Synthesis, crystal structure, CN– ion recognition property and computational studies of a novel hydrazinyl-dihydroimidazole Schiff base

Abstract

A novel hydrazinyl-dihydroimidazole receptor, (E)-2-(2-(thiophen-2-ylmethylene)hydrazinyl)-4,5-dihydro-1H-imidazol-3-ium bromide (L) has been presented as a colorimetric chemosensor for rapid and selective and sensitive detection of CN– ions in aqueous medium. L has been characterized by FTIR, UV–Vis, 1H NMR, 13C NMR, EI-MS spectrometry, elemental analyses and single crystal X-ray diffraction studies. Interaction of L with CN– ion provides remarkable color change from colorless to yellow along with change in the absorption maxima, enabling naked-eye sensing without the use of any expensive instrument. 1:1 binding stoichiometry of chemosensor L towards cyanide ion has been confirmed by Job’s plot analysis. The limit of detection the chemosensor L has been found 0.89 µM, which is lower than the maximum permissible level of CN– in drinking water set by WHO. The other competitive anions (OAc-, F-, Cl-, Br-, I-, H2PO4-, NO2-, NO3-, SO42-, HSO4- and N3-) showed negligible interference for detection of cyanide ion. The sensing mechanism has been accounted by deprotonation from the exocyclic –NH site of the receptor L, which was confirmed by an 1H NMR titration experiment and DFT studies. L can be successfully applied in colorimetric test kit experiment and for the determination of CN− ions in real samples.