论文标题

合作O-H $ \CDOTSπ$和C-H $ \ CDOTS $ o氢键在苯甲醇解决方案中:弱相互作用的强结构

Cooperative O-H$\cdotsπ$ and C-H$\cdots$O Hydrogen Bonding in Benzene-Methanol Solution: Strong Structures from Weak Interactions

论文作者

Di Mino, Camilla, Seel, Andrew G., Clancy, Adam J., Sella, Andrea, Headen, Thomas F., Földes, Támas, Rosta, Edina, Skipper, Neal T.

论文摘要

弱氢键,例如O-H $ \cdotsπ$和C-H $ \ cdots $ O,在广泛的重要自然和工业过程中至关重要,包括生物化学组装,分子识别和化学选择性。在这项研究中,我们将中子衍射与全面的H/D同位素取代结合使用,以获得苯甲醇溶液中结构的详细空间和定向图片。该系统为我们提供了一种典型的情况,在该情况下,芳环可以充当氢键受体(通过$π$电子密度)和/或氢键供体(通过CH组),具有合作效应的潜力。我们的分析将苯置于参考框架的中心,并在解决方案中首次揭示了O-H $ \cdotsπ$相互作用是高度局部的,并且定向性,氢原子位于环形质心上方/下方,距离为2.30Å,并且与羟基键合为芳族平面。甲醇形成链和循环基序的趋势在高度模板的对称赤道溶剂化结构中表现出来。甲醇分子围绕苯围绕苯,因此O-H键与芳香环相聚,而氧气通过同时分叉的氢键与C-H基团相互作用。相比之下,C-H $ \cdotsπ$相互作用被降级为更遥远的观众的作用。因此,实验观察到的溶剂化表明,在液相,弱氢键的键合可能也会导致强烈有序的合作结构基序。

Weak hydrogen bonds, such as O-H$\cdotsπ$ and C-H$\cdots$O, are pivotal in a wide range of important natural and industrial processes including biochemical assembly, molecular recognition, and chemical selectivity. In this study we use neutron diffraction in conjunction with comprehensive H/D isotopic substitution to obtain a detailed spatial and orientational picture of the structure in benzene-methanol solution. This system provides us with a prototypical situation where the aromatic ring can act as an hydrogen bond acceptor (via the $π$ electron density) and/or a hydrogen bond donor (via the CH groups), with the potential for cooperative effects. Our analysis places benzene at the centre of our frame-of-reference, and reveals for the first time that in solution the O-H$\cdotsπ$ interaction is highly localised and directional, the hydrogen atom being located directly above/below the ring centroid at a distance of 2.30 Å and with the hydroxyl bond axis normal to the aromatic plane. The tendency of methanol to form chain and cyclic motifs in the bulk liquid is manifest in a highly templated, symmetrical equatorial solvation structure; the methanol molecules surround the benzene so that the O-H bonds are coplanar with the aromatic ring while the oxygens interact with C-H groups through simultaneous bifurcated hydrogen bonds. By contrast, C-H$\cdotsπ$ interactions are relegated to the role of more distant spectators. The experimentally observed solvation therefore demonstrates that weak hydrogen bonding can give rise to strongly-ordered cooperative structural motifs also in the liquid phase.

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