Para‑Xylyl bis‑1‑methylimidazolium bis(trifluoromethanesulfonyl)imide: Synthesis, crystal structure, thermal stability, vibrational studies

Abstract

In this study, a new para‑xylyl linked di‑imidazolium [p‑C6H4(CH2ImMe)2+] ionic liquid (DIL) containing the bis(trifluoromethanesulfonyl)imide [(CF3SO2)2N−] anion is synthesized. The method is based on the alkylation reaction of 1‑methyl imidazole, followed by anion exchange. The obtained DIL is characterized by 1H NMR, 13C NMR, 19F NMR and FT-IR spectroscopy. The melting point and the subsequent decomposition of [p‑C6H4(CH2ImMe)2+][(CF3SO2)2N−]2 are measured by using differential scanning calorimetry (DSC) and thermogravimetric (TGA) analyses in the temperature range from 25 to 700°C. Thermal analysis indicated that this DIL melted below 100°C and can, therefore, be classified as an ionic liquid. Vibrational spectroscopy studies were conducted by infrared (IR), Raman (FT-Raman) spectroscopy and DFT calculations. Moreover, the crystal structure is investigated by single crystal X-ray diffraction (XRD) method. The X-ray studies on [p‑C6H4(CH2ImMe)2+][(CF3SO2)2N−]2 show that it crystallizes in the monoclinic system with space group P21/c. The theoretical structural parameters such as bond lengths, bond angles and dihedral angles determined by DFT methods are in good agreement with the XRD results.