Solvent-Induced Self-Assembly of Pd₆L₃ and Pd₈L₄ Coordination Cages for Benzene-Cyclohexane Separation

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Coordination Chemistry

Background:

• Development of molecular cages for host-guest chemistry and separations.
• Need for water-soluble and recyclable separation agents.
• Challenges in stabilizing sensitive guest molecules.

Purpose of the Study:

• To synthesize novel bowl-shaped palladium cages with tunable structures.
• To investigate the solvato-controlled formation and interconversion of these cages.
• To explore their applications in guest encapsulation, molecular stabilization, and selective separations.

Main Methods:

• Self-assembly of a planar tetratopic ligand with cis-blocked Pd(II) acceptors.
• Solvent-controlled synthesis and interconversion of trifacial and tetrafacial cages.
• Encapsulation studies with protonated merocyanine and separation experiments with benzene/cyclohexane.

Main Results:

• Successful synthesis of novel Pd2L-based trifacial (n=3) and tetrafacial (n=4) cages.
• Demonstrated solvato-controlled cage formation and reversible structural transformations.
• Effective encapsulation and stabilization of protonated merocyanine, enabling reversible photoisomerization.
• Selective aqueous extraction of benzene over cyclohexane (>99% purity) with high recyclability.

Conclusions:

• First report of water-soluble molecular hosts for selective benzene/cyclohexane separation via aqueous extraction.
• These cages offer potential for guest stabilization, molecular encapsulation, and efficient chemical separations.
• The solvato-controlled synthesis provides a versatile route to tunable supramolecular structures.