P115
Effects of Molecular Charge on Photoinduced Electron-Transfer Reactions
Taeko N. Inada,
Chika Sato,
Koichi Kikuchi,
Masayo Yamauchi*,
Takesi Nagata*,
Yasutake Takahashi**,
Hiroshi Ikeda* and
Tsutomu Miyashi*
Kitasato Univ.,*Tohoku Univ.,**Mie Univ
The fluorescence quenching due to full and partial electron transfer
(ET) and the back ET within geminate radical pairs are studied (i) in
acetonitrile using N-methylacridinium ion as a monocationic fluorescer and aromatic compounds as neutral quenchers and
(ii) in methanol using aromatic compounds as neutral fluorescers and
methyl- and benzyl-viologens as dicationic quenchers.
By comparison with the results previously obtained for the system
of neutral fluorescer and quencher it is demonstrated that the free
energy dependence of rates of fluorescence quenching and back ET is
not affected by molecular charge, but the rate of geminate radical
separation into free radicals is. In the system of aromatic fluorescer
and quencher, in general, the fluorescence quenching is induced by a
full ET at long-distance when the free energy change DG in full ET
is more negative than -0.5 eV and by a partial ET at contact distance
when DG is more positive than -0.4 eV.
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