Insights into Thiol-Aromatic Interactions: A Stereoelectronic Basis for S-H/π Interactions.
Insights into Thiol-Aromatic Interactions: A Stereoelectronic Basis for S-H/π Interactions.
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DOI：
10.1021/jacs.6b08415
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发表时间：
2017-02-08
影响因子：
15
通讯作者：
Zondlo NJ
中科院分区：
文献类型：
--
作者：
Forbes CR;Sinha SK;Ganguly HK;Bai S;Yap GP;Patel S;Zondlo NJ
在非生物系统和蛋白质中，硫醇可以很好地与芳香环进行S-H /π相互作用。然而，S-H /π相互作用的基本原理尚不清楚。boc - l -4-巯基苯丙氨酸叔丁基酯的晶体结构揭示了其晶体结构以巯基S-H与相邻分子芳香环的相互作用为中心。Caromatic距离为2.71 Å，低于H和c的范德华半径之和2.90 Å。通过DFT计算、红外光谱、固体核磁共振光谱和剑桥结构数据库的分析进一步检验了这种相互作用的性质。S-H /π相互作用是由芳香π给体轨道和S-H σ*受体轨道（π→σ*相互作用）之间有利的分子轨道相互作用驱动的。为了比较，对碱金属阳离子与芳香环的O-H /π相互作用和阳离子/π相互作用进行了结构分析。Na+和K+表现出对芳香环质心的明显偏好，距离接近范德华半径和离子半径的总和，正如预期的主要是静电相互作用。Li+与Na+和K+的偏离很大。S-H /π相互作用与经典阳离子/π相互作用的不同之处在于S-H σ*偏向环碳和芳香π轨道而不是芳香质心。这些结果描述了一种潜在的广泛适用的方法来理解弱极性键与π系统的相互作用。
Thiols can engage favorably with aromatic rings in S–H/π interactions, within abiological systems and within proteins. However, the underlying bases for S–H/π interactions are not well understood. The crystal structure of Boc-L-4-thiolphenylalanine tert-butyl ester revealed crystal organization centered on the interaction of the thiol S–H with the aromatic ring of an adjacent molecule, with a through-space Hthiol...Caromatic distance of 2.71 Å, below the 2.90 Å sum of the van der Waals radii of H and C. The nature of this interaction was further examined by DFT calculations, IR spectroscopy, solid-state NMR spectroscopy, and analysis of the Cambridge Structural Database. The S–H/π interaction was found to be driven significantly by favorable molecular orbital interactions, between an aromatic π donor orbital and the S–H σ* acceptor orbital (a π→σ* interaction). For comparison, a structural analysis of O–H/π interactions and of cation/π interactions of alkali metal cations with aromatic rings was conducted. Na+ and K+ exhibit a significant preference for the centroid of the aromatic ring and distances near the sum of the van der Waals and ionic radii, as expected for predominantly electrostatic interactions. Li+ deviates substantially from Na+ and K+. The S–H/π interaction differs from classical cation/π interactions by the preferential alignment of the S–H σ* toward the ring carbons and an aromatic π orbital rather than toward the aromatic centroid. These results describe a potentially broadly applicable approach to understanding the interactions of weakly polar bonds with π systems.
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