Coumarin-based urea-amide scaffold in ratiometric fluorescence sensing of CN−

Abstract

Coumarin-based urea and urea–amide scaffolds 1–3 have been designed and synthesized for the selective and naked eye detection of cyanide ion. Of the three, compound 3 exhibits ratiometric fluorescence change selectively in the presence of CN− and validates the rationality in designing anion receptor. Upon interaction with CN−, the color of the solution of 3 in CH3CN under UV exposure becomes bright yellow, which is beneficial for its naked eye detection. Addition of CN− of ∼10−4M brings nice color change from colourless to yellow in ordinary light. The sensing event is supposed to be due to nucleophilic addition of CN− to the coumarin unit enabling intramolecular charge transfer (ICT) mechanism.