Synthesis,Structure And Properties Of Coordination Polymers Constructed From Bidentate Ligands With Imidazolyl/Triazolyl Group-Carboxylic Acid

The combination of bidentate ligands containing imidazol/triazolyl groups,thiophenedicarboxylic acid,different metal ions,including Zn²⁺、Cd²⁺、Cu²⁺、Co²⁺ions,have gave eleven metal-organic complexes under hydrothermal/solvothermal condition.Their structures have beencharacterized by these methods of single crystal X-ray diffraction analysis,thermogravimetric analysis（TGA）,FT-IR spectra（IR）,powder X-ray diffraction analysis（PXRD）.Additionally,the fluorescence,electrochemical,catalytic,magnetic properties have been also investigated according to the structural features of these complexes.1.Selecting semi-rigid N-donor ligands,1,4-bis（1H-imidazol-1-yl-methyl）benzene（bimb）,4,4’-bis（1H-imidazol-1-ylmethyl）-1,1’-biphenyl（bidp）,seven metal-organic complexe are synthesized in the presence of 2,5-thiophenedicarboxylic acid（H₂tdc）or 3,4-thiophenedicarboxylic acid（H₂tdc’）,metal ions,such as Zn²⁺、Cd²⁺、Co²⁺.The influence on the structure of bimb,bidp,carboxylic acid ligands are studied.And,the fluorescence and magnetic properties are also investigated here.[Zn₃（bimb）（tdc）₃（DMA）₂]·DMA（1）[Zn（bidp）_0.5（tdc）]（2）[Cd₃（bimb）（tdc）₃（DMA）₂]·2DMA（3）[Cd₃（bidp）（tdc）₄（HDMF）₂]·4H₂O（4）[Co₂（bimb）（H₂O）（tdc）₂（DMF）₂]·H₂O（5）[Zn（bimb）（NO₃）₂]·H₂O（6）[Cd（bimb）（NO₃）₂]·H₂O（7）bimb=1,4-bis（1H-imidazol-1-yl-methyl）benzenebidp=4,4’-bis（1H-imidazol-1-ylmethyl）-1,1’-biphenylH₂tdc=2,5-thiophenedicarboxylic acidThere exist some binuclear clusters in compounds 2,3,5,including{Zn₂}（2）、{Cd₂}（3）、{Co₂}（5）,which are constructed from tdc ligands and metal ions,respectively,but trinuclear clusters in compounds 1 and 4,namely,{Zn₃}（1）and{Cd₃}（4）.In the presence of bimb ligand for compounds 1,3,5,the coordination between metal ions and tdc ligands gives a 2D network layer containing the binuclear clusters,forming a 3D six-connected framework,where the bimb ligands act as the bridged linkers.Replacing the tdc with tdc’ligand,compounds 6 and 7 are obtained,but the tdc’ligands are not included in two structures except that a kind of 1D chains and the nitrate ions.Tuning the lengths of ligands through choosing bidp as N-donor ligands with biphenyl group,as well as tdc ligand,compounds 2 and 4 are prepared.In 2,the 2D layer constructed from tdc ligands and Zn（Ⅱ）ions are linked by bidp ligands to give a 3D six-connected framework structure.A kind of 2D layer similar to that in of 2 can be also generated in 4,the combination of such two layer results in a 3D two-fold interpenetrating framework,which is different from the structure of 2.Compounds 1,2,3,4,6,7 display good fluorescence properties,and 5 exhibits not only antiferromagnetic interactions,but also electrocatalytic activity toward the oxidation of ascorbic acid.2.The benzonitrile organic ligands containing bidentate ligands with imidazol/triazolyl groups,3,5-di-imidazol-1-yl-benzonitrile（DICN）、3,5-di-[1,2,4]triazol-1-yl-benzonitrile（DTCN）are chosen,due to the transformation in situ from nitrile to carboxyl group under hydrothermal/solvothermal condition,namely,HDICA and HDTCA genareted from DICN and DTCN,respectively,four metal-organic complexes（8-11）are synthesized In the presence of Zn（Ⅱ）,Cu（Ⅱ）,Co（Ⅱ）.Their structures are characterized and described in details,and the corresponding properities on them are further studied.[Co（DIBA）₂（H₂O）₂]·H₂O（8）[Cu（DIBA）₂]（9）[Cu（DTBA）₂]（10）[Zn（DTBA）C1]（11）HDIBA=3,5-di-imidazol-1-yl-benzoic acidHDTBA=3,5-di-[1,2,4]triazol-1-yl-benzoic acidIt can be found that the DICN and DTCN ligands are transformed in situ into DICA and DTCA ligands during reaction,respectively.In compound 8,a kind of metal-organic circles are formed by the coordination between the N atoms from imidazol groups and the metal Co（Ⅱ）ions,further extended a 1D circle-to-circle chain with a aid of the shared Co（Ⅱ）ions.Both 9 and 10 have2D layer structures,which are formed by metal ions and DIBA for 9,DTBA for 10.A 2D layer represent compound 11,where the DTBA acts a tridentate ligand to coordinate with metal centres.Compound 9 exhibits electrocatalytic activity toward the oxidation of ascorbic acid.Compound 10 displays good fluorescence property.Compound 11 has a photocatalytic activity toward the degradation of organic dye methylene blue.