Modeling Electron Transfers Using Quasidiabatic Hartree–Fock States

Electron transfer processes are ubiquitous in chemistry and of great importance in many systems of biological and commercial interest. The ab initio description of these processes remains a challenge in theoretical chemistry, partly due to the high scaling of many post-Hartree–Fock computational methods. This poses a problem for systems of interest that are not easily investigated experimentally. We show that readily available Hartree–Fock solutions can be used as a quasidiabatic basis to understand electron transfer reactions in a Marcus framework. Nonorthogonal configuration interaction calculations can be used to quantify interactions between the resulting electronic states, and to investigate the adiabatic electron transfer process. When applied to a titanium–alizarin complex used as a model of a Gratzel-type solar cell, this approach yields a correct description of the electron transfer and provides information about the electronic states involved in the process.