Standard Gibbs Energy Research Articles

Towards enhanced understanding of the synergistic effects between potassium and calcium in biomass catalyzed pyrolysis

In this study, the influences of different parameters on the products of K-Ca synergistically catalyzed biomass pyrolysis and the possible chemical reactions during the process were investigated. Results indicated that, according to the standard Gibbs energy calculations, Ca(OH)2 was more likely to react with carboxyl groups (precursors of CO2) in biomass than KOH at low temperature ( < 600 °C), effectively preventing the generation of CO2. Increasing the amount of Ca(OH)2 significantly enhanced this interaction, resulting in gradually decrease of CO2 and CO, and remarkably promoted the generation of H2. With a considerable decrease in the O-containing species, the hydrocarbons and phenols (phenol accounting for 49%) became the main species in organic liquid products. For solid products, KOH can react and remove most of the oxygen-containing functional groups, while Ca(OH)2 can fixed O-C=O groups, resulting in a large amount of O-C=O groups remaining. Additionally, bimetallic carbonate K2Ca(CO3)2 was formed at Ca(OH)2/KOH/soybean straw ratios below 0.25:1:2, whereas K2Ca2(CO3)3 was generated at higher ratios exceeding 0.25:1:2. At higher temperatures (> 600 °C), the O-C=O groups transformed into more stable C=O groups, and K2Ca2(CO3)3 decomposed into K2Ca(CO3)2, which increased the content of CO via hydrogenation. As analyzed above, the mechanism of K-Ca synergistically catalyzed biomass pyrolysis was elucidated.

Molecular Properties of Branched Aliphatic α-Amino Acids in Water.

Four branched-chain aliphatic α-amino acids─α-alanine, valine, leucine, and isoleucine (1-4)─were investigated by quantum-chemical calculations in water as a solvent by two methods. The B3LYP variant of DFT calculations was used to obtain the electronic structure and molecular descriptors of these species in their canonical amino acid form as well as the related zwitterionic form in three oxidation states (cation, neutral molecule, and anion). A total of 24 species were subjected to full geometry optimization and complete vibration analysis. Quantities related to ionization or affinity processes were evaluated under adiabatic conditions. The calculated standard reaction Gibbs energy facilitates evaluation of the absolute oxidation and reduction potential. The absolute reduction potential correlates with the electrophilicity index, and the absolute oxidation potential correlates with the adiabatic ionization energy. This finding makes it possible to skip the tedious vibrational analysis and use electronic properties to estimate the redox potentials. The molecular descriptors were compared with the calculated properties of four linear amino acids (glycine, β-alanine, GABA, and DAVA). Parallel calculations using the DLPNO-CCSD(T) method gave analogous results for 24 species. The absolute oxidation potential was related to the antioxidant activity index, which showed only a moderate antioxidant activity of 1-4.

Oxygen exchange in MIEC layered perovskite-like oxide Nd2NiO4+δ: Kinetics and equilibrium parameters

Layered Ruddlesden-Popper (RP) neodymium nickelate oxide, Nd2NiO4+δ, is considered a potential cathode material in solid oxide fuel cells. In this study, the equilibrium properties of NNO were investigated by using quasi-equilibrium oxygen release to contract the isothermal equilibrium diagram “lg pO2 – (4+δ) – T”. Furthermore, the kinetic properties of NNO were studied by oxygen partial pressure relaxation to determine the equilibrium oxygen exchange rate (R0), chemical diffusion coefficient in oxide (Dchem), and surface exchange rate constant (kchem). The Brønsted-Evans-Polanyi-type linear free energy relationship was shown to exist between the standard Gibbs energy of the reaction and the activation energy of the reaction rate constant.

Ion exchange selectivity for protons by sodium ion-form crystalline silicotitanate

ABSTRACT At the Fukushima Daiichi Nuclear Power Station site, crystalline silicotitanate (CST) ion exchangers containing sodium ions (Na+) as exchange ions are used as an adsorbent to remove radioactive cesium (Cs) and strontium (Sr) from groundwater and contaminated water. The ion exchange reactions to remove Cs+ and Sr2+ compete with the reactions with other cations in the water sources. Since the groundwater and contaminated water have low concentrations of metal cations, the influence of competitive ion exchange reactions with protons (H+) is relatively large in the removal of Cs+ and Sr2+ from the water. In this paper, the H+/Na+ ion exchange property of the aqueous solution-CST system was evaluated. Results of batch tests were used to draw the isotherm and Kielland plot for the H+/Na+ ion exchange. The thermodynamic equilibrium constant K and the standard Gibbs energy ΔG 0 of the H+/Na+ ion exchange reaction were evaluated from the Kielland plot. CST exhibited high H+ selectivity in the H+/Na+ ion exchange reaction. The values of K and ΔG 0 were determined to be 7.3 × 104 and − 28 kJ mol−1, respectively. The selectivity of CST for H+ decreased with increasing H+ concentration on the ion exchange sites in CST.

1-Ethyl (butyl)-3-methylimidazolium methanesulfonaties: Low-temperature heat capacity and standard thermodynamic functions of formation

A comprehensive study of the thermodynamic properties of two ionic liquids 1-ethyl-3-methylimidazolium (EmimMS) and 1-butyl-3-methylimidazolium methanesulfonate (BmimMS) was carried out. The isobaric heat capacity of the crystal and liquid phases of EmimMS and BmimMS was determined in the temperature range from 80 to 380 K by vacuum adiabatic calorimetry. The heat capacities of EmimMS and BmimMS were assessed at temperatures from 5 to 80 K by the Kelly method. The temperature dependencies of EmimMS and BmimMS main thermodynamic functions were determined in the temperature range from 5 to 380 K (isobaric heat capacity Cp,m(T), standard entropy Som(T), heat content Hom(T) – Hom(0), Gibbs energy content Gom(T) – Hom(0). Melting points and fusion enthalpies of EmimMS and BmimMS have been refined by DSC. The enthalpies of dissolution in water of EmimMS and BmimMS at 298.15 K were measured by the dissolution calorimetry. The standard enthalpies, entropies and Gibbs energies of EmimMS and BmimMS formation in the crystal and liquid state at 298.15 K were calculated from the experimental data. Comparison of the obtained thermodynamic characteristics with the literature data was carried out.

The determination of the solubility, enthalpy, and entropy of solutions of methyl Furan-2,5-Dimethylenedicarbamate and its hydrides in different solvents

The solubilities of methyl furan-2,5-dimethylenedicarbamate (FDC) and methyl tetrahydrofuran-2,5-dimethylenedicarbamate (THFDC) in dimethyl carbonate (DMC), anhydrous ethanol (EtOH) and benzene were studied using the static equilibrium method combined with high-performance liquid chromatography under atmospheric pressure at temperatures ranging from 278.15 K to 318.15 K. The experimental results demonstrate that the solubility of FDC and THFDC exhibits an upward trend as temperature increases. Among the six correlation models used, all of them (modified Apelblat equation, Buchowski-ksiazczak (λh) model, simplified two-parameter equation, polynomial equation, NRTL model and Wilson model) can effectively correlate the solubility data. Notably, the Wilson model demonstrates superior correlation performance compared to others in FDC system and the NRTL model demonstrates superior correlation performance compared to others in THFDC system. Using the modified Van’t Hoff equation and Gibbs equation, we calculated the apparent standard dissolution enthalpy (ΔHsol), the standard dissolution entropy change (ΔSsol), and the standard dissolution Gibbs energy (ΔGsol) for FDC and THFDC in different solvents. The research resulted indicate that all these dissolution processes are non-spontaneous, entropy-increasing endothermic processes. This study provides valuable reference data for crystallization and purification in industrial production.

Thermodynamic characteristics and surface free energy analysis of bifonazole and lecithin with sodium dodecyl sulfate in hydroethanolic solvent systems

The thermodynamic investigations of the well-recognised antifungal drug bifonazole and lecithin with anionic surfactant sodium dodecyl sulphate have been established. The experiments were conducted using five distinct hydro-ethanolic concentrations, namely 0% v/v, 10% v/v, 30% v/v, 70% v/v, and 90% v/v ethanol, throughout a range of five temperatures (ranging 20 ℃, 25 ℃, 30 ℃, 35 ℃ and 40 ℃) with an increment of drug concentration. The study involved the determination of several parameters, including surface tension (σ), density (ρ), conductivity (κ), contact angle (θ) and surface free energy. Conductivity and surface tension data was used for calculating critical micelle concentration (CMC). CMC was utilised to calculate various thermodynamic properties, such as the standard entropy change (ΔS°m), standard Gibbs energy change (ΔG°m) and standard enthalpy change (ΔH°m) of micellization. This study represents a comparative analysis of the critical micelle concentration (CMC) by utilising surface tension and conductivity measurements. Contact angle is used to determine the hydrophobicity and hydrophilicity of the system. These investigations are valuable for examining the magnitude of hydrophobic interactions within the system, which might be used to ascertain an optimal concentration of bifonazole, lecithin and surfactant to prepare ethosomal formulations.

Thermodynamic study of tin tetraiodide (SnI4) sublimation by effusion techniques

This study presents the first investigation of the sublimation behavior of tin tetraiodide, SnI4, using effusion-based techniques, within a low temperature range (313–340) K. The temperature range covered in the experiments was lower than in previously reported studies based on static methods. Knudsen Effusion Mass Loss (KEML) measurements were performed in the range of (317.1–339.6) K using effusion cells with different orifice sizes. The vapor pressures were measured in the range (0.13–1.13) Pa and were found to be independent of the orifice size. The standard molar enthalpy and Gibbs energy of sublimation at 298.15 K obtained by the Clarke and Glew fit of experimental data are (88.1 ± 0.9) kJ⋅mol−1 and (38.96 ± 0.08) kJ⋅mol−1, respectively. Knudsen Effusion Mass Spectrometry (KEMS) experiments were also performed in the range (313.3–331.7) K, resulting in a sublimation enthalpy value in good agreement with the KEML values and not negligibly higher vapor pressure values. KEMS vapor pressure data were also analyzed by the third-law method. A comparison of our experimental results with the literature data available for both sublimation and evaporation properties of SnI4 is reported. Additionally, ancillary DFT and ab initio calculations were performed to estimate the molecular properties of SnI4(g) and the extent of the gas-phase dissociation to SnI2 and I2.

Mechanism and rate of anomalous extraction of chloride salts from water to 1,2-dichloroethane

Open circuit potential (OCP) measurements, potentiostatic pulse (PP) amperometry and cyclic voltammetry (CV), were used to investigate and to sort by rate the anomalous extraction of the chloride salts RCl of the cations R+ = tetrabutylammonium (TBA+), tetrapentylammonium (TPeA+), tetrahexylammonium (THexA+), tetraheptylammonium (THepA+) and bis(triphenyl-phosphoranylidene)ammonium (BA+) from water to 1,2-dichloroethane (DCE). A tentative mechanism is proposed comprising (a) the diffusion-controlled transport of the ion-pairs (RCl)ip from the aqueous to the organic solvent phase providing a major contribution to the chloride extraction, (b) decomposition of the multiple ion-pairs or clusters (RCl)ipx, which are formed by agglomeration of the single ion-pairs (RCl)ip in the aqueous phase (w), and (c) the exponential decay of the ion-pairs (RCl)ip accumulated on the organic solvent side of the interface at the beginning of the OCP measurements. This model enables to simulate successfully the experimental time dependence of the chloride concentration. A conclusion is made that the effect of the composition of the organic solvent electrolyte RX, where X- = tetraphenylborate (TPB-) or tetrakis(pentafluorophenyl) borate (TB-), on the rate and extent of the anomalous accumulation of the chloride anion in the phase (o) of the two-phase liquid system LiCl(w)/RX(o) can be related to the hydrophobicity of the electrolytes RCl and RX. The latter property can be characterized by the standard Gibbs energy of transfer from the aqueous (w) to the organic solvent (o) phase. The accumulation of the chloride anion in the phase (o) appears to be promoted by the decreasing value of the transfer Gibbs energy of RCl in the sequence TBACl > TPeACl > THexACl > THepACl > BACl, while the decreasing value of the transfer Gibbs energy of RX in the sequence TBATPB > TPeATPB > THexATPB > THepATPB > BATPB > BATB starts to block the cycle combining the energetically unfavorable extraction of RX from the phase (o) to the phase (w) with the energetically favorable extraction of RCl in the opposite direction. IR spectroscopy provides evidence of the formation of the water clusters in the organic solvent phase equilibrated with the aqueous phase in the presence of the tetraalkylammonium cation in both phases, which are supposed to drive the anomalous accumulation of the chloride anion in the phase (o).

Experimental and theoretical studies on thermodynamic activities of binaries ferric and magnesium chlorides in aqueous solutions at various temperatures

The investigation of the thermodynamic properties of binary systems of ferric and magnesium chlorides in aqueous solutions was reported at various temperatures using both the hygrometric method and thermodynamic modeling. Water activities were measured over a molality range of 0.100 up to mmax(FeCl3)= 2.500 mol·kg−1 and to mmax(MgCl2)=(5.798, 6.090, 6.394, and 6.839) mol·kg−1at temperatures from 298.15 K to 353.15 K, respectively. From the new measurements, the osmotic coefficients of water were evaluated and compared with the existing literature data at ambient temperature. These coefficients were treated at various temperatures using established thermodynamic models of the Pitzer, Filippov–Charykov–Rumyantsev, extended ion interaction, and Clegg–Pitzer–Brimblecombe. The relevant properties of ferric and magnesium electrolyte solutions were determined in the temperature range. Indeed, the parameterizations of FeCl3(aq) and MgCl2(aq) were evaluated and employed for the computation of solute activity and osmotic coefficients. Based on literature emf data for MgCl2(aq) at a temperature of 298.15 K, the consistency of the activity coefficients was evaluated using an adequate model, and an excellent description of the prediction activity coefficients is obtained by the extended ion interaction model. Then, the recommended activity coefficients were given at various temperatures by extending this procedure. An experimental investigation was also carried out to evaluate the solubility equilibrium of MgCl2 in aqueous solutions at different temperatures. The solubility product and standard Gibbs energies of dissolution and formation were also calculated at different temperatures and compared with those existing in the literature.

Exploring the solubility and intermolecular interactions of biologically significant amino acids l-serine and L-cysteine in binary mixtures of H2O + DMF, H2O + DMSO and H2O + ACN in temperature range from T = 288.15 K to 308.15 K

In the presented work, a study on the solubility and intermolecular interactions of l-serine and L-cysteine was carried out in binary mixtures of H2O + dimethylformamide (DMF), H2O + dimethylsulfoxide (DMSO), and H2O + acetonitrile (ACN) in the temperature range of T = 288.15 K to 308.15 K. l-serine exhibited the highest solubility in water, while L-cysteine was more soluble in water-DMF. The solvation process was assessed through standard Gibbs energy calculations, indicating the solvation stability order: water-ACN > water-DMSO > water-DMF for l-serine, and water-DMF > water-DMSO > water-ACN for L-cysteine. This study also explored the influence of these amino acids on solvent–solvent interactions, revealing changes in chemical entropies and self-association patterns within the binary solvent mixtures.

Thermodynamic insights of ternary compounds of NiO - V2O5 system

We present the first experimental investigation on thermochemical stability of three ternary nickel vanadates, namely, NiV2O6(s), Ni2V2O7(s) and Ni3V2O8(s) in the NiO-V2O5 system. The standard molar entropies of formation of the compounds were determined by low temperature heat capacity measurements from 2 to 300 K using relaxation calorimetry. The standard molar enthalpy of formation and molar heat capacities were determined employing high temperature oxide melt solution calorimetry in conjunction with differential scanning calorimetry. Using the experimentally obtained thermochemical data, the standard molar Gibbs energy of formation of these compounds were derived and the corresponding expressions are given as follows:∆Gf,m°<NiV2O6>±1.4kJmol−1=−1839.4+0.5132(T/K)(T:298.15−1000K)∆Gf,m°<Ni2V2O7>±1.4kJmol−1=−2101.8+0.5971(T/K)(T:298.15−1000K)∆Gf,m°<Ni3V2O8>±3.2kJmol−1=−2360.5+0.6538(T/K)(T:298.15−1000K)

Electrode potentials involving atoms and ions of metals in intermediate oxidation states in aqueous solutions

The electrode potentials of metal atoms (M+/M0 and M2+/M0 couples) were calculated from their standard electrode potentials in water minus the standard molar Gibbs energy of formation of the atoms in the gas phase, ΔfG0(Mgas0), and the Gibbs energy of hydration in solution, ΔhydG°. Electrode potentials are appreciably shifted (by 2.0–2.5 V) toward negative values relative to the potentials of the solid metals. For the univalent metals Cu0, Ag0, and Au0 (d10s1 electronic configuration), the electrode potentials of M+/M0 couples are –2.73, –1.90, and –1.82 V; for Ga0, In0, and Tl0 (d10s2p1 electronic configuration), they are –3.14, –2.45, and –1.99 V, respectively. For bivalent transition metals of period IV with the d5+ns2 configuration, the potentials of M2+/M0 couples are –2.50 V for Mn0, –2.45 V for Fe0, –2.33 V for Co0, –2.34 for Ni0, –1.29 V for Cu0, and –1.34 V for Zn0. For Cd0 and Hg0 (d10s2 configuration), the potentials are –0.87 and + 0.42 V. Estimation of the electrode potentials of bivalent metals in the intermediate and unstable oxidation states (M2+/M+ and M+/M0 couples) revealed their significant difference. In the case of Zn, Cd, and Hg, this difference is particularly noticeable, as large as 2–3 V, because of different configurations of the M+ (d10s1) and M0 (d10s2) electronic shells. Regular trends in variations of the electrode potentials in the periods and groups of the periodic table were revealed. In going from the atomic-molecular to the solid state, the chemical activity of the metals decreases. The metal surface catalyzes the reactions that are thermodynamically unfavorable in the solution volume.

Cheap and effective potentiometric PVC sensor for the determination of imidazolium based ionic liquids in aqueous and aqua-organic media

Owing to the extensive research on imidazolium based ionic liquids; the present study aims to design a potentiometric sensor for alkyl methylimidazolium ion. For this, poly(vinyl chloride) PVC membrane based on the neutral ion-pair complexes of cetylpyridinium chloride and sodium dodecyl sulfate (CPy+DS−) has been developed. The synthesized ion selective electrode (ISEs) have been found to show linear response with near-Nernstian slope for CnMeImCl (C10MeImCl, C12MeImCl and C14MeImCl). The proposed ISEs show quick response (5–6 s) and provide wide pH range for working. The influence of various ions on the performance of ion-selective electrode is investigated in terms of potentiometric selectivity coefficients, which were determined by separate solution method. The performance of synthesized ISE in examining the critical micellar concentration (cmc) of CnMeImCl in aqueous, aqua-organic media and in the presence of amino acids (glycine, L-glutamic acid and L-phenylalanine) has been found to be satisfactory and confirmed through conductivity and fluorescence measurements. This emphasizes its worth for in-situ analysis of alkyl methylimidazolium ions, during an organic reaction, and hence possible reaction mechanism evaluation. Different thermodynamic parameters such as Standard Gibbs energies of micellization (ΔGm∘), degree of counterion dissociation (α), amphiphile tail transfer Gibbs free energy (ΔGm,trans∘) have been evaluated. Further, the analytical application of synthesized electrode as end point indicator in the potentiometric titration of C14MeImCl with SDS has also been explored, which compared well with improved two-phase titration method. The current study is novel as it involves the use of a cheaper material (CPyCl) as ionophore and that the same electrode can be used for different chain alkyl methylimidazolium ions simply by changing the internal reference solutions.

Optical, electrical and thermal investigations on brucinium di-hydrogen citrate tri-hydrate single crystal: An optimistic tool for microelectronics, OPO and OLED applications

Highly capable nonlinear optical brucinium di-hydrogen citrate tri-hydrate (BDHCTH) single crystal under organic material category has been grown-up successfully by slow evaporation method. Optical, electrical, and thermal investigations were made on title crystal to discover the suitability of fabrication of an optical as well as electrical device for the first time. Crystal structure analysis confirms that, the BDHCTH crystal belongs to triclinic crystal system with non-centro symmetric space group P1. The SLDT value of BDHCTH crystal was found to be 4.22 GW/cm2. Second harmonic generation efficiency of the BDHCTH compound is 1.08 times superior to the reference sample KDP. An attribution of single and sharp peak with lesser full width half maximum value confirms the presence of very fewer defects in the grown crystal. An electric response of the title compound shows the normal dielectric behavior. The piezoelectric charge co-efficient (d33) was found to be 4.5 p C/N. Photo luminescence study confirms that the synthesized sample possess violet, blue and red emission behaviors. Presences of various functional groups in the title sample were identified by FT-IR study. Thermal stability of the compound BDHCTH was found to be 135 °C. Kinetic parameters such as activation energy, Arrhenius factor, standard entropy of activation, standard enthalpy of activation, standard Gibb's energy of activation (ΔG*) and induction time of the grown sample were found to be 161.6396 k J mol−1, 7.4854 s−1, -230.8278 J K mol−1, 154.854 k J mol−1, 249.0314 k J mol−1 and 52 days respectively. At the end of an optical, electrical and thermal analysis, we concluded that the grown crystal is an optimistic tool for microelectronics, OPO and OLED applications due to existence of good SHG value, lesser defect and red emission behavior.

Oxygen exchange kinetics on La0.6Sr0.4FeO3−δ

Equilibrium properties and kinetic properties of strontium-doped lanthanum ferrite La0.6Sr0.4FeO3−δ were studied by an original approach involving two methods: oxygen partial pressure relaxation (with determination of equilibrium exchange rate R0 and a chemical diffusion coefficient in oxide: Dchem) and a quasi-equilibrium oxygen release [with construction of equilibrium isothermal diagram “lg pO2 vs. (3 − δ) vs. T”]. Activation energies determined for R0 and Dchem were 120 ± 20 and 30 ± 2 kJ/mol, respectively. It was shown that the linear free-energy relationship—between activation energy of the reaction rate constant and standard Gibbs energy of the reaction—is of the Brønsted–Evans–Polanyi type.

Sublimation of pyridine derivatives: fundamental aspects and application for two-component crystal screening.

The saturated vapour pressures of five heterocyclic compounds containing the pyridine fragment, namely, three isomers of aminopyridine (2-aminopyridine (2AmPy), 3-aminopyridine (3AmPy), and 4-aminopyridine (4AmPy)); 3-hydroxypyridine (3OHPy) and 2-(1H-imidazol-2-yl)pyridine (ImPy), were measured at appropriate temperature intervals using a transpiration (inert gas flow) method. The standard molar enthalpies, entropies, and Gibbs energies of sublimation for all the studied substances were determined. Among the compounds studied, the largest value of ΔH298sub was observed for ImPy. The influence of substitution and the effects of hydrogen bonds in the crystal lattices on sublimation parameters are discussed herein. The reliable dependences relating ΔG298sub to Tfus and ΔH298sub to ΔG298sub were plotted. A comparative analysis of several calculation schemes for the estimation of sublimation enthalpy and Gibbs free energy was carried out. Thermodynamic parameters obtained in this study were applied for the evaluation of cocrystallisation thermodynamic functions for two-component crystals (virtual screening) on the basis of the studied substituted pyridines.

Stabilisation of solid-state cubic ammonia confined in a glass substance at ambient temperature under atmospheric pressure.

Ammonia, a widely available compound, exhibits structural transitions from solid to liquid to gas depending on temperature, pressure, and chemical interactions with adjacent atoms, offering valuable insights into planetary science. It serves as a significant hydrogen storage medium in environmental science, mitigating carbon dioxide emissions from fossil fuels. However, its gaseous form, NH3(g), poses health risks, potentially leading to fatalities. The sublimation pressure (psub) of solid cubic ammonia, NH3(cr), below 195.5 K is minimal. In this study, we endeavoured to stabilise NH3(cr) at room temperature for the first time. Through confinement within a boric acid glass matrix, we successfully synthesised and stabilised cubic crystal NH3(cr) with a lattice constant of 0.5165 nm under atmospheric pressure. Thermodynamic simulations affirmed the stabilisation of NH3(cr), indicating its quasi-equilibrium state based on the estimated standard Gibbs energy of formation, . Despite these advancements, the extraction of H2(g) from NH3(cr) within the boric acid glass matrix remains unresolved. The quest for an external matrix with catalytic capabilities to decompose inner NH3(cr) into H2(g) and N2(g) presents a promising avenue for future research. Achieving stability of the low-temperature phase at ambient conditions could significantly propel exploration in this field.

Disrupting the Hofmeister bias in salt liquid-liquid extraction with an arylethynyl bisurea anion receptor.

Host-mediated liquid-liquid extraction is a convenient method for the separation of inorganic salts. However, selective extraction of an anion, regardless of its hydrophilicity or lipophilicity as qualitatively described by its place in the Hofmeister series, remains challenging. Herein we report the complete disruption of the Hofmeister-based ordering of anions in host-mediated extraction by a rigidified tweezer-type receptor possessing remarkably strong anion-binding affinity under the conditions examined. Experiments introduce a convenient new method for determination of anion binding using phosphorus inductively coupled plasma mass spectrometry (ICP-MS) to measure extraction of tetra-n-butylphosphonium (TBP+) salts from water into nitrobenzene, specifically examining the disrupting effect of the added arylethynyl bisurea anion receptor. In the absence of the receptor, the salt partitioning follows the expected Hofmeister-type ordering favoring the larger, less hydrated anions; the analysis yields the value -24 kJ mol-1 for the standard Gibbs energy of partitioning of TBP+ cation from water into nitrobenzene at 25 °C. Selectivity is markedly changed by the addition of receptor to the nitrobenzene and is concentration dependent, giving rise to three selectivity regimes. We then used SXLSQI liquid-liquid equilibrium analysis software developed at Oak Ridge National Laboratory to fit host-mediated extraction equilibria for TBP+ salts of Cl-, Br-, I-, and NO3- to the distribution data. While the reverse-Hofmeister 1 : 1 binding of the anions by the receptor effectively cancels the Hofmeister selectivity of the TBPX partitioning into nitrobenzene, formation of unexpected 2 : 1 receptor : anion complexes favoring Cl- and Br- dominates the selectivity at elevated receptor concentrations, producing the unusual order Br- > Cl- > NO3- > I- in anion distribution wherein a middle member of the series is selected and the most lipophilic anion is disfavored. Density functional theory calculations confirmed the likelihood of forming 2 : 1 complexes, where Cl- and Br- are encapsulated by two receptors adopting energetically competitive single or double helix structures. The calculations explain the rare non-Hofmeister preference for Br-. This example shows that anion receptors can be used to control the selectivity and efficiency of salt extraction regardless of the position of the anion in the Hofmeister series.

Effect of indomethacin on the electrical conductance and electrochemical voltammetry of copper chloride in methanol, ethanol, and their binary mixture with water

This study investigated the physicochemical properties of the interaction of indomethacin and copper chloride using the electrical conductance measurement in methanol, ethanol, and their binary mixture with water at room temperature (298.15 K), to determine the solvation behavior, redox behavior, and kinetics. The association parameters were computed using the Fuoss-Hsia-Fernández-Prini and Fuoss-Shedlovsky models. The standard Gibbs energy for association (ΔGoA), Walden product (Λoηo), and hydrodynamic radii (RH) were calculated to study the interaction of indomethacin and copper chloride. On the other hand, cyclic voltammetry examines the electrochemical redox behavior of copper chloride using a gold electrode and its interactions with indomethacin. Results showed changes in peak potentials and currents density in the presence of indomethacin, indicating alterations in redox behavior and reaction rates. Overall, this research can be valuable in understanding the electrochemical properties and potential applications of indomethacin and copper chloride, as well as in developing new drugs or therapeutic agents, which could have has implications in various fields, including drug development, electrochemistry, and materials science.