A Red‐Emissive Fluorescent Probe with a Compact Single‐Benzene‐Based Skeleton for Cell Imaging of Lipid Droplets

Abstract Lipid droplets (LDs) are important organelles associated with many physiological processes as well as diseases. To visualize LDs and study their versatile functions, the fluorescence imaging technique is one of the most powerful tools. Thus, the development of fluorescent probes for LDs imaging has attracted increased attention in recent years. Herein, a new LDs fluorescent probe Ph‐Red is developed and its application in fluorescence imaging is carefully demonstrated. The probe Ph‐Red has a compact single‐benzene‐based molecular structure and can be easily synthesized via a one‐step reaction. Impressively, the probe displays strong red emission based on a very small π‐system consisting of only one benzene ring. Moreover, the probe shows high LDs staining selectivity and good cellular viability, and is tolerant for repeatedly fluorescence imaging. Given these advantages, the 3D confocal imaging in fixed cells as well as multicolor confocal imaging in live cells are successfully realized, highlighting the utility of the single‐benzene‐based fluorescent probe Ph‐Red for LDs imaging. In addition, the hydrophobicity of the probe and the molecular size are revealed to play critical roles for efficiently staining LDs, which are important insights for the development of new LDs fluorescent probes.