Inclusion complexation of (11-ferrocenylundecyl)trimethylammonium bromide by β-cyclodextrin and its effects on electrochemical behavior of the surfactant

This report describes the influence of β-cyclodextrin complexation on thermodynamic and kinetic parameters of the electrode reaction of (11-ferrocenylundecyl)trimethylammonium bromide in aqueous media. The host attracted the reduced form having a less positive charge more strongly than the corresponding oxidized one. Thus, a hydrophobic interaction between the non-polar host cavity and the ferrocene moiety plays an important role in the inclusion complexation. Fast-scan voltammetric behavior of the amphiphilic ion suggested that inclusion–ejection processes practically attain equilibrium in the scan-rate range below 10 V s−1, because of their fast rates. The relation between the peak current and peak potential leads to the conclusion that the enveloped guest exchanges no electrons directly with an electrode. The mean diffusion coefficient of the surfactant can be written as a linear combination of the contributions from a free monomolecular, a micelle-forming, and a host-bound surfactant. Since the binding affinity of the ferrocene moiety for the host cavity is much stronger than the aggregation force between the amphiphilic molecules in aqueous media, the host disrupts the micelles by incorporating the surfactant molecule into its cavity. [Copyright &y& Elsevier]