BOPHY Dyes Bearing Arylsulfenyl Moieties as Highly Efficient Triplet Photosensitizers

Encouraged by the successful application of BOPHY dyes in a wide range of scientific fields, from energy to biology, the design of novel compounds based on this type of scaffold appears to be warranted. Herein, we have synthesized a family of symmetric BOPHY dyes bearing arylsulfenyl groups at the 2- and 7-position of the main core, which were fully characterized. The molecular structures were confirmed by the X-ray diffraction (XRD) technique. The photophysical properties were investigated in detail, including spectroscopic measurements and laser flash photolysis experiments. Both the singlet and the triplet excited states of the novel BOPHY dyes were characterized in different solvents. Considering their intersystem crossing quantum yields, these dyes were found to be suitable triplet photosensitizers in bimolecular systems for photon upconversion based on triplet-triplet annihilation. Furthermore, not only direct but also indirect experiments revealed that they effectively acted as photosensitizers for singlet oxygen generation, making them potential candidates for biological applications.