Electron transfer reaction between cytochrome c and trisoxalatocobalt(III)†

Kinetics of the reduction of cytochrome c by [FeII(edta)(H2O)]2−: outer-sphere vs. inner-sphere electron transfer mechanisms

“…To prepare horse heart cytochrome c II , cytochrome c III was first reduced by the addition of an excess of sodium dithionite (50 mM), then hexacyanoiron() (< 50 mM) was added, which was subsequently removed by repeated ultrafiltration through a 3000 Da molecular weight cut-off membrane (Amicon) with degassed ultra-pure water. 25 The buffered solutions of cytochrome c II/III were stored under anaerobic conditions and analysed spectrophotometrically. Characteristic UV-Vis bands were found for cytochrome c III at 416 nm (ε = 4.16 × 10 5 M Ϫ1 cm Ϫ1 ) and 530 nm (ε = 9.1 × 10 3 M Ϫ1 cm Ϫ1 ), and for cytochrome c II at 420 nm (ε = 1.29 × 10 5 M Ϫ1 cm Ϫ1 ) and 550 nm (ε = 2.67 × 10 4 M Ϫ1 cm Ϫ1 ).…”

“…K IP = 253 ± 34 M Ϫ1 at 298 K, to cause a significant deviation from linearity of the plot of k obs vs. the complex concentration at low ionic strength. 25 Possible electrostatic interactions between reactant molecules results from the net positive charge of the reduced form of cytochrome c and the negative charge on the cobalt complex, i.e. ϩ6.5 and Ϫ3, respectively.…”

“…ϩ6.5 and Ϫ3, respectively. 25 In another reaction between cytochrome c II and trans-bis(2-ethyl-2-hydroxybutanoato(2Ϫ))oxochromate(), the complex has negatively charged donor centres, and the concentration dependence shows slight deviation from linearity at high concentrations of the chromium() species. In comparison to the trisoxalatocobalt() system, the ion-pair formation constant is significantly smaller, viz.…”

27 Mechanisms of reactions in solution

“…48 The outersphere electron exchange process between [Co(ox) 3 ] 3Ϫ and horse heart cytochrome c occurs via rapid formation of an ion-pair precursor species (charge on the cytochrome c is ϩ6.5) prior to electron transfer. 49 From the kinetics it is possible to separate out the electron transfer rate constant, k et with a value of 0.158 s Ϫ1 at 25 ЊC. Outer-sphere reduction of [Co(en) 2 Br 2 ] ϩ by [Fe(CN) 6 ] 4Ϫ occurs in three steps; ion pair formation, electron transfer and successor dissociation and the rates could be correlated to the properties of the solvent in H 2 O-MeOH/1,4-dioxane mixtures.…”

Kinetic study of the promazine oxidation to promazine 5-oxide by trisoxalatocobaltate(III) in basic aqueous media

“…Trisoxalatocobaltate(III) is an effective electron acceptor in many electron-transfer reactions [2][3][4][5][6]. Its ability to undergo the electron transfer is resulted in the reduction potential, viz.…”