Stability Constants of Cu(II) Chelates with o-Phenylenediamine Derivatives

Abstract

Abstract The stability constants of copper(II) chelates with o-phenylenediamine derivatives have been determined by the pH titration method. The measurements have been carried out at 25.0±0.1°C and μ=0.10(by KNO3). o-Phenylenediamine derivatives, which have a substituent group (CH3, CH3O, COOH, or Cl, etc.) at the 4 positions, were used as ligands. The overall stability constants of the copper chelates are of the order: CH3, CH3O, H, COO−, Cl, COOH; their values were 8.50, 8.42, 7.72, 7.06, 5.76, and 5.35 respectively. The effects of substituent groups on the stability constants have been studied. The plot of the overall stability constants against the sum of Hammett σm and σp values was found to be linear. The chelate stability and acid dissociation constants of the acido complexes of 3,4-diaminobenzoic acid were determined by the use of an augmented matrix.