Controlling the Reactivity of Copper(II) Acylperoxide Complexes

Area of Science:

• Bioinorganic Chemistry
• Coordination Chemistry
• Organometallic Chemistry

Background:

• Metallomonooxygenases are crucial enzymes that utilize redox-tuned metal centers to activate oxygen for substrate oxygenation.
• The coordination environment around the metal center is critical for controlling the enzyme's reactivity and catalytic efficiency.

Purpose of the Study:

• To investigate how varying coordination environments in copper(II) complexes affect the reactivity of their acylperoxide adducts.
• To understand the relationship between ligand structure, electronic properties, and catalytic activity in copper-mediated oxygenation reactions.

Main Methods:

• Synthesis and characterization of copper(II) complexes with a series of tetradentate ligands (L6, L7, L8) featuring different cyclic diamine ring sizes.
• Spectroscopic analysis (UV-vis, EPR) to determine ligand-field splitting energies of copper(II) complexes.
• Reactivity studies involving the reaction of copper(II) complexes with *m*-chloroperbenzoic acid (m-CPBA).
• Density functional theory (DFT) calculations to analyze electronic structures and reaction mechanisms of acylperoxide adducts.

Main Results:

• Ligand-field splitting energy of copper(II) complexes increases with increasing diamine ring size (L6 < L7 < L8).
• Copper(II) complexes with larger ring ligands (L7, L8) form less stable acylperoxide adducts, rapidly converting to the corresponding acid adducts, compared to the L6 complex.
• DFT calculations confirm that increased ligand-field splitting energy correlates with enhanced reactivity of the acylperoxide adducts.

Conclusions:

• The coordination environment, specifically the ligand-field splitting influenced by ligand ring size, significantly modulates the reactivity of copper(II) acylperoxide complexes.
• These findings provide insights into the design of synthetic catalysts for oxygenation reactions, mimicking metalloenzyme active sites.
• The study highlights the delicate balance between electronic structure and reactivity in copper-oxygen chemistry.