Theoretical study of ultrafast photoinduced electron transfer processes in mixed-valence systems

The recently proposed self-consistent hybrid method is applied to study photoinduced electron transfer (ET) reactions in mixed-valence compounds (NH3)(5)(RuNCRuII)-N-II(CN)(5)(-) and (NH3)(5)(RuNCFeII)-N-III(CN)(5)(-) in solution. To describe these ET processes in the condensed phase, both intramolecular modes (inner sphere) and the solvent environment (outer sphere) are taken into account using a model that is based on the analysis of experimental optical line shapes. The dynamics of the back ET process after photoexcitation is studied in detail. In particular we investigate the effects of intramolecular vibrational modes and solvent dynamics, as well as the influence of important physical parameters such as the electronic coupling and the temperature. In qualitative agreement with results of time-resolved optical experiments, the simulations predict an ultrafast decay of the population of the charge-transfer state. Oscillatory features are observed superimposed on the population decay, and their relations to electronic and vibrational coherence effects are discussed. Furthermore, we present comparisons with results of approximate methods such as golden rule type perturbation theory and the classical Ehrenfest model, demonstrating the necessity of using accurate quantum dynamical simulation methods to study intervalence electron-transfer processes.