Oxatub[4]arene: a smart macrocyclic receptor with multiple interconvertible cavities.

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry

Background:

• Numerous synthetic macrocyclic receptors exist, but a single receptor is rarely optimal for all guests or applications.
• A macrocycle with multiple interconvertible cavities offers advantages for broader guest binding scope and diverse functionalities.

Purpose of the Study:

• To report a novel naphthalene-based macrocyclic receptor, oxatub[4]arene, with an adaptable cavity.
• To investigate the conformational flexibility and guest-binding properties of this new macrocycle.

Main Methods:

• Synthesis of the naphthalene-based macrocycle, oxatub[4]arene.
• Characterization of the four distinct conformations using 2D NMR spectroscopy.
• Determination of conformational structures via X-ray single crystal analysis.

Main Results:

• Oxatub[4]arene exhibits four representative conformations due to naphthalene ring flipping, each possessing a well-defined cavity.
• Different guests selectively bind to specific conformers or combinations thereof.
• Thermodynamic analysis reveals conformers act as a reservoir, adapting to guest structures to maximize binding energies.

Conclusions:

• The adaptable cavity of oxatub[4]arene allows for optimized guest association.
• This smart macrocycle presents a promising platform for developing molecular machines, devices, and stimuli-responsive materials.