Spectroscopic and Thermodynamic Properties of Some Transition Metal Complexes Derived from 2-(Hydroxyimino)-1-(2-hydroxyphenyl)butane-1,3-dione

The protonation constants of the syn ketoxime, 2-(hydroxyimino)-1-(2-hydroxyphenyl)butane-1,3-dione (HPDO) were determined by a pH-metric method in solutions of dioxane, methanol and dimethylformamide (75 % v/v) at 20 ± 0.1 °C and ionic strength of 0.1 mol·L−1 supported by KNO3. The complexation reaction of the ligand HPDO with the transition metal ions Cu(II), Ni(II), Co(II), Cr(III), Fe(III), and Mn(II) in solution has been also studied potentiometrically. The stability constants of the respective species were determined and show that their values decrease in the order: 1,4-dioxane