Correlations and Differences between Uranium(VI) Arsonates and Phosphonates

Three new uranium arsonate compounds, UO2(C6H5)2As2O5(H2O) (UPhAs-1), UO2(HO3AsC6H4AsO3H)­(H2O)·H2O (UPhAs-2), and UO2(HO3AsC6H4NH2)2·H2O (UPhAs-3) have been synthesized under mild hydrothermal conditions. UPhAs-1 is constructed from UO7 pentagonal bipyramids that are chelated by the pyroarsonate moiety, [PhAs­(O2)­OAs­(O2)­Ph]2–, forming chains of layered uranyl polyhedra. Two of the phenylarsonic acids are condensed in situ to form the fused tetrahedra of the pyroarsonate moiety through a metal-mediated, thermally induced condensation process. The structure of UPhAs-2 consists of UO7 pentagonal bipyramids that are chelated by phenylenediarsonate ligands, forming one-dimensional chains of uranyl polyhedra. UPhAs-3 consists of a rare UO6 tetragonally distorted octahedron (D4h) that is on a center of symmetry and linked to two pairs of adjacent 4-aminophenylarsonate ligands. This linear chain structure is networked through hydrogen bonds between the lattice water molecules and the −NH2 moiety. All three of these compounds fluoresce at room temperature, showing characteristic vibronically coupled charge-transfer based emission.