The potentiometric and thermodynamic properties of some divalent metal ions with biologically active 2-phenyl-3-(2′-hydroxy-5′-methylbenzylidine)-quinazoline-4-(3h)-one Schiff’s base

The formation constants of 1: 1 and 1: 2 complexes between 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) metal ions and 2-phenyl-3-(2′-hydroxy-5′-methylbenzylidine)-quinazoline-4-(3H)-one [PHBMeQ] were determined potentiometrically at 30 ± 0.1 °C and different ionic strengths (0.025, 0.05, 0.10, 0.15, and 0.20 M NaNO3) in 60: 40 (v/v) alcohol-water solutions. The proton-ligand and metal-ligand formation constants were determined pH-metrically by the Calvin-Bjerrum titration technique. The order of stability constants was found. The negative ΔG° values suggest that the reactions occur spontaneously. Correlations between the log K1 values and some fundamental central metal ion properties are discussed.