Nucleophilic approach to cyanide sensing by chemosensors

: Cyanide anion has wide use in industrial areas and high toxic effect on the environment as waste. Moreover, plant seeds contain cyanide which occurs in excessive consumption. Therefore, many studies are carried out to determine cyanide. Especially, optical sensors showing colorimetric and fluorimetric changes have been of considerable interest due to their easy, cheap, and fast responses. This review discusses recent developments in the colorimetric and fluorimetric detection of cyanide by nucleophilic addition to different types of receptors via the chemodosimeter approach. The sensitivity and selectivity of the sensors have been reviewed for changes in absorption and fluorescence, naked-eye detection, real sample application, and detection limits when interacting with cyanide.

Synthesis of Symmetrical Acetophenone Azine Derivatives as Colorimetric and Fluorescent Cyanide Chemosensors

Cyanide is a highly toxic anion and poison to the environment. Therefore, fast, effective, and efficient analysis methods to detect cyanide are needed. Herein, symmetrical chemosensor of 2’-hydroxy acetophenone azine (1) and 2’,4’-dihydroxy acetophenone azine (2) has been synthesized tested as colorimetric and fluorescent cyanide chemosensor. The azines were produced from the condensation of acetophenone derivatives with hydrazine hydrate in ethanol under reflux or ultrasonic irradiation methods. Colorimetric and fluorescent chemosensor tests showed selectivity to acetate and cyanide anions in DMSO. The limit of detection (LOD) for colorimetric measurement of cyanide anion was 9.68×10–4 M for compound (1) and 9.63×10–5 M for compound (2), while the fluorescent method showed 15.90×10–4 M for compound (1) and 8.95×10–5 M for compound (2), respectively. In addition, test paper-strips containing sensor 2 indicated noticeable results for 'naked eye' detection of cyanide in an aqueous medium.

NMR Properties of the Cyanide Anion, a Quasisymmetric Two-Faced Hydrogen Bonding Acceptor

The isotopically enriched cyanide anion, (13C≡15N)−, has a great potential as the NMR probe of non-covalent interactions. However, hydrogen cyanide is highly toxic and can decompose explosively. It is therefore desirable to be able to theoretically estimate any valuable results of certain experiments in advance in order to carry out experimental studies only for the most suitable molecular systems. We report the effect of hydrogen bonding on NMR properties of 15N≡13CH···X and 13C≡15NH···X hydrogen bonding complexes in solution, where X = 19F, 15N, and O=31P, calculated at the ωB97XD/def2tzvp and the polarizable continuum model (PCM) approximations. In many cases, the isotropic 13C and 15N chemical shieldings of the cyanide anion are not the most informative NMR properties of such complexes. Instead, the anisotropy of these chemical shieldings and the values of scalar coupling constants, including those across hydrogen bonds, can be used to characterize the geometry of such complexes in solids and solutions. 1J(15N13C) strongly correlates with the length of the N≡C bond.

Ring Opening of 1,1’-sulfonyl bis-aziridines Derived from L-Amino Acids and DFT Study on their Affinity Toward Different Nucleophiles

: We describe herein the ring-opening reaction of chiral 1,1’-sulfonyl bis-aziridines with various neutral and anionic nucleophiles, including benzylamine, piperidine, acetate, allyl thiolate, cyanide anion, and sodium ethoxide. These reactions afforded bis-opened or/and mono-opened compounds via a regioselective attack on the non-substituted methylene of aziridine ring. The structures of the products were confirmed based on spectral analysis (IR, 1H NMR, and 13C NMR). A theoretical study involving density functional theory (DFT) was used to rationalize the region-selective ring-opening of starting bis-aziridines.

Cyanovinylation of Aldehydes: Organocatalytic Multicomponent Synthesis of Conjugated Cyanomethyl Vinyl Ethers

A novel organocatalytic multicomponent cyanovinylation of aldehydes was designed for the synthesis of conjugated cyanomethyl vinyl ethers. The reaction was implemented for the synthesis of a 3-substituted 3-(cyanomethoxy)acrylates, using aldehydes as substrates, acetone cyanohydrin as the cyanide anion source, and methyl propiolate as the source of the vinyl component. The multicomponent reaction is catalyzed by N-methyl morpholine (2.5 mol%) to deliver the 3-(cyanomethoxy)acrylates in excellent yields and with preponderance of the E-isomer. The multicomponent reaction manifold is highly tolerant to the structure and composition of the aldehyde (aliphatic, aromatic, heteroaromatics), and it is instrumentally simple (one batch, open atmospheres), economic (2.5 mol% catalyst, stoichiometric reagents), environmentally friendly (no toxic waste), and sustainable (easy scalability).

Synthesis of 5-nitrovanillin in low temperature as cyanide anion sensor

In the synthesis of the organic sensor, the molecular structure will affect the ability of a compound to be used as a colorimetric chemosensor. Here, we present a simple synthesis technique for 5-nitrovanillin. It has been successfully synthesized using nitric acid as a source of nitro groups. Dichloromethane DCM was used as a solvent, and the synthesis was carried out at low temperatures (under 5°C). The method produces a good yield. The nitro group attached to the structure of the chemosensor plays a role in prolonging the electron delocalization. Its effect is in the process of anion recognition by the chemosensor. The formation of a sensor-analyte complex between the chemosensor and anion produces a color change in the solution.

A Theoretical Approach to Demystify the Role of Copper Salts and O2 in the Mechanism of C-N Bond Cleavage and Nitrogen Transfer

<b>C≡N bond scission accomplished by protonation, reductive cleavage and metathesis techniques are well-known to execute nitrogen transfer reactions. Herein, we have conducted an extensive computational study, using DFT and molecular dynamics simulations, to unravel the mechanistic pathways traversed in CuCN and CuBr₂ promoted splitting of coordinated cyanide anion under a dioxygen atmosphere, which enables nitrogen transfer to various aldehydes. Our detailed electronic structure analysis using <i>ab initio</i> multi-reference CASSCF calculations reveal that both the promoters facilitate radical pathways, in agreement with the experimental findings. This is a unique instance of oxygen activation initiated by single electron transfer from the nitrile carbon, while the major driving force is the operation of the Cu^II/Iredox cycle. Our study reveals that the copper salts act as the “electron pool” in this unique nitrogen transfer reaction forming aryl nitrile from aryl aldehydes.</b><br>