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Journal of the Serbian Chemical Society 2003 Volume 68, Issue 10, Pages: 729-749
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Potentiometric and spectrophotometric studies of the complexation of Schiff-base hydrazones containing the pyrimidine moiety

Seleem H.S., El-Shetary B.A., Khalil S.M.E., Shebl M.

Three Schiff-base hydrazones (ONN – donors) were prepared by condensation of 2-amino-4-hydrazino-6-methylpyrimidine with 2-hydroxyacetophenone 2-methoxybenzaldehyde and diacetyl to yield 2-OHAHP, 2-OMeBHPand DHP respectively. The structures of these ligands were elucidated by elemental analysis, UV, IR, 1H-NMR and mass spectra. The metal–ligand stability constants of Mn2+, Fe3+,Co2+,Ni2+,Cu2+, Zn2+,Cd2+,UO22+ and Th4+ chelates were determined potentiometrically in two different media (75%(v/v) dioxane–water and ethanol–water) at 283, 293, 303 and 313 K at an ionic strength of 0.05 M (KNO3). The thermodynamic parameters of the 1:1 and 1:2 complexes were evaluated and are discussed. The dissociation constants of 2-OHAHP, 2-OMeBHP and DHPligands and the stability constants of Co2+, Ni2 and Cu2+ with 2-OHAHP were determined spectrophotometrically in 75 % (v/v) dioxane–water.

Keywords: stability constants, thermodynamic parameters, spectrophotometric determination of stability, Schiff-base hydrazones containing the pyrimidine moiety