Marcus Theory of Electron Transfer

The dependence of rate constants of electron transfer on the driving force of electron transfer is well analyzed on the basis of the Franck–Condon principle by the Marcus theory of electron transfer, which provides basic principles to analyze the rate constant of electron transfer quantitatively. When the magnitude of the driving force of electron transfer becomes the same as the reorganization energy, the electron-transfer rate reaches a maximum and is basically controlled by the magnitude of electronic coupling between the donor and acceptor moieties. The smaller the reorganization energy, the faster is the forward photoinduced charge-separation process, but the charge-recombination process becomes slower when the driving force for back electron transfer is larger than the reorganization energy of electron transfer. The components of artificial photosynthesis, which are not necessarily natural components in photosynthesis, must have small reorganization energy values of electron transfer.