Syntheses and crystal structures of three coordination polymers based on terphenyl-2,5,2′,5′-tetracarboxylic acid

Solvothermal reactions of terphenyl-2,5,2',5'-tetracarboxylic acid (H(4)qptc) and M-II (M=Co, Ni, Cu) in the presence of 2,2'-bipyridine (2,2'-bpy) afford three new coordination polymers, [M(qptc)(0.5)(2,2'-bpy)(H2O)](n) (M=Co (1), Ni (2)) and [Cu(H(2)qptc)(2,2'-bpy)](n) (3). The structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR, and TGA. Complexes 1 and 2 are isostructural and display a 2-D layer wherein qptc(4-) is a twisted H-shaped ligand connecting Co-II centers. Furthermore, 3-D structures in 1 and 2 are formed via inter-chain pi center dot center dot center dot pi interactions between neighboring 2,2'-bpy ligands, with the centroid-centroid distances of 3.619-3.822 angstrom. In 3, two deprotonated carboxyl groups of H(2)qptc2(-) are a Z-shaped ligand linking Cu-II centers to a 1-D zigzag polymeric chain. A 2-D layer structure is built with the help of inter-chain pi center dot center dot center dot pi interactions between the 2,2'-bpy and H(2)qptc(2-).