A Cu 2þ -specific colorimetric sensor of bis-triazole-appended azobenzene receptors I and II was designed and synthesized. Receptor II shows high selectivity toward Cu 2þ in acetonitrile/water (80:20, v/v) solution based on the internal charge transfer (ICT) mechanism. The tridentate coordination behavior was proposed with 1:1 stoichiometry between receptor II and Cu 2þ . Herein, the Cu 2þ gives rise to a large change in the absorption spectra (from red to pale yellow) that is clearly visible to the naked eye.

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A new chalcone-based probe containing coumarin and naphthol at both ends has been synthesized via aldol condensation. The uniqueness of the newly derived probe can be ascribed to the presence of naphthol and coumarin units acting as binding site and signaling element, respectively. The fluorogenic behaviors toward various anions were investigated. The probe was characterized by various spectroscopic techniques and the in-depth study led to show excellent selectivity and sensitivity for fluoride ions. The hydrogen bonding thus formed with fluoride anion provides remarkable fluorometric responses. The interactions of the probe with fluoride ions were determined by fluorescence, FT-IR and NMR spectroscopic techniques. The exploratory studies by fluorescent spectral changes augur well for the naked-eye sensing applications.

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