OPTICAL AND THERMAL OUTER-SPHERE ELECTRON SELF-EXCHANGE REACTION OF THE HEXACYANOFERRATE(II III) COUPLE - COMPARATIVE-ANALYSIS OF BAND-SHAPE AND ACTIVATION PARAMETERS AND LARGE SOLVENT KINETIC ISOTOPE EFFECT/
De. Khoshtariya et al., OPTICAL AND THERMAL OUTER-SPHERE ELECTRON SELF-EXCHANGE REACTION OF THE HEXACYANOFERRATE(II III) COUPLE - COMPARATIVE-ANALYSIS OF BAND-SHAPE AND ACTIVATION PARAMETERS AND LARGE SOLVENT KINETIC ISOTOPE EFFECT/, Journal of physical chemistry, 99(11), 1995, pp. 3592-3597
The optical and thermal outer-sphere electron self-exchange reactions
of the hexacyanoferrate(II/III) couple in concentrated solutions of th
e reactants in both H2O and D2O as the solvent have been studied by me
ans of vis/near-IR and C-13-NMR spectroscopy, respectively. Spin-orbit
splitting effects show up in the band shape of the optical transition
and have to be considered also for the rate constant of the correspon
ding thermal reaction. The rate constant of the electron self-exchange
reaction pathway, involving reactants and products only in the lowest
electronic state, k(AA,calc)(H) = 5.1 X 10(4) M(-1) s(-1) (299 K, H2O
), has been calculated from the band-shape parameters of the optical t
ransition using a semiclassical model which is in a convincing agreeme
nt with the experimental value, k(AA,ex)(H) = 5.45 x 10(4) M(-1) s(-1)
(299 K, H2O). A H2O/D2O kinetic isotope effect of 1.8 of both the obs
erved and calculated rate constants has been found and interpreted in
terms of the contribution of weakly hydrogen-bonded solvent molecules,
present in the first solvational sphere of the reactants, to the reor
ganization free energies of both optical and thermal self-exchange pro
cesses.