Air‐Stable Luminescent Schlenk Diradical With Triplet Ground State

Luminescent diradicals hold great promise for optomagnetic applications, yet those with a triplet ground state remain largely underexplored for the inherent high reactivity from two spin‐parallel unpaired electrons, which hinders synthesis and enhances non‐radiative quenching. Herein, we report the first luminescent Schlenk diradical 2 with a distinct triplet ground state, concisely assembled from a methoxybenzene core and four polychlorobenzene pendants and readily isolated under air by routine silica‐gel chromatography. Good stability results from the steric hindrance of its propeller conformation, which effectively safeguards the two carbon radical centers. Comprehensive characterization elucidated the molecular structure and confirmed a triplet ground state with strong magnetic exchange interaction ( J/k B > 320 K). Notably, diradical 2 shows a red emission at 619 nm with a quantum yield of 9.6% in cyclohexane, facilitated by its rigid propeller conformation and the D–A electron distribution for the coexistence of electron‐rich methoxybenzene and electron‐deficient polychlorobenzenes. The luminescence predominantly originates from the T 1 → T 0 transition, as the large energy gaps (T 0 → S 0 and T 1 → S 1 ) prohibit singlet‐state luminescence. This work not only enlarges the Schlenk hydrocarbon family but also opens new avenues for the understanding and design of luminescent high‐spin species.