Spectrophotometric and Thermodynamic Studies of Complexation between Catechin and Some of Transition Metals (II)

Cadimum and Nickel are toxic heavy metal when presented in a high level over it allowable limit. To detoxify this heavy metal a chelators were used as in a chelation therapy. This work studies the complexation of some chelator (Catechin) with Cd II, Ni II ions. A spectrophotometric technique was applied in water solvent in PH=7-7.5, at four different temperatures. No shift in it ?max but wrer increases in absorbance indicating the complex formation. The stoichiometry of these complexes were determined by a method of the continuous variation (Job's) method, it was found that Catechin-Cd, Catechin-Ni were (11). These chelators have a high tendency to complex with Ni II ion which was reflected by its high values of their equilibrium constants. Thermodynamic parameters indicate a spontaneous interaction (negative free energy change ?G), and the enthalpy changer for Catechin-Cd complex were positive and Catechin-Ni have negative ?H which depends on type of the interaction and the structures of the complexes.