Maximizing Electron Exchange in a [Fe3] Cluster.
Maximizing Electron Exchange in a [Fe3] Cluster.
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在[Fe3]群集中最大化电子交换。
DOI：
10.1021/jacs.5b12181
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发表时间：
2016-02-24
影响因子：
15
通讯作者：
Betley TA
中科院分区：
文献类型：
--
作者：
Hernández Sánchez R;Bartholomew AK;Powers TM;Ménard G;Betley TA
(TbSL)Fe3(THF)1的单电子还原生成[M][(TbSL)Fe3]([M]+=[(18-C-6)K(THF)2]+(1，76%)或[(Cryt-222)K]+(2，54%))。还原时，配体tbsL6−在三铁核心周围重新排列，采用几乎理想的C3对称。伴随着(TBSL)配体重排，结合到中性起始物质上的THF被排出，三核团簇内的Fe-Fe距离收缩了约0.13in 1。变温磁化率数据表明，在室温下存在很好的隔离自旋基态。在4.2K时，交流磁化率数据的异相分量和零场57Fe穆斯堡尔谱中出现超精细分裂，证明了低温下观察到了缓慢的磁弛豫。对交流磁化率的分析得到了22.6(2)cm−1的有效自旋反转势垒，与从约化磁化数据中提取的轴向零场分裂参数(D=−1.29 cm−1)计算的理论势垒38.7 cm−1几乎一致。1的多晶样品在4.2K(Hext=0)的穆斯堡尔谱中显示三个六重态，它们在冻结的2-MeTHF玻璃样品中会聚为单一的六线图样，表明了独特的铁环境和强烈的电子离域。在完全离域团簇的框架内讨论了自旋基态和配体重排，该团簇表现出很强的双交换和直接交换作用。
The one-electron reduction of (tbsL)Fe3(thf)1 furnishes [M][(tbsL)Fe3] ([M]+ = [(18-C-6)K(thf)2]+ (1, 76%) or [(crypt-222)K]+ (2, 54%)). Upon reduction, the ligand tbsL6− rearranges around the triiron core to adopt an almost ideal C3-symmetry. Accompanying the (tbsL) ligand rearrangement, the THF bound to the neutral starting material is expelled, and the Fe–Fe distances within the trinuclear cluster contract by ~0.13 Å in 1. Variable-temperature magnetic susceptibility data indicates a well-isolated spin ground state that persists to room temperature. Slow magnetic relaxation is observed at low temperature as evidenced by the out-of-phase component of the alternating current (ac) magnetic susceptibility data and by the appearance of hyperfine splitting in the zero-field 57Fe Mössbauer spectra at 4.2 K. Analysis of the ac magnetic susceptibility yields an effective spin reversal barrier (Ueff) of 22.6(2) cm−1, nearly matching the theoretical barrier of 38.7 cm−1 calculated from the axial zero-field splitting parameter (D = −1.29 cm−1) extracted from the reduced magnetization data. A polycrystalline sample of 1 displays three sextets in the Mössbauer spectrum at 4.2 K (Hext = 0) which converge to a single six-line pattern in a frozen 2-MeTHF glass sample, indicating a unique iron environment and thus strong electron delocalization. The spin ground state and ligand rearrangement are discussed within the framework of a fully delocalized cluster exhibiting strong double and direct exchange interactions.
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