Near-Infrared Phosphorescent Switch of Diarylethene Phenylpyridinium Derivative and Cucurbit[8]uril for Cell Imaging.

Near-infrared (NIR) pure organic room-temperature phosphorescence (RTP) materials have received growing research interest due to their wide application in the fields of high-resolution bioimaging and luminescent materials. In this work, the authors report a macrocycle-confined pure organic RTP supramolecular assembly, which is constructed by diarylethene phenylpyridinium derivative (DTE-TP) and cucurbit[8]uril (CB[8]). Compared with CB[6] and CB[7], the larger cavity of CB[8] induces molecular folding and enhances the intramolecular charge transfer interactions, which leads to the obtained assembly emitting efficient NIR phosphorescence at 700 nm. Due to the photochromism of the diarylethene core, the NIR phosphorescence is reversibly regulated by light irradiation at wavelengths of 365 and >600 nm. Furthermore, cell-based experiments show that this supramolecular assembly is located in the lysosomes and displays a NIR phosphorescence at 650-750 nm. In addition, by means of phosphorescence resonance energy transfer, the obtained assembly exhibits a red-shifted NIR emission at 817 nm. This supramolecular phosphorescent switch provides a convenient path for the modular design of water-soluble pure organic room-temperature NIR phosphorescent materials.