Stability constant of ternary complexes of copper(II) involving Schiff bases as primary ligands and amino acids as secondary ligands

Abstract

The formation constant of mixed ligand complexes of copper(n) with Schiff bases 1-(2'-hydroxyl benzamido)-2-phenyl azomethine (L 1 ) and 1-(2'-hydroxyl benzamido)-2-(2-methyl phenyl) azomethine (L 2 ) as primary ligands and glycine (R 1 ), DL-valine (R 2 ) as secondary ligands have been determined potentiometrically in 40% (v/v) THF-water mixture at 30 °C and ionic strength of 0.1 M NaClO 4 . The protonation constants of free ligands and stability constant for ternary systems involving Schiff bases and amino acids were also determined under identical conditions. The pH titration data were analysed using the computer SCOGS programme. The relative stability of ternary complexes as compared to that of corresponding binary complexes has been quantitatively explained in terms of A log K, K R , K L and K r values.