Azimuthal Dipolar Rotor Arrays on Surfaces.

Area of Science:

• Surface Science
• Supramolecular Chemistry
• Molecular Engineering

Background:

• 4,8,12-trioxatriangulene (TOTA) platforms are known to physisorb on metal surfaces.
• Molecular rotors are crucial for nanoscale mechanical devices and controlled molecular motion.
• Self-assembled monolayers (SAMs) on metal surfaces enable precise control over molecular arrangement.

Purpose of the Study:

• To design and synthesize novel dipolar molecular rotor compounds.
• To investigate their self-assembly into 2D arrays on Ag(111) surfaces.
• To explore the intermolecular interactions between the molecular dipoles.

Main Methods:

• Chemical synthesis of dipolar molecular rotor compounds.
• Adsorption and self-assembly on Ag(111) surfaces.
• Scanning tunneling microscopy (STM) for surface imaging.
• Theoretical calculations for electronic structure and interactions.

Main Results:

• Successful design and synthesis of TOTA-based molecular rotors with phenyl pivot joints and dipolar pyridine/pyridazine units.
• Formation of self-assembled 2D arrays of these rotors on Ag(111).
• Evidence from STM and theoretical calculations suggests through-space dipole-dipole interactions.
• Observation of energetically favorable head-to-tail arrangements between neighboring rotor dipoles.

Conclusions:

• The designed molecular rotors can form ordered 2D arrays on metal surfaces.
• Intermolecular dipole-dipole interactions play a significant role in the self-assembly.
• The head-to-tail arrangement indicates potential for controlled molecular ordering and functionality.