Effect of structural and solvation factors on aggregation, pH stability, lipophilicity, and antimicrobial activity of mono- and diiodo-substituted boron(iii) dipyrromethene luminophores

A comparative analysis was carried out to examine the effect of solvent nature and the specific features of molecular structure on aggregation behavior, pH stability, hydrophobicity, and antimicrobial activity of 2-iodo-tetramethyl-ethyl-BODIPY (where BODIPY is boron(iii) dipyrromethene) (1), 2,6-diiodo-tetramethyl-BODIPY (2), and 2,6-diiodo-tetramethyl-BODIPY containing an ester residue of butanoic acid (3) in the meso-spacer as potential photosensitizers for antimicrobial photodynamic therapy. All the studied compounds demonstrated a sufficiently high stability in both acidic and alkaline media. The introduction of iodine atoms into the pyrrole rings and the substitution of the hydrogen atom at the meso-position of the BODIPY core with an ester residue significantly (up to ∼1.4 times) increase the hydrophobicity of the luminophores compared to the tetramethylated analogue. In this case, compound 1 exhibits bactericidal activity against Staphylococcus aureus under irradiation at a wavelength of 530 nm, compound 2 demonstrates an activity that is 16 times lower, and BODIPY 3 does not show any antimicrobial activity under these experimental conditions.