A Study On The Regulation Of Coordination Geometry And Magnetostructural Relationship In Several Series Of Air-stable Rare Earth Complexes

In recent years,the huge of rare earth single-molecule magnets in the potential application of information storages has attracted people's attention.More and more single-molecule magnets systems have been explored,but there are still great challenges for practical applications.In this thesis,we mainly studied the regulation of coordination geometry and the magnetostructural relationship in three series of air-stable 3d-4f coordination compounds,including two cyano-bridged systems respectively with the auxiliary coordination of pyridine N-oxide and tris(4-morpholinyl)phosphine oxide,and one system of ion-pair structure.1.Using K₃Fe(CN)₆ or K₃Co(CN)₆ as bridging ligand,Pyridine N-oxide as auxiliary ligand,nine 1D 3d-4f cyanide bridged complexes were synthesized with the rare earth metal ions(Y³⁺,Dy³⁺,Gd³⁺,Tb³⁺,Er³⁺).The magnetic relaxation properties of the compounds 1YFe,2Dy Fe and 3Dy Co were studied.The magnetic studies showed that the compounds 1YFe did not show magnetic relaxation properties at zero DC field,while the complexes 2Dy Fe and3Dy Co showed magnetic relaxation behaviors with obvious quantum tunneling magnetization process.The complex 2Dy Fe showed slow magnetic relaxation characteristics under an applied DC field of 4 k Oe,and the complex 3Dy Co had a slow magnetic relaxation behavior under an applied DC field of 1 k Oe,both with suppressed QTM effects.2.Using PF₆^–as counter anion,3-Methylpyridine N-oxide as auxiliary ligand,three rare earths coordination compound with ion-pair structure were synthesized with rare earth metal ions(Dy³⁺,Er³⁺,Tb³⁺).The magnetic studies of the complexes 10Dy and 11Er indicated that their magnetic properties are derived from the magnetic anisotropy of the single metal ion.When the DC magnetic field was zero,there was a strong quantum tunneling effect.When a 2k Oe DC magnetic field was applied,the out-of-phase ac susceptibility of the two complexes showed weak frequency dependence owing to the unsuppressed quantum tunneling.Therefore these complexes had poor magnetic relaxation properties.3.Using K₃[Fe(CN)₆]as short bridging ligand,tri(4-morpholinyl)phosphine oxide as auxiliary ligand,two isomorphous 3d-4f cyano-bridged rare earth complexes were synthesized with rare earth ions(Dy³⁺,Er³⁺).The crystal structures of the complexes 13Dy Fe and 14Er Fe were characterized.The results showed that they are promising seven-coordinate pentagonal bipyramidal coordination geometry,indicating the successful introduction of large sterically hindered organic ligands.It is expected that these compounds will exhibit good single molecule magnet properties.