One and two-dimensional NMR investigations of the inclusion of the monosulfonated triphenylphosphine in the β-cyclodextrin

The interaction between the sodium salt of the monosulfortated triphenylphosphine and the beta-cyclodextrin has been investigated in aqueous solution by high field nuclear magnetic resonance and UV-Vis spectroscopies. Continuous variation and titration plots obtained from NMR and UV-Vis data indicate formation of a 1:1 inclusion complex and allow to calculate an association constant of 12,000 M-1 at 25degreesC. The T-ROESY NMR experiments complemented by molecular modelling suggest that one of non-sulfonated aromatic rings is included into the hydrophobic cavity of the beta-cyclodextrin from the side of secondary hydroxyl groups. Formation of inclusion complex with the alpha- and gamma-cyclodextrin is also briefly discussed.