Ionic Liquid Accelerates Electrochemically Driven Single-Molecule Oxidative Coupling

Molecular adsorption covers a broad spectrum of chemical processes and device fabrications at solid/liquid interfaces. The unraveling of the underlying mechanisms relies on regulating molecular adsorption. However, achieving such regulation at the single-molecule level remains a challenge. Herein, we utilized a combined ionic liquid and scanning tunneling microscope break junction methods to tune single 4-(pyridin-4-yl)aniline molecules gradually from the flat configuration to the upright one and found that only the upright configuration can trigger the oxidative coupling. Experimental and theoretical findings demonstrated that the ionic liquid reduced the electron density of the Au electrode, giving rise to the evolution of the interaction between molecule and electrode from the Au-π dominated coupling to the Au-σ dominated one. This work will inspire the exploration of strategies that can control the molecular assembly, accelerate the chemical reaction, and promote the fabrication of organic devices.