Interfacial Gold-Gold Interactions Govern the Mechanical Stability of N-Heterocyclic Carbene Self-Assembled...

N-heterocyclic carbenes (NHCs) have emerged as robust anchoring groups for the construction of ultrastable self-assembled monolayers (SAMs) on gold. However, the microscopic failure mechanism of this organic-inorganic interface under mechanical stress remains elusive. Herein, we investigate the mechanochemical behavior of NHC-Au interfaces using single-molecule force spectroscopy (SMFS). We reveal that while the NHC-Au coordination bond exhibits high intrinsic mechanical strength (∼1200 pN), the interfacial stability is limited by the cohesive strength of the gold lattice, leading to substrate failure via gold atom extraction at significantly lower forces (∼500 pN). In situ cyclic force spectroscopy and tip-transfer assays collectively confirm that mechanical force induces the extraction of gold atoms, which retain their coordination reactivity as NHC-Au complexes. These findings not only provide mechanochemical evidence for the adatom-mediated binding model but also offer a novel atomic-level strategy for generating single-atom metal centers for future mechano-gated catalysis.