N-methyl-N-alkylpyrrolidinium nonafluoro-1-butanesulfonate salts: ionic liquid properties and plastic crystal behaviour

A series of N-methyl-N-alkylpyrrolidinium nonafluoro-1-butanesulfonate salts were synthesised and characterised. The thermophysical characteristics of this family of salts have been investigated with respect to potential use as ionic liquids and solid electrolytes. N-Methyl-N-butylpyrrolidinium nonafluoro-1-butanesulfonate (p1,4NfO) has the lowest melting point of the familyat 94 °C. Electrochemical analysis of p1,4 NfO in the liquid state shows an electrochemical window of ∼6 V. All compounds exhibit one or more solid–solid transitions at sub-ambient temperaturesindicating the existence of plastic crystal phases.