Photocatalytic C-C Coupling by a Au(I) Complex: Mechanistic Elucidation and SET Modulation

Area of Science:

• Organometallic Chemistry
• Photocatalysis
• Computational Chemistry

Background:

• Photocatalytic C-C coupling reactions are crucial in synthetic chemistry.
• Gold (Au)-based catalysts show promise in these reactions.
• Understanding reaction mechanisms is key to catalyst optimization.

Purpose of the Study:

• To elucidate the mechanistic pathway of aryldiazonium salt and alkynyl-silane coupling catalyzed by an Au(I) complex.
• To investigate the role of photophysical processes and electron transfer in the catalytic cycle.
• To explore strategies for enhancing catalytic efficiency and cost-effectiveness.

Main Methods:

• Integrated computational strategy combining MS-CASPT2 and DFT.
• Kinetic analyses of photophysical processes (fluorescence, phosphorescence, ISC, IC).
• Analysis of electron transfer (ET) and reaction energetics.

Main Results:

• A four-state photophysical model (S0, S1, T2, T1) was identified.
• The reaction proceeds via a triplet-state mechanism initiated by single electron transfer (SET).
• Electron-withdrawing groups on aryldiazonium salts enhance SET efficiency by reducing reorganization energy.

Conclusions:

• Nonradiative decay is dominant along the reaction coordinate.
• The SET modulation strategy can be extended to Ag and Cu complexes for efficient and cost-effective C-C coupling.
• Fundamental structure-reactivity relationships were established for Au-photocatalyzed cross-couplings.