L-Mimosine, an amino acid with maltol-type binding properties toward copper(II), oxovanadium(IV) and other metal ions

The complex formation between L-mimosine, alpha-amino-beta-(3-hydroxy-4-oxo-1,4-dihydropyridin-1-yl)-propanoic acid, a rare a-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 L-mimosine prefers the maltol-like donor set of the 3-hydroxypyridin-4 (IH)one fragment for binding copper(II) and oxovanadium(IV). However, the presence of two alternative donor centres in the ligand, (COO-, NH,) and (CO, O-), both suitable for chelating behaviour, makes possible the formation of very stable polynuclear species in which the L-mimosine ligand coordinates at both the (CO, O-) maltol-like and the (COO-, NH2) alpha-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. (C) 1999 Elsevier Science Inc. All rights reserved.