Communications
1054 (< 1, M+); Elemental analysis calculated for C41H20Cl14NO2: C
46.68, H 1.91, N 1.33; found: C 46.53 H 2.11 N 1.27.
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Received: April 29, 2004
Revised: July 12, 2004
Keywords: electron transfer · mixed-valent compounds ·
.
solvatochromism · triarylamines · vibronic coupling
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À
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[34] The usually employed Pekar factor g = 1/n2À1/D from Marcus
theory yields a quite similar linear correlation. We refrain from
using the Pekar factor as it is negative for very apolar solvents
and as it refers to an ion in a spherical cavity. The Onsager model
employed here refers to the more realistic situation of a dipole in
a spherical cavity, see ref. [32]. If one uses the Marcus theory for
calculating the solvent reorganization energy with l0 =
(De)2(rÀ1ÀdÀ1)g, where De = 1 is the charge transferred, r=
7 is the mean radius of the redox centers, and d = 12.3 is
the distance between the nitrogen of the triarylamine group and
the methyl carbon of the triarylmethyl radical (both values
estimated from the AM1 computation), a linear correlation with
l0 from Jortner theory is obtained with a slope of almost unity.
However, this good correlation is to some extent fortuitous
because the dipole moment differences measured by EOAM
indicate a much smaller electron-transfer distance than the
geometric distance of the redox centers.
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5856
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2004, 43, 5851 –5856