Through bond mechanism versus exciplex formation in the photochemistry of fullerene / ferrocene donor-bridge-acceptor dyads |
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Authors: | Dirk M Guldi Michele Maggini Gianfranco Scorrano Maurizio Prato |
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Institution: | 1. Radiation Laboratory, University of Notre Dame, 46656, Notre Dame, IN, U.S.A. 2. Centro Meccanismi di Reazioni Organiche del CNR, Dipartimento di Chimica Organica, Via Marzolo 1, 35131, Padova, Italy 3. Dipartimento di Scienze Farmaceutiche, Universita di Trieste Piazzale Europa 1, 34127, Trieste, Italy
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Abstract: | A systematic fluorescence and flash photolytic investigation of a series of covalently linked fullerene / ferrocene based donor-bridge-acceptor dyads is reported as a function of the nature of the bridge between the donor site and acceptor site. The fluorescence of the investigated dyads 2 (Φrel = 0.17 × 10?4, 3 (Φrel = 0.78 × 10?4), 4 (Φrel = 1.5 × 10?4), 5 (Φrel = 0.7 × 10?4), and 6 (Φrel = 2.9 × 10?4) were substantially quenched, relative to N-methyl fulleropyrrolidine (1) (Φrel = 6.0 × 10?4). Photolysis of N-methyl fulleropyrrolidine (1) in toluene revealed formation of the excited singlet state which was followed by a rapid intersystem crossing to the excited triplet state. On the other hand, the fate of the excited singlet state of 2, 3, 4, 5, and 6 was found to be governed by rapid intramolecular quenching, with rate constants of 28×109 s?1, 6.9×109 s?1, and 3.4×109 s?1, 14×109 s?1, 2.3×109 s?1 respectively. The electron transfer process and the charge separation were confirmed by monitoring the characteristic π-radical anion bands at λmax = 400 and 1055 nm in degassed benzonitrile with τ1/2 = 1.8 μs (3) and 2.5 μs (4). |
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