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

The Study discusses the possible binding of molecular oxygen to some new Co11 complexes with the Schiff base ligands of the Co(Salen) type. The investigated complexes of Co11 with the Schiff bases are: (bis(5-nitro-salicylaldehyde)ethylenediaminato)cobalt(II), Co-(NSalen); (bis(a-ethylene-salicylaldehyde)ethylenediaminato)cobalt(II), Co(EtSalen); (bis(a-ethylene-3,5-diiode-salicylaldehyde)-ethylenediaminato)cobalt(II), Co(DIEtSalen); (bis(a,5-dimethyl-3-iode-sahcylaldehyde)ethylenediaminato)cobalt(II), Co(DMISalen) and (bis(salicylaldehyde)methylene-p,p\u27-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 ΔH° and ΔS° values of oxygenation that fali in the range -37 to -50 kJ mol-1 for ΔH° and -117 to -157 J mol-1 K-1 for ΔS0, which is in line with the values reported for analogous dioxygen complexes described in literature