Shape-persistent linear, kinked, and cyclic oligo(phenylene-ethynylene-butadiynylene)s: self-assembled monolayers

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Surface Science

Background:

• Shape-persistent rigid molecules are building blocks for self-assembled monolayers (SAMs).
• Controlling molecular interactions is key to designing ordered surface structures.
• Scanning Tunneling Microscopy (STM) provides submolecular resolution for surface studies.

Purpose of the Study:

• To investigate the self-assembly of rigid phenylene-ethynylene-butadiynylene rods.
• To explore the impact of specific functional groups on molecular packing and interactions.
• To synthesize and characterize novel half-ring and oligomeric structures.

Main Methods:

• Formation of lamellar self-assembled monolayers (SAMs) at the HOPG/TCB interface.
• High-resolution Scanning Tunneling Microscopy (STM) for molecular imaging.
• Copper and Palladium-catalyzed oligomerization reactions.

Main Results:

• Rigid rods formed lamellar SAMs with defined packing distances.
• Polar substituents induced 2D phase separation and controlled rod-rod interactions.
• Novel half-ring structures and acyclic/cyclic oligomers were synthesized and characterized.
• STM revealed that side chains and backbone angle dictate adlayer orientation.

Conclusions:

• Molecular design of rigid rods influences self-assembly behavior and surface patterning.
• Functionalization with polar groups and clamp units allows precise control over molecular arrangement.
• STM is a powerful tool for elucidating the molecular origins of surface structures.