Double Salt Ionic Liquids Prepared by Mixing Partially Miscible Ionic Liquids: Tuning the Solubility of Lipophilic Molecules

摘要

Double Salt Ionic Liquids (DSILs) were prepared by mixing 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C_2mim][NTf_2]) and trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide ([P_(66614)][NTf_2]) in their miscible range: [C_2mim]x[P_(66614)]_(1-x)[NTf_2] (0 ≤ x ≤ 0.29). ~1H NMR, ~(19)F NMR, and FT-IR spectroscopic studies indicated that the [NTf_2]- anions preferentially interact with the [C_2mim]+ cations. Solubility studies showed that solutes with long alkyl chains (e.g., heptane, methyl palmitate), which have good solubility in [P_(66614)][NTf_2] but are not totally miscible, have tunable solubility in the DSILs and the presence of even minor amounts of [C_2mim]~+ significantly decreases their solubility. However, the solubilities of benzene, toluene, 1-octanol, and poly(ethylene glycol) (PEG-300) in [C_2mim]_x[P_(66614)]_(1-x)[NTf_2] were controlled by their miscibility with [P66614][NTf_2], and can't be tuned by changing the ion concentrations within the miscibility range.