A 4H⁺/4e^- Electron-Coupled-Proton Buffer Based on a Mononuclear Cu Complex.

Area of Science:

• Inorganic Chemistry
• Electrochemistry
• Catalysis

Background:

• Development of efficient electron-coupled-proton buffer (ECPB) systems is crucial for catalytic applications.
• Copper-based complexes with redox-active ligands offer promising avenues for multi-electron transfer processes.

Purpose of the Study:

• To design and characterize a novel 4H+/4e- ECPB based on copper and a redox-active ligand.
• To investigate the catalytic activity of the ECPB system in oxygen reduction and organic substrate dehydrogenation.
• To elucidate the mechanistic pathways governing the ECPB's function in both coupled and decoupled reaction modes.

Main Methods:

• Synthesis and characterization of copper complexes using X-ray diffraction, 1H-NMR spectroscopy.
• Electrochemical studies to probe the redox behavior of the ECPB system.
• Density Functional Theory (DFT) calculations to understand electronic structures and reaction mechanisms.

Main Results:

• A 4H+/4e- ECPB (complexes 1 and 5) based on Cu(I)/Cu(II) and a redox-active bis(urea) ligand was successfully synthesized and characterized.
• The ECPB system demonstrated catalytic activity for the 4H+/4e- reduction of O2 to H2O.
• The system also catalyzed the dehydrogenation of organic substrates in both coupled and decoupled modes.
• Mechanistic studies revealed fast disproportionation reactions that maintain the ECPB equilibrium.

Conclusions:

• The developed Cu-based ECPB system provides an efficient platform for mediating multi-proton and multi-electron transfer reactions.
• The system's ability to catalyze both oxygen reduction and organic dehydrogenation highlights its potential in various catalytic applications.
• Decoupled and coupled reaction pathways offer tunable control over oxidation and reduction processes.