Binding of Molecular Dioxygen to the Cobalt(II) Complexes in Nonaqueous Solution

The study discusses the possible binding of molecular oxygen to some new CoII complexes with the Schiff base ligands of the Co(Salen) type. The investigated complexes of CoII with the Schiff bases are: (bis(5-nitro-salicylaldehyde)ethylenediaminato)cobalt(II), Co(NSalen); (bis( -ethylene-salicylaldehyde)ethylenediaminato)cobalt(II), Co(EtSalen); (bis( -ethylene-3,5-diiode-salicylaldehyde)ethylenediaminato)cobalt(II), Co(DIEtSalen); (bis( ,5-dimethyl-3iode-salicylaldehyde)ethylenediaminato)cobalt(II), Co(DMISalen) and (bis(salicylaldehyde)methylene-p,p’-diphenylenediaminato)cobalt(II), Co(Salmbfn). The studies were based on cyclic voltammetry and UV-Vis spectrometry, in DMF solution. Electron-withdrawing substituents on the Schiff bases were found to decrease the affinity of the cobalt Schiff bases for dioxygen. Equilibrium dioxygen uptake measurements over a large range of temperatures provide the H° and S values of oxygenation that fall in the range –37 to –50 kJ mol–1 for H and –117 to –157 J mol–1 K–1 for S , which is in line with the values reported for analogous dioxygen complexes described in literature.