Synthesis and physical studies of coumarin-based chemosensor for cyanide ions

Abstract

A series of novel coumarin-based chemosensor azine derivatives L1, L2 and L3 were synthesized and characterized by various spectroscopic methods such as 1H NMR, mass spectrometry, FT-IR and elemental analysis. The sensing property of the sensor L derivatives was confirmed by the UV–Vis absorption, emission spectra and the naked eye sensing. The sensor L derivatives showed the absorption band at 320–330 nm. The fluorescence emission band was observed at 550–560 nm. In the presence of CN− ions, the chemosensor L derivatives show the “turn-on” fluorescence response over the other competing anions such as Br−, I−, HSO4−, ClO4− and PF6−, and the new absorption band appeared at 385 nm and the emission band also shifted to the blue region at 440 nm. The sensor L derivatives bind to cyanide ions in a 1:1 binding stoichiometry calculated from the job’s plot experiments. The detection limit of sensor L1 towards CN− was 5.79 × 10−8 M. Additionally, the binding constant was determined to be 1.0209 × 106 M−1 from the Benesi-Heilbrand equation. The theoretical calculations were performed by Gaussian 9 software. The sensing mechanism of the interaction between the cyanide ion and imine carbon was confirmed by the 1H NMR titration method and mass spectra.