Yuexin Liu, Zihan Yan, Weiwei Niu, Daisuke Shiomi, Kazunobu Sato, Zhao-Yang Li, Guangwu Li, Zhe Sun
The synthesis of triplet-ground-state 1,14:11,12-dibenzopentacene (DP) has been sought after for over 60 years, but the isolation of stable derivatives in crystalline form has been unsuccessful. Herein, we report the synthesis and first single-crystal isolation of a stable DP derivative via a protection-oxidation-protection (POP) strategy. X-ray diffraction analysis reveals a twisted helical geometry, while variable-temperature electron paramagnetic resonance (EPR) and magnetic susceptibility measurements confirm its triplet ground state. Pulsed-EPR spectroscopy yields long spin-lattice (T1) and spin-spin (Tm) relaxation times of 3.58 ms and 0.49 µs at 70 K, respectively. Furthermore, electrochemical investigations unveil a unique four-stage redox profile. This work demonstrates that the POP strategy can provide synthetic access to triplet-ground-state DP diradical.