Fine‐Tuning of Triphenylamine Pyridinium Salt Structure: A Tool for Detecting Organelle Microenvironments

Abstract The homeostasis of various organelles within cells is essential for maintaining cellular functions. Designing fluorescent probes with organelle‐targeting capabilities is a significant challenge. Mitochondria and lipid droplets (LDs) are two critical organelles. We have designed and synthesized four triphenylamine‐based fluorescent probes (1–4), each incorporating D–π–A and pyridinium salt structures, yet exhibiting distinct properties. Probe 1 and 2 demonstrate specific responses to viscosity, while probe 3 exhibits a pronounced response to polarity. Both probe 2 and 3 possess favorable cell membrane permeability and excellent photostability. Bioimaging results demonstrate that probe 2 and 3 selectively target LDs and mitochondria, respectively. Ultimately, probe 2 was employed to trace the dynamics of LDs within cells, while probe 3 was utilized to visualize mitophagy processes.