Transmitting Stepwise Rotation among Three Molecule-Gear on the Au(111) Surface

Area of Science:

• Surface science
• Molecular engineering
• Scanning tunneling microscopy

Background:

• Achieving stable molecular anchoring to metal surfaces is crucial for constructing molecular machines.
• Radical states induced by dissociation reactions can promote molecular anchoring.

Purpose of the Study:

• To design and demonstrate a molecule-gear system for controlled manipulation and rotation using scanning tunneling microscopy (STM).
• To investigate methods for stable molecular anchoring and efficient manipulation of molecular gears.

Main Methods:

• Utilizing density functional theory (DFT) calculations to rationalize molecular behavior.
• Synthesizing and manipulating star-shaped pentaphenylcyclopentadiene (PPCP) derivatives with specific functional groups.
• Employing scanning tunneling microscopy (STM) for molecular manipulation and observation of rotations.

Main Results:

• An open radical state in the core of pentaphenylcyclopentadiene (PPCP) was found to significantly favor anchoring to metal surfaces.
• Incorporation of a tert-butyl group at the gear's tooth enhanced tip-molecule interactions, facilitating manipulation and rotation monitoring.
• Reproducible, stepwise rotations of single molecule-gears were achieved, with successful transmission of motion to up to three interlocked units.

Conclusions:

• A strategy involving radical states and specific functional groups enables stable anchoring and controlled manipulation of molecule-gears.
• The optimized molecule-gear system demonstrates the potential for building complex molecular machines through precise STM control.