Dual‐Color Photoconvertible BODIPY Dyes Based on Visible‐Light Photouncaging of Nitrobenzyl Moieties for Living‐Cell Imaging

Abstract Photoactivatable fluorophores are useful tools in live cell imaging due to precise spatial and temporal control. Herein, a tandem visible‐light photodecaging and tautomerization strategy is proposed as an activation mechanism for the construction of photoconvertible boron dipyrromethenes (BODIPY) dyes, from which nitro‐benzyloxy BODIPY derivatives are developed as a new class of visible light photoactivated fluorophores. Upon exposure to visible light, the nitro‐benzyloxy moiety is released and the BODIPY moiety is converted to the keto‐form BODIPY analog by tautomerization. The photoconversion process not only achieves over 50 nm blue shift of absorption/emission maxima but also provides bright fluorescence for both the pre‐ and post‐activation forms. Mechanism studies indicate that no indications of radical species and singlet oxygen are involved in this unique photoconversion and both UV and visible light irradiation can efficiently activate this photoinduced release of the nitrobenzyl alcohol through photoexciting of BODIPY core rather than classical nitro‐benzyloxy photocage. Cell and vesicle imaging is successfully performed using the new photoconversion dyes. The results show that these new photoconvertible dyes are highly efficient, universal, and non‐cytotoxic, which are valuable for the development of promising photoactivated molecules.