Identifying π–π and π–Lone Pair Interactions in a Single-Molecule Junction

Noncovalent interactions are essential in determining molecular conformations and assembly architectures, serving as key factors in regulating material properties. Achieving a comprehensive understanding and precise control of these interactions is crucial in molecular design and the development of functional devices. Here, we utilize scanning tunneling microscopic break junction measurements and first-principles calculations to identify π–π and π–lone pair (π–lp) interactions within diphenyl disulfide derivatives at the single-molecule level. The competition between π–π and π–lp interactions regulates molecular conformation and conductance, leading to switching between high- and low-conductance states. Specifically, π–π interactions promote the high-conductance state, while π–lp interactions drive the molecule into a low-conductance state. Chemical modifications provide efficient methods to adjust π–π and π–lp interactions. These findings not only reveal the underlying mechanism of how π–π and π–lp interactions influence molecular conformation and induce the stereoelectronic effect but also offer a novel approach for creating practical devices.