Multi-Frequency and Single-Crystal EPR on V4+ in W-Doped β-Vanadyl(V) Phosphate: Hyperfine Coupling- and g-Tensor Values and Orientation

Abstract Different structure types of vanadyl(V) orthophosphate [i.e. (V V ≡O) 3+ orthophosphate] have been subjects research due to their catalytic activity in the oxidation n -butane maleic anhydride. Electron paramagnetic resonance (EPR) spectroscopy can be exploited elucidate electronic such compounds. When tuning state vanadium 1-x W x )OPO 4 , X-band EPR spectra confirmed presence 4+ ions. However, some features these could not explained. Here, powder samples β -(V IV 0.01 .98 VI .01 are investigated at S-, X- and Q- band, along with measurements on single crystals. Thereby, discrepancies between simulations resolved. In particular, it shown that g A tensors coaxial. The resulting consistent picture refined parameters reported. work underlines indispensability a multi-frequency approach for unequivocal conclusions.