Syntheses, Crystal Structures And Property Studies Of Coordination Polymers Based On2-(pyirdin-2-yl)-1H-imidazole-4,5-dicarboxyiic Acid

In recent years, metal-organic coordination polymers have been paid much attention notonly owing to their enormous varieties of intriguing structural topologies, but also their greatpotential applications in areas of catalysis, magnetism, separation, gas adsorption,luminescence，molecular recognition，nonlinear optics，ion exchange and so on. The designand synthesis of different dimensions framework influenced by many factors, such as thecoordination trend of metal centers, ligand structure, the ratio of the metal and ligand, reactionsolvent system, counterion, reaction time, reaction temperature, pH value of the reactionsolution, and templates. Although various coordination polymers have been reported based on4,5-imidazole dicarboxylic acid and its derivatives, there are still rare examples ofcoordination polymers on the basis of2-(pyridin-2-yl)-1H-imidazole-4,5-dicarboxylic acid.Herein, in this work, we report seven novel coordination polymers based on2-(pyridin-2-yl)-1H-imidazole-4,5-dicarboxylic acid between transition metal Cd and maingroup metal Pb, which have been synthesized under hydrothermal or solvothermal conditions.These compounds have been structurally characterized by single-crystal X-ray diffraction（XRD）、infrared spectrum（IR）、elemental analyses, and powder X-ray diffraction (PXRD).In addition, the thermogravimetric analysis（TGA）and fluorescent properties in the solid stateof these seven compounds have been studied.1. Three new supramolecular compounds,[Cd(H2PIDC)2(H2O)]·H2O (1),{[Cd(H2PIDC)2(H2O)]·2H2O}n(2) and {[CdCl(H2PIDC)(H2O)2]·H2O}2(3)(H3PIDC=2-(pyridin-2-yl)-1H-imidazole-4,5-dicarboxylic acid), have been synthesized underhydrothermal or solvothermal conditions. Compound1contains discrete mononuclearstructure, compound2consists of one-dimensional left-and right-helix chains, and compound3displays a0D closed loop structure. They are constructed into high-dimensionalsupramolecular frameworks by strong non-covalent hydrogen bonding and π···π stackinginteractions.2. One Cd（Ⅱ）coordination polymer,[Cd4(HPIDC)4]n(4), has been prepared underhydrothermal conditions. The X-ray structure determination reveal that the compound4exhibits a3D framework, in which consists of metallacalix[4]arene building blocksCd4(HPIDC)4with1D interconnected channels along c axis. The structure of4can bedescribed as a (3,3)-connected net with the (8210) topology.3. Three lead coordination polymers,[PbCl(H2PIDC)(H2O)·H2O]n(5),[Pb(H2PIDC)2(H2O)]n(6) and [Pb3(HPIDC)3]n(7), have been hydrothermally synthesized andstructurally characterized by single-crystal X-ray diffraction. In5, Cl anions connected neighboring wave-like2D layers, which are constructed with left-and right-handed helicalchains, into a3D network structure with a (63)(65·8) topology. In6, Pb cations are linked intoa3D66network with left-and right-handed helixes by μ2-bridging H2PIDC–ligands. In7,HPIDC2–ligands link Pb6O12clusters into a3D (412·63) network.