Institute of Chemistry, University of São Paulo, P. O. Box 26077, 05513-970, S. P., São Paulo, Brazil.
Phys Chem Chem Phys. 2010 Feb 28;12(8):1764-71. doi: 10.1039/b921391k. Epub 2010 Jan 6.
The thermo-solvatochromism of 2,6-dibromo-4-[(E)-2-(1-methylpyridinium-4-yl)ethenyl] phenolate, MePMBr(2), has been studied in mixtures of water, W, with ionic liquids, ILs, in the temperature range of 10 to 60 degrees C, where feasible. The objectives of the study were to test the applicability of a recently introduced solvation model, and to assess the relative importance of solute-solvent solvophobic interactions. The ILs were 1-allyl-3-alkylimidazolium chlorides, where the alkyl groups are methyl, 1-butyl, and 1-hexyl, respectively. The equilibrium constants for the interaction of W and the ILs were calculated from density data; they were found to be linearly dependent on N(C), the number of carbon atoms of the alkyl group; van't Hoff equation (log K versus 1/T) applied satisfactorily. Plots of the empirical solvent polarities, E(T) (MePMBr(2)) in kcal mol(-1), versus the mole fraction of water in the binary mixture, chi(w), showed non-linear, i.e., non-ideal behavior. The dependence of E(T) (MePMBr(2)) on chi(w), has been conveniently quantified in terms of solvation by W, IL, and the "complex" solvent IL-W. The non-ideal behavior is due to preferential solvation by the IL and, more efficiently, by IL-W. The deviation from linearity increases as a function of increasing N(C) of the IL, and is stronger than that observed for solvation of MePMBr(2) by aqueous 1-propanol, a solvent whose lipophilicity is 12.8 to 52.1 times larger than those of the ILs investigated. The dependence on N(C) is attributed to solute-solvent solvophobic interactions, whose relative contribution to solvation are presumably greater than that in mixtures of water and 1-propanol.
2,6-二溴-4-[(E)-2-(1-甲基吡啶鎓-4-基)乙烯基]苯酚盐，MePMBr(2) 的热溶剂变色性质已在水，W，与离子液体，ILs 的混合物中进行了研究，温度范围为 10 至 60 摄氏度，在可行的情况下。该研究的目的是测试最近引入的溶剂化模型的适用性，并评估溶质-溶剂疏溶剂相互作用的相对重要性。ILs 是 1-烯丙基-3-烷基咪唑氯化物，其中烷基分别为甲基、1-丁基和 1-己基。W 和 IL 相互作用的平衡常数从密度数据中计算得出；它们被发现与 N(C)，即烷基的碳原子数呈线性相关；van't Hoff 方程（log K 对 1/T）应用令人满意。经验溶剂极性 E(T) (MePMBr(2))（以 kcal mol(-1)为单位）与二元混合物中水的摩尔分数 chi(w)的图显示出非线性，即非理想行为。E(T) (MePMBr(2))对 chi(w)的依赖性已经以 W、IL 和“复杂”溶剂 IL-W 的溶剂化的方式方便地进行了量化。非理想行为是由于 IL 和更有效地 IL-W 的优先溶剂化所致。这种偏离线性的行为随着 IL 的 N(C)的增加而增加，并且比 MePMBr(2)在水性 1-丙醇中的溶剂化观察到的偏离更强烈，1-丙醇的亲脂性是研究的 ILs 的 12.8 至 52.1 倍。这种对 N(C)的依赖性归因于溶质-溶剂疏溶剂相互作用，其对溶剂化的相对贡献可能大于水和 1-丙醇混合物中的贡献。
