Azobenzene chemosensor based on nitrogen chelator for the detection of Cu (II) ion in aqueous medium

• Cu2 + ion was chemo selectively detected by naked eye.
• Bathochromic shift is observed in the absorption spectra, especially for Cu2 + ion.
• Job's plot shows 1:1 binding stoichiometry for receptor I with Cu2 + ion.
• 1:1 association constant of receptor I with Cu2 + is found to be Ka = 1.45 × 106 M− 1.

A bis-pyridine unit containing azobenzene chemosensor for Cu2 + ion is designed and synthesized with good yield. The structure of the receptor I is determined by FT-IR, 1H NMR, 13C NMR, ESI-MS and single crystal XRD. The receptor I is constructed on the basis of internal charge transfer (ICT) mechanism with bis-pyridine unit acting as the binding part for Cu2 + ion. In solution, the proposed receptor I produces a cation induced 120 nm blue shift for Cu2 + ion from 457 nm to 337 nm with remarkable colour change from red to colourless. Whereas no significant colour change is observed upon addition of other metal ions in aqueous HEPES buffer (pH 7.0). Moreover, spectroscopic studies confirm the formation of 1: 1 stoichiometry between the receptor I and Cu2 + ion with an association constant of ca. 1.45 × 106 M− 1. The receptor I is highly specific to Cu2 + ions in aqueous solution attributed to the rational design of the molecular structure.

A new bis-pyridine containing azobenzene receptor I was designed, synthesized and characterized. Receptor I was found to be an excellent chemosensor for Cu2 + ions than the other tested metal ions. The strong binding affinity and remarkable colour change with Cu2 + ion make the receptor I ideal for sensor applications.Figure optionsDownload as PowerPoint slide