THE ORIGINAL STRUCTURE OF ZN3V4(PO4)(6) INVOLVING BIOCTAHEDRAL V2O10 UNITS AND ZNO5 TRIGONAL BIPYRAMIDS

A new monophosphate of trivalent vanadium and zinc Zn3V4(PO4)(6) was i solated and its structure has been determined from a single crystal X- ray diffraction study. It crystallizes in the space group P $$($) over bar 1 with a = 6.349(2) Angstrom, b = 7.869(1) Angstrom, c = 9.324(2) Angstrom, alpha = 105.32(1)degrees, beta = 108.66(2)degrees, and gamm a = 101.23(2)degrees. This tridimensional framework consists of biocta hedral V2O10 units of two edge-sharing octahedra, monophosphate groups , distorted ZnO6 octahedra, and distorted ZnO5 trigonal bipyramids. In fact, the [V4P6O24](infinity) framework can be described as a stackin g along b of [V4P4O24](infinity) layers parallel to the (a, c) plane, interconnected through layers of PO4 tetrahedra. The [V4P4O24](infinit y) layers are themselves built up from two kinds of [V2P2O14](infinity ) ribbons running along a; the latter are obtained by the assemblage o f two [VPO8](infinity) single chains sharing the edges of their octahe dra in two different ways. The ZnO5 bipyramids share two edges with tw o different V2O10 units, whereas the ZnO6 octahedra share their apices with the VO6 octahedra, the PO4 tetrahedra, and the ZnO5 bipyramids. A remarkable feature of this structure deals with the presence of nume rous triply bonded oxygen atoms. (C) 1995 Academic Press, Inc.