Amino Acid-based Ionic Liquids Research Articles

A facilitated transport membrane composed of amine-containing ionic liquid confined in a GO/CNT network for highly efficient carbon capture

Carbon capture is a key approach to manage carbon dioxide (CO2) emissions and promote net removal of CO2 from the atmosphere. Post combustion flue gas emissions from power plants contribute a significant fraction of CO2 released into the atmosphere. Membrane-based separation strategies offer environmentally sustainable and economically viable solutions for efficient CO2 capture from power plants. Facilitated transport membranes, although showing strong capability for CO2 capture at low concentrations and under humid conditions, suffer from the loss of facilitators, such as amines, leading to decline in performance over long-term operation. Ionic liquids (ILs) are chemically and thermally stable and have low vapor pressure, which is ideal to prevent aforementioned losses. However, making a thin network for effective IL confinement is still a challenge. In this work, we developed a stable high performing IL based CO2 selective membrane that can operate at temperatures as high as 80 °C under humid conditions. An amino acid-based IL (containing facilitated carriers), 1-ethyl-3-methylimidazolium glycinate, [EMIM][GLY], was used as the separating agent. In order to selectively load and confine the IL in a thin selective layer, we designed and fabricated a network composed of stacked graphene oxide (GO) nanosheets intercalated by carbon nanotubes (CNT). While CNT acts as a nanowedge that helps in increasing the nanochannels to facilitate low-resistance gas transport, GO nanosheets act as anchoring sites due to presence of various functional groups resulting in electrostatic interaction between GO and cation of IL. Due to the aforementioned reason, distribution of GO in the network plays a critical role in forming a thin, uniform selective IL layer. The GO distribution was optimized by adjusting the pH of the coating solution; after optimizing IL coating, this results in a thin, defect free selective layer, providing a membrane with high CO2 permeance of ∼1600 GPU and CO2/N2 selectivity of 400, superior to most of the reported IL membranes. This network composed of GO/CNT network not only facilitates fabrication of a stable, ultrathin, high permeance and high selectivity supported IL membrane but also provides a platform for preparation of other IL-based membranes for desired separations.

Development of cyclodextrin-electrokinetic chromatography-based strategies for the separation of ketorolac enantiomers

The development of analytical strategies enabling the chiral separation of ketorolac by electrokinetic chromatography is presented in this work. This anti-inflammatory drug is commercialised as racemic mixture but its physiological activity resides in the S-enantiomer. Different experimental conditions were investigated at acidic and neutral pH, including the use of cyclodextrins (CD) or amino acid-based ionic liquids (AAILs) ([TMA][L-Cit], [TMA][L-Arg], [TMA][L-Harg], [TBA][L-Cit], [TBA][L-Arg], and [TBA][L-Harg]) as the sole chiral selectors or the combination of a CD with AAILs or their cationic components (tetramethylammonium (TMA-OH) or tetrabutylammonium (TBA-OH)). The best conditions in terms of migration times and enantiomeric resolutions were obtained using 2 mM heptakis(2,3,6-tri-O-methyl)-β-CD (TM-β-CD) in 50 mM phosphate buffer at pH 7.0 or 2 mM TM-β-CD with 60 mM TMA-OH in 50 mM formate buffer at pH 3.0. The presence of TMA-OH in the separation medium affected considerably the electroosmotic flow (EOF) mobility which, in turn, significantly shortened the migration times for ketorolac enantiomers at pH 3.0 due to an inversion in the EOF. The multivariate optimization of the experimental conditions for the single system and for the combined system with TMA-OH enabled to obtain the separation of ketorolac enantiomers in less than 11 min with enantiomeric resolutions of 2.5 and 1.9, respectively. The single system was selected to evaluate its analytical characteristics in terms of limits of detection/quantification, accuracy, and precision, according to the International Council for Harmonization (ICH) guidelines, which resulted adequate to be applied to the analysis of pharmaceutical formulations.

Pretreatment of wastepaper with an aqueous solution of amino acid-derived ionic liquid for biochar production as adsorbent

The carbonization of lignocellulosic biomass with ionic liquids (ILs) are considered as an advantageous approach for the preparation of carbonaceous materials. The commonly used imidazolium and pyridinium based ILs have drawbacks such as toxicity, resistance to biodegradation, high cost and viscosity. These issues can be mitigated by diluting ILs with water, although excessive water content above 1 wt% can reduce the solubility of biomass. This research aims to investigate the potential of pretreating wastepaper with a “fully green” ILs, amino acid-based IL with high water content, followed by pyrolysis without IL, in enhancing the properties of biochar. For this purpose, the paper was treated with an aqueous solution of IL cysteine nitrate ([Cys][NO3]), and the IL was not involved in the pyrolysis process to prevent the formation of secondary gaseous pollutants. The findings revealed that the hemicellulose and mineral filler in the paper were eliminated during pretreatment, leading to higher carbon content but lower oxygen content. As a result, the biochar exhibited micropores of 0.42 cm3g-1 and a specific surface area of 1011.21 m2 g−1. The biochar demonstrated high adsorption capacities for Cd2+, enrofloxacin, bisphenol A, ciprofloxacin, and tetracycline, with values of 45.20 mg g−1, 49.82 mg g−1, 49.90 mg g−1, 49.88 mg g−1, and 49.65 mg g−1, respectively. The proposed mechanism for the adsorption of enrofloxacin by the biochar primarily involves physical adsorption such as pore filling and electrostatic interactions, along with chemical adsorption facilitated by graphitic nitrogen.

Dissecting the stability of Atezolizumab with renewable amino acid-based ionic liquids: Colloidal stability and anticancer activity under thermal stress

Monoclonal antibodies (mAbs) have revolutionised the biopharmaceutical market. Being proteinaceous, mAbs are prone to chemical and physical instabilities. Various approaches were attempted to stabilise proteins against degradation factors. Ionic liquids (ILs) and deep eutectic solvents (DESs) have been established as green solvents for ever-increasing pharmaceutical and biopharmaceutical applications. Hence, amino acid (AA)-based ILs, were used for the first time, for mAb stabilisation. Choline (Ch)-based DESs were also utilised for comparison purposes. The prepared ILs and DESs were utilised to stabilise Atezolizumab (Amab, anti-PDL-1 mAb). The formulations of Amab in ILs and DESs were incubated at room temperature, 45 or 55 °C. Following this, the structural stability of Amab was appraised. Interestingly, Ch-Valine retained favourable structural stability of Amab with minimal detected aggregation or degradation as confirmed by UV–visible spectroscopy and protein Mass Spectroscopy. The measured hydrodynamic diameter of Amab in Ch-Valine ranged from 10.40 to 11.65 nm. More interestingly, the anticancer activity of Amab was evaluated, and Ch-Valine was found to be optimum in retaining the activity of Amab when compared to other formulations, including the control Amab sample. Collectively, this study has spotlighted the advantages of adopting the Ch-AA ILs for the structural and functional stabilising of mAbs.

Amino Acid-Based Ionic Liquids as Biocompatible Extractants for Critical and Precious Metals

Amino Acid-Based Ionic Liquids as Biocompatible Extractants for Critical and Precious Metals

Amino acid-based ionic liquids as water-ethylene glycol additives towards superior lubricity and corrosion resistance

Two novel amino acid-based ionic liquids (AAILs) were synthesized and their tribological properties as water-ethylene glycol (W-EG) lubricant additives were investigated. The addition of 1 wt% of both AAILs to W-EG can significantly enhance the anti-corrosion, friction-reducing and anti-wear properties of the lubricants. Compared to W-EG, the coefficient of friction and wear volume are reduced by about 50% and 75%, respectively. The physical adsorption film and the tribochemical reaction film derived from AAILs collectively establish a protective barrier at the friction interface, endowing the lubricants with superior lubricity and load-carrying capacity. These two sulfur-free and halogen-free AAILs are promising for application in metal working fluids and hydraulic fluids.

Functionalization of Ordered Mesoporous Silica (MCM-48) with Task-Specific Ionic Liquid for Enhanced Carbon Capture.

This work presents new composites of AAILs@MCM-48 obtained by functionalizing ordered mesoporous silica MCM-48 with two amino acid-based ionic liquids (AAILs) ([Emim][Gly] and [Emim][Ala]) to improve carbon capture and the selectivity of CO2 over nitrogen. Thermogravimetric and XRD analyses of the composites showed that the MCM-48 support's thermal and structural integrity was preserved after the AAILs were encapsulated. An N2 adsorption-desorption study at 77 K confirmed AAIL encapsulation in the porous support. Under post-combustion flue gas conditions, both [Emim][Gly]@MCM-48 and [Emim][Ala]@MCM-48 demonstrated improved CO2 adsorption in comparison to the unmodified MCM-48, with a CO2 partial pressure of around 0.15 bar. Regarding the maximal CO2 uptake, the 40 wt.%-[Emim][Gly] composite outperformed the others at 303 K, with values of 0.74 and 0.82 mmol g-1, respectively, at 0.1 and 0.2 bar. These numbers show a 10× and 5× increase, respectively, compared to the pure MCM-48 under identical conditions. In addition, the selectivity of the composites was improved significantly at 0.1 bar: the selectivity of composites containing 40 wt.% [Emim][Ala] increased to 17, compared to 2 for pristine MCM-48. These composites outperform other silica-based studies reported in the literature, even those using amines as solvents. The presented composites offer therefore promising prospects for advancing carbon capture technology.

Probing the effect of amino acid-based ionic liquids on the CO2 (sI) and THF (sII) hydrate formation

In the present work, four acetyl glycinate-based ionic liquids (ILs) with distinct cations, namely 1-alkyl-3-methylimidazolium acetyl glycinate [C2mim][AcGly], ammonium acetyl glycinate [NH4][AcGly], N-(2-hydroxyethyl)-N,N,N-trimethyl ammonium N-acetylglycinate [N111(2OH)][AcGly] ≈ [Ch][AcGly], and N-Butyl-N,N-dimethyl-N-(2-hydroxyethyl) ammonium N-acetylglycinate [N411(2OH)][AcGly] ≈ [C4Ch][AcGly], were synthesized and tested for their effect on the formation of CO2 hydrates at elevated pressures and tetrahydrofuran (THF) hydrate formation at atmospheric pressure. The phase behaviour of the CO2 hydrates, sI type, was studied in the presence of the selected ILs using the isochoric pressure search method. The ILs shifted the phase boundary towards lower temperatures indicating a thermodynamic inhibition characteristic. The constant cooling method was used to determine the onset nucleation temperature of CO2 hydrates in the presence and absence of additives. The isothermal method was used to determine the induction time of CO2 hydrates in the presence of additives. The pressure drops in both experiments indicate the hydrate growth in the absence/presence of additives. Later, the THF hydrate crystal growth experiments at atmospheric pressure were carried out to understand the effect of additives on the sII-type hydrate growth. The crystal morphology also points out the mode of action of the tested additives on hydrate formation and growth. The extensive testing using the same additives at identical concentrations revealed the importance of the method and conditions, which become crucial in the absence of a standard screening procedure for kinetic hydrate additives.

Amino acid based ionic liquids for revitalization of sulfated lead anodes

Lead acid batteries (LABs) are currently recycled using hazardous, polluting, and energy intensive procedures. Here we report a novel LAB recycling strategy with hydrophilic amino acid-based ionic liquids (ILs) to dissolve the water-insoluble PbSO4 crystals formed during deleterious hard sulfation at the anodes and then electrodeposit metallic Pb on a new surface. We identified two ILs, [Ch][Ser] and [Ch][Thr] ILs that show dramatic solubility towards PbSO4 at room temperature. [Ch][Ser] IL was successfully used in refurbishing hard sulfated anodes that had lost 99 % of their original capacity into a fresh Pb surface. More than 75 % of the capacity was renewed after a complete treatment on a half-cell. Electrodeposition of Pb from the Pb-[Ch][Ser] complex produced a uniform Pb microstructure. A remarkable 99 % of the IL-dissolved Pb2+ ions was electrodeposited. Furthermore, we solved the first crystal structure of the compound formed between Pb2+ and the amino acid-based IL. Based on 1H Nuclear Magnetic Resonance (NMR) spectrum of PbSO4 dissolved in the [Ch][Ser] IL and single crystal X-ray diffraction (XRD) studies, we discovered that the Pb2+ was coordinated with two [Ser] molecules and displayed a hemidirected five-coordinate geometry. ILs that can selectively dissolve PbSO4 thus hold promise for an environment-friendly alternative recycling paradigm for the LAB industry.

Incorporation of Amino Acid-Functionalized Ionic Liquids into Highly Porous MOF-177 to Improve the Post-Combustion CO2 Capture Capacity.

This study presents the encapsulation of two amino acid-based ionic liquids (AAILs), 1-ethyl-3-methylimidazolium glycine [Emim][Gly] and 1-ethyl-3-methylimidazolium alanine [Emim][Ala], in a highly porous metal-organic framework (MOF-177) to generate state-of-the-art composites for post-combustion CO2 capture. Thermogravimetric analysis (TGA) demonstrated a successful encapsulation of the AAILs, with a dramatic reduction in the composites' surface areas and pore volumes. Both [Emim][Gly]@MOF-177 and [Emim][Ala]@MOF-177 had close to three times the CO2 uptake of MOF-177 at 20 wt.% loading, 0.2 bar, and 303 K. Additionally, 20-[Emim][Gly]@MOF-177 and 20-[Emim] [Ala]@MOF-177 enhanced their CO2/N2 selectivity from 5 (pristine MOF-177) to 13 and 11, respectively.

Effect of Choline Amino Acid-Based Ionic Liquids on Stability and Structure of Hemoglobin.

Ionic liquids (ILs) can stabilize or destabilize proteins, which motivates us to examine their effect on hemoglobin. The native state of hemoglobin (Hb) is disrupted at different physical conditions such as pressure, temperature, and solvents. Herein, we have monitored the stability of Hb in a nontoxic and biocompatible IL, i. e., choline amino acid-based Ils (ChAAILs), using various spectroscopic techniques like UV-Vis and fluorescence spectroscopy, circular dichroism (CD), and isothermal titration calorimetry (ITC) measurements. It was observed that Hb stays neither in its native state nor in its fully denatured state; rather, it achieves an intermediate state in the presence of ChAAILs. The research on the intermediate state of Hb is still unexplored. Research has been pursued to find a suitable ligand or IL that can stabilize the intermediate state of Hb. In that context, ChAAILs are among the best choices. Molecular docking studies unravel the binding of ChAAILs with Hb. The obtained binding energies of the docked complex are -7.2 kcal/mol and -8.7 kcal/mol for binding of Hb with [Chl][Gly] and [Chl][Met], respectively, which was in line with the ITC results. The quantum chemical calculations show that H-bond plays a significant role for the interaction between Hb and ChAAILs.

The potential of the use of deep eutectic solvents and amino acid-based ionic liquids to enhance the chiral discrimination ability of different chiral selectors in capillary electrophoresis

The effect of the combined use of amino acid-based ionic liquids (AAILs) and deep eutectic solvents (DESs) with either cyclodextrin- (CD) or cyclofructan- (CF) based chiral selectors for the chiral separation of amphetamine derivatives was investigated in the present study. A non-significant improvement in enantiomeric separation of target analytes was observed when AAILs were combined with either CF or CD. On the other side, a markedly improved chiral separation of enantiomers was obtained using the dual carboxymethyl-β-cyclodextrin/DES system, highlighting the existence of a synergistic effect. After the addition of 0.5% v/v of choline chloride-ethylene glycol, the resolution of the enantiomers of amphetamine, methamphetamine and 3-fluorethamphetamine, increased from 1.4, 1.1, 1.0 to 1.8, 1.8, and 1.5 min, and the analysis times increased from 19.54, 20.48, 18.71 to 35.71, 35.78 and 32.90 min, respectively. This was not the case for the CF/DES dual system, in which the separation of amphetamines worsened, indicating an antagonistic effect. In conclusion, DESs are a very promising additive in capillary electrophoresis that can improve the separation of chiral molecules in combination with CDs but not CFs.

CO2 adsorption on ionic liquid–modified cupper terephthalic acid metal organic framework grown on quartz crystal microbalance electrodes

BackgroundMetal-organic frameworks (MOFs) has shown ability in adsorption and separation of gases. Recently, for enhancement of efficiency of MOFs in gas adsorption, impregnation with ionic liquids are more attention. Therefore in this research, CO2 adsorption performance of Cu2(BDC)2 (Cu-MOF) and Cu3(H2N-BDC)2 (Cu-MOF–NH2) impregnated with cholinium-amino acid ionic liquids were investigated. MethodsTo improve adsorption performance, MOF was grown on the gold electrode of a quartz-crystal microbalance (QCM) which was patterned using micro-contact printing (μCP). The synthesized MOFs thin-films characterized using attenuated total reflective-Fourier transform infrared (ATR-FTIR) spectroscopy and their morphology investigated by scanning electron microscopy (SEM). Significant findsCO2 adsorption isotherms of the Cu-MOF, Cu-MOF–NH2 thin-films, and impregnated Cu-MOF with three choline amino acid-based ionic liquids (choline arginate ([Cho][Arg], choline Tyrosinate ([Cho][Tyr] and choline prolinate ([Cho][Pro]) were measured at temperatures range of 283.15–303.15 K and pressures up to 5 bar. A hybrid law (Henry–Redlich–Peterson) were successfully used to correlation experimental adsorption. The results reveal that Cu-MOF–NH2 has CO2 adsorption of 2.5 times higher than that of Cu-MOF at 5 bar and 298.15 K. Also the results reveal that [Cho][Arg]/ Cu-MOF has CO2 adsorption of 2.97 times higher than that of Cu-MOF at 5 bar and 298.15 K which helps to guide the logical design of new mixtures for gas separation applications.

Effect of Soil Washing with an Amino-Acid-Derived Ionic Liquid on the Properties of Cd-Contaminated Paddy Soil.

To reduce contamination levels in Cd-contaminated paddy soil while retaining soil characteristics, we have studied the Cd-removing ability of 15 different amino acid-based ionic liquids, which are considered to be green solvents, as soil washing agents and their impact on soil. The results indicated that the glycine hydrochloride ([Gly][Cl]) removed the most Cd, and under optimized conditions could remove 82.2% of the total Cd. Encouragingly, the morphology of the soil had not been significantly changed by the washing process. After the soil was rinsed twice with water and the pH was adjusted to 6.2 by adding Ca(OH)2, the germination index of the rice increased by 7.5%. The growth of the rice was also stimulated, with lengths and weights of the rice plants increasing by 56% and 32%, respectively, after two weeks. These experiments demonstrate that amino-acid-derived ionic liquids can be promising soil-washing agents of Cd-contaminated paddy soil.

Tracing the Effect of Replacing [Gly]- with [Ala]- and Hydroxylation of [emim]+ on the Fine-Tuning of the Transport Properties of the Corresponding Amino Acid-Based Ionic Liquids Using MD Simulation.

Natural amino acid-based ionic liquids (AAILs) composed of deprotonated amino acids, [AA]-, as anions and hydroxylated imidazolium cations provide an eco-friendly nontoxic IL family with the growing number of chemical and biochemical revolutionary applications. In this paper, the transport properties of four AAILs composed of 1-(2-hydroxyethyl)-3-methylimidazolium ([HOemim]+) and 1-ethyl-3-methylimidazolium ([emim]+) cations with alaninate and glycinate anions were studied by molecular dynamics (MD) simulations. A nonpolarizable all-atom force field with the scaled charge (±0.8e) on each of the ions was applied and compared with the unit charge model in some cases. The tunable effects of the presence of the hydroxyl group in the side chain of the imidazolium cation, the type of amino acid anion, and the varied temperature on the dynamical behavior of AAILs were investigated in detail. The experimentally compatible trends of the simulated ionic self-diffusion coefficients, ionic conductivity, and ionicity were found to be inverse to the viscosity and ionic association of these ILs as [emim][Gly] > [emim][Ala] > [HOemim][Gly] > [HOemim][Ala]. The main reason behind these trends is the higher ability of the hydroxylated cation for the hydrogen-bond formation with [AA]-. The mean square displacement (MSD), self-diffusion, and transference number of imidazolium cations are larger than those of [AA]- anions, except in the case of [HOemim][Gly]. It was found that the activation energy for diffusion of [AA]- is lower than that of [HOemim]+ but higher than that of [emim]+ in [HOemim][AA] and [emim][AA] ILs, respectively. The computed velocity autocorrelation function (VACF) showed that [Gly]-, as the lightest ion, has the shortest mean collision time and velocity randomization time among the ions, especially in the [HOemim][Gly] IL. Replacing [emim]+ with [HOemim]+, similar to the effect of decreasing temperature, causes significant decreasing of the ionic self-diffusion and increasing of the well depth of the first minimum of the ionic VACFs. Current findings show that introducing suitable functional groups in the side chain of imidazolium cations can be a viable approach for efficient engineering design and fine-tuning of the transport properties of these AAILs.

Measurement of physicochemical properties of green aqueous amino acid‐based ionic liquids and their correlation with temperature and concentration

AbstractIonic liquids have attracted immense attention due to their unique properties and potential industrial applications. Green ionic liquids such as amino acid‐based ionic liquids (AAILs) are promising solvents due to their proven low toxicity. The properties of newly known substances are unavailable, especially when they are in aqueous solutions. This information is essential, and they must be understood before employing these materials in any application for technical, safety, and economical reasons. In this study, three types of AAILs were examined, namely; 1‐octyl‐3‐methylimidazolium glycine [OMIM][Gly], 1‐octyl‐3‐methylimidazolium alanine [OMIM][Ala], and 1‐octyl‐3‐methylimidazolium proline [OMIM][Pro]. The aqueous solutions were prepared at concentrations of 1, 10, 20, and 30 wt.%. The pH and electrical conductivity were measured at room temperature and atmospheric pressure. Moreover, volumetric properties such as density, molar volume, excess molar volume, and thermal expansion were also determined at atmospheric pressure over a temperature range of 298.15–338.15 K. An empirical correlation was also developed to correlate the volumetric parameters with temperature and concentration. The results showed that AAILs solutions are alkaline in nature. Moreover, they increase the electrical conductivity of water. Additionally, molar volume, excess molar volume, and isobaric thermal expansion increased as the temperature increased, whereas the density decreased with an increase in temperature. A discussion on the effect of anions was presented. The developed empirical correlation exhibited an accurate prediction of the volumetric properties with R2 > 0.9762.

Direct Air Capture of CO2 via Ionic Liquids Derived from “Waste” Amino Acids

Direct capture of CO2 from anthropogenic emissions is an imperative societal task as the concentration of global atmospheric CO2 continues to increase drastically. The long-term goal of negative emission requires methods to remove carbon directly from the atmosphere, oceanwater, and nonpoint sources. Ionic liquids (ILs) have had a pivotal impact on finding and implementing innovative solutions that enable a more sustainable future. Here, we report the first example of an IL-enabled approach for direct CO2 capture from the atmosphere on a laboratory scale. These de novo bioderived materials represent an ideal milieu for direct carbon capture applications because of their nonvolatility and a priori low toxicity. Easily prepared liquid salts based on a mixture of three common amino acids, valine, leucine, and isoleucine, were found to be effective sorbents for ready and reversible CO2 sequestration from air despite its very low concentration. Collectively known as branched-chain amino acid, they are commonly derived from biowaste products, for example, feathers, fur, and even human hair. Therefore, the resultant ILs from the “waste” amino acids provide an exciting prospect in terms of CO2 transformation and waste utilization. We provided valuable design insights for engineering structure–property relationships in amino acid-based ILs. The impact of moisture on the absorption characteristics and capacity was evaluated in ambient conditions. We postulate that the high capture efficiency and stability of these ILs make them superior to present amine- and alkali-assisted approaches for the direct air capture of CO2 as a scalable process.

A polarisable force field for bio-compatible ionic liquids based on amino acids anions

ABSTRACT We present a polarisable force field parametrisation for amino acid-based ionic liquids based on the Amoeba framework. The force field has been obtained using accurate ab initio data and has been conceived to be as compatible as possible with the existing Amoeba parametrisation. We present here a validation mainly carried out using reference ab initio calculations and we show how the parametrisation is able to provide the structural features of the fluids to an excellent extent as well as to reproduce the intermolecular interaction energies.

Structural effects of amino acid-based ionic liquids on thermophysical properties, and antibacterial and cytotoxic activity

Mono- and dicationic amino acid-based (l-Glycine, l-Lysine, l-Arginine) ionic liquids (AAILs) were synthesized and evaluated in respecting to thermal stability, kinetic of decomposition, phase change profile, density, solubility, heat capacity, thermal storage density, antimicrobial activity and cytotoxicity. The presence of amino acid-based anion reduced the thermal stability of mono and dicationic AAILs and additional cationic head increased their thermal stability and heat capacity. AAILs with the highest number of carbon chains have the lowest glass transition temperature (Tg). The AAILs with the bulkier anion has greater thermal stability than the one with the smaller anion, which indicate that the decomposition depends on the anion reactivity and, therefore, mobility. In turn, the density of the dicationic AAILs was lower than the monocationic ones. Monocationic AAILs were more active against bacteria strains than dicationic AAILs, however all AAILs were cytotoxic at all concentrations tested. Thus, results showed that the amino AAILs synthesized may represent a potent strategy for uses requiring antimicrobial activity but biocompatibility is not a requisite.

A Computational Analysis of the Reaction of SO2 with Amino Acid Anions: Implications for Its Chemisorption in Biobased Ionic Liquids

We report a series of calculations to elucidate one possible mechanism of SO2 chemisorption in amino acid-based ionic liquids. Such systems have been successfully exploited as CO2 absorbents and, since SO2 is also a by-product of fossil fuels’ combustion, their ability in capturing SO2 has been assessed by recent experiments. This work is exclusively focused on evaluating the efficiency of the chemical trapping of SO2 by analyzing its reaction with the amino group of the amino acid. We have found that, overall, SO2 is less reactive than CO2, and that the specific amino acid side chain (either acid or basic) does not play a relevant role. We noticed that bimolecular absorption processes are quite unlikely to take place, a notable difference with CO2. The barriers along the reaction paths are found to be non-negligible, around 7–11 kcal/mol, and the thermodynamic of the reaction appears, from our models, unfavorable.