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

Uranyl-carboxyl­ate hybrid materials dominate the catalog of uranyl compounds owing in part to the affinity between COO⁻ functional groups and UO₂²⁺. Polycarboxyl­ate 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 hydro­thermally as a result of reacting uranyl nitrate with benzene-1,2,3,4,5,6-hexa­carb­oxy­lic acid (mellitic acid). The structure is comprised of a single unique monomeric uranyl cation adopting a penta­gonal 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 mol­ecule. 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 coordin­ation between the uranyl penta­gonal 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 inter­actions between the components.