Fig. 2. (a) Frequency dependence of the imaginary component of the AC susceptibility of 1bulk in B_dc = 0.2 T multiplied by temperature to be readable in the whole 2–80 K temperature range. (b) Temperature dependence of the relaxation time of the magnetic susceptibility measured in B_dc = 0.2 T for the pure and the diluted samples of 1: two dispersions in polystyrene with 1 : 5 and 1 : 10 mass ratio and a 200 mM CH₂Cl₂ : toluene frozen solution (see legend). The black solid line corresponds to the best-fit of 1bulk data using eqn (1), while the broken lines correspond to simulation with T^–n law. T₁ for the diluted sample, extracted from pulsed EPR spectra, are shown for comparison. (c) Field dependence of the relaxation time of the magnetic susceptibility of 1bulk and 1sol_{200 mM} frozen solution sample (see legend). The solid lines represent the best fit obtained with eqn (3). Best fit parameters are reported in Table 1.