Imidazole Research Articles

Carbon dioxide interaction with a series of ionic liquids consisting of fluorophenyltrifluoroborate anions studied by in situ ATR-FTIR spectroscopy

Fluorinated ionic liquids have new and unique properties by combining the properties of highly fluorinated compounds and ionic liquids. In this work, the interaction of CO2 with ionic liquids containing fluorophenyltrifluoroborate anions ([BMIM][C6H5BF3], [BMIM][4-F-C6H4BF3], [BMIM][C6F5BF3], [BMIM][4-BuO-C6F4BF3]) has been studied for the first time using high-pressure in situ ATR-FTIR spectroscopy. Analysis of the IR spectra of ionic liquids recorded under CO2 pressure showed disaggregation of alkyl groups and a slight decrease in cation–anion interaction, based on the appearance of a blue shift of absorption bands characteristic of stretching vibrations of CH bonds in alkyl groups, aromatic and imidazolium rings. It was found that fluorination of the phenyl group and introduction of a butoxy group significantly increased the solubility of CO2. The enthalpy and entropy of CO2 dissolution also increase with the increase of fluorine atoms in the anion. Theoretical calculations using the DFT method also showed an increase in the energy of interaction of CO2 with ionic liquids with an increase in the number of fluorine atoms. The use of an independent gradient model based on Hirshfeld partition (IGMH) analysis allowed the patterns of splitting of the CO2 bending ν2 mode to be explained. It was found that in this series of ionic liquids, the degree of the splitting of the CO2 bending mode depends on the contributions of the CO2 atoms to the interaction with the ionic liquid, rather than on the interaction energy.

Oxime chemistry in crop protection.

An overview is given on the significance of the oxime moiety in crop protection chemistry. This review focuses on the two most important aspects of agrochemical oximes, which are the occurrence and role of oxime groups in compounds with herbicidal, fungicidal and insecticidal activity, as well as the application of oxime derivatives as intermediates in the synthesis of crop protection agents not bearing any oxime function. Especially noteworthy is the fact, that in the synthesis of agrochemicals, oximes can be cyclized to isooxazoline, isoxazole, oxadiazole, oxazine, pyrrole, isothiazole and imidazole rings. © 2024 Society of Chemical Industry.

Mechanism of the Low-Temperature Organic Removal from Imidazolium-Containing Zeolites by Ozone Treatment: Fluoride Retention in Double-4-Rings.

For zeolites synthesized using imidazolium cations, the organic matter can be extracted at very low temperatures (100 °C) using ozone. This is possible for zeolites with 12-ring or larger pores but requires higher temperatures in medium-pore zeolites. The first chemical events in this process occur fast, even at room temperature, and imply the loss of aromaticity likely by the formation of an adduct between ozone and the imidazole ring through carbons C4 and C5. Subsequent rupture of the imidazole ring provides smaller and more flexible fragments that can desorb more readily. This process has been studied experimentally, mainly through infrared spectroscopy, and theoretically by density functional theory. Amazingly, fluoride anions occluded in the small double-four-ring units (d4r) during the synthesis remain inside the cage throughout the whole process when the temperature is not too high (≤150 °C). However, fluoride in larger cages in MFI ends up bonded to silicon in penta or hexacoordinated units, likely out of the cages, after ozone treatment at 150 °C. For several germanosilicate zeolites, the process allows their subsequent degermanation to yield stable high-silica zeolites. Quaternary ammonium cations require harsher conditions that eventually also extract fluoride from zeolite cages, including the d4r unit.

Iodide enhances degradation of histidine sidechain and imidazoles and forms new iodinated aromatic disinfection byproducts during chlorination

Peptide-bound histidines and imidazoles are important constituents of dissolved organic matter in water, and understanding the formation of halogenated disinfection byproduct (DBP) formation from these compounds during disinfection is important for ensuring a safe drinking water supply. Previous studies suggested that histidine has low reactivity with chlorine only; this study indicates that iodide substantially enhances histidine reactivity with the disinfectant at a time scale from days to hours. Mono- and di-iodinated histidines were identified as dominant transformation products with cumulative molar yields of 3.3 % at 6 h and they were stable in water over 7 days. These products were formed via electrophilic substitution of iodine to imidazole ring when hypoiodous acid reacted with histidine sidechain. Bromide minimally influenced the formation yields of these iodinated products, and higher pH increased yields up to 12 % for pH in the range 5–9. The cumulative concentration of low-molecular-weight DBPs, such as trihalomethanes and haloacetic acids, was less than 0.3 % under the same conditions. Similar iodinated imidazole analogs were also identified from other imidazoles (i.e., imidazole-carboxylic and phenyl-imidazole-carboxylic acids). This study demonstrated that peptide-bound histidine and imidazoles can serve as important precursors to iodinated aromatic DBPs, facilitating the identification of less-known iodinated DBPs.

Novel Imidazole‐based Hydrazonoyl Cyanides and Amidrazones Containing N(N,O)‐Heterocycles: Selective Synthesis, Reaction Mechanisms and Preliminary Anticancer Evaluation

AbstractTwo series of novel hybrid heterocyclic compounds that combine the imidazole ring with bioactive piperidine, morpholine or piperazine heterosystems, through a hydrazone unit, were easily obtained by two competitive pathways. Starting from 5‐amino‐4‐cyanoformimidoyl imidazoles and 1‐aminopiperidine, 4‐aminomorpholine or 1‐amino‐4‐methylpiperazine under mild acidic media led to the selective synthesis of 5‐aminoimidazole 4‐carboxamidrazones, whereas the corresponding 4‐hydrazonoyl cyanide derivatives were obtained under stronger acidic conditions. These highly functionalized imidazoles provide convenient synthetic precursors to a vast array of heterocycles with potential pharmaceutical applications. The reaction mechanisms were elucidated on the basis of experimental assays and in silico calculations. The compounds were screened against colorectal cancer HCT116‐p53 wt cell line, and significant IC50 values of 3.69 μM and 4.83 μM were obtained.

Structure‐Activity Relationships of Glucose‐based PdII‐Bis(NHC) Complexes in a Model Suzuki‐Miyaura Reaction

AbstractThe authors of this work have optimized a novel synthetic route towards glucose‐based PdII‐bis(NHC) complexes in only 4 steps with total yields up to 73 %. The synthesis route encompasses an Appel reaction towards 6‐iodo‐glucopyranosides, followed by acyl‐protection, then quaternization with imidazoles and finally the conversion of these acyl‐protected glucosyl imidazolium salts to their respective palladium(II)bis(NHC) complexes, via an intermediary silver(I) complex. Overall, 11 acyl‐protected glucosyl imidazolium iodides as NHC‐precursors and 15 complexes have been synthesized. The structure‐activity relationships of different functionalizations in these complexes and their reactivity in a model Suzuki‐Miyaura between bromobenzene and 4‐tolueneboronic acid reaction has been investigated, and a highly reactive complex leading to >99 % yield at 0.005 mol% catalytic loading has been found.

Reusable, Green, Portable Ionogels Based on Terpyridine-Imidazole Salt for Visual Monitoring of Pork Spoilage.

Ionogels have emerged as a promising approach because they combine the advantageous properties of ionic liquids and gels. Herein, a novel gelator bearing terpyridine and imidazolium salt units was designed and synthesized, which assembled into ionogels in three ionic liquids by a heating-cooling procedure. The properties of ionogels were characterized by FT-IR, UV-vis spectroscopy, POM, XRD, and rheology, and resonance light scattering and opacity measurements were conducted to investigate the gelation kinetics. Furthermore, the ionogels incorporating pH-sensitive dyes (BTB and MR) were exploited as colorimetric sensor to monitor total volatile basic nitrogen (TVB-N) of meat at -4 °C, which can easily and reliably estimate the quality of meat by naked eye recognition, and the results demonstrated a positive correlation between the color variation and TVB-N levels. Notably, the hydrophobic ionogel indicators are more suitable for potential application at high humidity thanks to their antiswelling advantage, which could prevent the inaccurate information produced by hydrogel indicators. In addition, the ionogels could be reused up to three times as colorimetric indicators, suggesting potential applications and competitiveness. Our research sheds new light on the novel application of ionogels in the food industry.

Valorization of Afzelia bella oilseeds cake in bioethanol production using 1-butyl-3-methyl-imidazolium chloride ionic liquid and dilute sulfuric acid pretreatment

The use of renewable feedstocks and the variability of lignocellulosic feedstocks generating fermentable sugars also offer the advantages of the most abundant, sustainable and competitive non-food biomass. The aim of this study is to valorize the oilcake obtained from non-conventional Congolese Afzelia bella oilseeds, after extraction of the oil used in biodiesel production. The conversion of A. bella oilseeds cake into ethanol was carried out using the two methods of pretreatment (with the synthesized ionic liquid 1-butyl-3-methyl imidazolium chloride and dilute sulfuric acid), followed by hydrolysis with dilute sulfuric acid and fermentation by Saccharomyces cerevisiae. The lignocellulosic composition of the sample was 47.98% cellulose, 28.15% hemicellulose and 22.3% lignin. Pretreatment with 1-butyl-3-methyl-imidazolium chloride (ionic liquid) showed an increase in cellulose content of around 4.25% and hemicellulose content of around 7.7%, with simultaneous delignification of 12.25%. In contrast, with dilute sulfuric acid, the lignin and cellulose content of the sample fell to 3.88% and 1.88% respectively. Hemicellulose content, on the other hand, increased by only 3.58%. After dilute acid hydrolysis (5% H2SO4), the values for total reducing sugar, glucose and xylose were 66.06±1.34 mg.g-1; 36.25 ± 1.2 mg.g-1 and 29.71 ± 0.6 mg.g-1 respectively. The percentage conversion of sugars was 55.16 ± 0.5% for cellulose to glucose and 53.76 ± 0.75% for hemicellulose to xylose. The hydrolyzed product of the complex polysaccharide was then converted to ethanol using commercial yeast. Results showed an ethanol yield of around 10.3%, and Fourier Transform Infrared (FTIR) spectroscopy results confirmed bioethanol production. A. bella oilseeds cakes are therefore a potential source for ethanol production.

Dendrite-free and highly stable Zn metal anode with ZIF-8 ions-transport layer

As a promising anode for rechargeable aqueous batteries for grid energy storage, zinc metal has received considerable attention. However, its practical use is severely hampered by uncontrollable dendrite growth and surface parasitic reactions. In this paper, zeolite imidazole salt framework-8 (ZIF-8) interphase with open metal sites (OMSs) was constructed on the Zn anode as a highly zinc-friendly medium and ion-screening agent to synergistically induce rapid and uniform Zn nucleation/deposition. In addition, the interfacial shielding of the interphase significantly inhibited surface corrosion and hydrogen evolution. As a result, the ultra-stable zinc plating/stripping process significantly boosts cycle life by 1350 hours compared to bare Zn at 1 mA cm−2 with 1 mAh cm−2, achieving a cumulative plating capacity of 0.75 Ah cm−2. Moreover, the modified Zn anode ensures exceptional stability and cycling performance for the MnO2-based full cell, maintaining a capacity of 166.2 mAh g−1 after 1000 cycles at 1 A g−1, with a capacity retention rate of 73.2%.

Ionic liquid-functionalized transition-metal oxides as highly recyclable and efficient nano-adsorbent for fluoride removal

The modification of functionalized ionic liquids into sewage adsorbents addresses key limitations of traditional adsorption methods, offering enhanced selectivity, good adsorption, and renewability. In this work, imidazole-amino ionic liquid was successfully modified into transition-metal oxide CuOX through coordination interactions between the imidazole ring and Cu+. Most importantly, specific and thermal-responsive hydrogen bonds between amino and fluoride exhibited excellent selectivity for capturing fluorine while providing effective renewability through thermal activation. As expected, the adsorbents exhibited a rapid adsorption rate in fluorine solution (adsorption saturation time tS = 38 h, fluoride concentration 2 mg·L−1) and significant adsorption capacity (maximum adsorption capacity qm = 337.8 mg·g−1, 293 K). Moreover, a recovery rate was exceeded 95 % after incubation with the boiling water. As for industrial application, the adsorbent demonstrated an impressive fluoride removal efficiency exceeding 80 % and a remarkable recovery rate exceeding 70 % when treating wastewater from the photovoltaic cell and semiconductor industry. This not only significantly reduced expenses associated with wastewater treatment but also alleviated the incidence of secondary pollution. By offering a recyclable and effective solution for sewage adsorbents, this strategy holds promise for addressing water pollution challenges in industrial settings.

Nickel-Catalyzed Cross-Coupling Reaction of Aryl Bromides/Nitriles with Imidazolium Salts Involving Inert C-N Bond Cleavage.

We herein present a nickel-catalyzed cross-coupling reaction of aryl halides and nitriles with imidazolium salts. A series of 2-arylated imidazoles could be obtained in moderate to good yields through inert C-N bond cleavage. The imidazolium salt in this reaction acts as both a coupling partner and N-heterocyclic carbene (NHC) ligand precursor. Mechanistic studies reveal that consecutive steps of migratory insertion of the NHC into the aryl C-Ni bond and β-C elimination might be involved in the proposed reaction mechanism.

The Suppressive Effect of Novel Hydrazones‐Tethered Imidazoles in HCT‐116 and HT‐29 Colorectal Cancer Cells: Synthesis, Biological Activity and Molecular Modeling Studies

AbstractA series of hybrid compounds containing both the imidazole ring and the hydrazone moiety have been synthesized. Synthesized compounds were characterized by various spectral techniques, including FT‐IR, 1H‐NMR, 13C‐NMR, and HRMS. The compounds were evaluated for their antiproliferative activities on colorectal cancer cells HCT‐116 and HT‐29 in a time‐dependent manner. Among them, some compounds exhibited remarkable anti‐cancer activity with a less cytotoxic effect on non‐cancerous cell lines, especially HRK‐2 with IC50 value of 1.35±0.18 μM in HCT‐116 cells and HRK‐5 with IC50 value of 2.67±0.61 μM in HT‐29 cells. Investigations of colon cancer cell death were performed, and the most active compounds were found to trigger cell death via nuclear localization and induce S phase arrest of the colon cancer cell. Moreover, molecular modeling studies for the synthesized compounds was performed to predict their binding affinities toward the active site of BCL‐2. The findings of the molecular modeling investigations were highly consistent with those of the cytotoxicity results.

Prediction of adsorption performance of ZIF-67 for malachite green based on artificial neural network using L-BFGS algorithm

Given the necessity and urgency in removing organic pollutants such as malachite green (MG) from the environment, it is vital to screen high-capacity adsorbents using artificial neural network (ANN) methods quickly and accurately. In this study, a series of ZIF-67 were synthesized, which adsorption properties for organic pollutants, especially MG, were systematically evaluated and determined as 241.720 mg g−1 (25 ℃, 2 h). The adsorption process was more consistent with pseudo-second-order kinetics and Langmuir adsorption isotherm, which correlation coefficients were 0.995 and 0.997, respectively. The chemisorption mechanism was considered to be π-π stacking interaction between imidazole and aromatic ring. Then, a Python-based neural network model using the Limited-memory BFGS algorithm was constructed by collecting the crucial structural parameters of ZIF-67 and the experimental data of batch adsorption. The model, optimized extensively, outperformed similar Matlab-based ANN with a coefficient of determination of 0.9882 and mean square error of 0.0009 in predicting ZIF-67 adsorption of MG. Furthermore, the model demonstrated a good generalization ability in the predictive training of other organic pollutants. In brief, ANN was successfully separated from the Matlab platform, providing a robust framework for high-precision prediction of organic pollutants and guiding the synthesis of adsorbents.

Regulating intramolecular hydrogen bonds of p-phenylenediimidazole-based small-molecule compounds towards the enhanced lithium storage capacity

The use of redox-active organic electrode materials in energy storage is restricted due to their inferior solvent resistance, abysmal conductivity, and the resultant low practical capacity. To address these issues, a class of bipolar p-phenylenediimidazole-based small-molecule compounds are designed and fabricated. The π-conjugated backbone of these small molecules allows for electron delocalization on a big conjugation plane, endowing them with good conductivity and reaction reversibility. Furthermore, when the para-positions of phenylene are occupied by hydroxyl groups, as-formed intramolecular hydrogen bonds (N–H…O) between phenolic hydroxyl groups and the –NH groups of imidazole rings further enhance the structural planarity, resulting in higher π-conjugation degree and better conductivity, and thus higher utilization of active sites and electrode capacity, proved by both experimental results and theoretical calculations. The optimized composite electrode DBNQ@rGO-45 shows a high specific capacity (∼308 mA h g−1 at 100 mA g−1) and a long cycling stability (112.9 mA h g−1 after 6000 cycles at 2000 mA g−1). The significantly better electrochemical properties for hydroxyl group-containing compounds than those without hydroxyl groups attributed to intramolecular hydrogen bond-induced conjugation enhancement will inspire the structure design of organic electrodes for better energy storage.

Photothermal/photodynamic synergistic antibacterial study of MOF nanoplatform with SnFe2O4 as the core

Drug-resistant bacterial infections cause significant harm to public life, health, and property. Biofilm is characterized by overexpression of glutathione (GSH), hypoxia, and slight acidity, which is one of the main factors for the formation of bacterial resistance. Traditional antibiotic therapy gradually loses its efficacy against multi-drug-resistant (MDR) bacteria. Therefore, synergistic therapy, which regulates the biofilm microenvironment, is a promising strategy. A multifunctional nanoplatform, SnFe2O4-PBA/Ce6@ZIF-8 (SBC@ZIF-8), in which tin ferrite (SnFe2O4, denoted as SFO) as the core, loaded with 3-aminobenzeneboronic acid (PBA) and dihydroporphyrin e6 (Ce6), and finally coated with zeolite imidazole salt skeleton 8 (ZIF-8). The platform has a synergistic photothermal therapy (PTT)/photodynamic therapy (PDT) effect, which can effectively remove overexpressed GSH by glutathione peroxidase-like activity, reduce the antioxidant capacity of biofilm, and enhance PDT. The platform had excellent photothermal performance (photothermal conversion efficiency was 55.7 %) and photothermal stability. The inhibition rate of two MDR bacteria was more than 96 %, and the biofilm clearance rate was more than 90 % (150 μg/mL). In the animal model of MDR S. aureus infected wound, after 100 μL SBC@ZIF-8+NIR (150 μg/mL) treatment, the wound area of mice was reduced by 95 % and nearly healed. The serum biochemical indexes and H&E staining results were within the normal range, indicating that the platform could promote wound healing and had good biosafety. In this study, we designed and synthesized multifunctional nanoplatforms with good anti-drug-resistant bacteria effect and elucidated the molecular mechanism of its anti-drug-resistant bacteria. It lays a foundation for clinical application in treating wound infection and promoting wound healing.

Electronic Effect of the [Au(PPh3)]+ Fragment in the Stabilization of Imidazolium Salts and the Destabilization of NHCs

AbstractThis work presents the synthesis and characterization of mono‐ (1) and di‐nuclear (2) imidazolium salts stabilized by [AuPPh3]+ fragments. The presence of the gold moiety induces a significant decrease in the carbenic proton‘s acidic character (high pKa). This high stability is consistent with the pronounced instability of the conjugate bases obtained through deprotonation using strong bases. The formation of carbene species is accompanied by the identification of a 1,2‐rearrangement process in which a preference for the C‐bound species over the N‐bound species is observed. Experimental techniques such as NMR, single‐crystal X‐ray diffraction analysis, mass spectrometry, and computational calculations are employed to investigate the reactivity exhibited by the imidazolium salts. Additionally, the electrochemical properties of the two imidazolium salts were also investigated. This study reveals that both species 1 and 2 display two cathodic peaks which are related to two electro‐chemical irreversible reduction events. The results obtained from both experimental and theoretical studies of this system reveal a strong tendency of the [AuPPh3]+ fragment to stabilize imidazolium salts. Additionally, they demonstrate the preference of this fragment for C‐bound species over N‐bound ones, with the former proving to be highly unstable even under severe conditions of air and moisture exclusion.

A Recent Trends on Green Synthesis and Bioactivity of Imidazole

Imidazole is a five-membered, planar heterocyclic ring made up of 3C, 2N, and N in the 1st and 3rd places. Purine, histamine, histidine, and nucleic acid are only a few significant natural compounds that contain the imidazole ring. It is utilised as a cure to optimize the solubility and bioavailability properties of proposed weakly soluble lead compounds since it is an aromatic chemical that is polar and ionizable and so improves the pharmacokinetic features of lead molecules. Derivatives of imidazole have a special place in medicinal chemistry. An essential synthesis technique in the process of discovering new drugs is the integration of the imidazole nucleus. Due to the remarkable therapeutic efficacy of medications related to imidazole, medicinal chemists have been inspired to create numerous innovative chemotherapy agents. This review summarized the work that has been done in recent years about different synthetic approaches of imidazole derivatives and their potential activity as anti-HIV, anticancer, anticovid, antifungal, antidiabetic, antidepressant, antioxidant, and antituberculosis.

Solvent-Switchable Remote C-H Activation via 1,4-Palladium Migration Enables Site-Selective C-P Bond Formation: A Tool for the Synthesis of P-Chiral Phosphinyl Imidazoles.

Solvent-switchable and site-selective phosphorylation of imidazoles at the C2 or C5 position of the imidazole ring was achieved via 1,4-palladium migration. P-Chiral tert-butyl(aryl)phosphine oxides were cross-coupled to 1-(2-bromophenyl)-1H-imidazoles with high enantiospecificity, thereby leading to a novel class of chiral imidazole-based phosphine oxides. As proof of concept, reduction of an analogue yielded the corresponding P-chiral 2-phosphinyl imidazole ligand, which was shown to induce high enantioselectivity in the formation of axially chiral molecules synthesized via Pd-catalyzed Suzuki-Miyaura cross-coupling.

Investigation of ionic liquid adsorption and interfacial tension reduction using different crude oils; effects of salts, ionic liquid, and pH

The results revealed the significant effect of NaCl, KCl, CaCl2, MgCl2, CaSO4, MgSO4, and Na2SO4 and pH values of 3.5–11 on the interfacial tension (IFT) reduction using three types of neutral, acidic, and basic crude oils, especially for acidic crude oil (crude oil II) as the pH was changed from 3.5 to 11 (due to saponification process). The findings showed the highest impact of pH on the IFT of crude oil II with a reducing trend, especially for the pH 11 when no salts exist. The results revealed that the salts except MgCl2 and CaCl2 led to a similar IFT variation trend for the case of distilled water/crude oil II. For the MgCl2 and CaCl2 solutions, a shifting point for IFT values was inevitable. Besides, the dissolution of 1-dodecyl-3-methyl imidazolium chloride ([C12mim][Cl]) with a concentration of 100–1000 ppm eliminates the effect of pH on IFT which leads to a reducing trend for all the examined crude oils with minimum IFT of 0.08 mN/m. Finally, the [C12mim][Cl] adsorption (under pH values) for crude oils using only Na2SO4 was measured and the minimum adsorption of 0.41 mg surfactant/g Rock under the light of saponification process was obtained.

Cryo-EM combined with image deconvolution to determine ZIF-8 crystal structure

Abstract Metal–organic frameworks (MOFs) are crystalline porous materials with tunable properties, exhibiting great potential in gas adsorption, separation and catalysis.[1,2] It is challenging to visualize MOFs with transmission electron microscopy (TEM) due to their inherent instability under electron beam irradiation. Here, we employ cryo-electron microscopy (cryo-EM) to capture images of MOF ZIF-8, revealing inverted-space structural information at a resolution of up to about 1.7 Å and enhancing its critical electron dose to around 20 e −/Å2. In addition, it is confirmed by electron-beam irradiation experiments that the high voltage could effectively mitigate the radiolysis, and the structure of ZIF-8 is more stable along the [100] direction under electron beam irradiation. Meanwhile, since the high-resolution electron microscope images are modulated by contrast transfer function (CTF) and it is difficult to determine the positions corresponding to the atomic columns directly from the images. We employ image deconvolution to eliminate the impact of CTF and obtain the structural images of ZIF-8. As a result, the heavy atom Zn and the organic imidazole ring within the organic framework can be distinguished from structural images.