Internal Dynamics and Modular Peripheral Binding in Stimuli-Responsive 3 : 2 Host:Guest Complexes.

Area of Science:

• Supramolecular Chemistry
• Macrocyclic Chemistry
• Host:Guest Chemistry

Background:

• The chemistry of 1:1 host:guest complexes is well-established.
• Higher stoichiometry (oligomeric) complexes, particularly with excess host, are largely unexplored.
• Protein oligomerization leads to novel functions in cellular machinery.

Purpose of the Study:

• To investigate the formation and properties of higher stoichiometry host:guest complexes.
• To explore the potential of cucurbit[n]uril (CB[n]) macrocycles in forming such complexes.
• To understand the dynamic and responsive behaviors of these novel supramolecular assemblies.

Main Methods:

• Synthesis and characterization of host:guest complexes using cucurbit[n]uril (CB[n]) macrocycles and symmetric, linear di-viologens.
• Investigation of complex stoichiometry, structural dynamics, and self-sorting properties in aqueous solutions.
• Evaluation of the responsiveness of the complexes to various external stimuli including chemicals, pH, and redox conditions.

Main Results:

• Formation of unusual 3:2 host:guest complexes between CB[n] macrocycles and di-viologens.
• Observation of remarkable dynamic properties, including host self-sorting and external ring-translocation.
• Demonstration of the structural tunability of cucurbit[8]uril (CB[8]) based 3:2 complexes.
• Confirmation of the complexes' responsiveness to chemical, pH, and redox stimuli in water.

Conclusions:

• Cucurbit[n]uril macrocycles can form higher stoichiometry, oligomeric host:guest complexes.
• The discovered 3:2 CB[8]:di-viologen complexes exhibit unique dynamic and responsive characteristics.
• These findings expand the understanding of supramolecular complex formation and highlight potential applications in stimulus-responsive materials.