Anion Transfer Research Articles

A Potential-Induced Transformation in the Double Electrical Layer on the Rhenium Electrode in Alkali Chloride Melts.

Structural transformations in the adsorption layer caused by an electric potential are investigated using the experimental data on the capacitance of a double electric layer for a rhenium electrode in molten sodium, potassium and cesium chlorides at 1093 K. Likening the double electric layer to a flat capacitor, as well as the effective length of the shielding of the electrode charge and changes in the charge sign depending on the applied potential are estimated. It is found that near the minimum potential of the capacitance curve, the shielding length decreases proportionally to the square of the potential due to the deformation of the double layer. The deformation reaches critical values at the potentials of −0.65, −0.38 and −0.40 V for the Re|NaCl, Re|KCl and Re|CsCl systems respectively, and decreases sharply at more positive potentials. The analysis of the dependence of the charge density on the electrode revealed the effect of shielding of potential-induced rhenium cations by salt phase anions. The strong Raman-active Re–Cl stretching mode was observed at 292 cm−1. This can be explained by the transfer of anions across the interface resulting in the formation of ordered layers of ion associations (possibly, ReXn(n − 1)−) on a positively charged surface.

Polystyrene-b-Poly(2-(Methoxyethoxy)ethyl Methacrylate) Polymerization by Different Controlled Polymerization Mechanisms.

Functional polymers have been an important field of research in recent years. With the development of the controlled polymerization methods, block-copolymers of defined structures and properties could be obtained. In this paper, the possibility of the synthesis of the functional block-copolymer polystyrene-b-poly(2-(methoxyethoxy)ethyl methacrylate) was tested. The target was to prepare the polymer of the number average molecular weight (Mn) of approximately 120 that would contain 20–40% of poly(2-(methoxyethoxy)ethyl methacrylate) by mass and in which the polymer phases would be separated. The polymerization reactions were performed by three different mechanisms for the controlled polymerization—sequential anionic polymerization, atomic transfer radical polymerization and the combination of those two methods. In sequential anionic polymerization and in atomic transfer radical polymerization block-copolymers of the desired composition were obtained but with the Mn significantly lower than desired (up to 30). The polymerization of the block-copolymers of the higher Mn was unsuccessful, and the possible mechanisms for the unwanted side reactions are discussed. It is also concluded that combination of sequential anionic polymerization and atomic transfer radical polymerization is not suitable for this system as polystyrene macroinitiator cannot initiate the polymerization of poly(2-(methoxyethoxy)ethyl methacrylate).

Technologies for Chemical Utilization of Imitation Recipes and Components of Special Products on a Chemical Basis

There are problems of destruction of educational and simulation formulations and components of special chemical-based products and degassing formulations based on organic solvents. Their solution requires the search for cost-effective and environmentally friendly solutions and approaches to their disposal, especially paying attention to the fact that it is practically impossible to completely free the components of products from toxic chemicals. In turn, it is necessary to minimize toxic and unpleasant-smelling emissions into the atmosphere during neutralization and destruction. The purpose of the work is to propose chemical methods for neutralizing and disposing of toxic substances and foul-smelling compounds during the disposal of educational and simulation formulations and special tools. To neutralize compositions based on odorant substances, it is advisable to use compounds of oxidizing-chlorinating action, quaternary ammonium bases and a co-catalyst. The role of each of the used components of the formulation is established. Sodium hypochlorite is an oxidizer, «Katamin AB» is an interphase transfer catalyst that ensures the transfer of anion from the aqueous phase to the organic one, methanesulfonic acid is a co-catalyst that ensures the reaction in both the aqueous and organic phases. The optimal quantitative and qualitative composition of the degassing formulation for neutralizing odorants is considered. The composition of the formulation should include the following components, expressed in % by weight: an aqueous solution of sodium hypochlorite (5%) «Whiteness» – 99.0; dimethylalkyl(C 8 -C 18 ) benzylammonium chloride «Katamin AB» – 0.5; methanesulfonic acid – 0.5.

Cation and Anion Transfer in Quinuclidinium Hexafluorophosphate Plastic Crystal: Role of Constituent Ions and the Crystalline Structure

Cation and Anion Transfer in Quinuclidinium Hexafluorophosphate Plastic Crystal: Role of Constituent Ions and the Crystalline Structure

Structural Characterization of the Delithiated Noncrystalline Phase in a Li-Rich Li2VO2F Cathode Material

As a cathode material for lithium-ion batteries, the disordered rock-salt-type Li2VO2F has a high theoretical capacity of 462 mA h/g; however, this capacity fades rapidly upon cycling. Here, we performed X-ray total scattering measurements of the material to gain insights into the battery properties of Li2VO2F. The atomic pair distribution function obtained from these measurements indicates that the disordered rock-salt crystal partially transforms to an amorphous phase on delithiation. Structural information of the amorphous phase was extracted by precisely evaluating the structural parameters of the disordered rock-salt crystal. Using the structural information, we modeled an atomic three-dimensional structure by the reverse Monte Carlo method. The structural model reproduced the tetrahedral or pyramidal structure with the anions at the vertices and a V ion at the center. These polyhedral structures are likely to involve the anion transfer between the crystalline and amorphous phases. It induces the concentration fluctuation of anions in the crystalline phase and might be a factor for capacity fading of the Li2VO2F cathode material.

Highly Hydrophilic and Lipophilic Derivatives of Bile Salts.

Lipophilicity of 15 derivatives of sodium cholate, defined by the octan-1-ol/water partition coefficient (log P), has been theoretically determined by the Virtual log P method. These derivatives bear highly hydrophobic or highly hydrophilic substituents at the C3 position of the steroid nucleus, being linked to it through an amide bond. The difference between the maximum value of log P and the minimum one is enlarged to 3.5. The partition coefficient and the critical micelle concentration (cmc) are tightly related by a double-logarithm relationship (), meaning that the Gibbs free energies for the transfer of a bile anion from water to either a micelle or to octan-1-ol differ by a constant. The equation also means that cmc can be used as a measurement of lipophilicity. The demicellization of the aggregates formed by three derivatives of sodium cholate bearing bulky hydrophobic substituents has been studied by surface tension and isothermal titration calorimetry. Aggregation numbers, enthalpies, free energies, entropies, and heat capacities, ΔCP,demic, were obtained. ΔCP,demic, being positive, means that the interior of the aggregates is hydrophobic.

Transport of Anions across the Dialytic Membrane Induced by Complexation toward Dendritic Receptors.

A novel approach to inducing anion transport over the dialytic membrane was proposed and successfully tested using the dihydrogen phosphate anion. The anion receptor based on isophthalamide was anchored on a dendritic skeleton, resulting in a macromolecular structure with a limited possibility to cross the dialytic membrane. The dendritic receptor was placed in a compartment separated from a mother anion solution by a membrane. The resulting anion complexation reduced the actual concentration of the anion and induced the anion transfer across the membrane. The anion concentration in mother solution decreased, while it was found to be increased in the compartment with the dendritic receptor. This phenomenon was observed using dendritic receptors with four and eight complexation sites. A detailed analysis of a series of dialytic experiments by 1H NMR spectroscopy enabled an assessment of the complexation behavior of both receptors and an evaluation of the dendritic effect on the anion complexation.

An overlooked issue for high-voltage Li-ion batteries: Suppressing the intercalation of anions into conductive carbon

Summary High-voltage Li-ion batteries have been extensively studied to increase energy density of batteries. However, their cycling stability has remained poor, despite various strategies being proposed to overcome the issues of high-potential cathodes, such as electrolyte oxidation and transition metal dissolution. Herein, we report anion intercalation into the cathode conductive carbon as an overlooked yet critical issue. We propose a concentrated sulfolane (SL)-based electrolyte that prevents anion intercalation via two mechanisms: (1) by offering a high activation barrier to intercalation via its strong anion-Li+ interaction and (2) by forming a sulfur-containing, anion-blocking SL-derived interphase. This electrolyte, used with graphitized acetylene black, which is oxidatively stable but usually susceptible to anion intercalation, enables the stable operation of a Li2CoPO4F/graphite full cell (cut-off voltage = 5.2 V), with 93% capacity retention after 1,000 cycles and an average Coulombic efficiency of ≥99.9%. This is a pivotal strategy to enhance the reversibility of >5 V Li-ion batteries on a commercial level.

Reactivity of transition metal dioxide anions MO2− (M = Co, Ni, Cu, Zn) with sulfur dioxide in the gas phase: An experimental and theoretical study

The reactivity of transition metal dioxide anions of cobalt, nickel, copper and zinc with sulfur dioxide has been investigated in the gas phase by mass spectrometric techniques and theoretical calculations. Dioxide anions of the late transition metals Cu and Zn promote an unprecedented fast and efficient oxidation to the sulfate radical anion through a double oxygen transfer, whereas the earlier transition metals Ni and Co only undergo the addition of two SO2 molecules. The ligation of a water molecule to ZnO2− switches the reaction path to a single oxygen anion transfer, forming SO3−.

Multi-State Dynamic Coordination Complexes Interconverted through Counterion-Controlled Phase Transfer.

We studied a series of dynamic weak-link approach (WLA) complexes that can be shuttled between two immiscible solvents and switched between two structural states via ion exchange. Here, we established that hydrophobic anions transfer cationic, amphiphilic complexes from the aqueous phase to the organic phase, while a chloride source reverses the process. As a result of the dynamic metal coordination properties of WLA complexes, the denticity of these complexes (mono- to bi-) can be modulated as they partition into different phases. In addition, we discovered that heteroligated complexes bearing ligands of different donor strengths preferentially rearrange into two homoligated complexes that are phase-partitioned to maximize the number of stronger coordination bonds. This behavior is not observed in systems with one solvent, highlighting the dynamic and stimuli-responsive nature of hemilabile ligands in a multiphasic solvent environment. Taken together, this work shows that the highly reconfigurable WLA modality can enable the design of biphasic reaction networks or chemical separations driven by straightforward salt metathesis reactions.

Synthesis of Long‐Chain n‐Alkylphosphonic Acids by Phosphonylation of Alkyl Bromides with Red Phosphorus and Superbase under Micellar/Phase Transfer Catalysis

AbstractLong‐chain n‐Alkylphosphonic acids, AlkP(O)(OH)2, are synthesized in up to 91 % yield (mostly 40–60 %) by straightforward phosphonylation of alkyl bromides (AlkBr, Alk=C4–C18) with red phosphorus (Pn) in the multiphase KOH/H2O/toluene system in the presence of 2–10 mol % of cetyltrimethylammonium bromide (CTAB), acting as a micellar/phase transfer catalyst and as a generator/transporter of superbasic hydroxide anions, the intermediate potassium phosphinates being in situ oxidized/neutralized by nitric acid. The key steps of the phosphonylation mechanism are the P−P bond cleavage of Pn polymeric molecules by superbasic −OH anions, dissolved in the CTAB micelles, and phase transfer of polyphosphide anions to the organic phase and their alkylation with AlkBr.

Characterizing the electronic structure of ionic liquid/benzene catalysts for the isobutane alkylation

When a small amount of benzene was introduced into the chloroaluminate ionic liquid (IL), the IL − alkylation can produce premium alkylation gasoline. In order to deepen our understanding of IL − alkylation in general, the electronic properties of [BMIm][AlCl4]/benzene/reactant system were analyzed by the ADCH charge analysis, DOS analysis, frontier molecular orbital analysis, non − covalent interactions (NCI), and energy decomposition analysis (EDA). ADCH analysis reveals that benzene could markedly affect the charge transfer of alkanes and chloroaluminate anions, which weakened the super−acidity of the IL. Frontier molecular orbital analysis shows that the IL system has a significant decrease of H − Lgap, and it increases the sensitivity of the reactants. The anchoring effect of [BMIm]+ cation was observed in the DOS spectra, which enhanced stabilization of the IL structure. NCI analysis shows that π − H bonds could be formed between benzene and the IL. It is believed that better alkylation performance of IL/benzene system is due to these weak interactions.

Molten salt synthesis of neodynium oxyfluoride with tetragonal structure

Neodynium oxyfluoride has been applied for luminescence materials and solid electrolytes because of its structure combined advantages of rare-earth cations with F− and O2− anions. Since the neodynium oxyfluoride with tetragonal structure retains a defect structure having anion vacancies where anions transfer, it shows higher anion conductivity than that with cubic and rhombohedral structures. The feasibility of synthesizing tetragonal neodynium oxyfluoride in molten fluorides was investigated in this work. The neodynium oxyfluoride was not dissolved in molten LiF–CaF2 based on the in-situ observation using confocal scanning laser microscope, therefore neodynium oxyfluoride can be easily collected from molten fluorides. The neodynium oxyfluoride with tetragonal structure was successfully synthesized by the reaction of Nd2O3 with molten fluorides. The synthesis process was analyzed by differential scanning calorimetry combining X-ray diffraction and scanning electron microscope. The reaction model was described and the reaction rate constant was calculated. According to the mathematical description of kinetic equation, the reaction rate could be proportional to the interface difference between molten fluorides and solid Nd2O3.

Electrochemical oxidation of sulphite in neutral media on graphite

In this paper, electrochemical behavior of sulphite ions on graphite electrode in neutral solution (1 molL−1 Na2SO4) has been studied in order to identify the relationship between the sulphite concentration in the electrolyte solution (10−3, 10−2, 10−1, 5·10−1 and 1 mol L−1) and kinetic parameters of the anodic process. Electrochemical behavior of sulphite in the test solutions has been studied by square wave voltammetry (SWV) and differential pulse voltammetry (DPV), as well as by linear (LV) and cyclic voltammetry (CV). Tafel slopes between 167 and 191 mV dec−1 have been obtained, corresponding to an anionic transfer coefficient in the range of 0.31–0.34. Exchange current density values up to 0.80 A m−2 reveals that the rate of the electrochemical oxidation of sulphite in the neutral media is at the same order of magnitude as in the alkaline solution. The general aim of these studies is to obtain new anodes with electrocatalytic properties for sulphite oxidation in SO32−/O2 alkaline fuel cells.

Electrochemistry of catalase at a liquid|liquid micro-interface array

The electrochemistry of catalase (CAT) was investigated at the interface between two immiscible electrolyte solutions (ITIES) as a step towards its detection. Electrochemistry at the ITIES offers advantages such as the non-redox detection of biomolecules. The electrochemical behaviour of CAT at the ITIES, in a micro-interface array format, displayed a distinct cyclic voltammogram when the aqueous phase pH was lower than the isoelectric point (pI) of CAT. No voltammetric response was observed when the aqueous phase pH > pI of CAT, indicating that neutral or negatively charged CAT has no capability to facilitate anion transfer from the organic phase. Adsorptive stripping voltammetry (AdSV) was assessed for detection of low concentrations at the µITIES array. Application of a positive preconcentration potential for a fixed time enabled interfacial accumulation of CAT as a complex; subsequently, a voltammetric scan to lower potentials desorbed the complex, providing the electroanalytical signal. Assessment of sample matrix effects by examining the electrochemistry of CAT in artificial serum indicated that detection in pH-adjusted samples is feasible. Together, these results demonstrate that CAT is electroactive at the liquid–liquid interface and this may be useful as a strategy to detect and characterize the enzyme in a label-free manner.

Probing the Electrolyte Transfer in Ultrathin Polypyrrole Films by In Situ X-ray Reflectivity and Electrochemistry.

This study reports on the potential-induced charge and mass transfer between an ultrathin polypyrrole (PPy) film and an electrolyte by simultaneous in situ X-ray reflectivity (XRR) and electrochemistry (EC) utilizing their sensitivity to electrons. An about 30 nm thin PPy film was deposited on a silicon single crystal by fast potential cycling, providing a dense film of an extraordinary small surface roughness. XRR was recorded from the PPy film in an aqueous 0.1 M perchloric acid at electric potentials between -0.2 V and +0.5 V vs Ag/AgCl. The PPy film shows typical reversible and linear changes in film thickness and electron density arising from the potential-dependent electrolyte incorporation. By introducing EC-XRR, a comprehensive analysis combining in situ XRR and EC, the net number of electrons passing through the PPy-electrolyte interface was deduced along with the potential-induced thickness variations, indicating a complex exchange mechanism. Evidently, along with the anion transfer, parallel charge compensation by protons and a volume and electron compensating counterflow of solvent molecules take place. Complementary time-dependent EC-XRR scans indicate that these exchange mechanisms are individual in two potential ranges. The low actuation along with a high pseudocapacitance suggest the fast potentiodynamically deposited PPy film as a promising supercapacitor material.

Hydride Abstraction as the Rate-Limiting Step of the Irreversible Inhibition of Monoamine Oxidase B by Rasagiline and Selegiline: A Computational Empirical Valence Bond Study.

Monoamine oxidases (MAOs) catalyze the degradation of a very broad range of biogenic and dietary amines including many neurotransmitters in the brain, whose imbalance is extensively linked with the biochemical pathology of various neurological disorders, and are, accordingly, used as primary pharmacological targets to treat these debilitating cognitive diseases. Still, despite this practical significance, the precise molecular mechanism underlying the irreversible MAO inhibition with clinically used propargylamine inhibitors rasagiline and selegiline is still not unambiguously determined, which hinders the rational design of improved inhibitors devoid of side effects current drugs are experiencing. To address this challenge, we present empirical valence bond QM/MM simulations of the rate-limiting step of the MAO inhibition involving the hydride anion transfer from the inhibitor α-carbon onto the N5 atom of the flavin adenin dinucleotide (FAD) cofactor. The proposed mechanism is strongly supported by the obtained free energy profiles, which confirm a higher reactivity of selegiline over rasagiline, while the calculated difference in the activation Gibbs energies of ΔΔG‡ = 3.1 kcal mol−1 is found to be in very good agreement with that from the measured literature kinact values that predict a 1.7 kcal mol−1 higher selegiline reactivity. Given the similarity with the hydride transfer mechanism during the MAO catalytic activity, these results verify that both rasagiline and selegiline are mechanism-based irreversible inhibitors and offer guidelines in designing new and improved inhibitors, which are all clinically employed in treating a variety of neuropsychiatric and neurodegenerative conditions.

A bis(silylene)-stabilized diphosphorus compound and its reactivity as a monophosphorus anion transfer reagent

In contrast to the well-established transition-metal-mediated activation of white phosphorus (P4), the metal-free direct functionalization of P4 has remained rare. The conversion of P4 into a reactive zero-valent diphosphorus compound (P2) has proven challenging to carry out without relying on metal reactivity. Herein, we describe the facile degradation of P4 mediated by two divalent silicon atoms in a bis(silylene) scaffold, resulting in a silylene-stabilized zero-valent P2 complex. The presence of two lone pairs of electrons on each P atom in the silylene-stabilized P2 complex enables a rich reactivity towards small molecules; reaction of the P2 species with CO2, water or a borane leads to the formation of P-C, P-H or P-B bonds, respectively. Notably, the P2 complex also serves as a single phosphorus anion (P-) transfer reagent towards metal carbonyls and a chlorogermylene compound, leading to the synthetically valuable phosphaketenide (PCO-) ligand and a phosphinidene germylene complex, respectively.

ANALYSIS OF KINETIC CHARACTERISTICS OF BAROMEMBRANE AND ELECTROBARMEMBRANE SEPARATION OF AMMONIUM NITRATE SOLUTION

The paper presents a generalized analysis of literature data on the current-voltage, omics characteristics and electrical conductivity of membrane systems. Based on an analysis of the literature, it is noted that electrodialysis is a promising method for the separation of solutions for the production of ammonium nitrate. An analysis of literature revealed that the application of an external constant electric field to the membrane separation of solutions containing charge-transporting components (nitrate ions and ammonium ions) causes the directed transfer of cations and anions through the membranes. The studies revealed that with the baromembrane separation of the studied solutions with increasing transmembrane pressure, the specific output stream increases. This is due to an increase in the driving force of the process. For the OFAM-K anode membrane, with an increase in the current density, with the electrobaromembrane separation of the ammonium nitrate solution, the specific output stream decreases, which is associated with a change in the pH value of the acidified anode permeate. nd for the OPMN-P cathode membrane, the specific output stream increases with a change in the pH of the alkalized cathode permeate. A modified mathematical equation is proposed for theoretical calculation of the specific output stream and the retention coefficient of the OFAM-K and OPMN-P nanofiltration membranes. Experimental studies of membrane systems equipped with the anode OFAM-K and the near-cathode OPMN-P membranes from voltage and transmembrane pressure revealed that for the aqueous solution of ammonium nitrate there are two characteristic periods on the current-voltage, omics characteristics and electrical conductivity of the membrane system (the first period is beyond regime, dissociation of water (H+ and OH-) at the phase boundary with the advent of additional electric current carriers, the second is the degradation of the active layer of a semipermeable membrane). When studying the current-voltage characteristics of a membrane system equipped with an anode OFAM-K and a near-cathode OPMN-P membranes, when separating model and technological solutions, a decrease in the total omics resistance of the system is observed, which is associated with the solution throttling process.

A DFT study on the cleavage of dichalcogenide bridges in cystines and selenocystines: Effect of hydrogen bonding

Density functional theory calculations were employed to quantify the effect of hydrogen bonding interactions in the reactions involving cleavage of dichalcogenides in cystines and selenocystines. The computed gas phase reaction has a multistep mechanism involving hydrogen bond transfers from one heteroatom to another across the reaction coordinate along with the anionic charge transfer from the nucleophile to the product. The solution phase mechanism, however, is simple SN2 irrespective of the nature of the reaction centre or hydrogen bonding interaction at the reaction site, or the nucleophile. When compared to similar reactions without any hydrogen bonding interactions at the reaction centre, these were found to be very facile both in gas phase as well as in aqueous solution.