The magnetic susceptibility-temperature products (χT) measured in a 0.1 T dc field at 300 K are 12.75 cm 3 K mol -1 for 3-Dy•C6H6 and 13.13 cm 3 K mol -1 for 4-Dy, with the deviation from the Dy(III) free-ion value ( 6 H15/2, χT = 14.17 cm 3 K mol -1 ) expected due to significant splitting of the mJ states by the crystal field; we do not discuss the corresponding data for that 𝑒 〈ln 𝜏〉 extracted from stretched exponential fits to magnetization decays is the most accurate way of characterizing magnetic relaxation on long timescales, providing the best agreement with 𝜏debye (ESI Section 7.5). Estimated standard deviations for ac, waveform and dc data were derived from the variance in logarithmic relaxation times, 𝜎 〈ln 𝜏〉 2