Abstract: The dissociation constants of N-salicylideneamino acids(Sal:A)and stability contants of binary complexes of Ni(Ⅰ)-salicylideneamino acid and Ni(Ⅱ)-α-amino acid and ternary mixed ligand complexes of Ni(Ⅱ)-N-salicylideneamino acid(ligand A)-α-amino acid (ligand B)at(25±0.1)℃ and in the presence of 0.1mol/dm³ KNO₃ have been determined by pH method.The a-amino acids(Aa)used were glycine(Gly),L-serine(Ser),L-valine (Val),L-leucine(Leu),L-isoleucine(Iso)and L-proline(Pro).It was found that the linear free energy relationship(LFER)exists nicely between the following parameter pairs logβ₁₂₀ and pK₂^A,logβ₁₀₂and pK₂^B,logβ₁₁₁ and pK₂^A,logβ₁₁₁and pK₂^B.The △logK was used to characterize the stability of ternary complexes related to the stability of parent binary complexes. The hydrophobic ligand-ligand interaction in the Ni(Sal:P)(P denotes phenylalanine)was studied.

Key words: nickel(Ⅱ), linear free energy relationship, Schiff base, hydrophobic ligancl-ligand interaction