Dynamics of Bimolecular Photoinduced Electron-Transfer Reactions

From the accumulated results of several research groups over the last 25 years, it is clear that photoinduced electron-transfer reactions have significantly broadened the scope of organic photochemistry.1 The fundamental mechanistic principle is that when quenching of an excited state via electron transfer is sufficiently exothermic, the reaction occurs at or close to the diffusion-controlled limit (kdiff). In polar solvents, where most reactions are carried out, the primary intermediate is a geminate radical-ion pair, A•-/D•+ (eq 1).3 Return electron transfer within the