Multicolor Tuning of Perylene Diimides Dyes for Targeted Organelle Imaging In Vivo.

The adjustment of the emission wavelengths and cell permeability of the perylene diimides (PDI) for multicolor cell imaging is a great challenge. Herein, based on a bay-region substituent engineering strategy, multicolor perylene diimides () were rationally designed and synthesized by introducing azetidine substituents on the bay region of PDIs. With the fine-tuned electron-donating ability of the azetidine substituents, these showed high brightness, orange, red, and near infrared (NIR) fluorescence along with Stokes shifts increasing from 35 to 110 nm. Interestingly, azetidine substituents distorted to the plane of the dyes, and the twist angle of monosubstituted was larger than that of disubstituted , which might efficiently decrease their π-π stacking. Moreover, all of these dyes were cell-permeable and selectively stained various organelles for multicolor imaging of multiple organelles in living cells. Two-color imaging of lipid droplets (LDs) and other organelles stained with dyes was performed to reveal the interaction between the LDs and other organelles in living cells. Furthermore, a NIR-emitting dye with a mitochondria-targeted characteristic was successfully applied for tumor-specific imaging. The facile synthesis, excellent stability, high brightness, tunable fluorescence emission, and Stokes shifts make these promising fluorescent probes for biological applications.