Femtosecond intermolecular electron transfer in condensed systems |
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Authors: | Keitaro Yoshihara Yutaka Nagasawa Arkadiy Yartsev Shigeichi Kumazaki Hideki Kandori Alan E Johnson and Keisuke Tominaga |
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Institution: | a Institute for Molecular Science, Myodaiji, Okazaki 444 Japan b The Graduate University for Advanced Studies, Myodaiji, Okazaki 444 Japan |
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Abstract: | We have investigated the ultrafast intermolecular electron transfer (ET) from an electron-donating solvent (aniline (AN) or N, N-dimethylaniline (DMA)) to an excited dye molecule (oxazines (Nile blue and oxazine 1) or coumarins). A non-exponential time dependence was observed in AN and can be explained by solvent reorientation and nuclear motion of the reactants. However, in DMA, a single exponential process was observed for Nile blue (160 fs) and oxazine 1 (280 fs), which can be explained by assuming that the rate of ET is limited mainly by ultrafast nuclear motion. A clear substituent effect on intermolecular ET was observed for the 7-aminocoumarins. When the alkyl chain on the 7-amino group is extended and a hexagonal ring with the benzene moiety is formed, the rate of ET is reduced by three orders of magnitude. This effect can be explained by a change in the free energy difference of the reaction and by the vibrational motion of the amino group. |
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