An Ionic Liquid Consisting of Crown Ether – Coordinated Hydronium Cation and Amide Anion

Abstract

We first report an ionic liquid (IL) that consists of hydronium (H3O+) ion encapsulated by 18–crown–6–ether (18C6) and an amide anion. The composition of the crown ether–coordinated hydronium amide IL was estimated to be as [H3O+•18C6][Tf2N–]. The presence of H3O+ was revealed from the characteristic bands of the hydronium ion present in the infrared spectra. The melting point of [H3O+•18C6][Tf2N–] was 68–70 °C. At 70 °C, the viscosity of [H3O+•18C6][Tf2N–] was 39.5 mPa s, the conductivity was 1.9 mS cm–1, and the density was about 1.32 g cm–3. These bath properties of [H3O+•18C6][Tf2N–] were similar to those of common ILs at room temperature.