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 T₁ → T₀ transition, as the large energy gaps (T₀ → S₀ and T₁ → S₁) 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.