IRON-SULFUR DIMERS WITH BENZIMIDAZOLATE-THIOLATE, BENZIMIDAZOLATE-PHENOLATE OR BIS(BENZIMIDAZOLATE) TERMINAL CHELATING LIGANDS - MODELS FOR RIESKE-TYPE PROTEINS
IRON-SULFUR DIMERS WITH BENZIMIDAZOLATE-THIOLATE, BENZIMIDAZOLATE-PHENOLATE OR BIS(BENZIMIDAZOLATE) TERMINAL CHELATING LIGANDS - MODELS FOR RIESKE-TYPE PROTEINS
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DOI：
10.1039/dt9920002457
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发表时间：
1992-08-21
期刊：
影响因子：
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通讯作者：
GIBSON, JF
中科院分区：
文献类型：
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作者：
BEARDWOOD, P;GIBSON, JF
合成了由配体L1-L5末端配位的配合物[FeS2L2]2-1-5作为Rieske型蛋白质的模型[H-2L1=2-(2-巯基苯基)苯并咪唑；H-2L2=2-(2-羟基苯基)苯并咪唑；H-2L3=2-(2-羟基苯基)甲基苯并咪唑；H-2L4=2，2-双(苯并咪唑-2-基)丙烷；H-2L5=4，4-双(苯并咪唑-2-基)庚烷]。报道了首次分离的[2Fe-2S]+还原络合物[Net_4]_3[Fe_2S_2L42]_6的制备方法。用UV/Vis、H-1核磁共振和穆斯堡尔谱对其进行了表征。铁(II)-铁(III)络合物6的H-1核磁共振谱缺乏异质性，揭示了价态平均。在穆斯堡尔时间尺度上，随着温度的降低，络合物变得价俘获。1-4的第一个还原过程发生在-0.82~-1.13V的电位范围内。苯并咪唑与硫代铁氧还蛋白配位产生的正移与Rieske型蛋白质相对于四半胱氨基铁氧还蛋白的正移相当。苯并咪唑配位对稳定三阴离子化学还原产物也有相当大的作用。结合[2Fe-2S]+络合物的前人数据分析表明，配体类型中SS>；NS>；NN>；OS>；NO几乎等于OO的有序性与最低的两个g值的大小相关。Rieske类型的蛋白质的g值与该系列的最后两种配体类型最匹配，这表明需要氧配合。
Complexes [FeS2L2]2- 1-5 having terminal co-ordination by the ligands L1-L5 have been prepared and studied by a range of physical techniques as models for the Rieske-type proteins [H-2L1 = 2-(2-mercaptophenyl)benzimidazole; H-2L2 = 2-(2-hydroxyphenyl)benzimidazole; H-2L3 = 2-(2-hydroxyphenyl)methylbenzimidazole; H-2L4 = 2,2-bis(benzimidazol-2-yl)propane; H-2L5 = 4,4-bis(benzimidazol-2-yl)heptane]. A preparation is described for [NEt4]3[Fe2S2L42] 6, the first [2Fe-2S]+ reduced complex to be isolated. The complexes have been characterised by UV/VIS, H-1 NMR and Mossbauer spectroscopies. Lack of heterogeneity in the H-1 NMR spectrum of the iron(II)-iron(III) complex 6 reveals valence averaging. On the Mossbauer time-scale the complex becomes valence-trapped as the temperature is lowered. The first reduction processes for 1-4 occur at potentials in the range -0.82 to -1.13 V. The positive shift produced by benzimidazolate co-ordination compared to thiolate is comparable to that for the Rieske-type proteins relative to tetracysteinyl ferredoxins. Benzimidazolate co-ordination is also found considerably to stabilise the trianionic chemical reduction products. These display frozen-solution ESR spectra with a range of lineshapes, analysis of which, taken together with previous data for [2Fe-2S]+ complexes, indicates the ordering SS > NS > NN > OS > NO almost-equal-to OO in ligand type as correlated with the magnitude of the lowest two g values. The Rieske-type proteins have g values which fit best with the last two ligand types of this series, suggesting a requirement for oxygen co-ordination.