Abstract

The complex formation between -mimosine, α-amino-β-(3-hydroxy-4-oxo-1,4-dihydropyridin-1-yl)-propanoic acid, a rare α-amino acid provided with a 3-hydroxypyridin-4(1H)one moiety, and some metal ions — Cu(II), VO(IV), Ni(II) and Zn(II) — was studied by spectroscopic (EPR and electron absorption) and potentiometric techniques in aqueous solution. It was found that -mimosine prefers the maltol-like donor set of the 3-hydroxypyridin-4(1H)one fragment for binding copper(II) and oxovanadium(IV). However, the presence of two alternative donor centres in the ligand, (COO^-, NH₂) and (CO, O^-), both suitable for chelating behaviour, makes possible the formation of very stable polynuclear species in which the -mimosine ligand coordinates at both the (CO, O^-) maltol-like and the (COO^-, NH₂) α-aminocarboxylate sites. Nickel(II) interacts with the ligand, but prefers a mixed bonding mode in the bis chelated species. Zn(II) only forms complexes with the 3-hydroxypyridin-4(1H)one fragment.

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