Aggregation Models of Potential Cyclical Trimethylsulfonium Dicyanamide Ionic Liquid Clusters

Raman and infrared spectra of trimethylsulfonium dicyanamide [(CH3)3SN(CN)2] are reported and accurately reproduced by DFT methods (B3LYP and B3PW91), MP2, and MP3, and to a lesser extent by the RHF method. The (CH3)3SN(CN)2 ionic liquid forms two isomeric dimers that are of cyclic structure, one of which is 13 kcal/mol lower in energy than the other. Both isomeric cyclic pairs (versions 1 and 2), [(CH3)3SN(CN)2]2, have the potential to further combine and form a common structure containing four pairs of (CH3)3SN(CN)2. This structure can then conceivably undergo a stacking procedure to form extended ionic liquid nanotubes of eight ionic liquids, [(CH3)3SN(CN)2]8. The possible formation of gas phase ionic liquid clusters of two, four, and eight trimethylsulfonium dicyanamide ionic liquids is supported by highly exergonic free energy changes obtained from B3LYP/(6-311+G(d,p)) density functional calculations.