Abstract
Host-guest equilibria have been investigated involving inclusion sites of the microparticulate amorphous β-cyclodextrin polymer, β-CDP-25, and a range of redox guests comprising regioisomeric nitrobenzene derivatives and ferrocene. The equilibria were studied by the batch method. Inclusion-governed, Langmuir-type sorption equilibria occurred in the β-CDP-25/guest systems studied in 1:1 (v/v) aqueous methanolic solutions. A 1:1 (host inclusion site)/guest stoichiometry was found and sorption equilibrium constants were determined. The values of the constants changed by a factor of 20 between the most weakly and strongly included guests. Regioselective discrimination of β-CDP-25 was most pronounced with respect to nitrophenols. Transport phenomena of guest molecules in the β-CDP-25 matrix have also been studied. The apparent diffusion coefficients of guest molecules were determined in the β-CDP-25 matrix by chronamperometry at the (β-CDP-25)-PTFE-carbon composite electrodes. These diffusion coefficients were almost four orders of magnitude lower than the corresponding coefficients of guest molecules in solution in the absence of β-CD. The diffusion mechanism was postulated for the guest molecules in the β-CDP-25 matrix, which invoked hopping of the molecules between inclusion sites.
Published Version
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