Neutral and reduced Roussin's red salt ester [Fe(2)(mu-RS)(2)(NO)(4)] (R = n-Pr, t-Bu, 6-methyl-2-pyridyl and 4,6-dimethyl-2-pyrimidyl): synthesis, X-ray crystal structures, spectroscopic, electrochemical and density functional theoretical investigations.
Neutral and reduced Roussin's red salt ester [Fe(2)(mu-RS)(2)(NO)(4)] (R = n-Pr, t-Bu, 6-methyl-2-pyridyl and 4,6-dimethyl-2-pyrimidyl): synthesis, X-ray crystal structures, spectroscopic, electrochemical and density functional theoretical investigations.
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DOI：
10.1039/b810230a
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发表时间：
2009-02-07
期刊：
影响因子：
--
通讯作者：
Li L
中科院分区：
文献类型：
--
作者：
Wang R;Camacho-Fernandez MA;Xu W;Zhang J;Li L
用Fe(NO)2(CO)2与硫醇或硫醇酸盐反应，合成了一系列鲁辛红盐[Fe2(μ-RS)2(NO)4](R=n-Pr(1)，t-Bu(2)，6-甲基-2-吡啶(3)和4，6-二甲基-2-嘧啶(4))。通过红外光谱、紫外-可见光谱、核磁共振氢谱、电化学和单晶X-射线衍射法对配合物1-4进行了表征。配合物1-4在溶液中有一个弱的和两个强的NO伸缩峰(ν-NO)，而在固体中只有两个强的ν-NO。以络合物1为模型的密度泛函理论(DFT)计算表明，这些络合物的两个空间异构体在溶液中具有3kcal的能量差。这两个异构体的频率计算提供了对振动带来源的洞察，并解释了配合物1-4在固体和溶液中的红外观察。循环伏安分析表明，配合物1-2有两个准可逆的单电子还原反应，配合物3-4有一个准可逆的单电子还原反应。用电子顺磁共振波谱研究了中性络合物[Fe2(μ-RS)2(NO)4]−(1−-4−)(1-4)的化学还原制备的顺磁性配合物[Fe2(μ-RS)2(NO)4](1-4)。有趣的是，配合物[Fe_2(μ-RS)_2(NO)_4]−(1−-4−)的EPR谱在180K-298K温度范围内呈现g=1.998-2.004的各向同性信号，没有超精细分裂。观察结果与计算结果一致，表明未成对电子主要离域在两个硫和两个铁原子上。首次用未成对电子分布的差异解释了还原形式的Roussin红酯与典型的二硝基铁络合物的g值不同，为用g值作为区分这些生物活性络合物的光谱工具提供了理论依据。
A series of Roussin’s red salt esters [Fe2(μ-RS)2(NO)4] (R = n-Pr (1), t-Bu (2), 6-methyl-2-pyridyl (3) and 4,6-dimethyl-2-pyrimidyl (4)) were synthesized by the reaction of Fe(NO)2(CO)2 with thiols or thiolates. Complexes 1–4 were characterized by IR, UV-vis, 1H-NMR, electrochemistry, and single-crystal X-ray diffraction analysis. The IR spectra of complexes 1–4 display one weak and two strong NO stretching frequencies (νNO) in solution, but only two strong νNO in the solid. Density functional theoretical (DFT) calculations using complex 1 as model suggest that two spatial isomers of these complexes bear a 3 kcal energy difference in solution. Frequency calculations of the two isomers provide insight on the origin of the vibrational bands and explain the IR observation of complexes 1–4 in the solid state and in solution. Cyclic voltammetry shows two quasi-reversible, one-electron reductions for complexes 1–2 and one quasi-reversible, one-electron reduction for complexes 3–4. The paramagnetic complexes [Fe2(μ-RS)2(NO)4]− (1−–4−), which are prepared by the chemical reduction of neutral complexes [Fe2(μ-RS)2(NO)4] (1–4), have also been investigated by EPR spectroscopy. Interestingly, the EPR spectra of complexes [Fe2(μ-RS)2(NO)4]− (1−–4−) exhibit an isotropic signal of g = 1.998–2.004 without hyperfine splitting in the temperature range 180–298 K. The observations are consistent with the results of the calculations, which reveal that the unpaired electron is dominantly delocalized over the two sulfur and two iron atoms. The difference of the g values between the reduced form of Roussin’s red ester and the typical dinitrosyl iron complexes is explained, for the first time, by the difference in unpaired electron distributions between the two types of complexes, which provides the theoretical bases for the use of g values as a spectroscopic tool to differentiate these biologically active complexes.
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