Hydrothermal synthesis and structure determination of the new vanadium molybdenum mixed oxide V1.1Mo0.9O5 from synchrotron X-ray powder diffraction data

A new vanadium molybdenum mixed oxide V_1.1Mo_0.9O₅ V(V)_0.2V(IV)_0.9Mo(VI)_0.9O₅] has been synthesized, as a pure phase, via hydrothermal methods in the presence of molybdic acid and vanadyl sulfate. Its crystal structure has been solved ab initio from high-resolution powder diffraction data collected at the ESRF beamline ID31. This compound crystallizes in the monoclinic symmetry, space group C2/m, with cell dimensions , , , β=90.625(3)° and Z=2 per formula. The structure consists of double strings of VO₅ square pyramids sharing edges and corners along 100] and 010], and more weakly bound along 001]. In this latter direction, the bond (V,Mo)-O=2.377 Å, while remaining long, leads for the first time to the interpenetration of the apical oxygens of the (V,Mo)₂O₅]_n layers, resulting in a three-dimensional (3D) structure closely related to R-Nb₂O₅. This structure will be compared to the pure layer structure of V₂O₅ where this bond reaches 2.793 Å.