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

Electron transfer-oxygen transfer reactions of vanadium polyoxomolybdates have been investigated in the homogeneously catalysed oxidation of xanthene and biomass-derived compounds. At room temperature, we observed the formation of a stable adduct between the polyoxometalate and xanthene after 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 VV to VIV and there are changes in the coordination around the vanadium during the electron transfer with significant changes in the valence to core Kβ̎ and Kβ2,5 lines. This fundamental investigation of molecular catalysis tackles some of the key questions during electron transfer-oxygen transfer reactions with state-of-the-art techniques.