Toward interlocked molecules beyond catenanes and rotaxanes

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis
• Materials Science

Background:

• Development of novel molecular architectures is crucial for advancing materials science.
• Crown ethers and their host-guest chemistry offer unique possibilities for molecular recognition.
• Linear scaffolds provide versatile platforms for constructing complex supramolecular systems.

Purpose of the Study:

• To synthesize a novel linear bis secondary dialkylammonium ion-containing scaffold.
• To investigate the complexation of dibenzo[24]crown-8 (DB24C8) macrocycles with the scaffold.
• To characterize the resulting pseudorotaxane structures in solution and the gas phase.

Main Methods:

• Synthesis of an anthracenyl core-based scaffold.
• Host-guest complexation studies with DB24C8 macrocycles.
• (1)H NMR spectroscopy for quantifying association constants in solution.
• Fast Atom Bombardment (FAB) mass spectrometry for gas-phase analysis.
• X-ray crystallography for determining crystal superstructure.

Main Results:

• Successful synthesis of a linear bis secondary dialkylammonium ion-containing scaffold.
• Formation of [2]- and [3]pseudorotaxanes through the docking of one or two DB24C8 macrocycles.
• Quantification of association constants for pseudorotaxane formation in solution.
• Confirmation of pseudorotaxane stability in the gas phase.
• Determination of the X-ray crystal superstructure of the [3]pseudorotaxane.

Conclusions:

• The anthracenyl scaffold effectively binds DB24C8 macrocycles to form stable pseudorotaxanes.
• The study demonstrates controllable supramolecular assembly of rotaxane-like structures.
• The combined spectroscopic and crystallographic data provide a comprehensive understanding of these molecular architectures.