Site-selective anion recognition of an interlocked dimer

Area of Science:

• Supramolecular Chemistry
• Host-Guest Chemistry
• Molecular Recognition

Background:

• Interlocked dimers are supramolecular structures capable of encapsulating guest molecules.
• Understanding anion binding within these structures is crucial for developing selective molecular sensors and separation materials.
• The interplay between cavity size, shape, and anion properties dictates recognition.

Purpose of the Study:

• To investigate the selective encapsulation of anions (nitrate and tetrafluoroborate) by an interlocked dimer.
• To elucidate the factors governing anion selectivity, including cavity structure and anion templating effects.
• To explore the influence of cavity volume on anion recognition in a new interlocked dimer.

Main Methods:

• Synthesis and characterization of interlocked dimers 2 and 3.
• Anion encapsulation studies using nitrate (NO3-) and tetrafluoroborate (BF4-) anions.
• Anion competition experiments to determine selectivity.
• Structural analysis to correlate cavity environment with anion binding.

Main Results:

• Interlocked dimer 2 exhibits selective formation of encapsulation patterns C (mixed anions) and F (nitrate only).
• Anion exchange experiments reveal that nitrate is a stronger template than tetrafluoroborate, and cavity accessibility influences expulsion.
• A smaller interlocked dimer (3) preferentially encapsulates nitrate, forming pattern F, indicating cavity volume is a key recognition factor.

Conclusions:

• The molecular structure of interlocked dimers, specifically cavity accessibility and ligand arrangement, dictates selective anion binding.
• Nitrate anions are preferentially recognized and retained over tetrafluoroborate anions due to templating effects and structural constraints.
• Cavity volume plays a significant role in anion recognition, with smaller cavities favoring the encapsulation of nitrate.