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

1 H and 19 F NMR spectra were recorded for D 2 O solutions of sodium perfluoroheptanoate with defined concentrations up to 200 mM, in the absence and presence of b-cyclodextrin (15 mM). Analysis of 1 H 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 b-cyclodextrin and leads to an estimate for the apparent inclusion constant ( ‡10 4 M -1 ). In addition, analysis of 19 F 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 bcyclodextrin (104 and 116 mM). It is shown that the self-association of perfluoroheptanoate and its inclusion in b-cyclodextrin lead to shielding and deshielding of the fluorine atoms, respectively.