Broadband Visible Light-Absorbing [70]Fullerene-BODIPY-Triphenylamine Triad: Synthesis and Application as Heavy Atom-Free Organic Triplet Photosensitizer for Photooxidation.

A broadband visible light-absorbing []fullerene-BODIPY-triphenylamine triad () has been synthesized and applied as a heavy atom-free organic triplet photosensitizer for photooxidation. By attaching two triphenylmethyl amine units (TPAs) to the π-core of BODIPY via ethynyl linkers, the absorption range of the antenna is extended to 700 nm with a peak at 600 nm. Thus, the absorption spectrum of almost covers the entire UV-visible region (270-700 nm). The photophysical processes are investigated by means of steady-state and transient spectroscopies. Upon photoexcitation at 339 nm, an efficient energy transfer (ET) from TPA to BODIPY occurs both in and , resulting in the appearance of the BODIPY emission at 664 nm. Direct or indirect (via ET) excitation of the BODIPY-part of is followed by photoinduced ET from the antenna to C, thus the singlet excited state of C (C) is populated. Subsequently, the triplet excited state of C (C) is produced via the intrinsic intersystem crossing of C. The photooxidation ability of was studied using 1,5-dihydroxy naphthalene (DHN) as a chemical sensor. The photooxidation efficiency of is higher than that of the individual components of and , and even higher than that of methylene blue (MB). The photooxidation rate constant of is 1.47 and 1.51 times as that of and MB, respectively. The results indicate that the C-antenna systems can be used as another structure motif for a heavy atom-free organic triplet photosensitizer.