Extended charge decomposition analysis and its application for the investigation of electronic relaxation

A general and comprehensive molecular orbital method for the investigation of the electronic relaxation contribution to redox processes is presented. This method is based on the population analysis of the molecular orbitals of the final electronic state in terms of the occupied and unoccupied molecular orbitals of the Koopmans’ state. The DFT calculations for oxidation and reduction of transition-metal species indicate a dramatic magnitude of electronic relaxation in these systems. The passive molecular orbitals play a more significant role in electronic relaxation than the redox-active molecular orbital that directly participates in the redox process. The mechanism of electronic relaxation in the oxidation of Fe^II and Cu^I species varies from the ligand to metal 3d charge transfer (LMCT) interactions to the ligand to metal 4s,4p LMCT. For systems with significant electronic delocalization, electronic relaxation becomes smaller leading to much smaller contributions to the redox processes. Dedication: This contribution is to celebrate Philip Stephen’s seminal contributions to theory and experiment. An erratum to this article can be found at