Perylenebisimide-fullerene dyads as heavy atom free triplet photosensitizers with unique singlet oxygen generation efficiencies

We report the synthesis, characterization, photophysical and photochemical properties of two novel perylenebisimide-fullerene dyads (7 and 8) bearing one or two perylenebisimide (PBI) units as light harvester and a fullerene as spin converter. The molecular structures of all synthesized compounds were elucidated by elemental analyses, mass spectrometry, FT-IR, H-1 and C-13 NMR techniques. Their optical properties were investigated by UV-vis absorption and 2D/3D fluorescence emission spectroscopies. The photochemical studies via direct and indirect method endorsed PBI-fullerene dyads (7 and 8) as efficient heavy atom free triplet photosensitizers whereas perylene derivatives did not exhibit any singlet oxygen production. The PBI-fullerene dyads exhibit excellent singlet oxygen quantum yields of 0.93 and 0.95. The PBI-fullerene dyads (7 and 8) are also able to use in the photooxidation of 1,5-dihydroxynaphtalene (DHN) to produce juglone and are recognized as stronger than MB as conventional triplet photosensitizers.