Synthesis and properties of NIR aza-BODIPYs with aryl and alkynyl substituents on the boron center

NIR diaryl aza-borondipyrromethene dyes (C-aza-BODIPY) and dialkynyl aza-borondipyrromethene dyes (E-aza-BODIPY) were synthesized from difluoro aza-borondipyrromethene dyes (F-aza-BODIPY) in 45–83% yields. By X-ray analysis the N–B distances (1.603 and 1.606 Å) in C-aza-BODIPY were found to be longer than the corresponding bond of C-BODIPY by 0.02–0.04 Å. C-aza-BODIPYs display remarkable blue shifts and low fluorescence quantum yields, and E-aza-BODIPYs have moderate fluorescence quantum yields (0.16–0.29). C- and E-aza-BODIPYs display good stability in weak acidic and basic conditions. E-aza-BODIPY was dialytic and suitable to staining of living cells.