Synthesis of imidazolium and pyridinium-based ionic liquids and application of 1-alkyl-3-methylimidazolium salts as pre-catalysts for the benzoin condensation using solvent-free and microwave activation

Modified nano magnetic Fe2O3-MgO as a high active multifunctional heterogeneous catalyst for environmentally beneficial carbon-carbon synthesis

In this study, novel nanomagnetic catalysts, namely Fe2O3-MgO@choline formate (Ch. F.) and Fe2O3-MgO@choline cyanide (Ch. CN), were synthesized through immobilizing choline-based ion liquids to magnetic support via a simple and cost-effective methodology. FT-IR, TGA, FE-SEM, VSM, EDS, BET, and XRD techniques were employed to assess and characterize these organic-inorganic compounds. Following the successful preparation of nanoparticles, the catalysts were utilized in Knoevenagel and benzoin condensations. Fe2O3-MgO@Ch.F. exhibited exceptional activity in Knoevenagel condensation under solvent-free conditions at room temperature, achieving high yields (91-98%) in a short timeframe. Similarly, Fe2O3-MgO@Ch.CN demonstrated remarkable activity in benzoin condensation under environmentally friendly solvent conditions, yielding higher isolated yields (76-88%). Furthermore, these magnetically recyclable multifunctional catalysts displayed the ability to be reused up to five times without a significant loss in efficiency. Additionally, the heterogeneity of this nanocatalyst was investigated using the hot filtration technique. The findings indicated that the reaction primarily occurs via a heterogeneous pathway.

Microwave-assisted synthesis of iridium oxide and palladium nanoparticles supported on a nitrogen-rich covalent triazine framework as superior electrocatalysts for the hydrogen evolution and oxygen reduction reaction

Iridium oxide (IrOx-NP) and palladium nanoparticles (Pd-NP) were supported on a 2,6-dicyanopyridine-based covalent-triazine framework (DCP-CTF) by energy-saving and sustainable microwave-assisted thermal decomposition reactions in propylene carbonate and in the ionic liquid [BMIm][NTf2]. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) confirm well-distributed NPs with sizes from 2 to 13 nm stabilized on the CTF particles. Metal contents between 10 and 41 wt% were determined by flame atomic absorption spectroscopy (AAS). Nitrogen sorption measurements of the metal-loaded CTFs revealed Brunauer–Emmett–Teller (BET) surface areas between 904 and 1353 m2 g−1. The composites show superior performance toward the hydrogen evolution reaction (HER) with low overpotentials from 47 to 325 mV and toward the oxygen reduction reaction (ORR) with high half-wave potentials between 810 and 872 mV. IrOx samples in particular show high performances toward HER while the Pd samples show better performance toward ORR. In both reactions, electrocatalysts can compete with the high performance of Pt/C. Exemplary cyclic voltammetry durability tests with 1000 cycles and subsequent TEM analyses show good long-term stability of the materials. The results demonstrate the promising synergistic effects of NP-decorated CTF materials, resulting in a high electrocatalytic activity and stability.

Properties of Bromine Fused Salts Based on Quaternary Ammonium Molecules and Their Relevance for Use in a Hydrogen Bromine Redox Flow Battery

Bromine complexing agents (BCA) in aqueous electrolytes for hydrogen bromine flow batteries are used to reduce bromine‘s vapour pressure, while an insoluble and liquid fused salt is formed. The properties (concentrations, composition, conductivity and viscosity) of this fused salt are investigated in this study systematically ex situ by using 7 BCAs at different state of charge in HBr/Br₂/H₂O electrolytes with a theoretical capacity of 179.6 Ah L⁻¹. Bromine is stored in the fused salt at concentrations up to 13.6 M, reaching theoretical volumetrical capacities up to 730 Ah L⁻¹ in fused salts. The fused salt consists of a pure, bromine‐ and water‐free ionic liquid of organic [BCA]⁺ cations and polybromides, and its conductivity bases on a hopping mechanism among the polybromides. Alkyl side chain length of the BCAs and distribution of polybromides influence strongly the conductivity and viscosity of the fused salts. 1‐ethylpyridin‐1‐iumbromide results to be favoured BCA for application.

Comparable Studies on Nanoscale Antibacterial Polymer Coatings Based on Different Coating Procedures

The antibacterial activity of different antibiotic and metal-free thin polymer coatings was investigated. The films comprised quaternary ammonium compounds (QAC) based on a vinyl benzyl chloride (VBC) building block. Two monomeric QAC of different alkyl chain lengths were prepared, and then polymerized by two different polymerization processes to apply them onto Ti surfaces. At first, the polymeric layer was generated directly on the surface by atom transfer radical polymerization (ATRP). For comparison purposes, in a classical route a copolymerization of the QAC-containing monomers with a metal adhesion mediating phosphonate (VBPOH) monomers was carried out and the Ti surfaces were coated via drop coating. The different coatings were characterized by X-ray photoelectron spectroscopy (XPS) illustrating a thickness in the nanomolecular range. The cytocompatibility in vitro was confirmed by both live/dead and WST-1 assay. The antimicrobial activity was evaluated by two different assays (CFU and BTG, resp.,), showing for both coating processes similar results to kill bacteria on contact. These antibacterial coatings present a simple method to protect metallic devices against microbial contamination.

Ionic Liquids: Environment-Friendly Greener Solvents for Organic Synthesis

Constituted by ions, ionic liquids (ILs) are evolving as greener solvents for many organic syntheses. Due to their high solvent power and low volatility, ionic liquids are serving as an environment-friendly substitute to conventional volatile organic solvents. The present review introduces ionic liquids as an insight into the diverse recent applications of ILs in organic synthesis.

Review on Amphiphilic Ionic Liquids as New Surfactants: From Fundamentals to Applications

The demand for lowering interfacial tension (IFT) in different processes has persuaded researchers to use stable and resistant surfactants with low environmental impact. For this purpose, surface-active ionic liquids (SAILs) have attracted much attention owing to their good amphiphilic nature and prominent properties like recyclability and high performance under harsh conditions. This review initially explains how the IFT and critical micelle concentration of different systems vary in the presence of different SAILs with a variety of alkyl chain lengths, head groups, and counter anions. Towards this aim, some physicochemical properties of SAILs as well as the corresponding theoretical aspects of adsorption are considered. Then, recent advances in utilizing SAILs for reducing IFT of different chemical systems are surveyed. Relevantly, the role of important operating parameters of temperature, pH, presence of electrolytes, and the chemical nature of involved phases are adequately discussed. Further, an overview of different SAILs applications in stabilization, separation, and in petroleum industries is scrutinized. To allow better judgment, precise comparisons between different types of SAILs and conventional surfactants are provided. Finally, challenges and possible directions of future research on SAILs are highlighted.

Synthesis, biological evaluation (antioxidant, antimicrobial, enzyme inhibition, and cytotoxic) and molecular docking study of hydroxy methoxy benzoin/benzil analogous

In this work, due to the biological activity evaluation, a series of hydroxy methoxy benzoins (1-8), benzils (10-16) and methoxy benzoin/benzil-O-β-d-glucosides (17-28) were synthesized. Antioxidant (FRAP, CUPRAC, DPPH), antimicrobial (16 microorganisms, and two yeast), enzyme inhibition (α-amylase, α-glucosidase, AChE, BChE, and tyrosinase) of all synthesized benzoin/benzil analogs were investigated. Benzoins (1-8) showed the most effective antioxidant properties compared to all three methods. Compound 28 against α-amylase, compound 9 against α-glucosidase, compound 11 against AChE, compound 2 against BChE, and compound 13 against tyrosinase showed the best activities with the better or similar IC₅₀ values as used standards. Hydroxy methoxy benzoin compounds (1-8) among all four groups were seen as the most effective against the tested microorganism. Molecular docking analysis showed that all tested compounds 1-28 (0.01-2.22 µM) had the best binding affinity against AChE enzyme. Cytotoxic effects of the many of compounds (1-16, 21, and 24) also investigated and it was found that they caused different effects in different cells. The LDH tests of compounds 1a + b, 4, 7, 8, 9, 11, 12, 21, and 24, seemed to be effective compared to the positive control cisplatin. The cytotoxicity of compounds 6 (9.24%) for MCF7 cancer cells, 8 (5.16%) and 4 (8.26%) for HT29 cancer cells, 24 (9.84%) for Hep3B cells and 8 (8.52%), 7 (5.70%), 4 (6.94) and 9 (7.22%) for C6 cells were at normal values. And also cytotoxic activity of four compounds (5, 9, 21, and 24) among the all synthetic groups, were evaluated to the HeLa and RPE. Compound 5 showed anticancer activity on HeLa and RPE cancer cells as much as or better than cisplatin which was used as standard.

Scrutinizing Self-Assembly, Surface Activity and Aggregation Behavior of Mixtures of Imidazolium Based Ionic Liquids and Surfactants: A Comprehensive Review

The desire of improving various processes like enhanced oil recovery (EOR), water treatment technologies, biomass extraction, organic synthesis, carbon capture etc. in which conventional surfactants have been traditionally utilized; prompted various researchers to explore the self-assembly and aggregation behavior of different kinds of surface-active molecules. Ionic liquids (ILs) with long alkyl chain present in their structure constitute the advantageous properties of surfactant and ILs, hence termed as surface-active ionic liquids (SAILs). The addition of ILs and SAILs significantly influence the surface-activity and aggregation behavior of industrially useful conventional surfactants. After a brief review of ILs, SAILs and surfactants, the prime focus is made on analyzing the self-assembly of SAILs and the mixed micellization behavior of conventional surfactants with different ILs.

Systematic Study of Quaternary Ammonium Cations for Bromine Sequestering Application in High Energy Density Electrolytes for Hydrogen Bromine Redox Flow Batteries

Bromine complexing agents (BCAs) are used to reduce the vapor pressure of bromine in the aqueous electrolytes of bromine flow batteries. BCAs bind hazardous, volatile bromine by forming a second, heavy liquid fused salt. The properties of BCAs in a strongly acidic bromine electrolyte are largely unexplored. A total of 38 different quaternary ammonium halides are investigated ex situ regarding their properties and applicability in bromine electrolytes as BCAs. The focus is on the development of safe and performant HBr/Br2/H2O electrolytes with a theoretical capacity of 180 Ah L-1 for hydrogen bromine redox flow batteries (H2/Br2-RFB). Stable liquid fused salts, moderate bromine complexation, large conductivities and large redox potentials in the aqueous phase of the electrolytes are investigated in order to determine the most applicable BCA for this kind of electrolyte. A detailed study on the properties of BCA cations in these parameters is provided for the first time, as well as for electrolyte mixtures at different states of charge of the electrolyte. 1-ethylpyridin-1-ium bromide [C2Py]Br is selected from 38 BCAs based on its properties as a BCA that should be focused on for application in electrolytes for H2/Br2-RFB in the future.

Ionic Liquid-Based Surfactants: Recent Advances in Their Syntheses, Solution Properties, and Applications

The impetus for the expanding interest in ionic liquids (ILs) is their favorable properties and important applications. Ionic liquid-based surfactants (ILBSs) carry long-chain hydrophobic tails. Two or more molecules of ILBSs can be joined by covalent bonds leading, e.g., to gemini compounds (GILBSs). This review article focuses on aspects of the chemistry and applications of ILBSs and GILBSs, especially in the last ten years. Data on their adsorption at the interface and micelle formation are relevant for the applications of these surfactants. Therefore, we collected data for 152 ILBSs and 11 biamphiphilic compounds. The head ions of ILBSs are usually heterocyclic (imidazolium, pyridinium, pyrrolidinium, etc.). Most of these head-ions are also present in the reported 53 GILBSs. Where possible, we correlate the adsorption/micellar properties of the surfactants with their molecular structures, in particular, the number of carbon atoms present in the hydrocarbon "tail". The use of ILBSs as templates for the fabrication of mesoporous nanoparticles enables better control of particle porosity and size, hence increasing their usefulness. ILs and ILBSs form thermodynamically stable water/oil and oil/water microemulsions. These were employed as templates for (radical) polymerization reactions, where the monomer is the "oil" component. The formed polymer nanoparticles can be further stabilized against aggregation by using a functionalized ILBS that is co-polymerized with the monomers. In addition to updating the literature on the subject, we hope that this review highlights the versatility and hence the potential applications of these classes of surfactants in several fields, including synthesis, catalysis, polymers, decontamination, and drug delivery.

Sterically modulated silver(I) complexes of coumarin substituted benzimidazol-2-ylidenes: Synthesis, crystal structures and evaluation of their antimicrobial and antilung cancer potentials

In this contribution, a series of sterically-encumbered coumarin substituted benzimidazole-based N-heterocyclic carbene (NHC) precursors (1-12) and their silver(I)-NHC complexes (13-24) are reported. Molecular structure of NHC precursors 8 and 12 and cationic complexes 15 and 16 was established by single crystal X-ray diffraction method. The silver(I) complexes demonstrated various significant intramolecular agostic-like interactions operating between the metal center and the hydrogen atoms of the substituents alongside a variety of feeble π-π stacking interactions. A distorted linear coordination geometry is documented at the silver(I) center with the anti-arrangement of the ligands. Further, the complexes demonstrated promising antibacterial properties against Gram positive and Gram negative bacterial strains, especially complex 18 displayed a minimum inhibitory concentration (MIC) of 2 and 4 μg/mL against S. aureus and E. coli, and P. aeruginosa, respectively. Furthermore, complexes 14, 15, 16 and 18 were found cytotoxic against the human lung cancer cell lines A549 and H1975 with the IC₅₀ (concentration of the test sample required to kill 50% of the cell population) value under 10 μM, while mono-NHC complex 20 displayed a potential drug window with the IC₅₀ of 13.7 ± 2.70 and 14.5 ± 1.20 μM against the cancer cell lines H1975 and A549, respectively. Notably, these complexes displayed relatively lesser cytotoxic behaviour against the normal skin fibroblast cell line, Hs68. All the NHC precursors displayed significantly lower biological activities compared with their respective complexes, indicating the utility of silver(I) ions in antimicrobial and antilung cancer applications.

The Beneficial Sinergy of MW Irradiation and Ionic Liquids in Catalysis of Organic Reactions

The quest for sustainable processes is becoming more and more important, with catalysis playing a major role in improving atom economy and reducing waste. Organic syntheses with less need of protecting/de-protecting steps are highly desirable. The combination of microwave irradiation, as energy source, with ionic liquids, as both solvents and catalysts, offered interesting solutions in recent years. The literature data of the last 15 years concerning selected reactions are presented, highlighting the importance of microwave (MW) technology coupled with ionic liquids.

N-Alkylated 1,4-Diazabicyclo[2.2.2]octane-Polyethylene Glycol Melt as Deep Eutectic Solvent for the Synthesis of Fisher Indoles and 1H-Tetrazoles

1,4-Diazabicyclo[2.2.2]octane (DABCO)-based ionic liquids (ILs) 2-4 were synthesized by the N-alkylation of DABCO using alkyl halides of varying chain lengths (C₂, C₅, and C₇). The N-alkylated DABCO-ILs were mixed with polyethylene glycols (PEGs) of varying molar masses as hydrogen bond donors (HBDs) to prepare new deep eutectic solvents (DESs). These DABCO-PEG-based DESs were successfully employed for the synthesis of a variety of indoles 7a-7h (by Fischer indole synthesis) and 1H-tetrazoles 9a-9i (by click chemistry). For comparison, DESs of DABCO-ILs with different alcohols (as HBD) were also prepared and investigated for the synthesis of indoles. Although comparable yields were observed in DES-containing alcohols and PEGs, the use of PEG as HBD in DES (as an alternative to alcohols) provides a much safer, nonvolatile, and environmentally benign reaction medium for synthetic reactions. The first successful application of PEG-polymer-based DES as benign reaction media for organic syntheses offers exciting opportunities to be explored in the realm of green synthesis.

Toxicity study of ionic liquid, 1-butyl-3-methylimidazolium bromide on guppy fish, Poecilia reticulata and its biodegradation by soil bacterium Rhodococcus hoagii VRT1

This study deals with the toxic effect of ionic liquid, 1-butyl-3-methylimidazolium bromide (BMImBr) on guppy fish, Poecilia reticulata. The fishes were exposed to various concentrations of ionic liquid for 96h. The activity of antioxidant enzymes viz. catalase, glutathione S-transferase and superoxide dismutase were found to be increased with increase in concentration. The BMImBr resistant bacterium were isolated from garden soil by enrichment method and identified as Rhodococcus hoagii VRT1 by 16S rDNA sequencing. An isolated bacterium was effective in biodegradation of compound in 8 days which was analyzed by changes in BOD and COD and later on confirmed by HRMS analysis. Higher concentrations of compound induced DNA damage in liver cells while degraded product did not show adverse impact on the DNA integrity.

Conductive Hybrid Crystal Composed from Polyoxomolybdate and Deprotonatable Ionic-Liquid Surfactant

A polyoxomolybdate inorganic-organic hybrid crystal was synthesized with deprotonatable ionic-liquid surfactant. 1-dodecylimidazolium cation was employed for its synthesis. The hybrid crystal contained δ-type octamolybdate (Mo₈) isomer, and possessed alternate stacking of Mo₈ monolayers and interdigitated surfactant bilayers. The crystal structure was compared with polyoxomolybdate hybrid crystals comprising 1-dodecyl-3-methylimidazolium surfactant, which preferred β-type Mo₈ isomer. The less bulky hydrophilic moiety of the 1-dodecylimidazolium interacted with the δ-Mo₈ anion by N-H···O hydrogen bonds, which presumably induced the formation of the δ-Mo₈ anion. Anhydrous conductivity of the hybrid crystal was estimated to be 5.5 × 10(-6) S·cm(-1) at 443 K by alternating current (AC) impedance spectroscopy.

Synthesis of dual functional pyrimidinium ionic liquids as reaction media and antimicrobial agents

This article describes a two-step synthesis of twenty N-alkyl pyrimidinium ionic liquids through N-alkylation of pyrimidine with n-alkyl (C₁–C₁₀) halides followed by anion metathesis and their dual applications as reaction media and antibacterial agents.

Multifunctional electropolymerizable carbazole-based ionic liquids

Electropolymerizable carbazole-functionalized ionic liquids with adjustable properties (via changing counter anions) show interesting electrochemical, electrochromic, and solvatochromic behavior.

New eco-friendly 1-alkyl-3-(4-phenoxybutyl) imidazolium-based ionic liquids derivatives: a green ultrasound-assisted synthesis, characterization, antibacterial activity and POM analyses

In view of the emerging importance of the ILs as "green" materials with wide applications and our general interests in green processes, a series of a twenty five new 1-alkyl-3-(4-phenoxybutyl) imidazolium-based ionic liquids (ILs) derivatives is synthesized using a facile and green ultrasound-assisted procedure. Their structures were characterized by FT-IR, 1H-NMR, 13C-NMR, 11B, 19F, 31P, and mass spectrometry. Antimicrobial screens of some selected ILs were conducted against a panel of Gram-positive and Gram-negative bacteria. The antimicrobial activity of each compound was measured by determination of the minimal inhibitory concentration (MIC) yielding very interesting and promising results. Their antibacterial activities are reported, and, on the basis of the experimental and virtual POM screening data available, attempt is also made to elucidate the structure activity relationship.

1-Butylimidazole-derived ionic liquids: synthesis, characterisation and evaluation of their antibacterial, antifungal and anticancer activities

The reaction of 1-butylimidazole (1a) with aryl/alkoxy halides (2a–h) using a microwave solvent-free approach delivered imidazolium-based ILs (3a–h) in good yield. Some of them showed promising antibacterial and antifungal activities.

Microwave-assisted one pot-synthesis of amino acid ionic liquids in water: simple catalysts for styrene carbonate synthesis under atmospheric pressure of CO2

A novel variety of ionic liquids based on amino acids is synthesized in water using microwave energy.

A brief overview of the potential environmental hazards of ionic liquids

Over past decades ionic liquids, a promising alternative to traditional organic solvents, have been dramatically expanding in popularity as a new generation of chemicals with potential uses in various areas in industry. In the literature these compounds have often been referred to as environmentally friendly; however, in recent years the perception of their greenness dramatically changed as the scientific community began to proactively assess the risk of their application based on the entire life-cycle. This review gives a brief overview of the current knowledge regarding the potential risks linked to the application of ionic liquids - from preparation to their disposal, with special emphasis on their potential environmental impacts and future directions in designing inherently safer ionic liquids.