In situ X-ray absorption and emission spectroscopy to understand the electron transfer–oxygen transfer reaction of vanadium polyoxomolybdate in a homogeneous medium

Abstract

Electron transfer–oxygen transfer reactions of vanadium polyoxomolybdates have been investigated in the homogeneous catalytic oxidation of xanthene and biomass-derived compounds. At room temperature, we observed the formation of a stable adduct between the polyoxometalate and xanthene following the initial electron transfer in acetonitrile. The high energy resolved fluorescence detected X-ray absorption near edge structure spectroscopic investigations revealed that vanadium occupies a distorted octahedral position within a defect site in the polyoxometalate framework. In situ X-ray emission spectroscopy further revealed that, at first, vanadium is reduced from V^V to V^IV and there are changes in the coordination around the vanadium during the electron transfer with significant changes in the valence to core Kβ″ and Kβ_2,5 lines. This fundamental investigation of molecular catalysis tackles some of the key questions regarding electron transfer–oxygen transfer reactions using state-of-the-art spectroscopic techniques.