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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Methanethiol Dimer and Trimer. An ab Initio and DFT Study of the Interaction
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Methanethiol Dimer and Trimer. An ab Initio and DFT Study of the Interaction

机译：甲硫基二聚体和三聚体。交互的从头算和DFT研究

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Clusters consisting of two and three methanethiol molecules were subjected to HF, DFT/B3LYP, and MP2 calculations using the aug-cc-pvdz/cc-pvdz basis set. Overall, five structures corresponding to minima on the potential surface for methanethiol dimer were located that allowed the identification of interactions of the S-H…S and C-H…S types. While the latter type of interaction prevails in the dimer, the former is only observed in tow of the five minima. Overall, the S-H…S contacts present angles that depart considerably from linearity. The use of a method that considers intermolecular electron correlation is indispensable with a view to obtaining accurate results. In fact, the HF and DFT/B3LYP methods provided significantly longer intermolecular distances than the MP2 method and underestimated interaction energies by more than 50%. The interaction energy of the most stable minimum was -11.2 kJ/mol with the MP2 method and was associated with the two interactions between the sulfur atom and the hydrogen atoms is the methyl group. Five possible minima for methanethiol trimer were also examined. the predominating interaction in these structures was of the S-H…S type, which was found to occur in all five minima and was accompanied by interactions with the methyl groups that contributed to stabilizing the cluster.s The interaction energy for the most stable structure was -28.1 kJ/mol. The contribution of nonadditive pairwise terms to the interaction was fairly low, but significant (ca. 6% of the overall interaction energy). The analysis of vibration modes revealed the dimer to exhibit no specially significant frequency shifts, which suggests that no S-H…S hydrogen bonds re established. However, the structures that present S-H…S contacts exhibited red shifts of ca. 60 cm~(-1). The situation with the trimer was different: all structures exhibited S-H…S interactions, which resulted in red shifts of ca. 80-90 cm~(-1), suggesting the presence of a cooperative phenomenon. Other vibration modes exhibited virtually no shifts; by exception, the frequency of the H_s-S-C-H_p torsion underwent a marked blue shift (about 130 cm~(-1) for the dimer and up to 200 cm~(-1) for the trimer).
机译：使用aug-cc-pvdz / cc-pvdz基集对由两个和三个甲硫醇分子组成的簇进行HF，DFT / B3LYP和MP2计算。总的来说，找到了与甲硫醇二聚体的潜在表面上的最小值相对应的五个结构，这些结构可以识别S-H…S和C-H…S类型的相互作用。尽管后者的相互作用主要存在于二聚体中，但前者仅在五个极小值的两个峰中观察到。总体而言，S-H…S触头呈现出的角度与线性度大不相同。为了获得准确的结果，必须使用考虑分子间电子相关性的方法。实际上，与MP2方法相比，HF和DFT / B3LYP方法提供的分子间距离明显更长，并且相互作用能被低估了50％以上。用MP2方法测得的最稳定最小值的相互作用能为-11.2 kJ / mol，与硫原子和氢原子之间的两个相互作用是甲基有关。还对甲烷硫醇三聚体的五个可能的最小值进行了检查。这些结构中最主要的相互作用是SH…S型，发现在所有五个极小值中都发生，并且伴随着与有助于稳定团簇的甲基的相互作用。最稳定结构的相互作用能为- 28.1 kJ /摩尔。非加性成对项对相互作用的贡献很小，但很明显（约占总相互作用能的6％）。振动模式的分析表明，该二聚体没有特别明显的频移，这表明没有建立S-H…S氢键。但是，呈现S-H…S接触的结构表现出大约红色的偏移。 60厘米〜（-1）三聚体的情况有所不同：所有结构均表现出S-H…S相互作用，这导致ca发生红移。 80-90 cm〜（-1），表明存在合作现象。其他振动模式几乎没有变化。例外，H_s-S-C-H_p扭转的频率发生了明显的蓝移（二聚体约为130 cm〜（-1），三聚体高达200 cm〜（-1））。

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