Physicochemical studies on biologically important benzothiazole Schiff bases with some transition metal ions: Ionization constants and stability constants

Abstract

Ionization constants of Schiff bases derived from 6-fluro-7-chloro-2-amino benzothiazole with substituted salicylaidehydes have been determined in 30% (v/v) dioxan - water medium as pet Irving- Rossotti method at constant ionic strength and at 25 ± 1°C. Stability constants of these ligands with some transition metal ions such as Cu(II), Ni(II), Co(II), Zn(II), Cd(II) and Hg(II) have also been evaluated. Ionization constant values (pKa) fall in the range of 10.7 to 11.8 attributable to ionization of phenolic - OH group. Log k and log ? values fall in the order of Cu(II) > Co(II) ? Ni(II) which is in agreement with Irving - Williams stability order. Metal-ligand stability constants for Zn(II), Cd(II) and Hg(II) fall in the order Hg(II) > Cd(II) > Zn(II). The effect of electron withdrawing and electron donating groups on stability constants have been investigated.