Synthesis and Photophysical Properties of AIE-Type Carbazole-Capped Triphenylmethyl Organic Radicals Featuring Non-Aufbau Electronic Structure and Enhanced Photostability

In this study, we report two novel donor–acceptor (D-A•)-type triphenylmethyl radicals, TTM-1TPE-2Cz and TTM-2TPE-2Cz, synthesized by integrating an aggregation-induced emission (AIE)-active 2-(1, 2, 2-triphenylethenyl)-9H-carbazole (TPE-2Cz) donor with tris(2,4,6-trichlorophenyl)methyl (TTM) radical core. Despite the AIE unit’s conventional ACQ-suppressing capability, both radicals exhibit complete emission quenching in solid/solution states but demonstrate 655 nm red emission in polymethyl methacrylate (PMMA)-doped films. Theoretical and experimental analyses reveal that the flexible TPE moiety unexpectedly enhances non-radiative decay while establishing a non-Aufbau electronic configuration through its strong electron-donating nature (−5.16 eV HOMO vs. −5.75 eV SOMO). Remarkably, these radicals achieve unprecedented photostability with half-lives (t₁/₂) 39,000- and 12,000-fold greater than pristine TTM, respectively. This work not only presents a synthetic strategy for stable radicals through non-Aufbau electronic engineering but also elucidates critical structure–property relationships between AIE units and radical photophysics.