Operating a Multi-Level Molecular Dimer Switch through Precise Tip-Molecule Control

Controlling the state of molecules on surfaces is crucial for the advancement of molecular electronics. While reversible control of bistable molecule switches has been demonstrated, achieving controllable multi-state switching at the molecular scale remains a formidable challenge. In this study, we introduce a simple and effective strategy for the on-demand control of a multi-level molecular switch by creating a molecular dimer. We explore the transition behavior of a pyrrolidine dimer system on the Cu(100) surface using low-temperature scanning tunneling microscopy. By fine-tuning the voltage and tip-molecule distance, we can selectively determine the dominant state of the dimer system. Both intermolecular and tip-molecule interactions play a role in modifying the transition pathways, enabling precise multi-state control.