Photoinduced electron transfer in porphyrin-oligothiophene-fullerene linked triads

Takumi Nakamura, Mamoru Fujitsuka, Yasuyuki Araki, Osamu Ito, Junya Ikemoto, Kazuo Takimiya, Yoshio Aso, Tetsuo Otsubo

Research output: Contribution to conferencePaperpeer-review

Abstract

Photoinduced charge-separation (CS) and recombination (CR) processes of porphyrin(H2P)-oligothiophene(nT)-fullerene(C60) linked triads (H2P-nT-C60, n = 4, 8, and 12), which were designed to reveal the function of nT as a molecular wire for the electron transfer (ET) process, have been investigated by time-resolved fluorescence and absorption spectroscopic methods, By excitation of the H2P moiety in toluene, 1H2P*-nT-C60 showed predominantly the energy transfer (EN) process generating H 2P-nT-1C60*, while the CS process was not observed. The EN rate constant depends on the length of nT. In benzonitrile (PhCN) and o-dichlorobenzene (o-DCB), H2P+-nT-C 60- was produced from 1H 2P*-nT-C60. The most energetically stable final CS state was confirmed to be H2P-nT.+-C60 .-, which was produced via the hole-shift process from H 2P.+-nT-C60.-. The rate constant for the CS process from 1H2P*-nT-C60 to H2P.+-nT-C60 decreased with the length of the nT moiety, indicating that the nT moiety acts as a molecular wire. The small damping factor showed a pronounced solvent polarity effect (0.03 Å -1 in PhCN and 0.11 Å-1 in o-DCB), indicating that a long range ET process through the nT moiety is feasible in poiar solvent. The final CS state (H2P-nT.+-C60.-) returned to neutral triad by the CR process between the vicinal electron (radical anion) and hole (radical cation). The lifetime of the CS state showed the solvent polarity effect ranging from 1.5 - 2.4 μs in PhCN to 14-27 μs in o-DCB at room temperature. The longest lifetime (27 (μs) was observed with H2P-8T.+-C60.- in o-DCB. From the temperature dependence of the CR rate constant, the reorganization energies were evaluated to be 0.8 -1.1 eV for all triads in PhCN and o-DCB.

Original languageEnglish
Pages210-231
Number of pages22
Publication statusPublished - 2004 Dec 1
EventECS Annual Spring Meeting -Fullerenes and Nanotubes: Materials for the New Chemical Frontier - International Symposium on Fullerenes, Nanotubes, and Carbon Nanoclusters - San Antonio, TX, United States
Duration: 2004 May 92004 May 13

Other

OtherECS Annual Spring Meeting -Fullerenes and Nanotubes: Materials for the New Chemical Frontier - International Symposium on Fullerenes, Nanotubes, and Carbon Nanoclusters
Country/TerritoryUnited States
CitySan Antonio, TX
Period04/5/904/5/13

ASJC Scopus subject areas

  • Engineering(all)

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