Fig. 2: 27Al MAS NMR and Raman spectroscopy on chloroaluminate ionic liquids.

a ²⁷Al MAS NMR spectra of [C₄Py]Cl-xAlCl₃ (x = 1-2.5). b Integrated FWHM of ²⁷Al resonances as a function of temperatures over [C₄Py]Cl-xAlCl₃. c Integrated FWHM of ²⁷Al resonances as a function of mole ratio of AlCl₃/[C₄Py]Cl (x) at different temperatures. d DFT-simulated Raman spectra of AlCl₄⁻, Al₂Cl₇⁻, and DCM. e Plot of the Raman area ratio of Al₂Cl₇⁻ versus the molar ratio of AlCl₃/ [C₄Py]Cl (x); (Note that the area ratio of Raman signals at 310 cm⁻¹ and 350 cm⁻¹ depends closely on the molar ratio of Al₂Cl₇⁻and AlC₄⁻, respectively, derived from the Raman spectra in Supplementary Fig. 9). f Relationship between integrated FWHM of ²⁷Al resonances and the Raman area ratio of Al₂Cl₇⁻ at 30 °C.