Thermodynamics,formation constants,spectrophotometry and infrared spectroscopy of complexes between some divalent metal ions and 3-hydrazino-6-phenylpyridazine and related ligands

The stepwise formation constants of complexes of Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Cd(II) and UO₂(II) ions with 3-hydrazino-6-phenylpyridazine (HPP) and its condensation products with benzil (BHPP) and p-methoxyacetophenone (p-MeOAHPP) were determined in a 75% (v/v) dioxane-water mixture at μ = 0.05 M (KNC₃). The effect of temperature (at 10, 20, 30 and 40 °C) was also examined for Cu(II) and UO₂(II)-BHPP complexes. The overall changes in ΔG, ΔH and ΔS have been calculated. The solid complexes of Cu(II)-, Co(II)- and Ni(II)-BHPP were prepared and examined by elemental analysis and IR spectroscopy. Analysis of the data indicates chelation of the BHPP ligand through the nitrogens of both hydrazone and the pyridazine ring and the carbonyl oxygen group. The spectrophotometric studies were performed on solutions of Cu(II), Ni(II) and Co(II) with BHPP in order to obtain the optimum pH values for complex formation. The compositions of the chelates formed were determined. Analytical determinations of the micro amounts of Cu(II), Ni(II) and Co(II) were also done using BHPP as the complexing agent.