Interactions of Cu (II) with Hydroxy Salicylic Acids

Chemistry Department, Marathwada University, Aurangabad

Manuscript received 16 December 1972; accepted 28 May 1973

The interactions between Cu²⁺ and 4-hydroxy, 5-hydroxy and 6-hydroxy salicylic acids have been investigated in aqueous medium and — 0.1 M ionic strength by Calvin-Bjerrum potentio­metric titration technique. It was observed that Cu²⁺ forms 1 : 1 and 1 : 2 complexes with these ligands in the pH ranges of 4-6 and 7-8 respectively. The complexation occurs by the reactions (1) Cu²⁺+ H₂L^{-\(\rightleftharpoons\)}CuHL+H⁺ and (ii) CuHL+H₂L^{-\(\rightleftharpoons\)} Cu(HL)₂^2-+H⁺, (the ligand being H₃L). The stability constants of these complexes are determined and their relation with ligand basicities are discussed.

The possibility of a different type of 1 : 1 complex between Cu²+ and 6-hydroxy salicylic acid by the reaction Cu^2+-+ CuHL^{\(\rightleftharpoons\)}Cu₂L-H⁺ is proposed. Evidence for such reaction is given by conductometric and potentiometric measurements