Solvent role on cobalt(II) dioxygen carriers based on simple polyamine ligands

Abstract

The kinetics and thermodynamics of O2 addition to Co II complexes containing the simple triamine ligand (L) diethylenetriamine (= N-(2-aminoethyl)ethane-1,2-diamine; dien) or N,N″-dimethyldiethylenetriamine (= N-methyl-N′-[2-(methylamino) ethyl]ethane-1,2-diamine; dmdien) in the aprotic solvent dimethyl sulfoxide (DMSO) were studied by UV/VIS spectrophotometry, potentiometry, and O 2 absorption measurements. A parallel investigation on the anaerobic formation of CoII complexes with dmdien, as well as on their reactivity towards O2, was carried out in aqueous 0.1M NaClO 4 solution. [CoL]2+ and [CoL2]2+ were the common species formed under anaerobic conditions in both aqueous and DMSO solutions. Under aerobic conditions, O2 adducts of different stoichiometry were formed: a superoxo complex [CoL2O2]2+ in DMSO and dimeric species in H2O. The role of the reaction medium as well as effects of N-alkylation of the triamine ligand in the formation and reactivity of the [CoII(triamine)] complexes are discussed. © 2005 Verlag Helvetica Chimica Acta AG.