Unveiling Intermolecular Frustrated Lewis Pairs in Single-Molecule Junctions

Intermolecular frustrated Lewis pairs (FLPs) play vital roles in catalysis yet remain undetectable at the single-molecule scale due to their ultralow interaction energies and transient nature. This limitation obstructs mechanistic understanding of weak orbital coupling in molecular systems. To address this, we engineered a sterically hindered molecular probe (OPE-Py-M) that forms stable in situ FLP adducts with B(C₆F₅)₃ (BCF) within single-molecule junctions. Using scanning tunneling microscopy break junction (STM-BJ) techniques, we observed a quantifiable conductance attenuation from 10^-4.39 to 10^-4.78 G₀ upon FLP formation, a signature validated by NMR upfield shifts and UV-Vis charge-transfer bands. This work establishes single-molecule conductance as an ultrasensitive probe for orbital perturbations below hydrogen-bond energy thresholds, enabling unprecedented investigation of noncovalent interactions in molecular electronics and self-assembly.