Structures and Stabilities of Tungstate Complexes of .alpha.-Hydroxy Acids. 183W NMR Study of the Influence of Ligand Substitution

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

“…In this sense and in the my works published [7][8][9][10] we have demonstrated, experimentally, that the composition and stability of the colored sacrificial complex were determined, we found a complex type (3, 2, 3) and stability constant 16.27 323 logK  in pH range 5.50 -7.50, and the probable reaction for this complex faormation is :…”

“…The absence of doubling new peaks, which appeared, gives us the idea that complexes structures are symmetrical. So the general formulas of the three characterized complexes are : [8][9][10], [28], [34]. The complexes identified, in this work, are the type (2,2,2) for system Gd-mandelate and (3,2,4) for Gd-Serine complex.…”

“…Thus, the importance of IPD technique was also revealed by its adaptation to other techniques of separation and determination, such as liquid chromatography [3], [4], capillary electrophoresis [5] and continuous flow analysis (FIA) [6]. Some studies show that this technique is very effective in identifying some colorless gadolinium [7], [8], [9] and tungstate complexes of sugars and organic acids [10]. The detection or monitoring of certain diseases, sometimes requires injection gadolinium complexes because of the interesting electro nic and magnetic properties of this ion [11], [12].…”

“…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 …”

Multinuclear NMR study of the complexes of 6-phospho-d-gluconic acid with W(VI) and Mo(VI)

“…[4][5][6][7][8][17][18][19][20][21] The oxygen shifts are typical of terminal M@O groups, and there is no evidence for any bridging oxygen atoms. 4,[6][7][8][17][18][19][22][23][24][25][26] The high frequency shifts observed for the carboxylic and the adjacent carbinol C nuclei are characteristic of the involvement of these groups in complexation; [4][5][6][7][8][17][18][19]21,27-33 the other carbon shifts upon complexation are much smaller.…”