Conjugation Engineering Boosts Alkynyl-Copper Photocatalysis for Efficient Selective Aerobic Oxidation

Area of Science:

• Materials Science
• Photochemistry
• Organic Chemistry

Background:

• Phenylacetylide-copper (PACu) is a key photoactive intermediate in copper-catalyzed cross-couplings.
• PACu exhibits limitations including poor visible-light absorption, rapid recombination, and low photostability, restricting its practical use.

Purpose of the Study:

• To engineer novel alkynyl-copper photocatalysts with enhanced photophysical properties and stability.
• To investigate the impact of extended π-conjugation on the performance of copper-alkynyl photocatalysts.

Main Methods:

• Conjugation engineering strategy by replacing phenylacetylene with extended π-system ligands (naphthalene, phenanthrene, pyrene).
• Synthesis and characterization of new alkynyl-copper photocatalysts (NACu, FACu, BACu).
• Experimental and theoretical studies (DFT) to analyze electronic structures and photophysical properties.

Main Results:

• Extended π-conjugation narrowed the band gap (e.g., 1.95 eV for BACu) and red-shifted absorption (>600 nm).
• Enhanced charge separation and suppressed Cu(I) oxidation were observed.
• The optimized BACu catalyst demonstrated high activity and stability in [4+2] cycloaddition, Glaser coupling, and benzylamine oxidation (>99% conversion).

Conclusions:

• Conjugation engineering is a viable strategy for designing efficient and stable metal-alkynyl photocatalysts.
• The developed alkynyl-copper photocatalysts offer superior performance compared to traditional PACu.
• This work provides insights into structure-property relationships for photocatalyst development.