Rational design of halo-imidazolium-based ionic liquids: tailoring the charge distribution to mimic the structure of real charge inverted analogues

This work aims at getting deeper insights into the relationship between electrostatics and nanostructure in ionic liquids (ILs). We hypothesize that, for (almost) isostructural ions, the key factor driving differences in structures is the distribution of charge around them. To test this idea, we have computationally examined the feasibility of inverting the charge distribution in the well-known di-alkyl imidazolium (Im) core through the fluorination of the 2-, 4- and 5-ring positions, expecting to create a distinct template at the nanoscale for these ILs. Our results suggest that (i) this strategy successfully inverts cation aromaticity, (ii) it induces different inter-ionic interactions, leading to polar threads of stacked anions and cations that form a (more branched) specular image of those observed in cyclopentadienyl salts, and (iii) additional strategies, such as further fluorination or simultaneous increment of both alkyl-tail lengths, allow further refinement of the resulting nanostructuration.