A bioinspired model for copper monooxygenase: direct aromatic hydroxylation using O₂

Area of Science:

• Bioinorganic Chemistry
• Catalysis
• Coordination Chemistry

Background:

• Copper monooxygenases are crucial enzymes in biological systems.
• Developing synthetic models for these enzymes aids in understanding their mechanisms.
• Bioinspired copper complexes offer potential for selective oxidation reactions.

Purpose of the Study:

• To synthesize and characterize a novel copper(I) complex as a bioinspired model for copper monooxygenases.
• To investigate the catalytic activity of the copper(I) complex in benzene hydroxylation.
• To elucidate the mechanism of benzene hydroxylation using various oxygen sources and spectroscopic techniques.

Main Methods:

• Synthesis and characterization of copper(I) and copper(II) complexes.
• Aerobic and peroxide-driven benzene hydroxylation reactions.
• Electron Paramagnetic Resonance (EPR) spectroscopy.
• Fourier-transform infrared (FT-IR) spectroscopy.
• Density Functional Theory (DFT) calculations.
• Kinetic Isotope Effect (KIE) studies.

Main Results:

• A novel copper(I) complex ([Cu(L)(CH3CN)]CF3SO3) was synthesized and characterized.
• The copper(I) complex selectively hydroxylates benzene to phenol, with significantly enhanced yield (19%) using H2O2 compared to O2 (7%).
• Spectroscopic and DFT studies identified a key copper-peroxo intermediate ([(L)CuII-OOH]+) responsible for hydroxylation.
• Dicopper complexes showed poor catalytic activity and produced byproducts.

Conclusions:

• The synthesized copper(I) complex serves as an effective bioinspired model for copper monooxygenases.
• Hydrogen peroxide significantly enhances the catalytic efficiency of benzene hydroxylation via a copper-peroxo intermediate.
• The study provides mechanistic insights into copper-catalyzed hydroxylation reactions.