Colorimetric Cyanide Chemosensor Based on 1′,3,3′,4-Tetrahydrospiro[chromene-2,2′-indole]

Abstract

A new class of chemosensors based on the 1′,3,3′,4-tetrahydrospiro[chromene-2,2′-indole] ring system, which detects cyanide with high specificity, is described. These chemosensors show a distinct color change when treated with cyanide in acetonitrile solution buffered with sodium phosphate, and this procedure is not affected by the presence of other common anions. The chemisensors exhibit high sensitivity to low concentrations of cyanide, meeting the European Union water quality control criterion of sensitivity below 0.05 mg L−1, and show a very fast response within tens of seconds. The mechanism for detection is rationalized by the nucleophilic substitution of the phenolic oxygen atom at the indoline C-2 atom by the cyanide anion to form a stable indolylnitrile adduct and to generate the colored 4-nitrophenolate chromophore. These chemosensors can be synthesized by a simple procedure from commercially available starting materials.

Cyanide Anion Determination Based on Nucleophilic Addition to 6-[(E)-(4-Nitrophenyl)diazenyl]-1′,3,3′,4-tetrahydrospiro[chromene-2,2′-indole] Derivatives

“…In such cases, the equilibrium ring-openingclosing reaction of 7a-f becomes irreversible (Scheme 3). The covalent character of the bond between the C-2 carbon atom and the carbon atom of the nitrile group was shown earlier by NMR spectroscopy [25] and was confirmed by a mass spectra experiment for 7c (Figure 2). The covalent character of the bond between the C-2 carbon atom and the carbon atom of the nitrile group was shown earlier by NMR spectroscopy [25] and was confirmed by a mass spectra experiment for 7c (Figure 2).…”

“…It is known that 1 ,3,3 ,4-tetrahydrospiro[chromene-2,2 -indoles] are sensitive to cyanides and that, upon their action, these chemosensors become yellow in color due to the opening of a partially saturated pyran ring and the formation of a 4-nitrophenolate chromophore [25]. The attachment of the 4-nitrophenyldiazenyl substituent to the main core of the molecule lengthens the conjugated π-electron system and expands the color palette of the opened form.…”

Fluorescent Carbon Dots: Aggregation-Induced Emission Enhancement, Application as Probe for CN− and Cr2O7−2, Sensing Strips and Bio-imaging Agent

“…[20][21][22]. CN − is also found in some natural sources, it is present in seeds of several fruits, certain plants and in some food stuffs [23,24]. Another extremely toxic ion is Cr(VI)/Cr 2 O 7 − 2 , industrial activities such as preservation of wood, textile dyeing, leather tanning, electroplating and metal nishing processes release hexavalent chromium Cr(VI), which contaminates with water and soil creating environmental pollution [25][26][27].…”

Synthesis of 5‐[(1H‐indol‐3‐yl)methyl]‐1,3,4‐oxadiazole‐2(3H)‐thiones and their protective activity against oxidative stress

“…[19] It is built into proteins in the form of the amino acid tryptophan and it provides the skeleton to neurotransmitters serotonin and melatonin, [20] as well as a number of phytoconstituents such as the plant hormone auxin, [21] perfumes, [22] and indole alkaloids. [23,24] Moreover, it is a common structural motif in a variety of natural or synthetic biologically active or otherwise relevant compounds, for instance, antioxidants, [25][26][27][28] anticancer agents, [29][30][31] photosensitizers for photodynamic therapy, [32][33][34] dyes, [35,36] colorimetric sensors, [37][38][39] or fluorescent probes. [40][41][42] Therefore, it might be of advantage to design compounds that would offer the opportunity of combining indole and 1,3,4oxadiazole systems.…”