Effect of iodine substitution pattern on the singlet oxygen generation and solvent depended keto-enol tautomerization behavior of BODIPY photosensitizers

The novel iodinated-BODIPY derivatives (la and 1c) containing one or three iodine atoms were synthesized for the first time. The photochemical and photophysical properties of these BODIPYs were investigated and results were compared with two (lb) and four (1d) iodine bearing BODIPY derivatives. Surprisingly, the addition of iodine atoms to the meso-aryl positions of the phenyl moiety caused a color change due to the transformation of the enol form of the aromatic OH group to its keto form depending on the using solvent. This solvent affected keto-enol tautomerization on the BODIPY compounds was determined for the first time.