Abstracts Terenin Memorial International Symposium on Photochemistry and Photophysics of Molecules and Ions, July 29 - August 2, 1996, v. 2, p. 234.
ABSTRACT.
The evidences are obtained for the mechanism of transient
formation of exciplexes with partial electron transfer and
relatively long lifetimes (up to 10-60 ns) in excited-state electron
transfer reactions in polar media rather than for direct complete
electron transfer after preliminary reorganization of the reactants
and medium as it was supposed by conventional Marcus
mechanism. Therefore electron transfer occurs by gradual shift of
an electron density form the donor to acceptor concerted with
the reorganization of the reactants and medium.
Transient formation of exciplexes, in contrast to
conventional mechanism, provides adequate quantitative
description of experimental peculiarities of excited-state electron
transfer reactions, in particular small (and sometimes even
negative) activation enthalpies, quantum yields of radical ion and
triplet formation, effects of the solvent polarity, and even better
coincidence with the experimental data for the dependence of
apparent rate constants on the driving force of electron transfer.