This review focuses on classifying different types of long wavelength absorbing BODIPY dyes based on the wide range of structural modification methods that have been adopted, and on tabulating their spectral and photophysical properties. The structure–property relationships are analyzed in depth with reference to molecular modeling calculations, so that the effectiveness of the different structural modification strategies for shifting the main BODIPY spectral bands to longer wavelengths can be readily compared, along with their effects on the fluorescence quantum yield (Φ_F) values. This should facilitate the future rational design of red/NIR region BODIPY dyes for a wide range of different applications.

The synthesis and characterization of a highly photostable bromo-substituted BODIPY dye (I) fused-ring-expanded with thienopyrrole moieties is reported. The results of MTT assays and flow cytometric analyses in living HeLa cells demonstrate that I has a high singlet oxygen quantum yield (Φ_Δ = 0.63) and exhibits photocytotoxicity upon irradiation in the NIR region making it potentially suitable for use in PDT.

Two energy transfer cassettes that exhibit a large pseudo Stokes' shift (up to 400 nm) due to efficient through-bond energy transfer (up to 99%) have been constructed. Selective binding of Fe(III) with the donor entity significantly suppresses the excitation energy transfer resulting in fluorescence quenching in aqueous solution and in living cells.