Heteroligand Copper(II), Nickel(II), and Cobalt(II) Complexes with L-Aspartic Acid and L-Threonine

The stability constants of the Cu(II), Ni(II), and Co(II) complexes with L-aspartic acid and (L1 L-threonine (L2) (1:1 and 1:2) and of the heteroligand ML1L2 complexes were determined by pH-metric titration (logβ = 16.77 ± 0.26 (Cu); 12.47 ± 0.29 (Ni); 10.52 ± 0.32 (Co)). The M(C4H8NO3)(C4H6NO 4) complexes, where M = Cu, Ni, or Co, were synthesized. The data of the IR spectra (400-4000 cm-1 and 200-500 cm1) indicate that the metal ions are coordinated by the ligands that exist in the anionic form through amino and carboxy groups. These ligands are bidentate cyclic ligands. One COOH group of the aspartate ion is not involved in coordination.