KINETIC AND THERMODYNAMIC PARAMETERS OF COPPER-DIOXYGEN INTERACTION WITH DIFFERENT OXYGEN-BINDING MODES

Kinetic and thermodynamic parameters for metal ion-O-2 interaction hav e been obtained for a variety of copper(I) complexes with different bi nding modes for dioxygen. In general, favorable binding enthalpies of up to 80 kJ mol(-1) are compensated by strongly negative reaction entr opies up to -220 J K-1 mol(-1), restricting the range of overall stabi lities. Sequential formation of superoxo and peroxo complexes, as well as concomitant formation of eta(1):eta(1) and eta(2):eta 2 mu-peroxo complexes has been established by low-temperature stopped-flow experim ents. In several cases, pseudoreversible binding of dioxygen is follow ed by an irreversible oxidation of the organic ligand. A recent result is the identification of a rapid equilibrium between an eta(2):eta(2) mu-peroxo complex and the isomeric bis-mu-oxo compound with broken O- O bond which maybe fundamental to several O-2 dependent redox enzymes.