Wavelength dependent photochemistry of BODIPY-phenols and their applications in fluorescent labeling of proteins

A series of BODIPY dyes were synthesized, that were at the 3, or 3 and 5 positions, substituted by photochemically reactive quinone methide (QM) precursor moieties. Fluorescence properties of the molecules were investigated and we demonstrated that the molecules undergo wavelength dependent photochemistry. Photodeamination to deliver QMs takes place only upon excitation to higher excited singlet states, showing unusual anti-Kasha photochemical reactivity. The findings were corroborated by TD-DFT computations. Laser flash photolysis experiments could not reveal QMs due to low efficiency of their formation, but enabled detection of the phenoxyl radicals. The applicability of the molecules for fluorescent labeling of bovine serum albumin as a model protein upon photoexcitation at 350 nm was demonstrated