The complexation of several alkyldimethyl(ferrocenylmethyl)ammonium cations, where the alkyl group is -CH3 (1+), -(CH2)6CH3 (2+), or -(CH2)7COOH (3+), by the hosts α- and β-cyclodextrin (α- and β-CD) was investigated in aqueous media using calorimetric and 1H NMR spectroscopic measurements. The calorimetric results indicate that the complexation of all the ferrocene-containing guests is enthalpically driven. β-Cyclodextrin binds all the guests primarily by including the ferrocenyl groups into its cavity. By contrast, α-cyclodextrin binds guests 2+ and 3+ by threading the aliphatic chains of these guests through its cavity. The zwitterionic, deprotonated form (3) of the latter guest is bound by partial inclusion of the ferrocenyl group, a mechanism similar to that prevalent in the complexation of 1+. The complexation processes of 1+ by β-CD and 2+ by α-CD were also investigated in water-urea mixtures. Our calorimetric data reveal that large concentrations of urea cause a substantial decrease in the binding constant for the complexation process. The presence of urea considerably diminishes the enthalpic stabilization of both complexes.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry