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NMR study of the inclusion complex formed between γ‐cyclodextrin and TmDOTP 5−
Author(s) -
Sherry A. Dean,
Zarzycki Ryszard,
Geraldes Carlos F. G. C.
Publication year - 1994
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260320610
Subject(s) - chemistry , lanthanide , titration , cyclodextrin , stability constants of complexes , binding constant , nuclear magnetic resonance spectroscopy , crystallography , proton nmr , aqueous solution , reagent , paramagnetism , chemical shift , stereochemistry , ion , binding site , organic chemistry , biochemistry , physics , quantum mechanics
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.