Thermodynamic Study of the formation of transition metal ion complexes carrying medicinal drug in mixed solvent media

Abstract

Stability constant of Labetalol drug with transition metal ions Fe3+, Co2+, Ni2+, Cu2+, Zn2+ and Cd2+ using a pH metric titration technique in 20%(v/v) ethanol-water mixture at three different temperatures 300K, 310K & 320K at an ionic strength of 0.1M NaClO4 were studied. Calvin-Bjerrum method as adopted by Irving-Rossotti has been employed to determine metal-ligand stability constant logK values. The trend in the formation constants for transition metal ions follows the orderFe3+>Cu2+ > Zn2+ > Cd2+ >Ni2+ > Co2+.The thermodynamic parameters such as, Gibb’s free energy change ΔG, entropy change ΔS and enthalpy change ΔH associated with the complexation reactions were calculated.