How does β-cyclodextrin affect the aggregation of sodium perfluoroheptanoate in aqueous solution:: a 19F NMR study

H-1 and F-19 NMR spectra were recorded for D2O solutions of sodium perfluoroheptanoate with defined concentrations up to 200 mM, in the absence and presence of beta-cyclodextrin (15 mM). Analysis of H-1 chemical shift data obtained by the method of continuous variations (Job's method) confirms the formation of 1:1 inclusion complexes for the perfluoroheptanote anion in beta-cyclodextrin and leads to an estimate for the apparent inclusion constant (>= 10(4) M-1). In addition, analysis of F-19 chemical shift data based on two simplifying assumptions (monodisperse perfluoroheptanoate solutions below the critical micellar concentration (CMC), and a single self-associated state after the CMC) enables to interpret all the experimental chemical shift data and allows to determine CMC values for the absence and presence of beta-cyclodextrin (104 and 116 mM). It is shown that the self-association of perfluoroheptanoate and its inclusion in beta-cyclodextrin lead to shielding and deshielding of the fluorine atoms, respectively.