Two novel uranyl complexes of a semi-rigid aromatic tetracarboxylic acid supported by an organic base as an auxiliary ligand or a templating agent: an experimental and theoretical exploration

摘要

Two novel uranyl coordination polymers, namely, UO2(bptc)(H(2)bpy)center dot(bpy) (1) and (UO2)(3)(bptc)(1.5)(phen)(2)(H2O)(2)center dot H2O (2) (H(4)bptc = 3,3',4,4'-benzophenonetetracarboxylic acid; bpy = 4,4'-bipyridine; phen = 1,10-phenanthroline), have been obtained via a hydrothermal method based on a semi-rigid aromatic tetracarboxylic ligand and two different auxiliary or templating N-containing ligands. Complex 1 shows a one-dimensional (1D) structure derived from double chains with two types of rings arranged alternately, which further exhibits an intriguing 3D supramolecular network induced by diverse non-covalent interactions. Complex 2 displays a dislocated "double floor" of a 2D structure (2D zigzag layers), in which the carboxylate groups of the bptc(4)-ligand adopt a variety of fascinating bridging modes. In addition, quantum chemical calculations were used to investigate the coordination properties and bonding nature of the as-synthesized complexes, and the results indicate that in these two complexes the 5f, 6d, and 7p orbitals of uranium and 2p orbitals of O and N atoms mainly contribute to the covalency of the U-O and U-N bonds.