Trace level CN− measurement by ‘turn-on’ emission using Coumarinyl-Benzothiazolyl Schiff base probe in living and non-living environment

Abstract

Coumarinyl-benzothiazolyl Schiff base (HL) is spectroscopically (FTIR, UV–Vis, NMR, Mass) characterized and the Single Crystal X-Ray Diffraction measurement confirms the structure. The molecule is water insoluble and DMSO solution shows weak emission which may be due to ESIPT assisted H-transfer quenching process. The emission is significantly enhanced in presence of CN−, one of the most toxic anions, through ‘turn-on’ emission (λem = 449 nm; λex = 350 nm) even in presence of many other anions. The mechanism of sensing towards CN− has been described by 1H NMR titration which reveals deprotonation of –OH group and nucleophilic attack to the imine (-CHN-) bond. Further, the Job's plot supports 1:1 molar binding ratio, [HL + CN−] (Kd, 0.696 x 104 M−1) and has been confirmed by ESI-MS. The detection limit (LOD), 0.75 μM, is third best literature. MTT assay of HL shows no-toxicity up to 100 μM and Intracellular Imaging in MDA-MB 231 cell line has been performed for the sensing of CN−.