Bioinspired copper(II) complexes catalyzed oxidative coupling of aminophenols with broader substrate scope

Area of Science:

• Inorganic Chemistry
• Catalysis
• Organic Synthesis

Background:

• Ligand design significantly influences metal complex catalytic activity.
• Biomimetic reactions require efficient and specific catalysts.
• Aminoquinoline ligands offer a promising scaffold for copper(II) complexes.

Purpose of the Study:

• To synthesize and characterize novel aminoquinoline-based copper(II) complexes.
• To evaluate the catalytic performance of these complexes in oxidative coupling reactions.
• To investigate the impact of ligand substituents on catalytic efficiency and substrate scope.

Main Methods:

• Synthesis and characterization of four copper(II) complexes with varying amine substituents (di-n-methyl, di-n-ethyl, di-n-propyl, di-n-butyl).
• Catalytic evaluation using oxidative coupling of aminophenol derivatives.
• Mechanistic studies involving mass-spectrometry to elucidate reaction pathways.

Main Results:

• Complex 1 (methyl substituent) achieved 86% conversion of o-aminophenol to 2-amino-phenoxazin-3-one with a Kcat of 9.7 × 10^4 h^-1.
• The catalyst demonstrated broad substrate scope and high activity.
• Mass-spectrometry confirmed complex-substrate adduct formation, aiding mechanistic understanding.

Conclusions:

• Systematic variation of ligand substituents in aminoquinoline-based copper(II) complexes enhances catalytic performance.
• Complex 1 represents a new benchmark for copper(II) catalysts in oxidative coupling.
• This study expands the known substrate scope for PHS activity with copper(II) complexes.