Donor-acceptor BODIPY dyads, functionalized at the 2 and 6 positions with benzyl ester (BDP-DE) or carboxylic acid (BDP-DA) groups, were synthesized and characterized for their optoelectronic properties. The introduction of carbonyl groups increased the reduction potential of the BODIPY core by 0.15-0.4 eV compared to alkyl-substituted analogs. These dyads exhibited efficient intramolecular charge separation and triplet state formation through spin-orbit charge transfer intersystem crossing (SOCT-ISC), achieving singlet oxygen quantum yields of up to 92%, modulated by solvent polarity. The fluorescence and singlet oxygen generation of BDP-DAs depended on the ionization state of the carboxylic groups. Complexation of BDP-DAs with bovine serum albumin (BSA) significantly extended their excited state lifetimes, as shown by time-resolved fluorescence measurements. Fluorescence lifetime imaging microscopy (FLIM) studies in human colorectal carcinoma (HCT116) cells and pig small intestinal organoids (enteroids) revealed subcellular localization patterns. Specifically, the diacid with a dimethoxyphenyl group (DA1) displayed longer lifetimes in lipid-droplet-like structures, while the diacid containing a meso-anthracenyl group (DA2) formed distinct 'islands' in cell monolayers, exhibiting a lifetime gradient. These results underscore the potential of donor-acceptor BODIPYs as fluorescent probes for distinguishing cellular environments.
Keywords: BODIPY; Triplet state; fluorescence lifetime imaging; photoinduced electron transfer; singlet oxygen.
© 2024 Wiley‐VCH GmbH.