The thermodynamics of complexation of transition and lanthanide ions by 3-(α-carboxymethylaminobenzyli-denehydrazino)-5,6-diphenyl-1,2,4 triazine (HipHt)

• Published in: Thermochimica acta Vol. 222; no. 2; pp. 291 - 303
• Main Authors: Ramadan, A.A.T., Abdel-Rahman, R.M., El-Behairy, M.A., Ismail, A.I., Mahmoud, M.M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 09.08.1993; Elsevier Science
• Subjects: Chemical thermodynamics; Chemistry; Elements, mineral and organic compounds; Exact sciences and technology; General and physical chemistry; Thermodynamic properties; Water; Complexation; Dioxane; Gibbs free energy; Enthalpy; Temperature effect; Electrostatic induction; Stability constant; Transition metal Complexes; Experimental study; Amidrazone; Organic solvent; α-Aminoacid; Heat of reaction; Aqueous solution; Thermodynamic properties; Organic compounds
• DOI: 10.1016/0040-6031(93)80562-O
• ISSN: 0040-6031

The metal-ligand stability constants of the Ni(II), Co(II), Zn(II), Mn(II), Cd(II), Fe(III), UO 2(II) and Ln(III) chelates of HipHT were determined in 75% (v/v) dioxane-water medium at 10, 20 and 30°C and μ = 0.1M(KNO 3). The thermodynamic parameters for the proton-ligand and metal-ligand stability constants were obtained by the temperature coefficient method. The thermodynamic functions Δ G and Δ H of the complexes were analyzed in terms of the electrostatic (el) and non-electrostatic (non) components. The values of Δ H non and Δ H el show a linear variation with the hardness and softness E ν n of the metal ion and with the heat of hydration Δ H h, of the metal ion, respectively. HipHT behaves as a diprotic tridentate (NNO) donor towards the metal ions, as inferred from the infrared spectra of its metal chelates.