Spectrophotometry and voltammetry of cobalt triethanolamine complexes in aqueous solutions in the absence and presence of oxygen

The absorption spectra of solutions of Co^II and Co^III in the presence of triethanolamine (TEA) are reported. For the former complexes there is no evidence for chelation, but a bischelate is formed with the latter. Saturation of Co^II-TEA solutions with oxygen yields more than one new, dioxygen-containing, species that age slowly. The oxygen may be partly removed by bubbling nitrogen through the solutions. The electroreduction of cobalt-triethanolamine complexes in aqueous solutions in the presence of oxygen was followed voltammetrically on a stationary Pt disk electrode. Strong catalytic enhancement of the electroreduction current of oxygen involved with the complex was achieved. A mechanism for the formation of the electrochemically active species, involving OH- and O₂-bridged dimeric species of both Co^II and Co^III, was suggested. A pseudo first order was established for the reversible reaction of this complex formation. Relevant rate and equilibrium constants were obtained.