Synthesis, Structure And Magnetic Properties Based On Pyrazine Hydrazone Ligand Polynuclear Lanthanide Metal Complexes

Taking into account the coordination preference of Ln ions for hard lewis based (HSAB theory), In this thesis, we designed a series of pyrazine hydrazone ligands and successfully synthesize three pure lanthanide polynuclear complexes. In doing so, the crystal structures of the compounds were determined by X-ray crystallographic methods, and all of them were characterized by element analyses, IR and DC/AC magnetic susceptibility. This thesis could be divided into three chapters:1, One new ligand of pyrazine hydrazone was designed, at the same time, the unique Dy6compound has been synthesized based on the former ligand. Meanwhile, X-ray crystallographic method was used to determine the structure of this compound and the MPMS-XL SQUID magnetometer was applied to detected magnetic properties of this compound. Through the Direct-current (dc) magnetic susceptibility studies, these signs indicated obvious antiferromagnetic interactions between the metal centres for the complex. With additional research, the two relaxation regimes were observed in this compound.2, When the first ligand was designed to become the second ligand with rational substitution reaction, one special Dy8has been successfully assembled. The structure of this compound show novel a novel square anti-prism configuration based on quadruple-CO32-Bridged. DC magnetic susceptibility studies of a polycrystalline sample reveal remarkable ferromagnetic interactions between the metal centres for the complex. The alternating current (ac) susceptibilities under a zero-dc field reveal a slow relaxation of the magnetization that is typical for SMM behaviour and utilizing approximate theoretical model to analyse, there is a single slow relaxation of the magnetization in this compound. Specifically, the hysteresis loops were clearly observed at1.9K with a traditional SQUID magnetometer.3, Because the first two ligands have been successfully applied, a new Dy6compound was synthesized with the third analogous pyrazine hydrazone ligand. Its crystal structures show particular trigonal prism architecture. Furthermore, Through the DC magnetic susceptibility studies, these signs indicated complex antiferromagnetic interactions between the metal centres and Argand plots reveal a approximatively single slow relaxation of the magnetization in the complex. Using the SQUID-VSM magnetometer, hysteresis loops were clearly observed, which were strongly temperature dependent down to1.8K. The coercivities of the hysteresis loops increase with decreasing temperature, as expected for an SMM. This behaviour confirms further the SMM nature of this compound.