A proton nuclear magnetic resonance relaxation study of the glycine, alanine, and lactate complexes of gadolinium(III) in aqueous solution

Abstract

, 1508 (1987). The 'H nuclear magnetic resonance spin-lattice and spin-spin relaxation rate enhancements induced by the gadolinium(II1) ion were measured in solutions of glycine, alanine, and sodium lactate containing different amounts of Gd(II1). The proton relaxation rates in the Gd(II1) complexes were calculated from these data, and were used to calculate metal-hydrogen atom distances.Comparison of these data with corresponding distances calculated from literature X-ray crystallographic data for model compounds shows that in the two amino acid complexes the Gd(II1) ion is coordinated in a four-membered ring through the two oxygen atoms of the carboxyl,ate group. By contrast, in the lactate complex coordination is via a five-membered ring involving one oxygen atom of the carboxylate group and the a-hydroxyl oxygen.

Novel gadolinium complexes in aqueous solution : characterization, identification and probable structures

“…Thus, we find that the intense peak of OH in α position of the free acid (very intense peak) is reduced (weak intensity) when Gd-mandelate complex is formed, we explained this decrease by the OH group is related to Gd 3+ by free pair electron of oxygen without deprotonation of OH, thus the participation of the NH 2 group in α position by the free doublet of the nitrogen at the formation of the GdSerine complex. These results are identical with other work established for certain complexes of lanthanide ions with organic compound and amino substances [33]. In addition, there is the appearance of new peak at 1640 ± 40 cm -1 , it is the vibration of the water molecules [8], [27], [28] attached on Gd metal.…”

“…The new complex obtianed by interaction with Gd(III) and amino acid « serine » is trinuclear complex and its compositions are (3,2,4), with the intervention of four H + protons, it was explained that the high number of H + by the condensation of two gadolinium ions to form a one dinuclear hexadentate site and one mononuclear didentate site, then we propose, in figure 7 the probable structure for this trinuclear complex. This trinuclear complex with the formation of a mononuclear bidentate site (Gd between two OH groups in β position) and 2 nd dinuclear hexadentate (majority site) requires four H + protons, whose formation is due to the high basicity of the amine group -NH 2 in α position compared to OH group in β position, the OH and NH 2 groups in serine participate in chelations sites without protonation [8][9][10], [28], [33][34][35]. If we suppose that the serine ligand is not rotate, we obtain a trinuclear complex, but three sites are mononuclear, between them two sites mononuclear tridentate (Gd between OH in β position of one acid and two oxygen of COOH of 2 nd acid), these two sites needed one H + for esch site, is to say in a total : two protons (H …”

Luminescent probing of the simplest chiral α‐amino acid–alanine in an enantiopure and racemic state

“…Transition metals including rare earth metals are able to form a diversity of complexes with organic compounds bearing groups that are Lewis bases. Alanine is not an exception, and a number of its complexes with lanthanides [14][15][16][17][18][19] and actinides [20][21][22] have been reported. Three main types of complexation between amino acids and lanthanides are known ( Figure 2).…”

Use of a laboratory robot for repetitive solution NMR sample preparation

“…4 for details). Using the nonlinear least-squares routine Sigmaplot, the value of Ka was refined to obtain the 3~trictly speaking, activity, but we will neglect consideration of activity coefficients here for simplicity, since it [2], [3], and [4]. See text for further details.…”

“…We have found a combination of both of these techniques to be a potent method for elucidation of a variety of multiequilibrium systems (3)(4)(5)(6)(7). Details of implementation have been discussed therein; a simple example of the application of NMR studies is given later in this paper (see Performance evaluation).…”