Syntheses, Structures And Magnetic Properties Of Lanthanide Complexes Based On Tetramethyl-3,5-heptanedione

Single-molecule magnets?SMMs?exhibiting slow relaxation of the magnetization and magnetic hysteresis below a blocking temperature?T_B?have been attracting interest in view of their potential application in molecular spintronics,ultrahigh density magnetic information storage and quantum computing at the molecular level.The lanthanide ions,especially dysprosium?III?ions could be used to construct SMMs due to huge magnetic moments and significant intrinsic anisotropy from large unquenched orbital angular momentum.As ideal candidates,?-diketone ligands have been widely adopted to construct Dy?III?-based SIMs due to their stable bidentate chelating modes.Herein,2,2,6,6-tetramethyl-3,5-heptanedione?Hthd?and various auxiliary ligands were employed in the reaction to synthesize four series and twenty six lanthanide complexes.The FT-IR/UV spectra,TG-DSC,Elemental analyses and P-XRD were performed.The crystal structure was determined by X-ray crystallography radiation,the terminal steric hindrance of Hthd and employment of auxiliary ligand has effect on coordination number and local symmetry of lanthanide ions in crystal structure.The direct and alternating current magnetic susceptibilities measurement were performed,the eigenstate was obtained by fitting crystal field Hamiltonian equation and analyzed the strength of quantum tunneling of magnetization?QTM?.The local symmetry and distortion degree of lanthanide ions were calculated by various methods and the orientation of anisotropy axis were calculated by electrostatic model.Hence,the relationship between the structure and magnetism of Dy?III?ions SMMs was further discussed.In chapter 3,a series of four eight-coordination Dy?III?ions complexes with D_4d symmtry were isolated by reactions of Hthd and auxiliary capping ligands.The presence of slow magnetic relaxation under 0 dc field were found with the highest energy barrier is 128 K in complex 3.In chapter 4,the discussion between potential distribution of ligand and molecular magnetism by employment three Dy?III?ions complexes with various coordination geometries.In chaper 5 and 6,sever-coordination Dy?III?ions complexes were isolated by introducing single dentate auxiliary ligands to explore the origin of quantum tunneling of magnetization and distinction of magnetic dynamics under various local symmetry and nuclearity,the magnetic and luminescence data of 1D chain Hthd lanthanides complexes have also measured.