Structures and luminescent properties of a series of zinc(II) and cadmium(II) 4,4′-oxydiphthalate coordination polymers with various ligands based on bis(pyridyl imidazole) under hydrothermal conditions

Six coordination polymers constructed from three structurally related ligands, 1,2-bis[2-(2-pyridyl)imidazol-1-yl-methyl]benzene (C), 1,3-bis[2-(2-pyridyl)imidazol-1-ylmethyl]benzene (L-2), and 1,4-bis[2-(2-pyridyl)imidazol-1-ylmethyl]benzene (L-3) have been synthesized: [Zn-2(ODPT)(L-1)(0.5)(H2O)]center dot 3H(2)O (1), [Zn-2(ODPT)(L-2)(H2O)(2)]center dot 3H(2)O (2), [Zn-2(ODPT)L-3(H2O)]center dot 6H(2)O (3) [Cd-2(ODPT)(L-1)(0.5)(H2O)]center dot 4H(2)O (4), [Cd(H2ODPT)(L-2)]center dot 2H(2)O (5), and [Cd-1.5(HODPT)(L-3)(0.5)] (6), where H4ODPT is 4,4'-oxidiphthalic acid. Their structures have been determined by single crystal X-ray diffraction analyses. All compounds are also characterized by elemental analyses, IR spectra, and thermogravimetric (TG) analyses. Compound I exhibits a two-dimensional (2D) layer structure with tetra-nuclear zinc clusters as building units, and intermolecular pi center dot center dot center dot pi stacking interactions link these sheets to a three-dimensional (3D) supramolecular structure. Compound 2 shows infinite chains and is extended into a 2D supramolecular sheet by intermolecular hydrogen bonds. The structure of 3 is built by L-3 ligands connecting ODPT-Zn double-chains to a 3D network with a (4(2)center dot 6 center dot 10(2)center dot 12)(4(2 center dot)6)(10(2 center dot)12) topology. Compound 4 is isostructural with compound 1. In 5, partly deprotonated H2ODPT2- anions link the L-2-Cd 24-membered rings to generate an infinite chain that extends into a 2D supramolecular sheet by intermolecular pi center dot center dot center dot pi stacking interactions. In 6, L-3 ligands and the ether O atoms of HODPT3- anions link Cd-O chains formed by phthalic groups into a 3D network. In addition, the luminescent properties of these compounds are discussed.