Synthesis and Sorption Analysis of Task-specific Fluorous Ionic Liquids

Abstract

Six 1-alkyl-4-tridecafluorooctyl-1,2,4-triazolium triflimides 2a-f and 4-amino-1-tridecafluorooctyl- 1,2,4-triazolium triflimide (4) were prepared from the respective iodides 1a-f (1a, 2a: n-propyl; 1b, 2b: n-butyl; 1c, 2c: n-hexyl; 1d, 2d: n-heptyl; 1e, 2e: n-octyl; 1f, 2f: n-decyl) and iodide 3 by ion metathesis. Compounds 2a and 4 are liquid at room temperature. Two liquid fluorous imidazolium salts bearing functionalized polar substituents were synthesized in an analogous manner, namely 1-(2- (diethylamino)ethyl)-3-(heptadecafluorodecyl)imidazolium triflimide (5b) and 1-(2-hydroxyethyl)- 3-(heptadecafluorodecyl)imidazolium triflimide (6b) from the respective bromides 5a and 6a. The bis(triflimide) 5c has a melting point slightly above room temperature. Three fluorous ionic liquids (ILs; 2a, 5b, and 6b) were subjected to vapor sorption analysis at 25 °C and exhibited dual affinity to water and, even much more pronounced, to methoxynonafluorobutane (hydrofluoroether HFE-7100). Thus, IL 6b absorbed 3:2% (by weight) water and 200% HFE, whereas ILs 2a and 5b absorbed 0.4 and 0:5% water, but 300 and 1200% HFE, respectively. Commercial 1-butyl-2,3- dimethyl-imidazolium triflimide and 1-ethyl-3-methyl-imidazolium triflimide were used as reference compounds and absorbed 0.9 and 2:2% water, respectively, but only 17% HFE.