Structures,Near-infrared Luminescence,and Modulating The Magnetic Behavior Of 8-hydroxyquinoline Rare Earth Complexes

Rare-earth complexes have been widely studied in recent years due to their potential applications in luminescence and magnetism,especially the research of rare earth luminescent materials and single-molecule magnets（SMMs）.In view of this,twelve lanthanide complexes based on 8-hydroxyquinoline Schiff Base derivatives andβ-diketones coligands were synthesized in this thesis.The near-infrared luminescent properties and the influence of the solvents on magnetic behavior were studied.The main results are as follows:1.With 2-[（2-（amino）benzhydrazide）-methyl]-8-hydroxyquinoline（H₂L）as ligand and dibenzoylmethane as coligand,nine dinuclear Ln³⁺complexes[Ln₂（dbm）₂L₂（DMF）₂]·2DMF（Ln=Nd（1）,Eu（2）,Tb（3）,Dy（4）,Er（5）,Yb（6））,[Ln₂（dbm）₂L₂（CH₃OH）₂]·2CH₃OH（Ln=Dy（7）,Yb（8））and[Dy₂（dbm）₂L₂（C₂H₅OH）₂]·2C₂H₅OH（9）have been synthesized.2.Single crystal X-ray diffraction data reveals that complexes 1-8 crystallize in the monoclinic P2₁/c space group,while complex 9 crystallizes in the triclinic Pīspace group.The near-infrared luminescence of complexes 1,5 and 6 reveal that complex 1 exhibites the characteristic emission peak of Nd³⁺at 1053 nm;complex 5exhibites the characteristic emission peak of Er³⁺at 1521 nm;complex 6 has a characteristic emission band of Yb³⁺ions in the range of 915–1070 nm,which splits into doublets at 975 and 1018 nm.Magnetic studies show that there are no frequency dependence signals of in-phase（χ′）because of a fast quantum tunneling relaxation of the magnetization（QTM）for complexes 4 and 7 at zero dc field.On the contrary,frequency-dependent out-of-phase（χ″）signals are in existence.While ac susceptibilities were measured under a 3000 Oe dc field,the in-phase（χ′）and out-of-phase（χ″）curves exhibit clear frequency-dependent signals and give full peak shapes with one maximum for complex 7.Only frequency-dependent out-of-phase（χ″）signals were clearly observed for complex 4.The relationship of the structures and magnetic properties for 4 and 7 illustrates that a different coordination environment can be formed by changing the solvents,which can lead to subtle changes in crystal structure and significant difference in magnetic behavior.3.With2-[（2-amino-4,5-difluoro）benzhydrazide)-methyl]-8-hydroxyquinoline（H₂L?）as ligand and dibenzoylmethane as coligand,three dinuclear Ln³⁺complexes[Ln₂（dbm）₂L?₂（DMF）₂]·2CH₃OH（Ln=Nd（10）,Eu（11））,[Yb₂（dbm）₂L?₂（DMF）₂]·2DMF（12）have been synthesized.These complexes were characterized by the single crystal X-ray diffraction,elemental analysis,powder X-ray diffraction,thermogravimetric analysis.Single crystal X-ray diffraction data reveals that complexes 10-12 crystallize in the monoclinic P2₁/n space group.The near-infrared luminescence of complex 12 reveals that there is a characteristic emission band of Yb³⁺ions in the range of 915–1070 nm and it splits into doublets at975 and 1017 nm,which corresponds to the electronic transition of ²F_5/2→²F_7/2.