Synthesis and Spectroscopy of Benzylamine-Substituted BODIPYs for Bioimaging

Three new boron dipyrromethene (BODIPY) dyes substituted with a benzylamino group at the 3-position have been synthesized from halogenated BODIPYs by nucleophilic substitution. The spectroscopic and photophysical properties have been explored in different solvents and have been compared with an analogous 8-benzylaminoBODIPY derivative. The position of the benzylamino group has a significant influence on the spectral band positions, fluorescence quantum yields, and fluorescence lifetimes. The 8-benzylaminoBODIPY emits in the blue range, whereas the 3-substituted shows green fluorescence. Additionally, the extension of the conjugation at the 5-position of 3-benzylaminoBODIPY produces a bathochromic shift of the absorption and emission spectra. The effect of solvents on their spectroscopic features has been investigated using the generalized Catalán solvent scales. Quantum-chemical calculations have been performed to assess the effect of the position of the substitution on the spectroscopic properties. Finally, the BODIPY dyes have been employed as probes in fluorescence lifetime imaging of living cells, demonstrating their high potential for bioimaging.