Inorganic Chemistry, Vol.34, No.15, 3998-4000, 1995
Uphill Electron-Transfer in Pentaammineruthenium(III)-Modified Ferrocytochrome-C - Rates, Thermodynamics, and the Mediating Role of the Ruthenium Moiety
The rate of thermodynamically-unfavorable (uphill) Fe-II-to-Ru-III electron transfer in pentaammineruthenium-modified horse-heart cytochrome c was obtained by using sufficiently high Co(oxalate)(3)(3-) concentrations to saturate the pre-equilibrium. The rate of uphill intramolecular electron transfer at 25 degrees C is 0.40 s(-1) (Delta H-double dagger = 12.5 +/- 0.2 kcal mol(-1), Delta S-double dagger = -18.3 +/- 0.7 cal deg(-1) mol(-1)). The net reaction thermodynamics are as follows : Delta G(o) = -0.125 eV, Delta H degrees = -9.0 +/- 0.2 kcal mol(-1), and Delta S degrees = -20.7 +/- 0.8 cal deg(-1) mol(-1).