New sensitive and selective fluorescent probes for fluoride using boronic acids

Area of Science:

• Chemical Sensing
• Molecular Probes
• Analytical Chemistry

Background:

• Fluoride detection is crucial in various environmental and biological applications.
• Boronic acid derivatives offer unique interactions for developing selective chemosensors.
• Excited-state charge transfer (ICT) mechanisms are effective for fluorescent sensing.

Purpose of the Study:

• To synthesize and spectroscopically characterize six novel fluorescent probes for fluoride sensing.
• To investigate the mechanism of fluoride interaction with boronic acid-based probes.
• To evaluate the probes' performance for wavelength-ratiometric fluoride detection.

Main Methods:

• Synthesis of six distinct fluorescent probe molecules incorporating boronic acid moieties.
• Spectroscopic characterization (UV-Vis absorption and fluorescence emission) in the presence of varying fluoride concentrations.
• Analysis of spectral changes (shifts and intensity variations) to determine sensing mechanisms.
• Evaluation of probe selectivity and stability through binding studies.

Main Results:

• All six probes exhibited distinct spectral responses upon interaction with fluoride ions.
• The boronic acid group's transformation from electron-withdrawing to electron-donating upon fluoride binding was confirmed.
• Wavelength-ratiometric detection was achieved for most probes, enhancing accuracy.
• Probes based on stilbene, diphenyl-1,4-butadiene, diphenyloxazole, and chalcone structures showed promising sensing capabilities.

Conclusions:

• The developed boronic acid-based fluorescent probes are effective for sensitive and selective fluoride detection.
• The probes leverage the electronic changes of the boronic acid group upon fluoride interaction for ratiometric sensing.
• These probes represent a valuable toolkit for real-time fluoride monitoring in diverse analytical scenarios.