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This work is on the synthesis and the characterization of natural deep eutectic solvents based on monoterpenoids. Low viscous fluids with suitable physicochemical properties are produced. Therefore, considering their null toxicity, biodegradability, and low cost make them a suitable platform for developing sustainable solvents for various processes and applications. A theoretical study considering quantum chemistry and classical molecular dynamics is reported providing a nanoscopic characterization of structure, dynamics, and hydrogen bonding in the considered fluids. The reported results provide an analysis of the properties of this new family of solvents, thus providing the required information for developing structure–property relationships for proper solvent design into a sustainable chemistry framework.
This work presents a generic strategy to create a series of metal mercaptides complexes via coordination self-assembly between transition metals (Mn, Cu, Co, Fe, and Ni) and cysteine (Cys) by forming the sulfur-metal bridges. This strategy involves dissolving metal chlorides and Cys into deep eutectic solvents (DES), followed by the precipitation of metal mercaptides complexes (such as Cys-Mn) by adding water as an antisolvent, where DES serves as the solvent, shape directing, and capping agent, thereby preventing the formation of other metal impurities. Interestingly, the prepared complexes possess both laccase and peroxidase-like properties, allowing the design of a technique for the detection of L-3,4-dihydroxyphenylalanine (l-DOPA) and uric acid, respectively. The prepared Cys-Mn can linearly oxidize l-DOPA with its concentrations from 0.1-130 μM and the detection limit was calculated to be 75.5 nM. Additionally, the Cys-Mn can mimic the activity of peroxidase towards oxidization of o-phenylenediamine at neutral pH, allowing single-step and one-pot cascade reactions for visual and fluorometric measurements of uric acid that could work in the range of 0.2–500 μM uric acid with a detection limit of 0.06 μM and 0.054 μΜ, respectively. The assay was successful in detecting uric acid in serum and urine samples with RSD ranging from 7.3%-10.2% and 3.0%–8.5% respectively, suggesting that it may prove useful in medical diagnostic testing.
During the past decade, deep eutectic solvents (DESs), emerging as green, versatile and adjustable alternatives to traditional solvents, have attracted intensive interests and immense research in various research fields. Especially DESs show quite a remarkable potential dissolving capability, due to their ability to donate as well as accept protons and electrons. A thorough and deep understanding of the microstructure, interactions and dissolving mechanism within DESs plays a key role in acquiring a task-specific DES. Quantum chemistry (QC) calculations provide structure-property-function relationship based on the molecular description and make up for the limitations of the current experimental techniques, showing promises for DESs screening and design. This paper summarizes the current research involving QC calculations and combined experiments, on investigating the structure, physicochemical properties and dissolving capability of DESs from the macroscopic and microcosmic perspective. This paper highlights and discusses the dissolving mechanism of various compounds in DESs, covering the recent successes in applying QC calculations to select the appropriate DESs as dissolving media. Furthermore, a brief analysis of perspectives and challenges for the future research in this field is presented. It is expected that this paper will inspire the future development of DESs from synthesis design to various designated applications.
Deep eutectic solvents (DES) are recently synthesized to cover limitations of conventional solvents. These green solvents have wide ranges of potential usages in real-life applications. Precise measuring or accurate estimating thermophysical properties of DESs is a prerequisite for their successful applications. Density is likely the most crucial affecting characteristic on the solvation ability of DESs. This study utilizes seven machine learning techniques to estimate the density of 149 deep eutectic solvents. The density is anticipated as a function of temperature, critical pressure and temperature, and acentric factor. The LSSVR (least-squares support vector regression) presents the highest accuracy among 1530 constructed intelligent estimators. The LSSVR predicts 1239 densities with the mean absolute percentage error (MAPE) of 0.26% and R² = 0.99798. Comparing the LSSVR and four empirical correlations revealed that the earlier possesses the highest accuracy level. The prediction accuracy of the LSSVR (i.e., MAPE = 0. 26%) is 74.5% better than the best-obtained results by the empirical correlations (i.e., MAPE = 1.02%).
Deep eutectic solvents (DESs) are one of the most rapidly evolving types of solvents, appearing in a broad range of applications, such as nanotechnology, electrochemistry, biomass transformation, pharmaceuticals, membrane technology, biocomposite development, modern 3D-printing, and many others. The range of their applicability continues to expand, which demands the development of new DESs with improved properties. To do so requires an understanding of the fundamental relationship between the structure and properties of DESs. Computer simulation and machine learning techniques provide a fruitful approach as they can predict and reveal physical mechanisms and readily be linked to experiments. This review is devoted to the computational research of DESs and describes technical features of DES simulations and the corresponding perspectives on various DES applications. The aim is to demonstrate the current frontiers of computational research of DESs and discuss future perspectives.
With the growth of protein structure data, the analysis of molecular interactions between ligands and their target molecules is gaining importance. PLIP, the protein–ligand interaction profiler, detects and visualises these interactions and provides data in formats suitable for further processing. PLIP has proven very successful in applications ranging from the characterisation of docking experiments to the assessment of novel ligand–protein complexes. Besides ligand–protein interactions, interactions with DNA and RNA play a vital role in many applications, such as drugs targeting DNA or RNA-binding proteins. To date, over 7% of all 3D structures in the Protein Data Bank include DNA or RNA. Therefore, we extended PLIP to encompass these important molecules. We demonstrate the power of this extension with examples of a cancer drug binding to a DNA target, and an RNA–protein complex central to a neurological disease. PLIP is available online at https://plip-tool.biotec.tu-dresden.de and as open source code. So far, the engine has served over a million queries and the source code has been downloaded several thousand times.
Graphically revealing interaction regions in a chemical system enables chemists to quickly recognize where significant interactions have formed. Reduced density gradient (RDG) has already been widely employed in literatures to visually exhibit weak interaction regions, in fact it also has the ability of revealing chemical bonding regions. Unfortunately, RDG cannot clearly show both types of the interactions at the same time. In this work, we propose a new real space function named interaction region indicator (IRI), which is a slight modification on RDG. We found IRI can reveal chemical bonding and weak interaction regions equally well, which brings great convenience in the study of various chemical systems as well as chemical reactions. IRI is also compared with atom‐in‐molecules (AIM) topology analysis of electron density, it is demonstrated that IRI has the ability to reveal additional interactions to provide chemists a more complete picture. In addition, we put forward a variant of IRI named IRI‐π, which is dedicated to reveal interactions of π electrons. It is found that IRI‐π can not only distinguish type of π interactions but also exhibit π‐interaction strength. IRI and IRI‐π have been efficiently implemented in our freely available Multiwfn wavefunction analysis code (http://sobereva.com/multiwfn), and are expected to become new useful members of computational chemists′ toolbox in studying chemical problems. Finding IRI: Interaction region indicator (IRI) is a very simple function able to graphically reveal all kinds of interactions in a chemical system, and its variant IRI‐π is able to distinguish types and exhibit strengths of π‐interactions.
Treatment of microbial-related infections remains a clinical challenge that has been slowly aggravating over recent years, due to the dissemination of resistance against currently applied treatment protocols. In this current scenario, the design of novel treatment approaches is of great importance, being a prominent focus of the scientific community. In recent years deep eutectic systems (DES) have gained the attention of the scientific community due to their remarkable physicochemical and biological properties, versatility, and compliance with the green chemistry metrics. In this work, DES containing a monoterpenoid (thymol (THY) and menthol (ME)) in combination with ibuprofen (IBU) were formulated and characterized via thermal analyses and NMR spectroscopy. The biological activity of the most promising formulations was then explored, with focus on its antimicrobial and anticancer activity. Both ME and THY-based formulations presented relevant antibacterial activity against the panel of microorganisms tested. Among the THY-based formulation tested, THY:IBU 3:1 molar ratio, showed the highest antibacterial activity, affecting all tested microorganisms, while ME:IBU 3:1 molar ratio was only effective against Gram-positive bacteria and Candida albicans. Furthermore, both ME and THY-based formulations revealed cytotoxic effect towards the cancer cell model used (HT29), where ME:IBU 3:1 stood out as the most selective towards cancer cells without compromising normal cells viability. Overall, the results obtained highlight the potential use of terpene-based THEDES formulations that, due to their enhanced thermal properties, may represent a versatile alternative in several biomedical applications where an effective antimicrobial or anticancer therapeutic action remains a challenge.
The characterization of terpene-based eutectic solvent systems is performed to describe their solid–liquid phase transitions. Physical properties are measured experimentally and compared to computed correlations for deep eutectic solvents (DES) and the percentage relative error er for the density, surface tension, and refractive index is obtained. The thermodynamic parameters, including the degradation, glass transition and crystallization temperatures, are measured using DSC and TGA. Based on these data, the solid–liquid equilibrium phase diagrams are calculated for the ideal case and predictions are made using the semi-predictive UNIFAC and the predictive COSMO RS models, the latter with two different parametrization levels. For each system, the ideal, experimental, and predicted eutectic points are obtained. The deviation from ideality is observed experimentally and using the thermodynamic models for Thymol:Borneol and Thymol:Camphor. In contrast, a negative deviation is observed only experimentally for Menthol:Borneol and Menthol:Camphor. Moreover, the chemical interactions are analyzed using FTIR and 1H-NMR to study the intermolecular hydrogen bonding in the systems.
The aim of this work is to shed light on the origins of unique properties by studying the relationship between viscosity and hydrogen‐bonding interactions of terpene‐based natural deep eutectic solvents (NADES). Five systems including camphor/formic acid, menthol/acetic acid, menthol/β‐citronellol, menthol/lactic acid, and thymol/β‐citronellol are prepared (molar ratio 1:1). Their structures and nature of the associated hydrogen bonds are investigated through multiple methods and theories. The viscosity of NADES is consistent with the product of hydrogen‐bond number and lifetime. Through visualization of non‐covalent interactions, terpene‐acid‐based NADES with single sites show the lowest viscosity among the studied systems because of weak and unstable hydrogen bonding. Inversely, multi‐site terpene‐acid‐based NADES possess relatively high viscosity. Owing to the stability of hydrogen bonds in the network, the terpene‐terpene‐based system is in the middle level of viscosity. In‐depth analysis of these hydrogen bonds shows that they can be classified as “weak to medium” and are mainly derived from electrostatic interactions. Moreover, there is an obvious connection between viscosity and hydrogen‐bonding strength (integrated core‐valence bifurcation index) in the networks. The discovery of intrinsic rules between viscosity and hydrogen‐bonding interactions is beneficial for the design of novel low‐viscosity NADES in the future.
Monoterpenes, comprising hydrocarbons, are the largest class of plant secondary metabolites and are commonly found in essential oils. Monoterpenes and their derivatives are key ingredients in the design and production of new biologically active compounds. This review focuses on selected aliphatic, monocyclic, and bicyclic monoterpenes like geraniol, thymol, myrtenal, pinene, camphor, borneol, and their modified structures. The compounds in question play a pivotal role in biological and medical applications. The review also discusses anti-inflammatory, antimicrobial, anticonvulsant, analgesic, antiviral, anticancer, antituberculosis, and antioxidant biological activities exhibited by monoterpenes and their derivatives. Particular attention is paid to the link between biological activity and the effect of structural modification of monoterpenes and monoterpenoids, as well as the introduction of various functionalized moieties into the molecules in question.
A series of long-chain imidazolium-based ionic liquids (ILs) 1-dodecyl-3-methylimidazolium chloride (1), 1,3-bis(octyloxycarbonylmethyl)imidazolium chloride (2) and 1-dodecyloxycarbonylmethyl-3-methyloxycarbonylmethylimidazolium chloride (3), were synthesized and evaluated as antimicrobials against a wide range of bacteria and fungi. Toxicological risks of selected compounds were assessed using the biomodels of various organizational and functional levels. All compounds demonstrated significant antibacterial and antifungal activity. The toxicity results indicate that ILs containing an ester functional group in the alkyl side chain exhibited much lower toxicity to D. magna and acetylcholinesterase inhibition than ILs with long alkyl chain without polar substituents, while toxicity toward Danio rerio was on a par. The HSA-binding properties of ILs have been investigated by FT-IR spectroscopy technique and the evidences have suggested that the test compounds could induce the protein unfolding and changes in the secondary structure of HSA. The docking studies were carried out to provide structural insights of the ILs–HSA-binding interactions. The docked compounds exhibit a high binding affinity to HSA and the hydrogen bonding, hydrophobic and electrostatic interactions played a major role in the process. ILs 2 and 3 may be perspective for further investigation as potential low-toxic biocides with high antimicrobial activity against reference and clinical multidrug-resistant strains.
The thermal conductivities of selected deep eutectic solvents (DESs) were determined using the modified transient plane source (MTPS) method over the temperature range from 295 K to 363 K at atmospheric pressure. The results were found to range from 0.198 W·m−1·K−1 to 0.250 W·m−1·K−1. Various empirical and thermodynamic correlations present in literature, including the group contribution method and mixing correlations, were used to model the thermal conductivities of these DES at different temperatures. The predictions of these correlations were compared and consolidated with the reported experimental values. In addition, the thermal conductivities of DES mixtures with water over a wide range of compositions at 298 K and atmospheric pressure were measured. The standard uncertainty in thermal conductivity was estimated to be less than ± 0.001 W·m−1·K−1 and ± 0.05 K in temperature. The results indicated that DES have significant potential for use as heat transfer fluids.
Deep eutectic solvents have aroused a great level of interest in recent years. In this regard, a simple model is presented for the calculation of viscosities of a wide range of deep eutectic solvents. Based on a databank covering 156 deep eutectic solvents of different natures, a straightforward, simple, accurate, and global correlation is proposed. This model, which covers wide ranges of temperatures, requires the critical pressure, critical temperature, and one reference viscosity data as its input parameters. Since the model has one set of global constants, it can be used for any DES. Apart from this correlation, a second approach was also taken in this study, which was to obtain the constants of the Vogel-Fulcher-Tamman (VFT) model for all of the investigated DESs. With this approach, the constants are individually fit to each DES, therefore, no physical properties are required as input. The average absolute relative deviation errors of 10.4% and 1.7% for the proposed model and the VFT model, respectively, are compared to literature models. The results indicate that the proposed correlation, in addition to its acceptable accuracy and simplicity, is a general model for the estimation of the viscosities of different-natured deep eutectic solvents.
A stricter definition of a deep eutectic solvent (DES) is urgent, so that it may become a sound basis for further developments in this field. This communication aims at contributing to deepening the understanding of eutectic and deep eutectic mixtures concerning their definition, thermodynamic nature and modelling. The glut of literature on DES applications should be followed by a similar effort to address the fundamental questions on their nature. This hopefully would contribute to correct some widespread misconceptions, and help to establish a stringent definition of what a DES is. DES are eutectic mixtures for which the eutectic point temperature should be lower to that of an ideal liquid mixture. To identify and characterize them, their phase diagrams should be known, in order to compare the real temperature depression to that predicted if ideality is assumed, and to define composition ranges for which they are in the liquid state at operating temperatures. It is also shown that hydrogen bonding between the DES components should not be used to define or characterize a DES, since this would describe many ideal mixtures. The future of deep eutectic solvents is quite promising, and we expect that this work will contribute to the efficient design and selection of the best DES for a given application, and to model properties and phase equilibria without which the process design is impractical.
Deep eutectic solvents (DESs) constitute a new class of ionic solvents that has been developing at a fast pace in recent years. Since these solvents are commonly suggested as green alternatives to organic solvents, it is important to understand their physical properties. In particular, polarity plays an important role in solvation phenomena. In this work, the polarity of different families of DESs was studied through solvatochromic responses of UV-vis absorption probes. Kamlet-Taft α, β, π* and ETN parameters were evaluated using different solvatochromic probes, as 2,6-Dichloro-4-(2,4,6-triphenyl-N-pyridino)-phenolate (Reichardt’s betaine dye 33), 4-nitroaniline, and N,N-diethyl-4-nitroaniline for several families of DESs based on cholinium chloride, DL-Menthol and a quaternary ammonium salt ([N4444]Cl). In addition, a study to understand the difference in polarity properties between DESs and the corresponding ILs, namely ILs based on cholinium cation and carboxylic acids as anions ([Ch][Lev], [Ch][Gly] and [Ch][Mal]), was carried out. The chemical structure of the hydrogen bond acceptor (HBA) in a DES clearly controls the dipolarity/polarizability afforded by the DES. Moreover, Kamlet-Taft parameters do not vary much within the family, but they differ among families based on different HBA, either for DESs containing salts ([Ch]Cl or [N4444]Cl) or neutral compounds (DL-Menthol). A substitution of the HBD was also found to play an important role in solvatochromic probe behaviour for all the studied systems.
The nanostructure of a series of choline chloride-urea-water deep eutectic solvent mixtures was characterized across a wide hydration range, using neutron total scattering and empirical potential structure refinement (EPSR). Since structure is significantly altered, even at low hydration levels, reporting DES water content is important. However, DES nanostructure is retained to a remarkably high level of water (10w, ~42 wt.% H2O) because of solvophobic sequestration of water into nanostructured domains around cholinium cations. At 51 wt. % / 83 mol % H2O this segregation becomes unfavorable, and the DES structure is disrupted, instead dominated by water-water and DES-water interactions. At and above this hydration level, the DES-water mixture is best described as an aqueous solution of DES components.
Type V deep eutectic solvents are a novel class of sustainable solvents. They are prepared by physically mixing solid, non-ionic components and are characterized by strong negative deviations from thermodynamic ideality. This work provides guidelines for the rational design of these solvents and reviews some of their recent applications. Emphasis is given on the choice of hydrogen bond donors and acceptors to achieve the necessary liquid phase non-ideality, namely on the use of pairs of molecules with high polarity asymmetry, and stresses the importance of assessing their solid-liquid phase diagrams. Polymorphism and cocrystal formation are also briefly addressed, together with predictive methodologies that have been developed to estimate their properties.
Deep eutectic solvents (DESs) are binary or ternary mixtures of compounds that possess significant melting point depressions relative to the pure isolated components. The discovery of DESs has been a major breakthrough with multiple fields benefitting from their low cost and tunable physiochemical properties. However, tailoring DESs for specific applications through their practically unlimited synthetic combinations can be as much a hindrance as a benefit given the expense and time‐required to perform large‐scale experimental measurements. This emphasizes the need for fast computational tools capable of making accurate predictions of DES physiochemical properties exclusively from molecular structure. Yet, these systems are not trivial to model or simulate at the atomic level given their exceedingly nonideal behaviors, asymmetry of components, and the complexity of their molecular electrostatic interactions. Despite the challenge, computational reports featuring quantum mechanical (QM) methods have provided significant understanding into the relationship between the melting point depression and the unique and complex hydrogen bond network present in DESs. Classical molecular dynamics (MD) methods have examined bulk‐phase solvent organization in conjunction with thermodynamic and transport properties. Machine learning (ML) algorithms have shown great potential as structure–property prediction tools. Overall, this review highlights computational accomplishments that have meaningfully advanced our understanding of DESs and strives to give the reader a sense of the overall strengths and drawbacks of the methodologies employed while hinting at promises of advances to come. This article is categorized under: Software > Simulation Methods This review highlights computational accomplishments that have meaningfully advanced our understanding of deep eutectic solvents (DESs).
The suitability of using Deep Eutectic Solvents for chemical Enhanced Oil Recovery operations are analyzed from the nanoscopic viewpoint using classical molecular dynamics simulations. Four different eutectics were considered based on Choline Chloride, as hydrogen bond acceptor, plus urea, glycerol, ethylene glycol or levulinic acid, as hydrogen bond donors. Two main effects were studied to study their suitability: i) eutectic solutions – oil interfacial tension and ii) wettability of oil droplets on calcite surfaces in presence of eutectic solutions to study the possible evolution from oil wet to water wet behavior. Different eutectic concentrations in water halide solutions, as a model of brine in reservoirs, are studied. The main physical properties such as interfacial tension or contact angle are analyzed as well as the behavior of the oil in presence of the eutectic solutions in terms of intermolecular forces, energy of interactions, molecular arrangements and adsorption at the corresponding interfaces. The reported results allow to infer the nanoscopic effects on the basis of the use of eutectics for enhanced oil recovery operations, thus providing the information which may contribute to the development of environmentally friendly operations using these low-cost green solvents.
Biomass recalcitrance hinders efficient utilization of lignocellulosic biomass, making pretreatment process a crucial step for successful biorefinery process. Pretreatment processes have been developed for processing biomass, while technical obstacles including intensive energy requirement, high operational cost, equipment corrosions resulted from currently applied techniques promote the development of new pretreatment process for biomass. The deep eutectic solvent (DES) has been recognized as a promising solvent for biomass pretreatment, although the DES application toward biomass is still in its nascent stage. This review summarized the current researches using DES for biomass pretreatment, focusing particularly on lignin extraction and saccharification enhancement of lignocellulosic biomass. The mechanisms for biomass fractionation using DES as agents are introduced. Prospect and challenge were outlined.
As promising green alternative solvents for ionic liquids, deep eutectic solvents (DESs) have been widely used in separation, catalysis, synthesis, etc. Most of the researches have focused on the application of DESs formed by hydrogen bonding interaction. In this paper, amide-based type IV DESs were synthesized from metal chloride and amides with coordination interaction, and they were used for extractive desulfurization of fuels. The experimental results showed the DES ZnCl2/N-methylformanilide (ZnCl2/MFA) had the highest desulfurization efficiency with the Nernst partition coefficient (KN) as 2.41. The extraction mechanism was firstly explored by Fourier transform infrared spectrometer (FT-IR) and ¹H nuclear magnetic resonance (¹H NMR). Then density functional theory (DFT) study suggested that π-π interactions and C-H···π interactions contribute mainly to effective removal of DBT from fuel oil by DESs.
The viscosity of natural deep eutectic solvent (NADES) plays an important role in determining how they are used industrially. However, most of NADES systems exhibit a relatively high viscosity. Terpene-based mixtures have attracted widespread interest as relatively low-viscosity solvents. The goal of this work was to shed light on the nature of their unique properties by exploring the relationship between viscosity and non-covalent interactions. The microstructure and characteristics of different NADES were investigated through multiple methods and theories. Among these systems, ketone-based and alkenyl alcohol-based terpenoids act as hydrogen bond acceptors, and phenol-based terpenoids are prone to be hydrogen bond donors. The viscosity of studied NADES was low and was synthetically influenced by the number and lifetime of hydrogen bond. To some extent, their viscosity was consistent with the hydrogen-bond lifetime. Additionally, a positive correlation was found between their viscosity and non-bonded interactions energy. The relatively high viscosity mainly was driven by the enhancement of van der Waals force. Through visualization of non-covalent interactions, the results indicated that the appropriate strength and high fluctuations of interactions in the systems were necessary for forming low-viscosity NADES. Furthermore, the vertices on the electrostatic potential of terpenoids are pivotal factors influencing the property of final complex via quantitative analysis of molecular surface. It can be utilized to preliminarily assess the viscosity of NADES without the study of the entire system. The discovery of intrinsic rules paves the way for rational and effective design of novel low-viscosity NADES in the future.
Deep eutectic solvents have emerged in green chemistry only seventeen years ago and yet resulted in a plethora of publications covering various research areas and diverse fields of application. Deep eutectic solvents appear as promising alternatives to conventional organic solvents due to their straightforward preparation using highly accessible and natural compounds. They display also high tunability. Here we present the classification and preparation methods of deep eutectic solvents. We detail their physicochemical properties such as phase behavior, density, viscosity, ionic conductivity, surface tension, and polarity. Properties are controlled by the choice of the forming compounds, molar ratio, temperature, and water content.
The use of deep eutectic solvents in the electrochemical treatment of the surfaces of manganese stainless steel has been demonstrated for the first time. The comparative characteristics of Ethaline, Glyceline and Reline, choline chloride based deep eutectic solvents, are examined in this work. It is proved that the process of anodic treatment of the manganese stainless steel in these electrolytes takes place under diffusion control and is characterized by selective dissolution of Fe. Moreover, it was shown that the anodic processing mechanism for Mn-containing stainless steel does not differ between electrolytes. At the same time, however, it was found that the process of anodic dissolution of stainless steel in Ethaline, Glyceline and Reline proceeds at noticeably different rates, due to the different physicochemical properties of these electrolytes. Special attention was paid to the surface characterization of stainless steel samples electropolished in Ethaline, Glyceline and Reline.
In the current study, molecular dynamics simulations were conducted to investigate the structural and dynamical properties of glucose-based Deep Eutectic Solvents (DESs) at different molar ratios (the mixture of glucose and choline chloride with the molar ratios of 1:3, 1:1 and 3:1). Accordingly, the interaction energies of different species and structural properties such as atom-atom radial distribution functions (RDFs), the hydrogen-bonding network between species, and spatial distribution functions (SDFs) were computed to understand effective interactions in the eutectic mixture formation. It was found that the insertion of glucose molecules reduced the accumulation of chloride anions around choline cations, eventually decreasing the interaction between the choline chloride ion pairs. Moreover, the possible explanations for the thermos-physical properties of DESs, such as the shear viscosity and density, have been provided. Dynamical properties of DES were evaluated by calculating the mean-square displacement (MSD) and the velocity autocorrelation function (VACF) for the centers of the mass of the ions and glucose molecules. MSD analysis results were then used to calculate the self-diffusion parameter by applying the Einstein relation. The simulation results indicated that increasing the temperature led to easing the migration of the molecules and decreasing the dependence of the movement of the molecules on each other. This growing trend of migration may lead to an increase in the self-diffusion coefficient of molecules. Structural analysis revealed that a ratio of 1:1 of glucose: choline chloride could provide the best condition to maintain the low melting point of the mixture due to the strong hydrogen-bonded network between the two species.
Nowadays large quantities of volatile organic compounds (VOCs) are used, although they present serious disadvantages. Developing alternative reaction media capable of replacing VOCs is of the upmost relevance. Among the surrogates, deep eutectic solvents (DESs) have received particular attention. This revision gathers all the organocatalytic transformations carried out in DESs, benchmarking these protocols against the corresponding transformation operating in traditional VOC solvents.
The structural properties of choline chloride-based deep eutectic solvents (DESs) are investigated using the molecular dynamics simulations approach. The effect of different donor groups i.e. ethylene glycol, malic acid, tartaric acid, glycerol and oxalic acid with choline chloride acceptor in the formation of supramolecular structures are studied by employing different functionals. Different thermodynamic properties such as heat of formation, charge mobility, interaction energies, electronic energy, zero-point energy, dipole moment, heat capacity, entropy, bond angles and dihedral angles of the eutectic mixture are anticipated. Among all the deep eutectic solvents, DES3 is found to be more stable in terms of an extensive hydrogen-bonded network with maximum heat of formation (-5.94×10⁴ eV). The extensive hydrogen bond network in DES3 also leads to substantially higher polarizability (222.124 au), thermal stability (345.14 kcal mol⁻¹), heat capacity (121.43 Calmol⁻¹K) and entropy (222.04 Calmol⁻¹K⁻¹). However, the viscosity of DES1 is found lowest (37 cP) with the highest conductivity (6.34 mS cm⁻¹), dipole moment (16.14 Debye) and electron mobility (0.0919644 eV) and hole mobility (0.0477745 eV). This work will provide a new visualization of the supramolecular structure of choline chloride-based DESs with physical and electronic properties
Nuclear energy owing its low cost and being environmentally benign extensively uses uranium dioxide as fuel and is one such alternative which can solve global issues related to energy requirements. With the same intention, firstly we synthesized uranium type (IV) deep eutectic solvent (UT4D) employing uranyl nitrate hexahydrate (UNH) and Urea via mechanochemical synthesis which is indeed the first report on actinide deep eutectic solvent (AnDES). The optimum mole fraction for formation of DES was found to be 0.2:0.8 for UNH: Urea respectively which was further confirmed using thermodynamic phase diagram. The formation of DES was confirmed using Fourier Transform Infrared (FTIR) spectroscopy. Various physical properties were also evaluated for UT4D such as melting point, moisture contents, viscosity, and density. Thermal studies suggested that UT4D is stable from − 5.2 to 300 °C and there is a strong interaction parameter obtained in the present UT4D which was attributed to hydrogen bonding and the complexation of urea with UNH. Uranium ion was found to exist in U(VI) oxidation state in the form of oxo uranyl ion in UT4D. Electrochemical investigation suggested the stabilization of most unstable U(V) state by virtue of the formation of hydrogen bonded complex uranium and urea in the DES. Further scanning the potential to more negative direction leads to further reduction of U(V) ion to UO2. The optimized electrochemical parameters were further used for the electrosynthesis of UO2 nanoparticles (UDNPs) and thus offer a very green and cost-effective synthesis of UDNPs.
The precise regulation of the deep eutectic solvents (DESs) system has an important influence on its structure, performance and application. In this work, choline chloride (ChCl) and three kinds of butanediols are used as hydrogen bond acceptors and donors, respectively. The research focuses on the influence of two hydroxyl positions in butanediols on the structure and properties of DES systems with various characterization techniques. The results show that the DES system composed of 1, 2-butanediol and ChCl (the distance of two hydroxyl group is closest) possesses the largest conductivity (1.26 mS cm⁻¹) and the lowest viscosity (56.99 cP). Moreover, using ChCl and 1, 2-butanediol as the electrolyte, the corresponding voltage of activated carbon (AC) based supercapacitor can reach 2 V, the specific capacitance can reach 116 F g⁻¹ and the highest energy density is 16.14 Wh kg⁻¹. More importantly, this work uses the DFT model to design and verify the DES systems in detail, and then explain the mechanism of the influence of the hydroxyl position on the structure and electrochemical performance of the DES system from a theoretical perspective. Obviously, the DES systems having difference structures and DFT calculation proposed in this article provide a significant way and reference for in-depth understanding of DES electrolytes and applications.
Deep eutectic solvents (DESs) are an emerging class of mixtures characterized by significant depressions in melting points compared to those of the neat constituent components. These materials are promising for applications as inexpensive "designer" solvents exhibiting a host of tunable physicochemical properties. A detailed review of the current literature reveals the lack of predictive understanding of the microscopic mechanisms that govern the structure-property relationships in this class of solvents. Complex hydrogen bonding is postulated as the root cause of their melting point depressions and physicochemical properties; to understand these hydrogen bonded networks, it is imperative to study these systems as dynamic entities using both simulations and experiments. This review emphasizes recent research efforts in order to elucidate the next steps needed to develop a fundamental framework needed for a deeper understanding of DESs. It covers recent developments in DES research, frames outstanding scientific questions, and identifies promising research thrusts aligned with the advancement of the field toward predictive models and fundamental understanding of these solvents.
Deep eutectic solvents (DES) were introduced as an alternative to ionic liquids (IL) to overcome the drawbacks of IL solvents. However, some authors consider them to be a subclass of ILs. In contrast, other authors emphasize that these are by their nature independent, different groups of substances. Thus, the question arises: Which solvent group should DESs belong to? Maybe a new class should be added to the existing ones. The aim of this work is to attract the attention of researchers using DES in their studies to the need for a proper use of terms.
Ab initio molecular dynamics simulations at elevated temperature are carried out to investigate the microscopic structure of liquid mixtures (deep eutectic solvents) com- posed of 1:1, 1:2 choline chloride:ethylene glycol ([Ch]Cl:EG) and 1:2:1 ([Ch]Cl:EG:water). In the present study, we aim to understand the composition effect on the choline chlo- ride:ethylene glycol deep eutectic solvent and whether there is a specific composition in these solvents with marked special behavior at the microscopic level. The role of hydrogen bonds between all components was investigated through distribution func- tions. The structures are governed by the balance of hydrogen bond networks and the different populations of the EG molecule conformations. In the water-containing system, water competes for association with the anion. Also, the charge distribution analysis, which is consistent with structural analysis, indicates that the results are not impacted by changing composition. In addition, the charge transfer observed between ions, EG and water molecules appears to be sizable.
The current study deals with modeling of CO2 solubility in various deep eutectic solvents (DESs). Various artificial intelligent methods including PSO-ANN, PSO-ANFIS, LSSVM, and newly proposed correlation were developed, examined and comparatively evaluated. Comprehensive data were gathered from literature and LSSVM and MPR models were found robust and precise models for estimating CO2 solubility in DESs.
Natural deep eutectic solvents (NADES) are mixtures of naturally derived compounds with a significantly decreased melting point due to the specific interactions among the constituents. NADES have benign properties (low volatility, flammability, toxicity, cost) and tailorable physicochemical properties (by altering the type and molar ratio of constituents), hence they are often considered as a green alternative to common organic solvents. Modeling the relation between their composition and properties is crucial though, both for understanding and predicting their behavior. Several efforts were done to this end, yet this review aims at structuring the present knowledge as an outline for future research. First, we reviewed the key properties of NADES and relate them to their structure based on the available experimental data. Second, we reviewed available modeling methods applicable to NADES. At the molecular level, density functional theory and molecular dynamics allow interpreting density differences and vibrational spectra, and computation of interaction energies. Additionally, properties at the level of the bulk media can be explained and predicted by semi‐empirical methods based on ab initio methods (COSMO‐RS) and equation of state models (PC‐SAFT). Finally, methods based on large datasets are discussed; models based on group contribution methods and machine learning. A combination of bulk media and dataset modeling allows qualitative prediction and interpretation of phase equilibria properties on the one hand, and quantitative prediction of melting point, density, viscosity, surface tension and refractive indices on the other hand. In our view, multiscale modeling, combining the molecular and macroscale methods, will strongly enhance the predictability of NADES properties and their interaction with solutes, yielding truly tailorable solvents to accommodate (bio)chemical reactions.
We present the new and entirely mechanistic COSMOperm method to predict passive membrane permeabilities for neutral compounds, as well as anions and cations. The COSMOperm approach is based on compound specific free energy profiles within a biomembrane of interest from COSMO-RS (Conductor-like Screening Model for Realistic Solvation) calculations. These are combined with membrane layer specific diffusion coefficients, for example, in the water phase, the polar head groups and the alkyl tails of biochemical phospholipid bilayers. COSMO-RS utilizes first-principle quantum chemical structures and physically sound intermolecular interactions (electrostatic, hydrogen bond and van der Waals). For this reason, it is unbiased towards different application scenarios, such as cosmetics, industrial chemical or pharmaceutical industries. A fully predictive calculation of passive permeation through phospholipid bilayer membranes results in a performance of r2 = 0.92; rmsd = 0.90 log10 units for neutral compounds and anions, as compared to gold standard black lipid membrane (BLM) experiments. It will be demonstrated that new membrane types can be generated by the related COSMOplex method and directly used for permeability studies by COSMOperm.
the solvation and solubilization of selected anesthetic active pharmaceutical ingredients (bupivacaine, prilocaine and procaine) in arginine-based deep eutectic solvents is studied using a theoretical approach considering quantum chemistry and classical molecular dynamics. The intermolecular forces between the anesthetics and the solvent are characterized, with particular attention to hydrogen bonding, in terms of strength, topological properties, interaction mechanism, structuring and dynamic properties of solvation shells. The reported results show the nanoscopic properties that confirm these solvents as suitable materials for anesthetics drug delivery in liquid phase.
A simple and ecofriendly sample preparation method was developed for quantifying fluoroquinolone (FQ) antibiotics in surface water. Seventeen combinations of monoterpenes (menthol, thymol, and camphor), fatty acids (heptanoic, octanoic, nonanoic, and decanoic acids), and a benzoate ester (salol) were utilized for the in situ formation of hydrophobic deep eutectic solvents (hDESs) for liquid-liquid microextraction (LLME). The hDES comprising thymol and heptanoic acid (HA) exhibited the highest extraction efficiency for ofloxacin, norfloxacin, ciprofloxacin, and enrofloxacin. Optimization via the one-variable-at-a-time strategy revealed that a 2:1 ratio of thymol to HA yielded the highest efficiency for antibiotic extraction at pH 4-7. Further, response surface methodology-based optimization suggested that the optimal extraction conditions involved the use of appropriate amounts of thymol and HA to generate 100 μL of hDES in 10 mL of aqueous sample with incubation at 52 °C for 5 min, followed by automated shaking for 1 min. The collected hDES phase was diluted and subjected to liquid chromatography-ultraviolet detection analysis. The established method based on in situ formation of hDES coupled with shaker-assisted LLME (in situ hDES-SA-LLME) was validated. The method was specific and showed good linearity in the 15-3000 ng mL-1 concentration range (r2 ≥ 0.9997), with a limit of detection of 3.0 ng mL-1, limit of quantification of 9.0 ng mL-1, accuracy of 84.1-113.65%, and intra-day and inter-day precision of ≤7.78% RSD and ≤7.91% RSD, respectively. The method was successfully applied to three different types of real surface water samples. Without toxic volatile organic solvents, the developed method allows for safe and rapid, yet reliable, analysis of FQ antibiotics.
Mixtures of non-ionic compounds have been reported as DES but most are just ideal mixtures. In the thymol–menthol system, an abnormal strong interaction was identified stemming from the acidity difference of the phenolic and aliphatic hydroxyl groups. This type of interaction is found to be the key to prepare non-ionic DES, that may be classified as type V.
Deep eutectic solvents (DESs) have been intensively investigated as promising “green” solvents for a range of industrial processes, although most research continues to be focused on binary DESs. This paper reports on a class of ternary DESs formed by choline chloride (ChCl), polyethylene glycol (PEG), and boric acid (BA) that may be viewed as a new system for extraction and oxidative desulfurization (ODS) of diesel fuel. Compared with organic acid-based DESs, ternary DESs offer advantages including low volatility, low toxicity, and high activity. After tuning the molar ratio of the three compositions, sulfur removal reached 96.4% in 2 h at 60oC when the molar ratio of H2O2 to dibenzothiophene was 4. The binary DESs, ChCl/PEG and ChCl/BA, showed unsatisfactory extraction and oxidation efficiency. The reaction mechanism identified through experimental and theoretical methods showed that superoxide radical may be the main active oxygen species, and BA-based peroxides may also play an important role. The results of this study may expand the use of BA and supply a new class of DESs for ODS and other possible applications.
Deep eutectic solvents (DESs) consist of a mixture of two or more solid components leading to a drop of the melting point of the mixture when compared to the starting materials. Until recently, only hydrophilic DESs were available, and despite their revolutionary role in the alternative solvents scenario, important issues in chemistry and chemical engineering, such as water related problems or the replacement of toxic volatile organic compounds, could not be tackled. Hydrophobic (Deep) ‐ here in parenthesis due to the different depths of the eutectic´s melting points ‐ Eutectic Solvents are a sub‐class of DESs where both components are hydrophobic. The choice of low cost, naturally occurring compounds, with low toxicity and high biodegradability and straightforward preparation without purification steps, are among the key advantages that distinguish them as innovative solvents. Although research on hydrophobic DESs is scarce, since the first paper on the subject was only published in 2015, some interesting features and applications have been published and deserve to be reviewed and comparisons established. The current review is divided into two parts: first, a brief general introduction to DESs and the second part details on nomenclature using solid‐liquid phase diagram analysis, chemical stability, thermophysical properties comparison and finally the most important emerging fields of application.
The nanomicelles have recently drawn a great deal of attention for drug delivery into the skin. However, these carriers have only deposited in hair follicles and furrows, and drug in the micelles may not therapeutically reach into viable skin layers. The aim of this study was to formulate a combination of nanomicelles with terpenes to overcome this challenge and evaluate their potential for topical drug delivery into the skin. The nanomicelles were characterised with respect to size, size distribution (PDI), zeta potential, morphology and encapsulation efficiency (%). The drug accumulation and penetration were examined by tape stripping method in the skin. The colloidal stability of nanomicelles was followed with respect to size and PDI values. The nanomicelles were about 25-30 nm in size with narrow distribution. All of them had slightly negative surface charge, spherical shapes and high encapsulation efficiency (%). The tape stripping data revealed that nanomicelles consisting of terpinolene led to accumulation of more drug in the stripped skin as compared with commercial product and nanomicelles without terpene. Also, micelle formulations consisting of terpinolene (2.0 %) had the highest colloidal stability. Consequently, combination of nanomicelles with terpinolene could be a feasible approach for enhancement of skin drug delivery.
The concept of sustainable development has impacted in analytical chemistry changing the way of thinking processes and methods. It is important for analytical chemists to consider how sample preparation can integrate the basic concepts of Green Chemistry. In this sense, the replacement of traditional organic solvents is of utmost importance. Natural Deep Eutectic Solvents (NADES) have come to light as a green alternative. In the last few years, a growing number of contributions have applied these natural solvents proving their efficiency in terms of extraction ability, analyte stabilization capacity and detection compatibility. However, the arising question that has to be answered is: the use of NADES is enough to green an extraction process? This review presents an overview of knowledge regarding sustainability of NADES-based extraction procedures, focused on reported literature within the timeframe spanning from 2011 up to date. The contributions were analyzed from a green perspective in terms of energy, time, sample and solvent consumption. Moreover, we include a critical analysis to clarify whether the use of NADES as extraction media is enough for greening an analytical methodology; strategies to make them even greener are also presented. Finally, recent trends and future perspectives on how NADES-based extraction approaches in combination with computational methodologies can contribute are discussed.
A molecular dynamics study on the solvation of metal nanoparticles in deep eutectic solvents is reported in this work. The solvation process was analysed in terms of the type of metal, geometry of the nanoparticles and properties of the deep eutectic solvent. Simulations results in the microsecond range allowed to infer the properties of the solvation shells and the effects of the nanoparticles on the liquid structuring. The possible aggregation of metal nanoparticles in the studied solvents was analysed and discussed in terms of the screening effect of the solvents and the efficient nanoparticle – solvent intermolecular forces. The reported results show deep eutectic solvents acting as metal nanoparticle stabilizers, thus providing a new platform for nanoparticles technologies.
As functional liquid media, natural deep eutectic solvent (NADES) species can dissolve natural or synthetic chemicals of low water solubility. Moreover, the special properties of NADES, such as biodegradability and biocompatibility, suggest that they are alternative candidates for concepts and applications involving some organic solvents and ionic liquids. Owing to the growing comprehension of the eutectic mechanisms and the advancing interest in the natural eutectic phenomenon, many NADES applications have been developed in the past several years. However, unlike organic solvents, the basic structural unit of NADES media primarily depends on the intermolecular interactions among their components. This makes NADES matrices readily influenced by various factors, such as water content, temperature, and component ratio and, thus, extends the metabolomic challenge of natural products (NPs). To enhance the understanding of the importance of NADES in biological systems, this review focuses on NADES properties and applications in NP research. The present thorough chronological and statistical analysis of existing report adds to the recognition of the distinctiveness of (NA)DES, involves a discussion of NADES-related observations in NP research, and reportes applications of these eutectic mixtures. The work identifies potential areas for future studies of (NA)DES by evaluating relevant applications, including their use as extraction and chromatographic media as well as their biomedical relevance. The chemical diversity of natural metabolites that generate or participate in NADES formation highlights the growing insight that biosynthetically primordial metabolites (PRIMs) are as essential to the biological function and bioactivity of unrefined natural products as the biosynthetically more highly evolutionary metabolites (HEVOs) that can be isolated from crude mixtures.
The search for both new and sophisticated materials that meet the needs of the modern era, and for sustainable eco-efficient processes, has raised deep eutectic solvents (DES) to a prominent position. Research focused on the use of these solvents – highly advantageous in economic, practical, and environmental terms – for the creation of innovative materials has been growing fast, and a very large number of publications reporting the use of DES as valuable alternatives to overcome the limitations of conventional solvents, and even ionic liquids, has been published. DES have proved to offer tremendous opportunities and have opened new perspectives to produce novel and refined materials.
This review focuses on recent advances concerning these new materials and on the practices that have been developed employing DES as solvents. The definition, preparation and unique properties of DES are first addressed, followed by a more extensive description of their applications in polymer, metal deposition and nanomaterial science and sensing technologies. Their impact in the production processes and in the properties of the materials obtained, as well as their key role as designer solvents, is highlighted.
Forward osmosis (FO) can aptly contribute to increased water reuse at the expense of low energy expenditure. The distinctive feature for FO lies with the exploitation of the natural osmotic pressure gradient generated by a concentrated draw solution for water transport across a semi-permeable membrane. The selection of a suitable draw solution remains to be a grey area of commercial development of FO process. The present review summarizes the importance of ionic liquid (IL) and deep eutectic solvent (DES) with natural product components and their potential as draw solutions in FO and their industrial applications. Various factors affecting performances of ILs and DESs as draw solutions are briefly assessed and critically compared with pertinent literature. Regeneration of IL and DES as spent solution from the process, as well as pure water recovery is discussed with special reference to heat energy optimization. A future pathway for research in IL and DES as draw solute and their economic aspects are also highlighted.
Is hydration the solution to the viscosity of deep eutectic solvents (DESs)? In their Communication (DOI: 10.1002/anie.201702486), K. J. Edler and co-workers determine the nanostructure of DES/water mixtures over a wide hydration range by neutron diffraction and atomistic modeling. The mixture retains the characteristics of the DES structure up to remarkably high water levels and is then converted into a state best described as a simple aqueous solution of the DES molecular components.