Low melting ionic compounds of the general formula (cation) (R′SO4) in which R′ is a branched or linear, saturated or unsaturated, aliphatic or alicyclic functionalized or non-functionalized hydrocarbon chain with 3-36 carbon atoms are provided. These compounds can serve as ionic liquids, e.g. as solvents or solvent additives in chemical reactions, as extraction agents or as heat carriers. The compounds comprise a cation and anionic sulfate ester.