Cobalt complexes able to bind dioxygen: Thermodynamic studies and DFT calculations

• A Co(II)-polyamino-phenol complex able to bind dioxygen.
• Crystal structure and DFT calculation of Co(III) and Co(II) dinuclear species.
• Thermodynamic comparison {C}{C}among μ-peroxo-μ-hydroxo dinuclear species.

The ligational properties of the ligand 2-[bis-(2-aminoethyl)-aminomethyl]phenol (L) towards Co(II) ion were studied by means of potentiometric measurements in aqueous solution (298.1 ± 0.1 K, I = 0.15 mol dm−3). L forms a stable mononuclear [CoH−1L]+ (log K = 13.42), a hydroxylated mononuclear [CoH−1LOH] and a dinuclear [(CoH−1L)2]2+ species in which the ligand/metal ratio is 2:2.The Co(II) species is prone to bind dioxygen forming a μ-peroxo-μ-hydroxo [(CoH−1L)2(μOH)(μO2)]+ dinuclear species. The stability constants of μ-peroxo-μ-hydroxo dinuclear and μ-peroxo-mono-hydroxo species were analyzed in a series of open-chain polyamine and polyamino phenol ligands pointing out the role played by the ligand on the stability and the reversibility of the bound dioxygen.DFT calculations were carried out to predict the structure of the oxygenated Co(II)–dinuclear species for L and the related LI amino-phenol ligand.The crystal structure of the Co(III) species, derived from the oxydation of the Co(II)–oxygenated one, was also reported.

Poly-aminophenol ligand L binds Co(II); the Co(II)-complex are able to bind dioxygen forming a stable μ-peroxo-μ-hydroxo dinuclear species. Stability constants of μ-peroxo-μ-hydroxo species were analyzed and compared for several ligands. The crystal structure of the Co(III) dinuclear species was reported.Figure optionsDownload as PowerPoint slide