Alkyl Chain Length Of Cation Research Articles

Experimental and theoretical studies of physicochemical properties of Gemini imidazolium ionic liquids: hydroxyl group in spacer chain and alkyl chain length of cation

Experimental and theoretical studies of physicochemical properties of Gemini imidazolium ionic liquids: hydroxyl group in spacer chain and alkyl chain length of cation

Flipping Water Orientation at the Surface of Water-in-Salt and Salt-in-Water Solutions.

Salt-in-water and water-in-salt mixtures are promising for battery applications and fine-tuning of room-temperature ionic liquid (RTIL) properties. Although critical processes take place at interfaces of these systems, including charge transfer and heterogeneous catalytic reactions, the microscopic interfacial structures remain unclear. Here, we apply heterodyne-detected sum-frequency generation spectroscopy to aqueous solutions of imidazolium-based RTILs to unveil the microscopic structure of the interfaces of these solutions with air. Our results show that, under salt-in-water conditions, the orientation of the OH group hydrogen-bonded to the other water molecules flips from the OH group pointing down into the liquid for pure water to up due to the accumulation of anions in the cation-rich interfacial region. However, under the water-in-salt condition, the interfacial water molecules are confined by RTIL, and their orientation is down. Details of the water organization depend critically on the alkyl chain length of the imidazolium cation. Our results demonstrate that the surface structure can be tuned by altering the molecular structure and concentration of the RTIL.

Crystallization Kinetics of Phosphonium Ionic Liquids: Effect of Cation Alkyl Chain Length and Thermal History.

The effects of alkyl chain length on the crystallization kinetics and ion mobility of tetraalkylphosphonium, [P666,n][TFSI], (n = 2, 6, 8, and 12) ionic liquids were studied by differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS) over a wide temperature range. The liquid-glass transition temperature (Tg) and ion dynamics examined over a broad T range were almost insensitive to structural modifications of the phosphonium cation. In contrast, the crystallization kinetics were strongly affected by the length of the fourth alkyl chain. Furthermore, the thermal history of the sample (cold vs melt crystallization) significantly impacted the crystallization rate. It has been found that the nature of crystallization phenomena is the same across the homologous series, while the kinetic aspect differs. Finally, electric conductivity in supercooled liquid and crystalline solid phases was measured for all samples, revealing significant ionic conductivity, largely independent of the cation structure.

The self-assembly of water reverse micelles with imidazolium ionic liquids in supercritical carbon dioxide: A molecular dynamics simulation study

Molecular dynamics (MD) simulations were employed to investigate the self-assembly of water reverse micelles (RMs) with imidazolium ionic liquids (ILs) stabilized by dodecyl polyoxyethylene (3) polyoxypropylene (6) ether (LS-36) in supercritical carbon dioxide (scCO2) at 308 K and 20 MPa. The study explored the impact of various factors, including the IL concentration, the alkyl chain length of the imidazolium cations (1-ethyl-3-methylimidazolium [EMIM]+, 1-octyl-3-methylimidazolium [OMIM]+), and the anion type (bis(trifluoromethylsulfonyl)imide [NTf2]-, tetrafluoroborate [BF4]-, acetate [ACE]-) on the solubilization of ILs by water reverse micelles. The findings revealed that water, ILs, and the surfactant formed spherical RMs in the fluid phase, with varying structures depending on the hydrophobicity of the IL. The presence of ILs was found to expedite the self-assembly process and increase the number of assembled surfactants. Higher IL concentrations resulted in greater water content in the polar core of the RMs and reduced water solubility in scCO2. The intermolecular interactions occurring between components of the systems as well as dynamical properties are discussed in terms of radial distribution functions, density distribution, hydrogen bond number and lifetime, number of contacts, and self-diffusion coefficients.

Synthesis, Characterisation, and In Vitro Evaluation of Biocompatibility, Antibacterial and Antitumor Activity of Imidazolium Ionic Liquids.

In recent decades, ionic liquids (ILs) have garnered research interest for their noteworthy properties, such as thermal stability, low or no flammability, and negligible vapour pressure. Moreover, their tunability offers limitless opportunities to design ILs with properties suitable for applications in many industrial fields. This study aims to synthetise two series of methylimidazolium ILs bearing long alkyl chain in their cations (C9, C10, C12, C14, C16, C18, C20) and with tetrafluoroborate (BF4) and the 1,3-dimethyl-5-sulfoisophthalate (DMSIP) as counter ions. The ILs were characterised using 1H-NMR and MALDI-TOF, and their thermal behaviour was investigated through DSC and TGA. Additionally, the antimicrobial, anticancer, and cytotoxic activities of the ILs were analysed. Moreover, the most promising ILs were incorporated at different concentrations (0.5, 1, 5 wt%) into polyvinyl chloride (PVC) by solvent casting to obtain antimicrobial blend films. The thermal properties and stability of the resulting PVC/IL films, along with their hydrophobicity/hydrophilicity, IL surface distribution, and release, were studied using DSC and TGA, contact angle (CA), SEM, and UV-vis spectrometry, respectively. Furthermore, the antimicrobial and cytotoxic properties of blends were analysed. The in vitro results demonstrated that the antimicrobial and antitumor activities of pure ILs against t Listeria monocytogenes, Escherichia coli, Pseudomonas fluorescens strains, and the breast cancer cell line (MCF7), respectively, were mainly dependent on their structure. These activities were higher in the series containing the BF4 anion and increased with the increase in the methylimidazolium cation alkyl chain length. However, the elongation of the alkyl chain beyond C16 induced a decrease in antimicrobial activity, indicating a cut-off effect. A similar trend was also observed in terms of in vitro biocompatibility. The loading of both the series of ILs into the PVC matrix did not affect the thermal stability of PVC blend films. However, their Tonset decreased with increased IL concentration and alkyl chain length. Similarly, both the series of PVC/IL films became more hydrophilic with increasing IL concentration and alkyl chain. The loading of ILs at 5% concentration led to considerable IL accumulation on the blend film surfaces (as observed in SEM images) and, subsequently, their higher release. The biocompatibility assessment with healthy human dermal fibroblast (HDF) cells and the investigation of antitumoral properties unveiled promising pharmacological characteristics. These findings provide strong support for the potential utilisation of ILs in biomedical applications, especially in the context of cancer therapy and as antibacterial agents to address the challenge of antibiotic resistance. Furthermore, the unique properties of the PVC/IL films make them versatile materials for advancing healthcare technologies, from drug delivery to tissue engineering and antimicrobial coatings to diagnostic devices.

Vinyl chloride capture by ionic liquids: Structural effects and molecular thermodynamic insights

Ionic liquids (ILs) have been proposed as potential environmentally friendly and efficient solvents for gas absorption and purification. In this study, we propose the utilization of ILs for vinyl chloride (VC) capture. The structural effects, including the cationic skeleton and alkyl chain length on the cation, as well as the anionic structures such as alkyl chain length for phosphate and sulfate anions and the fluorination effect, were systematically investigated at a microscopic level using COSMO-RS mode and quantum chemical calculations. ILs screening results reveal that noncyclic cationic skeletons with long alkyl chains on both cations and phosphate/sulfate-based anions, without fluorinated derivatives, are favorable for VC absorption due to their large fractional free volume and nonpolar nature. Both the anion and cation contribute to the absorption process; however, the anion effect plays a more significant role. The interaction between VC and the cation is mainly governed by van der Waals forces, while both hydrogen bonding interactions and van der Waals forces exist between VC and the anion.

Nanostructure and Dynamics of Aprotic Ionic Liquids at Graphite Electrodes as a Function of Potential.

Atomic force microscope (AFM) videos reveal the near-surface nanostructure and dynamics of the ionic liquids (ILs) 1-butyl-3-methylimidazolium dicyanamide (BMIM DCA) and 1-hexyl-3-methylimidazolium dicyanamide (HMIM DCA) above highly oriented pyrolytic graphite (HOPG) electrodes as a function of surface potential. Molecular dynamics (MD) simulations reveal the molecular-level composition of the nanostructures. In combination, AFM and MD show that the near-surface aggregates form via solvophobic association of the cation alkyl chains at the electrode interface. The diffusion coefficients of interfacial nanostructures are ≈0.01nm2s-1 and vary with the cation alkyl chain length and the surface potential. For each IL, the nanostructure diffusion coefficients are similar at open-circuit potential (OCP) and OCP + 1V, but BMIM DCA moves about twice as fast as HMIM DCA. At negative potentials, the diffusion coefficient decreases for BMIM DCA and increases for HMIM DCA. When the surface potential is switched from negative to positive, a sudden change in the direction of the nanostructure motion is observed for both BMIM DCA and HMIM DCA. No transient dynamics are noted following other potential jumps. This study provides a new fundamental understanding regarding the dynamics of electrochemically stable ILs at electrodes vital for the rational development of IL-based electrochemical devices.

Removal of diclofenac sodium from aqueous solution using different ionic liquids functionalized tragacanth gum hydrogel prepared by radiation technique

Diclofenac sodium (DCF) was reported as an important emerging environmental pollutant and its removal from wastewater is very urgent. In this study, different alkyl substituted ionic liquids (1-alkyl −3-vinyl- imidazolium bromide [CnVIm]Br, n = 4, 6, 8, 10, 12) functionalized tragacanth gum (TG-CnBr) are prepared by radiation induced grafting and crosslinking polymerization. The adsorption behaviors of ionic liquids functionalized tragacanth gum for diclofenac sodium from aqueous solutions are examined. The adsorption capacity of TG-CnBr for diclofenac sodium increases with the increasing of alkyl chain length of the imidazolium cation and the hydrophobicity of the hydrogels. The maximum adsorption capacity by TG-C12Br for diclofenac sodium at 30, 40 and 50 °C were 327.87, 310.56 and 283.29 mg/g, respectively. The adsorption of TG-C12Br towards diclofenac sodium was little decreased with NaCl increasing. The removal efficiency was still remained 94.55 % within 5 adsorption-desorption cycles by 1 M HCl. Also, the adsorption mechanism including electrostatic attraction, hydrophobic interaction, hydrogen bonding, and π − π interaction was proposed.

Computational insight into the effect of alkyl chain length in tetraalkylammonium-based deep eutectic solvents

The effect of the increase in the alkyl chain length of cation on the properties of deep eutectic solvents based on ethylene glycol has been investigated employing classical molecular dynamics simulations. The change in the structural and dynamic properties in both the bulk and liquid–vapor interface is explored through various analyses. The interaction between the anion and the ethylene glycol increases with an increase in the alkyl chain length of the cation, as observed in the increase of the lifetime of the hydrogen bond formed between the two. The terminal carbon atoms are found to be closer to each other when the cation changes from tetraethylammonium to tetrabutylammonium. The cations are located closer to the interface, and the association of the alkyl chains becomes more significant with increased alkyl chain length, decreasing the surface tension values.

Efficacy of Novel Quaternary Ammonium and Phosphonium Salts Differing in Cation Type and Alkyl Chain Length against Antibiotic-Resistant Staphylococcus aureus.

Antibacterial resistance poses a critical public health threat, challenging the prevention and treatment of bacterial infections. The search for innovative antibacterial agents has spurred significant interest in quaternary heteronium salts (QHSs), such as quaternary ammonium and phosphonium compounds as potential candidates. In this study, a library of 49 structurally related QHSs was synthesized, varying the cation type and alkyl chain length. Their antibacterial activities against Staphylococcus aureus, including antibiotic-resistant strains, were evaluated by determining minimum inhibitory/bactericidal concentrations (MIC/MBC) ≤ 64 µg/mL. Structure-activity relationship analyses highlighted alkyl-triphenylphosphonium and alkyl-methylimidazolium salts as the most effective against S. aureus CECT 976. The length of the alkyl side chain significantly influenced the antibacterial activity, with optimal chain lengths observed between C10 and C14. Dose-response relationships were assessed for selected QHSs, showing dose-dependent antibacterial activity following a non-linear pattern. Survival curves indicated effective eradication of S. aureus CECT 976 by QHSs at low concentrations, particularly compounds 1e, 3e, and 5e. Moreover, in vitro human cellular data indicated that compounds 2e, 4e, and 5e showed favourable safety profiles at concentrations ≤ 2 µg/mL. These findings highlight the potential of these QHSs as effective agents against susceptible and resistant bacterial strains, providing valuable insights for the rational design of bioactive QHSs.

Interaction and antibacterial activity of ciprofloxacin with choline based ionic liquid and CTAB: A comparative spectroscopic study

In this study, the complexation of potential chemo-therapeutic antibacterial drug, ciprofloxacin (CIP) with varying concentrations of surface active compounds (SACs) i.e., (N-(2-hydroxyethyl)-N,N-dimethyl-1-dodecanaminium bromide (12Cho.Br) and cetyltrimethylammonium bromide (CTAB) has been studied. Multispectroscopic techniques were exploited to carry out the study. The higher binding constant (Kb) value for CIP-CTAB than CIP-12Cho.Br obtained from fluorescence data revealed stronger binding of CTAB than 12Cho.Br, owing to the stronger hydrophobic-hydrophobic interaction betweeen CIP and CTAB compared to CIP and 12Cho.Br. The time resolve fluorescence decay shows changes in average lifetime (τavg) with the increasing concentration of 12Cho.Br and CTAB. The changes in τavg suggests that complex formation is taking place between CIP and 12Cho.Br / CTAB. Further, the formation of micelles by 12Cho.Br / CTAB and the effect of alkyl chain length was studied by dynamic light scattering (DLS) and zeta potential to confirm the drug complexation with 12Cho.Br and CTAB. The antibacterial activity has been performed for CIP and 12Cho.Br and CTAB. It was observed that in presence of lower concentrations of 12Cho.Br/ CTAB, the activity of the drug increased. The activity was also found cationic alkyl chain length dependent. Moreover, in-vitro cytotoxicity of CIP and its combinations with 12Cho.Br and CTAB was performed using MTT assay on HEK293 (Human embryonic kidney cells).

Impact of ionic liquid's cation alkyl chain length and reaction time on cellulose nanocrystals preparation

Traditional methods to obtain cellulose nanocrystals typically involve mechanical and chemical processes and develop an improved process in terms of efficiency, sustainability, and the quality of CNCs produced are interesting. In this sense, we aimed to prepare cellulose nanocrystals (CNCs) from the hydrolysis of microcrystalline cellulose using protic ionic liquids (PILs), named 3-diethylamino-propylammonium hexanoate ([DEAPA][Hex]), 3-dimethylamino- 1-propylammonium hexanoate ([DMAPA][Hex]), and propylammonium hexanoate ([PA][Hex]) at different reaction times. The PILs demonstrated efficiency in producing cellulose nanocrystals, regardless of the cation size and reaction times. However, as expected the properties of the CNCs varied depending on the studied condition. The highest yield was observed in DMAPA[Hex], with a 34 % conversion. Crystalline indices decreased independent of the cation sizes and reaction times. Thermal stabilities were shifted to higher temperatures up to 92 ºC probably due to PILs cation sizes. In contrast, increasing reaction times decreased nanocrystals’ thermal stabilities up to 51ºC. So, protic ionic liquids (PILs) can be considered more environmentally friendly or sustainable solvents compared to traditional organic solvents for preparing cellulose nanocrystals. In the present work, it is reported an alternative method for obtaining CNCs and additionally provide the best preparation conditions for achieving important properties of this nanomaterial, with the potential for various applications.

Correlation between absorbed acetylene spectral characteristic and nature of ionic liquids studied by in situ ATR-FTIR spectroscopy

Ionic liquids (ILs) are believed to be a prospective replacement for molecular solvents and are suggested to be used for storing and/or purifying acetylene. Systematic studies of the nature of the interaction between acetylene and different ILs may be necessary to predict new types of ionic liquids. Therefore, in order to investigate the absorption of acetylene by ionic liquids, in situ ATR-FTIR spectroscopy has been applied for the first time. Two series of ILs, such as [C2‍–‍10MIM][BF4] and ILs based on imidazolium with various anions, have been considered. A detailed analysis of the spectra of absorbed acetylene is given, with special attention being paid to the basicity of IL anions as well as the influence of the cation alkyl chain length. It has been found that the magnitude of the band shift associated with the CH stretching vibration and the antisymmetric CH bending vibration of absorbed acetylene correlates well with the change in the Kamlet-Taft β parameter of the ILs. Moreover, neither the free volume nor the IL polarity plays a key role in acetylene solubility. In addition, the enthalpy and entropy of absorption have been calculated for several ILs.

Structure, aggregation dynamics and crystallization of superfolder green fluorescent protein: Effect of long alkyl chain imidazolium ionic liquids

Green fluorescent protein (GFP) and its variants are widely used in medical and biological research, especially acting as indicators of protein structural integrity, protein-protein interactions and as biosensors. This study employs superfolder GFP (sfGFP) to investigate the impact of varying alkyl chain length of 1-Cn-3-methylimidazolium chloride ionic liquid (IL) series ([Cnmim]Cl, n = 2, 4, 6, 8, 10, 12) on the protein fluorescence, structure, hydration, aggregation dynamics and crystallization behaviour. The results revealed a concentration-dependent decrease in the sfGFP chromophore fluorescence, particularly in long alkyl chain ILs ([C10mim]Cl and [C12mim]Cl). Tryptophan (Trp) fluorescence showed the quenching rate increased with longer alkyl chains indicating a nonpolar interaction between Trp57 and the alkyl chain. Secondary structural changes were observed at the high IL concentration of 1.5 M in [C10mim]Cl and [C12mim]Cl. Small-angle X-ray scattering (SAXS) indicated relatively stable protein sizes, but with IL aggregates present in [C10mim]Cl and [C12mim]Cl solutions. Dynamic light scattering (DLS) data showed increased protein size and aggregation with longer alkyl chain ILs. Notably, ILs and salts, excluding [C2mim]Cl, promoted sfGFP crystallization. This study emphasizes the influence of the cation alkyl chain length and concentration on protein stability and aggregation, providing insights into utilizing IL solvents for protein stabilization and crystallization purposes.

Investigation of capillary waves and thermal diffusion at the air–liquid interface of imidazolium-cation-based ionic liquids using transient grating spectroscopy

The capillary wave and thermal diffusion at the gas–liquid interface of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide [Cnmim][NTf2] (n = 4, 8, 12; where n indicates the number of carbons in the alkyl chain) were investigated using interface-selective transient grating (TG) spectroscopy. At the interface, the TG signal exhibited capillary wave damping (with no capillary wave oscillation). Moreover, the capillary wave damping constant was greater than that predicted by the hydrodynamic theory; the deviation increased with the cation alkyl-chain length. The thermal diffusivities at the gas–liquid interface of [C8mim][NTf2] and [C12mim][NTf2] were lower than those in the bulk, whereas both the values at the interface and in the bulk were similar for [C4mim][NTf2]. The difference is possibly owing to the formation of a layered structure at the interface.

Effect of water addition on caprylic acid: Quaternary ammonium salts (QAS) deep eutectic solvents: Characterization of their structural and dynamical properties

Physicochemical properties of the binary mixtures based on Caprylic acid: Quaternary ammonium salts (QAS) (7:3 mol ratio) are investigated using MD simulations. Considering the hydrophobic character of eutectic solvents based on long-chain fatty acids, the stability of the binary mixtures was investigated in the adjacent water. In order to investigate the effect of water on intermolecular interactions in binary mixtures, the structural properties of the binary mixtures in the pure state and adjacent to water were investigated at 310 K. Assessed structural properties include the combined distribution functions (CDFs), the radial distribution functions (RDFs), the angular distribution functions (ADFs), and the Hydrogen bonding network between HBA and HBD and Spatial distribution functions (SDF). We aimed to represent the structural stability of eutectic solvents based on Caprylic acid and Quaternary ammonium salts (QAS) as a function of the alkyl chain length of cations, the evidence was found for the interaction between the chloride anion leads to the transition of HBA to the water-rich phase. The alkyl chain length of cations of Quaternary ammonium salts shows the stability of eutectic solvents in the adjacent water.

Preparation of hydroxyapatite nanofibers by using ionic liquids as template and application in enhancing hydrogel performance.

Introduction: Hydroxyapatite (HAP or HA) nanofibers are very attractive in the field of biomedical engineering. However, templates used for preparing HAP nanofibers are usually hydrophobic molecules, like fatty acids and/or surfactants, which are difficult to remove and potentially toxic. Therefore, it is important to develop a green approach to prepare HAP nanofibers. Methods: Imidazolium-based ionic liquids (ILs) were used as templates to control the crystallization of HAP. The obtained HAP nanofibers were composited into polyvinyl alcohol-sodium alginate (PVA-Alg) hydrogel (HAP@H). The rheological performance, stretching, and compression properties were tested. Scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), and differential scanning calorimetry (DSC) were adopted to characterize the morphology, size, crystallographic orientations, and phase of HAP@H. Results: HAP nanofibers with a length of ∼50μm were harvested. The DSC results proved that water loss temperature increased from 98°C (for pure hydrogel) to 107°C (for HAP@H). Also, HAP@H hydrogel presented much better porous structure, tensile performance, and compressive performance than that of pure hydrogel. Discussion: The morphology, size, and growth direction of HAP could be modulated easily by altering the alkyl chain length of ILs' cations. This is possibly due to face-specific adsorption of imidazolium moieties on HAP nanocrystals. The enhancing performance of HAP@H is probably due to the composited highly oriented HAP nanofibers.

Liquid–Liquid Demixing Behavior of Aqueous 1-Butanol Solutions in the Presence of Various Organic and Inorganic Ammonium Salts: Effect of Temperature, Cation Alkyl Chain Length, and Anion Type of Salts on Salting Coefficients and Thermodynamic Functions

Liquid–Liquid Demixing Behavior of Aqueous 1-Butanol Solutions in the Presence of Various Organic and Inorganic Ammonium Salts: Effect of Temperature, Cation Alkyl Chain Length, and Anion Type of Salts on Salting Coefficients and Thermodynamic Functions

Probing the impact of alkyl chain length of imidazolium ionic liquids on the conformational stability of collagen type-I from skin of Lutjanus erythropterus

Multispectroscopic techniques and molecular docking study were carried out to inspect the role of concentrations and cationic chain length of ionic liquids (ILs), on the secondary structure of collagen type-I. To attain this objective, a series of imidazolium ILs having same anion (Cl−) and a set of cations with varying chain length were used in this study. The ILs studied utilized are 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), 1-hexyl-3-methylimidazolium chloride ([Hmim][Cl]), and 1-decyl-3-methylimidazolium chloride ([Dmim][Cl]). The effect of these ILs on collagen type-I was analyzed by using UV-vis, circular dichroism (CD), steady state fluorescence, time resolve fluorescence (TRF), synchronous fluorescence, dynamic light scattering (DLS), fourier transform infrared spectroscopy (FT-IR) and molecular docking approach. The results obtained shows the stability of the collagen was dependent on the alkyl chain length of cation as well as concentration of these ILs. The alteration in hydrogen bonding and hydrophobic interactions due to the different cations of ILs, with the amino acid residues, play a key role in unfolding/destabilization of collagen. Consequently, the destabilization propensity of the ILs toward the collagen increases with increasing chain length of ILs. In addition, when organized in the order of providing destability to collagen triple helix structure, the cations of the ILs obeyed the Hofmeister series. Molecular docking also confirms more hydrophobic interaction and reduced hydrogen bonding due to long alkyl chain length of cations in ILs. The docking results are in agreement with the spectroscopic results and provide the information about the ligand binding site on the protein.

Synthesis and characterization of amide-Functionalized analogues of glycine-betaine based ionic liquids and an exemplified use for the separation of copper(II) and cobalt(II)

ABSTRACT Novel series of amide functionalized analogues of glycine-betaine-based ionic liquids (AGB-ILs), namely, [N,N,N-tri(n-butyl)(2-aminoalkyl-2-oxoethyl)]ammonium (alkyl = n-butyl, and n-octyl) associated with tetrafluoroborate (BF4 −), hexafluorophosphate (PF6 −), bis(trifluorosulfonyl)imide (Tf2N−), dicyanamide (Dca−), 4-chlorosalicylate (ClSal−) and saccharinate (Sac−) anions have been synthesized and fully characterized by spectroscopic methods (IR, 1H and 13C NMR) and elemental analysis. The alkyl chain length of the organic cation and the chemical nature of inorganic or organic anion on physicochemical properties such as melting point, glass transition and decomposition temperatures, and viscosity have been described. To determine the sensitivity of Dca ligand to pH, the effect of the pH on the extraction properties of aqueous Cu2+ and Co2+ ions has been investigated in the pH range 1 to 5.