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首页> 外文期刊>Chemistry: A European journal >Remarkable Anion-Dependent Spin-State Switching in Diiron(III) mu-Hydroxo Bisporphyrins: What Role Do Counterions Play?
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Remarkable Anion-Dependent Spin-State Switching in Diiron(III) mu-Hydroxo Bisporphyrins: What Role Do Counterions Play?

机译：Diiron（III）mu-Hydroroxo双卟啉中显着的阴离子依赖性自旋态转换：抗衡离子起什么作用？

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摘要

Addition of 2,4,6-trinitrophenol (HTNP) to an ethene-bridged diiron(III) mu-oxo bisporphyrin (1) in CH2Cl2 initially leads to the formation of diiron(III) mu-hydroxo bisporphyrin (2 center dot TNP) with a phenolate counterion that, after further addition of HTNP or dissolution in a nonpolar solvent, converts to a diiron(III) complex with axial phenoxide coordination (3 center dot(TNP)(2)). The progress of the reaction from m-oxo to m-hydroxo to axially ligated complex has been monitored in solution by using H-1 NMR spectroscopy because their signals appear in three different and distinct spectral regions. The X-ray structure of 2 center dot TNP revealed that the nearly planar TNP counterion fits perfectly within the bisporphyrin cavity to form a strong hydrogen bond with the mu-hydroxo group, which thus stabilizes the two equivalent iron centers. In contrast, such counterions as I-5, I-3, BF4, SbF6, and PF6 are found to be tightly associated with one of the porphyrin rings and, therefore, stabilize two different spin states of iron in one molecule. A spectroscopic investigation of 2 center dot TNP has revealed the presence of two equivalent iron centers with a high-spin state (S = 5/2) in the solid state that converts to intermediate spin (S = 3/2) in solution. An extensive computational study by using a range of DFT methods was performed on 2 center dot TNP and 2(+), and clearly supports the experimentally observed spin flip triggered by hydrogen-bonding interactions. The counterion is shown to perturb the spinstate ordering through, for example, hydrogen-bonding interactions, switched positions between counterion and axial ligand, ion-pair interactions, and charge polarization. The present investigation thus provides a clear rationalization of the unusual counterion-specific spin states observed in the mu-hydroxo bisporphyrins that have so far remained the most outstanding issue.
机译：在CH2Cl2中将2,4,6-三硝基苯酚（HTNP）添加到乙烯桥联的二铁（III）互氧双卟啉（1）中最初导致形成二铁（III）互氧双卟啉（2中心点TNP）含酚酸酯抗衡离子，在进一步添加HTNP或溶解于非极性溶剂后，可转化为具有轴向酚盐配位的二铁（III）配合物（3个中心点（TNP）（2））。由于溶液的信号出现在三个不同且不同的光谱区域，因此已使用H-1 NMR光谱监测了溶液中m-羰基，间羟基和轴向连接的络合物的反应进程。 2个中心点TNP的X射线结构表明，近乎平面的TNP抗衡离子完美契合在双卟啉腔内，与mu-hydroxo基团形成强氢键，从而稳定了两个等效的铁中心。相反，发现诸如I-5，I-3，BF4，SbF6和PF6之类的抗衡离子与卟啉环之一紧密结合，因此使铁的两个不同自旋态稳定在一个分子中。对2个中心点TNP的光谱研究表明，存在两个等效的铁中心，它们在固态时具有高自旋态（S = 5/2），在溶液中转化为中间自旋（S = 3/2）。通过使用一系列DFT方法对2个中心点TNP和2（+）进行了广泛的计算研究，清楚地支持了由氢键相互作用触发的实验观察到的自旋翻转。所示抗衡离子通过例如氢键相互作用，抗衡离子与轴向配体之间的转换位置，离子对相互作用和电荷极化来扰动自旋态序。因此，本研究为迄今为止在多羟基双卟啉中观察到的不寻常的抗衡离子特异性自旋态提供了明确的合理化依据，而自旋态至今仍是最突出的问题。

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