Achieving Intrinsic Luminescence of Pure Organic Mono- and Di-Radicals in Aggregated States

Organic luminescent radicals are promising for optoelectronic applications, yet their practical implementation remains hindered by aggregation-caused quenching (ACQ) in aggregated states. In this study, we present a molecular design strategy that enables unprecedented intrinsic luminescence from pure radicals across multiple aggregated states, including crystalline states, powders, and amorphous films, through the incorporation of sterically demanding TPP (2,4,6-triisopropylphenyl) groups. Comprehensive photophysical characterization coupled with structural analysis reveals that the TPP moieties effectively suppress detrimental intermolecular interactions, particularly exchange coupling and π–π stacking between radical centers. The luminescent properties were analyzed via systematic theoretical calculations. The universality of this design principle is further demonstrated through its successful application to diradical systems, including Chichibabin's and Müller's hydrocarbons, which exhibit significantly enhanced emission in aggregated states. This work establishes a generalizable strategy for designing stable and efficient luminescent radicals in aggregated states, opening new avenues for radical-based optoelectronic devices.