The various architectures and properties of a series of coordination polymers tuned by the central metals

Five new metal-organic coordination polymers based on the mixed ligands of a semi-rigid bis-pyridyl-bis-amide N,N'-bis(3-pyridinecarboxamide)-1,2-cyclohexane (3-bpah) and 1,4-benzenedicarboxylic acid (1,4-H2BDC), namely [Co(3-bpah)(1,4-BDC)(H2O)3] (1), [Ni(3-bpah)(1,4-BDC)(H2O)3] (2), [Cu(3-bpah)(1,4-BDC)] (3), [Zn(3-bpah)(1,4-BDC)]·H2O (4) and [Cd(3-bpah)(1,4-BDC)(H2O)] (5), have been hydrothermally synthesized and structurally characterized. Complexes 1 and 2 are isostructural and display the similar 1D infinite chains, which are further linked via hydrogen-bonding interactions to generate 3D supramolecular frameworks. Complex 3 features a 3D polymeric framework with CdSO4-like topology. Complexes 4 and 5 show two similar 2D (2,4)-connected networks with (4·8(5))(4) topology, in which the 3-bpah ligands adopt different μ2-bridging coordination modes via the ligation of two pyridyl nitrogen atoms in 4 and via the ligation of one pyridyl nitrogen and one amide oxygen atom in 5. In addition, the central metals show different coordination geometries in 4 and 5. The adjacent layers of complexes 4 and 5 are finally extended into 3D supramolecular architectures through hydrogen-bonding interactions. The effects of the central metals on the structures and properties of complexes 1-5 have been discussed. The electrochemical properties of complexes 1-3 and fluorescent sensing behaviors of 4-5 toward ethanol and nitrobenzene have been investigated in detail.