Another important property of cg-2 is its ability to maintain spin state, which is crucial for exploring spin-based applications . In radical systems, spin relaxation from excited state to ground state is mainly triggered by the interactions with surrounding environment or itself, as the rate of spontaneous relaxation is negligible. Thereby, the spin-lattice relaxation time (T1) and coherence time (Tm) of cg-2 were measured to be 96 μs and 0.8 μs at 100 K and the field of 3401 G (Supplementary Fig. ), respectively, using inversion-recovery method (π-T-π/2-τ-π-τ-echo) and modified Hahn-echo pulse sequency (π/2-τ-π-τ-echo). The relatively shorter relaxation time of cg-2, compared with typical carbon-centered radicals , are probably due to the influence of numerous magnetic proton nuclei on the substituents. Moreover, the Rabi frequency 𝛺𝛺 𝑚𝑚 ±1 ↔𝑚𝑚 0 of 8.21 MHz for cg-2 provides the experimental timescale (τspin-flip = 61 ns) for one spin-flip operation