Gold(III) Semiquinone Complexes: Synthesis, Structure, and Application in Photocatalysis

Area of Science:

• Organometallic Chemistry
• Photocatalysis
• Gold Catalysis

Background:

• Hemilabile ligands facilitate two-electron gold redox cycling.
• Single-electron processes and redox-active ligands in gold chemistry are underexplored.

Purpose of the Study:

• Report the synthesis and photocatalytic application of Au(III) semiquinone complexes.
• Investigate the mechanism of single-electron transfer in gold complexes.
• Establish a new strategy for gold-mediated photoredox catalysis.

Main Methods:

• Synthesis and characterization of Au(III) catecholate and semiquinone complexes.
• Experimental studies and Density Functional Theory (DFT) calculations.
• Photocatalytic C-H arylation reactions using visible-light irradiation.

Main Results:

• Au(III) semiquinone complexes were synthesized via one-electron oxidation of Au(III) catecholates.
• Oxidation occurs at the O^O ligand, maintaining the Au(III) oxidation state.
• Au(III) catecholate complexes form electron donor-acceptor adducts, enabling photoinduced single-electron transfer.
• Efficient photocatalytic C-H arylation of heterocycles was achieved under mild conditions.
• Ligand variation allows tuning of catalytic activity and optimization for challenging substrates.

Conclusions:

• This work presents the first photocatalytic application of Au(III) semiquinone complexes.
• A new mechanism for gold-mediated photoredox catalysis involving single-electron transfer is established.
• Redox-active ligands offer a versatile platform for expanding gold complex reactivity.