EPR investigation of photoinduced radical pair formation and decay to a triple state in a carotene-porphyrin-fullerene triad

Donatella Carbonera, Marilena Di Valentin, Carlo Corvaja, Giancarlo Agostini, Giovanni Giacometti, Paul A. Liddell, Darius Kuciauskas, Ana L Moore, Thomas A Moore, John Devens Gust

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Abstract

The photochemistry of a molecular triad consisting of a porphyrin (P) covalently linked to a carotenoid polyene (C) and a fullerene derivative (C60) has been studied at 20 K by time-resolved EPR spectroscopy following laser excitation. Excitation of the porphyrin moiety yields C-1P-C60 which decays by photoinduced electron transfer to yield C-P.+-C60.-. This state rapidly evolves into a final charge-separated state C.+-P-C60.-, whose spin polarized EPR signal was observed and simulated. There is a weak exchange interaction between the electrons in the radical pair (J - 1.2 G). The C.+-P-C60.- state decays to give the carotenoid triplet in high yield with a time constant to 1.2 μs. The spin polarization of 3C-P-C60 is characteristic of a triple formed by charge recombination of a single- derived radical pair. The kinetics of the decay of 3C-P-C60 to the ground state were also determined. The photoinduced electron transfer from an excited singlet state at low temperature and the high yield of charge recombination to a spin-polarized triplet mimic similar processes observed in photosynthetic reaction centers.

Original languageEnglish
Pages (from-to)4398-4405
Number of pages8
JournalJournal of the American Chemical Society
Volume120
Issue number18
DOIs
Publication statusPublished - May 13 1998

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Fullerenes
Porphyrins
Carotenoids
Paramagnetic resonance
Electrons
Genetic Recombination
Photosynthetic Reaction Center Complex Proteins
Polyenes
Photochemistry
Spin polarization
Laser excitation
Photochemical reactions
Exchange interactions
Excited states
Ground state
Spectrum Analysis
Lasers
Spectroscopy
Derivatives
Kinetics

ASJC Scopus subject areas

  • Chemistry(all)

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EPR investigation of photoinduced radical pair formation and decay to a triple state in a carotene-porphyrin-fullerene triad. / Carbonera, Donatella; Di Valentin, Marilena; Corvaja, Carlo; Agostini, Giancarlo; Giacometti, Giovanni; Liddell, Paul A.; Kuciauskas, Darius; Moore, Ana L; Moore, Thomas A; Gust, John Devens.

In: Journal of the American Chemical Society, Vol. 120, No. 18, 13.05.1998, p. 4398-4405.

Research output: Contribution to journalArticle

Carbonera, Donatella ; Di Valentin, Marilena ; Corvaja, Carlo ; Agostini, Giancarlo ; Giacometti, Giovanni ; Liddell, Paul A. ; Kuciauskas, Darius ; Moore, Ana L ; Moore, Thomas A ; Gust, John Devens. / EPR investigation of photoinduced radical pair formation and decay to a triple state in a carotene-porphyrin-fullerene triad. In: Journal of the American Chemical Society. 1998 ; Vol. 120, No. 18. pp. 4398-4405.
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