BODIPY dyes are widely used as fluorescent labels and sensors, due to their high molar extinction coefficients, biocompatibility, sharp fluorescence with high quantum yields and photochemical stability.1Notably the stability of BODIPYs, particularly under acidic conditions, is critical for these applications. In this research, the stability of a series of 4,4′-disubstituted BODIPYs (−CN, −F, −Me, −Ph, −OMe) toward the addition of excess trifluoroacetic acid was investigated via 1H and 11B NMR, infrared, UV−vis, fluorescence, mass spectrometry, and thin layer chromatography.2 The results indicate that 4,4′- dicyano-BODIPY 2 show significantly enhanced stability to acidic conditions and remains unchanged even 3 days after addition of excess TFA.2,3 In contrast, 4,4′-dimethyl-BODIPY 3 and 4,4′- dimethoxy-BODIPY 5 are the least stable, and the 4,4′-diphenyl and 4,4′-difluoro-BODIPYs 1 and 4 were found to have intermediate stability upon the addition of TFA.2 The theoretical calculations indicate that upon TFA addition the 4,4′-dicyano-BODIPY forms an unusually stable BODIPY 2-TFA complex. Computational modeling demonstrates that this complex stabilizes the B−N bond, resulting in the most stable compound from the series studied. This characteristic of this fluorescent dye 2 is very important for its future applications, especially for its covalent attachment to peptides, antibodies, and other molecules for bioanalytic and bioimaging purposes.

Investigation on the stability of a series of BODIPYs in acidic conditions: Experimental and computational study into the role of the substituents at boron

2019 Fall National Meeting

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