NMR study of the inclusion complex formed between γ-cyclodextrin and TmDOTP5−

✍ Scribed by A. Dean Sherry; Ryszard Zarzycki; Carlos F. G. C. Geraldes

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 448 KB
• Volume: 32
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260320610

✦ Synopsis

Abstract

The host–guest complex formed in aqueous solution between γ‐cyclodextrin (γ‐CD) and the macrocyclic paramagnetic shift reagent TmDOTP^5−^ was examined by NMR spectroscopy. Paramagnetic lanthanide‐induced shifts (LIS) and spin‐lattice relaxation rate enhancements in the proton resonances of γ‐CD on binding of TmDOTP^5−^ were used to define the position of the guest anion within the host cavity. A proportionality constant which relates pseudo‐contact shifts induced by TmDOTP^5−^ to the geometrical position of each ligand nucleus (previously determined from a LIS study of the TmDOTP^5−^ complex) was used to determine a fully bound LIS value for each γ‐CD proton. These values, in combination with experimental LIS data from TmDOTP^5−^ titrations at constant γ‐CD concentration, were then used to obtain the association constant for the host‐guest complex (3.9–4.5 mol l^−1^). These constants were indicative of a weak host‐guest interaction and consistent with the location of the TmDOTP^5−^ binding site reported by the LIS values well above the center of the γ‐CD cavity.