Reversible oxygen‐binding to poly(ethyleneimine)‐cobalt complexes in aqueous solution

Cobalt(II) complexes of poly(ethyleneimine)s 1 in aqueous solution are able to form with oxygen a μ‐peroxo adduct as is evidenced from stoichiometry and spectral properties. The oxygen adduct of Co/1 is characterized by its higher rate constant and activation entropy of the oxygen dissociation step, in comparison with those of the low‐molecular‐weight analogue Co/tetraethylenepentamine (2). This is related with the smaller affinity of Co/1 to oxygen and the reversibility in oxygen‐binding. The dissociation of the oxygen molecule coordinated to and bridged with Co/1 is facilitated by a distortion of its μ‐peroxo structure due to electrostatic repulsion of polycationic 1.