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M. Ya. Mel'nikov, V. I. Pergushov and J. A. Weinstein
Chemistry of the Electroncally Excited Intermediates
(Radicals, Radical Ions, the Excited States of Coordination Compounds). The Matrix Effects and Molecular
Organization of Processes
Abstract
Reactivity of electronically excited
intermediates of different types (radicals, radical-ions, excited states of
coordination compounds) is discussed. For different classes of radical anions
the main types of photochemical transformations have been identified and
characterised quantitatively through establishing kinetic rules governing these
transformations. The ways of controlling efficiency and direction of competitive
photochemical pathways through changes in the molecular organization of the
media and intermediates, and by using various matrix effects have been
established. The mechanism of photoradical ageing of various polymer materials
has been elucidated. The new type of unbranched chain reactions in solid state
- photoradical chain reactions - has been discovered and studied experimentally
in detail. The development of such reactions in solid state has been followed
in spatial and time domains, which has enabled us to predict the changes in the
properties of the materials, including those associated with photoradical
ageing. A conceptually new method of investigating of radical reactions -
matrix isolation on activated surfaces - has been developed and allowed for
obtaining unique information on novel, previously unknown reactions of radical
species, and on inversion of selectivity in these processes. A new method of
controlling photoreactivity of coordination compounds -structural
reorganization in the excited state through formation of a transient
three-electron sulphur-sulfur bond - has been designed and tested by a
combination of advanced spectroscopic techniques.
Copyright (C) Chemistry Dept., Moscow State University, 2002
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