NMR-STUDY OF THE INCLUSION COMPLEX FORMED BETWEEN GAMMA-CYCLODEXTRIN AND TMDOTP5-

The host-guest complex formed in aqueous solution between gamma-cyclod extrin (gamma-CD) and the macrocyclic paramagnetic shift reagent TmDOT P5- was examined by NMR spectroscopy. Paramagnetic lanthanide-induced shifts (LIS) and spin-lattice relaxation rate enhancements in the prot on resonances of gamma-CD on binding of TmDOTP5- were used to define t he position of the guest anion within the host cavity. A proportionali ty constant which relates pseudo-contact shifts induced by TmDOTP5- to the geometrical position of each ligand nucleus (previously determine d from a LIS study of the TmDOTP5- complex) was used to determine a fu lly bound EIS value for each gamma-CD proton. These values, in combina tion with experimental LIS data from TmDOTP5- titrations at constant g amma-CD concentration, were then used to obtain the association consta nt For the host-guest complex (3.9-4.5 mol l(-1)). These constants wer e indicative of a weak host-guest interaction and consistent with the location of the TmDOTP5- binding site reported by the LIS values well above the center of the gamma-CD cavity.