Analytical properties of the amidoxime group: spectrophotometric and thermometric behaviour of ethanediamidoxime and its Cu(II) and U(VI) complexes

Abstract

The spectrophotometric behaviour of ethanediamidoxime (EDA) and its Cu(II) and U(VI) complexes has been studied. EDA p K values were first calculated and then refined using the MINISPEF (p K 1 = 2.84 and p K 2 =11.23) and SQUAD programs (p K 1 = 2.84 and p K 2 =11.25). The optimum formation conditions for the EDA complexes with Cu(II) and U(VI) have been established, as well as the precision for the spectrophotometric determination of these elements. Stoichiometries for the EDA-Cu(II) complexes are found to be 1:1 and 1:2. The behaviour of the Cu(II)-EDA complexes has also been studied thermometrically. A green 1:2 complex is formed in an acetic acid medium (Δ H= −35.6 kJ mol −1) and a brown precipitate in a sodium acetate medium with 1:1 stoichiometry (Δ H= −23.01 kJ mol −1).