THERMODYNAMIC STUDIES OF SOME COMPLEXES OF 2-BENZOYLPYRIDINE 4-PHENYL-3-THIOSEMICARBAZONE

The stability constants of the Co(II), Ni(II), Cu(II) and Zn(II) compl exes with 2-benzoylpyridine 4-phenyl-3-thiosemicarbazone were determin ed using a spectrophotometric method at different temperatures (25, 30 , 35 and 40 +/- 0.1 degrees C) and ionic strengths (0.05, 0.01 and 0.2 0 M KNO3) in 50 % (v/v) aqueous ethanol. Plots of thermodynamic stabil ity constants at zero ionic strength (ln K degrees) versus T-1 gave li near curves and Delta H degrees and Delta S degrees were also calculat ed from these plots. Moreover, the changes in free energy for each met al-ligand system were calculated from the following equation. Delta G degrees = -RT ln K degrees.