Thermodynamic and Kinetic Studies on Novel Platinum(II) Complex Containing Bidentate N,N-Donor Ligands in Ethanol-Water Medium

Abstract

Kinetic and mechanistic investigations have been made on the displacement of the two aqua molecules from the complex 1 i.e., [Pt(2,2′-bipyridine)(H₂O)₂]²⁺ represented as {Pt(bpy)} (bpy = 2,2′-bipyridine) at pH 4.0. All the substitution reactions have been monitored at 264, 284 & 317 nm respectively where the spectral difference between the reactant and product is maximum. Two consecutive reaction steps were observed for the substitution of aqua molecules with some didentate N- and N-donor ligands namely, dimethylglyoxime (L₁H), 1, 2-cyclohexanedionedioxime (L₂H) and α-furildioxime (L₃H) in ethanol-water medium using variable-temperature and stopped-flow spectrophotometry. Among the two steps, the former is ligand dependent and the later is ligand independent, where chelation observed. All rate and activation parameters are consistent with associative substitution mechanisms. The thermodynamic parameters were also calculated, which gives a negative DG⁰ value at all temperatures studied, supporting the spontaneous formation of an outer sphere association complex.  The products of the reaction have been characterized with the help of IR and ESI-MS spectroscopic analysis.