On the Interaction of Ionic Liquid 1-Butyl-3-Methylimidazolium Hexafluorophosphate with β-Cyclodextrin in Aqueous Solutions

The formation of inclusion complex of beta-cyclodextrin (beta-CD) with the hydrophobic room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF(6)) in aqueous solutions was studied at 298 IS K using H-1, C-13, F-19 and P-31 NMR spectroscopy and isothermal titration calorimetry (ITC) Currently there is a disagreement in the literature concerning the structure of the complex formed In contrast to some results published recently in the literature. we found no reasonable support for beta-CD to form an inclusion complex with 1-butyl-3-methylimidazolium cation of bmimPF(6) in water Our measurements on bmimPF(6). the ionic liquid 1-butyl-3-methylimidazolium chloride (bmimCl), and the inorganic salt potassium hexafluorophosphate (KPF6) consistently support the formation of a weak I 1 inclusion complex of beta-CD with hexafluorophosphate anion instead of the bmim(+) cation The thermodynamic parameters of the respective complexation were calculated The binding constant was evaluated from ITC and proton. fluorine and phosphorus NMR measurements. and the complex formation enthalpy and entropy were obtained from ITC