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

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.