Construction And Magnetic Properties Of Co(?)/Ln(?) Based Complexes

With the rapid development of information technology,molecular-based magnetic materials are increasingly favored by researchers because of their potential applications in high-density information storage,magnetic switches,quantum computers and spintronics.Among them,the research based on single-molecule magnets?SMMs?,single-ion magnets?SIMs?and single-chain magnets?SCMs?is the hotspot in this field.Two Co???-based and two Ln???-based complexes were synthesized by solvothermal method.Their structures were characterized by X-ray single crystal diffraction,elemental analysis,powder diffraction?PXRD?,TG and their magnetic properties were studied in detail.Thetwoligands2-methyl-8-hydroxyquinoline?HCHQ?and2-amino-8-hydroxyquinoline?HNHQ?that have similar structures with different substituents were selected to synthesize the complexes Co?CHQ?₂Py₂?1?and Co?NHQ?₂Py₂?2?.Magnetic measurements show that both 1 and 2 exhibit field-induced single-ion magnet behavior with slow magnetic relaxation.The slow magnetic relaxation processes of 1 and 2 include direct,Raman and Orbach processes.The fitting results of 1 as follows:U_eff=60.10 K,?₀=3.83×10^-8 s.For 2,U_eff=56.44 K,?₀=2.82×10^-8 s.The energy barrier U_eff of 1 is greater than 2.Because of the similar structure,the different functional groups lead to the difference of magnetic relaxation behavior.By comparing the perturbation of donor to SIM performance,the correlation between the properties of Co???SIMs and magnetic structure is further discussed.The high-field and high-frequency electron paramagnetic resonance?HF-EPR?studies reveal that the easy-plane magnetic anisotropy of both 1 and 2.Two4f-basedisomorphicMOFs[Dy?BDC??NO₃??DMF?₂]_n?3?[Tb?BDC??NO₃??DMF?₂]_n?4?were constructed using terephthalic acid?H₂BDC?as ligand and lanthanide metal as spin carrier.Magnetic studies show that complex 3 and 4 have good single-molecule magnet?SMM?behavior.Magnetic studies show that complexes 3 and 4exhibit good single-molecule magnets?SMMs?behavior.The magnetic relaxation process of complex 3 includes Raman process and Orbach process under zero dc field.Fitting results show that?₀=1.05×10^-77 s,U_eff=42.27 K.However,the magnetic relaxation process is only the Orbach process under 1.0 kOe dc field.Fitting results show that U_eff=42.27 K,?₀=9.62×10^-8 s.Complex 3 transforms into complex 3a after lossing the coordinated DMF molecule by heating,and its structural transformation is reversible.The magnetic study shows that complex 3 has a frequency dependent slow magnetic relaxation behavior,while complex3a does not.Therefore,the molecular magnetic switch effect can be achieved by changing its coordination mode.