High-Yield Formation of Graphdiyne Macrocycles through On-Surface Assembling and Coupling Reaction

Area of Science:

• Surface science
• Organic chemistry
• Materials science

Background:

• Halogenated hydrocarbons are key precursors for surface-based carbon nanostructure fabrication.
• On-surface reactions enable controlled synthesis of complex molecular architectures.

Purpose of the Study:

• To comprehensively investigate the on-surface homocoupling of 1,3-bis(2-bromoethynyl)benzene on Au(111).
• To elucidate the reaction pathway for synthesizing graphdiyne nanostructures.
• To understand factors influencing the formation of graphdiyne chains versus macrocycles.

Main Methods:

• Submolecular resolution scanning tunneling microscopy (STM).
• Noncontact atomic force microscopy (NC-AFM).
• Surface-assisted chemical reactions on Au(111).
• Statistical analysis and theoretical calculations.

Main Results:

• Identification of organometallic intermediates and their self-assembly during dehalogenation.
• Formation of butadiyne moieties upon demetallization.
• Spontaneous formation of graphdiyne zigzag chains and macrocycles.
• Coverage-dependent ratio of chains to macrocycles, with macrocycles favored at optimal conditions.
• High-yield (up to 95%) production of graphdiyne macrocycles.

Conclusions:

• The on-surface homocoupling reaction pathway involves organometallic intermediates and butadiyne formation.
• The ratio of graphdiyne structures is controllable by initial precursor coverage.
• Thermodynamic and kinetic factors govern the favored formation of graphdiyne macrocycles.