Control of Interlocking Mode in Pd₄L₈ Cage Catenanes

Area of Science:

• Supramolecular Chemistry
• Coordination Chemistry
• Materials Science

Background:

• Precise control over catenation in interlocked supramolecular systems is a persistent challenge.
• Existing methods often lack the ability to fine-tune the degree of interlocking in complex architectures.

Purpose of the Study:

• To develop a supramolecular system capable of forming distinct catenanes with controllable interlocking degrees.
• To investigate the thermodynamic stability and structural characteristics of different catenane isomers.

Main Methods:

• Dimerization of a lantern-shaped Pd2L4 cage to form Pd4L8 catenanes.
• X-ray crystallography and electronic structure calculations for structural and stability analysis.
• Nuclear Magnetic Resonance (NMR), Mass Spectrometry (MS), and Time-of-Flight Mass Spectrometry (TIMS) for monitoring transformations.

Main Results:

• Two distinct Pd4L8 catenanes were synthesized: a quadruply interlocked D4 symmetry cage and a novel triply interlocked C2h symmetry structure.
• The triply interlocked species is thermodynamically more stable due to enhanced noncovalent interactions.
• The degree of interlocking can be modulated by temperature changes and anion exchange.

Conclusions:

• A new supramolecular system provides precise control over catenation and interlocking degree in Pd4L8 cages.
• Thermodynamic stability is linked to ligand interactions, favoring the novel triply interlocked structure.
• Dynamic control over topological isomerism is achievable, opening avenues for responsive molecular materials.