Three Transition Metal(II) Coordination Polymers Constructed by a Semirigid Bis-pyridyl-bis-amide and Dicarboxylates Mixed Ligands: Assembly, Structures and Properties

Three coordination polymers, namely [Co(BDC)(L)]center dot H2O (1), [Co(NPH)(L)]center dot H2O (2), and [Ni(NPH)(L)(H2O)(3)]center dot H2O (3) [H2BDC = 1,3-benzenedicarboxylic acid, H2NPH = 3-nitrophthalic acid, L = N,N'-bis(3-pyridyl)-terephthalamide] were hydrothermally synthesized by self-assembly of cobalt/nickel chloride with a semirigid bis-pyridyl-bis-amide ligand and two aromatic dicarboxylic acids. Single crystal X-ray diffraction analyses revealed that complexes 1 and 2 are two-dimensional (2D) coordination polymers containing a one-dimensional (1D) ribbon-like Co-dicarboxylate chain and a 1D zigzag Co-L chain. Although the coordination numbers of Co-II ions and the coordination modes of two dicarboxylates are different in complexes 1 and 2, they have a similar 3,5-connected {4(2).6(7).8}{4(2).6} topology. In complex 3, the adjacent Ni-II ions are linked by L ligands to form a 1D polymeric chain, whereas the 1D chains does not extend into a higher-dimensional structure due to the ligand NPH with monodentate coordination mode. The adjacent layers of complexes 1 and 2 and the adjacent chains of 3 are further linked by hydrogen bonding interactions to form 3D supramolecular networks. Moreover, the thermal stabilities, fluorescent properties, and photocatalytic activities of complexes 1-3 were studied.