A versatile quinoxaline derivative serves as a colorimetric sensor for strongly acidic pH

Area of Science:

• Analytical Chemistry
• Supramolecular Chemistry

Background:

• Monitoring strongly acidic environments is crucial for various chemical processes.
• Existing methods may lack specificity or reliability in harsh conditions.
• Development of novel chemosensors is essential for precise pH and metal ion detection.

Purpose of the Study:

• To develop a facile and reliable method for monitoring strongly acidic pH.
• To investigate the sensing mechanism of a synthesized probe, HQphy.
• To explore the probe's ability to sense Fe3+ ions and discriminate between different haloacetic acids.

Main Methods:

• Synthesis and characterization of the HQphy probe and its complexes.
• Investigation of protonation-deprotonation using 1H NMR and single crystal X-ray diffraction (SC-XRD).
• Analytical studies including UV-Vis titration, ESI-MS spectrometry, and theoretical calculations.

Main Results:

• HQphy functions as a reliable sensor for strongly acidic pH in the range of 0.7-2.7.
• Sensing of Fe3+ ions is linked to the acidity generated during hydrolysis.
• Single crystal to single crystal transformation was observed between the probe and its perchlorate salt.
• Theoretical studies confirmed a 100 nm red shift in π(L) → π*(L) transition upon protonation.

Conclusions:

• The developed HQphy probe offers a robust method for monitoring strong acidity.
• The probe's mechanism involves pH-dependent protonation and interaction with Fe3+ ions.
• HQphy demonstrates potential for discriminating between trihaloacetic acids and their analogues.