Kinetics and mechanism of the interaction of L- cysteine with diaquaethylenediamineplatinum(II) perchlorate in aqueous solution

Abstract

The kinetics of the interaction of L-cysteine with [Pt(en)(H₂0)₂]²⁺ has been studied spectrophotometrically as a function of [Pt(en(H₂0)²⁺], [L-cysteinel, pH and temperature. The reaction has been monitored at 230 nm, where the spectral difference is maximum although the λ_max, of the L-cysteine saturated product is at 213 nm. The activation parameters have been evaluated from temperature coefficient of the reaction rates. The low value of ΔH^# (61.1 kJ mol^-1) and large negative value of ΔS^# (- 83 J k^-1 mol^-1) indicate an associative mode of activation for the substitution process. The additional advantage of using aquaamine complexes as an amino acid binder is also discussed.