Cosolvent Molecules Research Articles

New cosolvent-dependent electrochemical sensing behavior of a pair of isostructural ionic nickel(II) coordination polymers

A pair of isostructural ionic nickel(II) chain coordination polymers, {[Ni(bbbm)(H2O)4]·ATBIP·2DMF·2H2O}n (CP 1) and {[Ni(bbbm)(H2O)4]·ATBIP·2DMA·2H2O}n (CP 2) with the multi-functional ATBIP2- anion and flexible bbbm linker was synthesized under ambient condition [H2ATBIP = 5-amino-2,4,6-tribromoisophthalic acid, bbbm = 1,4-bis(benzimidazole-1-methyl)benzene]. Furthermore, the composite of CP 1 with carbon nanotubes (CP 1@CNTs) was constructed by adopting “one pot” synthesis strategy. With the help of the hydrogen-bonded chain, CPs 1–2 extend into a 3D supramolecular framework with 1D channels occupied by the cosolvent molecules (DMF/DMA). Remarkably, CPs 1–2/GCE demonstrate cosolvent-dependent electrochemical sensing behavior to H2O2 and Fe3+. CP 1/GCE shows more sensitive oxidation sensing to H2O2 than CP 2/GCE in 0.1 M NaOH. Meanwhile, CP 1/GCE demonstrates sensitive reduction sensing to Fe3+ in 0.1 M H2SO4, while CP 2/GCE doesn't. Both CPs 1–2/GCE have similar oxidation sensing capabilities to ascorbic acid (AA) in 0.1 M H2SO4. Moreover, CP 1@CNTs/GCE shows superior electrochemical sensing performance to CP 1/GCE. The LOD of CP 1@CNTs/GCE for sensing of H2O2, AA and Fe3+ reaches 0.1 μM, 1.7 μM and 3.4 μM, respectively. Moreover, CP 1@CNTs/GCE was used in the sensitive detection of H2O2, AA and Fe3+ in the real-world samples.

Thermodynamic parameters of L-carnosine dissolution and solvation in binary aqueous-organic mixtures at T = 298.15 K.

Isothermal calorimetry was used to measure the enthalpies of L-carnosine digestion in aqueous solutions of acetonitrile (AN) 1,4-dioxane (DO), acetone (AC), dimethyl sulfoxide (DMSO), ethanol EtOH), 1-propanol (1-PrOH), and 2-propanol (2-PrOH). The values of ΔsolH° obtained were combined with the standard enthalpies of L-carnosine sublimation to obtain the corresponding enthalpies of solvation ΔsolvH°. In addition, the enthalpic coefficients of pairwise interactions (hxy) of L-carnosine with organic solvent molecules and the enthalpy of transfer (ΔtrH°) from water in their mixture with the latter were calculated. It is established that the solvation of L-carnosine is weakened in a series of (H2O + EtOH) > (H2O + 1-PrOH) > (H2O + 2-PrOH). This may be due to an increase in the hydrophobicity of alcohols of the same order as well as the presence of CH3-groups within the alcohol molecule. The weakening of the solvation energy of L-carnosine by co-solvent molecules in a series of mixed solvents: (H2O + AN) < (H2O + AC) < (H2O + DO) < (H2O + DMSO) is associated both with an increase in the hydration energy of co-solvents in the same order and with their physicochemical properties. The enthalpic coefficients of water-organic solvent pairwise interactions were discovered to be linearly related to the corresponding coefficients of L-carnosine-organic solvent interactions. An increase in the polarity and acidity of an organic solvent increases the energy of pairwise interactions between L-carnosine and the organic solvent. Increasing the cohesion energy density, molar volume, and basicity of the organic solvent reduces the energy of the pairwise interactions between L-carnosine and the organic solvent.

Preventing lipophilic aggregation in cosolvent molecular dynamics simulations with hydrophobic probes using Plumed Automatic Restraining Tool (PART)

Cosolvent molecular dynamics (MD) simulations are molecular dynamics simulations used to identify preferable locations of small organic fragments on a protein target. Most cosolvent molecular dynamics workflows make use of only water-soluble fragments, as hydrophobic fragments would cause lipophilic aggregation. To date the two approaches that allow usage of hydrophobic cosolvent molecules are to use a low (0.2 M) concentration of hydrophobic probes, with the disadvantage of a lower sampling speed, or to use force field modifications, with the disadvantage of a difficult and inflexible setup procedure. Here we present a third alternative, that does not suffer from low sampling speed nor from cumbersome preparation procedures. We have built an easy-to-use open source command line tool PART (Plumed Automatic Restraining Tool) to generate a PLUMED file handling all intermolecular restraints to prevent lipophilic aggregation. We have compared restrained and unrestrained cosolvent MD simulations, showing that restraints are necessary to prevent lipophilic aggregation at hydrophobic probe concentrations of 0.5 M. Furthermore, we benchmarked PART generated restraints on a test set of four proteins (Factor-Xa, HIV protease, P38 MAP kinase and RNase A), showing that cosolvent MD with PART generated restraints qualitatively reproduces binding features of cocrystallised ligands.

A Green Asymmetric Bicyclic Co-Solvent Molecule for High-Voltage Aqueous Lithium-Ion Batteries.

Hybridizing aqueous electrolytes with organic co-solvents can effectively expand the voltage window of aqueous electrolytes while reducing salt usage, but most reported co-solvents are usually flammable and toxic, hardly achieving compatibility between safety and electrochemical performance. Here, a new non-flammable and non-toxic low-salt-concentration (1.85 m) aqueous electrolyte is reported using the green co-solvent isosorbide dimethyl ether (IDE). Owing to its unique 3D molecular structure, IDE can form a five-membered ring structure by binding the Li ion. The steric hindrance effect from IDE weakens its solvation ability, generating anion-participated solvation structures that produce a robust and uniform LiF-rich solid electrolyte interphase layer while containing elastic IDE-derived organics. Moreover, the multiple O atoms in IDE can effectively regulate the intermolecular hydrogen bonding networks, reducing H2O molecule activity and expanding the electrochemical window. Such unique solvation structures and optimized hydrogen bonding networks enabled by IDE effectively suppress electrode/electrolyte interfacial side reactions, achieving a 4.3 V voltage window. The as-developed Li4Ti5O12(LTO)||LiMn2O4(LMO) full cell delivers outstanding cycling performance over 450 cycles at 2 C. The proposed green hybrid aqueous electrolyte provides a new pathway for developing high-voltage aqueous lithium batteries.

Effects of cosolvents on CO2 displacement of shale oil and carbon storage

Molecular dynamics method was used to establish composite wall/inorganic nanopores of three pore sizes, three shale oil systems, five CO2-cosolvent systems, and pure CO2 system. The process of CO2-cosolvent displacement of crude oil in shale nanopores and carbon storage was simulated and the influencing factors of displacement and storage were analyzed. It is shown that the attraction of the quartz wall to shale oil increases with the degree of hydroxylation. The higher the degree of quartz hydroxylation, the more difficult it is to extract the polar components of shale oil. Nanopore size also has a great impact on shale oil displacement efficiency. The larger the pore size, the higher the shale oil displacement efficiency. The closer the cosolvent molecules are to the polarity of the shale oil, the higher the mutual solubility of CO2 and shale oil. The more the non-polar components of shale oil, the lower the mutual solubility of CO2 and shale oil with highly polar cosolvent. Ethyl acetate is more effective in stripping relatively high polar shale oil, while dimethyl ether is more effective in stripping relatively low polar shale oil. Kerogen is highly adsorptive, especially to CO2. The CO2 inside the kerogen is not easy to diffuse and leak, thus allowing for a stable carbon storage. The highest CO2 storage rate is observed when dimethyl ether is used as a cosolvent, and the best storage stability is observed when ethyl acetate is used as a cosolvent.

Unlocking the Effect of Chain Length and Terminal Group on Ethylene Glycol Ether Family Toward Advanced Aqueous Electrolytes.

Constructing high-performance hybrid electrolyte is important to advanced aqueous electrochemical energy storage devices. However, due to the lack of in-depth understanding of how the molecule structures of cosolvent additives influence the properties of electrolytes significantly impeded the development of hybrid electrolytes. Herein, a series of hybrid electrolytes are prepared by using ethylene glycol ether with different chain lengths and terminal groups as additives. The optimized 2m LiTFSI-90%DDm hybrid electrolyte prepared from diethylene glycol dimethyl ether (DDm) molecule showcases excellent comprehensive performance and significantly enhances the operating voltage of supercapacitors (SCs) to 2.5V by suppressing the activity of water. Moreover, the SC with 2m LiTFSI-90%DDm hybrid electrolyte supplies a long-term cycling life of 50000 cycles at 1Ag-1 with 92.3% capacitance retention as well as excellent low temperature (-40ºC) cycling performance (10000 times at 0.2Ag-1). Universally, Zn//polyaniline full cell with 2m Zn(OTf)2-90%DDm electrolyte manifests outstanding cycling performance in terms of 77.9% capacity retention after 2,000 cycles and a dendrite-free Zn anode. This work inspires new thinking of developing advanced hybrid electrolytes by cosolvent molecule design toward high-performance energy storage devices.

Modulating electron distributions by integrating ligands with metal molecules in THF

While the complex structures and dynamic behavior of alkali metal cations in solvents have been fully understood, insights into the structures, properties and dynamic behaviors of metal dimers in aprotic solvents (e.g. tetrahydrofuran/THF) are quite scarce, and especially the bonding characteristics, valence electron distribution and effect of co-solvents (e.g. crown ether/18-crown-6 (18C6)) are poorly understood. We here perform ab initio molecular dynamics simulation characterization on K2 molecular solute in THF with and without co-solvent molecule (18C6). Our findings indicate that K2 can be integrated by different numbers of THF molecules and 18C6 (if available), forming various chemical identities with unique structures and electron distributions in THF solvent ((THF)xK-K(THF)y, x + y ≤ 9; (THF)x(18C6)K-K(THF)y, x + y ≤ 4). These identities have considerable lifetimes in time evolution and the structure fluctuation dynamics of solution can realize interconversion among these identities through removing and/or adding THFs from/to two K subcluster moieties. In general, compared with the gaseous K2, integration of THFs considerably expands the K2 electron cloud and exhibit much more active states featuring distorted diffuse distributions which can be viewed as electron-expanded chemical entities. Further 18C6 coordination can tightly bind an end K and keep one THF coordinating a K at the axis direction and another K keeps a low coordination status. Such a coordination mode largely forces valence electrons to THF bulk acting as the electron-expanded complexes. In particular, the coordination of 18C6 greatly polarizes the bonding electron, changing the K-K covalent bond into highly ionic one with a Kδ+-Kδ− core structure. All these identities present lower ionization potentials than that of the gaseous K2, and thus have highly reductive reactivity, in agreement with the experiments. This work provides a promising strategy for how to modulate the bonding electrons around the electron-flexible metal–metal bonds.

Molecular mechanism of the common and opposing cosolvent effects of fluorinated alcohol and urea on a coiled coil protein.

Alcohols and urea are widely used as effective protein denaturants. Among monohydric alcohols, 2,2,2-trifluoroethanol (TFE) has large cosolvent effects as a helix stabilizer in proteins. In contrast, urea efficiently denatures ordered native structures, including helices, into coils. These opposing cosolvent effects of TFE and urea are well known, even though both preferentially bind to proteins; however, the underlying molecular mechanism remains controversial. Cosolvent-dependent relative stability between native and denatured states is rigorously related to the difference in preferential binding parameters (PBPs) between these states. In this study, GCN4-p1 with two-stranded coiled coil helices was employed as a model protein, and molecular dynamics simulations for the helix dimer and isolated coil were conducted in aqueous solutions with 2 M TFE and urea. As 2 M cosolvent aqueous solutions did not exhibit clustering of cosolvent molecules, we were able to directly investigate the molecular origin of the excess PBP without considering the enhancement effect of PBPs arising from the concentration fluctuations. The calculated excess PBPs of TFE for the helices and those of urea for the coils were consistent with experimentally observed stabilization of helix by TFE and that of coil by urea. The former was caused by electrostatic interactions between TFE and side chains of the helices, while the latter was attributed to both electrostatic and dispersion interactions between urea and the main chains. Unexpectedly, reverse-micelle-like orientations of TFE molecules strengthened the electrostatic interactions between TFE and the side chains, resulting in strengthening of TFE solvation.

The Effect of Temperature on the Mechanical Properties of Alginate Gels in Water/Alcohol Solutions.

Alginate organohydrogels prepared in water/alcohol mixtures play an important role in electronic and superconductor applications in low-temperature environments. The study deals with the preparation of Ca-alginate organohydrogels and the analysis of their equilibrium swelling and mechanical properties at sub-zero temperatures. It is shown that the equilibrium degree of swelling at room temperature is noticeably affected by the concentration of co-solvents (methanol, ethanol, and 2-propanol) in the mixtures and the number of carbon atoms in the co-solvent molecules. Mechanical properties are studied in small-amplitude oscillatory tests. The data are fitted with a model that involves three material parameters. The influence of temperature is investigated in temperature-sweep oscillatory tests under a cooling-heating program, where a noticeable difference is observed between the storage and loss moduli under cooling and heating (the hysteresis curves). The hysteresis areas are affected by the cooling/heating rate and the number of carbon atoms in the co-solvents.

Equilibrium solubility, solvation and dissolution thermodynamics, and DFT study of 18β-glycyrrhetinic acid in solutions of 1,4-dioxane/N,N-dimethylformamide/ethanol/isopropanol + water

This study investigated the solubility, solvation behavior, dissolution thermodynamics, and intermolecular interactions of 18β-glycyrrhetinic acid (GA) in binary aqueous blends of 1,4-dioxane, N,N-dimethylformamide (DMF), ethanol and isopropanol. The solubility experiments were performed using the shake-flask technique at 101.0 kPa and temperatures ranging from 278.15 to 323.15 K. The lowest and highest GA solubility was observed in water and neat organic solvent, respectively. Experiments based on XRD analysis revealed no crystal transition or solvation. Modified van't Hoff–Jouyban–Acree and Jouyban–Acree models connected the solubility with relative average deviations (RAD) not exceeding 3.63 %. The extended Hildebrand solubility parameter method was utilized here to examine the equilibrium solubility at 298.15 K, yielding a RAD of 3.95 %. According to the linear solvation energy relationship examination, the dipolarity-polarizability and solubility parameter of solutions significantly influence the solubility variation. Using the inverse Kirkwood–Buff integrals, the preferential solvation of GA by organic solvents and water was investigated quantitatively. Positive preferential solvation parameter for organic solvents in rich and moderate organic solvent blends indicated that GA was preferentially solvated by the organic solvents. GA is a Lewis acid with respect to the cosolvent molecules. Thermodynamic investigation of dissolution characteristics and enthalpy–entropy compensation revealed an endothermic process and enthalpy-driven mechanism for dissolving GA in various blends. Finally, microscopic quantitative examination of molecular surface was used to highlight the electrostatic properties of acidity/basicity of GA. The –C = O, OH, and > COOH groups are the main targets of electrophilic and nucleophilic attack. The weak interactions between GA and solvent were visually examined using an independent gradient model based on Hirshfeld partition analysis.

Preferred intermolecular cation···anion interactions within the [EMIM][DCA] ionic liquid and its interaction with a water co-solvent molecule

A theoretical study intended to investigate the preferred geometry arrangement of the cation/anion units within the 1-ethyl-3-methyl-imidazolium dicyanamide ([EMIM][DCA]) ionic liquid (IL) and its geometry arrangement and energetic properties upon interaction with a water co-solvent molecule has been performed for the first time. DFT and MP2 methods have been selected for the investigation in order to compare the performance of the methods. The standard 6-31++G(d,p) basis set was utilised for the geometry optimisation while the 6-311++g(3d2f,3p2d)//6-31++G(d,p) was utilised to estimate the energy and to eliminate the basis set superposition error on the energies. The result of the investigation suggests that the cation/anion units within the ionic liquids are preferably held through a combination of hydrogen bonding and dispersion interactions. This confirmed through the use of energetic and bond distance parameters as well as the H1 NMR analysis of the available geometries. Geometries held solely by hydrogen bonding are minimally preferred. The explicit co-solvent water molecule preferably interact with [EMIM][DCA] in which the cation/anion units are stabilised predominantly by the presence of dispersion interactions. The inclusion of the implicit solvation is associated with significant decrease in the magnitude of the cation⋯anion interaction energy, largely due to the increased separation distance between the units. A comparison of the ionic liquid – co-solvent interaction energy estimated by different calculation methods suggests minimal differences among the methods in the estimated energy values.

Features of l-Tryptophan Solvation in Some Water–Organic Mixtures at T = 298.15 K

The effect of changes in the composition of some water–organic mixtures on the thermodynamic parameters of dissolution and solvation of l-tryptophan was studied by the method of calorimetry of dissolution at T = 298.15 K. To explain the experimental results, the enthalpic coefficients of pairwise interactions between l-tryptophan and organic cosolvent molecules and the energy contributions of the side chain to the energy of intermolecular interactions are calculated, and the influence of some properties of organic solvents on these interactions is estimated. All the data obtained were compared with those for l-phenylalanine to reveal the influence of the side chain structure on the energy of intermolecular interactions of aromatic amino acids with organic solvent molecules in aqueous solutions.

Structural evolution of the butylated hydroxytoluene/menthol hydrophobic eutectic solvent upon methanol and ethanol cosolvent addition

The changes upon methanol (MeOH) and ethanol (EtOH) addition in the structural arrangement of the hydrophobic eutectic solvent formed by butylated hydroxytoluene (BHT) and L-menthol (MEN) in 1:3 M ratio have been studied using molecular dynamics (MD) simulations integrated by small- and wide-angle X-ray scattering (SWAXS) measurements. Different mixtures containing the eutectic solvent and a variable amount of MeOH and EtOH have been investigated and the cosolvent introduction at any concentration has been found to break the hydrogen-bonds (H-bonds) among the MEN molecules, that are the most relevant interactions in the pristine eutectic, while the BHT component remains substantially non-interacting through all the explored composition range. This H-bond network is replaced by interactions between the MEN component and the cosolvent molecules, where the MEN species acts preferentially as H-bond donor towards the MeOH and EtOH molecules that behave mostly as H-bond acceptors. An increasing interplay between the excess cosolvent molecules is also observed upon increasing their concentration. SWAXS data show a contraction of the electron-dense regions corresponding to the hydroxyl groups upon cosolvent addition. This evidence is compatible with the intercalation of the MeOH and EtOH molecules in the MEN-MEN H-bond network to promote MEN-cosolvent and cosolvent-cosolvent interactions, in agreement with the MD results.

Cononsolvency Effect: When the Hydrogen Bonding between a Polymer and a Cosolvent Matters

Despite the fact that the observation of cononsolvency was reported as early as four decades ago, its phase-transition mechanism is still under debate. In this work, we provided a comprehensive study of the phase behaviors of poly(N-isopropylacrylamide) (PNiPAAm) in sulfoxide or sulfone aqueous solutions. We observed a sharp collapse transition of PNiPAAm brushes in sulfoxide but not in sulfone aqueous solutions by equilibrium measurements of in situ spectroscopic ellipsometry. We found that the hydrogen-bond formation between sulfoxide oxygens and amide hydrogens of the polymer chains plays a critical role in regulating the cononsolvency of PNiPAAm. We have extended the concept of preferential adsorption by taking into account hydrophobic interactions between cosolvent molecules, which are adsorbed on the polymer by hydrogen bonds. This can explain the experimental observations of PNiPAAm brushes in these solvent mixtures and sheds light on understanding the phase behaviors of polymer solutions where hydrogen bonds and hydrophobic interaction play a critical role. Our results can also be of interest for the liquid–liquid phase separation in the living cell where the condensation of proteins bound to large biomacromolecules plays an essential role.

Efficient continuous dehydration of fructose to 5-hydroxymethylfurfural in ternary solvent system

Biomass-derived 5-hydroxymethylfurfural (HMF) has been identified as a versatile precursor for clean fuels and degradable polymers. Here, we developed an efficient flow-through system to continuously produce HMF in high selectivity from fructose dehydration. Effects of solvent, the relative ratio of aqueous to organic phase, the proportion of different cosolvents in the organic phase as well as the reaction variables on reactivity of fructose dehydration to HMF were comprehensively investigated to obtain the optimal results. The conduction of a H2O/dioxane/methyl isobutyl ketone (MIBK) ternary solvent system in combination with Amberlyst 70 as catalyst contributed to 93 % selectivity and 84 % yield of HMF in residence time as short as 1.6 min. The strengthened hydrogen bonding interactions by the addition of dioxane accounted for an increase in the interactions of fructose with water and cosolvent molecules, accelerating the dehydration rate. Meanwhile, the in-situ extraction of HMF from active aqueous phase to organic phase by MIBK protected it from unfavorable side reactions. The reaction system exhibited good stability without significant change on the catalytic performance over 10 h reaction. Additionally, fructose was selectively dehydrated from fructose-glucose mixtures, holding great promises for the integration with the industrial operations producing mixture of sugars (such as fructose corn syrup).

Hydrogen bonding between 1-ethyl-3-methyl-imidazolium dicyanamide ionic liquid and selected co-solvents with varying polarity: A DFT study

A theoretical study was performed to investigate the solute-solvent interactions between 1-ethyl-3-methyl-imidazolium ([EMIM]+) dicyanamide ([DCA]-) ionic liquid (IL) and each of the three traditional molecular solvents, namely, water, methanol and chloroform, to elucidate the geometry of the stable IL⋯co-solvent structures as well as the interaction strength at different possible sites. The study was performed by utilising a simplified structure approach in which one solvent molecule interacts with the IL at different possible interaction sites. Geometry optimisations were performed by using the density functional theory (DFT) method in combination with the 6-31++G(d,p) basis set; the energy was improved by using the B3LYP/6-311++G(3df,3pd)// B3LYP/6-31++G(d,p) approach to eliminate the basis set superposition error on the energies. The results of the study show that IL forms a strong interaction with the co-solvent at nearly all possible interaction sites. The C–H⋯N intermolecular interactions between the cation and the anion units of the IL are weakened when the solvent molecule interacts simultaneously with the hydrogen bond donor involved between the cation and the anion units of the IL. The polar solvents (methanol and water) interact more strongly with the IL than the nonpolar chloroform solvent. The results presented herein have fundamentally advanced the understanding of the specific structural, energetic and electronic changes induced on [EMIM]DCA cation–anion units by the selected co-solvents and provided a detailed description of the interaction patterns between [EMIM]DCA and the selected co-solvent molecules. Such information, which had not previously been provided, could serve as a basis for further studies on derivatives of [EMIM]DCA with the selected co-solvents or with other solvents not considered in this work.

Equilibrium Swelling of Thermo-Responsive Gels in Mixtures of Solvents

Thermo-responsive (TR) gels of the LCST (lower critical solution temperature) type swell in water at temperatures below their volume phase transition temperature Tc and collapse above the critical temperature. When water is partially replaced with an organic liquid, these materials demonstrate three different types of equilibrium solvent uptake diagrams at temperatures below, above, in the close vicinity of Tc. A model is developed for equilibrium swelling of TR gels in binary mixtures of solvents. It takes into account three types of phase transitions in TR gels driven by (i) aggregation of hydrophobic side groups into clusters from which solvent molecules are expelled, (ii) replacement of water with cosolvent molecules in cage-like structures surrounding these groups, and (iii) replacement of water with cosolvent as the main element of hydration shells around backbone chains. The model involves a relatively small number of material constants that are found by matching observations on covalently cross-linked poly(N-isopropylacrylamide) macroscopic gels and microgels. Good agreement is demonstrated between the experimental data and results of numerical analysis. Classification is provided of the phase transition points on equilibrium swelling diagrams.

Tailoring Atomistic Interactions in Li-S Battery Via a Computational Multi-Scale-Data-Driven Approach

A major breakthrough in battery materials is required to meet the ever-increasing proliferation of portable electronic devices, electric vehicles and their variants, as well as the need for incorporating renewable energy resources into the main energy supply [1]. In this context, lithium-sulfur (Li-S) batteries attract attention owing to their very high energy density (2,600 Wh kg-1) and specific capacity (1,675 mAh g-1) and significantly lower weight and cost, compared to lithium-ion batteries (LIBs) [2]. Fully packaged, it is expected that future Li-S batteries can operate at close to 500 Wh kg-1, which is more than twice the energy density of LIBs (200 Wh kg-1) [3]. The problem of realizing the expected high energy density is defined by several issues including the dissolution of Li-Polysulfide (PS) species into the electrolyte, insulating properties of sulfur and Li-PS species, and volume change at the cathode [4]. Overcoming these challenges requires a fundamental understanding of the interplay between events occurring over wide spatial and temporal scales, and accurate prediction of electrode and electrolyte properties to obtain design metrics for new improved materials.In this talk, I will first discuss the details of a high-throughput multi-scale computational infrastructure developed by our group called MISPR (Materials Informatics for Structure-Property-Relationship) to design optimal materials for different applications such as Li-S batteries. MISPR is a high-fidelity and robust computational tool that seamlessly integrates classical molecular dynamics (MD) simulations with density functional theory (DFT) calculations through force field generation and information flow between the two-length scales. It allows automatic handling of thousands of computational materials science simulations and multiple systems with a strong focus on data provenance.I will then discuss the usage of MISPR to mitigate dissolution of LiPS species by altering the atomistic interactions between the electrolyte components through high-throughput screening of potential co-solvent molecules. This approach guides and accelerates our rational selection of co-solvents that enable optimal compromise between the solubility of PS species and the transport properties of the electrolyte through automated DFT calculations. We use the selected candidates in detailed MD studies to comprehend the relationship between the structure of the co-solvent and the electrolyte properties. The approach allows for creating a database of well-characterized materials to be used in machine learning-based methods as well as for testing computationally identified structures in experiments. This work provides crucial information to alleviate the dissolution of PS species during cycling, which is the main reason for rapid capacity decay in Li-S batteries.References Larcher, D. and J.-M. Tarascon, Towards greener and more sustainable batteries for electrical energy storage. Nature chemistry, 2015. 7(1): p. 19. Manthiram, A., X. Yu, and S. Wang, Lithium battery chemistries enabled by solid-state electrolytes. Nature Reviews Materials, 2017. 2(4): p. 1-16. Fang, R., et al., More reliable lithium‐sulfur batteries: status, solutions and prospects. Advanced materials, 2017. 29(48): p. 1606823. Manthiram, A., Y. Fu, and Y.-S. Su, Challenges and prospects of lithium–sulfur batteries. Accounts of chemical research, 2013. 46(5): p. 1125-1134. Figure 1

Structure, dynamics and ionic conductivities of ternary ionic liquid/lithium salt/DMSO mixtures

In this paper we report classical Molecular Dynamics and ab initio Density Functional Theory simulations of the structure and single particle dynamics of ternary mixtures of a protic (ethylammonium nitrate, EAN) and an aprotic (1-Ethyl-3-methylimidazolium tetrafluoroborate, EMIMBF4) ionic liquid, lithium salts with common anion and a molecular cosolvent, dimethyl sulfoxide (DMSO). The coordination numbers and electrical conductivities of the different mixtures have been calculated throughout the whole concentration range, and the differences between mixtures with the protic and aprotic ionic liquids were analyzed. In both cases, the evolution of the electrical conductivity is seen to correlate well with the formation of mixed tetrahedral solvation complexes of lithium cations with ionic liquid anions and cosolvent molecules. The differences in the solvation and charge transport mechanisms in hydrogen bonded mixtures and those based in the aprotic ionic liquid are analyzed. Our conclusions indicate that the major feature behind the electrical conductivity of the ternary mixtures is the composition of the solvation shell of the metal cations in the mixtures and the rate at which anions in it are replaced by DMSO molecules.

Extracting Atomic Contributions to Binding Free Energy Using Molecular Dynamics Simulations with Mixed Solvents (MDmix).

Mixed solvents MD (MDmix) simulations have proved to be a useful and increasingly accepted technique with several applications in structure-based drug discovery. One of the assumptions behind the methodology is the transferability of free energy values from the simulated cosolvent molecules to larger drug-like molecules. However, the binding free energy maps (ΔGbind) calculated for the different moieties of the cosolvent molecules (e.g. a hydroxyl map for the ethanol) are largely influenced by the rest of the solvent molecule and do not reflect the intrinsic affinity of the moiety in question. As such, they are hardly transferable to different molecules. To achieve transferable energies, we present here a method for decomposing the molecular binding free energy into accurate atomic contributions. We demonstrate with two qualitative visual examples how the corrected energy maps better match known binding hotspots and how they can reveal hidden hotspots with actual drug design potential. Atomic decomposition of binding free energies derived from MDmix simulations provides transferable and quantitative binding free energy maps.