Pyridinium-based Ionic Liquids Research Articles

A theoretical study of the comparison of gas-phase electronic properties and structure of pyridinium-based ionic liquids with different anions (chloride, bromide and iodide)

A theoretical study of the comparison of gas-phase electronic properties and structure of pyridinium-based ionic liquids with different anions (chloride, bromide and iodide)

Highly Active W2C-Based Composites for the HER in Alkaline Solution: the Role of Surface Oxide Species.

The hydrogen evolution reaction (HER) is a crucial electrochemical process for the proposed hydrogen economy since it has the potential to provide pure hydrogen for fuel cells. Nowadays, hydrogen electroproduction is considerably expensive, so promoting the development of new non-noble catalysts for the cathode of alkaline electrolyzers appears as a suitable way to reduce the costs of this technology. In this sense, a series of tungsten-based carbide materials have been synthesized by the urea-glass route as candidates to improve the HER in alkaline media. Moreover, two different pyridinium-based ionic liquids were employed to modify the surface of the carbide grains and control the amount and nature of their surface species. The main results indicate that the catalyst surface composition is modified in the hybrid materials, which are then distinguished by the appearance of tungsten suboxide structures. This implies the action of ionic liquids as reducing agents. Consequently, differential electrochemical mass spectrometry (DEMS) is used to precisely determine the onset potentials and rate-determining steps (RDS) for the HER in alkaline media. Remarkably, the modified surfaces show high catalytic performance (overpotentials between 45 and 60 mV) and RDS changes from Heyrovsky-Volmer to Heyrovsky as the surface oxide structures get reduced. H2O molecule reduction is then faster at tungsten suboxide, which allows the formation of the adsorbed hydrogen at the surface, boosting the catalytic activity and the kinetics of the alkaline HER.

Synthesis, evaluation, and in silico studies of imidazolium and pyridinium-based ionic liquids with Dioctyl succinamic acid anion for enhanced antibacterial applications

A substantial public health risk is bacterial infections, but the effectiveness of antibiotics has declined due to their overuse. In the quest for effective antimicrobial agents, Ionic liquids (ILs) have emerged as promising candidates. We have described the synthesis and comparison of pyridinium- and imidazolium-based ILs using bromide and dioctyl succinamate (DOSA) anions. These synthesized ILs were tested for their antibacterial efficacy against gram-positive Staphylococcus aureus, gram-negative Escherichia coli, and Pseudomonas aeruginosa using the agar disc diffusion method. The ILs based on Imidazolium cation showed better antibacterial activities against Staphylococcus aureus. The least MIC values of 0.244 mM and 0.488 mM are shown by [C88im] [Br] and [C88im] [DOSA] respectively, showing the key effect of a counter ion with Imidazolium ILs.

Preparation of pyridinium-based ionic liquid and application as a green catalyst for the synthetic route of 4H-1-benzopyran-5(6H)-ones

1-(4-sulfobutyl)pyridinium chlorozincate ionic liquid was synthesised in high yield (89%) through a simple route and characterised using FT-IR, NMR, and HRMS spectroscopy. The one-pot reaction was employed for the condensation reaction of benzaldehydes, 5,5-dimethyl-1,3-cyclohexanedione, and dicyanomethane, utilising the prepared ionic liquid catalyst. The optimal conditions for the reaction were achieved with a catalyst loading of 10 mol%, a solvent mixture of water and ethanol (1:1, v/v), maintained at 100°C for 180 minutes. A broad spectrum of benzopyran-5(6H)-one derivatives was prepared, yielding moderate to good results. The notable features of this procedure include readily available substrates, short reaction times, the use of environmentally friendly solvents, and the elimination of the need for chromatography in the isolation of products. Anew acidic pyridinium-based ionic liquid was successfully synthesised and used as a catalyst in the synthetic process of 2-amino-3-cyano-4-phenyl-7,7-dimethyl-7,8-dihydro-4H-1-benzopyran-5(6H)-ones. These reactions involved a condensation reaction of aromatic benzaldehydes, 5,5-dimethyl-1,3-cyclohexanedione, and dicyanomethane in a solvent mixture of ethanol and water, resulting in the desired products in moderate to good yields. The procedure is efficient and eco-friendly, and the products can be easily obtained by recrystallisation. Thus, this protocol offers an alternative to existing methods.

Pyrylium- and Pyridinium-Based Ionic Liquids as Friction Modifiers for Greases.

The use of ionic liquids (ILs) as lubricants or additives has been studied extensively over the past few decades. However, the ILs considered for lubricant applications have been part of a limited structural class of phosphonium- or imidazolium-type compounds. Here, new pyrylium- and pyridinium-based ILs bearing long alkyl chains were prepared and evaluated as friction- and wear-reducing additives in naphthenic greases. The physical properties of the synthetic ILs and additized naphthenic grease were measured. The tribological performance of the greases was measured by using standard benchtop tests. The addition of ILs was detrimental to wear, causing an increase in the amount of material removed by sliding relative to the base greases in most cases. In contrast, the friction performance improved under nearly all conditions tested due to the IL additives. The compatibility of the synthetic ILs with the naphthenic greases and its potential influence upon miscibility and tribological performance are tentatively proposed to be a result of the molecular structure.

Extractive Mechanism and Process Design of Hydroxyl-Functionalized Pyridinium-Based Ionic Liquids for Separating m-Cresol and Cumene

Extractive Mechanism and Process Design of Hydroxyl-Functionalized Pyridinium-Based Ionic Liquids for Separating <i>m</i>-Cresol and Cumene

Ionic liquid Supported Quinuclidine Catalyzed Morita-Baylis-Hillman Reaction

Abstract: The Morita-Baylis-Hillman (MBH) reaction is an important method for forming carboncarbon bonds between carbonyl-containing compounds and activated olefins. However, the slow reaction rate with electron-rich electrophilic partners has limited its wider use. To overcome this drawback, the effects of pyridinium-based ionic liquids mediated quinuclidine catalytic system for MBH reactions were studied. The method is simple, involving neat and open-flask conditions, and is compatible with a wide range of reagents. We offered general pyridinium-based ionic liquids-mediated quinuclidine catalysis mechanism that is responsible for the observed rate increase. The synthetic versatility of the MBH adducts is demonstrated by the synthesis of important building blocks for the natural product (-)-sitophilure. The authors anticipate that this pyridinium-based ionic liquids-mediated quinuclidine protocol could serve as a general methodology for the MBH reaction. In summary, the study presents a simple and effective method to enhance the reaction rate of the MBH reaction. The authors believe this method has the potential for broader applications and may contribute to developing new synthetic strategies for organic synthesis. We successfully recycled the catalytic system up to 7 runs without losing any catalytic activity.

Modelling mixtures of ammonium and pyridinium-based ionic liquids and carbon dioxide with the Cubic Plus Association Equation of state

Modelling mixtures of ammonium and pyridinium-based ionic liquids and carbon dioxide with the Cubic Plus Association Equation of state

Exploring the mechanisms of eco-friendly pyridinium ionic liquids for corrosion inhibition of carbon steel in saline mediums: Unveiling deeper understanding through experimental and computational approaches

Addressing the ongoing issue of carbon steel corrosion, this study evaluates the corrosion inhibition performance of two eco-friendly pyridinium-based ionic liquids, 4-(dimethylamino)-1-nonylpyridin-1-ium Bromide (4DMN) and 4-(dimethylamino)-1-(prop-2-yn-1-yl)pyridin-1-ium Iodide (4DMP), in a 3.5 wt% NaCl solution. Weight loss tests, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), quantum chemical calculations (QCCs), and molecular dynamics (MD) simulations were employed to carried out experimental and theoretical studies. Both 4DMN and 4DMP showed concentration-dependent inhibitory effects with 94 % and 92 % effectiveness, respectively. Potentiodynamic data showed that these compounds control both anodic and cathodic reactions without changing the corrosion mechanism. EIS results indicated a decrease in double-layer capacitance, suggesting adsorption of IL molecules on steel surface. Over a 60-h period, 4DMN maintained its effectiveness, although it decreased at higher temperatures. Surface analyses using Field Emission Scanning Electron Microscopy (FE-SEM) and Atomic Force Microscopy (AFM) showed improvements in surface morphology and roughness. Computational studies supported these findings, showing the reactivity and adsorption patterns of the ILs on the Fe (110) surface. Overall, this study contributes to understanding how pyridinium-based ILs can be used for effective and sustainable corrosion control.

Investigation on the synergistic effect of pH and pyridinium-based ionic liquid on the wettability alteration of dolomite rock and IFT of formation brine/alkaline crude oil at the presence and absence of SiO2 nanoparticles

Investigation on the hybrid enhanced oil recovery solutions and methods is gaining attention during the last decade since they can activate multiple mechanisms such as viscosity reduction, interfacial tension (IFT) reduction, and wettability alteration. So, the current work is concentrated on the application of 1-octyl-3-methyl pyridinium chloride ([C8py][Cl]) and 1-dodecyl-3-methyl pyridinium chloride ([C12py][Cl]) as novel surfactants in the absence and presence of SiO2 nanoparticles (SiO2-NPs) for the first time for possible IFT reduction and rock wettability change (contact angle (CA) measurement). In this way, the concentration of ionic liquids (ILs) and SiO2-NPs ranged between 0–2000 ppm and 0–1000 ppm, respectively, to see the influence of these chemicals on the wettability change and IFT reduction. The point is that the higher concentrations of these chemicals were not examined since using higher concentrations makes it expensive and uneconomic for field-scale applications. The obtained results revealed that as the pH increases from 3 to 11 in the absence of different chemicals (formation brine/basic crude oil), the IFT experiences an increase from 20.3 to 31.2 mN/m, while the situation for CA is more complicated. In detail, the results revealed that increasing the pH in the range of 3–11 leads to an increase in the CA from 103.2° to 121.3° (increasing pH from 3 to 7) while a further increase in the pH leads to a reduction in CA value from 121.3° to 118.3°. Moreover, the results revealed that increasing the concentration of [C8py][Cl] from 0 to 2000 ppm led to a reduction in IFT value from 20.3 to 0.95 mN/m for pH of 3, from 27.3 to 2.2 mN/m for pH of 7 and from 31.2 to 5.4 mN/m for pH of 11. Besides, the measurements for [C12py][Cl] revealed that increasing the concentration from 0 to 2000 ppm leads to IFT reduction from 20.3 to 0.74 mN/m for pH of 3, from 27.3 to 0.9 for pH of 7, and from 31.2 to 1.4 mN/m for pH of 11. The results demonstrated a higher influence of [C12py][Cl] on the IFT reduction compared with the [C8py][Cl] due to the longer alkyl chain length of [C12py][Cl] which means more detergency power. Furthermore, the effects of these two ILs are examined on the wettability change which showed that both of the examined ILs are capable to manipulate the wettability of the rock surface toward water-wet conditions (53.3°) from oil-wet conditions (121.3°). Also, the influence of SiO2-NPs in the range of 0–1000 ppm is investigated on the IFT reduction and wettability change while the concentration of ILs is held constant at 2000 ppm since the concentration of 2000 ppm leading to the lowest CA and IFT values for both examined ILs. The obtained results reveal that not only the presence of SiO2-NPs with a maximum concentration of 1000 ppm leads to a reducing trend on the IFT in particular for the pH of 11 regardless of the used IL but also it changes the surface wettability to strongly water-wet condition with minimum CA value of 28.5°. In the last stage, the efficiency of the optimum chemical formulations was examined through core flooding experiments using conventional core flooding procedure and the core flooding experiments concomitant with the soaking time (30 days). The experiments revealed that the chemical formulation under a pH of 3 leads to the highest oil recovery factors while the lowest oil recovery factors are obtained under a pH of 11. Besides, the core flooding experiments followed by soaking reveal the ultimate oil recovery of 10.1 and 13.3% based on the original oil in place (OOIP) due to better activation of the wettability change mechanism which was 46% higher than the situation no soaking was performed. The findings of this study can help for a better understanding of the feasibility and applicability of using new hybrid surfactant-NPs-based EOR methods to activate wettability alteration and IFT reduction, especially with a main focus on one specific fraction of crude oil (resin fraction) instead of crude oil.

Voltammetric determination of organic UV filters by carbon paste electrodes modified with pyridinium-based ionic liquids

The rapid and sensitive voltammetric determination of organic UV filters benzophenone-3 (BP-3) and avobenzone (AVO) was performed by an ionic liquid carbon paste electrode (IL-CPE). Namely, the synthesized pyridinium-based ILs, 1-butyl-3-methylpyridinium chloride ([N–C4–3C1Py]Cl) and 1-ethoxyethyl-3-methylpyridinium chloride ([N–C2OC2–3C1Py]Cl) were compared as bulk CPE modifiers for BP-3 determination. [N–C4–3C1Py]Cl-CPE showed more favorable interactions with the target analyte, and it was tested for AVO determination, too. Cyclic voltammetric (CV) studies suggested that the irreversible electrode reaction is adsorption controlled in the case of both UV filters. Also, the square-wave adsorptive stripping voltammetric (SW-AdSV) method was optimized for quantifying selected UV filters. In the model solutions, the linear calibration curve was obtained by the SW-AdSV method in the concentration range from 0.05 to 0.89 μg mL−1 at pH 3.0 for BP-3 (Eacc = −0.7 V, tacc = 100 s), and from 0.05 to 1.77 μg mL−1 at pH 11.98 for AVO (Eacc = 0.2 V, tacc = 100 s). The evaluated limit of detection (LOD) was 0.015 μg mL−1 in both cases, while the relative standard deviation (RSD) was lower than 1.5%. The affordable IL-based voltammetric sensor fulfills the main requirements for application in real samples due to an adequate selectivity towards selected analytes in the presence of interferents usually found in swimming pool water. Therefore, the BP-3 and AVO were quantified in a swimming pool water matrix with good repeatability and recovery. The obtained results demonstrate an excellent potential of the IL-CPEs, especially of the [N–C4–3C1Py]Cl-CPE, for determining selected UV filters in various real samples.

An insight into the influence of chlorine position on the ion-solvation and ion-association behaviour of pyridinium-based ionic liquids in alcohol-water mixed media and temperatures

An insight into the influence of chlorine position on the ion-solvation and ion-association behaviour of pyridinium-based ionic liquids in alcohol-water mixed media and temperatures

Evaluation of corrosion mitigation properties of pyridinium-based ionic liquids on carbon steel in 15% HCl under the hydrodynamic condition: Experimental, surface, and computational approaches

The corrosion process severely damages the carbon steel during the acidization. The present investigation described the corrosion inhibition application of two ionic liquids: 1-Butylpyridinium chloride (BPC) and 1-Butylpyridinium hexafluorophospate (BPH), for the protection of carbon steel in 15 % HCl under the hydrodynamic condition at 1500 rpm. The estimated results obtained by weight loss support the inhibitive performance of BPs are 90.0 % (BPC) and 72.5 % (BPH). The EIS results point out the rising values of Rct with the increasing amount of BPs and approach the highest value of 262.4 Ω cm2 (BPC) and 125.4 Ω cm2 (BPH). The PDP reveals the anodic nature of BPs inhibitive action. The Dubinine Radushkevich (d-RIM) adsorption isotherm model provides accurate fitting estimated data. The negative values of ΔHoads represent the exothermic nature of adsorption. The contact angle value is less (26.4°) for BPs free steel sample. However, a significant increase occurs in the contact angle values upon adding BPC (84.9°) and BPH (67.8°). The SEM, optical profilometry, contact angle, and XPS confirmed the presence of an adsorptive layer of BPs. DFT further suggests the better inhibitive performance of BPC than BPH.

Effect of anions and cations on the self-assembly of ionic liquid surfactants in aqueous solution

Ionic liquid surfactants have shown increasing promise for substituting the traditional amphiphiles due to their flexible tunability and superior physicochemical properties. However, the effect of cationic structure and anion type on the surface properties of ionic liquid surfactants remains unclear. Herein, four ionic liquid surfactants [C12mim][BF4], [PyC12][Br], [C12mim][Br] and [PyC12][BF4] with the same alkyl side chain length were designed and synthesized. Their surface properties, such as micelle-free energy (ΔGmθ), surface tension reduction efficiency (ПCMC), and adsorption efficiency (pC20), and the influence of the type and structure of the anion and cation on their micellar physicochemical properties in aqueous solution were discussed according to the data. The proposed approach demonstrates that the critical micelle concentration (CMC) is determined by combining electrostatic and hydrophobic effects. When the anion is BF4−, the ionic liquid has a lower CMC, and BF4− has a superior hydrophobic effect, which allows the ionic liquid to form micelles more easily. In addition, the ionic liquid of tetrafluoroborate has higher interfacial activity (larger pC20) at the same temperature and its aqueous solution has lower surface tension, making it a more desirable surfactant. All four types of ionic liquids have negative values of ΔGmθ, implying that micelle formation is a spontaneous process. The surface activity of imidazolium- and pyridinium-based ionic liquids was slightly different from the critical micelle concentration under the same anion and carbon chain length. Imidazole and pyridine have highly similar hydrophobic and electrostatic effects, and the cation may not be the most critical factor affecting the surface properties.

Thermal and Electrochemical Properties of Ionic Liquids Bearing Allyl Group with Sulfonate-Based Anions-Application Potential in Epoxy Resin Curing Process.

Sulfonate-based ionic liquids (ILs) with allyl-containing cations have been previously obtained by us, however, the present study aims to investigate the thermal, electrochemical and curing properties of these ILs. To determine the temperature range in which ionic liquid maintains a liquid state, thermal properties must be examined using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Melting, cold crystallization and glass transition temperatures are discussed, as well as decomposition temperatures for imidazolium- and pyridinium-based ionic liquids. The conductivity and electrochemical stability ranges were studied in order to investigate their potential applicability as electrolytes. Finally, the potential of triflate-based ILs as polymerization initiators for epoxy resins was proven.

Synthesis of pyridinium-based ionic liquids and their application to improve Candida rugosa lipase stability in a methanol-water solvent system.

This paper studied the effect of pyridinium-based ionic liquids as cosolvents in a methanol-water solvent system on the hydrolytic activity of Candida rugosa lipase. These ionic liquids were successfully synthesized using imidazolium-based ionic liquid synthesizing methods with a certain adjustment. The hydrolytic activity of Candida rugosa lipase was analyzed using 4-nitrophenol acetate (pNPA) and 4-nitrophenol palmitate (pNPP) as substrates. The addition of ionic liquids had no significant effect on the hydrolytic activity of lipase in a water solvent, and it had a greater effect in methanol. The addition of [C6Py] Br ionic liquid as a methanol cosolvent (methanol: ionic liquid, 10:5) could increase the hydrolytic activity of lipase. The use of ionic liquid as a cosolvent could increase the hydrolytic activity of lipase by about 15.61% while using pNPP as a substrate in the methanol system. A molecular dynamics study for the interaction between lipase and ionic liquids supported the experimental results. The ionic liquid using bromide as an anion provided more stability on lipase conformation. It tends to form the short-range interaction between the lipase and bromide anion.

Cancer-specific cytotoxicity of pyridinium-based ionic liquids by regulating hypoxia-inducible factor-1α-centric cancer metabolism

Owing to their unique properties and biological activities, ionic liquids (ILs) have attracted research interest in pharmaceutics and medicine. Hypoxia-inducible factor (HIF)− 1α is an attractive cancer drug target involved in cancer malignancy in the hypoxic tumor microenvironment. Herein, we report the inhibitory activity of ILs on the HIF-1α pathway and their mechanism of action. Substitution of a dimethylamino group on pyridinium reduced hypoxia-induced HIF-1α activation. It selectively inhibited the viability of the human colon cancer cell line HCT116, compared to that of the normal fibroblast cell line WI-38. These activities were enhanced by increasing the alkyl chain length in the pyridinium. Under hypoxic conditions, dimethylaminopyridinium reduced the accumulation of HIF-1α and its target genes without affecting the HIF1A mRNA level in cancer cells. It suppressed the oxygen consumption rate and ATP production by directly inhibiting electron transfer chain complex I, which led to enhanced intracellular oxygen content and oxygen-dependent degradation of HIF-1α under hypoxia. These results indicate that dimethylaminopyridinium suppresses the mitochondria and HIF-1α-dependent glucose metabolic pathway in hypoxic cancer cells. This study provides insights into the anticancer activity of pyridinium-based ILs through the regulation of cancer metabolism, making them promising candidates for cancer treatment.

CO2 conversion into carbonate using pyridinium-based ionic liquids under mild conditions

A sequence of pyridinium-based acidic-ionic liquids (PyAILs) as dual-functional ILs were synthesized and applied as metal-free, stable and homogeneous catalysts to convert economical, renewable, sustainable and inert CO2 into carbonates. These PyAILs were used to synthesize high-efficiency terminal carbonate from epoxide and greenhouse CO2. Various factors that affected the conversion and selectivity of the reaction including the amount of catalyst, chain length of acidic pendant, anion type, reaction temperature, solvent and reaction time were investigated. The special design of the dual acid-functionalized PyAILs, activated CO2 and epoxide, and the reaction was carried out under mild conditions, solvent-free, low pressure with great TOF and excellent conversion and selectivity above 99% for different types of terminal epoxides. A conceivable reaction mechanism was proposed and it was signified that the carboxylic group and halide ions had a synergetic effect on cyclic carbonates synthesis. In addition, PyAILs can be easily separated by simple extraction from the reaction medium.

Separation of m-cresol from model oil by pyridinium-based ionic liquids: COSMO-RS screening, experimental study, and process simulation

The separation of phenolic compounds from low-temperature coal tar is conducive to the rational utilization of resources and environmental protection. In this work, pyridinium-based ionic liquids (ILs) were used as extractants for m-cresol/cumene separation. 70 pyridinium-based ILs formed by 10 cations and 7 anions were screened combining the calculation of the extraction ability of ILs for m-cresol and the mutual solubility of ILs with cumene by COSMO-RS model. The influences of cation and anion structures were studied and further explored by σ-profile and σ-potential. Among 70 ILs, the IL 1-ethyl-pyridinium dicyanamide ([C2py][N(CN)2]) was finally identified. Then [C2py][N(CN)2] was synthesized and used to separate m-cresol from model oil. The influences of stirring time, temperature, IL: model oil mass ratio, and initial m-cresol content on the separation performance of [C2py][N(CN)2] were investigated. The regeneration of [C2py][N(CN)2] was carried out and was characterized by FT-IR. The formation of hydrogen bond between [C2py][N(CN)2] and m-cresol was confirmed by FT-IR. Moreover, the process simulation and optimization were investigated by Aspen Plus based on the NRTL model. For the separation process using [C2py][N(CN)2], products with high recovery ratio (99.97% for m-cresol and 99.99% for cumene) and high mass purity (99.97 wt% for m-cresol and 99.80 wt% for cumene) were obtained. The simulation results could provide a guidance for industrial application.

Highly Efficient, Reusable, Functionalized Pyridinium Salts as a Catalyst for the Simple and Cost-effective Preparation of Tetrahydro [b] Benzopyran Derivatives

Background:In this work, a series of pyridinium-based ionic liquids (PBILs) were synthesized.Methods:Pyridinium-based ionic liquids (PBILs) were synthesized through a simple method, which was initially evaluated as catalysts for the synthesis of tetrahydro[b]benzopyran derivatives via a one-pot three-component reaction involving aldehydes, malononitrile, and dimedone.Results:The PBILs perform well in this condensation reaction, especially 1-methylpyridin-1-ium dimethyl phosphate (MPDMP).Conclusion:The advantages of this procedure are good yields, short reaction time, simplicity of implementation, and inexpensive starting materials.