A Study On The Construction And Magnetostructural Relationship Of Several Types Of Cyano-bridged 3d-4f Single-Molecule Magnets Induced By Auxiliary Ligands

In recent years,single-molecule magnets,single-ion magnets,and single-chain magnets based on the one-,two-,and three-dimensional structures of transition metal and rare earth metals of the cyanide bridge have attracted attention.These complexes can be used as promising raw materials for creating new multifunctional materials.But the realization of its application is still the long-term goal of people.This dissertation aims to design and synthesize a series of novel 3d-4f single-molecule magnets and single-ion magnets with special structures and functions by using transition metallocyanate as precursors.The effects of coordination geometry and magnetic interactions on the magnetic relaxation behavior of 3d-4f single-molecule magnets or single-ion magnets are discussed.The main work is as follows:1.Eleven isostructural cyano-bridged 3d-4f heterodinuclear complexes have been synthesized using K3[Fe(CN)6]and K3[Co(CN)6]as bridging ligands,N-Acetylmorpholine as ancillary ligand with rare earth metal ions.The magnetic properties of the complex lODyCo were studied.When no dc field was applied,magnetic relaxation phenomenon was hardly observed in the complex lODyCo,and the fast relaxation might be due to the quantum tunneling effect.The quantum tunneling was suppressed when a 2 kOe dc field was applied,and 1 ODyCo showed a slow magnetic relaxation behavior.2.A type of single-molecule magnets with three-dimensional porous structure have been synthesized by the reported method with RE(NO3)·6H2O and isonicotinic acid N-Oxide as starting materials.Then the complexes were used as precursors to construct a new series of three-dimensional 3d-4f cyano-bridged complexes with K3[Fe(CN)6]and K3[Co(CN)6]as bridging ligands.The complexes were subjected to X-ray diffraction at low temperature and room temperature.It was found that this system consists of two types of complexes with two different sizes of unit cells.The magnetic properties of complexes 16DyFe,20DyCo were studied.Magnetic studies showed that the complex 20DyCo exhibited slow magnetic relaxation behavior under a 2 kOe dc field.3.Using K3[Fe(CN)6],K3[Co(CN)6]as the building blocks,two types of 3d-4f complexes were synthesized with N-Methyl morpholine N-oxide and rare earth ions.The structure of complexes 23NdFe,29NdCo is one-dimensional zigzag chain.The structure of the rest of the complexes is an ionic pair.In this chapter,single-ion magnets of the Dy? ion with excellent magnetic relaxation properties were obtained in a 3d-4f ion-pair system.The magnetic properties of complexes 22YFe,27DyFe and 33DyCo were studied.The complex 22YFe has quantum tunneling when no external dc field is applied.When a 4 kOe dc field was applied,22YFe showed magnetic relaxation behaviour of a single Fe? ion,and the effective energy barrier was extracted to be Ueff=48 K.For compound 27DyFe,the rexalation parameters of ?0= 5.5 × 10-12 s,Ueff=622 K in zero dc field and ?0= 7.6 × 10-12 s,Ueff = 609 K under a 4 kOe dc field were extracted.For complex 33DyCo,the relaxation parameters were ?0 = 4.5 × 10-12 s and Ueff=638 K in zero dc field.