Functionalized 2-Hydrazinobenzothiazole with Bithiophene as a Colorimetric Sensor for Lethal Cyanide Ions and Its Application in Food Samples.

A newly synthesized Schiff's base 2-(2-([2,2'-bithiophen]-5-ylmethylene)hydrazinyl)benzothiazole ( BT ) was obtained from the condensation reaction between 2-hydrazinobenzothiazole and 2,2-bithiophene-5-carboxaldehyde. The prepared probe BT was subjected to a confirmation of the structural arrangement through NMR, FTIR, ESI-HRMS, and single-crystal XRD spectral analysis. The BT colorimetric sensor showed selectivity and sensitivity toward the cyanide (CN - ) ion over other common anions such as ClO 4 - , Cl - , Br - , F - , I - , NO 2 - , OH - , HSO 4 - , and H 2 PO 4 - in a partial aqueous system CH 3 CN/H 2 O (8:2, v/v). The probe BT detects CN - with the lowest detection range as low as 1.33 × 10 -8 M (3.59 ppm); in comparison to that given by WHO guidelines, it is significantly lower. The stoichiometric interaction between the probe BT and analyte CN - was found to be 1:1 (BT/CN - ) binding mode using Jobs plot, and further association binding affinity was calculated to be 6.64 × 10 -3 M -1 . Additionally, these results were further supported by the FTIR and DFT calculations, as well as the 1 H NMR titration analysis, which complemented the binding data. The sensor probe BT was successfully employed in a cotton swab test kit approach and also in smartphone-assisted applications for the determination of CN - ions. Finally, the outstanding sensing properties of probe BT aided the quantitative detection of CN - ions, and it could be further applied to a variety of food samples, including apple seeds, sprouting potatoes, and cassava.