Toward Two-Dimensional Tessellation through Halogen Bonding between Molecules and On-Surface-Synthesized Covalent...

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Engineering complex two-dimensional (2D) organic nanoarchitectures is crucial for advanced materials.
• On-surface synthesis offers a pathway to create intricate molecular structures.
• Controlling self-assembly of bespoke molecular building blocks is key to designing functional nanomaterials.

Purpose of the Study:

• To investigate the engineering of 2D tessellation organic nanoarchitectures using triangular molecules.
• To explore the formation of covalent multimers via on-surface synthesis.
• To understand the self-assembly behavior and limitations in achieving specific tiling patterns.

Main Methods:

• Scanning tunneling microscopy (STM) was employed to visualize the nanoarchitectures.
• Ullmann coupling was induced by depositing 1,3,5-Tris(3,5-dibromophenyl)benzene molecules on Au(111) surfaces at controlled temperatures.
• Analysis of molecular self-assembly and superstructure formation was performed.

Main Results:

• A semi-regular rhombitrihexagonal tiling superstructure was observed at 145 °C, composed of intact triangular molecules and covalent dimers.
• The structure featured triangular domains of intact molecules and rectangular rows of covalent dimers.
• Nearly hexagonal vertices were formed by covalent multimers.
• A perfect semi-regular tiling was not achieved due to the absence of coexisting covalent hexagons.

Conclusions:

• The formation of specific 2D organic tessellation nanoarchitectures depends critically on the synthesis and ratio of molecular building blocks.
• The required covalent hexagons for a perfect rhombitrihexagonal tiling only form above 165 °C and do not coexist with the necessary dimers and intact molecules at lower temperatures.
• Precise control over temperature is essential for directing on-surface synthesis and achieving desired self-assembled structures.