Electron Transfer in a Trichromophoric System
J. Phys. Chem. A, Vol. 102, No. 12, 1998 2115
108 s-1. During this excited-state reaction, a negative charge
is transferred from one end of the molecule to the other. The
large solvent reorganization that accompanies the reaction results
in a large activation energy for electron transfer. The rate of
electron transfer is given by
Van der Auweraer and J. van Stam (KU Leuven) are thanked
for fruitful discussions.
References and Notes
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(∆G° + λ)2
ket ) k0 exp -
(12)
[
]
4λkT
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k0 is the maximum rate of reaction in absence of activation
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λ denotes the reorganization energy dominated by the solvent
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e2
1
1
1
1
ꢀs
λs )
-
-
(13)
2
(
)(
)
4πꢀ0 r Rc
n
If the rate of reaction in the absence of the activation energy is
assumed equal to 1 × 1013 s-1 and if the driving force of the
reaction is equal to zero, the reorganization energy must be
smaller than 1.18 eV to obtain a rate constant of 1 × 108 s-1
.
This means that for a distance of 8 Å between the chromophores,
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If in diethyl ether only one CT state would be formed,
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picosecond range) indicating a fast formation of the charge-
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might even possibly be too small to be observed within the time
resolution of the experimental setup. In diethyl ether, two decay
times in the range of nanoseconds are observed, which is not
in accordance with the model of formation of only one CT state.
The contribution of the short decay time becomes negative at
longer wavelengths and the ratio of the preexponential factors
approaches -1 at long wavelengths. This indicates that only
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Acknowledgment. The continuous support of the Ministry
of Science Programming through IUAP 4-11 is gratefully
acknowledged. S.D. thanks the KU Leuven and the IWONL
for financial support. N. Boens (KU Leuven) is thanked for the
development of the algorithms for the analysis of the “single-
photon-timing” analysis and global compartmental analysis. M.
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