SPECTROPHOTOMETRIC STUDIES, STABILITY-CONSTANTS AND THERMODYNAMICS FOR COMPLEXES OF O-HYDROXYACETOPHENONE ISOBUTYROYLHYDRAZONE WITH SOME BIVALENT TRANSITION-METAL IONS

The u.v. spectra of o-hydroxyacetophenone isobutyroylhydrazone (HAIBuH) were investigated in pure organic solvents as well as in Britton Robinson buffer solutions of varying pH values. The interaction of HAIBuH with Co(II), Ni(II) and Cu(II) were studied spectrophotometrically. The optimum pH favouring the formation of the highly coloured complexes are 8.5, 8.0 and 7.5 for Co(II), Ni(II) and Cu(II), respectively. The stoichiometries of these complexes were determined and indicated the formation of 1:2 (metal:ligand) complexes of Co(II) and Ni(II) and a 1:1 complex of Cu(II). The dissociation constants pK(H) of HAIBuH and the overall stability constants log beta of their complexes were determined at different temperatures (293, 303 and 313 K). The corresponding thermodynamic parameters (Delta G, Delta H and Delta S) in 20% (v/v) ethanol-water mixture were derived and discussed.