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Correction for ‘Ion pair extractant selective for LiCl and LiBr’ by Nam Jung Heo et al. , Chem. Sci. , 2024, 15 , 13958–13965, https://doi.org/10.1039/D4SC03760J.
Na- acenaphthene reaction temperature dependence, studying optical density, precipitation, ion pair formation, coupling constants and hyperfine structure
Empirical measurements of solution vapor pressure of ternary acetonitrile (MeCN) H 2 O–NaCl–MeCN mixtures were recorded, with NaCl concentrations ranging from zero to the saturation limit, and MeCN concentrations ranging from zero to an absolute mole fraction of 0.64. After accounting for speciation, the variability of the Henry's law coefficient at vapor–liquid equilibrium (VLE) of MeCN ternary mixtures decreased from 107% to 5.1%. Solute speciation was modeled using a mass action solution model that incorporates solute solvation and ion-pairing phenomena. Two empirically determined equilibrium constants corresponding to solute dissociation and ion pairing were utilized for each solute. When speciation effects were considered, the solid–liquid equilibrium of H 2 O–NaCl–MeCN mixtures appear to be governed by a simple saturation equilibrium constant that is consistent with the binary H 2 O–NaCl saturation coefficient. Further, our results indicate that the precipitation of NaCl in the MeCN ternary mixtures was not governed by changes in the dielectric constant. Our model indicates that the compositions of the salt-induced liquid–liquid equilibrium (LLE) boundary of the H 2 O–NaCl–MeCN mixture correspond to the binary plateau activity of MeCN, a range of concentrations over which the activity remains largely invariant in the binary water–MeCN system. Broader comparisons with other ternary miscible organic solvent (MOS) mixtures suggest that salt-induced liquid–liquid equilibrium exists if: (1) the solution displays a positive deviation from the ideal limits governed by Raoult's law; and (2) the minimum of the mixing free energy profile for the binary water-MOS system is organic-rich. Finally, this work is one of the first applications of speciation-based solution models to a ternary system, and the first that includes an organic solute.
A direct approach utilizing ion pairing reversed-phase chromatography coupled with suppressed conductivity detection was developed to monitor biodegradation of anionic surfactants during wastewater recycling through hydroponic plant growth systems and fixed-film bioreactors. Samples of hydroponic nutrient solution and bioreactor effluent with high concentrations (up to 120 mS electrical conductance) of inorganic ions can be analyzed without pretreatment or interference. The presence of non-ionic surfactants did not significantly affect the analysis. Dynamic linear ranges for tested surfactants [Igepon TC-42, ammonium lauryl sulfate, sodium laureth sulfate and sodium alkyl (C10-C16) ether sulfate] were 2 to approximately 500, 1 to approximately 500, 2.5 to approximately 550 and 3.0 to approximately 630 microg/ml, respectively.
Here, formal reduction potentials of highly oxidizing and short-lived radical cations of substituted biphenyls generated by pulse radiolysis in 1,2-dichloroethane (DCE) were measured using a redox equilibrium ladder method. The effect of halide ion–radical interactions on reduction potentials of biphenyls was examined by utilizing the ability of DCE to release Cl – in the vicinity of the radical cation. The Hammett correlation of measured potentials across a range of over 700 mV shows saturation at high Hammett sigma values. This effect has been explained by both ion-pairing and hemicolligation interactions between biphenyl radical cations and Cl – and appears to modulate reduction potentials by as much as 400 mV. This finding offers a convenient way to manipulate the energetics of electron transfer involving organic redox species.
Abstract Controlling which products one can access from the predefined biomass‐derived sugars is challenging. Changing from CH 2 Cl 2 to the greener alternative toluene alters which C−O bonds in a sugar are cleaved by the tris(pentafluorophenyl)borane/HSiR 3 catalyst system. This increases the diversity of high‐value products that can be obtained through one‐step, high‐yielding, catalytic transformations of the mono‐, di‐, and oligosaccharides. Computational methods helped identify this non‐intuitive outcome in low dielectric solvents to non‐isotropic electrostatic enhancements in the key ion pair intermediates, which influence the reaction coordinate in the reactivity‐/selectivity‐determining step. Molecular‐level models for these effects have far‐reaching consequences in stereoselective ion pair catalysis.
Sharp line spectrum of exchange-coupled chromium ion pairs in ruby, using piezospectroscopic techniques
Ion exchange membranes materials according to the present disclosure exhibit improved conductivity at low and intermediate relative humidity without sacrificing mechanical strength. Polymers are provided that include a backbone with one or more aryl groups, a halocarbyl group, and a halocarbyl side chain attached to the backbone, wherein the halocarbyl side chain includes a halide separated from the backbone by a hydrocarbyl chain, a hydrocarbyl ring, or combinations thereof. The halide is substituted with a tertiary amine and halide anions are then exchanged with hydroxide anions. The polymers are then contacted with phosphoric acid, which is deprotonated by the hydroxide ions, forming anions which enhance interactions with adjacent quaternary ammonium groups and induce excess phosphoric acid molecules to cluster around those quaternary ammonium groups. The membranes exhibit negligible dopant leaching even at high relative humidity.
Here, described in this work, are calix[4]pyrrole-based ion-pair receptors, cis/trans-1 and cis/trans-2, designed for the extraction of sodium hydroxide. An X-ray diffraction analysis of a single crystal of the cis-1·NaOH isomer isolated from a mixture of cis/trans-1 revealed a unique dimeric supramolecular structure. An average dimer in toluene-d 8 solution was inferred on the basis of diffusion-ordered spectroscopy (DOSY). Support for the proposed stoichiometry came from density functional theory (DFT) calculations. The structural stability of the dimeric cis-1·NaOH complex in toluene solution was further confirmed by ab initio molecular dynamics (AIMD) simulation with explicit representation of solvent. Under conditions of liquid–liquid extraction (LLE), purified receptors cis- and trans-2 were both found to remove NaOH from a pH 11.01 aqueous source phase into toluene with extraction efficiencies (E%) of 50–60% when used equimolar to NaOH. However, in all cases, precipitation was observed. Complexities associated with precipitation could be avoided by immobilization of the receptors onto a chemically inert poly(styrene) resin by means of solvent impregnation. The use of solvent-impregnated resins (SIRs) eliminated precipitation in solution while retaining the extraction efficiency toward NaOH. This allowed both the pH and salinity of the alkaline source phase to be lowered.
Understanding the structure and composition of aluminate complexes in extremely alkaline systems such as Bayer liquors has received enormous attentions due to its fundamental and industrial importance. However, obtaining direct molecular information of the underlying ion-ion interactions using traditional approaches such as NMR or Raman spectroscopy is challenging due to the weakness of these interactions and/or their complex overlapping spectral signatures. Here, we exploit in situ liquid secondary ion mass spectrometry (SIMS) as a new approach and show how it enables new insights. In contrast with traditional techniques, using SIMS we succeeded in acquiring information on dominant ion clusters in these alkaline systems. In Na + /K + mixed alkaline aluminate solutions we clearly observe preferential formation of Na + -anion clusters over K + -anion clusters. Further, evaluation of these clusters by density functional theory (DFT) calculations shows that these structures are stable and that their relative bond energies are consistent with their observed SIMS signal intensity differences. This demonstrates a key advantage of in situ liquid SIMS for overcoming ambiguities obscuring important information in these systems on constituent molecular clusters defined by relatively weak ion pair competition and ion-solvent interactions.
Liquid/liquid interfaces play a central role in scientific fields ranging from nanomaterial synthesis and soft matter electronics to nuclear waste remediation and chemical separations. This diversity of functions arises from an interface’s ability to respond to changing conditions in its neighboring bulk phases. Understanding what drives this interfacial flexibility can provide novel avenues for designing new functional interfaces. However, limiting this progress is an inadequate understanding of the subtle intermolecular and interphase interactions taking place at the molecular level. Here, we use surface-specific vibrational sum frequency generation spectroscopy combined with atomistic molecular dynamics simulations to investigate the self-assembly and structure of model ionic oligomers consisting of an oligodimethylsiloxane (ODMS) tail covalently attached to a positively charged methyl imidazolium (MIM + ) head group at buried oil/aqueous interfaces. We show how the presence of seemingly innocuous salts can impart dramatic changes to the ODMS tail conformations in the oil phase via specific ion effects and ion-pairing interactions taking place in the aqueous phase. These specific ion interactions are shown to drive enhanced amphiphile adsorption, induce morphological changes, and disrupt emergent hydrogen-bonding structures at the interface. Tuning these interactions allows for independent control over the oligomer structure in the oil phase versus interfacial population changes and represents key mechanistic insight that is needed to control chemical reactions at liquid/liquid interfaces.
Hydrophilic-interaction liquid chromatography (HILIC) of intact proteins offers high-resolution separations of glycoforms of glycoproteins differing in the number of (neutral) glycans. However, to obtain efficient separations it is essential that the positively charged sites of the proteins are shielded by acidic (negative) ion-pair reagents (IPRs), so as to enhance the contribution of the hydroxyl groups of the (neutral) sugars in the glycoprotein. Here, we studied the influence of various IPRs that differ in physico-chemical properties, such as hydrophobicity and acidity, on the capillary-scale HILIC separation of intact (glyco)proteins. We evaluated the use of fluoroacetic acid (MFA), difluoroacetic acid (DFA), trifluoroacetic acid (TFA), and heptafluorobutyric acid (HFBA) as diluents for sample preparation, as solvents for sample loading on a reversed-phase trap prior to the HILIC separation, and as mobile-phase components for HILIC and HILIC-MS. To reduce the contribution of ion-exchange interaction with the (silica-based) stationary phase, we used an acrylamide-based monolithic column. We studied the influence of the different IPRs on each step of the separation of a mixture of proteins of different size and hydrophilicity and on the separation of the five glycoforms of ribonuclease B. The content of IPR in the sample was shown not to affect the separation and the MS detection. However, a low content of TFA and DFA in the mobile phase is favourable, as it reduces adduct formation and leads to higher signal intensity. The optimized HILIC conditions successfully resolved nine major glycoforms groups of a ~40 kDa glycoprotein horseradish peroxidase (HRP), as an example of a complex glycoprotein.
Multivalent batteries are a promising new technology for energy storage, but they face challenges to developing suitable electrolytes that can support reversible deposition/dissolution at the metal anode and enable compatibility with high voltage oxide cathode materials. Here, in this work, we investigate the solvation behavior of Zn 2+ , Mg 2+ , Ca 2+ and Cu 2+ in mixed anion electrolytes containing TFSI - and Cl - . Raman and nuclear magnetic resonance spectroscopies are utilized to probe the bulk solvation structure of these electrolytes and demonstrate that mixed anion contact ion pairs (CIPs) are formed in all four systems, indicating this behavior is likely general to divalent cations. Furthermore, the relative population of mixed anion CIPs can be tuned by controlling the relative ratio of TFSI : Cl, with significant CIP populations observed even at low relative fractions of Cl - . These findings imply that modifying the anion chemistry can easily adjust the solvation structure of bulk cations, which has important implications for the development of next-generation electrolytes. By understanding the factors that influence the formation of mixed anion CIPs, we can design systems that promote the formation of electrochemically-active solvation structures that can enable multivalent batteries with improved performance and lifetimes.
Lanthanide (Ln) elements are critical materials that are typically extracted/mined together. Their separation by solvent extraction from acidic media is well known; however, there are few studies in basic media with carbonate anions. We investigated the complexation of Eu(III) and Tb(III) carbonates as solids and solutions in alkaline K2CO3, wherein we sought to access a Tb(IV) carbonate complex through ozonolysis. L3-edge XANES of Eu and Tb carbonate solids, colorless solutions, and a red-hued Tb solution (obtained by ozonolysis) all showed Ln(III) cations. The absence of evidence for a Tb(IV) complex was confirmed through XAS and EPR analyses, despite the solution exhibiting a deep red color. For solids and solutions, EXAFS results indicate molecular Ln(III)-carbonato anions. In terms of the Eu(III) carbonate coordination number, the coordination does not change upon dissolution of the solid sample. Furthermore, EXAFS for the solutions revealed evidence for the association of potassium cations with the Ln(III)-carbonato anions. Furthermore, this direct observation of contact ion pairing by EXAFS at room temperature is rare. The insights into Ln(III) carbonate complexation and solution speciation afforded by XANES-EXAFS, FT-IR, and EPR provides perspectives that serve as benchmarks for future computational and experimental efforts focused on caustic-side solvent extraction of Ln(III) ions.
The effects of the ionophores 15-crown-5 (15C5), 18-crown-6 (18C6), dibenzo-18-crown-6 (DBC) and cryptand 222 (C222) on intramolecular cation exchange in ion pairs of the sodium salt of the durosemiquinone anion in benzene solution are investigated. Electron paramagnetic resonance spectra of the 18C6 and 15C5 complexes with durosemiquinone reduced by contact with a sodium mirror show an alternating line width which indicates that the sodium ion is being exchanged between equivalent sites near the oxygens of the semiquinone with activation energies of 8.7 and 6.0 kcal/mole and Arrhenius preexponential factors of 9 x 10 to the 12th/sec and 10 to the 12th/sec, respectively. Spectra obtained for the DBC complexes show no evidence of exchange, while those of C222 indicate rapid exchange. It is also noted that the hyperfine splitting constants measured do not change over the 50-K temperature interval studied.
Abstract Solutes and their concentrations influence many natural and anthropogenic solution processes. Electrolyte and solution models are used to quantify and predict such behavior. Here we present a mechanistic solution model based on mass action equilibria. Solvation and ion pairing are used to model speciated solute and solvent concentrations such that they correlate to a solution’s vapor pressure (solvent activity) according to Raoult’s law from dilute conditions to saturation. This model introduces a hydration equilibrium constant ( K ha ) that is used with either an ion dissociation constant ( K id ) or a hydration modifier ( m ) with an experimentally determined ion dissociation constant, as adjustable parameters to fit vapor–liquid equilibrium data. The modeled solvation equilibria are accompanied by molecular dynamics (MD) studies that support a decline in the observed degree of solvation with increased concentration. MD calculations indicate this finding is a combination of a solvent that solvates multiple solutes, and changes in a solute’s solvation sphere, with the dominant factor changing with concentration. This speciation-based solution model is lateral to established electrostatics-based electrolyte theories. With its basis in mass action, the model can directly relate experimental data to the modeled solute and solvent speciated concentrations and structures.
Proteins can perform ideal therapeutic functions. However, their large size and significant surface hydrophilicity and charge prohibit them from reaching intracellular targets. These chemical features also render them poorly encapsulated by nanoparticles used for intracellular delivery. In this work, a novel combination of protein vesicles and hydrophobic ion pairing (HIP) was used to load protein cargo and achieve cytosolic delivery to overcome the limitations of previous protein vesicle properties. Protein vesicles are thermally self-assembling nanoparticles made from elastin-like polypeptide (ELP) fused to an arginine-rich leucine zipper and a globular protein fused to a glutamate-rich leucine zipper. To impart stimuli-responsive disassembly, physiological stability, and small size, the ELP sequence was modified to include histidine and tyrosine residues. HIP was used to load and release protein cargo requiring endosomal escape for cytosolic function. HIP vesicles enabled delivery of cytochrome c, a cytosolically active protein, and a significant reduction in viability in both a traditional two-dimensional (2D) human cancer cell line culture and a biomimetic three-dimensional (3D) organoid model of acute myeloid leukemia. By examining the uptake of positively and negatively charged fluorescent protein cargos loaded by HIP, this work revealed the necessity of HIP for cytosolic cargo delivery and how HIP loading influences protein vesicle self-assembly and disassembly using microscopy, small-angle X-ray scattering, and nanoparticle tracking analysis. HIP protein vesicles have the potential to broaden the use of intracellular proteins as therapeutics for various diseases and extend protein vesicles to deliver other biomacromolecules, as the strategy developed here resulted in the first cytosolic protein cargo delivery using protein vesicles.
Enabling new electrochemical technologies requires systems that can operate under ever-more demanding conditions, and progress in energy storage applications reveals tantalizing opportunities to reimagine electrolyte design for performance at extreme potentials. Here, a common thread among these innovations is the formation of significant populations of contact ion pairs (CIPs) in the electrolyte, regardless of the specific cation chemistry or solvent system. The examples summarized in this review suggest that a set of general electrolyte design rules likely exists, where the purposeful selection of anion chemistry can yield CIP structures with tunable control over reaction thermodynamics, kinetics, and interphase chemistry. Identifying the relevant descriptors for high-performance, anion-derived CIP structures can be achieved utilizing a combined experimental and computational approach, aided by machine learning and artificial intelligence, to more rapidly survey the vast combinatorial space available and to enable a new generation of electrolytes for decarbonized electrochemical processes at scale.