Theoretical analysis of the coordination-state dependency of the excited-state properties and ultrafast relaxation dynamics of bacteriochlorophyll a

Abstract

The coordination-state dependency of the excited-state properties and ultrafast relaxation dynamics from the S2 to the S1 state of bacteriochlorophyll a were analyzed using quantum chemical calculations and nonadiabatic molecular dynamics simulations. TDDFT calculations and orbital analysis clarified the molecular mechanism of the decrease in the excitation energy difference caused by ligand coordination. The results of dynamics simulations also showed that the ligand accelerated the relaxation, and the estimated time constant was in quantitative agreement with the experimental data. We demonstrated the importance of the environmental effects for the relaxation dynamics, which have not been investigated theoretically.