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

摘要

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_4bpta) with C2 symmetry have recently attracted attention because of their variable bridging and multidentate chelating modes. The new luminescent three-dimensional coordination polymer poly[(μ_5-1,1'-biphenyl-2,2',4,4'-tetracarboxylato)bis[μ_2-1,4-bis(1H-imidazol-1-yl)benzene]dizinc(II)], [Zn_2(C_16H_6O_8)(C_12H_10N_4)]_n, was synthesized solvother-mally 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 three-dimensional network. In the solid state, the compound exhibits blue photo-luminescence and represents a promising candidate for a thermally stable and solvent-resistant blue fluorescent material.