Cobalt(II)-2,4-diaminobutanoate complexes: stability and oxygenation in aqueous solution

Abstract

Equilibrium constants are reported for the protonation of L-2,4-diaminobutanoic acid (HL) and for the formation of the complexes [CoL]⁺, [CoL]₂], [Co(HL)²⁺, and [CoL(HL)]⁺ at 25 °C and I= 0.1 mol dm^–3 NaCl. The stoicheiometries and stabilities of the cobalt(II) complexes are compared with those for homologous amino-acids H₃[graphic omitted]·[CH₂]_n·CH(NH₂)CO₂^–(n= 1–4). Equilibrium data for the formation of the µ-dioxygen adduct [L₂CoO_2- CoL₂] in aqueous solution (log K_O2= 7.77 ± 0.04) have been obtained by use of a polarographic oxygen analyser.