Water-soluble coumarin based sequential colorimetric and fluorescence on-off chemosensor for copper(II) and cyanide ions in water

A new colorimetric and fluorescent water-soluble chemosensor Lg for the sequential detection of copper(II) and cyanide ions has been synthesized and characterized. This probe comprises two coumarin sugar units linked by an ethylenediamine spacer. The chemosensor Lg exhibits selectively a quenched fluorescence in the presence of copper(II) cations, as well as a redshift of the absorbance at 380 nm. However, in the presence of other cations, Lg exhibits a strong fluorescence at 492 nm. Furthermore, the formed complex Lg/Cu2+ is selectively fluorescent in the presence of cyanide anions, and its absorbance data show a clear blue shift due to the release of the starting probe Lg and the formation of the highly stable complex Cu(CN)(2). The detection limit was calculated to be 0.34 and 0.13 mu M for copper(II) and cyanide ions, respectively.