TY - JOUR
T1 - 1,2-Phenylene-Bridged Diporphyrin Linked with Porphyrin Monomer and Pyromellitimide as a Model for a Photosynthetic Reaction Center
T2 - Synthesis and Photoinduced Charge Separation
AU - Osuka, Atsuhiro
AU - Nakajima, Satoshi
AU - Maruyama, Kazuhiro
AU - Mataga, Noboru
AU - Asahi, Tsuyoshi
AU - Yamazaki, Iwao
AU - Nishimura, Yoshinobu
AU - Ohno, Takeshi
AU - Nozaki, Koichi
PY - 1993/6/1
Y1 - 1993/6/1
N2 - The synthesis and excited-state dynamics are described for fixed-distance zinc diporphyrin-zinc porphyrin-pyromellitimide molecules 1-3 (D-M-Im) and zinc porphyrin-pyromellitimide molecule 7 (M-Im). In molecules 1-3, D and M-Im moieties are bridged by aromatic spacers such as 4,4′-biphenylylene-1,4-phenylene-, and methylenebis-(1,4-phenylene) groups, respectively. The rates of charge separation (CS) and charge recombination (CR), kCS and kCR, of 7 were determined in C6H6, THF, and DMF. kCS in 7 is essentially solvent polarity independent, while kCR increases with solvent polarity. A small kCR in C6H6 has been interpreted in terms of the small electron-transfer probability, which arises from the small solvent reorganization energy and large reaction exothermicity in the inverted region. In molecules 1–3, 1(M)* is competitively quenched by D through the intramolecular singlet-singlet energy transfer to give 1(D)*-M-Im and by Im through intramolecular CS to give D-(M)+-(Im)-. The 1(D)*-M-Im state decays to the ground state with a lifetime to that of the reference 1(D)* and does not undergo any intramolecular electron-transfer reactions. On the other hand, from the initially formed ion pair (IP) state, D-(M)+-(Im)−, a secondary IP state, (D)+-M-(Im)−, is formed by hole transfer from (M)+ to D in THF or DMF. Such hole transfer does not occur in less polar C6H6. The lifetimes of the secondary IP states formed from 1, 2, and 3, which range from 0.25 to 23 µs, depend upon both the spacer connecting the D and M and the polarity of solvent. In contrast to the case of (M)+-(Im)-, the lifetime of (D)+-M-(Im)− increases with increasing solvent polarity. Marked differences in solvent polarity effects observed on the lifetime of the (M)+-(Im)− and (D)+-M-(Im)− states may have important practical implications for the design of artificial photosynthetic models.
AB - The synthesis and excited-state dynamics are described for fixed-distance zinc diporphyrin-zinc porphyrin-pyromellitimide molecules 1-3 (D-M-Im) and zinc porphyrin-pyromellitimide molecule 7 (M-Im). In molecules 1-3, D and M-Im moieties are bridged by aromatic spacers such as 4,4′-biphenylylene-1,4-phenylene-, and methylenebis-(1,4-phenylene) groups, respectively. The rates of charge separation (CS) and charge recombination (CR), kCS and kCR, of 7 were determined in C6H6, THF, and DMF. kCS in 7 is essentially solvent polarity independent, while kCR increases with solvent polarity. A small kCR in C6H6 has been interpreted in terms of the small electron-transfer probability, which arises from the small solvent reorganization energy and large reaction exothermicity in the inverted region. In molecules 1–3, 1(M)* is competitively quenched by D through the intramolecular singlet-singlet energy transfer to give 1(D)*-M-Im and by Im through intramolecular CS to give D-(M)+-(Im)-. The 1(D)*-M-Im state decays to the ground state with a lifetime to that of the reference 1(D)* and does not undergo any intramolecular electron-transfer reactions. On the other hand, from the initially formed ion pair (IP) state, D-(M)+-(Im)−, a secondary IP state, (D)+-M-(Im)−, is formed by hole transfer from (M)+ to D in THF or DMF. Such hole transfer does not occur in less polar C6H6. The lifetimes of the secondary IP states formed from 1, 2, and 3, which range from 0.25 to 23 µs, depend upon both the spacer connecting the D and M and the polarity of solvent. In contrast to the case of (M)+-(Im)-, the lifetime of (D)+-M-(Im)− increases with increasing solvent polarity. Marked differences in solvent polarity effects observed on the lifetime of the (M)+-(Im)− and (D)+-M-(Im)− states may have important practical implications for the design of artificial photosynthetic models.
UR - http://www.scopus.com/inward/record.url?scp=0001018006&partnerID=8YFLogxK
U2 - 10.1021/ja00064a021
DO - 10.1021/ja00064a021
M3 - 学術論文
AN - SCOPUS:0001018006
SN - 0002-7863
VL - 115
SP - 4577
EP - 4589
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 11
ER -