Triptycene-based expanded oxacalixarenes: synthesis, structure, and tubular assemblies in the solid state.

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis
• Materials Science

Background:

• Triptycene's rigid 3D structure offers unique molecular scaffolding.
• Oxacalixarenes are macrocyclic compounds with potential applications in host-guest chemistry.
• Designing novel macrocyclic structures with tunable properties is an ongoing challenge.

Purpose of the Study:

• To synthesize novel triptycene-based expanded oxacalixarenes.
• To investigate the structural characteristics and conformational behavior of these new compounds.
• To explore the self-assembly properties and potential applications of these molecules in the solid state.

Main Methods:

• Single-step SNAr reactions utilizing 2,7-dihydroxytriptycene with various halogenated aromatic precursors.
• Structural elucidation using Nuclear Magnetic Resonance (NMR) spectroscopy, Mass Spectrometry (MS), and X-ray crystal structure analysis.
• Investigation of solid-state self-assembly and intermolecular interactions.

Main Results:

• Efficient synthesis of three pairs of triptycene-based expanded oxacalixarenes (5a/5b, 7a/7b, 9a/9b).
• Identification of dynamic conformational interconversion (boat-chair) in compound 9b.
• Observation of self-assembly into organic tubular and porous architectures by compounds 5a, 5b, and 9a.
• Significant role of chlorine bonding (C-Cl...Cl, C-Cl...O, C-Cl...pi) in directing solid-state assembly.

Conclusions:

• Novel triptycene-based expanded oxacalixarenes can be readily synthesized.
• These compounds exhibit interesting structural and conformational properties.
• The molecules demonstrate propensity for self-assembly into ordered supramolecular structures, facilitated by specific non-covalent interactions, paving the way for new porous materials.