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

A novel hydrazinyl-dihydroimidazole receptor, (E)-2-(2-(thiophen-2-ylmethylene)hydrazinyl)-4,5-dihydro-1Himidazol-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 mu M, 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.

Automated summary

A novel chemosensor L has been developed for rapid, selective, and sensitive detection of CN- ions in aqueous medium, showing remarkable color change and high detection efficiency. The 1:1 binding stoichiometry, low detection limit, and minimal interference from other anions make L a promising tool for cyanide ion detection in real samples.