2004 Fiscal Year Final Research Report Summary
Spectroscopic study on specific intermolecular interactions in aromatic biomolecules in the isolated state.
| Project/Area Number |
15350015
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | KYUSHU UNIVERSITY |
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Principal Investigator |
SEKIYA Hiroshi Kyushu University, Department of Chemistry, Faculty of Sciences, Professor, 大学院・理学研究院, 教授 (90154658)
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| Co-Investigator(Kenkyū-buntansha) |
OHASHI Kazuhiko Kyushu University, Department of Chemistry, Faculty of Sciences, Associate Professor, 大学院・理学研究院, 助教授 (80213825)
SAKOTA Kenji Kyushu University, Department of Chemistry, Faculty of Sciences, Research Associate, 大学院・理学研究院, 助手 (80346767)
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| Project Period (FY) |
2003 – 2004
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| Keywords | biomolecules / hydrogen-bonded cluster / double-proton transfer / gas phase / electronic spectrum / picosecond time-resolved study / cooperative effect / dimer |
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| Research Abstract |
Structures and the excited-state dynamics of hydrogen bonded molecules in supersonic jet expansion have been studied by both the frequency domain and time-domain measurements. We have measured hole-burning spectra of various deuterated isotomers of the hydrogen bonded 7-azaindole dimer. The spectra show that the exciton resonance interaction in the lowest excited state of the 7-azaindole dimer should be treated as a weak coupling limit of the exciton theory. The hole-burning spectra suggest that the vibronic states with short and long lifetimes are excited in the femtosecond time-resolved experiments by Zewail's group, providing bi-exponential decay profiles. The biexponential decay profiles had been a strong evidence of the stepwise excited-state double-proton transfer (ESDPT). However, we have found that the decay profiles excited by picoseond pulse are fitted with single-exponential functions. This result clearly shows that ESDPT occurs by the concerted mechanism. The dispersed fluo
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rescence spectra are measured for the undeuterated and deuterated 7-azaindole dimers. A remarkable H/D isotope effects on the reaction rate has been detected. We have found a cooperative nature of the ESDPT reaction.
The effect of substitution on the ESDPT reaction has also been studied. The substitution of the methyl group at the 3-position of the 7-azaindole does not affect the ESDPT rate, but the substitution of the Cl atom or the dimethylamino group at the 4-position significantly decrease the ESDPT rate due to the weakening of the intermolecular hydrogen-bonds.
We also measured various hydrogen bonded clusters in the neutral and ionic states to investigate the relation between the structure and dynamics. For example, we have examined the excited-state proton transfer of the 7-azaindole-(H_2O)_n(n=1-3). Previous report by Castleman et al. with femtosecond spectroscopy concluded that the excited-state proton transfer occurs in 7-azaindole-(H_20)_n(n=2-4). However, no red-shifted fluorescence has been observed in 7-azaindole-(H_2O)_n(n=1-3), indicating that the excited-state proton transfer is inhibited. Less
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[Journal Article] Electronic spectra of jet-cooled 3-mathyl-7-azaindole dimer. Symmetry of the lowest excited electronic state and double proton transfer2004
Author(s)
A.Hara, Y.Komoto, K.Sakota, R.Miyoshi, Y.Iuokuchi, K.Ohashi, K.Kubo, E.Yamamoto, A.Mori, N.Nishi, H.Sekiya
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Journal Title
J.Phys.Chem.A 108(49)
Pages: 10789-10793
Description
「研究成果報告書概要(欧文)」より
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