Anionic chromogenic chemosensors highly selective for fluoride or cyanide based on 4-(4-Nitrobenzylideneamine)phenol

Abstract

4-(4-Nitrobenzylideneamine)phenol was used in two strategies allowing the highly selective detection of F -and CN -. Firstly, the compound in acetonitrile acts as a chromogenic chemosensor based on the idea that more basic anions cause its deprotonation (colorless solution), generating a colored solution containing phenolate. The discrimination of CN -over F -was obtained by adding 1.4% water to acetonitrile: water preferentially solvates F -, leaving the CN -free to deprotonate the compound. Another strategy involved an assay comprised of the competition between phenolate dye and the analyte for calix [4]pyrrole in acetonitrile, a receptor highly selective for F -. Phenolate and calix[4]pyrrole form a hydrogen-bonded complex, which changes the color of the medium. On the addition of various anions, only F -was able to restore the original color corresponding to phenolate in solution due to the fact that the anion dislodges phenolate from the complexation site.

Anionic chromogenic chemosensors highly selective for cyanide based on the interaction of phenyl boronic acid and solvatochromic dyes

“…Since CN − is less hydrated with the addition of water, it can act more efficiently as an attacking nucleophilic species. This aspect is similar to that observed for detection systems based on acid-base strategies [37,38,[62][63][64][65][66][67][68]. Another interesting issue concerns the fact that selectivity toward CN − is obtained even when water is added only after the addition of the anions, because this means that the chromogenic system is reversible.…”

A Novel 4-(1H-Benzimidazol-2-yl)-2-methoxy-phenol Derived Fluorescent Sensor for Determination of CN– Ion

“…2. The selectivity of a chemosensors for an anionic species is related to its differential ability to interact with the receptor site in the chemosensor, for instance, through intermolecular hydrogen-bonding [25].…”

Counter-ion and solvent effects on the acidity of calix[4]arene and para-tert-butylcalix[6]arene

“…Machado showed that the values of pK a of phenols in acetonitrile and water displayed a linear relationship [17] (pK a (CH 3 CN) = 1.68 pK a (water) ? 9.80), and when this approach is applied to calix [4]arene results in a pK a of 4.05 when applied to the value obtained by Nachtigall.…”