Shape-persistent macrocycles with intraannular polar groups: synthesis, liquid crystallinity, and 2D organization

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Organic Chemistry

Background:

• Macrocyclic compounds are of interest for their unique structural and self-assembly properties.
• Liquid crystals (LCs) exhibit ordered phases with applications in displays and sensors.
• Controlling molecular organization at interfaces is crucial for nanotechnology.

Purpose of the Study:

• To synthesize novel macrocycles with specific functional groups (intraannular polar ester, extraannular oligo-alkyl).
• To investigate the liquid crystalline behavior and molecular ordering of these macrocycles.
• To explore the 2D organization and surface functionalization capabilities of macrocycles at the graphite interface.

Main Methods:

• Chemical synthesis of macrocyclic compounds.
• Polarizing microscopy to observe liquid crystalline textures.
• X-ray powder diffraction to analyze molecular ordering in the LC phase.
• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy to study molecular dynamics.
• Surface characterization at the solvent-highly oriented pyrolytic graphite (HOPG) interface.

Main Results:

• Stable liquid crystalline phases with fan-shaped textures were observed, indicating columnar molecular order.
• X-ray diffraction and solid-state NMR data suggest restricted rotation of macrocycles within the columnar stacks.
• Macrocycles demonstrated the ability to nanofunctionalize the highly oriented pyrolytic graphite (HOPG) surface at the multinanometer scale.

Conclusions:

• The synthesized macrocycles exhibit unique liquid crystalline properties driven by their specific structure.
• Restricted molecular rotation within the columnar phase influences the material's bulk properties.
• These macrocycles hold potential for surface nanofunctionalization applications.