Effects of side chain amino nitrogen donor atoms on metal complexation of aminohydroxamic acids: New diamino-hydroxamates chelating Ni(II) more strongly than Fe(III)

Enyedy, Éva Anna and Csoka, H. and Lázár, István and Micera, G. and Garribba, E. and Farkas, Etelka (2002) Effects of side chain amino nitrogen donor atoms on metal complexation of aminohydroxamic acids: New diamino-hydroxamates chelating Ni(II) more strongly than Fe(III). JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS (13). pp. 2632-2640. ISSN 1472-7773

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Abstract

Complexes of diaminohydroxamic acids 2,6-diamino-N-hydroxyhexanamide (lysinehydroxamic acid, Lysha), 2,4-diamino-N-hydroxybutanamide (2,4-diaminobutyrohydroxamic acid, Dambha) and 2,3-diamino-N-hydroxypropanamide (2,3-diaminopropionohydroxamic acid, Dampha) with manganese(II), cobalt(II), iron(II), nickel(II), copper(II), zinc(II), iron(III), aluminium(III) and molybdenum(VI) in aqueous solution were studied by pH-potentiometric, UV-visible spectrophotometric and EPR methods. The two latter diaminohydroxamic acids were synthesised as new ligands and characterised. The results were compared to those of a simple alpha-amino acid derivative, alpha-alaninehydroxamic acid (alpha-Alaha) and the effects of the side chain amino group on the co-ordination mode and on the stability of the complexes formed were evaluated. As expected, the side chain amino nitrogen atom of Lysha does not co-ordinate to any of the studied metals but remains free for possible further interactions. The amino groups do not co-ordinate to aluminium(III) or iron(III) at all and the closer the side chain amino group is situated to the alpha-aminohydroxamic residue the less stable the hydroxamate complex formed in the order of Lysha, Dambha, Dampha, and hydrolytic processes become increasingly dominant. The co-ordination of the side chain amino nitrogen of Dampha and Dambha to nickel(II) and copper(II) was unambiguously observed.

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