Cyanide and fluoride colorimetric sensing by novel imidazo-anthraquinones functionalised with indole and carbazole

Exploring the Mechanism of Anionic Chemosensing by Imidazoles: A Review

Chemosensing of ions has gained considerable attention by chemists. Insight into the mechanism involved between sensors and ions always fascinates researchers to develop economical, sensitive, selective, and robust sensors. This review comprehensively explores the mechanism of interaction between Imidazole sensors and anions. With most of the research concentrating only on fluoride and cyanide, this review has highlighted a large gap in various anions detection including SCN-, Cr2O72-, CrO42-, H2PO4-, NO2-, and HSO4-.This study also includes a critical analysis of different mechanisms and their respective limits of detection, with a discussion of the reported results.

Chromogenic hydrazide Schiff base reagent: Spectrophotometric determination of CN- ion

A Schiff base reagent, Picolinohydrazide-naphthol (HL), is used for trace level detection of toxic CN^- selectively in presence of eighteen other anions (SCN^-, OCN^-, S₂O₃^2-, HPO₄^2-, H₂PO₄^-, I^-, ClO₄^-, HSO₄^-, SO₄^2-, AsO₄^3-, NO₂^-, AsO₂^-, Cl^-, F^-, HF₂^-, NO₃^-, Br^-, N₃^-) by visual color change, colorless to yellow, in DMSO/H₂O (9:1, v/v) at pH, 7.2 (HEPES buffer) medium. The sensitivity of the probe shows that the limit of detection (LOD) is 7.08 μM. The probable mechanism for the sensing behavior involves the deprotonation of naphthol-OH by CN^- that has been authenticated by ¹H NMR titration and Mass spectra. The composition (1:1 mol ratio) is supported by Job's plot and binding constant (K_a, 1.5 × 10⁴ M^-1) is reported by Benesi-Hildebrand plot. Furthermore, a simple paper strip device is fabricated for the determination of CN^- ion in water. DFT computation is carried out to explain the electronic spectral feature of the sensor.

New dimensions in calix[4]pyrrole: the land of opportunity in supramolecular chemistry

The quest for receptors endowed with the selective complexation and detection of negatively charged species continues to receive substantial consideration within the scientific community worldwide. This study is encouraged by the utilization of anions in nature in a plethora of biological systems such as chloride channels and proteins and as polyanions for genetic information. The molecular recognition of anionic species is greatly interesting in terms of their favourable interactions. In this comprehensive review, in addition to giving accounts of some selected syntheses, we illustrated diverse applications ranging from molecular containers to ion transporters and drug carriers of a supramolecular receptor named calix[4]pyrrole. We believe that the present review may act as a catalyst in enhancing the novel applications of calix[4]pyrrole and its congeners in the other dimensions of science and technology.

The quest for receptors endowed with the selective complexation and detection of negatively charged species continues to receive substantial consideration within the scientific community worldwide.

Synthesis of Bisimidazole Derivatives for Selective Sensing of Fluoride Ion

Rapid and efficient analysis of fluoride ion is crucial to providing key information for fluoride ion hazard assessment and pollution management. In this study, we synthesized one symmetrical structure called 1,4-bis(4,5-diphenyl-1H-imidazol-2-yl)benzene (1a) and two asymmetrical structures, namely 2-(4-(4,5-diphenyl-1H-imidazol-2-yl)phenyl)-1H-phenanthro(9,10-d)imidazole (1b) and 2-(4-(4,5-diphenyl-1H-imidazol-2-yl)phenyl)-1H-imidazo(4,5-f)(1,10)phenanthroline (1c), which served as an efficient anion sensor for fluoride ion over a wide range of other anions (Cl-, Br-, I-, NO₃-, ClO₄-, HSO₄-, BF₄-, and PF₆-) owing to imidazole group in the main backbone. The absorption intensity of compound 1a at λmax 358 nm slightly decreased; however, a new band at λmax 414 nm appeared upon the addition of fluoride ion, while no evident change occurred upon the addition of eight other anions. The photoluminescence intensity of compound 1a at λmax 426 nm was nearly quenched and fluorescence emission spectra were broadened when fluoride ion was added into dimethyl sulfoxide (DMSO) solution of compound 1a. Compared with the optical behaviors of the DMSO solution of compound 1a in the presence of Bu₄N⁺F-, compounds 1b and 1c exhibited considerable sensitivity to fluoride ion due to the increase in coplanarity. Furthermore, compared with the fluorescence emission behaviors of the DMSO solutions of compounds 1a and 1b in the presence of Bu₄N⁺F-, compound 1c exhibited the most significant sensitivity to fluoride ion due to the charge transfer enhancement. Consequently, the detection limits of compounds 1a-1c increased from 5.47 × 10-6 M to 4.21 × 10-6 M to 9.12 × 10-7 M. Furthermore, the largest red shift (75 nm) of the DMSO solution compound 1c in the presence of fluoride ion can be observed. Our results suggest that the increase in coplanarity and the introduction of electron-withdrawing groups to the imidazole backbone can improve the performance in detecting fluoride ion.

Anthraimidazoledione Based Reversible and Reusable Selective Chemosensors for Fluoride Ion: Naked-Eye, Colorimetric and Fluorescence "ON-OFF"

Novel anthraimidazoledione-based compounds (1-3) are synthesized as selective colorimetric and fluorescent sensors for fluoride ion. The binding properties of the probes (1-3) are studied with different anions in acetonitrile solvent. Spectral red shifts in the absorption spectra and 'turn-off' emission are observed when fluoride is added to 1-3. The striking green to orange color change in the ambient light is thought to be due to the deprotonation of the N-H proton of the imidazole moiety of the probes by the basic F^- ion. Interestingly, in all three cases the nonfluorescent probe-F^- solutions, on treatment with copper perchlorate, show distinct color change from orange to golden yellow with resumption of fluorescence intensity. Furthermore, the reversibility of sensors (1-3) for the detection of F^- ion is tested for four cycles indicating that "ON-OFF-ON" mechanism is operative. Test strip based on sensor 2 acts as a reusable cost-effective F^- sensor.

A reusable multichannel anthraimidazoledione-based receptor for Hg2+and Cu2+ions: ultrasensitive, economical and facile detection of Hg2+in real water sources through fluorescence readout

A multichannel, ultrasensitive and selective receptor (1) has been developed for practical detection of Hg²⁺in various drinking waters.

One-pot protocol for J-aggregated anthraimidazolediones catalyzed by phosphotungstic acid in PEG-400 under aerobic condition

One-pot protocol for anthra[1,2-d]imidazole-6,11-dione was developed via tandem cyclocondensation cum oxidation, catalyzed by phosphotungstic acid in PEG-400 support in open air. J-aggregation properties of products were confirmed by photophysical studies.

Benzoquinone–imidazole hybrids as selective colorimetric sensors for cyanide in aqueous, solid and gas phases

One of the five new receptors developed, which works via the formation of H-bonds, exhibited a striking visible colour change selectively with cyanide ion in solid, aqueous and gas phases.

Recognition of fractional non-innocent feature of osmium coordinated 2,2′-biimidazole or 2,2′-bis(4,5-dimethylimidazole) and their interactions with anions

The non-innocent feature of osmium coordinated doubly deprotonated 2,2′-biimidazole derivatives in symmetric dimeric complexes leads to a mixed electronic structural configuration.

Colorimetric probes designed to provide high sensitivity and single selectivity for CN− in aqueous solution

Easily-made probe L1 recognized CN⁻ by the deprotonation process and the detecting limit is 5 × 10⁻⁶ mol L⁻¹.

Silver(I)-directed growth of metal-organic complex nanocrystals with bidentate ligands of hydroquinine anthraquinone-1,4-diyl diethers as linkers at the water-chloroform interface

Immiscible liquid-liquid interfaces provide unique double phase regions for the design and construction of nanoscale materials. Here, we reported Ag(I)-directed growth of metal-organic complex nanocrystals by using AgNO3 as a connector in the aqueous solution and bidentate ligand of 1,4-bis(9-O-dihydroquininyl)anthraquinone [(DHQ)2AQN] and its enantiomer of (DHQD)2AQN in the chloroform solutions as linkers. The Ag-(DHQ)2AQN and Ag-(DHQD)2AQN complex nanocrystals were formed at the liquid-liquid interfaces and characterized by using UV-vis absorption and fluorescence spectroscopy and X-ray photoelectron spectroscopy, as well as by using scanning electron microscopy. Screw-like nanocrystals were formed at the initial 30 min after the interfacial coordination reaction started, then they grew into nanorods after several days, and finally became cubic microcrystals after 2 weeks. The pure ligand showed two emission bands centered at about 363 and 522 nm in the methanol solution, the second one of which was quenched and shifted to about 470 nm in the Ag-complex nanocrystals. Two couples of reversible redox waves were recorded for the Ag-complex nanocrystals; one centered at about -0.25 V (vs. Ag/AgCl) was designated to one electron transfer process of Ag - (DHQ)2AQN and Ag - (DHQ)2AQN(+), and the other one centered at about 0.2 V was designated to one electron transfer process of Ag - (DHQ)2AQN and Ag(+) - (DHQ)2AQN.