Block-Localized Wavefunction (BLW) Based Two-State Approach for Charge Transfers between Phenyl Rings

The block-localized wave function (BLW) method is the simplest and most efficient variant of ab initio valence bond (VB) theory which defines electron-localized resonance states following the conventional VB concepts. Here, a BLW-based two-state approach is proposed to probe the charge/hole transfer reactions within the Marcus--Hush model. With this approach, both the electronic coupling and reorganization energies can be derived at the ab initio level. Pilot applications to the electron/hole transfers between two phenyl rings are presented. Good exponential correlation between the ele:tronic coupling energy and the donor acceptor distance is shown, whereas the inner-sphere reorganization shows little geometric dependency. Computations also support the assumption in Marcus theory that the thermal electron transfer barrier (Delta G*), which is a sum of the reaction barrier (Delta E-a) for electron/hole transfer and the coupling energy (V-AB), is a quarter of the reorganization energy (lambda).