Hydrophilic, Red-Emitting, and Thermally Activated Delayed Fluorescence Emitter for Time-Resolved Luminescence Imaging by Mitochondrion-Induced Aggregation in Living Cells.

Abstract

Thermally activated delayed fluorescence (TADF) materials have provided new strategies for time‐resolved luminescence imaging (TRLI); however, the development of hydrophilic TADF luminophores for specific imaging in cells remains a substantial challenge. In this study, a mitochondria‐induced aggregation strategy for TRLI is proposed with the design and utilization of the hydrophilic TADF luminophore ((10‐(1,3‐dioxo‐2‐phenyl‐2,3‐dihydro‐1H‐benzo[de]isoquinolin‐6‐yl)‐9,9‐dimethyl‐9,10‐dihydroacridin‐2‐yl)methyl)triphenylphosphonium bromide (NID‐TPP). Using a nonconjugated linker to introduce a triphenylphosphonium (TPP+) group into the 6‐(9,9‐dimethylacridin‐10(9H)‐yl)‐2‐phenyl‐1H‐benzo[de]isoquinoline‐1,3(2H)‐dione (NID) TADF luminophore preserves the TADF emission of NID‐TPP. NID‐TPP shows clear aggregation‐induced delayed fluorescence enhancement behavior, which provides a practical strategy for long‐lived delayed fluorescence emission in an oxygen‐containing environment. Finally, the designed mitochondrion‐targeting TPP+ group in NID‐TPP induces the adequate accumulation of NID‐TPP and results in the first reported TADF‐based time‐resolved luminescence imaging and two‐photon imaging of mitochondria in living cells.