Physicochemical properties of imidazo-pyridine protic ionic liquids

A new class of protic ionic liquids (PILs) were prepared by reacting imidazo-[1,2a]-pyridine (ImPr) with benzene-1,2-dithiol (BDT), oxalic acid (Ox), phthalic acid (Phth), pimelic acid (Pim), and sulfuric acid. [ImPr][HSO4] was determined to be the most thermally stable PIL with a decomposition temperature of 326 degrees C and could potentially be used as an electrolyte in fuel cells and lithium ion batteries. X-ray crystallography on oxidized [ImPr][BDT] indicated the formation of the first reported disulfide PIL. [ImPr][Pim] and [ImPr][Phth] showed fragile behaviour. A Walden plot indicated ionic behaviour close to ideal for [ImPr][Phth].