Tuning Photoinduced Electron Transfer in POM-bodipy Hybrids by Controlling the Environment, Experiment and Theory.

The optical and electrochemical properties of a series of polyoxometalates (POMs) oxoclusters decorated with two bodipy (boron-dipyrromethene) light harvesting units were examined. We evaluated in this polyanionic donor-acceptor system the effect of the solvent and associated counterions on the intramolecular photoinduced electron transfer. Our results show that both solvents and counterions have a major impact upon the energy of the charge transfer state by modifying the solvation shell around the POM. This leads to a significantly shorter charge separation time in case of smaller counterion and slower charge recombination in a less polar solvent. We rationalize these results in terms of Marcus theory and show that solvent and counterion both affect the driving force for photoinduced electron transfer and the reorganization energy. This was corroborated with theoretical investigations combining DFT and molecular dynamics simulations.