The identification of structural details in catalyst particles is of paramount importance for a reliable description of structure-reactivity relationships in catalysis. In this study we consider an oxo-peroxovanadium(V) compound chelated with N-(2-hydroxyethyl) iminodiacetic acid, [VO(O2)Hheida]. This complex is an efficient functional model for the vanadium haloperoxidase enzyme which acts as halide oxidant but also as a catalyst for sulfoxidation and alcohol oxidation. It includes oxygen species in very different local coordination next to vanadium: terminal vanadyl (V=O), dioxo (V-O2), hydroxyl (V-OH), bridging V-O-C, and embedded C-O species. Thus, the [VO(O2)Hheida] complex offers an ideal test case for examining differently coordinated oxygen in the same system and finding out about structure sensitivity of corresponding spectroscopies.DFT calculations are performed to determine the equilibrium geometry of the [VO(O2)Hheida]- ion and the results agree nicely with experimental data for the K[VO(O2)Hheida] single crystal. The analysis of vibrational modes, computed in harmonic approximation, allows an identification of differently coordinated oxygen species, such as vanadyl and di-oxo, although corresponding modes are not well localized. The theoretical spectrum agrees quite reasonably with experimental data from IR and Raman measurements. Further, theoretical O 1s NEXAFS spectra are evaluated for the [VO(O2)Hheida]- complex. The corresponding partial NEXAFS spectra, providing a highly localized oxygen probe, show substantial differences amongst the different oxygen species which allows easy discrimination. These results can be compared with experimental O K-shell NEXAFS data obtained in this work.DFT calculations are also performed on reduced [VO(O)Hheida]- where oxidation reactions are assumed to remove one oxygen from the di-oxo site of the [VO(O2)Hheida]- complex. The theoretical IR and O1s NEXAFS spectra show substantial differences between the two complexes which can be compared with experimental data to help the interpretation of the spectral properties.

Structure and reactivity of oxygen in particles of catalytic interest: DFT studies on K[VO(O<sub>2</sub>)Hheida] compared with infrared spectroscopy and X-ray absorption

247th National Meeting (2014)

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Structure and reactivity of oxygen in particles of catalytic interest: DFT studies on K[VO(O2)Hheida] compared with infrared spectroscopy and X-ray absorption

Structure and reactivity of oxygen in particles of catalytic interest: DFT studies on K[VO(O₂)Hheida] compared with infrared spectroscopy and X-ray absorption