A high-potential supramolecular triad (TPE-AlPor → Im-C60) composed of aluminum(III) porphyrin (AlPor), fullerene (C60), and tetraphenylethylene (TPE) has been constructed. The fullerene and tetraphenylethylene units are bound axially to opposite faces of the porphyrin plane via coordination and covalent bonds, respectively. The ground and excited-state properties of the triad and reference dyads are studied using steady-state and time-resolved spectroscopic techniques. The transient data show that photoexcitation results in charge separation from tetraphenylethylene to the excited singlet state of the porphyrin (1AlPor∗), generating a high-energy (2.14 eV) charge-separated state, (TPE)•+-(AlPor)•-, in toluene. A subsequent electron migration from the AlPor-• to fullerene generates a second high-energy (1.78 eV) charge-separated state (TPE)•+-AlPor → Im-(C60)•-. The lifetime of the charge separation is about 25 ns. The high energy stored in the form of charge-separated states along with their reasonable lifetimes makes these donor-acceptor systems potential electron-transporting catalysts to carry out energy-demanding photochemical reactions, especially in artificial photosynthesis for conversion of solar energy into chemical energy.
Bibliographical noteFunding Information:
This work was supported by the University of Minnesota Duluth (startup funds to P.P.K.) and by the National Science Foundation (Grant No. 1401188, to F.D.). V.S.B. acknowledges support by LEAP, an Energy Frontier Research Center funded by the U.S. DOE under Award No. DE-SC0001059 and DOE supercomputer time from NERSC. C.A. thanks the Natural Sciences and Engineering Research Council of Canada for a postdoctoral fellowship. A.J.M. is supported by the National Science Foundation Graduate Reseacrh Fellowship under Grant No. DGE-1122492.
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