Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, UK CB2 1EW.
Phys Chem Chem Phys. 2010 Feb 28;12(8):1733-40. doi: 10.1039/b916987c. Epub 2009 Nov 12.
The properties of pairs of solute ions in the ionic liquid, dimethylimidazolium chloride or [dmim][Cl], are studied as a function of their separation. The potential of mean force curves show that there is only a small stabilisation of ion pairs with opposite charges followed by a barrier to separation. Ion pairs with the same charge are also stabilised by solvent screening due to induced polarisation of the solvent. In both cases screening is essentially complete outside the first shell, but is large even when there is no solvent between the ions. Charge distributions in the solvation shells around ion pairs are shown and the results interpreted with the aid of a simple model of two ions in an spheroidal cavity in a conducting medium. The actual or Madelung potential experienced by the second solute ion is found to decay rapidly with distance and does not show the oscillations found in the Poisson potential around a single solute ion. We conclude that ionic liquids provide very effective electrostatic screening between solute molecules.
研究了离子液体二甲基咪唑氯化物或 [dmim][Cl] 中溶质离子对的性质与其分离的关系。平均力势曲线表明，只有少量带相反电荷的离子对被稳定，然后是分离的障碍。由于溶剂的诱导极化，带有相同电荷的离子对也被溶剂屏蔽稳定。在这两种情况下，屏蔽在第一层壳外基本完全，但即使在离子之间没有溶剂时，屏蔽也很大。展示了离子对周围溶剂化壳中的电荷分布，并借助于在导电介质中的球形腔中两个离子的简单模型对结果进行了解释。发现第二个溶质离子所经历的实际或Madelung 势随距离迅速衰减，并且不显示在单个溶质离子周围的泊松势中发现的振荡。我们得出结论，离子液体在溶质分子之间提供了非常有效的静电屏蔽。
