NMR study of the kinetics of the proton-exchange reactions in aqueous solutions of copper(II)-amino acid parent complexes

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Abstract

The rate constants of the proton-exchange reactions in aqueous solutions of the complexes of the copper(II) ion with the amino acids glycine, α-alanine, α-aminobutyric acid, norvaline, β-alanine, serine, threonine, asparagine, glutamine, aspartic acid, glutamic acid, ornithine and lysine were determined at 28°C by an NMR method. From a comparison of the literature formation rate constants and the exchange-rate data obtained in this work it was concluded that for the copper(II)-serine complex the kinetic activity of the zwitterion is caused by the axial coordination of the alcoholic OH group. The data obtained for the β-alanine complex indicate that the rate-determining step in the complex-formation is ring-closure. Equilibrium and kinetic data show that the thermodynamic and kinetic stabilities of the complexes of ligands containing an alcoholic OH group, an amide group or a carboxyl group in the β-position are higher than those of the complexes of ligands not containing a third potential donor group. The stability increase is explained by axial coordination of the functional group in the β-position. A third functional group in the γ or δ-position does not modify the equilibrium and kinetic behaviour of the complexes.

Original languageEnglish
Pages (from-to)2145-2149
Number of pages5
JournalJournal of Inorganic and Nuclear Chemistry
Volume37
Issue number10
DOIs
Publication statusPublished - Oct 1975

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