A Benzothiadiazole-Based Thiourea Receptor for Selective Chloride Extraction and Reversible Fluoride Sensing.

Area of Science:

• Supramolecular Chemistry
• Anion Recognition
• Hydrogen Bonding Interactions

Background:

• Thiourea binding sites are crucial in supramolecular chemistry for anion recognition.
• Hydrogen bonding (HB) interactions are key to the efficacy of these sites.

Purpose of the Study:

• To design and synthesize a new thiourea-based anion receptor, BDTU.
• To investigate the anion binding affinity, selectivity, and signaling capabilities of BDTU.
• To explore the potential applications of BDTU in anion extraction and sensing.

Main Methods:

• Synthesis of the BDTU anion receptor.
• ¹H NMR, UV-vis, and fluorescence spectroscopy for binding studies.
• Single crystal X-ray diffraction for structural elucidation.
• Solid-liquid extraction experiments.
• Photophysical studies for sensing applications.

Main Results:

• BDTU exhibits moderate selectivity for chloride (Cl^-) over other anions.
• A stable 1:2 host-guest complex with Cl^- is formed, stabilized by thiourea NH HBs.
• X-ray crystallography confirms strong, directional N─H⋯Cl^- hydrogen bonds.
• BDTU demonstrates successful solid-liquid extraction of chloride.
• Reversible anion sensing behavior toward fluoride (F^-) was observed.

Conclusions:

• BDTU is an effective anion receptor with dual functionality.
• The receptor shows promise for selective chloride extraction and anion sensing applications.
• The study highlights the utility of incorporating electron-deficient signaling units in anion receptor design.