A Molecular Transformer: A π-Conjugated Macrocycle as an Adaptable Host

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis
• Materials Science

Background:

• Macrocycles are cyclic molecules with diverse applications.
• Controlling macrocycle conformation is crucial for host-guest chemistry.
• Phenanthrene units can facilitate supramolecular assembly through pi-pi interactions.

Purpose of the Study:

• To develop a facile method for synthesizing macrocycles with tunable conformations.
• To investigate the supramolecular assembly behavior of synthesized macrocycles.
• To explore the host-guest properties of a flexible macrocyclic tetramer.

Main Methods:

• Facile synthesis of macrocycles.
• X-ray single-crystal analysis for structural elucidation.
• Investigation of solid-state supramolecular assembly via pi-pi interactions.
• Host-guest complexation studies with planar and spherical guests.

Main Results:

• A series of macrocycles including a planar dimer (1), twisted trimer (2), and figure-eight tetramer (3) were synthesized.
• X-ray analysis confirmed the structures and revealed electron-rich phenanthrene units.
• Macrocycles 1 and 3 self-assembled into columnar stacks and interlocking dimers, respectively.
• Tetramer 3 exhibited conformational flexibility, transforming from figure-eight to boat-shaped and belt-shaped geometries.
• Tetramer 3 successfully hosted planar electron-deficient guests and spherical C60 fullerenes.

Conclusions:

• The synthesized macrocycles, particularly tetramer 3, demonstrate adaptable host-guest capabilities.
• Conformational flexibility allows tetramer 3 to accommodate diverse guests.
• The study highlights the potential of phenanthrene-based macrocycles in supramolecular chemistry and materials science.