Imidazole-containing ratiometric receptor for the selective and sensitive detection of cyanide and fluoride via deprotonation and a receptor-anion ensemble for Cu2+ sensing

A novel imidazole-functionalized receptor, M, containing anthraquinone as a signaling unit was synthesized and characterized. Its potential application to detect CN and F ions in DMSO was investigated using UV-Vis and fluorescence spectroscopy. A color change and bathochromic shift corresponding to the intramolecular charge transfer (ICT) transition in the absorption spectra were observed upon addition of CN- and F- ions. Fluorescence enhancement and quenching at 532 and 581 nm, respectively, were observed in the emission spectra of M upon addition of CN- and F- The receptor senses cyanide and fluoride via the deprotonation of the imidazole N-H unit, which was further confirmed by H-1 NMR. For practical applications, electrospun nanofiber test strips of M were successfully used to recognize CN- and F in aqueous media. The reversibility of the deprotonation of the imidazole N-H was successfully examined through treatment with Cu2+ ions.