Complexation of Lanthanide(III) Ions with Polyhydroxy Carboxylic Acids in Aqueous Solutions

Abstract

The complexation of lanthanum(III), europium(III), dysprosium(III), erbium(III), and lutetium(III) with D‐gluconic acid (LH) was studied by pH potentiometry and NMR. The set of complexes formed in aqueous solutions and their stability constants β were determined, and the results were compared to those previously found for praseodymium(III) (S. Giroux et al., Polyhedron 2000, 19, 1567). A regular evolution of the β values was observed along the lanthanide series, particularly for the neutral complex MLH−2 (where two hydroxy functions were deprotonated) with a selectivity similar to that of EDTA. For the ML2+ complex, where the ligand was coordinated via the carboxylate groups, the analysis of the 13C NMR pseudo‐contact shift showed that the carboxylate group was not bidentate and that there was a participation of the α‐hydroxy group in the coordination. The study of the complexation of PrIII with other hydroxy carboxylic acids: glyceric, threonic, 2‐hydroxybutanoic, and 3‐hydroxybutanoic acids confirms that in the complex MLH−2 the deprotonated hydroxy groups, that intervene in the coordination with the metal ion, are those in α and γ positions relative to the carboxylate group. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Complexation of gluconic acid with Nd(III) in acidic solutions: A thermodynamic study

“…The thermodynamic observation for the participation of the hydroxyl group into the complexation is also in agreement with Giroux et al's work [7], where 13 C NMR data confirmed the involvement of ␣-hydroxyl group of gluconate in the coordination to Pr(III). Table 3 summarizes the measured thermodynamic parameters of gluconate protonation [11] and its complexation with Ca 2+ and NpO 2 + [11] at 25 • C and 1.0 M NaClO 4 .…”

“…Several studies on the complexation of gluconic acid with lanthanides [1][2][3][4][5][6][7][8] and actinides [9,10] can be found in the literature. Stability constants were reported in these studies, but no other thermodynamic properties (e.g., enthalpies) were provided.…”

Conformational analyses of 2,3‐dihydroxypropanoic acid as a function of solvent and ionization state as determined by NMR spectroscopy

“…The solution of 1 in D 2 O was adjusted to pH 1 with DCl (20% w/w in D 2 O, 99.5 at.% D, from CIL) to ensure near complete protonation of the carboxyl group. In organic solvents, 1 (pK a in H 2 O D 3.52) 39 was assumed to exist essentially as the undissociated acid. The anion 2 was prepared by addition of tetrabutylammonium cyanide and dissolution in methanol under a nitrogen atmosphere, followed by concentration to dryness.…”

Complex formation and lactonization reactions in aqueous solutions containing Ca2+ or Nd3+ ions and sugar-type ligands

“…[105]. The proton displacement from the OH group of gluconate also holds for other lanthanides, such as La 3+ , Pr 3+ and Eu 3+ [31,126]. Along with the 1:1:-1 and 1:1:-2 species, complexes with the stoichiometry of 1:2:-1, 1:2:-2 and 1:2:-3 were also reported [121][122][123][124].…”

“…It is noteworthy that the dependence of the complexation on the metal ion concentration was not investigated in spite of its importance in detecting multinuclear complexes. Such species were found to be formed with copper(II) [28,30,108], calcium(II) [62] and europium(III) [126].…”