Forcing a Molecule to Switch: Quantifying Mechanical Control at the Atomic Scale.

Mechanically induced conformational switching at the single-molecule level represents a fundamental mechanism for molecular functionality, yet quantitative characterization of the underlying force and energy landscape remains limited. Here, we study individual TBrPP-Co(II) molecules on Au(111) using qPlus atomic force microscopy. By reconstructing interaction potentials from 3D Δf(x,y,z) data, we determine a threshold force of ∼96 ± 8 pN and a tip-induced switching interaction energy of ∼38 ± 4 meV associate with the conformational transition. The isolated tip-molecule force follows a power law (exponent ∼6), indicating dominance of long-range van der Waals interactions. At closer distances, deviations reveal force-induced deformation preceding the transition. Validation via the inflection point test confirms measurement reliability. These findings show that long-range dispersive interactions can mechanically deform a molecule and facilitate conformational switching through a deformation-assisted pathway, providing a quantitative framework for controlling mechanically driven functionality at the single-molecule scale.