Aromatic aldehyde based chemosensors for fluoride and cyanide detection in organic and aqueous media: Ascertained by characterization, spectroscopic and DFT studies

[Display omitted] •Colorimetric responses of S1-S4 anions in organic and organo: aqueous medium visible to the naked eye.•Detection of F- and CN- by S1-S4 was monitored by means of UV–Visible and test stripes techniques.•The S1-S4 an excellent sensitivity with the detection limits under micro molar concentration.•The method was validated and applied for the detection F- ion in real samples (mouth freshener and toothpaste). In the present investigation, a series of new aromatic aldehyde based chemosensors (S1-S4) have been sensibly designed and synthesized by the simple condensation reaction and their anion sensing properties were investigated. The compounds were characterized by spectroscopic techniques such as FT-IR, UV–Visible, 1H NMR, 13C NMR and ESI-MS. The probes exhibited high sensitivity and selectivity towards fluoride and cyanide ions over the anions such as Br−, HSO−4, Cl−, OH−, I−, NO−2 and NO−3 in dry DMSO and DMSO-water mixture (DMSO: H2O 9:1 v/v). The binding mechanism of fluorometric chemosensors with NHF and NHCN ion was determined based on 1H NMR titration and were also theoretically supported by DFT (Density functional theory) calculation. The stoichiometry and binding constant (Ka) of the host-guest complexes formed were determined by the Benesi–Hildebrand (B–H) plot and Job's method respectively. Finally, economically visible paper-based colorimetric “test stripes” of (S1-S4) were fabricated to the detection of F− and CN− ions in 100% aqueous solution.