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

Abstract

The effects of α-, β-, dmβ-(heptakis(2,6-di-O-methyl)-β-) and γ-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°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 the1H NMR and kinetic data, and the order of the stability constants was found to be β-CD≈dmβ-CD≫γ-CD>α-CD.