Metal complexes of glutamic acid-γ-hydroxamic acid (Glu-γ-ha)(N-Hydroxyglutamine) in aqueous solution

Abstract

Stability constants and assumptions concerning the bonding mode are summarized for the complexes formed in aqueous solution in nickel(II)–, copper(II)–, zinc(II)– and iron(III)–L-glutamic acid-γ-hydroxamic acid (Glu-γ-ha) systems and nickel(II)–, copper(II)– and zinc(II)–acetohydroxamic acid-α-alanine ternary systems as models. Mononuclear species have been found with bidentate co-ordination of the HA^–(monoprotonated) and tridentate co-ordination of the A^2–(deprotonated) form of Glu-γ-ha under the conditions employed. Co-ordination of the hydroxamate and carboxylate oxygens is proposed in the case of iron(III). Complexes with different bonding modes existing in equilibria are formed with nickel(II) and copper(II), while preference for co-ordination via hydroxamate oxygens and amino-N is found with zinc(II).