Synthesis And Properties Of Transition Metal Coordination Polymers Constructed By Pyridine Carboxylic Acid

Pyridine carboxylic acid ligands take an increasing significant part in ligand selection of coordination polymers for its strong coordination ability and extensive coordination modes. The metal-organic coordination polymers of pyridine carboxylic acid constructing with different metal ions have shown their novel and diverse structures. Potential applications in the fields of optics, catalysis, gas storage, molecular recognition and magnetic materials have also been proved. In conclusion, more and more attention will be attached on pyridine carboxylic acid ligands.In this paper, six new coordination polymers have been synthesized under solvothermal conditions based on 2,6-di(2',4'-dicarboxylphenyl) pyridine(H4pyip) respectively, formulated as {[Cd2(H4pyip)(DMF)3]?2H2O?DMF}n(1), [Zn5(H4pyip)3(DMF)(H2O)4]n(2), {[Zn2(H4pyip)2]?3.5H2O}n(3), [Zn2(H4pyip)(DMF)(H2O)2]n(4), {[Cu(H3pyip)(OH)]?6H2O}n(5), {[Cu1.5(H4pyip)(H2O)]?H2O}n(6). All complexes have been characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, thermogravimetric analysis and powder X-ray diffraction measurements.Their crystal structures and properties have been orderly studied as below:(1) Complex 1 belongs to monoclinic,space group P21/c and it is composed of binuclear Cd to form a three-dimensional structure with microporous network. Complex 2 belongs to monoclinic, space group C2/m, it is a three-dimensional coordination polymer contains two kinds of binuclear Zn with five kinds of Zn. Complex 3 belongs to triclinic,space group P-1,and the binuclear Zn are extended by the ligands linke to construct a two-dimensional structure.Complex 4 belongs to monoclinic, space group C2/c, and it is composed one-dimensional Zn(II) chains to form a special structure with a the approximate circular microporous network.The thermogravimetric analysis result shows that the complexes 1-4 have good thermal stability.(2) Complex 5 and 6 are monoclinic coordination polymers,both belong to monoclinic, their space groups are C2 and C2/c.Complex 5 is five-coordinated in a distorted octahedron,it is composed of a separated unit which contains two Cu(II) ions in the same symmetry environment,and the separated unit through the H-binds to build a novel structure.Complex 6 exhibits a original framework based on one-dimensional symmetrical Cu(II) chains.The thermogravimetric analysis result shows that both the complexes 5 and 6 have good thermal stability.