Magnetic Properties Of Molecular Magnets Based On "Molecular Alloys" And "Hybrid" Cyano-bridged Complexesr

Molecule-based magnets which can be synthesized by chemical process and have a main property of supramolecular structure exhibit magnetic properties due to magnetic exchange interaction between magnetic ions. Design and synthesis of molecule-based magnets, involving many fields has become one of the hot research projects on the physics and chemistry nowadays. Ones have attracted extensive attention recently because high Tc molecular ferromagnets were discovered and the molecule-based magnets show photo-magnetic effect, thermal induced magnetic properties and magn etic-pole reversal which have important potential application. In that field cyano-bridged complexes play an important roledue to their special structure and outstanding magnetic properties as molecule-based magnets. In this paper, four molecular magnetic materials are selected and have been studied for their magnetic properties through elemental analysis, IR, Mossbauer spectrum and magnetic measurements, etc. We further study molecular magnets, microstructure and mechanism of magnetic coupling interaction in cyanide-bridged multi-metal complexes, make recommendations for the design and synthesis of molecular magnets.In this paper, some results are obtained, as following:1. Multimetallic prussian blue compounds Ni0.25Mn1.25[Fe(CN)6]·6.1H2O were prepared by co-precipitation. The temperature-dependent magnetic susceptibilities show the magnet transition for the compound at 8.5 K; According to DC variable-temperature magnetic susceptibility paramagnetic Curie temperature (?) is-9.32 K; The observed value of coercive field (Hc) and remanent magnetization (Mr) for the compound are 0.32 KOe and 0.36μB.According to study of Zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves, and AC magnetization curves, there exist a spin-glass behave in the compound,which exhibits freezing temperature Tg=7.76 K,below magnetic transition Tc=8.5 K,that glass behavior is termed "reeentrant" spin glass.2. Multimetallic prussian blue compounds Co0.25Mn1.25[Fe(CN)6]·5.9H20 were prepared by co-precipitation. The temperature-dependent magnetic susceptibilities show the magnet transition for the compound at 9.5 K; According to DC variable-temperature magnetic susceptibility paramagnetic Curie temperature (?) is-15 K; The observed value of coercive field (Hc) and remanent magnetization (Mr) for the compound are 230 Oe and 0.72μB. According to study of Zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves, and AC magnetization curves, there exist a spin-glass behave in the compound.Room temperature Mossbauer spectrum reveals a doublet with the isomer shift parameter(-0.15(4)mm/s) and quadrupole splitting(QS= 0.41(9)mm/s) characteristic for low-spin Fe(Ⅲ) ions in compounds Co0.25Mn1.25[Fe(CN)6]·5.9H2O, Two peaks was the result of the low-spin (S= 1/2) of the Fe (Ⅲ) ion of valence electrons on the electric field gradient (EFG) caused by non-zero contribution.3. Hybrid Prussian blue analogue compound [Co(en)3] [Fe(CN) 6]·6.1H2O was prepared. Infrared spectra with stretching vibration vCN= 2117.27 cm-1 illustrates that there exists the bridged cyanide on the compound; By magnetic susceptibility measured in order to study its magnetic exchange interaction; According to DC variable-temperature magnetic susceptibility study, the compound shows a weak anti-ferromagnetic, paramagnetic Curie temperature (?) is-8.23117 K, indicating the magnetic interaction between the metal ions in the compound [Co(en)3][Fe(CN)6]·H2O is very weak. Calculation of molecular magnets obtained from the effective magnetic the experimental value and theoretical value.4. Hybrid Prussian blue analogue compound{Mn(OH2)2[Mn((bipy)(OH2)]2[Fe(CN)6]2}∞was prepared. Infrared spectra with stretching vibration vCN= 2117.27 cm-1 illustrates that there exists the bridged cyanide on the compound; By magnetic susceptibility measured in order to study its magnetic exchange interaction; According to DC variable-temperature magnetic susceptibility study, the compound shows a strong anti-ferromagnetic, paramagnetic Curie temperature (?) is-10.966K K, indicating the magnetic interaction between the metal ions in the compound{Mn(OH2)2[Mn((bipy)(OH2)]2[Fe(CN)6]2}∞is very strong. Calculation of molecular magnets obtained from the effective magnetic the experimental value and theoretical value.At last, we summarize the work in the thesis and discuss the prospects of the study of molecular magnets based on multi metal complexes by cyanides.