Alternating current (AC) magnetic susceptibility measurements were conducted using an AC susceptometer insert with an applied field of 1000 Oe. Fitting of the AC susceptibility was achieved using the generalised Debye model (Equation S1 and S2). The samples were prepared in gelatine capsules and sealed in eicosane. The diamagnetic contribution of the eicosane and the gelatine capsule were corrected for each measurement using Pascal's constant approximation of 0.5•Mr × 10 -6 emu mol -1 . 38