Synthesis,fluorescent And Magnetic Properties Of 1,4-bis (2'-carboxyphenoxy) Benzene Transition Metal Coordination Polymers

With diverse structures and rich fluorescence properties,coordination polymers have always attracted the attention of researchers.In recent years,their performances(stable structure,high sensitivity,fast response and reusable)in sense has been particularly eye-catching.The ether-bonded dicarboxylic acid ligands have the characteristics of both rigid and flexible ligands.They can rotate around the ether-bonded oxygen atoms and coordinate easily with metal ions.Thus,they can be used to synthesize coordination polymers with rich structures and potential applications in fluorescence properties and magnetism.Herein,we select an ether linkage dicarboxylic acid ligand 1,4-bis(2'-carboxyphenoxy)benzene(H₂bcpb),auxiliary ligands(phen,2,2?-bipy,4,4?-bipy)and Zn(II),Cd(II),Mn(II),Ni(II)ions,and successfully construct 10 kinds of coordination polymers with novel structures by hydrothermal synthesis method.Using single crystal X-ray diffraction,powder X-ray diffraction and infrared spectroscopy methods,the structures have been fully characterized.The thermal stability of 10 compounds has been analyzed by the thermogravimetric curve.Furthermore,the fluorescence properties of the synthesized zinc and cadmium coordination polymers were tested,and the magnetic properties of the manganese and nickel coordination polymers were analyzed.The detailed research content is as follows:1.Three new coordination polymers were constructed with ligand H₂bcpb,auxiliary ligands(phen,2,2?-bipy)and metallic zinc:[Zn₃(?₃-bcpb)₂(OH)₂]_n(1),[Zn₂(?₂-bcpb)(?₄-bcpb)(phen)₂]_n(2)and[Zn₂(?₂-bcpb)(?₄-bcpb)(2,2?-bipy)₂]_n(3).Among them,the complex 1 is a one-dimensional chain structure,and the complexes 2 and 3 are two-dimensional planar structures.Their different dimensions might be related to the introduced auxiliary ligands.Fluorescence spectroscopy analysis shows that complexes 1-3can effectively detect organic small solvent molecule acetone and metal cation Cu²⁺.Besides,complex 1 can also effectively detect rare earth metal ion Tb³⁺,and is not affected by other organic small molecule solvents,metal cations and rare earth metal ions,and can be used by recycling.In comparison,complex 1 shows a good detection effect on Cu²⁺ions,with a higher quenching constant and a lower detection limit.2.Three new coordination polymerizations were constructed with ligand1,4-bis(2'-carboxyphenoxy)benzene,auxiliary ligands(phen,2,2'-bipy,4,4?-bipy)and metal cadmium cation:{[Cd(?₂-bcpb)(phen)₂]_n·[Cd(?₂-bcpb)(phen)(H₂O)]_n}·n H₂O(4),[Cd₂(?₄-bcpb)₂(2,2?-bipy)₂]_n·n H₂O(5)and[Cd(?₂-bcpb)(4,4?-bipy)₂]_n·n H₂O(6).Among them,complex 4 is a one-dimensional chain structure,and complexes 4 and 5 are two-dimensional planar structures.The difference in dimensions among them might result from the difference of the auxiliary ligands introduced.The fluorescence spectroscopy analysis shows that complexes 4-6 have no specificity to sense any organic small molecule solvents,transition metal cations,anions,and rare earth metal ions.3.Four new coordination polymers are constructed with ligand1,4-bis(2'-carboxyphenoxy)benzene,auxiliary ligands(phen,2,2'-bipy),manganese(II)and nickel(II)salts:[Mn(?₂-bcpb)(phen)₂]_n·n H₂O(7)?[Mn₂(?₂-bcpb)(?₄-bcpb)(2,2?-bipy)₂]_n(8)?[Mn₂(?₃-bcpb)₂(2,2?-bipy)₂(H₂O)]_n(9)and[Ni(?₁-Hbcpb)(2,2?-bipy)₂(OH)](10).Among them,complexes 7 and 9 are one-dimensional chain structures,complex 8 has a two-dimensional planar structure,and complex 10 has a zero-dimensional structure.The difference in dimensions might be related to the difference in the introduced metal ions and auxiliary ligands.Interestingly,we found that for complexes 8 and 9,two completely different complexes can be obtained at the same time when the reactants are the same as the reaction conditions.After repeated experiments,we found that the production of two different crystals is related to the filling degree of the experimental device.Subsequently,the magnetic susceptibility of complexes 7-10 was analyzed,and the results showed that complexes 7,9,and 10 are antiferromagnetic,and complex 8 is ferromagnetic.