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.