Tetrafunctionalized Azocalix[4]resorcinarene Dye: A Chromogenic Supramolecule Used for the Selective Liquid-Liquid Extraction and Spectrophotometric Determination of Cu(II)

Background: The detection and extraction of trace metal ions, particularly copper(II), are critical for environmental monitoring and industrial processes. Calixresorcinarene, with its unique cavity structure, offers excellent platforms for designing selective chemosensors and extractants. Functionalization of calixresorcinarene with azo groups can enhance their chromogenic properties, enabling both extraction and detection in a single step. Objective: This study aimed to evaluate its (Azocalix[4]resorcinaren) efficacy as a selective chemosensor for the liquid-liquid extraction and spectrophotometric determination of Cu(II) ions. Methods: Application in Extraction and Detection: The ability of the dye to selectively extract Cu(II) ions from aqueous solutions was investigated via liquid-liquid extraction experiments. The dye-Cu(II) complex formation was monitored by UV-Vis spectrophotometry, with systematic optimization of experimental conditions, including pH, solvent system, and extraction duration. Results: The synthesized azocalix[4]resorcinarene dye exhibited a pronounced selectivity towards Cu(II) ions, forming a stable, colored complex. The complexation induced a distinct bathochromic shift in the absorption spectrum, allowing for precise spectrophotometric detection. Optimal extraction was achieved at a specific pH and solvent combination, with the method demonstrating a low detection limit and high sensitivity. The dye showed minimal interference from other metal ions, confirming its selectivity for Cu(II). Conclusion: The tetrafunctionalized azocalix[4]resorcinarene dye is a highly effective chromogenic agent for the selective extraction and detection of Cu(II) ions. Its robust performance in both extraction efficiency and spectrophotometric detection underscores its potential utility in environmental analysis and industrial applications where trace metal detection is crucial.