Unforgeable Red: Design and Application of SO‐Annulated Perylene Diimides for Anti‐Counterfeiting

ABSTRACT The modernization of counterfeiting activities represents a threat to society, making difficult to detect and eliminate fraudulent products. In this context, innovation in anti‐counterfeiting technologies is crucial to protect intellectual property and increase the level of security. Herein, we report the first sulfoxide‐annulated perylene diimides (PDI‐SO) as versatile photoactive materials for advanced anti‐counterfeiting. Chemoselective mono‐oxidation of S‐bridged perylene diimides affords a red‐emissive PDI‐SO dye that undergoes rapid, quantitative visible light‐induced deoxygenation to give the green‐emissive PDI‐S. The materials retain high fluorescence efficiency, thermal robustness, and excellent processability, allowing patterning from the centimeter to micrometer scale using low‐cost masks, high‐resolution photolithography, and maskless photopatterning, and enabling dual optical readouts. Applications on textiles and electronic substrates coupled with molecular verification via swab‐mass spectrometry demonstrate that SO‐bridged PDIs provide a powerful, multi‐level, and difficult‐to‐replicate platform for secure authentication technologies.