A focus on caging radicals: a catch-and-release mechanism for BODIPY photocages

Photocages enable the on-demand release of a payload in a closed chemical system upon irradiation with a suitable wavelength of light. Most photocages are described as releasing their payload through heterolytic cleavage of the photolabile bond, producing anionic and cationic fragments. Homolytic cleavage to form radicals is less commonly exploited as they react more indiscriminately and can generate unintended products. Poryvai and co-workers (A. Poryvai, A. Vasiļevska, K. Bangievská, J. Tarábek, S. Gerber-Lemaire and T. Slanina, Chem. Sci., 2026, 17, 11430, https://doi.org/10.1039/D6SC01848C) show how homolytic bond scission can instead be used to achieve a catch-and-release mechanism for radical payloads. Using a BODIPY-based photocage that responds to green light (525 nm), they demonstrate the capture of TEMPO and its subsequent release on demand. This behaviour was also applied to radical-based polymerisation. This work establishes design principles for the catch-and-release mechanism, and draws attention back to the often overlooked homolytic pathway in photocage chemistry.