The Research On Synthesis,Structure And Photomagnetic Properties Of Multivariant Rare Earth Complexes

Rare earth elements have been highly favored due to their unique electronic structure[Xe]4fⁿ during the recent years,especially in magnetic and near-infrared luminescent materials with the excellent achievements.In this thesis,three major ligands1,1'-[(2-hydroxy-5-methylphenyl)methylene]-[2,2'-(4,6-pyrimidinediyl)dihydrazone](H₂L1)with a symmetric structure,o-vanillin(HL2),N?-(2-hydroxy-5-methoxybenzylidene)-2-(hydroxyimino)-propanohydrazide(H₂L3)with oxime group and two kinds of?-diketone auxilary ligands were used to construct eleven RE-organic complexes.Meanwhile,the crystal structures,near-infrared luminescence and magnetic properties of them were characterized and investigated correspondingly.The main works are shown below:1.Based on H₂L1 and acetylacetone ligand,four tetranuclear cluster RE-complexes and one mononuclear Dy-complex were synthesized:[Y₄(acac)₄(L1)₄(DMF)₄]·8CH₃OH·4DMF·4H₂O(1),[Tb₄(acac)₄(L1)₄(DMF)₄]·4CH₃OH·2DMF(2),[Dy₄(acac)₄(L1)₄(DMF)₄]·4CH₃OH(3),[Er₄(acac)₄(L1)₄(DMF)₄]·4CH₃OH(4),[Dy(HL1)(NO₃)₂(H₂O)(C₂H₅OH)]·3CH₃OH(5).They were characterized by X-ray diffraction,infrared spectroscopy,powder X-ray diffraction,thermogravimetric analysis and UV-visible spectroscopy.Complexes 1-4crystallize in the tetragonal space group P4₂/n.In addition,all RE³⁺ions adopt a twisted square antiprism configuration.Complex 5 is a mononuclear complex,in which Dy³⁺ion is coordinated by solvent molecules,nitrates and HL1^-ligand.Complex 5 crystallize in triclinic space group P?,the Dy³⁺ion being nine-coordinated.The geormetry configuration of 5 is similar to the Muffin configuration.2.With HL2 and dibenzoylmethane ligands,four dinuclear rare earth cmplexes wereconstructed:[Dy₂(dbm)₄(L2)₂]·CH₃CN(6),[Dy₂(dbm)₄(L2)₂]·0.25C₂H₅OH·0.5CH₂Cl₂(7),[Er₂(dbm)₄(L2)₂](8),[Er₂(dbm)₄(L2)₂]·CH₂Cl₂(9).They were characterized by X-ray diffraction,infrared spectroscopy,elemental analysis,powder X-ray diffraction,thermogravimetric analysis,UV-visible spectroscopy,near-infrared luminescence and low-temperature susceptibility tests.The four complexes crystallize in triclinic P?space group.In complexes 6-8,RE1 adopts distorted biaugmented trigonal prism configuration,RE2being distorted square antiprism configuration.However,for complex 9,both RE1and RE2 adopt distorted biaugmented trigonal prism configuration.Magnetic tests indicate that complexes 6 and 7 exhibit not only the behavior of single-molecule magnets but also multiple relaxation processes.The relaxation energy barriers and pre-exponential factors are 71.37 K,3.0×10^-8 s(6)and 99.49 K,3.76×10^-9 s(7),respectively.In addition,the obvious quantum tunneling effects exist in their system.Both complexes 8 and 9 exhibit characteristic emission peaks of Er³⁺ions,showing a strong and broad emission band in the range of 1475–1650 nm.And the maximum emission peaks of them are same in 1526 nm,corresponding to ⁴I_13/2?⁴I₁₅ transition of Er³⁺ions.The emission peak of them at 1526 nm is located in the minimum window of optical communication,giving rise to potential application in optical amplifiers of telecommunication network.3.Two dinuclear RE-complexes with central-semmetry structure were obtained by the coordination effects between RE metals and H₂L3,dibenzoylmethane ligands:[Er₂(dbm)₂(L)₂(C₂H₅OH)₂](10),[Yb₂(dbm)₂(L)₂(C₂H₅OH)₂](11).X-ray diffraction,infrared spectroscopy,elemental analysis,powder X-ray diffraction,thermogravimetric analysis and UV-visible spectroscopy were carried on them.The complexes 10-11 crystallize in orthorhombic Pbca space group.The RE³⁺ions in complexes 10-11 all adopt a twisted triangular dodecahedral configuration with low symmetry.