Novel Heterometallic Uranyl-Transition Metal Materials: Structure, Topology, and Solid State Photoluminescence Properties

Six new uranyl hybrid materials have been synthesized solvothermally utilizing the ligands 2,2'-bipyridine-3,3'-dicarboxylic acid (H2L) and 2,2':6',2''-terpyridine (TPY). The six compounds are classified as either molecular complexes (I0O0 connectivity), [(UO2)(L)(TPY)]center dot H2O (1), [Ni(TPY)(2)][(UO2)(L)(2)]center dot 3H(2)O (2), and [Cu(TPY)(2)][(UO2)(L)(2)]center dot 3H(2)O (3), or 3D metal-organic frameworks (MOFs, I0O(3) connectivity), [Cu-2(UO2)(2)(OH)(C2H3O2)(L)(3)(TPY)(2)]center dot 6H(2)O (4), [Zn-2(UO2)(2)(OH)(NO3)(C2H3O2)(L)(3)(TPY)(2)]center dot 4H(2)O (5), and Na[Ni(UO2)(3)(OH)(O)(L)(3)]center dot 9H(2)O (6). A discussion of the influence of transition metal incorporation, chelating effects of the ligand, and synthesis conditions on the formation of uranyl materials is presented. The structure of compound 6 is of particular note due to large channel-like voids with a diameter of approximately 19.6 angstrom. A topological analysis of 6 reveals a new topology with a 9-nodal 3,3,3,3,3,3,3,4,5-connected network, designated geg1 hereafter. Further, solid state photoluminescence experiments show emission and lifetimes values consistent with related uranyl compounds.