THE EFFECTS OF CYCLODEXTRIN INCLUSION OF THE FERROCENEMONOCARBOXYLATE ANION ON THE KINETICS OF ITS OXIDATION BY BIS(PYRIDINE-2,6-DICARBOXYLATO)COBALTATE(III) IN AQUEOUS-SOLUTION

The effects of alpha-, beta-, dmbeta-(heptakis(2,6-di-O-methyl)-beta-) and gamma-cyclodextrins (CD) on the kinetics of the electron-transfer reaction of the ferrocenemonocarboxylate anion (FCA-) with bis(pyridine-2,6-dicarboxylato)cobaltate(III) have been investigated in aqueous solution (0.20 M Na2HPO4, pH 9.2) at 25.0-degrees-C. Substantial decreases in the rate constants for the electron-transfer reactions were observed upon cyclodextrin inclusion of the reductant, due to an increase in the FCA0/- reduction potential and to the insulation of the reductant from oxidant. The inclusion stability constants for {FCA-CD}- were evaluated from the H-1 NMR and kinetic data, and the order of the stability constants was found to be beta-CD almost-equal-to dmbeta-CD >> gamma-CD > alpha-CD.