168 Topics in Current Chemistry

Transcription

1 168 Topics in Current Chemistry

2 Photoinduced Electron Transfer V Editor: J. Mattay With contributions by A. Albini, R. A. Bissell, E. Fasani, P. K. Freeman, H. Q. N. Gunaratne, S. A. Hatlevig, P. L. M. Lynch, G. E. M. Maguire, E Maslak, C. E McCoy, M. Mella, G. Pandey, K. R. A. S. Sandanayake, A.P. de Silva, J.-P. Soumillion With 33 Figures and 11 Tables Springer-Verlag Berlin Heidelberg NewYork London Paris Tokyo Hong Kong Barcelona Budapest

3 This series presents critical reviews of the present position and future trends in modern chemical research. It is addressed to all research and industrial chemists who wish to keep abreast of advances in their subject. As a rule, contributions are specially commissioned. The editors and publishers will, however, always be pleased to receive suggestions and supplementary information. Papers are accepted for "Topics in Current Chemistry" in English. ISBN Springer-Verlag Berlin Heidelberg New York ISBN Springer-Verlag New York Berlin Heidelberg Library of Congress Catalog Card Number This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Vedag. Violations are liable for prosecution under the German Copyright Law. Springer-Verlag Berlin Heidelberg 1993 Printed in Germany The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Typesetting: Macmillan India Ltd., Bangalore-25 Printing: Saladruck, Berlin, Binding: Liideritz & Bauer, Berlin 51/ Printed on acid-free paper

4 Preface to the Series on Photoinduced Electron Transfer The exchange of an electron from a donor molecule to an acceptor molecule belongs to the most fundamental processes in artificial and natural systems, although, at the primary stage, bonds are neither broken nor formed. However, the transfer of an electron determines the chemical fate of the molecular entities to a great extent. Nature has made use of this principle since the early beginnings of life by converting light energy into chemical energy via charge separation. In recent years man has learnt, e.g. from X- ray analyses performed by Huber, Michel and Deisenhofer, how elaborately the molecular entities are constructed within the supermolecular framework of proteins. The light energy is transferred along cascades of donor and acceptor substrates in order to prevent back electron transfer as an energy wasting step and chemical changes are thus induced in the desired manner. Today we are still far away from a complete understanding of light-driven electron transfer processes in natural systems. It is not without reason that the Pimentel Report emphasizes the necessity of future efforts in this field, since to understand and "to replicate photosynthesis in the laboratory would clearly be a major triumph with dramatic implications". Despite the fact that we are at the very beginning of knowledge about these fundamental natural processes, we have made much progress in understanding electron transfer reactions in "simple" molecular systems. For example most recently a unified view of organic and inorganic reaction mechanisms has been discussed by Kochi. In this context photochemistry plays a crucial role not only for the reasons mentioned above, but also as a tool to achieve electron transfer reactions. The literature contains a host of examples, inorganic as well as organic, homogeneous as well as heterogeneous. Not surprisingly, most of them were published within the last decade, although early examples have been known since the beginning of photochemistry (cf. Roth's article in Vo1.156). A reason is certainly the rapid development of analytical methods,

5 Preface which makes possible the study of chemical processes at very short time ranges. Eberson in his monograph, printed by this publishing company two years ago, nicely pointed out that "electron transfer theories come in cycles". Though electron transfer has been known to inorganic chemists for a relatively long time, organic chc 'nist have still to make up for missing concepts (cf. Eberson). A major challenge for research in future, the "control of chemical reactions" as stated by the Pimentel Report, can be approached by various methods; light-driven processes are among the most important ones. Without interaction of the diverse scientific disciplines, recent progress in photochemistry, as well as future developments would scarcely be possible. This is particularly true for the study of electron transfer processes. Herein lies a challenge for science and economy and the special facsination of this topic - at least for the guest editor. The scope of photochemistry and the knowledge about the fundamentals of photoinduced electron transfer reactions have tremendously broadened within the last decade, as have their applications. Therefore I deeply appreciate that the Springer- Verlag has shown interest in this important development and is introducing a series of volumes on new trends in this field. It is clear that not all aspects of this rapidly developing topic can be exhaustively compiled. I have therefore tried to select some papers which most representatively reflect the current state of research. Several important contributions might be considered missing by those readers who are currently involved in this field, however, these scientists are referred to other monographs and periodical review series which have been published recently. These volumes are meant to give an impression of this newly discovered reaction type, its potential and on the other hand to complement other series. The guest editor deeply appreciates that well-known experts have decided to contribute to this series. Their effort was substantial and I am thankful to all of them. Finally, I wish to express my appreciation to Dr. Stumpe and his coworkers at the Springer-Verlag for helping me with all the problems which arose during the process of bringing the manuscript together. Mtinster, December 1989 Jochen Mattay VIII

6 Preface to Volume V Included in this volume are six articles devoted to a process which is basic not only in chemistry, but in biology and physics. The intent is to provide a critical review of some topics in photoinduced electron transfer (PET) in order to complement existing works. All articles are concerned with experimental and theoretical aspects of PET in organic chemistry. The interdisciplinary character of PET is already reflected in the preceding volumes of this series as will be so in the following volumes for electron transfer in general. PET V starts with a survey of fragmentation reactions which, as one of the most important events after the initial transfer of an electron, competes with back-electron transfer. The factors controlling this latter process as well as the thermodynamics, kinetics and the stereochemistry of the fragmentations are comprehensively discussed. The second article deals with dehydrohalogenation of polyhalocompounds emphasizing both the nature of excimers in the phototransformation and the nature of exciplexes formed in the presence of electron transfer reagents. The impact photochemistry has on toxic waste disposal concludes this chapter. The special features of organic anions in PET-reactions are critically discussed in the following article. Despite the advantages such as the increased electron donating capacity, the reactivity is strongly influenced by the experimental conditions. SRN 1 reactions, alkylations of carbanions and reductions initiated by oxyanions are discussed in detail as well as the quenching of excited states by anions in their ground state. Aromatic compounds have been used as electron acceptors and electron donors in PET-processes since the early beginnings of photochemistry. Chapter 4 of this volume is devoted to this still fascinating area mainly from the synthetic point of view. Special emphasis is given to recombination reactions of radical ions, electrophilic, nucleophilic and radicalic additions. The following article extends this topic to recent advances of PET in organic

7 Preface to Volume v synthesis. Several new reactions are discussed covering photosensitized electron transfer processes and donor-acceptor reactions. The final chapter turns to new developments in the field of fluorescent PET sensors. In this article the design of an efficient model system containing both a selective receptor and a fluorophore is vividly described. A variety of sensor systems with an eventually high potential for application is discussed. The guest editor deeply acknowledges that colleagues wellknown as experts for years have agreed to contribute to this series. Their effort was substantial just as the support of Dr. Stumpe and his coworkers at Springer-Verlag in preparing the volume. Mfinster, May 1993 Jochen Mattay

8 Attention all "Topics in Current Chemistry" readers: A file with the complete volume indexes Vols. 22 (1972) through 167 (1993) in delimited ASCII format is available for downloading at no charge from the Springer EARN mailbox. Delimited ASCII format can be imported into most databanks. The file has been compressed using the popular shareware program "PKZIP" (Trademark of PKware Inc., PKZIP is available from most BBS and shareware distributors). This file is distributed without any expressed or implied warranty. To receive this file send an message to: DHDSPRI6.BITNET. The message must be: "GET/CHEMISTRY/TCC_CONT.ZIP". SVSERV is an automatic data distribution system. It responds to your message. The following commands are available: HELP returns a detailed instruction set for the use of SVSERV, DIR (name) returns a list of files available in the directory "name", INDEX (name) same as "DIR", CD (name) changes to directory "name", SEND (filename) invokes a message with the file "filename", same as "SEND". GET rxfilename ) For more information send a message to: INTERNET: STUMPE@ SPINT. COMPUSERVE. COM

9 Table of Contents Fragmentations by Photoinduced Electron Transfer. Fundamentals and Practical Aspects P. Maslak... The Photochemistry of Polyhalocompounds, Dehalogenation by Photoinduced Electron Transfer, New Methods of Toxic Waste Disposal P.K. Freeman, S.A. Hatlevig Photoinduced Electron Transfer Employing Organic Anions J.-P. Soumillion PET-Reactions of Aromatic Compounds A. Albini, E. Fasani, M. Mella Photoinduced Electron Transfer (PET) in Organic Synthesis G. Pandey Fluorescent PET (Photoinduced Electron Transfer) Sensors R.A. Bissell, A.P. de Silva, H.Q.N. Gunaratne, P.UM. Lynch, G.E.M. Maguire, C.P. McCoy, K.R.A.S. Sandanayake Author Index Volumes

10 Table of Contents of Volume 156 A Brief History of Photoinduced Electron Transfer and Related Reactions H.D. Roth Fundamental Concepts of Photoinduced Electron Transfer G.J. Kavarnos Photoinduced Electron Transfer (PET) Bond Cleavage Reactions F.D. Saeva Photoinduced Electron Transfer of Carbanions and Carbocations E. Krogh and P. Wan Photoinduced Electron Transfer Oxygenations L. Lopez Photoinduced Electron Transfer Polymerization H.J. Timpe Electron Transfer Processes in Imaging D.F. Eaton Table of Contents of Volume 158 Photochemistry of Transition Metal Complexes Induced by Outer-Sphere Charge Transfer Excitation A. Vogler and H. Kunkely Metal Complexes as Light Absorption and Light Emission Sensitizers V. Balzani, F. Barigelletti and L. De Cola Photoinduced Electron and Energy Transfer in Polynuclear Complexes F. Scandola, M.T. Indelli, C. Chiorboli and C.A. Bignozzi Photoinduced Electron Transfer in Ion Pairs R. Billing, D. Rehorek and H. Hennig

11 Table of Contents of Volume 159 Photoinduced Electron Transfer Across Membranes S.V. Lymar, V.N. Parmon and K.I. Zamaraev Photoinduced Electron Transfer in Arranged Media M.A. Fox Photosynthetic Model Systems D. Gust and T.A. Moore Artificial Photosynthetic Model Systems Using Electron Transfer Reactions in Catalytic and Biocatalytic Assemblies I. Willner and B. Willner Light-Induced Contact and Solvent-Separated Radical Ion Pairs in Organic Photochemistry J. Mattay and M. Vondenhof Table of Contents of Volume 163 Photoinduced Electron Tunneling Reactions in Chemistry and Biology K.I. Zamaraev and R.F. Khairutdinov The Marcus Inverted Region P. Suppan Structure and Reactivity of Organic Radical Cations H.D. Roth