Yao Fei, Gong Nan, Fang Wenhui, Men Zhiwei
School of Science, Changchun University of Science and Technology, Changchun, 130022, China.
Phys Chem Chem Phys. 2020 Mar 14;22(10):5702-5710. doi: 10.1039/c9cp05886a. Epub 2020 Feb 27.
Halogen bonding, an attractive interaction that is analogous to hydrogen bonding, has been widely investigated by computational methods. However, halogen bonding in solution is hard to study by spectroscopic techniques since the intermolecular interaction often gives overlapping bands and may be difficult to interpret. The traditional interpretation of iodomethane-ethanol mixtures considered only hydrogen bonding effects and the experimental investigation was limited. Here, we employed near-infrared (NIR) spectroscopy, Raman, density functional theory calculation, and two-dimensional (2D) correlation analysis to find evidence of the halogen bonding in iodomethane-ethanol mixtures. Our results suggest that the blue-shifting C-I stretching band is probably due to the cooperative influence from halogen bonding, hydrogen bonding, and the solvent effect, while the O-H band is a cumulative band from three dimer complexes. The 2D correlation spectra further validate the hypothesis above and reveal the interaction evolution from the ethanol-rich region to the iodomethane region. These results indicate that the unique nature of the iodomethane-ethanol mixture and the larger σ-hole strengthen the halogen bond, leading to particular spectroscopic results which are different from those of the other halogenated alkanes.
卤键是一种类似于氢键的吸引相互作用，已通过计算方法进行了广泛研究。然而，由于分子间相互作用常常产生重叠谱带且可能难以解释，因此溶液中的卤键很难通过光谱技术进行研究。对碘甲烷 - 乙醇混合物的传统解释仅考虑了氢键效应，且实验研究有限。在此，我们采用近红外（NIR）光谱、拉曼光谱、密度泛函理论计算以及二维（2D）相关分析来寻找碘甲烷 - 乙醇混合物中卤键的证据。我们的结果表明，C - I伸缩带的蓝移可能是由于卤键、氢键和溶剂效应的协同影响，而O - H带是来自三种二聚体复合物的累积谱带。二维相关光谱进一步验证了上述假设，并揭示了从富乙醇区域到碘甲烷区域的相互作用演变。这些结果表明，碘甲烷 - 乙醇混合物的独特性质以及更大的σ - 空穴增强了卤键，导致了与其他卤代烷烃不同的特殊光谱结果。
