2000 Fiscal Year Final Research Report Summary
Molecular control and ultrafast dynamics of specific interaction of photogenerated radicals
| Project/Area Number |
10450322
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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 |
工業物理化学
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| Research Institution | SHIZUOKA UNIVERSITY |
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Principal Investigator |
NAGAMURA Toshihiko Shizuoka University, Professor, 電子工学研究所, 教授 (90117200)
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| Co-Investigator(Kenkyū-buntansha) |
KAWAI Hideki Shizuoka University, Research Associate, 電子工学研究所, 助手 (80324341)
SAKAGUCHI Hiroshi Shizuoka University, Associate professor, 電子工学研究所, 助教授 (30211931)
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| Project Period (FY) |
1998 – 2000
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| Keywords | charge resonance band / nitrostyrylpyridinium / near-infrared (NIR) region / dimer radical cation / Langmuir-Blodgett film / NIR responsive molecular films / ultrafast absorption changes |
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| Research Abstract |
The CR band is characterized by its absorption spectrum in the near-infrared (NIR) region, due to the splitting of the energy levels of both the ground and the excited states resulting from the electronic interaction between two chromophores of the dimer radical cation. In the present research project, efforts were made to elicidate factors affecting the stability of dimer radical cations and their ultrafast dynamics.
Followings are the main results from the present project, which will contribute a great deal to the development of novel materials for molecular pohotonics showing strong and ultrafast photoresponses in the near infrared region.
1) Femtosecond laser excitation of nitro-and dicyanovinyl-substituted styrylpyridinium tetraphenylborates in 1, 2-dimethoxyethane revealed ultrafast rise of absorptions both in the visible and NIR regions in less than 1 picosecond (ps). The decay was single-exponential in the NIR region with a lifetime of about 3 ps and double-exponential in the visible region with lifetimes of about 3 ps and 17 ps. The faster component was assigned to the back electron transfer from dimer radical cations to oxidized tetraphenylborate. The slower one was assigned to the back electron transfer from radical monomers to oxidized tetraphenylborate.
2) Newly synthesized tricyanovinylstyrylpyridinium derivatives gave much more stable radicals and dimer radical cations in a wide variety of solvents. Langmuir-Blodgett films were prepred from these and the CR band was observed for the first time in solid films at 1000 nm which was considerably redshifted than that in benzene.
3) Intramolecular dimer radical cations were observed in bichromophoric compounds bridged with 1, 3-substituted propane or 2, 4-substituted pentane. In propane-bridged nitrostyrylpyridinium derivatives, two CR bands were observed with peaks at 948 and 1742 nm. They were assigned to sandwich-and partially overlapped type dimer radical cations.
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