A colorimetric and absorption ratiometric anion sensor based on indole & hydrazide binding units

Area of Science:

• Chemical Sensing
• Molecular Recognition
• Organic Synthesis

Background:

• Development of selective anion sensors is crucial for environmental and biological monitoring.
• Indole and hydrazide moieties offer promising functionalities for molecular recognition.

Purpose of the Study:

• To design and synthesize a novel colorimetric and absorption ratiometric anion sensor.
• To investigate the selective recognition properties of the sensor towards various anions.

Main Methods:

• Synthesis of the indole and hydrazide-based sensor (L).
• Anion sensing studies using naked-eye observations, UV-vis spectroscopy, and (1)H NMR titration.
• Analysis of complex formation stoichiometry and binding mechanisms.

Main Results:

• The sensor L selectively detected fluoride (F-), acetate (AcO-), and dihydrogen phosphate (H2PO4-) anions in DMSO.
• Significant colorimetric and spectral changes were observed upon anion binding.
• Complex formation occurred at 1:2 (L/F-) and 1:1 (L/AcO-, L/H2PO4-) ratios.
• (1)H NMR studies confirmed deprotonation for F- and hydrogen bonding for AcO- and H2PO4-.

Conclusions:

• The synthesized sensor L demonstrates high selectivity and sensitivity for biologically relevant anions.
• The sensor's mechanism involves deprotonation and hydrogen bonding interactions.
• This sensor holds potential for practical applications in chemical sensing.