Tailoring the properties of acetate-based ionic liquids using the tricyanomethanide anion

Abstract

The equilibrium and transport properties of mixtures of two ionic liquids – [C₄C₁Im][OAc] and [C₄C₁Im][C(CN)₃] – were determined and interpreted at the molecular level using vibration spectroscopy, NMR and molecular dynamics simulation. The non-ideality of the mixtures [C₄C₁Im][OAc]_(1−x)[C(CN)₃]_x was characterized by V^E = +0.28 cm³ mol⁻¹ (293 K, x = 0.65) and H^E = −2.2 kJ mol⁻¹ for x = 0.5. These values could be explained by a rearrangement of the hydrogen-bond network of the mixture that favours the interaction of the acetate anion with the imidazolium cation at position C2. The dynamic properties of the mixture are also dramatically influenced by the composition with a decrease of the viscosity and an increase of self-diffusion coefficients of the ions when the amount of tricyanomethanide anion increases in the mixture.