Rate Constants for Electron Transfer from Organic Crystals to Redox Ions in Solution

Abstract

AbstractThe time dependence of saturation currents in organic crystals is governed quantitatively by the consumption of charge injecting redox ions in the electron transfer reaction at the crystal surface. Rate constants for electron transfer have been derived from the absolute magnitude of the saturation currents and indepently from their time dependence. These rate constants have been determined in the absence of a voltage drop in the Helmholtz‐layer i.e. for an ideal non‐equilibrium situation. In dependence on the sign and magnitude of the standard free energy of reaction, saturation currents in organic crystals are larger, equal to or smaller than the exchange current of the same redox ion at a metal electrode. If one can assume the applicability of current electron transfer theory as developed by Marcus and others, a quantitative comparison between theory and experimental results yields proof for non‐adiabatic electron transfer reactions between organic crystals and redox ions in solution.