Étude cinétique et thermodynamique de l'interaction d'un complexe de Pd(II) avec l'inosine et l'acide polyinosinique

Abstract

Reactions of the (dien)Pd(II) complex with inosine and polyinosinic acid were studied by spectroscopic and stopped-flow methods. In both cases, the metal initially binds at the N7 site of the hypoxanthine base. The results of kinetic studies indicate the existence of a two-path mechanism: a direct nucleophilic substitution and a solvent path with formation of an aquo intermediate. The reactions are faster for poly(I), due to the high density of negative charges for this polymer. The initial reaction at N7 is followed by a slow redistribution of the metal towards the thermodynamically more stable N1 site. Binding of (dien)Pd(II) to poly(I) leads to formation of a stable, multistranded helicoidal structure of the polymer. This structure was characterized by absorption and circular dichroism measurements and by the melting curve of the polymer. It was also observed that in presence of the Pd(II) complex, poly(I) can be hydrolyzed at relatively mild conditions at high pH.