Kinetic and Mechanistic Studies on the Interaction between L-Asparagine and cis-Diaquabis(bipyridine)ruthenium(II) Complex in Aqueous Medium

The kinetics of interaction between L-asparagine and cis-[Ru(bipy)2(H2O)2]2+ have been studied spectrophotometrically as a function of [Ru(bipy)2(H2O)2+ 2 ], [Lasparagine] and temperature at a particular pH 4.8 where the substrate complex exists predominantly as a diaqua species and L-asparagine as a zwitterion. The reaction has been found to proceed through two consecutive steps. The first step involves the ligand assisted anation while the second step involves chelation when the second aqua ligand is displaced. Rate constants have been evaluated and activation parameters are calculated. The low enthalpy of activation and large negative value of entropy of activation indicate an associative mode of activation for both the steps.