Effective coupling in bridged electron transfer molecules: Computational formulation and examples

The effective electronic donor/acceptor coupling (HDA) for a bridged electron transfer system is defined. An expression for HDA in terms of the bridge Green’s function is developed for systems represented by a tight-binding Hamiltonian. HDA is computed exactly for two systems and the existence of a dimensionless parameter which determines whether the effective coupling oscillates or decays with increasing donor/acceptor distance is demonstrated. A numerical technique for computing HDA is developed and shown to be significantly more powerful than conventional techniques.