Reactions Of Cations Research Articles

PH dependence of glyphosate adsorption from aqueous solution using a cationic cellulose microfibers (cCMF) biosorbent

Abstract Currently, the agricultural sector is responsible for the contamination of groundwater and springs due to the excessive use of pesticides, which represents a risk to human and environmental health. Among pesticides, glyphosate is the most used herbicide to increase agricultural production, however, it can cause intoxication in humans and has been classified as a potentially carcinogenic agent. Alternatives for removing these contaminants from water have been studied and discussed, including biosorption, a physical-chemical process that removes substances from solutions using a natural and renewable material. In this sense, this work studied the process to obtain cationic cellulose microfibers (cCMF) from sugarcane bagasse residue, by cellulose isolation followed by cationization reaction with Girard T reagent to promote a new adsorbent for glyphosate removal from water. It was observed that cCMF structure maintains the fibrillar morphology after the microfiber production (1.375 mmol g−1 oxidation degree). Results of zero charge of cCMF microfibers showed an isoelectric point pH = 5.4 ± 0.016 and the highest adsorption capacity was reached at pH 14 (59.21 %), showing a clear pH dependence on the adsorption process. Thereby, the cCMF can be produced from sugarcane bagasse residue being applied as a potential biomaterial for removing organic compounds from water.

Facile access to redox responsive self-healing coating materials via living cationic block copolymerization of styrene and 2-chloroethyl vinyl ether

Poly(alkyl vinyl ether)-based functional copolymers have wide applications in many high-tech areas. However, their synthesis is still challenging which limits their applications. This article describes the synthesis of an unprecedented redox-responsive polystyrene-block-poly(2-thioethyl vinyl ether) (PSt-b-PTEVE) diblock copolymers via sequential “water tolerant” cationic polymerization of St and CEVE, followed by post-polymerization transformation of the pendant -CH2CH2Cl functionalities of PCEVE segment to -CH2CH2SH functionalities. The initiating system enabled controlled cationic polymerization of styrene (St), yielding well-defined PSt (at least up to 22500 g/mol) with relatively low dispersity (Đ ≤ 1.36) and polystyrene-block-poly(2-chloroethyl vinyl ether) (PSt-b-PCEVE) diblock copolymers with acceptable dispersity values (Đ ≤ 1.38) thereof, demonstrating high chain-end fidelity. The controlled character of the cationic polymerization reaction was confirmed by linear kinetic plots, linear increase of Mns (with low Đs) and synthesis of PSts of changing Mns simply by varying initial [St]0/[Initiator]0 feed ratio. The synthesized PSt-b-PTEVE diblock copolymers exhibited redox responsivity and self-healing behaviour. The self-healing property of the PSt-b-PTEVE diblock copolymer was studied by optical microscopy. For this, first, a mechanical cut was introduced in the cross-linked PSt-b-PTEVE thin films and then images were taken at regular intervals to investigate the healing. These promising PSt-b-PTEVE diblock copolymers might have potential applications in many emerging areas, including functional coating.

Cation-Promoted Strain-Release-Driven Access to Functionalized Azetidines from Azabicyclo[1.1.0]butanes.

Access to 1,3-functionalized azetidines through diversity-oriented approach is highly sought-after for finding new applications in drug-discovery. To this goal, strain-release-driven functionalization of azabicyclo[1.1.0]-butane (ABB) has generated significant appeal. Through appropriate N-activation, C3-substituted ABBs are shown to render tandem N/C3-fucntionalization/rearrangement, furnishing azetidines; although, modalities of such N-activation vis-à-vis N-functionalization remain limited to a selected set of electrophiles. Current work showcases a versatile cation-driven activation strategy of ABB. This process is capitalized on the use of Csp3-precursors amenable to form reactive (aza)oxyallyl cation in situ. Herein, N-activation that translates into forming a congested C-N bond, stipulates effective C3 activation. The concept can be further extended to formal [3+2]-annulation involving azaoxyallyl cation and ABB, leading to bridged bicyclic-azetidines. Besides fundamental appeals to this new activation paradigm, operational simplicity and remarkable diversity should engender its prompt use in synthetic and medicinal chemistry.

Cation‐Promoted Strain‐Release‐Driven Access to Functionalized Azetidines from Azabicyclo[1.1.0]butanes

AbstractAccess to 1,3‐functionalized azetidines through a diversity‐oriented approach is highly sought‐after for finding new applications in drug‐discovery. To this goal, strain‐release‐driven functionalization of azabicyclo[1.1.0]‐butane (ABB) has generated significant interest. Through appropriate N‐activation, C3‐substituted ABBs are shown to render tandem N/C3‐fucntionalization/rearrangement, furnishing azetidines; although, modalities of such N‐activation vis‐à‐vis N‐functionalization remain limited to selected electrophiles. This work showcases a versatile cation‐driven activation strategy of ABBs. And capitalizes on the use of Csp3 precursors amenable to forming reactive (aza)oxyallyl cations in situ. Herein, N‐activation leads to formation of a congested C−N bond, and effective C3 activation. The concept was extended to formal [3+2] annulations involving (aza)oxyallyl cations and ABBs, leading to bridged bicyclic azetidines. Besides the fundamental appeal of this new activation paradigm, operational simplicity and remarkable diversity should engender its prompt use in synthetic and medicinal chemistry.

Origin of the Seriously Limited Anionic Redox Reaction of Li-Rich Cathodes in Sulfide All-Solid-State Batteries.

Li-rich layered oxide (LLO) cathode materials with mixed cationic and anionic redox reactions display much higher specific capacity than other traditional layered oxide materials. However, the practical specific capacity of LLO during the first cycle in sulfide all-solid-state lithium-ion batteries (ASSLBs) is extremely low. Herein, the capacity contribution of each redox reaction in LLO during the first charging process is qualitatively and quantitatively analyzed by comprehensive electrochemical and structural measurements. The results demonstrate that the cationic redox of the LiTMO2 (TM = Ni, Co, Mn) phase is almost complete, while the anionic redox of the Li2MnO3 phase is seriously limited due to the sluggish transport kinetics and severe LLO/Li6PS5Cl interface reaction at high voltage. Therefore, the poor intrinsic conductivity and interface stability during the anionic redox jointly restrict the capacity release or delithiation/lithiation degree of LLO during the first cycle in sulfide ASSLBs. This study reveals the origin of the seriously limited anionic redox reaction in LLO, providing valuable guidance for the bulk and interface design of high-energy-density ASSLBs.

Controlling Phase Conversion of Cu-Sb-Se Nanoparticles through the Use of an Amide Base.

The family of copper antimony selenides is important for renewable energy applications. Several phases are accessible within narrow energy and compositional ranges, and tunability between phases is not well-established. Thus, this system provides a rich landscape to understand the phase transformations that occur in hot-injection nanoparticle syntheses. Rietveld refinements on X-ray diffraction patterns model anisotropic morphologies to obtain phase percentages. Reactions targeting the stoichiometry of CuSbSe2 formed Cu3SbSe3 before decomposing to thermodynamically stable CuSbSe2 over time. An amide base was added to balance cation reactivity and directly form CuSbSe2. Interestingly, Cu3SbSe3 remained present but converted to CuSbSe2 more rapidly. We propose that initial Cu3SbSe3 formation may be due to the selenium species not being reactive enough to balance the high reactivity of the copper complex. The unexpected effect of a base on cation reactivity in this system provides insight into the advantages and limitations for its use in other multivalent systems.

Reactions of Acetonitrile with Trapped, Translationally Cold Acetylene Cations.

The reaction of the acetylene cation (C2H2+) with acetonitrile (CH3CN) is measured in a linear Paul ion trap coupled to a time-of-flight mass spectrometer. C2H2+ and CH3CN are both noted for their astrochemical abundance and predicted relevance for understanding prebiotic chemistry. The observed primary products are c-C3H3+, C3H4+, and C2NH3+. The latter two products react with excess CH3CN to form the secondary product C2NH4+, protonated acetonitrile. The molecular formula of these ionic products can be verified with the aid of isotope substitution via deuteration of the reactants. Primary product reaction pathways and thermodynamics are investigated with quantum chemical calculations and demonstrate exothermic pathways to two isomers of C2NH3+, two isomers of C3H4+, and the cyclopropenyl cation c-C3H3+. This study deepens our understanding of the dynamics and products of a pertinent ion-molecule reaction between two astrochemically abundant molecules in conditions that mimic those of the interstellar medium.

Cationic hybridization produces core–shell structure MOF derivatives for reducing electromagnetic pollution

Microstructure design and genetic modification with metal–organic frameworks is one of the key strategies for combating electromagnetic pollution, albeit it continues to face constraints. Since inappropriate parameter selection during microstructure modification is extremely likely to result in pore collapse, metal agglomeration and other issues. Herein, we propose an efficient cation hybridization strategy where we etch the precursor MIL-53 by different etching concentrations and anneal it at various temperatures. Ultimately, light and efficient MOFs-derived microwave absorption materials are obtained. Notably, the magnetic heterogeneous atoms introduced by the cationic hybridization reaction not only provide perfect heterogeneous interfaces but improve the electromagnetic synergistic effect. Benefiting from the optimized impedance matching provided by electric–magnetic synergistic loss mechanism and the polarization effect generated by a large number of heterogeneous interfaces and defects, the MD-2 has shown ultra-high electromagnetic parameters and excellent microwave absorption performance with a qualified absorption bandwidth of 6.97 GHz (2.36 mm) and a minimum reflection loss of −75.61 dB. In addition to broadening the permittivity-magnetic synergistic mechanism of microwave absorption materials under the morphology-property relationship, the general approach inspired by this strategy also lays a solid foundation for the EMW absorption of artificial intelligence microdevices in the 5G era.

Unexpected Reactivity of Cationic-to-Cationic Thiolate Ligand-Exchange Reaction on Au25 Clusters.

Thiolate-protected molecular noble metal clusters have attracted significant attention due to their unique physicochemical properties, which make them applicable in diverse fields such as catalysis, sensing, and bioimaging. Ligand-exchange reactions are a crucial technique for synthesizing and functionalizing these clusters, as they allow for the introduction of new ligands onto the cluster surface, which can alter their properties. While numerous studies have investigated neutral-to-neutral, neutral-to-anionic, and neutral-to-cationic ligand-exchange reactions, the cationic-to-cationic ligand-exchange reaction has never been reported, making the study of such reactions intriguing. In this study, the cationic ligand-exchange reaction on Au25(4-PyET-CH3+)x(4-PyET)18-x (x ≈ 9) clusters, which contain both neutral and cationic ligands in nearly equivalent amounts, was investigated. Contrary to our expectation that the cationic-to-cationic ligand-exchange reaction would be suppressed due to Coulombic repulsion between the surface cationic ligands and incoming cationic ligands, the originally existing cationic ligand was selectively exchanged. The choice of counterions for cationic ligands played a crucial role in controlling the selectivity of ligand exchange. For instance, bulky and hydrophobic counterions such as PF6- can cause steric hindrance and reduce Coulombic repulsion, which promotes cationic-to-cationic ligand exchange. Conversely, counterions like Cl- can lead to neutral-to-cationic ligand exchange due to reduced steric hindrance and increased Coulombic repulsion between cationic ligands. These findings provide a novel method for tailoring the properties of molecular gold clusters through controlled ligand exchange without requiring the design of thiolate ligands with varying geometrical structures.

Recent Advances in the Gold-Catalyzed Reactions of Propargyl Esters.

ConspectusLate-transition-metal-based complexes represent an indispensable catalytic tool in chemical synthesis due to their ability to increase molecular complexity rapidly and efficiently from readily accessible substrates in a single operation. Added to this is the exquisite control of product chemo-, diastereo-, enantio-, and site-selectivities achieved by catalytic systems of the transition-metal salts that have been developed to mediate a wide range of functional group transformations. Within this venerable synthetic toolbox, complexes and salts of Au(I) and Au(III) have emerged in recent years as an invaluable addition as a result of their potent σ- and π-Lewis acidities and ability to stabilize cationic reaction intermediates. The insights provided by mechanistic studies examining the various electronic, steric, and stereoelectronic factors at play in the organogold species that are expected to be formed in the catalytic chemistry of the transition-metal complex have also been pivotal in understanding and exploring their potential synthetic utility. Illustrative of this, for example, is the contribution made by the gold-catalyzed cycloisomerization chemistry of propargyl esters in synthetic strategies to a variety of bioactive natural products and compounds of current pharmaceutical and materials interest. This Account summarizes our efforts over the past decade toward realizing new single-step strategies for carbocyclic and heterocyclic synthesis that relied on the gold-catalyzed reactions of propargyl esters. It outlines synthetic methods developed by the group that exploited the unique reactivities of the gold-carbene species typically generated from the [2,3]-sigmatropic rearrangement of the compound class containing a terminal or electron-deficient alkyne moiety on exposure to the transition-metal salt. This Account also describes the realization of synthetic methods initiated by the gold-catalyzed 1,3-acyloxy migration of propargyl esters with an electronically unbiased disubstituted C≡C bond that delivers the corresponding allenyl ester that is primed for further reactivity on activation by the group 11 metal complex. The studies formed a part of an ongoing overarching program within our group that was focused on determining reactivities in gold catalysis that would enable their application as readily recognizable disconnections in retrosynthetic analysis. They were additionally a part of efforts aimed at evaluating the opportunities offered by the relativistic effects possessed by a Au(I) and Au(III) complex, the most pronounced among the d-block elements and thus the catalyst of choice in alkyne activation chemistry, to generate new chemical space. For instance, we demonstrated in several studies the cycloisomerization of 1,3- and 1,4-enyne esters to be a reliable strategy for the in situ formation of a wide range of 1,4-cyclopentadienyl derivatives. Their further reaction with an appropriately placed functional group or a second starting material was then shown to afford a variety of synthetic targets containing the five-membered ring structure. An example of this was the assembly of a new member of the 1H-isoindole compound family that was found to exhibit potent TNF-α (tumor necrosis factor-α) inhibitor activity.

Occurrence of anionic redox with absence of full oxidation to Ru5+ in high-energy P2-type layered oxide cathode

The anionic redox has been widely studied in layered-oxide-cathodes in attempts to achieve high-energy-density for Na-ion batteries (NIBs). It is known that an oxidation state of Mn4+ or Ru5+ is essential for the anionic reaction of O2−/O− to occur during Na+ de/intercalation. However, here, we report that the anionic redox can occur in Ru-based layered-oxide-cathodes before full oxidation of Ru4+/Ru5+. Combining studies using first-principles calculation and experimental techniques reveals that further Na+ deintercalation from P2-Na0.33[Mg0.33Ru0.67]O2 is based on anionic oxidation after 0.33 mol Na+ deintercalation from P2-Na0.67[Mg0.33Ru0.67]O2 with cationic oxidation of Ru4+/Ru4.5+. Especially, it is revealed that the only oxygen neighboring 2Mg/1Ru can participate in the anionic redox during Na+ de/intercalation, which implies that the Na–O–Mg arrangement in the P2-Na0.33[Mg0.33Ru0.67]O2 structure can dramatically lower the thermodynamic stability of the anionic redox than that of cationic redox. Through the O anionic and Ru cationic reaction, P2-Na0.67[Mg0.33Ru0.67]O2 exhibits not only a large specific capacity of ∼172 mA h g−1 but also excellent power-capability via facile Na+ diffusion and reversible structural change during charge/discharge. These findings suggest a novel strategy that can increase the activity of anionic redox by modulating the local environment around oxygen to develop high-energy-density cathode materials for NIBs.

Nature-inspired catalytic asymmetric rearrangement of cyclopropylcarbinyl cation

In nature, cyclopropylcarbinyl cation is often involved in cationic cascade reactions catalyzed by natural enzymes to produce a great number of structurally diverse natural substances. However, mimicking this natural process with artificial organic catalysts remains a daunting challenge in synthetic chemistry. We report a small molecule-catalyzed asymmetric rearrangement of cyclopropylcarbinyl cations, leading to a series of chiral homoallylic sulfide products with good to excellent yields and enantioselectivities (up to 99% enantiomeric excess). In the presence of a chiral SPINOL-derived N-triflyl phosphoramide catalyst, the dehydration of prochiral cyclopropylcarbinols occurs rapidly to generate symmetrical cyclopropylcarbinyl cations, which are subsequently trapped by thione-containing nucleophiles. A subgram-scale experiment and multiple downstream transformations of the sulfide products are further pursued to demonstrate the synthetic utility. Notably, a few heteroaromatic sulfone derivatives could serve as "covalent warhead" in the enzymatic inhibition of severe acute respiratory syndrome coronavirus 2 main protease.

Cyclopropylcarbinyl-to-Homoallyl Carbocation Equilibria Influence the Stereospecificity in the Nucleophilic Substitution of Cyclopropylcarbinols

The synthesis of quaternary homoallylic halides and trichloroacetates from cyclopropylcarbinols, as reported by Marek (J. Am. Chem. Soc. 2020, 142, 5543-5548), is one of the few reported examples of stereospecific nucleophilic substitution involving chiral bridged carbocations. However, for the phenyl-substituted substrates, poor specificity is observed and mixtures of diastereomers are obtained. To understand the nature of the intermediates involved and explain the loss of specificity for certain substrates, we have performed a computational investigation of the reaction mechanism using ωB97X-D optimizations and DLPNO-CCSD(T) energy refinements. Our results indicate that cyclopropylcarbinyl cations are stable intermediates in this reaction, while bicyclobutonium structures are high-energy transition structures that are not involved. Instead, multiple rearrangement pathways of cyclopropylcarbinyl cations were located, including ring openings to homoallylic cations. The activation barriers required to reach such structures are correlated to the nature of the substituents; while direct nucleophilic attack on the chiral cyclopropylcarbinyl cations is kinetically favored for most systems, the rearrangements become competitive with nucleophilic attack for the phenyl-substituted systems, leading to a loss of specificity through rearranged carbocation intermediates. As such, stereospecific reactions of chiral cyclopropylcarbinyl cations depend on the energies required to access their corresponding homoallylic structures, from which selectivity is not guaranteed.

Bond Energies of UO+ and UC+: Guided Ion Beam and Quantum Chemical Studies of the Reactions of Uranium Cation with O2 and CO

AbstractGuided ion beam tandem mass spectrometry was used to examine the kinetic energy dependent reactions of U+ with O2 and CO. In the reaction of U+ with O2, the UO+ product is formed in a barrierless and exothermic process with a reaction efficiency at low energies of k/kcol=1.1±0.2, but increases at higher collision energies. Formation of both UO+ and UC+ in the reaction of U+ with CO is endothermic. 0 K bond dissociation energies (BDEs) of D0(U+‐O)=7.88±0.09 eV and D0(U+‐C)=4.03±0.13 eV were determined by analyzing the kinetic energy dependent cross sections in the latter endothermic reactions. These values are within experimental uncertainty of previously reported experimental values. Additionally, the electronic states of UO+ and UC+ and the potential energy surfaces for the reactions were explored by quantum chemical calculations. The former include a full Feller‐Peterson‐Dixon composite approach with correlation contributions up to CCSDT(Q) for UO and UO+, yielding D0(U‐O)=7.82 eV and D0(U+‐O)=7.99 eV, as well as more approximate CCSD(T) calculations where a semi‐empirical model was used to estimate spin‐orbit energy contributions, which are generally found to improve the agreement with experiment. Both experimental BDEs are observed to be close to those of their transition metal congeners, ScL+, YL+, and GdL+ (L=O and C).

Nuclear Magnetic Resonance Analysis of Hydrothermal Reactions of Ethyl- and Octylamine in Sub- and Supercritical Water

Hydrothermal reactions of aliphatic amines have recently gained importance in relation to the application of amines as film-forming corrosion inhibitors for steam-water cycles. The kinetics and mechanism of the hydrothermal reactions of ethylammomiun cation (EtAH+) and n-octylammonium cation (OctAH+) were studied for comparison with the corresponding neutral amines to elucidate their reaction products and pathways at sub- and supercritical temperatures of 300-400 °C as model reactions of aliphatic ammonium cations. We analyzed the reaction of 13C-15N-labeled EtAH+ using NMR spectroscopy and revealed that the initial hydrolysis to ethanol, known as the main path, is followed by the elimination reaction producing ethene and the disproportionation reaction giving diethylammonium cation. The OctAH+ yields octene and octanol, each of which isomerizes to thermodynamically more stable species as the major products. Comparisons were made between the reactions of the neutral amines and ammonium cations to highlight their different reactivity. The hydrolysis, alkene formation, and dehydration of alcohols to alkenes were all found to be accelerated at low pH. The formation of low-molecular-weight organic acids such as acetic acid and formic acid was not observed. These results indicate that the corrosion protection effect of film-forming amines will be maintained under practical conditions with pH values as high as around 9 to 10, and hence side reactions involving byproducts will be suppressed.

Comparison of the Reactivity of Platinum Cations and Clusters Supported on Ceria or Alumina in Carbon Monoxide Oxidation

Comparison of the Reactivity of Platinum Cations and Clusters Supported on Ceria or Alumina in Carbon Monoxide Oxidation

Discovery of Bonding-active Chemical Species Containing Nitrogen Atoms

In this review, the authors review and explain their research on "Discovery of Bonding Active Species Containing Nitrogen Atoms" from the past to the present. The authors are interested in new chemical phenomena, especially in the activation of chemical bonds containing nitrogen atoms, and have conducted research to discover chemical bonds with new properties. The activated chemical bonds containing nitrogen atoms are the following (Fig. 1). (1) Rotationally activated C-N bonds by pyramidalization of amide nitrogen atoms (2) N-N bond cleavage ability with reduced bond strength by pyramidalization of nitrosamine nitrogen atoms (3) Transient hetero atom-N bond formation by neighboring group participation of a halogen electron to the nitrogen cation. (4) A unique carbon cation reaction involving nitrogen atoms, especially nitro groups (C-NO2 bond) and ammonium ions (C-NH3+ bond). These purely basic chemistry discoveries unexpectedly led to the creation of functional materials, especially biologically active molecules. We will explain how new chemical bonds led to the creation of new functions.

The Interplay of Weakly Coordinating Anions and the Mechanical Bond: A Systematic Study of the Explicit Influence of Counterions on the Properties of (Pseudo)rotaxanes

Weakly coordinating anions (WCAs) have attracted much attention in recent years due to their ability to stabilise highly reactive cations. It may well be argued, however, that a profound understanding of what truly defines a WCA is still lacking, and systematic studies to unravel counterion effects are scarce. In this work, we investigate a supramolecular pseudorotaxane formation reaction, subject to a selection of anions, ranging from strongly to weakly coordinating, which not only aids in fostering our knowledge about anion coordination properties, but also provides valuable theoretical insight into the nature of the mechanical bond. We employ state-of-the-art DFT-based methods and tools, combined with isothermal calorimetry and 1H NMR experiments, to compute anion-dependent Gibbs free association energies ΔGa, as well as to evaluate intermolecular interactions. We find correlations between ΔGa and the anions' solvation energies, which are exploited to calculate physico-chemical reaction parameters in the context of coordinating anions. Furthermore, we show that the binding situation within the (pseudo)rotaxanes can be mostly understood by straight-forward electrostatic considerations. However, quantum-chemical effects such as dispersion and charge-transfer interactions become more and more relevant when WCAs are employed.

Enhanced thermoelectric properties for p-type BiSbTe by incorporating multiferroic BiFeO3 nanoparticles

Thermoelectric materials can directly convert electrical energy and thermal energy by regulating carrier and phonon transport under electrical and thermal fields. However, further enhancement of thermoelectric properties is hindered by limited available methods that can synergistically tune transport properties. Here, multiferroic BiFeO3 nanoparticles with spontaneous electrical and magnetic polarization are synthesized and incorporated into p-type Bi0.5Sb1.5Te3, to probe the impact of simultaneous local electrical field and magnetic field on the transport properties of the BiFeO3/Bi0.5Sb1.5Te3 nanocomposites. The BiFeO3/Bi0.5Sb1.5Te3 atomic-resolution interfacial structure is revealed using aberration-corrected scanning transmission electron microscopy. The selective reaction of Sb cations leads to reduced carrier concentration and decreased electrical conductivity. The Seebeck coefficient is enhanced by additional scattering from local electrical and magnetic field. Phonon scattering is boosted by the nanostructures from interfacial reaction and local lattice distortion caused by the polarization. As a result, the ZT values and the cooling performance are improved by 9% and 31% for the nanocomposites, respectively.

Selectivity in Cationic Cyclizations Involving Alkynes: A Computational Study on the Biomimetic Synthesis of Steroids

Invited for the cover of this issue are Abel de Cózar, Ana Arrieta and Fernando P. Cossío at the University of the Basque Country. The image depicts the evolution of a reactive cation to the corresponding cyclic intermediate in the course of a regio- and stereocontrolled biomimetic cyclization. Read the full text of the article at 10.1002/chem.202204028.