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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Theoretical Study of the CH…O Interaction in Fluoromethanes centre dot H_2O and Chloromethanes centre dot H_2O Complexes
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Theoretical Study of the CH…O Interaction in Fluoromethanes centre dot H_2O and Chloromethanes centre dot H_2O Complexes

机译：氟甲烷中心点H_2O与氯甲烷中心点H_2O配合物中CH…O相互作用的理论研究

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MP2/6-31+G(d,p) calculations are used to analyze the CH…O interaction between X_nH_(3-n)CH(n=1,2,3, X=F, Cl) as proton donors and H_2O as acceptor. Only the constrained linear structures are considered, although they do not correspond, for the CH_3X and CH_2X_2 complexes, to any global minima on the potential energy surface. The interaction energies range from 0.29 to 3.68 kcal mol~9-1) and are correlated to the intermolecular H…O distances and the acidities of the proton donors, similar to conventional OH…O hydrogen bonds. Interaction with H_2O results in a contr5action of the CH bond and an elongation of the external CH and CX ones. The CH stretching vibrations are analyzed for the fully or partially deuterated isotopomers in order to decouple them from the other vibrational modes. The CH(D) stretching vibrations are blue-shifted and the CH(D) stretching vibrations of the external CH bonds are red-shifted. Linear correlations are established between the shifts of the CH(D) stretching vibrations and the variations of the distances in the corresponding CH bond. Complex formation results in a substantial decrease in intensity of the CH(D) stretching vibrations in the methane or fluoromethanes complexes and an increase in intensity in the chloromethanes complexes. In all the studied complexes, the charge transfer from the proton acceptor to the proton donor goes mainly to the lone pair of the X atom(s). By analogy with the conventional hydrogen bonds, there is also an increase in the population of the recipient antibonding molecular orbital, in the present case the #singma#*(CH) orbital. The interaction energies are correlated to the percentage of s character of the CH bonds in the isolated monomers. The results suggest that the interaction in the CH…O and OH…O systems is characterized by several similar properties, in relatively good agreement with the statements of Gu, Kar and Scheiner (J. Am. Chem. Soc. 1999, 121, 9411). In many aspects, the CHCl_3 centre dot H_2O complex appears as a precursor of the standard hydrogen bonds.
机译：MP2 / 6-31 + G（d，p）计算用于分析质子供体X_nH_（3-n）CH（n = 1,2,3，X = F，Cl）与H_2O之间的CH…O相互作用作为接受者。对于CH_3X和CH_2X_2配合物，尽管它们不对应，但仅考虑受约束的线性结构与势能面上的任何全局最小值。相互作用能介于0.29至3.68 kcal mol〜9-1之间，与分子间的H…O距离和质子给体的酸度相关，类似于常规的OH…O氢键。与H_2O的相互作用导致CH键的控制以及外部CH和CX的伸长。为了完全或部分氘化的异构体，分析CH拉伸振动，以使它们与其他振动模式脱钩。 CH（D）拉伸振动发生蓝移，外部CH键的CH（D）拉伸振动发生红移。在CH（D）拉伸振动的位移与相应CH键中距离的变化之间建立了线性相关性。配合物的形成导致甲烷或氟代甲烷配合物中CH（D）拉伸振动的强度大大降低，而氯代甲烷配合物强度增加。在所有研究的络合物中，电荷从质子受体转移至质子供体主要到达X原子的孤对。与常规氢键类似，受体反键分子轨道（在当前情况下为#singa＃*（CH）轨道）的总数也有所增加。相互作用能与分离的单体中CH键的s特性百分比相关。结果表明，CH…O和OH…O系统中的相互作用具有几个相似的特性，与Gu，Kar和Scheiner的陈述相对较好地吻合（J. Am。Chem。Soc。1999，121，9411）。 ）。在许多方面，CHCl_3中心点H_2O配合物似乎是标准氢键的前体。

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