Oxygen Delivery as a Limiting Factor in Modelling Dicopper(II) Oxidase Reactivity

Area of Science:

• Coordination Chemistry
• Biomimetic Catalysis
• Bioinorganic Chemistry

Background:

• Copper complexes are crucial models for catechol oxidase enzymes.
• Understanding copper-oxygen interactions is key to developing efficient catalysts.
• Product inhibition often limits the catalytic efficiency of catechol oxidase models.

Purpose of the Study:

• To synthesize and characterize novel mononuclear and dinuclear copper(II) complexes.
• To investigate their catalytic activity as catechol oxidase models.
• To explore the effect of dioxygen on catalytic turnover and identify factors limiting efficiency.

Main Methods:

• Synthesis of N,O ligand-appended mononuclear copper(II) complexes.
• Formation of dinuclear complexes with Cu2O2 cores via deprotonation.
• Structural characterization using X-ray diffraction (XRD).
• Electronic structure analysis via UV/Vis, 1H NMR, EPR, and DFT calculations.
• Catalytic studies using 3,5-di-tert-butyl-catechol oxidation.

Main Results:

• Successfully synthesized and characterized mono- and binuclear copper(II) complexes.
• Dinuclear complexes exhibited moderate activity in quinone formation from catechol.
• Catalytic activity was significantly enhanced by administering additional dioxygen during turnover.
• Increased maximum reaction rates (vmax) were observed, while substrate affinity (KM) remained unaffected.
• Dioxygen administration mitigated product inhibition, a key limitation.

Conclusions:

• The dinuclear copper complexes serve as effective catechol oxidase models.
• Additional dioxygen administration is a potent strategy to enhance catalytic rates.
• This approach overcomes product inhibition, offering broader applicability to biomimetic catalysts.
• The findings provide new insights into optimizing copper-based oxidation catalysis.