Hydroxide Anion Research Articles

Triton-X-100 as an Organic Catalyst for One-Pot Synthesis of Arylmethyl-H-phosphinic Acids from Red Phosphorus and Arylmethyl Halides in the KOH/H2O/Toluene Multiphase Superbase System

Triton-X-100, a polyethylene glycol 4-(tert-octyl)phenyl ether, has been found to be an active micellar organic catalyst for the one-pot selective synthesis of arylmethyl-H-phosphinic acids in up to 65% yields by the direct phosphinylation of arylmethyl halides with red phosphorus in the KOH/H2O/toluene multiphase superbase system. The catalyst demonstrates a good recyclability. As a result, an expeditious method for the chemoselective synthesis of arylmethyl-H-phosphinic acids—versatile sought-after organophosphorus compounds—has been developed. The synthesis is implemented via direct alkylation/oxidation of red phosphorus with arylmethyl halides, promoted by superbase hydroxide anions using Triton-X-100 (a commercial off-the-shelf organic recyclable micellar catalyst). The reaction comprises the hydroxide anions-assisted disassembly of Pred 3D polymer molecules triggered by the separation from the potassium cation in ordinary crown-like micelles to produce polyphosphide anions in aqueous phase. Further, polyphosphide anions are alkylated with arylmethyl halides in organic phase in the presence of the catalytic Triton-X-100 reverse micelles and alkylated polyphosphide species undergo the double hydroxylation. The advantages of the strategy developed include chemoselectivity, benign and accessible starting reagents, catalyst recyclability, and facile one-pot implementation.

Excited State Nonadiabatic Molecular Dynamics of Hot Electron Addition to Water Clusters in the Ultrafast Femtosecond Regime

Dissociative electron attachment (DEA) reactions of water result in the production of hydrogen atoms and hydroxide anions. This has been studied for a long time and is relatively slow in liquid water for thermalized hydrated electrons but much faster with a higher-energy electron. Here, we probe the nonadiabatic molecular dynamics after the addition of a hot electron (6-7 eV) to a neutral water cluster (H2O)n, where n = 2-12, considering the 0-100 fs time scale using the fewest switches surface hopping method, in conjunction with ab initio molecular dynamics and the Tamm-Dancoff approximation density functional theory method. The nonadiabatic DEA occurs within 10-60 fs, and with high probability, giving H + OH- above an energy threshold. This is faster than time scales estimated previously for autoionization or adiabatic DEA. The change in threshold energy with cluster size is modest, ranging from 6.6 to 6.9 eV. Dissociation on a femtosecond time scale is consistent with pulsed radiolysis experiments.

Rational design of composite supporting electrolyte required for achieving high performance aqueous organic redox flow battery

Although aqueous organic redox flow batteries (AORFBs) have many benefits, their organic active materials have the limitations in solubility and chemical instability. To overcome the problems, efforts to develop new organic active materials is usually made. However, these efforts have still limitations in some prospects. Thus, in this study, instead of developing new organic active materials, a rationally designed composite supporting electrolyte is suggested to improve energy density, power density, life-cycle, and efficiency of AORFB using 2-hydroxy-1,4-naphthoquinone (Lawsone) and potassium ferrocyanide as redox couple. The composite supporting electrolyte consists of potassium hydroxide (KOH) and potassium sulfite and is optimized by density functional theory (DFT). DFT predicts that sulfite anions help the solubility and stability of Lawson to improve, while hydroxide anions promote reactivity. The predictions are proved by electrochemical evaluations. With that, when the optimal composite supporting electrolyte is used, high capacity and excellent retention of AORFB (90 % at 100th cycle (from 20.27 to 18.42 Ah·L−1)) are achieved, while high power of 12.4 W is produced by AORFB short stack.

Boryl Radical-Promoted Dehydroxylative Alkylation of 3-Hydroxyoxindole Derivatives

A boryl radical-promoted dehydroxylative alkylation of 3-hydroxy-oxindole derivatives is achieved. The reaction starts from addition of 4-dimethylaminopyridine (DMAP)-boryl radical to the amide carbonyl oxygen atom, which induces a spin-center shift process to promote the C-O bond cleavage. The elimination of a hydroxide anion from a free hydroxy group is also accomplished. Capture of the generated carbon radical with alkenes furnishes a variety of C-3 alkylated oxindoles. This method features a simple operation and broad substrate scope.

Electrochemical Oxidation of Methane to Methanol on Electrodeposited Transition Metal Oxides

Electrochemical partial oxidation of methane to methanol is a promising approach to the transformation of stranded methane resources into a high-value, easy-to-transport fuel or chemical. Transition metal oxides are potential electrocatalysts for this transformation. However, a comprehensive and systematic study of the dependence of methane activation rates and methanol selectivity on catalyst morphology and experimental operating parameters has not been realized. Here, we describe an electrochemical method for the deposition of a family of thin-film transition metal (oxy)hydroxides as catalysts for the partial oxidation of methane. CoOx, NiOx, MnOx, and CuOx are discovered to be active for the partial oxidation of methane to methanol. Taking CoOx as a prototypical methane partial oxidation electrocatalyst, we systematically study the dependence of activity and methanol selectivity on catalyst film thickness, overpotential, temperature, and electrochemical cell hydrodynamics. Optimal conditions of low catalyst film thickness, intermediate overpotentials, intermediate temperatures, and fast methanol transport are identified to favor methanol selectivity. Through a combination of control experiments and DFT calculations, we show that the oxidized form of the as-deposited (oxy)hydroxide catalyst films are active for the thermal oxidation of methane to methanol even without the application of bias potential, demonstrating that high valence transition metal oxides are intrinsically active for the activation and oxidation of methane to methanol at ambient temperatures. Calculations uncover that electrocatalytic oxidation enables reaching an optimum potential window in which methane activation forming methanol and methanol desorption are both thermodynamically favorable, methanol desorption being favored by competitive adsorption with hydroxide anion.

Increasing the Resistance of Archival Cardboards against Thermal Destruction

Abstract Valuable books and archival documents are stored in protective packaging, most frequently made of cardboard, in the depositories of archives, libraries, museums or galleries. As part of preventive conservation, the cardboard could theoretically be treated during production with suitable substances delaying ignition or decelerating flaming combustion. This work describes a study of the short-term and long-term effectiveness of selected inorganic additive flame retardants and their influence on the properties of cardboards. Substances containing silicon, boron or hydroxide anions were tested on Prolux solid cardboard and Klug corrugated cardboard. Parameters such as the linear burning rate, oxygen index, heat release rate, weight loss during heating, pH of an aqueous extract, and total colour difference were evaluated. A mixture of mica and bentonite Cloisite-Na+ in a solution of Tylose MH6000 was found to be most useful for this purpose. This mixture doubled the time to ignition of Klug cardboard; in measurements of the linear burning rate, it caused early flame self-extinction for both kinds of cardboard and, simultaneously, had no observable detrimental effect on the stability of the treated cardboard.

Promotive or suppressive effect of co-existing nucleophiles on lignin condensation in alkaline pulping processes

This study aimed to quantitatively examine how the addition of a strong or weak nucleophile (1.0 mol/L) to a soda cooking treatment (1.0 mol/L NaOH) at 150 °C affects the disappearance and condensation reactions of a simple phenolic lignin model compound, vanillyl alcohol (Va). All the observed phenomena could basically be attributed to the adduct formation of each reagent with the quinone methide intermediate derived from Va (QMVa) and the stabilization of the adduct. The adduct is irreversibly stabilized to be its conjugate base when the reagent was MeNH2 or Me2NH, resulting in the accumulation of the adduct and consequent consumption of QMVa without the reformation of Va from QMVa and condensation reactions of Va with QMVa. The adduct is not stabilized to be its conjugate base and reproduce QMVa when the reagent was Me3N, CO3 2¯, or SO4 2¯ (the sodium salt), resulting in the increased concentration of QMVa to promote the condensation reactions of Va with QMVa. These suppressive and promotive effects were more visible in the same treatment of Va with each nucleophile without the addition of NaOH, in which the concentration of hydroxide anion was low.

The Role of Reactive Oxygen Species in Plant Response to Radiation.

Radiation is widespread in nature, including ultraviolet radiation from the sun, cosmic radiation and radiation emitted by natural radionuclides. Over the years, the increasing industrialization of human beings has brought about more radiation, such as enhanced UV-B radiation due to ground ozone decay, and the emission and contamination of nuclear waste due to the increasing nuclear power plants and radioactive material industry. With additional radiation reaching plants, both negative effects including damage to cell membranes, reduction of photosynthetic rate and premature aging and benefits such as growth promotion and stress resistance enhancement have been observed. ROS (Reactive oxygen species) are reactive oxidants in plant cells, including hydrogen peroxide (H2O2), superoxide anions (O2•-) and hydroxide anion radicals (·OH), which may stimulate the antioxidant system of plants and act as signaling molecules to regulate downstream reactions. A number of studies have observed the change of ROS in plant cells under radiation, and new technology such as RNA-seq has molecularly revealed the regulation of radiative biological effects by ROS. This review summarized recent progress on the role of ROS in plant response to radiations including UV, ion beam and plasma, and may help to reveal the mechanisms of plant responses to radiation.

From Metal Complexes to BioMOFs: An Experimental Proposal for Teaching Coordination Chemistry Concepts

Reactions between metal carbonates from d5 to d10 systems and glutamic acid are used to obtain molecular metal complexes and metal–organic frameworks (MOFs). When the ligand is an amino acid, these MOFs belong to the BioMOF class (metal–organic frameworks for biological and medical applications). The metal carbonates of the d5, d6, and d8 systems produce molecular complexes with general formulas [M(GluH)2(H2O)2], whereas those of the d7, d9, and d10 systems produce compounds of the type [M(Glu)(H2O)·H2O]n. Through these syntheses one can explore, among others, concepts largely related to coordination chemistry such as crystal field splitting, weak and strong fields, the chelate effect, coordination number, metal–ligand stability series, Jahn–Teller distortion, acidity and basicity concepts, and crystal structure. In addition, these experiments also provide an opportunity to discuss interaction stability between metal ions with carbonate and hydroxide anions expressed by physical–chemical parameters such as absolute hardness and natural indices for chemical softness, as well as by the respective Pourbaix diagrams.

Effective N‐formylation of Amines with CO2 in Anaerobic Fermentation Gas Catalyzed by Triply Synergistic Effect of Ionic Porous Organic Polymer

AbstractThe anaerobic fermentation gas (AFG) with CO2 removed is a sustainable energy resource, and converting CO2 in AFG to value‐added chemicals can kill two birds with one stone. Herein, an ionic porous organic polymer (IPOP‐3) catalyst, with triply synergistic effect of its hydroxide anions, nitrogen activation sites and porous structure, is synthesized. IPOP‐3 exhibits an excellent ability to enrich and convert 50 vol.% CO2 by the reactions with various amines into corresponding formamides. The catalyst is also successfully applied to the N‐formylation of CO2 in AFG, and can be easily recovered and reused. The plausible mechanism for the catalytic N‐formylation is proposed. The hydroxide anion in IPOP‐3 activates the Si−H bond of phenyl silane which reacts with the captured CO2 to form formate anion to facilitate the subsequent conversion into formamide. Our work provides a new idea for the purification of AFG and the resource utilization of CO2.

Model-based insights into the decarbonation dynamics of anion-exchange membranes

We present a model-based analysis of the transport of anions in anion exchange membranes (AEMs) with the aim of understanding the decarbonation process and its dynamics. The dynamic simulation model covers the diffusive and migrative transport of water, carbonate anions, and hydroxide anions through an AEM. To the best of our knowledge, this is the first model studying decarbonation process in AEMs. The model is validated using decarbonation data from anion conductivity measurements of ten different AEM materials. Driven by migrative transport, strong concentration gradients develop inside the membranes. A parameter study reveals that the ion-exchange capacity and the applied current have the largest effect on the decarbonation dynamics. Further, high hydroxide diffusivities increase the decarbonation time constant, whereas high carbonate diffusivities decrease it. The results further indicate that high diffusivities of both carbonates and hydroxide result in slower membrane decarbonation. This work provides new insights into properties determining the carbonation and decarbonation of AEMs, which is critical for AEM-based electrochemical devices such as fuel cells and electrolysers.

The Laccase of Myrothecium roridum VKM F-3565: A New Look at Fungal Laccase Tolerance to Neutral and Alkaline Conditions.

Most of the currently known fungal laccases show their maximum activity under acidic environmental conditions. It is known that a decrease in the activity of a typical laccase at neutral or alkaline pH values is the result of an increase in the binding of the hydroxide anion to the T2/T3 copper center, which prevents the transfer of an electron from the T1 Cu to the trinuclear copper center. However, evolutionary pressure has resolved the existing limitations in the catalytic mechanism of laccase, allowing such enzymes to be functionally active under neutral/alkaline pH conditions, thereby giving fungi an advantage for their survival. Combined molecular and biochemical studies, homological modeling, calculation of the electrostatic potential on the Connolly surface at pH 5.0 and 7.0, and structural analysis of the novel alkaliphilic laccase of Myrothecium roridum VKM F-3565 and alkaliphilic and acidophilic fungal laccases with a known structure allowed a new intramolecular channel near the one of the catalytic aspartate residues at T2-copper atom to be found. The amino acid residues of alkaliphilic laccases forming this channel can presumably serve as proton donors for catalytic aspartates under neutral conditions, thus ensuring proper functioning. For the first time for ascomycetous laccases, the production of new trimeric products of phenylpropanoid condensation under neutral conditions has been shown, which could have a potential for use in pharmacology.

N-Electron Valence Perturbation Theory with Reference Wave Functions from Quantum Computing: Application to the Relative Stability of Hydroxide Anion and Hydroxyl Radical

Quantum simulations of the hydroxide anion and hydroxyl radical are reported, employing variational quantum algorithms for near-term quantum devices. The energy of each species is calculated along the dissociation curve, to obtain information about the stability of the molecular species being investigated. It is shown that simulations restricted to valence spaces incorrectly predict the hydroxyl radical to be more stable than the hydroxide anion. Inclusion of dynamical electron correlation from nonvalence orbitals is demonstrated, through the integration of the variational quantum eigensolver and quantum subspace expansion methods in the workflow of N-electron valence perturbation theory, and shown to correctly predict the hydroxide anion to be more stable than the hydroxyl radical, provided that basis sets with diffuse orbitals are also employed. Finally, we calculate the electron affinity of the hydroxyl radical using an aug-cc-pVQZ basis on IBM's quantum devices.

Organic porous heterogeneous composite with antagonistic catalytic sites as a cascade catalyst for continuous flow reaction.

One-pot cascade catalytic reactions easily allow the circumvention of pitfalls of traditional catalytic reactions, such as multi-step syntheses, longer duration, waste generation, and high operational cost. Despite advances in this area, the facile assimilation of chemically antagonistic bifunctional sites in close proximity inside a well-defined scaffold via a process of rational structural design still remains a challenge. Herein, we report the successful fusion of incompatible acid-base active sites in an ionic porous organic polymer (iPOP), 120-MI@OH, via a simple ion-exchange strategy. The fabricated polymer catalyst, 120-MI@OH, performed exceedingly well as a cascade acid-base catalyst in a deacetylation-Knoevenagel condensation reaction under mild and eco-friendly continuous flow conditions. In addition, the abundance of spatially isolated distinct acidic (imidazolium cations) and basic (hydroxide anions) catalytic sites give 120-MI@OH its excellent solid acid and base catalytic properties. To demonstrate the practical relevance of 120-MI@OH, stable millimeter-sized spherical composite polymer bead microstructures were synthesized and utilized in one-pot cascade catalysis under continuous flow, thus illustrating promising catalytic activity. Additionally, the heterogeneous polymer catalyst displayed good recyclability, scalability, as well as ease of fabrication. The superior catalytic activity of 120-MI@OH can be rationalized by its unique structure that reconciles close proximity of antagonistic catalytic sites that are sufficiently isolated in space.

A bis-calix[4]arene-supported [CuII16] cage.

Reaction of 2,2'-bis-p-tBu-calix[4]arene (H8L) with Cu(NO3)2·3H2O and N-methyldiethanolamine (Me-deaH2) in a basic dmf/MeOH mixture affords [CuII16(L)2(Me-dea)4(μ4-NO3)2(μ-OH)4(dmf)3.5(MeOH)0.5(H2O)2](H6L)·16dmf·4H2O (4), following slow evaporation of the mother liquor. The central core of the metallic skeleton describes a tetracapped square prism, [Cu12], in which the four capping metal ions are the CuII ions housed in the calix[4]arene polyphenolic pockets. The [CuII8] square prism is held together "internally" by a combination of hydroxide and nitrate anions, with the N-methyldiethanolamine co-ligands forming dimeric [CuII2] units which edge-cap above and below the upper and lower square faces of the prism. Charge balance is maintained through the presence of one doubly deprotonated H6L2- ligand per [Cu16] cluster. Magnetic susceptibility measurements reveal the predominance of strong antiferromagnetic exchange interactions and an S = 1 ground state, while EPR is consistent with a large zero-field splitting.

Uniform titania-supported Ce(iii) carbonate cluster catalysts for degradation of reactive oxygen species.

We report the synthesis of uniform 2.5 ± 0.4 nm diameter Ce(iii) carbonate clusters deposited on the surface of TiO2 nanoparticles and characterize them using HAADF-STEM and EELS, as well as UV-Vis and FTIR spectroscopies. This material is a highly proficient catalytic antioxidant for the degradation of photocatalytically generated reactive oxygen species (ROS). We observed an unusual U-shaped pH-dependence in its photoprotection catalytic activity, with an optimum function in the near-neutral pH range of 7.7 ± 0.7. This sharp pH dependence is not observed in previously reported bulk Ce(iii) carbonate materials, and it is also not a consequence of Ce(iii) carbonate cluster decomposition. However, it is consistent with a tandem reaction sequence consisting of a biomimetic superoxide dismutase and catalase function, which is dependent on a balance of protons and hydroxide anions for function. Our dissolution-deposition approach for synthesizing nanoscale Ce(iii) carbonate clusters on TiO2 should be generalizable to other carbonates and metal-oxide supports.

Substrate-Free Fabrication of Single-Crystal Two-Dimensional Gold Nanoplates for Catalytic Application.

Two-dimensional (2D) gold nanoplates (AuNPLs) have shown potential in catalysis, photonics, electronics, sensing, and biomedicine fields due to their high aspect ratio, fascinating surface chemistry, and quantum-size effect. Therefore, the synthesis of substrate-free, size-controlled single-crystal gold (Au) nanoplates is highly desirable for the development of catalysis and optical near-field enhancement applications. EDTA and hydroxide anions were used in this study to stimulate the formation of microscale single-crystal gold nanoplates under hydrothermal conditions. The reaction temperature, amount of EDTA, and hydroxyl anions all have a significant effect on the morphologies and size distributions of the gold nanoplates. The gold nanoplates had an average side length of between 3 and 11 μm. The application of the microscale single-crystal gold nanoplates as a nanocatalyst proved their excellent catalytic activity and recyclability for the catalysis of 4-nitrophenol to 4-aminophenol, implying that the large-size gold nanoplates were promising in heterogeneous catalysis applications.

Rare‐Earth Hydroxometalates Ba[RE(OH)5] with RE=Tb, Dy, Ho

AbstractColorless crystals of the new hydroxometalates Ba[RE(OH)5] with the rare‐earth elements RE=Tb, Dy, Ho were synthesized under ultra‐alkaline conditions in a KOH hydroflux at 200 °C. Single‐crystal X‐ray diffraction revealed that the three compounds crystallize isostructural in the monoclinic space group P21/n (no. 14). In the crystal structure, the rare‐earth cations are coordinated by the oxygen atoms of seven hydroxide anions, which define a distorted pentagonal bipyramid. These polyhedra share edges of their basal ring forming infinite chains that run parallel to the [010] direction. Hydrogen bonds connect the chains into layers parallel to the (101) plane. The Ba2+ cations are located between these layers and surrounded by nine oxygen atoms. Ba[Dy(OH)5] is paramagnetic and shows no luminescence under UV light. When heated in synthetic air or argon, water is released in well‐defined steps. Ba[Dy(OH)5] decomposes via DyOOH to Dy2O3, which then reacts with the remaining Ba(OH)2 to form BaDy2O4. Thus, the hydroxometalates can be used as carbon‐free precursors for oxides.

The Hydrated-electron Absorption Spectrum in the View of the Band Theory of Liquid Water

At photo-ionization of liquid water, its inherent species such as hydroxonium cation and hydroxide anion are considered in the band theory as electron acceptor and its donor respectively with forming their excited radicals. In this case, there are also other carriers for hydrated electrons and holes like negatively and positively onecharged molecular pairs that are nonequilibrium to each other and in attitude to mentioned radicals. Here offered model of 4 electron transitions between these natural species gives good consent with the experimental data for absorption spectrum of hydrated electrons in the bulk of liquid water

Effect of Carbonate Anions on the Stability of Quaternary Ammonium Groups for Aemfcs

Anion-exchange membrane fuel cells (AEMFCs) have been attracting significant attention as a promising green and effective technology for energy conversion, suitable for both automotive and stationary applications. AEMFCs operate in an alkaline environment and thus allow the use of non-precious metal electrocatalysts from a wide selection of materials, as well as lower cost anion-exchange membranes (AEMs). In spite of the significant progress recently achieved, the commercial development of AEMFCs is hampered by both AEM degradation and the carbonation processes. The chemical decomposition of the AEMs during fuel cell operation is still considered as the main challenge that needs to be addressed. The combination of high pH environment and high current densities in the AEMFCs results in hydroxide anions with limited solvation, becoming extremely reactive towards positively charged quaternary ammonium (QA) salts. This decomposition leads to detrimental reduction in anion conductivity and therefore in fuel cell performance. Understanding the carbonation process is also critical to allow AEMFCs to operate with ambient air. Hydroxide anions created in the oxygen reduction reaction react with CO2 even at low concentrations, to form bi/carbonates ions. The lower diffusion coefficients and ionic mobility of CO3 -2 and HCO3 - increases resistivity and reduces power output.In this study we experimentally show for the first time the effect of carbonation on the degradation processes of the AEM. The experimental results are compared to modeling by MD. This study provides insights into the carbonation effect on cation stability in alkaline systems, which has significant implications for the final stability of AEMs resulting in long term operation of AEMFCs under real ambient air conditions.