Tracing fingerprints. Key IR and UV/Vis spectroscopic signatures to differentiate oxidation states of the manganese-oxo vanadate catalyst [(Mn4O4)(V4O13)(OAc)3]n– are identified. During oxidation from [MnMn] to [Mn], in the UV/Vis spectrum a band at about 570 nm increases while another one at 850 nm vanishes. In the IR spectra, oxidation leads to a remarkable shift of the V=O stretch mode to higher energies.
We report IR and UV/Vis spectroscopic signatures that allow discriminating between the oxidation states of the manganese-based water oxidation catalyst [(Mn4O4)(V4O13)(OAc)3]3−. Simulated IR spectra show that V=O stretching vibrations in the 900–1000 cm−1 region shift consistently by about 20 cm−1 per oxidation equivalent. Multiple bands in the 1450–1550 cm−1 region also change systematically upon oxidation/reduction. The computed UV/Vis spectra predict that the spectral range above 350 nm is characteristic of the managanese-oxo cubane oxidation state, whereas transitions at higher energy are due to the vanadate ligand. The presence of absorption signals above 680 nm is indicative of the presence of MnIII atoms. Spectroelectrochemical measurements of the oxidation from [MnMn] to [Mn] showed that the change in oxidation state can indeed be tracked by both IR and UV/Vis spectroscopy.
Wiley: Chemistry – A European Journal: Table of Contents
Authors: Sebastian Mai, Sarah Klingler, Ivan Trentin, Julian Kund, Marcus Holzer, Anastasia Andreeva, Robert Stach, Christine Kranz, Carsten Streb, Boris Mizaikoff, Leticia González