Synthesis and study of meso-phenothiazinyl 3-pyrrolyl BODIPY and its derivatives

Herein, we unveil the synthesis of meso-phenothiazinyl 3-pyrrolyl BODIPY and its derivatives via the condensation of 3-formyl phenothiazine with pyrrole, followed by oxidation using DDQ and complexation with BF₃·OEt₂. Subsequent oxidation with hydrogen peroxide afforded the corresponding sulfone derivative (3·SO2), while α-formylation of the appended pyrrole via the Vilsmeier-Haack reaction enabled further derivatization with diamines to yield bis(BODIPY) conjugates. The compounds were characterized by HR-MS, 1D/2D NMR spectroscopy, and photophysical studies revealed strong absorptions and emissions in the visible-NIR region with low to moderate quantum yields (3-21%). Biological evaluation demonstrated that the sulfone derivative 3·SO2 selectively stains cell membranes in non-permeabilized cells and lipid droplets in permeabilized cells without any cytotoxicity. Compared with the commercially available FAST DiO fluorescent dye, the probe exhibited a higher signal-to-noise ratio and strong fluorescence under 561 nm excitation, highlighting its potential for multiplex cellular imaging applications.