Assembly and properties of four new metal-organic coordination polymers with flexible bis-pyridyl-bis-amide ligands: effect of aromatic dicarboxylates and central metal ions on the structures

Four coordination polymers, [Cu(4-dpyh)(0.5)(1,2-BDC)(H2O)(3)]H2O (1), [Cu(4-dpyh)(1,3-BDC)(H2O)] (2), [Cd(3-dpyh)(0.5)(1,3-BDC)(H2O)(2)]H2O (3), and [Zn(3-dpyh)(1,3-BDC)]3H(2)O (4) [4-dpyh=N,N-bis(4-pyridinecarboxamide)-1,6-hexane, 3-dpyh=N,N-bis(3-pyridinecarboxamide)-1,6-hexane, 1,2-H2BDC=1,2-benzenedicarboxylic acid and 1,3-H2BDC=1,3-benzenedicarboxylic acid], have been hydrothermally synthesized. X-ray diffraction analyses reveal that 1 is a discrete [Cu-2(4-dpyh)(1,2-BDC)(2)] dinuclear structure. Compound 2 exhibits a 2-D grid layer constructed from 1-D linear [Cu(1,3-BDC)](n) chains and [Cu(4-dpyh)](n) chains. Compound 3 features a 1-D ladder-like chain formed by the 1-D linear [Cd(1,3-BDC)](n) chains and 3-dpyh bridging ligands. Compound 4 displays a 2-D undulated layer containing meso-helical [Zn(3-dpyh)](n) chains and linear [Zn(1,3-BDC)](n) chains. The neighboring dinuclear complexes for 1, adjacent chains for 3, and adjacent layers for 2 and 4 are further linked by hydrogen bonding interactions to form 2-D (for 1) or 3-D supramolecular networks (for 2-4). The influences of the different dicarboxylates and metal on the structures of 1-4 have been discussed. The electrochemical behaviors of 1 and 2, the thermal stabilities and fluorescent properties of 1-4, and the fluorescent selectivities of 3 and 4 have been investigated.