Solvothermal syntheses, crystal structures and photoluminescent properties of four coordination polymers with pamoic acid and pyridine mixed ligands

Four new mixed-ligand coordination polymers, namely [Co-1/2(pam)(1/2)center dot(py)(2)center dot(H2O)(2)](n) (1), [Ni-1/2(pam)(1/2)center dot(py)(2)center dot(H2O)(2)](n) (2), [Zn-1/2(pam)(1/2)center dot(py)(2)](n) (3), and [Cd(pam)(py)(2)](n) (4) (H(2)pam = pamoic acid, py = pyridine) have been synthesized under hydro(solvo) thermal conditions. X-ray single crystal structure analysis shows that 1 and 2 are isomorphic and possess a linear chain. 3 is also a linear chain without coordinated water molecules in the structure. 4 is an unusual 2D structure constructed by a binuclear cadmium building block. It appears that the chelate ligands and metal ions of the larger size favor the formation of high-dimensional structures, whereas those of the smaller size favor the formation of low-dimensional structures in the present system. The solid-state fluorescence spectra of 3, 4 and free pamoic acid show that 3 and 4 exhibit a greatly enhanced emission compared to free pamoic acid ligand. (C) 2013 Elsevier B. V. All rights reserved.