Structure–property trends in cyanido-bridged tetranuclear FeIII/NiII single-molecule magnets
Structure–property trends in cyanido-bridged tetranuclear FeIII/NiII single-molecule magnets
复制标题
DOI：
10.1016/j.poly.2012.10.039
复制
发表时间：
2013-03
期刊：
影响因子：
2.6
通讯作者：
Yuan-Zhu Zhang;U. P. Mallik;R. Clérac;N. Rath;S. Holmes
中科院分区：
文献类型：
--
作者：
Yuan-Zhu Zhang;U. P. Mallik;R. Clérac;N. Rath;S. Holmes
[NEt 4][（Tp <$Me）FeIII（CN）3]·H2O与三氟甲磺酸镍反应得到{[（Tp <$Me）FeIII（CN）3]2[NiII（DMF）4]2[OTf]2}·2DMF（1），而Ni（ClO 4）2·6 H2O与2，2 ′-联吡啶反应得到{[（Tp <$Me）FeIII（CN）3]2[NiII（bpy）2]2[ClO 4]2}·3 MeCN·2 H2O·MeOH（2）。在各向同性Heisenberg模型的框架下，实验χT与T数据的关系可以用以下最佳参数组很好地建模：1和2的J/kB=+9.0（4）和+8.5（4）K和gav=2.4（1）和2.5（1）; 1和2的第一激发态（S=2）约为2.5（1）。18和16.8K。交流磁化率的分析表明，1表现出快速量子隧穿的磁化以上约。1.8K，而2在许多SMM的范围内显示出缓慢的弛豫;在Hdc=2.2kOe时，估计2的SMM能垒Δeff=15.7K。在空气中长时间放置后，1很容易转变成一个新的系统，表现出可观的能垒（Δeff=20.4K），这表明去溶剂化能够显着改变正方形{FeIII 2（μ-CN）4 NiII 2}SMM的动力学和量子特性。
Treatment of [NEt4][(Tp∗Me)FeIII(CN)3]·H2O with nickel(II) trifluoromethanesulfonate affords {[(Tp∗Me)FeIII(CN)3]2[NiII(DMF)4]2[OTf]2}·2DMF (1) while {[(Tp∗Me)FeIII(CN)3]2[NiII(bpy)2]2[ClO4]2}·3MeCN·2H2O·MeOH (2) is obtained from Ni(ClO4)2·6H2O and 2,2′-bipyridine mixtures. In the frame of an isotropic Heisenberg model, the experimental χT versus T data were modeled well with the following best set of parameters: J/kB=+9.0(4) and +8.5(4)K and gav=2.4(1) and 2.5(1) for 1 and 2, respectively; the first excited state (S=2) for 1 and 2 are ca. 18 and 16.8K above the ST=3 ground state. Analysis of the ac susceptibility suggests that 1 exhibits fast quantum tunneling of the magnetization above ca. 1.8K while 2 displays slow relaxation in the range seen for many SMMs; at Hdc=2.2kOe an SMM energy barrier of Δeff=15.7K is estimated for 2. Upon prolonged standing in air, 1 is readily transformed into a new system that exhibits a respectable energy barrier (Δeff=20.4K) suggesting that the desolvation is able to dramatically alter the dynamics and the quantum properties of the square-shaped {FeIII2(μ-CN)4NiII2}SMM.