Light-driven electron transfer in a modular assembly of a ruthenium(II) polypyridine sensitiser and a manganese(II) terpyridine unit separated by a redox active linkage. DFT analysis

A series of ruthenium polypyridine-based complexes covalently bound to a terpyridine coordinating site for MnII ion coordination has been developed. A redox active unit separates the photoactive unit and the manganese complex. Introducing ester groups on the bipyridine skeleton allows modulation of redox properties of the chromophore. Intramolecular electron transfer from the MnII to the photogenerated RuIII was studied by time-resolved transient absorption and EPR. Photophysical studies support the participation of the imidazole unit in the electron transfer process from the Mn(II) complex and Ru(III) in the case of ester containing chromophores. DFT calculations were performed and used to rationalize the photophysical behavior of the complexes, in particular the effect of coordination of the MnII ion to the terpyridine cavity as well as the influence of the electron withdrawing groups on the Ru chromophore.