Luminescent radicals are an emerging class of materials for organic electronics, bioimaging, and quantum applications. Circularly polarized luminescence (CPL) from luminescent radicals with propeller-type chirality remains challenging because it is difficult to simultaneously achieve high photoluminescence quantum yield (PLQY), high stability, and high racemization barriers. A series of brominated chiral luminescent radicals, CzTTBrM, 2CzTTBrM, and 3CzTTBrM, was obtained by attaching carbazole donors to TTBrM. The donor-acceptor-type design induces red to near-infrared (NIR) emission via charge transfer (CT) excited states with remarkably high PLQY (up to 76%) and high photostability. The new radicals possess high racemization barriers (ΔG‡(353K) = 27.9-29.1 kcal/mol), allowing the isolation of enantiopure compounds at room temperature. The enantiopure radicals exhibit CPL with broad emission across the red to NIR range (650-800 nm) and display BCPL values (0.76-1.1), nearly one order of magnitude higher than that of TTBrM (BCPL = 0.16). Moreover, doping these radicals into polystyrene microspheres produces whispering gallery mode (WGM) resonances, marking the first observation of WGM emission from luminescent radicals. This strategy establishes a versatile platform for integrating spin, chirality, and luminescence, offering new opportunities for applications in electroluminescence, bioimaging, and quantum photonics.
NAKAMURA et al. (Fri,) studied this question.
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