Study On Synthesis And Properties Of Metal Complexes Based On 4-(5-Mercaptotetrazole-1-yl)Benzoic Acid

In this paper,4-（5-mercapto-tetrazolium-1-yl）benzoic acid（H₂PMTZ）was used as main ligand,2,2’-bipyridine,4,4’-bipyridine,1,10-phenanthroline and 2’:6’,2’’-terpyridine as second ligands.Herein,twoπ-bonded polymers with four coordination polymers were synthesized by solvothermal synthesis with transition metal Cd（II）Zn（II）by supramolecular self-assembly.The compounds was characterized by single crystal/X-ray powder diffraction（XRD/PXRD）,FT-IR spectroscopy,thermogravimetric analysis（TGA）,elemental analysis and scanning electron microscopy（SEM）.The gas Sorption and heavy metal adsorption properties of twoπ-πstacking framework structures were studied.（1）Four novel coordination polymers were prepared by hydrothermal synthesis that4-（5-mercaptotetrazol-1-yl）benzoic acid（H₂PMTZ）as the main ligand,4,4’-bipyridyl and2,2’:6’,2’’-tripyridine as the second ligand,and Cd（II）Zn（II）as metal node:{[Zn（PMTZ）（2,2’:6’,2’’-Tpy）]·2H₂O}_n（1）,{[Cd（PMTZ）（2,2’:6’,2’’-Tpy）]·CH₃OH·H₂O}_n（2）,{[Zn（PMTZ）（4,4’-Bpy）]·2H₂O}_n（3）and{[Cd（PMTZ）（4,4’-Bpy）]·H₂O}_n（4）.The structure of the four complexes was analyzed by X-ray single crystal diffraction,in which both complex 1 and complex 2 were crystallized in the P2₁/c space group,and belongs to 1D chain.The complex 3crystallizes in the P-1 space group to form a 2D layered structure.The complex 4 crystallizes in the P2₁/n space group,and in forming a two-dimensional layered structure,the second ligand4,4’-bipyridyl connected each structural monomer.The four complexes were detected as pure phases by powder X-ray diffraction（PXRD）.The thermostability of the four complexes was studied by thermogravimetric analysis.The complexes 1,complex 2 and complex 3 show good thermal stability at 200°C,and poor thermal stability of complex 4.（2）Then introduce new second ligand 1,10-phenanthroline and 2,2’-bipyridine,two porous supramolecular frameworks([Zn（PMTZ）（Phen）₂]（3CH₃OH·6H₂O）（5）and{[Cd（PMTZ）（Bpy）]2H₂O}_n（6）,merely stabilized by intermolecularπ-πstacking interactions,are presented.The structural units within these frameworks are a mononuclear Zn（II）complex and a one-dimensional Cd（II）coordination polymer.The complex 5 crystallizes in the space group of R-3 and belongs to the triclinic system.The deprotonated carboxyl groups on the main ligand and N from the1,10-phenanthroline coordinated with Zn（II）form monuclear hexagonal coordination unit structure.It is worth noting that the monomer the monomer structure of complex 5 is independent.A total of 33π-πstacking interactions were produced between each monomer structure and the surrounding 6 monomer structures.The strong three-dimensional frame structure of complex 5 is formed only by the denseπinteraction.Powder X-ray diffraction shows that the complex 5 can keep stable in all kinds of solvents,but also in aqueous solution with a broad pH range and high thermostability.Other than this,complex 5 shows excellent adsorption properties of the heavy metal Hg（II）,such as high adsorption amount of 786.67 mg·g^-1,high selectivity and cyclic adsorption were studied.The compound 6 crystallizes in C_2cc space group and belongs to monoclinic system.Three metal ions Cd（II）and two O atoms of PMTZ^2-（O1,O2）,respectively.A trinuclear six-coordinated octahedral configuration was formed by deprotonation of thiol tetrazolium sulfhydryl group with S atom and N atom（N7）and two pyridine N atoms（N5 N6）on the auxiliary ligand 2,2’-bipyridine.Each monomer is bridged by the sulfhydryl and carboxyl groups on the ligand to form 1D chain structure,while the 2,2’-bipyridine on the linked chain forms fourπ-πstacking to form a 3D supramolecular pore structure.Compound 6 represents a supramolecularπframework.On the other hand,it shows excellent thermal stability,solvent stability and acid-base stability.