Physicochemical properties of N-methoxyethyl-N-methylpyrrolidinum ionic liquids with perfluorinated anions

Four room-temperature ionic liquids (RTILs) based on N-methyl-N-methoxyethylpyrrolidinium (PYR12O1+) and fluorinated sulfonylimides, bis(fluorosulfonyl)imide (FSI−), bis(trifluoromethanesulfonyl)imide (TFSI−), bis(pentafluoroethylsulfonyl)imide (BETI−) and (trifluoromethanesulfonyl) (nonafluorobutanesulfonyl)imide (IM14−) anion have been synthesised and intensively investigated from an electrochemical and physico-chemical point of view, including thermal behaviour, viscosity, conductivity and electrochemical stability. The prepared ionic liquids are thermally stable (over 200 °C in N2 and over 180 °C in O2 atmosphere) and electrochemically stable with electrochemical stability windows on platinum in the range from 4.7 V (PYR12O1FSI) to 5.4 V (PYR12O1IM14). Conductivity decreases in the series FSI-TFSI-BETI-IM14 according to the viscosity increase. DSC measurements showed no crystallisation down to −150 °C for PYR12O1TFSI and PYR12O1IM14.

► Synthesis of high purity pyrrolidinium-based ionic liquids.
► The side chain ether groups leads to room temperature ionic liquids.
► Non-crystallisable ionic liquids.
► High thermal and electrochemical stability.