Firaha Dzmitry S, Kavalchuk Mikhail, Kirchner Barbara
Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, University of Bonn, Beringstraße 4+6, Bonn, Germany.
J Solution Chem. 2015;44(3-4):838-849. doi: 10.1007/s10953-015-0321-5. Epub 2015 Mar 31.
We have carried out an ab initio molecular dynamics study on the sulfur dioxide (SO) 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 SO. Whereas, the anions tend to form a thiocyanate- and much less often an isothiocyanate-SO adduct, the cations create a "cage" around SO with those groups of atoms that donate weak interactions like the alkyl hydrogen atoms as well as the heavy atoms of the [Formula: see text]-system. Despite these similarities between the solvation of SO and CO in ionic liquids, an essential difference was observed with respect to the acidic protons. Whereas CO avoids accepting hydrogen bonds form the acidic hydrogen atoms of the cations, SO can from O(SO)-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 SO acts in this way was termed a linker effect by us, because the SO can be situated between cation and anion operating as a linker between them. The particular contacts are the H(cation)[Formula: see text]O(SO) hydrogen bond and a S(anion)-S(SO) sulfur bridge. Clearly, this observation provides a possible explanation for the question of why the SO solubility in these ionic liquids is so high.
我们对二氧化硫（SO）在1-乙基-3-甲基咪唑硫氰酸盐中的溶剂化作用进行了从头算分子动力学研究，在此过程中我们观察到阳离子和阴离子在SO的溶剂化过程中都起着至关重要的作用。阴离子倾向于形成硫氰酸根 - 二氧化硫加合物，而异硫氰酸根 - 二氧化硫加合物形成的频率要低得多，阳离子则利用那些能提供弱相互作用的原子基团，如烷基氢原子以及[化学式：见原文]体系中的重原子，在SO周围形成一个“笼子”。尽管SO和CO在离子液体中的溶剂化作用存在这些相似之处，但在酸性质子方面观察到了一个本质区别。CO避免接受来自阳离子酸性质子的氢键，而SO可以形成O(SO)-H(阳离子)氢键，因此它与强阴离子加合物一起积极地融入到这种特定离子液体的氢键网络中。我们将SO以这种方式起作用的事实称为连接效应，因为SO可以位于阳离子和阴离子之间，起到它们之间的连接作用。特定的接触包括H(阳离子)[化学式：见原文]O(SO)氢键和S(阴离子)-S(SO)硫桥。显然，这一观察结果为SO在这些离子液体中的溶解度为何如此之高这一问题提供了一种可能的解释。
