Theoretical Study Of Protic Ionic Liquids Composed Of N- Hexylethylenediaminium Trifluoromethanesulfonate

intermolecular hydrogen bonding interactions, and protonation sites of chelating mono-protic ionic liquids composed of N- Hexylethylenediaminium cations with a trifluoromethanesulfonate anion (TFS), forming [HHex][TFS], were studied using DFT calculations with the M06-2X functional and 6-311G(d, p) basis set. The BSSE-corrected interaction energies (∆E0BSSE) for all the investigated structures range from -98.3 to -108.3 kcal∙mol-1 . NBO and AIM analyses were applied to quantify the relative strengths of the hydrogen bonding interactions and to account for their effect on the stability of various molecular structures. The values of ∆E0BSSE decrease with increasing alkyl chain length and upon introduction of an ethyl branch in the cation. The second-order perturbation energy and electron density indicate that [HAlkyl]1＋[TFS] (protonated at the primary amine) are more stable than [HAlkyl]2＋[TFS] (protonated at the secondary amine).