Extended Data Fig. 4: Ground state ESR.

a, Room temperature X-band cw-ESR of 200 µM toluene solutions of TTM-1Cz-An and TTM-1Cz-PhAn in the dark confirming their spin doublet ground states. The black traces are data, and the grey lines are simulations. The respective acquisition parameter values were microwave frequencies 9.3923 & 9.3927 GHz, field modulations of 5 & 20 μT, microwave powers of 200 & 100 nW, both being non-saturating. Simulation employed experimental parameter values with S = 1/2, g = 2.00355 (±0.00005), six A_iso(¹H) = 0.121 mT, one A_iso(C_{nat. abund.}) = 2.7 mT, and six A_iso(C_{nat. abund.}) = 0.55 mT. b, cw-ESR at X-band of 200 µM toluene solution of (TTM-1Cz)₂-An at 295 K, shown in the black trace with two simulations. The acquisition microwave frequency was 9.7715 GHz with power of 2 µW, the field modulation amplitude was 2 µT. As J > A, the hyperfine values are divided by a factor of two compared to TTM-1Cz-An. The best fit is provided by increasing the number of contributing protons with A(¹H) = 0.06 mT from twice the TTM-1Cz-An simulation in panel a (12 protons, sim2) to 14 protons (sim1). The conformational degrees of freedom in solution provide a range of exchange values, leading to an average in excess of the apparent hyperfine values.