Long-lived charge-separated state generated in a ferrocene-meso,meso-linked porphyrin trimer-fullerene pentad with a high quantum-yield

Hirosh Imahori, Yuji Sekiguchi, Yukiyasu Kashiwagi, Tohru Sato, Yasuyuki Araki, Osamu Ito, Hiroko Yamada, Shunichi Fukuzumi

Research output: Contribution to journalArticle

190 Citations (Scopus)

Abstract

A meso,meso-linked porphyrin trimer, (ZnP)3, as a light-harvesting chromophore, has been incorporated for the first time into a photosynthetic multistep electron-transfer model including ferrocene (Fc) as an electron donor and fullerene (C60) as an electron acceptor, to construct the ferrocene-meso,meso-linked porphyrin trimer-fullerene system Fc-(ZnP)3-C60. Photoirradiation of Fc-(ZnP) 3-C60 results in photoinduced electron transfer from both the singlet and triplet excited states of the porphyrin trimer, 1(ZnP)3* and 3(ZnP)3*, to the C60 moiety to produce the porphyrin trimer radical cation-C60 radical anion pair, Fc-(ZnP)3 .+-C60.-. Subsequent formation of the final charge-separated state Fc+-(ZnP)3-C60 .- was confirmed by the transient absorption spectra observed by pico- and nanosecond time-resolved laser flash photolysis. The final charge-separated state decays, obeying firstorder kinetics, with a long lifetime (0.53 s in DMF at 163 K) that is comparable with that of the natural bacterial photosynthetic reaction center. More importantly, the quantum yield of formation of the final charge-separated state (0.83 in benzonitrile) remains high, despite the large separation distance between the Fc+ and C 60.- moieties. Such a high quantum yield results from efficient charge separation through the porphyrin trimer, whereas a slow charge recombination is associated with the localized porphyrin radical cation in the porphyrin trimer. The light-harvesting efficiency in the visible region has also been much improved in Fc-(ZnP)3-C60 because of exciton coupling in the porphyrin trimer as well as an increase in the number of porphyrins.

Original languageEnglish
Pages (from-to)3184-3196
Number of pages13
JournalChemistry - A European Journal
Volume10
Issue number13
DOIs
Publication statusPublished - 2004 Jul 5

Keywords

  • Donor-acceptor systems
  • Electron transfer
  • Fullerenes
  • Photosynthesis
  • Porphyrinoids

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Organic Chemistry

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