Phenoxazines with a Phototransferable N -Acetyl Group and Acrylate Linker: Assembly by C–H Activation, Photoconversion to Fluorescent Dyes, Biolabeling, and Super-Resolution Imaging

-acetylphenoxazine scaffold results in a red shift (ca. 50 nm) in the absorption spectra, provides a site trapping the acetyl group cleaved off upon irradiation, and enables PA above 400 nm. Red-emitting PA oxazines having a CH═CHCONHR group were prepared and delivered to living and fixed cells. The PA probes incorporating HaloTag or BG-PEG amine (for labeling of Halo- or SNAP-Tags) were found to be cell-permeable and provided good images in (two-color) fluorescence microscopy and nanoscopy techniques, such as PALM (Photoactivation Localization Microscopy) and MINFLUX (MINimal FLUXes), based on the activation and detection of single molecules.