains are evidenced by only fluorescent probes whereas the latter requires the inclusion of a molecular rotor. The presence of salt alters the extent of the interactions of poly(oxyethy1enes) with surf act ant^^^^ whilst oligomeric micelles have been identified in hydrophobic cores of poly(N-alkyla~rylamides)~~~ The same polymer has been studied with azobenzene hydrophobic side ~ h a i n s . 4Exposure ~~ of the hydrophobe to UV light results in a decrease in the interaction between the hydrophobe and the surfactant and consequent decrease in the clearing point due to conversion of the chromophore from a more hydrophobic trans into the less hydrophobic cis isomer. Fluorescence recovery has been useful for measuring the dynamic behaviour of poly(styrene) mixtures495as has the depolarisation technique for studying the local motions in a whole variety of vinyl and vinyl methacrylate polymer mixtures.496 For a series of poly(ethy1ene)-co-(propyiene oxides) their critical micelle temperature decreases with increasing hydrophobic segments in the chain.497The hydrophobic moieties were located at the ends of the polymer chains causing some degree of crosslinking. Poly(isopropylacry1amide) has been labelled with acenaphthalene and through fluorescence aniso-
III: Polymer Photochemistry
349
tropy has been found to exhibit a thermoreversiblediscontinuity at 32 "C.498This observation apparently supports the theory that thermally induced separation in this system occurs by a dual mode mechanism where intermolecular aggregation is preceded by conformational shrinkage of the polymer coils. Nanometer sized spheres composed of a hydrophilic mobile core with a crosslinked hydrophilic shell have been made from block copolymers of poly(styrene) and poly(viny1 pyridine)?w By controlling the stirring rate a range of micelle sizes were obtained. The thermal stability of transparent polyimide films was not influenced by incorporating fluorinated dianhydride and 3-vinylpyridinium salts form compact coils in aqueous sol~tions.'~'Other studies of interest include excimer emission from micelles at low surfactant c o n c e n t r a t i ~ n ,sonication ~~~ effects on vesicles to trap calceinW3and the use of crosslinkable polycations to obtain solvent resistant coating^.^^ A number of articles have appeared on the preparation and optical characteristics of liquid crystalline polymers. The microscopic anisotropy in the dynamics of neat isotropic liquid crystals of p-methoxybenzylidene-n-butylanilinehas been found to have no influence on the reorientation dynamics of dopant dye molecules such as Nile Red and Oxazine 725.505Methacrylate polymers with butoxyphenylazo groups have been investigated for image productionso6 while liquid crystalline polymers with aryl cinnamate groups exhibit marked aggregation effects that can perturb their photophysical characteristic^.^'^ The angular distribution of side chains in poly(viny1 cinnamate) has been measured508 as has the molecular dynamics in numerous other polyester, polyether and polyacrylate ~ y s t e m s . ~Orientational ~-~~ effects in cyanobiphenyl side chain polymers have been associated with anisotropic photochemical reactions induced by the absorption of polarised light.512Poly(ary1ene vinylenes) with cyanobiphenyl groups give strongly yellow-green fluorescent LC polymers513while the diacrylate group has an important effect on the alignments of cyanobiphenyl groups.514The presence of azobenzene side groups in LC polymers with cyanobiphenyl groups induces alignment, even with low intensity light.515Polymer azobenzene LCs have been made which show nematic behaviour in the trans form but none in the cis isomer Reversible LC behaviour was found to be slow when acrylic groups were incorporated in the main chain due to the slow mobility of the polymer segments. Poly(acety1enes) with azobenzene groups have also been ~ynthesised.~"A novel mean-field theory of photoinduced reorientation and optical anisotropy in LC polymers has been while a diffusion-enforcedphoto-assembly during polymerisation of a chiral-nematic monomer blend yields a cholesteric network in which the helical pitch gradually changes over the cross-section of the film.519 The polarisation selective reflection band of cholesterics can apparently be made much wider than those of single pitch materials and may expand across the whole visible range. A highly luminescent LC poly(2,5-dialkoxy-p-phenyleneethynylene) has also been made by the Heck reaction.s20 A number of papers have appeared on the optical characteristics of dendrimer polymers. A new class of photofunctional dendrimers with porphyrin groups have been made in an aryl ether framework.521Effective long-range energy transfer was found to occur through the dendrimer. New dendritic metallophthalocyanines
'
350
Photochemistry
have also been made522while the ability of a dendritic shell to afford site isolation to a porphyrin core has been investigated by electron transfer experiments.523 Apparently, large generation dendrimers inhibit electron transfer efficiency. However, absorption and fluorescencemeasurements did indicate that the photophysical characteristics of the porphyrin core is unaffected by the growth in dendritic surroundings. Charge-separation in dendrimers is also important and is influenced by the dendritic order.524Amphiphilic macromolecules have been made with poly(styrene) and poly(propy1eneimine) d e n d r i m e r ~ A .~~ five ~ generation dendrimer was formed with a poly(styrene) core with the amphiphilic behaviour affecting the aggregation behaviour. Organosilicon dendrimers with pyrene tags have been prepared526as have other polymers where excimer and monomer emissions indicated enhanced mobility of the e n d - g r o ~ p sPyrene . ~ ~ ~ fluorescence in solubilised poly(amidoamine) dendrimers is significantly quenched5283529 while in the same dendrimers 9-anthryldiazomethane has been used to detect unreacted carboxylic acid moieties.530cis-trans Isomerism has been observed in benzyl aryl ether dendrimers.531 Excimer formation as a probe of macromolecular behaviour extends across many systems. High pressure studies on poly(vin ylbenzophenone-styrene) excimer and delayed fluorescence are observed532at small pressure increases followed by a marked decrease as the pressure is increased further. Bright yellowgreen fluorescent polymers have been made by doping poly(acry1ics) with a new N-substituted naphthalamide molecule.533 In poly(N-vinylcarbazole) only excimer emission is observed on the nanosecond time scale.534This originates from three species, a sandwich excimer and two high energy conformations. When dispersed in poly(styrene) poly(N-vinylcarbazole) excimer emission was found to be a useful probe for applied tensile stresses.535Excimer emission increases from poly(styrene-&methylmethacrylate) with increasing concentration due to polymer coil shrinkage.536In micelles the poly(styrene) units act as the core while the PMMA chains act as the corona. The anti-Hirayama excimer has been observed in phenylsil~xanes”~while in pyrene labelled 2-naphthyl acrylates two distinct environments are observed for excimer formation.538 Excimer formation is observed to increase with increasing concentration and decreasing pH of poly(styrene-acrylic)copolymers539presumably due to chain shrinkage. In poly(pheny1ene sulfide-sulfones) intermolecular excimer formation is also enhanced with increasing c o n c e n t r a t i ~ n .Squarane ~~ chromophores in polymers have been used to study nonphotochemical hole burning techniques coupled with multichannel fluorescence line narrowing.”’ Studies on grafted and labelled polymers continue to attract interest. Naphthyl labelled poly(styrene) and PMMA have been used to investigate polymer blend miscibility with anthracene as the acceptor system.542As interphase volume mixing increases so does non-radiative energy transfer. Blends of poly(pheny1ene vinylene) and poly(N-vinylpyrrolidone) aggregate to give ionic crystals.543 Apparently, this process did not influence the photoluminescence intensity. Nonradiative energy transfer has been investigated to study the structure of polymer latex Pyrene and naphthalene labelled PMMA and poly(styrene) were used and from the energy transfer efficiencies and annealing times polymer
III: Polymer Photochemistry
351
chain diffusion coefficients could be measured. The effectiveness of amine grafted polyethylene membranes has been investigated through tagging the amine with dansyl groups.547 In aqueous media the amino group was found to stretch whereas in DMF and benzene it shrank. These effects corresponded with the permeability efficiencies of the membrane to different solvents. Anthracene has been bound to cellulose by an acylation reactionM8 and poly(pheny1ene) films have been synthesised with norbornadiene groups.s49 Rotational studies have while been made on acenaphthylene groups on poly(N,N-dimethylacrylamide)5so poly(esterurethanes) have been tagged with fluorescent dansylcadaverine group^.'^' In the latter case biocompatibility studies were undertaken. Polymeric N-acryloylphenothiazine oxides are more fluorescent when the suphur atom is o ~ i d i s e dIn . ~non-oxidised ~~ polymers the sulfur atom causes self-quenching. The solubility of Cm fullerene has been enhanced by grafting onto poly(propiony1ethyleneimine-co-ethyleneimine).ss3 On irradiation intramolecular electron transfer takes place between the fullerene and the amine groups. A donor bridgeacceptor fluorophore has been connected to a polyamino crosslinker in a polyacrylate dispersionsM as have similar systems with quinolyl moieties.sss The polymeric chromophores were significantly more fluorescent than those in the monomeric form and could be quenched by electron deficient vinyl monomers. Excimer formation from probes has been used to measure mobility in poly(butad i e n e ~ ) ~while ’ ~ the hyperpolarisability of a red azo dye is not influenced by polymer tagging.557 Poly(hydroxybutyric) acid has been labelled with dansyl groups at the chain ends in order to investigate the biocompatibility of the polymer.558Anthracene labels have been used to determine the glass transition temperatures of poly(ethylacrylate).ssgCrosslinking was found to influence the transition temperature. When Cm is doped in aromatic polymers it acts as an effective electron acceptor and appears to undergo strong interaction with the A number of dye doping studies have been phenyl rings upon irradiation.s609s61 undertaken to determine the nature of the microscopic dynamics. In poly(butadiene) dynamic transitions have been observed the Tgusing Malachite Green as a molecular probe.s62 Cyanine labels have been used as fluorescent concentration tags in p o l y ( a m i d e ~ ) while ~ ~ a series of natural dyes have been used to characterize ancient Japanese silks.s64 A number of other studies relate to dye , ~ ~ ~~ t r u c t ~ rtemperature e , ~ ~ ~ effects on aggreprobes for Tg m e a ~ u r e m e n t s local g a t e ~ irreversible ,~~~ changes in mercocyanine dyes568 and solvent effects on acridinedione dyes.s69 Polymer gel systems have attracted some interest. Leucohydroxide has been used to control the ion-exchange mechanism in acrylamide hydro gel^.^^^ On irradiation the leucohydroxide forms cationic charges on the surface of the membrane gel ready to exchange anions. Using anthracene labelling as a molecular probe a-methyl groups in poly(acry1ics) have been found to act as inhibitors of rotational relaxation processes.571Thionin and Nile Blue have been found to form dimers in orthosilicate gels.5729s73 Bilayer membranes have been synthesised from mixed poly(acrylamide~)~~~ while in poly(acry1amide)gel the use of the probe 4-aminopht halimide indicated the presence of multiple microenvironment~.’~’At least two distinct fluorescence emission spectra were observed
352
Photochemistry
from the probe. Using anthracene as a probe, the local motion of PMMA gels has been found to increase with increasing swelling.576The ageing of gels has been monitored through resonance energy transfer using Rhodamine 6G and Malachite Green.577From these measurements on silica gels it was possible to determine the surface areas of the particles. Swelling processes in gels have also been measured through the use of pyrene fluorescence578and excimer emission has been observed from benzyl ether groups attached to the OH groups of cellulose.579Thermoreversibility in poly(styrene) gels has been measured through naphthalenes and anthra~ene.~~’ Probe molecules larger than naphthalene were found to be mobile in the gel. Under these conditions the probe can break in to the helical rods where the chains associate. Pyrene continues to be used quite widely as a macromolecular probe. In poly(norbornenes), pyrene forms two excimer states581while the desorption rate of pyrene in labelled PMMA has been monitored by its fluorescence.582 In micelles 1,1,2,2-tetrahydroheptadecafluorodecylpyridini~mchloride failed to quench pyrene emission in micelles in fluorocarbon solvents.583In this case there appears to be competition for the fluorocarbon solvent with the micelle. The same effect was seen in poly(N-isopropylacrylamide) where the presence of nitromethane did not quench the pyrene emission.584 In this case the pyrene remained located within the micelles. Swelling effects on PMMA in solvents have been measured by pyrene emission585while in polyethylene, emission specific to the probe being located at the crystallites has been observed.586Pyrene excimers have been used to examine the nature of template formation between cations and electron lone pairs in ethylene glycol ether linkages.587 The introduction of cations such as nickel enhances the excimer formation due to chain coiling. Pyrene labelled (aborescent) poly(styrene) has been characterised using nitrobenzene as a q u e n ~ h e r . Reduced ~~~.~~ diffusion ~ rates were observed for small molecules inside the poly(styrene) matrix. Relaxation studies in poly(styrene)block-poly(2-cinnamoylethyl methacrylate) micelles results in an enhancement in pyrene monomer emission590while hydrophobic domains have been detected in poly(3-hexadecy l- 1-vinylimidazolium br~mide),’~’ Interdiffusion in latex particles has also been measured by pyrene as a molecular probe5’* as have hydrophobic interactions in polymer complexes.593Polyacrylic complexes were found to have reduced hydrophobicity when mixed with poly(ethy1ene glycols). Site isolation in crosslinked poly(styrene) has been measured using 4-( 1-pyrene)butanol labels.594 Pendant groups were found to be more mobile than crosslinked groups. The optical clarity of PMMA films has been measured by pyrene emission probes.595 Energy transfer reactions have been investigated in detail between fullerenes and polymer systems.59“600 In f~llerene-poly(ethyleneimine),~~~ cornpo~ites~~’ and conjugated polymers598 electron transfer has been observed. Poly(N-4cyanophenylacrylamide) forms an exciplex with fullerene5” while in poly(Nvinylcarbazole) hole migration was found to be highly effective in the initial charge-separation state when doped with fullerenem giving rise to high photoconductivity. A new perylene-3,4,9,1O-tetracarboxylicacid-bis-(N,N-dodecylpolyimide) has been made with excellent photothermal stability.@’ Conjugated polymers have been made with metal to ligand charge-transfer complexes based
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353
on 4,4'-biphenylyl and 5,5'-(2,2'-bipyridyl) repeat units.602Singlet energy transfer has been observed in PMMA doped with 2,6-dihydroxynaphthaleneand aliphatic dicarboxylic acids.603 Delayed emission has been observed from alternating random copolymers of 9-phenanthrylmethyl methacrylate and 2-(9-carbazo1yl)ethyl methacrylatern with styrene. N-Vinylcarbazole has been grafted onto cellulose605 which undergoes photoelectron transfer with 1,4-dicyanobenzene. Non-radiative energy transfer between donor-acceptor chromophores has been used to measure polymer associations in solution.m6 Electron and energy transfer has been observed in poIy(4-~inylbiphenyl)~~ while distance studies on chromophore interactions indicate that decreasing distances between chromophores increases the charge-transfer interaction.m8 Calculations according to a recent model of radiative energy migration indicate good agreement between theory and experiment.609 On the other hand in non-radiative energy transfer studies corrections have to be applied to the concentration profiles for diffusion times.610 N-Octylamide-substituted copoly(sodium maleate-ah-ethyl vinyl ethers) have been synthesised with naphthyl and dansyl groups.61 Using non-radiative energy transfer the polymer coils collapse into compact aggregates at low pH in aqueous media. As the pH is raised the chains expand. Chains with long spacers were found to be more sensitive than those with short spacers. In systems like the latter it has been claimed that chromophore interactions are screened out because of intermolecular correlation effects.612This causes a lower energy transfer efficiency than would be expected. Several articles have appeared dealing with europium and other metal complexes in polymer systems. The ion-exchange properties of resins are influenced by the presence of hydrated europium complexes613 while others based on poly(chloromethy1 styrene)-bound 1,4,8,11 -tetraazacyclotetradecane are highly fluorescent6I4 as are mixed complexes with terbium.615 Ionomers synthesised from europium methacrylate have been characterised by fluorescence analysis616 as have thin films of metal chelates based on mixed aluminium and e ~ r o p i u m . 6 ~ ~ Europium fluorescent complexes with naphthoate and 1,lO-phenanthroline have been copolymerised into PMMA and poly(styrene).6'8 Styryl dye complexes have also been made of different metal ions619where ion pair formation is influenced by the cis-trans isomerism. The quenching of excited ruthenium 2,2'-bipyridyl complexes by alkylviologens in poly( 1-vinylimidazole) decreases with increasing degree of quaternisation.620This was due to steric effects of the alkyl groups and repulsion between the viologen cations and the imidazolium residues. A polymeric terbium complex has been synthesised based on poly(bis(benzylsu1finyI)ethane)62' and gives rise to a total of seven different emission spectra depending upon the nature of the complexation. The presence of Y ions enhances the fluorescence emission from Ce complexes in PMMA622while site isolation of lanthanide cations has been achieved by the self-assembly of three convergent polyether dendrons, each with a carboxylate anion focal point, around the central trivalent cation.623Here the luminescence intensity was found to be dependent upon the size of the dendritic shell essentially isolating each of the lanthanide cations. This decreases the rate of self-quenching enhancing the emission intensity.
Photochemistry
354
Finally, a few articles have appeared on chemiluminescenceof polymers. This technique has been used to detect hydroxy radicals in wood oxidation,624yirradiation effects on polyethylene,625oxidation of nitrile-butadiene rubber under antioxidant efficiencies in polyethylene,628reactions of peroxy stereoregularity in poly(pr0pylene),6~'colour development in epoxy resins631 and structural changes in thermally aged poly(pheny1ene
4
Photodegradation and Photooxidation Processes in Polymers
A new book has appeared on the principles of polymer stabilisation processes633 while there have been other reviews on weathering634and bio and photodegradable Articles of topical interest include humidity effects during weatheringM0and the role of sulfur and nitrogen oxides.M' Polyokfins - Irradiation of tensile bars of polyethylene induces cracking predominantly at the crack tip whereas in poly(propy1ene) the orientation of the molecules at the crack tip appears to provide some resistance to photooxidative chain scission.642On irradiation of poly(propy1ene) the crystallinity increases by 6 7 % and is independent of the source of polymer.6Q39644 This process is further restricted by the development of impurity by-products in the polymer. Thermal analysis of photodegraded and reprocessed poly(propy1ene) however, shows an initial increase in crystallinity followed by a decrease due to the presence of oxidation dominating the chain scission. In the same work the presence of the nucleating agent, talc, had no effect on the photoinduced crystallisation process in p o l ~ p r o p y l e n eThe . ~ ~ photooxidation rates of poly(propy1ene) have been found to obey typical reaction kinetics in terms of the square root of the light intensity.6Q8Environmental oxidation of yellow polyethylene gas pipe material has shown that oxidation occurs on the outer surface layer, and to a lesser extent on the bore with little or no change in the central layers.a9 UV irradiation consumes the antioxidants in the pipe at the surface and bore but the UV absorbers remain unaffected. Surface degradation causes severe problems during subsequent electrowelding and joining of the pipes resulting in the necessity of scraping during in service applications. Oxygen-polymer charge transfer complexes are still considered to play an important role in the photoinduced oxidation of poly(propylene)650while the adhesion of this polymer is enhanced to glass plates after i r r a d i a t i ~ n . ~Carbon ~' monoxide evolution has been measured during the irradiation of poly(ethy1ene-CO) copolymers652as have tacticity changes in propylene-ethylene copolymers,653methyl vinyl ketone has been grafted to poly(ethy1ene) to induce photodegradation,6s4as has ferric teara ate.^^^ Product formation in the photooxidation of ethylene-propylene copolymers has been shown to be unaffected by photon flux or temperature656 while in another study such products have been detected by in-situ gas derivatisation reactions.657Such products can influence the conduction of the polymer?* At 77 K irradiation of polyethylene produces ally1 radicals659while the application 4.1
355
111: Polymer Photochemistry
of strain influences the polymer surface properties.m Ferrocenic additives photosensitize the oxidation of polyethylene%*while the photooxidation of carbon black filled polyethylene shows a dependence of tensile strength on crack depth?62 4.2 Poly(viny1halides) - Biodegradable PVC has been made by grafting sucrose acrylate to the surface of the while the effects of weathering have been examined on UPVC windows.664Here comparable studies were undertaken in order to compare natural with artificial ageing conditions.
4.3 Poly(acry1ates) and (alkyl acrylates) - The photosensitising effect of naphthalene and fkarotene have been measured in PMMA.665 The thermal stability of the polymer was also reduced in the presence of these additives. During the photooxidation of mixed latexes of poiy(methy1 and butyl methacrylate) the rates as determined by hydroperoxide measurements show predominantly end-chain oxidation in the PMMA (Scheme 1) and PBMA (Scheme 2) with additional side chain oxidation in PBMA (Scheme 3).666 In the case of PMMA stable tertiary based hydroperoxides develop while for PBMA unstable secondary hydroperoxides develop. The side chain hydroperoxides in PBMA are extremely unstable due to the fact that they are adjacent to an ether oxygen atom. The incorporation of dialkylacrylamides gives rise to high light stability associated with the oxygen scavenging ability of the alkylamino radicals as shown in Scheme 4. Endchain oxidation of PMMA Me I
Me
I
CQMe
CQMe
C02Me
Me
I
I CQMe
CQMe
Me -CH2-c' n
I
I C02Me
Me I -CH2-C-O2'
C02Me n
I
C02Me
P-HI hv
Me I CaMe
Me I
Me I vCH2-C-02H
I
CO2Me
n
+
I"
C02Me
Scheme 1
4.4 Polyamides and Polyimides - The dominant structure formed in the photodegradation of nylon 6,6 is the terminal methyl group associated with main chain scis~ion.~' Aldehyde and formamide structures have also been identified along with evidence for hydroxylation adjacent to the amide group. The forma-
Photochemistry
356 Endchain oxidation of PBMA *C-CH2-C H I
'.3CH2--;+7-&
I 1 C ~ B U CO~BU
H
CO~BU
I CO~BU
I
*C-CH2-C HI I CQBU
'{CHy--~-}-H2-~-02'
H
I CO~BU
I CO~BU
P-H
1
CO~BU hv
H H * , I- C H 2 -I ~ ~ C H 2 - ~ ~ 7 - ~ - 0I 2 H CQBU
CO~BU
CO~BU
+ P'
CO~BU
Scheme 2 Side-chain oxidation of PBMA *C--CHz-C H I I CQBu
'{CH2-!j:H2-&* I CQBU -H
H
I hv
CO~BU
I CO~BU
1
P-H
H - c - IC H 2 - ~ - I~ H 2 - ~ - C H 2 ~ ~ * CQBu
CQBu
COTHBu
I
+ P
CO~BU
02H
Scheme 3
tion of a-ketoimide structures in the photooxidation of polyamides is also important. Polyamides incapable of forming such species have been found to be more photostable.668 Poly(alky1 and aromatic ethers) - Organic acids accelerate the photodegradation of poly(isobuty1ene oxide)669while epoxy glass fiber composites can be
4.5
357
111: Polymer Photochemistry CH2Me -N
\
CH2Me
FH
-N
/CHMe \
CH2Me
.O
I CHMe
-N
/ \
CH2Me + 'OH
-
'CHMe
hv
p-H
-
-N
\
CH2Me
1
O2
.y2
CHMe -N CH2Me
-N
+MeCHO
\
CH2Me
1
O2
etc Oxidation of alkylamines Scheme 4 (1) Photolabilestructural irregularities,impurities
hv
X'
00'
(Formate 1734 cm-')
(Ester 1734 cm-')
Scheme 5
ablated by simply ph~toageing.~~' Perfluorinated polyethers undergo rapid photo~xidation~~' due to hydrogen atom abstraction at the a-carbon atom to the ether link (Scheme 5). This results in the formation of highly unstable hydroperoxides as shown. Apparently, end-capping the chains with urethane groups markedly enhances their light stability. Photooxidation studies on phenoxy resins have shown that the main photoproducts from long wavelength irradiation are phenyl formate end groups as shown in Scheme 6.672*673 Under short wavelength
Photochemistry
358
‘CH-CHp-0 I OH
PH
.--.
4 H O ’0 I CH-CH2-0 I OH
t
IT] H-C-OH
ms
+
‘CH2-0
-+
irradiation at 254 nm the formate end groups are unstable and photoreact further giving primarily carboxylic end groups as shown in Scheme 7. Polyesters - The photodegradation of poly(ethy1ene terephthalate) is a surface phenomenon and chain scission is primarily responsible for the changes in mechanical performance.674Aliphatic polyesters are claimed to be truly bioand ph~todegradable~’~ and detailed photooxidation studies have been undertaken on poly(ethy1ene and butylene n a ~ h t h a l a t e ) . The ~ ~ ~photooxidation -~~~ of these polymers is heavily confined to the near surface layer due to the strong absorption of the naphthalene groups. Discolouration occurs due to the formation of polyconjugated naphthalene groups as shown in Scheme 8. Hydrogen atom abstraction also occurs at the a-carbon atom adjacent to the ether oxygen to form the usual unstable hydroperoxides as shown in Scheme 9. Carboxylic acid groups are major products of photooxidation. 4.6
Silicone Polymers - High energy UV irradiation of poly(phenylmethy1 silane) results in end chain scission at the Si-Si bonds6” while alkoxypolysilanes show an increase in molecular weight.680Two photon excitation of poly(dihexylsilylene) gives controlled oligomer formation containing ten Si atoms each.68’
4.7
Polystyrenes and Copolymers - The chemical and structural changes occurring during the photodegradation of polystyrene have been described682 while polystyrene with methyl vinyl ketone groups has been investigated by realtime m~nitoring.~~’ There was a linear relationship in the magnitude of the rate of degradation with the ketone content in the copolymer. In another study the Norrish type I1 reaction was found to predominate in the same polymerw while in blends with acrylonitrile only the styrene was affected by the ketone.685Methyl vinyl ketone also induces a predominant Norrish type I1 reaction in EPDM
4.8
359
111: Polymer Photochemistry
HO1744 cm-'
I
1
HO-C-CH-C-OH 11 I 11 0 OH 0 1734-1 739 cm-'
1
+I
H
O
q
3 3 ~ ~ 3 3cm-' 0~1 Scheme 7
terpolymer6*' whereas in a series of carbon monoxide copolymers the Norrish type I reaction was p r e d ~ m i n a n t .Flame ~ ~ retardants have also been found to accelerate the rate of photodegradation of polystyrene.688
Polyurethanes and Rubbers - Polyoctenamer undergoes photooxidation to give high initial yields of ketones, unlike that of p~ly(butadiene).~'Eventual products are saturated acids coupled with high yields of hydroperoxides. Fullerenes act as photosensitisen for the photooxidation of cis-poly(butadiene).6w Low levels of carbonyl groups were formed under these conditions. Irradiation of poly(isobuty1ene) at temperatures above 50 OC causes dep~lymerisation.~~' Both hydrogen atom abstraction and main chain scission were observed. Polyurethanes with coumarin dimer units undergo photocleavage at the cyclobutane ri11gs.6~~ Aromatic urethanes were found to be more photolabile giving rise to reversible photodimerisation. Temperature effects on the photodegradation of poly(amide-
4.9
Photochemistry
360
0
Yellowing (entended conjugation) & gel formation
Scheme 8
a , 0
D ! - O - C H ~ C H ~ A -
A > 300 nm
_____t
R'
0 O"OH II I C-O-CHCH2-
I
/
\
\
/
-
II C-O-CHCH2-
OOH
0
hr
&Scission
0
0
II I1 C - 0 + H-CHCH2-
-
0
PEN
Scheme 9
hydroxyurethanes) have shown that at higher temperatures radical recombination processes dominate693while studies on aromatic diisocyanate based polymers show evidence for a photo-Fries type rearrangement.694 Under long wavelength irradiation aliphatic urethanes undergo a photosensitised oxidation reaction while under 254 nm light photolysis also occurs.695 4.10 Photoablation of Polymers - Several studies continue to appear on the
photoablation of polymer systems. Poly(ethy1ene terephthalate) has been investigated by a number of ~ o r k e r s . Under ~ ~ ~ vacuum - ~ ~ it is relatively stable giving off only carbon dioxide gas696while excimer laser ablation at 222 nm gives a good surface for a d h e ~ i o n . ~ ~Using ~ - ~ *248 nm excimer pulses monomer emission has been observed.700Laser etched PTFE has been found to adhere to epoxy resin^'^'^^*^ while relaxation effects during hole burning in polymers have been
III: Polymer Photochemistry
361
monitored through a tetraphenylporphyrin dye.7o3Hole burning on the first singlet transition of tetra-tert-butyl tetraazaporphine gives maxima for the pseudophonon side bands that are displaced from the 0-0 hole704but nevertheless compare favourably to the inelastic neutron scattering maxima and the first boson peaks in Raman spectra. The growth and decay of holes burnt in poly(ammonium styrene sulfonate) have been monitored7" as have holes burnt in PMMA doped with N,N,N',N'-tetramethyl-p-phenylene and near field optical microscopes have been used to modify the optical properies of surface modified polymers.708 4.11 Natural Polymers - Again wood and pulp degradation and yellowing have
attracted much interest. The production of oxygenated species in wood pulp has been monitored by chernil~minescence~~ as has the formation of hydroquinones by fluorescence analysis.710Photocatalytic processes have been used to clean-up pulps7" while Ag deposits on pulp are related to the concentration of aldehyde Bleaching of wood pulp with hypochlorite did not reduce the fluorescence intensity suggesting that the fluorescent species are not necessarily related to the lignin content.713Two types of species have been identified in lignin: the first is polyconjugated chromophores, while the second is possibly, aromatic s t r ~ c t u r e s . ~Ozone '~ is a good oxidant for bleaching wood pulp.715 Bleaching experiments and FTIR analysis have shown that carbonyl and conjugated species are not responsible for the y e l l ~ w i n g ~ 'while ~ * ~ 'in~ another study the yellowing is associated with the formation of quinones produced from the oxidation of phenolic species present in the Acetylation of the phenolic groups prevented the yellowing p r o c e ~ s . ~FT ' ~ NMR has also been useful in analysing the lignin products?20 The latter also react with singlet oxygen, causing while a number of other methods have been used to measure the rates.722-725 Some wood pulps have been found not to be stabilised by acetylation, indicating that other processes are involved in the yellowing.726 Sodium hydroxyalkyl phosphinites are very effective stabilisers for the yellowing of pulp.727 Hindered piperidine light stabilisers are ineff'ective in preventing yellowing whereas orthohydroxyaromatic light stabilisers are highly effective.728 The weathering of wood pulp has also been investigated.729 Wool photodiscolouration is also a problem and is normally associated with the photoproducts of trypt~phan.~~' These have been identified as N-formylkynurenine, kynurenine, tryptamine and oxyindolylalanine. Short wavelength blue light has been found to effectively photobleach the yellowing of ~ 0 0 1 . 7 ~ ~ These processes have been discussed in 4.12 Miscellaneous Polymers
- Soluble fluorescent extraction products from poly(acety1ene) have been compared with those present in PVC.733Photo-Fries rearrangements in the photodegradation of a Bis-Phenol-A poly(carbonate) are responsible for their stability.734PTFE has been irradiated using high energy UV and found to give volatile fluorocarbons735while photooxidation of poly(pheny1ene) gives crosslinked and quinone methide products.736A polyradical has been made based on poly(3,5-di-tert-butyl-4-[(2,4,6-tri-tert-butylphenyl)oxalato]phe-
362
Photochemistry
nyla~etylene).~~~ Chemical stress relaxation has been used to measure the rate of photocrosslinking of acrylic-melamine clear coats during irradiation738while graftable and biodegradable polymers have been made from 2-methylene-1,3,6trioxocane and methyl vinyl ether.739The quantum yield of photooxidation of poly(phenyleneviny1ene) has been measured740whereas the ionic interactions in polyelectrolytes with diazosulfonate chromophores are lost upon i r r a d i a t i ~ n . ~ ~ ’ Poly(bis-(4isopropylphenoxy)phosphazine) gives acetone as a volatile product and acetophenone and phenol as solid products on irradiati0n.7~~ Polyamides containing cyclobutane groups undergo reaction at the cyclobutane ring743while photodegradable polymers have been made with labile metal-metal bonds.744 Foly(ppheny1ene sulfide) undergoes extensive discolouration on irradiation possibly through biphenyl products.745On the other hand, poly(acryloy1acetate) undergoes a keto-enol tautomerism during irradiation.746Transition metal ions photosensitise the oxidation of while cage effects in the irradiation of model silane complexes have been found not to affect the quantum yield of bond scission.748 5
Photostabilisation of Polymers
A number of reviews on polymer photostabilisation have a ~ p e a r e d ~ ~ as ’ - ~well ~’ as the effect of flame retardants756i757 and the use of melanin as a stabiliser in coatings.758 Several modified phthalocyanine compounds have been found to effectively stabilise rubber.759Other unusual stabilisers include piperylene-methyl-styrene in p ~ l y ( e t h y l e n e ) ~ dioxynaphthylpropane ~*~~’ in p~ly(ethylene),~~~ ketones and anilines for poly(3-b~tyIthiophene),~~~~~@ thioglycerol for wood pulp765 and dibutylphthalate for PMMA.766N-Arylphthalimides are self stabilising due to their donor-acceptor energy transfer properties.767 Light absorbers still attract interest with studies in p o l y ~ a r b o n a t e sand ~~~ PMMA769concentrating on mechanisms of absorption. A new copolymerisable absorber based on 2-hydroxy-4-all yloxybenzophenone has been developed770for poly(styrene). A new theory has shown that excited state proton transfer in benzotriazoles results in the en01 form undergoing extensive rehybridisation at the nitrogen atom in the lowest excited singlet state.77’ This process facilitates deactivation of the singlet state and hence accounts for their good light stability. A number of studies have appeared on the use and development of hindered piperidine stabilisers (HAS). Not surprisingly, sulfides and HAS have been found to antagonise each other in their light stabilisation of Grafted HAS have been found to inhibit the hydroperoxidised degradation of natural while a number of studies have been undertaken on the general stabilisation efficiency of HAS.774-776 Siloxanebased HAS are claimed to be effective against the effects of brominated flame re tar dent^^^^ while amine terminated HAS are effective in poly(ph~sphazines).’~* Acylphosphine oxides are shown to be highly effective initiators in HAS stabilised polyurethane-acrylate UV curable coatings.779 Reactive HAS have been made for coatings780and polyolefin copolymer^^^'
III: Polymer Photochemistry
363
and p ~ l y ( s t y r e n e ) .The ~ ~ ~stabilising performance of silica filled polypropylene has been found to be highly dependent upon the nature of the metal ions in the silica materials.783Preabsorption of polymer stabilisers onto silica resulted in a major reduction in performance except for a low molecular weight HAS. On thermal oxidation stabilisation was enhanced due to controlled desorption of the stabilisers from the silica. Acrylated benzotriazole stabilisers have been found to be highly effective in acrylated fluorinated coatings when compared with acrylated HAS systems?84 Photochemistry of Dyed and Pigmented Polymers
6
Three reviews have appeared on pigment p h o t o c a t a l y ~ i s . Light ~ ~ ~ -stabilisers ~~~ and pigments are generally effective in p o l y o l e f i n ~especially ~ ~ ~ ~ ~carbon ~ ~ black which has been surface oxidised with nitric acid.790 Photocatalytic effects of titanium dioxide have been examined through the photohydroperoxidation of lineolic acid.79' A number of studies continue to appear on dye photofading processes. Silylated coumarin dyes attached to sol-gel hosts have been found to exhibit high light Many disperse dyes on polyester are stabilised by absorb e r as ~ is~ Rhodamine ~ ~ B in solution by singlet state q ~ e n c h e r s , ~ silk ~ ' dyes by semi~arbazides~~~ and vat dyes on cotton with absorbers.797 Ferric oxalate complexes can photocatalyse the decomposition of dyes in waste waters798while ethyl acetate has been found to be a good model system for the photofading of azo and anthraquinone dyes in a polyester environment.799 Reactive dyes on cotton exhibited an initial fast fade followed by a slower fading reaction.800This was suggested as due to competition between photoreduction and oxidation reactions. The central metal atom in metallised azo dyes imparted high light stability to the dye chromophore.80'The photochromic behaviour of phenoxyanthraquinones is wavelength dependent802 while the photochromic behaviour of naphtho[2,1-b]pyrans is dependent upon steric factors.803Finally, the lightfastness of a series of acid dyes on nylon 6,6 fibre has been found to be highly dependent upon the pretreatment and dyeing conditions of the fibre.804 Neutral dyeing conditions with an anionic levelling agent gave the greatest stability, as did fibres which had been heat set under dry conditions. At high and low pH conditions in the dyebath dye photofading was accelerated. Under these conditions higher concentrations of photoactive luminescent carbonylic chromophores were formed which acted as photosensitisers for the dye fading. Interestingly extraction of the nylon fibres with methanol to remove these species gave rise to enhanced dye stability. 7 I. 2.
References K.H. Chae, Kobunja Kwahuk Kwa Kisul., 1997,8,421. M. Mijuno, Kogyo Zairyo, 1997,45, 54.
364
Photochemistry
3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.
R.E. Peiffer, ACS. Symp. Sers., 1997,673, 1. L. Angiolini and C. Carlini, Chim. Ind (Milan), 1997,79,597. J.M. Abadie, Lat. Am. Appl. Rex, 1996,26,45. D.C. Neckers, IS&T's Annual Con$, Final Prog, Proc., 1996,49th, 494. M . Toya, Toso Kogaku, 1997,32,137. K. Kobayashi, Setchaku, 1997,41, 158. M . Yamamoto, Shin Kobunshi Jikkengaku, 1995,2, 387. T. Motoyama, Setchuku, 1997,41,337. N. Kimura and K. Ono, Konbatekku, 1997,25,6. T. Okitsu, Setchaku, 1997,41, 246. R.A.M. Hikmet, Prog. Polym. Sci., 1996,21, 1165. C.E. Hoyle, M.A. Trapp, J. Owens, M. Shimose, S. Jonsson, P.E. Sundell, S.C. Clark, M. Miller and D. Kang , Polym. Sci. Mat. Eng., 1997,77, 373. A. Matsumoto, Kobunshi, 1997,46, 703. S . Chikaoka, Hikuri Araiansu, 1997,8, 15. P. Marx, Adaes. Kleben Dichten, 1997,41, 24. M . Uchida and Y. Ikada, Curr. Trends Polym. Sci., 1996,1, 135. D. Nelson and H. Lara, Prog. Coat. Ink Technol. Lut. Am. Con$, 1996,2nd, 8. A.M. Van-Herk, Macromol. Sci., Rev. Macromol. Chem. Phys., 1997, C37,633. P.C. Eklund, J.M. Holden and A.M. Rao, Springer Sers SolidState Sci., 1997,124,256. 0.Nuyken and B. Voit, Macromol. Chem. Phys., 1997,198,2337. K . Ichimura, Heterogen. Chem. Rev., 1996,3,419. J. Wang, G. Qi and Z. Cao, Huadong Ligong Daxue Xuebao, 1997,23,53. L. Zhang, J. Wang and H. Hu, Ganguang Kexue Yu Guang Huaxue, 1997,15,7. Z. Cao, J. Wang and G. Qi, Ganguang Cailiao, 1996,4,26. N.S. Allen, N.G. Salleh, M. Edge, T. Corrales, M. Shah, F. Catalina and A. Green, J. Photochem. Photobiol., Chem. Ed., 1997,103, 185. N.S. Allen, M. Edge, F. Catalina, T. Corrales, M. Blanco-Pina and A. Green, J. Photochem. Photobiol., Chem. Ed., 1997, 10, 183. H.J. Hageman, Macromol. Rapid Commun., 1997,18,443. A. Costela, I. Garcia-Moreno, F. Diaz, J. Dabrio and R. Sastre, Acta Polym., 1997, 48,423. L. Pouliquen and X. Coqueret, Macromol. Chem. Phys., 1996,197,4045. C. Carlini, L. Angiolini, D. Caretti and E. Corelli, Macromol. Symp., 1996, 11I , 281. X.X. Ren, J. Su, H.B. Yin and J.Y. Feng, J. Photopolym. Sci. & Technol., 1997,37, 329. V.D. Titskaya. I.N. Kostenko and V.T. Skripkina, Ukr. Khim. Zh., 1996,62, 124. V. Jakubek, A.J. Lees, S.J. Fuerniss and K.I. Papothornas, Polym. Prep. (Am. Chem. Soc., Div. Polym. Chem.), 1997,38, 195. J.P. Fouassier F. Morlet-Savary, K. Yamashita and S. Imahashi, Polymer, 1997, 38, 1415. A.A. Degtyareva, N.V. Yarovaya and V.V. Magdinets, Ukr.Khim. Zh., 1996,62,63. K. Kimura, M. Sumida and M. Yokoyama, Chem. Commun.,1997,1417. N.A. Bus'ko, V.K. Grishchenko and D.P. Kochetov, Ukr. Khim. Zh., 1996,62,65. P. Ghosh and G. Pal ,J. Polym. Sci., Polym. Chem. Ed., 1997,35, 1681. P. Ghosh and G. Pal, J. Polym. Muter. ,1997,14, 147. S. Mah, K. Chang and C. Seoul, Nonmunjip-Sanop Kwahuk Kisul Yongsuo, 1995,23, 549. T.S. Kwon, S. Kumazawa, T. Yokoi, S. Kondo, H. Kunisada and Y. Kumazawa, J. Macromol. Sci., Pure Appl. Chem., 1997, A34, 1553.
15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33.
34. 35. 36. 37. 38. 39. 40. 41. 42.
43.
111: Polymer Photochemistry
44. 45. 46. 47. 48.
49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77.
365
Y. Liu, G. Jin and F. Li, Gaofenzi Xuebao, 1997,2,227. X.M. Yang and K.Y. Qiu, J. Macromol. Sci., Pure Appl. Chem., 1997, AM, 793. X.M. Yang and K.Y. Qiu, J. Macromol. Sci., Pure Appl. Chem.,1997,AM, 31 5. X.M. Yang and K.Y. Qiu, J. Appl. Polym. Sci., 1997,64,1169. K . Konno, M. Ueda and P.E. Cassidy, J. Macromol. Sci., Pure Appl. Chem., 1997, A34,929. N.S. Allen, M. Edge, A.R. Jasso, T. Corrales and M. Tellez-Rosas, J. Photochem. And Photobiol,, Chem. Ed., 1997,102,253. A. Altomare, F. Ciardelli, N. Tirelli and R. Solaro, Macromolecules, 1997,30, 1298. G.E. Lawson, B. Ma, H.R. Hollins, A.M. Hajduk and Y.P. Sun, Res. Chem. Intermed., 1997,23,549. H.J. Haitjema, R.Buruma, G.O.R.A. van Ekenstein, Y.Y. Tan and G. Challa, Eur. Polym. J., 1996,32, 1447. J. Pola, Radiat. Phys. Chem., 1996,49, 151. E.I. Alekseeva, LYu. Ruskol and S.R. Anush’yan, Vysokomol. Soedin., Ser. A, Ser., B., 1996,12,2042. C.I. Simionescu, G. David, B.C. Simionescu and V. Paraschiv, Eur. Polym. J., 1997, 33, 1251. M.A. Tlenkopatchev, S. Fomine, L. Fomina, R. Gavino and T. Ogawa, Polym. J (Tokyo), 1997,29,622. G.N. Babu, R.A. Newmark, S. Heilman, P.A. Percha and D.A. Weil, Polym. Prep. (Am. Chem. SOC.,Div. Polym. Chem.), 1997,38,510. P. Matusche. 0. Nuyken, B. Voit and M.V. Damme, J. Macromol. Sci., Pure Appl. Chem., 1997, AM, 201. B. Burger, J. Winter and H. Kuzmany, Syntheic Met., 1997,86,2329. R. Jacquelin, S. Kraus, K.M. Colbow and W. Eberhardt, Fullerenes, Fullerene Nanostructure, Proc. Int. Wintersch. Electron Prop. Novel Mat. Conf loth, ed. H. Kuzmany, Singapore 1996,349. Y. Chen and C.S. Jean, J. Appl. Polym. Sci., 1997,64, 1749. Y. Chen and C.S. Jean, J. Appl. Polym. Sci. , 1997,64, 1759. G.W. Coates, A.R. Dunn, L.M. Henling, D.A. Dougherty and R.H. Grubbs, Angew. Chem., Int. Ed Engl., 1997,36,248. C. Sentein, B. Mouanda, A. Rosilio and C. Rosilio, Synth. Met., 1996,83,27. R. Nagarajan, J.S. Bowers and S. Jonsson, Polym. Muter. Sci. Eng., 1997,76,76. W.S. Lyoo and W.S. Ha, J. Polym. Sci., Part A: Polym. Chem. E d , 1997,35,55. S. Nicolau, St. Levai and D. Sporea, An. Univ. Bucuresti, Fiz.,1995,44,63. H. Anderson and A. Hult, J. Coat. Technol., 1997,69,91. G.Z. Xu, J.H. Dong and Y.K.Qiu, J. Polym. Sci., Part A: Polym. Chem., 1997,35643. S.C. Clark, S. Jonsson and C.E. Hoyle, Polym. Prep. (Am. Chem. SOC.,Div. Polym. Chem.), 1997,38,363. C.E. Hoyle, S. Jonsson, M. Shinose, J. Owens and P. Sundell, ACS Symp. Sers., 1997,673, 133. G.K. Noren, ACS Symp. Sers., 1997,673,121. C.E. Hoyle, S.C. Clark, S. Jonsson and M. Shimose, Polymer, I997,38,5695. S.M. Kim and T.H. Kim, Kongop Hwahak, 1997,8,440. S.C. Clark, S. Jonsson and C.E. Hoyle, Polym. Mat. Sci. and Eng., 1997,76,62. S.C. Clark, G.J. Doucet, S. Joensson, G.A. Mattson and C.E. Hoyle, Polym. Prep. (Am. Chem. Soc., Div.Polym. Chem.), 1997,38, 178. S. Joensson, P.E. Sundell, M. Shinose, S. Clark, C. Miller, F. Morel, C. Decker and C.E. Hoyle, Nucl. Inst. Methods Phys. Res., Sect B, 1997, 131, 276.
366
Photochemistry
78. 79. 80.
M.D. Goodner and C.N. Bowman, Polym. Muter. Sci. Eng., 1997,76,32. Y.C. Lai and E. Quinn, ACS Symp. Sers., 1997,673,35. R. Braslau, L.C. Burrill, M. Siano, N. Naik, R.K. Howden and L.K. Mahal, Macromolecules, 1997,30,6445. X.M. Yang and K.Y. Qiu, J. Macromol. Sci.,Pure Appl. Chem., 1997, A M , 543. A. Kannurpatti, M.D. Goodner, H.R. Lee and C. Bowman, ACS Symp. Sers., 1997, 673, 51. J.L. Mateo, P. Bosch and A.E. Lozano, J. Polym. Sci., Part A: Polym. Chem. Ed., 1997,352889. M.V. Encinas, A.M. Rufs, E. Norambuena and C. Giannotti, J. Polym. Sci., Part A: Polym. Chem. Ed., 1997,35,3095. A. Costela, I. Garcia-Moreno, J. Dabrio and R. Sastre, J. Polym. Sci., Part A: Polym. Chem. Ed., 1997,353801. K. Subramanian, K.S. Murthy and K. Kishore, Polymer, 1997,38,527. M. Kamachi and K. Kajiwara, Macromol. Chem. Phys., 1997,198,787. K.D. Hungenberg, K. Knoll and M. Wulkow, Macromol. Theory Simulation, 1997, 6, 393. D.R. Kim and D.H. Napper, Macromol. Rapid Commun., 1996,17,845. I . Capek and J.P. Fouassier, Eur. Polym. J., 1997,33, 173. 0. Pekan, Y. Yilmaz and 0. Okay, Polymer, 1997,38,1693. J.M. Warman, R.D. Abellon, J.H. Verhey, J.W. Verhoeven and J.W. Hofstraat, J. Phys. Chem. B, 1997,101,4913. C. Decker and D. Decker, J. Macromol. Sci., Pure Appl. Chem., 1997, A34,605. J. He, M. Li, J. Wang, E. Erjian and N.S. Allen, GaofenziXuebao, 1996,6,667. R.B. Paul, J.M. Kelly, D.C. Pepper and C. Long, Polymer, 1997,38,2011. Y. Tong, S. Yao, F. Yu, W. Zheng, G. Wu and Y. Ye, Radiat. Phys. Chem., 1997, 49,415. Y. Zhang, S. Yu, C. Su, W. Zhu and B. Chen, Beijing Shifan Dame Xuebao Ziran Kexueban, 1996,32,5 12. K.D. Belfield and G. Zhang, Polym. Bull. (Berlin), 1997,38, 165. Y . Toba, M. Yasuike and Y. Usui, Chem. Commun., 1997,675. H.Q. Guo, A. Kajiwara, Y. Morishima, M. Kamachi and W. Schnabel, Polym. J., 1997,29,446. A. Goswami and S.D. Baruah, Polym. Int., 1997,43,22. K.D. Belfield and F.B. Abdelrazzaq, J. Polym. Sci., Part A: Polym. Chem. E d , 1997, 35,2207. J. Park, N. Kihara, T. Ikeda and T. Endo, Macromolecules, 1997,30,3414. I. Reetz, V. Bacak and Y. Yagci, Polymer Int., 1997,43,27. P. Monecke, W. Schnabel and Y. Yagci, Polymer, 1997,38,5389. D. Anderson, N. Cullum and E. Sands, Radcure Coat. Inks: Appl. Perform., 1996, Paper 16, 18. C. Wang, Y. Wei, K. Simone, H. Gruber and 3. Wendrinsky, Polym. Prep. (Am. Chem. SOC.,Div. Polym. Chem.)., 1997,38,217. M. Kohler, Furbe Lacke, 1997,103,28. C. Wang, Y. Wei, H. Gruber and J. Wendrinsky, Prep. (Am. Chem. SOC.,Div. Polym. Chem.), 1997,38,219. J. Nie, Z. Ling, M. Li and E. Wang, Fushe Yanjiu Yu Fushe Gongyi Xuebao, 1996,14, 162. L. Pouliquen, P. Leclercq, J. M. Buisine and X.Coqieret, Calorimetr. Anal. Therm., 1997,28, 59.
81. 82. 83. 84. 85.
86. 87. 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 99. 100. 101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111.
MI: Polymer Photochemistry 112. 113. 114. 115. 116. 117. 118. 119. 120. 121. 122. 123. 124. 125. 126. 127. 128. 129. 130. 131. 132. 133. 134. 135. 136. 137. 138. 139. 140. 141. 142. 143. 144. 145.
367
M.J. Moore, V. Lungu and T. Marino, Radtech Rep., 1997,11,30.
T.E.Serhalti, Y. Yagci, I. Tomida, M. Suzuki and T. Endo, J. Macromol. Sci., Pure
Appl. Chem., 1997, A34,383. Y. Tajima, Y. Tezuka, H. Yajima, T. Ishii and K. Takeuchi, Polymer, 1997, 38, 5255. R. Nagarajan, J.S. Bowers and S. Jonsson, Ratech. Prep., 1997,11,26. J.V. Crivello and Z. Mao, Chem. Muter., 1997,9, 1562. I . Zadrozna, Z.K. Brzozowski, K. Noniewicz and M. Dyrda, Polym. Polym. Compos.,1997,5,57. J. Ji, B.J. Trushinski, R.F. Childs, J.M. Dickson and B.E. McCarry, J. Appl. Polym. Sci., 1997,64,238 I . L. Angiolini, D. Caretti, E. Corelli, C. Carlini and A.P. Rolla, J. Appl. Polym. Sci., 1997,64,2247. I. Shimizu, Y.Ito, H. Kawato, S. Matsushita, H. Kinoshita, H. Toyota, M. Obara, K. Koseki and T. Yamaoka, IS&T’s Ann. Conf, Final Prog. Proc., 49th, Springfield, VA, 1996,497. K. Rosche, C. Decker, G. Israel and J.P. Fouassier, Eur. Polym. J., 1997,33,849. T . Urano, H. Nagasaka, M. Shimizu and T. Yamaoka, , IS&T’s Ann. Conf, Final Prog. Proc., 49th, Springfield, VA, 1996,491. A. Hafner, A. Muhlebach and P.A. Van Der Schaaf, Angew. Chem., Int. Ed. Engl., 1997,36,2121. L. Lecamp, C. Vaugelade, B. Youssef and C. Bunel, Eur. Polym. J., 1997,33,1453. J.V. Crivello, G. Lohden, W.G. Kim and B. Yang, Proc. Annual Meet Adhes. SOC., 19th 1996,260. J.V. Crivello and Z . Mao, Chem. Mater., 1997,9, 1554. J.V. Crivello and R. Malik, J. Polym. Sci: Part A: Polym. Chem. Ed., 1997,35407. C. Peng, X.She and W. Shen, Gongneng Gaofenzi Xuebao, 1997,10,393. U. Muller, A. Kunze, C. Decker, C. Herzig and J. Weiss, J. macromol. Sci., Pure Appl. Chem., 1997, A34,15 15 . D. Patnaik and S.P.Rout, J. Teach. Res. Chem., 1996,3,56. W. Shi, H. Liu and F. Wang, Yingyong Huaxue, 1997,14,53. M. Shirai, T. Sumino and M. Tsnooka, Eur. Polym. Eur., 1997,33, 1255. J. Woods, M. Masterson, C. McArdle and J. Burke, ACS Symp. Sers., 1997, 673, 107. K. Yamamoto, K. Oya, S. Kobayashi and E. Tscuhida, Phosph. Sulph. Silicon Relat. Elem., 1997, 120, 120. K.D. Belfield and F.D. Abdelrazaq, Macromolecules, 1997,30,6985. J.V. Crivello and U. Varlemann, ACS Symp. Sers., 1997,673,82. N. Pietschmann and H. Schulz, FATIPEC Congr.,1996,23rd, 18. E.A. Jurczak, Paint Ink Int.,1997,10,2. H . Itoh, A. Kameyama and T. Nishikubo, J. Polym. Sci., Part A: Polym. Chem. Ed., 1997,35,3217. B.F. Howell, A. de Raaff and T. Marion, ACS Symp. Sers., 1997,673,219. V.A. Khranovskii, A.F. Maslyuk and S.N. Ostayuk, Dopov. Nuts. Akad. Nauk Ukr., 1996,6, 121. K. Sharp, J. Mattson and S. Jonnson, J. Coat. Technol., 1997,69,77. T. Hannemann, R. Rurecht and J.H. Hausselt, Polym. Mar. Sci. & Eng., 1997, 77, 418. E.W. Nelson and A.B. Scranton, IS&Ts Annual ConJ, Final Prog., 49th 1996,504. J.G. Kloosterboer, C. Serbotoviez and F.J. Touwslager, Polymer, 1996,37,5937.
368 146. 147. 148. 149. 150.
151. 152. 153. 154. 155. 156. 157. 158. 159. 160. 161. 162. 163. 164. 165. 166. 167. 168. 169. 170. 171. 172. 173. 174. 175. 176. 177. 178. 179.
180. 181. 182. 183. 184. 185.
Photochemistry
T. Nakamoto and P.A. Abraha, Proc. Int. Symp. Micro Mach. Hum. Sci., 1996,7th, 53. F. Poncin-Epaillard, S. Vallon and B. Drevillon, Mucromol. Chem. Phys., 1997, 198, 2439. D. Skinner, Sur. Coat. Sci., 1997,80,274 S . Tada, Y. Takahashi, I. Serizawa and N. Adachi, Nippon Insatsu Gakkaishi, 1996, 33,307. B. Qu, X. Qu, Y. Xu, U. Jacobsson, B. Ranby, K.E. Russell and W.E. Baker, Macromolecules, 1997,30, 1408. B. Qu, Y. Xu and X. Qu, Gaodeng Xuexiao Huaxue Xuebao, 1997,18,317. B. Qu and X. Qu, J. Photopolym. Sci. Technol., 1997, 10,353. A. Harada and Q. Trang-Cong, Macromolecules, 1997,30, 1643. W. Wern, J. Hobisch and K. Hummel, Macrornol. Chem. Phys., 1997,198,3987. W. Kern, J. Hobisch and K. Hummel, Macromol. Chem. Phys., 1997,198,443. T. Chang, H.B. Chen and K.H. Wu, Polym. J., 1997,29,442. E. Andrzejewska, L. Linden and J.F. Rabek, Polym. Int.,1997,42, 179. 0. Kawana, Nippon Kugaku Kaishi., 1997,8,597. W. Shi, H. Liu and H. Huang, Gaofenzi Xuebao, 1997,4,400. C.N. Bowman and K.S. Anseth, Polym. Muter. Sci. Eng., 1997,77,375. L. Lecamp, B. Youssef and C. Bunel, Polymer, 1997,38,6089. Z. Wang, J.A. Arcenaux and J.A. Hall, Proc. Water Borne High Solids, Powder Coat. Symp., 1997,24th, 225. M.D. Goodner and C.N. Bowman, Polym. Prep. (Am. Chem. Soc., Div. Polym. Chem.), 1997,38,456. H. Kubota and A. Fukuda, J. Appl. Polym. Sci., 1997,65,1313. J.L. Mateo, J. Serrano and P. Bosch, Macromolecules, 1997,30, 1285. H. Liu, G.A. George and P.J. Halley, Polymer, 1997,38,2997. S.K. Moorjani, B. Rangarajan and A.B. Scranton, ACS Symp. Sers., 1997,673,95. Y. Chen and R.Z. Hong, J. Polym. Sci., Part A: Polym. Chem. Ed., 1997,35,2999. D.L. Woerdeman, J.K. Spoerre, K.M. Flynn and R.S. Parnas, Polym. Compos., 1997, 18, 133. K. Inoue, Y. Sasaki, T. Itaya and T. Tanigaki, Eur. Polym. J., 1997,33,841. J.W. YuandC.S.P. Sung, J. Appl, Polym. Sci., 1997,63, 1769. J.C. Phelan and C.S.P. Sung, Macromolecules, 1997,30,6845. J.C. Phelan and C.S.P. Sung, Macromolecules, 1997,30,6837. C. Decker, D. Decker and F. Morel, ACS Symp. Sers., 1997,673,63. C. Decker and D. Decker, Polymer, 1997,38,2229. B.S. Chiou, R.J. English and S.A. Khan, ACS Symp. Sers., 1997,673, 150. B.S. Chiou and S.A. Khan, Macromolecules, 1997,30,7322. G. Eisele, J.P. Fouassier and R. Reeb, J. Polym. Sci., Part A: Polym. Chem. Ed., 1997,35,2333. B. Sandner, N. Kotzian, J. Tubke, S. Wartewig and 0. Lange, Mucromol. Chem. Phys., 1997,198,2715. T . Renault and A.A. Ogale, J. Adu. Muter., 1996,28,42. J. Fournier, G. Williams and P.A. Holmes, Macromolecules, 1997,30, 2042. J.E. Dietz, B.A. Cowans, A. Scott and N.A. Peppas, ACS Symp. Sers., 1997,673,28. P. Leclercq, J.M. Buisine and X. Coqueret, Macromol. Chem. Phys., 1997,198,2977. V.V. Shilov, V.M. Grinkevich, Yu. P. Gomza and V.A. Kravchuk, Dopov. Nuts. Akad Nauk Ukr., 1996,2, 124. A. Bhatnagar, A. Schroeder and D.K. Mohanty, Polymer, 1997,38,239.
III: Polymer Photochemistry
369
186. H. Sarma, C. Mahabir and A. Shaikevich, Conf: Rec. IEEE Int. Symp. Electr. Insul., 1996,2,624. 187. P. Zhu, Z. Li, Q. Wang, W. Feng and L. Wang, J. Appl. Polym. Sci., 1997,64,1463. 188. F . Zhang, Y. Li, C. Xu C. Chao, Xi’an Jiaotong Daxue Xuebao, 1996,30,51. 189. K.D. Belfield and P. Geng, Polym. Prep. (Am. Chem. Soc., Div. Polym. Chem.), 1997,38,201. 190. L. Lecamp, B. Yussef, P. Lebaudy and C. Bunel, J. Macromol. Sci., Pure Appl. Chem., 1997,A34,2335. 191. T . Nishikubo, A. Kameyeama and Y. Toya, Polym. J., 1997,29,450. 192. F.C. Shilling and H.E. Katz, Polym. Prep. (Am. Chem. SOC.,Div. Polym. Chem), 1997,38,854. 193. Yu.P. Getmanchuk, L.P.Kunyts’ka and V.M. Staren’ka, Dopov. Nuts. Akad Nauk Ukr., 1997,3,142. 194. W.Herrmann, M. Schneider and G. Wenz, Angew Chem., Int. Ed., Engl., 1997,36, 251 1. 195. M. DeLoos, J. Van Esch, I. Skets, R.M. Kellogg and B.L. Feringa, J. Am. Chem. SOC.,1997,119,12675. 196. V. Narayanan and A.B. Scranton, Trends Polym. Sci., 1997,5,415. 197. L. Zhang, Z. Zeng, Y. Chen, C. Wu and J. Gao, J. Appl. Polym. Sci., 1997,66,2543. 198. A. Mohlebach, B. Moller, C. Pharisa, M. Hofmann, B. Seiferling and D. Guerry, J. Polym. Sci., Part A: Polym. Chem. E d , 1997,35,3603. 199. S. Hu and D.C. Neckers, Mucromolecules, 1998,31,322. 200. G. Rames-Langlade, P. Monjol and H. Sekiguchi, Macromol. Chem. Phys., 1997, 198,2139. 201. K. Feng, T. Matsumoto and T. Kurosaki, J. Photopolym. Sci. Technol., 1997,10,61. 202. S. Jayanthi, B. Hokuf and J. Lawton, Solid Freeform Fabr. Symp. Proc., 1996,393. 203. 0.Nuyken and U. Dahn, J.Polym. Sci., Part A: Polym. Chem. E d , 1997,35,3017. 204. W. Zhu, Y. Lin, M. Zhu and T. Wu, Huaxue Tongbao, 1997,6,45. 205. J. Pavlinec and N. Mosmer, J. Appl. Polym. Sci., 1997,65,165. 206. J. Tao, S. Stewart, G. Liu and M. Yang, Macromolecules, 1997,30,2838. 207. J. Jones, M.A. Meador, M.A.B. Meador, D.A. Scheiman and L.L. Williams, Polym. Prep. (Am. Chem. Soc., Div. Polym. Chem.)., 1997,38,99. 208. R.A. Newmark, S.M. Heilman and G.N. Babu, Polym. Prep. (Am. Chem. Soc., Div. Polym. Chem.)., 1997,38,831. 209. L.S. Coons, B. Rangarajan, D. Goshall and B. Scranton, ACS Symp. Sers., 1997,3, 203. 210. Y . Song, Pige Huagong, 1997,1,20. 21 1 . G. Pan and X.Tian, Reguxing Shuzhi, 1996,11,16. 212. C. Decker and T.H. Ngoc, Polym. Mat. Sci Eng., 1997,76,204. 213. A. Tsubata, A. Kameyama, S. Nakamura and T. Nishikubo, Kobunshi Ronbunshu, 1997,54,37. 214. 1. Campistron, D. Reyx, M. Hamza and A. Oulmidi, Macromol. Symp., 1997,122,329. 21 5. G. Malucelli, G. Gozzelino, F. Ferrero, R. Bongiovanni and A. Priola, J. Appl. Polym. Sci., 1997,65,491. 21 6. W. Shi, Ganguang Kexue Yu Guang Huaxue, 1997,15,165. 21 7. H . Huang, J. Zhang and W. Shi, J. Photopolym. Sci., Technol.,l997,10,341. 21 8. J.C. Bhatt, M.H. Dotrong, R.T.Pogue, J.S. Uilett and R.P. Chartoff, Polym. Prep. (Am. Chem. Soc., Div. Polym. Chem.)., 1997,38,149. 219. C.W. Miller, R. Kess, T. Hima and C.E. Hoyle, Polym. Prep. (Am. Chem. SOC.,Div. Polym. Chem.), 1997,38,258.
370
Photochemistry
C. Viklund, E. Ponten, B. Glad, K. Irgum, P. Hoerstedt and F. Svec, Chem. Muter., 1997,9,463. 221. S. Matsui, H. Sat0 and T. Nagawa, Polym. Muter. Sci. Eng,, 1997,77,297. 222, D. Barancok, J. Cirak, P. Tomcik, I. Cerven and 0. Foltin, J. Electrical Engl., 1996, 47,209. 223. R. Darkow, U. Hartmann and G, Tomaschewski, React. Functional Polym., 1997, 32, 195. 224. H.J. Haghash, 0.Okay and Y. Yagci, Polymer, 1997,38,1187. 225. R. Jantas, J. Appl. Polym. Sci., 1997,65,2123. 226. A.F. Maslyuk, V.V. Ageeva, G.K. Bereznitskii, V.A. Khranovskii, V.I. Shtompel and I.M. Sopina, Vysokomol. Soedin., Sers. A, Sers. B., 1997,39,773. 227. G. Rames-Langlade, P. Monjol, H. Sekiguichi, R. Mercier and B. Sillion, Polymer, 1997,38,4965. 228. J. Elisseeff, K. Anseth, R. Langer and J.S. Hrkach, Macromolecules, 1997,30,2182. 229. D. Skinner, Paint Ink Int., 1997,10, 12. 230. B.S. Seo, H.S. Lee and M.J. Jin, Han’guk Somyu Konghakhoechi., 1997,34, 148. 231. G. Gozzelino, A. Priola, G. Malucelli and A. Delmastro, Colloids Surf: A., 1997, 127,83. 232. B.F. Howell and M. O’Donnell, Proc.-Electrochem.Soc., 1997,95,29. 233. I.V. Kityk, J. Kasperczyk, B. Sahraoui, M.F. Yasinskii and B. Holan, Polymer, 1997,38,4803. 234. E.M. Battalov, V.I. Sugrobov, G.V. Leplyanin, A.M. Shakirov and L.A. Valeeva, Bashk. Khim. Zh., 1996,3,34. 235. C. Esen, T. Kaiser, A.M. Borchers and G. Schweiger, Polym. Muter. Sci. Eng., 1997, 275, 131. 236. Q. Tran-Cong, A. Harada, T. Ohta and 0. Urakawa, Phys. Rev. E: Stat. Phys., Plasmas, Fluids, Relat. Interdisciplinary Topics, 1997,55, R6340. 237. S. Maruo, 0.Nakamura and S. Kawata, Opt. Lett., 1997,22, 132. 238. V. Briskman, K. Kostarev and T. Yudina, Centrigugal Muter. Process., [Proc. Int. Workshop Muter. Process, High Gravity] 3 r , Plenum, N.Y .,1997,247. 239. T. Hanemann, R. Ruprecht and J. Hausselt, Adv. Muter., 1997,9,927. 240. S. Matsui, T. Ishiguro, A. Higuchi and T. Nakagaw, J. Polym. Sci., Part B: Phys. Ed., 1997,35,2259. 241. A. Terada, Y. Tanoue and S. Shimamoto, Prog. Org. Coat., 1997,31,81. 242. A. El-Achari and X. Coqueret, J. Polym. Sci, Part A: Polym. Chem. Ed., 1997, 35, 25 13. 243. H.A. AIi and K.S.V. Srinivasan, Polym. Int., 1997,43,310. 244. P. Kannan and K.K. Gangadhara, Polymer, 1997,38,4349. 245. S.C. Muragavel, T. Kaliyappan and C.S. Swaminathan, J. Appl. Polym. Sci., 1997, 65, 2151. 246. S.C. Muragavel, C.S. Swaminathan and P. Kannan, Polymer, 1997,38,5179. 247. C. Goretsky and H. Ritter, Macromol. Chem. Phys., 1997,198, 59. 248. Y . Tajima, H. Arai, Y. Tezuka, T. Ishii and K. Takeuchi, Fullerene Sci. Technol., 1997,5, 1531. 249. J. Onoe and K. Takeuchi, Phys. Rev. Lett., 1997,79,2987. 250. J. Onoe, A. Nakao and K. Takeuchi, Phys. Revs. B: Condens. Matter, 1997, 5, 10051. 251. S. Murase, K. Kinoshita, K. Horie and M. Kazuyuki, Macromolecules,1997, 30, 8088. 252. T.H. Kim and S.M.Kim, Pollimo, 1997,21, 1.
220.
III: Polymer Photochemistry
253. 254. 255. 256. 257. 258. 259. 260. 261. 262. 263. 264. 265. 266. 267. 268. 269. 270. 271. 272. 273. 274. 275. 276. 277. 278. 279. 280. 281. 282. 283. 284. 285. 286.
37 1
C.A. Guymon and C.N. Bowman, Macromolecules, 1997,30, 1594. C.A. Guymon, E.N. Hoggan, N.A. Clark, T.P. Rieker, D.M. Walba and C.N. Bowman, Science, 1997,275, 57. C.A. Guymon and C.N. Bowman, Macromolecules, 1997,30,5271. C.A. Guymon, L.A. Dougan and C.N. Bowman, ACS Symp. Sers., 1997,673,16. N. Kawatsuki, A. Kikai, R. Fukae, T. Yamamoto and 0. Sangen, J. Polym. Sci. Part A: Polym. Chem. Ed., 1997,35, 1849. N. Kawatsuki, K. Takatani, T. Yamamoto and 0. Sangen, Macromol. Chem. Phys., 1997,198,2853. J.W. Shultz and R.P. Chartoff, Polymer, 1997,39,319. J.C. Bhatt, M.H. Dotrong, R.T. Pogue, J.S. Ullett, R.P. Chartoff, M.H. Litt and X.T. Bi, Polym. Prep. (Am. Chem. SOC.,Div. Polym. Chem.), 1997,38,147. V.L. Khodzhaeva, 1.1. Konstantinov, P.L. Magaginini and E.L. Tassi, Vysokomol. Soedin., Sers. A. Sers. B., 1997,39, 1292. I.P. Buxton, A.W. Hall and D. Lacey, Macromol. Chem. Phys., 1997,198,2307. J.D. LeGrange, S.A. Carter, M. Fuentes, J. Boo, A.E. Frenny, W. Cleveland and T.M. Miller, J. Appl. Phys., 1997,81,5984. L. Marcot, P. Maldivi, J.C. Marchon, D. Guillon, M. Ibn-Elhaj, D.J. Broer and T. Mol, Chem. Muter., 1997,9,2051. J.B. Whitehead and M.M. Chandler, Proc. SPIE-Int. Soc. Opt. Eng., 1997, 3123, 128. H.R. Kricheldorf, S.J. Sun, B. Sapich and J. Stump, Macromol. Chem. Phys., 1997, la8,2197. M. Miyajima and T. Anazawa, Kawamura Rikagaku Kenkyusho Hokoku, 1996,7,63. N. Kawatsuki, H. Ono, H. Takatsuka, T. Yamamoto and 0. Sangen, Macromolecules, 1997,30,6680. C.F. Van Nostrum, R.J.M. Nolte, D.J. Broer, T. Fuhrman and J.H. Wendorff, Chem. Muter., 1998,10, 135. Y. Li, T. Kaneko, Y. Mochida, S. Nakamura and M. Tsuchiya, Anal. Sci., 1997,13, 273. D.J. Broer, Desk Rex Funct. Polym., 1997,451. N. Saito, S. Yamashita and T. Matsuda, J. Polym. Sci., Fart A: Polym. Chem. Ed., 1997,35,747. M.R. Yang and K.S. Chen, Mafer. Chem. Phys., 1997,50, 1 I . I. Noh and J.A. Hibbell, J. Polym. Sci., Part A: Polym. Chem. Ed., 1997,35,3467. Y. Morita, Y. Sugahara, A. Takahashi and M. Ibonai, Eur. Polym. J., 1997, 33, 1505. V. Viengkhou, L.T. Ng and J.L. Garnett, Radiat. Phys. Chem., 1997,49,595. H. Kubota, Y. Fukushima and S. Kuwabara, Eur. Polym. J . , 1997,33,67. N. Ichinose and S . Kawanishi, Langmuir, 1997,13,5805. Y. Li, J.M. Poon and E.T. Samulski, J. Appl. Polym. Sci., 1997,64,883. F.C. Chen and H.S. Lackritz, Macromolecules, 1997,30,5986. N. Tsubokawa and M. Satoh, J. Appl. Polym. Sci., 1997,65,2165. M. Ulbricht and H.H. Schwartz, J. Membr. Sci., 1997,136,25. S . Tsuneda, T. Endo, K. Saito, K. Sugita, K. Horie, T. Yamashita and T. Sugo, Chem. Phys. Lett., 1997,275,203. M.J. Swanson, Polym. Surf: Interf: [Proc. Symp.]., 1997, 19. J.A. Olmstead and D.G. Gray, J. Pulp. Paper Sci., 1997,23,5571. S.A. Silling, E.I. Lozinskaya and Yu. E. Boressevitch, Oxid. Comrnun., 1997, u), 1497.
372 287. 288. 289. 290. 291, 292. 293. 294. 295. 296. 297. 298. 299. 300. 301. 302. 303. 304. 305. 306. 307. 308. 309. 310. 31 1 .
312. 313. 314. 315.
316.
317. 318. 319. 320. 321. 322.
Photochemistry
I. Petkov, Proc. SPIE-Int. SOC.Opl. Eng., 1997,3227, 1 16. J. Cornil, D. Beljonne, A.J. Heeger and J.L. Bredas, ACS Symp Ser., 1997,672,308. N. Kawatsuki and T. Yamamoto, Nippon Setchaku Gakkaishi, 1997,33, 181. K. Ute, Kobunshi, 1997,46,749. J.D. Clark and A. Scranton, Polym. News, 1997,22,286. S. Aoshima, Kobunshi, 1997,46,493. J.L. Pozzo, H. Bouas-Laurent, A. Deffieux, D. Siedler and H. Durr, Mol. Cryst. Liq. Cryst. Sci. Technol.. Sect. A, 1997,298, 161. L. Hou, B. Hoffmann, H. Schmidt and M. Mennig, J. Sul-Gel Sci. Technol., 1997, 8, 923. M. Tibirna, V.M. Gorduza and C.I. Chiriac, Mod. Plast., 1996,33,215. B.B. Misty, R.G. Patel and V.S. Patel, J. Appl. Polym. Sci, 1997,64,841. C . Konak, R.C. Rathi, P. Kopeckova and J. K o p e k , Macromolecules, 1997, 30, 5553. B. Zinger, P. Schaer, G. Berkovic, G. Meshulam, Z. Kotler, L. Shapiro, R. Mazor and V. Khodorkovsky, Proc. SPIE-Int. SOC.Opt. Eng., 1997,3135,7 1. K. Arai, T. Ohyama and Y. Shitara, Polym. J., 1997,29,780. L. Zhijie, H. Yi and Z. Jianheng, IS&T's Annual Conf., Final Prog. Proc., 49th, 1996, 529. B.D. Hosangadi and S.K. Thakur, Synthesis, 1997,10,1137. H. Nakashima and M. Irie, Mucromol. Rapid Commun., 1997,18,625. N.S. Kicheva, F.P. Chernyakovskii and L.A. Blumenfield, BioJzika, 1997,42,628. A. Ahluwalia, R. Piolanti, D. De Rossi and A. Fissi, Langmuir, 1997,13,5909. Q. Li, D. Bi, X. Wei, W. Lin and D. Mo, Guangzi Xuebao, 1997,26,403. A. Fritz, A. Schoenhals and R. Ruhmann, Polym. Prep. (Am. Chem. SOC.,Div. Polym. Chem.), 1997,38,431. M. Ogawa, H. Kimura, K. Kuroda and C. Kato, Clay Sci., 1996,10,57. K. Se, M. Kijima and T. Fujimoto, Polymer, 1997,38, 5755. A. Altomare, F. Ciardelli, M.S. Ghiloni, R. Solaro and N. Tirelli, Mucromol. Chern. Phys., 1997,198,1739. A. Chyla, M. Bienkowski, J. Sworakoeski, T. Kozlecki and K.A. Wilk, Prog. Colloid Polym. Sci., 1997, 105, 153. T. Seki, K. Tanaka and K. Ichimura, Mol. Cryst. Liq. Cryst. Sci Technol., 1997,298, 235. H. Menzel and B. Rambke, Macromol. Chem. Phys., 1997,198,2073. Th. Fischer, H. Menzel and J. Stumpe, Supramol. Sci., 1997,4, 543. S.P. Gromov, E.N. Ushakov, O.A. Federova, V.A. Soldatenkova and M.V. Alfimov, Russ. Chem. Bull. (Trans. Izv. Akari., Ser. Khim.), 1997,46, 1143. B. Fischer, C. Thieme, T.M. Fischer, F. Kremer, T.Oge and R. Zentel, Liq. Cryst., 1997,22, 65. M.V. Alfimov, Y.V. Federov, O.A. Federova, S.P. Sergey, R.E. Hester, I.K. Lednev, J.N. Moore, V.P. Oleshko and .4.I. Vedernikov, Spectrochim. Acta, A 1997, 53, 1853. S. Zippel and G. Haucke, J. Chem. Res., Synop., 1997,11,386. P.Y. Wang and C.J. Wu, Dyes Pigments, 1997,35,279. S. Morino and K. Horie, ACS Symp. Sers., 1997,672,260. K. Kinoshita, K. Horie, S. Morino and T. Nishikubo, Appl. Phys. Lett., 1997, 70 , 2940. J.C. Peng, A m . Phys. Sin., 1997,6, 140. J.C. Peng, Commun. Theor. Phys., 1996,25,403.
III: Polymer Photochemistry
323. 324. 325. 326. 327. 328. 329. 330. 331. 332. 333. 334. 335. 336. 337. 338. 339. 340. 341. 342. 343. 344. 345. 346. 347. 348. 349. 350. 351. 352. 353.
373
M.L.C.M. Oosterling, M. Schoevaars, H.J. Haitjema and B.L. Feringa, Isr. J. Chem., 1997,36,341. K.B. Thakor, B.B. Mistry, R.G. Patel and V.S. Patel, Polym. Mater. Sci Eng., 1997, 4,7. H.R. Kricheldorf, S.J. Sun, C.P. Chen and T.C. Chang, J. Polym. Sci., Part A: Polym. Chem. Ed., 1997,35, 1611. Y. Ming, Z. Huang, M. Fan, B. Xu, S. Jin and S. Yao, Sci. Chin. Sers. B: Chem., 1997,40,373. N. Tamura, T. Sakai and T. Hashimoto, Sen’I Gakkaishi., 1997,53,489. J. Jonsson, B. Ranby, F. Massines, D. Mary and C. Laurent, IEEE Trans. Dielectric Electrical Insul., 1996,3,859. W.G. Charlston, D.M. Ryder, C.J. Olliff, C. Laurent, F. Massines, G. Teyssedre and P. Tiemblo, Annual Rep. Con$ Electr. Dielectric Phenomen., 1997, 1,250. C. Laurent, F. Massines, C. Mayoux, D.M. Ryder and C. Olliff, Annual Rep. Con$ Electr. Dielectric Phenomen., 1997 93. G.Z. Wen and W.P. Su, Springer Ser. Solid-Sate Sci., 1997,124, 121. H. Goto, K. Akagi and H. Shirakawa, Synth. Met., 1997,84,373. S . Koshihara, K. Akimoto, Y. Tokura, Y.Takeda and T. Koda, Springer Ser. SolidState Sci., 1997, 124, 105. A. Painelli, G. Girlando and Z.G. Soos, Synth. Met., 1997,85, 1079. E. Mulazzi, A. Ripamonti, C. Godon, S. Lefrant and G. Leising, Synth. Met., 1997, 84,911. Z.H. Yang, P. Zhang, D.J. Wang, D. Zhang, X.D. Chai and T.J. Li, Synth. Met., 1997,85, 1293. R.S. Guilardi, A. Castellan, M. Cotrait, S. Grelier, M.D. Guimaraes and D. Pilo Veloso, J. Mol. Struct., 1997,435, 77. K. Togashi, K. Urano, Y. Ehara, H. Kishida and T. Ito, Annual Rep. Con$ Electr. Dielectric Phenomen., 1996, 2,783. H. Ohkita, W. Sakai, A. Tsuchida and M. Yamamoto, Macromolecules, 1997, 30, 5376. T. Fujimura, K. Edamatsu, T. Itoh, R. Shimada, A. Imada, T. Koda, N. Chiba, H. Muramatsu and T. Ataka, Opt. Lett., 1997,22,489. K. Esfarjani, Y. Hashi, J. Onoe, K. Takeuchi and Y. Kawazoe, Phys. Rev. B: Condens. Matter Phys., 1998,57,223. V.V. Korolev, A.L. Mamaev, B.V. Bol’shakov and N.M. Bazhin, J. Polym. Sci., Part B: Polym. Phys. Ed., 1998,36,127. T. Shiga, Zairyo, 1997,46,480. A.A. Ishenko and N.N. Barashkov, Teor. Eksp. Khim., 1996,32,220. R.X. Ruan, C.H. Chen, H.W. Zhou, J.Z. Wang and Z.W. Wu, Gaodeng Xuexiao Huaxue Xuebao, 1997,18,655. P.B. Bisht, K. Fukuda and S. Hirayama, J. Phys. Chem. B, 1997,101,8052. A.C. Etile, C. Fiorini, F. Charra and J.M. Nunzi, Phys. Rev. A: /1t. Mol. Opt. Phys, 1997,56,3888. D. Wang, T.J. Liu, J. Chao and W.T. Slaven, Polym. Bull., 1997,39,265. M. Esser and J. Fuhrmann, Radiat. Efj Defects Solids, 1997, 143, 121. R.N. Nurmukhametov, L.V. Volkova, I.L. Belaitis, A.V. Pebalk, K.A. Mailyan and I.E. Kardash, Vysokomol. Seoedin., Sers. A, Sers. B., 1997,39,755. J. Cornil, A.J. Heeger and J.L. Bredas, Chem. Phys. Letts, 1997,272,463. F. Bai and L.A. Melton, Appl, Spectrosc., 1997,51, 1276. K.P. Dhake, S.N. Patil, R.V. Patil and P.M. Supe, Orient. J. Chem., 1997,13, 31.
374
Photochemistry
354.
1.0. Bashkin, A.N. Izotov, A.P. Moravsky, V.D. Negrii, R.K. Nikolaev, Yu.A. Ossipyan, E.G. Pontyatovsky and E.A. Steinman, Chem. Phys. Lett., 1997,272,32. W.G. Fisher, K.E. Meyer, E.A. Wachter, D. R. Per1 and P.J. Kulowitch, Mater. Eval., 1997,55,726. U. Geissler, M.L. Hallensleben and N. Rohde, Synth. Met., 1997,84, 173. F. Massines, P. Tiemblo, D. Mary, C. Laurent and C. Mayoux, C o n . Rec. ZEEE lnnt. Symp. Electr. Insul., 1996, 1,440. H. Okumoto, M. Shimomura, N. Minami and Y. Tanabe, Solid State Commun., 1997,104, 131 J.W. Yu and C.S.P. Sung, Macromolecules, 1997,30, 1845. L. Mangani, G. Rumbles, I.D.W. Samuel, K. Murray, S.C. Maratti, A.B. Holmes and R.H. Friend, Synth. Met., 1997,84, 84. R. Hattori, T. Sugano and J. Shirafuji, Appl. Surf: Sci., 1997, 113,472. X . Rao, R. Fu, X. Sun and K. Nasu, Phys. Lett., 1997,226,383. T. Yamamoto, T. Maruyama, H. Suganuma, M. Arai, D. Komarudin and S. Sasaki, Chem. Lett., 1997,2, 139. J.V. Grazulevicius, Chemija, 1996,1,89. S. Fomine, L. Fomina, C. Sanchez, A. Ortiz and T. Ogawa, Polym. J., 1997,29,49. J.D. Bhawalkar, J. Swiatkiewicz, S.J. Pan, J.K. Samarabandu, W.S. Liou, G.S. He, R. Berezney, P.C. Cheng and P.N. Prasad, Scanning, 1996,18,562. A.Ya. Ilchenko, V.O. Pavloschchuk, O.G. Tereschchenko and L.I. Shans’kii, Ukr. Khim. Zh., 1997,63,45. T. Itoh, J. Polym. Sci., Part A: Polym. Chem. Ed., 1997,35,3079. D. Berger, G. Klarner and R.D. Miller, J. Znorgunomef. Polym., 1997,7, I . B. Zhoui, D. Fortin and P.D. Harvey, J. Soc. Alger. Chem., 1996,6,231. S . Shimoyama and Y. Noda, Bunseki Kagaku, 1997,46,791. X. Liao, A.C. Grimsdale, R. Cervini, A.B. Holmes, S.C. moratti, T.M. Yong, J. Gruner and R.H. Friend, ACS Symp. Sers., 1997,672,322. P. Hrdlovic, Polym. News, 1997,7, 242. J.L. Bredas, J. Cornil, R. Lazzaroni and D.A. Santos, Annuul Technicul Con$-Soc. Plast. Eng., 1997,55tb, 1404. R.M. Tarka, X. Chen and S.A. Jenekhe, ACS Symp. Sers., 1997, 672, 475; W. Graupner, S. Eder, S. Tasch, G. Leising, G. Lanzani, M. Nisoli, S. De Silvestri and U. Scherf, J. Fluoresc., 1997,7, 199. G.R. Hayes, I.D.W. Samuel and R.T. Phillips, Synth. Met., 1997,84,889. I.D.W. Samuel, G. Rumbles, C.J. Collinson, R.H. Friend, S.C. Mariatti and A.B. Holmes, Synth. Met., 1997,84,497. J.Z. Zhang, M.A. Kreger, Q.S. Hu, D. Vitharana, L. Pu,P.J. Brock and J.C. Scott, J. Chem. Phys., 1997,106,3710. R. Kersting, B. Mollay, M. Rusch, J. Wenisch, G. Leising and H.F. Kaufmann, J. Chem. Phys., 1997,106,2850. G. Leising, F. Meghdadi, S.Tasch, C. Brandstaetter, W. Graupner and G. Kranzelbinder, Synth. Met., 1997,85, 1209. J. Cornil, D. Beljonne, C.M. HeHer, I.H. Campbell, B.K. Laurich, D.L. Smith, D.D.C. Bradley, K.Muellen and J.L. Bredas, Chem. Phys. Lett., 1997,278, 139. J. Gierschner, H.J. Egelhaaf and D. Oelkrug, Synth. Met., 1997,84,529. S.E. Doettinger, M. Hohloch, D. Hohnholz, J.L. Segura, E. Steinhuber and M. Hanack, Synth. Met., 1997,84,267. S.J. Chung, J. Jing and K.K. Kim, Adv. Mater. ( Weinheim)., 1997,9,551. H.J. Egelhaaf, J. Gierschner and D. Oelkrug, Synth. Met., 1996,83,221.
355. 356. 357.
358. 359. 360. 361. 362. 363. 364. 365. 366. 367. 368. 369. 370. 371. 372. 373. 374.
375. 376. 377. 378. 379. 380. 381.
382. 383. 384. 385.
III: Polymer Photochemistry 386. 387. 388. 389. 390. 391.
375
V. Dyakonov, G. Roesler, M. Schwoerer and E.L. Frankevich, Synth. Met., 1997, 84,483. V. Dyakonov, G. Roesler, M. Schwoerer and E.L. Frankevich, Phys. Revs. B: Condens. Matter, 1997,56,3852. D. Moses, H. Okumoto, D. Comoretto, C.H. Lee, A.J. Heeger, T. Ohnishi and T. Noguchi, Synth. Met., 1997,84,539. M.R. Anderson, M. Berggren, T. Olinga, T. Hjertberg, 0. Inganaes and 0. Wennerstroem, Synth. Met., 1997,84, 1383. K.K. Liang, J.H. Hsu, W.S. Fann, S.H. Lin, K.H. Lee, M.K. Leung, K.R. Chuang and S.A. Chen, Synth. Met., 1997,84,953. W . Graupner, S. Eder, K. Petritsch, G. Leising and U. Scherf, Synth. Met., 1997,84, 507.
392. 393. 394. 395. 396. 397. 398. 399.
L.J. Rothberg, M. Yan, E.W. Kwock and T.M. Miller, Annaul Techn. Con$-Soc. Plast. Eng., 55th, 1997, 1336. M.H. Hennessy and Z.G. Zoos, Synth. Met., 1997,84, 105 1. J. Shinar and J. Partee, Synth. Met., 1997,84, 525. E.M. Conwell, Mucromol. Symp., 1997,116, 39. G. Kranzelbinder, M. Nisoli, S. Stagira, G. Lanzani, K. Mullen, U. Scherf, W. Graupner and G. Leising, Appl. Phys. Lett., 1997,71,2725. M.R. Anderson, G. Yu and A.J. Heeger, Synth. Met., 1997,84, 1275. M.W. Wu and E.M. Conwell, Phys. Rev. B: Condens. Matter, 1997,56,10060. J. Wery, B. Dulieu, E. Launay, J. Bullot, M. Baietoul and J.P. Buisson, Synth. Met., 1997,84,277.
400. 401. 402.
S . Tasch, 0.Ekstoem, T. Jost, U. Scherf and G. Leising, Synth. Met., 1997,85, 1251. S . Tasch, G. Kranzelbinder, T. Jost, U. Scherf and G. Leising, Phys. Rev. B: Condens. Matter, 1997,55,5079. G. Kranzelbinder, H. Byrne, S. Hallstein, S. Roth and G. Leising, Synth. Met., 1997, 84,629.
409. 410.
G . Kranzelbinder, H.J. Byrne, S. Hallstein, S. Roth, G. Leising and U. Scherf, Phys. Rev. B: Condens. Matter, 1997,56, 1632. E. Conwell, Trends Polym. Sci., 1997,521 8. R.H. Friend, G.J. Denton, J.J.M. Halls, N.T. Harrison, A.B. Holmes, A. Kohler, A. Lux, S.C. Moriatti and K. Pichler, SolidState Commun., 1997, 102,249. G.J. Denton, N.T. Harrison, N. Tessler and R.H. Friend, Polym. Prep. (Am. Chem. SOC.,Div. Polym. Chem.), 1997,38,341. S.F. Alvarado, W. Riess, P.F. Seidler and P. Strohriegl, Phys. Rev. B: Condens. Matter, 1997,56, 1269. E.Z. Faraggi, D. Davidov, G. Cohen, S. Noach, M. Golosovsky, Y. Avny, R. Neumann and A. Lewis, Synth. Met., 1997,85, 1 187. H. Becker, S.E. Burne and R.H. Friend, Macromolecules, 1997,56, 1893. S.V. Frolov, W. Gellermann, Z.V. Vardeny, M. Ozaki and K. Yoshino, Synth. Met.,
41 1. 412. 413. 414.
C.H. Cheng, C.W. Tang, J. Shi and P. Klubeck, Macromol. Symp., 1998,125,49. N.T. Harrison and R.H. Friend, Synth. Met., 1997,84, 513. N.C. Greenham, X.Peng and A.P. Alivisatos, Synth. Met., 1997,84,545. A.J. Heeger, F. Wudl, N.S.Sariciftci, R.A.J. Janssen and N. Martin, J. Phys. I.,
415. 416. 41 7.
B. Jiang, S.W. Jang and E. Wayne, Chem. Muter., 1997,9,2031. N.N. Barashkov, T.S. Novikova and J.P. Ferraris, Synth. Met., 1996,83,39. Y . Fu, Polym. Prep. (Am. Chem. SOC.,Div. Polym. Chem.), 1997,38,410.
403. 404. 405. 406. 407. 408.
1997,84,493.
1996,6, 2151.
376
Photochemistry
41 8.
S.T. Kim, D.H. Hwang, A.B. Holmes, R.H. Friend and H.K. Shim, Synth. Met., 1997,84,655. M.T. Khan, M.L. Renak, G.C. Bazan and Z. Popovic, J. Am. Chem. Soc., 1997,119, 5344. B. Winkler, S. Tasch, E. Zojer, M. Ungerank, G. Leising and F. Stelzer, Synth. Met., 1996,83, 177. K. Kelnhofer, A. Knorr, Y.H. Tak, H. Bassler and J. Daub, Acta Polym., 1997, 48, 188. E.Z. Faraggi, H. Chayet, D. Davidov, Y. Avny and R. Neumann, Synth. Met., 1997, 85, 1247. V.E. Choong, Y. Park, Y. Gao, B.R. Hsieh and C.W. Tang, Macromol. Symp., 1998, 125,83. T.S. Novikova, N.N. Barashkov, A. Yassar, M. Hmyene and J.P. Ferraris, Synth. Met., 1996,83,47. D.Y. Kim, J.K. Kim, H.N. Cho and C.Y. Kim, (Am. Chem. Soc., Div. Polym. Chem.)., 1997,38,417. M. Hirohata, K. Tada, T. Kawai, M. Onoda and K. Yoshino, Synth. Met., 1997,85, 1273. M.W. Wagaman, E. Bellmann and R.H. Grubbs, Philos. Trans. R. Soc. London, Ser. A , 1997,355,727. M.W. Wageman and R.H. Grubbs, Macromolecules, 1997,30,3978. W.C. Wan, H. Antoniadis, V.E. Choong, H. Razafitrimo, Y. Gao, W.A. Feld and B.R. Hseih, Macromolecules, 1997,30,6567. S.E. Doettinger, M. Hohloch, J.L. Segura, E. Steinhuber, M. Hanack, A. Tompert and D. Oelkrug, A h . Muter. ( Weinheim), 1997,9,233. I. Benjamin, E.Z. Faraggi, G. Cohen, H. Chayet, D. Davidov, R. Neumann and Y. Avny, Synth. Met., 1997,84,401. M.S.H. Mao and T.D. Tilley, Macromolecules, 1997,30,5566. Z. Ma, S. Ijadi-Maghsoodi and T.J. Barton, Polym. Prep. (Am. Chem. SOC.,Div. Polym. Chem.), 1997, 38,249. J.A. Stephens, R.H. Friend, M. Remmers and D. Neher, Synth. Met., 1997,84,645. S.J. Lee, D.W. Kim, S.Y. Park and S. Hong, Korean Polym. J., 1997,5,52. J.I. Lee, J.Y. Han, H.K. Shim, S.C. Jeoung and D. Kim, Synth. Met., 1997,84,261. M. Hohloch, J.L. Segura, S.E. Doettinger, D. Hohnholz, E. Steinhuber, H. Sprweitzer and M. Hanack, Synth. Met., 1997,84,319. K. Kaeriyama, Y. Tsukahara, S. Negoro, N. Tanigaki and H. Masuda, Synth. Met., 1997,84,263. K. Honda, T. Maruyama and T. Yamamoto, Synth. Met., 1997,84, 153. A.C. Grimsdale, R. Cervini, R.H. Friend, A.B. Holmes, S.T. Kim and S.C. Moratti, Synth. Met., 1997,85, 1257. A. Edwards, S. Blumstengel, I. Sokolik, H. Yun, Y. Okamoto and R. Dornsville, Synth. Met., 1997,84,639. B. Winkler, S. Tasch, G. Leising and F. Stelzer, Synth. Met., 1997,84,383. J.H. Lee, J.W. Park and S.K. Choi, Synth. Met., 1997,88,31. X.C.Li, T.M. Yong, J. Gruener, A.B. Holmes, S.C. Moratti, F. Cacialli and R.H. Friend, Synth. Met., 1997,84,437. K . Kallitsis, K.G. Gravalos, A. Hilberer and G. Hadziioannou, Macromolecules, 1997,30,2898. M. Halim, I.D.W. Samuel, E. Rebourt and A.P. Monkman, Synth. Met., 1997, 84, 951.
419. 420. 421. 422. 423. 424. 425. 426. 427. 428. 429. 430. 431. 432. 433. 434. 435. 436. 437. 438. 439. 440. 441.
442. 443. 444.
445.
446.
III: Polymer Photochemistry 447. 448. 449. 450. 451. 452. 453. 454. 455. 456. 457. 458. 459. 460. 461. 462. 463. 464. 465. 466. 467. 468. 469. 470. 471. 472. 473. 474. 475. 476. 477. 478. 479.
377
A.J. Epstein, Y.Z. Wang, S.W. Jessen, J.W. Blatchford, D.D. Gebler, L.B. Lin, T.L. Gustafson, T.M. Swager and A.G. MacDiarmid, Macromol. Symp., 1997,116,27. O.H.J. Barashki and J.P. Ferraris, Synth. Met., 1997,84,41. S.W. Jessen, J.W. Blatchford, L.B. Lin, T.L. Gustafson, J. Partee, J. Shinar, D.K. Fu, M.J. Marsella, T.M. Swager, A.G. MacDiarmid and A.J. Epstein, Synth. Met., 1997,84,501. M. Suzuki, Y. Nakata, H. Nagai, T. Okutani, N. Kushibiki and M. Murakami, Mater. Sci Eng. B, 1997,49, 172. J.K. Politis, J. Nanos, Y. He and M.D. Curtis, Muter. Res. SOC. Symp. Proc., 1997, 424,495. M. Ranger and M. Leclerc, Macromolecules, 1997,30,7686. J. Einsiedler, 0. Freundel, R. Gompper, C. Harfmann, H.J. Mair and G. Nath, Polym. Prep. (Am. Chem. SOC.,Div. Polym. Chem.), 1997,38,318. R.Hidayat, M. Hirohata, K. Tada, M. Teraguchi, T. Masuda and K.Yoshino, Jpn. J. AppL Phys., Part I . , 1997,36,3740. A. Donat-Bouillud, L. Mazerolle, P. Gagnon, L. Goldenburg, M.C. Petty and M.Leclerc, Chem. Muter., 1997,9,2815. I. Levesque and M. Leclerc, Synth. Met., 1997,84,203. I. Levesque and M. Leclerc, Macromolecules, 1997,30,4347. Y. Ohmori, Y. Hironaka, M. Yoshida, M. Yoshida, N. Tada, A. Fijii and K. Yoshino, Synth. Met., 1997,85, 1241. K. Tada and K. Yoshino, Jpn. J. Appl. Phys., Part 2,1997,36,1351. T. Shiga, T. Ikawa and A. Okada, J. Appl. Polym. Sci., 1998,67, 1259. J. Li and Y. Pang, Macromolecules, 1997,30,7487. L.E. Bolivar-Martinez, M.C. dos Santos and D.S. Galvao, Synth. Met., 1997, 85, 1117. Y. Ohmori, Y. Hironaka, M. Yoshida, A. Fujii, N. Tada and K. Yoshino, Polym. Adv. Technol., 1997,8,403. S.B. Lee, A.A. Zakhidov, V.Yu. Sokolov, P.K. Khabibulaev, K. Tada, T. Kawai and K. Yoshino, Synth. Met., I997,84,567. S. Luzati, E. Prevosti and M. Catellani, Synth. Met., 1997,84, 551. M. Onoda, T. Yamaue, K. Tada, T. Kawai and K. Yoshino, Synth. Met., 1997,84, 983. M. Yang, Z. Lei, M. Wan, Y. Shen, J. Wang, J. Chen, H. Wang and T. Ye, J. Appl, Polym. Sci., 1997,64, 1657. M. Muccini, E. Lunedei, C. Taliani and H. Baessler, Synth. Met., 1997,84,599. H. Evertsson and C. Holmberg, Colloid Polym. Sci., 1997,275,830. H. Evertsson and S. Nilsson, Macromolecules, 1997,30,2377. Y.L. Loukas, J. Phys. Chem. B, 1997,101,4863. A. de la Maza and J.L. Parra, Colloid Polym. Sci., 1996,274,866. S.C. Bhattacharya, Chem. Environ. Res., 1996,5,207. X.Z. Du, X.B. Jiang, L.R.Lin, X.Z. Huang and G.Z. Chen, Chem. Phys. Lett., 1997, 268,31. K. Polewski and D. Napierala, Zywn Technol. Jakosc., 1996,2,41. A.K. Panda and A.K. Chakraborty, Indian J. Chem., Sect A: Inorg., Bio-Inorg., Phys. Theor. Anal. Chem, 1997,36, 184. Y. Hu, R.S.Armentrout and C.L. McCormick, Macromolecules, 1997,30,3538. S.Y. Yu, J. Qiu, Z.C. Li, G.Q. Yao, Q.Y. Gao, G.X. Yang, J.X. Zhang and F.M. Li, J. Appl. Polym. Sci., 1997,65,48 1. H. Yun, T.K. Kwei and Y. Okamoto, Macromolecules, 1997,30,4633.
378 480. 481. 482. 483. 484. 485. 486. 487. 488. 489. 490. 491. 492. 493. 494. 495. 496. 497. 498. 499. 500. 501. 502. 503. 504. 505. 506. 507. 508.
509. 510.
51 1 . 512. 51 3. 514. 515.
Photochemistry
D.J. Liaw, C.C. Huang and E.T. Kang, Colloid Polym. Sci., 1997,275,922. T. Rager, W.H. Meyer, G. Wegner and M.A. Winnik, Macromolecules, 1997, 30, 491 1. T. Ganguly and R.D. Burkhart, J. Phys. Chem., 1997,110,5633. Y. Shen, P. Wang, S. Wu, P. Huang and F. Shen, Ganguang Kexue Yu Guang Huaxue,1996, 14, 26 1. S.A. Zabin And C.R. Jejurkar, J. Polym. Muter., 1997,14,239. P. Marion and D. Juhue, F A TIPEC Congr.,2 3 r , 1996, A7 1 . S.Yu. Zaitsev, G.S.P. Vereschetin, O.A. Federova, M.V. Alfimov and M.D. Huesmann, Supramolecular Sci., 1997,4, 524. K. Schillen, A. Yekta, S. Ni and M.A. Winnik, Macromolecules, 1998,31,210. M. Li, M. Jiang and C. Wu, J. Polym. Sci., Part B: Polym. Phys. Ed., 1997,35, 1593. Y. Agi and D.R. Walt, J. Polym. Sci., Part A: Polym. Chem. Ed., 1997,35, 2105. K. de Meijere, G. Brezesinski and H. Moehwald, Macromolecules, 1997 30,2337. C. Damas, M. Adibenjad, A. Benjelloun, A. Brembilla, M.C. Carre, M.L. Viriot and P. Lochon, Coll. Polym. Sci., 1997,275,364. Z. Du, J. Zhong and S. Huang, Huadong Ligong Daxue Xuebao, 1997,23,327, A. Yamazaki, J.M. Song, F.M. Winnik and J.L. Brash, Macromolecules, 1998,31,109. C. Howley, D.G. Marangoni and J.C.T. Kwak, Coll. Polym. Sci., 1997,275,760. L. Meisterrmann, M. Duval and B. Tinland, Polym. Bull. (Berlin), 1997,39, 101. M. Yamamoto, J. Horinaka, H. Aoki, K. Tawa and S. Ito, Nihon Reoroji Gukkuishi, 1997,25,203. X.H. Zhang, P.C. Huang, P.F. Wang and S.K. Wu, Gaodeng Xuexiao Huaxue Xuebao, 1997,18,303. C.K.Chee, S. Rimmer, I. Soutar and L. Swanson, Polymer, 1997,38,483. K.B. Thurmond, T. Kowalewski and K.L. Wooley, Polym. Prep. (Am. Chem. SOC., Div. Polym. Chem.), 1997,38,592. Q. Li, K. Horie and R. Yokota, J. Photopolym. Sci. & Technol., 1997,10,49. A. Benjelloun, M. Adibnejad, A. Brembilla, M.C. Carre, M.L. Viriot, P. Lochon, T. Sousa and E. Reis, J. Fluoresc., 1997,7, 187s. M.G. Neumann and M.J. Tiera, Pure Appl. Chem., 1997,69,791. S . Szonyi, M. Gaysinski and A. Cambon, Con$ Colloid Chem., Proc., 7th, 1997, 180. A. Laschewsky and E. Wischerhoff, Macromol. Chem. Phys., 1997, 198,3239. M. Choi, D. Jin, H. Kim, T.J. Kang, S.C. Jeoung and D. Kim, J. Phys. Chem. B, 1997,101,8090. K. Hatada, T. Kitayama, T. Nishiura, M. Tawada, T. Harazono and T. Sugaya, J. Macromol. Sci., Pure Appl. Chem., 1997, A34,1183. D. Creed, R.A. Cozad, C.E. Hoyle, L. Jin, V. Krishnan and S.S. Varma, Polym. Prep. (Am. Chem. SOC.,Div. Polym. Chem.), 1997,38,82. H.G. Galabova, D.W. Allender and J. Chen, Phys. Rev. E: Stat. Phys., Plasmas, Fluids, Relut. Interdiscipl. Top., 1997,554 1627. K. Horie and H. Huang, Macromol. Symp., 1997, 118,229. V.P. Shibaev, S.G. Kostromin and S.A. Ivanov, Polym. Electroopt. Photoopt. Act. Mediu, 1996,37. K. Horie, H. Hsuwen, M. Sone and J. Watanabe, Mucromol. Symp., 1997,116, 105. T. Itadani and K. Saito, Nucl. Instrum. Methods Phys. Res. Sect. B, 1997,121,415. Y. Watanabe, T. Mihara and N. Koide, Macromolecules, 1997,30, 1857. B. Lee, Pollimo, 1997,21, 134. Y. Wu, Y. Demachi, 0. Tsutsumi, A. Kanazawa, T. Shiono and T. Ikeda, Macromolecules, 1998,31, 349.
III: Polymer Photochemistry
379
516. 0. Tsutsumi, T. Kitsunai, A. Kanazawa, T. Shiono and T. Ikeda, Macromolecules, 1998,31,355. 517. K. Akagi, H. Goto, S. Fujita and H. Shirakawa, J. Photopolym. Sci. Technol., 1997, 10,233. 518. T.G. Pedersen and P.M. Johansen, Phys. Rev. Lett., 1997,79,2470. 519. D.J. Broer, J. Lub and G.N. Mol, Macromol. Symp., 1997,117,33. 520. D. Steiger, P. Smith and C. Weder, Macromol. Rupid Commun., 1997,18,643. 521. T. Aida, Polym. Muter Sci.,1997,77,86. 522. M.Kimura, K. Nakada, Y. Yamaguchi, K. Hanabusa, H. Shirai and N. Kobayashi, Chem. Commun., 1997,1215. 523. K.W. Pollack, J.W. Leon, J.M.J. Frechet, M. Maskus and H.D. Abruna, Chem. Muter., 1998,10,30. 524. C. Devadoss, P. Bharathi and J.S. Moore, Angew. Chem., Int. Ed. Engl., 1997, 36, 1633. 525. J.C.M. Van Hest, D.A.P. Delnoye, M.W.P.L. Baars, C. Elissen-Roman, M.H.P. van Genderen and E.W. Meijer, Chem. Eur. J., 1996,2,161 6. 526. V.G. Krosovskii, G.M. Ignat-eva, V.D. Myakushev, N.A. Sadovskii, T.V. Strelkova and A.M. Muzafarov, Vysokomol. Soedin, Sers. A , Sers. B, 1996,38,1656. 527. R. Wilken and J. Adams, Macromol. Rapid Commun., 1997,18,659. 528. G. Pistolis, A. Malliaris, C.M. Paleos and D. Tsiourvas, Langmiur, 1997,13,5870. 529. S.A. Tucker, D.A. Bass and C.L. Larson, Polym. Muter. Sci. andEng., 1997,77,121. 530. G.R. Newkome, C.D. Weiss, C.N. Moorfield and I. Weiss, Macromolecules, 1997, 30,2300. 531. D.M. Junge and D.V. McGrath, Chem. Commun., 1997,857. 532. G. Yang, Z.A. Dreger and H.G. Drickamer, J. Phys. Chem., 1997,101,4218. 533. T.Z. Filipova, I. Grabchev and 1. Petkov, J. Polym. Sci., Part A: Polym. Chem. Ed., 1997,35,1069. 534. K. Davidson, I. Soutar and L. Swanson, J. Polym. Sci., Part B: Polym. Phys. Ed., 1997,35,963. 535. T. Ikawa, T. Shiga and A. Okada, J. Appl. Polym. Sci., 1997,66,1569. 536. H. Zhao, Z. Lei, F. Song and R. Huang, Yingyong Huaxue, 1997,14,87. 537. T. Itoh, Macromolecules, 1997,30,6999. 538. M.A. Fox and H.W. Thompson, Mucrornolecules,l997,30,7391. 539. Q.G. Wuyun, H. Wu, B. Gereltu and H.S. Wu, Gaodeng Xuexiao Huaxue Xuebao, 1997,18,492. 540. C . Hou, Q. Wu, Y. Chen, Z. Yu, M. Luo, J. Yang and N. Wang, Sichuan Daxue Xuebao, Ziran Kexueban, 1996,33,712. 541. J. Wolf and M.A. Myers, Macromol. Symp., 1997,116,15. 542. T.Z. Fabian and J.T. Koberstein, Polym. Muter. Sci. Eng., 1997,77,614. 543. K.F. Lin, L.K. Chang and H.L. Cheng, Polym. Prep. (Am. Chem. Soc., Div. Polym. Chem.), 1997,38,544. 544. P. Marion, G. Beinert, D. Juhue and J. Lang, J. Appl. Polym. Sci., 1997,64,2409. 545. J.W. Hofstraat, H.J. Verhey, J.W. Verhoeven, M.U. Kumke, G. Li, S.L. Hemmingsen and L.B. McGowen, Polymer, 1997,38,2899. 546. M. Canpolat and 0.Pekcan, Polymer, 1997,38,2595. 547. S. Tsuneda, T. Endo, K. Saito, K. Sugita, K. Horie, T. Yamashita and T. Sugita, Macromolecules, 1998,31,366, 548. A. Koschella, G.Haucke and T.Heinze, Polym. Bull. (Berlin), 1997,39,597. 549. M. Maafi, C. Lion and J.J. Aaron, Synth. Met., 1996,83,167. 550. C.Y. Zhu, S.H. WuandL.R. Li, Chin. Chem. Lett, 1997,8,719.
380
Photochemistry
G. Ciardelli, K. Kojima, A. Lendelein, P. Neuenschwander and U.W. Sueter, Macromol. Chem. Phys., 1997,198,2667. 552. X . Liu, F. Du, Z. Li and F. Li, Gaofenzi Xuebuo, 1997,5633. 553. Y.P. Sun, B. Liu and G.E. Lawson, Phofochem Photobiol., 1997,66,301. 554. H.J. Verhey, C.H.W. Bekker, J.W. Verhoeven, L.G.J. van der Ven and J.W. Hofstraat, Polymer, 1997,38,4491. 555. F. Li, Q.U. Gao, L. Wang, J.X. Zhang, S.J. Chen and Z.C. Li, J. Polym. Sci: Part A: Polym. Chem. Ed., 1997,35, 1087. 556. M.H. Kloffer, L. Bokobza and L. Monnerie, Macromol. Symp., 1997,119, 119. 557. O.K. Song, J.N. Woodford and C.H. Wang, J. Phys. Chem., 1997,101,3222. 558. G. Ciardelli, B. Saad, A. Lendlein, P. Neuenschwander and U.W. Suter, Macromol. Chem. Phys., 1997,198, 148 1. 559. T.D.Z. Atvars, A.P. Dorado and I.F. Pierola, Polym. Networks Blends, 1997,7, 1 1 1 . 560. E.K. Miller, K. Lee, J. Cornil, Q. Pei, F. Wudl, A.J. Heeger and J.L. Bredas, Synth. Met., 1997,84,631. 561. C.J. Brabec, V. Dyakonov, N.S. Sariciftci, W. Graupner and G. Leising, Proc. SPIE-Int. SOC.Opt. Eng., 1997,3145,516. 562. J.Y. Ye, T. Hattori, H. Natasuka, Y. Maruyama and M. Ishikawa, Phys. Rev. B: Condens. Matter, 1997,56, 5286. 563. J.W. Hofstraat, G.D.B. Houwelingen, Polymer, 1997,38,4033. 564. Y. Matsuda, Bunkazai Hozon Shujkuzu Gakkaishi, 1997,41,54. 565. H. Nakatsuka, J.Y. Ye, T. Hattori, Y. Maruyama and M. Ishikawa, Prog. Theor. Phys. Suppl., 1997,126,433. 566. M.A. Bopp, G. Tarrach, M.A. Lieb and A.J. Meixner, J. Vac. Sci. Technol., 1997, 15, 1432. 567. ZhS. Akylbaev, S.G. Karitskaya and S.G. Ponomarev,, Izv. Nuts. Akad Nauk Resp. Kuz., Ser. Fiz-Mat., 1995,6,65. 568. L. Sikurova and B. Cunderlikova, Spectrochim. Acta, A., 1997,53,293. 569. N. Srividya, P. Ramurthy and V.T. Ramakrishnan, Spectrochm. Acta, A., 1997, 53, 1743. 570. M.G. Kodzwa and D.G. Rethwisch, Polym. Muter. Sci. Eng., 1997,76, 279. 571. N. Sato, K. Sugiura, S. Ito and M. Yamamoto, hngmuir, 1997,13,5685. 572. M. Murtagh, H.C. Kwon and M.R. Shahriara, Proc. SPIE-Int. SOC. Opt. Eng., 1997, 3136,198. 573. M. Krihak, T. Murtagh and M.R. Shahriari, J. Sol-Gel. Technol., 1997,10, 153. 574. K. Tsujii, M. Hayakawa, T. Onda and T. Tanaka, Macromolecules, 1997,30,7397. 575. A. Datta, D. Mandal, S.K. Pal, K. Samir and D. Bhattacharyya, Langmuir, 1997, 13, 6922. 576. H. Aoki, J. Horinaka, S. Ito and M. Yamamoto, Polym. Bull., 1997 39, 109. 577. I. Black, D.J.S. Birch, D. Ward and M.J. Leach, J. Fluoresc., 1997,7, I 1 1. 578. 0.Peckan and Y. Yilmaz, J. Appl. Polym. Sci., 1997 63,1777. 579. H. Itagaki, M. Tokai and T. Kondo, Polymer, 1997,38,4201. 580. H. Itagaki and Y. Nakatani, Macromolecules, 1997,30,7793. 581. R.D. Fossum and M.A. Fox, Polym. Mat. Sci. Eng., 1997,76,389. 582. S . Ugur and 0. Peckan, Polymer, 1997,38,5579. 583. T. Asakawa, T. Okamoto and S. Miyagishi, Nithon Yukagaishi., 1997,46,777. 584. T.C. Barros, A. Adronov, F.M. Winnik and C. Bohne, Langmuir, 1997, 13,6089. 585. 0.Peckan, S. Ugur and Y. Yilmaz, Polymer, 1997,38,2183. 586. M.R. Vigil, J. Bravo, T.D.Z. Atvars and J. Baselga, Macromolecules, 1997,30,4871. 587. A.M. Mathur and A.B. Scranton, Sep. Sci. Technol., 1997,32,285. 551.
III: Polymer Photochemistry 588. 589. 590. 591. 592. 593. 594. 595. 596. 597. 598. 599. 600. 601. 602. 603. 604. 605. 606. 607. 608. 609. 610. 61 1. 612. 613. 614. 615. 616. 617. 618. 619. 620. 621. 622. 623. 624.
38 1
R.S. Frank, G. Merkle and M. Gauthier, Macromolecules, 1997,30, 5397. M. Gauthier, R.S. Frank and G. Merkle, Polym. Mater. Sci. Eng., 1997,77,114. R.S. Underhill, J. Ding, G. Liu and V.I. Birss Mucromolecules, 1997,30,300. A. Benjelloun, C. Damas, L. Dziadosz, M. Adibnejad, A. Brembilla, M.C. Carre, M.L. Viriot and P. Lochon, Macromol. Symp., 1997,119,283. M. Canpolat and 0.Peckan, Acta Polym., 1997,48, 326. M. Koussathana, P. Lianos and G. Staikos, Macromolecules, 1997,30,7798. M.E. Wilson, J.A. Wilson and M.J. Kurth, Macromolecules, 1997,30,3340. 0. Peckan and M. Canpolat, J. Appl. Polym. Sci., 1997,6,655. Y.P. Sun, C.E. Bunker and B. Liu, Chem. Phys. Lett., 1997,272,25. J. Bruening and B. Friedman, J. Chem. Phys., 1997,106,9634. K. Hasharoni, K.M. Keshavarz, A. Sastre, R. Gonzalez, C. Bellavia-Lund, Y. Greenwald, T. Swager, F. Wudl and A.J. Heeger, J. Chem. Phys., 1997, 107, 2308. J. Qiu, G. Yao, X. Zhou and F. Li, Gaufenzi Xuebao, 1997,3,367. A. Itaya, I. Suzuki, Y. Tsuboi and H. Miyasaka, J. Phys. Chem. B, 1997,101,5118. H. Icil and S. Icli, J. Polym. Sci. Part A: Polym. Chem. Ed., 1997,35,2137. K.D. Ley, C.E. Whittle, M.D. Bartberger and K.S. Schanze, J. Am. Chem. Soc., 1997,119,3423. A. Sanchez-Camacho, J. Pozuelo, F. Medicuti and W.L. Mattice, J. Fluoresc., 1997, 7 , 113. Y. Itoh, M. Inoue, A. Hachimori and K. Abe, Polym. Adv, Technol., 1997,8,35. S . Aich, A. Bhattacharyya and S . Basu, Radial. Phys. Chem., 1997,50,347. D. Vyprachticky, V. Pokorna, J. Pecka and F. Mikes, Macromolecules, 1997, 30, 7821. M. Ogasawara, Radial. Phys. Chem., 1996,49,71. M.W. Wu, Phys. Lett., 1997,230,237. M.N. Berberan-Santos, E.J. Pereiera and J.M.G. Martinho, J. Fluoresc., 1997, 7 , 119. G.A. O’Neil and J.M. Torkelson, Mucromolecules, 1997,30,5560. Y. Hu, G.L. Smith, M.F. Richardson and C.L. McCormick, Macromolecules, 1997, 30,3526. G.A. O’Neil and J.M. Torkelon, Macromol. Theor. Simul., 1997,6,93 1. Y. Takahashi, Y. Kato, Y. Minai and T. Tominaga, Chem. Commun., 1997,223. Y.P. Wang, R.M. Wang and L. Yuan, J. Appl. Polym. Sci., 1997,66,755. A.G. Mirochnik, N.V. Petrochenkova and V.E. Karasev, Vysokomul. Soedin., Sers. A, Sers. B, 1997,39,331. Q. Zhang and P. Wang, Chin. J. Polym. Sci., 1997,15, 187. S. Dirr, S. Wiese, H.H. Johannes, A. Boehler, D. Ammermann and W.Kowalsky, Macromol. Symp., 1998,125,69. C. Du, L. Ma, Y. Xu and W. Li, J. Appl. Polym. Sci., 1997,66, 1404. V.P. Tsybyshev, V.A. Livshits, B.B. Meshkov, O.A. Fedorova, S.P. Gromov and M.V. Alfimov, Russ. Chem. Bull., 1997,46, 1239. M . Suzuki, Y. Mori, N. Yokoyama, M. Kimura, K. Hanabusa and H. Shirai, Macromol. Chem. Phys., 1997,198,959. Z. Lei and Y. Wang, J. Appl. Polym. Sci., 1997,64, 1575. W.L. Li, T. Mishima, G.Y. Adachi and J. Shiokawa, Chem. Res. Chin. Univ., 1997, 13, 189. M. Kawa and J.M.J. Frechet, Chem. Makr., 1998,10,286. S. Backa, R.Jansbo and T. Reitberger, Holzforschung, 1997,51, 557.
382
Photochemistry
625.
P.V. Notingher, F. Ciuprina, I. Radu, J.C. Filippini, B. Gosse, S. Jipa, T. Setnescu, R, Setnescu and T. Mihalcea, ConJ: Rec. IEEE Int. Symp. Electr. Insul., 1996, 1, 163. G. Ahlblad, K. Jacobsen and B. Stenberg, Plast. Rubber Compos. Process Appl., 1996,25,464. L. Zlatkevich, Angew. Makromol. Chem., 1997,252,257. S. Jipa, Z. Osawa, H. Otsuki and M. Nishimoto, Polym. Deg. & Stabil., 1997,57,45. V.A. Belyakov, R.F. Vasil’ev, A.V. Trofimov and G.F. Fedorova, NATO ASZ Ser., Ser. 3., 1997,27,233. Z. Osawa, M. Kato and M. Terano, Macromol. Rapid Commun., 1997,18,667. M.I. Fulton, P.J. Pomery, N.A. St. John and G.A. George, Polym. Adv. Technol., 1998,9,75. T. Jimbo, S. Asai and M. Sumita, J. Macromol. Sci., Phys., 1997,36,381. H. Zweifel, Stabilisation of Polymeric Materials, Springer Verlag, Berlin, 1998. J. Boxhammer, B. Bentjerodt and C. Willwoldt, Polym. Test. 95, Book Pap. Two Day Rapra Con$, 1995,9. K. Sugita, Prog. Org. Coat., 1997,31,87. J. Guillet, Macromol. Symp., 1997, 123,209. E. Ikada, Zairyo, 1997,46, 1347. B.H. Chang, Polym. News, 1997,22,307. E. Ikada, Mem. Fac. Eng. Eng., Kobe Univ., 1996,43, 145. Y . Minematu and H. Kurosawa, Materiaru Raifu, 1997,9,29. L. Dulog, Angew. Makromol. Chem., 1997,252, I . C.T. Kelly and J.R. White, Polym. Deg. Stabil., 1997,56, 367. M.S. Rabello and J.R. White, Polymer, 1997,38,6379. L. Tong and J.R. White, Polym. Eng. Sci., 1997,37, 321. M.S. Rabello and J.R. White, Polymer, 1997,38,6389. M.S. Rabello and J.R.White, Annual Techn. Con$-Soc. Plast. Eng., 55th, 1997, 1738. M.S. Rabello and J.R. White, J. Appl. Polym. Sci., 1997,64,2505. J.L. Philippart, C. Sinturel and J.L. Gardette, Polym. Deg. & Stabil., 1997,58, 261. N.S. Allen, S.J. Palmer, G.P. Marshall and J.L. Gardette, Polym. Deg. & Stabil., 1997,56,265. P. Gisman, Angew Makromol. Chemie, 1997,252,45. A.S. Vasconcellos, H.F.C. Stocker and R. Baumhardt-Neto, Polim.: Cienc. Tecnol., 1997,7,44. S.I. Kuzina, A.P. Pivovarov, G.P. Belov and A.I. Mikhailov, High Energy Chem., 1997,31,382. J. Romeu, P. Pages and F. Carrasco, Rev. Plast. Mod., 1997,74,255. H.D. Hwu, H.M. Lin, S.F. Jiang and J.H. Chen, Annual Techn. Con$-Soc. Plast. Eng., 1997,55th, 2026. Y . Lin and H. Zhang, Suliao Gongye, 1996,2487. R. Mani, R.P. Singh and S. Sivaram, Polym. Int., 1997,44, 137. P.A. Vishwa, P.N. Thanki and R.P. Singh, J. Macromol. Sci., Pure and Appl. Chem., 1997, A34,349. S. Hwangbo, D.H. Yoon, D.H. Yi and M.K. Han, Chongi Hakhoe Nonmunchi, 1997, 46,112. S.I. Kuzina and A.I. Mikhailov, High Energy Chem., 1997,31, 239. M.I. Shestakova, I.P. Pronchenko and A.N. Stepanov, Plast. Massy, 1995,6,34. S.I. Kuzina, V.S. Yuran, E.A. Kalennikov and A.I. Mikhailov, High Energy Chem., 1997,31,333.
626. 627. 628. 629. 630. 631. 632. 633. 634. 635. 636. 637. 638. 639. 640. 641. 642. 643.
644. 645. 646.
647. 648. 649. 650. 651. 652. 653. 654. 655. 656. 657. 658. 659. 660. 661.
III: Polymer Photochemistry 662. 663. 664. 665. 666. 667. 668. 669. 670. 671. 672. 673. 674. 675. 676. 677. 678. 679. 680. 681. 682. 683. 684. 685. 686. 687. 688. 689. 690. 691. 692. 693. 694. 695. 696. 697. 698. 699.
Y.Kamei and S. Toaka, Proc. Int. Wire cable Symp., 1996,45th, 532.
383
P. Rios and H. Bertorello, J. Appl. Polym. Sci., 1997,64, 1195. A. Turnbul, N. Falla, A. Smith and D. White, Natl. Phys. Labs. (UK)Rep., (199), A45, 54. A. Kaminska, M. Swiatek and H. Kaczmarek, Pol. J. Chem., 1997,71, 1479. N.S. Allen, C.J. Regan, R.B. McIntyre, B.W. Johnson and W.A.E. Dunk, Macromol. Symp., 1997,115, 1. M.R. Krejsa, K. Udipi and J.C. Middleton, Macromolecules, 1997,30,4695. L.M. Postnikov, A.V. Dubovitskii and Ya. Shebenda, Vysokomol. Soedin., Sers A , Sers B., 1997,39,896. Y.B. Lee and J.H. Choi, Pollimo, 1997,21,961. L. Monney, C. Bubois and Chambaudet, Polym. Deg. & Stabil., 1997,56,357. J. Scheirs, G. Camino, L. Costa, C. Tonelli, S. Turri and M. Sciccitano, Polym. Deg. & Stabil., 1997,56,239. A. Rivaton, L. Moreau and J.L. Gardette, Polym. Deg. & Stabil., 1997,58, 321. A. Rivaton, L. Moreau and J.L. Gardette, Polym. Deg. & Stabil., 1997,58, 333. W. Wang, A. Tangiguchi, M. Fukuhara and T. Okada, J. Appl. Polym. Sci., 1998, 67,705. E. Ikada, J. Polym. Sci. & Technol., 1997,10,265. J.L. Gardette, Polym. Polym. Compos., 1997,5,7. J. Scheirs and J.L. Gardette, Polym. Deg. & Stabil., 1997,56, 339. J. Scheirs and J.L. Gardette, Polym. Deg. & Stabil., 1997,56, 351. J.A. Villegas, R. Olayo and J. Cervantes, J. Inorg. Organometall. Polym., 1997,7, 5 1 . K. Kabeta, S. Sugi, S. Wakamatsu and T. Imai, Polymer, 1997,38,5051. T. Miyazawa, T. Saeki, C. Liu and M. Kira, J. Am. Chem. Soc., 1998,120,1084. J. Pospisil, L. Rosik and S. Nespurek, Plusty Kuuc., 1997,34,324. L.H. Catalani, A.M. Rabello, F.H. Florenzano, M.J. Politi and W.F. Reed, Int. J. Polym. Anal. Churact., 1997,3,231. W.M. Choi, D. Jung, C.S. G a n g and W.J. Cho, J. Appl. Polym. Sci., 1998,67, 1237. J.H. Kim, Pollimo, 1997,21, 1006. S.W. Han, W.M. Choi, J.G. Park, C.S. Ha, S.K. Kwon and W.J. Cho, J. Appl. Polym. Sci., 1998, 67, 1721. Y. Feng, J. Sun, Y. Zhu, W. Chen and X. Wang, Gaofenzi cailiuo Kexue Yu Gongcheng, 1997,13,21. A. Torikai, T. Kabatake and F. Okisaki, J. Appl. Polym. Sci., 1998,67, 1239. S. Commereuc and J. Lacoste, Polym. Deg. & Stabil., 1997,57, 3 1 . T. Zhou, S. Chen, Z. Li, X.Zhou and F. Li, Gaofenzi Xuebao, 1997,1, 102. R. Pazur, M. Troquet and J.L. Gardette, J. Polym. Sci. Part A: Polym. Chem. Ed, 1997,35,1689. K Y. Chen and K.H. Chen, J. Polym. Sci. Part A: Polym. Chem. Ed, 1997,35, 1689. K A. Onu, M. Palamaru, E. Tutovan and C. Ciobani, Znt. J. Polym. Muter, 1997,37, 263. C. Wihelm, A. Rivaton and J.L. Gardette, Polymer., 1998,39, 1223. C . Wilhelm and J.L. Gardette, Polymer, 1997,38,4019. A. Hollander and J. Behnisch, S u Coat. ~ Technol., 1998,98,847. D. Praschak, T. Bahners, A. Bossman and E. Schollmayer, Melliand Int., 1997, 3, 174. D. Praschak, T. Bahners, and E. Schollmeyer, Melliancl Textilber., 1997,78,53 1. D. Praschak, T. Bahners, A. Bossman and E. Schollmayer, Appl. Phys. A: Muter. Sci. Process., 1998, A66,69.
384
Photochemistry
700. 701. 702.
D.J. Krajnovich, J. Appl, Phys., 1997,82,427. K. Revesz, B. Hopp and Z. Bor, Langmuir, 1997,13,5593. H. Esrom, J.Y. Zhou and U. Kogelschatz, Polym. Surf: Int. Int. Symp. (Nehterlands)., 1997,27. S. Machida, S. Tanaka and K. Horie, Polym. Mater. Sci. & Eng., 1997,76, 332. I . Renge, J. Chem. Phys., 1997,106,5835. S. Fei, Z. Chen and H.L. Strauss, J. Phys. Chem. B., 1997,101,3506. S. Nishiama, S. Machida, T. Yamashita and K. Horie, J. Phys. Chem. B., 1998, 102,
703. 704. 705. 706.
514.
707 708. 709. 710. 71 1. 712. 71 3. 714. 71 5.
716. 717. 71 8. 719. 720. 721. 722. 723 724 725. 726. 727. 728. 729. 730. 731. 732. 733. 734.
N. Takezoe, A. Yokotani, K. Kurosawa, W.Sasaki, K. Yoshida, T. Igarashi and H. Matsuno, Mater. Res. Soc.Symp. Proc., (1997), 451,515. P.K. Wei, J.H. Hsu, W.S. Fann and R.B. Hsieh, Synth. Met., 1997,85, 1421. M. Beyer, H. Koch and K. Fischer, C, 1995,3, 5. H. Tylli, I. Forsskahl and C. Olkkonen, Int. Symp. Wood Chem., 8th., 1995,3,45. R. Pelegrini, P. Peralta-Zamora, N. Duran and J. Reves, Braz. Symp. Chem. Lignins other Wood Compos., Proc., 5th, 1997,6, 125. H . Shin, Y. Moon, S. Tokino and M. Ueda, Sen’i Gukkuishi, 1997,53, 164. J.A. Olmstead, J.H. Zhu and D.G. Gray, Int. Symp. Wood Pulping Chem., 8th, 1995, 3, 15. E. Chupka, A. Chupka, G. Ljalin, A. Mikhalevkin and E. Artamonova, Int. Symp. WooclPulping Chem., 8th, 1995,3, 21. N . Do, A. Evandro, J.T. Francisco, A.L. Morais, Braz. Symp. Chem. Lignins other Wood Compos., Proc., Sth., 1997,6,252. U.P. Agarwal and J.D. McSweeny, J. Wood Chem. Technol., 1997,17,1. U.P. Agarwal and J.D. McSweeny, Int. Symp. Wood Pulping Chem., 8th., 1995, 1, 435. J. Wang, C. Heitner and R. St. John Manley, Int. Symp. Wood Pulping Chem. 8th, 1995,3,27. M.Paulsson, R. Simonson and U. Westermark, Int. Symp. Wood Pulping Chem. 8th, 1995,3,61. D.S. Argyropoulos, Bruz. Symp. Chem. Lignins Other Wood Compos., Proc. 5th, 1997,6, 166. K. Fischer, H. Koch and M. Beyer, Int. Symp. Wood Pulping Chem., 8th, 1995, 3, 429. I. Forsskahl, Int. Symp. Wood Pulping Chem., 8th, 1995,3,9. V . Heller, H. Koch, M. Beyer and K. Fischer, Int. Symp. Wood Pulping Chem., 8th, 1995,3, 33. K. Nemeth and V. Vano, Int. Symp. Wood Pulping Chem., 8th, 1995,3, 1. R.S. Pereira and J.M. Neves, Papel, 1997,58,73. M. Kiguchi, JARQ, 1997,31, 147. J.X. Guo, Y.C. Lin and D.G. Gray, J. Pulp. Pap. Sci., 1997,23,3 I 1. A. Castellan, A. Nourmamode, S. Grelier and P. Fornier de Violet, Cell. Chem. Techno!., 1996,30,431. H. Derbyshire, E.R. Miller and H. Turkulin, Holz Roh- Werkst., 1996,55,287. K. Schafer, D. Goddinger and H. Hocker, J. Soc. Dyers and Colourists, 1997, 113, 350. K. Schafer, D. Goddinger and H. Hocker, D WI Rep., 1997,120,l. S. Collins and R.S. Davidson, Rev. frog. Colouration, 1997,27,42. E.D. Owen and H.S.M. Al-Moh’d, Polym. Deg. & Stabil., 1997,56,235. G.J. Pratt and M.J.A. Smith, Polym. Deg. & Stabil., 1997,56, 179.
111: Polymer Photochemistry 735. 736. 737. 738. 739. 740. 741. 742,
385
V.E. Skurat, E.A. Barbashev, I.A. Budashov, Yu.1. Dorofeev, A.P. Nikiforov, A.I. Ternovoy, M. Van Eesbeek and F. Levadou, Eur. Space Agency, [Spec. Publ.] ESA SP, 1997,399,267. H. Toyotaka, T. Kobayshi and K.Takeda, Materiaru Raijiu., 1997,9, 127. P.M. Lahti, A.L. Inceli and F.C. Rossitto, J. Polym. Sci.,Part A: Polym. Chem. Ed., 1997,35,2167.
M.E. Nichols, J.L. Gerlock and C.A. Smith, Polym. Deg. & Stabil., 1997,56, 81. Y.Hiraguri and Y. Tokiwa, Macromolecules, 1997,30, 3691. E.G.J. Staring, A.J.M. Bernsten, S.T.R. Romme, G.L.J.A. Rikken and P. Urbach, Philos. Trans. R. SOC.,London, Sers A., 1997, 355, 695. M. Antonietti, R. Kublickas, 0. Nuyken and B. Voit, Macromol. Chemie Rapid Commun., 1997, 18, 287. M. Scoponi, F. Pradella, M. Gleria and F. Minto, J. Inorg. Organometall. Polym., 1996,6, 325.
743. 744. 745. 746.
K.H. Chae, J.S. Park, E.S. Kim and J. Man, Bull. Korean Chem. SOC.,1997,18, 243. B.L. Langsdorf, J.J. Wolcott and D.R. Tyler, Polym. Prep. (Am. Chem. Soc., Div. Polym. Chem.)., 1997,38,268. P.J. Deslauriers, J.P. Geibel and P.K. Das, Angew Makromol. Chem., 1997,247,45. S. Masuda, N. Sertova and I. Petkov, J. Polym. Sci., Part A: Polym. Chem. E d , 1997,35,3683.
747. 748. 749. 750. 751. 752. 753. 754. 755. 756.
Y. Li, Y. Liu, Z. Zhang, H. Li and H. Zhu, Suliao, 1996,25,19. J.L. Male, B.E. Lindfors, K.J. Covert and D.R. Tyler, Macromolecules, 1997, 30, 6404. M. Korouji and H. Goto, Kogyo Zairyo, 1997,45,34. K . Inoue, Kogyo Zairyo, 1997,45,67. H. Herbst, K. Hoffman, R. Pfendner and F. Sitek, Recycl. Recovery Plast., 1996,297. A. Valet and D. Wostratzky, RadTech Rep., 1996, 10, 18. A. Valet and D. Rogez, Surf. Coat. Aust., 1997,34,22. S. Constanzi and R. Farris, Adv. Plast. Technol. APT96 Int. Conf., 1996,7, 1. F.Catalina, Rev. Plast. Modernas, 1997,73, 542. E.A. Myszak and M.T. Sobus, Recent Adv. Flame Retard. Polym. Mater., 1996, 7, 145.
757. 758. 759. 760.
H. Nishihara, Kin0 Zairyo, 1997, 17, 5.
768.
J.M. Gallas, Melanin: Its Role Hum. Photoprot., Melanin Symp. 1994, 1995,277. S.H. Botros and M.A. Abd El-Ghaffar, J. Elastomers Plast., 1997,29, 216. V.P. Mardykin, V.D. Ryasnoi, I.F. Gvozdyukevich, L.V. Gaponik and V.I. Skripachev, Vestn. Beloruss. Gos. Univ., Ser. 2., 1997, 1, 12. V.P. Mardykin, A.V. Pavlovich, V.D. Ryasnoi, T.F. Gvozdyukevich, V.I. Skripachev and V.V. Gergalov, Plast. Massy, 1995,5, 14. R.A. Akhmedova and M.M. Gadzhiev, Plast. Massy, 1997,1,20. T. Caronna, M. Forte and M. Catellani, Synth. Met., 1997,84,227. T. Caronna, M. Forte, M. Catellani and S.V. Meille, Chem. Muter., 1997,9,991. S. Hassanpour, Iran J. Polym. Sci. Technol., 1996,9,83. B.J.W. Cole, C. Zhou and C. Raymond, J. Wood Chem. Technol., 1996,16,381. D. Creed, C.E. Hoyle, J.W. Jordan, C.A. Pandey, R. Nagarajan, S. Pankasem, A.M. Peeler and P. Subramanian, Macromol. Symp., 1997,116,116. G. Rytz, R. Hilfiker, E. Schmidt and A. Schmitter, Angew. Mukromol. Chem., 1997,
769. 770.
J.E. Pickett, Macromol. Symp., 1997, 115, 127. R.J. Parmar and J.S. Parmar, High Perform. Polym., 1997,9,41.
761. 762. 763. 764. 765. 766. 767.
247,213.
386
Photochemistry
771.
C.M. Estevez, R.D. Bach, K.C. Hass and W.F. Schneider, J. Am. Chem. Soc., 1997, 11 9, 5445. Z. Song, L. Wang and X . Duan, Guofenzi Cailiuo Kexue Yu Gongcheng, 1997,13,82. S . Chmela, J.F. Pilichowski and J. Lacoste, J. Polym. Sci., Part A: Polym. Chem. Ed., 1997,352599. Y . Wang, Xi’un Shiyou Xueyuan Xuebao, 1997,12,47. M. Povazancova, PIasty Kuuc., 1997,34,20 1. S.M. Andrews, M. Clauss and P. Michaelis, Rubber World, 1997,216,22. R.L. Gray and R.E. Lee, Angew. Mukromol. Chem., 1997,247,61. F. Minto, V. Borzatta, R. Bertani and M. Gleria, J. Appl. Polym. Sci., 1997,65,217. C. Decker and S. Biry, Prog. Org. Coatings, 1996,29,8 I . J. Lin, M. Cuscurida and H.G. Waddill, Ind Eng. Chem. Res., 1997,36, 1944. R . Mani, R.P. Singh, S. Chanrapani and S. Sivaram, Polymer, 1997,38, 1739. K.H. Chae, J.S. Oh and H.S. Ham, J. Photosci., 1996,3, 167. N.S. Allen, M. Edge, T. Corrales, A. Childs, C. Liauw, F. Catalina, C. Peinado and A. Minihan, Polym. Deg. Stubil., 1997,56, 125. N.S. Allen, C.J. Regan, W.A.E. Dunk, R. McIntyre and B. Johnson, Polym. Deg. Stabil., 1997,58, 149. A. Ichiryu, Shinsozai, 1996,7, 24. S. Murasawa, Konbatekku, 1997,25, I . S. Okamoto, Tuso to Turyu, 1997,565,27. Yu.A. Dmitriev and V.P. Gordienko, Plast. Mussy, 1995,5,20. H. Schmidt and K. Twarowska-Schmidt, Fibres Text. East. Eur., 1997,5, 51. E.C.D. Nunes, A.S. Babetto and J.A.M. Agnelli, Polim.:Cienc. Tecnol., 1997,7,66. K. Shiomori, Y. Kawano, Y. Baba, H. Mitani and Y. Hatate, Kaguku Koguku Runbunshu, 1997,23,694. T. Suratwala, Z. Gardlund, K. Davidson, D.R. Uhlmann, J. Watson and N. Peyghambarian, Chem. Muter., 1998,10, 190. T. Suratwala, Z. Gardlund, K. Davidson, D.R. Uhlmann, J. Watson and N. Peyghambarian, Chem. Muter., 1998, 10, 199. N. Katsuda, K. Otake, T. Omura and T. Takagishi, Dyes Pigments, 1998,36, 193. P. Meallier, M. Moullet, S. Guttonneau, F. Chabaud, P. Chevrou and C. Niemann, Dyes Pigments, 1998,36, 16 1. Y. Tsumura, Kyozome Seiren Senshoku, 1996,47, 5 1. M.R.H. Zarger, S. Moradian and F.M. Mazaheri, Iran J. Polym. Sci. Technol., 1996, 9, 175. D. Nansheng, W. Feng, L. Fan and L. Zan, Chemosphere, 1997,35,2697. N. Katsuda, T. Omura and T. Takagishi, Dyes Pigments, 1998,36,23 1. Y. Okada, F. Fumiko and Z. Morita, Dyes Pigments, 1997,35, 3 1 1 . J. Sokolowska-Gajda, Dyes Pigments, 1998,36, 149. P.Y. Wang and C.J. Wu, Dyes Pigments, 1997,35,279. R.M. Christie, J.D. Hepworth, C.D. Gabbutt and S. Rae, Dyes Pigments, 1997, 35, 139. N.S. Allen, J.L. Thomas, M. Edge, G.W. Follows and R. Heinz, Dyes Pigments, 1997,35, 169.
772. 773. 774. 775. 776. 777. 778. 779. 780. 781. 782. 783. 784.
785. 786. 787. 788. 789. 790. 791. 792. 793. 794. 795. 796. 797. 798. 799. 800. 801. 802. 803. 804.
Part IV Photochemical Aspects of Solar Energy Conversion By Alan Cox
Photochemical Aspects of Solar Energy Conversion BYALAN COX
1
Introduction
Topics which have formed the subjects of reviews this year include photocatalysis and solar energy conversion,’ the thermodynamics of energy-storing photoprocesses? water splitting using a range of multimolecular and supramolecular photochemical system^,^ new perspectives on hydrogen production by water ~plitting,~ photodecomposition of water by the layer-structure compound (K4Nb6017),~photobiological production of hydrogen from water: photocatalytic generation of hydrogen from hydrogen ~ulfide,~ inorganic chemistry in solar energy conversion,* photoinduced generation of dihydrogen and reduction of carbon dioxide using transition metal complexe~,~ photocatalysis on semiconductors,” and a gold complex for photoenergy storage. I The use of solar energy to drive chemical reactionsI2 and to synthesise active substances and intermediates has been de~cribed,’~ as well as some key developments in the field of solar chemistry and solar chemical engineering.14 2
Homogeneous Photosystems
Pathways for hydrogen production based upon electron transfer and using homogeneous catalysts have been discussed.15 In particular, two new Co(1I)polypyridinium catalysts [C~(pdt)~]’+and [Co(ttp)Z]’+ have been described, and successfully employed for solar hydrogen production in conjunction with [Ru(bpy)3]” as photosensitizer and ascorbic acid as sacrificial electron donor, for which quantum yields of up to 20% have been recorded. Photoinduced hydrogen evolution has been observed under steady state irradiation using the water soluble bisviologen linked zinc porphyrin (1) and hydrogenase.l 6 A range of new dithiolene complexes has been investigated for their ability to promote the photooxidation of water.I7 The most successful examples are nonsymmetric complexes of W, Mo, Re, and Ni, and incorporate phenyl groups bearing paraelectron donating substituents. As measured in terms of yield and stability, the most satisfactory complex is tris-[ 1-(4-dimethylaminophenyl)-2phenyl- 1,2-ethylenodithiolenic-S,S’]tungsten. Details have appeared of an innovative technique for hydrogen production using a system consisting of water, bromine, solar energy, and supplemental electric power, and which utilises a Photochemistry, Volume 30 0The Royal Society of Chemistry, 1999 389
390
Photochemistry
process dependent upon the photochemical production of HBr for off-peak electrolytic hydrogen generation.18 Irradiation of F v R u ~ ( C O (2; ) ~ Fv = q5:q5bicyclopentadienyl) induces isomerisation to (p-q':q5-cyclopentadieny1)2R u ~ ( C O )which ~, on heating in either the solid state or in solution reverts to @).I9 These observations may have relevance for the efficient storage of light energy. Photoinduced hydrogen evolution has been achieved using a system in which excited proflavin is quenched by triethanolamine, and following cytochrome c3 reduction hydrogen evolution is catalysed by hydrogenase.20 The dinuclear complexes [ C U~ L ~ ( ~ - N B D ) [Cu2L'2(p-NBD)17 ], [Cu2L"2(p-NBD)17 and [CU&"'~(~-NBD)] (L = Z-methyl-8-oxoquinolinato,L = 2-methyl-5,7-dichloro8-oxoquinolinato, L" = 4-oxoacridinato, and L"' = 2-(2-0~0-3,5-di-tert-butylpheny1)benzotriazole) have been found to be effective in the photoisomerisation of methanolic solutions of norbornadiene using birr = 405 nm (+ = 0.029).21 Turnover numbers of about 5000 have been obtained and increases in temperature significantly raise the quantum yield. Ruthenium-polyimidazole complexes have been employed as sensitizers for photoinduced hydrogen generation in reactions in solution and film systems,22and a study of the photointerconversion of norbornadiene and quadricyclane with the Rh(II1) diimine Complexes [Rh(phen)3I3' and [Rh(phi)2(phen)I3' (phen = 1,lO-phenanthroline, phi = 9,lOphenanthrenequinone diimine) as sensitizers has appeared.23 Use of [R h( ~h e n ) ~] ~' induces a slow reversible interconversion, although that of [Rh(phi)2(phen)13' is irreversible; both transformations occur by an exciplex intermediate. Electron transfer has been studied within a quadricyclane-steroiddibenzoylmethanatoboron difluoride and found to lead to isomerisation of the quadricyclane An example has been given of the use of this system as an
Photochemical Aspects of Solar Energy Conversion
39 1
antenna chromophore to harvest photon energy which can be used to activate a remote functional group by long-distance electron transfer. 3-Phenylnorbornadienes having conjugated substituents such as carbaldimine, carbaldoxime, amide, aroylvinyl, and heterocyclic groups in the 2-position are capable of being photoisomerised (& 310 - 420 nm) to the corresponding quadricyclane (4 = 0.1 0.7) for which the back reaction proceeds almost quantitatively on heating.25 Photoinduced electron- and energy-transfer processes in macromolecular assemblies which have significance for solar energy capture have been discussed,26and the application of highly concentrated sunlight to the photosynthesis of fine chemicals has been described and evaluated with particular reference to the [2+2] cycloaddition of a carbonyl compound to an ethene.27
3
Heterogeneous Photosystems
Addition of carbonate salts to Pt-Ti02 suspensions is reported to promote stoichiometric photocatalytic decomposition of liquid water into molecular hydrogen and molecular oxygen.28The carbonate probably assumes two roles in that the back reaction is suppressed as a consequence of the platinum surface becoming coated by the carbonate, and secondly by the titanium catalyst becoming covered with a layer of carbonate causing desorption of molecular oxygen. The same authors have also demonstrated that water can be photochemically decomposed to molecular hydrogen and molecular oxygen in stoichiometric proportions using a NiO-Ti02 catalyst and solar radiation; this procedure is applicable worldwide.29Further studies show that water can be stoichiometrically photodecomposed into hydrogen and oxygen over a Ru02-W03 catalyst suspended in an aqueous medium containing a Fe3+/Fe2+ redox system.30 Excitation of Fe3+ on the W 0 3 surface by visible light (Lirr < 460 nm) promotes evolution of 0 2 , and excitation of the Fe2+ ions @irr c 280 nm) reconverts these ions into Fe3+ with release of hydrogen. The overall process is somewhat analogous to the Z-scheme in photosynthesis. The activity of CdS supported on alumina for the photocatalytic production of hydrogen from water has been shown to be strongly affected by its dispersion and distribution on the support, and this is accounted for in terms of the microstructure of the upp port.^' Nanoparticles of CdS and ZnS incorporated into silicate matrices have a high activity for the photocatalytic production of hydrogen from and the photocatalytic oxidation of water to molecular oxygen on AgCI-coated electrodes has also been reported.33 In this last case the authors further claim that irradiation (hi, < 550 nm) of silver chloride supported on zeolite A in the presence of water-saturated argon similarly leads to the evolution of molecular oxygen.34The photoactivity of the system is related to the amount of Ag+ adsorbed on the AgCl surface, and a mechanism accounting for the experimental results is described. The photocatalytic activity of Na2W4013, a layered structure which possesses a band gap intermediate between those of bulk W03 and polyacid [Si(W3010)$-, is such as to enable hydrogen and oxygen to be photogenerated in the presence of
392
Photochemistry
sacrificial reagents,35 and native and NiO-loaded K3Ta3Si2013 which possess a pillared structure having three linear TaO6 chains have been found to be effective for the stoichiometric photodecomposition of water into molecular oxygen and molecular hydrogen.36 A new photochemical catalyst for the production of dihydrogen from water using visible light has been described.37 The catalyst consists of Cs(a)Ip(c)/Car(b) [a 6.0 wt%; Ip (inorg. promoter) = Ni, Co, or Fe; c 50.0 wt YO;Car = carrier consisting of a mixture of inorganic compound (e.g. SO2, A1203, Ti02, Zr02, niobate)] and ZnS, in which the low ionisation energy of the Cs atom may play a crucial role.38 Langmuir-Blodgett films comprising two types of viologen-linked porphyrin having different configurations between the porphyrin and the viologen have been prepared and their effect on photoelectric conversion by indium tin oxide electrodes and on photoinduced hydrogen evolution has been In the latter case, these Langmuir-Blodgett films were used in conjunction with H,PtC16 as catalyst and EDTA as a sacrificial electron donor. No effect on photocurrent generation was observed, but photoinduced hydrogen evolution was found to be dependent on the configuration. The same authors have reported photoreductants for water capable of hydrogen production, and composed of a support fabricated from glass or metals (eg Fe, Al), a catalyst layer (eg Pt) for the reduction of water, and a colour layer of porphyrin derivatives or ruthenium bipyridine derivatives:' A new system capable of splitting water has been described.42This consists of a three-layered structure in which the first layer is composed of a monolithic polypyromellitimide film, the second layer is [Ru(bpy)3I2' incorporated within the same polymer, and the third layer [Ru(bpy)3I2', EDTA.2Na and dispersed ultrafine platinum. This entire structure is suspended in methanolic methylviologen. Polymer-protected Pt/Ru bimetallic clusters and Pt and Ru monometallic clusters have been used for hydrogen generation in an electron transfer system consisting of tris(bipyridine)ruthenium(I1) dichloride/methyl viologen dichloride/metal cluster/EDTA disodium salt.43 At low concentrations, hydrogen production rates are reported to be proportional to the concentration of cluster metal. Details of a photochemical energy storage system which uses a spatially organised zeolite-based photoredox system have appeared and which is capable of forming long-lived chargeseparated states.# In this system, minimisation of back thermal eleztron transfer has been achieved by placing the active components such as donor, acceptor, and sensitizing intermediate molecule in adjacent cages within the zeolite framework, and this arrangement leads to an extraordinary degree of charge-separation efficiency. A dual bed photosystem has been described for the production of hydrogen and oxygen which is designed to divide the energy requirement for hydrogen production between two photosystems enabling lower energy photons to be used, and also to evolve the products separately from one another.45 The two catalysts are Ti02 and platinised InP, and Br-/Br03- and I-/IO3- have been found to be appropriate redox mediators. Poly[60]fullerenes have been obtained by covalently linking[60]fullerene molecules photochemically, and following Birch reduction these materials may be important as potential hydrogen storage systems:6 UV radiation obtained by irradiation of a scintillator with y- or X-
Photochemical Aspects of Solar Energy Conversion
393
radiation derived from waste nuclear fuels has been used to excite photocatalysts or photocatalytic electrodes and to achieve decomposition of water to give molecular hydr0gen.4~ 4
Photoelectrochemical Cells
A new type of photovoltaic cell has been described based upon the dye sensitization of thin films of TiOz nanoparticles which are in contact with a non-aqueous liquid ele~trolyte.~' The colour can be tuned through the visible spectrum and an efficiency of 11% has been recorded. In another new solar cell, a UV filtering photocatalyst layer, preferably anatase, is located on the light incident side of the cel!9 Rare earth complexes which absorb short wavelength incident radiation and emit at longer wavelengths have been examined with a view to coating silicon solar cells in order to improve their effi~iency.~'In particular, a CaF2:Eu single crystal is used in place of an anti-reflection film and electric power of high efficiency has been achieved. Mathematical modelling has been used to examine the formation and annihilation of metastable defects in amorphous semiconductors and consideration given to the effect of active hydrogen on defect annihilation in ~ilicon.~' A new model of the photocarrier generation rate of regularly textured silicon solar cells with microgrooves and pyramids on the front surface for application to numerical simulation has appeared.52 The performance of silicon solar cells has been monitored at high injection levels.53 These studies show that illumination during electron irradiation reduces the rate of radiation-induced output power degradation. Enhancement of a-Si:H solar cell characteristics by hydrogen treatment at the p/i interface using the mercury-sensitized photochemical vapour deposition method has been described,% and post hydrogen treatment effects of boron-doped hydrogenated aSiC:H film employed as a p-layer of a-Si:H solar cells using a mercury-sensitized photochemical vapour deposition method have been rep~rted.'~ The performance of the cell with a hydrogen treated p-layer was improved by -7%. Conversion efficiencies of silicon photovoltaic cells are enhanced by surface coating the organically modified silicate composite phosphor films incorporating Eu(1II) phenanthroline and Tb(II1) bipyridine c ~ m p l e x e s ,and ~ ~ the correspondence between photoluminescence measurement, monochromatic-light-beam-induced current measurement, and defect delineation in polycrystalline cast-Si solar cells has been inve~tigated.~' A study has appeared of the characteristics of a sandwich structure (All polymer/Se/Sn02 + In203) based on poly(hydroxyaminoester) which has been photochemically oxidised by CBr, incorporated within the polymer film." The photoconversion efficiency in the visible region is claimed to be up to four times greater than in an analogous system possessing a polymer cell containing no oxidation products. A photoluminescence analysis of In~.sGao.~P solar cells grown on GaAs and Si substrates has been carried out and a comparison made with the properties of Ino.5Gao,5Psolar cells." Increased efficiency has been achieved by improving minority-carrier lifetime. The first InP solar cells, InP/
394
Photochemistry
Ino.53Gao.47Astandem solar cells, and InP tunnel junctions to be grown using a solid phosphorus source cracker cell in a molecular beam epitaxy system have been reported.60 A study of CuInSe2 solar cells for various CdIn ratios has shown that the photoluminescence response is highly dependent upon their composition,6' and an examination of CuInS2 absorber layers for thin-film solar cells reveals that a simple defect model has been deduced in which sulfur vacancies are filled by oxygen.62A CIS/CdS solar cell incorporating a CuInSe2 thin film having a chalcopyrite structure has been prepared by depositing Cu, In, and Se on a Mo electrode and then subsequently depositing CdS,63 and the photoluminescence of CuInS2 thin films and solar cells modified by post-deposition treatments for different temperatures has been described.@A photoluminescence study of polycrystalline thin-film CdTe/CdS solar cells has appeared.65 The chemical bath deposition of CdS buffer layers for CIGS solar cells has been studied and this has led to a high efficiency solar cell using a CdS layer with stoichiometric composition being successfully fabricated.66 A report of the next generation of CuIn~-,Ga,(S,Se~-,)~(CIGS) based solar cells includes a description of wide gap devices, characterisation of the diffusivity of Ga in CIGS, and the modelling of conduction properties of ideal CIGS.67The testing of GaAs solar cells using the absolute room temperature photoluminescence quantum efficiency which may be important for the development of high performance solar cells has been reported,68 and the radiation-induced defects caused by irradiating space silicon solar cells in the high fluence region (1 MeV electrons, fluence > 1 x 10l6e cm-2and 10 MeV protons, fluence > 1 x lOI3 p cm-2)have been compared with some recently announced observations on those caused by irradiation in the low fluence region.69 A study has been made of the radiation-induced degradation and thermal recovery of silicon photocell performance:' selective doping and excitonic layers have been described as strategies for improving molecular donor-acceptor photoc e l l ~ , ~and ' a novel method has appeared for the patternwise metalization of . ~ ~ Ni and amorphous silicon solar cells, based on photocathodic d e p o ~ i t i o nBoth Au have been deposited using this method and in the case of Ni the cell exhibits good photovoltaic characteristics. The polarisation photosensitivity of silicon solar cells with indium tin oxide anti-reflection coatings has been discussed and the results indicate that such cells could be used as selective polarimetric photos ens or^.^^ A photochargeable secondary hydrogedair battery has been fabricated in which the charging process involves illuminating the photoelectrode with light to generate H to be absorbed by an alloy.74 A new photoelectrode system for the photoelectrolysis of water and employing In203-admixed with nanostructured Ti02 has been described.75 5
Biological Systems
Biologically produced photohydrogen has been obtained using the unicellular green alga S c e n e d e s m ~ s .The ~ ~ responsible enzyme hydrogenase must first be activated by anaerobic adaptation, and the process which involves coupling of
Photochemical Aspects of Solar Energy Conversion
395
the hydrogen production system to the photosynthetic electron transport chain is described. A photobattery using 2-hydroxynaphtho- 1,bquinone as electron carrier has been constructed based upon the photosynthetic microorganism Synechoccus S P . , and ~ ~ a design for a loop reactor for hydrogen production incorporating Rhodobacter cupsulatus and in which the cells are embedded in extracellular polymers has appeared; it is concluded that continuous processing with resting cells is possible with biofilms of purple bacteria.78 Photosensitized continuous evolution of hydrogen has been achieved over a 12 week period by Halobacterium halobium MMT22 coupled to Escherichia coli in a specially designed ~ h e m o s t a t and , ~ ~ in the presence of C 0 2 as carbon source, mutants of Chlamydomonas containing Photosystem I1 but lacking Photosystem I have been shown to be capable of growing photoautotrophically with hydrogen and oxygen evolution." References 1. 2. 3. 4. 5. 6. 7. 8.
9. 10.
11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25.
V. N. Parmon, Catal. Today, 1997,39. N. D. Gudkov, Zh. Tekh. Fiz., 1997,67, 54. E. Amouyal, WiIey Ser. Photosci. Photoeng., 1997,2,263. J . W. Lee and E. Greenbaum, ACS Symp. Ser., 1997,666,209. K. Domen, Taiyo Enerugi, 1997,23,19. J . R. Benemann, Int. J. Hydrogen Energy, 1997,22,979. S. V. Tambwekar and M. Subrahmanyam, Int. J. Hydrogen Energy, 1997,22,959. 1. Murakami, Y. Neyde, A. K. Nakano, and C. G. Garcia, An. Assoc. Bras. Quim., 1998,47,46. N. Sutin, C. Creutz, and E. Fujita, Comments Inorg. Chem., 1997,19,67. A. Sobczynski and A. Sobczynski, Pol. J. Appl. Chem., 1997,40,339. T. Kawamoto, Kagaku (Kyoto), 1998,53,63. Y. Li and F. Chen, Huagong Shikan, 1997,11, 19. J . Mattay, R. Hoffmann, K. Langer, M. Oelgemoller, and C. Schiel, Sol. Chem. Sol. Materialforsch., 1997,234. J . Lede and F. Pharabod, Entropie, 1997,33,47. C. Konigstein and R. Bauer, Int. J. Hydrogen Energy, 1997,22,471. Y . Amao, T. Kamachi, and I. Okura, J. Mol. Catal. A: Chem., 1997,120, L5. E. Lyris, D. Argyropoulos, C.-A. Mitsopoulou, D. Katakis, and E. Vrachnou, J. Photochem. Photobiol., A, 1997,108,51. H. Heaton, Proc. U.S. DOE Hydrogen Program Rev., 1996,1,449. R. Boese, J. K. Cammack, A. J. Matzger, K. Hug, W. B. Tolman, C. K. P. C. Vollhardt, and T. W. Weidman, J. Am. Chem. Soc., 1997,119,6757. T. Hiraishi, E. Kimura, T. Kamachi, and I. Okura, Chem. Lett., 1997,531. F. Franceschi, M. Guardigli, E. Solari, C. Floriani, A. Chiesi-Villa, and C. Rizzoli, Inorg. Chem., 1997,36,4099. M. Suzuki and H. Shirai, Kobunshi Kako, 1997,46,488. G. W . Sluggett, N. J. Turro, and H. D. Roth, J. Phys. Chem. A, 1997,101,8834. Z . Tong, L. Zhang, Z. Yuan, Y. Li, and H. Cao, Gunguang Kexue Yu Guang Huaxue, 1997,15,1. V. A. Chernoivanov, A. D. Dubonosov, V. A. Bren, V. I. Minkin, A. N. Suslov, and G. S. Borodkin, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A , 1997,297,239.
396
Photochemistry
26. 27.
L. M. Dupray, Diss. Abstr. Int., B, 1997,57,7520. B. Pohlman, H.-D. Scharf, U. Jarolimek, and P. Mauermann, Sol. Energy, 1997,61, 159. K. Sayama and H. Arakawa, J. Chem. Soc., Faraday Trans., 1997,93, 1647. H. Arakawa, Reza Kenkyu, 1997,25,425. K. Sayama, R. Yoshida, H. Kusama, K. Okabe, Y. Abe, and H. Arakawa, Chem. Phys. Lett., 1997,277,387. M. K. Arora, A. S. K. Sinha, and S. N. Upadhyay, Ind. Eng. Chem. Res., 1998,37, 1310. A. I. Kryukov, N. P. Smirnova, A. V. Korzhak, A. M. Eremenko, and S. Ya. Kuchmii, Theor. Exp. Chem., 1997,33,30. M. Lanz and G. Calzaferri, J. Photochem. Photobiol., A , 1997,109,87. F. Saladin, I. Kamber, K. Pfanner, and G. Calzaferri, J. Photochem. Photobiol., A, 1997,109,47. A. Kudo and H. Kato, Chem Lett., 1997,421. A. Kudo and H. Kato, Chem. Lett., 1997,867. D. C . Park and S. Y. Lim, PCT Int. Appl. WO 97 12,668. K.-H. Chung and D.-C. Park, J. Mol. Catal. A , 1998,129,53. H. Hosono and M. Kaneko, J. Chem. Soc., Faraday Trans., 1997,93, 13 13. M. Kaneko and H. Hosono, Jpn. Kokai Tokkyo Koho JP 09,234,374 [97,234,374]. H. Hosono, Jpn. Kokai Tokkyo Koho JP 09,173,840 [97,173,840]. M. Swarnkar, M. Gupta, and S. K. Nema, Int. J, Hydrogen Energy, 1997,22,989. N. Toshima and K. Hirakawa, Appl. Sur$ Sci., 1997,121,534. M. Sykora and J. R. Kincaid, Nature (London), 1997,387, 162. C. A. Linkous, Proc. U.S. DOE Hydrogen Program Rev., 1996, 1,389. G. E. Lawson, B. Ma, H. R. Rollins, A. M. Hajduk, and Y.-P. Sun, Res. Chem. Intermed., 1997,23, 549. Y. Iwamura, T. Ito, N. Goto, I. Toyoda, and H. Tonegawa, Jpn. Kokai Tokkyo Koho JP 09,142,804 [97,142,8O4]. A. J. Frank, B. A. Gregg, M. Gratzel, A. J. Nozik, A. Zaban, S. Ferrere, G. Schlichthorl, and S. Y. Huang, AIP Con$ Proc., 1997,404, 145. Y. Oka, Jpn. Kokai Tokkyo Koho JP 09,321,329 [97,321,329]. K. Kawano, N. Hashimoto, and R. Nakata, Mater. Sci. Forum, 1997,239,311. S . Zh. Karzhanov and A. Yu. Leiderman, Geliotekhnika, 1996, 1 1. H. Iwata and T. Ohzone, Jpn. J. Appl. Phys., Purt 2,1997,36, L 131 1. M. Ya. Bakirov, Inorg. Mater. (Transl. of Neorg. Mater.), 1997,33,997. H. Jang and K.4. Lim, Conf. Rec.IEEE Photovoltaic Spec. Conf., 25th, 1996, 1089. J. H. Jang and K. S. Lim, Jpn. J. Appl. Phys., Part I , 1997,36,6230. T. Jin, S. Inoue, K.-I. Machida, and G.-Y. Adachi, J. Electrochem. Soc., 1997, 144, 4054. R. Shimokawa, M. Tajima, M. Warashina, Y. Kashiwagi, and H. Kawanami, Sol. Energy Mater. Sol. Cells., 1997,48, 85. A. R. Tameev, E. B. Khailova, and A. V. Vannikov, Vysokomol. Soedin., Ser. A Ser. B, 1997,39, 127. M.-J. Yang, M. Yamaguchi, T. Takamoto, E. Ikeda, H. Kurita, and M. Ohmori, Sol. Energy Mater. Sol. Cells, 1997,45,331. A. Delaney, K. Chin, S. Street, F. Newman, L. Aguilar, A. Ignatiev, C. Monier, M. Velela, and A. Freundlich, AIP Con$ Proc., 1998,420,698. S . Zott, K. Leo, M.Ruckh, and H.-W. Schock, Con$ Rec. IEEE Photovoltaic Spec. Conf., 1996,25th, 817.
28. 29. 30. 31. 32. 33. 34.
35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48.
49. 50. 51. 52. 53. 54. 55. 56. 57. 58.
59.
60. 61.
PhotochemicalAspects of Solar Energy Conversion 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80.
397
K. Toepper, J. Krauser, J. Bruns, R. Scheer, A. Weidinger, D. Braeunig, Sol. Energy Mater. Sol. Cells, 1997,49, 383. C. Li, J. Zhu, H. Fei, J. Sun, and Z. Zhou, Taiyangneng Xuebao, 1996,17,297. K. Topper, J. Bruns, R. Sheer, M. Weber, A. Weidinger, and D. Braunig, Appl. Phys. Lett., 1997,71,482. D. P. Halliday, J. M. Eggleston, and K. Durose, J. Cryst. Growth, 1998,186,543. Y. Hashimoto, N. Kohara, T. Negami, N. Nishitani, and T. Wada, Sol. Energy Mater, Sol. Cells, 1998,50, 71. A. Rockett, R. Birkmire, D. Morel, S. Fonash, J.-Y. Hou, M. Marudachalam, J. DAmico, P. Panse, S. Zafar, and D. J. Schroeder, AIP Conf. Proc., 1997,404,403. X. Y. Lee, C. Q. Wu, A. K. Verma, R. Ranganathan, and E. Yablonovitch, ConJ Rec. IEEE Photovoltaic Spec. Conf., 1996,25th, 141. T. Hisamatsu, 0.Kawasaki, S. Matsuda, and K. Tsukamoto, JAERZ-Conf. 1997,97, 237. M. Ya. Bakirov, Znorg. Mater., 1997,33,649. A. A. Zakhidov and K.Yoshino, Synth. Met., 1997,85, 1299. E. S. Kooij, M. Hamoumi, J. J. Kelly, and R. E. 1. Schropp, J. Electrochem. SOC., 1997,144, L271. V. M. Botnaryuk, A. V. Kocal, V. Yu.Rud, Yu. V. Rud, A. V. Simashkevich, and D. A. Sherban, Fiz. Tekh. Poluprovoah. (St.-Peterburg), 1997,31,800. K. Akudo and J. Yamaki, Jpn. Kokai Tokkyo Koho JP 09,259,942 [97,259,9421. R. K. Karn and N. Srivastava, Znr. J. Hydrogen Energy, 1998,23,439. R. Wunschiers, J. Appel, K. Stangier, S. Phunpruch, and R. Schultz, Biomass Energy Environ., Proc. Eur. Bioenergy Conf., 9th, 1996,3, 1668. T. Yagishita, Nenryo oyobi Nensho, 1998,65, 1 1 . S. Tramm-Werner, M. Weng, W. Hartmeier, and M. Modigell, Biomass Energy Environ., Proc. Eur. Bioenergy Con$, 9th, 1996,3, 1674. M. M. Taqui Khan and J. P. Bhatt, Znt. J. Hydrogen Energy, 1997,22,995. E. Greenbaum, J. W. Lee, and C.V. Tevault, Proc. US.DOE Hydrogen Program Rev., 1996, 1,303.
Author Index
In this index the number in parenthesis is the Part a d , when appropriate, the Chapter number of the citation and this is followed by the reference number or numbers of the relevant citations, e.g., (2.2) 137 represents Part II, Chapter 2, Refirence 13 7. Aakennark, B. (1) 60,63,64,66 Aaron, J.-J. (2.3) 97; (2.5) 288;
(3) 549 Aartsma, T.J. (1) 59 Abadie, J.M. (3) 5 Abbot, S.C. (2.7) 147 Abdedaal, H.(2.1) 40 Abd El-Ghafh, M.A. (3) 759 Abdelrazzaq, F.B.(3) 102, 135 Abe, H. (1) 655; (2.3) 70; (2.4) 60 Abe, K. (1) 28; (2.5) 109; (3) 604 Abe, Y. (2.4) 93; (2.6) 57; (4) 30 Abellon, R.D. (3) 92 Abraha, P.A. (3) 146 Abraham, E. (1) 162 Abraham, W. (2.3) 119; (2.7) 195 Abramovich, 2.(2.2) 33 Abruna, H.D. (3) 523 Achun, C. (1) 75 Adachi, G.Y. (3) 622; (4) 56 Adachi, N. (3) 149 Adachi, T. (2.3) 67 Adam, W. (1) 441; (2.3) 116; (2.5) 118, 119,205,210,217; (2.6) 189, 190,305,310; (2.7) 173 Adamcik, V. (2.7) 10 Adamiak, R.W. (2.6) 251 Adams, J. (3) 527 Adeline, M.-T. (2.2) 78,79; (2.6) 135 Adhami, I.M.(2.6) 240 Adibenjad, M. (3) 491,501,591 Admasu, A. (1) 238; (2.7) 20 Adronov, A. (3) 584 Aebi, M.(2.4) 263
Agabekov, V.E.(2.4) 8 1 Agarwal, U.P.(3) 716,717 Aganval, Y .K.(1) 228 Ageeva, V.V.(3) 226 Agha, K.A. (1) 679 Agi, Y. (1) 600; (3) 489 Agnelli, J.A.M. (3) 790 Agostino, G. (1) 432 Aguiar, G. (2.2) 99; (2.4) 171; (2.6) 35 1
Aguilar, L. (4) 60 Agyin, J.K. (2.2) 64 Ahcarn, M.F. (2.7) 120 Ahlblad, G. (3) 626 Ahluwalia, A. (3) 304 Ahmadi, T.S.(2.3) 112 Ahn,J.S. (1) 387 Ahn, K.-H. (2.4) 85 Aich. S. (1) 158,654,656,658;
(2.2) 103; (2.5) 252,278; (3) 605 Aida, T. (2.5) 14; (3) 521 Ai-Tel, T.H. (2.2) 71; (2.4) 166 Ajit, K. (1) 494; (2.5) 150 Akaba, R. (2.6) 3 17 Akagi,K. (3) 332,5 17 Akayama, K. (1) 134 Akazawa, M.(2.6) 337,338; (2.7) 163 Akhmedova, R.A. (3) 762 Akimoto, I. (1) 389 Akimoto, K. (2.7) 23; (3) 333 Akimoto, S.(1) 202,443; (2.4) 188 Akinaga, Y. (2.7) 115 Akira, F. (1) 645 398
Akiyama, K. (2.1) 1; (2.5) 45 Akudo, K.(4) 74 Akylbaev, Zh.S. (3) 567 Alam, M.M. (1) 250,408,409;
(2.5) 98, 134, 135; (2.6) 318; (2.7) 170 AI-Amro, F.S.(1) 491 Alava-Moreno, F. (1) 576 Albers, R (2.4) 260; (2.7) 25 Albert, A. (2.3) 72; (2.5) 169; (2.6) 155 Alberti, A. (2.4) 83 Albini, A. (1) 463; (2.2) 48,98; (2.4) 255; (2.5) 184; (2.6) 142, 196,230,322-324; (2.7) 41,166 Albinsson, B. (1) 150 Albrecht, E. (2.6) 141 Aldoshin, S.M.(2.4) 91; (2.6) 48, 61 Alekseeva, E.I. (3) 54 Alekseyev, P.V.(2.7) 53 Alexandra, V.(2.1) 12 Alfimov, M.V.(1) 353; (2.4) 70, 72; (2.6) 100; (3) 3 14, 3 16, 486,619 Al-Hassan, L.A. (1) 491 Ali, H.A. (3) 243 Alicja, M. (1) 309 Alivisatos, A.P. (3) 413 Aliyan, H. (2.6) 107 Allcock, P.(1) 636 Allen, A.D. (2.2) 93 Allen, N.S.(3) 27,28,49,94, 649,666,783,784,804 Allender, D.W.(3) 508
399
Author Index Almgren, M. (1) 63,64,66 Al-Moh'd, H.S.M. (3) 733 Aloisi, G.G. (1) 367,368; (2.3) 11; (2.6) 286 Als-Nielsen, J. (2.2) 5 Altomare, A. (3) 50,309 Altundas, R (2.3) 44; (2.4) 53; (2.5) 259 Alvarado, S.F.(3) 407 Alxneit, I. (2.5) 166 Amada, I. (1) 440; (2.2) 101; (2.5) 53 Arnadelli, R (2.5) 189 Amador, U. (2.3) 5 1; (2.6) 154 Amao, Y. (2.5) 107, 108; (4) 16 Amaroli, N.(1) 485 Ambrose, W.P. (1) 173,701 Ameloot, M.(1) 562 Amesz, J. (1) 59 Ameta, R (2.5) 160 Ameta, S.C. (2.5) 160 h e y , D.M. (2.4) 155 Amijima, Y. (2.4) 161 Ammermann, D. (3) 617 Amouyal, E. (4) 3 Anazawa, T. (3) 267 Andersen, H.(2.6) 242 Andersen, K.B. (1) 280 Anderson, D. (3) 106 Anderson, H.L.(1) 676; (3) 68 Anderson, J.R (2.2) 131 Anderson, N.A. (1) 332,340; (2.3) 58 Anderson, M.(1) 64,66; (3) 389, 397 Ando, W. (2.6) 330; (2.7) 165 Ando, Y. (1) 563 Andraos, J. (2.4) 253; (2.6) 3 11; (2.7) 30 Andreis, C.(2.4) 224 Andresen, S.(2.2) 23,57; (2.6) 133 Andrw, D.L. (1) 636 Andrews, S.M. (3) 776 Andrzej, L. (1) 137, 139 Andrzejewska, E. (1) 437; (2.5) 36; (3) 157 Ang, K.H.(2.6) 182 Angeluts, A.A. (1) 703 Angiolini, L. (3) 4,32, 119 Anguille, S. (2.6) 68 Anilkumar, G.(2.3) 37,48; (2.4) 54; (2.6) 153 Annaji Rao, K. (2.7) 153 Anpo, M.(2.1) 13; (2.5) 32, 165 Anseth, K.S.(3) 160,228 Antoniadis, H.(3) 429 Antonietti, M.(3) 741
Anush'yan, S.R (3) 54 Aoki, H. (3) 496,576 Aono, T. (2.6) 53 Aoshima, S.(3) 292 Aota, H.(2.5) 111 Aoudia, M.(1) 207,304 Aoyagi, T. (1) 192; (2.4) 33 Aoyama, H. (2.2) 88; (2.4) 47; (2.5) 96; (2.6) 124,270 Aoyama, T. (2.5) 274 Apanasovich, V. (1) 69 1 Apeloig, Y.(2.3) 69; (2.6) 326; (2.7) 157 Appel, J. (4) 76 Aquino, A.J.A. (1) 82 Arai, H.(3) 248 h i , K. (3) 299 Arai, M.(3) 363 h i , S. (2.6) 78
Ami,T.(1)211,277,319,370;
(2.3) 12; (2.4) 26; (2.5) 44; (2.6) 15,26 Araiso, T. (1) 599 Arakawa, H.(4) 28-30 Arakawa, R (2.5) 123 Araki, S.4. (2.5) 111 Arce, R. (2.3) 105 Arcenaux, J.A. (3) 162 Arden-Jacob, J. (1) 714 Argtiello, J.E.(2.6) 3 10 Argyropoulos, D.S. (3) 720; (4) 17 Arif, A.M. (2.4) 164; (2.6) 345 Arikawa, Y.(1) 563 Arimura, T. (2.5) 12 Armaroli, N.(1) 41; (2.5) 289 Armas, M. (1) 637 Armentrout, R.S.(3) 477 Armesto. D. (2.3) 49,51, 72,73; (2.4) 56; (2.5) 169; (2.6) 154, 155 Armstrong, W.H. (1) 65 Arnaut,L.G. (1) 16,58 Arnold, D.R (2.3) 27-30; (2.4) 177-179; (2.6) 168-170 Arnold, M.A. (1) 580 Arnold, S.(1) 632 Arora, M.K.(4) 3 1 Arpigny, C. (2.7) 120 Arsen'ev, A.S. (2.6) 100 Artamonova, E. (3) 714 Asahi, T. (2.3) 113; (2.6) 128 Asai, S. (3) 632 Asakawa, T. (1) 710; (3) 583 Asfari, Z. (1) 567; (2.4) 35,38; (2.6) 33 Ashby, K.D. (1) 276; (2.5) 64 Ashida, M. (1) 389
Ashram, M. (2.4) 273; (2.6) 277 Askolin, C.-P. (2.6) 250
Asmus, K.-D. (1) 397,414; (2.5) 151 Asplund, M.C.(2.7) 90 Asta, S.(2.4) 1%; (2.6) 167 Astapovich, I.V. (2.4) 81 Ataka, T. (1) 63 1; (3) 340 Atasoy, B. (2.5) 212 Atvars, T.D.Z. (3) 559.586 Aubard, J. (2.4) 106 Aucken, C.J. (2.6) 40 Aumiller, W.D. (1) 565, 566 Auricchio, S.(2.4) 173; (2.6) 187 Aussenegg, F.R (1) 6 10 Austin, M. (2.4) 139 Avanessian, L. (1) 634 Aveline, B.M. (1) 256; (2.2) 109; (2.5) 86; (2.6) 94 Avent, A. (2.4) 44; (2.6) 298 Avlasevich, Yu.S. (1) 508; (2.5) 60 Amy, Y.(3) 408,422,43 1 Axten, J. (2.6) 115 Aycard, J.-P. (2.1) 58; (2.2) 56; (2.7) 63 Ayyad, S.N.(2.5) 267 Azarko, V.A. (2.4) 81 Azarwal, N. (2.4) 92; (2.6) 58 Azoz, N.E.(1) 574 Azuma. J. (1) 389 Azumi, T. (1) 677; (2.5) 48; (2.7) 193 Baars, M.W.P.L. (3) 525 Baba, Y. (2.5) 216; (3) 791 Babetto, A.S. (3) 790 Babu. G.N.(3) 57,208 Bacak, V. (3) 104 Bach, R.D.(3) 771 Bach, T. (2.1) 30-32 Bachilo, E.V.(1) 363 Bachilo, S.M.(1) 310,363,508; (2.5) 60 Bachrach, M.(1) 525 Baciocchi, E.(2.5) 299,300 Backs, S.(3) 624 Badaoui, F. (1) 559 Bae, E.Y. (1) 364; (2.3) 10; (2.4) 27; (2.6) 16 Baek, E.K. (2.3) 21; (2.4) 129, 130 Baerends, E.J.(2.7) 80 Baertschi, S.W. (2.6) 244 Baessler, H.(3) 421,468 Bagryansky, V.A. (1) 25 Bahners, T. (3) 697-699
400 Bai, F. (3) 352 Bai, J . 4 . (2.4) 102 Bai, J.-W. (1) 542; (2.5) 221 Bai, Y.(1) 639 Baietoul, M.(3) 399 Bakac, A. (2.5) 218 Baker, J.A. (2.5) 213 Baker, W.E. (3) 150 Bakirov, M.Ya. (4) 53,70 Bakker, B.H. (2.4) 42 Balashova, T.A. (2.6) 100 Balasubramaniam, E. (1) 216 Balci, M.(2.3) 44; (2.4) 53; (2.5) 207,208,259 Baldazzi, S. (2.6) 320 Baldini, G. (1) 617 Baldovi, M.V. (2.6) 3 11 Balduzzi, S.(2.7) 167 Bako, B.A. (2.3) 39; (2.7) 134 Ballardini, R. (1) 258; (2.4) 126 Bally, T. (2.3) 63 Balter, A. (1) 612 Balzani, V. (1) 48,485,570; (2.4) 126; (2.5) 289 Banares, L. (2.7) 77 Banerjee, A. (1) 26; (2.1) 70,71; (2.4) 274,275 Banerji, A. (2.2) 51; (2.4) 157 Bangal, P.R. (1) 167 Banin, U. (1) 20 Baptista, M.S. (I) 298 Bar, I. (2.7) 133 Baraldi, 1. (2.6) 73 Baran, P.S.(1) 427; (2.5) 139 Barancok, D. (3) 222 Barashki, O.H.J.(3) 448 Barashkov, N.N. (3) 344,416,424 Barbas, J.T. (2.3) 105 Barbashev, E.A. (3) 735 Barclay, G.G. (2.6) 3 11 Bardeq E.(1) 283,559; (2.4) 65 Baret, V. (2.6) 278 Bar-Haim, A. (1) 49 Barigelletti, F.(1) 485; (2.5) 289 Barisas, B.G. (1) 675 Barker, B. (2.3) 118; (2.4) 175; (2.7) 197 Barkhash, V.A. (2.3) 100 Barnes, M.D. (1) 178,179 Barnes, T.H. (1) 532 Ban;s M. (1) 679 Barros, T.C. (3) 584 Barry, N.P. (1) 644 Bartberger, M.D. (3) 602 Bartek, J. (1) 341; (2.3) 2; (2.4) 25; (2.6) 20 Barth, A. (2.7) 177 Barthelat, M. (2.2) 21
Photochemistry Bartko, A. (1) 303 Bartlett, R (2.7) 34 Bartlett,W.(2.1) 69; (2.4) 276 Bartolini, P. (1) 88, 141 Barton,D.H.R.(2.1) 51,52 Barton, T.J. (3) 433. Baruah, S.D. (3) 101 Bamk, T.(1) 295 Barzykin, A.V. (1) 95 Basche, T.(1) 174 Baselga, J. (3) 586 Bashkin, 1.0.(3) 354 Bashtanov, M.E. (1) 203,3 15,470 Baskin, 1.1. (2.6) 100 Bass, D.A. (3) 529 Basu, P. (1) 5 14; (2.5) 295 Basu, S.(1) 158, 654,656, 658; (2.2) 103; (2.5) 252,278; (3) 605 Batchelor, S.N.(1) 667 Bat- B. (2.1) 9 Bats, J.W. (2.2) 83 Batsanov, A.S. (2.6) 266 Bastalov, E.M. (3) 234 Battersby, A.R. (2.6) 40 Bauer, R (4) 15 Baumann, C.A. (2.7) 108 Baumann, W. (1) 301 Baumert, T. (2.7) 77 Baumhardt-Neto, R. (3) 65 1 Bavetta, F.S. (2.4) 181; (2.6) 227 Bayri, N.A.(1) 458 Bays, J.T. (2.7) 89, 102 Bazan,G.C. (1) 360; (3) 4 19 Bazhin, N.M. (1) 3 16; (3) 342 Bazin, M.(1) 121 Beaumont, P.C. (1) 219,220 Bebelaar, D. (1) 236 Beck, B. (1) 160 Beck, C. (2.7) 66 Beck, W.F. (1) 685 Becker, H. (3) 409 Becker, R.S. (1) 267 Becker, S.(1) 222 Beckert, D. (2.5) 37,54 Beckert, R (2.6) 280 Bedrik, A.I. (1) 235 Beeby, A. (1) 396; (2.5) 130 Beer, P.D. (1) 570 Beggs, M. (1) 204 Behnisch, J. (3) 696 Beinert, G.(3) 544 Bekker, C.H.W. (3) 554 Belaitis, 1.L.(3) 350 Belevskii, V.N. (2.1) 3 Belfield, K.D. (3) 98,102,135, 189 Belik, P.(2.2) 83
Beljonne, D. (3) 381 Bell, T.D.M. (1) 428; (2.5) 138 Bellavia-Lund, C.(3) 598 Belletele, M.(1) 193 Bellmann, E.(3) 427 Belopushkin, S.I.(2.1) 3 Belov, G.P. (3) 652 Belyakov, V.A. (3) 629 Bendas, G. (1) 6 14 Bender, J.A. (2.2) 86 Bendig, J. (1) 106, (2.4) 258; (2.5) 183; (2.7) 46 Benemann, J.R (4) 6 Benjamin, I. (3) 43 1 Benjelloun, A. (3) 491,501,591 Benniston, A.C. (1) 38,545; (2.4) 80; (2.5) 20; (2.6) 18 Benoit-Marquie, F.(2.1) 45 Bensasson,R.V. (1) 381,412 Bentjerodt, B. (3) 634 Bentrude, W.G. (2.3) 35,36; (2.4) 164; (2.6) 343-345 Bera, S.C. (1) 350; (2.6) 29 Berberan-Santos, M.N.(1) 9,103; (3) 609 Berezney, R. (1) 638; (3) 366 Bereznitskii, G.K. (3) 226 Berezovskii, M.V. (2.7) 52 Berg, K. (1) 64 Berg, U. (2.6) 204; (2.7) 113 Berger, D. (3) 369 Berggren, M.(3) 389 Berglund, H. (1) 60,64,66 Berglund-Baudin, H. (1) 63 Bergmark, W.(1) 496; (2.3) 50; (2.5) 49,226 Bergt, M. (2.7) 77 Berkovic, G.(3) 298 Bernardi, F. (1) 71,33 1; (2.3) 64, 80; (2.4) 30.94; (2.6) 23-25, 191; (2.7) 4 Bernier, P. (2.5) 193 Bems, M.W. (1) 633 Bemsten, A.J.M. (3) 740 Beroza, P.(1) 82 Benie, C.L. (2.7) 152 Bcrtani, R. (3) 778 Berthod, T. (2.5) 281 Bertolotti, S.G. (1) 492; (2.5) 5 1 Bemrello, H. (3) 663 BeS.(2.2) 19 Bethke, J. (2.2) 12; (2.4) 233; (2.6) 283,285 Bettinetti, G. (2.4) 255; (2.6) 196; (2.7) 41 Beyer, M. (3) 709,721,723 Bhanthumnavin, W. (2.4) 164; (2.6) 345
Author Index Bharathi, P. (3)524 Bhasikuttan,A.C. (1) 291 Bhatia, S.H.(2.4)44; (2.6)298 Bhatnagar, A. (3) 185 Bhatt, J.C. (3) 218,260 Bhatt, J.P. (4)79 Bhattacharjee, S.(2.5)232 Bhamchya, S.C. (1) 490;(3) 473 Bhattacha~yya,A. (3) 605 Bhattacharyya, D. (3)575 Bhawalkar, J.D. (1) 638;(3)366
188 Blatchford,J.W. (3) 447,449 Blatter, F. (2.5) 186 Blechert, S.(2.3)75, 114;(2.4) 169;(2.6)321 Blesinger, H.(2.6)71 Blokhin, A.A. (2.7) 169 Blokhin, A.P. (2.7) 169 Blume, F. (2.6) 171 Blumenfield, L.A. (3)303 Blumstengel, S.(3)44 1 Blunt, V.M. (2.7)120 Bi, D. (3) 305 Bobrowski, K.(2.5)39 Bi, X.T. (3) 260 Bochu, C. (2.4)92;(2.6)58 Bianchi, M.E. (1) 617 Bocian, D.F. (1) 464-466 B i w k , L.(1) 247,405 Bockman, T.M. (2.4)259;(2.5) 47,236;(2.6)195 Bied-Charreton, C.(1) 682 Bienkowski, M.(3) 310 Boddeke, F.R. (1) 643 Bienvenu, C.(2.5)280 Bodot, H.(2.2)56 Bienvenue, E.(1) 381,412 Bodunov, E.N.(1) 103 Biernat, J.F. (2.6)35 Boeckstegers, S.(2.4)201 Biju, V. (2.5)283 Boehler, A. (3) 617 Biju, Y.(1) 416 Boens, N.(1) 562,696 Billing, G.D. (2.7)116 Boerje, A. (1) 64,66 Bilmes, S.A. (1) 597 Boese, R (2.4)158; (4)19 Bilyarska, L. (2.5)297 Boese, W. (2.7)73 Binkley, E.R (2.6)313 Bogachev, A.A. (2.1)74 Binkley, R.W. (2.6)313 Bogdanova, R.(2.5)230 Birch, D.J.S. (1) 127,596,639, Bohne, C.(1) 269,662;(3) 584 640,646;(3) 577 Boilot, J.P.(2.2)112;(2.3)17; Birckner, E.(1) 160 (2.4)124 Birkett, P.R (1) 417 Boitchert, W.M. (I) 708 Birkmire, R.(4)67 Bojarski, P. (1) 479 Birmingham, J.J. (1) 574 Bokobza, L. (1) 604;(3) 556 Birss, V.I. (3) 590 Bolivar-Martinez, L.E.(3)462 Biry, S. (3) 779 Bolletta, F. (1) 469 Bise, R.T.(2.7)62 Bol'shakov, B.V. (3)342 Bisht, P.B.(1) 273;(3)346 Bol'shakova, S.A. (2.6)319 Biswas, N.(1) 349 Bolte, M. (2.5)233,234 Biteau, J. (2.2)112;(2.3)17;(2.4) Bominaer, E.L. (1) 75 124 Bondarev, S.L.(1) 254 Bitit, N. (2.6)129 Bonesi, S.M. (2.4)246;(2.6)161 Bitterwolf, T.E. (2.7)89,102,103 Bongiovanni, R.(3)215 BjelakoviC, M.(2.6)201 Bonitatebus, P.J., Jr. (1) 65 Blache, Y.(2.6)99 Bonnichon, F.(1) 328;(2.4)59; Black,1. (1) 596;(3)577 (2.5)234;(2.6)156 Blackstock, S.C. (2.5)247;(2.6) Boo,J. (3) 263 177 Boody, F.P.(1) 375 Blackwell, B.A. (2.6) 163;(2.7) Booker-Milburn, K.I. (2.2)105; 175 (2.6) 112 Blair, J.T. (1) 322 Bow, M.A. (1) 177;(3)566 Blair, S.L.(2.7)99 Bor, Z.(3)701 Blakemore, D.C. (2.4) 155;(2.6) Borah, R.(2.6)303 325 Borchers, A.M. (3) 235 Blanchard, G.J.(1) 226 Boressevitch, Yu.E. (3)286 Blanco, C.C. (1) 189 Bormann, D. (2.5)193 Blanco-Pina, M.(3)28 Borodkin, G.S. (2.4)40,86;(2.6) 74;(4)25 Blank, D.A. (2.2)54;(2.7)136,
40 1 Borovkov, V.I. (1) 25 Borowicz,P.(1) 293 Borsarelli, C.D.(1) 442 Borshch, S.A. (1) 75 Bortolus, P.(1) 446 Bomtta, V. (3)778 Bosch, E.(1) 459;(2.2)120,121; (2.4) 174;(2.5)93 Bosch, P. (3) 83, 165 k c h i , T.(I) 469 Bossman, A. (3)697,699 Botnaryuk, V.M. (4)73 Botoshansky, M.(2.4)67 Botros,S.H.(3)759 Botsi, A. (2.4)145 Bottle, S.E.(2.6)228 Bottomlcy, L.A. (2.2) 131 Boturyn, D.(1) 620 Botzem, J. (2.3)75;(2.4)169 Bouas-Laurent, H.(2.3)3; (2.6) 130;(3)293 Boudali, A. (1) 620 Boukherroub, R. (2.6)328;(2.7) 155 Boule, P. (2.6)241 Bourdelande, J.L. (1) 200,395; (2.5)176 Boumnet, P.(1) 649 Bouwman, W. (2.2)5 BouzBouz, s.(2.I) 45 Bowdery, D. (1) 61 1 Bowen, C.M. (1) 560 Bowers, J.S. (3) 65, 115 Bowman, C.N.(3) 78,82, 160, 163,253-256 Boxhammer, J. (3) 634 Boyd, M.K. (2.3) 1 IS Boylc, P.D. (2.2)70;(2.4) 147; (2.6)117 Brabec, C.J.(3)561 Brackenhoff, G.J. (1) 642 Bradaric, C.J. (2.7) 156 Bradford, C.L. (2.2)37;(2.4)3 Bradley, D.D.C. (3) 381 Bnrwning, D. (4)62,64 Branch, T.M. (1) 648 Brand,L.(I) 169, 170, 181 Brand, S.(2.3)90 Brandl, T. (2.1)30 Bmxbetter, C. (3) 380 Brash, J.L.(3)493 Braslau,R. (3)80 Braslavsky,S.E.(1) 214 Brauer, H.D. (1) 106;(2.5)173, 183 Braun, A.M. (2.1)45 Bmun, D. (1) 147 Braun, M.(2.2) 125;(2.4)143
402 Braussaud, N.(2.2)29; (2.4) 144 Bravo, J. (3) 586 Bravo-Zhivotovskii, D. (2.3)69; (2.6)326;(2.7)157 Brazgun, E.F.(1) 403 Bredas, J.L. (3)288,351,374, 381,560 Brede, 0.(1) 25 1; (2.4)79;(2.5) 37.54 Breite, A.G. (2.5)213 Brembilla, A. (3)491,501,591 Bren, V.A. (2.3)95,96;(2.4)40, 86;(2.6)74;(4)25 Brennan, J.D. (1) 595 Brenner, V.(2.5)27 Breslin, D.T.(2.2) 13 1 Brewer, K.J. (2.5)106 Brezesinski, G.(3)490 Bridges, RJ. (2.7)34 Bridson, J.N.(2.4)273;(2.6)277 Brigham, E.S. (1) 533 Briskman, V. (3)238 Brisson, J.R (2.3)57 Britto, P.J. (1) 71 1 Broadhum P.V. (2.7)86 Brock, P.J. (3) 378 Brockelhurst, B. (1) 335 Brody, F.P.(1) 399 Broer, D.J. (3) 264,269,271,519 Bronstert, B. (2.2)83 Broo, A. (1) 252 Brook, M.A. (2.6)320;(2.7)167 Broring, M. (1) 214 Brouwer, A.M. (1) 236 Brown, A.B. (2.2)17 Brown, D.(2.2)43 Brown, R.G.(2.4)44, 187;(2.6) 298 Browne, E.P.(1) 625 Brownsword, R.A. (2.7)67, 131, 132 Bruckner, U. (2.1)63 Bruening, J. (3) 597 Brumer, P.(1) 10 Brun, P.(2.6)68 Brunner, J. (2.4)263 B m , 1. (4)62,64 Bryce, M.R. (2.5)121;(2.6)265, 266 Bmzowski, Z.K. (3) 1 17 Bubois, C. (3) 670 Bucher, G.(2.7)19 Buckley, D.M. (2.4)44;(2.6)298 Budashov, I.A. (3) 735 Buddrus, J. (2.4)201 Budyka, M.F.(1) 369; (2.4)22, 23;(2.7)42,43 Bufie, J. (1) 705
Photochemistry Buhr, S. (2.6)126 Buisine, J.M. (3) 11 1, 183 Buisson, J.P. (3) 399 Buist, A.H.(1) 642 Bulgarevich, D. (1) 15 1 Bullot, J. (3) 399 Buma, W.J. (1) 236 Bunce, R.A. (2.2)41;(2.4)132 Bunel, C. (3) 124, 161, 190 Bunker, C.E. (1) 112;(3)596 Buntinx, G.(2.4)92;(2.6)58 Bur, A.J. (1) 590 Buranda, T. (1) 23,514;(2.5)295 Burdzy, A. (2.6)25 1 Burger, B. (3)59 Burgess, K.(2.4)269;(2.6)213, 215 Burget, D. (1) 444 Burke, J. (3) 133 Burke, N.A. (1) 53 Burkhart, RD. (3) 482 Burmeister, J.S. (1) 708 Bume, S.E.(3)409 Bumll, L.C. (3)80 BUKOWS, H.D. (2.5)233 Burshtein, A.I. (1) 90,97,110; (2.5)26 Buruma, R (3)52 Buscemi, S.(2.4)196;(2.6)167 Buslco, N.A. (3) 39 Busson, R. (2.4)140, 154 Butenschon, H. (2.1)36;(2.7)71 Butler, D.N. (2.6)13 1 Butts, C.P. (2.4)190-192;(2.6) 204-207,309;(2.7)109, 110, 113,114 Buxton, 1.P.(3) 262 Bykova, E.A. (2.7)45 Byloos, M.(2.3)68;(2.6)327 Byme, H.I. (3) 402,403 Caballero, 0. (2.3)51; (2.4)56; (2.6)154 Cacialli, F.(3) 444 Cadet, J. (2.5)280,281 Caf€ieri, S.(2.6)286 Cai, L.(2.5)245 Callahan, J.H. (1) 152 Callis, P.R. (1) 12 Calza, P.(2.5)245 Calzafem, G.(4)33,34 Cambon, A. (3) 503 Cameron, J.F. (2.4)284 Cameron, T.S.(2.3)29 Camino, G.(3)671 Cammack, J.K. (4)19 Campbell, LH.(3)381
Campistion, I. (3)214 Campredon, M. (2.4)83 Camps, F. (2.1)53;(2.6)198 Cano,F.H. (2.3)72;(2.5)169; (2.6)155 Cano, M.(2.1)53; (2.6) 198 Canpolat, M. (3) 546,592,595 Cao, H. (2.3)98;(2.5)254;(4)24 Cao, P.(2.4)128 C ~ OX.-Z. , (2.5)58.59 Cao,Y.(1) 542;(2.5) 221 Cao, 2. (3)24,26 capek, I. (3) 90 Carassiti, V. (2.5)189 Carbonera, D. (1) 432 Cardenas, J. (2.5)154;(2.6)316 Cardoso, S.L.(1) 57 Caretti, D. (3) 32,119 Carlini, C. (3) 4,32,119 Carlson, D. (2.6)268 Caronna, T.(2.4)181, 196;(2.6) 167,227;(3)763,764 Carrasco, F. (3) 653 Carre, M.C. (3) 491,501,591 Carreira, E.M. (2.2)35.39; (2.4) 146 Carretero, A.S. (1) 189 Carter, S.A. (3) 263 Cantso, F.(1) 114 Casida, J.E. (2.7)28 Cassara, L.(1)225 Cassidy, P.E.(3) 48 Castellan, A. (3) 337,728 Castillejo, M. (2.7)160 Castle, R N . (2.4)229;(2.6)77 Castner, E.W., Jr. (1) 276;(2.5) 64 Catalan,J. (1) 272;(2.1)22 Catalani, L.H. (3) 683 Catalina, F.(3) 27,28,755,783 Catellani, M. (3)465,763,764 Cattaneo, P.(2.7)3 Caudle, M.T.(1) 67 Cavaleiero, J.A.S. (2.7)32 Celani, P.(1) 331;(2.3)64,80; (2.4)30,94;(2.6)23-25,191; (2.7)4 Cerfontain, H. (2.4)42 Cennenati, L. (2.2)98;(2.6)323 Cermola, F. (2.5)271 Ceroni, P.(1) 418; (2.5)10 Cervantes, J. (3) 679 Cewen, I. (3)222 Cemini, R (3) 372,440 Cemy, C. (1) 309 Cha, J.K. (2.5)247; (2.6)177 Chabaud, F.(3) 795 Chae, K.H.(3) 1,743,782
403
Author Inahc Chae, W.K.(2.1) 16; (2.3) 74;
Chen, G.-Z. (1) 184, 186, 187; (3)
Chae, Y.S. (2.3) 21; (2.4) 129, Chai, X.D.(3) 336 Chakraborty, A.K. (3) 476 Chakravoh, S.(1) 167 Chalchat, J.C. (2.5) 204 Challa, G.(3) 52 Chambaudet, C. (3) 670 Chamberlin, A.R (2.7) 34 Chamontin, K. (2.4) 82; (2.6) 53,
Chen, H.B.(3) 156 Chen, H.L.(1) 678 Chen, J. (3) 467,508 Chen, J.-F. (2.2) 127 Chen, J.H. (3) 654 Chen, J.-R (1) 542; (2.5) 221 Chen, K. (1) 478 Chen, K.H.(3) 692 Chen, K.S.(3) 273 Chen, L. (2.1) 60; (2.6) 178; (2.7)
Chan, M.S.W. (2.3) 27,28; (2.4)
Chen, M.-F.(1) 314; (2.5) 180,
(2.4) 151; (2.5) 81 130
60
178, 179; (2.6) 169, 170 chan, S.I. (2.2) 122 Chan, T.-T. (2.6) 221 Chan, W.Y.(2.7) 69 Chan, Y.-P. (2.4) 89 Chand, U.(2.6) 228 Chandler, M.M. (3) 265 Chandra, A.K. (2.1) 33; (2.5) 79, 80 Chang, A.H.H. (2.7) 119 Chang, B.H.(3) 638 Chang, C.P. (1) 281 Chang, C.S. (3) 684 C h g , G.(1) 207 Chang, K. (3) 42 chang, L.K.(3) 543 Chang, Q.(1) 586 Chang, T.(2.4) 85; (3) 156,325 Changenet, P. (1) 244 Chanrapani, S. (3) 781 Chao, C. (3) 188 Chao, 3. (3) 348 Chapat, J.-P. (2.6) 99 Chaput, F. (2.2) 112; (2.3) 17; (2.4) 124 Charlston, W.G. (3) 329 Charra, F. (3) 347 Chartoff, RP. (3) 218,259,260 Chase, C.E. (2.2) 86 Chavignon, 0. (2.6) 99 Chayet, H.(3) 422,43 1 Chee, C.K.(3) 498 Cheer, C.J. (2.2) 68; (2.6) 87 Chekhov, D.I. (1) 102 Chemla, D.S.(1) 171 Chen, B. (3) 97 Chen, B.Z.(2.2) 2 Chen, C. (2.5) 69,284 Chen, C.H. (3) 345 Chen, C.P. (3) 325 Chen, D. (1) 168; (2.5) 287 Chen, F.(4) 12 Chen, F.C. (3) 280 Chen, G.(1) 185,391
474
196
30 1
Chen, N. (1) 206; (2.5) 175 Chen, P. (1) 119,526,551; (2.5) 270; (2.6) 224; (2.7) 121
Chen, Q:Y. (2.4) 128 Chen, R.(1) 4 Chen, S.(3) 690 Chen, S.A. (3) 390 Chen, S.H. (1) 34 Chen, S.-J. (1) 3 12; (3) 555 Chen, W.(3) 687 Chen, X.(1) 175; (2.7) 172; (3) 375
Chen, Y.(1) 234; (3) 61,62, 168, 197,540,692
Chen, Y.4.(1) 312 Chen, Y . 4 . (1) 544; (2.5) 255 Chen, 2.(1) 516; (2.5) 104; (2.6) 255; (3) 705
Cheng, C.H. (3) 4 11 Cheng, H.L.(3) 543 Cheng, P.C. (1) 638; (3) 366 Cheng, X.N.(2.2) 11 Cheng, Y.(2.5) 238 Cheong, B . 4 . (2.6) 47 Chemoivanov, V.A. (2.3) 95.96;
(2.4) 40,86; (2.6) 74; (4) 25 Chemyakovskii, F.P. (3) 303 Chesta, C.A. (1) 96 Chewou, P. (3) 795 Chi, 2.(2.6) 301 Chiang, L.Y.(1) 413,414; (2.5) 82, 151 Chiang, Y.(1) 275; (2.2) 53, 123; (2.4) 253,264; (2.5) 90; (2.7) 30 Chiapperino, D. (2.6) 200 , Chiapperino, F. (2.7) 194 Chiavassa, T.(2.7) 63 Chiba, K. (2.4) 98 Chiba, N . (1) 63 1; (3) 340 Chibisov, A.K. (I) 342; (2.6) 54 Chiesi-Villa, A. (2.3) 99; (4) 21 Chikaoka, S. (3) 16
Chikkur, G.C. (1) 117 Childress, R.S.(2.2) 41 Childs, A. (3) 783 Childs, R.F.(3) 118 Chin, K. (4) 60 C~~MITO, E. (2.5) 121; (2.6) 265 Chiou, B.S.(3) 176, 177 Chiriac. C.I. (3) 295 Chirico, G. (1) 6 17 Chiron, F.(2.5) 204
Chisaka, Y.(2.1) 42; (2.5) 237
Chisdes, S.J.(1) 33 Chiyonobu, K. (2.4) 167; (2.6) 116
C h e l a , S. (3) 773 Cho, D.W.(1) 156 Cho, H . 4 . (2.6) 47 Cho, H.N. (3) 425 Cho, S.J.(2.2) 104; (2.4) 218; (2.6) 92
Cho, W.J. (3) 684,686 Choi, C.N. (2.3) 14; (2.6) 44 Choi, H. (2.7) 62 Choi, J.H. (3) 669 Choi, L . 4 . (1) 151, 152 Choi, M.(1) 86; (3) 505 Choi, S.K. (3) 443 Choi. S.W. (1) 371; (2.6) 17 Choi, W.M. (3) 684,686 Choi, Y.S.(2.7) 13 Chojnacki, K.T. (1) 607 Choo, D.J.(2.2) 38 Choong, V.E. (3) 423,429 Chou, P.-T. (1) 281,312 Chou, T.C.(2.3) 91 Chow, Y.L.(1) 461; (2.2) 11; (2.6) 194; (2.7) 17
Choy, A.L. (2.2) 26 Christiaens, L.E. (2.4) 233; (2.6) 283
Christic, R.M. (3) 803 Christl, M. (2.2) 125; (2.4) 143 Chu, G.4. (2.2) 127 Chu, K.T. (1) 529; (2.5) 249 Chuang, H. (1) 580 Chuang, K.R (3) 390 Chung, K.-H. (4) 38 Chung, S.J. (3) 384 Chupka, A. (3) 714 Chupka, E. (3) 714 Chyla, A. (3) 3 10 Ciardelli, F.(3) 50,309 Ciardelli, G. (3) 551,558 Cina, I.A. (1) 8 Ciobani, C. (3) 693 Cirak, J. (3) 222 Cires, L. (2.4) 186 Ciuprina, F.(3) 625
404 Ciurla, H.(2.4)8 Clark, C.D. (1) 455 Clark, C.G. (1) 120 Clark, J.D. (3) 291 Clark, N.A.(3) 254 Clark, S.C. (3) 14,70,73,75-77 Clauss, M. (3) 776 Clegg, R.M. (1) 698 Clennan, E.L. (1) 3 14;(2.5)21, 180,301 Cleveland, W.(3)263 Clifton, C. (1) 314;(2.5)180 Clivio, P. (2.2)76-79;(2.4)195; (2.6)135,287-289 Close, M. (2.2)106;(2.4)214 Closs, G.(1) 2 co, Y.(1) 473 Coates, G.W.(2.2)6;(3) 63 Cobane, S. (1) 651 Coffin, M.A. (2.6)266 Cohen, G.(3) 408,431 Cohen, J.L. (1) 553 Colbow, K.M. (3) 60 Cole, B.J.W. (3) 766 Cole, C.G.B.(1) I 1 Collin, J.-P. (1) 39,485,549;(2.5) 289 Collini, M. (1) 617 Collins, G.E. (1) 152 Collins, S. (3) 732 Collinson, C.J. (3) 377 Colomvakos, J.D. (2.2)93 Comins, D.L. (2.2)70;(2.4)147; (2.6)117 Commereuc, S . (3) 689 Comoretto, D. (3) 388 Conger, B.M. (1) 34 Connick, W.B. (1) 581 Connolly, T.J. (2.1)21;(2.5)92 Constable, E.C. (2.7)87 Constant, J.-F. (1) 620 constanzi, s.(3)754 Constien, R.(2.2) 15;(2.6) 123 Conti, F. (1) 424 Conwell, E.M.(1) 78;(3) 395, 398,404 Cook, A.R. (2.5)30 Cooke, J. (2.7)79 Coons, L.S. (3) 209 Cooper, T.M.(1) 37;(2.6)62 Coppey-Moisan, M. (1) 641 Coqueret, X.(3) 3 1, 111,183,242 Corbett, RM. (2.2)60 Corbin, D.R.(2.2)40;(2.5)3 1 Corelli, E.(3) 32, 119 Corens, D. (1) 344 Comelisse, J. (2.4)152 Cornelissen-Gude, C. (1) 165
Comil, J. (3) 288,351,374,381, 560 Cornwell, P. (2.4)278 Comles, T.(3) 27,28,49,783 Corrent, s.(2.1) 2 Come, J.E.T.(2.1)68;(2.4)271; (2.7)177 Corvaja, C. (1) 415,424,432 Corval, A. (2.6)220 Cosa, G.(1) 96 Cosa, J.J. (1) 118,442;(2.5)149 Cossy, J. (2.1)45 Costa, L. (3) 671 Costa, S.M.B. (1) 217 Costa-Femandez, J.M. (1) 587 Costela, A. (1) 221,239;(3) 30, 85 Cotrait, M. (3)337 couris, s. (1) 375 Courtney, M.C. (2.6)324;(2.7) 166 Courtney, S.H.(2.5)197 Coury, J.E. (2.2)13 1 Covell, C. (2.4)139 Covert, K.J. (3) 748 Cowans, B.A. (3) 182 Coyle, J.D. (2.2)106;(2.4)214 C o d , R.A. (3) 507 Cozens, F.L. (2.5)230 Craig, D.C.(2.5)103 C m e r , C. (2.4)194 Crecelius, T.(2.2)83 Credi, A. (1) 48 Creed, D. (3)507,767 Cremer, D. (2.7)19 Crepin, C.(2.7)200 Crescenzi, C. (2.5)299 Creutz, C. (4)9 Crimmins, M.T. (2.2)26,27,31 Crissman, H.A. (1) 653 C r i ~ e l lJ.V. ~ , (3) 116, 125-127, 136 Crocker, P.J. (1) 238 Crooks, E.R.(1) 396;(2.5)130 Cui, Q.(2.7)60,65,117 Cullmann, 0.(2.6)157 Cullum, N. (3) 106 Cumaranatunga, P.K. (2.1)67 Cunderlikova, B.(3) 568 Curry, S.L.(1) 487 Curtis, M.D. (3) 45 1 Curtis, L.A. (2.5)30 Cuscurida, M. (3) 780 Czernik, A.W. (1) 565,566 Dabestani, R. (2.3)105 Dabrio, J. (3) 30,85
Photochemistry da Cunha, M.F.V. (1) 249
Dagdigian, P.J. (2.7) 130 Dahn, U.(2.7)9;(3) 203 Dai, C.-S. (2.4)182;(2.7)16 Dai, Z.(1) 206 Dailey, W.P. (2.6)115 Dainty, J.C. (1) 644 Dalbavia, J.-0. (1) 485;(2.5)289 Dalibart, M. (1) 688 Dall'Acqua, F. (2.6)286 Dallakian, P.(2.2)108;(2.6)93 Damas, C. (3)491,591 DAmico, J. (4)67 Damme, M.V. (3) 58 Daniel, C.(2.7)72,98 Daniels, L.B. (2.3)38;(2.7)135 Dapprich, J. (1) 619 Darkow, R. (3) 223 Darmanyan, A.P. (1) 242;(2.6) 299 Darraq, B. (2.3)17;(2.4)124 Das, A. (2.5) 273 Das, K.(1) 276;(2.5)64 Das, P.K. (3) 745 Das, R (1) 194 Das, S.(1) 416;(2.3)46; (2.5)16, 283;(2.6)5 Dashkevich, S.N.(1) 212 da Silva, A.P. (1) 51,554,555, 569 Datta, A. (3) 575 Daub, J. (1) 375;(3) 421 Dauben, W.G.(2.3)85 D'Auria, M.(2.2)7,80;(2.4)50, 183,184, 189,231;(2.5)229; (2.6)11, 106,235-237,306 Davadoss, C. (1) 477 Dave, P.R. (2.6)105 David, G.(3) 55 Davidov, D.(3) 408,422,431 Davidson, K.(3) 534,792,793 Davidson, R.S.(3) 732 Davies, J.E.(1) 43 Davis, F.J. (1) 355;(2.4)16 Davis, L.M. (1) 172 Davydov, R.(1) 63,64,66 Dax, C. (2.7)56 Day, M.W. (2.2)122;(2.4)226 De, A.K. (1) 1 16;(2.5)232 De, R (1) 116, 199,501,502 Debrecney, M.P.(1) 471 De Bmyn, A. (2.2)74 Decker, C. (3) 77.93, 121,129, 174, 175,212,779 Decker, D. (3) 93,174,175 De Costa, M.P.D. (2.1)67 Decurtins, S.(1) 50 Dee& 0.(2.5)210;(2.6)305;
405
Author Index (2.7) 173 De Feyter, S. (1) 20 1 Defieux, A. (3) 293 Dcfranoq. E. (1) 620 Degra, S.K. (1) 278 DeGraff, B.A. (1) 556,568,573 Degtyareva, A.A. (3) 37 de Guidi, G.(1) 195; (2.1) 47; (2.5) 97 de Haan, R (2.4) 152 De Haen, W.(1) 344 Dejima, M.(1) 563 Deka, C. (1) 653 De Keukeleire, D. (2.2) 74; (2.4) 140,154 Dekkers, H.P.J. (1) 681 Delaire, J. (1) 474 de la Maza, A. (3) 472 Delaney, A. (4) 60 de la Pena, A.M. (1) 189 de la Pena, M.(2.5) 288 Delbaere, S. (2.4) 92; (2.6) 58 Del Giacco, T. (2.5) 300 Deligeorgiev, T. (2.6) 72 De Lijser, H.J.P. (2.3) 29,30; (2.4) 177; (2.6) 168 Deljonne, D. (3) 288 DeIl'Aquila, C.(2.6) 217 Dell'Erba, C. (2.6) 3 15; (2.7) 12 Dclmastro, A. (3) 23 1 Delmond, S.(1) 146, 147; (2.5) 258 Delnoye, D.A.P. (3) 525 DeLoos, M.(3) 195 De Luca, E.(2.4) 184, 189; (2.6) 235,236 De Lucas, N.C. (2.1) 6;(2.4) 254; (2.7) 3 1 Demachi, Y. (3) 5 15 D e w , J.N. (1) 556,568,573 Demchenko, A.P. (1) 257 de Meijere, K.(3) 490 De Mello, A.J. (1) 676 Demin, P.M. (2.7) 55 Demuth, M. (2.3) 84; (2.5) 6; (2.6) 95 de Nalda, R (2.7) 160 Denari, J.M. (1) 436,541; (2.3) 3 1; (2.5) 268; (2.6) 89,252 Dencausse, A. (1) 649 Deng, F.(1) 285 Deng, L.X.(2.1) 72; (2.5) 146; (2.6) 293 Deniel, M.H. (2.6) 70 Denisov, G.S.(1) 274 Denti, S.W. (1) 570 Denton, G.J. (3) 405,406 Depaemelaere, S.(1) 538,591;
(2.6) 254 Deponte, R. (1) 2 14 de Raaf€,A. (3) 140 Derbyshire, H.(3) 729 De Rossi, D. (3) 304 De Rossi, R.H.(2.4) 248 Desai, M.K. (1) 228 de Schryver, F.C.(1) 149,201, 344,450,538,562,591; (2.5) 257; (2.6) 254 De Silvestri, S.(3) 375 Deslauriers, P.J. (3) 745 Desvergne, J.P. (2.3) 3; (2.6) 129, 130 Detty, M.R.(1) 3 13; (2.5) 181 Devadoss, C. (3) 524 Devasagayaraj, A. (2.2) 16 Devol, I. (1) 283; (2.4) 65 Dey, J. (1) 198; (2.4) 66 Deyerl, H.-J. (2.7) 121 de Zwart, E.W. (2.4) 152 Dhake, K.P. (3) 353 Dhavale, D.P. (2.1) 59; (2.4) 46 Diamond, D. (1) 29 Diao, L. (2.3) 118; (2.4) 175; (2.7) 197 Dias, R.M.B. (2.5) 282 Diau, E.W.4. (1) 21 Diaz, A.N. (1) 598 Diaz, A.R. (2.7) 59 Diaz, C. (1) 272; (2.1) 22 Diaz, F. (3) 30 Diaz, L. (2.7) 160 DiazGarcia, M.E.(1) 576,578, 587 Dicelio, L.E. (2.5) 176 Dickcw, R.S.(1) 35 Dickson, J.M.(3) 118 Diederich, F. (1) 41, 341; (2.2) 93; (2.3) 2; (2.4) 25; (2.6) 20 Dieks, H.(1) 5 10; (2.5) 70 Dietrich-Buchecker, C.O.(1) 4 1 Dietz, J.E. (3) 182 Dilung, 1.1. (2.5) 40 Ding, I. (3) 590 Ding, K.L. (2.1) 42; (2.5) 237 Dirr, S.(3) 617 Dityapak, I. (1) 456 Di Valentin, M.(1) 432 Dmitrenko, O.G. (1) 36; (2.3) 88 Dtnitriev, Yu.A. (3) 788 Dmitruk, S.L.(I) 235 Dmitry, S.(1) 151 Do, N. (3) 715 Dobrikov, M.I.(2.7) 54 Dobrin, S.(1) 356,361 Dobson, G.R (2.7) 83-85 Dockery, K.P. (2.3) 35
Doe,H. (2-5) 123
Doettinger, S.E. (3) 383,430,437 D6tz, K.H.(2.7) 93 Dogadkin, D.N. (2.4) 22 Dogra, S.K. (2.6) 149 Doherty, E.M. (2.2) 36 Doho, R. (2.5) 239; (2.6) 346 Domcke, W. (1) 137 Domen, K. (4) 5 Donald, F.(1) 127 Donat-Bouillud, A. (3) 455 Donath, E. (1) 114 Donati, D. (2.4) 257; (2.6) 199; (2.7) 58
Dong, J.H. (3) 69 Dong, S.-M. (2.5) 177 Dong, X.(2.5) 220 Dong, Y. (2.4) 100 Dopp, D. (2.4) 158 Dorado, A.P. (3) 559 Domsville, R.(3) 441 Dorofeev, Yu.1. (3) 735 Doroshenko, A.O. (1) 279,457; (2.6) 147
dos Santos, M.C.(3) 462 Dotrong, M.H. (3) 218,260 Doucet, G.J. (3) 76 Dougan, L.A. (3) 256 Dougherty, D.A. (3) 63 Douhal, A. (1) 15,282 Dovinchi, N.J. (1) 168 Dowling, K. (1) 644 DOZO~, J.-F. (2.4) 35,38; (2.6) 33 Draxler, S.(I) 564,647 Dreger, Z.A. (1) 223; (3) 532 Drevillon. B. (3) 147 Drew, M.G.B. (1) 570; (2.4) 155; (2.6) 325
Drexhage, K.H. (1) 169,176, 181, 714
Drickamer, H.G. (1) 223; (3) 532 Driessen, M.D. (2.5) 203 Dritz, J.H. (2.2) 35 Drozdova, N.N. (1) 470 DrozGeorget, T. (2.7) 64 Druzhinin, S.L. (1) 235 Du, C. (3) 618 Du, F.(3) 552 Du, X.-Z.(1) 184, 186, 187; (3) 474
Du, 2.(3) 492
Duan, S.(2.6) 313 Duan, X.(3) 772 Dube, C.E.(1) 65 Dubest, R. (2.4) 106 Dubonosov, A.D. (2.3) 95.96; (2.4) 40; (4) 25
Dubovitskii, A.V. (3) 668
406 Dubrin, J. (1) 239 Duburs, G. (2.5)266 Duddu, R.(2.6) 105 Duerner, G.(2.2) 83 Dun; H.(2.4)224;(2.6)70,71; (3) 293 Dulieu, B. (3)399 Dulog, L.(3)641 Dunk, W.A.E. (3)666,784 Dunkin, I.R. (2.7)40,48, 101, 176 Dunn, A.R. (2.2)6;(3) 63 Dunwoody, N.(2.7)95 Dupont, L.(2.4)233;(2.6)283 Duportail, G.(1) 593 Dupray, L.M.(4)26 Duran, N.(3)7 1 1 D u m d , A.-P. (2.4)187 Durocher, G. (1) 193 Durose, K.(4)65 Durst, T.(2.1)21;(2.5)92 Dusan, C. (1) 699 hsan, C., Jr. (1) 699 Duschek, F. (2.7)127 Dutta, B.K. (2.5)232 Duval, M. (3)495 Dvorak, C.A. (2.2)25 Dvorak, M.A. (1) 650 Dvornikov, A.S. (2.6)224 Dyakonov, V.(3)386,387,561 Dyker, G.(2.4)209 Dyl, D. (2.5)23 1 Dymoke-Bradshaw, A.K.L. (1) 644 Dyrda, M. (3) 117 Dzhabiev, T.S.(2.5) 157 Dziadosz, L.(3) 591 Eastoe, J. (1) 396;(2.5)130 Ebel, A. (2.2)83 Eberhardt, W.(3)60 Eberson, L. (2.4)190-192;(2.6)
202-207,309;(2.7)109-114 Edamatsu, K. (3)340 Eder, S.(3)375,391 Edge, M.(3)27,28,49,783,804 Edington, M.D. (1) 685 Edo, S. (2.4)13 1 Edstrom, E.D. (2.4)282;(2.6) 214;(2.7) 178 Edwards, A.J. (2.7)87;(3)441 Edwards, O.E. (2.6)163;(2.7) I75 Egelhaaf, H.J. (3)382,385 Eggeling, C. (1) 169, 170, 181, 182 Eggleston, J.M. (4)65
Pholochemistry Egle, I. (2.2)93 Egorov, M.P. (1) 25 Egorova, G.D. (1) 218 Eguchi, S.(1) 421;(2.4)168; (2.6)88 Ehara, Y.(3) 338 Eichen, Y.(2.4)67 Eigendorf, G.K.(2.3)48;(2.4)54; (2.6)153 Einsiedler, J. (3)453 Eisele, G.(3) 178 Eisele, S.(2.4)279;(2.6)208; (2.7)183 Eisenberg, R.(I) 581 Eisenstein, M. (2.4)204 Eklund, P.C. (2.5)19; (3)21 Ekstoem, 0.(3) 400 El-Achari, A. (3)242 El Ayeb, A.A. (2.7)48 Eldho, N.V.(2.3)46 Elerman, Y.(2.6)146 Elgendy, E.M. (2.5)267 Elger, G.(1) 5 11;(2.5)62 Elisei, F. (1) 267,367,368;(2.3) 11;(2.6)230,286 Elisseeff, 1. (3) 228 Elissen-Roman, C. (3)525 Elligsen, G.(1) 584 Elliott, J.A. (1) 676 Ellis-Davies, G.C.R (2.6)218 Elmali, A. (2.6)146 Eloy, D. (2.5)124 El-Sayed, M.A. (2.3)112 El'tsov, A.V. (2.6) 159 Emeline, A. (2.5)245 Encinas, M.V. (3) 84 Encinas, S.(2.6)304 Enderle, Th.(1) 171 Enderlein, J. (1) 173,701 Endeward, B. (1) 402;(2.5)132 Endicott, J.F. (1) 23 Endo, S. (2.2)55; (2.6)134 Endo, T.(3)103,113,283,547 Enemark, J.H. (1) 5 14 Engel, P.S. (2.6)186;(2.7)6 English, D.S. (1) 276;(2.5)63.64 English, R.J. (3) 176 Enjouji, K.(2.5)155 Ensley, H.E. (1) 204 Epstein, A.J. (3)447,449 Eremenko, A.M. (1) 447,594; (2.5)148;(4)32 Erentova, K.(2.7)10 Erickson, B.W.(1) 488,526 Eriguchi, T.(2.3)16; (2.4)75 Eritja, R. (2.7)59 Erjian, E.(3)94 Erley, W.(2.7)151
Ermilov, E.A. (1) 130,131 Em-Balsell~,R.(2.4)246;(2.6) 161 Eryutov, A.V. (2.5)244;(2.7)44 Esat, B. (2.3)56 Eschrich, R. (1) 630 Esen, C.(3)235 EsfarJani, K (3)341 Esposito, V.(2.5)229;(2.6)306 Esrom, H.(3)702 Essam, M. (2.1)25 Esser, M. (3)349 Estcvcz, C.M.(3) 771 Etchevemy, J.L. (1) 673 Etile, A. (3)347 Etinger, M.(2.2)95 Evandro, A. (3)715 Evans, C.H. (1) 201 Evans, D.G. (1) 76 Evemhav, A. (1) 645;(2.3) 81, 82;(2.4)21 1 Everdij, F.P.X.(1) 19 Evertsson, H.(3)469,470 Evstigneeva, R.P.(1) 518 Ewell, T.(2.4)282;(2.6)2 14; (2.7)178 Ezhevskii, A.A. (2.5)244;(2.7) 44,45 Fabbrizzi, L. (I) 558,572 Fabian, T.Z.(3)542 Fabre, C.(1) 412 Fabrega, C. (2.7)59 Fabrih, G. (2.1)53; (2.6)198 Fagart, J. (2.7)35 Fagnoni, M. (1) 463;(2.2)48; (2.5) 184;(2.6)142,230 Falchi, A. (1) 232 Falconer, J.L. (2.5)214 Falla, N.(3)664 Falvey, D.E. (1) 26;(2.1)70.7 1; (2.4) 194,274,275;(2.5)116; (2.6)200; (2.7)194 Fan, G.(2.4)100 Fan, L.(3) 798 Fan,M. (2.2)1 1 1; (2.4)84, 119; (2.5)242; (2.6)41,52,56, 143;(3) 326 Fang, J.-Y. (1) 68 Fann, W.S. (3)390,708 Faraggi, EZ.(3)408,422,43 1 Faraneh, F.(2.2)59 Faravelli, I. (1) 572 Faria, J.L.(2.1)8 Farinas, E.T. (2.5)191 Farrant, E. (2.2)44 Farris, R.(3)754
Auihor Index Fasani, E. (2.5) 184
Fathhi, A. (2.4) 114; (2.6) 296 Fatkulbayanov, R.M. (2.7) 42 Faure, J. (1) 149; (2.5) 257 Faure, V.(2.6) 241 Favre, A. (2.2) 76; (2.4) 195; (2.6) 287,289
Fayer, M.D. (1) 113,529; (2.5) 249,250
Federov, Y.V.(3) 316 Federova, O.A. (2.6) 100; (3) 3 14, 316,486
Federspiel, R.F. (2.4) 229; (2.6) 77
Fedorov, Y.V. (1) 353 Fedorova, G.F. (3) 629 Fedorova, O.A. (1) 353; (2.4) 72; (2.7) 5 1; (3) 619 Fei, H. (4) 63 Fei, S.(3) 705 Feikema, D.A. (1) 607 Feiters, M.C. (1) 517 Feld, W.A. (3) 429 Feng, J.Y. (3) 33 Feng, K.(3) 201 Feng, W.(3) 187,798 Feng, Y. (3) 687 Feringa, B.L.(3) 195,323 Ferraris, J.P.(3) 416,424,448 Ferrere, S.(4) 48 Ferrero, F. (3) 215 Ferrero, M.I. (2.5) 300 Ferry, J.L. (2.5) 113; (2.6) 232 Fery-Forgues, S.(1) 584 Feurer, A. (1) 506; (2.5) 61; (2.6) 256 Fiebig, T. (1) 452,660,661 Figuera, J.M.(1) 221 Filipova, T.Z. (3) 533 Filippini, J.C. (3) 625 Findsen, E.W. (1) 514; (2.5) 295 Finger, K.(2.7) 72 Finaenova, E.F. (2.7) 202 Fiorini, C. (3) 347 Fischer, B. (3) 315 Fischer, E. (2.4) 204 Fischer, I. (2.7) 12 1 Fischer, K.(3) 709,721,723 Fischer, M.(1) 674; (2.3) 20 Fischer, P.(1) 50 Fischer, T.M. (3) 3 13,3 15 Fisher, W.G.(1) 637; (3) 355 Fissi, A. (2.6) 8; (3) 304 Fister, J.C.,111 (1) 172,702 Fisz, J.J. (1) 142 Flamant, G.(2.5) 193 Flamigni, L. (1) 4 1,258,485, 549; (2.5) 289
407
Fleming. G.R (1) 294 Fleming, S.A. (2.1) 29; (2.2) 37; (2.4) 3; (2.5) 94
Florenzano, F.H. (3) 683 Floriani, C. (2.3) 99; (4) 21 Flory, W.C. (1) 226 Flothmann, H.(2.7) 66 F l y , K.M. (3) 169 Foley, S.(1) 209; (2.5) 178 Follows, G.W. (3) 804 Foltin, 0. (3) 222 Fomina, L. (3) 56,365 Fomine, S.(3) 56,365 Fonash, S. (4) 67 Font, J. (1) 395 Font-Sanchis, E.(2.3) 109; (2.7) 141
Foote, C.S.(1) 203; (2.5) 182 Foote, R.S.(2.4) 278 Forbes, M.D.E. (2.1) 12 Ford, F. (2.7) 14. I5 Ford, P.C. (2.7) 73.88 Forrnosinho, S.J. (1) 16,58 Forsskahl, I. (3) 710,722 Forte, M.(3) 763,764 Fortin, D. (3) 370 Fossum, R.D. (3) 58 1 Fouassier, J.P. (1) 233; (3) 36,90, 121, 178
Foumier, J. (3) 181 Foumier, T. (I) 460; (2.4) 250 Foumier de Violet, P.(3) 728 F O U ~ J.L. Y , (2.2) 76-79; (2.4) 195; (2.6) 135,287-289
Fowler, C.J. (1) 214 Fox, M.A. (1) 527; (2.6) 264; (3) 538,581
Franceschi, F. (2.3) 99; (4) 2 1 Francese, G.(1) 558 Francisco, J.T. (3) 715 Frank, A.J. (4) 48 Frank, C.W. (1) 359 Frank, J. (1) 99 Frank, R.S. (3) 588,589 Frankevich, E.L. (3) 386,387 Frantsuzov, P.A. (I) 97 Franzke, D. (2.7) 11 Fraser-Reid, B. (2.4) 280; (2.6) 216; (2.7) 185
Freccero, M. (2.5) 184; (2.6) 322 Frechet, J.M.J. (2.4) 284; (3) 523, 623
Frci, H. (2.5) 186 Frcitag, B.-J. (2.2) 83 French, P.M.W. (I) 644 Frenny, A.E. (3) 263 Freundel, 0. (3) 453 Freundlich, A. (4) 60
Frew, M.G.B. (2.2) 43 Frcyer, W. (1) 215 Friedman, B. (3) 597 Friend, R.H. (3) 360,372,377,
40$,406,409,412,418,434, 440,444 Fritz, A. (3) 306 Froijo, A. (I) 469 Frolov, A.N. (2.4) 221; (2.6) 79 Frolov, S.V.(3) 410 Frontana, B.A. (2.5) 154; (2.6) 316 Fu, D.K.(3) 449 Fu, R (3) 362 Fu, S.W. (1) 678 Fu, T.Y. (2.2) 132; (2.6) 269, 271 Fu, Y.(1) 203; (3) 417 Fiilscher, M.(2.7) 15 Fuentes, M. (3) 263 Fuerniss, S.J.(3) 35 Fuhrman, T. (3) 269 Fuhrmann, J. (3) 349 Fuhs, M. (1) 511; (2.5) 62 Fujihira, M.(1) 631 Fujii, A. (3) 458,463 Fujii, T. (2.4) 272; (2.6) 294,295 Fujii, Y.(2.5) 165 Fujimaki. M. (1) 202; (2.4) 37 Fujimatsu, H. (2.4) 20 Fujimori, K. (1) 370; (2.3) 12; (2.4) 26 Fujimoto, K. (1) 528; (2.2) 73; (2.6) 174 Fujimoto, M. (2.4) 103 Fujimoto, T. (2.4) 39; (3) 308 Fujimura, T. (3) 340 Fujisawa, M.(2.6) 222 Fujisawa, S. (2.5) 224 Fujisuka, M. (1) 376 Fujita, E. (4) 9 Fujita, K.(2.2) 4; (2.4) 232; (2.6) 102 Fujita, M.(2.5) 209 Fujita, S. (3) 517 Fujita, T.(2.2) 88; (2.4) 205; (2.5) 96; (2.6) 124,291 Fujitsuka, M.(1) 250, 383,385, 410,419; (2.5) 98, 126, 127, 142, 198; (2.6) 318 Fujiwara, H. (2.5) 167 Fujiwara, M. (1) 308; (2.7) 191 Fujiwara, Y.(2.4) 49; (2.6) 302 Fukac, R. (3) 257 Fukuda, A. (3) 164 Fukuda, K.(2.4) 262; (2.6) 3 14; (2.7) 174; (3) 346 Fukuhara, M.(3) 674 Fukuju, T. (2.7) 193
408
Fukunaga, K.(2.4) 103 Fukushima, M.(1) 192; (2.4) 33 Fukushima, N.(2.4) 37 Fukushirna, Y.(3) 277 Fukuzumi, S.(1) 379,404,497;
(2.3) 122; (2.5) 9, 128, 131, 241; (2.6) 7,96 Fulton, M.I. (3) 63 1 Fultz, A. (1) 648 Fumiko, F. (3) 800 Funabiki, T. (2.5) 156, 187 Funasaka, H. (1) 385; (2.5) 142, 198 FuM, G.G. (2.7) 38 Furukawa, N.(2.6) 294 Furuya, Y. (2.6) 26 Fusi, S.(2.4) 257; (2.6) 199; (2.7) 58 Fuss, A. (2.7) 7 Fuss, W.(1) 339; (2.3) 86,87 Fyfe, M.C.T. (1) 517
Gabbutt, C.D. (3) 803 Gaber, A.E.-A.M. (2.1) 5; (2.5) 42 Gade, R.(2.4) 13 Gadella, T.W.J., Jr. (1) 652 Gadzhiev, M.M. (3) 762 Gaebert, C.(2.4) 165; (2.6) 140 Gael, V.I. (1) 467 Gagnon, P.(3) 455 Gahan, S.L. (1) 552 Gaisin, V.A. (1) 393 Gajewski, J.J. (2.7) 148 Galabova, H.G. (3) 508 Galaup, J.-F. (1) 682 Galiazzo, G. (1) 446 Galie, M. (2.7) 108 Galili, N. (2.2) 30 Gallagher, M.L.(2.7) 94 Gallas, J.M. (3) 758 Gallay, J. (I) 257,562,609 Gallivan, S.L.(2.7) 48 Galons, H.(2.4) 145 Galoppini, E. (1) 527; (2.6) 264 Galvao, D.S. (3) 462 Gamlin, J.N. (2.2) 132 Gan,H. (2.3) 108; (2.4) 156 Gan, L. (1) 419; (2.5) 196; (2.6) 225,226
Gan,R (1) 391 Ganapathy, S.(2.3) 35; (2.4) 164; (2.6) 345
Gandini, A. (2.6) 278 Gangadhara, K.K. (3) 244 Ganguly, T. (1) 116, 199,501, 502; (3) 482 Gao, D.B. (2.5) 190
Gao, H. (2.7) 81 Gao, JJ. (2.1) 29; (2.2) 37; (2.4) 3; (2.5) 94; (3) 197 Gao, Q.(2.4) 100; (3) 555 Gao, Y. (3) 423,429 Gdplovskj, A. (2.6) 307 Gaponik, L.V. (3) 760 Garas, S.K.(2.6) 166; (2.7) 192 Garavelli, M.(1) 33 1; (2.3) 64, 80; (2.4) 30; (2.6) 23-25 Garcia, C.G. (4) 8 Garcia, H. (2.1) 10; (2.5) 41,230 Garcia, S.(2.1) 10; (2.5) 41 Garcia-Moreno, I. (1) 221,239; (3) 30,85 Gardette, J.L.(3) 648,649,672, 673,676478,691,694,695 Gardlund, Z. (3) 792,793 Gareis, T. (1) 375 Garg, S.(2.2) 96 Garnett, J.L. (3) 276 Garros, G. (2.6) 60 Garry, R.P. (2.5) 204 Gaspcr, S.M. (2.2) 130 Gauduel, Y.(1) 18 Gaur, H.A. (2.6) 3 12 Gauthier, M.(3) 588,589 Gavina, P.(1) 39 Gavino, R. (3) 56 Gay, C. (2.5) 124 Gayncss, T.P.( I ) 516; (2.5) 104; (2.6) 255 Gaysinski, M. (3) 503 Gdaniec, Z. (2.6) 251 Gebert, H. (1) 357 Gebicki, J. (2.7) 20, 101, 176 Gebler, D.D. (3) 447 Gee, K.R.(2.6) 208; (2.7) 181 Gehlen, M.R (1) 687 Geibel, J.P. (3) 745 Geissler, U. (3) 356 Gelabert, H. (1) 18 Gelin, M.F. (2.7) 169 Gellermann, W. (3) 410 Gellini, C. (1) 232 Geng. P. (3) 189 Gennadii, G.S.(2.3) 95,96 Gennari, G. (1) 446 Gentemann, S. (1) 464-466 George, A. (1) 627 George, G.A. (3) 166.63 1 George, M.V. (1) 4 16; (2.3) 45, 46; (2.5) 283 Georges, J. (1) 674 Georghiou, P.E. (2.4) 273; (2.6) 277 Gcorgicvskii, Y.(1) 85 Gerassimova, Y.V.(2.7) 53
Pho&chemisoy Gerber, G. (2.7) 77 Gerca, L. (1) 35 1 Gerdan, V.M. (2.7) 32 Gereltu, B. (3) 539 Gergalov, V.V.(3) 761 Gericke, K.-H. (1) 27 Gerlock, J.L. (3) 738 Gershgoren, E.(1) 20 Getmanchuk, Yu.P. (3) 193 Gevaert,M. (2.5) 194 Geysen, H.M. (2.4) 280; (2.6) 216; (2.7) 185
Ghandi, M.(2.2) 59 Ghatak, A. (2.3) 93 Ghelli, S. (2.6) 73 Ghiggino, K.P.(I) 428; (2.5) 103, 138
Ghiloni, M.S.(3) 309 Gholamkhass, B. (1) 74,550 Ghorai, M.K.(2.2) 45.46; (2.5) 74
Ghosh, P. (3) 40,41 Ghosh, S.(2.3) 92,93 Ghoshal, N. (2.3) 93 Giacornetti, G. (1) 432 Giannotti, C. (1) 474; (3) 84 Giegrich, H. (2.4) 278 Gierschner, J. (3) 382,385 Giwe, B. (2.1) 9 Gijsbers. E.J. (1) 642 Gilardi, R. (2.6) 105 Gilat, S.(2.3) 17; (2.4) 124 Gilbert, A. (1) 355; (2.4) 16, 139, 155; (2.6) 325
Gilbert, B.C.(2.5) 117 Gilbert, T. (2.7) 121 Gillbro, T. (1) 363 Gillispie, G.D. (1) 650 Ginyama, H.(2.6) 341 Giraddi, T.P. (1) 117 Girerd, J.-J. (1) 75 Girlando, G. (3) 334 Gisman, P.(3) 650 Giuliano, K.A. (1) 6 16 Giusti, G. (2.4) 83; (2.6) 69 Givens, R.S.(2.1) 69; (2.4) 276 Glad, B.(3) 220 Glasbeek, M.(1) 17,87,292,293 Glass, J. (1) 171 Glaze, W.H. (2.5) 113; (2.6) 232 Gleiter, R (2.3) 90 Gleria, M.(3) 742,778 Glover-Fischer, D.P. (1) 33 Goddard, G.L. (1) 632 Goddinger, D. (3) 730,73 1 Godon, C. (3) 335 Godovikova, T.S.(2.7) 52.53 Goebel, L. (2.4) 79
Author Index Goeldner, M. (2.6)211;(2.7)180 Giimer, H. (1) 259,326,342,524; (2.1)49;(2.3)84;(2.4)96; (2.6)22,54,95, 137,223 Goertz, J.K. (1) 553 Goez, M. (1) 666 Goldenberg, L.M. (2.6)35 Goldenburg, L. (3)455 Goldman, A.S. (2.7)97 Golic, M.(2.6)131 Golosovsky, M. (3) 408 Golubev, N.S.(1) 274 Gomez, A.M. (2.2)42 Gomez, D. (2.2)124;(2.4)207 Gompper, R (3) 453 Gomza, Yu.P. (3) 184 Goncalves, H.(2.2)21 Godes-Luque, R.(2.4)192; (2.6)206;(2.7)109 Gonzalez, R.(3)598 Gonzalez-Moreno, R.(1) 395 Goodbrand, H.B. (1) 210 Goodman,A.L. (2.5)203 Goodman,J.L. (2.3)70;(2.4)60 Goodner, M.D. (3)78,82, 163 Goodwin, P.M. (1) 173, 180,701 Gopal, V.R. (1) 365 Gopidas, K . R (1) 494;(2.5)150 God, J.R (1) 112 Gordienko, V.P. (3)788 Gordon, C.M. (2.7)101 Gorduza, V.M. (3) 295 Goretsky, C. (3) 247 Gormin, D.A. (1) 334 Gorokhova, O.V. (2.4)240 Gom, S.M. (1) 62 Goshall, D.(3)209 Gosse, B. (3)625 Goswami, A. (1) 448; (3)101 Gosztola, D.J. (1) 522,540;(2.6) 260 Goto, H.(3) 332,517,749 Goto, M.(2.6)337,338;(2.7)163 Goto, N.(4)47 Goto, T.(2.6)145 Gottardo, C. (2.6)320;(2.7)167 Gotteland, J.-P. (2.7)56 Gou, J. (2.5)287 Gou, 2.(2.2)114;(2.4)120 Gougousi, T.(2.7)126 Goushcha, A. (1) 81 Gozzelino, G. (3)215,231 Grabchev, I. (3) 533 Grabner, G. (1) 145,325,328; (2.4)59;(2.6)156 Grabowska, A. (1) 293 Gradwell, M.J. (2.7)177 Grady, T.(1) 29
G m h , J.-C. (2.4)217;(2.6)80, 99 Grampp, G. (1) 663 Granchak, V.M. (2.5)40 Grant, A.S. (2.2)53;(2.4)264 Granucci, G. (1) 69 Grassi, D. (2.4)263 Grassi, G.(2.7)171 Grassian, V.H.(2.5)201,203 Grattan, K.T.V. (1) 692 Gratzel, M. (4)48 Graupner, W.(3) 375,380,391, 396,561 Gravalos, K.G. (3) 445 Gray, D.G. (3) 285,713,727 Gray, H.B.(1) 525 Gray, R.L.(3)777 Grazulevicius,J.V. (3) 364 Green, A. (2.5)121;(2.6)265, 266;(3) 27,28 Green, N. (1) 2 Green, W.H.(1) 269 Greenbaum, E. (4)4.80 Greene, J.B. (2.7)94 Greenfield, S.R.(1) 540;(2.6)260 Greenham, N.C. (3) 413 Greenwald, Y.(3) 598 Greer, A. (2.5)301 Gregg, B.A.(4)48 Gregor, I. (1) 222 Gregory, D.D. (2.5)22;(2.6)2 Greiner, G. (1) 14;(2.6) 188 Grelier, S.(3)337,728 Griesbeck, A.G. (2.2)107,108; (2.5)71;(2.6)93,126 Grigor'ev, LA. (2.4)45;(2.6)158 Grigoryan, E.A. (2.5)152 Grihkov, A.A. (1) 5 18 Grimsdale, A.C. (3)372,440 Grinkevich, V.M. (3) 184 Grisham, C.M. (1) 30 Grishchenko, V.K.(3) 39 Gritsan, N. (2.2)128, 129;(2.4) 68, 134;(2.5)57,88 Grob, J. (2.6)201 Grobys, M. (1) 143, 163;(2.5) 261 Groenenboom, C.J. (2.6)27 Gromov, A.V. (2.7)124 Gromov, S.P.(1) 353;(2.4)70, 72;(2.6)100;(3)314,619 Gross, H. (2.7)171 Grosshenny, V.(1) 545 Grubbs, R.H.(2.2)6;(3) 63,427, 428 Gruber, H. (3) 107,109 Gruener, J. (3) 444 Grue-Ssrensen, G. (2.6) 163;(2.7)
409 175 GIUIWTI~, U.-W. (1) 160 Gruner, J. (3) 372 Gryczynski, I. (1) 101,635,700 Gryczynski, Z.(1) 635,700 Gum, x.-P. (2.2)102 Guardigli. M.(2.3)99;(4)21 Gudkov, N.D. (4)2 Gudrnundsdottir, A.D.(1)238; (2.7)20 Gueimil Garcia, R. (2.7)59 Gueny, D. (3) 198 Gugger, A. (2.1)9 Guglielmetti, R.(2.4)10,82,88, 106;(2.6)53,60,63,68,69 Guigaon, E.F.(1) 651 Guilardi, R.S.(3) 337 Guillaume, D. (2.2)78,79;(2.4) 217;(2.6)80, 135 Guillet, J.E.(1) 53;(2.3)89;(3) 636 Guillon, D.(3) 264 Guimaraes, M.D. (3) 337 Guise, L.E. (2.2)3 1 Guitto, A. (2.5)271 Gulbinas, V. (1) 225 Guldi, D.M. (1) 380,397,407, 414,416,418,422,423,425, 426;(2.5)10, 136, 137, 143, 15 I, 283 Gulis, I.M.(1) 130, 13 1 Gulten, S.(2.2)105;(2.6)112 Gunaratne, H.Q.N. (1) 5 1,554, 555,569 Gun'kin, LF. (2.7)202 Gunnlaugsson, T. (1) 5 1,554,555 Gunter, M.J. (1) 516; (2.5)104; (2.6)255 Gunthcr, G. (2.5)253 Guo, H.Q. (3) 100 GUO,H.-X. (2.2)53; (2.4)264 Guo, J.X. (3) 727 Guo, M.(2.5)190 Guo, N. (1) 469 GUO,Q.-X. (2.2)65;(2.6)175 Guo,Y.(1) 242,391;(2.5)22; (2.6)2,299 Guo, Z.X. (2.2)113;(2.4)71 Gupta, M. (4)42 Gupta, N. (1) 405 Gupta, V. (2.4)213 Gurol, I. (1) 107 Gurzadyan, G.G. (1) 225,261 Gust, D.(1) 430-432,470,509, 5 19,520;(2.5)294;(2.6)263 Gustafson, T.L. (3)447,449 Gustafsson, C.M. (1) 618 Gustavsson, T.(1) 225,261
Photochemisiry
410
Gustina, D. (1) 35 I Gutenberger, G. (2.3) 114; (2.6) 32 1
Gutierrez, A.F. (1) 189 G u ~ ~ o M S. ~ u(3), 795 Guymon, C.A. (3) 253-256 Gvozdyukevich, I.F. (3) 760, 761 Gysling, H.J. (1) 581
Ha, C.S.(3) 686 Ha, T. (1) 171 Ha, W.S.(3) 66 Haas, Y. (2.7) 189 Habara, H. (1) 237 Haber, K. (2.4) 28; (2.6) 21 Haberl, U. (2.3) 75; (2.4) 169 Hachimori, A. (3) 604
Hada,M.(2.1) 13; (2.5) 32
Haddad, N. (2.2) 30,33,34; (2.4)
136; (2.6) 115 Hadjoudis, E.(2.4) 145 Hadziioannou, G. (3) 445 Haener, J.L. (2.7) 103 Haher, A. (3) 123 Hafher, K. (1) 232 Haga, N.(2.3) 103, 104 Hage, M. (I) 550 Hageman, H.J. (2.4) 230; (2.6) 27, 185, 312; (3) 29 Haghash, H.3. (3) 224 Hagihara, M. (2.3) 102 Haire, G.R. (2.7) 87 Haitjema, H.J. (3) 52, 323 Hajduk, A.M. (3) 5 1; (4) 46 Hajra, S. (2.2) 45,46; (2.5) 74 Hakiki, A. (2.1) 45 Halazy, S. (2.7) 56 Halfon, S. (2.3) 108; (2.4) 156 Halim, M. (3) 446 Hall, A.W. (3) 262 Hall, G.E. (2.2) 54; (2.7) 136, 188 Hall, J.A. (3) 162 Hall, M. (2. I) 60 Hall, M.A. (2.7) 6 I Hall, M.G. (1) 525 Hallensleben, M.L.(3) 356 Halley, P.J. (3) 166 Halliday, D.P.(4) 65 Halls, J.J.M. (3) 405 HalIstein, S. (3) 402,403 Ham, H . 4 . (2.7) 138; (3) 782 Hamaguchi, H. (1) 435; (2.3) 19; (2.4) 138; (2.6) 75; (2.7) 139 Hamaguchi, Y.(1) 621 Hamanaka, Y.(1) 449,530; (2.5) 290 Hamanoue, K. (1) 260,443; (2.4)
161, 188 Hamasaki, T.(2.2) 14; (2.4) 238; (2.6) 108, 110, 122 Hamilton, D.G.(1) 43 Hammarstroem, L. (1) 60,63,64, 66
Hammes-Schiffer, S. (1) 68 Hamon, J. (2.2) 79; (2.6) 135 Hamoumi, M. (4) 72 Hamplova, v. (1) 375,399 Hamza, M. (3) 214 Han, G.S. (2.2) 9; (2.4) 141; (2.6) 125
Han, J.Y. (3) 436 H a , I(.-L. (2.7) 143 Han, M.K. (3) 658 Han, S.W. (3) 686 Han, X . 4 . (2.4) 102 Hanabusa, K. (1) 307; (3) 522, 620
Hanack, M. (3) 383,430,437 Handa, M. (2.5) 168 b e y , W.A. (2.5) 49 Hanne, H. (2.6) 242 Hannemann, T. (3) 143,239 k e n , R.L. (1) 706,707 Hao, X.K. (2.2) 93 Haque. A. (2.3) 93 Hara, K. (1) 151,154 Ham, M.(2.5) 168 Hara, S. (1) 496; (2.3) 50; (2.5) 226
Ham,T.(1) 28; (2.4) 105; (2.5) 109
Harada, A. (3) 153,236
Ham@ E.(2.5) 85 Harazono,T. (3) 506 Harder, T. (2.4) 258; (2.7) 46 Hadinam, C. (3) 453 Harms, K. (2.1) 30 Harper, T.F.(2.5) 46 Harriman, A. (1) 38,532,545; (2.4) 80; (2.6) 18
Hams, C.B. (2.7) 90 Harris,J.M. (1) 702,706,7007 Harris, S.J. (1) 29 Harrison, N.T.(3) 405,406.4 12
Hartland, G.V. (2.5) 235 Hartmann, T. (1) 630 Ha~imam,U. (3) 223 Hartmann, W.K. (1) 582 Harbneier, W. (4) 78 Hartschuh, A. (1) 536 Hartshom, C.M.(2.4) 192; (2.6) 206; (2.7) 109 Hartshow M.P.(2.4) 190-192; (2.6) 202-207,309; (2.7) 109114
Hartwich, G.(I) 56 Harvey, P.D.(3) 370 Hasan, A. (2.4) 278
Hasegawa, E.(2.1) 25,61; (2.4) 225; (2.5) 99 Hasegawa, H. (2.5) 296 Hasegawa, M.( I ) 433; (2.5) 140 Hasegawa, T. (2.1) 28; (2.2) 97; (2.5) 29,76,77; (2.6) 85,276 Haselbach, E. (2.5) 38 Hasharoni, K.(3) 598 Hashi, Y.(3) 341 Hashida, I. (2.6) 97 Hashimoto, N. (4) 50 Hashimoto, S.(2.5) 147 Hashimoto, T. (3) 327 Hashimoto, Y. (4) 66 Haskell, T.C.(1) 532 Hass, K.C. (3) 771 Hassanpour, S. (3) 765 Hastings, C.A. (2.2) 39; (2.4) 146 Hatada, K. (3) 506 Hatakeyama, J. (2.6) 208; (2.7) 187 Hatate, Y,(2.5) 216; (3) 791 Hatbridge, T.A. (1) 625 Hatrick, D.A. (1) 639,640 Hatsui, T. (2.2) 1 Hattori, R.(3) 361 Hattori, T. (3) 562,565 Hatzopoulos, I. (2.5) 173 Hauck, R. (1) 507; (2.6) 257 Haucke, G. (2.4) 77; (3) 317,548 Haughland, R.P. (2.6) 208; (2.7) 181 Haupl, T. (1) 25 1 Hauser, A. (1) 50 Hausselt, J.H.(3) 143,239 Havlas, 2.(2.7) 1 Haws, E.J.(2.2) 106; (2.4) 214 Hayakawa, M. (3) 574 Hayakawa, T. (1) 645 Hayashi, C.(2.4) 268; (2.6) 91 Hayashi, H. (1) 655 Hayashi, S. (2.6) 267 Hayashi, Y. (1) 202; (2.4) 37 Hayashida, Y. (2.3) 101; (2.4) 142, 150 Hayes, G.R (3) 376 He, G. (2.5) 69 He, G.J.(2.7) 143 He, G.S.(1) 638; (3) 366 He, H. (2.5) 179 He, I. (2.5) 293; (3) 94 He, S.L. (2.6) 186; (2.7) 6 He, W. (2.6) 353 He. Y. (2.51 188: (31 451 Heath, P. (2.4) 155;-(2.6) 325
Author Index Heaton, H. (4)18 Hebecker, A. (1) 143;(2.5)261 Hecht, J. (2.1)30 Hector, S.(1) 496;(2.3)50;(2.5) 226 Heeger, A.J. (3) 288,351,388, 397,414,560,598 Heilman, S.M.(3)57,208 Heine, N.(2.4)77 Heinemann, C. (2.5)6 Heinz, R (3)804 Heinze, T.(3) 548 Heitner, C.(3) 718 Heitz, M.C. (2.7)72,98 Heitz, V.(1) 39,485;(2.5)289 Helaja, J. (1) 512;(2.2) 126;(2.5) 56,292;(2.6)258 Heller, C.M. (3) 38 1 Heller, H.G. (2.4)104, 109, 122; (2.6)50,5 1,64 Heller, V.(3) 723 Hellrung, B. (1) 275;(2.2)123; (2.5)90 Helnja, J. (1) 505 Hemetsberger, H. (2.4)201 Hemmingsen, S.L.(3) 545 Hendricks, R (2.4)139 Henling, L.M.(2.2)6;(3)63 Hennessy, M.H.(3) 393 Henning, H . 4 . (2.1)24;(2.5)72, 248;(2.6)179 Henseler, A. (1) 669 Hens A. (2.2)107; (2.5)71 Henze, B. (2.3)3 Hepworth, J.D. (3) 803 Herbertz, T.(2.3)54;(2.6)171 Herbst, H. (3) 751 Hercek, R.(2.6)307 Herdewijn, P. (2.2)74;(2.4)140, 154 Herek, J. (1) 21 Herges, R. (2.3)107 Hermann, H.(1) 25 1 Hernnann, W.(2.3)7,8;(2.4)21; (2.6)101;(3) 194 Herst, C. (2.6)332 Herzig, C. (3) 129 Hess. W.P. (2.1)57 Hesse, M.(2.6)19 Hester, R.E. (1) 561;(2.6)14, 266;(3) 316 Hibbell, J.A. (3) 274 Hibbs, D.E.(2.4)104;(2.6)64 Hidaka, H.(2.5)245,262 Hidayat, R (3)454 Higashida, N.(2.3) 117;(2.5) 122;(2.6)180;(2.7)198 . Higa&K:(1)515
Higuchi, A. (3) 240 Higuchi, J. (2.6)222 Hikmet, R.A.M. (3) 13 Hilberer, A. (3) 445 Hild. M. (1) 215 Hilfker, R.(3) 768 Hilger, A. (1) 341; (2.3)2;(2.4) 25;(2.6)20 Hilgeroth, A. (2.2)66;(2.6) 120 Hill, R.H. (2.7)99 Hill, S.C. (1) 178, 179 Hillenkamp, M.(2.7)67, 131, 132 Hima, T. (3) 219 Hioki, H. (2.4) 19 Hiraguri, Y.(3) 739 Himishi, T.(2.5) 107; (4)20 Hirakawa, K.(4)43 Hiraki, K.(2.5)145 Hirano, T.(1) 240; (2.3)71;(2.6) 172 Him, K.(2.7)115 Him@ Y.(1) 164 Hiratsuka, H. (2.6)13 Hirayama, N.(2.2)13.14; (2.4) 238,239;(2.6)11,108 Hirayama, S.(1) 273;(3) 346 Hirohata, M. (3)426,454 Hironaka, Y.(3)458,463 Hiroshi, T.(1) 645 Hirota, M. (2.7)145 Hirota, N. (I) 133,136,668,670; (2.7)168 Hirotsu, K.(2.3) 113;(2.4)62; (2.5)237;(2.6)128 Hirsch, T.(1) 536 Hirt, J. (2.2)108;(2.6)93 Hisada, K.(1) 480 Hisarnatsu, T.(4)69 Hishikawa, A. (2.7)68 Hishimoto, S.(1) 680 Hitchcock, P.B.(2.4)44;(2.6) 298 Hixson, S.S. (2.3)53 Hjertberg, T.(3)389 Hmyene, M. (3) 424 Ho, C.S.(2.4)137 Ho, J. (1) 472 Ho, T.I. (2.3)52;(2.4)127, 137; (2.5)251;(2.6)165 Ho, Y.(1) 84 Hobisch, J. (3) 154, 155 Hoche, R.(1) 348;(2.4)3 1 Hochstrasser, R.B. (1) 354;(2.4) 14 Hocker, H. (3) 730,731 Hodak, J.H. (2.5)235 Hoerstedt. P.(3)220 Hoe&& D. (2.2)83
41 1 Hoffman, K. (3) 75 1 Hoffman, M.Z.(1) 120,455 Hof€inann, B. (3) 294 Hoffmann, N.(2.2)19,29;(2.4) 144 Hoffmann, R. (2.5)129;(4)13 Hofmann, M.(3) 198 Hofstraat, J.W. (3) 92,545,554, 563 Hoggan, E.N.(3) 254 Hohloch, M.(3) 383,430,437 Hohmann, F. (2.7)93 Hohnholz, D.(3) 383,437 Hokuf, B. (3) 202 Holan, B. (3) 233 Holden, J.M.(2.5)19;(3)21 Hollander, A. (3)696 Holler, S.(1) 632 Hollins, H.R. (3) 5 1 Holmberg, C.(3) 469 Holmes, A.B. (3) 360,372.377, 405,418,440,444 Holmes, C.P. (2.6)208;(2.7)186 Holmes. P.A. (3) 181 Holt, E.M. (2.2)41;(2.4)132 Holten, D.(1) 464-466 Hornbrecher. H.K. (2.7)32 Homma,K.(2.2)63;(2.6) 173 Honda, K.(3)439 Honda, T.(1) 30 1 Hong, F.-T.(2.2)81 Hong, H. (2.7)146 Hong, R.Z.(3) 168 Hong, S.(3) 435 Hopkins, T.A.(1) 33 Hopp, B.(3)701 Horaguchi, T.(2.1)25,26;(2.4) 202,225 Hori, H. (2.5)155 Hone, K.(1) 603;(3)25 1,283, 319,320,500,509,511,547, 703,706 Hone, T.(2.7)23 Horiguchi, Y.(2.4)203 Horii, T. (2.4)93,98;(2.6)57 Horikoshi, S.(2.5)245 Horinaka, J. (3)496,576 Horn, E.(2.6)294 Honpool, W.M.(2.3)73;(2.4)56 Hosangadi, B.D. (3) 301 Hoshi, T.(2.6)334;(2.7)158 Hoshina, H.(2.6)160 Hoshino, K. (2.4)180 Hosokawa, H. (2.5)167 Hosono, H. (4)39-41 Hosono, M.(1) 7" Hossain, M.D.(1) 550 Hotta, H. (2.3)67
412 Hou, C. (2.5) 182; (3) 540 HOU,J.-Y. (4) 67 Hou, L. (3) 294 HOU,Y .-J. (1) 473 Houwelingen, G.D.B. (3) 563 Hovancssian, V. (1) 634 Howard, J.A.K. (1) 35; (2.6) 266 Howden, R.K. (3) 80 Howell, B.F.(3) 140,232 Howley, C. (3) 494 Hoyle, C.E. (3) 14,70,71,73,7577,219,507,767
Hozumi, Y. (1) 370; (2.3) 12; (2.4) 26
Hrdlovic, P. (3) 373 Hrkach, J.S. (3) 228 Hmjez, B.(2.3) 108; (2.4) 156 Hsaio, G.S.(2.7) 15 1 Hsieh, B.R.(3) 423,429,708 Hsieh, Y.-H. (2.3) 40 HSU,C.-P. (1) 85 Hsu, J.H.(3) 390,708 Hsuwen, H. (3) 511 Hu, A.T. (2.4) 87 Hu, H (3) 25 Hu, L. (1) 530; (2.5) 291 Hu, M.(1) 530; (2.5) 291 Hu, Q.S.(3) 378 Hu, S. (1) 601; (2.2) 90-92; (2.5)
83,84,95; (2.6) 273-275, 281; (3) 199 Hu, S.K. (2.2) 89 Hu, W. (2.6) 19 Hu, Y.(3) 477.61 1 Hum, J.-X.(1) 31 Huang, C. (2.5) 196; (2.6) 225, 226 Hwng, C.C. (3) 480 H m g , C.-H. (1) 419 Huang, D. (1) 185 H u g , H. (2.7) 14,69; (3) 159, 2 17,509 Huang, J. (1) 206; (2.5) 175 Huang, P.C. (3) 483,497 Huang, R (3) 536 Huang, S. (3) 492 Huang, S.Y. (4) 48 Huang, T . C . (2.4) 182,223; (2.6) 193, 194; (2.7) 16-18 Huang, X. (2.4) 270; (2.6) 212 X.-2. (1) 184, 186,187; (3) 474 Huang, Y. (1) 419; (2.6) 344 Huang, 2.(I) 206; (2.6) 143; (3) 326 Z.-N. (2.4) 84; (2.6) 41 Hubig, S.M.(1) 459; (2.2) 120, 121; (2.4) 174; (2.5) 47,50,
Phoiochemishy 93,236
Huesmann, M.D. (3) 486 Hug, G.L. (1) 437; (2.5) 36,39 Hughes, A.J. (1) 644 Hughes, D. (2.6) 50 Hughes, D.S.(2.4) 104; (2.6) 64 Hughes, F.J. (2.4) 113, 117; (2.6) 53
Hult, A. (3) 68 Hummel, K. (3) 154, 155 Hung, P.-T. (1) 281 Hung, S . 4 . (1) 520 Hungenberg, K.D. (3) 88 Hungerford, G. (1) 127 H u m J.R (1) 535 Hursthouse, M.B.(2.4) 104; (2.6) 50,64
Hutter, J. (1) 99 Hwdey, A.J.M. (1) 51,554,555 Hwang, C.C. (2.4) 215; (2.6) 81 Hwang, D.H. (3) 418 Hwang, K.C. (1) 384 Hwang, S.J. (2.3) 40 Hwang, Y.L. (1) 384 Hwangbo, S. (3) 658 Hwu, H.D. (3) 654 Hwu, J.H. (2.6) 165
Hwu, 3.R (2.5) 25 1 Hyde, S.C.W. (1) 644 Hynninen, P.H. (1) 505.5 12; (2.2) 126; (2.5) 292; (2.6) 258
Ibach, H. (2.7) 151 Ibn-Elhaj, M. (3) 264 Ibonai, M. (3) 275 Ibtahim-Ouali, M.(2.4) 217; (2.6) 80
Ibusuki, T. (2.5) 155 1 c h i 4 M. (1) 386 Ichijima, Y. (2.6) 53 Ichimura, K. (1) 202; (2.4) 37; (3) 23,311
Ichimura, T. (2.7) 144 Ichinose, N. (2.6) 97; (3) 278 Ichiryu, A. (3) 785 Icil, H. (1) 107,456; (3) 601 Icli, S. (1) 107,456; (3) 601 Iesce, M.R (2.5) 271 Igaki, Y. (2.3) 41; (2.4) 51 Igarashi, T. (3) 707 Ignat'eva, G.M. (3) 526 Ignatiev, A. (4) 60 Iguchi, M. (2.6) 75 Ihmels, H.(2.3) 47; (2.4) 55; (2.6) 152
Iida, I. (2.2) 88; (2.5) 96;(2.6) 124
Iida, S. (2.5) 102 Ijadi-Maghsoodi, S. (3) 433 h d a , E. (3) 637,639,675
M Y .(3) 18
h w a , T. (1) 605; (3) 460,535 Ikebukuro, K. (2.5) 101 Ikeda, E. (4) 59 Ikedq H. (I) 498; (2.3) 70; (2.4) 60
Ikeda, T. (3) 103,515,516 Ikegami, M.(1) 319 Ikeno, T. (1) 497; (2.3) 122; (2.5) 241; (2.6) 96
Ikoma, K.(2.5) 206 Ilchenko, A.Ya. (3) 367 lleva, A. (2.5) 297 Il'ichev, Y.V. (1) 143,144,159; (2.4) 17; (2.5) 261
lliev, V. (2.5) 297 Imada, A. (3) 340 Imada, M. (2.5) 296 Imada, T. (I) 32 Imae, T. (2.4) 232; (2.6) 102 Imae, Y. (2.2) 4 Imahasbi, S. (3) 36 Imahori, H.(1) 429,433,515;
(2.5) 11, 140 Imai, S. ( I ) 40 I d , T. (3) 680 Imakubo, T. (2.6) 75 Imanishi, Y.(1) 48 1 Irnans, F. (1) 201 Imase, Y.(2.5) 296 Imbach, J.-L.(2.6) 217 Imura, S. (2.4) 97 In,L. (1) 593 Inabe, T. (2.4) 64 Inaguki, Y.(1) 645 Inayosbi, T. (2.4) 262; (2.6) 3 14; (2.7) 174 Inaar,T.(2.4) 2 Inceli, A.L. (3) 737 Indelli, M.T. (1) 549 Indig, G.I. (1) 298 Ingames, 0. (3) 389 Inomata, K. (1) 233 Inoue, H. (1) 287,288,296; (2.5) 5.123 Inoue, K. (3) 170,750 Inoue, M.(3) 604 Inoue, S. (4) 56 Inoue, Y, (1) 47; (2.3) 1; (2.5) 228 Insins4 M. (1) 286; (2.6) 151 Irgum, K.(3) 220 hie, M.(2.2) 110, 116; (2.3) 13, 14, 16, 18; (2.4) 9,24,75, 115,116,118,125,200,208; (2.6) 9,4245; (3) 302
Author Iitlfex Iriyama, K. (1) 475
Isham, K.R(2.4)278 Ishenko, A.A. (3)344 Ishida, A. (1) 404,497;(2.3) 122; (2.5) 128, 131,241;(2.6)96 Ishigum, T. (3) 240 Ishihara,H.(2.6)88 Ishihara, K.4. (2.5) 158 Ishii, H.(2.3)71;(2.6) 172 M i , K.(2.3) 120; (2.6)139 Ishii, T.(3) 114,248 Ishikawa, H.(1) 498 Ishikawa, M. (3)562,565 Ishikawa, T.(2.6)43 Ishikura, A. (2.4)180 Ishikura, M.(2.6)78 Ishitani, 0.(2.5)155 Ishizuka, M.(2.5) 155 Iskrenova, E. (2.5)263 Israel, G.(3) 121 Isshiki. T.(2.4)48 Itadani, T.(3)5 12 Itagaki, H.(3)579,580 Ira&, M.(1) 704 Itaya, A. (1) 449,450;(2.5) 141, 290;(3)600 Itaya, T.(3) 170 Ito, K.(1) 504 Ito, M. (1) 483 Ito, 0.(1) 210,250,376,378, 383,385,408410,419;(2.5) 7, 8,98, 126, 129, 134, 135, 142, 198;(2.6)318;(2.7)170 Ito, S.(1) 480; (3)496,571,576 Ito, T.(1) 664; (3) 338;(4)47 Ito, Y. (2.1)43;(2.2)55; (2.4) 131; (2.6)134;(3) 120 Itoh, H.(1) 645;(3) 139 Itoh, K.(2.6)222 Itoh, M. (2.2)4;(2.4)232;(2.6) 102 Itoh, T.(3)340,368,537 Itoh, Y.(3)604 Ittah, Y.(2.4)204 Ivakhenko, E.P.(2.4)86;(2.6)74 Ivanov, S.A. (3)510 Ivanov, V.L.(2.4) 185 Iwahashi, M.(1) 498 Iwai, M.(1) 621 Iwama, T.(2.6)290 Iwamoto, T.(2.6) 340 Iwamura, H.(2.7)27 Iwamura, M. (2.4)281;(2.6)209; (2.7)182 Iwamura,Y. (4)47 Iwasa, Y. (1) 387 Iwasaki, T. (2.6)208;(2.7) 187 Iwata, H.(4)52
lwata,K. (1) 435;(2.3) 19;(2.4) 138;(2.6)75;(2.7)139 Izotov, A.N. (1) 388;(3) 354 Jackoon, W.M.(2.7) 118-120 Jacobsen, K.(3)626 Jacobson, S.C.(1) 172 Jacobsson, U.(3) 150 Jacquelin, R.(3)60 Jacques, P.(1) 444 Jacutia, S.E.(2.4)269; (2.6)213 Jaeger, W.(1) 123 Jain, S.(2.2)50 Jakobs, A. (2.2)12;(2.6)285 Jakubek, V. (3) 35 Janesch, C.P.(1) 132 Jan& H.(4)54 Jan& J.H. (4)55 Jan& S.(2.3)65;(2.4)160;(2.7) 125;(3) 415 Janet, J.-M. (I) 381,412 Jansbo, R.(3) 624 Jansen, A.W. (1) 420 Janssen, R.A.J.(3)414 Jantas, R (3)225 Jardon, P.(2.5) 124 Jarolimek, U.(4)27 Jas, G.S.(1) 324 Jasso, A.R (3) 49 Jayan, C.N.(2.3)37 Jayanthi, G. (2.4)222;(2.6)272 Jayanthi, S.(1) 500; (3) 202 Jayathritha, V. (1) 365 Jean, C.S.(3)61,62 Jeandon, C.(2.2) 15; (2.6)123 Jejurkar. C.R(3) 484 Jcncks, W.S.(2.6)2 Jenekhe, S.A. (3)375 Jeng, G.-Y. (2.6)221 Jeng, S.-M. (1) 588 Jenks, W.S. (1) 242; (2.5)22; (2.6)299 Jenniskens, H.G.(2.7)107 Jensen, A.W. (2.2)22 Jensen, F.(2.5)301 Jensen, J.O. (1) 253 Jeon, G.S. (2.3)36;(2.6)343 Jeon, K.(2.4)163 Jeong, Y.-T. (2.7) 138 Jeoung, S.C.(1) 86;(3) 436,505 Jessen, S.W.(3) 447,449 Jeziorek, D.(2.5)231 Ji, H.(2.4)159 Ji, J. (3) 118 Jia, F.(2.5)269 Jia, S.-L. (1) 534 Jia, Y. (2.4)100
413 Jiang, B. (1) 109; (3)415 Jiang, G.J. (2.2)2 Jmg, J. (2.5)196;(2.6)225,226 Jig, M. (3)488 Jiang, S.F.(3) 654 Jiang, S.-Y.(2.4) 182,223;(2.6) 193, 194;(2.7)1618 Jiang, W.(2.1)44;(2.4)36,266; (2.6)37 Jiang, X. (2.7)69 Jiang, X.B. (3)474 Jiang, X.X. (1) 109 Jiang, Y.(2.5)260 J i g , Y.-B. (1) 184,186,187 Jiang, 2.(2.5)23,269 Jiang, 2.4.(2.5)215 Jianheng, 2. (3)300 limbo, T.(3) 632 Jimencz, M.C.(2.2)84; (2.3)2325;(2.4)206,247,267 Jib,D.(1) 86;(3) 505 Jin, G. (3) 44 Jin, L.(3) 507 Jin, M.J. (3) 230 Jin, S.(2.4)84;(2.6)41, 143;(3) 326 Jin, T. (2.4)12;(4)56 Jin, W. (1) 406 Jin, X. (1) 487 Jing, J. (3)384 Jipa, S.(3) 625,628 Jochum. T.(1) 25 1 Jockusch, S. (1) 243;(2.6)350 Joglar, J. (2.1)53;(2.6) 198 Johannes,H.H.(3) 617 Johansen, P.M. (3)518 Johne, P.(2.5) 159 Johnen, E.(1) 5 1 1; (2.5)62 Johnson, B.W.(3)666,784 Johnson, C.K.(1) 324 Johnson, D.G.(1) 219,220 Johnson, M.R(1) 2,516;(2.5) 104;(2.6)255 Johnson, R (2.7) 147 Johnson, S.A. (1) 533 Johnston, L.J.(2.3)57 Jolliffk, K.A.(2.5) 103 Jones, G., II (1) 209,454,496, 628;(2.3)50; (2.5)49, 178, 226; (2.6)82,260 Jones, J. (3) 207 Jones, M.,Jr. (2.3)56;(2.7)146 Jones, P.G.(2.3)107; (2.6)333; (2.7)162 Jones, R (1) 61 1 Jonkman, A.M. (1) 87 Jonsson, J. (3)328 Jonsson, S.(3)14,65,70,71,73,
414 75-77,115,142 Jonusauskas, G.(1) 162 Joo, J. (2.4)282;(2.6)214;(2.7) 178 Jordan, J.W. (3)767 Jorgensen, K.(1) 255 Joselevich, E.(1) 516;(2.5)104; (2.6)255 Joshi, H.C.(1) 270 Jost, T.(3)400,401 Journet, C.(2.5)193 Jovanovic, S.V.(1) 248,657; (2.1)4;(2.5)43 Joy, A. (2.3)43 Joyce, T.(1) 29 Juha, L.(1) 375,399 Juhue, D.(3) 485,544 Julliard, M. (2.3)33 Jung, A. (2.1)69;(2.4)276 Jug, D.(3) 684 Jung, P.M.J. (2.4)193 Junge, D.M.(3)531 Jurczak, E.A. (3) 138 Juris, A. (1) 547 Kabatake, T. (3)688 Kabeta, K.(3) 680 Kabuto, C.(2.6)334;(2.7)158 Kaczmarek, H.(3) 665 Kadadevannath, J.S. (1) 117 Kadish, K.M. (1) 469 Kadodwala, M. (2.7) 107 Kadokawa, J. (2.4)98 Kaeriyama, K.(3)438 Kaganer, E.(1) 516;(2.5)104; (2.6)255 Kagawa, S.(2.7)82 Kai, Y.(1) 623 Kaila, M.(2.1)2 Kaiser, T.(3) 235 Kajimoto, 0.(1) 151,154 Kajiwara, A. (3) 100 Kajiwara, K.(3) 87 Kako, M.(2.4)135, 199;(2.6) 336,339;(2.7)161, 164 Kalena, G.P. (2.2)5 1; (2.4)157 Kalennikov, E.A. (3)661 Kaliyappan, T. (3)245 Kallitsis, K. (3)445 Kallny, M.(1) 377 Kalvoda, J. (2.6)201 Kamachi, M.(2.5)1 1 1; (3)87, 100
Kamachi, T.(2.5)108;(4) 16,20 Kamat, P.V. (1) 380,416;(2.5) 143, 194,283 Kamata, M.(2.6)317
Photochemistry Kamber, I. (4)34 Kamei, Y.(3) 662 Kameka, H.F.(1) 253 Kameyama, A. (3) 139,191,213 Kaminska, A. (3) 665 Kamiyama, H.(2.4)272;(2.6) 295 Kammermeier, S.(2.3)107 Kampf, J.W. (1) 67,544;(2.5) 255
Kan, YZ.(2.2)131 Kanaur, T.(2.6)354 Kanazawa, A. (3) 515,516 Kaneco, S.(2.5) 163 Kaneko. J. (1) 28;(2.5) 109 Kaneko, M.(4)39.40 Kaneko, T. (2.1)65;(2.4)249; (2.6)164;(3) 270 Kaneko, Y.(I) 21 1; (2.6)239, 281 Kanemoto, M. (2.5)158 Kang, D.(3) 14 Kang, E.T. (3) 480 Kang, H.K. (1) 364;(2.3)10; (2.4)27;(2.6)16 Kang, J.T. (1) 263 Kang, T.J. (1) 86;(3) 505 Kang, Y.S.(2.5)100 Kankare, J. (1) 33 Kannan, P. (3) 244,246 Kan'no, K. (1) 389 Kannurpatti, A. (3) 82 Kanoh, T.(2.5)85 Kanouchi, S.(2.6)335 Kanta Pal, M. (1) 448 Kantor, M.M. (2.7)42,43 Kao, P.(2.4)223;(2.6)193;(2.7) 18 Kapon, M.(2.2)95 Kapoustina, M. (1) 81 Kaptutkiewicz, A.(1) 24 Kaiakizawa, A.(2.6) 85 Karakostas, N.(2.6) 166;(2.7) 192 Karall, P.(1) 60 Karasawa, S.(2.7)27 Karasev, V.E.(3)615 Karatsu, T.(2.5)17,285;(2.6)6, 192 Karch, R. (2.7)91 Kardash, I.E. (2.7)124;(3) 350 Karitskaya, S.G.(3) 567 Karlsbeck, W.A. (1) 464-466 Karlsen, J. (2.6)247 Karn, R.K.(4)75 Karthaus, 0.(2.4)19 Karthikeyan, M. (2.3)26 Karube, I. (2.5)101
Kanazi, M. (2.5) 176 Kanhanov. S.Zh. (4)51 Kasai, H. (1) 383;(2.5) 126 Kashiwagi, Y.(4)57 Kasperczyk, J. (3) 233 Kasuga, K. (2.5)24, 168 Kaszynski, P.(1) 356,361 Katahira, A. (2.5)127 Katakis, D.(4) 17 Kataoka, T.(2.6)290 Kau, C.(3)307 Kato, H.(4)35,36 Kato, M. (2.6)329; (3) 630 Kato, N.(2.2)133;(2.4)237 Kato, Y.(3)613 Katsis, D.(1) 34 Katsu, H.(2.2)4;(2.4)232;(2.6) 102 Katsuda, N. (3) 794,799 Katsumura, S.(2.5)206 Katz, H.E. (3) 192 Kaufmann, H.F.(3)379 Kaula, I. (1) 35 1 Kaur, J. (2.5)160 Kaveleski, J.M. (1) 712 Kawa, M. (3) 623 Kawahara, S.(2.4)37 Kawahata, S.(1) 468 Kawai. H.(2.3) 106 Kawai. S. (2.3) 17;(2.4)124; (2.6)46 Kawai, T. (3) 426,464,466 Kawai, Y.(2.1)48;(2.6)249 Kawakami, H. (2.2) 133, 134; (2.4)237 Kawakami, Y.(2.6)148 Kawamoto, T.(4) 1 1 Kawamura, S.(2.5)131 Kawamura, Y.(2.7)23 Kawana, 0.(3) 158 Kawanami, H.(2.4)41;(2.6)349; (4)57 Kawanishi, S. (3)278 Kawanishi, Y.(2.4)95;(2.6)55 Kawano, H.(2.5)145 Kawano, K.(4)50 Kawano, Y.(2.5)216;(3) 791 Kawasalo, A. (1) 589 Kawasaki, 0.(4)69 Kawashima, H. (2.6)26 K a ~ h i m a K.4. , (2.2)24 Kawata, S.(3) 237 Kawato, H.(3)120 Kawatsuki, N.(3) 257,258,268, 289 K a m , Y.(3)341 Kawski. A. (1) 140 Kazuyuki, M.(3)25 1
Auihor Inder Keana, J.F.W. (2.7)50 Kebede, N. (2.6) 162 Keene, F.R.(1) 55 1 Keller, R A . (1) 173, 180,701 Keller, S.W. (1) 533 Kellett, P.A. (1) 644 Kellis, D.(2.7) 106 Kellogg, R.M. (3) 195 Kelly, C.A. (1) 548 Kelly, C.T.(3)642 Kelly, J.J. (4)72 Kelly, J.M. (3) 95 Kelly, L.A. (1) 690 Kelnhofer, K.(3) 421 Kemnitz, K. (1) 641 Kennedy, V.O. (1) 207 Kenney, M.E.(1) 207 Kennis, J.T.M. (1) 59 Kern, W.(3) 155 Kerr, W.J. (2.7)101 Kerst, C.(2.3)68;(2.6)327, 328; (2.7)155 Kcrsting. R.(3)379 Kerth, J. (2.6)348 Keshavarz, K.M.(3)598 Kess, R (3)2 19 Ketsle, G.A. (1) 129 Kevan, L. (2.5)100 Khabibulaev, P.K. (3) 464 Khachatryan, L. (2.7)189 Khailova, E.B.(4)58 Khairutdinov, R.F. (1) 535 Khan, M.I. (3) 419 Khan, S.A. (3) 176, 177 Khannanov, N.K. (2.5) 152 Kharkyanen, V. (1) 81 Khasanova, T.(2.7)26 Khatib, S.(2.4)67 Khodorkovsky, V. (3)298 Khodyakov, D.V. (1) 672 Khodzhaeva, V.L. (3) 26 1 Khong, A. (1) 420;(2.2)22 Khranovskii, V.A. (3) 141,226 Kicheva, N.S.(3) 303 Kido, G.(1) 655 Kiefer, B. (2.7)77 Kiefer, W. (2.7) 127 Kieslinger, D.(1) 647 Kiguchi, M.(3) 726 Kihara, N. (3) 103 Kijima, M. (2.4)39;(3) 308 Kikai, A. (3)257 Kikieva, T.(1) 447 Kikteva, T.A. (1) 594;(2.5) 148 Kikuchi, H.(1) 323;(2.7)36 Kikuchi, K. (1) 498 Kilpelainen, I. (1) 512;(2.5)56 Kim,A.R. (2.2)117-119;(2.4)
415
133, 153 Kim, C. (2.4)170;(3)425 Kim, D. (1) 86, 156; (2.3)65,66; (2.4) 160, 162, 163, 170,215; (2.6)81, 114;(2.7)125;(3) 436,505 Kim, D.R. (3) 89 Kim, D.W. (3) 435 Kim, D.Y.(3)425 Kim, E.S.(3)743 Kim, H. (1) 86; (2.4)85;(3)505 Kim, H.J. (2.2)49;(2.5)246; (2.6)238 Kim, J.H. (2.2)49;(2.6)238;(3) 685 Kim, J.K. (3)425 Kim, J.W. (2.2) 104;(2.4)85, 218;(2.6)92 Kim, K.J. (2.2)118;(2.4) 133 Kim, K.K. (3)384 Kim, K.-W. (2.4)215;(2.6)81 Kim, S.H. (1) 364;(2.3)10;(2.4) 27;(2.6)16 Kim, S.K.(2.7)13 Kim, S.M. (3)74,252 Kim, S.S. (2.2)117-119;(2.4) 133,153 Kim, S.T.(3)418,440 Kim, T.H. (3)74,252 Kim, T . 4 . (1) 264;(2.7)13 Kim, T.Y.(2.1)16;(2.5)73.81 Kim, W.G. (3) 125 Kim, Y.(1) 157 Kim, Y.H. (1) 156 Kim, Y.I.(2.5)100 Kim, Y.-1. (2.6)114 Kim, Y.4.(2.5) 101 Kim, Z.-H. (1) 21 Kimoto, H. (2.6)88 Kimura, C. (1)28;(2.5)109 Kimura, E. (4)20 Kimura, H. (3)307 Kimura, K. (3)38 Kimura, M.(1) 307;(2.4)58;(3) 522,620 Ihmura, N.(1) 599; (3) 11 Kimura, S.(1) 481 Kimura, T.(2.3)42;(2.4)52 Kimura, Y. (I) 133,668;(2.7)168 Kincaid, J.R (4)44 King, B.W. (2.2)3 I King, N.R (1) 355;(2.4) 16 Kinoshita, H.(3) 120 Kinoshita, K. (1) 645; (3)251, 320 Kipp, R.A. (1) 204 Kira, M.(2.6)340,341;(3)681 Kirby, J.P. (1) 523,546
Kirchoff, M.M. (2.7)147 Kirk, M.L. (1) 67,514;(2.5)295 Kirmaier, L. (2.6)333;(2.7)162 Kirmse, W. (2.7)24 Kirste, B. (1) 5 10;(2.5)70 Kisch, H. (2.5)159 Kishida, H. (3) 338 Kishikawa, K. (2.2)62 Kishore, K. (3)86 Kiszka, M.(2.7) 101,176 Kitamura, A. (2.5) 17,285;(2.6) 6,192 Kitamura, T. (2.4)49 Kitano, H. (2.2)75;(2.6) 1 1 1 Kitayama, T.(3)506 Kitsopoulos, T.N. (2.7)126 Kitsunai, T. (3)5 16 Kityk, I.V. (3)233 Kiu, B.(1) 394 Kiyomori, A. (2.6)208;(2.7)187 Kjaer, K. (2.2)5 Klafter, J. (1) 49 Klan, P.(2.1) 14 Klarner, G.(3)369 Klaus, C.P. (2.6)284 Kleinman, M.H. (1) 662 Klessinger, M. (1) 22;(2.7)2 Kletskii, M.E. (2.6)150 Klevickis, C.A. (1) 30 Kleyn, A.W. (2.7) 107 Klimenko, L.(2.2)128;(2.4)134; (2.5)57 Klishchenko, A.P. (1) 153, 161 Kloffer, M.H. (3)556 Kloosterboer, J.G. (3) 145 Klopffer, M.H.(1) 604 Klossika, J.-J. (2.7)66 Klubeck, P. (3) 41 1 Kneas, K.A. (1) 573 Knight, L.P. (1) 6 Knobbe, E.T.(2.6)56 Knoll, K.(3) 88 Knorr, A. (1) 527;(2.6)264;(3) 421 Knorre, D.G. (2.7)52,53 Knowles, D.B. (2.4)107;(2.6)53 Knox, R.S. (1) 128 Knyazhansky, M.I. (2.4)86, 91; (2.6)48,61,66,67,74,150 Knyukshto. V.N. (1) 218 KO, D.-H. (1) 334 KO, E.S. (2.1)16;(2.5)81 KO, S.-K. (2.7) 138 Kobayakawa, T. (2.4)97 Kobayashi, H. (2.5)145, 167 Kobayashi, K. (2.6)75;(3) 8 Kobayashi, N. (1) 205,210,211, 307;(3) 522
Photochemistry
416
Kobayashi, S. (2.5) 298; (3) 134 Kobayashi, T. (2.4) 64; (3) 736 Kobayashi, Y. (2.7) 82 Koberstein, J.T. (3) 542 Koblik, A.V. (2.6) 67 Kobori, Y. (1) 134; (2.1) 1; (2.5) 45
Kobmna, L.S.(2.1) 74 Kocal, A.V. (4) 73 Koch, H. (3) 709,721,723 Kochetov, D.P.(3) 39 Kochev, D.M.(2.7) 55 Kochi, J.K. (1) 459; (2.2) 120,
121; (2.4) 174,259; (2.5) 47, 50,93,236; (2.6) 195 Kocsk, 0. (1) 458 Koda, T. (3) 333,340 Kodama, H. (2.4) 283; (2.7) 184 Kodymova, J. (1) 375 Kodzwa, M.G. (3) 570 Koeberg-Telder, A. (2.4) 42 Kiihler, G. (1) 138, 145,325; (2.5) 256 Koehorst, R.B.M. (1) 305 Koekler, G. (1) 83 Koerning, J. (2.4) 209 Koga, N.(2.7) 27 Koga, Y.(2.4) 176; (2.7) 5,47, 170,199 Kogelschatz, U. (3) 702 Koh, K. (2.4) 122; (2.6) 50,5 1 Kohara, N.(4) 66 Kohiro, K. (2.5) 228 Kohler, A. (3) 405 Kohler, M. (3) 108 Kohli, J.C.(2.2) 96 Kohmoto, S. (2.2) 62 Kohno, Y. (2.5) 156 Koide, N.(1) 421; (2.4) 168; (3) 513 Koike, A. (1) 63 1; (2.6) 3 17 Koike, K. (2.5) 155 Kojima, K. (3) 551 Kojima, M. (2.4) 283; (2.7) 184 Kojima, R. (2.3) 83; (2.4) 210 Komarudin, D. (3) 363 Komatsu, M. (2.3) 110; (2.7) 140 Kometani, N.(1) 154 Komissarov, V.N. (2.4) 78; (2.6) 65,66 Komiyama, M. (2.6) 85 Konak, C. (3) 297 Konami, H. (1) 205,409; (2.5) 135 Kondo, T. (1) 5 13; (2.5) 110; (3) 579 Kong, F. (1) 84 Kong, Y.-C. (2.2) 38
Konigstein, C. (4) 15 Konishi, G. (2.4) 167; (2.6) 116 KOMO,A. (2.3) 70; (2.4) 60 KOMO,H. (2.5) 155 Konno, K. (3) 48 KOMO,T. (2.3) 62; (2.4) 197 Konstantinov, 1.1. (3) 261 Konya, K. (2.3) 109; (2.7) 141 Kooij, E.S.(4) 72 Kopecek, J. (3) 297 Kopeckova, P. (3) 297 Kopelman, R (1) 477 Kopf, 1. (2.4) 233; (2.6) 283 Koptyug, LV. (1) 243; (2.6) 350 Koput, J. (1) 265; (2.6) 282 Korall, P. (1) 64,66 Korchagina, D.V. (2.3) 100 Koreteev, N.I. (1) 703 Korolev, V.V. (1) 316; (3) 342 Korouji, M. (3) 749 Kombe, 1. (1) 563 Konhak, A.V. (4) 32 Kosa, Cs. (2.3) 4 Koschella, A. (3) 548 Kose, M. (2.4) 122; (2.6) 5 1 Koseki, K. (3) 120 Koshiba, M. (2.6) 160 Koshihara, S. (3) 333 Koshima, H. (2.1) 41,42; (2.3)
113; (2.5) 153,237; (2.6) 127, 128 Kossanyi, J. (2.4) 224; (2.6) 71 Kostarev, K. (3) 238 Kostenko, I.N. (3) 34 Kostromin, S.G. (3) 5 10 Kosynlun, D. (2.4) 259; (2.6) 195 Kotani, S. (1) 449,450; (2.5) 290 Kotera, M. (2.3) 120; (2.6) 139 Kothe, 0. (1) 375 Kotler, 2. (3) 298 Kotsyuba, T.S. (2.5) 40 Kotz, K.T. (2.7) 90 Kotzian, N. (3) 179 Koudoumas, E. (1) 375 Koulikov, S.G. (1) 682 Koussathana, M. (3) 593 Kovacs, I. (2.7) 150 Koval, C.A. (1) 105,606 Koval, V.V. (2.7) 51 Kowalewski, T. (3) 499 Kowalsky, W. (3) 617 Koyanagi, M. (2.7) 122 Koyano, K. (2.5) 165 Koyukshto, V.N. (1) 467 Kotina, O.A. (2.4) 91; (2.6) 61 Koziov, I.N. (1) 161 Kozlecki, T. (3) 3 10 Kozlowski, J. (1) 265; (2.6) 282
Kpissay, A. (2.4) 28; (2.6) 21 Krajnovich, D.J. (3) 700 Kraka, E.(2.7) 19 Kral, A. (2.4) 77 Kramer, A. (1) 630 Kramer, W. (2.2) 107, 108; (2.5) 71; (2.6) 93
Kranzelbinder, G. (3) 380,396, 40 1403
Krasa, J. (1) 375 Krasnaya, Z.A. (2.6) 73 Krasnovskii, A.A., Jr. (1) 203, 315,470
Kraus, G.A. (2.1) 20; (2.5) 63 Kraus, s. (3) 60 Krauser, J. (4) 62 Kravchuk, V.A. (3) 184
Krawiec, M. (2.5) 259 Kreber, C. (1) 27 Kreger, M.A. (3) 378 Krejsa, M.R.(3) 667 Kremer, F. (3) 3 15 Krenn, J.R. (1) 6 10 Kresge, A.J. (1) 275; (2.2) 53, 123; (2.4) 253,264; (2.5) 82, 90; (2.7) 30 Kricheldorf, H.R. (3) 266,325 Krieger, C. (1) 451,506; (2.5) 61, 223; (2.6) 256 K h a k , M. (3) 573 Krishna, M.M.G. (1) 711 Krishnan, V. (1) 476; (3) 507 Krisinel, E. (1) 110 Kristensen, S. (2.6) 248 Kritzenberger, J. (2.7) 11 Krivopalov, V.P. (2.4) 216; (2.7) 57 Krochmal, E.C.(2.2) 95 Kroes, G.-J. (2.7) 116 Kroon, J.M. (1) 305 Krosovskii, V.G. (3) 526 Krueger, M. (1) 347; (2.6) 30 Kruppa, A.I. (2.5) 266 Krystyna, S. (1) 309 Kryukov, A.I. (4) 32 Krzossa, B. (2.7) 24 Kuba!, P. (1) 375,399 Kubin, J. (1) 285 Kubista, M. (1) 618 Kubler, N.(2.2) 69 Kublickas, R. (3) 741 Kubo, A. (1) 262 Kubo, K. (1) 296; (2.1) 65; (2.3) 121; (2.4) 249; (2.6) 160, 164, 229 Kubo, Y. (2.6) 12 Kubota, H. (3) 164,277 Kubota, T. (2.4) 61
Author Index Kuchmii, S.Ya. (4)32 Kuciauskas, D.(1) 431,432.5 19; (2.5)294;(2.6)263 Kudinova, M.A. (1) 343 Kudo, A. (4)35,36 Kudo, K.(2.4)37 Kuech, T.F.(1) 629 Kuehale, W.(1) 660 K h , H.J. (1) 259;(2.1)49 Kuehnle, W.(1) 143, 144,452, 661;(2.5)261 Kuester, J. (1) 336;(2.3)76 Kuhl, C.N.(2.4)28;(2.6)21 Kuhn, A. (2.7)39 Kulak, L.(1) 479 KuldovB, K.(2.6)220 Kulinkin, B.S.(1) 393 Kulowitch, P.J. (3) 355 Kultgen, S.G. (2.3)32;(2.6)90 Kumagai, T.(1) 4%; (2.3)50; (2.5)226 Kumamoto, S. (1) 622 Kumar, A. (2.4) 107, 108;(2.6) 53,233,234;(2.7)153 Kumar, A.S. (1) 506;(2.5)61; (2.6)256 Kumar,J.S.D. (2.5)16;(2.6)5 Kumar, K.R. (2.2)45;(2.5)74 Kumar, S.(2.3)46;(2.6)233,234 Kumazawa, Y. (3)43 Kume, M.(2.3)18;(2.4)116 Kumke, M.U.(3) 545 K u ~ &C.-Y. (1) 179 Kunkely, H. (2.7) 100 Kunyts'ka, L.P.(3) 193 Kunq T.(2.7)1 1 Kunzc, A. (3) 129 Kurt@ P. (2.6)307 Kurdoglyan, M.S. (1) 321 Kurimoto, H. (2.5) 163 Kurita, H. (4)59 Kuriyama, Y.(2.6)317 Kuroda, K.(3)307 K u r d , T.(3)201 Kurosawa, H. (3) 640 Kurosawa, K. (3) 707 Kurreck, H.(1) 510,511;(2.5)62, 70 Kurth, M.J.(3)594 Kusama, H.(4)30 Kushibiki, N.(3)450 Kusukawa, T.(2.6)330;(2.7) 165 Kusumi, A. (1) 645 Kutal, C.(2.7)203 Kutateladze, A.G. (2.1)72;(2.5) 146;(2.6)293 Kuwabara, S. (3) 277 Kuwahara, Y.(2.5)102
Kuzcera, K. (1) 324 Kuzina, S.I.(3) 652,659,661 Kuwnany, H. (3)59 Kuzmin, M.G.(1) 524 Kuz'mitskii, V.A. (1) 108,467 Kumetov, S.V. (I) 121 Kveder, V.V.(1) 388 Kwaitkowski. S.(1) 238 Kwak, I. (1) 264 Kwak, J.C.T. (3)494 Kwei, T.K.(3) 479 Kwock, E.W. (3)392 Kwon, H.C.(3) 572 Kwon, S.K.(3) 686 Kwon, T.S.(3) 43 Kwon, Y.S.(2.5)100 Kyotani, M. (2.4)272;(2.6)295 Kyu, K.(1) 264 Kyushin, S.(2.4)61 Laassis, B. (2.5)288 Laatsch, H.(2.4)77 Lablache-Combier, A. (2.4) 186 Lacey, D. (3)262 Lachicotte, R.(1) 360,581 Lackritz, H.S. (3) 280 Lacoste, J. (2.5)204;(3) 689,773 L a d o m S. (2.7)83-85 Lahav, M. (2.2)5 Lahlou,S.(2.6)129 Lahmani, F.(1) 271;(2.1)23; (2.4)63 Lahti, P.M. (2.3)56;(3) 737 Lai, C.-Y. (2.7)92 Lai, Y.C.(3) 79 Laiblc, P.D.(1) 128 Lakowicq J.R. (1) 101,586,635, 700
Lal, T.K.(1) 61 Lam, B.V.(2.5)213 Lam,J.Y.L. (2.3)85 Lamare, V.(2.4)38 Lambert, H.M.(2.7) 130 Lance, M. (2.4)38 Land, E.J. (1) 381,412 Lang, A. (2.7)10, 1 1 Lang, J. (3) 544 Lan& K. (1) 375,399 Lang,M.J.(1) 294 Lange, 0.(3)179 Langer, K.(4)13 Langer, R.(3)228 Lan&ord, C.H.(2.7)74 Langford, S.J.(2.5)103 Langsdorf, B.L.(3)744 Lantukh, Y.D. (1) 129 Lanq M.(4)33
417 Lanzalunga, 0. (2.5)299 Lanzani, G. (1) 338;(3)375,396 Lao,X.-F. (2.5) 133 Laplazc, D. (2.5)193 Lapouyade, R.(1) 146, 147, 162; (2.5)258 Lara, H. (3) 19 Lany,B. (1) 283;(2.4)65 Larsen, S.C.(2.5)201 Larson,C.L.(3) 529 Laschewsky, A. (3)504 Latli, B.(2.7)28 Latowski, T. (2.4)261 Latterhi, L.(1) 367,368;(2.3)1 1 Lattes,A. (2.2)21 Laukhina,O.D.(1) 369;(2.4)22, 23 Launay, E. (3) 399 Launikonis, A. (1) 486 b u r n t , C.(3) 328330,357 Laurent, T.(2.7)67, 131, 132 Lauricella, R. (2.4)83 Launch, B.K. (3) 381 Launch, C. (1) 259;(2.1)49 Lavabre, D.(2.6)70 Lavallee,R.J. (2.7)203 Lawson, E. (1) 611 Lawson, G.E. (1) 394;(3) 51,553; (4)46 Lawton, J. (3) 202 Lawton, R.G. (1) 544;(2.5)255 Lazzaroni, R.(3) 374 Leaback, D.H. (1) 689 Leach, M.J. (1) 596;(3)577 Leach, S.(1) 412 Leadbeater, N.E.(2.7)86,87, 104, 105 Leal, P. (2.3)23 Lebaudy, P. (3) 190 Leboulaire, V. (1) 412 Lebrun, C. (2.5)280 Lebrun, M.(2.5) 193 Lecamp, L. (3) 124, 161,190 Leclerc, M.(3)452,45547 Leclercq, P.(3) 1 1 1, 183 M e , J. (4) 14 Lednev, 1.K. (1) 561;(2.6)14, 266; (3)316 Lee, B. (2.7)73;(3) 514 Lee, B.A. (2.5)114 Lee, B.E. (1) 191 Lee, B.I. (1) 157 Lee,C.H. (3) 388 Lee,C.-S. (2.2)60 k, C.T. (1) 628 Lee, D.K.(2.5)100 Lee, H . 4 . (2.5)246 k, H.-J. (2.4)87
418 Lee, H.R.(3)82 Lee, H.S.(3)230 Lee, J. (2.5)247;(2.6) 177 Lee, J.H. (3) 443 Lee, J.I. (3)436 Lee, J.K. (1) 297 Lee, J.W. (4)4,80 Lee, K.(3) 560 Lee, K.H. (3) 390 Lee, K . 4 . (2.2)81 Lee, M. (1) 445 Lee, R.E.(3) 777 Lee, S. (1) 93,300 Lee, S.B. (3) 464 Lee,S.J. (2.2)49;(2.6)238;(3) 435 Lee, S.-K. (1) 579 L ~ cS.-Y. , (1) 191;(2.5)114 Lee, W. (2.5)22;(2.6)2;(2.7)49 Lee, W.W.-S. (1) 592 Lee, X.-Y. (4)68 Lee, Y.B. (3) 669 Lee, Y.H. (1) 445 h e , Y.-R. (2.7)137 Lee, Y.S.(2.2)70;(2.4) 147;(2.6) 117 Lee, Y.T. (2.2)54;(2.3)39;(2.7) 118, 134,136,152,188 Leeper, F.J. (2.6)40 Lee-Ruff, E.(2.1)73 Lees, A.J. (2.7)95,96;(3) 35 Lefevre, J.P. (1) 559
Photochemistry
(2.5)254;(2.6)144,231;(3) 188,270,279,747;(4) 12,24 Leonenko. Z.(2.2)128;(2.4)134; Li, Z.(1) 372,543;(2.5)33;(2.6) (2.5)57,88 253;(3) 187,552,690 Leonov, A.G. (1) 102 Li, Z.C.(3)478,555 Leopold, D. (1) 215 Lian, 2.R (1) 400,401;(2.5)199, Jqlyanin, G.V.(3) 234 200 Lemer, N.(1) 179 Liang, K.K. (3) 390 Leshina, T.V.(2.5)266 Lianos, P. (3) 593 Leszek, L. (1) 309 Letard, J.-F. (1) 146, 147;(2.5) Liao, C.C. (2.2)8 1 258 Liao, F.-L. (2.2)68;(2.6)87 Liao, X.(3)372 Leung, M.K. (3)390 Liashik, O.T. (2.6)48 Leupold, D.(1) 56 Liauw, C. (3)783 Levadou, F. (3) 735 Liaw, D.J.(3)480 Levai, S.(3) 67 Levanon, H.(1) 402;(2.5)132 Libusa, S.(1) 699 Liddell, P.A. (1) 431,432,470, Levell. J.R. (2.4)104, 109;(2.6) 64 509,520;(2.5)294 Lieb, M.A. (1) 177;(3) 566 Lever, M.J. (1) 644 Levesque, I. (3)456,457 Liebemm, S.H. (1) 583 Levinson, E.G.(1) 467 Lifka, T.(2.3)14;(2.4) 125;(2.6) 42 Levshin, L.V. (1) 129 Levy, D.H. (1) 139 Likhitvorik, I. (2.7) 147 L.cvy, H.(1) 593 Likhtenshtein, G.(1) 358;(2.3)6 Levy, R. (1) 651 Lillo, A. (1) 62 Levy, Y. (2.3)17;(2.4)124 Lim, D.(2.4)269;(2.6)213 Lew, C.S.Q. (2.3)57 Lim, G.4. (2.7)13 Lewis, A. (3) 408 Lim, H. (2.3)66;(2.4) 162, 163 Lewis, F.D. (1) 148,436,541; Lim, K.-S. (4)54.55 (2.3)31.32; (2.4)18;(2.5) Lim, S.-M. (2.7)13 268;(2.6)89,90,252 Lim, S.Y. (4)37 Lewis, J. (2.7)86,87, 104, 105 Lima, J.C. (1) 124 Lefrant, s.(3) 335 Lex, J. (1) 214;(2.2)107;(2.5) Lin, C.-H. (2.2)71 Legay-Sommaire, N . (2.7)200 71;(2.6)126 Lin, C.-T. (2.1)62;(2.3)91;(2.6) LeGrange, J.D. (3) 263 Ley, K.D. (3)602 98 Lehmann, F. (1) 564 Leyva, E.(2.6)197 Lin, E. (2.5)188 Lehn, J.-M. (2.3)17;(2.4)124; Lhomme, J. (1) 620 Lin, H.(2.7)120 (2.6)220 Li, B. (2.2)65;(2.6)175 Lin, H.M. (3) 654 Lehnberger, C. (2.4)241;(2.6) Li, C. (2.5)238;(4)63 Lin, J. (3) 780 132 Li, F. (1) 464;(3) 44,552,555, Lin, K.F. (3) 543 Lehnert, B.E.(1) 653 599,690 Lin, L.B. (3)447,449 Lehnert, N.M. (1) 653 Li, F.M. (3)478 Lin, L.R (1) 184;(3)474 Lei, 2. (3) 467,536,621 Li, G.(1) 678;(2.5)52;(3)545 Lin, N.Y. (1) 400,401;(2.2) 127; Leidennan, A.Yu. (4)5 1 Li, H.(3) 747 (2.5)199,200 Leigh, W.J. (2.3)68,69;(2.6) Li,J. (2.5)270;(2.6)105;(3) 461 L q S.(1) 509,519,520;(2.6) 326-328,332;(2.7)155-157 Li, L.R (3)550 263 Leinweber, D. (2.1)36;(2.4)265; Li, M. (1) 213;(3) 94, 110,488 Lin, S.H.(2.7) 118, 119;(3) 390 (2.7)71 Li, M.-F. (2.5)177 Lin, S.-J. (2.4) 182,223;(2.6) Leiserowitz, L. (2.2)5 Li, Q.(2.5)188;(3) 305,500 193, 194;(2.7)16-18 Lcising, G. (3) 335, 375,379,380, Li, S.(1) 543;(2.5)33, 220,279; Lin, S.-M. (2.7)137 391,396,400-403,420,442, (2.6)253 Lin, T.-C. (1) 28 1 561 Li, T.J. (3)336 Lin, W.(3) 305 Leitner, A. (1) 610 Li, W. (3) 618 Lin, W.-Y. (1) 183 Leitner, M.B.(2.7) 10 Li, W.L. (3)622 Lin, W.Z. (1) 400,401;(2.5) 199, Lemmetyinen, H.(2.4)185 Li, X. (1) 575;(2.5)69,188;(2.6) 200 Lemp, E.(2.5)253 144 Lin, Y. (3)204,655 Lendelein. A. (3) Li. X.C.(3)444 Lin, Y.C.(3) 727 .~551.558 Leo, K. (4)61 Li; Y. (lj223;(2.3)98;(2.4)220; Lin, Y.-N. (2.6)221 ~
Leon, J.W. (3) 523
Author Index Lin, Y . 4 . (2.4) 182,223; (2.6) 193, 194; (2.7) 16-18
Lin, 2. (1) 303 Lindauer, H.(1) 160 Lindeman, A.V. (2.6) 100 Lindeman, S.V. (1) 459; (2.2) 121; (2.4) 174 Lindemann, U.(2.1) 27; (2.6) 83 Linden, L.(3) 157 Lindford, B.E.(3) 748 Lindsey, J.S. (1) 464466 Linchan, J.C. (2.7) 89 Ling, Z. (3) 110 Linke, E.(2.1) 63 Linker, T. (2.5) 219 Linkous, C.A. (4) 45 Linschitz, H. (1) 405 Lion, C. (2.3) 97; (3) 549 Liorhelli, M. (1) 558 Liou, W.S.(1) 638; (3) 366 Lippitsch, M.E. (1) 564,647 Lippuner, V. (2.4) 263 Lisch, D.(2.2) 83 Litchford, R.J. (1) 588 Litt, M.H. (3) 260 Litter, M.I. (2.5) 176 Liu, B.-J. (2.5) 161; (3) 553,596 Liu, C. (2.5) 286; (3) 681 Liu, D. (I) 416; (2.5) 143,283 Liu, E.(1) 206; (2.5) 175 Liu, G. (3) 206,590 Liu, H. (3) 131, 159, 166 Liu, J. (1) 629 Liu, R.H. (2.2) 93 Liu, T.J. (3) 348 Liu, W.(2.1) 44; (2.4) 266 Liu, W . 4 . (2.1) 5 1,52 Liu, X.(3) 552 Liu, Y. (3) 44,747 Liu, Y . 4 . (2.2) 65; (2.5) 171; (2.6) 175 Liu, Z.F. (2.6) 34 Liuui, R.(1) 209; (2.5) 178 Livshits, V.A. (2.4) 72; (3) 619 Liwo, A. (2.5) 23 1 Ljalin, G.(3) 714 Lluch, J.M. (1) 327; (2.2) 85 Lobovsky, E.B.(2.2) 6 Lochbrunner, S.(1) 339; (2.3) 86, 87 Lochon, P.(3) 491,501,591 Loehmannroeben, H.G.(1) 336, 453; (2.3) 76 Lohden, G. (3) 125 Lokshin, V. (2.4) 82,88; (2.6) 53, 60 Long, C. (2.6) 322; (3) 95 Lon& T.M. (1) 148
419
Long, 2.-Y. (2.4) 128 Longfellow, C.A. (2.7) 152 Longin, T. (1) 105,606 Lopez, J.C. (2.2) 42 Lopez Arbeloa, F. (1) 22 1 Lopez Arbeloa, I. (1) 22 1 Lopez Arbeloa, T. (1) 22 1 Lopez-Cornejo, P. (1) 217 Lorenc, L. (2.6) 201 Losev, A.P. (1) 3 10,508; (2.5) 60
Lott,K.A. (2.7) 102
Lou, N.Q. (2.7) 143 Loukas, Y.L. (3) 471 Lovering, F.E.(2.7) 34 Lovillo, J. (1) 598 Lozano,A.E. (3) 83 Lozinskaya, E.I. (3) 286 Lozovskaya, E.L. (2.5) 265 Lu, H.-L. (1) 3 12 Lu, J. (2.5) 123 Lii, M. (2.6) 226 Lu, T. (2.5) 52 Lu, Y.(2.6) 268 Lu, Z. (2.5) 291 Lub, J. (3) 5 19 Luboradzki, R. (1) 145 Lucas, M.A. (2.6) 352 Luccioni-Houze, B. (2.4) 83 Lucia, L.(2.6) 178; (2.7) 196 Liithi, H.P. (1) 341; (2.3) 2; (2.4) 25; (2.6) 20
Luettke, W.(2.4) 204 Luftmann, H.(2.5) 195 Luftmano, H. (1) 376 Lukac, I. (2.3) 4 Lukjanetz, E.A. (1) 2 12 Lukyanov, B.S.(2.4) 91; (2.6) 61 Lukyanov, S.M.(2.6) 67 Lunedei, E.(3) 468 Lungu, v. (3) I12 Luo, C. (1) 419 LUO,J.-K. (2.4) 229; (2.6) 77 Luo, L.B.(1) 678 Luo, M. (3) 540 Luo, X.(1) 482 Luo, Y.(2.6) 34 Lusis, V. (2.5) 266 Lustig, S.R(2.2) 40; (2.5) 3 1 Lusztyk, A.J. (2.7) 3 1 Lusztyk, J. (2.2) 93; (2.4) 254 Luthem, J.J. (2.4) 112 Lux, A. (3) 405 Luzati, S.(3) 465 Luzina, O.A. (2.3) 100 Lyashkevich, S.Yu. (2.4) 185 Lymar, S.V.(1) 535 Lynch, M.A. (2.7) 40,48 Lynch, V. (2.4) 236
Lyoo, W.S.(3) 66 Lyris, E. (4) 17 Lytle, F.E.(I) 637
Ma, B. (3) 51; (4) 46 Ma, J . 4 . (1) 534
Ma, J.H. (2.2) 93 Ma, L.(3) 618 Ma, Y.A. (2.5) 190 Ma, Z. (3) 433 Maafi, M. (2.3) 97; (2.5) 288; (3) 549
Maas, G.(2.6) 348 Mac, M. (1) 489 McAllister, M.A. (2.2) 93 McAlpine, F. (2.7) 40 Ma~anita,A.L. (1) 124,267 McArdle, C. (3) 133 McAvoy, C.(2.4) 80; (2.6) 18 McCabe, RW.(2.4) 44; (2.6) 298 McCafftey, J.G.(2.7) 200 McCarry, B.E.(3) 118 Macciantclli, D. (2.4) 83 McCleskey. T.M. (1) 525 McCormick, C.L. (3) 477,611 McCoy, C.P. (1) 5 1,555 McCue. J.T. (2.5) 214 MacDiarmid, A.G. (3) 447,449 MacDonald, P.J. (1) 197 McFaillsom, L. (2.2) 131 McFarlane, K.L. (2.7) 73,88 McGany, P.F.(I) 243; (2.6) 350 McGarvey, D.J. (1) 209; (2.5) 178 McGimpsey, W.G.(2.1) 60 McGown, L.B. (1) 5; (3) 545 McGrath, D.V. (3) 53 1 Machado, R (2.2) 99; (2.4) 171; (2.6) 35 1
Machara, M.P. (1) 180 Machida, K.-I. (4) 56 Machi&, S.(3) 703,706 Maciejewski, A. (1) 196,265; (2.4) 251; (2.6) 282
McIlroy, S.(2.3) 94; (2.5) 192 Mchskey, D. (I) 646 McIntyre, RB. (3) 666,784 McKay, S.E.(2.2) 17 McKeever, S.W.S. (1) 4 McKerlie, L.A. (2.2) 27 McLauchla~~, K.A. (1) 3 M a c w P.J. (1) 329 McManus, K.A. (2.3) 27; (2.4) 178; (2.6) 169
McNamara, K.P. (1) 575 McNiven, S.(2.5) 101 Macphail, M. (1) 61 1 Macpherson, A.N. (1) 509,520
420 McSweeny, J.D. (3) 716,717 Maeda, K. (2.5) 48; (2.7) 193 Maeda, M. (2.2) 75; (2.6) 111 Maeda, T. (1) 623 Maeda, Y.(2.2) 75; (2.6) 111; (2.7) 177
Maehara, M. (2.6) 267 Miintele, W.(2.7) 177 Maestri, M. (1) 258.570; (2.4) 126
Magaginini, P.L. (3) 261 Magdinets, V.V. (3) 37 Maggini, M. (1) 415,418,422426; (2.5) 10, 136, 137
Magnes, B.-2. (1) 294,295 Magnitskii, S.A. (1) 703 Magnus, P. (2.4) 236 Magnuson, A. (1) 60 Mah, S. (3) 42 Mah, Y.J. (2.2) 117 Mahabir, C. (3) 186 Mahal, L.K. (3) 80 Mahedero, M.C. (2.5) 288 Mahuzier, G. (1) 649 Mai, J.C. (2.3) 52; (2.4) 127 Maier, G. (2.1) 38 Mail, V.P. (2.1) 59 Mailyan, K.A. (3) 350 Mair, H.J. (3) 453 Maiti, M. (2.5) 273 Maiti, N.C. (1) 306,711 Majidi, V. (1) 648 Majima, T. (2.3) 83; (2.4) 210; (2.5) 239; (2.6) 346
Makareyeva, E.N. (2.5) 265 Makarova, N.I.(2.4) 86; (2.6) 74 Makedonov, Yu.V. (2.5) 265 Maki, S. (2.3) 71; (2.6) 172 Makino, T. (2.4) 20 Maksakova, G.A. (2.7) 5 1,53 Malak, H. (1) 635 Maldivi, P.(3) 264 Maldotti, A. (2.5) 189 Male, J.L. (3) 748
Mali, V.P. (2.4) 46
Maliakal, D. (2.3) 48; (2.4) 54; (2.6) 153
Malik, R. (3) 127 Malinen, P.K.(2.2) 126; (2.5) 292; (2.6) 258
Malliaris, A. (1) 337; (2.3) 77; (3) 528
Mallouk, T.E. (1) 533 Malnen, P.K.(1) 505 Malucelli, G. (3) 215,231 Malysheva, E.V. (2.6) 100 Mamaev, A.L. (1) 3 16; (3) 342 Mamatyuk, V.I. (2.4) 216; (2.7)
Photochemistry 57
Man, J. (3) 743 Mancheno, M.J. (2.4) 56
Mandal, D.(3) 575 Manfrin, M.F. (1) 44 Mangani, L. (3) 360 Mani, R.(3) 656.78 1
Manley, R.S. (3) 718 Mann, J. (2.2) 43.44 Manoj, N. (1) 494; (2.5) 150 Manon, S.K.(1) 228 Manriquez, M.E. (2.5) 154; (2.6) 3 16 Mansour, M.A. (1) 58 1 Mantecon, S.(2.2) 42 Manz, B. (2.6) 348 Mao, M.S.H. (3) 432 Mao, Y. (2.5) 218 Mao, Z. (3) 116,126 Marangoni, D.G. (3) 494 Maras, A. (2.5) 208 Maratti, S.C. (3) 360 Marchand, A.P. (2.2) 16 Marchi, C.M.(1) 597 Marchon, J.C. (3) 264 Marcinek, A. (2.7) 20 Marciniak, B.(1) 268,437; (2.5) 36,39 Marcani, G. (1) 41, 195,368; (2.1) 47; (2.3) 11; (2.5) 97; (2.6) 304 Marmni, M.C. (1) 673 Marcat, L. (3) 264 Marcus, RA. (1) 85 Mardirosjan, 2. (2.5) 263 Mardykin, V.P. (3) 760,761 Marevtsev, V.S. (2.4) 90; (2.6) 59 Margaretha, P. (2.2) 12, 15,23, 28,57; (2.4) 233; (2.6) 4, 113, 119, 123,133,283-285 Mariano, P.S. (2.2) 104; (2.4) 218; (2.6) 92 Mariatti, S.C. (3) 377 Marino, T. (3) 112 Marion, P. (3) 485,544 Marion, T. (3) 140 Markarayaq Sh.A. (2.1) 7 Miukarova, E.A. (1) 2 12 Markava, E. (1) 35 1;(2.4) 32 Markovskii, O.L. (1) 130 Marks, D.(1) 292,293 Marquet, A. (2.7) 35 Maquet, J. (1) 200 Marquis, D. (2.3) 3 Marsau, P.(2.6) 130 Marsella, M.J. (3) 449 Marshall, G.P.(3) 649 Marsmann, H.(2.6) 333; (2.7) 162
Marti, V.(2.5) 230 Martin, A. (2.2) 16 Martin, F. (2.3) 17; (2.4) 124 Martin, M.M. (1) 244 Martin. M.T. (1) 709 Martin, N. (2.3) 72.73; (2.5) 121,
169; (2.6) 155, 265,266; (3) 4 14 Martin, R.E. (1) 34 1; (2.3) 2; (2.4) 25; (2.6) 20 Martinez, C.I. (2.6) 215 Martinez, L.J. (1) 246; (2.1) 46 Martinez-Diaz, M.V. (1) 5 17 Martinho, J.M.G. (1) 9, 103; (3) 609 Martini, I. (2.5) 235 Martino, D.M. (2.5) 115 Martinsen, B.K.(2.6) 243 Martyanov, I.N. (2.5) 264 Marubayashi, N. (2.2) 13, 14; (2.4) 238,239; (2.6) 108, 110 Marudachalam, M. (4) 67 Marumo, S.(1) 521 Maruo, S.(3) 237 Maruyama, T. (3) 363,439 Maruyama, Y. (3) 562,565 Manr, D. (1) 99 Mam, P.(3) 17 Mary, D. (3) 328,357 Masaaki, H.(2.5) 270 Masartensson, J. (1) 64 Mascharak, P.K. (2.5) 191 Masilamani, V. (1) 227 Maskus, M. (3) 523 Maslyuk, A.F. (3) 141,226 Mashes, F. (3) 328-330,357 Masterson, M. (3) 133 Masuda, H.(3) 438 Masuda, S.(3) 746 Masuda, T. (3) 454 Masuhara, A. (1) 383; (2.5) 126 Masuhara, H.(1) 149; (2.3) 113; (2.5) 257; (2.6) 128 Mataga, N. (1) 54,449,450,521. 530; (2.5) 290 Mataka, S. (2.2) 8 Mam, J.L. (3) 83, 165 Mateo, M.E. (2.6) 76 Materny, A. (2.7) 127 Mathur, A.M. (3) 587 Matisova, G.(1) 351; (2.4) 32 Matsubayashi, K.(2.1) 48; (2.6) 249 Matsuda, S.(4) 69 Matsuda, T.(3) 272 Matsuda, Y.(3) 564 Matsugo, S.(1) 256; (2.2) 109; (2.5) 86; (2.6) 94
Author Index Matsui, M. (1) 28,504;(2.5) 109 Matsui, S.(3) 221,240 Matsuishi, K.(1) 390
Meghdadi, F.(3) 380 Megimpsey, W.G. (1) 266 Meier, T. (2.7)177 Matsumoto, A. (3) 15 Meijer, E.W.(3) 525 Matsumoto, H.(2.4)61;(2.5) Meiklyar, V.(1) 402;(2.5)132 161;(2.6)290 Meille, S.V.(3) 764 Matsumoto, M. (2.4)142 Meister. E.C.(1) 341;(2.3)2; Matsumoto, S.(2.2)52 (2.4)25;(2.6)20 Matsumoto, T. (1) 233;(2.6)38; Meistermann, L.(3) 495 (3) 201 Meixner, A.J. (I) 177;(3) 566 Melchior, A. (2.7)133 Matsunaga,D.(1)211 Matsuno, H.(3) 707 Mella, M. (1) 463;(2.2)48,98; Matsuo, K. (2.2)24 (2.5)184;(2.6)142,230,324; (2.7)166 Matsuo, T. (2.5)102, 123 Matsuo, Y. (2.5)105 Meller, R. (2.7)190 Matsusaki, K.(2.5) 105 Mellinger, A. (2.7)61 Matsushita, S.(3) 120 Mel'nikov, G.V.(1) 129 Matsushita,T. (2.7)21 Mel'nikov, M.Ya. (2.1)3 Matsuum, T. (2.1)41,42;(2.3) Mel'nikova, O.L.(2.1)3 113; (2.5) 153,237;(2.6)127, Melo, E.C. (1) 124 Melo, M.J. (1) 258;(2.4)126 128 Matsuzaki, A. (1) 659;(2.4)73 Melton, L.A. (3) 352 Matsuzawa, Y.(2.4)37 Melzig, M. (2.4)110,1 1 1; (2.6) Matiay, J. (1) 376;(2.4)165;(2.5) 53 129, 195;(2.6) 140, 141;(4) Memarian, H.R.(2.4)158;(2.6) 13 107 Mattice, W.L.(3)603 Menchikova, G.N. (2.5) 152 Mattinen, J. (2.6)250 Meng, J.-B. (2.4)102 Mattson, G.A. (3) 76 Meng, X.J. (2.6)56 Mattson, J. (3) 142 Mennig, M. (3) 294 Matusche, P.(3) 58 Menzel, H. (3) 3 12,313 Matzger, A.J. (4) 19 Menzer, S.(1) 517 Matzinger, S.(2.7)15 Merchb, M.(2.4) 192;(2.6)206; Mau, A.W.-H. (1) 486 (2.7)109 Mauermann, P. (4)27 Mercier, R.(3) 227 Maupin, C.L.(1) 681 Merkle, G. (3) 588,589 Mautette, M.-T. (2.1)45 Meshkov, B.B.(2.4)72;(3)619 Mauriello, G. (2.4) 184, 189;(2.6) Meshulam, G.(3) 298 235,236 Meskers, S.C.J. (1) 681 Mayer, Y .H. (I) 244 Metcalf, D.H. (1) 33 Mayer-Figge, H.(2.4)201 Metelitsa, A.V.(2.4)91;(2.6)48, Mayo, J. (1) 210 61,66,67,150 Mayoral, E.P.(2.4)56 Meuwis, K. (1) 562 Mayoux, C.(3) 330,357 Meyer, A. (2.3)5 Mazaheri, F.M. (3) 797 Meyer, G.J. (1) 548 Mazerolle, L. (3)455 Meyer, K.E. (3)355 Mazor, R. (3)298 Meyer, 0.(I) 609 Mazumdar, S.(1) 306 Meyer, T.J. (1) 119,488,526,551 Mazzocchi, P.H.(2.5)120 Meyer, W.H. (3) 481 Mazzucato, U.(1) 368;(2.3)1 1 Mialocq, J.4. (1) 225 Meador, M.A.B. (3)207 Miao, Y.J. (1) 360 Meadow, M.A. (3)207 Micallef, A.S. (2.6)228 MeaIlier, P. (3) 795 Michaeli, S.(1) 402;(2.5) 132 Mebel, A.M. (2.7)118, 119 Michaelis, K.-P.(2.2)83 Medeiros, D.R. (2.6)3 1 1 Michaelis, P.(3) 776 Medicuti, F. (3) 603 Michalak, J. (2.7)20 Medyantseva, E.A. (2.6)48 Micheau, J.C. (2.6)70 Meeroff, D.E.(2.2)17 Michelet, V.(1) 560
42 1 Michl, J. (2.7)1 Micka, Z, (2.5)174 Middleton, J.C. (3) 667 Migler, K.B.(1) 590 Mihailovik, M.Lj. (2.6)201 Mihalcea, T. (3) 625 Mihara, T.(3) 513 Mijuno, M. (3) 2 Mikami. K. (1) 404;(2.2)52; (2.5) 128, 131 Mikes, F. (3) 606 Mikhailov, A.I. (3) 652,659,661 Mikhailovskii, Yu.K. (2.4)81 Mikhalevkin, A. (3) 714 Miki, S.(1) 260; (2.4)161 Mikkelsen, K.V.(1) 3 1 1 Milewski, M. (1) 196;(2.4)25 1 Miller, B. (2.5)39 Miller, C. (3) 77 Miller, C.W. (3) 219 Miller, D.O.(2.4)273;(2.6)277 Miller, E.K. (3) 560 Miller, E.R. (3) 729 Miller, J.R. (1) 2;(2.5)30 Miller, M.(3) 14 Miller, RD.(3) 369 Miller, T.M. (2.5)203;(3)263, 392 Mill% M. (2.6)246 Millie, Ph. (2.5)27 Millov, A.A. (2.6)150 Mills, A. (1) 577 Mimura, M. (1) 46 Mimuro, M. (1) 483 Min, C . 4 .(2.5)58,59 Minai, Y. (3) 613 Minakova, R.A. (1) 235 Minami, H.(2.4)57 Minami, N.(3) 358 Mmmishin, H. (2.2)20 Mineda, K.(1) 677 Minegishi, T.(2.3)70;(2.4)60 Minematsu, T. (2.3)42;(2.4)52 Minematu, Y.(3) 640 Mineo, M. (2.3)102 Ming, Y.(2.4)84;(2.6)41, 143; (3) 326 Minihan, A. (3) 783 Minkin, V.I. (2.3)95,96;(2.4)40, 78.91;(2.6)48,61,65-67;(4) 25 Minoli, G.(2.4)255;(2.6)196; (2.7)41 Minoshima, K. (1) 162 Minto, F. (3) 742,778 Miolo, G.(2.6)286 Mir, M. (1) 196,200; (2.4)251 Miranda, M.A.(2.2)84;(2.3)23-
Photochemistry
422
25, 109;(2.4)206,247,267; (2.6)304;(2.7)141 Mirochnik, A.G. (3)6 15 Mironov, A.E. (1) 467 Misetic, A. (2.3) 115 Mishima, T.(3)622 Mishra, H.(1) 270 Mistry, B.B. (3)296,324 Mitani, H. (2.5)216;(3) 791 Mitani, T.(1) 387 Mitchell, A.C. (I) 695 Mitchell, G.R.(1) 355;(2.4)16 Mitchell, R.H. (2.4)42 Mitina, V.G.(1) 279;(2.6) 147 Mitra, S.(1) 194 Mitsopoulou, C.-A. (4) 17 Mitsuhashi, M. (1) 621 Mittal, J.P. (1) 291,382,413,414, 417,493;(2.5)151,222;(2.6) 342;(2.7) 153 Miura, M. (1) 534 Miyagawa, H. (2.4)48 Miyagawa, N. (2.5) 17,285;(2.6) 6, 192 Miyagawa, T. (2.2)97;(2.5)77; (2.6)276 Miyagishi, K.(1)7 10 Miyagishi, S. (3) 583 Miyahara, I. (2.3) 113;(2.5)237; (2.6) 128 Miyajima, M. (3)267 Miyake, Y. (2.4)93;(2.6)57 Miyasaka, H. (1) 449,450;(2.5) 141,290;(3)600 Miyashi, T. (1) 498;(2.3)70; (2.4)60 Miyata, K.(2.6) 85 Miyazaki, M. (2.7)36 Miyazawa, T.(3) 681 Mizoguchi, H.(1) 296 Mizukami, T.(2.3)79 Mizumo, T.(2.5)163 Mizuno, K.(1) 47;(2.4)4, 167, 268;(2.5)123;(2.6)91.97, I I6 Mizutani, H. (2.3)113;(2.6)128 Mo, D.(3)305 Moad, G.(1) 602 Mobius, D.(1) 709 Mobius, K.(1) 402,5 1 1 ;(2.5)62, 132 Mochida, K. (2.6)337,338,341; (2.7)163 Mochida, Y. (3) 270 Modigell, M. (4)78 Moehwald, H.(1) 1 14;(3)490 MBller, S. (2.6)280 Moggi, L.(1) 44
Mogi, K.4. (2.6)317 Mohamcd, M. (2.6)320;(2.7) 167 Mohammad, T. (2.4)28;(2.6)21 Mohan, H.(1) 382,413,414,417; (2.5) 151 Mohanty, D.K. (3) 185 Mohlebach, A. (3) 198 Mohr, G.J.(1)564 Mol, G.N. (3)519 Mol, T.(3)264 Molin, Y.N.(1) 25 Molinari, A. (2.5)189 Molko, D.(2.5)28 1 Mollay, B.(3)379 Moller, B.(3) 198 Moller, S.(1) 280 Molokov, I.F. (2.4)245 Moloney, J.M. (1) 35 Molski, A. (1) 696 Momicchioli, F.(2.6)73 Momoda, J. (2.4)97, 105 Mondini, S.(1) 418,425,426; (2.5) 10, 136, 137 Monecke, P. (3) 105 Monier, C. (4)60 Monjol, P. (3)200,227 Monjushiro, H. (1) 550 Monkman, A.P. (3)446 Monnerie, L. (1) 604;(3)556 Monney, L. (3)670 Monobe, H.(1) 631 Monosov, R. (2.2)95 Montejano, H.A. (1) 1 18;(2.5) 149 Monti, D. (1) 469 Monti, S.(1) 195,446;(2.1)47; (2.5)97;(2.6)304 Moon, J.T. (2.2)38 Moon, Y.(3) 712 Moore, A.J. (2.5)121;(2.6)265, 266 Moore, A.L. (1) 430,432,470, 509,519,520;(2.5)294;(2.6) 263 Moore, B.D. (1) 127 Moore, C.B. (2.7)61 Moore, H.W. (2.2)124;(2.4)207 Moore, J.N. (1) 561;(2.6)14, 266;(3) 316 Moore, J.S. (1) 477;(3)524 Moore, M.J. (3) 112 Moore, T.A. (1) 430432,470, 509,519,520; (2.5)294;(2.6) 263 Moorfield, C.N. (3)530 Moojani, S.K.(3) 167 Moorlag, C.P. (I) 269 Moortgat, G.K. (2.7)190
Moorthy, J.N. (1) 441;(2.5) 118, 119;(2.6) 189, 190 Moradian, S. (3) 797 Morais, A.L. (3)715 Moran, RJ. (2.4)194 Moratti, S.C. (3)372,440,444 Moravsky, A.P. (3)354 Morawski, 0.(1) 143;(2.5)26 1 Mordaunt, D.H.(2.7)62 Mordzinski, A. (1) 139 M o m , L.(3)672,673 Morel, I).(4)67 Morel, F. (3)77, 174 Moreno, M. (1) 327;(2.2)85 Morgan, C.G.(1) 695 Mori, A. (2.2) 1, 133, 134 Mori, H.(2.5) 158,206 Mori, Y.(2.7) 144; (3)620 Moriatti, S.C. (3)405 Morii, H. (1) 333;(2.3)78 Morimoto, H.(2.7)28 Morino, S.(1) 603;(3)319,320 Morishima, Y.(1) 40;(2.5) 1 1 1; (3) 100 Morita, A. (1) 713 Morita, H.(2.4)272;(2.6)295 Morita, M. (2.2)24 Morita, T.(1) 481 Morita, Y.(3)275 Morita, Z.(3)800 Moriwaki, H. (2.5)15 Moriyama, M. (2.I ) 56;(2.2)100; (2.6)148;(2.7)70 Morizane, K.(2.4)49;(2.6)302 Morlet-Savary, F.(1) 233;(3)36 Moro, S.(2.6)286 Moroder, L. (1) 347;(2.6)30 Morokuma, K.(2.7)60.65, 117 Morozov, S.V.(1) 316 Morozov, V.A. (1) 91,697 Morozova, O.B. (2.1)12 Morozumi, T.(1) 352;(2.4)34; (2.6)32 Moms, D.G.(1) 248,657;(2.1)4; (2.5)43 Moms, J.C. (2.4)236 Morrison, H. (2.2)64;(2.4)28; (2.6)21,268 Mortellaro. M.A. (1) 582 Mortensen, A. (1) 434 Morwood,M.(1)611 Moses, D.(3)388 Mosingcr, J. (2.5) 174 Moss, J.A. (1) 526 Moss, RA. (2.4)36;(2.6)37 Mossler, H.(1) 51 1; (2.5)62 Moszner, N.(2.3)4;(3)205 Motherwell, W.B. (2.4) 193
Author Index Motoyama, T. (3) 10 Mouanda, B. (3) 64 Moudjoodi, A. (2.4) 114; (2.6) 296
Mouli, N. (2.5) 49 Mwlik, S.P.(1) 490 Moullet, M. (3) 795 Mouradzadegun, A. (2.4) 114; (2.6) 296
Moutiez, E. (1) 649 Muccini, M. (3) 468 Muceniece, D. (2.5) 266 Muellen, K.(1) 301; (3) 381,396 Mueller, U.(1) 92, 301; (2.3) 119; (2.7) 195; (3) 129 Muenck, E.(1) 75 Muggli, D.S.(2.5) 214 Muhlebach, A. (3) 123 Mukai, T. (1) 496; (2.3) 50; (2.5) 226 Mukherjee, R. (1) 6 1 Mukherjee, S.(1) 194,241,350; (2.6) 29 Mukherjee, T. (1) 117,284,289 Mulazzi, E. (3) 335 MuIler, A.M.(1) 339; (2.3) 86 Muller, M. (1) 214,642 Muncer, M. (2.3) 45 Munnelly, H.M. (1) 675 Mudyan, LA. (2.6) 67 Muragavel, S.C.(3) 245,246 Murai, €3. (1) 677; (2.5) 48; (2.7) 193 Murakami, H. (1) 665 Murakami, I. (4) 8 Murakatni, M. (3) 450 Murakoshi, K. (2.5) 167 Muramatsu, H.(1) 63 1; (3) 340 Mumka, 0. (2.3) 41,42; (2.4) 51,52 Murasawa, S. (3) 786 Murase, S.(3) 25 1 Murphy, R.S.(1) 269 Murphy, S. (1) 203 Murray, A. (1) 611 Murray, J.G.(1) 695 Murray, K.(3) 360 Murtagh, M. (3) 572,573 Murtaza, Z. (1) 586 Murthy. A.K.(2.6) 181 Murthy, K.S.(3) 86 Murugan, A. (2.3) 26 Mustafa, G.(1) 167 Muszkat, K.A. (2.4) 204 Muthusamy, S.(2.4) 222; (2.6) 272 Muzafarov, A.M. (3) 526 Muzikante, I. (1) 351; (2.4) 32
423
Myakushev, V.D. (3) 526 Myers, A.B. (2.7) 129 Myers, A.G. (2.4) 203 Myers, M.A. (3) 541 Myli, K.B.(2.5) 201 Myszak, E.A. (3) 756 Nadtochenko, V.A.(1) 403,672 Niigele, T. (1) 347,348; (2.4) 3 1; (2.6) 30
Naemura, K.(2.4) 57 Nagahara, K.(2.3) 110; (2.7) 140 Nagai, H.(3) 450 Nagaoka, T. (2.4) 98 Nagarajan, R (3) 65,115,767 Nagasaka, H. (3) 122 Nagasaki, T. (2.4) 74; (2.6) 38 Nagasawa, J. (2.1) 40 Nagashima, T. (1) 677; (2.5) 48 Nagashima, U. (1) 245 Nagawa, T. (3) 221 Naik, N. (3) 80 Nadi, P.D.(2.7) 153 Nair, V.(2.3) 37,48; (2.4) 54; (2.6) 153
Najafi, H.M. (2.2) 59 Najbar, J. (1) 80 Nakada, K. (1) 307; (3) 522 Nakada, M. (2.7) 145 Nakadaira, Y.(2.4) 135,199;
(2.6) 329,335-339; (2.7) 161, 163, 164 Nakagawa, H. (2.1) 41 Nakagawa, T. (2.5) 153; (2.6) 127; (3) 240 Nakahara, H.(2.4) 123 Nakai. T. (1) 659; (2.4) 73 Nakajima, H. (2.3) 104 Nakajima, S.(1) 449,530; (2.5) 290 Nakajima, T. (2.1) 13; (2.5) 32, 209 Nakajima, Y.(1) 288; (2.3) 67 Nakamoto, T. (3) 146 Nakamura, A. (1) 386; (3) 270 Nakamura, H. ( I ) 352; (2.4) 34; (2.6) 32 Nakamura, M. (2.5) 239; (2.6) 346 Nakamura, N. (2.6) 122 Nakamura, 0. (3) 237 Nakamura, S.(3) 213 Nakamura, T.(2.2) 4; (2.4) 20, 219,232; (2.6) 102, 103, 121, 136; (2.7) 5 Nakamura, Y.(2.3) 101; (2.4) 142, 150
Nakanishi, H. (1) 383; (2.5) 126 Nakano, A.K. (4) 8 Nakano, H. (1) 622 Nakao, A. (3) 250 Nakao, R.(2.4) 93; (2.6) 57 Nakashima, H. (2.4) 115; (3) 302 Nakashima, K. (1) 188,475 Nakashima, N. (2.7) 123 Nakashini, F. (2.1) 40 Nakata, M. (2.5) 211 Nakata, R. (4) 50 Nakata, Y.(3) 450 Nakatani, K.(2.2) 18; (2.3) 117;
(2.5) 122; (2.6) 118, 180; (2.7) 33, 198 Nakatani, Y. (3) 580 Nakatsuji, H. (2.1) 13; (2.5) 32 Nakatsuka, H. (3) 565 Nakayama, T. (1) 260,443; (2.4) 161,188 Nakazono, T. (2.6) 122 Nandy, S.K.(1) 116 Nanos, J. (3) 45 1 Nansheng, D. (3) 798 Napierala, D. (3) 475 Napper, D.H. (3) 89 Narasaka, K. (1) 497; (2.3) 122; (2.5) 241; (2.6) 96 Narayanan, V. (3) 196 Narita, H. (2.4) 180 Narita, T. (1) 605 Nash, B.(1) 43 1; (2.5) 294 Nasr-Esfahani, M. (2.4) 158 Nasu, K.(3) 362 Natarajan, L.V.(1) 37; (2.6) 62 Natarajan, P. (1) 216 Natasuka, H.(3) 562 Nath, D.N. (1) 656 Nath, G.(3) 453 Nau, W.M. (1) 13, 14,441; (2.5) 28, 118, 119; (2.6) 188-190 Naumann, I. (1) 611 Navio, J.A. (2.5) 225 Nay& S.K.(2.7) 85 Neal, S.L.(1) 693 Nechepurcnko, I.V. (2.4) 45; (2.6) 158
Neckers, D.C. (1) 601; (2.2) 89-
92; (2.5) 83,84,95; (2.6) 239, 273-275,281; (3) 6, 199 Nefedov, O.M. (1) 25 Negami, T. (4) 66 Negele, S. (2.5) 185 Negi, D.P.S.(2.5) 275; (2.6) 233 Negoro, S. (3) 438 Negri, R M . (1) 597 Negrii, V.D. (I) 388; (3) 354 Neher, D. (3) 434
424 Neilsen, B.O. (1) 255 Nekipelova, T.D.(2.5)272 Nelson, D.(3) 19 Nelson, E.W. (3)144 Nema, S.K.(4)42 Nemeth, K. (1) 377; (3) 724 Nerowski, F.(2.2)107;(2.5)71 Nespurek, S. (3)682 Nessler, H.-P. (2.2)83 Netto-Ferreira, J.C.(2.1)6,37; (2.4)254;(2.5)91;(2.7)31 Neuenschwander, P. (3)551,558 Neuhauser, D.(2.7)116 Neumann, M.G. (3) 502 Neumann, R.(3) 408,422,431 Neumark, D.M. (2.7)62 Neves, J.M. (3) 725 Neves, M.G.P.M.S.(2.7)32 Newkome, G.R.(3) 530 Newman, F. (4)60 Newmark, R.A. (3) 57,208 Neyde, Y.(4)8 Ng, L.T.(3) 276 Ngoc, T.H.(3) 212 Nguyen, C.V.(2.5)191 Nguyen, D.(1) 431;(2.5)294 Nguyen, M.T.(2.1)33 Nguyen, T.H.(2.4)252 Ni, S.(3) 487 Ni, W.(1) 478 Nichikubo, T.(3) 191 Nichiporovich, I.N. (1) 3 10 Nichols, M.E.(3) 738 Nickel, B.(1) 132 Nicodem, D.E. (1) 249 Nicolau, S.(3) 67 Nie, J. (3) 110 Nie, Y.(2.5)29 1 Nieger, M.(2.7)93 Niemann, C.(3) 795 Niemczyk, M.P. (1) 522 Nierengarten, J.-F.(1) 41 Nierlich, M.(2.4)38 Nijegorodov, N. (1) 229,230 Nikiforov, A.P. (3) 735 Nikogosyan, D.N. (2.6)137 Nikolaenkova, E.B.(2.4)216; (2.7)57 Nikolaev, E.K. (1) 388;(3)354 Nikolaitchik,A.V. (2.6)239 Nilsson, S.(3) 470 Ninomiya, M. (2.4)135;(2.6) 339;(2.7)164 Nishi, N. (2.7)144 Nishiama, S. (3) 706 Nishida, S.(2.3)62;(2.4)197 Nishie, K. (2.5) 168 Nishigaichi, Y.(2.6)354
Photochemisiry Nishigaki, A. (1) 245 Nishihara, H.(3) 757 Nishikubo, T.(3) 139,213,320 Nishimoto, M.(3) 628 Nishimura, J. (2.3)101,102;(2.4) 142, 150 Nishimura, Y. (1) 211,468,521, 665 Nishinaka, Y. (2.6)122 Nishino, N. (1) 300 Nishio, S.(1) 659;(2.4)73 Nishio, T. (2.2)88;(2.4)172; (2.5)96;(2.6)124,292 Nishitani,N. (4)66 Nishiura, T.(3) 506 Nishiyama., K.(1) 301 Nishizawa, H.(1) 202 Nishizawa, K.(1) 655;(2.6)85 Nisoli, M. (3) 375,396 Nitzao, A. (1) 76 Niwa, H.(I) 240;(2.3)71;(2.6) 172 Noach, S. (3) 408 Noble, R.D.(1) 105,606 Nocera, D.G.(1) 523,546,582 Noda, Y.(3) 371 Noguchi, A. (2.6)38 Noguchi, T.(3) 388 Noguchi, Y.(2.2)72;(2.6)138 Noh, I. (3) 274 Noh, T.(2.3)65,66,108;(2.4) 160, 162, 163, 170;(2.6) 114; (2.7)125 Nojiri, T. (1) 409;(2.5)135 Nolte, R.J.M. (1) 517;(3) 269 Nonell, S.(1) 395 Noniewicz, K.(3) 117 Norambuena, E. (3) 84 Nord, K.(2.6)242,247,248 Nordio, P.L.(1) 77,88, 141 Noren, G.K.(3)72 Norikane, Y.(2.5)44 Norikano, Y.(1) 277 Norrby, T.(1) 64.66 Noms, T.B.(1)642 North, S.W. (2.2)54;(2.7)136, I88 Ndingher, P.V. (3) 625 Nourmamode, A. (3) 728 Novaira, A.I. (1) 442 Novi, M. (2.6)315;(2.7)12 Novikov, B.V.(1) 393 Novikova. T.S.(3) 416,424 Novokov, E.G. (1) 691 Nowacka, M.(2.5)23 1 Nowakowska, M.(1) 53;(2.3)89 Nowienski, A. (2.4)201 Noy, D. (1) 56
Nozaki, K. (1)74,79,521,550 No&, T.(2.2)75;(2.6)1 1 1 Nozawa, T.(1) 59 Nozik, A.J. (4)48 Nozoe, T.(2.2)133, 134;(2.4) 182,223,237;(2.6)193;(2.7) 16, 18 Niidling, W. (2.7)7 Nuhn, P.(1) 614 Nunes, E.C.D. (3) 790 Nunomura, M.(2.7)37 Nunzi, J.-M. (2.6)72;(3) 347 Numukhametov, RN.(2.7)124; (3) 350 Nuyken, 0. (2.7)8-11;(3)22,58, 203,741 Oba, S. (2.4)199;(2.6)329;(2.7) 161 Obara, M. (3) 120 Oberle, J. (1) 162 Obukhov, A.E. (1) 72 Oda, K.(2.5)120 ODonnell, M. (3) 232 Odum, R.A. (2.3)59;(2.6)39 Oc,M. (2.7)23 Oelgemoller, M. (2.2)107;(2.5) 71;(4)13 Oelkrug, D.(3) 382,385,430 Oesterhelt, D.(2.6)30 Ofenberg, H.(2.4)186 Ogale, A.A. (3) 180 Ogasawara, M.(3) 607 Ogawa, A. (2.5)3 Ogawa, M.(3) 307 Ogawa, T.(2.2) 13, 14;(2.4)238, 239;(2.6)85, 108, 110;(3) 56,365 Oge, T.(3) 3 15 Ogilby, P.R (1) 3 1 1 Ogino, K.(2.4)74;(2.6)38 Ogirenko, A.A. (2.4)240 Ogvawa, H.(2.6)353 Oh,C.(1) 496;(2.3)50;(2.5)226 Oh,J. (2.7)138 Oh, J.S. (3) 782 oh,s.-H.(2.2)47 Oh, S.-W. (2.2)49,104;(2.4) 218;(2.6)92,238 Ohana, T. (2.7)47 Ohashi, M. (1) 240;(2.3)71,79; (2.6)172 Ohashi, Y.(2.6)337,338;(2.7) 163 Ohba, S.(2.2)55; (2.4)13 1 Ohba, Y. (2.3)121;(2.6)229 Ohde, K.(2.7)68
Author Index Ohfime, Y. (2.2)18;(2.6)118 Ohkita, H.(3) 339
Oliver, A.M. (1) 73;(2.6)259 Oliver, C.E. (1) 335 Ohkita, M.(2.3)61,62,106;(2.4) Oliveros, E. (2.1)45 197, 198 Olivier, L.A. (1) 708 Ohkura, K.(2.2)72;(2.6) 138 Olivucci, M.(1) 14,71;(2.4)30, Ohler, N.E.(1) 565,566 94;(2.6)23-25,188, 191; Ohmori, M.(4)59 (2.7)4 Ohmori, Y.(3)458,463 Olkkonen, C. (3) 710 Ohnishi, I. (1) 245 Olley, J. (I) 61 1 Ohnishi, T.(3) 388 Olliff, C.J. (3) 329,330 Ohno, M.(1) 300,421;(2.4) 168 Ollino, M.A. (2.7)102 Ohno, T. (1) 74,79,390,521 Olmstead, J.A. (3) 285,713 Ohshima, S.(1) 245;(2.5)224 Olovsson, G.(2.2)68,94,132; Ohta, K.(1) 263;(2.5)163 (2.5)78;(2.6)87 Ohta, N.(1) 46,664,665 Olsen, R.J. (1) 330;(2.4)29;(2.6) Ohta, T.(3) 236 28 Ohtani, B. (2.4)1 Omoto, Y. (2.4)268;(2.6)91 Ohyama, T.(3) 299 Omura, T.(3) 794,799 Ohzone, T.(4)52 O ~ r iS. , (1) 390 Oikawa, H.(1) 383;(2.5)126 Onda, T. (3) 574 Oishi, 0.(1) 300 Ondrais, M. (1) 514;(2.5)295 Oka, M. (2.4)172 OWeil, G.A. (3) 610,612 oka,Y.(4)49 On& K.K.(1) 253 Okabe, K. (4)30 Onishi, M. (2.5) 145 Okada,A. (1) 605;(3) 460,535 Onishi, Y.(2.4)99;(2.6)53 Okada, K.(1) 268,439;(2.4)62; Ono, H. (3) 268 (2.5)34 Ono, I. (2.4)262;(2.6)3 14;(2.7) Okada, S.(1) 383;(2.5)126 I74 Okada, T.(1) 54,301,515,521; Ono, K. (3)1 1 (2.5)140, 167;(3)674 Ono, M. (2.3)42;(2.4)52 Okada, Y.(2.3) 102;(3) 800 Ono, S.(2.4)272;(2.6)295 Okamoto, H.(2.4)58 Onoda, M. (3) 426,466 Okamoto, K.(1) 136,670 Onoe, J. (3) 249,250,341 Okamoto, M.(1) 273 Onofiey, T.J. (2.2)124;(2.4)207 Okamoto, S.(3) 787 Onu, A. (3) 693 Okarnoto, T. (3)583 Onuchic, J.N. (1) 82 Okamoto, Y.(2.5)240;(2.6)347; Oonishi, I. (2.5)224 (2.7)82;(3) 441,479 Oosaki, K.(2.5)110 Okamura, M. (2.1)25; (2.4)225 Oosterhoff, P. (2.6)27,3 12 Okano, T.(2.6)88 Oosterling, M.L.C.M. (3) 323 Okay, 0.(3) 91,224 OrfBnopoulos, M.(2.4)148, 149 Okazaki, S.(1) 664 Orsteen, A.-L. (2.6)247,248 Okisaki, F.(3) 688 Orti, E. (2.6)266 Okitsu, T. (3) 12 Ortiz, A. (3) 365 Okoyuma,M.(2.3)61 Ortiz, M.J. (2.4)56 Okubo, Y.(2.2)52 Osa, T. (1) 192;(2.4)33 Okumoto, H. (3) 358,388 Osamu. I. (2.5)127 Okura, I. (1) 579;(2.5)107, 108; Osawa, 2.(3) 628,630 (4)16,20 Osoda, K.(1) 497; (2.3)122;(2.5) Okutani, T.(3) 450 241;(2.6)96 Okuyama, M. (2.4) 198 Ossipyan, Yu.A. (1) 388;(3) 354 Olayo, R. (3) 679 Ossowski, T. (2.5) 23 1 Oldham, W.J., Jr. (1) 360 Ostayuk, S.N.(3) 14 I Olea,A.F. (1) 115 Osterhelt, D.( I ) 347 Oleinik, A.V. (2.5)244;(2.7)44, Osuka,A. (1) 46,54,55,449, 45 468,471,521,530;(2.5)25, Oleshko, V.P. (3)3 16 290 Olinga, T.(3)389 Oswald, G.A. (1) 650
425 M e , K. (3) 794 Otsuki, H.(3) 628 Ottolenghi, M. (1) 594 Ouchi, A.(2.4)176;(2.7)170, 199 Ouija, M. (2.7)160 Oulmidi, A. (3) 214 Ouyang, R. (2.5)175 Overeem, T.(2.6)27,312 0vreb0, H.H. (2.3)55; (2.5)144; (2.7)142 Owen, E.D.(3) 733 Owens, J. (3) 14.71 Oya, K.(3) 134 Oyaim, K.(2.5)298 Ozaki, M. (3) 410 ozaki,Y.(1) 475 Ozen, R.(2.5)212 Ozheredov, LA. (1) 703
Pa, K. (2.4)137 Paavo, P.H. (2.5)56 P a , C.(1) 211;(2.6)122 Pace-Asciak, C.R (2.7)55 Paddon-Row, M.N.(1) 73,428; (2.5) 103, 138;(2.6)259 Pages, P. (3)653 Pagliano, N.(1) 354 Paine, S.W. (2.2)53;(2.4)264 Painelli, A. (3)334 Pal, G.(3) 40.41 Pal, H.(1) 503 Pal, S. (1) 65 Pal, S.K.(3) 575 Palamaru, M. (3) 693 Paleos, C.M. (3)528 Palit, D.K.(I) 284,291,354,382, 414,417,493;(2.4)14;(2.5) 151,222;(2.6)342 Pallavicini, P. (1) 558 Palm, W.-U. (2.6)246 Palmer, A.W.(1) 692 Palmer, S.J.(3) 649 Pan, G.(3) 21 1 Pan, J. (2.6)226 Pan, K.(2.3)52; (2.4)127 Pan, S.J. (1) 638;(3)366 Pan, W.T. (2.3)56 Panda, A.K. (3) 476 Pandey, C.A. (3)767 Pandey, G.(2.2)45.46; (2.3)26; (2.5) 2.74;(2.6)342 Pandit, C.R (2.1)60 Pang, S.-Z. (2.5)177 Pang, Y. (3) 461 Panitzsch, T.(2.3)60 Pankasem, S. (3) 767
Photochemistry
426
Panov, V. (2.6) 326; (2.7) 157 Panse. P. (4) 67 Pansu, R (1) 149; (2.5) 257 Paolesse, R. (1) 469 Paolucci, F. (1) 418; (2.5) 10 Papohmas, K.I. (3) 35 Papper, V. (1) 358; (2.3) 6 Paramasivam, T. (2.4) 222 Paramasivan, R. (2.6) 272 Paraschiv, V. (3) 55 Parigger, C. (1) 588
Park, B . 4 . (2.1) 16, 19; (2.5) 73, 81,89
Park, C.H. (2.1) 69; (2.4) 276 Park, D.C. (4) 37,38 Park, H.-R. (2.5) 246; (2.7) 138 Park, J. (1) 276; (2.5) 64; (3) 103 Park, J.G.(3) 686 Park, J.-S. (2.7) 49; (3) 743 Park, J.W. (1) 191; (2.5) 114; (3) 443
Park, S.E. (1) 191 Park, S.H.(2.5) 114 Park, S.K.(2.4) 130; (2.6) 331 Park, S.Y.(3) 435 Park, W.W. (2.2) 49; (2.6) 238 Park, Y . (3) 423 Park, Y.-T. (2.4) 215; (2.6) 81 Parker, A.W. (1) 460; (2.4) 250 Parker, D. (1) 35,571 Parmar, J.S. (3) 770 Parmar, RJ. (3) 770 Parmon, V.N.(4) 1 Parnas, RS. (3) 169 Parra, J.L. (3) 472 Parret, S. (1) 233 Paninello, M. (1) 99 Parsons, A.F. (2.5) 117 Parsons, B.J. (1) 219,220 Partch, RE. (2.4) 220; (2.6) 23 1 Partee, J. (3) 394,449 Parthasarathy, V. (2.7) 153 Parusel, A.B.J. (1) 83, 138; (2.5) 256
Paszyc, S. (1) 286; (2.6) 151,251 Patel, R.G. (3) 296, 324 Patel, V.S.(3) 296,324 Patemostre, M. (1) 609 Patil, R.V. (3) 353 Patil, S.N. (3) 353 Patnak, D. (3) 130 Patonay, G. (1) 627 Patra, D. (2.3) 92 Pa& M. (1) 404; (2.5) 128 Paul, G.C.(2.7) 148 Paul, H. (1) 667 Paul, R.(1) 64 1 Paul, RB. (3) 95
Pauls. S.W.(1) 324 Paulsson, M. (3) 719 Pavlik, J.W. (2.4) 7;(2.6) 3, 162 Pavlincc, J. (3) 205 Pavloschchuk, V.O. (3) 367 Pavlovich, A.V. (3) 761 Pavlovich, V.S. (1) 70 Paz, J.J. (1) 327; (2.2) 85 Pazur, R (3) 691 Peacock, R.D. (1) 35 Pebalk, A.V. (2.7) 124; (3) 350 Pecka, J. (3) 606 Peckan, 0. (3) 91,546,578,582, 585,592,595
Pedersen, T.G.(3) 5 18 Pccler, A.M. (3) 767 Pegg, D.T. ( I ) 7 Pci, Q. (3) 560 Peiffer, R.E. (3) 3 Peinado, C. (3) 783 Pcinado, M.C.R. (1) 598 Pelegrini, R. (3) 7 11 Pelizzetti, E. (2.5) 245 Pellaux, R (1) 50 Peiisory, A.B. (2.6) 310 Penfield, K. (1) 2 Peng. C. (3) 128 Peng, J.C. (3) 321,322 Peng, L.(2.6) 211; (2.7) 180 Peng, W. (1) 392 Peng, X. (3) 413 Penzkofer, A. (1) 346 Peoraro, V.L.(1) 67 Pcppas, N.A. (3) 182 Pepper, D.C. (3) 95 Peralta-Zamora, P. (3) 7 11 Percha, P.A. (3) 57 Pereira, E.J. (1) 9; (3) 609 Pereira, R.S. (3) 725 Perez-Prieto, J. (2.3) 109; (2.7) 141
Periasamy, N.(1) 306.71 1 Perl, D.R (3) 355 Perlstein, J. (2.6) 36,279 Perotil, A. (1) 558 Pemer, H. (2.7) 55 Perry, C.J. (2.2) 106; (2.4) 214 Perry, M.H.(1) 209; (2.5) 178 Persico, M. (1) 69; (2.7) 3 Persson, 0. (2.4) 191; (2.6) 202205, 207; (2.7) 110-114
Peschanel, M. (2.3) 60 Pete, J.-P. (2.2) 19, 32 Peters, E.M. (2.2) 107; (2.3) 60; (2.5) 71
Peters, K.(2.2) 107; (2.3) 60; (2.5) 7 1
Petersen, J.D. (1) 552
Peterson, 0.(2.4) 190 Petkov, I. (2.6) 72; (3) 287,533, 746
Petrenko, O.P. (2.4) 45; (2.6) 158 Petrich, J.W.(1) 276; (2.5) 63,64 Petrillo, G.(2.6) 315; (2.7) 12 Petritsch, K. (3) 391 Petrochenkova,N.V. (3) 615 Petrov, N.K.(1) 89,660 Petty, M.C. (1) 411; (2.6) 35; (3) 455
Petucci, C. (2.3) 40 Pevenage, D. (1) 344 Peyghambarian, N. (3) 792,793 Pfanner, K. (4) 34 Pfeifer, L. (1) 64 1 Pfendner, R. (3) 751 Pfennig, B.W.(1) 553 Pfleiderer, W. (2.4) 278,279; (2.6) 208; (2.7) 183
Pflug, K. (4) 19 Phadke, A.S. (2.7) 50 Pharabod, F. (4) 14 Pharisa, C. (3) 198 Phelan, J.C. (3) 172, 173 Philippart, J.L. (3) 648 Philippe, L. (2.7) 107 Phillips, D. (1) 460; (2.4) 250; (2.7) 128, 129
Phillips, R.T.(3) 376 Philouze, C. (1) 64,66 Phunpruch, S. (4) 76 Piazza, G.(2.6) 286 Pichler, K. (3) 405 Pickett, J.E.(3) 769 Pierolq I.F. (1) 124; (3) 559 Pieroni, 0. (2.6) 8 Pi&ri, N. (2.1) 58; (2.7) 63 Pietschmann, N. (3) 137 Pignon, B. (2.4) 233; (2.6) 283 Pikramenou, 2.(1) 582 Pilichowski, J.F. (2.5) 204; (3) 773
Pilo Veloso, D. (3) 337 Pina, F. (1) 258; (2.4) 126 Pincock, A.L. (1) 329 Pincock, J.A. (1) 329 Pines, D. (1) 295,358; (2.3) 6 Pines, E. (1) 294,295,358; (2.3) 6 Pinkerton, A.A. (2.2) 16 Piolanti, R. (3) 304 Piot, J. (2.1) 58 Piotrowiak, P. (1) 122,362,487 Pirelahi, H. (2.4) 43, 114; (2.6) 296,297
Pirogov, N.O. (2.5) 272 Pischel, U. (2.3) 119; (2.7) 195 Pistolis, G. (1) 337; (2.3) 77; (2.4)
Author Index 145;(3) 528 Piszcek, G.( I ) 140 Pitchumani, K.(2.3)43 Piu, F.(1) 424 Piuzzi, F. (2.5)27 Piva, 0.(2.2)32 Piva-Le Blanc, S.(2.2)32 Pivnitsky, K.R. (2.7)55 Pivovarov, A.P. (3) 652 Plagemann, B. (1) 684 Platz, M.S. (2.7) 14, 15.20, 146, 147 Platz, M.W. (1) 238 Plaza, P. (1) 244 Plemmons, D.H. (1) 588 Pliva, C.N.(1) 248;(2.1)4;(2.5) 43 Poggi, A. (1) 558 P o p e , R.T.(3) 218 Pohlman, B.(4)27 Pokorna, V. (3)606 Pokorna, Z.(1) 375,399 Pola, J. (2.7)189;(3) 53 Polevaya, Y.(1) 594 Polewski, K.(3)475 Polimeno, A. (1) 77,88,141 Politi, M.J.(3) 683 Politis, J.K. (3) 451 Pollack, K.W.(3) 523 Pollak, C.(2.7)80 Polubisok, S.A. (2.7)169 Polyakov, N.E.(2.5)266 Polyani, J.C.(2.7)149 Pomery, P.J. (3)631 Poncin-Epaillard, F. (3) 147 Ponomarev, O.A. (1) 279,457; (2.6) 147 Ponomarev, S.G.(3) 567 Ponten, E.(3)220 Ponterini, G. (2.6)73 Ponticelli, F.(2.4)257;(2.6)199; (2.7)58 Pontyatovsky, E.G.(3)354 Poon, J.M. (3)279 Popielarz, R (1) 601 Popik, V.V.(2.4)253;(2.5)82; (2.7)30 Popova, E. (2.5) 263 Popova, G.(2.6)8 Popovic, 2.(3) 419 Popp, B. (1) 507;(2.6)257 Poque, R.T. (3) 260 Porada,Th. (2.4)13 Port, H.(1) 536 Porting, S.(1) 214 Posokhov, E.A. (1) 279;(2.6)147 Pospisil, J. (3)682 Postnikov, L.M. (3) 668
427 Pouliquen, L. (3) 3 1, 111 Poulsen, T.D. ( I ) 3 1 1 Povazancova, M.(3) 775 Pozhidaev, Y .N.(2.6)3 19 Pozuelo, J. (3)603 Pozzo, J.L. (2.4)106;(3)293 Prabhakaran, J. (2.3)48;(2.4)54; (2.6) 153 P d c l l a , F. (3) 742 Pdera, M.A. (2.5)225 Pradhan, P.P. (2.2)51;(2.4)157 Prager, R.H. (2.1)54.55; (2.4) 227,228;(2.6)182-184 Prakash, G. (2.5)116 P d , P.N. (1) 638;(3) 366 Praschak, D. (3) 697-699 Pmt, F. (2.5)182 Prato, M. (1) 418,422,423,425, 426;(2.5)10, 136,137 Pratt, A. (2.6)322 Pratt, G.J.(3) 734 Pregnolato, M.(2.4)181;(2.6) 227 Premkumar, J. (2.5)164 Prescher, G.(2.2)83 Previtali, C.M.(1) 1 18,442,492; (2.5)51, 149 Prevosti, E. (3) 465 Price, J.M. (1) 568 Prinzbach, H.(2.6) 157 Priola, A. (3) 215,231 Priyadarshy, S.(1) 303 Prochorov, J. (1) 126 Prodi, L.(1) 43,469 Prognon, P. (1) 649 Pronchenko, I.P. (3) 660 Prudhomme, D.R. (2.1)50 Pu, L. (3) 378 Puech-Costes, E.(2.1)45 Puell, B.(1) 347;(2.6)30 Pugh, V.J. (1) 33 Pugliano, N.(2.4)14 Pullen, S.H.(1) 332,340;(2.3)58 Purcell, W.(2.7)84 Purushothaman,E. (2.6)308 Pushpa, K.K.(2.7)153 Qi, F. (2.7)81 Qi, G.(3) 24.26 Qi, X.(2.5)284 Qian, C.Y.(2.2)3 Qian, J. (1) 392 Qian, S.(1) 392 Qian, X. (1) 454;(2.5)242;(2.6) 82 Qian, X . N . (2.5)243 Qiao, G.C.(2.4)256;(2.7)29
Qiao, J. (1) 406 Qiu, J. (2.2)3; (3) 478,599 Qiu, K.Y.(3)4547,69,81 Qu, B. (3) 150-152 Qu, P. (2.5)262 Qu, X.(3) 150-152 Quack, M. (2.7)171 Quast, H.(2.7)7 Quinkert, G.(2.2)83 Quinn, E. (3)79 Rabek, J.F. (3)157 Rabello, A.M. (3) 683 Rabello, M.S. (3) 643,645-647 Rabor, 1. (2.7)73 Racioppi, R.(2.2)7,80;(2.4)184, 189,231;(2.6) 106,235,236 Rademacher, J.T. (1) 51,554,555 Radner, F.(2.6)309 Radu, I. (3) 625 Rac, S.(3)803 Raferty, D. (2.3)40 Rager, T.(3) 481 Raha, C.(1) 158;(2.2) 103;(2.5) 252 Rahmani, H.(2.4)43, 114;(2.6) 296,297 Raithby, P.R (2.7)86,87,104, 105 Rajagopal, S.(1)499 Rajasekharan, K.N.(2.5)227; (2.6)219 Rajendrcn, T. (1) 499 Rakicioglu, Y.(1) 104 Ramachandram, V. (1) 229 Ramaiah, D. (2.3)46 Ramakrishnan, V.T.(1) 224,290, 608;(2.4)222;(2.6)272;(3) 569 Ramamurthy, P. (1) 224,290, 499,500,608;(2.4)222;(2.6) 272 Ramamurthy, V. (2.2)40;(2.3) 43;(2.5) 1,31 Ramamj, R (I) 499;(2.5)164 Ramasamy, N.K.(2.4)222;(2.6) 272 Rambke, B. (3)3 12 Rames-Langlade, G.(3) 200,227 Rammert, K.F.(2.4)201 Ramnauth, J. (2.1)73 Ramos, A. (2.3)72,73;(2.4)56; (2.5) 169;(2.6)155 h e y , J.M. (1) 172,178,179 Ramurthy, P. (3) 569 Ranasinghe, M.G. (1) 428;(2.5) 138
428 Ranby, B. (3) 150,328 Ranganathan, R. (4)68 Rangarajan, B.(3) 167,209 Ranger, M. (3)452 Ranjit, K.T. (2.5) 125, 170 Rao,A.M. (2.5)19;(3)21 Rao, G.(1) 586 Rao,K.S.S.P. (2.6)342 Rao, V.J. (2.2)40;(2.5)3 1 Rao, V.R (2.3)53 Rao, V.S.(2.5)79, 80 Rao, X. (3)362 Raschke, U.(2.6)245 Rasmussen, P.G. (1) 67 Rassat, A. (1) 412,461 Rath, M.C. (1) 117,284,289 Rath, N.P. (2.3)37,45,46;(2.5) 213 Rathi, RC. (3)297 Rathmore, R. (2.5)50 Ratner, M.A. (1) 76 Rau, H.(1) 14;(2.6) 188 Rawal, V.H. (2.2)25 Ray, P.(1) 490 Raymond, C.(3)766 Raper, B. (2.6)217 Razafitrimo, H.(3)429 Razumov, V.F. (1) 369;(2.4)23 Reagan, J. (1) 82 Rebien, F. (2.5)219 Rebourt, E.(3)446 Rechthaler, K. (1) 145,325 Reck, G.(2.1)15,27;(2.4)212; (2.6)83,84 Redmond, RW. (1)256;(2.2) 109;(2.5) 86;(2.6)94 Reeb, R. (3) 178 Reed, W.F. (3)683 Reetz, I. (3) 104 Regan, C.J.(3)666,784 Regenstein, W.(1) 357 Regimbald, M. (2.5)230 Rehm, D.(2.2)83 Reibenspies, J. (2.2)60 Reichert, D. (2.2)83 Reid, W.R (1) 595 Rcilly, J.P. (2.1)34 Reindl, S. (1) 346 Reinhard, R. (2.7) 179 Reinhardt, D. (2.5)205;(2.6)210 Reis, E.(3)50 1 Reis, H.(1) 30 1 ReiscN, W.(1) 36;(2.3)88 Reisenauer, H.P. (2.1)38 Reisinger, A. (2.4)256;(2.7)29 Reisler, H.(2.7)64 Reitberger, T. (3) 624 Remmers, M.(3)434
Photochemisby Ren, X.X. (3) 33 Renak, M.L. (3)4 19 Renamayer, C.S. (1) 124 Renault, T. (3) 180 Renge, I. (1) 683,684;(3) 704 Renn, A.(1)684 Rentzepis, P.M. (2.6)224 Renze, J. (2.5)217 Rest, A.J. (2.7)102 Rethwisch, D.G. (3) 570 Rettig, W. (1) 146, 147, 165,244; (2.5)258 Reves, J. (3)71 1 Revesz, K. (3)701 Reyes, C. (2.3)105 Reyes, V.M. (1) 124 Reynier, N.(2.4)35.38; (2.6)33 Reyx, D.(3)214 Rheingold, A.L. (2.7)103 Ricci, M.(1) 88, 141 Rice, T.E.(1) 51,555,569 Richard, C.(1) 328;(2.4)59;(2.6) 156 Richardson, F.S.(I) 30,33 Richardson, M.F. (3)611 Riche, C. (2.2)79; (2.6)135 Richter, C. (2.6)323 Riehl, J.P. (1) 681 Rieker, T.P. (3)254 Riess, W.(3) 407 R i d , T.(1) 52 Rigby, J.H. (2.6)76 Riggenberg, J.D. (2.2)39;(2.4) 146 Righini, R (1) 88, 141 Rigler, R (1) 182 W e n , G.L.J.A. (3)740 Riley, S.W. (2.6)130 R i m e r , S.(3)498 Rinmenthal, J.L. (1) 27 Rios, P. (3)663 Ripamonti, A. (3) 335 Rist, G. (2.1)9 kter, R.E. (1) 685 Ritter, H.(3) 247 Rivas, C.(2.2)99;(2.4)171;(2.6) 35 1 Rivaton, A. (3) 672,673,694 Rizzo, C.J. (2.1)50 Rizzoli, C. (2.3)99;(4)21 Robb, M.A. (1) 14,71,331;(2.3) 64,80; (2.4)30, 94;(2.6)2325, 188, 191;(2.7)4 Robbins, D.L. (1) 701 Robbins, R.J. (2.3)43 Robert, B.(1) 609 Robert, M.(2.7) 146, 147 Roberts, E.L. (1)198;(2.4)66
Roberts, J.A. (1) 523,546 Roberts, J.J. (1) 1 1 Roberts, R (1) 611 Robinet, G. (2.2)21 Robinson, W.T. (2.4)191, 192; (2.6)205,206,309;(2.7)109, 110 Roch, Th.(1) 688 Rockett, A. (4)67 Rodebaugh, R. (2.4)280;(2.6) 216; (2.7)185 Rcdgers, M.A.J. (1) 207,304,367 Rodriguez, A.D. (2.3)34 Rodriguez, M. (2.3)72;(2.5)169; (2.6) 155 Rodriguez-Hahn, L. (2.5)154; (2.6)316 Roeckert, I. (1) 143 Roesler, G. (3)386,387 Roess, D.A. (1) 675 Roest, M.R.(1) 73;(2.6)259 Rofia, S.(1) 418;(2.5)10 Rogby, J.H. (2.4)213 Rogez, D.(3) 753 Rohde, N.(3)356 Rol, C. (2.5)300 Rolla, A.P. (3) I19 Rollins, H.R.(4)46 Rollins, S.B.(2.5)75;(2.6)86 Romeu, I. (3)653 R o m e , S.T.R (3) 740 Romstad, D. (1) 69 Ronco, S.E.(1) 552 Rooney, A.D. (2.7)94 Roos, B.O.(2.4) 192;(2.6)206; (2.7) 109 Rosa, A. (2.7)80 Rosche, K.(3) 121 Rosenbluth, H. (1) 1 15 Rosenwaks, S.(2.7)133 Rosenwcig, Z.(1) 575 Rosik, L. (3)682 Rosilio, A. (3) 64 Rosilio, C. (3)64 Rosini, G.P. (2.7)97 Ross, RT. (1) 297 Rossi, M.(1) 415 Rossitto, F.C. (3)737 Roth, H.D.(2.3)54.94; (2.5)192; (2.6)171, 176;(4)23 Roth, S.(3)402,403 Rothberg, L.J. (3)392 Rotkiewicz, K.(1) 145 Rotomskis, R. (1) 160 Rwsset, E.(2.6)278 Rout, S.P.(3) 130 Roux, S. (1) 412 R O W ~ ~ NB. ~ , (2.1)57
Author Index Rowles, N. (2.4) 122;(2.6)51 Rtishchev, N.I. (2.4)221;(2.6) 79, 159 Ruan, R.X. (3)345 Rubin, M.B.(2.2)95 Rubin, Y.(2.2)93 Rubtsov, I.V. (1) 125,672 Rucando, D. (2.2)71;(2.4)166 Ruckh, M. (4) 61 Rud, V.Yu. (4)73 Rud, Yu.V. (4)73 Rudolph, T.(2.1)1 1 Rudolph-Bijhner, S.(1) 347;(2.6) 30 Rueckert, 1. (2.5)261 Ruffolo, R (2.6)332 Rufs, A.M. (3)84 Ruhman, S.(1) 20 Ruhmann, R. (3) 306 Rukhman, I. (2.2)33 Rullicrc, C.(1)162 Rurnblcs, G.(1) 676;(3) 360,377 Ruppel, R. (2.1)38 Ruprecht, R. (3) 143,239 Rusch, M.(3) 379 Ruskol, LYu. (3) 54 Rusnock, J.M. (2.7)108 Russell,D.H.(2.6)215 Russell, K.E.(3) 150 Rutherford, T.J. (1) 55 1 Ruthkosky, M.(1) 548 Rutkis, M. (1) 35 1 Ryasnoi, V.D. (3) 760,761 Rybalkin, V.P. (2.3)96;(2.4)40 Ryder, D.M. (3) 329,330 Rytz, G. (3) 768 Ryu, D.S. (2.2)38 Ryu, 1. (2.3)110;(2.7)140 Ryu, J.Y.(2.2)104;(2.4)218; (2.6)92 Ryzhakov, N.V. (2.7)124 Rzadek, P.(2.1)9 Saad, B.(3) 558 Saadioui, M. (2.4)35,38;(2.6)33 Sacher, M. (1) 663 Sachleben, R.A. (2.4)278 Sadeghi, M.M. (2.6)107 Sadeghpoor, R. (2.2)59 Sadovskii, N.A. (1) 524;(3)526 Saeki, T. (3) 681 Saeuberlich, J. (2.5)37,54 Saeyens, W.(2.2)74;(2.4)140, 154 Safonov, I.G.(2.5)139,197 Safvi, S.A. (1) 629 Sagdeev, R.Z. (2.1) 12;(2.4)245
429 Salvador, S.M. (1) 651 Salvi, P.R (1) 232 Salz, U.(2.3)4 Sahraoui, B. (3) 233 Samajdar, S.(2.3)92 Sahyun, M.R.V. (1) 322 Samanta, A. (1) 365 Saielli, G.(1) 77,88 Samarabandu, J.K.(3) 366 Saikan, S.(1) 262 Samartzis, P.C.(2.7)126 Saiki, S. (2.4)57 Samat, A. (2.4)82,88, 106;(2.6) Sailor, M.J. (2.5)46 53,60 Sainsbury, M. (2.4)6;(2.5)18 Samir, K. (3) 575 St.Jolm, N.A. (3)631 Samstov, M.P.(1) 345 St.Louis, E.(1) 651 Samuel, I.D.W. (1) 41 1; (3)360, 376,377,446 Saintome, C.(2.2)76;(2.4)195; Samuels, A.C.(1) 253 (2.6)289 Samulski, E.T.(3)279 Saito, A. (2.6)180 Saito, I. (1) 528;(2.2)73;(2.3) Sanchez, A.M. (2.4)248 117;(2.5)122;(2.6)136,174; Sanchez, C.(3)365 (2.7)33, 198 Shchez, L.(2.5)121;(2.6)265, Saito, K.(3)283,512,547 266 Saito, N. (3) 272 Sanchez-Camacho, A. (3) 603 Saito, R (1) 240 Sandcr, W.(2.2)95;(2.4)260; (2.7)19,25,39 Saitou, A. (2.5)224 Saji, A. (2.5)163 Sanders, G.M.(1) 305 Sakaguchi, Y.(1) 655 Sanders, J.K.M. (1) 43 Sakai, A. (2.5)274 Sandner, B. (3) 179 Sakai, K.(2.4)180 Sando, S.(2.7)33 Sakai, M. (1) 386 Sands, E.(3) 106 Sakai, T.(3) 327 Sang, C.(1) 264 Sakai, W. (3)339 Sangen, 0.(3) 257,258,268 Sakakibara, K.(2.7)145 Sanin-Leira, D. (2.7)176 Sakamoto, K.(2.5)155 Sanji, T.(2.6)334;(2.7)158 Sakamoto, M. (2.2)88;(2.3)120; San Roman, E.(2.5)176 (2.4)205;(2.5)96;(2.6)124, Santhosh, K.C. (2.1)62;(2.6)98 139,291 Santos, D.A. (3) 374 Sakata, T.(2.5)158 Santos, M.(2.7)154, 160 Sakata, Y.(1) 429,515;(2.5)11, Santos, M.N.B.E.(2.5)4 140;(2.7)123 Santra, S.(1) 278;(2.6)149 Sakharuk, S.A. (1) 131 Santus, R (1) 121 Sakuragi, H.(1) 211;(2.6)317 Sanz-Medel, A. (1) 576,587 Sakuragi, M.(1)333; (2.3)78; Sapich, B.(3) 266 (2.4)95;(2.6)55 Sapre, A.V. (1) 291,493;(2.5) Sakurai,H.(2.6)334,335;(2.7) 222 158 Sapunov, V.V. (1) 94 Sakurai, T. (1) 296;(2.1)65;(2.3) Sarakha, M. (2.5)233,234 121;(2.4)249;(2.6)160, 164, Sareta, A. (1) 710 229 Sariciftci, N.S. (3) 414,561 Sala, C.M.(1) 570 Sarkar, S.K. (2.7)153 Saladin, F. (2.5)166;(4)34 Sarker, A.M. (2.6)239 Salakhutdinov,N.F. (2.3)100 Sarma, H.(3) 186 Salamci, E.(2.5)207 Sarma,J.C.(2.6)303 Salemi-Delvaux, C.(2.6)69 Saroja, G.(1) 365 Salhi, S.(1) 682 Sasaki, H.(2.4)48 Salinaro, A. (2.5)245 Sasaki, N.(1) 205 Salinas, F.(2.5)288 Sasaki, S.(1) 563;(2.2)8; (3) 363 Salingue, F. (1) 619 Sasaki, W.(3) 707 Salleh, N.G. (3) 27 Sasaki,Y. (1) 410;(2.5) 127, 129; Salman, H.(2.2)34;(2.4)136 (3) 170 Saltiel, J. (1) 334,366;(2.3) 9 Sasamoto, K. (1) 52 Sagredo, R. (2.6)197 Sahonov, I.G. (1) 427 Sahoo, N.(2.1)39
430 Sase, M. (1) 440; (2.2) 101; (2.5) 53 Sasse, W.H.F. (1) 486 Sastikumar, D. (1) 227 Sastre, A. (3) 598 Sastre, R. (1) 239; (3) 30,85 Sasuga, T. (2.6) 97 Sata, T. (2.5) 105 Satake, K. (2.4) 5 8 Sato, C. (1) 498 Sato, H. (1) 42 1,659; (2.4) 73, 168; (3) 22 1 Sato, K. (2.6) 222 Sam, N. (2.1) 13; (2.5) 32; (3) 571 Sato, S.(1) 231; (2.4) 262; (2.6) 314; (2.7) 174 Sato, T. (1) 231; (2.2) 47; (2.5) 209 Satoh, M. (3) 281 Satomura, M. (2.6) 53 Sauer, M. (1) 169 Saunders, M. (1) 420; (2.2) 22 Saupc, G.B. (1) 533 Sauvage, J.-P. (1) 39,41,485, 549; (2.5) 289 Sauvajol, J.L.(2.5) 193 Savarino, P.(2.6) 230 Savinov, E.N. (2.5) 264 Saviron, M. (2.6) 266 Savitskaja, A.V. (1) 212 Savitsky, A.N. (1) 667 Sawaki, Y. (2.2) 4; (2.4) 219,232; (2.5) 85; (2.6) 102, 103, 121 Sawayanagi, Y. (2.2) 47 Sawicki, D.A. (1) 128 Sayama, K. (4) 28, 30 Sayil, C. (1) 456 Scaiano, J.C. (1) 246,248,441, 657; (2.1) 2,4, 10,37,46; (2.2) 84; (2.3) 23, 109; (2.4) 247,254; (2.5) 41,43,91, 118, 119,230; (2.6) 189, 190, 311; (2.7) 31, 141 Scandola, F. (1) 549 Scamell, M.P.(2.5) 116 Scavarda, F. (1) 328; (2.4) 59; (2.6) 156 Schacl, F. (1) 336,453; (2.3) 76 Schaer, P. (3) 298 Schafer, K. (1) 524; (3) 730,73 1 Schafher, K. (1) 214 Schamschule, R.(1) 83, 138; (2.5) 256 Schanze, K.S.(3) 602 Scharf, H.-D. (2.2) 29; (2.4) 144; (4) 27 Schatz, T.R. (1) 487 Scheer, H. (1) 56
Photochemistry Scheer, R. (4) 62 Schcffer, J.R (2.2) 68,94, 132; (2.3) 47; (2.4) 55; (2.5) 78; (2.6) 87, 152,269,271 Scheidhauer, P. (2.6) 71 Scheiman, D.A.(3) 207 Scheirs, J. (3) 671,677,678 Scheller, D. (2.4) 241; (2.6) 132 Schcnkevcld, V.M.E.(1) 694 Schepp, N.P. (2.5) 82 Scherer, S. (2.2) 83 Scherf, U. (3) 375,391,396,400, 401,403 Schershukov, V.M.(1) 457 Scherz, A. ( I ) 56 Schiel, C. (4) 13 Schiesser, C.H. (2.6) 352 Schillen, K. (3) 487 Schiller, S.(2.1) 24; (2.5) 72 Schinke, R. (2.7) 66 Schirmeister, T. (2.4) 69 Schlichthorl, G. (4) 48 Schmaile, H.W. (1) 50 Schmall, B. (2.3) 59; (2.6) 39 Schmehl, R.H. (1) 204,487 Schrnickler, H. (1) 214 Schmid, W.E. (1) 339; (2.3) 86 Schmidt, A.J. (2.4) 77 Schmidt, B.F. (2.6) 210; (2.7) 179 Schmidt, E.(3) 768 Schmidt, G.M.J. (2.6) 109 Schmidt, H. (3) 294,789 Schniitt, M. (2.7) 127 Schrnittcr, A. (3) 768 Schnabel, W. (2.3) 119; (2.7) 195; (3) 100,105 Schneider, K. (2.3) 116 Schneider, M. (2.3) 8; (3) 194 Schneider, P.C. (1) 698 Schneider, S. (1) 123 Schneider, W.F. (3) 771 Schwk, H.-W. (4) 61 Schoeneich, C. (2.5) 39 Schoenhals, A. (3) 306 Schoevaars, M. (3) 323 Scholes, G.D. (1) 460; (2.4) 250 Schollmaycr, E.(3) 697-699 Scholz, P. (1) 214 Schrami, J. (2.4) 140 Schreiber, V.M. (1) 274 Schroeder, A. (3) 185 Schroeder, D.J. (4) 67 Schroeder, J. (2.1) 30,3 1; (2.3) 5; (2.4) 15 Schropp, R.E.I.(4) 72 Schubert, K. (1) 614 Schubert, U. (2.7) 91 Schuetz, A. (1) 302; (2.4) 235
Schulman. S.G. (1) 104 Schultz, R.(4) 76 Schulz, H. (3) 137 Schunemann, P. (1) 275; (2.2) 123; (2.5) 90 Schuster, D.I.(1) 420,427; (2.2) 22; (2.5) 139, I97 Schuster, G.B. (2.2) 130, 131 Schwack, W. (2.1) 11 Schwartz, H.H. (3) 282 Schwarz, J. (2.1) 15; (2.4) 2.12; (2.6) 84 Schwan, S. (2.2) 40; (2.5) 31 Schweiger, G. (3) 235 Schweitzcr, G.(1) 450 Schwoerer, M. (3) 386,387 Sciccitano, M. (3) 671 Scoponi, M. (3) 742 SCOIIWIO, G. (1) 415,418,422426; (2.5) 10, 136, 137 Scott, A. (3) 182 Scott, J.C. (3) 378 Scott, J.S. (2.7) 101 Scranton, A.B. (3) 144, 167, 196, 291,587 Scranton, B.(3) 209 Se, K. (2.4) 39; (3) 308 Sears, D.F.,Jr. (1) 366; (2.3) 9 Seaton, C. (1) 637 Sebastiani, G.V. (2.5) 300 Secen, H. (2.5) 207,208 Sechin, A.Y. (1) 102 Seely, G.R. (1) 509,520 Segawa, T. (1) 496; (2.3) 50; (2.5) 226 Segura, J.L. (2.3) 72; (2.5) 169; (2.6) 155; (3) 383,430,437 Seidel, C.A.M. (1) 169, 170, 181, 182 Seidler, P.F. (3) 407 Seiferliiig, B. (3) 198 Seixas de Melo, J. (1) 267 Seki, K. (2.2) 72; (2.4) 95; (2.6) 55, 138 Seki, T. (3) 3 1 1 Sekiguchi, H. (3) 200,227 Sekiguchi, S. (1) 134; (2.1) 1; (2.5) 45 Sekikawa, T. (2.4) 64 Sekine, A. (2.6) 337,338; (2.7) 163 Selitrenkov, A.V. (2.6) 159 Selva, A. (2.4) 173; (2.6) 187 Semin, D.J. (1) 173 Senanayake, K. (1) 57 1 Senge, M.O. (1) 510; (2.5) 70 Sengupta, D. (2.1) 33 Sension, R.J.(1) 332,340; (2.3)
43 1
A U C ~ OIndex T 58
Sentein, C. (3) 64 Senyuk, M.A. (1) 153 Seo, B.S. (3) 230 Seoane. C. (2.3) 72, 73; (2.5) 121, 169; (2.6) 155,265
Seoul, C. (3) 42 Serbotoviez, C. (3) 145 Sergey, S .P. (3) 3 16 Serguievski, P. (1) 313; (2.5) 181 Serhalti, I.E. (3) 113 Scrizawa, I. (3) 149 Serpone, N. (2.5) 245 Serrano, J. (3) 165 Sertova, N. (2.6) 72; (3) 746 Sessler, J.L. (1) 2 14 Seta,P. (1) 381,412 Setchell, P.K. (2.5) 117 Seth, J. (1) 464-466 Setnescu, R. (3) 625 Setnescu, T. (3) 625 Severin, T. (2.5) 185 Sha, C.-K. (2.1) 62; (2.6) 98 Shade, J.E. (2.7) 103 Shah, M. (3) 27 Shahiara, M.R.(3) 572,573 Shaikevich, A. (3) 186 Shajakhmedov, S.S. (1) 274 Shakirov, A.M. (3) 234 Shans’kii, L.I.(3) 367 Shapiro, L.(3) 298 Sharma, B.K. (2.5) 160 Sharma, U.(2.2) 58 Sharp, K. (3) 142 Shape, A. (2.2) 105; (2.6) 112 Sharshira, E.(2.1) 25,26; (2.4) 202,225 Shaw, L.E. (2.7) 74 Shawn, C.R. (2.4) 132 She, X. (3) 128 Shebenda, Ya. (3) 668 Sheer, R (4) 64 Sheldrick, W.S. (2.4) 201; (2.7) 19 Shelnutt, J.A. ( I ) 534 Shen, F. (3) 483 Shen, S.Y. (1) 208 Shen, T. (1) 3 17,3 18,462,472, 539; (2.2) 82; (2.5) 55,65,67, 68,262,276,277, 286,293; (2.6) 261,262 Shen, W. (3) 128 Shen, X. (1) 193 Shen, Y. (1) 557; (3) 467,483 Sheng, L. (2.7) 81 Shepard, M.J.(1) 428; (2.5) 138 Sherban, D.A. (4) 73 Sheridan, R.S. (2.7) 26
Shershukov, V.M. (1) 279; (2.6) 147
Sheshtakova, M.I. (3) 660 Shevchenko, T. (1) 662 Shi, H.(1) 34 Shi,J. (2.4) 100; (3) 41 1 Shi,J . 4 . (2.3) 34
Shi,W.(3) 131, 159,216,217 Shi,Y. (2.1) 68; (2.4) 271; (2.6) 226
shi, z.-Y. (1) 477 Shibaev, V.P.(3) 510 Shibuya, K.(2.5) 21 1 Shichi, T. (2.5) 85 Shiff, A.I. (2.4) 86; (2.6) 74 Shiga, T. (1) 605; (3) 343,460, 535
Shigeri, Y. (2.2) 18; (2.6) 118 Shikata, T. (I) 40 Shilling, F.C. (3) 192 Shilov, V.V. (3) 184 Shim, H.K. (3) 4 18,436 Shim, S.C. (2.2) 9, 117-119; (2.3)
10,21,22; (2.4) 27, 129, 130, 133, 141, 153; (2.6) 16, 125, 33 1 Shim, K. (2.3) 83; (2.4) 2 10; (2.6) 122 Shimada, H. (1) 62 1 Shimada, R (2.6) 334; (2.7) 158; (3) 340 Shimamoto, K. (2.2) 18; (2.6) 118 Shimamoto, S.(3) 241 Shimoa, T. (1) 288 Shimasaki, C. (2.4) 272; (2.6) 295 Shimizu, H. (2.3) 1 Shimizu, I, (2.2) 47; (2.5) 209; (3) 120 Shimizu, M. (3) 122 Shimizu, S. (2.5) 224; (2.7) 123 Shimizu, T. (1) 260 Shimizu, Y. (2.2) 115; (2.4) 121; (2.6) 49 Shimo, T.(2.2) 20; (2.6) 104 Shimohge, T. (1) 440; (2.2) 101; (2.5) 53 Shimokawa, R (4) 57 Shimomura, M.(2.4) 19,34; (2.6) 32; (3) 358 Shimoyama, S. (3) 371 Shimura, K. (2.4) 62 Shin, E.J. (1) 364,371; (2.3) 10; (2.4) 27; (2.6) 16, 17 Shin, H. (2.6) 215; (3) 712 Shin, K.J. (1) 93 Shin, S. (2.7) 49 Shin, S.C. (1) 364 Shin, S.M. (2.4) 137
Shinar, J. (3) 394,449 Shinji, 0. (2.4) 20 Shinkai, S . (1) 32,585; (2.6) 3 1 Shinnai, T. (2.4) 61 Shinoda, S. (1) 471 S h i n o w H. (2.7) 144 Shinomori, H. (1) 585; (2.6) 3 1 Shinomura, M.(1) 352 Shinose, M. (3) 14, 71,73, 77 Shioiri, T. (2.5) 274 Shiokawa, J. (3) 622 Shiomori, K. (2.5) 216; (3) 791 Shiono, H. (2.4) 283; (2.7) 184 Shiono, T. (3) 5 15,516 Shipp, D.A. (1) 602 Shirafuji, J. (3) 361 Shiragami, T.(2.3) 83; (2.4) 210; (2.5) 5; (2.6) 122 Shirai, H. (1) 307; (3) 522,620; (4) 22 Shirai, J. (2.7) 33 Shimi, M. (3) 132 Shirakawa, H. (3) 332,517 Shirasaka,Y. (2.3) 79 Shirota. H. (1) 503 Shishkin, G.V.(2.7) 54 Shim, A. (2.6) 213 Shitangkoon, A. (2.4) 269 Shitara,Y.(3) 299 Shizuka, H.(1) 268,438440, 484; (2.2) 101; (2.5) 34,35, 53; (2.6) 148 Shobu, S. (2.7) 82 Shortreed, M.R. (1) 477 Shruka, H. (1) 166 Shteingartz, V.D. (2.7) 54 Shtompel, V.I. (3) 226 Shu, L.-H. (2.5) 133 Shugyo, M.(2.5) 145 Shukuronov, A.P. (1) 703 Shulga, A.M. (1) 467 Shultz, J.W. (3) 259 Shurakhina, A.V. (1) 274 Siano, M. (3) 80 Sidorenko, L.V.(2.4) 240 Sieburth, S.McN. (2.2) 71; (2.4) 166 Siedler, D. (3) 293 Siedschlag, C. (1) 376; (2.5) 129, 195 Siegel, M.G. (2.6) 115 Siemoneit, S. (2.7) 93 Sigman, M.E.(2.3) 105 Sikorski, M. (1) 196; (2.4) 25 1 Sikurova, L. (3) 568 Siligardi, G. (1) 35 Silling, S.A. (3) 286 Sillion, B. (3) 227
Photochemistry
432
Silnikov, V.N. (2.7) 53 Silva, C.R (2.1) 34 Simashkevich,A.V. (4) 73 Simionescu, B.C. (3) 55 Simionescu, C.I. (3) 55 Simo, T. (2.2) 67 Simon, J.A. (1) 204,487 Simone, K. (3) 107 Simonin, I. (1) 56 Simonson, R (3) 719 Sinbaldi-Troin, M.-E. (2.4) 217; (2.6) 99,80
Singh, A.K. (1) 291 Singh, R.P. (3) 656,657,78 1 Singh, T.P. (2.2) 5 1; (2.4) 157 Singh, V. (2.2) 58,61 Sinha, A.S.K. (4) 3 1 Sinha, S. (1) 116, 199,501,502 Sinnwell, V. (2.2) 15; (2.6) 123 Sinta, R (2.6) 3 11 Sinturel, C. (3) 648 Sisido, M.(1) 615; (2.6) 10 Siskos, M.G. (2.6) 166; (2.7) 192 Sitek, F. (3) 75 1 Sivachenko, A.Yu. (1) 90; (2.5) 26
Sivaram, B.M. (I) 626 Sivaram, S. (3) 656,781 Sjoeback, R. (1) 6 18
Skalski, B. (1) 286; (2.6) 151,251 Skets, I. (3) 195 Skibsted, L.H. (1) 255,434 Skinner, D. (3) 148,229 Skrede, G. (2.6) 243 Skripachev, V.I. (3) 760,761 Skripkina, V.T. (1) 457; (3) 34 Skurat, V.E. (3) 735 Slate, C.A. (1) 526 Slaven, W.T. (3) 348 Siavik, 3. (1) 613 Sleiter, G. (2.4) 189; (2.6) 235 Slominski, Y.L. (I) 343 Sluch, M.I.(1) 41 1 Sluggett, G.W. (1) 243; (2.3) 69; (2.6) 326,350; (2.7) 157; (4) 23 Smirnova, N.P.(1) 594; (4) 32 Smit, J.P. (2.7) 83-85 Smith, A. (3) 664 Smith, C.A. (3) 738 Smith, D.L. (3) 381 Smith, G.J. (1) 532 Smith, G.L. (3) 61 1 Smith, J.A. (2.1) 54; (2.4) 227; (2.6) 183 Smith, J.R.L. (2.5) 117 Smith, L.M. (2.7) 102 Smith, M.J.A. (3) 734
Smith, P. (3) 520 Smith, T.A. (1) 428,602; (2.5) 138
Smith, W.B. (2.6) 186; (2.7) 6 Smyth, M.R. (1) 29 Snoonian, J.R (2.7) 146 Sobczak, M. (2.1) 18, 19; (2.5) 89 Sobczynski,A. (4) 10 Sobolewski, A.L. (1) 137, 139 Sobrio, F. (2.7) 35 Sobus, M.T. (3) 756 Sokolik, I. (3) 441 Sokolov, V.Yu. (3) 464 SokolowskaGajda,J. (3) 801 Solari, E. (2.3) 99; (4) 21 Solaro, R. (3) 50,309 Soldatenkova, V.A. (3) 3 14 Solomon, D.H. (I) 602 Solov'yov, K.N. (1) 2 18,508; (2.5) 60
Solymosi, F. (2.7) 150 Somekawa, K. (2.2) 20,67; (2.6) 104
Sonada,Y.(1) 333; (2.3) 78
Sonawane, H.R. (2.1) 59; (2.4) 46 Sone, M. (3) 5 11 Sonek, G.J. (1) 633 Song, F. (3) 536 Song, J. (1) 392; (3) 493 Song, N.W. (1) 156; (2.4) 215; (2.6) 81
Song, O.K. (3) 557 Song, X. (1) 23,534; (2.2) 113,
114; (2.4) 71,120; (2.6) 36, 279 Song, Y.-Q. (2.7) 145; (3) 210 Song, 2.(3) 772 Sonoda, N. (2.3) 110, 111; (2.7) 140 Soos, Z.G.(3) 334 Soper, S.A. (1) 5 Sopina, I.M.(3) 226 Sorensen, T.S. (2. I) 35 Sorkhabi, 0. (2.7) 120 Sortino, S . (1) 195; (2.1) 47; (2.5) 97 Sosnowski, T.S. (1) 642 Soubra, S. (2.7) 97 Soulet, A. (1) 559 Sour, A. (1) 549 Sousa, T. (3) 501 Soutar, 1. (3) 498,534 Spahni, H. ( I ) 683 Spalek, 0. (1) 375 Spanger-Larsen, J. (1) 280 Spider, M.T. (2.5) 115 Spochik, A.E. (2.3) 35 Spoem, J.K. (3) 169
Sporea, D. (3) 67 Spnveitzer,H. (3) 437 Squier, J. (1) 642 Sreekumar, R (2.4) 270; (2.6) 212 srinivasan, c. (1) 499 Srinivasan, K.S.V. (3) 243 Srivastava, N. (4) 75 Srividya, N. (1) 224,608; (3) 569 Sryanimallika, K.A.D. (2.1) 67 Staab, H.A. (I) 45 1,506,507; (2.5) 61,223; (2.6) 256,257 Staerk, H. (1) 89,452,660,661 Staerk, R (1) 6 19 Stagira, S. (3) 396 Staikos, G. (3) 593 Stangier, K. (4) 76 Starakhin, A. (1) 356 Starchov, K. (1) 705 Staren'ka, V.M. (3) 193 Staring, E.G.J. (3) 740 Starmtin, A.N. (1) 102 Stasko, A. (2.7) 10 Steckhan, E.(2.3) 75, 114; (2.4) 169; (2.6) 321
Steel, H. (1) 56 Steenken, S.(2.1) 8; (2.3) 116; (2.6) 141, 166; (2.7) 192
Steiger, D. (3) 520 Steinhuber, E. (3) 383,430,437 Steinkamp, J.A. (1) 653 Steinman, E.A. (1) 388; (3) 354 Stelmach, J.E. (2.6) 115 Stelzer, F. (2.6) 157; (3) 420,442 Stenbcrg, B. (3) 626 Stengele, K.-P. (2.4) 278 Stenhagen, G. (1) 64 Stepanov, A.N. (3) 660 Stephens, J.A. (3) 434 Stevens, J.E.(2.7) 65 Stewart, S. (1) 569; (3) 206 Stibor, I. (1) 375,399 Stiel, H. (1) 215 Stilbrany, R.T. (1) 62 Stilzel, D. (1) 37 Stirner, W. (2.4) 209 Stitzel, D. (2.6) 62 Stochel, G. (2.7) 76 Stock, G. (1) 92 Stocker, H.F.C. (3) 651 Stockman,T.G. (1) 30 Stoddart, J.F. (1) 5 17 Stone, S. ( I ) 519; (2.6) 263 Stosscr, R. (2.4) 258; (2.7) 46 Stottmeister, U. (2.6) 245 Stowell, M.H.B. (2.2) 122; (2.4) 226
Strachan, J.-P. (1) 465,466 Strati, G. (1) 362
Author Index Strausky, H. (1) 610 Strauss, H.L. (3)705 Street, S. (4)60 Strehmel, B.(1) 359 Strehmel, V. (1) 359 Strelkova, T.V. (3) 526 Streltsov, A.M. (1) 59 Striplin, D.R.(1) 488,526 Strohriegl, P.(3)407 Stull,A.D. (1) 575 Stunpe, J. (3)266,3 13 Styring, S.(1) 60,63,64,66 Su, B.(2.5)188 su, c.(3) 97 Su, H.(1) 543;(2.5)52 Su, J. (1) 478;(2.6) 177;(3) 33 su, W.P. (3) 33 1 Su,Y.(2.5)196;(2.6)225,226 su, 2.(2.2)102 Subarmanian, P.(3) 767 Subbash, C.B.(1) 241 Sub, M. (1) 504 Subtahmanyam, M.(4)7 Subramanian, K.(3)86 Succhi, D.(1) 558 S U M ,S.G.(2.1)59; (2.4)46 Suenobu, T. (1) 404,497;(2.3) 122;(2.5)128, 131,241;(2.6I) 96 Suetbeyaz,Y. (2.5)207,208 Sueter, U.W. (3)55 1 Suezawa, H. (2.7) 145 Sugano, T.(3) 361 Suganuma, H.(3) 363 Sugaya, T. (3)506 Sugi, S.(3) 680 Sugihara, G.(1) 300 Sugihara, K. (1) 668;(2.7) 168 Sugimori, T. (2.5)168 Sugirnoto, A. (2.4)4, 167,268; (2.6)91, 116 Sugimura, T. (2.3)1 Sugita, K.(3)283,547,635 Sugita, T. (3)547 Sugiura, K.(3) 571 Sugiyama,H.(1) 528;(2.2)73; (2.6)136, 174 Sugo, T. (3) 283 Sugrobov, V.I. (3) 234 Suguhara, Y.(3)275 Suhling, K.(1) 646 Suishi, T. (2.2)67 Suishu, T.(2.6)104 Suits, A.G. (2.2)54;(2.7) 136, 152, 188 Sukova, V.A. (1) 535 Sulekha, A. (2.5)227;(2.6)219 Sulikowski, G.A. (2.2)60
433 Sulikowski, M.M. (2.2)60 Sullivan, B.P.(1) 557 Sumarahundu, J.K. (1) 638 Sumida, J.P. (1) 431,509;(2.5) 294 Sumida, M. (3) 38 Sumiishi, S.(2.4)199;(2.6)329; (2.7)161 Surnino, T. (3) 132 Sumita, M. (3) 632 Sun, F. (2.1)35 Sun,H.(2.5)186 Sun,J. (1) 206;(3)687;(4)63 Sun, J.G.(2.2)102 Sun,L.(1) 60,63,64,66 Sun,S.J. (3)266,325 Sun,T. (1) 692 Sun, W.(2.7)136 Sun,W.-F. (2.5)177 Sun,X.(3)362 Sun, X.D.(2.6)56 Sun, Y.(1) 391 Sun, Y.-P. (1) 112,374,394;(3) 51,553,596;(4)46 Sundahl, M.(1) 63 Sundell, P.E. (3) 14,71,77 Sundholter, E.J.R. (1) 305 Sung, C.S.P. (3) 171-173,359 Sung, K.(2.2)93 Sunney, S.I. (2.4)226 Sup, P.M. (3) 353 Surapaneni, R.(2.6)105 Suratwala, T.(3) 792,793 Suresh, K.G.(2.5)273 Sujan, P.R(1) 377 Suslov, A.N. (2.3)95; (4)25 Susuki, K.(1) 166 Suter, U.W. (3) 558 Sutherland, J.C.(1) 690 Sutin, N.(4)9 Suwinska, K.(1) 145 Suzuki, H.(1)323 Suzuki, I. (2.5)141;(3) 600 Suzuki, K.(1) 262,387 Suzuki, M. (1) 497;(2.3)122; (2.5)5,241;(2.6)96;(3) 113, 450,620;(4)22 Suzuki, T. (2.3)38, 106;(2.7)135 Suzuki, Y.(1) 333; (2.3)78;(2.4) 95;(2.6)55 Svec, F. (3) 220 Swager, T.M. (3) 447,449,598 SwaIIen, S.F.(1) 477 S w a m i d a n , C.S. (3) 245,246 Swanson, L.(3) 498,534 Swanson, M.J. (3)284 Swaranlatha, Y.(2.2)51;(2.4) 157
Swarnkar, M.(4)42
Sweeney, D.(2.7)40 Swiatek, M.(3) 665 Swiatkiewicz, I. (1) 638;(3) 366 Sworakoeski, J. (3)310 Sydnes, L.V. (2.3)55; (2.5) 144; (2.7)142 Sykora, M. (4)44 Synaly, D.(2.2)56 Szajdzinska-Pietek, E. (1) 1 1 1 Szarka, A.Z. (1) 354;(2.4)14 Szczepanik, B. (2.4)261 SZ, N.S.-K. (2.7)149 Szemes, F.(1) 570 Szonyi, S. (3)503 Szulbinski, W.S.(2.5)112 S~yman~ka-Bu~ar, T. (2.7)75 Szymanski, M.(1) 265;(2.6)282 Tachikawa, H. (2.7)159 Tachikawa, Y.(2.7)78 Tachiya, M.(1) 95 Tada, K.(3) 426,454,459,464, 466 Tada, N. (3) 458,463 Tada, S.(3) 149 Tadashi, H.(1) 645 Taen, S.(1) 98 Taga, M.(2.2)1 Tagaya, H.(2.4)98 Tagliatesta, P. (1) 469 Taglietti, A. (1) 558 Tahara, R (1) 352;(2.4)34;(2.6) 32 Tahara, T. (1) 299 Tai, A. (2.3)1 Tajima, M.(4)57 Tajima, Y.(3) 114,248 Tak, Y.H. (3)421 Takada, H.(2.6)336 Takada, T.(2.3)16;(2.4)75, 199; (2.6)329;(2.7)161 Takagi, K. (2.2)4;(2.4)219,232; (2.5)85;(2.6)102, 103, 121 Takagi, S. (2.5)5 Takagishi, T. (3) 794,799 Takahashi, A. (3)275 Takahashi, H.(2.4)62 Takahashi, M.(2.2)88;(2.4)205; (2.5)96;(2.6)124,291,341 Takahashi, 0.(1) 370;(2.3)12; (2.4)26 Takahashi, Y.(1) 498;(3) 149, 613 Takakura, N.(2.6)88 Takami, S.(2.2)62 Takamoto, T. (4)59
Photochemistry
434 Tdamuku, S.(2.5)240;(2.6)347 Takane, N.(1) 21 1 Takasu, D.(2.5)14 Takatani, K.(3)258 Takats, J. (2.7)79 Takatsuka, H.(3) 268 Takayama, M. (2.6)136 Takayanagi, H.(2.3)103, 104 Takebayashi,Y.(1) 133 Takeda, K. (3) 736 Takeda, Y.(3) 333 Takemura, H.(2.4)2 Takenaka, S.(2.5)187 Takeshita, H.(2.2)1, 133, 134; (2.4)182,223,237;(2.6) 193; (2.7)16,18 Takeshita, M. (2.3)13, 14;(2.4) 24,200;(2.6)43-45 Taketsuga, T. (2.7)115 Takeuchi, K. (2.5)155;(3) 114, 248-250,341 Takeuchi, M. (1) 32,585;(2.6)3 1 Takeuchi, S.(1) 299 Takezoe, N.(3) 707 Takui, T. (2.6)222 Takuwa, A. (2.6)354 Talbot, M.F.J. (1) 128 Taliani, C. (3) 468 Tamagaki, S. (2.4)74;(2.6)38 Tamai, T. (2.6)97 Tamaki, T. (2.4)95;(2.6)55 Tamburelli, I. (2.7)63 Tambwekar, S.V.(4)7 Tameev, A.R.(4)58 Tamura, K.(2.2)47 Tamura, M. (1) 42 Tamura, N.(3) 327 Tamura, 0.(2.3)120;(2.6)139 Tamura, Y.(2.1)61;(2.5)99 Tan, Q.(I) 519;(2.6)263 Tan, W.(1) 477 Tanabe, G.(2.3)41,42;(2.4)51, 52 Tanabe, H. (1) 166 Tanabe, Y.(3) 358 Tanaka, F.(1) 100 Tanaka, K.(2.4)199;(2.6)329; (2.7)78, 161;(3) 31 1 Tanaka, M. (2.6)53;(2.7)27 Tanaka, N.(1) 496;(2.3)50;(2.5) 21 I, 226 Tanaka, S. (3)703 Tanaka, T. (1) 484;(2.5)156, 187;(2.6)97;(2.7)78;(3) 574 Tang, C.W.(3) 411,423 Tang, Y.(2.2)114;(2.4)120 Tang, Y.W.(2.2)113;(2.4)71
Tani, H.(2.5)274 Tani,M. (1) 659;(2.4)73 Tanigaki, N.(3)438 Tanigaki, T. (3) 170 Taniguchi, A.(3) 674 Taniguchi, H.(2.4)49;(2.6)302 Taniguchi, S.(1) 433,521;(2.5) 140 Tanimoto, Y. (2.3)98;(2.5)254 Tanoue, Y.(3)241 Tao, J. (3) 206 T ~ o2.-F. , (2.5)242 Taqui Khan, M.M. (4)79 Taran, S.G. (2.4)240 Tarka, R.M.(3) 375 Tarrach, G.(1) 177;(3) 566 Tasch, S.(3) 375,380,400,401, 420,442 Tashiro, M. (2.2)8;(2.4)42 Tashiro, Y.(2.6) 145 Tassi, E.L.(3)261 Tatarova, L.E.(2.3)100 Tatikalov, A.S. (2.6)73 Tatsumi, T. (2.5) 165 Tatsuno, T. (2.5)240;(2.6)347 Tauber, A.Y.(1) 505,5 12;(2.2) 126;(2.5)56,292;(2.6)258 Tauchner, K.(1) 215 Tauer, E. (1) 163 Tavani, C. (2.6)315; (2.7)12 Tavender, S.M. (1) 460;(2.4)250 Tavernicr, H.L.(1) 113,529;(2.5) 249,250 Tawa, K.(3) 496 Tawada, M. (3)506 Taylor, D.L.(1) 616 Taylor, M.R.(2.1)55;(2.4)228; (2.6)184 Taylor, T.R. (2.7)62 Tellez-Rosas, M. (3) 49 Tenetova, E.D. (2.7)54 Tepper, D. (1) 295 Terada, A. (3) 241 Teraguchi, M.(3) 454 Terano, M.(3) 630 Teraoka, Y.(2.7)82 Terauchi, M. (2.5)168 Terazima, M.(1) 135,136,668, 670,671;(2.1)17; (2.5)87; (2.7)168 Tercnetskaya, 1.P. (1) 36;(2.3)88 Tereschchenko, O.G.(3) 367 Temovoy, A.I. (3) 735 Tero-Kubota,S.(1) 134;(2.1)1; (2.2)101;(2.5)45,53 Terreni, M. (2.4)181;(2.6)227 Tessler, N.(3) 406 Testa, A.C.(1) 285
TetzlafF, T. (2.5)22;(2.6)2 Teuchner, K.(1) 56 Teulade, J.-C.(2.6)99 Tevault, C.V.(4)80 Tcyssedre, G.(3) 329 Tezuka, Y.(3) 114,248 Thakor, K.B.(3) 324 Thakur, S.K.(3)301 Thamattoor, D.M. (2.7)146 Thanasekaren, P.(1) 499 M i , P.N.(3) 657 Thiel, E.(1) 222 Thiel, W.R (2.5)173 Thiemann, C.(2.2)8 Thiemann, T. (2.2)8 Thieme, C.(3) 3 15 Thoma, K. (2.2)69 Thomas, B.(2.2)61 Thomas, J.K. (1) 447;(2.5)148 Thomas, J.L. (3)804 Thomas, K.G.(1) 416;(2.5)283 Thompson, D.W.(1) 552 Thompson, H.W.(3)538 Thompson, K.A. (1) 329 Thompson, R.S.(2.4)191;(2.6) 205;(2.7) I10 Thuery, P. (2.4)38 Thummel, R.P.(1) 487 Thurmond, K.B.(3) 499 Tian, H.(1) 478,482,543;(2.5) 33,279;(2.6)253 Tian, P. (1) 5 11; (2.5)62 Tian, X.(3)21 1 Tibima, M. (3) 295 Tidwell, T.T. (2.2)93 Tiemblo, P.(3) 329,357 Tiera, M.J. (3) 502 Tikhomirov, S.A. (1) 153 Tilley, T.D. (3)432 Timberlake, L.D.(2.2)64 Tinland, B.(3) 495 Tirelli, N.(3) 50,309 Titskaya, V.D.(3) 34 Tixier, J. (2.6)70 Tlenkopatchev, M.A. (3)56 Toaka, S. (3) 662 Toba, Y.(3)99 Tobe, Y.(2.4)57 Tobita, S.(2.6)148 Tochizawa,T. (2.7)36 Tochtennann, W. (2.3)60 Toepper, K.(4)62,64 Toffoletti, A. (1) 415,424 Togashi, K. (3)338 Togo, H.(2.6)353 Tokai, M.(3) 579 Tokareva, O.G. (2.5)172 Tokino, S.(3) 712
Author Index Tokita, S. (2.4)123 Tokiwa, Y.(3) 739 Tokumaru, K.(1) 211; (2.3)103, 104;(2.6)26 Tokura, Y. (3) 333 Tolkachev, V.A. (2.7)169 Tolmachev, A.I. (1) 343 Tolman, W.B. (4)19 Tolstorozhev, G.B.(1) 153 Tomaschewski, G.(3) 223 Tomcik, P.(3) 222 Tomida, I. (3)113 Tominaga, K.(1) 263,503 Tominaga, T.(3)613 Tomioka, H. (2.7)21,22 Tomov, I.V.(2.6)224 Tompert, A. (3)430 Tonegawa, H. (4)47 Tonelli, C. (3) 671 Tong, L.(3) 644 Tong, Y.(3)96 Tong, Z.(2.4) 159,243;(2.5)202; (4)24 Temnesen, H.H. (2.6)243,247, 248 Tonokura, K. (2.3)38;(2.7)135 Torga, J.R. (1) 673 Torii, Y.(1) 260 Torikai, A. (3) 688 Torimoto, T. (2.5)161 Torkelson, J.M. (3)610,612 T O ~ OR. S ,(2.2)84;(2.3)23-25; (2.4)206,247,267 Torniainen, K. (2.6)250 Torrealba, A. (2.2)99;(2.4)171; (2.6)35 1 Tomano, J.A. (2.7)154 TorresGucia, G.(1) 376 Tosaka, E.(2.1)61;(2.5)99 Toscano, J. (2.7)14 Toshima, N. (4)43 Toshimori, M. (1) 645 Tossell, J.A. (2.7)201 Toth, G. (2.5)219 Touwslager. F.J. (3) 145 Toya, M. (3) 7 Toya, Y.(3) 191 Toyami, K.(1) 308 Toyoda, I. (4)47 Toyomi, K.(2.7)191 Toyota, H. (3) 120 Toyota, K.(2.4)41,62;(2.6)349 Toyotaka, H.(3) 736 Tramer, A. (2.5)27;(2.7)200 Tramm-Werner, S.(4)78 Tran, A. (1) 64 Tran, N.B. (2.4)252 Tranasel, K.(1) 564
435 Tran-Cong, Q. (1) 713;(3) 153, 236 Tm-Thi, T.N. (1) 261 Trapp, M.A. (3) 14 Travnicek, E.A. (2.4) 117 Treadwey, J.A. (1) 55 1 Trentham, D.R. (2.7)177 Tripathi, H.B.(1) 270 Troe, J. (I) 320;(2.3)5 Trofimov, A.V. (3)629 Troin, Y.(2.4)217; (2.6)80 Tromberg, B.J. (1) 633 Trommsdodf, H.P.(2.6)220 Troquet, M. (3) 691 Trotter, J. (2.2)68,94,132;(2.5) 78; (2.6)87,269,271 Tnmk, J.G.(I) 690 Truscello, A.M. (2.4)173;(2.6) 187 Truscott, T.G. (1) 209;(2.5)178 Trushinski, B.J. (3) 118 Truskey, G.A. (1) 708 Trutbna~,L.(2.3)63 Tsai, H.-X. (2.3)40 Tsai, P.-F. (2.4) 182,223;(2.6) 193;(2.7)16, 18 Tsai, Y.-F. (2.2)81 Tsay, S . 4 . (2.5)251;(2.6) 165 Tschuhida, E. (2.5)298;(3)134 Tmg, C.-T. (2.1)62;(2.6)98 Tmg, H.-Z. (2.3)91 Tsentalovich, Yu.P. (2.1) 12;(2.4) 245 Tsiourvas, D.(3) 528 Tsivgoulis, G.M. (2.3)17;(2.4) 124 Tsnooka, M. (3) 132 Tsubata,A. (3)213 Tsuboi, Y.(2.5)141;(3)600 Tsubokawa, N.(3) 28 1 Tsubomura, T. (2.4) 180 Tsuchida, A. (3) 339 Tsuchiya, M.(3) 270 Tsuge, H. (2.6)88 Tsuji, T. (2.3)61,62,106; (2.4) 197, 198 Tsujii, K.(3) 574 Tsujimoto, K. (2.3)79 Tsujioka, T. (2.3)18;(2.4)116 Tsujishima, H.(2.2)18; (2.6)118 T s U K.(1) 28,504;(2.5) 109 Tsukahara, Y. (3) 438 Tsukamoto, K.(4)69 Tsukayama, M.(2.7)23 Tsumura, Y.(3) 7% Tsuneda, S.(3)283,547 Tsuneishi, H.(2.3)1
Tsuncki, 0.(2.5)270 Tsuru, S.(2.2)67;(2.6)104 Tsutsumi, 0.(3) 5 15,516 Tsybyshev, V.P. (2.4) 72 Tubke, J. (3) 179 Tucker, J.H.R (2.6) 130 Tucker, S.A. (3) 529 Tug, C.-H. (2.1)64, 66;(2.3)98; (2.4) 159,244;(2.5)202,254; (2.6)300 Tuniz, C. (1) 611 Tura, G.M. (2.5) 176 Turkulin, H. (3) 729 Turnbul, A. (3) 664 Turov, A.V. (2.4)240 Turri, S.(3)671 T m ,N.J. (1) 243;(2.3)81,82; (2.4)21 1; (2.6)350;(4)23 Tu~van,E. (3) 693 Twarowska-Schmidt, K.(3) 789 Tykwinski, R.R (1) 341;(2.3)2; (2.4)25;(2.6)20 Tyler, D.R.(3) 744,748 Tylli, H.(3) 710 Tysbyshev, V.P. (3) 619 Uchida, A. (1) 245;(2.5)224 Uchida, K. (2.2)116;(2.3) 14, 16; (2.4)75, 125,208;(2.6)9,42, 43 Uchida, M. (2.4)9;(3) 18 Uchida, S.(2.2)115;(2.4)121; (2.6)49 Uchida, T. (1) 621 Uchimura, S.(2.7)37 Uddin, F. (2.6)240 Udipi, K.(3) 667 Veda, M. (3) 48,712 Uejoh, K.(2.7)122 Ueno, A. (1) 42, 190, 192;(2.4) 33 Uesugi, R. (2.4)199;(2.6)329; (2.7)161 Ugur, S. (3) 582,585 Uhlma~, D.R (3)792,793 Uilett, J.S.(3)218 Ukraine&, LV. (2.4)240 Ulbricht, M. (3) 282 Ullett, J.S. (3) 260 Ulmer, L.(1) 376 Umapathy, S.(1) 349 Umemoto, S.(2.3)1 Umeuchi, S.(1) 665 Underhill, RS.(3) 590 Ungar, L.W.(1) 8 Ungerank, M.(3) 420 Unob, F.(1) 567
436 Unsaki, K. (1) 5 13 Upadhyay, S.N. (4) 3 1 Uppili, S.R. (2.2) 40; (2.5) 3 1 Urakawa, 0. (3) 236 Urano, K. (3) 338 Urano, T. (3) 122 Urbach, P. (3) 740 Urbahns, K.(2.2) 83 Usami, H. (2.4) 20 Ushakov, E.N. (2.6) 100; (3) 314 Usui, Y.(3) 99 Ute, K. (3) 290 Uzhinov, B.M. (1) 235 Vaijayanthimala, G. (1) 476 Valat, P. (2.4) 224; (2.6) 71 Valeeva, L.A. (3) 234 Valencia-Gonzalez, M.J. (1) 576, 578
Valesco-Garcia, N. (1) 578 Valet, A. (3) 752,753 Valeur, B. (1) 283, 559; (2.4) 65 Vallance, C. (2.4) 192; (2.6) 206;
(2.7) 109 Vallon, S.(3) 147 Valverse, S. (2.2) 42 van Am, M.E. (1) 50 van Benthem, M.H. (1) 650 van Caemelbecke, E. (1) 469 Vance, D.H. (1) 565,566 van der Aunveraer, M. (1) 149, 344; (2.5) 257 van der Eycken, E. (2.4) 140, 154 van der Haar, Th. (1) 143 van der Meulen, P. (1) 87 van der Schaaf, P.A. (3) 123 van der Ven, L.G.J. (3) 554 van der Werf, S. (2.6) 312 van Dijk, M. (1) 305 van Eesbeek, M. (3) 735 van Ekenstein, G.O.RA. (3) 52 van Eldik, R. (2.7) 76 Van Esch, J. (3) 195 van Essenberg, W. (2.7) 107 Van Geest, L.K. (1) 643 Van Gemert, B. (2.4) 107; (2.6) 53 van Genderen, M.H.P. (3) 525 van Hemert, M.C. (2.7) 116 Van Herk, A.M. (3) 20 Van Hest, J.C.M. (3) 525 van Hoek, A. (1) 142,652 van Kan, J.M. (1) 517 Vannikov, A.V. (4) 58 Van Nostrum, C.F.(3) 269 Vano, V. (3) 724 van Orden, A. (1) 180
Photochemistry Vanossi, D. (2.6) 73 van Stam, J. (1) 201,591 van Willigen, H. (2.5) 115 Vardeny, Z.V. (3) 4 10 Vargas, F. (2.2) 99; (2.4) 171; (2.6) 351
Varlemann, U.(3) 136 Varma, S.S.(3) 507 Vasconcellos, AS. (3) 65 1 Vasella, A. (2.4) 263 Vasil'ev, R.F. (3) 629 Vassilikogiannakis, G. (2.4) 148, 149
Vatsa, R.K. (2.7) 67, 131, 132 Vaugelade, C. (3) 124 Vauthey, E.(1) 669 Vedaldi, D. (2.6) 286 Vedernikov, A.I. (1) 353; (3) 316 Veglia, A.V. (2.4) 248 Velela, M. (4) 60 Venedictoy, E.A. (2.5) 172 Venkatachalapathy, B. (1) 290, 499
Venkateshwarlu, G. (2.6) 181 Venturi, M. (1) 48,547 Verbeck, J. (2.6) 27 Verbouwe, W. (1) 149; (2.5) 257 Vereschetin, G.S.P. (3) 486 Verhey, H.J. (3) 92,545,554 Verhoeven, J.W. (1) 73, 123, 538;
(2.4) 230; (2.6) 254,259; (3) 92,545,554 Verma, A.K. (4) 68 Verma, A.L. (1) 475 Vermeersch, G. (2.4) 92; (2.6) 58 Verrall, R.E. (1) 286; (2.6) 15 1 Vetchinov, V.P. (2.4) 216; (2.7) 57 Vetrivel, L. (1) 626 Viaene, L. (1) 149,201; (2.5) 257 Viard, M. (1) 609 Vicens, J. (1) 567; (2.4) 35,38; (2.6) 33 Vieira, A.J.S.C. (2.5) 282 Viengkhou, V. (3) 276 Vigil, M.R (3) 586 Viklund, C. (3) 220 Vill, V. (2.2) 8 Villegas, J.A. (3) 679 Vincent, M. (1) 257,562,609 Vincent, V. (2.5) 176 Vinodgopal, K. (2.5) 194 Viriot, M.L. (3) 491,501,591 Viruela, P.M. (2.6) 266 Viruela, R (2.6) 266 Viscardi, G. (2.6) 230 Vishwa, P.A. (3) 657 Visser, A.J.W.G. (1) 652
Visser, P. (2.4) 256; (2.7) 29 Viswanathan, B. (2.5) 125, 170 Vitharana, D. (3) 378 Vivona, N. (2.4) 196; (2.6) 167 Vixamar, M.(2.7) 97 Vlahacos, C.P. (1) 253 Vlahovici, A. (2.4) 186 Vlasove, N.N. (2.6) 3 19 Voelker, T.(2.4) 282; (2.6) 214; (2.7) 178
Vogel, E. ( I ) 214 Vogler, A. (2.7) 100 Vogt, P. (2.7) 127 Vogtle, M. (2.6) 157 Voit, B. (2.7) 8; (3) 22,58,741 Voldoire, A. (2.6) 99 Volkmer, A. (1) 639,640 Volkova, L.V. (3) 350 Volkovich, D.I. (1) 508; (2.5) 60 Vollhardt, C.K.P.C. (4) 19 Volodarskii, L.B. (2.4) 45; (2.6) 158
Volpp, H.-R (2.7) 67, 131, 132 von dcr Haar, Th. (2.5) 261 Von Rawer, P. (2.5) 38 von Schnering, H.G. (2.3) 60 Voronkov, M.G. (2.6) 3 19 Voropai, E.S.(I) 345 Votsmeier, M. (2.3) 5 Vrachnou, E. (4) 17 Vrana, L.M. (2.5) 106 Vreven, T. (1) 331; (2.3) 64,80; (2.6) 25
Vulto, S.I.E. (1) 59 Vyprachticky, D. (3) 606 Waarzecha, K.D.(2.5) 6 Wachter, E.A. (1) 637; (3) 355 Wachtveitl, J. (1) 347,348; (2.4) 3 1; (2.6) 30
Wacker, D.A. (2.7) 34 Wada, T. (4) 66 Wada, Y.(2.3) 101; (2.4) 150; (2.5) 158, 167
Waddill, H.G. (3) 780 Wade, E.A. (2.7) 61 Wageman, M.W. (3) 427,428 Wagner, A. (2.4) 204 Wagner, B.D. (1) 197; (2.2) 93; (2.4) 254; (2.7) 3 1
Wagner, K.(2.2) 83 Wagner, P.J. (2.1) 14, 18, 19; (2.5) 89
Wagner-Brennan, J.M. (1) 436,
54 1; (2.3) 3 1; (2.5) 268; (2.6) 89,252 Wakamatsu, S. (3) 680
Author Index Walba, D.M. (3) 254 Waldeck, D.H. (1) 303 Walker, J.W. (2.4) 270; (2.6) 212 Walker, L.A., I1 (1) 332,340;
(2.3) 58 Wail, C.G. (1) 488 Wall, E.J. (1) 695 Wall, J. (1) 14; (2.6) 188 Wall, M.H., Jr. (1) 5 14; (2.5) 295 Wall, S.T. (1) 546 Wallen, S.L.(2.7) 89 Walsh, G. (1) 61 1 Wait, D.R. (1) 600; (3) 489 Walter, N.G. (1) 619 Walton, W.B. (2.7) 83 Waluk, J. (1) 280,356,361 Wan, M. (3) 467 Wan, P.(2.1) 68; (2.3) 20, 118; (2.4) 175,271; (2.7) 197 Wan, Q. (2.5) 66, 177 Wan, W.C. (3) 429 Wan, Y. (2.5) 215 Wanaska, G. (1) 495 Wandel, H. (2.7) 19 Wang, B. (1) 31 1; (2.4) 277 Wang, C.(1) 398; (3) 107,109 Wang, C.H. (3) 557 W a g , C.-X. (2.5) 58, 59 W a g , C.-y. (2.5) 286 Wang, D. (1) 314,530; (2.5) 66, 180,291; (3) 348 Wang, D.J. (3) 336 Wang, D.-Y. (2.5) 177 Wang, E. (3) 110 Wang, F. (2.6) 144; (3) 131 Wang, G.(2.4) 226 Wang, G.J. (2.2) 113; (2.4) 71; (2.7) 143 W a g , G.-W. (2.5) 133 Wang, G.Y. (2.2) 122 Wang, H. (1) 338; (2.4) 220; (2.5) 202,287; (2.6) 23 1; (3) 467 Wang, H.-Y. (2.5) 171 W a g , J. (1) 391; (3) 24-26,94, 467,718 Wang, J.J. (2.2) 2, 3 W a g , J.-X. (2.7) 149 Wang, J.2, (3) 345 W a g , K.-H. (2.3) 40 Wang, L. (3) 187,555,772 Wang, L.-P.(2.5) 58,59 Wang, M.(2.4) 242 Wang, N. (3) 540 W a g , N.-J. (2.3) 91 Wang, P.(3) 483,616 Wang, P.F.(3) 497 Wang, P.Y.(2.4) 76; (3) 318,802 Wang, Q.(2.5) 238; (3) 187
437
Wang, Q.-M. (2.5) 58,59 Wang, R.M. (3) 614 Wang, S.(1) 334; (2.5) 287; (2.7) 91
Wmg, S.-L.(2.2) 68; (2.6) 87 w a g , S.S.(2.2) 11 W a g , T.-F. (2.7) 92 Wang, W. (3) 674 Wang, W.F. (1) 400,401; (2.2) 127; (2.5) 199,200
wang, w.4. (1) 473 Wang, X.(3) 687 Wang, X . 4 . (2.5) 58,59 Wang, Y. (1) 324,391; (2.3) 113;
(2.6) 128, 301; (3) 621,774 W a g , Y.-M. (2.4) 102 W a g , Y.P.(3) 614 Wang, Y.Q.(2.6) 34 wang, Y.Z. (3) 447 Wang, Z. ( I ) 84; (2.1) 50; (2.2) 27; (3) 162 Warashina, M. (4) 57 Ward, D. (1) 596; (3) 577 Ward, G.N. (2.7) 104 Ward, M.D. (1) 45; (2.5) 13 Waring, P.G.(1) 236 Warman, J.M. (3) 92 Warner, I.M. (1) 5, 198; (2.4) 66 Warrener, R.N. (2.6) 131 Wartewig, S.(3) 179 Warze~ha,K.-D. (2.3) 84; (2.6) 95 Wasche, M.(2.1) 63 Wasielcwski, M.R (1) 471,522, 540; (2.6) 260 Watanabc, A. (1) 250,376,383, 385,408-410,419; (2.5) 98, 126, 127, 129, 134, 135, 142, 198; (2.6) 318 Watanabe, H. (2.3) 67 Watanabe, J. (3) 511 Watanabe, K.(1) 704 Watanabe, S.(2.2) 88; (2.4) 205, 281; (2.5) 96; (2.6) 124,209, 291; (2.7) 182 Watanabc, T. (2.4) 123 Watanabe, Y.(3) 5 13 Watkins, D.M.(1) 243; (2.6) 350 Watson, J. (3) 792,793 Watson, P.G.(2.2) 3 1 Watson, W.H. (2.5) 259 Watt, D.S. (1) 238 Watzky, M.A. (1) 23 Wayne, E.(3) 415 Weaver, H.A. (2.7) 120 Weber, B. (2.1) 54; (2.4) 227; (2.6) 183 Weber, J. (2.1) 69; (2.4) 276 Weber, M. (4) 64
Weder, C. (3) 520 Weedon, A. (2.4) 5; (2.6) 1 Weghorn, S.J.(1) 214 Wegner, G. (3) 481 Wehrle, S.(2.3) 7; (2.4) 21; (2.6) 101
Wehry, E.L.(1) 686 Wei, C.-Y. (1) 281,312 Wei, P.K.(3) 708 Wei, T.-H. (1) 3 12 Wei, X.(1) 633; (3) 305 Wei, Y. (3) 107, 109 Weidemaier, K.(1) 113,529; (2.5) 249,250
Weidenbruch, M. (2.6) 333; (2.7) 162
Weidinger, A. (4) 62,64 Weidman, T.W. (4) 19 Weidner-Wells, M.A. (2.5) 120 Weigel, W. (2.1) 24; (2.5) 72, 248; (2.6) 179
Weil, D.A. (3) 57 Weinar, B.R.(2.7) 172 Weink&, S.(2.5) 210; (2.6) 305; (2.7) 173
Weiss, C.D. (3) 530 WeiR, D. (2.6) 280 Weiss, I. (3) 530 Weiss, J. (3) 129 Wciss, S.(1) 171 Weissbuch. I. (2.2) 5 Weiss-Lopez, B. (1) 1I5 Weldon, D. (1) 3 11 Wen, G.Z. (3) 33 1 WendorfF, J.H. (3) 269 Wendrinsky, J. (3) 107,109 Weng, H.(2.3) 54,94; (2.5) 192; (2.6) 176
Weng, M.(1) 317,318,462; (2.5) 65,67,68; (4) 78
Wenisch, J. (3) 379 Wennemers, H. (2.2) 83 Wennerstroem, 0.(3) 389 Wenska, G.(1) 286; (2.6) 15 1 Wentrup, C.(2.4) 256; (2.7) 29 Wenz, G. (2.3) 7, 8; (2.4) 21; (2.6) 101; (3) 194
Wern, W. (3) 154 Werner, G. (2.6) 19,245 Wery, J. (3) 399 Wessig, P. (2.1) 15,27; (2.4) 212, 258; (2.6) 83,84; (2.7) 46
West, F.G. (2.2) 86.87 Westermark, U. (3) 719 Westwell, J.R (2.5) 155 Whale, E.A. (1) 355; (2.4) 16 White, D. (3) 664 White, 1.0.(1) 223
43 8
White, J.R. (3) 642-647 Whitehead, J.B. (3) 265 Whitten, D.G. (1) 456; (2.6) 36,
178,279; (2.7) 196 Whitten, W.B. (1) 178, 179 Whittle, C.E. (3) 602 Wicke, I. (2.2) 83 Wicks, B.S.(1) 514; (2.5) 295 Widnegren, J. (1) 182 Wiech, G.(2.2) 83 Wiedenfeld, D. (1) 525 Wierlacher, S.(2.2) 95 Wiersma, D.A. (1) 19 Wiese, S.(3) 617 Wieser, K. (2.5) 185 Wieslaw, W. (1) 309 Wiessner, A. (1) 89 Wihelm, C. (3) 694 Wild, U.P.(1) 683,684 Wilde, H. (2.6) 245 Wilhelm, H.E. (1) 132,357; (3) 695 Wilk, K.A. (3) 3 10 Wilken, R. (3) 527 Wilkie, J. (1) 10 Wilkinson, F. (1) 196,200,447, 531; (2.4) 187, 251; (2.5) 148 Williams, A.S. (2.4) 193 Williams, C.M.(2.1) 54, 55; (2.4) 227,228; (2.6) 183, 184 Williams, D.J. ( I ) 5 17 Williams, F.C. (1) 577; (2.3) 63 Williams, G. (3) 18 1 Williams, J.A.G. (1) 571 Williams, L.D. (2.2) 13 I William, L.L. (3) 207 Wifliams, P.G.(2.7) 28 Williams, R.M. (2.5) 75; (2.6) 86 Williams, S.L.(1) 53 1 Williard, P.G.(2.3) 48; (2.4) 54; (2.6) 153 Willis, C. (2.7) 34 Willner, I. (1) 5 16; (2.5) 104; (2.6) 255 Willson, C.G. (2.4) 284 Willwoldt. C. (3) 634 Wilson, G.J. (1) 486 Wilson, J.A. (3) 594 Wilson, M.E.(3) 594 Wilson, S . R (1) 420; (2.2) 22 Windolph, C. (1) 25 1 Winkler, B. (3) 420,442 Winklcr, J.D. (1) 560; (2.2) 36; (2.6) 115 Winkler, J.R (1) 525 Winkoun, D.F. (1) 229,230 Winnik, F.M. (3) 493,584 Winnlk, M.A. (3) 481,487
Winter, 1. (3) 59 Winter, RE.K. (2.5) 213 Winters, M. (2.2) 124; (2.4) 207 Wintgens, V. (2.1) 37; (2.4) 224; (2.5) 91; (2.6) 71
Wirp, C. (1) 106; (2.5) 183 Wirth, M.J. (1) 712 Wirth, T. (2.5) 217 Wirz, J. (1) 275; (2.2) 123; (2.5) 90; (2.6) 21 1; (2.7) 180
Wischerhoff, E.(3) 504 Wishart, J.F. (1) 1 Wittenberg, R. (2.5) 225 Woerdeman, D.L.(3) 169 Wokaun, A. (2.7) 11 Wolcott, J.J. (3) 744 Wolf, H.C. (1) 536 Wolf, J. (3) 541 Wolff, C. (1) 376; (2.3) 60; (2.5) 195
Wolff, D.W. (1) 553 Wolff, T. (1) 302; (2.4) 235,241; (2.6) 132
Wolfrum, J. (1) 169; (2.7) 131, 132
Wolleb, H. (1) 683
Wolszczak, M.(1) 11 1 Wong, K.S. (1) 338 Wong, K.-Y. (1) 592 Wong, Y.G. (2.6) 221 WOO,K:W. (2.3) 112 Wood, B.R.(2.4) 192; (2.6) 206, 309; (2.7) 109 Woodford, J.N. (3) 557 Woods, J. (3) 133 Wooley, K.L. (3) 499 Woolhouse, A.D. (1) 532 Worrall, D.R. (1) 200,53 I; (2.4) 187 Wostratzky, D. (3) 752 Woznicki, W.(2.5) 23 1 Wright, D.W. (1) 65 Wrobel, M.N.(2.2) 28; (2.6) 113, 119 Wu, C. (3) 197,488 Wu, C.H. (2.2) 94; (2.5) 78 Wu, C.J. (2.4) 76; (3) 318,802 Wu, C.Q. (4) 68 Wu, D. (2.5) 175 Wu, F.(2.7) 172 Wu, G.(2.7) 146; (3) 96 Wu, H. (3) 539 WU, H.-M. (2.5) 133 Wu, H.S. (3) 539 Wu, J.Y. (2.3) 52; (2.4) 127 Wu, K.H. (3) 156 Wu, L.C.(2.2) 68; (2.6) 87 Wu, M.W.(1) 78; (3) 398,608
Photochemistry Wu, Q.(3) 540 Wu, S.(1) 372; (2.2) 10; (2.3) 15; (2.5) 269; (3) 483
WU, S.-H. (2.5) 133; (3) 550 WU,S.-K. (1) 234; (3) 497 wu, S.P.(2.2) 11 Wu, T. (2.1) 12; (3) 204 Wu, Y. (1) 206; (2.6) 226; (3) 5 15 wu, Z.W. (3) 345 Wudl, F. (3) 414,560,598 Wulff-Molder. D. (2.1) IS, 27; (2.4) 212; (2.6) 83,84
Wulkow, M. (3) 88 Wwchiers, R (4) 76 Wuyun, Q.G.(3) 539
Xia, J. (2.4) 270; (2.6) 212 Xiao, M. (1) 175 Xie, J. (1) 31, 185; (2.5) 179 Xiong, G.X. (1) 208 Xiong, Y. (1) 84 Xu, B.(2.6) 143; (3) 326 Xu, C. (1) 392; (3) 188 Xu, G. (2.5) 69 Xu, G.Q. (2.7) 69 Xu, G.Z. (3) 69 Xu, H. (2.5) 33, 220,279; (2.6) 253
Xu, H.J. (1) 208 Xu, J. (1) 185,206 XU,J.-F. (2.5) 133 Xu, W. (1) 568,573 Xu, Y. (3) 150, 151,618 Xu, Z. (1) 213,477 Ya. P.(2.4) 234 Ya, Y .P.(1) 208 Yabe, A. (2.1) 56; (2.2) 100; (2.7) 70
Yablonovitch, E.(4) 68 Yagci, Y. (3) 104, 105, 113,224 Yagi, M. (2.6) 222 Yagihashi, F. (2.6) 208; (2.7) 187 Yagishita, T. (4) 77 Yajima, H. (2.2) 62; (3) 114 Yajima, T. (1) 386 Yamada, K.(1) 5 15; (2.2) 62; (2.5) 102, 140
Yamada, S. (2.2) 63; (2.6) 173 Yamada, Y. (1) 433 Yamagida, M. (1) 5 13 Yamagishi, T. (2.6) 78 Yamaguchi, H. (1) 23 1 Yamaguchi, M.(4) 59 Yamaguchi, T. (2.2) 116; (2.4) 208; (2.5) 105
Author Index Yamaguchi, Y. (1) 307;(3) 522 Yamaji, M.(1) 268,439,440, 484;(2.2)101;(2.5)34,53 Yamakage, Y. (1) 677;(2.5)48 Yamakawa, G.(2.4)123 Yamaki, 3. (4)74 Yamamoto, E.(2.3)42;(2.4)52 Yamamoto, J. (2.4)48 Yamamoto, K.(1) 385;(2.5)142, 198,298;(3)134 Yamamoto, M. (1) 480;(2.2)62; (3) 9,339,496,571,576 Yamamoto, N.(1) 631;(2.6)191; (2.7)4 Yamamoto, S.(I) 237 Yamamoto, T.(3) 257,258,268, 289,363,439 Yamana, K.(1) 622 Yamano, Y. (1) 483 Yamanouchi, K.(2.7)68 Yamaoka, T.(3)120, 122 Yamashita, H. (2.1)13; (2.5)32, 165 Yamashita, K.(2.3)38;(2.6)354; (2.7)66, 135;(3) 36 Yamashita, M. (1) 665 Yamashita, S.(1) 300;(3)272 Yamashita, T.(3)283,547,706 Yamashita, Y. (2.6)267 Y d i , A. (3)493 Yamazaki, I. (1) 46,202,443, 468,521,664,665;(2.4) 188 Yamazaki, Y. (2.1)28;(2.2)97; (2.5)29,76,77,296;(2.6)85, 276 Yamazuki, T.(1) 202 Yan, D.-X. (2.6)260 Yan, M.(3) 392 Yan, X. (1) 462 Yan, Y.Z. (2.2)133;(2.4)237 Yanagi, N.(2.3)1 1 1 Yanagida, M. (2.5)110 Yanagida,S. (2.5)158, 167 Yanaue, T.(3) 466 Yang, B.(3) 125 Yang, C . 4 . (2.5)215 Yang, G.(1) 223;(3) 478,532 Yang, H. (2.7)90 Yang, J. (3) 540 Ymg, J . 4 . (2.4)18 Yang, K.(I) 482 Yank M. (1) 93;(3) 206,467 Yang, M.-J. (4) 59 Yang, M.R (3) 273 Yang, N.C.(2.3)108;(2.4)156 Yang, S.(1) 206;(2.5)175;(2.7) 81 Yang, X.M. (3) 45-47.8 1
439
Yang, Y. (1) 391;(2.6)15 Yang, Z.H.(3) 336 Ymg, Z.-P. (1) 31 Yao, C.J.(2.2)2 Yao, G.(3) 599 Yao, Q.Y. (3) 478 Yao, S.(1) 398;(2.6)143;(3) 96, 326 Yao, S.D.(1) 400,401;(2.2)127; (2.5)199,200 Yap, G.P.A. (2.7) 103 Yarovaya, N.V.(3) 37 Yashimoto, S.(2.6)53 Yashiro, H.(2.7)193 Yasinskii, M.F.(3)233 Yassar, A. (3) 424 Yasuda, M.(2.3)83;(2.4)210; (2.6)122 Yasuda, S. (1) 188 Yasuike, M. (3)99 Yasunam, M.(1) 23 1 Yatskov, N.N.(1) 691 Yarsuhashi, T.(1) 287,288 Yau, C.S. (2.5)251;(2.6)165 Ye, J.Y. (3) 562,565 Ye,T.(3)467 Ye, T.-Q. (1) 561;(2.6)14,266 Ye,W.(2.7)81 Ye, Y.(3) 96 Yekta, A. (3) 487 Yen, G.-F. (2.6)221 Yevich, M.E.(2.7)I08 Yi, D.H. (3)658 Yi, H.(2.4)101;(3) 300 Yilmaz, Y. (3) 91,578,585 Yin, H.B. (3) 33 Yin, J.M. (2.5)190 Ying, Y.-M. (2.1)64,66;(2.4) 243,244;(2.6)300 Yoda, S.(1) 32 Yokota, R.(3) 500 Yokotani, A. (3) 707 Yokoyama, M.(2.6)353; (3) 38 Yokoyama, N.(3)620 Yokoyama, Y. (2.2)112, 115; (2.4)11, 121;(2.6)49 Yonekura, M.(2.5)145 Yonemoto, E.H.(1) 533 Yonemura, H.(2.5)102 Yoneyama, H. (2.5) 161,162 Yoneyama, M.(1) 475 Yong, T.M.(3) 372,444 Yonker, C.R (2.7)89 Yoo, D.J. (2.2)119;(2.4)153 YOO,H . 4 . (2.7) 132 Yoon, D.H.(3) 658 Yoon, H.(2.1)16;(2.3)74;(2.4) 151; (2.5)81
Yoon,J. (1)565,566
Yoon, M. (1) 156, 157 Yoon, U.C.(2.2)49, 104;(2.4) 218;(2.6)92,238 Yoshaki, 0.(1) 504 Yoshida, A. (2.6)222 Yoshida, K.(3) 707 Yoshida, M. (2.1)40;(3) 458,463 Yoshida, R.(4)30 Yoshida, S.(2.5)156, 187 Yoshifuji, M.(2.4)41,62;(2.6) 349 Yoshihara, K.(1) 125,263,503 Yoshikawa, Y.(1) 210 Yoshimoto, S.(2.4)99 Yoshimura, A. (1) 79 Yoshimura, T. (2.4)272;(2.6) 295 Yoshino, K.(3)410,426,454, 458,459,463,464,466;(4) 71 Yoshinobu, M. (1) 23 1 Yoshioka, M.(2.1)28;(2.5)29, 76,296;(2.6)85 Yoshioka, Y. (2.2)110;(2.4)118 Yoshizawa, K.(1) 5 15 Yoshizawa, M. (1) 262 You, X. (1) 213 Young, D.T.(2.2)132 Young, I.T. (1) 643,694 Young, M.(1) 104 Young. R.N.(1) 335 Young, S.(1) 264 Youssef, B. (3) 124, 161 Yousufiai, M.A. (2.6)240 Yu, F. (3) 96 Yu, G.(2.5)23;(3) 397 Yu, H.Z. (2.6)34 Yu, J.W.(3) 171,359 Yu, L.(2.2)1 1 1; (2.4)119;(2.6) 52 Yu, L.-X.(2.5)58,59 Yu, S.(2.7)81;(3) 97 Yu, S.Y. (3) 478 Yu,W . 4 . (1) 28 1 Yu, Y. (2.5) 190 Yu, Y.-z. (2.2)102 Yu, Z.(3) 540 Yuan, L.(2.4)243;(3)614 Yuan, X.(1) 406 Yuan, Z. (4)24 Yudina, T.(3) 238 Yue, C.J. (2.2)3 Yue, J.-C. (2.5)177 Yufit, D.S. (1) 38 Yumoto, N. (2.2) 18;(2.6) 118 Yun,H. (3) 441,479 Yuran, V.S.(3) 661
440 Yurkovskaya, A.V. (2.1) 12; (2.4) 245 Yussef, B. (3) 190 Yuzawa, T. (2.7) 15 Yuzuri, T. (2.7) 145 Zaban, A. (4) 48 &bin, S.A. (3) 484 Zaccheroni, N. (1) 469 Zachariasse, K.A. (1) 143, 144, 159, 163; (2.4) 17; (2.5) 261 Zadroma, I. (3) 117 Zafar, S.(4) 67 Zaharias, G.A. (2.5) 203 Zaichenko, N.L.(2.4) 90; (2.6) 59 Zaitsev, S.Yu. (3) 486 Zakhidov, A.A. (3) 464; (4) 71 Zakrzewski, J. (1) 474 Zan, L.(3) 798 Zana, R. (I) 593 Zander, C. (1) 169, 176, 181 Zang, L. (2.5) 262 Zang, W. (2.5) 63 Zanini, G.P.(1) 118; (2.5) 149 Zanocco, A.L. (2.5) 253 Zarger, M.RH. (3) 797 Zarkadis, A.K. (2.6) 166; (2.7) 192 Zaros, M.C.(1) 548 Zehaf, S.(1) 649 Zehnacker-Rentien, A. (1) 271; (2.1) 23; (2.4) 63 Zelcntsov, S.V. (2.5) 244; (2.7) 44,45 Zemtsov, Y.K. (1) 102 Zeng, Z. (3) 197 Zenkevich, E.I. (1) 467 Zentel, R.(3) 315 Zetzsch, C.(2.6) 246 Zewail, A.H. (1) 2 1 Zhai, Y .-Q. (1) 3 1 Zhang, A.J. (2.6) 215 Zhang, B.-W. (1) 473,542; (2.5) 22 1 Zhang, D. (3) 336 Zhang, D.Q. (1) 451; (2.5) 223 Zhang, D.-W. (2.5) 133 Zhang, F. (2.2) 114; (2.4) 120; (3) 188 Zhang, G. (1) 447; (2.5) 148; (3) 98
Photochemistry Zhang, H. (1) 292,293,539; (2.2) 82; (2.5) 55,66,276,277; (2.6) 261,262; (2.7) 143; (3) 655 Zhang, J. (1) 705; (2.3) 39; (2.4) 101; (2.6) 144; (2.7) 134; (3) 217 Zhang, J.X. (3) 478,555 Zhang, J.Z. (3) 378 Zhang, L.(3) 25, 197; (4) 24 Zhang, L.-P. (2.3) 98; (2.5) 254 Zhang, M. (1) 462,472,539; (2.2) 82; (2.5) 55, 276,277,293; (2.6) 261,262 Zhang. M.-H. (1) 3 17.3 18; (2.5) 65,67,68 Zhang, M.-W. (2.2) 127 Zhang, P. (2.5) 23; (3) 336 Zhang, Q. (3) 616 Zhang, S.G.(2.5) 165 Zhang, S.Y.(1) 678 Zhang, W. (2.4) 242; (2.5) 52, 196; (2.6) 225, 226 Zhang, X.H. (3) 497 Zhang, X.-Q. (2.5) 110 Zhang, Y. (1) 184,366; (2.3) 9; (2.7) 81; (3) 97 Zhang, Y.-H. (1) 109,461 Zhang, Y.-L. (2.5) 243 Zhang, Z. (1) 475,633; (2.5) 66; (3) 747 Zhang, Z.-C. (2.2) 127 Zhang, Z.-Q. (1) 513 Zhang, Z.Y. (1) 692 Zhao, C.X.(2.6) 34 Zhao, F. (2.2) 114; (2.4) 120 Zhao, G. (2.1) 20 Zhao, H. (3) 536 Zhao, J. (2.5) 262,270 Zhao, L. (1) 530; (2.5) 291 Zhao, (1) 473 Zharov, H. (2.6) 326 Zharov, I. (2.7) 157 Zharov, V. (2.3) 69 Zheng, A. (2.4) 277 Zheng, D. (2.5) 270 Zheng, L. (1) 595; (2.5) 52 Zheng, M.X.(1) 461 Zheng, W. (3) 96 Zheng, X.(2.7) 128 Zhijie, L. (2.4) 101; (3) 300 Zhiu, D. (2.6) 52 Zhmud, B.V. (1) 594
w.
Zhong, J. (3) 492
Zhou, B. (2.5) 284 Zhou, B.L. (2.3) 85 Zhou, C. (3) 766 Zhou, D. (2.3) 54 Zhou, H.W. (3) 345 Zhou, J.Y. (3) 702 Zhou, Q. (1) 543; (2.5) 33,279; (2.6) 253 Zhou, Q.F.(1) 208 Zhou, T. (3) 690 Zhou, X. (3) 599,690 Zhou, Z. (2.1) 44; (2.4) 266; (4) 63 Zhoui, B. (3) 370 Zhu, A. (2.2) 10 Zhu, C.Y. (3) 550 Zhu, D. (2.2) 111; (2.4) 119 Zhu, H. (3) 747 Zhu, J. (4) 63 Zhu, J.H. (3) 713 Zhu, L. (2.7) 106 Zhu, M. (3) 204 Zhu, N.R. (1) 706 Zhu, P. (3) 187 Zhu, Q. (1) 84 Zhu, R . 4 . (2.7) 143 Zhu, W. (3) 97,204 Zhu, X.-Q. (2.5) 171 Zhu, Y. (3) 687 Zhuzhgov, E.L. (2.7) 38 Ziessel, R. (1) 545,547 Ziller, J.W. (2.2) 6 Zimmerman, H.E.(2.3) 49 Zimmermann, G.(2.2) 83 Zimmermann, T. (2.4) 79 Zimmt, M.B. (1) 537 Zinger, B. (3) 298 Zinner, H.(2.4) 110, 111; (2.6) 53 Zinth, W.(1) 347,348; (2.4) 31; (2.6) 30 Zippel, S. (3) 3 17 Zlatkevich, L. (3) 627 Zojer, E.(3) 420 Zoos, Z.G. (3) 393 Zott, S.(4) 61 Zou, J. ( I ) 213 Zou, Z. (2.7) 69 Zweifel, H. (3) 633 Zwicr, J.M. (1) 236 Zyrianov, M.(2.7) 64 Zyubina, T.S.(2.7) 43
