Radiative and nonradiative electron transfer in donor-acceptor phenoxazine and phenothiazine derivatives

Radiative and nonradiative electron transfer (exemplified by the CT fluorescence and nonradiative charge recombination process in the singlet manifold, respectively) in a series of donor-acceptor phenoxazine and phenothiazine derivatives is reported. An analysis of the CT fluorescence leads to the quantities relevant for the radiative electron transfer in the Marcus inverted region. Using a nonadiabatic theory of electron transfer and the latter parameters, the rate constants for nonradiative electron transfer can be predicted. Electronic coupling elements V-0 between the (CT)-C-1 state and the ground state obtained from the radiative rates are in agreement with those calculated from the simple LCAO MO model which assumes that V-0 are mainly determined by the interactions between the atoms forming the A-D bond. (C) 1999 Elsevier Science B.V. All rights reserved.