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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >CH…F Hydrogen Bonds. Dimers of Fluoromethanes
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CH…F Hydrogen Bonds. Dimers of Fluoromethanes

机译：CH…F氢键。氟甲烷二聚物

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摘要

The nature of the CH…F H-bond is studied by examining the potential energy surfaces for dimers of the fluoromethanes, including all homo- and heterodimers involving CH4, CFH3, CF2H2, CF3H, and CF4. Several of the surfaces encompass two separate minima. Any pair capable of forming a cyclic structure does so, this geometry being more stable than any other minima that might occur on the surface. Such cyclic dimers are bound by 2-3 kcal/mol. Noncyclic geometries are only very weakly bound. In all cases, the C-H bonds that participate directly in the H-bonds undergo a contraction and associated blue shift in their stretching frequencies, whereas the C-F bonds manifest an elongation. The most strongly bound of all dimers studied pairs CH_3F with CHF_3, for which the C-H bond contracts by 0.0023 A, and its stretching frequency increases by 39 cm~(-1). The most stable cyclic dimer of fluoroform, containing one single and one bifurcated hydrogen bond, is reported for the first time and thus resolves the longstanding problem of the structure of the fluoroform dimer.
机译：通过检查氟甲烷二聚体的势能表面，包括所有涉及CH4，CFH3，CF2H2，CF3H和CF4的均二和杂二聚体，研究CH…F H键的性质。几个表面包含两个单独的最小值。能够形成环状结构的任何一对都可以这样做，这种几何形状比表面上可能出现的任何其他最小值更稳定。这样的环状二聚体以2-3kcal / mol结合。非循环几何形状的结合非常弱。在所有情况下，直接参与H键的C-H键在其拉伸频率中都会发生收缩和相关的蓝移，而C-F键则表现出伸长。在研究的所有二聚体中，结合最强的对是CH_3F和CHF_3，其C-H键收缩0.0023 A，并且其拉伸频率增加39 cm〜（-1）。首次报道了含一个和一个分支氢键的最稳定的氟仿环状二聚体，从而解决了氟仿二聚体长期存在的问题。

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