Novel ionic liquids composed of only heterocycles

Abstract

We prepared novel ionic liquids containing halogen-free anions. Heterocyclic anions were selected to prepare ionic liquid with low melting point and viscosity. Salts were prepared by neutralization between 1-ethyl-3-methylimidazolium hydroxide and corresponding heterocyclic acids. Some of sulfide salts having heterocyclic structure became ionic liquid and showed relatively low glass transition temperature (Tg). On the other hand, the salts containing azolate anion such as triazolate, became excellent ionic liquids, they showed the Tg at -80°C by the effect of negative charge derealization. The ionic liquid containing azole anion showed high ionic conductivity of 8.9 × 10-3 S cm-1 at room temperature reflecting low Tg and low viscosity (42.5 cP at room temperature). This paper reports the preparation and characteristics of novel ionic liquids composed of halogen-free heterocyclic anions and cations.