Amino Donor–Acceptor Stenhouse Adducts as Visible‐Light‐Responsive Intrinsically Emissive Photoswitches for Dynamic Cellular Imaging

ABSTRACT Combining efficient photoswitching with emission into a single chromophore remains a major challenge, as the structural requirements for one function are often antagonistic to the other. Here, we report amino donor–acceptor Stenhouse adducts (aDASAs) as a new class of intrinsically emissive photoswitches that overcome this limitation. By introducing a sulfonamide at the C 2 position, we interrupt the full isomerization pathway and impact isomer distribution ratios under irradiation, enabling single‐wavelength visible‐light photoswitching and fluorescence to coexist within the same thermodynamically favored chromophore. Optimizations yield compounds with red‐shifted absorption, record photoluminescence quantum yields representing a six‐fold improvement over previous donor–acceptor Stenhouse adducts, and enhanced stability in biologically relevant solvents. These new intrinsically emissive photoswitches correlate fluorescence intensity with switching equilibria, allowing reversible light‐induced dimming that creates a fluorescence winking effect. Optimized aDASAs enable robust cytoplasmic visualization in both fixed and live human embryonic kidney (HEK293T) cell imaging, and repeated on/off fluorescence dimming occurs with minimal irreversible photobleaching in fixed cells and with little to no impact on cell viability. This shared‐chromophore design provides precise spatiotemporal control for dynamic biological imaging and establishes aDASAs as potential light‐responsive probes for confocal and super‐resolution microscopy.