MEDIATED ELECTRON-TRANSFER ACROSS NAFION(R)VERTICAL-BAR-SOLUTION INTERFACES - COMPARISON WITH MARCUS THEORY FOR CASES INVOLVING GAUSSIAN ARRAYS OF MEDIATOR COUPLES
E. Sabatani et Fc. Anson, MEDIATED ELECTRON-TRANSFER ACROSS NAFION(R)VERTICAL-BAR-SOLUTION INTERFACES - COMPARISON WITH MARCUS THEORY FOR CASES INVOLVING GAUSSIAN ARRAYS OF MEDIATOR COUPLES, Journal of electroanalytical chemistry [1992], 386(1-2), 1995, pp. 111-119
The kinetics of electron transfer between cationic complexes of Ru-II
confined within Nafion(R) coatings on electrodes and anionic oxidants
in solution were measured and analyzed according to a model in which t
he reactants in the Nafion(R) exhibit an array of formal potentials wi
th a Gaussian distribution. The variety of anionic co-reactants employ
ed provided a range of driving forces for the electron-transfer cross-
reactions involved. With thermodynamically disfavored cross-reactions
the experimental results could be accommodated only by taking into acc
ount the array of formal potentials of the mediating complexes within
the Nafion(R) coatings. For thermodynamically favored reactions it was
possible to approximate the array of formal potentials by a single fo
rmal potential at the center of the array. It is shown that the linear
correlation between the rate constants and driving forces of electron
-transfer cross-reactions predicted by Marcus theory is not affected w
hen one of the co-reactants presents a distributed array of formal pot
entials instead of a single value. Kinetic data are presented for the
reactions of Ru(NH3)(6)(2+) and/or Ru(NH3)(5)py(2+) with Ru-III(edta)(
-), Fe-III(edta)(-) and FeXW(11)O(39)(m-) (X = P, m = 4; X = Ge, Si, m
= 5).