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Force Reveals Hidden Conformations and Dissociation Pathways in Individual π-Interacting Dimers
Célia Franceschini1, Dorothée Brandt2, Maxime Ledent1
1Research Unit Molsys, NanoChem, University of Liège, Liège, Belgium.
Angewandte Chemie (International Ed. in English)
|June 3, 2026
Summary
Mechanical force controls molecular structure using noncovalent interactions. Atomic force microscopy revealed hidden parallel and anti-parallel perylene diimide conformers, detailing their distinct mechanical stability and rupture pathways.
Area of Science:
- Supramolecular Chemistry
- Materials Science
- Chemical Physics
Background:
- Mechano-responsive materials leverage mechanical force to alter molecular structure.
- Noncovalent interactions offer tunable mechanical stability and reversibility.
- Conventional ensemble techniques struggle to access conformational energy landscapes of noncovalent motifs.
Purpose of the Study:
- To probe individual π-interactions within a perylene diimide dimer using single-molecule force spectroscopy.
- To reveal hidden conformational states and map their force-dependent energy landscape.
- To provide molecular-level insight into the mechanics of π-π interactions.
Main Methods:
- Atomic force microscopy (AFM)-based force spectroscopy (single-molecule pulling experiments).
- Molecular dynamics (MD) simulations, including steered MD.
- Passive force spectroscopy for real-time conformer resolution.
Main Results:
- Two distinct, long-lived conformers (parallel and anti-parallel perylene diimide orientations) were identified, previously indistinguishable by ensemble methods.
- The parallel conformer showed greater mechanical stability and a sequential rupture pathway involving interconversion to the anti-parallel state.
- Passive force spectroscopy validated the force-induced interconversion pathway and quantified mechanical properties.
Conclusions:
- Combining passive force spectroscopy with MD simulations can uncover hidden conformational states in noncovalent assemblies.
- This approach maps the force-dependent energy landscape of supramolecular systems.
- Single-molecule force spectroscopy is a powerful tool for understanding the mechanics of π-π interactions and other noncovalent bonds.
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