Persistent and stable radicals remain challenging to generate via photoinduction, despite their vast potential in magnetics and energy storage. Trisubstituted amines offer a promising platform for photoinduced radicals, but rapid charge recombination prevents the formation of nitrogen radical cations. Herein, we report a series of BN-azepines featuring a negatively curved heptagon that enforces a twisted, rigid donor–acceptor architecture, enabling solution-stable radicals via photoinduced charge separation. In the twisted heptagon backbone, boron captures an electron from nitrogen upon photoexcitation, yielding a charge-separated singlet state, and the small singlet–triplet energy gap further facilitates the formation of a longer-lived triplet charge-separated state. This provides sufficient time for the boron-localized electron to be lost, ultimately generating the nitrogen radical cation. Importantly, these BN-azepines also exhibit anti-Kasha emission and singlet oxygen sensitization. This work establishes a novel molecular design strategy for photoinduced radical generation and positions BN-azepines as promising candidates for future optoelectronic applications.
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