A turn-on fluorescent chemosensor for selective responses of copper(ii) ion pairs.

A fluorescent chemosensor was designed and synthesized by incorporating the imidazolium and 1,8-naphthalimide dye moieties into a preorganized tripodal receptor. The novel sensor displays high selectivity for Cu(ClO₄)₂ and Cu(NO₃)₂ over a wide range of tested metal ions, anions, and Cu²⁺ salt ion pairs. Upon adding Cu(ClO₄)₂ or Cu(NO₃)₂ to the probe solution, the fluorescence emission was significantly turned on concomitant with a blue shift in the emission energy, due to an anion-induced conformational change and coordination effect. Further binding model studies by ¹H nuclear magnetic resonance spectroscopy and mass spectroscopy demonstrated that the receptor formed a 1 : 1 host–guest complex with Cu(ClO₄)₂ or Cu(NO₃)₂. [ABSTRACT FROM AUTHOR]