A pseudo-cubic metal-organic cage with conformationally switchable faces for dynamically adaptive guest encapsulation

Area of Science:

• Supramolecular Chemistry
• Materials Science

Background:

• Metal-organic cages (MOCs) are promising host materials for molecular recognition and separation.
• Rigid structures in traditional MOCs limit their adaptability to diverse guest molecules.
• Dynamic host-guest chemistry requires materials with adaptable cavities.

Purpose of the Study:

• To design and synthesize a conformationally adaptable pseudo-cubic metal-organic cage.
• To investigate the dynamic cavity expansion mechanism of the cage.
• To demonstrate the cage's ability to bind a wide range of guest molecules.

Main Methods:

• Synthesis of a novel pseudo-cubic metal-organic cage incorporating a tetramine subcomponent with 2,6-naphthalene arms.
• X-ray crystallography to determine the cage structure and guest binding modes.
• Variable temperature NMR spectroscopy to study the conformational dynamics of the cage.
• Computational modeling (e.g., DFT calculations) to elucidate the mechanism of cavity expansion.

Main Results:

• A pseudo-cubic cage with flexible faces capable of switching between endo and exo states was successfully synthesized.
• The cage demonstrated dynamic cavity expansion, accommodating guest molecules ranging from 46% to 154% of its empty volume.
• Experimental and computational data confirmed the flipping of cage faces, enabling adaptation to guest size.

Conclusions:

• The developed pseudo-cubic cage exhibits remarkable conformational adaptability, overcoming the rigidity limitations of conventional MOCs.
• This dynamic host-guest system shows significant potential for selective chemical purifications and molecular encapsulation.
• The cage's ability to adjust its cavity size represents a significant advancement in the design of functional supramolecular materials.