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 (H4qptc) and MII (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(H2qptc)(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 qptc4− is a twisted H-shaped ligand connecting CoII centers. Furthermore, 3-D structures in 1 and 2 are formed via inter-chain π···π interactions between neighboring 2,2′-bpy ligands, with the centroid–centroid distances of 3.619–3.822 A. In 3, two deprotonated carboxyl groups of H2qptc2− are a Z-shaped ligand linking CuII centers to a 1-D zigzag polymeric chain. A 2-D layer structure is built with the help of inter-chain π···π interactions between the 2,2′-bpy and H2qptc2−.