Electronic coupling in electron transfer and the influence of nuclear modes: theoretical and computational probes

Long-range electronic coupling of local donor and acceptor sites is formulated in the context of thermal and optical electron transfer and then illustrated with examples based on electronic structure calculations. The relationship of the calculated results to available experimental kinetic and optical data is discussed in detail. The influence of nuclear modes on the magnitude of the coupling (i.e., departures from the Condon approximation) is investigated in terms of both discrete molecular modes and solvent modes, and a general expression is presented for the modulation of the superexchange tunneling gap by motion along the electron transfer reaction coordinate. AcknowledgementsThe author is grateful to R.J. Cave and M. Rust for making available molecular coordinates for acridinium derivatives, and to R.J. Cave for several valuable discussions. This work was supported by the Division of Chemical Sciences, US Department of Energy, under grant DE-AC02-98CH10886.