Direct and Superexchange Couplings for Electron Transfer in Donor–Bridge–Acceptor Systems

This work investigates the direct and superexchange couplings in donor-bridge-acceptor electron transfer molecules by extracting diabatic information from the adiabatic wave functions obtained from multiconfigurational self-consistent field methods. Based on the numerical values of these couplings, the electron transfer mechanisms are derived for the three model systems, including 1,4-diazabicyclo[2.2.2]octane radical cation, [3,3]-spirarene, and [Fe(H₂O)₆-H₂O-Fe(H₂O)₆]⁵⁺, namely that spirarene and the other two molecules are controlled by the direct and superexchange mechanisms, respectively.