Magnetic and spectroscopic investigation of partially reduced vanadium pentoxides. III. (Mo xV 1- x) 2O 5
The magnetic, electron paramagnetic resonance (EPR), infrared (ir), and optical properties of the orthorhombic ( x ⩽ 0.20) and monoclinic ( x = 0.28) phases of (Mo xV 1- x) 2O 5 have been measured and interpreted. The magnetic data are interpreted in terms of a ligand-field model in which the octahedral 2T2 g term of V 4+ is split by the combined perturbations of axial distortion and spin-orbit coupling, with the result that the 2T2 g term is split into a magnetic ground level, a weakly magnetic intermediate level, and a magnetic highest level. The g-values and linewidth data are in good agreement with the magnetic results. The susceptibility and EPR studies indicate that the paramagnetic centers are deep-donor V 4+OMo 6+ pairs and that the oxygen symmetry is more nearly octahedral in the monoclinic phase. The ir spectra indicate a weakening of the shortest metal-oxygen bond in the monoclinic phase, and the optical spectra show a concomitant increase in the octahedral component of the ligand field in this phase. The implications of these results for oxidation catalysis by (Mo xV 1- x) 2O 5 are discussed.