Imidazolium dialkylphosphates—a class of versatile, halogen-free and hydrolytically stable ionic liquids

Abstract

In this article a systematic and detailed study on the synthesis and the properties of dialkylphosphate ionic liquids is presented. This class of halogen-free ionic liquids is easily available in high quality and great variability by direct alkylation of nucleophiles, such as 1-methylimidazole, 1-ethylimidazole, 1-butylimidazole and 1-(2-methoxyethyl)-imidazole with different trialkylphosphates, such as trimethylphosphate, triethylphosphate or tributylphosphate. In general, these dialkylphosphate ionic liquids were found to display very attractive physico-chemical properties with great technical potential, especially in low temperature (<200 °C) applications with water present. For this specific application area, the materials described here clearly show superior properties compared with alkylsulfate ionic liquids due to their obviously much higher hydrolytic stability.