Photoinduced Solution‐Stable Radicals via Intramolecular Charge Separation From anti‐Kasha Emissive BN‐Azepines

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.