Keefe C Dale, Isenor Merrill
Department of Chemistry, Cape Breton University, Sydney, Nova Scotia B1P 6L2, Canada.
J Phys Chem A. 2008 Apr 10;112(14):3127-32. doi: 10.1021/jp076563f. Epub 2008 Mar 14.
In this paper, the results of a study of the interaction of methane, fluoroform, chloroform, and bromoform with benzene and hexafluorobenzene are presented. The benzene complexes were studied at the MP2/6-31G(d) and MP2/6-311++G(2d,p) levels, and the hexafluorobenzene complexes were only studied at the MP2/6-31G(d) level. The optimized geometries, stabilization energies, potential energy surfaces, harmonic frequencies, and vibrational intensities are reported. A net attraction is predicted for all four benzene complexes, whereas for the CHX3.C6F6 complexes, it was found that MP2/6-31G(d) predicts a net attraction for the CH4, CHCl3, and CHBr3 complexes and does not predict a stable complex for CHF3.C6F6. The three complexes with net attractions all have blue-shifts of the CHX3 CH stretching wavenumber and a slight contraction (0.001-0.003 A) of the CH bond in CHX3. The MP2/6-31G(d) level predicts that the intensity of the CHX3 CH stretch will vary widely. For CH4.C6H6 and CHF3.C6H6, it is predicted that the intensity will be smaller for the complexes than the free molecules, whereas for the other complexes, anywhere from a 30% increase to an increase of 87 times is predicted. The atoms in molecules analysis showed that only three of the eight criteria for normal hydrogen bonding are satisfied for all eight complexes studied. Criterion 3 (value of the Laplacian at the bond critical point) is not satisfied for any of the eight complexes.
本文展示了甲烷、氟仿、氯仿和溴仿与苯及六氟苯相互作用的研究结果。苯配合物在MP2/6 - 31G(d)和MP2/6 - 311++G(2d,p)水平上进行了研究，而六氟苯配合物仅在MP2/6 - 31G(d)水平上进行了研究。报告了优化后的几何结构、稳定化能、势能面、谐频和振动强度。预测所有四种苯配合物都存在净吸引力，而对于CHX3·C6F6配合物，发现MP2/6 - 31G(d)预测CH4、CHCl3和CHBr3配合物存在净吸引力，而对于CHF3·C6F6则未预测到稳定配合物。具有净吸引力的三种配合物的CHX3 CH伸缩波数均有蓝移，且CHX3中CH键略有收缩（0.001 - 0.003 Å）。MP2/6 - 31G(d)水平预测CHX3 CH伸缩的强度变化很大。对于CH4·C6H6和CHF3·C6H6，预测配合物的强度比自由分子小，而对于其他配合物，预测强度增加范围从30%到87倍不等。分子中的原子分析表明，在所研究的所有八种配合物中，仅满足正常氢键八个标准中的三个。对于这八种配合物中的任何一种，标准3（键临界点处的拉普拉斯值）均不满足。
