The computer-based analysis of pH titration data obtained for the determination of the stability constants of M-A-B [M=Ni(II), Cu(II) or Zn(II), A=salicylaldehyde(Sal) and B=L-valine (Val), L-phenylalanine (Phe) and L-tryptophan (Trp) and AB the corresponding Schiff base] indicates preference for the formation of Schiff base complexes rather than the ligands binding as such to the metal ions without fusion of rings. The presence of aliphatic or aromatic side chains in the amino acids has no effect on the basicities of the coordinating sites of the Schiff bases. This is shown by the similarity of stability constant values for different Schiff base complex species.
