This computational study addresses the possible isomerisation of 1,2,3-trialkylimidazolium and 1-alkylpyridium ion pairs through proton transfer. The formation of neutral species in protic room temperature ionic liquids has been well studied, but the mechanism in other, “non-protic” species has been subject to less investigation.
Oldamur Hollóczki and László Nyulászi from Budapest University of Technology and Economics carried out the DFT study after observing that the “protic nature” of an ionic liquid depends not only on the cation, but on the cation/anion assembly. Their investigations determined that the formation of neutral species is a viable possibility for ion pairs containing sufficiently basic anions, such as organic acids . This, they say, means that the description of imidazolium or pyridinium based ionic liquids with basic anions as pure ionic substances is oversimplified. The presence of trace amounts of neutral species could affect the physical properties of the ILs and any basic anions present could result in unexpected reactions in “inert” IL solvents.
Neutral species from “non-protic” N-heterocyclic ionic liquids
Oldamur Hollóczki and László Nyulászi
Org. Biomol. Chem., 2011, Advance Article