Cyanide Anion Determination Based on Nucleophilic Addition to 6-[(<i>E</i>)-(4-Nitrophenyl)diazenyl]-1′,3,3′,4-tetrahydrospiro[chromene-2,2′-indole] Derivatives
2022
Miglė Dagilienė | Giedrė Markuckaitė | Sonata Krikštolaitytė | Algirdas Šačkus | Vytas Martynaitis
This work provides a novel approach for the instant detection of CN<sup>−</sup> anions based on chromogenic 6-[(<i>E</i>)-(4-nitrophenyl)diazenyl]-1′,3,3′,4-tetrahydrospiro[chromene-2,2′-indole] derivatives. New colorimetric detectors were synthesized and characterized. These compounds exhibited a substantial color change from orange to magenta and blue when treated with cyanide ions in a CH<sub>3</sub>CN solution buffered with sodium phosphate and demonstrated high selectivity to CN<sup>−</sup> anions. Common anions were tested, and they did not interfere with cyanide detection, except for carbonates and hydrosulfites. The simple preparation of a molecular sensor and the easily noticeable color change makes this a practical system for the monitoring of CN<sup>−</sup> ions. This color change is explained by nucleophilic substitution of the pyrane ring oxygen atom at the indoline C-2 atom by the cyanide anion. This generates the appearance of intensively colored 4-(4-nitrophenylazo)phenolate chromophore and allows for determining very low levels of CN<sup>−</sup> anion.
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