Complex formation equilibria between copper(II) and Pyridine-2-carbaldehyde

Abstract

Copper(II) complexes of pyridine-2-carbaldehyde can be derived either from the neutral molecule (A) or from the anionic form (AOH-) of the hydrate, so that there are two sets of complexes, CuA_n²⁺ and Cu(AOH)_n^2-n (n = 1, 2), related to each other as acid to conjugate base. There is also a mixed complex, CuA(AOH)⁺. In solution, several species are always present together in equilibrium, with the de- protonated species beginning to predominate above pH 5. The complete system of equilibria at 25° has been worked out and the constants have been evaluated by a combination of spectrophotometry and pH titrations.