On superexchange electron-transfer reactions involving three paraboloidal potential surfaces in a two-dimensional reaction coordinate

A stochastic Liouville theory is presented for the superexchange electron-transfer reactions involving three paraboloidal potential surfaces in a two-dimensional reaction coordinate. Its close relationship with the spin–boson model for photosynthesis is discussed. A triangle representation is used to explain the relationship between the reorganization energy and the degree of correlation for the solvent fluctuations experienced by the donor, the intermediate, and the acceptor. Explanations for a small reorganization energy for an efficient superexchange mechanism in natural photosynthesis are offered.