Electron transfer reactions in electrolyte solutions: effects of ion atmosphere and solvent relaxation

A molecular theory of the effects of solution dynamics on the rates of adiabatic outer-sphere electron transfer reactions in electrolyte solutions is presented. The theory correctly includes the dynamics of both ions and solvent molecules through frequency dependent ion and solvent susceptibilities. The rate of electron transfer is calculated by employing the well-known Grote-Hynes theory. The barrier-crossing frequency of electron transfer is found to depend rather strongly on the salt concentration dependent solvent longitudinal relaxation time and on the ionic conductivity. Numerical results are presented for some common aqueous and non-aqueous electrolyte solutions.