Kinetics and Mechanism of Ligand Exchange of Cu(methionine) 2 by Polyamines

The kinetics of ligand substitution reaction of Cu(methionine) 2 complex by polyamines has been followed conductometrically above pH 9.0 at 25 degrees C. Millimolar solution of the Cu(NO3)(2) and methionine in 1:2 molar ratio in water shows increase in conductance with time. When a polyamine (en, dien and trien) is added to the complex, the conductance increases at a rapid rate due to substitution of methionine by polyamine leading to the formation of [Cu(polyamine)(2)]. It was observed that the exchange of methionine by polyamine proceeds in a first order process. Since the rate of the reaction varies with the size of polyamines they can be placed in the following, en>dien>trien. In acidic pH range the absorption spectrum varies negligibly. However, the concentration of methionine does not have any influence on the absorption spectra.