Ready BODIPY-Tagging of Carboxylic Acids

Meso-aminoBODIPY and four functionalized analogues are presented as stable and efficient starting materials for the tagging of carboxylic acids via the classical Steglich amidation protocol (DCC, DMAP) at room temperature. Using this methodology, 18 new derivatives were synthesized in moderate-to-high yields (30-86%) from unsubstituted meso-aminoBODIPY, along with four additional analogues obtained from functionalized amino derivatives in yields ranging from 50 to 77%. This approach displayed excellent tolerance toward the functional groups present in the starting carboxylic acids. Photophysical studies on selected BODIPYS in chloroform reveal that the amidation results in a strong bathocromic shift (60-80 nm) in both absorption and emission maxima with a particular fluorochromism from blue to green. In addition, the meso-amide derivatives maintain a very high fluorescence quantum yield of their amine precursors with short lifetimes and properties that will be applied for fluorescence sensing.