Cucurbit[8]uril Confined 6‐Bromoisoquinoline Derivative Dicationic Phosphorescent Energy Transfer Supramolecular Switch for Lysosome Targeted Imaging

Abstract Phosphorescent materials constructed by macrocyclic host confined guest has become a research hotspot in bioimaging. Herein, a highly efficient phosphorescent light‐harvesting supramolecular switch constructed by cucurbit[8]uril (CB[8]) encapsulated dicationic 6‐bromoisoquinoline derivative (G), sulfonatocalix[4]arene (SC4AD), near‐infrared (NIR) fluorescence dyes, and diarylethene molecular switch (1) is reported. First, the resulting supramolecular foldamer formed by G and CB[8] works as a phosphorescent donor with phosphorescence at 605 nm. When secondary assembling with SC4AD, the phosphorescent emission peak of G⊂CB[8] generates a hypsochromic shift to 583 nm with a 6.4‐fold enhancement of intensity. Further, NIR fluorescence dyes Nile Blue (NiB) and Sulfo‐Cyanine 5 (cy5) are introduced to the assembly as acceptors to construct phosphorescent light‐harvesting systems. As expected, light‐harvesting systems with energy transfer efficiency of 57.5%/75.7% and a high antenna effect of 359.7/247.7 are constructed at an efficient donor/acceptor ratio of 100:1/15:2 for NiB and cy5, respectively. After co‐assembly with diarylethene derivative (1), the phosphorescence transferred from G⊂CB[8]@SC4AD/NiB (or cy5) to 1 and caused the photoluminescence quenching after irradiation by 365 nm light. And the photoluminescence of the light‐harvesting system was restored with the irradiation by >450 nm light. The highly efficient phosphorescent light‐harvesting system is applied to lysosome targeted imaging in HeLa cells and information encryption.