| Project/Area Number |
09640632
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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 |
Organic chemistry
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| Research Institution | Kyoto University |
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Principal Investigator |
NISHIMOTO Sei-ichi Kyoto University Energy and Hydrocarbon Chemistry Professor, 工学研究科, 教授 (10115909)
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| Co-Investigator(Kenkyū-buntansha) |
ZHOU Ling Kyoto University Energy and Hydrocarbon Chemistry Instructor, 工学研究科, 助手 (50293890)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 1998: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1997: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Keywords | Thymine Derivatives / Radiation Reductive Dimerization / C(5)-C(5)-Linked Dimers / Meso Isomer / Racemic Isomer / Laser Photolysis / Photo-Induced Electron Transfer / C(5)-C(5)-Linkege Splitting / C(5)-C(5)結合二量体 / 結晶構造 / コンホメーション |
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| Research Abstract |
Redox mechanism by which meso- and racemic forms of C(5)-C(5)-linked dihydrothymine dimers (5a-c), as derived from various thymine derivatives [1-methylthymine (1a) ; 1,3-dimethylthymine (1b) ; thymidine (1c)], undergo splitting to regenerate 1a-c was studied and the following results were obtained.
(1) Product studies on radiolytic and photosensitized redox splittings of 5a-c in aqueous solution were carried out to correlate with their structural characteristics.
(2) A structure-dependent reactivity was elucidated that 5a undergoes splitting by one-electron reduction, while 5b, c favor two-electron reductive splitting.
(3) Meso-form of 5a showed fluorescence spectrum with a maximum intensity at 370 nm, although the other dimers were of non-fluorescent.
(4) Conformation of 5a in aqueous solution was determined by NMR, indicating that the meso-form favors a conformation similar to that in the crystal phase.
(5) One-electron reduction potentials of 5a-c were evaluated from the corresponding rate constants of electron-transfer quenching for the fluorescence of ruthenium complex (Ru(bpy)_3Cl_2 6H_20).
(6) One-electron oxidative splitting of 5a by SO_4- as generated by laser photolysis was studied to observe transient spectra due to 1-methyl-5,6-dihydrothymin-5-yl radicals that were derived from both meso- and racemic- forms. The rate constants of second-order decay were evaluated as 2.2 - 2.7 x 10^9 M^<-1> s^<-1>.
(7) No transient spectra due to 5-yl radicals were observed in the laser photolysis of 5a-c in aqueous solution containing N,N-dimethylaniline as a reducing photosensitizer.
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