Through Bond and Through Space Limits of the Long Distance Electron Transfer Problem

Abstract

A model is presented for the long distance electron transfer problem in which the through bond and through space contributions to the tunneling matrix element can be extracted as particular limits of the interaction energy. The relative importance of through bond and through space coupling ill discussed. A first model for a donor interacting with a protein might be a “trap” interacting with a periodic potential. In this simple model the decay of the donor state with distance is found. Its decay includes both through bond and through space parts. We find the limits of the problem in which either the through bond or through space pathway dominates. The characteristic distance decay of the interaction energy is different in the two cases. In real systems the through bond pathway is considerably more favorably given the same tunneling distance. In proteins a combination of through bond and through space interactions probably contributes to the donor acceptor interaction.