Fluoride-selective colorimetric sensor based on thiourea binding site and anthraquinone reporter

Area of Science:

• Chemical Sensing
• Supramolecular Chemistry
• Organic Synthesis

Background:

• Development of selective and sensitive chemosensors for anion detection is crucial in various fields.
• Colorimetric sensors offer a simple and rapid method for analyte identification.
• Existing sensors often lack selectivity or sensitivity for specific anions.

Purpose of the Study:

• To synthesize and characterize a novel colorimetric sensor for anion recognition.
• To investigate the selectivity and sensitivity of the sensor towards various anions.
• To elucidate the structural and electronic factors governing the sensing mechanism.

Main Methods:

• Synthesis and characterization of N-4-nitrobenzene-N extquoteright-1 extquoteright-anthraquinone-thiourea (1) using NMR, ESI-MS, and IR spectroscopy.
• Colorimetric and spectrophotometric studies in acetonitrile upon addition of various anions (F(-), CH(3)CO(2)(-), H(2)PO(4)(-), HSO(4)(-), Cl(-), Br(-)).
• Computational analysis using AM1 calculations to determine the most stable conformation and understand binding interactions.

Main Results:

• The sensor (1) displayed a distinct color change from colorless to yellow upon addition of fluoride ions (F(-)) in acetonitrile.
• Other tested anions showed only slight spectral shifts without significant color changes, indicating high selectivity for F(-).
• Association constants revealed a strong preference for F(-) over other anions, differing from the expected order based on basicity.

Conclusions:

• The synthesized thiourea derivative (1) functions as a highly selective and sensitive colorimetric sensor for fluoride ions.
• Intramolecular hydrogen bonding and the resulting conformation of the thiourea moiety contribute to the observed selectivity for F(-).
• This sensor provides a simple and effective platform for the visual detection of fluoride anions.