Building 2D crystals from 5-fold-symmetric molecules

Area of Science:

• Surface Science
• Materials Chemistry
• Supramolecular Chemistry

Background:

• Close packing of molecules on surfaces is crucial for creating ordered 2D materials.
• Incompatible symmetries between molecular building blocks and surface lattices present challenges in achieving perfect tiling.
• Buckybowls, like corannulene, are polycyclic aromatic hydrocarbons with unique 5-fold symmetry.

Purpose of the Study:

• To investigate the self-assembly and close packing of 5-fold-symmetric buckybowls on a hexagonal surface lattice.
• To understand how molecular symmetry influences lattice formation and packing arrangements.
• To compare experimental observations with computational and mechanical modeling predictions.

Main Methods:

• Scanning Tunneling Microscopy (STM) to visualize molecular arrangements on Cu(111).
• Analysis of molecular tilt and symmetry adaptation during adsorption.
• Comparison with computational simulations of hard pentagonal discs.

Main Results:

• Corannulene forms a hexagonal lattice on Cu(111) by deviating from its inherent C(5) symmetry.
• Chiral 5-fold-substituted corannulene derivatives maintain their symmetry, leading to imperfect quasi-hexagonal lattices.
• Observed lattices include antiparallel arrangements and disordered hexagonal grids, agreeing with macroscopic modeling.

Conclusions:

• Molecular symmetry dictates packing strategies when incompatible with surface lattice symmetry.
• Deviations from inherent symmetry are essential for ordered packing on commensurate lattices.
• Macroscopic modeling effectively predicts 2D packing behavior of molecules with incompatible symmetries.