Selective assembly on a surface of supramolecular aggregates with controlled size and shape

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Surface Science

Background:

• Developing molecule-based miniature devices requires efficient methods for assembling molecular building blocks on substrates.
• Supramolecular assembly using non-covalent interactions can create ordered structures, but directing self-assembly of adsorbed molecules has been challenging.
• Existing methods primarily yield crystals or dissolved structures, limiting surface-based molecular construction.

Purpose of the Study:

• To demonstrate rational control over the size and pattern of surface-supported supramolecular structures.
• To investigate the role of non-covalent interactions in directing the self-assembly of adsorbed molecules.
• To establish a method for designing and constructing diverse supramolecular architectures on surfaces.

Main Methods:

• Adsorption of substituted porphyrin molecules onto a gold surface.
• Utilizing low-temperature scanning tunneling microscopy (LT-STM) to observe molecular arrangements.
• Systematically varying porphyrin substituents to probe their effect on intermolecular interactions.

Main Results:

• Substituted porphyrins formed distinct supramolecular structures: monomers, trimers, tetramers, and wire-like assemblies.
• The observed aggregation patterns directly correlated with the geometric and chemical properties of the porphyrin substituents.
• Non-covalent interactions between molecules were successfully tuned to control assembly outcomes.

Conclusions:

• Surface-supported supramolecular structures can be rationally controlled by manipulating non-covalent interactions.
• The findings enable the design of specific molecular architectures on surfaces through substituent engineering.
• This approach facilitates the construction of advanced functional materials and devices at the molecular level.