Synthesis of Carborane-Functionalized Macrocycles: Bond-Angle-Modulated Cavities and Cation-Mediated Assembly

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Organic Synthesis

Background:

• Macrocycles are large ring structures with diverse applications.
• Carboranes are unique boron-containing molecules offering distinct three-dimensional scaffolds.
• Developing novel synthetic routes for complex macrocyclic architectures remains a key challenge.

Purpose of the Study:

• To develop a novel synthetic strategy for constructing macrocycles utilizing a three-dimensional carborane skeleton.
• To investigate the tunability of macrocycle cavity size based on carborane geometry.
• To explore the self-assembly into nanotubes and the host-guest properties of these novel carborane-based macrocycles.

Main Methods:

• Cyclization reactions employing a three-dimensional carborane scaffold.
• Substrate scope experiments to assess reaction compatibility.
• Introduction of pyridine groups for coordination-driven self-assembly.
• Host-guest complexation studies using dichloromethane.

Main Results:

• A novel synthetic strategy for carborane-based macrocycles was successfully developed.
• Macrocycle cavity size was effectively regulated by the carborane's bonding angle (para-carborane yielding larger cavities than meta-carborane).
• Pyridine-functionalized macrocycles self-assembled into nanotubes via silver(I) and iodine(I) coordination.
• Specific encapsulation of dichloromethane molecules was observed, driven by van der Waals forces.

Conclusions:

• This study introduces a versatile synthetic approach for carborane-based macrocycles, enhancing structural diversity in supramolecular chemistry.
• The ability to tune cavity size and form nanotubes highlights the potential of carborane scaffolds in materials science.
• The identified host-guest properties offer insights into molecular recognition and encapsulation mechanisms.