Study On The Structure,Structure And Magnetic Properties Of Triazole-based Rare Earth Complexes

The effects of metal ions and coordination environment,bridge ligands and terminal ligands on the properties of metal complexes have important research value for the design and synthesis of complexes with excellent functions.Among them,the selection of metal ions and the design and synthesis of organic ligands are important factors affecting the properties of complexes.In a modern society where informationization is expanding,single-molecule magnets have broad application prospects due to their ultra-high density storage capabilities within a single molecule.Rare earth ions are widely used in the preparation of magnetic materials because of their high electron spin ground state,strong spin-orbit coupling and magnetic anisotropy.Due to the existence of a large number of unpaired f electrons,a high coordination number and a variety of coordination configurations,rare earth ions are also conducive to the construction of polynuclear clusters.Triazole is an aromatic five-membered heterocyclic ring containing two carbon atoms and three nitrogen atoms.Although 1,2,3-triazole derivatives are suitable for the formation of metal complexes,there are few studies on 1,2,3-triazole ligands due to the difficulty in the synthesis of 1,2,3-triazole derivatives.In this thesis,4-（2-pyridine）-NH-1,2,3-triazole ligands（L1）and 1,4-dipyridine-1,2,3-triazole ligand（L2）were synthesized and used,and these two ligands have multiple coordinating nitrogens,so that they have multiple coordination modes,which is conducive to obtaining complexes with novel structures.They have important research and application value for the design and synthesis of functional complexes with novel structures and unique properties.Based on these two ligands,we synthesized new complexes,including five isostructural mononuclear 1,4-dipyridine-1,2,3-triazole rare earth complexes,two1,4-dipyridine-1,2,3-triazole Cu（Ⅱ）complexes,two 4-（2-pyridine）-NH-1,2,3-triazole rare earth cluster,and their structures and magnetic properties were studied by single crystal X-ray diffraction,powder X-Ray diffraction,elemental analysis,magnetic testing,etc.The main research contents and conclusions of each chapter in this thesis are as follows:The first chapter was a literature review on 1,2,3-triazole based coordination compounds.Firstly,1,2,3-triazole and its synthesis methods were briefly introduced.Secondly,the research progress of rare earth complexes with 1,2,3-triazole ligands was reviewed.On this basis,the coordination characteristics of 1,2,3-triazole ligands and the advantages of rare earth elements were analyzed,and the design ideas and research contents of this paper were proposed.In the second chapter,five mononuclear rare earth complexes with the same configuration were synthesized first time by using 1,4-dipyridine-1,2,3-triazole and Ln（NO₃）₃·XH₂O（Ln = Nd,Sm,Gd,Dy,Ho）.The magnetic research results show that the exchange coupling within 1·Nd and 1·Ho are antiferromagnetic,while the ferromagnetic interactions are present within 1·Gd and 1·Dy.Furthermore,1·Dy exhibits magnetic relaxation behavior in the AC susceptibility test at zero DC,withIn the third chapter,two mononuclear complexes were synthesized by using1,4-dipyridine-1,2,3-triazole and CuCl₂·2H₂O.During the experiment,it was found that there was a reversible single crystal to single crystal transformation between the two complexes,and the process of transformation was traced by powder X-ray diffraction..Combined with the magnetic studies,it was found that the transformation of structure causes the change of magnetism.The intra-chain magnetic exchange between the adjacent CuⅡ ions of compounds 2·Cu·MeCN and 2·Cu are ferromagnetic(J = 0.91 cm^-1for 2·Cu·MeCN,J = 0.20 cm^-1 for 2·Cu),and the inter-chain magnetic exchange interaction of compound 2·Cu·MeCN is ferromagnetic(J’ = 0.35 cm^-1),while the inter-chain magnetic exchange interaction of compound 2·Cu is antiferromagnetic(J’ =-0.22 cm^-1).In the fourth chapter,a dodecanuclear Er（Ⅲ）cluster with4-（2-pyridyl）-1,2,3-triazole was synthesized first time.The core framework of the complex is formed by four hybrid cubes with four vertices shared.Each hybrid cube unit is composed of four Er^Ⅲ ions and four μ3-OH,which alternately occupy the vertices of the distorted cube.DC magnetic susceptibility measurements indicated the presence of weak ferromagnetic interactions between adjacent Er^Ⅲ ions...