Assembly, Structures, and Properties of a Series of Metal-Organic Coordination Polymers Derived from a Semi-rigid Bis-pyridyl-bis-amide Ligand

Four metal-organic coordination polymers [Cd(4-bpcb)(1.5)Cl-2(H2O)] (1), [Cd(4-bpcb)(0.5)(mip)(H2O)(2)]3H(2)O (2), [Co(4-bpcb)(oba)(H2O)(2)] (3), and [Ni(4-bpcb)(oba)(H2O)(2)] (4) [4-bpcb = N,N-bis(4-pyridinecarboxamide)-1, 4-benzene, H(2)mip = 5-methylisophthalic acid, and H(2)oba = 4, 4-oxybis(benzoic acid)] were synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectroscopy, powder X-ray diffraction, and TG analysis. In complex 1, two Cl- anions serve as bridges to connect two Cd-((1)-4-bpcb) subunits forming a dinuclear unit, which are further linked by (2)-bridging 4-bpcb to generate 1D zigzag chain. Complex 2 shows a 2D 6(3) network constructed by [Cd-mip](n) zigzag chains and (2)-bridging 4-bpcb ligands. Complexes 3 and 4 are isostructural 2D (4, 4) grid networks derived from [M-oba](n) (M = Co, Ni) zigzag chains and [M-(4-bpcb)](n) linear chains. The 1D chains for 1 and the 2D networks for 2-4 are finally extended into 3D supramolecular architectures by hydrogen bonding interactions. The roles of dicarboxylates and central metal ions on the assembly and structures of the target compounds were discussed. Moreover, the thermal stabilities, photoluminescent properties, and photocatalytic activities of complexes 1-4 and the electrochemical properties of complexes 3 and 4 were investigated.