Hydrophobic Ionic Liquids Composed of Perfluoroalkyltrifluoroborates for Ionic Liquid–Water Two-Phase Systems
作者:Naoya Nishi、Akihito Suzuki、Takashi Kakiuchi
DOI:10.1246/bcsj.82.86
日期:2009.1.15
Ionic liquids (ILs) composed of perfluoroalkyltrifluoroborate ions (CnF2n+1BF3−, n = 2, 3, 4, and 6) and highly hydrophobic cations are found to have properties suitable to the applications of ILs in IL–water (W) two-phase systems because of their high stability against hydrolysis, high hydrophobicity, and low melting points. The rate of hydrolysis of CnF2n+1BF3− is four orders of magnitude slower than that of BF4−. The ion-transfer voltammograms for the transfer of CnF2n+1BF3− across the interface between nitrobenzene and W show that these CnF2n+1BF3− have hydrophobicity comparable to or higher than those of PF6− and bis(trifluoromethylsulfonyl)imide depending on n. The physicochemical properties (density, viscosity, conductivity, and solubility of ILs in W) of CnF2n+1BF3−-based ILs are measured for the ILs having melting points lower than room temperature. The hydrophobicity of the CnF2n+1BF3− ions is well correlated with the solubility of the ILs in W and also with the width of the polarized potential window at the IL|W interface.
富氟烷基三氟硼酸盐离子(CnF2n+1BF3−,n = 2,3,4和6)和高度疏水性阳离子组成的离子液体(ILs)由于其在水解方面的高稳定性、高疏水性和低熔点,显示出在IL–水(W)双相系统中的应用潜力。CnF2n+1BF3−的水解速率比BF4−慢四个数量级。在硝基苯和水之间的界面上,CnF2n+1BF3−的离子转移伏安图显示,这些CnF2n+1BF3−的疏水性与PF6−和双(三氟甲基磺酰)亚胺的疏水性相当或更高,具体取决于n。对于熔点低于室温的基于CnF2n+1BF3−的离子液体,测量其物理化学性质(密度、粘度、电导率以及离子液体在水中的溶解度)。CnF2n+1BF3−离子的疏水性与离子液体在水中的溶解度以及IL|W界面上极化电位窗口的宽度有良好的关联。