Microheterogeneity in Ionic Liquid Mixtures: Hydrogen Bonding, Dispersed Ions, and Dispersed Ion Clusters

Mixtures of ionic liquids (ILs) having a common ion but differing in the identity of the anion or cation represent highly interesting media. By varying the composition, one can successfully modulate specific physicochemical, structural, and biological properties. The molecular interactions (coulombic, hydrogen-bonding, van der Waals, and π-π intermolecular forces) that determine the three-dimensional structure of pure ILs can indeed be modified by the addition of another IL. In this context, we present here a 1H NMR, Fourier transform (FT)-IR, thermogravimetric, and solvatochromic study of the structural features of IL binary mixtures based on a common imidazolium cation ([CnC1im]+) and anions of different size and hydrogen-bond acceptor ability. For each mixture, the analyses were carried out at different molar ratios of the two components.