Characterization of Ni(II) and Cu(II) complexes of 4-(2-Quinolylmethyleneamino)-1-phenyl-2,3-dimethyl-5-pyrazolone and their analytical applications

A synthesis of the new reagent 4-(2-quinolylmethyleneamino)-1-phenyl-2,3-dimethyl-5-pyrazolone (QPP) and of its complexes with Ni(II) and Cu(II) is described. The structure of the ligand itself and the nature of the bonding in complex molecules were determined by elemental analysis, IR, and mass spectrometry. The analysis of data showed that isolated crystal metal complexes are of the ML₂ type. The composition and stability constants of the complexes in water/methanol solutions, (methanol) = 0.16, at constant temperature 25 ±1 °C and ionic strength of 0.5 M (KNO₃) at different pH (4, 6, 8, and 10) have been determined spectrophotometrically. The results indicate that the metal complexes formed in the solution have a metal-to-ligand ratio 1:2. The reaction of QPP with Ni(II) and Cu(II) in solution was quantitatively studied. The lowest detection limit for the determination of Ni is 0.3 μg/ml while that for Cu is 0.05 μg/ml under the investigated experimental Conditions.