Synthesis, structure, and spectroscopic characterization of three uranyl phosphates with unique structural units

Single crystals of Zn-4(OH)(2)[(UO2)(PO4)(2)(OH)(2)(H2O)] (UZnP), Cs[(UO2)(HPO4)NO3] (UCsP), and In-3[(UO2)(2)(PO4)(4)OH(H2O)(6)]center dot 2H(2)O (UInP) were obtained from hydrothermal reactions and have been structurally and chemically characterized. UZnP crystallizes in space group Pbcn, a=8.8817(7), b=6.6109(5), c=19.569(1) angstrom; UCsP crystallizes in P-1, a=7.015(2), b=7.441(1), c=9.393(2) angstrom, alpha=72.974(2), beta=74.261(2), gamma=79.498(2); and UInP crystallizes in P-1, a=7.9856(5), b=9.159(1), c=9.2398(6) angstrom alpha=101.289(1), beta=114.642(1), gamma=99.203(2). The U6+ cations are present as (UO2)(2+) uranyl ions coordinated by five O atoms to give pentagonal bipyramids. The structural unit in UZnP is a finite cluster containing a uranyl pentagonal bipyramid that shares corners with two phosphate tetrahedra. The structural unit in UCsP is composed of uranyl pentagonal bipyramids with one chelating nitrate group that are linked into chains by three bridging hydrogen phosphate tetrahedra. In UInP, the structural unit contains pairs of edge-sharing uranyl pentagonal bipyramids with two chelating phosphate tetrahedra that are linked into chains through two bridging phosphate tetrahedra. Indium octahedra link these uranyl phosphate chains into a 3-dimensional framework. All three compounds exhibit unique structural units that deviate from the typical layered structures observed in uranyl phosphate solid-state chemistry. (C) 2012 Elsevier Inc. All rights reserved.