A direct carbon-13 and nitrogen-15 NMR study of europium(III) complexation-nitrate and europium(III)-isothiocyanate complexation in aqueous solvent mixtures
- California State Univ., Los Angeles, CA (United States); and others
A direct low-temperature nuclear magnetic resonance spectroscopic study of europium(III)-nitrate contact ion-pairing has been completed, and preliminary results for europium(III)-isothiocyanate have been obtained. In water-acetone-Freon mixtures, at - 110{degrees}C to - 120{degrees}C, four {sup 15}N NMR signals are observed for coordinated nitrate ion. Area evaluations of the signals and their concentration dependence indicate the formation of Eu(NO{sub 3}){sup 2+}, Eu(NO{sub 3}){sup 1}{sub 2}{sup +}, and two higher complexes, possibly the tetra-, with either the penta- or hexanitrato. This correlates well with similar {sup 15}N NMR results obtained for Ce(III), Pr(III), Nd(III), and Sm(III). As a result of a higher dielectric constant, complex formation is significantly less in water-methanol mixtures, wherein only three complexes form with Eu(NO{sub 3}){sup 1}{sub 2}{sup +} dominating at the highest anion concentrations. Competitive complexing experiments in water-methanol also were made by {sup 35}Cl NMR chemical shift and linewidth measurements, as well as {sup 15}N NMR. Initial experiments with the Eu{sup 3+}-NCS{sup -} system show four coordinated anion signals, displaced from the bulk anion peak by about -250 ppm and -2,500 ppm in the {sup 13}C and {sup 15}N NMR spectra, respectively. Area evaluations are consistent with the presence of Eu(NCS){sup 2+} through Eu(NCS){sup 1}{sub 4}{sup -} in these solutions. A consideration of the chemical shifts identified the nitrogen atom as the site of binding in the NCS{sup -}. A discussion of these preliminary results, as well as those for several other metal-ions, will be presented.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 430209
- Journal Information:
- Journal of Solution Chemistry, Vol. 25, Issue 4; Other Information: PBD: Apr 1996
- Country of Publication:
- United States
- Language:
- English
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