Fundamental properties of the CH•••O interaction: Is it a true hydrogen bond?
Fundamental properties of the CH•••O interaction: Is it a true hydrogen bond?
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DOI：
10.1021/ja991795g
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发表时间：
1999-10-13
影响因子：
15
通讯作者：
Scheiner, S
中科院分区：
文献类型：
--
作者：
Gu, YL;Kar, T;Scheiner, S
用从头算方法分析了CH…FnH_3-nCH作为质子供体与H_2 O、CH_3OH和H_2CO作为受体之间的O相互作用。与CH 4作为供体的相互作用是相当弱的，但增强了1千卡/摩尔与每个F添加到供体。CH…O相互作用的行为非常像一个传统的OH. O H键在大多数方面，包括电子密度的变化，伴随着键的形成和相互作用能的各种分量的大小。这两种氢键也倾向于相似的平衡几何结构，并且对该结构的变形非常敏感。在数量上，虽然CH…O和OH…O优选线性构型，前者稍微更容易弯曲，并且对从其平衡氢键长度的拉伸不太敏感。而OH键已被证明拉伸，并在形成H-键时经历其振动频率的红移，这里研究的分子的CH键遵循相反的趋势，收缩和蓝移。分析表明，这种相反的模式并不是因为两种相互作用之间有任何根本区别，因为作用在两者上的是同一组力。最后得出结论，CH…O相互作用确实可以被归类为真正的H键。
Ab initio calculations are used to analyze the CH ... O interaction between FnH3-nCH as proton donor and H2O, CH3OH, and H2CO as acceptor. The interaction is quite weak with CH4 as donor but is enhanced by 1 kcal/mol with each F added to the donor. The CH ... O interaction behaves very much like a conventional OH ... O H-bond in most respects, including shifts in electron density that accompany the formation of the bond and the magnitudes of the various components of the interaction energy. The two sorts of H-bonds also gravitate toward a similar equilibrium geometry and are comparably sensitive to deformations from that structure. In a quantitative sense, while both CH ... O and OH ... O prefer a linear configuration, the former is somewhat more easily bent and is less sensitive to stretches from its equilibrium H-bond length. Whereas the OH bond has been shown to stretch and undergo a red shift in its vibrational frequency upon formation of a H-bond, the CH bond of the molecules studied here follows the opposite trend, a contraction and a blue shift. Analysis demonstrates that this opposite pattern is not due to any fundamental distinction between the two interactions, since the same sets of forces are acting on both. It is concluded that the CH ... O interaction can, indeed, be categorized as a true H-bond.