Axial and equatorial ligand effects on biomimetic cysteine dioxygenase model complexes
Axial and equatorial ligand effects on biomimetic cysteine dioxygenase model complexes
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DOI：
10.1039/c2ob25406a
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发表时间：
2012-01-01
影响因子：
3.2
通讯作者：
de Visser, Sam P.
中科院分区：
文献类型：
--
作者：
Gonzalez-Ovalle, Luis E.;Quesne, Matthew G.;de Visser, Sam P.
采用密度泛函理论（DFT）方法对半胱氨酸双加氧酶的仿生模型复合物进行了计算，重点研究了轴向和赤道向配体位置的影响。最近的研究我们之一[Y。M. Badiei，M. A. Siegler和D. P. Goldberg，J. Am. 2011，133，1274]给出了使用异丙基-双（亚氨基）吡啶、赤道三齿配体的半胱氨酸双加氧酶的非血红素铁仿生模型的证据。此外，苯硫酚，阴离子-无论是氯或三氟甲磺酸根-和分子氧，导致几种可能的立体异构体的半胱氨酸双加氧酶仿生复合物。此外，观察到使用氯离子与三氟甲磺酸根相比作为结合阴离子的反应性存在很大差异。在这里，我们提出了一系列的DFT计算的起源，这些反应性的差异，并表明，这是由优先的配位位点的阴离子与苯硫酚结合到化学系统。因此，三氟甲磺酸酯和配体的大体积异丙基取代基的立体化学相互作用防止使用三氟甲磺酸酯在反式位置结合苯硫酚。相比之下，较小的阴离子，如氯离子，可以结合在顺式或反式配体位置，并得到具有类似稳定性的异构体。我们的计算有助于解释观察到的苯硫酚双氧化由这个仿生系统，并给出了详细的反应性差异与三氟甲磺酸盐的连接氯化物。
Density functional theory (DFT) calculations are presented on biomimetic model complexes of cysteine dioxygenase and focus on the effect of axial and equatorial ligand placement. Recent studies by one of us [Y. M. Badiei, M. A. Siegler and D. P. Goldberg, J. Am. Chem. Soc. 2011, 133, 1274] gave evidence of a nonheme iron biomimetic model of cysteine dioxygenase using an i-propyl-bis(imino) pyridine, equatorial tridentate ligand. Addition of thiophenol, an anion - either chloride or triflate - and molecular oxygen, led to several possible stereoisomers of this cysteine dioxygenase biomimetic complex. Moreover, large differences in reactivity using chloride as compared to triflate as the binding anion were observed. Here we present a series of DFT calculations on the origin of these reactivity differences and show that it is caused by the preference of coordination site of anion versus thiophenol binding to the chemical system. Thus, stereochemical interactions of triflate and the bulky iso-propyl substituents of the ligand prevent binding of thiophenol in the trans position using triflate. By contrast, smaller anions, such as chloride, can bind in either cis or trans ligand positions and give isomers with similar stability. Our calculations help to explain the observance of thiophenol dioxygenation by this biomimetic system and gives details of the reactivity differences of ligated chloride versus triflate.