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has been cited by the following article:

• TITLE: Potentiometric, spectrophotometric, conductimetric and thermodynamic studies on some transition metal complexes derived from 3-methyl-1-phenyl- and 1, 3-diphenyl-4-arylazo-5-pyrazolones

  AUTHORS: Samir A. AbdelLatif, Saber E. Mansour, Abdulrahman A. Fatouh

  KEYWORDS: Azopyrazolones; Lonization Constants; Stability Constants; Thermodynamic Parameters; Transition Metal Complexes; Potentiometry;Spectrophotometry

  JOURNAL NAME: Natural Science, Vol.2 No.8, August 25, 2010

  ABSTRACT: A new 3methyl1phenyl4arylazo5pyrazolone and 1, 3diphenyl4arylazo5pyrazolone have been synthesized and characterized by elemental analysis, IR, mass and 1H NMR spectra. The acid dissociation constants (pKa values) of the investigated ligands were determined potentiometrically and spectrophotometrically. The stability constants of the transition metal ions (VO2+, Cr3+, Mn2+, Co2+, Ni2+, Cu2+ and Zn2+) with the investigated ligands were determined potentiometrically at different ionic strengths (0.167, 0.1, 0.05 and 0.025 M) NaCl at 25oC and different temperature (25, 30, 35, and 45oC). The values of stability constants were found to decrease with increasing ionic strengths and temperature. The stoichiometries were studied using spectrophotometric and conductimetric methods, the results indicate the existence of 1:1 and 1:2 (M:L) metal:ligand species. The relationships between the stability constants of the complexes, ionization constants of the ligands have been discussed and correlated. The thermodynamic parameters (?G, ?H and ?S) and the thermodynamic stability constants for all of the investigated complexes were determined potentiometrically.