A chromogenic chemosensor based on a complex of Di–Hydroxymethyl–Di–2–(Pyrrolyl)Methane and 7,7,8,8–Tetracyanoquinodimethane for the detection of captopril

Di–hydroxymethyl–di–2–(pyrrolyl)methane (DMPM) and 7,7,8,8–tetracyanoquinodimethane (TCNQ) were dissolved in acetonitrile to form a π–π charge–transfer complex, which exhibits a deep blue color. This complex is decomposed with the addition of captopril. It was possible to observe a change from the vivid blue color to pale orange–yellow, which is related to the formation of a new n–π complex between TCNQ and captopril. The formation kinetics of the complex between DMPM and TCNQ in acetonitrile was studied, it being concluded that the interaction between the two compounds is a photochemical process. Spectrophotometric titrations of TCNQ with DMPM were carried out and the results demonstrated that, in acetonitrile, the complex formed comprises one molecule of TCNQ for two of DMPM while in an acetonitrile:water mixture (9:1; v/v) a change to a 1:1 stoichiometry was observed.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Spectrometric and kinetics studies involving anionic chromogenic chemodosimeters based on silylated imines in acetonitrile or acetonitrile–water mixtures

Three chromogenic anionic chemodosimeters (1–3) based on silylated imines were synthesized and characterized. Solutions of compound 1 in acetonitrile with 4.0% (v/v) of water are colorless, but with the addition of several anions only CN, and to a lesser extent F, changed the color of the solutions to orange. However, compounds 2 and 3 were selective toward F in acetonitrile. The nucleophilic attack of F or CN on the silicon center of the chemodosimeters, through an SN2@Si mechanism, released colored phenolates as leaving groups. PGSE NMR data corroborated the mechanism postulated for the reaction. Kinetics studies were carried out, revealing that a higher second-order rate constant was obtained for the reaction of 1 with F. The addition of water to the system reduces the nucleophilicity of F, showing a slower second-order rate constant in relation to CN, the latter anion being less hydrated and the more reactive species for the nucleophilic attack on the silicon center of 1

SELECTIVE DETECTION OF FLUORIDE BASED ON A PYRIDINIUM N

A two-step experiment is proposed for a third year class in experimental organic chemistry. Over a period of five weeks, the students synthesized calix[4]pyrrole, a receptor that is highly selective for fluoride, and a pyridinium N-phenolate dye. Subsequently, the students used the synthesized compounds to investigate a displacement assay on the basis of the competition in acetonitrile between fluoride and the dye for calix[4]pyrrole. The experiment increased the students' skills in organic synthesis and in the characterization of organic compounds, provided a very attractive and accessible illustration of important supramolecular phenomena, and allowed the study of a chromogenic chemosensor

Chromogenic Chemodosimeter for Highly Selective Detection of Cyanide in Water and Blood Plasma Based on Si–O Cleavage in the Micellar System

A novel silylated imine was designed to act efficiently in a chemodosimeter approach for the selective detection of cyanide in an aqueous micellar CTABr solution. This simple system allows the detection of cyanide, with high sensitivity and specific selectivity, in water and in human blood plasma

Optical Chemosensor for the Detection of Cyanide in Water Based On Ethyl(hydroxyethyl)cellulose Functionalized with Brooker’s Merocyanine

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 (<i>Manihot esculenta</i> Crantz) roots, which are a well-known source of endogenous biological cyanide

Synthesis and Solvatochromism of Substituted 4‑(Nitrostyryl)phenolate Dyes

4-(Nitrostyryl)­phenols <b>2a</b>–<b>9a</b> were synthesized, and by deprotonation in solution, the solvatochromic phenolates <b>2b</b>–<b>9b</b> 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 <b>4a</b>, <b>6a</b>, and <b>8a</b>. 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