Radical Enhanced Phosphorescence From Perylene‐Trityl Dyad in Solution at Room Temperature

ABSTRACT Phosphorescent organic chromophores are in high demand for diverse photonic and energy applications, including in electroluminescent and anti‐counterfeiting devices. Realizing phosphorescence typically requires heavy metal substitution, embedding chromophores within engineered matrices, or operating at low temperatures to suppress competing radiative and non‐radiative relaxations. Here we report that intramolecular interactions with a stable radical can promote phosphorescence, including at room temperature and in solution. We observe emission peaking at 840 nm in perylene covalently coupled to a tris(2,4,6‐trichlorophenyl)methane radical via a carbazole bridge. This metal‐free molecule exhibits strong magnetic exchange coupling that splits the triplet state into a pair of near‐degenerate levels of net doublet and quartet spin multiplicity, as verified by transient nutation data from pulsed electron paramagnetic resonance experiments. Optical spectroscopy and computational data confirmed a small energy gap between the triplet state of free perylene and the doublet‐quartet states in the dyad. We established that while residual prompt red emission originates from the luminescent radical state, the delayed NIR emission arises from radical‐enhanced phosphorescence along a spin‐conserving pathway with net doublet multiplicity. Our results indicate that stable radical elaboration is a new method for turning on room‐temperature phosphorescence in organic chromophores.