Impact Of Ionic Liquids Research Articles

Impact of Ionic Liquids on the Physicochemical Behavior of Vesicles.

The effects of two ionic liquids (ILs), 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) and 1-butyl-1-methyl pyrrolidinium tetrafluoroborate ([bmp]BF4), on a mixture of phospholipids (PLs) 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE), and 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG) (6:3:1, M/M/M, 70% PL) in combination with 30 mol % cholesterol (CHOL) were investigated in the form of a solvent-spread monolayer and bilayer (vesicle). Surface pressure (π)-area (A) isotherm studies, using a Langmuir surface balance, revealed the formation of an expanded monolayer, while the cationic moiety of the IL molecules could electrostatically and hydrophobically bind to the PLs on the palisade layer. Turbidity, dynamic light scattering (size, ζ-potential, and polydispersity index), electron microscopy, small-angle X-ray/neutron scattering, fluorescence spectroscopy, and differential scanning calorimetric studies were carried out to evaluate the effects of IL on the structural organization of bilayer in the vesicles. The ILs could induce vesicle aggregation by acting as a "glue" at lower concentrations (<1.5 mM), while at higher concentrations, the ILs disrupt the bilayer structure. Besides, ILs could result in the thinning of the bilayer, evidenced from the scattering studies. Steady-state fluorescence anisotropy and lifetime studies suggest asymmetric insertion of ILs into the lipid bilayer. MTT assay using human blood lymphocytes indicates the safe application of vesicles in the presence of ILs, with a minimal toxicity of up to 2.5 mM IL in the dispersion. These results are proposed to have applications in the field of drug delivery systems with benign environmental impact.

Impact of ionic liquids on the thermal properties of polymer composites

Abstract The integration of ionic liquids and polymer composites has become a promising way to improve their thermal properties, representing a notable advancement in the development of advanced materials for specific applications. Their thermal properties heavily influence the suitability of polymer composites for particular applications. It is imperative to understand and manipulate the thermal behavior of these composites to optimize their performance across various fields. In this mini-review, diverse polymer matrices and fillers utilized in polymer composites containing ionic liquids are categorized. Additionally, various ionic liquids employed in studies related to the thermal properties of polymer composites are identified. The impact of ionic liquids on the thermal properties of these composites is also briefly reviewed. The knowledge illustrated in this review enriches the understanding of the types of polymer matrices and fillers used in conjunction with ionic liquids, as well as their thermal properties. In a nutshell, imidazolium-based ionic liquids with tetrafluoroborate, bis(trifluoromethylsulfonyl)imide, hexafluorophosphate, halides, and hydrogen sulfate anions have the impact of improving the glass transition temperature, melting temperature, degradation temperature, and thermal conductivity of thermoplastic, thermosetting, and elastomer composites.

Unravelling ionic liquid solvent effects for a non-polar Cope rearrangement reaction.

The impact of ionic liquids (ILs) on polar reactions is well recognised, however the impact of ILs on non-polar reactions is less well understood or explored. Pericyclic Cope rearrangements are highly concerted, exhibit minimal charge localisation and pass through an uncharged but well-defined transition state, and thus provide a good mechanism for exploring the impact of IL polarizability on chemical reactivity. Recently, a 10× rate enhancement has been observed for the Cope rearrangement of 3-phenyl-1,5-hexadiene in the IL 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C4C1im][NTf2] compared to benzene. In this work we undertake a DFT based computational study (B3LYP-D3BJ/6-311+G(d,p) and M06-2X-D3/6-311+G(d,p)) of the Cope rearrangement of 3-phenyl-1,5-hexadiene and 3-propyl-hexa-1,5-diene in molecular solvents (acetonitrile, benzene and ethanol) and the IL [C4C1im][NTf2] using the SMD solvation model. The impact of benzene and [C4C1im][NTf2] on the Cope rearrangement of 3-phenyl-1,5-hexadiene is studied in more detail and we provide insight into the reason for the rate enhancement in an IL. The volume of activation is evaluated and the potential impact of 'solvent pressure' is discussed. We identify two potential mechanisms for volume effects to contribute to the rate enhancement. Solvent association energies are evaluated at the DLNPO-CCSD(T) level. Specific solvent interactions are explored through atomic partial charge, molecular orbital and bond critical point analysis, as well as via non-colvalent interaction (NCI) plots, electrostatic potential (ESP) differences and density difference Δρ(r) plots. We find that the cation and anion together form an extensive van der Waals pocket in-which the transition state (TS) sits. Electron density within the TS is anisotropically polarised via a 'push-pull' effect due to the dual cation-anion nature of the IL, stabilising the TS relative to benzene. We also provide experimental evidence that these effects are generalisable to other ILs. Overall, our aim is to provide a deeper moleuclar level understanding of the impact of ILs on non-polar reactions.

Effect of Imidazolium Nitrate Ionic Liquids on Conformational Changes of Poly(N-vinylcaprolactam).

Detailed information about molecular interactions and conformational changes of polymeric components in the presence of ionic liquids (ILs) is essential for designing novel polymeric ionic liquid-based biomaterials. In biomaterials science and technology, thermoresponsive polymers (TRPs) are widely viewed as potential candidates for the fabrication of biorelated medical devices. Here, we synthesized thermoresponsive poly(N-vinyl-caprolactam) (PVCL) polymer and investigated the effects of imidazolium-based ILs (1-ethyl-3-methyl imidazolium nitrate and 1-butyl-3-methylimidazolium nitrate) with common anion and different cations on the phase transition behavior of PVCL aqueous solution. The impact of ILs on the phase transition behavior of PVCL was monitored by using UV-visible absorption spectra, steady-state fluorescence spectroscopy, thermal fluorescence spectroscopy, and temperature dependent dynamic light scattering. Results showed significant changes in the absorbance, molecular interactions, agglomeration, and coil to globule transition behaviors of PVCL in the presence of two ILs. PVCL aqueous solution showed significant conformational changes after the addition of ILs.

Impact of Ionic Liquids on the (bio)degradability of Poly(butylene succinate)/Poly(lactic acid) blends

Bio-based and (bio)degradable polymers constitute an important material innovation because they reduce the amount of waste materials inducing persistent microplastics and can offer similar benefits to conventional polymer materials. Poly(butylene succinate) and poly(lactic acid) blends exhibit interesting properties and can be possible alternatives to some traditional polymers. Some of their properties can be tailored by adding small proportions of ionic liquids (IL) that can act as interfacial agents between PBS and PLA. In our study, samples formulated with ionic liquids display a broader morphology with thermal properties close to the PBS/PLA reference, whereas Young’s modulus is lowered in the presence of one of the IL studied. Nevertheless, the blends have a rather different ability to (bio)degrade. Indeed, disintegration experiments show that PBS/PLA/IL exhibit higher weight losses and faster fragmentation. DSC thermograms display an important decrease of PLA melting temperature after composting experiment, indicating that PLA phases are affected the most by degradation at 58°C. Our study shows that elaborating polymer materials, for which degradation processes are preferentially located in a “predegraded” dispersed phase, can be considered as a way to speed up macroscopic (bio)degradation. In the present work, morphologies, mechanical properties as well as (bio)degradability can be tailored by adding a small amount of ionic liquids.

The increase in diffraction efficiency of an azobenzene side-chain polymer using imidazolium and ammonium ionic liquids

The advancement of the information age has intensified the focus on photosensitive materials for information storage devices. To develop new photosensitive two azobenzene side-chain polymers i.e., poly(E)-3-(4-((4-nitrophenyl)diazenyl)phenoxy)propyl acrylate (polymer-1) and poly(E)-3-(4-((2-methoxy-4-nitrophenyl)diazenyl)phenoxy)propyl acrylate (polymer-2), were developed, and their diffraction efficiency was evaluated. The impact of ionic liquids (ILs) on the diffraction efficiency was evaluated by combining the polymers with imidazolium and ammonium families of ILs such as 1-butyl-3-methylimidazolium bromide [Bmim]Br, 1-ethyl-3-methyl-imidazolium-bromide [Emim]Br (imidazolium ILs), and triethylammonium methanesulfonate [TMEAS] (ammonium IL). The molecular interaction of both azobenzene side-chain polymers with the ILs was evaluated before the diffraction efficiency studies by employing UV–vis, FT-IR, and confocal Raman spectroscopies. The spectroscopic studies revealed the interaction of the polymers with the imidazolium and ammonium ILs. The mean diffraction efficiency of polymers-1 and −2 were ∼0.05 and ∼0.022%, respectively. After the addition of the ILs, the diffraction efficiency increased. The highest diffraction efficiency was achieved with the polymer-2 + [Emim]Br system of 3.5% and polymer-2 + TEMS combination of 4.03%. Therefore, although the diffraction efficiency of polymer-1 was higher than that of polymer-2, after adding the ILs, the diffraction efficiency of polymer-2 surpassed that of the polymer-1 + ILs system.

Impact of ionic liquids on absorption behaviour of natural fibers/biopolyethylene biocomposites

For many years, there has been a growing interest in technologies enabling the replacement of conventional polymer composites with new materials made from renewable raw materials. It is important to assess the behaviour of biocomposites in various environments, including humid conditions. Recently, ionic liquids have been studied as potential modificators of polymers properties, especially flame retardants. In previous study the impact of ionic liquids on thermal and mechanical properties of biocomposites was assessed. In this study the influence of ionic liquids on moisture absorption properties of biocomposites at different relative humidities (RH) was assessed. The biocomposites were built from polyethylene from renewable resources reinforced with flax or hemp fibers. The effect of the addition of 0.5, 1.0, 2.5 and 5 wt.% phosphonium ionic liquids on the moisture absorption properties of biopolyethylene biocomposite reinforced with natural fibers were tested. Mixtures of biopolyethylene, natural fibers and ionic liquid were calendered at 180 °C and then were compounded by injection moulding. The prepared samples were then characterized for their moisture uptake at 30%, 50% and 100% RH. Moisture absorption by biocomposites depended on the structure of the ionic liquid and the type of fiber. The saturation of moisture of about 0.054% was found for samples modified with tributylethylphosphonium diethyl phosphate and reinforced with flax and hemp fibers at RH 100%. The environmental resistance of the materials was found to be improved after the addition of trihexyltetradecylphosphonium bis (2,4,4-trimethylpentyl) phosphinate. Biocomposites with hemp fibers showed slightly less absorption than with flax fibers. It was also observed that ionic liquids: (bis (2,4,4-trimethylpentyl) phosphinate trihexyltetradecylphosphonate) and (bis (2-ethylhexyl) trihexyltetradecylphosphonium phosphate) protect PE biocomposites with plant fibers against mold in high humidity conditions (RH 100%).

Impact of Ionic Liquids on Effectiveness of Tuning the Emissivity of Multilayer Graphene.

Multilayer graphene has been employed as a functional material for tuning the emissivity in mid- and long-infrared range, which shows great potential for various applications, such as radiative cooling and thermal camouflage. However, the stability of the multilayer graphene is not sufficient for practical applications yet. Even though it is reported that the integrity of the multilayer graphene is compromised by ion intercalation, the detailed mechanism is rather unclear. Here, a set of ionic liquids is deployed as sources of electronic charges for tuning the emissivity of multilayer graphene. It is found that the emissivity modulator using 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([EMIm]NTf2) as the ionic liquid provides a modulation depth of about 0.52 (i.e., about 21% larger than the best-reported value) while maintaining a reasonable device lifetime. The microscopic structures of the multilayer graphene in an operational and failure modulator are investigated by scanning electron microscopy, Raman spectroscopy, X-ray diffraction. The results indicate that the modulation depth of emissivity is negatively correlated with the initial voltage, which represents the reaction potential between the ionic liquid and graphene. Furthermore, not only the chemical reactivity but also the size of both anion and cation in the ionic liquids play important roles in maintaining stability of the modulator. Therefore, a set of criteria (e.g., low initial voltage and small size of anion and cation) is proposed to select proper ionic liquids for emissivity modulation. This not only sheds light on the underlying physics of the modulator but also promotes its practical applications.

Ionic Liquids as a Sustainable Platform for Nanocellulose Processing from Bioresources: Overview and Current Status

The two-fold threats of the crisis of petrochemical industry-based plastics and serious environmental pollution have triggered the valorization of naturally occurring biopolymers to produce nanocellulose (NC). Nanocellulose has been used extensively in a variety of demanding applications due to its excellent features including biocompatibility, light weight, tunable surface properties, and improved environmental footprint. However, the sustainable production of NC is still confronted with bottlenecks to realize commercial feasibility due to poor solubility and hard processability of biopolymers using conventional hazardous solvents and reagents including concentrated sulfuric acid. The key might rest on the use of ionic liquids (ILs) that have induced a great deal of interest in recent years as powerful “green” solvents for biopolymer processing. ILs can be used as a catalyst and/or reaction medium and/or swelling agent for NC production with an eminent yield of high-quality NC under mild operating conditions coupled with proficient recoverability and recyclability. This review presents the recent technological developments of ILs-assisted proper valorization strategies of numerous bioresources for NC isolation and modification. The impact of IL cation/anion on structural changes of NC is also covered. The major advances in exploring ILs for NC surface modification reactions such as esterification, silylation, and surface plasticization as well as the microscopic insights of NC interaction with ILs are also reviewed. In view of the dominance of green chemistry principles for high purity of the recovered nanocellulose, close R&D endeavors for cheap and biodegradable ILs conjoined with emerging recycling techniques might boost sustainable commercialization.

Part II: Impact of ionic liquids as anticorrosives and additives on Ni-Co alloy electrodeposition: Experimental and DFT study

The impacts of 1-methyl-3-(2-oxo-2 ((2,4,5trifluorophenyl)amino)ethyle)-1H-imidazol-3-ium iodide ([MOFIM]I) and 1-(4-fluorobenzyl)-3-(4-phenoxybutyl)imidazol-3-ium bromide ([FPIM]Br) ionic liquids as additives on the corrosion behavior and the electrodeposition nucleation mechanism of a Ni-Co alloy were elucidated. A systematic investigation of the corrosion protection ability of Ni-Co alloys in a 3.5% NaCl solution was carried out using Tafel polarization and electrochemical impedance spectroscopy (EIS) studies. The mechanism of the Ni-Co alloy electrodeposition from the Ni70-Co30 bath was investigated using potentiodynamic cathodic polarization, cyclic voltammetry (CV) and anodic linear stripping voltammetry (ALSV). The studied ionic liquids (ILs) inhibit Co2+ and Ni2+ ion deposition due to their adsorption, which obeys the Langmuir adsorption isotherm. Quantum chemical calculations were performed at the B3LYP/6-311++G(d,p) level of the density functional theory (DFT). Several quantum parameters and natural atomic charges were calculated to investigate the correlation between the molecular structures of [MOFIM]I and [FPIM]Br and their corrosion inhibition performance. [MOFIM]I at 1 × 10−5 M shows a higher inhibition efficiency (IE%) of 53.05% than [FPIM]Br, at 44.3%. The results show that the calculated values of the quantum parameters are consistent with the experimental findings.

Impact of ionic liquids on the processing and photo-actuation behavior of SBR composites containing graphene nanoplatelets

The effects of butylpyridinium bromide-based ionic liquids (ILs) on the vulcanization kinetics, mechanical properties and photo-actuation ability of styrene-butadiene rubber (SBR) composites filled with graphene nanoplatelets (GnPs) were investigated. Two different ILs, 1-butylpyridinium bromide (BBP) and 4-methyl-1-butylpyridinium bromide (BMBP), were introduced into rubber compounds. The methodology of IL incorporation into the rubber compounds was studied as well. The ILs were added either directly as a single component or after immobilization onto the GnPs surface. High values of the modulus and tensile strength, which are important mechanical properties, were observed for the composites filled with immobilized BMBP. Freely dispersed BBP resulted in composites with the fastest scorch time, highest thermal and electrical conductivity, and best photo-actuation response of 0.230 mm.

Impact of ionic liquids on the processing and photo-actuation behavior of SBR composites containing graphene nanoplatelets

Impact of ionic liquids on the processing and photo-actuation behavior of SBR composites containing graphene nanoplatelets

Impact of Ionic Liquids on Induction of Wheat Microspore Embryogenesis and Plant Regeneration

Ionic liquids are novel compounds with unique chemical and physical properties. They can be received based on synthetic auxins like 2,4-dichlorophenoxyacetic acid or dicamba, which are commonly used hormones in microspore embryogenesis. Nevertheless, ionic liquids have not been adapted in plant in vitro culture thus far. Therefore, we studied the impact of ionic liquids on the ability to undergo microspore embryogenesis in anther cultures of wheat. Two embryogenic and two recalcitrant genotypes were used for this study. Ten combinations of ionic liquids and 2,4-dichlorophenoxyacetic acid were added to the induction medium. In most cases, they stimulated induction of microspore embryogenesis and green plant regeneration more than a control medium supplemented with only 2,4-dichlorophenoxyacetic acid. Two treatments were the most favorable, resulting in over two times greater efficiency of microspore embryogenesis induction in comparison to the control. The effect of breaking down the genotype recalcitrance (manifested by green plant formation) was observed under the influence of 5 ionic liquids treatments. Summing up, ionic liquids had a positive impact on microspore embryogenesis induction and green plant regeneration, increasing the efficiency of these phenomena in both embryogenic and recalcitrant genotypes. Herbicidal ionic liquids can be successfully used in in vitro cultures.

Evaluating Protic Ionic Liquid for Woody Biomass One-Pot Pretreatment + Saccharification, Followed by Rhodosporidium toruloides Cultivation

Woody biomass feedstocks pose challenges in their use as sustainable carbon sources due to their recalcitrance. One-pot ionic liquid-based processes are a promising bioproduction strategy to reduce water consumption (removing the washing of biomass), reduce costs, and minimize the presence of inhibitory compounds. We evaluated the one-pot ionic liquid pretreatment + saccharification configuration as a scheme for the deconstruction and conversion of two different woody feedstocks, eucalyptus, and pine. A comparative study of protic ionic liquids 2-hydroxylethylammonium acetate-based ionic liquids, bis-2-hydroxyethylammonium acetate, and cholinium lysinate for pretreatment of eucalyptus and pine was conducted. The impact of ionic liquids at 11% w/w on the saccharification and toxicity of hydrolysates containing the ionic liquid for downstream use for microbial cultivation was evaluated. Protic ionic liquids were more effective in eucalyptus than in pine pretreatment and less toxic than cholinium lysinate at concentrations ≤10% w/w. 2-hydroxylethylammonium acetate yielded the highest digestibility, of up to 75% in eucalyptus. As a proof of concept of an integrated feedstocks-to-biofuels process, we tested the growth of the fungal strain Rhodosporidium toruloides in hydrolysates with low amounts of ionic liquids and phenolic compounds. The proof of concept demonstrated the ability of Rhodosporidium toruloides to grow in the presence of 2-hydroxyethylammonium acetate (5% w/w), the importance to adjust the pH after saccharification, and the ability to consume lignin monomers. This work offers a valid starting point for further studies aimed at increasing cellulose digestibility in a one-pot configuration in the presence of protic ionic liquids.

An experimental study on the effect of ionic liquids on the structure and wetting characteristics of coal

To investigate the effect of ionic liquids on coal structure and wettability, three kinds of ionic liquids with good surface activity were selected to treat coal sample. Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to study the surface morphology, pore structure, and chemical structure of coals. Moreover, the effect of ionic liquids on the wetting characteristics of coal was studied by contact angle measurement. Compared with the raw coal, the surface morphology of coal treated with ionic liquids became rougher due to the formation of more pores and cracks. FTIR analysis showed that the skeleton of the coal was changed significantly by ionic liquids, and the content of oxygen-containing functional groups increased in the treated coal samples. XPS test revealed that the content of hydrophilic functional groups on the coal surface was increased and the hydrophobic functional group content was decreased obviously, which agreed with the results of FTIR analysis. From the results of contact angle measurement, it could be found that the treated coal samples with ionic liquids demonstrated smaller contact angle compared to the raw coal, which indicated the enhanced wettability of coal, mainly due to the changes in physicochemical structures including surface morphology and functional groups under the impact of ionic liquids. Typically, ionic liquid named [HOEtMIm][NTf2] showed the best wetting effect on coal as evidenced by smallest contact angle for the treated coal with [HOEtMIm][NTf2].

Understanding the effect of ionic liquids as adjuvants in the partition of biomolecules in aqueous two-phase systems formed by polymers and weak salting-out agents

Ionic liquids (ILs) as adjuvants in polymer-salt aqueous two-phase systems (ATPS) have been used to improve the extraction of biomolecules. However, the impact of ILs as adjuvants on the partition of biomolecules is still poorly understood. Previous works mostly focused on ATPS based on strong salting-out agents, which may mask the IL effect. In this work, ATPS formed by polyethylene glycol (PEG 400) and a weak salting-out salt ((NH4)2SO4) with a wide number of ILs as adjuvants (chloride-based combined with cholinium, imidazolium, pyrrolidinium, piperidinium, tetralkylammonium and tetralkylphosphonium cations) were investigated. The respective phase diagrams were determined, and the systems extraction performance for a wide range of biomolecules (phenolic compounds, alkaloids and amino acids) was investigated. The results obtained show that ILs as adjuvants in polymer-salt ATPS modulate the partition of biomolecules. In particular, more hydrophobic ILs significantly enhance the partition of more hydrophobic biomolecules to the PEG-rich phase (where the IL is enriched). Furthermore, the intensity of the IL effect is more pronounced when using weak salting-out agents. A linear correlation between the biomolecules and the ILs partition coefficients, and with the biomolecules octanol-water partition coefficients, was found. In most ATPS formed by polymers and salts using ILs as adjuvants, the biomolecules partition is driven by the ILs partition and by the difference in hydrophobicity between the coexisting phases.

Impact of Ionic Liquids on the Structure and Dynamics of Collagen.

The changes in the structure and dynamics of collagen treated with two different classes of ionic liquids, bis-choline sulfate (CS) and 1-butyl-3-methyl imidazolium dimethyl phosphate (IDP), have been studied at the molecular and fibrillar levels. At the molecular level, circular dichroic studies revealed an increase in molar ellipticity values for CS when compared with native collagen, indicating cross-linking, albeit pronounced conformational changes for IDP were witnessed indicating denaturation. The impedance was analyzed to correlate the conformational changes with the hydration dynamics of protein. Changes in the dielectric properties of collagen observed upon treatment with CS and IDP reported molecular reorientation in the surrounding water milieu, suggesting compactness or destabilization of the collagen. This was further confirmed by proton transverse NMR relaxation time measurements, which demonstrated that the water mobility changes in the presence of the ILs. At the fibrillar level, differential scanning calorimetry thermograms for rat tail tendon collagen fibers treated with CS show a 5 °C increase in denaturation temperature, suggesting imparted stability. On the contrary, a significant temperature decrease was noticed for IDP, indicating the destabilization of collagen fibers. The obtained results clearly indicate that the changes in the secondary structure of protein are due to the changes in the hydration dynamics of collagen upon interaction with ILs. Thus, this study on the interaction of collagen with ionic liquids unfolds the propensity of ILs to stabilize or destabilize collagen depending on the changes invoked at the molecular level in terms of structure and dynamics of protein, which also got manifested at the fibrillar level.

Evaluation of the effect of ionic liquids as adjuvants in polymer-based aqueous biphasic systems using biomolecules as molecular probes

Aqueous biphasic systems (ABS) have been largely investigated for the extraction, separation and/or purification of biomolecules. Recently, the use of ionic liquids (ILs) as additives in conventional polymer-based ABS was proposed to overcome the limited range of polarities of the coexisting phases. However, the impact of ILs on the partitioning of biomolecules on IL additivated ABS is not universal and is still poorly understood. Aiming at obtaining additional insights on this matter, the effects of the chemical structure of the IL, tie-line length (TLL) and biomolecule nature upon the partition of a series of model biomolecules were investigated. For this purpose, ternary ABS (composed of polyethylene glycol (PEG) 400, citrate buffer at pH 7.0, and water), and several quaternary ABS (composed of PEG 400, citrate buffer at pH 7.0, water and ILs at 5 wt%), were prepared using different chloride-based ILs ([C4mim]Cl, [C4mpyr]Cl, [C4mpip]Cl, [P4444]Cl and [N4444]Cl). The partition of a wide range of biomolecules in these systems (gallic acid, vanillic acid, eugenol, nicotine, caffeine, l-tryptophan, l-phenylalanine and l-tyrosine), used here as molecular probes, was studied. These solutes were chosen due to their wide range of polarities. The results obtained support the concept that ILs, when used as adjuvants in polymer-based ABS, change the coexisting phases' characteristics and modify the partition behavior of biomolecules. In general, a positive effect derived from the use of ILs as adjuvants in PEG-salt systems is observed, particularly when dealing with more hydrophobic biomolecules, whereas IL + salt ABS perform better in the extraction of more hydrophilic biomolecules. The favourable partition of more hydrophilic biomolecules in IL + salt ABS seems to be ruled by specific interactions with the IL, while the favourable partition of more hydrophobic biomolecules in PEG + salt and PEG + salt + IL seems to be governed by the differences in the phases hydrophobicities. It is shown that ILs preferentially migrate to the PEG-rich phase, and that there is a correlation between the partition coefficients of the biomolecules and ILs and the biomolecules octanol-water partition coefficients.

The impact of ionic liquids on the coordination of anions with solvatochromic copper complexes.

Solvatochromic transition metal (TM)-complexes with weakly associating counter-anions are often used to evaluate traditional neutral solvent and anion coordination ability. However, when employed in ionic liquids (IL) many of the common assumptions made are no longer reliable. This study investigates the coordinating ability of weakly coordinating IL anions in traditional solvents and within IL solvents employing a range of solvatochromic copper complexes. Complexes of the form [Cu(acac)(tmen)][X] (acac = acetylacetonate, tmen = tetramethylethylenediamine) where [X]- = [ClO4]-, Cl-, [NO3]-, [SCN]-, [OTf]-, [NTf2]- and [PF6]- have been synthesised and characterised both experimentally and computationally. ILs based on these anions and imidazolium and pyrrolidinium cations, some of which are functionalised with hydroxyl and nitrile groups, have been examined. IL-anion coordination has been investigated and compared to typical weakly coordinating anions. We have found there is potential for competition at the Cu-centre and cases of anions traditionally assigned as weakly associating that demonstrate a stronger than expected level of coordinating ability within ILs. [Cu(acac)(tmen)][PF6] is shown to contain the least coordinating anion and is established as the most sensitive probe studied here. Using this probe, the donor numbers (DNs) of ILs have been determined. Relative donor ability is further confirmed based on the UV-Vis of a neutral complex, [Cu(sacsac)2] (sacsac = dithioacetylacetone), and DNs evaluated via23Na NMR spectroscopy. We demonstrate that ILs can span a wide donor range, similar in breadth to conventional solvents.

NMR spectroscopic studies of a TAT-derived model peptide in imidazolium-based ILs: influence on chemical shifts and the cis/trans equilibrium state.

NMR spectroscopy was used to study systematically the impact of imidazolium-based ionic liquid (IL) solutions on a TAT-derived model peptide containing Xaa-Pro peptide bonds. The selected IL anions cover a wide range of the Hofmeister series of ions. Based on highly resolved one- and two-dimensional NMR spectra individual 1H and 13C peptide chemical shift differences were analysed and a classification of IL anions according to the Hofmeister series was derived. The observed chemical shift changes indicate significant interactions between the peptide and the ILs. In addition, we examined the impact of different ILs towards the cis/trans equilibrium state of the Xaa-Pro peptide bonds. In this context, the IL cations appear to be of exceptional importance for inducing an alteration of the native cis/trans equilibrium state of Xaa-Pro bonds in favour of the trans-isomers.