Synthesis of a Stable Crystalline Dibenzopentacene Triplet Diradical via a Protection–Oxidation–Protection Strategy

Abstract

ABSTRACT 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 ( T 1 ) and spin‐spin ( T m ) 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.