Gibbs Free Energy Of Solvation Research Articles

Ion-Pairing Mechanism for the Valinomycin-Mediated Transport of Potassium Ions across Phospholipid Bilayers.

The role of the anion on the ionophore properties of valinomycin was studied in a model floating bilayer lipid membrane (fBLM) using supporting electrolytes containing K+ with four different counter anion species (ClO4-, H2PO4-, Cl-, and F-). The electrochemical impedance spectra indicate that the membrane resistance of the bilayer decreases with the decrease of Gibbs free energy of anion solvation. The IR spectra demonstrate that valinomycin does not readily bind to K+ in the KH2PO4, KCl, and KF electrolyte solutions, but in the presence of KClO4, valinomycin readily binds to K+, forming a valinomycin-K+ complex. The results in the present paper reveal the role of the counter anion on the transport of cations by valinomycin across the lipid bilayer. The valinomycin-cation complex creates an ion pair with the anion, and this ion pair can enter the hydrophobic region of the bilayer transporting the cation across the membrane. Anions with low solvation energies facilitate the formation of the ion pair improving the ion conductivity of valinomycin-incorporated bilayers. This paper sheds new light on the transport mechanism of valinomycin ionophores and provides new information about the bioactivity of this molecule.

Development of a Detailed Kinetic Model for the Oxidation of n-Butane in the Liquid Phase.

The chemistry underlying liquid-phase oxidation of organic compounds, the main cause of their aging, is characterized by a free-radical chain reaction mechanism. The rigorous simulation of these phenomena requires the use of detailed kinetic models that contain thousands of species and reactions. The development of such models for the liquid phase remains a challenge as solvent-dependent thermokinetic parameters have to be provided for all the species and reactions of the model. Therefore, accurate and high-throughput methods to generate these data are required. In this work, we propose new methods to generate these data, and we apply them for the development of a detailed chemical kinetic model for n-butane autoxidation, which is then validated against literature data. Our approach for model development is based on the work of Jalan et al. [J. Phys. Chem. B 2013, 117, 2955-2970] who used Gibbs free energies of solvation [ΔsolvG(T)] to correct the data of the gas-phase kinetic model. In our approach, an equation of state (EoS) is used to compute ΔsolvG as a function of temperature for all the chemical species in the mechanism. Currently, ΔsolvG(T) of free radicals cannot be computed with an EoS and it was calculated for their parent molecule (H-atom added on the radical site). Theoretical calculations with the implicit solvent model were performed to quantify the impact of this assumption and showed that it is acceptable for radicals in n-butane and probably in all n-alkanes. New rate rules were proposed for the most important reactions of the model, based on theoretical calculations and the literature data. The developed detailed kinetic model for n-butane autoxidation is the first proposed model in the literature and was validated against the experimental data from the literature. Simulations showed that the main autoxidation products, sec-butyl hydroperoxides and 2-butanol, are produced from H-abstractions from n-butane by sec-C4H9OO radicals and the C4H9OO + C4H9OO reaction, respectively. The uncertainty of the product ratio ("butanone + 2-butanol"/"2-butoxy + 2-butoxy") of the latter reaction remains high in the literature, and our simulations suggest a 1:1 ratio in n-butane solvent.

First-principles study of the adsorption of chlormethine anticancer drug on C24, B12N12 and B12C6N6 nanocages

The chlormethine (CM) drug adsorption on C24, B12C6N6 and B12N12 nanocages has been investigated by using density functional theory at B3LYP/6-31G(d,p) method. Also, the adsorption energy (EAd) investigation of the CM adsorbed complexes has been done by using wB97XD functional to understand the non-local dispersion interactions. Our study reveals that C24 and B12C6N6 nanocages are unfavorable (very low value of EAd) for CM drug adsorption but B12N12 is a promising adsorbent for this drug as EAd of CM/B12N12 complex is −101.70 kJ/mol (−84.77 BSSE corrected) at B3LYP method and −139.70 kJ/mol (−123.43 BSSE corrected) at wB97XD method. NBO and Mulliken charge analysis predicts that large charge transfer occurs from CM to B12N12 about 0.324|e| and 0.259|e| respectively. Also, the spontaneous and favorable interaction between CM drug and B12N12 nanocage is also confirmed by the investigation of solvation Gibbs free energy and quantum theory of atoms in molecules analysis.

Predicting Entropic Effects of Water Mixing with Ionic Liquids Containing Anions of Strong Hydrogen Bonding Ability: Role of the Cation.

Ionic liquids (ILs) such as choline dihydrogen phosphate exhibit an extraordinary solubilizing ability for proteins such as cytochrome C when mixed with 20 wt % water. Most widely used imidazolium-based ionic liquids coupled with dihydrogen phosphate do not exhibit the same solubilizing properties, suggesting that a multifunctional cation such as choline might play a key role in enhancing these properties of ionic liquid mixtures with water. In this theoretical work, we compare intermolecular interactions between the water molecule and ionic liquid ions in two ion-paired clusters of choline- and 1-butyl-3-methyl-imidazolium-based ionic liquids coupled with acetate, dihydrogen phosphate, and mesylate. Gibbs free energy (GFE) of solvation of water in these ionic liquids was calculated. Incorporation of a water molecule into ionic liquid clusters was accompanied by negative GFEs of solvation in both types of cations. These results were in good agreement with previously reported experimental GFEs of solvation of water in ILs. Compared to imidazolium-based clusters, strong interionic interactions of choline ionic liquids resulted in more negative GFEs due to their smaller deformation upon the addition of a water molecule, with dihydrogen phosphate and mesylate predicting the lowest GFEs of -30.1 and -43.5 kJ/mol-1, respectively. Lower GFEs of solvation of water in choline-based clusters were also accompanied with smaller entropic penalties, suggesting that water easily incorporates itself into the existing ionic network. Analysis of the intramolecular bonds within the water molecule showed that the choline hydroxyl group donates electron density to the neighboring water molecule, leading to additional polarization. The predicted infrared spectra of clusters of ionic liquids with water showed a pronounced red shift due to strongly polarized O-H bonds, in excellent agreement with the experimentally measured infrared spectra of ionic liquid mixtures with water. Increased polarization of water in choline-based ionic liquids undoubtedly creates more effective solvents for stabilizing biological molecules such as proteins.

Studies on the solid–liquid equilibria and intermolecular interactions Urea binary mixtures with Sulfanilamide and Sulfacetamide

The binary phase diagrams of Sulfanilamide-Urea (SN-U) and Sulfacetamide-Urea (SC-U) were measured using differential scanning calorimetry technique (DSC). Both examined mixtures were found to form simple binary eutectics. The limited miscibility in the solid state observed by DSC, proving inability of co-crystallization in new multi-molecular form, was also confirmed using PXRD and FTIR-ATR measurements of solid dispersions obtained via liquid assisted co-grinding. The lack of intermolecular complex formation in the crystals does not imply the lack of interactions in the liquid state. Detailed characteristics of potential homo- and hetero-molecular pairs were offered using ab initio and the first principle quantum chemistry computations. The obtained results happened to be strongly dependent on the applied level of theory. The importance of including the zero point energy contributions and electron correlation corrections was emphasized. It was found that the mole fraction of hetero-complexes with urea is the highest among all other constituents of studied systems at their eutectic points. Finally, the importance of intermolecular interaction leading to complexes formation in the liquid state at saturated position was documented by computed values of solvation Gibbs free energy. Based on computed trends it was inferred that the eutectic mixtures can be interpreted as such equilibria for which mutual solvation of all components is maximized.

Ammonia Solubility, Density, and Viscosity of Choline Chloride–Dihydric Alcohol Deep Eutectic Solvents

In the present work, dihydric alcohols (including 1,4-butanediol, 2,3-butanediol, and 1,3-propanediol) were paired with choline chloride (ChCl) to form deep eutectic solvents (DESs) with the molar ratio of ChCl to dihydric alcohol fixed at 1:3 and 1:4. The solubility of NH3 in these DESs was systematically determined at 303.15, 313.15, 323.15, and 333.15 K under pressures up to 420.0 kPa using the isochoric saturation method and was correlated using the Krichevsky–Kasarnovsky (K–K) equation. The dissolution Gibbs free energy, enthalpy, and entropy changes of NH3 solvation were further calculated according to the temperature dependence of Henry’s constants. Based on the reported CO2 solubility data, the selectivities of NH3/CO2 in DESs used herein were calculated. The density and viscosity data of the DESs were also measured and fitted at a temperature range of 303.15–343.15 K. Overall, the dihydric alcohol-based DESs present quite promising NH3 absorption and separation performance, with a value of 3.0 mol NH3 per kg DES and an NH3/CO2 selectivity of 98 at 303.15 K and 100.0 kPa.

Solubility of sulfanilamide in binary solvents containing water: Measurements and prediction using Buchowski-Ksiazczak solubility model

The solubility of Sulfanilamide in binary mixtures comprising water and five organic solvents was studied at different temperatures using a spectrophotometric method. Additionally, the differential scanning calorimetry (DSC) measurements were performed to characterize the non-dissolved portion of Sulfanilamide obtained after shake-flask experiments. The Buchowski-Ksiazczak solubility model was applied to interpret the obtained experimental results. The model was successful in reproducing experimental data, as it was evidenced by several statistical measures, including the Akaike Information Criterion. The obtained parameters of the λh-equation were used for calculating the values of enthalpy of mixing. It was observed that the minimum value of enthalpy of mixing for each system is associated with those binary solvent compositions which result in the highest solubility of Sulfanilamide. Also the maximum value of the λ parameter corresponds to the composition of the mixture yielding the highest solubility. The application of COSMO-RS methodology revealed the sensitivity of solute activities and solvation Gibbs free energies to solvent-cosolvent composition. Also, there was noticed a strong correlation of these thermodynamic properties. It happened that low values of Sulfanilamide activities and their monotonous variations with the composition of considered binary solutions are associated with monotonous solubility profiles and also the reverse conclusion holds. Besides, differences in solvation of monomers and intermolecular complexes are the very probable origins of the observed trends in excess enthalpies of saturated solutions. The advanced quantum chemistry computations, including electron correlation and extended basis set, were used for quantification of affinities of systems components toward pairs formation. From the obtained values of activity equilibrium constants it was concluded that the highest affinity in all studied conditions should be attributed to Sulfanilamide dimers. It was also observed that pairs formed by Sulfanilamide with water are more thermodynamically stable than the ones with cosolvent molecules with only one exception, namely 1,4-dioxane.

Synthesis, Crystal Structure and Physicochemical Characterization of Two Ni(II)-Famotidine Metal Complexes

The coordination ability of the antisecretor agent Famotidine (FMT) was explored using Ni(II) as central ion. [NiFMTH-2] and [Ni(FMT)2]Cl2 were obtained by the solvent evaporation method from the corresponding starting solutions at pH 8 and 4, respectively; the crystal structure was elucidated by single crystal X-ray diffraction in both cases.[NiFMTH-2] resulted in a distorted square-planar geometry, where FMT acts as a tetradentate dianionic ligand through nitrogen atoms belonging to the guanidine group, the thiazolic ring and the side chain, and a sulfur atom from the thioether moiety. [Ni(FMT)2]Cl2 exhibits an octahedral environment composed by two FMT molecules that coordinate by nitrogen atoms deriving from guanidine and thiazole ring moieties, and the thioether sulfur atom. The physicochemical characterization was completed by means of FTIR and UV–Vis spectroscopies, and thermal analysis. Solubility measurements were performed and the results could be satisfactorily correlated with the solvation Gibbs free energy (ΔGsolv) values in aqueous solution obtained using the SDM model by DFT calculations. Ni(II) and famotidine form an octahedral complex at pH 4 where famotidine acts as a tridentate neutral ligand. In basic medium, it behaves as a tetradentate dianion, resulting in a quasi-planar complex. Spectroscopic and thermal data are consistent with single crystal X-ray diffraction structural elucidation. The relative stabilities were assessed by theoretical studies.

GAFF/IPolQ-Mod+LJ-Fit: Optimized force field parameters for solvation free energy predictions.

Rational drug design featuring explicit solubility considerations can greatly benefit from molecular dynamics simulations, as they allow for the prediction of the Gibbs free energy of solvation and thus relative solubilities. In our previous work (A. Mecklenfeld, G. Raabe. J. Chem. Theory Comput. 13 no. 12 (2017) 6266–6274), we have compared solvation free energy results obtained with the General Amber Force Field (GAFF) and its default restrained electrostatic potential (RESP) partial charges to those obtained by modified implicitly polarized charges (IPolQ-Mod) for an implicit representation of impactful polarization effects. In this work, we have adapted Lennard-Jones parameters for GAFF atom types in combination with IPolQ-Mod to further improve the accuracies of solvation free energy and liquid density predictions. We thereby focus on prominent atom types in common drugs. For the refitting, 357 respectively 384 systems were considered for free energies and densities and validation was performed for 142 free energies and 100 densities of binary mixtures. By the in-depth comparison of simulation results for default GAFF, GAFF with IPolQ-Mod and our new set of parameters, which we label GAFF/IPolQ-Mod+LJ-Fit, we can clearly highlight the improvements of our new model for the description of both relative solubilities and fluid phase behaviour.

Investigation of Physicochemical Properties of Aggregated Models of [MIM+]2[C(CN)3-]2 Ionic Liquid: A Theoretical Study

In present work, the aggregation behavior of ion-pairs in [MIM+]2[C(CN)3-]2 ionic liquid was investigated. The quantum chemical calculations were carried out to determine the structural parameters, interaction energies, hydrogen bonding, physical and topological properties of the clusters formed in the ionic liquid of [MIM+]2[C(CN)3-]2. The solvent effect on the stability of clusters was examined. The Gibbs free energy of solvation and the Gibbs free binding energy of clusters in various solvents were calculated. The results show that with decreasing the polarity of the solvent, the tendency to the formation of aggregate increases. Also, the solvation energies of the clusters increase with decreasing the solvent's dielectric constant. The NBO analysis was performed to evaluate the charge transfer in complexes. The AIM analysis was performed in order to characterize intermolecular interactions.

Breaking the limitation of sodium-ion storage for nanostructured carbon anode by engineering desolvation barrier with neat electrolytes

Abstract In the past, most of the studies monotonously focused on developing electrode materials for sodium ion batteries (SIBs), while the compatibility effects and mechanism of electrolytes with material microstructures on the sodiation behavior are barely involved. Here, we demonstrate the sodium-ion storage behavior of carbon anode in neat ether electrolytes with outstanding ion diffusion kinetics at electrode surface that breaks its innate limitation. Porous nanocarbon with small interlayer spacing but very high surface area exhibits a record high ICE over 91.1% and exceptional rate capability for Na-ion storage in ether-based electrolytes. This is due to the remarkably reduced Na+ desolvation barrier in ether electrolytes (~94.6 meV) that is less than one-third of that in ester electrolytes (~307.8 meV). The strong interaction of Na-ions with ester electrolytes and their decomposition on electrode surface can be suppressed by adopting ether solvents owing to lower Gibbs free energies of solvation and Na+ desolvation energy as revealed by DFT calculations. For electrode materials working with ether electrolytes, a large surface area is critical for better electrochemical performance. This study provides a reliable regulation parameter for tailoring electrolytes with materials that offers promising potential for nanostructured materials toward high-rate rechargeable devices.

Predictions of solvation Gibbs free energies with COSMO-SAC approaches

The modelling of a detailed kinetics mechanism in the liquid phase is still not well understood, and the description of solvent effect on reaction rates remains a challenge. Green and co-workers proposed an approach to predict the kinetic constants in liquid phases, which is based on a correction of the kinetic constants in the gas phase. The correction term in Green's approach involves the solvation Gibbs free energies of the chemical species involved in the reactions. Examples of applications of the method are the kinetic modelling of the oxidation of liquid fuels or the catalytic pyrolysis of biomass. However, an accurate thermodynamic model is required to predict the solvation energies. In this work, several predictive models of solvation energies are compared to the large set of experimental data reported recently by Moine et al. [J. Phys. Chem. Ref. Data, 46, 2017] in the CompSol database. Activity coefficients and solvation Gibbs free energies were calculated with different versions of the COSMO-SAC thermodynamic model. We propose a re-optimisation of the universal parameters of these COSMO-SAC models, and extend them to CPCM cavities. It is found that these approaches are in general much more accurate than the Abraham solvation model that is usually employed in Green's approach.

Roles of film-forming additives in diluted and concentrated electrolytes for lithium metal batteries: A density functional theory-based approach

Electrolyte for lithium-ion batteries should facilitate Li+-ion transport and control solid electrolyte interface (SEI). To improve their performance, most of the researches focused more on the effect of the solvation structure of bulk electrolytes on the SEI formation rather than adsorbed species on the Li-anode surface in the past. However, it was found recently that the adsorbed species on the Li-anode surface are strongly connected with the formation of SEI. In this study, diluted [Li+ fluoroethylene carbonate (FEC)/ethylene carbonate(EC)n, Li+(EC)n (n = 1–4)], and concentrated (Li+FEC(EC)n(PF6−) (n = 0–3) electrolyte are investigated in bulk phase and on Li-anode surface using density functional theory (DFT). The stability of the clusters is investigated by their solvation energy and Gibbs free energy change. From the Gibbs free energy change of the clusters, it is found that Li+(EC)4 cluster is the most stable structure in the bulk phase of the diluted electrolyte in the presence or absence of FEC. Pure EC solvated Li+-ion species in the dilute electrolyte in bulk solution is more stable, but the adsorption energy of pure EC-solvated Li+-ion species on Li-anode surface was found weaker than EC and FEC co-solvated Li+-ion species in the diluted electrolyte. DFT calculation suggesting that the dominant species on the Li-anode surface are found Li+FEC(EC)3 and Li+FEC(EC)2PF6− in the diluted and concentrated electrolyte, respectively. The decomposition of the anion-rich adsorbed species in the concentrated electrolyte is suggested to form a better SEI to stabilize Li-anode compared to anion-free adsorbed species in a diluted electrolyte.

Density Functional Theory Calculations of Redox Potentials of Neptunium Complexes in Ionic Liquid

A calculation procedure of redox potential with respect to the standard hydrogen electrode (SHE) in ionic liquid of 3-(2-carboxyethyl)−1-methyl-1H-imidazol-3-ium bis((trifluoromethyl)sulfonyl)amide () is developed based on density functional theory (DFT) and Nernst equation in terms of Gibbs free energy. The Gibbs free energy is evaluated at the theory level of B3LYP/6–311++G(d,p)/SDD and the solvation effect is corrected using conductor-like polarizable continuum model (CPCM). The solvation Gibbs free energy of proton in ionic liquid is evaluated using hybrid solvent models of explicit solvent molecules and implicit solvent model of CPCM. Our calculated redox potentials agree satisfactorily with experimental observations reported in literatures with maximum absolute of 0.237 V.

Prediction of aqueous free energies of solvation using coupled QM and MM explicit solvent simulations.

A method based on molecular dynamics simulations which employ two distinct levels of theory is proposed and tested for the prediction of Gibbs free energies of solvation for non-ionic solutes in water. The method consists of two additive contributions: (i) an evaluation of the free energy of solvation predicted by a computationally efficient molecular mechanics (MM) method; and (ii) an evaluation of the free energy difference between the potential energy surface of the MM method and that of a more computationally intensive first-principles quantum-mechanical (QM) method. The latter is computed by a thermodynamic integration method based on a series of shorter molecular dynamics simulations that employ weighted averages of the QM and MM force evaluations. The combined computational approach is tested against the experimental free energies of aqueous solvation for four solutes. For solute-solvent interactions that are found to be described qualitatively well by the MM method, the QM correction makes a modest improvement in the predicted free energy of aqueous solvation. However, for solutes that are found to not be adequately described by the MM method, the QM correction does not improve agreement with experiment. These preliminary results provide valuable insights into the novel concept of implementing thermodynamic integration between two model chemistries, suggesting that it is possible to use QM methods to improve upon the MM predictions of free energies of aqueous solvation.

Improving the Accuracy of PCM-UAHF and PCM-UAKS Calculations Using Optimized Electrostatic Scaling Factors.

The optimal electrostatic scaling factor (ESF) for the calculation of solvation Gibbs free energies with the polarizable continuum model (PCM) was determined via extensive benchmarking against 1719 experimental solvation Gibbs free energies and transfer free energies taken from the MNSol-v2012 database, as well as 45 aqueous pKa values covering nine solute types (amines, thiols, carbon acid cations, pyridines, alcohols, anilines, carboxylic acids, carbon acid neutrals, phenols) and 20 pKa values in acetonitrile covering four solute types (phenols, carbon acids, carboxylic acids, pyridines). Optimal values for the ESF in a range of solvents are reported. For example, in water, the optimal ESF value is 1.2 and this does not vary with solute charge, radius type, or method. For acetonitrile, we recommend 1.1 for neutrals, 1.0 and 1.1 respectively for cations with UAHF and UAKS radii types, 1.3 for anions for IEFPCM-UAHF, and 1.4 for other anions. At the same time, we show that ESF optimization does not address all errors in PCM, and is thus not a substitute for the appropriate use of explicit solvent molecules, nor for the use of isodesmic methods to enhance systematic error cancellation. For a representative subset of the data we show that the errors in PCM are somewhat larger than in SMD and somewhat smaller than in COSMO-RS, although the latter has not benefited from cavity scaling.

Density Functional Calculations for Aqueous Silver Clusters Containing Water and Nitrate Ligands.

The incorporation of a nitrate ion into silver-water aqueous clusters has been examined using PBE0 density functional theory with the solvent model density (SMD) solvation model. The Gibbs free energy of solvation and other thermodynamic variables are calculated using the harmonic/rigid rotor/ideal gas model at 298.15 K for aqueous solutes including the effects of solute relaxation in water and with London dispersive forces at the D3 level. Free energies of solvation for Ag+ and NO3- were found to agree well with experimental values of -118.2 and -60.1 kcal/mol, respectively, calculated using cluster-continuum models with six to eight water molecules and including solute relaxation and London D3 dispersive interactions. An analysis of data of varying cluster size upon calculated free energy is presented. A direct procedure is applied to aqueous clusters such as Agnz(NO3-)(H2O)5, Agnz(H2O)5, and (NO3-)(H2O)6 n = 1-4; z = 0, +1 in the SMD solvent representation to calculate equilibrium constants for nitrate association with silver clusters in solution that includes fully relaxed solutes. The equilibrium structures of the nitrate-containing clusters involve one or more bonds from nitrate oxygen to positive silver clusters. Water molecules interact with nitrate through H atoms, and overall, the structure represents a silver nitrate cluster with water ligands having similarity to a close ion pair in many aspects. The neutral silver atom is attached to nitrate through H-bonded water molecules. The ratio of nitrate-containing silver clusters to nitrate-free clusters using a calculated equilibrium constant of 0.51 L/mol for Ag+ is small in the range of many experiments. Similar values are found for positive silver clusters up to four atoms in size. The resulting procedures were applied to aqueous clusters of Agn(NO3)m+(n-m) that have been previously experimentally studied for silver reduction in aqueous solution. A chain-like structure with collinear and bidentate oxygen bonds to silver was found, and the equilibrium constants for clustering were determined. A simplified model calculation for the reduction of Ag(H2O)6+ clusters in the presence of silver clusters in aqueous media was studied to understand catalytic effects observed in these systems. The reduction potentials vary with silver cluster size indicating a more favorable reduction caused by the presence of larger silver clusters.

The Impact of Temperature and Ethanol Concentration on the Global Recovery of Specific Polyphenols in an Integrated HPLE/RP Process on Carménère Pomace Extracts.

Sequential extraction and purification stages are required to obtain extracts rich in specific polyphenols. However, both separation processes are often optimized independently and the effect of the integrated process on the global recovery of polyphenols has not been fully elucidated yet. We assessed the impact of hot-pressurized liquid extraction (HPLE) conditions (temperature: 90–150 °C; ethanol concentration: 15%–50%) on the global recovery of specific phenolic acids, flavanols, flavonols and stilbenes from Carménère grape pomace in an integrated HPLE/resin purification (RP) process. HPLE of phenolic acids, flavanols and stilbenes were favored when temperature and ethanol concentration increased, except for chlorogenic acid which showed an increment of its Gibbs free energy of solvation at higher ethanol contents. Ethanol concentration significantly impacted the global yield of the integrated HPLE/RP process. The lower the ethanol content of the HPLE extracts, the higher the recovery of phenolic acids, flavanols and stilbenes after RP, except for flavonols which present more polar functional groups. The best specific recovery conditions were 150 °C and ethanol concentrations of 15%, 32.5% and 50% for phenolic acids, flavanols and stilbenes, and flavonols, respectively. At 150 °C and 32.5% of ethanol, the extracts presented the highest total polyphenol content and antioxidant capacity. The integrated HPLE/RP process allows a selective separation of specific polyphenols and eliminates the interfering compounds, ensuring the safety of the extracts at all evaluated conditions.

Contrasting the solvation properties of protic ionic liquids with different nanoscale structure

The limiting activity coefficients of several hydrocarbons and aliphatic alcohols in protic ionic liquids: 2-hydroxyethylammonium nitrate (EOAN), propylammonium nitrate (PAN), butylammonium nitrate (BAN), and butylammonium thiocyanate (BASCN), were determined at 298K using gas chromatographic headspace analysis. The activity coefficients of hydrocarbons in EOAN turned out to be much higher than in BASCN or alkylammonium nitrates. The methylene group increments for the Gibbs free energies of solvation of various homological series in EOAN are also much higher than in BASCN, BAN, PAN as well as in aprotic ionic liquids or molecular solvents except water. Water-like solvation properties of EOAN are linked with the presence of a three-dimensional network of hydrogen bonds, high concentration of ion pairs, and the absence of nanoscale domain structure that exists in liquid alkylammonium salts and favors solvation of hydrocarbons in apolar domains. The sensitivity of solvation properties of PILs to their nanostructure suggests that the presence of apolar and polar domains in a liquid can be probed with the studies of solvation thermodynamics.

Scalar Relativistic Density Functional Theoretical Investigation of Higher Complexation Ability of Substituted 1,10‐Phenanthroline over Bipyridine Towards Am3+/Eu3+ Ions

The better selectivity of Am3+ over Eu3+ ion with N‐based CyMe4‐BTPhen compared to CyMe4‐BTBP for experimentally observed [ML2(NO3)]2+ complexes was demonstrated using scalar relativistic DFT in conjunction with Born‐Haber thermodynamic cycle and COSMO solvation model. The calculated free energy of extraction, ΔGext reveals strong dependence on the hydration free energies of Am3+ and Eu3+ ions and week dependence to the difference in Gibbs free energy of solvation of the ligand or metal‐ligand complexes. Further, for the first time, we have computed the effect of co‐anion species ([M(NO3)5]2–) on ΔGext of Am3+ and Eu3+ ions with CyMe4‐BTPhen and CyMe4‐BTBP, which adds a positive contribution and thus reduces the ΔGext. The calculated values of ΔΔΔGext (= ΔΔGext,L1 – ΔΔGext,L2, ΔΔGext = ΔGext,M1 – ΔGext,M2) can be used to avoid the very sensitive metal ion solvation energy, effect of co‐anionic species and thus provides a robust approach to determine the selectivity between two metal ions towards different competitive ligands. The natural population analysis (NPA), molecular orbital analysis, Mayer bond order analysis, and bond character analysis using Bader's quantum theory of atoms in molecules indicates slightly more covalency for complexes of Am3+ ion that are correlated to the experiental selectvity of Am3+ ion over Eu3+ ion and hence might be useful in the design and development of next generation extractants.