Multicomponent Self-Assembled Metal-Organic [3]Rotaxanes

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Chemical Engineering

Background:

• Mechanically interlocked macromolecules (MIMs) offer unique properties due to their complex architectures.
• Metal-organic rotaxanes represent a class of MIMs with potential applications in responsive materials.
• Developing efficient and stimuli-responsive synthetic strategies for MIMs is crucial.

Purpose of the Study:

• To describe the synthesis and characterization of novel environmentally responsive metal-organic [3]rotaxanes.
• To investigate the stimuli-responsive disassembly and reassembly mechanisms of these rotaxanes.
• To explore the potential for tuning the complex's nature through external stimuli.

Main Methods:

• One-pot self-assembly of a tetracationic macrocycle, tri-1,3,5-benzenetricarboxylate anion, and silver cations (Ag+).
• Stimuli-induced disassembly using competitive counteranions (e.g., I-) and reassembly with Ag+.
• Conformational changes induced by temperature and small molecules (e.g., D2O, methanol-d4) studied via NMR spectroscopy.
• Structural characterization using single-crystal X-ray diffraction.

Main Results:

• Quantitative yield of metal-organic [3]rotaxanes achieved via a facile one-pot procedure.
• Demonstrated reversible disassembly and reassembly triggered by specific anionic species and metal cations.
• Identified conformational flipping of the macrocycle in response to temperature and various small molecules.
• Explored the formation of 2D metal-organic rotaxane-containing frameworks (MORFs) using Cd2+.

Conclusions:

• Environmentally responsive metal-organic [3]rotaxanes can be efficiently synthesized through self-assembly.
• These rotaxanes exhibit tunable properties and reversible responses to external stimuli.
• The synthetic methodology is adaptable, allowing for the creation of diverse supramolecular architectures like MORFs.