Construction And Magnetic Properties Of Cyano-Bridged Low-dimensional Molecule-based Magnets With Bistability

Molecule-based magnetic materials with magnetic bistability have special status and broad application prospects in the field of high density information storage and molecular switches due to their macroscopic properties of bulk magnets and quantum properties at nano-scale.In this thesis,a series of cyano-bridged low-dimensional complexes were designed and synthesized through bottom-up assembly,and the magneto-structural correlations were discussed in detail,so as to provide certain experimental references for the construction of molecular nanomagnets with high relaxation energy barrier and charge transfer compounds with transition temperature close to room temperature.The main research results are as follows:(1)A series of cyano-bridged trinuclear Fe?2Ni? compounds of 1-7 were synthesized through self-assembly of paramagnetic tricyanometalate building blocks with different steric hindrance[Bu4N][Fe?(Tp)(CN)3],[Bu4N][Fe?(TpMc)(CN)3]and[Bu4N][Fe?(Tp*)(CN)3],transition metal Ni? ion,and auxiliary ligands with different structures.The magnetic data indicate that compounds 6 and 7 exhibit single molecule magnet behaviors with relaxation energy barrier of 75.7 and 81.5 K,respectively.Magneto-structural analysis indicates that the bond angle of Ni-N?C close to 1800 would benefit for the high-performance trinuclear single molecule magnets.(2)During the self-assembly of paramagnetic building blocks[Fe?(Tp)(CN)3]-,[Fe?(pzTp)(CN)3]-,[Fe?(Tp*)(CN)3]-and transition metal Ni? ion,three tetranuclear Fe?2Ni?2 compounds of 9-11 were synthesized through introducing bidentate ligands 2-(1H-pyrazol-3-yl)pyridine and 4,4'-dichloro-2,2'-bipyridine.The magnetic data indicate that 9-11 exhibit single molecule magnet behaviors with relaxation energy barrier of 10.9,68.9 and 12.6 K,respectively.Magneto-structural analysis indicates that the stronger intermolecular ?…? interactions of 9 and 11 would induce the fast relaxation of the magnetization and lead to the decrease of the relaxation energy barrier.(3)During the self-assembly of paramagnetic building block[Fe?(Tp)(CN)3]-and transition metal Co? ion,three 1D zigzag chains of 12-14 were designed and synthesized through introducing monodentate ligands with similar structures and different steric hindrances.The magnetic data indicate that 12 exhibits ferromagnetic coupling.Furthermore,by controlling the solvent adsorption/desorption,the single chain magnet behavior of dehydrated 12 has been achieved.(4)Three cyano-bridged Fe?LS2Co?LS2 tetranuclear charge transfer compounds of 15-17 were synthesized by reaction of transition metal Co? ion and bidentate ligand 4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenol in the presence of building blocks[Fe?(Tp)(CN)3]-and[Fe?(pzTp)(CN)3]-.Magneto-structural analysis indicates that compared with Tp,pzTp is higher in redox potential,and the trend of transition temperature T1/2 is pzTp>Tp.When introducing counterions with different bulk(ClO4-,BF4-and NO3-)in the presence of building block[Fe?(Tp)(CN)3]-and 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline,three Fe?LS2Co?LS2 tetranuclear charge transfer compounds of 19-21 were obtained.Magneto-structural analysis indicates that counterions can regulate the bending of Co-N?C bond angles through intermolecular interaction,so it has a certain regulating effect on the transition temperature T1/2 of the corresponding charge transfer compounds.