RESONANCES AND INTERFERENCE EFFECTS ON THE EFFECTIVE ELECTRONIC COUPLING IN ELECTRON-TRANSFER

We discuss the possibility of using the energy of the transmitted electron (epsilon) as a control parameter in electron transfer (ET) reactions. The change in response of the system is entirely contained, within the simplest model, in the effective electronic coupling, which exhibits sharp changes in the resonance region and near its minima as a function of epsilon. The positions of the minima are strongly influenced by the molecular geometry. To calculate the effective coupling, we use a Green's function approach. The electronic structure is calculated within an extended Huckel model. We show how the interference and resonance behavior appears even for a very simple four-site model with multisite interactions. The interference effects disappear in a tight binding model of the same system. Application to a molecular system dramatically shows these effects.