Stoichiometry, complex stability, molecular size and conformational variations of metal ion crown ether complexes subject to diffusion coefficients in nonaqueous solutions |
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Authors: | Philipp Wacker Erich Kleinpeter |
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Affiliation: | 1. Institut für Chemie, Universit?t Potsdam, P.O. Box 60 15 53, 14415, Potsdam, Germany
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Abstract: | Both the stoichiometry and complex stability constants of crown ether complexes with metal ions have been determined by examining gradual changes in their diffusional behavior in nonaqueous solution. Diffusion coefficients, D, were evaluated by pulsed field gradient (PFG) NMR titration experiments whilst complex stability constants were determined by nonlinear curve-fitting procedures, D versus csol., which also allow the treatment of multiple complexation equilibria (1:1 to 1:2 stoichiometries). Differences in the diffusion coefficients of the various free crown ethers with respect to their metal ion complexes indicate great sensitivity to both conformational changes and changes in molecular size upon complexation. |
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Keywords: | Metal ions complexation Complex stability constant Conformation Diffusion Crown ethers Flexibility PFG NMR spectroscopy Stoichiometry |
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