Amphiphilic Near-IR-Emitting 3,5-Bis(2-Pyrrolylethenyl)BODIPY Derivatives: Synthesis, Characterization, and Comparison with Other (Hetero)Arylethenyl-Substituted BODIPYs.

A series of 3,5-bis(hetero)arylethenyl-substituted BODIPY derivatives have been prepared by Knoevenagel-type condensation of alkyl-substituted BODIPY with the corresponding aldehydes. 2-Pyrrolylethenyl-substituted derivatives feature near-IR emission (λem > 700 nm) with a high fluorescence quantum yield. Both the emission maxima and fluorescence quantum yields are relatively insensitive to solvent polarity, contrary to the corresponding near-IR-emitting 4-(N,N-dimethylaminophenyl)ethenyl derivatives. Alkylation at the N-pyrrolic position of the ethenyl substituent allows for the installation of the hydrophilic PEG group and afforded amphiphilic BODIPY derivatives. Overall, 2-pyrrolylethenyl-substituted BODIPY derivatives appear to be versatile fluorophores with potential applications in near-IR imaging.