Chemically Induced Magnetic Polarization NATO ADVANCED STUDY INSTITUTES SERIES Proceedings oft he Advanced Study Institute Programme, which aims at the dissemination of advanced knowledge and theformation ofc ontacts among scientistsfrom different countries The series is published by an international board of publishers in conjunction with NATO Scientific Affairs Division A Life Sciences Plenum Publishing Corporation B Physics London and New York C Mathematical and D.Reidel Publishing Company Physical Sciences Dordrecht and Boston D Behavioral and Sijthofflnternational Publishing Company Social Sciences Leiden E Applied Sciences N oordhoffInternational Publishing Leiden Series C - Mathematical and Physical Sciences Volume 34 - Chemically Induced Magnetic Po/arizatioti Chemically Induced Magnetic Polarization Proceedings of the NA TO Advanced Study Institute held at Sogesta, Urbina, Italy, April 17-30, 1977 edited by L. T. M U US, Aarhus University, Denmark P. W. ATKINS, Oxford University, U.K. K. A. McLAUCHLAN, OxfordUniversily, U.K. J. B. PEDERSEN, Odense University, Denmark D. Reidel Publishing Company Dordrecht-Hollandf Boston-U.S.A. Published in cooperation with NATO Scientific Affairs Division Library of Congress Cataloging in Publication Data Nato Advanced Study Institute, Urbino, 1977. Chemically induced magnetic polarization. (NA TO advanced study institutes series: Series C, Mathematical and physical sciences; v. 34) 'Published in cooperation with NATO Scientific Affairs Division: I. Radicals (Chemistry)-Congresses. 2. Polarization (Nuclear phy sics)-Congresses. 3. Nuclearmagnetic resonance-Congresses. J. Muus, L. T. II. Title. Ill. Series. QD471.N29 1977 541'.378 77-10592 ISBN-13: 978-94-010-1267-6 e-ISBN-13: 978-94-010-1265-2 DOl: 10.1007/978-94-010-1265-2 Published by D. Reidel Publishing Company P.O. Box 17, Dordrecht, Holland Sold and distributed in the U.S.A., Canada, and Mexico by D. Reidel PUblishing Company, Inc. Lincoln Building, 160 Old Derby Street, Hingham, Mass. 02043, U.S.A. All Rights Reserved Copyright © 1977 by D. Reidel Publishing Company, Dordrecht, Holland No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any informational storage and retrieval system, without written permission from the copyright owner Softcover reprint of the hardcover 1st edition 1977 CONTENTS PREFACE VII LIST OF PARTICIPANTS IX R. Kaptein: I. INTRODUCTION TO CHEMICALLY INDUCED MAGNETIC POLARIZATION 1 R.G. Lawler: II. CIDNP EXHIBITED BY THERMALLY DECOMPOSING DIACYL PEROXIDES 17 R.G. Lawler: III. TIME-DEPENDENCE OF CIDNP INTENSITIES 29 H.D. Roth: IV. CHEMICALLY INDUCED NUCLEAR SPIN POLARIZATION IN PHOTO-INITIATED RADICAL ION REACTIONS 39 F.J. Adrian: V. RADICAL PAIR MECHANISM OF CHEMICALLY INDUCED MAGNETIC POLARIZATION 77 K.A. McLauchlan: VI. EXPERIMENTAL OBSERVATION OF ELECTRON SPIN POLARIZATION IN REACTIONS 107 R.W. Fessenden: VII. CHEMICALLY INDUCED ELECTRON POLARIZATION OF RADIOLYTICALLY PRODUCED RADICALS 119 K.A. McLauchlan: VIII. FLASH-PHOTOLYSIS ELECTRON SPIN RESONANCE 151 J.B. Pedersen: IX. TIME-DEPENDENCE OF ESR INTENSITIES 169 P.W. Atkins: X. PHOTOCHEMICAL PROCESSES 181 VI TABLE OF CONTENTS P.W. Atkins: XI. THE TRIPLET MECHANISM 191 L.T. Muus: XII. LIGHT MODULATED CIDEP EXPERIMENTS 205 G.L. Closs: XIII. LOW FIELD EFFECTS AND CIDNP OF BlRADICAL REACTIONS 225 R. Kaptein: XIV. PAIR SUBSTITUTION EFFECTS IN CIDNP 257 R.G. Lawler: XV. CIDNP FROM BIMOLECULAR REACTIONS OF ORGANOMETALLIC COMPOUNDS 267 R.G. Lawler: XVI. THE PROBLEM OF PARALLEL RADICAL AND NON RADICAL MECHANISMS 275 J.B. Pedersen: XVIII. EFFECTS OF DIFFUSION ON REACTION RATES 283 J.B. Pedersen: XlIX. GENERAL RELATIONS FOR HIGH-FIELD CIDNP 297 J.H. Freed: XIX. NUMERICAL METHODS AND MODEL DEPENDENCE IN CHEMICALLY INDUCED DYNAMIC SPIN POLARIZATION 309 G.L. Closs: XX. CHEMICALLY INDUCED MAGNETIC POLARIZATION IN SYSTEMS OF BIOCHEMICAL INTEREST 357 F.J. Adrian: XXI. TRIPLET OVERHAUSER MECHANISM OF CIDNP 369 P.W. Atkins: XXII. THE EFFECTS OF MAGNETIC FIELDS ON CHEMICAL REACTIONS 383 J. Bargon: XXIII. CIDNP FROM TRIPLET PAIR RECOMBINATION 393 A.J. Hoff and H. Rademaker: XXIV. LIGHT-INDUCED MAGNETIC POLARIZATION IN PHOTOSYNTHESIS 399 SUBJECT INDEX 405 PREFACE Magnetic resonance has constantly been able to surprise with its ability to exhibit new phenomena. Just when it appears to be entering a quiet middle age it bursts into activity with some new manifestation of its versatility. This happened a few years ago, when observations on anomalous intensities were looked at more closely, and the pursuit of explanations and further evidence laid the foundations of the subjects treated in this volume. In organizing the NATO Advanced Study Institute we attempted to bring together a number, but by no means all, of those who had contributed significantly to the subject, and to obtain from them a comprehensive and detailed exposition of the subject. We were particularly anxious to avoid a set of lectures that dealt solely with the theory of the subject, because much of the interest in chemically induced magnetic polarization is due to its usefulness in applications to chemical problems: it is a real chemical tech nique, not just an amusing diversion for theoreticians. We set about organizing the course with the idea of making it useful to people who wanted to use the technique (for, after all, in the case of nuclear polarization, CIDNP, the technique can be used in any laboratory with minor modification of standard equipment). In order to do that we started the course, as we start thi5 vol ume, with a simple, straightforward introduction to the interpre tation of CIDNP spectra, the radical pair theory, and some appli cations to the elucidation of reaction mechanisms. Then we have an introduction to the more involved techniques needed to look at electron polarizations, and a similar survey of the range of its applications. At that point, in order to use the technique with confidence and to obtain the maximum amount of information, it is necessary to go more deeply into the underlying theory. At the ASI, and in this volume, we attempted to do this ~ithout losing sight of the reasons for doing it, and the chapters in this volume represent the mixture of theory and experiment often encountered in labora tories. The chapters also represent the various theories that VIII PREFACE are encountered:· at this level of expos~t~on, and in a subject where the interplay of quantum mechanical, statistical, and re active processes is so intricate, there are several ways of look ing at the processes involved. People new to the subject initial ly may find one way of talking about the subject more congenial than a more sophisticated version: both approaches will be found here. This volume would not have appeared without the sustained effort of a large number of people. First there are the lectur ers: they all worked very hard to prepare an interesting and au thoritative set of lectures well before the ASI, and gave unstint ingly of their time and expertise during.the duration of the In stitute. The editors of this book (who were also the organizers of ASI) were greatly assisted by the authorities at "Sogesta", where the Institute was held, and drew heavily on both their ex cellent facilities and their cooperation, for both the Institute itself and a portion of the editing of this book. We all would like to thank Mrs. Ruth Buch, who yet again devoted so much effort and efficiency to the organization of the ASI for several months before it took place. Finally, but by no means least, we would like to record our gratitude to the NATO Scientific Affairs Divi sion for their generous financial support. Aarhus, Odense, and Oxford. L.T. Muus May 1977. P.W. Atkins K.A. McLauchlan J.B. Pedersen LIST OF PARTICIPANTS Professor Frank J. ADRIAN: The Johns Hopkins University, Applied Physics Laboratory, Johns Hopkins Road, Laurel, Maryland 20810, U.S.A. Dr John AMMETER: Institute of Inorganic Chemistry, ETH, CH-8001 Zurich, Switzerland Dr P. W. ATKINS: Physical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, U.K. Mr Paul BARBARA: Department of Chemistry, Brown University, Providence, Rhode Island 02912, U.S.A. Dr Joachim BARGON: IBM Corporation, Research Division, Monterey and Cottle Roads, San Jose, California 95193, U.S.A. Dr Fuat BAYRAK~EKEN: Orta Dogu Teknik Universitesi, Teorik Kimya Bolumu, Ankara, Turkey Dr Hans-Dieter BECKHAUS: Chem. Laboratorium der Universitat, Albertstr. 21, D-7800 Freiburg, B.R.D. Dr Reinhard BENN: Max-Planck-Institut fur Kohlenforschung, Kaiser-Wilhelm Platz I, 433-Mulheim a.d. Ruhr, B.R.D. J.W.M. de BOER: Dept. of Physical Chemistry, Faculty of Science, University of Nijmegen, Toernooiveld, Nijmegen, Netherlands Dr Marie BORZO: Institut de Chimie, Universit€ de Liege, Liege, Belgium Dr Robert E. BOTTO: Caltech, Pasadena, California 91109, U.S.A. Dr Roselyne BRIERE: C.E.N.G., Laboratoire COP/DRF-B.P.85-Centre de TRI, 38041 Grenoble Cedex, France x LIST OF PARTICIPANTS Dr Charles BROWN: University Chemical Laboratory, University of Kent, Canterbury, Kent CT2-7NH, U.K. Dr Marina BRUSTOLON: Physical Chemistry Institute, Padua, Italy Mrs Ruth BUCH: Department of Chemistry, Aarhus University, 140 Langelandsgade, SOOO Aarhus C, Denmark Dr Serge CAPLAIN: Univ. des Sciences et Techniques de Lille, Lab. de Chimie Organique Physique, B.P.36, 59650 Villeneuve d'Ascq, France Professor G.L.CLOSS: Department of Chemistry, The University of Chicago, Chicago, 111.60637, U.S.A. Dr Odile CONVERT: Faculte des Sciences Paris VI, Lab. de Chimie Organique Structurale, S Rue Cuvier, 75230 Paris Cedex 05, France Mr Karl-Michael DANGEL: Institut fur Organische Chemie, Universitat Tubingen, Auf der Morgenstelle IS-74 Tubingen I, B.R.D. Professor Nadine FEBVAY-GAROT: Facult€ de Pharmacie, Laboratoire de Physique, Rue du Prof.Laguesse, 59045 Lille Cedex, France Professor R.W. FESSENDEN: Radiation Laboratory, University of Notre Dame, Notre Dame, Ind. 46556, U.S.A. Professor H. FISCHER: Physikalisch-Chemisches Institut der Universitat, Ramistrasse 76, CH SOOI Zurich, Switzerland Dr J. FOSSEY: CNRS, GR.12, 2 rue H.Dunant, 94 Thiais, France Professor Jack H. FREED: Department of Chemistry, Cornell University, Ithaca, New York 14S53, U.S.A. Mr S0REN FRYDKJAER: Department of Chemistry, 140 Langelandsgade, DK-SOOO Aarhus C, Denmark W. Carl GOTTSCHALL: Department of Chemistry, University of Denver, University Park, Denver, Colorado S0210, U.S.A. Dr Maurizio GUERRA: Lab. dei composti del carbonio contenenti etero-atomie e loro applicazioni, CNR, Via Tolara di Sotto SI/A, 40064 Ozzano Emi1ia(Bologna) , Italy Mr Richard A. HEARMON: Dpt. of Organic Chemistry, The University of Liverpool, The Robert Robinson Lab., P.O.Box 147, Liverpool, L69 3BX, U.K.