Use Of Anions Research Articles

Abbildung des Photoelektronen‐Zirkulardichroismus im Detachment massenselektierter, chiraler Anionen

AbstractPhotoelektronen‐Zirkulardichroismus (im folgenden PECD, nach der englischen Bezeichnung) zeigt sich als eine Vorwärts‐Rückwärts‐Asymmetrie in der Photoemission nicht‐razemischer Proben, ausgelöst durch zirkular polarisiertes Licht. Gegenüber anderen chiroptischen Methoden hat die PECD‐Spektroskopie potentielle analytische Vorteile bei der Differenzierung chiraler Substanzen, da sie sehr sensitiv auf das chirale Potential von Molekülen ist. Anionen können für die PECD‐Spektroskopie entsprechend ihrer Masse selektiert werden und ihr Einsatz eröffnet Wege zu einfachen experimentellen Aufbauten, die auf handlichen (table‐top) Lasern basieren. Die Nachweise für den PECD von Anionen sind noch rar und das genaue Verständnis der Triebkräfte, welche die PECD‐Elektronendynamik im Photodetachment bestimmen, sind unklar. Hier zeigen wir den PECD‐Effekt im Photodetachment von massenselektierten, deprotonierten 1‐Indanol‐Anionen. Der PECD wird über einen großen Bereich von Photonenenergien mit einem Velocity‐Map‐Imaging(VMI)‐Photoelektronenspektrometer energieaufgelöst analysiert. Ein PECD von bis zu 11 % wird nachgewiesen, was vergleichbar mit gemessenen Werten für neutrale Moleküle ist.

Imaging Photoelectron Circular Dichroism in the Detachment of Mass-Selected Chiral Anions.

Photoelectron Circular Dichroism (PECD) is a forward-backward asymmetry in the photoemission from a non-racemic sample induced by circularly polarized light. PECD spectroscopy has potential analytical advantages for chiral discrimination over other chiroptical methods due to its increased sensitivity to the chiral potential of the molecule. The use of anions for PECD spectroscopy allows for mass-selectivity and provides a path to simple experimental schemes that employ table-top light sources. Evidence of PECD for anions is limited, and insight into the forces that govern PECD electron dynamics in photodetachment is absent. Here, we demonstrate a PECD effect in the photodetachment of mass-selected deprotonated 1-indanol anions. By utilizing velocity map imaging photoelectron spectroscopy with a tunable light source, we determine the energy-resolved PECD over a wide range of photon energies. The observed PECD reaches up to 11 %, similar to what has been measured for neutral species.

Anions Distorting Triggering Ferroelectricity in a Molecular Crystal†

Comprehensive SummaryRecently, molecular ferroelectrics have attracted more and more attention due to their structural diversity, low cost of manufacture, and environmental‐friendly processing. However, most of the design strategies for molecular ferroelectrics have focused on the selection and modification of cations, and the use of anions has been rarely reported. Here, introducing distorted [CuBr4]2– tetrahedra, we obtained a high curie temperature (Tc) ferroelectric, [cyclopentylammonium]2CuBr4, with a Tc as high as 393 K, and exceeding commercial and most of reported molecular ferroelectric BaTiO3 (393 K). Variable‐temperature hysteresis loop shows the nonlinear P‐E loop of the crystal under a wide temperature range. Variable‐temperature single‐crystal X‐ray diffraction revealed that the Aizu expression can be written as mmmFmm2. In short, this work will inspire more creative strategies by exploiting the tunability of the anion module.

Lessons learned from FeSb2O4 on stereoactive lone pairs as a design principle for anion insertion

Fluoride-ion batteries are an attractive energy storage concept analogous to lithium-ion batteries but feature an inverted paradigm where anions are the principal charge carriers. Insertion hosts that can reversibly insert fluoride ions at room temperature are exceedingly sparse. Here, we report that topochemical insertion of fluoride ions in FeSb 2 O 4 involves Fe 2+ /Fe 3+ redox but is mediated by multi-center synergies between iron and antimony centers. Separation of the redox center from the p-block coordination site alleviates structural strain by enabling compensatory contraction and expansion of FeO 6 and SbO 3 polyhedra, respectively. p-block electron lone pairs play a critical role in weakening anion-lattice interactions, enabling reversible fluoride-ion diffusion across microns. The results illuminate the key principle that interactions traceable to stereoactive lone pairs can be used to mediate anion-lattice interactions and suggest that anion insertion hosts can be designed by pairing redox-active transition metals with p-block cations bearing stereochemically active electron lone pairs. Topochemical insertion of fluoride ions is mediated by synergies between Fe and Sb centers p-block electron lone pairs weaken anion-lattice interactions X-ray ptychography imaging demonstrates bulk fluoride-ion diffusion Sb 5 s 2 electron lone pairs enable fluoride-ion deinsertion and facile diffusion Despite several decades of research, fundamental design principles for anion insertion in crystalline lattices remain poorly explored. Zaheer et al. provide a fundamental design principle based on electronic structure considerations that allows use of anions (fluoride ions) instead of cations for electrochemical energy storage.

The Use of Anion - Exchange Resin (A 162) as A Bromine Carrier for the Bromination Of 2 Acylfurans. (Dept. P)

The Use of Anion - Exchange Resin (A 162) as A Bromine Carrier for the Bromination Of 2 Acylfurans. (Dept. P)

Noncovalent and Dynamic Covalent Chemistry Strategies for Driving Thermoresponsive Phase Transition with Multistimuli and Controlled Encapsulation/Release.

We report the development of multiresponsive thermally sensitive polymers through both supramolecular and reversible covalent strategies as well as their use in controlled encapsulation and release. Novel acylhydrazone-based dynamic covalent polymers displaying lower critical solution temperature (LCST) or upper critical solution temperature (UCST) were synthesized. A remarkable control over thermal phase transition can be tuned through multimodes, such as anions, cations, solvent, pH, and competing components. In particular, anion recognition allowed disassembly and thus led to a significant decrease of UCST in dimethyl sulfoxide, and the combination of anion and solvent effects offered additional handle for control. Moreover, the use of anions, cations, as well as pH change was employed for the modulation of LCST-type polymer in water. Furthermore, switching on/off thermoresponsiveness was readily achieved by dynamic covalent exchange. Mechanistic studies also shed light on stimuli-induced changes in aggregation behaviors. Finally, thermally controlled encapsulation and release of hydrophobic and hydrophilic dyes were realized with great repeatability and reversibility, respectively, showing potential in delivery and sensing. The results and strategies described should provide opportunities for many aspects, including dynamic assemblies, complex systems, and adaptive materials.

Remediation of hydrocarbon–heavy metal co-contaminated soil by electrokinetics combined with biostimulation

Successful remediation of organics and heavy metals compound pollution is challenging, and their removal using conventional techniques is often difficult. This study developed an enhanced electrokinetics technology to decontaminate a hydrocarbon–heavy metal co-contaminated soil by applying biostimulation and selective membranes (cationic and anionic). A 30-day experiment was conducted in the laboratory to remediate the soil co-contaminated with total petroleum hydrocarbon (TPH) (9075 mg/kg) and Ni (446.6 mg/kg). The results demonstrated that the addition of anion- and cation-exchange membranes maintained soil pH stability. BioEK remediation under pH control improved microbial growth, microbial degradation of petroleum and reduced biological toxicity. Microbial action immobilized metals (e.g., reduction in exchangeable Ni and the increase in residual Ni). The degradation rate of TPH in contaminated soil was linearly correlated with the increase in TPH degradation population (P < 0.05). Under the optimum operating conditions, electro-bioremediation achieved 77.4% TPH degradation and 58.5% Ni removal after 30 days. Thus, the application of EK with the use of anion- and cation-exchange membranes improved microbial growth and biodegradation, and indigenous bacteria could effectively reduce metal toxicity. The proposed technique can effectively remediate the soil contaminated by heavy metal and organic pollutants.

On the Reliability of Half-Cell Tests for Monovalent (Li+, Na+) and Divalent (Mg2+, Ca2+) Cation Based Batteries

A comprehensive study is reported entailing a comparison of Li, Na, K, Mg, and Ca based electrolytes and an investigation of the reliability of electrochemical tests using half-cells. Ionic conductivity, viscosity, and Raman spectroscopy results point to the cation-solvent interaction to follow the polarizing power of the cations, i.e. Mg2+ > Ca2+> Li+ > Na+ > K+ and to divalent cation based electrolytes having stronger tendency to form ion pairs – lowering the cation accessibility and mobility. Both increased temperature and the use of anions with delocalized negative charge, such as TFSI, are effective in mitigating this issue. Another factor impeding the divalent cations mobility is the larger solvation shells, as compared to those of monovalent cations, that in conjunction with stronger solvent - cation interactions contribute to slower charge transfer and ultimately a large impedance of Mg and Ca electrodes. An important consequence is the non-reliability of the pseudo-reference electrodes as these present both significant potential shifts as well as unstable behaviors. Finally, experimental protocols in order to achieve consistent results when using half-cell set-ups are proposed.

Synthesis of hybrid metal-organic frameworks of {FexMyM'1-x-y}-MIL-88B and the use of anions to control their structural features.

The controlled formation of metal-organic frameworks (MOFs) or coordination polymers (CPs) with suitable components and structural features is one of the most important themes in MOF research. In particular, the reliable preparation of hybrid MOFs containing more than two different kinds of metal ions or organic linkers and a comprehensive understanding of the structural flexibility of MOFs are the central issues for the production of MOFs with the desired properties. We report the synthesis of micro-sized hybrid MOF particles [also known as coordination polymer particles (CPPs)] containing two or three kinds of metal ions in each particle: {FexMyM'1-x-y}-MIL-88B (MIL stands for Materials of Institut Lavoisier, M and M' = Ga, Co, or Mn). Scanning electron microscopy images revealed the formation of well-defined uniform micro-sized hexagonal rods, and energy-dispersive X-ray spectroscopy and elemental mapping images verified the simultaneous incorporation of two or three kinds of metal ions within the CPPs. Interestingly, the structural features of CPPs made from MIL-88B were controlled by altering the anions involved in the structure. Incorporating large acetylacetonate anions within the structure resulted in the closed MIL-88B structure with a small cell volume. However, the open MIL-88B structure with a large cell volume was obtained when small chloride anions were incorporated. The intermediate semi-open MIL-88B structure was also prepared using nitrate anions. Three different structural forms of MIL-88B were verified by powder X-ray diffraction, whole pattern fitting, and thermogravimetric analysis.

Anions in Nucleic Acid Crystallography.

Nucleic acid crystallization buffers contain a large variety of chemicals fitting specific needs. Among them, anions are often solely considered for pH-regulating purposes and as cationic co-salts while their ability to directly bind to nucleic acid structures is rarely taken into account. Here we review current knowledge related to the use of anions in crystallization buffers along with data on their biological prevalence. Chloride ions are frequently identified in crystal structures but display low cytosolic concentrations. Hence, they are thought to be distant from nucleic acid structures in the cell. Sulfate ions are also frequently identified in crystal structures but their localization in the cell remains elusive. Nevertheless, the characterization of the binding properties of these ions is essential for better interpreting the solvent structure in crystals and consequently, avoiding mislabeling of electron densities. Furthermore, understanding the binding properties of these anions should help to get clues related to their potential effects in crowded cellular environments.

Magnetic Droplet Microfluidics as a Platform for the Concentration of [18F]Fluoride and Radiosynthesis of Sulfonyl [18F]Fluoride.

The radioisotope 18F is often considered the best choice for positron emission tomography (PET) owing to its desirable chemical and radiochemical properties. However, nucleophilic 18F-fluorination of large, water-soluble biomolecules, based on C-F bond formation, has traditionally been difficult. Thus, several aqueous fluorination approaches that offer significant versatility in radiopharmaceutical synthesis with sensitive targeting vectors have been developed. Furthermore, because 18F decays rapidly, production of these 18F-labeled compounds requires an automated process to reduce production time, reduce radiation exposure, and minimize losses due to the transfer of reagents during tracer synthesis. Herein, we report the use of magnetic droplet microfluidics (MDM) as a means to concentrate [18F]fluoride from the cyclotron target solution, followed by the synthesis of an 18F-labeled compound on a microfluidic platform. Using this method, we have demonstrated 18F preconcentration in a small-volume droplet through the use of anion exchanging magnetic particles. By using MDM, the preconcentration step took approximately 5 min, and the [18F]fluoride solution was preconcentrated by 15-fold. After the preconcentration step, an 18F-labeling reaction was performed on the MDM platform using the S-F bond formation in aqueous conditions to produce an arylsulfonyl [18F]fluoride compound which can be used as a prosthetic group to label PET targeting ligands. The high radiochemical purity of 95±1% was comparable to the 96% previously reported using a conventional method. In addition, when MDM was used, the total synthesis time was improved to 15 min with lower reagent volumes (50-60 μL) used.

ChemInform Abstract: Advances in Anion Supramolecular Chemistry: From Recognition to Chemical Applications

AbstractReview: [255 refs.

ChemInform Abstract: Taming the Carboxyl Group for Directed Carbometalation: Observations on the Use of Anions, Dianions and Ester Enolates.

AbstractThe copper‐mediated directed metalation of allenic acid (I) and ester (XIV) is investigated to yield β,γ‐unsaturated products (III) and (XV) regioselectively.

Advances in anion supramolecular chemistry: from recognition to chemical applications.

Since the start of this millennium, remarkable progress in the binding and sensing of anions has been taking place, driven in part by discoveries in the use of hydrogen bonding, as well as the previously under-exploited anion-π interactions and halogen bonding. However, anion supramolecular chemistry has developed substantially beyond anion recognition, and now encompasses a diverse range of disciplines. Dramatic advance has been made in the anion-templated synthesis of macrocycles and interlocked molecular architectures, while the study of transmembrane anion transporters has flourished from almost nothing into a rapidly maturing field of research. The supramolecular chemistry of anions has also found real practical use in a variety of applications such as catalysis, ion extraction, and the use of anions as stimuli for responsive chemical systems.

Utilization of a ligand containing 2,2'-bipyridyl and tetrazolate groups to construct a 2D Co(II) coordination polymer: spin canting and metamagnetism.

The use of anions of 6,6'-bis(1H-tetrazol-5-yl)-2,2'-bipyridine (H2btzbp) as chelating ligands in preparing a coordination polymer is described. The synthesis, X-ray crystal structure and magnetic properties of a new Co(II) coordination polymer, [Co(btzbp)]n (1), are reported. The in situ [2 + 3] cycloaddition reaction of 6,6'-dicyano-2,2'-bipyridine with sodium azide in the presence of Co(ClO4)2 under hydrothermal conditions afforded compound 1. Structural characterization revealed that 1 features a distorted two-dimensional (2D) grid layer generated by both tetrazolate and 2,2'-bipyridyl bridges of the btzbp(2-) ligand. Variable temperature and field magnetic susceptibility measurements indicate that compound 1 exhibits spin canting with T(N) = 4.0 K and metamagnetism with H(c) = 300 G.

Taming the carboxyl group for directed carbometalation: observations on the use of anions, dianions and ester enolates.

Carboxylate anions, dianions and ester enolates provide simultaneous protection and activation for directed carbometalation reactions. Advantage can be taken of the bis-carbanionic character of the intermediate for further controlled C-C bond forming reactions.

Metal Supramolecular Frameworks with Silver and Ditopic Bis(pyrazolyl)methane Ligands: Effect of the Anions and Ligand Substitution

A study of the self-assembly of different silver salts and the potentially ditopic ligands bis(pyrazol-1-yl)(pyridine-4-yl)methane (L1) and bis(3,5-dimethylpyrazol-1-yl)(pyridine-4-yl)methane (L2) was undertaken and species’ with discrete or polymeric structures were obtained. Reactions with L1 always yielded derivatives that had a box-like cyclic dimer structure with two metal centers and two ligands. However, on using ligand L2, the resulting structure strongly depended on the coordination ability of the anion. On using anions that have coordinating ability (X = NO3–, CF3SO3–, PF2O2–), a similar box-like structure was formed. However, the use of anions with lower coordinating ability (X = PF6–, ClO4–) led to coordination polymers with a helical disposition. Spontaneous resolution was observed in the two compounds, and only one enantiomer was present in the crystals studied. Solid-state circular dichroism spectroscopy was applied to bunches of crystals, and the results indicate that growth of single colo...

1,3‐Bis(2′‐hydroxyethyl)imidazolium ionic liquids: correlating structure and properties with anion hydrogen bonding ability

A series of 1,3‐bis(2′‐hydroxyethyl)imidazolium ionic liquids is reported where 1H NMR chemical shift values and thermal stabilities (Td), as determined by thermogravimetric analysis, are correlated with the hydrogen bonding capability of various anions ([Cl−], [Br−], [CF3CO2−], [NO2−], [MsO−], [NO3−], [TfO−], [BF4−], [NTf2−], and [PF6−]). Use of anions with the strongest hydrogen bonding capability, such as chloride [Cl−], bromide [Br−], and trifluoroacetate [CF3CO2−], led to the furthest observed downfield chemical shift values in DMSO‐d6 and the poorest thermal stabilities ([CF3CO2−] &lt; 200 °C). Thermal stabilities in excess of 350 °C and upfield chemical shift values were observed for ionic liquids, which employed the weakly coordinating triflate [OTf−], tetrafluoroborate [BF4−], or bis(trifluoromethylsulfonyl)imide [NTf2−] anion. Optimized structures of selected ionic liquids, as determined by density functional theory calculations at the B3LYP/6‐31G + (d,p) level, indicated that the anion preferred to be located above the imidazolium ring and in close proximity to the hydroxyl groups. Calculated dissociation energies (ΔE) and a comparison of key bonding distances (C2―H, (C2)H···X, O―H, and (O)H···X) also confirmed this structural preference. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Use of anion–aromatic interactions to position the general base in the ketosteroid isomerase active site

Although the cation-pi pair, formed between a side chain or substrate cation and the negative electrostatic potential of a pi system on the face of an aromatic ring, has been widely discussed and has been shown to be important in protein structure and protein-ligand interactions, there has been little discussion of the potential structural and functional importance in proteins of the related anion-aromatic pair (i.e., interaction of a negatively charged group with the positive electrostatic potential on the ring edge of an aromatic group). We posited, based on prior structural information, that anion-aromatic interactions between the anionic Asp general base and Phe54 and Phe116 might be used instead of a hydrogen-bond network to position the general base in the active site of ketosteroid isomerase from Comamonas testosteroni as there are no neighboring hydrogen-bonding groups. We have tested the role of the Phe residues using site-directed mutagenesis, double-mutant cycles, and high-resolution X-ray crystallography. These results indicate a catalytic role of these Phe residues. Extensive analysis of the Protein Data Bank provides strong support for a catalytic role of these and other Phe residues in providing anion-aromatic interactions that position anionic general bases within enzyme active sites. Our results further reveal a potential selective advantage of Phe in certain situations, relative to more traditional hydrogen-bonding groups, because it can simultaneously aid in the binding of hydrophobic substrates and positioning of a neighboring general base.

The Clinical Efficacy, Safety and Functionality of Anion Textile in the Treatment of Atopic Dermatitis

BackgroundSeveral previous studies have suggested the improvement of atopic dermatitis (AD) in response to special fabrics. In particular, beneficial effects have been reported, following the use of anion textiles.ObjectiveThe purpose of this study is to evaluate the effectiveness and safety of an anion textile in patients suffering from AD.MethodsWe compared an anion textile with a pure cotton textile. Fifty-two atopic patients (n=52) were enrolled and divided into two groups. The patients in the test (n=25) and control (n=19) groups wore undergarments made of an anion textile or pure cotton over a period of 4 weeks. The overall severity of disease was evaluated using the SCORing atopic dermatitis (SCORAD) index, whereas, the treatment efficacy was measured using a Tewameter® (Courage & Khazaka, Cologne, Germany), Mexameter® (Courage & Khazaka) and Corneo meter® (Courage & Khazaka).ResultsAt the end of the study, a significant decrease in the SCORAD index was observed among the patients with AD in the test group (mean SCORAD decreased from 47.2 to 36.1). Similarly, improvements in the mean transepidermal water loss, skin erythema and stratum corneum hydration were significantly greater among the patients with AD in the test group than in the control group.ConclusionAnion textiles may be used to significantly improve the objective and subjective symptoms of AD, and are similar in terms of comfort to cotton textiles. The use of anion textiles may be beneficial in the management of patients with AD.