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.

4-(Nitrostyryl)phenols 2a-9a were synthesized, and by deprotonation in solution, the solvatochromic phenolates 2b-9b were formed. Their absorption bands in the vis region of the spectra are due to π-π* electronic transitions, of an intramolecular charge-transfer nature, from the electron-donor phenolate toward the electron-acceptor nitroarene moiety. The frontier molecular orbitals and natural bond orbitals were analyzed for the protonated and deprotonated forms. The calculated geometries are in agreement with X-ray structures observed for 4a, 6a, and 8a. The HOMO-LUMO energy gaps suggest that, after their deprotonation, an increase in the electron delocalization is observed. In the protonated compounds, the HOMO is primarily localized over the phenol ring and the C═C bridge. After deprotonation, it extends toward the entire molecule, including the NO2 groups. The solvatochromism of each dye was studied in 28 organic solvents, and it was found that all compounds exhibit a reversal in solvatochromism, which is interpreted in terms of the ability of the media to stabilize their electronic ground and excited states to different extents. The Catalán multiparameter equation is used in the interpretation of the solvatochromic data, revealing that the most important contribution to the solute/solvent interaction is the hydrogen-bond donor acidity of the solvent.

Herein, we present an overview of recent advances in the electrochemical halogenation of organic compounds. Halogen-containing compounds are essential building blocks for post-functionalization in academic research and in different industrial...

Ethyl(hydroxyethyl)cellulose was functionalized with Brooker's merocyanine. The modified polymer was easily transformed in a film, which could be used as a highly selective chromogenic and fluorogenic chemosensor for the detection of cyanide in water, with detection limits of 1.9 × 10(-5) and 1.0 × 10(-7) mol L(-1). The film was successfully applied to the detection of cyanide in cassava (Manihot esculenta Crantz) roots, which are a well-known source of endogenous biological cyanide.