Poly[di­ammonium [di­aqua­(μ7-benzene-1,2,3,4,5,6-hexa­carboxyl­ato)tetra­oxido­diuranium(VI)]]

Uranyl-carboxyl-ate hybrid materials dominate the catalog of uranyl compounds owing in part to the affinity between COO(-) functional groups and UO2 (2+). Polycarboxyl-ate organic ligands may present a degree of steric hindrance and could thus influence the resulting uranyl topology. Single crystals of the title compound, {(NH4)2[(UO2)2(C12O12)(H2O)2]} n , were synthesized hydro-thermally as a result of reacting uranyl nitrate with benzene-1,2,3,4,5,6-hexa-carb-oxy-lic acid (mellitic acid). The structure is comprised of a single unique monomeric uranyl cation adopting a penta-gonal bipyramidal geometry. The uranyl coordination sphere is composed of four O atoms originating from one half of a fully deprotonated mellitic acid ligand and a single water mol-ecule. The observed axial U-O bonds display an average distance of 1.765 (8) Å, whereas equatorial O atoms are found at an average distance of 2.40 (5) Å. All uranium-oxygen bond lengths are in good agreement with literature values. Furthermore, the coordin-ation between the uranyl penta-gonal bipyramids and the mellitic acid anion constructs a three-dimensional anionic framework which is charge-balanced with ammonium cations. Additional stabilization of the structure is provided by O-H⋯O and N-H⋯O hydrogen bonding inter-actions between the components.