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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Hydration of Sulfo and Methyl Groups in Dimethyl Sulfoxide Is Accompanied by the Formation of Red-Shifted Hydrogen Bonds and Improper Blue-Shifted Hydrogen Bonds: An ab Initio Quantum Chemical Study
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Hydration of Sulfo and Methyl Groups in Dimethyl Sulfoxide Is Accompanied by the Formation of Red-Shifted Hydrogen Bonds and Improper Blue-Shifted Hydrogen Bonds: An ab Initio Quantum Chemical Study

机译：红移氢键和不正确的蓝移氢键的形成伴随着二甲基亚砜中磺基和甲基的水合：从头算量子化学研究

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摘要

In this study, the hydration of dimethyl sulfoxide was investigated by means of molecular dynamic (MD) simulations and quantum chemical correlated ab inito calculations. MD simulations show the hydration sites when the systems are exposed to 1, 3, 6, 16, and 32 water molecules. Various DMSO…(H_2O)_n (n = 1 - 3) complexes where waters hydrate sulfo and methyl groups were then reoptimized at the ab initio level. The hydration of DMSO leads to an elongation of the S=O bond and a contraction of methyl C-H bonds. Whereas the elongation of the S=O bond is accompanied by a red shift of the respective stretch frequency, the contraction of the C-H bonds gives a blue shift to the C-H stretch frequencies. The former effect is easily explained by the transfer of electron density to the antibonding orbitals of the S=O bond, yielding its weakening. Various mechanisms leading to the contraction of the methyl CH bonds were suggested. They were based on secondary geometry changes originating from the significant elongation of the S=O bond and also on the changes of the electron density in DMSO upon complexation, resulting in a rehybridization of the CH bonds. The influence of the electrostatic field of hydrating waters was also considered. Predicted frequency shifts fully agree with the observed data. Also, the observed blue shift increase occurring as a consequence of progressive hydration was interpreted theoretically, and the mechanisms of the phenomenon are suggested.
机译：在这项研究中，通过分子动力学（MD）模拟和量子化学相关的从头计算来研究二甲亚砜的水合。 MD模拟显示了系统暴露于1、3、6、16和32个水分子时的水合位点。各种DMSO…（H_2O）_n（n = 1-3）络合物，其中的水合了磺基和甲基，然后从头开始重新优化。 DMSO的水合导致S ＝ O键的伸长和甲基C-H键的收缩。尽管S ＝ O键的伸长伴随着相应拉伸频率的红移，但是C-H键的收缩使C-H拉伸频率产生了蓝移。前者的影响很容易通过将电子密度转移到S = O键的反键轨道上来解释，从而削弱了它。提出了导致甲基CH键收缩的各种机制。它们基于源自S = O键显着伸长的次级几何形状变化，也基于络合后DMSO中电子密度的变化，从而导致CH键重新杂化。还考虑了水合静电场的影响。预测的频移与观测数据完全一致。此外，从理论上解释了观察到的由于逐渐水合而发生的蓝移增加，并提出了这种现象的机理。

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