Indexed by:期刊论文

Date of Publication:2013-12-16

Journal:CHEMISTRY-A EUROPEAN JOURNAL

Included Journals:PubMed、SCIE、Scopus

Volume:19

Issue:51

Page Number:17472-17482

ISSN No.:0947-6539

Key Words:fullerenes; photochemistry; photooxidation; sensitizers; UV; Vis spectroscopy

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 (450-650nm). 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 ((T)=132.9s) than the C-60-localized T-1 state (ca. 27.4s). We found that the C-60 triads and tetrads can be used as dual functional photocatalysts, that is, singlet oxygen (O-1(2)) and superoxide radical anion (O-2(.-)) photosensitizers. In the photooxidation of naphthol to juglone, the O-1(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.