Studies On Synthesis And Properties Of Reduced Schiff Base Ligand Transition/Rare Earth Metal Complexes Containing Imidazolyl And Carboxyl

Coordination polymers(CPs)are a kind of porous materials composed of multi-functional organic linkers and inorganic building units(metal ions or metal clusters).Due to their abundant organic active sites,novel topological structures and specific properties,they have attracted extensive attention of researchers.In the past few decades,the unique structure of coordination polymers has made them have potential applications in the fields of gas adsorption,fluorescent sensors,dye degradation,magnetism and drug delivery.In particular,coordination polymers based on d¹⁰metal centers(Cd²⁺and Zn²⁺)and lanthanide metal centers(Eu³⁺and Tb³⁺)can be used as fluorescent probes to identify and detect pollutants in the environment.Compared with other detection methods,coordination polymer fluorescent sensor detection technology has the advantages of high sensitivity,fast detection,low cost and easy operation.Based on the novel structure and potential application of the complex,reduced Schiff base imidazole carboxylic acid ligand was designed and synthesized in this paper.Under hydrothermal/solvothermal synthesis conditions,sixteen multifunctional complexes with different structures were obtained by self-assembly of H₂L ligands with different transition and rare earth metals.The structure and properties of the complexes were characterized by X-ray single crystal diffraction,PXRD,TG,and IR.The structure,fluorescence and magnetic properties of the complexes and their selective detection and recognition of small solvent molecules,metal ions were studied in this paper.The full text mainly includes the following parts:1.5-((4-(1H-imidazol-1-yl)benzyl)amino)isophthalic acid(H₂L),as the bifunctional reduced Schiff base imidazole carboxylic acid ligand was designed and synthesized,and further characterized by ¹H NMR and IR.Under the solvothermal synthesis condition,H₂L ligands were used to coordinated with transition metal salts,formed new multifunctional CPs:{[Cd(L)(H₂O)]}_n(1),{[Co(L)(H₂O)]}_n(2),{[Mn(L)(H₂O)]}_n(3).X-ray single crystal diffraction structure analysis shows that the complexes are similar in structure,and they are connected by H₂L ligands using bidentate and chelating bidentate coordination modes((?²)-(?¹-?¹)-(?¹)-?₄),the adjacent two-dimensional plane structures were further connected by hydrogen bonds(O4-H1W…O1W)to form the entire three-dimensional supramolecular structure,and the fluorescence and magnetic were carried out.Complex 1 can selectively recognize and detect THF and Fe³⁺ions.Complexes 2 and 3 have antiferromagnetic interactions.The main magnetic interaction exists between two metal ions connected by H₂L ligands or between dinuclear clusters connected by H₂L ligands.2.Under the solvothermal synthesis condition,H₂L ligands were used to coordinated with rare earth metal salt formed three-dimensional complexes:{[Eu(L)(HL)(H₂O)₃]}_n(4),{[Ho(L)(HL)(H₂O)₃]}_n(5),{[Gd(L)(HL)(H₂O)₃]}_n(6),{[Dy(L)(HL)(H₂O)₃]}_n(7),{[Tm(L)(HL)(H₂O)₃]}_n(8),{[Er(L)(HL)(H₂O)₃]}_n(9),{[Yb(L)(HL)(H₂O)₃]}_n(10),{[Y(L)(HL)(H₂O)₃]}_n(11),{[Sm(L)(HL)(H₂O)₃]}_n(12),and their structures,fluorescence and magnetism were characterized.Compared with the H₂L ligand,the maximum emission peaks of 4 exhibits varying degrees of red shift,the fluorescence behaviour of complex 4may be assigned to intraligand?*–?transitions,which is neither metal-to-ligand charge-transfer(MLCT)nor ligand-to-metal charge transfer(LMCT)in nature.Complexes 5,7 and 9 have antiferromagnetic properties.The antiferromagnetic interaction is mainly caused by the splitting of the crystal field,especially the gradual quenching of the excited Stark sub-level or the weak intermolecular dipole-dipole effect.3.Under the solvothermal synthesis condition,H₂L ligands were used to coordinated with rare earth metal salt,formed two-dimensional complexes:{[Eu(L)(HL)(DMF)₃]}_n(13),{[Nd(L)(HL)(DMF)₃]}_n(14),{[Pr(L)(HL)(DMF)₃}_n(15),{[La(L)(HL)(DMF)₃]}_n(16),and their structures,fluorescence and magnetism were characterized.Compared with the H₂L ligand,the maximum emission peaks of 13 exhibits varying degrees of red shift,the fluorescence behaviour of complex 13 may be assigned to intraligand?*–?transitions,which is neither metal-to-ligand charge-transfer(MLCT)nor ligand-to-metal charge transfer(LMCT)in nature.Complexes 14 and 15 have antiferromagnetic properties.The antiferromagnetic interaction is mainly caused by the splitting of the crystal field,especially the gradual quenching of the excited Stark sub-level or the weak intermolecular dipole-dipole effect.