Ultrafast Photoinduced Electron Transfer in Rigid Porphyrin—Quinone Dyads

Alisdair N. Macpherson, Paul A. Liddell, Su Lin, Lori Noss, Gilbert R. Seely, Janice M. DeGraziano, Ana Moore, Thomas Moore, Devens Gust

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84 Scopus citations


Three dyad molecules, each consisting of a porphyrin (P) linked to a quinone (Q) through a rigid bicyclic bridge, have been prepared, and their photochemistry has been investigated using time-resolved fluorescence and absorption techniques. In all three molecules, photoinduced electron transfer from the porphyrin first excited singlet state to the quinone occurs with rate constants of ~1012 s_1 in solvents ranging in dielectric constant from ~2.0 to 25.6 and at temperatures from 77 to 295 K. The transfer rate is also relatively insensitive to thermodynamic driving force changes up to 0.4 eV. This behavior is phenomenologically similar to photosynthetic electron transfer. The rapid rate of photoinduced electron transfer and its lack of dependence on environmental factors suggests that transfer is governed by intramolecular vibrations. Charge recombination of P.+—Q._, on the other hand, is substantially slower than charge separation and sensitive to both driving force and environmental conditions. Thus, by changing conditions, charge recombination rates can be varied over a wide range while photoinduced electron transfer rates are relatively unaffected. This suggests that rigid dyads of this general type may be useful building blocks for more complex molecular devices.

Original languageEnglish (US)
Pages (from-to)7202-7212
Number of pages11
JournalJournal of the American Chemical Society
Issue number27
StatePublished - 1995

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry


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