Kinetics of multistep photoinitiated electron transfer reactions in a molecular triad

Su Chun Hung, Su Lin, Alisdair N. Macpherson, Janice M. DeGraziano, Pamela K. Kerrigan, Paul A. Liddell, Ana Moore, Thomas Moore, Devens Gust

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27 Scopus citations


Time-resolved fluorescence and subpicosecond transient absorption experiments have been carried out on a triad molecular device (CPQ) comprising a porphyrin (P) covalently linked to an electron-donating carotenoid pigment (C) and a quinone (Q), which acts as an electron acceptor. Rate constants governing the intramolecular electron transfer processes originating from the excited singlet state of the porphyrin have been determined. Excitation of the porphyrin moiety of the triad in benzonitrile solution results in photoinduced electron transfer to give CP.+Q.- (k1=2.5 × 109s-1) followed by rapid non-photochemical electron transfer to yield C.+ PQ.- (k3 ≈ 1 × 1011 s-1). The intermediate CP.+Q.-, also decays by charge recombination to the ground state with a rate constant k2 of about 6 × 1011 s-1. Nanosecond laser flash experiments were used to measure a quantum yield of 0.13 for the long-lived (370 ns) charge-separated species C.+PQ.-. Excitation of the carotenoid moiety of the triad results in singlet energy transfer to the attached porphyrin with a quantum yield of about 0.07.

Original languageEnglish (US)
Pages (from-to)207-216
Number of pages10
JournalJournal of Photochemistry and Photobiology, A: Chemistry
Issue number2-3
StatePublished - Jan 25 1994

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Physics and Astronomy(all)


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