Synthesis,Structure And Luminescent Properties Of Zn(Ⅱ)/Cd(Ⅱ) Coordination Polymers Based On Aromatic Carboxylic Acids And N-donor Ligands

Coordination polymers（CPs）consist of organic ligands and metal ions or clusters.They have been attracted widespread attention due to their diverse structures and potential applications in magnetism,catalysis,gas storage,and fluorescence sensing,etc.The fluorescence properties of coordination polymers make their applications in the detection of metal ions,volatile organic compounds and explosive substances widely studied.In this paper,10 new luminescent coordination polymers based on carboxylic acid and N-donor ligands have were synthesized with different metal ions（Zn（II）/Cd（II））.The structures of the coordination polymers were characterized by single X-ray diffraction,powder X-ray diffraction,elemental,thermogravimetric and IR spectroscopy.The fluorescence properties of the coordination polymers were also studied and the application in the detection of Fe³⁺in aqueous solution.The molecular formula of the 10 CPs are as followed:（1）[Zn（tbtb）₂]_n（2）[Zn₂（4,4′-ncb）₂biyb]_n（3）{[Zn₂（4,4′-ncb）₂（biyb）₂]·（H₂O）}_n（4）[Zn（3,4′-ncb）（2,2′-bipy）（H₂O）]_n（5）{[Zn（3,4′-ncb）（phen）]·H₂O}_n（6）{[Zn₃（btc）₂（bimb）₂（H₂O）₂]·H₂O}_n（7）[Cd（tbtb）₂（H₂O）]_n（8）[Cd（4,4′-ncb）₂（phen）]_n（9）[Cd（3,4′-ncb）（2,2′-bipy）（H₂O）]_n（10）[Cd（3,4′-ncb）（bib）]_nIn the above formula,4,4′-H₂ncb=4-（3-nitro-4-carboxylphenyl）benzoic acid;3,4′-H₂ncb=3-（3-nitro-4-carboxylphenyl）benzoic acid;H₃btc=1,3,5-benzenetricarboxylat;Htbtb=1-（tetrazol-5-yl）-3,5-bis（trizol-1-yl）benzene;biyb=1,4-bis（1-imidazol-1-ylmethyl）benzene;2,2′-bipy=2,2’-bipyridine;phen=1,10-Phenanthroline monohydrate;bimb=4,4′-bis（1-imidazolyl）biphenyl;bib=1,4-bis（1-imidazolyl）benzene.1.Coordination polymers 1-6 with different structures were successfully synthesized by reacting metal Zn（II）ions as central ions.Structure analysis showed that 1 displays an uncommon 3D（3,6）-connected network.2 and 3 exhibit a 3D framework composed of Zn（II）bridged by 4,4′-ncb^2-and biyb.The 2D layered structure of 2 composed of Zn（II）bridged by4,4′-ncb^2-that adopts two different coordination modes,then biyb connects adjacent 2D layers to extend into a 3D framework.The two carboxylic acids of the 4,4′-ncb^2-adoptingη¹ coordination mode and biyb connect metal Zn（II）ion to form a 3D framework in 3.4 presents a 1D linear structure composed of Zn（II）bridged by 3,4′-ncb^2-.5 exhibit a 3D framework composed of Zn（II）bridged by 3,4-ncb²and 6 also exhibit a 3D framework composed of Zn（II）bridged by btc^3-and bimb.The emission studies indicated that 1-6 showed a strong emission.Experiments show that1-6 have highly sensitivity and selective detection for Fe³⁺ion via fluorescence quenching（turn off）at low concentration.Meanwhile,6 exhibits highly sensitivity and selective detection for Mn²⁺ion via fluorescence enhancement（turn on）at low concentration.2.Coordination polymers 7-10 with different structures were successfully synthesized by reacting metal Cd（II）ions as central ions.The 2D layered structure of 7 composed of Cd（II）bridged by tbtb^-.8 shows a 2D layer structure by 4,4-ncb^2-bridged metal Cd（II）.9 presents a 1D linear structure composed of Cd（II）bridged by 3,4′-ncb^2-.10 shows a 2D layer structure by3,4-ncb^2-and bib bridged metal Cd（II）.The emission studies indicated that 7-10 showed a strong emission.Experiments show that 7-10 have highly sensitivity and selective detection for Fe³⁺ion via fluorescence quenching（turn off）at low concentration.