A highly selective coumarin-based chemosensor for dual sensing of Cu2+ and Zn2+ ions with logic gate integration and live cell imaging

Abstract

In this paper, a coumarin-based Schiff base chemosensor has been synthesized and developed to detect Cu²⁺ and Zn²⁺ ions in nanomolar concentrations. The probe selectively distinguishes Cu²⁺ and Zn²⁺ from among several metal ions in DMF : H₂O (7 : 3, v/v, pH 7.4) HEPES buffer. The structure of the probe and its sensing behavior were investigated by FT-IR, UV-vis, fluorescence, HRMS, and NMR analyses, along with X-ray crystallography and computational studies. CIH detects Zn²⁺ and Cu²⁺ using different strategies: CHEF-induced fluorescence enhancement and paramagnetic fluorescence quenching, respectively. Job's plots show a 1 : 1 binding interaction between CIH and Cu²⁺ or Zn²⁺ ions. The binding constant values for Cu²⁺ (1.237 × 10⁵ M⁻¹) and Zn²⁺ (1.24 × 10⁴ M⁻¹) suggest a better ability for Cu²⁺ to interact with CIH than Zn²⁺. An extremely high sensitivity of the probe was highlighted by its very low detection limits (LOD) of 5.36 nM for Cu²⁺ and 3.49 nM for Zn²⁺. The regeneration of the probe with the addition of EDTA in its complexes allows the formation of molecular logic gates. CIH has been successfully employed in mitotracking and intracellular detection of Zn²⁺ and Cu²⁺ in SiHa cells.