‘Catalysis’ by anionic and cationic polyelectrolytes on reactions between cationic species: outer and inner sphere electron transfer reactions of Co complexes

Abstract
Electron transfer reactions of Co complexes with Fe2+ (inner sphere) and with V2+ (outer sphere) are studied in the presence of polyelectrolytes. Anionic polyelectrolytes accelerate the reactions remarkably, as expected. Two points are noteworthy: (1) the acceleration for the Fe2+ systems is larger than that for the V2+ reactions, in spite of the fact that both are divalent, and (2) electron transfer reaction between cationic species (Co(NH3)4(N3)2+ and Fe2+) is accelerated, though slightly, by addition of a cationic polyelectrolyte. This is in qualitative agreement with predictions based on Brönsted-Bjerrum-Manning theory. Temperature dependence study shows that the acceleration observed for the Fe2+ cases is due to entropic gain whereas that in the case of V2+ is ascribed to decrease in the enthalpy of activation.

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