A colorimetric and fluorescent turn-on chemosensor operative in aqueous media for Zn²⁺ based on a multifunctionalized spirobenzopyran derivative

By conjugating spiropyran chloride 8 with 2-amino-N-(quinolin-8-yl) acetamide (5), multifunctionalized spirobenzopyran derivative SPQN was designed and synthesized as a water soluble colorimetric and fluorescent turn-on chemosensor for Zn²⁺. In 50% aqueous ethanol buffer solution, SPQN displayed a selective chelation fluorescence enhancement (16-fold) at 650 nm and visible color change (from colorless to red) with Zn²⁺ among the metal ions examined. In addition, as the third channel to display the metal binding characteristics of SPQN, operating on an efficient FRET process between the quinoline and the merocyanine moiety of the sensor, ratiometric determination of Zn²⁺ can be realized.