Publisher： John Wiley & Sons Inc
E-ISSN： 1861-471x|10|12|2708-2719
ISSN： 1861-4728
Source： CHEMISTRY - AN ASIAN JOURNAL, Vol.10, Iss.12, 2015-12, pp. : 2708-2719
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Abstract
AbstractClosely positioned donor–acceptor pairs facilitate electron‐ and energy‐transfer events, relevant to light energy conversion. Here, a triad system TPACor‐C60, possessing a free‐base corrole as central unit that linked the energy donor triphenylamine (TPA) at the meso position and an electron acceptor fullerene (C60) at the β‐pyrrole position was newly synthesized, as were the component dyads TPA‐Cor and Cor‐C60. Spectroscopic, electrochemical, and DFT studies confirmed the molecular integrity and existence of a moderate level of intramolecular interactions between the components. Steady‐state fluorescence studies showed efficient energy transfer from 1TPA* to the corrole and subsequent electron transfer from 1corrole* to fullerene. Further studies involving femtosecond and nanosecond laser flash photolysis confirmed electron transfer to be the quenching mechanism of corrole emission, in which the electron‐transfer products, the corrole radical cation (Cor⋅+ in Cor‐C60 and TPA‐Cor⋅+ in TPACor‐C60) and fullerene radical anion (C60⋅−), could be spectrally characterized. Owing to the close proximity of the donor and acceptor entities in the dyad and triad, the rate of charge separation, kCS, was found to be about 1011 s−1, suggesting the occurrence of an ultrafast charge‐separation process. Interestingly, although an order of magnitude slower than kCS, the rate of charge recombination, kCR, was also found to be rapid (kCR≈1010 s−1), and both processes followed the solvent polarity trend DMF>benzonitrile>THF>toluene. The charge‐separated species relaxed directly to the ground state in polar solvents while in toluene, formation of 3corrole* was observed, thus implying that the energy of the charge‐separated state in a nonpolar solvent is higher than the energy of 3corrole* being about 1.52 eV. That is, ultrafast formation of a high‐energy charge‐separated state in toluene has been achieved in these closely spaced corrole–fullerene donor–acceptor conjugates.
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