C. A. M. Vijverberg

An nmr study of gadol inium (iii) hydroxycarboxtlate complexes in aqueous medium using gd(iii) induced 13c relaxation rate enhancements

Abstract The complexation of gadolinium(III), as a model cation for calcium(II), with a series of (hydroxy)carboxylates in aqueous medium has been studied by NMR using the Gd(III) Induced relaxation rate enhancement of the 13C nuclei of the ligands. In this way the coordination behaviour of a number of essential structural units has been investigated, i.e. the carboxylate group, the 2- and the 3-hydroxycarboxylate moiety, the 2,3-dihydroxycarboxylate moiety, and combinations thereof. The results show that (i) an isolated carboxylate group coordinates in a bidentate fashion, (ii) a 2-hydroxycarboxylate moiety coordinates bidentately through a carboxylate oxygen and a hydroxyl oxygen, (iii) a 3-hydroxycarboxylate moiety largely acts as a bidentate ligand through the two carboxylate oxygens, (iv) a 2,3-dihydroxycarboxylate moiety acts largely as a bidentate ligand through one of the carboxylate oxygens and the α-hydroxyl group; the contribution of the β-hydroxyl group to the complexation is of minor importance.

Lanthanide(III) salts of (S)-carboxymethyloxysuccinic acid: chiral lanthanide shift reagents for aqueous solution

Abstract The use of lanthanide(III) salts of (S)-carboxymethyloxysuccinic acid for the NMR separation of enantiomeric mixtures of amino acids and (oxy)carboxylic acids in aqueous solution is described.