A highly sensitive and selective fluorescent turn-on chemosensor bearing 7-Diethylaminocoumarin moiety for detection of cyanide in organic and aqueous solutions

New Schiff bases bearing salicylidene moiety with different substituents and 7-Diethylaminocoumarin-thiazole were synthesized and characterized by spectroscopic methods. Also, four of the synthesized compounds (4, 6, 7, and 9) were characterized by X-ray analysis. Chemosensor property of compounds (4-9) were investigated by UV-vis and fluorescence spectroscopy as well as visual changes, and the compounds except 7 found that they showed selectivity to cyanide anion in both organic and aqueous solution by observed drastic increment at emission intensity. The mechanism of interaction between cyanide anion and imine carbon at the Schiff base was determined by the 1H NMR titration method. The determination of the thermal stability of the compounds was performed by TGA. The Density Functional Theory (DFT) calculations were also employed to gain insight into the experimental data. Furthermore, the most stable tautomeric form was determined by DFT.