INTERACTION OF GLUTATHIONE (REDUCED) WITH [(H2O)(TAP)2RUORU(TAP)2(H2O)]2+ (TAP ={2-(MTOLYLAZO)PYRIDINE}) ION AT PHYSIOLOGICAL PH IN AQUEOUS MEDIUM.

Life Science-Bio chemistry

Abstract

Kinetic and mechanistic studies on the interaction of glutathione (reduced) with the title complex at physiological pH and in aqueous medium have been done spectrophotometrically as a function of [(H2O)(tap)2RuORu(tap)2(H2O)2+], [glutathione], pH and temperature at constant ionic strength. The interaction reaction followed two parallel paths: both the paths are dependent on [ligand] and showed a limiting nature at higher concentration of the ligand. Rate constants (k1∼10-3 s-1, k2 ∼10-5 s-1), activation parameters and thermodynamic parameters (∆H1 o , ∆S1 o ) were calculated. A rate law involving the outer sphere association complex formation has been established at pH 7.4 for path 1 as Rate = k1KE[{(H2O)(tap)2RuORu(tap)2(H2O)}2+][ligand]/(1+KE[ligand]) A mechanism involving the prior formation of an outer sphere complex followed by associative interchange (Ia) is proposed for both the paths where bond making and bond breaking are equally important in the transition state. Negative ∆Go values at all temperatures studied, also supports this proposition. IR and ESI-MS studies all help to propose the plausible mechanism.