Determination of Stability Constants of Some Substituted 4-Pyrazolone Dyes Containing o-Methoxy, o-Carboxy, and o-Nitro Groups with Trivalent Lanthanide Ions

Article abstract of DOI:10.1007/BF00811283

The relative stabilities of the metal derivatives of hydrazo pyrazolone dyes containing ortho-OCH3, -COOH, and -NO2 groups have been measured potentiometrically in 75percent (ν/ν) dioxane-water mixture at 30 degC and < 0.1 ionic strength.The stability constant of their 1:1 and 1:2 chelates with twelve trivalent lanthanide ions Ln(III) have also been determined.The effects of substituents on the hydrazo-moiety of the ligand on the equilibria are discussed.The affinity of different ligands for complexation with lanthanide ions reaches its highest value with ortho-carboxyphenylhydrazopyrazolone.The data were correlated and the results were used to explain the stabilization of such chelates by dative ?-bonding between Ln(III) and the ligand. - Keywords: 1-Phenyl-3-methyl-4-(x-phenylhydrazo)-5-pyrazolone ligands; Stabilty of lanthanide (III)