Halogen-substituted meso-BODIPY ethers as effective photosensitizers for antimycotic photodynamic therapy

We conducted a comprehensive study of the influence of the molecular structure and solvent nature on the photophysical properties of the halogen-substituted meso-BODIPY ethers. The compounds were found to be stable over a wide range of pH values and exhibited intense chromophoric properties (lgε ∼ 4.60–5.02) at 497–536 nm. The halogenation at the 2,6-positions of the pyrrole rings of dyes causes a noticeable (up to 36 nm and 44 nm) red shift of the maximum of the absorption and fluorescence bands, respectively, and sharp fluorescence quenching up to φfl ∼ 2–32 %. The introduction of a bulky ester substituent into the meso-position of the dipyrromethene core increases the photostability of the dyes up to ∼ 2.7 times due to screening of the methine spacer. Moreover, the halogen-substituted BODIPYs demonstrated a high ability to generate singlet oxygen (up to ФΔ ∼50–78 %) regardless of the nature of the solvent. Among the studied dyes, the diiodo-substituted meso-BODIPY ether has an appreciable inhibitory effect on the vital activity of fungal cells. In summary, the combination of the meso-substitution and halogenation of the BODIPY core is an excellent way to enhance the affinity of dyes to biostructures and to increase the possibilities of the practical application of dyes as effective photosensitizers for antibacterial photodynamic therapy.