Synthesis And Characterization Of Transition-Metal Organic Coordination Polymers

Metal-organic coordination polymers have attracted much attention owning to their various topologies, flexible tailoring, and a wide range of potential applications in ion-exchange, adsorption and molecular recognization, catalysts along with optics, electrics, magnetism and enantioselective separation. At present, coordination polymers research focus on the use of reasonably designed the secondary building units (SBUs) with a specific geometry as node to build the supposed network topology. Based on the crucial impact of the SBUs for the final configuration of the network topology, chemists have designed and synthesized a lot of coordination polymers with special SBUs.In building porous materials, multi-carboxylic acid ligand has following advantages: (1) a large number of experimental results show that, the carboxylic acid ligand can build various zeolite-like materials which have large cavities sizes and channels volumes; (2) compared with containing nitrogen ligand, carboxylic acid is easy to form strong coordination bonds with metal ions, and this kind of coordination polymer has better stability; (3) carboxylic acid ligand is easy to form clusters with metal ions, to a certain extent, reducing the interpenetrating phenomenon and the possibility of forming linear with a low-dimensional structure. Based on the above characteristics, multi-carboxylic acid as organic ligand to build porous crystalline materials has attracted much more attention. According to the principle of molecular engineering, we have focused on the synthesis of metal-organic coordination polymers under mild synthetic conditions by choosing transition metal ions with various coordination models and specific functions, and 3,3′,5,5′-azobenzenetetracarboxylic acid (H4ATC) as organic ligand which is rigid, chelated and serves as bridging nodes.By using pyridine as the structure-directing agent, the compound [Co4(C16N2O8H6)2·(C5NH5)4·(C3NOH7)2] was solvothermally synthesized. The structure was determined by single-crystal X-ray diffraction analysis and characterized by IR, TGA, CHN analysis. It crystallized in tetragonal system with space group P43, cell parameters a = b = 13.6625 ?, c = 44.8507 ?. It is constructed from Co2(CO2)4(Py)2(DMF) units and H4ATC ligands which based on cobalt-carboxylate dimers to form a 3D MOF with the PtS topology.The compound [FeNa(C16N2O8)2(H2O)4] has been synthesized in hydrothermal condition. The structure exhibits a 3D supermolecular structure, which is built by 2D layer and hydrogen-bonded helix. It crystallized in monoclinic system with space group C2/c,a = 19.548(4)?, b = 12.435(3) ?, c = 7.2474(14)?。...