Identification of the most suitable anion through 3p-ESEEM measurements. [C2C1im]+-based ILs containing 2 mM of TEMPOL as a spin probe. Frequency peaks are shown from the Fourier transformed,-summed, 3p-ESEEM measurements (measured at 50 K), with the Larmor frequency of the corresponding nuclear isotope at X-band shown for each anion studied and normalised to the 1H peak. All data sets were recorded at the maximum of the TEMPOL EDFS spectrum (Figure S1).
