Towards synthetic unimolecular [Fe2S2]-photocatalysts sensitized by perylene dyes

Abstract

A new set of perylene-based [Fe2S2(CO)6] photocatalyst dyads was synthesized and characterized. Four different strategies were employed to facilitate photoinduced electron transfer from the chromophore to the catalytically active site, increasing the chance for successful photocatalytic proton reduction. X-ray photoelectron spectroscopy measurements demonstrated the covalent attachment of the catalyst and provided insights on oxidation states of the iron. Visible light absorption maxima of the presented complexes reached up to 550 nm with reduction potentials between −1.14 V and −1.20 V because of increased electron density of the photoactive moiety. Quantum chemical calculations were performed to evaluate the employed design strategies based on the energy levels of the frontier orbitals and allowed to elucidate the electronic states involved in the initial photoactivation as well as to assess the charge transfer phenomena within the Franck-Condon point.