Construction And Magnetic Properties Of Rare Earth Complexes Based On Sulfur-containing Ligands

Lanthanide compounds have attached extremely interests because of their large angular momentum and unrivalled single-ion magnetic anisotropies in the ground electronic states,most notably in the high-spin lanthanide ions,than they posses potential properties in luminescent,magnetic and electricity,which have a broad application prospect in the new materials,biological imaging,catalyst,high-density information storage and magnetorefrigerants.Currently,chemists have attempted to employ the different soft-donors ligands within the field environment being constructed required for single-molecule magnets?SMMs?,but so far the dithiocarboxylate is not available.Since the weak magneto-chiral dichroism phenomenon of chiral paramagnetic compound firstly was observed,the chiral magnets have attracted great interests for their potential application as multifunctional materials.Among the chiral magnetic materials,the chiral SMMs with great potential applications in high-density information storage and quantum computing have been studied less,but attracted much more attention.The flexible carboxylic acid ligands have received huge attention for the application of function materials,which were widely employed in construct of molecular magnetic complexes,because the varied conformations and geometries of these ligands make it difficult to forecast and control the final structures.In this paper,soft-donors pyrrolidine dithiocarbamate,auxiliary ligands chiral bipyridyl and thiodiglycolic acid ligands were employed to develop twelve chiral lanthanide complexes based on dithiocarboxylate and four Lanthanide-based metal-organic frameworks?Ln-MOFs?under solvent evaporation and hydrothermal conditions,which was structurally characterized by X-ray single-crystal diffraction,IR spectroscopy,circular dichroism?CD?spectroscopy,fluorescence spectrum,powder X-ray diffraction analysis,thermogravimetric analysis and elemental analysis.Herein,the magnetism,particularly the single-ion magnets?SIMs?and the magnetocaloric effect?MCE?of the part complexes,has been investigated in detail.In chapter 1,a brief introduction of coordination chemistry and crystal engineering of rare earth complexes are presented.Illustrate and brief review the research status of the rare earth complexes based on organic sulfur ligands,SMMs of rare earth,Ln-MOFs and molecular cryogenic magnetorefrigerants of lanthanide complexes.In chapter 2,the chiral rare earth complexes [Ln?Pytc?₃?R-bipy?]?Ln = La?1?,Pr?2?,Nd?3?,Sm?4?,Eu?5?,Gd?6?,Tb?7?,Dy?8?,Ho?9?,Er?10?;pytc·NH₄ = 1-pyrrolidine dithiocarbamate;R-bipy = R-bipyridyl??R-Ln?and [(Ln?Pytc?₃?S-bipy??CH₃CN?]?Ln =Tb?11?,Dy?12?;S-bipy = S-bipyridyl??S-Ln?were synthesized and characterized by single-crystal X-ray diffraction,CD spectroscopy and magnetism studies.X-ray single crystal diffraction revealed that complexes 1-10 crystallizes in the orthorhombic system and chiral space group P2₁2₁2₁,while complexes 11-12 crystallizes in the monoclinic system and chiral space group P21 due to exist solvent CH₃CN molecule.Magnetic investigations for compounds 7 and 8 indicate that the complex 7 exhibits a ferromagnetic coupling,while the complex 8 exhibits a antiferromagnetic coupling and field-induced SIM behavior with single relaxation processes.In chapter 3,four lanthanide complexes with the formulas [Ln₂?tda?₃?H₂O?₂]n [Ln = Gd?13?,Tb?14?,Dy?15?,Ho?16?;H₂tda = thiodiacetic acid]?Ln-TDA?have been prepared by using the corresponding lanthanide oxide and H₂ tda under hydrothermal conditions.Single crystal X-ray diffraction studies show that the four compounds are isostructural and present a 2D network,crystallizes in the triclinic system and space group P-1.Magnetic studies reveal that compound 13 shows the presence of weak antiferromagnetic interaction between Gd³⁺ ion and significant magnetocaloric effect with -?S_m^max=39.2JKg^-1K^-1.While the complexes 14 shows weak ferromagnetic interaction,exhibit field-induced SMM behaviors.The 15 shows ferromagnetic interaction.