Conformationally Adaptive Molecular Cages Enabled by Metal Cluster-Mediated Assembly.

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Chemical Crystallography

Background:

• Natural macromolecules exhibit complex adaptability through multiple conformational states.
• Replicating this conformational adaptability in synthetic systems presents a significant scientific challenge.
• Developing stimuli-responsive synthetic molecular architectures is crucial for advanced materials.

Purpose of the Study:

• To introduce a novel cluster-mediated conformational assembly (CMCA) strategy.
• To design and synthesize adaptive molecular cages with stimuli-responsive dynamics.
• To explore the conformational diversity and interconversion mechanisms of these assemblies.

Main Methods:

• Utilizing two metal clusters bridged by flexible arylthioether ligands (bpmb).
• Employing single-crystal X-ray diffraction to resolve molecular cage conformers.
• Conducting computational predictions and density functional theory (DFT) calculations to map energy landscapes.

Main Results:

• Successfully synthesized caged conformational assemblies (CCAs) exhibiting extensive structural diversity.
• Resolved 20 distinct conformers experimentally, aligning with computational predictions.
• Demonstrated stimuli-responsive interconversion driven by solvent polarity, halide binding, and guest encapsulation.
• Observed reversible switching between static and gyroscopic states upon guest encapsulation.
• Identified key non-covalent interactions (C-H···π, C-H···S, cation···π) stabilizing the structures.

Conclusions:

• The CMCA strategy provides a robust design principle for creating chemically addressable conformational adaptability.
• These adaptive molecular cages offer significant potential in molecular recognition and responsive materials.
• The dynamic behavior is underpinned by a near-degenerate energy landscape, as revealed by DFT calculations.