The complexation behaviour of bivalent metal complexes of dehydroacetic acid-4-methyl-2-quinolylhydrazone (DAMQH) has been studied potentiometrically in 75% (v/v) aqueous dioxan medium at different ionic strengths with respect to sodium perchlorate and at different temperature in order to determine their stability constants. The method of Bjerrum and Calvin as modified by Irving and Rossotti has been used to determine the {ie497-1} andp L values.S_min values which have the same significance as ‘x²’, have also been calculated. The thermodynamic stability constants and the standard free energy change (ΔG) have also been calculated. ΔG values are negative in all cases. Thus complexation is spontaneous. The order of stability constants of bivalent metal complexes of DAMQH has been determined.

The ligand diacetylmono(lepidyl) hydrazone(DALH) has been synthesized in four steps and characterized by melting point, thin layer chromatography, elemental analysis, NMR and IR. Complex formation between transition metal ions Mn(II), Pb(II), Cd(II), Co(II), Ni(II), Cu(II), U0₂(II) and DALH has been investigated by potentiometric measurements of hydrogen ions liberated on complexation at 25, 30, 40 and 50±0·5°C in 0·02, 0·05, 0·1 and 0·2 M (NaCl) ionic strength and in 75% ethanol-water medium. From the potentiometric titration curves dissociation constants of the ligand and stability constants of its complexes have been determined. Using these stability constants, thermodynamic parameters such as free energy changes (ΔG), enthalpy changes (ΔH) and entropies (ΔS) of complex formation have calculated and reported. Thermodynamic stability constants (logK₁⁰) have also been reported. The ligand field stabilization energy (δH) has been calculated for the first row transition metals which is in good agreement with the theory.

The electrochemical redox behaviour of paraquet has been studied by employing an advanced electrochemical technique at different concentrations. The conformation of adsorption of paraquet radical cation is characterised by cyclic voltammetry, laser Raman spectroscopy and a graph betweenip andv^1/2.