A quinoline based colourimetric chemosensor SK-2 is responding to colourless to yellow on interaction with CN- ions in the analyte at LOD value of 2.88 × 10⁻⁶ M. SK-2 is effectively detecting CN⁻ ions in real sample extracts of tobacco, flax seeds, cigarettes, almonds, and apple seeds.

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 (ΔE) 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.