1993 Fiscal Year Final Research Report Summary
Studies on the Control of Photoinduced Electron Transfer Reaction of Porphyrins by Amphiphilic Polyelectrolytes
| Project/Area Number |
04453116
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
高分子合成
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| Research Institution | Osaka University |
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Principal Investigator |
KAMACHI Mikiharu Osaka University, faculty of Science, Department of Macromolecular Science, Professor, 理学部, 教授 (40028163)
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| Co-Investigator(Kenkyū-buntansha) |
HARADA Akira Osaka University, faculty of Science, Department of Macromolecular Science, Assi, 理学部, 助手 (80127282)
MORISHIMA Yotaro Osaka University, faculty of Science, Department of Macromolecular Science, Asso, 理学部, 助教授 (70028249)
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| Project Period (FY) |
1992 – 1993
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| Keywords | Porphyrin / Amphiphilic Polyelectrolytes / Electron Transfer / Excited Triplet State / Phosphorescence / Fluorescence / Hydrophobic Cluster / Charge Separation |
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| Research Abstract |
Cyclododecyl (Cd) groups, bulky and rigid hydrophobic goups with a ring structure, covalently attached to a polysulfonic acid were found to form hydrophobic clusters in aqueous solution due to self-organization. Thus, the polymer, as a whole, forms unimolecular micelle. Zinc(II) tetraphenylporphyrin (ZnTPP) moieties covalently linked to such an amphiphilic polysulfonic acid were found to be tightly compartmentalized in the Cd clusters, leading to very unusual photophysical and photochemical properties. Particularly anomalous behavior was that phosphorescence and E-type delayd fluorescence due to thermal repopulation from the triplet-excited state were emitted by the compartmentalized ZnTPP moieties in aqueous solution at room temperature. These unusual observations are primarily due to the fact that triplet-triplet annihilation is rigorously prevented because the chromophores are statically isolated in the Cd cluster from each other and also protected from the bulk aqueous phase such that the ZnTPP triplets have virtually no chance to encounter each other and also protected from impurities in the bulk phase during their lifetimes. This leads to enormously long triplet lifetime even in fluid aqueous solution at room temperature. In the photoinduced electron transfer from the ZnTPP long-lived triplets to sulfonium salts, self-destructive electron acceptors, as studied by laser photolysis, efficient electron transfer was found to occur and generate radicals coming from the ZnTPP and the acceptors. A characteristic feature of this compartmentalized ZnTPP system was that the ZnTPP cation radical persisted for extremely long time (the radical was recognized for several hours by ESR).
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