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  • Energy‐Funneling‐Based Broa...
    Huang, Ling; Cui, Xiaoneng; Therrien, Bruno; Zhao, Jianzhang

    Chemistry : a European journal, 12/2013, Letnik: 19, Številka: 51
    Journal Article

    Abstract C 60 –bodipy triads and tetrads based on the energy‐funneling effect that show broadband absorption in the visible region have been prepared as novel triplet photosensitizers. The new photosensitizers contain two or three different light‐harvesting antennae associated with different absorption wavelengths, resulting in a broad absorption band (450–650 nm). The panchromatic excitation energy harvested by the bodipy moieties is funneled into a spin converter (C 60 ), thus ensuring intersystem crossing and population of the triplet state. Nanosecond time‐resolved transient absorption and spin density analysis indicated that the T 1 state is localized on either C 60 or the antennae, depending on the T 1 energy levels of the two entities. The antenna‐localized T 1 state shows a longer lifetime ( τ T =132.9 μs) than the C 60 ‐localized T 1 state (ca. 27.4 μs). We found that the C 60 triads and tetrads can be used as dual functional photocatalysts, that is, singlet oxygen ( 1 O 2 ) and superoxide radical anion (O 2 . − ) photosensitizers. In the photooxidation of naphthol to juglone, the 1 O 2 photosensitizing ability of the C 60 triad is a factor of 8.9 greater than the conventional triplet photosensitizers tetraphenylporphyrin and methylene blue. The C 60 dyads and triads were also used as photocatalysts for O 2 . − ‐mediated aerobic oxidation of aromatic boronic acids to produce phenols. The reaction times were greatly reduced compared with when Ru(bpy) 3 Cl 2 was used as photocatalyst. Our study of triplet photosensitizers has shown that broadband absorption in the visible spectral region and long‐lived triplet excited states can be useful for the design of new heavy‐atom‐free organic triplet photosensitizers and for the application of these triplet photosensitizers in photo‐organocatalysis.