A Quinoline Appended Isonicotino Hydrazide‐Based Colorimetric Chemosensor for Selective Detection of Cyanide Ion in Real Samples

Abstract A quinoline‐based colorimetric chemosensor was designed and synthesized from 2(2,4‐dimethyl phenoxy) quinolin‐3‐carbaldehyde and isonicotino hydrazine. The formation of the SK‐2 ( E )‐ N 1 ‐((2‐(2,4‐dimethyl phenoxy) quinolin‐3‐yl) methylene) isonicotino hydrazide was confirmed by FTIR, NMR, and HRMS spectral techniques. The receptor SK‐2 displayed a noticeable colorimetric response, that is, a color change from colorless to yellow, upon interaction with the CN − ion. The color change is attributed to the deprotonation process and intra‐ligand charge transfer (ILCT) when it encounters the CN − ion. The sensor demonstrated a detection limit of 2.88 × 10 −6 M; and showed a stoichiometric interaction with CN − ions in a 1:1 ratio. Additionally, SK‐2 can be regenerated by treatment with TFA. Theoretical studies indicated a reduction in the energy gap (Δ E ) of the Frontier molecular orbitals from 3.3480 eV for SK‐2 down to 2.6487 eV for the SK‐2+CN − ion complex. This probe is highly effective for detecting CN − ions in real sample extracts of tobacco, flax seeds, cigarettes, almonds, and apple seeds.