A three-dimensional ZnII coordination polymer constructed from 1,1'-biphenyl-2,2',4,4'-tetra-carboxylate and 1,4-bis(1H-imidazol-1-yl) benzene ligands exhibiting photoluminescence

Ligands based on polycarboxylic acids are excellent building blocks for the construction of coordination polymers; they may bind to a variety of metal ions and form clusters, as well as extended chain or network structures. Among these building blocks, biphenyltetracarboxylic acids (H(4)bpta) with C-2 symmetry have recently attracted attention because of their variable bridging and multidentate chelating modes. The new luminescent three-dimensional coordination polymer poly[(mu(5)-1,1'-biphenyl-2,2',4,4'-tetracarboxylato) bis[mu(2)-1,4-bis(1H-imidazol-1-yl) benzene] dizinc(II)], [Zn-2(C16H6O8)(C12H10N4)](n), was synthesized solvothermally and characterized by single-crystal X-ray diffraction, elemental analysis and IR spectroscopy. The crystal structure contains two crystallographically independent Zn-II cations. Both metal cations are located on twofold axes and display distorted tetrahedral coordination geometries. Neighbouring Zn-II centres are bridged by carboxylate groups in the syn-anti mode to form one-dimensional chains. Adjacent chains are linked through 1,1'-biphenyl-2,2',4,4'tetracarboxylate and 1,4-bis(1H-imidazol-1-yl) benzene ligands to form a threedimensional network. In the solid state, the compound exhibits blue photoluminescence and represents a promising candidate for a thermally stable and solvent-resistant blue fluorescent material.