Triptycene-Based Molecular Rods for Langmuir-Blodgett Monolayers.

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Organic Synthesis

Background:

• Development of rigid molecular structures is crucial for advanced materials.
• Triptycene units offer unique structural properties for molecular design.
• Self-assembly into ordered monolayers is key for surface functionalization.

Purpose of the Study:

• To synthesize novel rigid molecular rods with interlocking triptycene units.
• To investigate the self-assembly properties of these molecules into monolayers.
• To characterize the structural and physical properties of the synthesized molecules and their films.

Main Methods:

• Fully modular synthesis of rigid molecular rods.
• X-ray diffraction (synchrotron) for crystal structure analysis.
• Capillary electrophoresis for pKa determination.
• Langmuir-Blodgett (LB) technique for monolayer formation.
• Atomic Force Microscopy (AFM) for film visualization.

Main Results:

• Three rigid molecular rods with a "double-decker" triptycene structure were synthesized.
• X-ray diffraction revealed detailed 3-D crystal packing.
• Acidity measurements showed pKa values between 2.06-2.53.
• Stable Langmuir-Blodgett monolayers (LBMs) were formed with tight intermolecular packing (55-59 Ų/molecule).
• Transferred films on gold (111) surfaces reached ~19 Å thickness with maximal molecular tilt of 38°.
• AFM visualized the monolayer structure on gold.

Conclusions:

• The synthesized rigid molecular rods are suitable for forming sturdy monolayers.
• The "double-decker" triptycene structure facilitates dense molecular packing.
• These molecules are promising building blocks for supramolecular architecture and surface science applications.