Uranium(VI) complexes with isonicotinic acid : from monomer to 2D polymer with unique U-N bonding

Two new uranium(VI) complexes with isonicotinic acid (HINT) have been synthesized and characterized. [(UO2)(NO3)2(HINT)2] (1) has a monomeric structure constructed of a hexagonal bipyramidal uranyl centre, two nitrate anions and two monodentate HINT in trans-positions. [(UO2)(OH)(INT)] (2) has a two-dimensional (2D) polymeric structure constructed of uranyl hydroxyl 1D pillars and µ3-bridging INT anions; the first observation of INT in µ3-bridging mode for U(VI) ion via U-N bonding. Thermal analysis confirmed both complexes lost coordinated INT ligands followed by further decomposition to form U3O8. Raman spectroscopy has confirmed the presence of uranyl ion and INT ligand in both complexes as well as the existence of nitrate vibrations in 1 and hydroxyl vibrations in 2. Their photoluminescence properties have been investigated.