Solvent Relaxation Dynamics Research Articles

Importance of molecular size on the dynamics of solvent relaxation

Importance of molecular size on the dynamics of solvent relaxation

Adiabaticity of electron transfer at an electrode

A simple description of the kinetics of electron transfer at an electrode is developed which includes the effects of both outer-sphere solvent dielectric relaxation and electron tunneling. From this description, an adiabaticity criterion is obtained which determines when the rate of the electron transfer is adiabatic, that is, determined by solvent relaxation dynamics, or diabatic, determined by electron tunneling dynamics. Rate constants are also obtained for the diabatic and adiabatic limiting cases and the intermediate regime in which the dynamics of both processes are important. The degree of localization of the electron transfer and the dependence of the rate on the electrode potential, the Miller indices of the electrode surface, the surface site of the reacting ion, and the distance of the ion from the electrode are examined. Possible extensions of the formalism to include other important factors are also discussed.

The effect of solvent relaxation dynamics on outer-sphere electron transfer

We analyse outer-sphere electron transfer (ET) in a dielectric medium, which is characterised by a continuous distribution of dielectric relaxation times. An explicit expression for the averaged ET rate is derived in the particular case of the Davidson-Cole dielectric susceptibility function. A quantitative account of recent experimental data for ET in the Ru(phen 3) 2+ methylviologen 2+ system in glycerol is provided.

How do solvent relaxation dynamics affect electron transfer rates? A study in rigid solution

Nonadiabatic electron transfer has been studied in glycerol in which the solvent relaxation time (tau/sub L/ is varied (by temperature) from 10/sup -8/ to 10/sup -1/ s. A strong dependence of rate on tau is observed with kappa approx. (tau/sub L/)/sup -0/ /sup 6/. A qualitative rationale suggests that the actual dependence for a nonadiabatic process can range from (tau/sub L/ )/sup 0/ to (tau/sub L/)/sup -1/ depending on whether the electronic coupling strength or solvent polarization determines the frequency factor for reaction. Such intermediate cases may be significant in a variety of condensed-phase electron-transfer processes.