ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Metal Complexes of Triazine Schiff Bases Spectroscopic and Thermodynamic Studies of Complexation of Some Divalent Metal Ions with 3-[2-(l-Acetylethylidene)hydrazino]-5,6-diphenyl-l,2,4-triazine

M. Mashaly, H. A. Bayoumi, and A. Taha

Faculty of Education, Ain Shams University, Roxy, Cairo, Egypt

Abstract: Metal complexes of some divalent metal ions (Co, Ni, Cu, and Zn) with 3-[2-(1-acetylethylidene)-hydrazino]-5,6-diphenyl-1,2,4-triazine (AHDT) as a Schiff base have been investigated potentiometrically and spectrophotometrically and found to have stoichiometric formulae 1 : 1 and 1 : 2 n(M) : n(L). Formation constants of the proton-ligand and metal-ligand complexes have been determined potentiometrically at different temperatures (10-50°C) and 0.1 mol dm^-3 ionic strength (KNO₃) in 75 vol. % dioxane-water solution. The standard thermodynamic parameters, viz. ∆G°, ∆H°, and ∆S°, terms for the proton-ligand and the stepwise metal-ligand complexes have been evaluated. Thermodynamic functions have been analyzed in terms of the electrostatic (el) and nonelectrostatic (cratic, c) components. ∆H_c° was found to be linearly correlated with the acceptor number of the metal ion (AN_M), whereas ∆H_el° was linearly correlated with the ionic radii of the metal ion. UV VIS and IR spectroscopy have been used to characterize the free ligand AHDT and the compositions, structures, formation constants, and analytical applications of its complexes with Cu(II), Ni(II), and Co(II) ions. The formation constant values obtained from spectrophotometric studies are found to be consistent with those obtained from potentiometric studies.

Full paper in Portable Document Format: 535a299.pdf

Chemical Papers 53 (5) 299–308 (1999)