Pb(UO2)(V2O7), a novel lead uranyl divanadate

A new lead uranyl divanadate, PbUO2(V2O7), has been synthesized by high temperature solid-state reaction and its crystal structure was solved by direct methods using single-crystal X-ray diffraction data. It crystallizes in the monoclinic system with space group P21/n and following cell parameters: a=6.9212(9)A, b=9.6523(13)A, c=11.7881(16)A, β=91.74(1)o, V=787.01(2)A3, Z=4, ρmes=5.82(3), ρcal=5.83(1)g/cm3. A full-matrix least-squares refinement on the basis of F2 yielded R1=0.029 and wR2=0.064 for 2136 independent reflections with I>2σ(I) collected with a Bruker AXS diffractometer (MoKα radiation). The crystal structure of PbUO2(V2O7) consists of a tri-dimensional framework resulting from the association of V2O7 divanadate units formed by two VO4 tetrahedra sharing corner and UO7 uranyl pentagonal bipyramids and creating one-dimensional elliptic channels occupied by the Pb2+ ions. In PbUO2(V2O7), infinite ribbons of four pentagons wide are formed which can be deduced from the sheets with Uranophane type anion-topology that occurs, for example, in the uranyl divanadate (UO2)2(V2O7), by replacement of half-U atoms of the edge-shared UO7 pentagonal bipyramids by Pb atoms. Infrared spectroscopy was investigated at room temperature in the frequency range 400-4000cm-1, showing some characteristic bands of uranyl ion and of VO4 tetrahedra