Strapped-porphyrin-based molecular turnstiles.

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis
• Materials Science

Background:

• Molecular machines offer precise control over molecular motion.
• Designing components with specific hydrogen-bonding capabilities is crucial for constructing dynamic molecular systems.
• Tetra-aryl porphyrin frameworks provide a versatile platform for developing complex supramolecular architectures.

Purpose of the Study:

• To synthesize novel molecular turnstiles incorporating both hydrogen-bond donor and acceptor functionalities.
• To investigate the controllable switching mechanism between closed and open states of the synthesized molecular turnstiles.
• To characterize the structural and dynamic properties of these molecular turnstiles in solution and solid states.

Main Methods:

• Synthesis of tetra-aryl tin(IV) porphyrins functionalized with pyridyldiamide rotors.
• Nuclear Magnetic Resonance (NMR) spectroscopy (1D and 2D) for solution-state structural and dynamic analysis.
• Single-crystal X-ray diffraction for solid-state structure determination.

Main Results:

• Successful synthesis of molecular turnstiles featuring H-bond acceptor (tin(IV) porphyrin) and H-bond donor (pyridyldiamide) sites.
• Demonstrated reversible switching between intramolecularly H-bonded closed states and open states induced by external H-bond acceptors like DMSO.
• Elucidation of the closed-state solid-state structure via X-ray crystallography, confirming the intramolecular hydrogen-bonding interactions.

Conclusions:

• The developed molecular turnstiles exhibit controlled, external stimulus-responsive switching behavior.
• The combination of porphyrin scaffolds and pyridyldiamide rotors provides an effective design for dynamic supramolecular systems.
• These findings contribute to the advancement of molecular machines and responsive materials.