Self-assembled conjoined-cages.

Area of Science:

• Coordination Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Traditional coordination cages typically feature a single three-dimensional (3D) cavity.
• Designing discrete coordination cages with multiple 3D cavities presents a significant synthetic challenge.
• Metal-organic frameworks offer numerous cavities but lack discrete structural definition.

Purpose of the Study:

• To develop a synthetic strategy for constructing discrete coordination cages with multiple 3D cavities.
• To explore the self-assembly of complex, multi-cavity palladium-based coordination cages.
• To investigate the guest binding properties of the different sized cavities within the conjoined cages.

Main Methods:

• Peripheral decoration of a trinuclear [Pd3L6] core with [Pd2L4] units.
• Utilizing integrative self-sorting for the formation of tetranuclear and pentanuclear complexes.
• Employing cage-fusion and ligand-displacement reactions for cage transformations.

Main Results:

• Successfully synthesized multi-3D-cavity conjoined-cages with formulations [Pd4(La)2(Lb)4], [Pd5(Lb)4(Lc)2], and [Pd6(Lc)6].
• Demonstrated selective binding of anions (NO3-, F-, Cl-, Br-) in the smaller [Pd2L4] cavity.
• Showcased the larger [Pd3L6] cavity's ability to encapsulate multiple DMSO molecules.

Conclusions:

• The peripheral decoration strategy enables the construction of complex, multi-cavity coordination cages.
• The conjoined cages exhibit distinct cavities with selective guest encapsulation capabilities.
• This work provides a blueprint for designing sophisticated molecular architectures with multiple functional cavities.