Electrocatalytic Benzylic C-H Activation Enables Direct Au-C Single-Molecule Junctions

Area of Science:

• Electrochemistry
• Surface Science
• Organic Chemistry

Background:

• Selective C-H bond activation under mild, sustainable conditions is a significant challenge in chemistry.
• Externally applied bias can drive bond transformations without reagents, but ensemble measurements obscure key details.
• Understanding individual chemical bond reactivity requires single-molecule interrogation.

Purpose of the Study:

• To directly investigate electrocatalytic benzylic C-H activation at the single-molecule level.
• To reveal the mechanism of C-H bond cleavage and subsequent junction formation.
• To establish a framework for bias-driven C-H functionalization using atomically precise electrochemical methods.

Main Methods:

• In situ scanning tunneling microscopy break-junction (STM-BJ) measurements were employed.
• Single-molecule level interrogation of electrocatalytic benzylic C-H activation.
• Complementary theoretical calculations, electrochemical analyses, and radical trapping experiments were performed.

Main Results:

• Direct observation of highly conductive gold-carbon (Au-C) covalent junction formation.
• Identification of single-electron transfer (SET) as the mechanism for C-H bond cleavage.
• Demonstration of covalent coupling of molecules to gold electrodes via C-H activation.

Conclusions:

• Bias-driven C-H activation enables the transformation of inert C-H bonds into robust Au-C junctions under mild conditions.
• Single-molecule techniques capture bond-forming dynamics with single-bond resolution.
• This work advances C-H functionalization toward atomically precise electrochemical manipulation.