Studies On The Synthesis,Structures And Magnetic Properties Of Lanthanide Complexes With Nitrogen Heterocyclic Ligands

The interest in nanoscale magnetic materials has been driven by the rapid growth in high-speed computers and high-density magnetic storage devices with the promise of a revolution in information technology.In recent years,Lanthanide complexes have attracted much attention owing to their unique properties and potential applications in fields such as magnetism,electricity and optics.Scientists have focused on synthesis,structure and properties of these complexes and made a series of breakthroughs.In this paper,we mainly choose three ligands and reaction with rare earth salt,a series 4f complexes were synthesized for the detailed studies on their structure and magnetic properties.The main research works of this thesis are listed below.1.The solvothermal reactions of Ln(NO3)3 with the Shiff-base ligand 2-[(2-pyridinylmethylene)amino]-ethanol in the presence of triethylamine afforded a series of lanthanide complexes[Ln9L4(?4-OH)2(?3-OH)8(NO3)8(CH3OH)2(H2O)2](NO3)·xMeOH·yH2O(Ln = Eu(1.x = 1,z = 6),Tb(2,x = 2,z = 4),Dy(3,x = 4,y = 7),Ho(4,x = 1,y = 8),Er(5,x=3)?They were determined by single-crystal X-ray diffraction analysis and elemental analysis,IR spectra and magnetic susceptibility.All of them are sandglass-like topology and constructed by two square pyramidal pentanuclear units via the apical metal center Ln? ion.The luminescent studies of(1)-(5)at room temperature revealed that the emissions of complexe(2)?(3)?(4)?(5)are assigned to intraligand ???*transition.However,complexe(1)exhibits strong characteristic emissions of Eu3+ ions,indicating the effective energy transfer form the ligand to lanthanide ions.Variable-temperature solid state magnetic susceptibilities measurements of(1)-(5)in the temperature 2-300 K were performed,indicating dominant antiferromagnetic exchange interactions between the metal centres in five complexes.And alternating current susceptibility data indicated that only the complexe(3)shows single-molecule magnetism behavior.2.The reaction of 2-Pyridinecarboxaldehyde with 2-(2-hydroxyethoxy)ethanaminium gave an Shiff-base ligand.The solvothermal reactions of Gd(N03)3 with this Shiff-base ligand afforded a[Gd2(C10H13N2O2)2(NO3)4]·CH3OH·6H2O(6)complexe.When we modified the synthetic steps,we get another two complexes[Gd9(C4H10NO2)8(?3-OH)8(?4-OH)2(NO3)8](NO3)-CH30H.6H20(7)and[Gd12(C6H4NO2)8(?3-OH)16(NO3)8](NO3)4·3CH3OH·15H2O(8).However,the complexes(7)was consisted of 2-(2-hydroxyethoxy)ethanaminium,2-Pyridinecarboxaldehyde was not involved in the structure.The complexe(8)was consisted of 2-Pyridinecarboxaldehyde,but the 2-Pyridinecarboxaldehyde has been turned into 2-Picolinic acid,2-(2-hydroxyethoxy)ethanaminium was not involved in the structure.In all cases the core topology is a defect-dicubane motif.Magnetic susceptibility measurements were carried out on compounds(6)-(8),complexe(6)presents stronger ferromagnetic exchange interaction between metal ions,complexe(7)and complexe(8)exhibit antiferromagnetic interactions between the metal ions.We also researched the Magnetocaloric Effect(MCE)for the three complexes,The maximum of-?Sm reaches 20.1 Jkg-1K-1 for complexe(6)at 4.0 K,23.9 Jkg-1K-1 for complexe(7)at 2.0 K and 26.5 Jkg-1K-1 for complexe(8)at 2.0 K.3.The solvothermal reactions of Dy(NO3)3 and Dy(CH3COO)3 with the 8-hydro-xyquinoline-2-carboxaldehyde-(2-hydroxybenzoyl)hydrazine ligand afforded three lanthanide complexes Dy2(C17H13N3O3)2(CH3COO)2(DMF)2](9),[Dy4(C17H13N3O3)4(CH3O)4]-2CH3OH(10)and[Dy4(C17H13N3O3)4(H2O)2(CH3O)2].3H2O(11).Magnetic susceptibility measurements were carried out on complexes(9)-(11),complexes(10)and complexes(11)exhibit antiferromagnetic interactions between the metal ions,complexes(10)presents stronger ferromagnetic exchange interaction between metal ions.Alternating current susceptibility data indicated that all the three complexes show single-molecule magnetism behavior.