Ion pairing and electron transfer

Several scenarios are considered for the effect of electrolytes, specifically for ion pairing, on the rates of electron transfer reactions: (i) electron transfer followed by ion transfer, (ii) ion-pair dissociation followed by electron transfer, or (iii) ion transfer accompanying the electron transfer. The latter may involve fast or slow (diffusive) ionic motion. A distinction is made between ion reorganization (case (iii)) and the formation of real chemical intermediates. The ion pairs themselves may be tight (contact) or loose (solvent separated). The discussion is illustrated with an example in the literature. Differences in degree in behavior of intramolecular and intermolecular electron transfer, due to differences in extent of ionic motion, are noted.