Sugar-based carboxamidoquinoline conjugate for sensing Cu²⁺ and Au³⁺ ions in water through different binding modes...

A simple water-soluble carboxamidoquinoline derivative of glucofuranose 1 exhibited reversible selectivity toward Cu²⁺ and Au³⁺ ions in different binding modes. Sensor 1 is an example of a dual sensor for identifying copper and gold ions in the water medium. Sensor 1 exhibited excellent selection ability and sensitivity for Cu²⁺ and Au³⁺ ions rather than several metal ions and anions with a wide pH range (5-10). The association constants for both ions were determined to be 3.58 × 10⁴ M^-1 and 1.84 × 10⁴ M^-1, respectively. The 1:1 binding chemistry of the complexes was verified from the Job method and again validated through mass spectra. Sensor 1 can detect Cu²⁺ and Au³⁺ ions at very low concentrations, such as 0.014 μM for Cu²⁺ and 0.058 μM for Au³⁺. The different sensing strategies of sensor 1 towards Cu²⁺ and Au³⁺ were manifested from the photophysical properties of sensor 2 with metal ions, FT-IR spectra, and theoretical (DFT) observations. The useful relevance of the sensor for Cu²⁺ and Au³⁺ ions was tested in different water samples.