Manifestation of the dynamic properties of the solvent in electron transfer reactions

Abstract

The ability of the multichannel stochastic model to adequately describe the basic features of the kinetics of thermal electron transfer is demonstrated. It is shown that the solution-controlled regime can be realized in the normal Marcus region, whereas it is almost completely suppressed in the inverted region by the reorganization of high-frequency vibrational modes. The continuous transition between the two regions in the neighborhood of the activationless is quantitatively described. It is found that the dynamic properties of the solvent manifest themselves not only in the dependence of the electron transfer rate on the medium relaxation time τ L , but also in the free energy gap law, shifting the position of the maximum effective rate constant to higher reaction exergonicities. This shift depends on the longitudinal relaxation time of the medium. In slow solvents, the maximum rate constant of electron transfer can exceed 1/τ L by several orders of magnitude.