Brønsted Acid−Base Ionic Liquids as Proton-Conducting Nonaqueous Electrolytes

A new series of Brønsted acid−base ionic liquids were derived from the controlled combination of a monoprotonic acid with an organic base under solvent-free conditions. Appropriate amounts of solid bis(trifluoromethanesulfonyl)amide (HTFSI) and solid imidazole (Im) were mixed at various molar ratios to have compositions varying from an equimolar salt to HTFSI- or Im-rich conditions. The mixture at equivalent molar ratio formed a protic neutral salt with a melting point of 73 °C, which was thermally stable at temperatures even above 300 °C. The melting points of other compositions were lower than those of the equimolar salt and Im or HTFSI, giving eutectics between the equimolar salt and HTFSI or Im. Some of…