Regulation Mechanism of Electron Transfer Reaction Rate
| Project/Area Number |
62580218
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
生物物性学
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| Research Institution | Nagoya University |
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Principal Investigator |
TOSHIAKI KAKITANI Faculty of Science, Nagoya University, 理学部, 助教授 (90027350)
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| Project Period (FY) |
1987 – 1988
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| Project Status |
Completed (Fiscal Year 1988)
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| Budget Amount *help |
¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1988: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1987: ¥500,000 (Direct Cost: ¥500,000)
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| Keywords | Electron Transfer / Energy Gap Law / Inverted Region / Dielectric Saturation / Variation of the Free Energy Curvature / Photoinduced Charge Separation Reaction / 反応速度の制御機構 / モンテ・カルロ・シミュレイション |
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| Research Abstract |
Electron transfer reactions are an entity of the oxidation-reduction reaction in the electronic level and play a central role in biological energy conversion systems, in addition to the importance in the general chemical reaction. As mechanisms of regulating the electron transfer rate, we can count the electronic tunneling factor which depends on the intermolecular distance and the Franck-Condon factor which depends on the energy gap. We have made theoretical study on the role of the latter factor in this project.
According to the current theory on the electron transfer as first developed by marcus, the electron transfer rate decreases when the energy gap exceeds the reorganization energy of the surroundings and solute molecules. This tendency is called the inverted region of the energy gap law. The experimental result obtained by Rehm and Weller on the photoinduced charge separation reaction, however, represented that the inverted region was not observable for the wide energy gap regio
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n. In order to resolve this disagreement of the results between the theory and experiment, we proposed a new model that the polar solvent molecules surrounding the charged molecule are dielectrically saturated and the free energy curvature as a function of the polarization coordinate is much larger than that surrounding the neutral molecule. Based on this new model, we have succeeded in reproducing the experimental result that the inverted region does not substantially appear in the charge separation reaction.
In order to investigate whether the above assumption is good or not, we have conducted a Monte Carlo simulation for the polar solution involving a charged or neutral solute molecule. As a result, we got the results that solvent molecules surrounding a charged molecule with a valency 1 are dielectrically saturated and the ratio of the free energy curvatures between the charged and neutral solute molecules is about eight. We have also investigated the width and strength of the dielectric saturation layer by changing a various kind of molecular parameters. As results, we have found that so far as the size of the charged molecule is not so large, the dielectric saturation occurs universally and the width of the dielectric saturation layer is rather thin, Ca, about the radius of the solvent molecules. Less
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Report
(3 results)
Research Products
(19 results)
