The Electrostatic Effect on the Electron-transfer Reaction of Co(III)-Poly(4-vinylpyridine) Complex

Abstract

The reduction (electron-transfer reaction), of'cis-[Co(III)(en), PVPCI] C12 PVP:poly-(4-vinylpyridine) by Fe(ll)Z or FeEDTA2- (ethylenediaminetetracetato-iron(ll)2-) was studied.The reductien by Fe(ll)2 was very slQw and the reactivity of PVP complex decreased to 1/3.v 1/5 and was lower than that of corresponding monomeric Py.(pyridine) complex, beeause of the electrostatic repulsion. On the other hand, the reduction by.FeEDTA2- was very rapid because of the electrostatic attraction ahd the reactivity of the' PVP complex' was higher by the factor of 20 than the Py complex. An increase in the degree of coordination of PVP to Co(M) brought abo'ut an increase in the rate constant ratio (kpvp/kp, , kvrate const; of PVP complex, kp, rate const.of Py complex) and an ihcrease in the ionic strength decreased the ratio. This result was interpreted in terms of the electrostatic interaction of FeEDTA2 with the PVP complex as a polycation, These electrostatic-effect were, discussed, by comparing it with the catalytic action of, polyelectrolyte, in the ioni, c, reaction