Reversible Dioxygen Binding to Co(II) Complexes with Noninnocent Ligands.

Area of Science:

• Inorganic Chemistry
• Coordination Chemistry
• Materials Science

Background:

• Metal-ligand cooperativity is crucial for reversible oxygen binding in biological systems.
• Designing synthetic analogues requires understanding redox-active ligands and their interaction with metal centers.

Purpose of the Study:

• To synthesize and characterize mononuclear cobalt(II) complexes featuring noninnocent ligands.
• To investigate the mechanism of reversible O2 binding mediated by metal-ligand cooperativity.
• To explore the electronic and structural properties of cobalt-oxygen adducts.

Main Methods:

• Synthesis of mononuclear Co(II) complexes with o-aminothiophenolate and hydrotris(pyrazol-1-yl)borate ligands.
• Exposure to O2 at room temperature and reduced temperatures to study oxygenation.
• Spectroscopic and electrochemical characterization of complexes and O2 adducts.
• Thermodynamic measurements to determine O2 affinity and redox potentials.

Main Results:

• Novel Co(II) complexes with redox-active ligands were successfully prepared.
• Metal-ligand cooperativity was observed during reversible O2 binding.
• Oxidized complexes exhibited significant singlet diradical character.
• Co/O2 adducts formed via addition of O2 to both cobalt and ligand radical, yielding cobalt(III)-alkylperoxo structures.

Conclusions:

• Noninnocent ligands are effective in designing cobalt complexes for reversible O2 absorption.
• The study provides insights into the mechanism of oxygenation driven by metal-ligand cooperativity.
• These findings contribute to the development of advanced materials for gas storage and catalysis.