We have carried out an ab initio molecular dynamics study on the sulfur dioxide (SO2) solvation in 1-ethyl-3-methylimidazolium thiocyanate for which we have observed that both cations and anions play an essential role in the solvation of SO2. Whereas, the anions tend to form a thiocyanate- and much less often an isothiocyanate-SO2 adduct, the cations create a “cage” around SO2 with those groups of atoms that donate weak interactions like the alkyl hydrogen atoms as well as the heavy atoms of the $$\pi $$π-system. Despite these similarities between the solvation of SO2 and CO2 in ionic liquids, an essential difference was observed with respect to the acidic protons. Whereas CO2 avoids accepting hydrogen bonds form the acidic hydrogen atoms of the cations, SO2 can from O(SO2)–H(cation) hydrogen bonds and thus together with the strong anion-adduct it actively integrates in the hydrogen bond network of this particular ionic liquid. The fact that SO2 acts in this way was termed a linker effect by us, because the SO2 can be situated between cation and anion operating as a linker between them. The particular contacts are the H(cation)$$\cdots $$⋯O(SO2) hydrogen bond and a S(anion)–S(SO2) sulfur bridge. Clearly, this observation provides a possible explanation for the question of why the SO2 solubility in these ionic liquids is so high.

中文翻译：

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SO2 在 1-Ethyl-3-Methylimidazolium 硫氰酸盐离子液体中通过加入扩展的阳离子-阴离子网络进行溶剂化

我们对硫氰酸 1-乙基-3-甲基咪唑鎓中的二氧化硫 (SO2) 溶剂化进行了从头分子动力学研究，我们观察到阳离子和阴离子在 SO2 的溶剂化中都起着重要作用。然而，阴离子倾向于形成硫氰酸盐 - 而很少形成异硫氰酸盐 - SO2 加合物，阳离子在 SO2 周围形成一个“笼子”，这些原子团提供弱相互作用，如烷基氢原子以及$$\pi $$π 系统。尽管在离子液体中 SO2 和 CO2 的溶剂化之间存在这些相似性，但在酸性质子方面观察到了本质上的差异。而 CO2 避免接受形成阳离子的酸性氢原子的氢键，SO2 可以由 O(SO2)–H(阳离子) 氢键形成，因此与强阴离子加合物一起，它主动整合到这种特定离子液体的氢键网络中。SO2 以这种方式起作用的事实被我们称为链接器效应，因为 SO2 可以位于阳离子和阴离子之间，作为它们之间的链接器。特定的接触是 H(cation)$$\cdots $$⋯O(SO2) 氢键和 S(anion)-S(SO2) 硫桥。显然，这一观察结果为 SO2 在这些离子液体中的溶解度为何如此之高的问题提供了可能的解释。特定的接触是 H(cation)$$\cdots $$⋯O(SO2) 氢键和 S(anion)-S(SO2) 硫桥。显然，这一观察结果为 SO2 在这些离子液体中的溶解度为何如此之高的问题提供了可能的解释。特定的接触是 H(cation)$$\cdots $$⋯O(SO2) 氢键和 S(anion)-S(SO2) 硫桥。显然，这一观察结果为 SO2 在这些离子液体中的溶解度为何如此之高的问题提供了可能的解释。