Picosecond raman studies of solvent-assisted proton transfer to the charge transfer excited state of pentaammine (4,4′-bipyridine) ruthenium(II)

Abstract

Previous nanosecond experiments on the title compound have obtained evidence for intermolecular proton transfer occurring at rates significantly faster than are estimated for this reaction from equilibrium kinetics. The possibility that this fast reaction is driven by solvent relaxation around the highly charged MLCT states is investigated using picosecond Raman spectroscopy. No evidence is found for prealigned solvent states which facilitate proton transfer. It is more likely that the high concentrations of proton transfer species previously observed on the nanosecond time scale resulted from repeated cycling between the ground and excited states throughout the duration of the nanosecond pulse.