Synthesis, thermal properties, vibrational spectra and computational studies of Trioctylmethylammonium bis(trifluoromethylsulfonyl)imide ionic liquid

• Published in: Journal of molecular structure 2021-05, Vol.1232, p.130085, Article 130085
• Main Authors: Assenine, Mohammed Amin, Haddad, Boumediene, Paolone, Annalisa, Brandán, Silvia Antonia, Goussem, Mimanne, Villemin, Didier, Boumediene, Mostefa, Rahmouni, Mustapha, Bresson, Serge
• Format: Article
• Language: English
• Subjects: Aliquat 336; Bis (trifluoromethylsulfonyl) imide; Chemical Sciences; DFT calculations; FTIR/Raman measurements; or physical chemistry; Organic chemistry; Theoretical and; Thermal analysis; Trioctylmethylammonium
• ISSN: 0022-2860; 1872-8014; 0022-2860
• DOI: 10.1016/j.molstruc.2021.130085

•Aliquat bis (trifluoromethylsulfonyl) imide [NTF2−] is successfully synthesized.•Thermal stability investigated by TGA and DTA techniques.•The infrared and Raman spectra were measured and interpreted for the first time.•Complete vibrational assignments for [Aliquat+][NTf2−] have been reported.•The harmonic force fields of cation and anion were calculated by using SQMFF. In this work, Aliquat 336 ([Aliquat+]) based ionic liquids containing the fluorinated anion bis(trifluoromethylsulfonyl)imide [NTf2−] was successfully prepared by the anionic exchange replacement of the chloride anion. The reaction of lithium bis(trifluoromethylsulfonyl)imide with N-Methyl-N,N,N-trioctylammonium chloride ([N1,8,8,8][Cl] in water lead to the corresponding IL, namely ([Aliquat+][NTf2−]). The obtained ionic liquid was characterized by using infrared and Raman spectra and its structure was confirmed by 1H NMR, 13C NMR, and 19F-NMR. The thermal properties were investigated by two complementary thermal analysis techniques: TGA and DTA. A hexadentate coordination mode between cation-anion was predicted by atoms in molecules (AIM) studies for the [Aliquat+][NTf2−] IL by using B3LYP/6–31G* calculations where three O atoms of the anion in Cis conformation are linked to six H atoms of cation by S-O•••H interactions. Changes in the bond orders of S and O atoms of the cation supported such observations. The predicted cation-anion distances were in the range 2.30–2.60 Å. The harmonic force fields of cation and anion were calculated and the complete assignments were performed for both species while the most important bands observed in the infrared and Raman spectra of the IL were assigned. In addition, the scaled force constants of cation and anion of the IL were also reported. [Display omitted]