A 1,8-Naphthalimide-based Tripodal Fluorescent Chemosensor to Selectively Detect Copper Ions

Area of Science:

• Materials Chemistry
• Analytical Chemistry
• Supramolecular Chemistry

Background:

• 1,8-naphthalimide derivatives are versatile fluorophores.
• Tripodal ligands with nitrogen-donating atoms can chelate metal ions.
• Selective detection of metal ions is crucial for environmental monitoring.

Purpose of the Study:

• Synthesize a novel tripodal fluorescent ligand (L3) based on 1,8-naphthalimide.
• Investigate the selective detection of Cu(II) ions using L3.
• Determine the binding properties and sensing mechanism of L3 for Cu(II).

Main Methods:

• Copper (I) catalyzed Huisgen azide-alkyne cycloaddition reaction for ligand synthesis.
• Fluorescence spectroscopy for metal ion sensing.
• Job's plot, Benesi-Hildbrand analysis, and mass spectrometry for binding studies.
• Theoretical calculations for structural and stability analysis.

Main Results:

• Successful synthesis of the 1,8-naphthalimide-based tripodal fluorescent ligand (L3).
• L3 exhibited selective fluorescence turn-off response for Cu(II) ions in aqueous acetonitrile.
• Confirmed 1:1 binding stoichiometry with a high binding constant (7.8 x 10^5 M^-1).
• Demonstrated reversibility of Cu(II) binding using disodium EDTA.
• Achieved a low limit of detection for Cu(II) (0.3 µM), below WHO guidelines.

Conclusions:

• The synthesized ligand L3 is a selective and sensitive fluorescent sensor for Cu(II).
• The naphthalimide fluorophore and triazole/amine chelating groups enable effective Cu(II) detection.
• L3 has potential applications in monitoring copper levels in environmental samples, such as drinking water.