A C Symmetric Nitrate Complex with a Thiophene-Based Tripodal Receptor

Area of Science:

• Supramolecular Chemistry
• Anion Recognition
• Organic Synthesis

Background:

• Development of selective anion receptors is crucial for sensing and separation technologies.
• Tripodal receptors offer defined binding pockets for guest molecules.
• Thiophene-based scaffolds provide unique electronic and structural properties for receptor design.

Purpose of the Study:

• To synthesize and characterize a novel thiophene-based tripodal receptor.
• To investigate the binding interactions of the receptor with nitrate and iodide anions.
• To evaluate the selectivity of the receptor for nitrate over other anions.

Main Methods:

• Synthesis of a thiophene-based tripodal receptor.
• Single-crystal X-ray diffraction analysis of receptor-anion complexes.
• High-level Density Functional Theory (DFT) calculations.
• (1)H Nuclear Magnetic Resonance (NMR) titration studies in chloroform.

Main Results:

• The nitrate complex reveals a C(3) symmetric structure with nitrate encapsulated via six NH···O hydrogen bonds.
• DFT calculations confirm the stability of trigonal binding of nitrate oxygen atoms.
• In the iodide complex, iodide anions remain outside the receptor cavity.
• NMR titration indicates a 1:1 complex formation with nitrate (K = 315 M⁻¹) and moderate selectivity.

Conclusions:

• The synthesized thiophene-based tripodal receptor exhibits selective nitrate binding.
• Structural and computational studies elucidate the binding mechanism and stability.
• The receptor demonstrates potential for nitrate sensing applications.