2003 Fiscal Year Final Research Report Summary
Ultrafast Electron Transfer Dynamics of Directly Linked Porphyrin-Electron Acceptor Dyads
| Project/Area Number |
14540481
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical chemistry
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| Research Institution | Institute for Laser Technology |
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Principal Investigator |
TANIGUCHI Seiji Institute for Laser Technology, Laser Photoscience Research Team, Researcher, レーザーバイオ科学研究チーム, 研究員 (00342725)
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| Co-Investigator(Kenkyū-buntansha) |
OSUKA Atsuhiro Kyoto University, Graduate School of Science, Department of Chemistry, Professor, 大学院・理学研究科, 教授 (80127886)
CHUSROWJAN Haik Institute for Laser Technology, Laser Photoscience Research Team, Assistant Chief Researcher, レーザーバイオ科学研究チーム, 副主任研究員 (70291036)
MATAGA Noburu Institute for Laser Technology, Laser Photoscience Research Team, Team Reader, レーザーバイオ科学研究チーム, グループリーダー (30029368)
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| Project Period (FY) |
2002 – 2003
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| Keywords | Femtosecond Fluorescence Dynamics / Porphyrin-Electron Acceptor Dyads / S_2 Fluorescence / Photoinduced Electron Transfer / Energy Gap Dependence / Medium Effect |
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| Research Abstract |
We have investigated the photoinduced electron transfer processes from S_2 excited states of directly linked Zinc porphyrin-imide (ZP-Im) dyads and its solvent effects by using femtosecond fluorescence up-conversion method with 〜120fs time resolution. The S_2 fluorescence lifetime changed from 〜130fs to 〜800fs with the species of imide. The energy gap dependence of the charge separation rate constants (k_<CS>) calculated form S_2 fluorescence lifetimes showed obvious "bell shapes" in low polar solvents (methylcyclohexane and toluene). S_2 fluorescence dynamics in polystyrene film were measured for the research of solvent viscosity effects. The energy gap dependence of k_<CS> was nearly the same with those in other solvents (like as toluene), which shows the ultrafast electron transfer from S_2 state can occurs even in the case that the freedom of the dynamic motion of the solvents around are restricted. In alcohol (ethanol and butanol) solutions, k_<CS> were larger than those in other solutions in the normal region, which caused by the hydrogen-bond interaction between ZIP-Im and the solvents. We have also measured the S_1 fluorescence dynamics with S_2 state excitation. In THF the lifetimes of S_1 state conversion (S_1 fluorescence rise) corresponded to the S_2 fluorescence decays, but in toluene and methylcyclohexane they were larger for 〜150fs than the S_2 fluorescence decays in top region. These results show that the S_1state conversion mainly caused by the back electron transfer reaction from the charge separation state and the rates of back electron transfer smaller than the charge separation rates from S_2 state. The S_2 fluorescence dynamics of directly linked ZP-quinone dyads were also investigated, and ultrafast electron transfer with 〜130fs lifetimes were also observed.
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