First principles treatment of electron transfer in mixed-valent systems

The thesis offers insight into electron transfer mechanisms in mixed-valent compounds. A theoretical methodology based on ab initio calculations is established to identify the exact nuclear coordinate that drives intramolecular electron transfer in mixed-valent systems. By application of this methodology, the origin of the characteristic absorption band structure of the well-known Creutz–Taube ion is explained, and a quantitative measure of concertedness in proton-coupled electron transfer reactions is established. These findings allow us to understand different mechanisms of electron transfer and in turn, will help us in future to design new compounds with custom properties. Furthermore, a simulation of the formation of a photoinduced mixed-valent excited state in an analogue of the Creutz–Taube ion is presented. Vibrational coherences induced by electronic states which do not possess mixed-valent character are characterized with a femtosecond time resolution in the calculations. Finally, a new methodology is developed to study the charge-separation in the reaction center of Photosystem II. With the inclusion of thermal effects and the environment of the protein, the calculated electronic states are computationally processed to the correct ordering with respect to their charge transfer character. With this analysis, the pigment pair that is responsible for the charge-separation can be identified.