Selective Lower‐Occupied Through‐Bond Interactions for Efficient Organic Phosphorescence Enabling High‐Resolution Long‐Wavelength Afterglow

Abstract Persistent organic room‐temperature phosphorescence (RTP) enables high‐resolution afterglow bioimaging, independent of autofluorescence. However, the yield of organic RTP in the long‐wavelength region is generally low, which limits the high‐resolution information that can be obtained from the long‐wavelength region. Moreover, this makes it impossible to obtain multicolor and high‐resolution afterglow images. This report describes a molecule containing no atoms from the fourth or higher period that exhibits efficient red RTP in high yield. A molecule with red phosphorescent chromophores substituted with multiple phenylthio groups reached an RTP yield of 46.3% and an RTP lifetime of 0.43 s in an appropriate crystalline host medium. The selective lower‐occupied through‐bond or through‐space interactions among molecules significantly enhance the phosphorescence in the long‐wavelength region. The highly efficient and bright red persistent RTP induces a red afterglow from individual nanoparticles. Tuning the selective lower‐occupied through‐bond or through‐space interactions allows for the design of high‐performance RTP dyes and offers a novel approach to explore high‐resolution full‐color afterglow imaging.