Exploratory spectroscopic and computational studies of the anion binding properties of methyl hyocholate in organic solvent

The binding properties of methyl hyocholate 1a toward F−, Cl−, Br− and CH3CO2− anions were explored by 1H and 13C NMR, ESI-MS measurements and computational calculations. The 1H NMR titration suggested that 1a forms a 1:1 complex with the selected anions. These complexes have also been detected by ESI-MS measurement even though the MS spectra showed that the stoichiometry of the predominant host-guest species in the gas phase is 2:1. 13C NMR and computational data suggested that the hydroxyl groups at C6 and C7 positions are more involved than the hydroxyl group at C3 position in the binding of spherical F−, Cl−, Br− anions while in the case of the Y-shaped acetate ion two different conformers (in equilibrium) are present: the first showing interaction with both the two hydroxyl groups at C6 and C7 positions, the second also involving the participation of the third hydroxyl group at C3 position.

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