Steering Metal-Organic Network Structures through Conformations and Configurations on Surfaces

Area of Science:

• Surface Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Molecular adsorption conformations and arrangement configurations are key to surface stereochemistry.
• Their role in directing metal-organic network (MON) structures is not well understood.
• Understanding this relationship is crucial for designing novel MONs.

Purpose of the Study:

• To investigate how surface stereochemistry influences the construction of MONs.
• To demonstrate the steering effect of isocyanide adsorption conformations and arrangement configurations on MON structures.
• To explore the formation of complex MONs, including fractal structures.

Main Methods:

• Coordination self-assembly of isocyanides on Cu(111) and Ag(111) surfaces.
• Utilizing different diisocyanobenzene isomers (1,4-phenylene diisocyanobenzene and 1,3-phenylene diisocyanobenzene).
• Characterization of adsorption conformations and resulting MON structures.

Main Results:

• Honeycomb MONs formed on Cu(111) with 1,4-phenylene diisocyanobenzene via (isocyano)₃-Cu motifs.
• 1,3-phenylene diisocyanobenzene failed to form MONs on Cu(111) due to its standing adsorption conformation.
• On Ag(111), 1,3-phenylene diisocyanobenzene adopted a flat conformation, enabling MON formation with (isocyano)₃-Ag motifs.
• Sierpiński triangle fractals (up to fourth order) were formed from subunits with heterotactic configurations, while homotactic configurations yielded triangular MONs.

Conclusions:

• Surface stereochemistry, specifically molecular adsorption conformation and arrangement, effectively steers MON structures.
• The choice of metal surface (Cu vs. Ag) and ligand geometry significantly impacts MON formation.
• This work opens avenues for designing complex, hierarchical MONs, including fractal architectures, by controlling surface interactions.