TY - JOUR
T1 - Long-lived charge-separated state generated in a ferrocene-meso,meso-linked porphyrin trimer-fullerene pentad with a high quantum-yield
AU - Imahori, Hirosh
AU - Sekiguchi, Yuji
AU - Kashiwagi, Yukiyasu
AU - Sato, Tohru
AU - Araki, Yasoyuki
AU - Ito, Osamu
AU - Yamada, Hiroko
AU - Fukuzumi, Shunichi
PY - 2004/7/5
Y1 - 2004/7/5
N2 - 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.
AB - 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.
KW - Donor-acceptor systems
KW - Electron transfer
KW - Fullerenes
KW - Photosynthesis
KW - Porphyrinoids
UR - http://www.scopus.com/inward/record.url?scp=3142728629&partnerID=8YFLogxK
U2 - 10.1002/chem.200305308
DO - 10.1002/chem.200305308
M3 - Article
AN - SCOPUS:3142728629
SN - 0947-6539
VL - 10
SP - 3184
EP - 3196
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 13
ER -