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-ylmethyl]benzene (L1), 1,3-bis[2-(2-pyridyl)imidazol-1-ylmethyl]benzene (L2), and 1,4-bis[2-(2-pyridyl)imidazol-1-ylmethyl]benzene (L3) have been synthesized: [Zn2(ODPT)(L1)0.5(H2O)]·3H2O (1), [Zn2(ODPT)(L2)(H2O)2]·3H2O (2), [Zn2(ODPT)L3(H2O)]·6H2O (3), [Cd2(ODPT)(L1)0.5(H2O)]·4H2O (4), [Cd(H2ODPT)(L2)]·2H2O (5), and [Cd1.5(HODPT)(L3)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 1 exhibits a two-dimensional (2D) layer structure with tetra-nuclear zinc clusters as building units, and intermolecular π···π 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 L3 ligands connecting ODPT-Zn double-chains to a 3D network with a (42·6·102·12)(42·6)(102·12) topology. Compound 4 is isostructural with compound 1. In 5, partly deprotonated H2ODPT2− anions link the L2-Cd 24-membered rings to generate an infinite chain that extends into a 2D supramolecular sheet by intermolecular π···π stacking interactions. In 6, L3 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.