Wang Cai-Feng, Zuo Jing-Lin, Bartlett Bart M, Song You, Long Jeffrey R, You Xiao-Zeng
Coordination Chemistry Institute and State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093, China.
J Am Chem Soc. 2006 Jun 7;128(22):7162-3. doi: 10.1021/ja061788+.
Reaction of [(Me3tacn)Cu(H2O)2]2+ (Me3tacn = N,N',N' '-trimethyl-1,4,7-triazacyclononane) with [TpFe(CN)3]- (Tp- = hydrotris(pyrazolyl)borate) in a mixture of ethanol and acetonitrile affords the pentanuclear cluster [Tp2(Me3tacn)3Cu3Fe2(CN)6]4+. Single-crystal X-ray analysis reveals a trigonal bipyramidal structure featuring a D3h-symmetry core in which two opposing FeIII (S = 1/2) centers are linked through cyanide bridges to an equatorial triangle of three CuII (S = 1/2) centers. Fits to variable-temperature dc magnetic susceptibility data are consistent with ferromagnetic coupling to give an S = 5/2 ground state, while fits to low-temperature magnetization data indicate the presence of a large axial zero-field splitting (D = -5.7 cm-1). Frequency dependence observed in the ac magnetic susceptibility data confirms single-molecule magnet behavior, with an effective spin reversal barrier of Ueff = 16 cm-1. When compared with the much lower anisotropy barrier previously observed for the face-centered cubic cluster [Tp8(H2O)6Cu6Fe8(CN)6]4+, the results demonstrate the enormous influence of the geometry in which a given set of metal ions are arranged.
[(Me3tacn)Cu(H2O)2]2+（Me3tacn = N,N',N''-三甲基-1,4,7-三氮杂环壬烷）与[TpFe(CN)3]-（Tp- = 氢三（吡唑基）硼酸根）在乙醇和乙腈的混合溶液中反应，得到五核簇合物[Tp2(Me3tacn)3Cu3Fe2(CN)6]4+。单晶X射线分析揭示了一种三角双锥结构，其具有D3h对称性的核心，其中两个相对的FeIII（S = 1/2）中心通过氰基桥连接到由三个CuII（S = 1/2）中心组成的赤道三角形上。对变温直流磁化率数据的拟合结果与铁磁耦合一致，给出了S = 5/2的基态，而对低温磁化数据的拟合表明存在较大的轴向零场分裂（D = -5.7 cm-1）。交流磁化率数据中观察到的频率依赖性证实了单分子磁体行为，有效自旋反转势垒Ueff = 16 cm-1。与之前在面心立方簇合物[Tp8(H2O)6Cu6Fe8(CN)6]4+中观察到的低得多的各向异性势垒相比，结果表明给定一组金属离子排列的几何结构具有巨大影响。
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