The 𝜒 quadrupolar parameter for FSPA ethanol was taken from a fit of the low temperature experimental data, as shown in Figure . The corresponding values for the methyl group of the acetone solvate were taken from the literature , with the effect of rapid rotational diffusion accounted for by applying Eq. S2, with the angles α = 0, β = 70.50°, resulting in the values χ = 53.25 kHz, η = 0.