Reversible Sliding Motion by Hole-Injection in Ammonium-Linked Ferrocene, Electronically Decoupled from Noble Metal...

Area of Science:

• Molecular nanotechnology
• Surface science
• Supramolecular chemistry

Background:

• Artificial molecular machines offer mechanical motion via external stimuli.
• Ferrocene (Fc) is crucial but unstable on metal surfaces above 300 K.
• On-surface synthesis provides a platform for constructing complex molecular architectures.

Purpose of the Study:

• To develop a novel method for constructing and controlling molecular complexes on a metal surface.
• To investigate the mechanical motion of ferrocene-based molecular machines.
• To explore voltage-controlled manipulation of molecular components for nanomolecular devices.

Main Methods:

• Utilized scanning tunneling microscopy (STM) and spectroscopy (STS) for imaging and characterization.
• Constructed a molecular complex of ammonium-linked ferrocene (Fc-amm) and tetrabrominated crown ether (BrCR) on a Cu(111) surface.
• Applied hole injection via STM to induce and control molecular motion.

Main Results:

• Achieved periodic arrangement of Fc-amm molecules on a BrCR monolayer.
• Observed reversible lateral sliding motion (≈0.1 nm) of Fc groups upon hole injection.
• Demonstrated voltage-controlled manipulation of the molecular motion.

Conclusions:

• The observed motion is attributed to Coulomb repulsion in hole-doped Fc-amm+ ions and weakened CH-π interactions.
• This work presents a new strategy for on-surface bottom-up fabrication of functional nanomolecular devices.
• The findings open avenues for designing responsive molecular machines with precise control.