Synthesis,structure And Magnetic Properties Of Rare Earth Complexes Assembled By Multi-dentate Chelate Schiff Base Ligands

With the wide application of magnetic molecular materials in modern science and technology,rare earth complexes based on lanthanide metals have entered the field of vision due to their excellent magnetic properties.Further probing,the researchers found that schiff bases,a class of nitrogen-containing ligands,are easily synthesized and have flexible structures.The 4f orbitals of rare earth ions will not be quenched in the crystal field,so they can produce strong spin orbit coupling and large magnetic anisotropy.Therefore,the selection of multi-dentate Chelate chelated Schiff base ligands with high symmetry can improve the symmetry of rare earth ions in the complexes,which is conducive to the synthesis of lanthanide single molecule magnets with high energy barrier and high blocking temperature.Based on this,we prepared the crystals of two systems by volatilization at room temperature using polydentate chelated Schiff base ligands and rare earth metal salts,tested and explored the crystal structure and magnetic properties of these rare earth metal complexes,and characterized some crystals by solid powder diffraction and other optical techniques.Mainly included:1.Two mononuclear complexes[Dy(L₁)](1),[Ho(L₁)](2)were synthesized by the reaction of polydentate chelated Schiff base ligand(H₃L₁),auxiliary ligand sodium formate and lanthanide metal salt Ln(NO₃)·6H₂O(Ln=Dy,Ho)obtained by the condensation of triethylenetetramine and 5-Bromosalicylaldehyde.The structural study reveal that complex 1 and complex 2 have C_3v symmetry,and the structure is capped octahedron.The magnetic study reveal that complex 1 has a slow relaxation behavior of monomolecular,and the energy barrier of complex 1 is 6.43 K,?₀=6.41×10^-5 s?2.The polydentate chelated Schiff base ligand(H₂L₂)obtained by condensation of1,2-bis(2-aminoethoxy)ethane and 3-bromo-5-chlorosalicylaldehyde reacts with lanthanide metal salt Ln(NO₃)·6H₂O,respectively,the polydentate chelated Schiff base ligand(H₂L₃)obtained by the condensation of 1,2-bis(2-aminoethoxy)ethane and 3,5-dibromosalicylic aldehyde reacts with Dy(NO₃)·6H₂O,four mononuclear complexes[Ln(L₂)(C₇H₃Br Cl O₂)][Ln=Dy(3),Gd(4),Ho(5)],[Dy(L₃)(C₇H₃Br₂O₂)](6)were prepared by room temperature volatilization method.Structural studies reveal that complexes 3-6 have C_2vsymmetry and biaugmented trigonal prism J50 structure.Magnetic studies reveal that complex 3 and complex 6 exhibit monomolecular slow relaxation.