Construction,Structure And Properties Of Magnetic Function-oriented Rare Earth Complexes

In recent years,rare earth complexes have aroused considerable interest from many researchers due to their unique optical and magnetic properties.Among them,single-molecule magnet on rare earth metal has become a hot spot of current research.In general,rare earth complexes with high energy barriers can be obtained by selecting appropriate organic ligands and auxiliary ligands.In this thesis,2-hydroxy-3-methoxybenzoicacid[(2-hydroxy-3-ethoxyphenyl)methylene]hydrazide(H₃L1)and pyridine-2-carboxylic acid[(2-hydroxy-3-methoxyphenyl)methylene]hydrazide(H₂L2)ligands were used to construct sixteen dinuclear rare earth complexes.What's more,the crystal structures,near-infrared luminescence and magnetic properties of these complexes were studied.The main research results are as follows:1.Six phenoxy bridged binuclear rare earth complexes[RE₂(HL1)₂(dbm)₂(CH₃OH)₂]·2CH₃OH(RE=Y(1),Tb(2),Dy(3),Ho(4),Er(5),Yb(6))were synthesized with 2-hydroxy-3-methoxybenzoicacid[(2-hydroxy-3-ethoxyphenyl)methylene]hydrazide(H₃L1)and dibenzoylmethane(Hdbm)as the main and auxiliary ligands,respectively.Single crystal X-ray diffractions show that the complexes 1-6 are isostructural and crystallize in the monoclinic P2₁/n space group.The central ions in the complexes are eight-coordinated,and adopt the distorted triangular dodecahedron configuration.The near-infrared luminescent studies indicate that 5 and 6 exhibit the characteristic emission peaks of the corresponding Er³⁺and Yb³⁺ions.The magnetic studies reveal that the quantum tunneling effect is significantly suppressed under the direct current field of 3000 Oe,and the alternating current variable temperature susceptibility of complex 3 shows frequency dependence,indicating the existence of slow magnetic relaxation.The effective barrier of 3 is 12.45 K,and the pre-exponential factor is 1.08×10^-6s.2.Ten binuclear rare earth complexes,namely[RE2(L2)2(acac)2(H2O)2]·i-Pr OH(RE=Y(7),Eu(8),Tb(9),Dy(10),Ho(11),Er(12),Yb(13)),[Dy_1.64Y_0.36(L2)₂(acac)₂(H₂O)₂]·i-Pr OH(14)and[RE₂(L2)₂(acac)₂(C₂H₅OH)₂](RE=Tb(15),Dy(16))were constructed with pyridine-2-carboxylic acid[(2-hydroxy-3-methoxyphenyl)methylene]hydrazide(H₂L2)and acetylacetone(Hacac)as the main and auxiliary ligands,respectively.Single crystal X-ray diffractions show that complexes 7-14 are isostructural and crystallize in the monoclinic P2₁/n space group.Complexes 15 and 16 are also isomorphous,both crystalize in the triclinic system P?space group.Both complexes 10 and 16 form an eight-coordinate structure through two nitrogen atoms and six oxygen atoms.The difference is that one coordination oxygen atom of complex 10 comes from water,one oxygen atom of complex 16 comes from ethanol,resulting in Dy³⁺of complexes 10 and 16 adopt different coordination configurations,and the Dy³⁺of complex 10 adopts distorted square antiprism configuration,while 16 adopts a twisted biaugmented trigonal prism configuration.The near-infrared luminescent studies indicate that 12 and 13 exhibit the characteristic emission peaks of the corresponding Er³⁺and Yb³⁺ions.Alternating current magnetic susceptibility measurements reveal that the complexes 10 and 14 exhibit similar frequency dependence and temperature dependence under the optimal dc field of 800Oe,the effective energy barriers of the complexes 10 and 14 are 42.93 K and 48.34 K,respectively,and the pre-exponential factors?₀ are 1.65×10^-8 s and 5.03×10^-9 s.The effective barrier of complex 16 is 40.24 K in zero dc field,the pre-exponential factor is4.06×10^-7 s,the effective barrier is 63.67 K in 1500 Oe dc field,and the pre-exponential factor?₀is 5.07×10^-8 s.Through the structure and magnetic analysis of complexes 10and 16,it is shown that different solvents can change the coordination environment of the central ions in the complex,and finally change their magnetic properties.