Syntheses And Characterization Of Cyano-bridged Bimetallic Clusters With Intra-molecular Electron Transfer Behavior

The study of cyanide compounds is one of the most active research areas in the field of molecular magnetism. These compounds have a variety of magnetic properties, such as single-molecule magnetism, high-temperature magnetic ordering, photomagnetism, single-chain magnetism, spincrossover (SCO), and charge transfer induced spin transition (CTIST). The CTIST behavior involves intramolecular electron transfer with spin-state changes at the metal centers and can be induced by changes in temperature.We have synthesized a series cyano-bridged bimetallic compounds of FeⅢ-CN-Co", FeⅢ-CN-Fe", FeⅢ-CN-NiⅡ:[(Tp*)FeⅢ(CN)3CoⅡ(PY5)]·PF6(1),[(Tp*)FeⅢ(CN)3CoⅡ (PY5Me2)]OTs (2),[(TpMe)FeⅢ(CN)3CoⅡ(PY5Me2)]·BF4(3),[(Tp)FeⅢ(CN)3CoⅡ (PY5Me2)]·OTf (4),[(Tp*)FeⅢ(CN)3Fe"PY5]·Cl (5),[(Tp)FeⅢ(CN)3FeⅡPY5Me2)]· C1O4(6),[(Tp)FeⅢ(CN)3Fe"(PY5Me2)]·OTf (7),[(TpMe)FeⅢ(CN)3FeⅡ (PY5Me2)]·C104(8),[(pzTp)FeⅢ(CN)3Fe"(PY5Me2)]·OTf (9),[(pzTpMe)FeⅢ(CN)3(FeⅡ PY5Me2)3]·5OTf (10),[(Tp)FeⅢ(CN)3Ni"(PY5Me2)]-C104(11),[(TpMe)FeⅢ(CN)3NiⅡ(PY5Me2)]·C104(12),[(Tp*)FeⅢ(CN)3Ni"(PY5Me2)]·C104(13). Among these compounds,.Tp*=tris(3,5-dimethyl)pyrazolyl borate, TpMe=tris(4-methyl)pyrazolyl borate; Tp=trispyrazolyl borate; pzTpMe=tetra(4-methyl)pyrazolyl borate; pzTp=tetrapyrazolyl borate; PY5=2,6-(bis-(bis-2-pyridyl)-methoxymethane)pyridine, PY5Me2=2,6-bis(1,1-bis(2-pyri-dyl)ethyl)pyridine. These bimetallic compounds are characterized by using X-ray single-crystal diffraction and variable temperature magnetic measurements.Among these compounds,[(Tp)FeⅢ(CN)3Co"(PY5Me2)]·OTf (4) occurred intramolecular electron transfer between the metals.χMT value of the compound4is3.50cm3·K-mol-1at300K, which is consistent with the calculated values (3.16cm3·K-mol-1) of FeⅢ(LS,g≈2.7)-CN-CoⅢ(HS,g≈2.3), implying that compound4exists in FeⅢ(LS)-CN-CoⅡ(HS) state at room temperature. The χMT value decreases to0.1cm3·K·mol-1at160K, implying the compound4changes to Fe"(LS)-CN-CoⅢ(LS) state. but the other FeⅢ-CN-CoⅡ compounds exist Fe-Co antiferromagnetic coupling effect and don’t occur intramolecular electron transfer between the metals.χMT value of the FeⅢ-CN-Fe" compounds is about1.00cm3·K-mol-1at300K, which is consistent with the calculated values (0.68cm3·K-mol-1) of FeⅢ(LS, g≈2.7)-CN-FeⅡ(LS), implying FeⅢ-CN-FeⅡ compounds exists in FeⅢ(LS)-CN-FeⅡ(LS) state at room temperature. χMT value decreases with temperature decreases, implying FeⅢ-CN-Fe" compounds exists intermolecular Fe-Fe antiferromagnetic effect and don’t occurre intramolecular electron transfer between the metals.