Stability Constants of Ternary Complexes of Cu(II) and Ni(II) With N-Substituted Anthranilic Acids with Some Amino Poly Carboxylic Acids

Abstract

Potentiometric titrations were carried out for the formation   of binary and ternary complexes of the type MA, ML and   MAL where M = Cu(II) and Ni(II), A = iminodiacetic acid   (IMDA), hydroxyiminodiacetic acid (HIMDA) or nitrilotriacetic   acid (NTA) and L = N-methyl anthranilic acid (N-Me.An.A.),   N-butyl anthranilic acid (N-Bu.An.A.) or N-phenyl anthranilic   acid (N-Ph.An.A.) at 303 K and 0.1 M ionic strength in   50 % (v/v) ethanol-water medium. The stabilities of the ternary   metal complexes have been quantitatively compared with the   stabilities of the corresponding binary metal complexes   determined under identical experimental conditions and   expressed in terms of Δ log K. The Δ log K values calculated   for all the systems indicate the extent of stabilization and   destabilization of ternary chelates compared to their binary   chelates. The order of stability constants of ternary systems   with respect to polyamino carboxylic acids is found to be   IMDA > HIMDA > NTA. These were explained in the light   of their basicities, charge neutralization and electrostatic   interactions.