Lanthanum-139 nuclear magnetic resonance studies of polyaminocarboxylate-lanthanum complexes in aqueous solution

Abstract

Several complexes of La(III) with aminocarboxylate and polyaminocarboxylate ligands in aqueous solution have been studied using 139La chemical-shift and linewidth measurements. The ligand-induced shifts of the 139La NMR resonance were found to depend, at least to first order, on additive substituent contributions, and were empirically related to the number and type of coordinated oxygen and nitrogen atoms. A previously proposed relationship between the number of coordinated carboxylate oxygen atoms and observed 139La shifts does not seem to hold for the polyaminocarboxylate complexes and we propose a new empirical relationship which allows an accurate prediction of the number and types of ligand donors in these systems. The 139La linewidths also provide qualitative information about the symmetry of each La 3+ chelate. The results show that 139La NMR can be a powerful technique for elucidating the structure and dynamics of lanthanide complexes in solution.