Switch Phenomena in Molecular Three-Centre Electron Transfer Systems with Strong Electronic-Vibrational Coupling

Abstract

Abstract Three-centre molecular and supramolecular electron transfer (ET) is important in device-like function of organized assemblies of bridge-group separated donor and acceptor units in solid-state or electrochemical systems. Other areas are solid-state phonon-kick charge capture, electrochemical ET via adsorbates or film impurities, large adsorbate STM, and long-range ET in redox metalloproteins. Optical three-level analogues are molecular Raman scattering and two-photon absorption. Three-level ET behaviour rests on coupling to environmental nuclear motion. A frame is second order perturbation theory including full vibrational manifolds in all three states. We discuss such a formalism. Common superex-change is recovered for high intermediate state energies while vibrationally unrelaxed state population emerges for low energies. These limits are separated by finite resonances in characteristic “switch” patterns. Intermediate state vibrational friction is briefly addressed and we note some biological and synthetic systems to which the formalism is appropriate.