Tuning affinity and reversibility for O2 binding in dinuclear Co(II) complexes.

Area of Science:

• Coordination Chemistry
• Bioinorganic Chemistry
• Materials Science

Background:

• Dicobalt(II) complexes are studied for oxygen binding properties relevant to biological systems.
• Tuning ligand environments is crucial for controlling metal complex reactivity.

Purpose of the Study:

• To investigate the effect of varying chloroacetato ligands on the O2 binding affinity of dicobalt(II) complexes.
• To correlate O2 affinity with ligand properties and electronic structures.

Main Methods:

• Synthesis and characterization of [Co2(bpbp)(CH(3-n)ClnCO2)(CH3CN)2](2+) complexes.
• Measurement of O2 binding affinity (p(O2)50%) at 40 °C.
• Redox potential measurements of peroxide-bridged complexes.
• X-ray crystallography and resonance Raman spectroscopy.
• Density Functional Theory (DFT) calculations.

Main Results:

• O2 binding affinity varied significantly with the number of chlorine atoms on the acetato ligand.
• A linear decrease in O2 affinity was observed as chlorination increased.
• O2 affinities correlated with the pKa of parent acids and redox potentials of peroxide species.
• DFT calculations suggested solvent coordination and ligand conformation changes are key to O2 binding.

Conclusions:

• The electronic and steric properties of bridging ligands critically influence O2 binding affinity in these dicobalt(II) complexes.
• Ligand conformation changes and solvent coordination play significant roles in the O2 binding mechanism.
• Structural and spectroscopic data did not show clear trends correlating with O2 affinity, highlighting the importance of electronic factors.