Synthesis,Structure And Magnetic Properties Of Low-Nuclearity Complexes Constructed By 4f Ions

Since the first mononuclear lanthanide metal single-molecule magnets?SMMs?with milestone significance have been reported,with the deepening of their understanding,relevant experts have gradually realized that lanthanide metal ions with strong anisotropy tend to have higher U_effff single-molecule magnets?SMMs?when preparing complexes.In addition,the main ligand used in the preparation will also affect the U_effff of the complex.As research deepens at this stage,the Salen-type Schiff base coordination has gradually come to the attention of scientific researchers,because its molecule contains two-C=N-group,which has a strong coordination ability,and there are many coordination modes that are easy to obtain more interesting magnetic structure relationships.At present,most of the research based on this has focused on the research of 3d complexes and heteronuclear 3d-4f heterometallic complexes.However,there are few researches on the structure and magnetic properties of 4f complexes.Therefore,we used the Salen-type Schiff ligand and 4f metal nitrate to prepare two systems of crystals by solvothermal method,four novel binuclear Ln₂-Salen complexes and three novel tetranuclear Ln₄-Salen complexes.The obtained crystals were characterized by Elementar Vario EL analyzer and Bruker Tensor 27 spectrometer.Among them:1.A series of new binuclear Ln₂-Salen complexes[Ln₂?L₁?₂?MeOH?₂?NO₃?₂][Ln=Gd?1?,Tb?2?,Dy?3?,Ho?4?]were prepared by using Salen Schiff base H₂L₁ and lanthanide metal salt Ln?NO₃?·6H₂O by solvothermal method.The two Ln^IIIII ions in complexes 1-4 are connected by two O_phenoxohenoxo atoms in two L₁^2-ligands and are used to build a binuclear backbone.Magnetic measurement found that[Dy₂]is a single-molecule magnet with an energy barrier of 47.68K,?₀=3.17×10^-66 s,while the[Ho₂]complex exhibits fast QTM,which can be found by theoretical calculations.2.A series of new tetranuclear Ln₄-Salen complexes[Ln₄??₄-O^-??L₂?₄]?Et₃N⁺?[Ln=Tb?5?,Dy?6?,Ho?7?]were prepared by using Salen Schiff base H₃L₂ and Ln?NO₃?·6H₂O by solvothermal method.X-ray single crystal diffraction indicated that complexes 5-7 contained an unusual Ln₄O₇ boat-shaped unit to form a new Ln₄cluster.Magnetic measurement found that[Dy₄]is a single-molecule magnet with double relaxation,U_eff?14.92 K and 27.08 K,?₀=3.49×10^-66 s and?₀=4.12×10^-66 s.