A dinuclear MnIII-CuII single-molecule magnet.
A dinuclear MnIII-CuII single-molecule magnet.
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DOI：
10.1002/chem.200400368
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发表时间：
2005-01
期刊：
影响因子：
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通讯作者：
H. Oshio;M. Nihei;Ayano Yoshida;H. Nojiri;M. Nakano;A. Yamaguchi;Y. Karaki;H. Ishimoto
中科院分区：
文献类型：
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作者：
H. Oshio;M. Nihei;Ayano Yoshida;H. Nojiri;M. Nakano;A. Yamaguchi;Y. Karaki;H. Ishimoto
1/3当量的CuCl_2·2 H_2 O与MnCl_2·4 H_2 O和5-溴-2-亚水杨基氨基-1-丙醇（H（2）5-Br-sap）在甲醇中反应，得到深棕色晶体[MnIIICuIICl（5-Br-sap）_2（MeOH）]（1）。配合物1具有烷氧基桥接的双核核心的锰III和铜II离子，分别具有拉长的八面体和正方形平面的配位几何形状。在直流磁化率测量中，chi（m）T值随着温度降低而增加，然后在20 K以下突然下降。这种行为表明分子内存在铁磁相互作用，拟合得到S=5/2自旋基态，交换耦合常数J（MnCu）为+78 cm（-1）。通过使用具有各向同性塞曼和轴向零场分裂（ZH）项的自旋哈密顿量分析作为温度和施加磁场的函数收集的磁化数据，并获得负D（5/2）值（-1.86 cm（-1））。在4.2 K的高场EPR（HFEPR）谱（342.0 GHz）由四个峰组成，随着温度的升高，在高磁场下出现两个额外的峰。HFEPR光谱中的温度依赖性指示负D（5/2）值，并且数据拟合给出D（5/2）=-1.81 cm（-1）。在交流磁化率测量中，观察到频率相关的同相（chi（m ′））和异相（chi（m ′））信号，其峰值在0.7-1.5 K之间，并且出现低于0.7 K的小峰。交流磁化率数据支持1是单分子磁体（SMM）。从0.7-1.5 K的chi（m）峰的Arrhenius图给出了10.5 K的再取向能垒（Δ E），指前因子为8.2 × 10（-8）s。
The reaction of 1/3 equivalent of CuCl2.2H2O with MnCl2.4H2O and 5-bromo-2-salicylideneamino-1-propanol (H(2)5-Br-sap) in methanol gave dark brown crystals of [MnIIICuIICl(5-Br-sap)2(MeOH)] (1). Complex 1 has an alkoxo-bridged dinuclear core of MnIII and CuII ions, which have elongated octahedral and square-planar coordination geometries, respectively. In dc magnetic susceptibility measurements, chi(m)T values increased as the temperature was lowered, followed by a sudden decrease below 20 K. This behavior is indicative of the occurrence of intramolecular ferromagnetic interactions, and fitting gave an S=5/2 spin ground state with an exchange coupling constant J(MnCu) of +78 cm(-1). Magnetization data collected as a function of temperature and applied magnetic field were analyzed by using a spin Hamiltonian with isotropic Zeeman and axial zero-field splitting (ZFS) terms, and a negative D(5/2) value (-1.86 cm(-1)) was obtained. A high-field EPR (HFEPR) spectrum (342.0 GHz) at 4.2 K was composed of four peaks, and two additional peaks at higher magnetic field appeared as the temperature was increased. The temperature dependences in the HFEPR spectra are indicative of a negative D(5/2) value, and fitting of the data gave D(5/2)=-1.81 cm(-1). In the ac magnetic susceptibility measurements, frequency dependent in-phase (chi(m)') and out-of-phase (chi(m)'') signals with peak maxima at 0.7-1.5 K were observed and small peaks below 0.7 K appeared. The ac susceptibility data supports that 1 is a single-molecule magnet (SMM). Arrhenius plots for the chi(m)'' peaks from 0.7-1.5 K gave the re-orientation energy barrier (DeltaE) of 10.5 K with a pre-exponential factor of 8.2x10(-8) s.