Laboratoire de Thermodynamique et Interactions Moléculaires, CNRS, UMR 6272, 24 avenue des Landais, BP 80026, 63171 Aubière, France.
Chemphyschem. 2012 May 14;13(7):1753-63. doi: 10.1002/cphc.201100779. Epub 2012 Mar 20.
The solvation of glycine in two ionic liquids (ILs), namely, 1-butyl-3-methylimidazolium acetate, [C(1)C(4)Im][OAc], and 1-butyl-3-methylimidazolium trifluoroacetate, [C(1)C(4)Im][TFA], was studied by a combination of experimental and theoretical methods. The solubility of glycine in both ILs was determined at 333.15 K to be (8.1±0.5) and (1.0±0.5) wt % in [C(1)C(4)Im][OAc] and [C(1)C(4)Im][TFA], respectively. By IR spectroscopy it was found that, when dissolved in the ILs, glycine was mainly present in its zwitterionic form. Structural and energetic aspects of the solvation of glycine in the ILs and in mixtures of ILs and water were investigated by ab initio calculations and molecular dynamic simulations. It was observed that the firstly solvation shell around glycine consisted predominantly of acetate or trifluoroacetate anions, which formed hydrogen bonds either with the carboxylic group of neutral glycine or with the protonated ammonium group of the zwitterionic form. When water is present in the solutions, hydrogen bonds between water and the anion prevail. The overall energy of the system was decomposed into its components between pairs of species. It was established that the dominant contribution to the interaction energy between glycine and the IL was due to hydrogen bonds with the anions and the statistics of hydrogen bonds were analysed.
采用实验和理论相结合的方法研究了甘氨酸在两种离子液体（ILs）中的溶解情况，这两种 ILs 分别为 1-丁基-3-甲基咪唑醋酸盐[C(1)C(4)Im][OAc]和 1-丁基-3-甲基咪唑三氟醋酸盐[C(1)C(4)Im][TFA]。在 333.15 K 下测定了甘氨酸在这两种 ILs 中的溶解度，结果分别为（8.1±0.5）wt%和（1.0±0.5）wt%。通过红外光谱研究发现，当甘氨酸溶解在 ILs 中时，其主要以两性离子形式存在。通过从头算计算和分子动力学模拟研究了甘氨酸在 ILs 中和 ILs 与水混合物中的溶解的结构和能量方面。结果表明，甘氨酸的第一个溶剂化壳层主要由醋酸盐或三氟醋酸盐阴离子组成，它们与中性甘氨酸的羧酸基团或两性离子形式的质子化铵基团形成氢键。当溶液中存在水时，水与阴离子之间的氢键占主导地位。系统的总能量被分解为对物种对之间的相互作用能。结果表明，甘氨酸与 IL 之间的相互作用能主要归因于与阴离子的氢键，并且分析了氢键的统计数据。
