Determination of the quantum yield of singlet oxygen sensitized by halogenated boron difluoride dipyrromethenes

The spectral–luminescent, photophysical, and photochemical properties of dichloro-, dibromo-, and diiodo-derivatives of boron dipyrromethenate (BODIPY) have been studied, as well as the feasibility of generating singlet oxygen ( 1 O 2 ) via its photosensitization by the dihalogenated derivatives of BF 2 dipyrromethene in solutions. Quantum yields of singlet oxygen have been determined using 1,3-diphenylisobenzofuran as the 1 O 2 trap. The lowest fluorescence quantum yields have been shown to correspond to the maximum yields of singlet oxygen. It has been found that the best 1 O 2 photosensitizer among the three test dihalotetraphenylaza- BODIPY is dibromotetraphenylaza-BODIPY, which in addition possesses the highest photostability. Diiodotetramethyl-BODIPY results in the singlet oxygen yield close to unity, but it has significantly lower photostability. The yield of singlet oxygen is affected by the solvent. Dibromtetraphenylaza-BODIPY and diiodotetramethyl-BODIPY may find use as a medium in photodynamic therapy and photocatalysis of oxidation reactions.