Uranyl Carboxyphosphonates Derived from Hydrothermal in Situ Ligand Reaction: Syntheses, Structures, and Computational Investigations

Two uranyl carboxyphosphonates (H2dipy)­[(UO2)3­(H2O)2(H2DPTP)2]·2H2O (DPTP-U1) and (H2bbi)­[(UO2)4­(H2O)2(HDPTP)2] (DPTP-U2) [H6DPTP = 2,5-diphosphonoterephthalic acid, dipy = 4,4′-bipyridine, bbi = 1,1′-(1,4-butanediyl)­bis­(imidazole)] were synthesized under hydrothermal conditions. The carboxyphosphonate ligand was formed through the in situ oxidation of (2,5-dimethyl-1,4-phenylene)­diphosphonic acid mediated by UO22+. Single-crystal X-ray diffraction analyses reveal that DPTP-U1 possesses uranyl carboxyphosphonate layers that are separated by protonated dipy cations. Whereas DPTP-U2 is in a three-dimensional framework structure with channels filled by protonated bbi cations. The computational investigations give an insight into the nature of bonding interactions between uranium­(VI) and carboxyphosphonate ligand. The spectroscopic properties were also studied.