A potentiometric investigation of complex formation between some metal ions and biologically active quinazoline-4-3(H)-one Schiff's base

Abstract

The proton dissociation constant of the ligand and the stability of the complexes of Co(II), Ni(II), Zn(II), Cd(II), Hg(II), Pb(II), Cu(II), Ba(II), Mg(II), Mn(II), Th(IV), and UO2(II) ions with 2-phenyl-3-(2-hydroxy- 5-benzylidine)-quinazoline-4-(3H)-one [PBQ] were determined potentiometrically at 30 ± 0.1°C and ionic strengths of 0.025, 0.05, 0.10, 0.15 and 0.20 M NaNO3 in a 60:40 (v/v) ethanol-water medium. The proton-ligand and metal-ligand stability constants of the complexes were determined pH metrically by the Calvin-Bjerrum titration technique. The order of stability constants obeys the Irving-Rossotti rule. The negative values of ?G° suggest that the reactions are spontaneous. © 2007 Pleiades Publishing, Ltd.