Stepwise sequential and parallel photoinduced charge separation in a porphyrin-triquinone tetrad

Joseph Springer, Gerdenis Kodis, Linda De la Garza, Ana L. Moore, Thomas A. Moore, Devens Gust

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31 Citations (Scopus)

Abstract

A molecular tetrad consisting of a free base porphyrin (P) linked to a triquinone moiety consisting of a naphthoquinone bearing two benzoquinones (NQ-BQ2) has been synthesized and its photochemistry has been investigated using time-resolved spectroscopic techniques. Excitation of the porphyrin chromophore of the P-NQ-BQ2 tetrad in benzonitrile solution is followed by photoinduced electron transfer with a rate constant of 8.3 × 1010 s-1 to produce an initial P.+-NQ.--BQ2 state with a quantum yield of unity. A charge shift reaction gives a final P.+-NQ-(BQ.-BQ) charge-separated state, which decays to the ground state with a rate constant of 1.9 × 1010 s-1. The tetrad features both sequential and parallel multistep electron-transfer pathways. No evidence was found for significant involvement of direct electron transfer from the porphyrin first excited singlet state to a benzoquinone.

Original languageEnglish
Pages (from-to)3567-3575
Number of pages9
JournalJournal of Physical Chemistry A
Volume107
Issue number18
DOIs
Publication statusPublished - May 8 2003

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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