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Proton- and lanthanide-coordinating properties of the tetraaza macrocycle (EDDA-KA)(2) in aqueous solution

TitleProton- and lanthanide-coordinating properties of the tetraaza macrocycle (EDDA-KA)(2) in aqueous solution
Publication TypeJournal Article
Year of Publication2001
AuthorsSong, B, Kurokawa, GS, Liu, S, Orvig, C
JournalCanadian Journal of Chemistry-Revue Canadienne De Chimie
Volume79
Pagination1058-1067
Date PublishedMay
Type of ArticleArticle
ISBN Number0008-4042
KeywordsACID-BASE, acidity constants, ALKALINE-EARTH, amino, BINDING-PROPERTIES, carboxylate chelator, CHEMISTRY, CONTRAST AGENTS, DERIVATIVES, DYNAMICS, Fe3+, GADOLINIUM, Gd3+, La3+, Lu3+, METAL-COMPLEXES, STABILITIES, stability constants
Abstract

{The new potentially multidentate ligand (EDDA-KA)(2) has been prepared and its acid-base properties determined. Its coordination properties with three lanthanide ions (La3+, Gd3+, and Lu3+) and Fe3+ have been studied in aqueous solution (I = 0.16 M NaCl, 25degreesC) by potentiometric pH, spectrophotometric, and H-1 NMR titrations. In total, eight pK(a) values could be determined by these diverse methods. From the H-1 NMR titrations, all the deprotonation steps could be determined and assigned (in groups). Strong hydrogen bonding among two nitrogen atoms and one oxygen atom on the pyrone ring was observed, and the corresponding pK(a) values were estimated to be 13.2 and 14.0. By comparison with similar systems, an equilibrium constant for the formation of the hydrogen bond was estimated

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