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Complexation of gallium(III) by 2-hydroxynicotinic acid and 3-hydroxypicolinic acid in aqueous solution

TitleComplexation of gallium(III) by 2-hydroxynicotinic acid and 3-hydroxypicolinic acid in aqueous solution
Publication TypeJournal Article
Year of Publication1998
AuthorsStephens, AKW, Orvig, C
JournalInorganica Chimica Acta
Volume273
Pagination47-53
Date PublishedMay
Type of ArticleProceedings Paper
ISBN Number0020-1693
Keywords3-HYDROXY-4-PYRIDINONES, aluminum, CHELATION, CHEMISTRY, COMPLEXES, EQUILIBRIUM, GA-68, gallium complexes, hydroxynicotinic acid, hydroxypicolinic acid complexes, INDIUM COMPLEXES, INVIVO, LIGANDS, RADIOPHARMACEUTICALS
Abstract

The deprotonations of 2-hydroxynicotinic acid (H(2)nic) and 3-hydroxypicolinic acid (H(2)pic) and the complexation of these molecules with Ga3+ were studied by H-1 NMR, UV-Vis spectrophotometry and potentiometric titration. Both ligands bind Ga3+ at very low pH; the ligand binds in the monodeprotonated form. The stability constants of the [Ga(HL)(n)]((3-n)+) (L = nic or pic; n = 1, 2, or 3) complexes were measured at 25 degrees C, 1.0 M NaCl (for beta(1)) and 0.16 M NaCl (for beta(2) and beta(3)); for H(2)nic (H(2)pic), log beta(1) = 6.78 (7.04), log beta(2) = 12.43 (13.09) and log beta(3) = 16.20 (17.74). At higher pH, polynuclear mixed ligand-hydroxo species form, although their composition and stability could not be determined. These complexes undergo hydrolysis to form [Ga(OH)(4)](-) above pH 7. (C) 1998 Elsevier Science S.A. All rights reserved.

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