Synthesis And Properties Of Molecule-based Magnetic Complexes Derived From 8-Hydroxyquinoline Derivatives

The synthesis of rare earth complexes have attracted much attention not merely for their unique optical,electrical and magnetic properties,but also for their potential applicability in catalytic,adsorption,optic,bio-pharmaceutical,and magnetic systems.Studies on the synthesis of polynuclear lanthanide-based single-molecule magnets have received considerable attention,especially Gd³⁺,Tb³⁺,Dy³⁺,Ho³⁺,Er³⁺and Yb³⁺ions.To obtain lanthanide clusters with novel topologies the selection of ligand and bridging ligand is one of the key factors.In this dissertation,ten lanthanide complexes by 8-hydroxyquinoline Schiff base derivatives were synthesized.The fluorescent and magnetic properties of some complexes have been investigated.The main works have been carried out in this paper as following:Two series of dinuclear Ln^IIIII complexes,namely,[Ln（tfa）₂（L1）]₂（Ln=Gd（1）Tb（2）,Dy（3）,Ho（4）,Er（5））and[Ln（tfa）₂（L2）]₂（Ln=Gd（6）,Tb（7）,Dy（8）,Ho（9）,Er（10））（tfa=trifluoroacetylacetonate,HL1=2-[[（4-methylphenyl）imino]methyl]-8-hydroxyquinoline and HL2=2-[[（4-ethylphenyl）imino]methyl]-8-hydroxyquino-line）,have been synthesized,and structurally and magnetically characterized.Using single crystal X-ray diffraction,elemental analysis,IR,TG,PXRD,luminescent spectra and magnetic measurements were investigated these coordination polymers.Single-crystal X-ray analysis reveals that complexes 1–5 and 6–10 are isomorphic dinuclear complexes,respectively.The structures of two series of complexes are very similar.The magnetic studies reveal that 1 and 6 feature a magnetocaloric effect with the magnetic entropy change of-ΔS_m values for 1 and 6 are separately 19.72 J kg^-1K^-11 and 19.37 J kg^-11 K^-1.Measurements of alternating-current（ac）susceptibility reveal that complexes 3 and 8 display significant zero-field single-molecule magnetic（SMM）behavior with barrier energy U_eff/k_B=9.14 K,τ₀=4.76×10^-66 s and U_eff/k_B=17.50 K,τ₀=3.96×10^-66 s,respectively.The different SMM behaviors of complexes 3and 8 may be ascribed to the different electron donating effect induced by the two alkyl（–CH₃ and–C₂H₅）of the 8-hydroxyquinoline Schiff base ligands,which further influence the chemical environment of Dy³⁺ ions.