Reactions Of Cations Research Articles

Carbon–Carbon Bond Forming Reactions of Vinyl Cations: A Personal Perspective

Carbon–Carbon Bond Forming Reactions of Vinyl Cations: A Personal Perspective

Cation reactivity inhibits perovskite degradation in efficient and stable solar modules.

Perovskite solar modules (PSMs) show outstanding power conversion efficiencies (PCEs), but long-term operational stability remains problematic. We show that incorporating N,N-dimethylmethyleneiminium chloride into the perovskite precursor solution formed dimethylammonium cation and that previously unobserved methyl tetrahydrotriazinium ([MTTZ]+) cation effectively improved perovskite film. The in situ formation of [MTTZ]+ cation increased the formation energy of iodine vacancies and enhanced the migration energy barrier of iodide and cesium ions, which suppressed nonradiative recombination, thermal decomposition, and phase segregation processes. The optimized PSMs achieved a record (certified) PCE of 23.2% with an aperture area of 27.2 cm2, with a stabilized PCE of 23.0%. The encapsulated PSM retained 87.0% of its initial PCE after ~1900 hours of maximum power point tracking at 85°C and 85% relative humidity under 1.0-sun illumination.

Asymmetric Counteranion‐Directed Electrocatalysis for Enantioselective Control of Radical Cation

AbstractThe control of enantioselectivity in radical cation reactions presents long‐standing challenges, despite a few successful examples. We introduce a novel strategy of asymmetric counteranion‐directed electrocatalysis to address enantioselectivity in radical cation chemistry. This concept has been successfully demonstrated in two reactions: an asymmetric dehydrogenative indole‐phenol [3+2] coupling and an atroposelective C−H/N−H dehydrogenative coupling. These reactions have enabled the synthesis of benzofuroindolines and C−N axially chiral indoles with high yields and excellent enantiomeric excesses. Detailed mechanistic studies confirmed a radical‐radical coupling mechanism. Moreover, density functional theory (DFT) calculations supported the indole radical cation as the pivotal intermediate, rather than a neutral indolyl radical, shedding new light on the underlying processes driving these reactions.

New Insights into Anionic Redox in P2-Type Oxide Cathodes for Sodium-Ion Batteries.

Manganese/nickel-based layered transition metal oxides have caught the attention of studies as promising cathodes for sodium-ion batteries (SIBs). It is reported that utilizing both cationic and anionic redox reactions is a promising method for higher energy density cathodes. However, the anionic redox reaction comes at the expense of irreversible oxygen release. Hence, a Li-Mg cosubstituted P2-Na0.67Li0.07Mg0.07Ni0.28Mn0.58O2 material with a honeycomb-ordered superstructure was designed. The Ni3+/Ni4+ redox couple and the anionic redox reaction are proven to have a competitive relationship. Density functional theory calculations reveal the effect of O 2p nonbonding states from Li and prove that Mg-O bonds can stabilize the Ni-O eg states. In situ electrochemical impedance spectroscopy measurements and galvanostatic charging/discharging derived dV/dQ, representing resistance changes with time, are obtained to reveal the mechanism of the anionic redox reaction. This study presents the effect and mechanism of the O 2p nonbonding state and Mg-O bonds of manganese/nickel-based layered oxides.

Local electronic structure modulation via S substitution enables fast-discharging capability for Li-rich Mn-based oxides cathodes

Anionic and cationic redox reaction contribute to the ultrahigh specific capacities of Li-rich Mn-based oxides cathodes (LMNC). However, the irreversible oxygen evolution and sluggish kinetics result in the continuous capacity decay and poor rate performance, which limited its application as cathode material in lithium-ion batteries. Herein, the local electronic structure of LMNC is appropriately modulated via S2− doping to alleviate oxygen release, stabilize the crystal structure stability, and facilitate Li+ diffusion via facile surface defect engineering. The effect of S2− doping site on the systematically energy is investigated by DFT. Under the guidance of this result, LNMC-S is prepared by co-precipitation and high-temperature solid-phase reaction method. The effect of doping concentration on electrochemical property of LMNC was systematically investigated. The results exhibit that S2− doping can effectively suppress the electronic insulation of Li2MnO3, enhance the transport dynamics of lithium ion and inhibit the phase transition of LMNC sample during charge-discharge process. Thereby, the modified sample exhibits superior electrochemical property, such as the 200th discharge capacity is 184.3 mAh·g−1 under 1C, with a capacity retention rate of 87.6 %. This paper is beneficial for enriching the existing theoretical findings and discoveries, providing theoretical guidance for the preparation of high-performance material.

Novel Synthesis Route of Plasmonic CuS Quantum Dots as Efficient Co-Catalysts to TiO2/Ti for Light-Assisted Water Splitting.

Self-doped CuS nanoparticles (NPs) were successfully synthesized via microwave-assisted polyol process to act as co-catalysts to TiO2 nanofiber (NF)-based photoanodes to achieve higher photocurrents on visible light-assisted water electrolysis. The strategy adopted to perform the copper cation sulfidation in polyol allowed us to overcome the challenges associated with the copper cation reactivity and particle size control. The impregnation of the CuS NPs on TiO2 NFs synthesized via hydrothermal corrosion of a metallic Ti support resulted in composites with increased visible and near-infrared light absorption compared to the pristine support. This allows an improved overall efficiency of water oxidation (and consequently hydrogen generation at the Pt counter electrode) in passive electrolyte (pH = 7) even at 0 V bias. These low-cost and easy-to-achieve composite materials represent a promising alternative to those involving highly toxic co-catalysts.

"Cation Pool" generated from DMSO and 1,2-dihaloethanes and their application in organic synthesis.

Conventionally, carbenium and onium ions are prepared in the presence of nucleophiles due to their instability and transient nature. The nucleophiles that are unstable or inert to the reaction media cannot be used for reaction with the cationic species to access the desired compounds. To overcome these limitations, developing methods for generating organic cations irreversibly in the absence of nucleophiles is essential. The "cation pool" method developed by Yoshida and co-workers stands out as a reliable strategy to generate and accumulate the reactive cations in solution in the absence of nucleophiles. The cation pool method involves the electrolysis of the substrate in the absence of nucleophiles, usually at low temperature. Moreover, the generation of halogen and chalcogen cations through electrolysis needs extra care because of their low stability. This review covers our effort in generating and accumulating halogen cations as "cation pools", most importantly by simply heating a mixture of dimethyl sulfoxide (DMSO) and 1,2-dihaloethane (DXE, X = Cl, Br, I), and their use in the halogenation reactions. Furthermore, condition-dependent Pummerer-type fragmentations of DMSO-stabilized halogen cations to methyl(methylene)sulfonium ions and chlorodimethylsulfonium ions for synthetic applications are described.

Rational Design of Cyclopentadiene-Based Super- and Hyperacids Based on Aromaticity.

The design and synthesis of neutral organic superacids have been of interest recently due to their vast applications in chemistry and material sciences, for example, olefinic polymerization, isolation of highly reactive short-lived cations, etc. Cyclopentadiene behaves as a mild organic acid, producing a stable conjugate base by gaining aromaticity and conjugation after deprotonation. To stabilize conjugate bases of organic acids to show superacidities and hyperacidities, we considered aromatic phenyl substituents with cyclopentadiene (mono-, di-, and triphenyl-substituted cyclopentadiene and their cyano derivatives). The MP2, DFT (B3LYP, M06-2X), and CBS-QB3 methods were used to calculate the gas-phase proton affinities of the parent cyclopentadiene, and the DFT methods were chosen for the substituted cyclopentadiene as they yield an experimental proton affinity of cyclopentadiene of 253.66 kcal/mol (Expt. 253.6 ± 1.3 kcal/mol). The stable trisubstituted cyclopentadiene derivative shows gas-phase enthalpies of deprotonation (ΔHacid) of 245 and 239 kcal/mol with DFT B3LYP and M06-2X methods, respectively, with values in the range of hyperacidity. Some of the tautomers of cyclopentadiene derivatives show hyperacidity, with proton affinity values of 205-240 kcal/mol. Triphenyl-substituted cyclopentadiene behaves as a moderate acid but transforms into a superacid after replacing the phenyl group with nitrobenzene, which is a stronger acid than H2SO4 (ΔHacid = 298 kcal/mol). The nucleus-independent chemical shift (NICS) shows the extent of conjugation in the derivatives of cyclopentadienyl anions after deprotonation, which affects the stabilities of conjugate bases, i.e., the acidities of the protonated species. The calculated harmonic oscillator model of aromaticity and NICS indices reveal that the stability of conjugate bases as well as their acidities increase with increasing aromaticity of cyclopentadiene rings after deprotonation in all molecules.

Asymmetric Counteranion-Directed Electrocatalysis for Enantioselective Control of Radical Cation.

The control of enantioselectivity in radical cation reactions presents long-standing challenges, despite a few successful examples. We introduce a novel strategy of asymmetric counteranion-directed electrocatalysis to address enantioselectivity in radical cation chemistry. This concept has been successfully demonstrated in two reactions: an asymmetric dehydrogenative indole-phenol [3 + 2] coupling and an atroposelective C-H/N-H dehydrogenative coupling. These reactions have enabled the synthesis of benzofuroindolines and C-N axially chiral indoles with high yields and excellent enantiomeric excesses. Detailed mechanistic studies confirmed a radical-radical coupling mechanism. Moreover, density functional theory (DFT) calculations supported the indole radical cation as the pivotal intermediate, rather than a neutral indolyl radical, shedding new light on the underlying processes driving these reactions.

Reactions of Aluminum Oxide Cluster Cations with Ethane: A Mass-Spectrometric and Vibrational Spectroscopy Study.

The pathways for the reactions of aluminum oxide cluster ions with ethane have been measured. For selected ions (Al2O+, Al3O2+, Al3O4+, Al4O7+) the structure of the collisionally-stabilized reaction intermediates were explored by measuring the photodissociation vibrational spectra from 2600 cm-1 to 3100 cm-1. Density functional theory was used to calculate features of the potential energy surfaces for the reactions and the vibrational spectra of intermediates. Generally, more than one isomer contributes to the observed spectrum. The oxygen-deficient clusters Al2O+ and Al3O2+ have large C-H activation barriers, so only the entrance channel complexes in which intact C2H6 binds to aluminum are observed. This interaction leads to a substantial (~200 cm-1) red shift of the C-H symmetric stretch in ethane, indicating significant weakening of the proximal C-H bonds. In Al3O4+, the complex formed by interactions with three C2H6 is investigated and, in addition to entrance channel complexes, the C-H activation intermediate Al3O4H+(C2H5)(C2H6)2 is observed. For oxygen-rich Al4O7+, the C2H6 is favored to bind at an aluminum site far from the reactive superoxide group, reducing the reactivity. As expected, oxygen-rich species and open-shell cluster ions have smaller barriers for C-H bond activation, except for Al3O4+ which is predicted and observed to be reactive.

Electrocatalytic Radical Cation Diels-Alder Reactions Using Enol Ethers As Dienophiles

Single-electron oxidation enables the conversion of electron-rich alkenes such as styrene derivatives to radical cation species. We have been developing various cycloaddition reactions of radical cations produced by single-electron oxidation using electrochemical and TiO2 photochemical methods. Introducing an electron-rich aryl group which we call a redox tag is a critical part of the process to control the reactivity of the radical cations. During carbon-carbon bonds formation the motif functions as both electron donor and electron acceptor. In addition to styrene derivatives, enol ethers can also be readily oxidized by single electron transfer (SET) electrochemically or photochemically to generate the radical cations. For instance, enol ethers tethered redox tag serves efficient radical cation precursors for [2+2] cycloadditions.[1] The cycloadditions are net redox-neutral reactions and are initiated by the formation of a radical cation by single-electron oxidation and completed by reduction after ring formation.Herein, we present [4+2] cycloadditions using enol ethers as dienophiles by electrochemical oxidation in lithium perchlorate (LiClO4)/nitromethane (MeNO2) system. In the case of disubstituted enol ethers prepared from aldehydes, the approach involving redox tag was successful in obtaining the corresponding cycloadducts, while the desired products were not obtained when the substrates without redox tag were subjected.[2] This result suggests that intramolecular electron transfer from the redox tag is crucial for the formation of the cyclohexene ring systems. In contrast, the trisubstituted enol ethers prepared from ketones allowed the cycloaddition reaction to proceed without the involvement of redox tag. It is expected that the methyl group significantly stabilizes the cyclohexene radical cations to have enough lifetime to be reduced by intermolecular SET. Furthermore, since the cycloaddition reaction of enol ether was completed with a catalytic amount of electricity (0.4 F/mol), a radical cation chain mechanism is proposed in which electron acts as a catalyst.

Photoelectrochemistry and Photochemistry for Sustainable Organic Synthesis

To address the sustainability issues of the existing industrial processes for producing fine chemicals and pharmaceuticals, we should develop alternative methods that raise energy efficiency, atom economy and eliminate toxic chemicals.1 One way to do that is to take inspiration from biological systems - Nature itself offers paradigms for sustainability. For decades, the natural systems, and in particular photosynthesis, have provided the principal model for solar-energy science and engineering. Therefore, electron and charge transfer are not only at the core of life-sustaining biological processes (photosynthesis), but also at the core of modern sustainable technology (solar cells, energy storage, energy conversion).2 Regarding sustainable organic synthesis chemists also realized the potential of electron and charge transfer. Electrochemistry3 together with photochemistry4 are one of the greenest ways for driving chemical transformations, since their application improves atom economy, efficiency and prevents generation of toxic wastes.Both of them have given rise to new and efficient access to some of the most reactive intermediates,that are challenging or impossible to generate by traditional chemical methods. Our main efforts concern development of new methods for an ecological and sustainable organic synthesis. On one hand, our work describe the application of NHC-Cu three-coordinate complexes as photocatalysts in energy and electron transfer reactions. Taking into account photophysical properties of NHC-Cu(I) complexes along with the fact that they are straightforward in synthesis, non-toxic, inexpensive and abundant, we envisioned that their application as photocatalysts could provide a general alternative for toxic, expensive and rare Ir- and Ru-based complexes.5 On the other hand, the constructive merge of electrochemistry and photochemistry offers the potential to overcome the drawbacks of one method through the complementary advantages of the other. One of the effective ways for their merge is interfacial photoelectrochemistry (iPEC), where the reaction occurs at photoelectrode surface.6 Our work in this area describes mild and efficient electrochemical methods for [2+1], [2+2] and [2+4] cycloaddition reactions of alkene radical cations.7 Anodic oxidation of olefins at the photoanode surface produces electrophilic alkene radical cations, which further react with nucleophiles in a formal [2+1], [2+2] and [2+4] cycloaddition towards synthesis of 3-,4-,6-membered rings. The advantages of the application of photoelectrodes in organic synthesis include high selectivity, the use on reusable materials, non-precious metal catalysts and lost but not least significant energy savings.[1] R. Gorini at all Energy Strateg. Rev. 2019, 24, 38 [2] Y. Wang, H. Suzuki, J. Xie, O. Tomita, D. J. Martin, M. Higashi, D. Kong, R. Abe, J. Tang Chem. Rev. 2018, 118, 5201 [3] a) S. Waldvogel at all Chem. Sci. 2020, 11, 12386; b) K. D. Moeller Tetrahedron 2000, 56, 9527; c) P. S. Baran at all Chem. Rev. 2017, 117, 13230; [4] a) D.W.C. MacMillan at all J. Org. Chem. 2016, 81, 6898; b) P. Melchiorre at all Angew. Chem. Int. Ed. 2019, 58, 3730; c) T. P. Yoon at all Chem. Rev. 2016, 116, 10035; d) M. Rueping at all Chem. Sci. 2020, 11, 4051; e) F. Glorius at all Chem. Soc. Rev. 2018, 47, 7190. [5] K. Rybicka-Jasińska at all unpublished results; [6] K. Rybicka-Jasińska, V. I. Vullev Charge Transfer & Organic Photoelectrochemistry ACS in focus 2023 DOI: 10.1021/acsinfocus.7e7025 [6] K. Rybicka-Jasińska et all unpublished results

Long Term Durability Investigation of Cu-Doped La2NiO4 Oxygen Electrodes in Solid Oxide Electrolysis Cells

State-of-the-art oxygen electrodes in SOECs, lanthanum strontium cobalt iron oxide (LSCF) and lanthanum strontium cobalt oxide (LSC), contain strontium. Undesired reactivity and migration of Sr cations during long-term operation was found to be detrimental to the electrochemical performance as they triggered formation of multiple oxide phases, including insulating phases and electrode or barrier layer delamination. Developing alternative electrodes that are devoid of Sr is very important for long-term operation of SOECs.In this work, we synthesized and evaluated properties of La2NiO4-based compositions with a Ruddlesden-Popper structure. The Cu-doped La2NiO4 compositions made of nano-size particles exhibited an enhanced electrochemical performance when tested in SOECs during steam electrolysis for hydrogen production. Long-term durability of these electrodes was studied using planar Ni-YSZ electrode-supported cells with an active area of 1.5 (button cells) and 13 cm2 (2.5 cm x 5 cm cells). Compared to the Sr-containing electrodes, the La2Ni0.8Cu0.2O4 (LNCuO-20) demonstrated lower degradation rate at 1.3 Volt resulting in a current density over 1 A/cm2 at 750⁰C. Chrome and sulfur tolerance of these electrodes during long term operation will be discussed as well.

Induced Anion Redox before Full Oxidation of Ru4+/Ru5+ through Local Configuration Modulation in P2-Na0.67[Mg0.33Ru0.67]O2

The study of anionic redox in layered-oxide cathodes for Na-ion batteries (NIBs) has been extensive, aiming to attain high-energy density. The involvement of Mn4+ or Ru5+ oxidation states is known to be crucial for the anionic O2 −/O− reaction during Na+ de/intercalation. Nevertheless, our findings indicate that anionic redox can activate in Ru-based layered-oxide cathodes prior to complete Ru4+/Ru5+ oxidation. By employing first-principles calculation and experimental techniques, we disclose that additional Na+ deintercalation from P2-Na0.33[Mg0.33Ru0.67]O2 relies on anionic oxidation after extracting 0.33 mol Na+ from P2-Na0.67[Mg0.33Ru0.67]O2, concomitant with cationic oxidation of Ru4+/Ru4.5+. Specifically, only the oxygen adjacent to 2Mg/1Ru is implicated in anionic redox during Na+ de/intercalation, indicating that the Na–O–Mg arrangement in the P2-Na0.33[Mg0.33Ru0.67]O2 structure significantly reduces the thermodynamic stability of anionic redox compared to cationic redox. Through O anionic and Ru cationic reactions, P2-Na0.67[Mg0.33Ru0.67]O2 demonstrates a substantial specific capacity of ∼172 mA h g− 1 and exceptional power capability, facilitated by facile Na+ diffusion and reversible structural changes during charge/discharge. These findings propose an innovative strategy to enhance anionic redox activity by modifying the local oxygen environment, paving the way for high-energy-density cathode materials in NIBs.

Chloroformate-mediated ring cleavage of indole alkaloids leads to re-engineered antiplasmodial agents.

Natural product ring distortion strategies have enabled rapid access to unique libraries of stereochemically complex compounds to explore new chemical space and increase our understanding of biological processes related to human disease. Herein is described the development of a ring-cleavage strategy using the indole alkaloids yohimbine, apovincamine, vinburnine, and reserpine that were reacted with a diversity of chloroformates paired with various alcohol/thiol nucleophiles to enable the rapid synthesis of 47 novel small molecules. Ring cleavage reactions of yohimbine and reserpine produced two diastereomeric products in moderate to excellent yields, whereas apovincamine and vinburnine produced a single diastereomeric product in significantly lower yields. Free energy calculations indicated that diastereoselectivity regarding select ring cleavage reactions from yohimbine and apovincamine is dictated by the geometry and three-dimensional structure of reactive cationic intermediates. These compounds were screened for antiplasmodial activity due to the need for novel antimalarial agents. Reserpine derivative 41 was found to exhibit interesting antiplasmodial activities against Plasmodium falciparum parasites (EC50 = 0.50 μM against Dd2 cultures), while its diastereomer 40 was found to be three-fold less active (EC50 = 1.78 μM). Overall, these studies demonstrate that the ring distortion of available indole alkaloids can lead to unique compound collections with re-engineered biological activities for exploring and potentially treating human disease.

Utilizing the Perfluoronaphthalene Radical Cation as a Selective Deelectronator to Access a Variety of Strongly Oxidizing Reactive Cations.

A selective deelectronation reagent with very high potential of +2.00 (solution)/+2.41 V (solid-state) vs. Fc+/0 and based on a room temperature stable perfluoronaphthalene (naphthaleneF) radical cation salt was developed and applied. The solid-state deelectronation of commercial naphthaleneF with [NO]+[F{Al(ORF)3}2]- generates [naphthaleneF]+⋅[F{Al(ORF)3}2]- (ORF=OC(CF3)3) in gram scale. Thermochemical analysis unravels the solid-state deelectronation potential of the starting [NO]+-reagent to be +2.34 V vs. Fc+/0 with [F{Al(ORF)3}2]- counterion, but only +1.14 V vs. Fc+/0 with the small [SbF6]- ion. Selective reactions demonstrate the selectivity of [naphthaleneF]+⋅ for deelectronation of a multitude of organ(ometall)ic molecules and elements in solution: providing the molecular structures of the acene dications [tetracene]2+, [pentacene]2+ or spectroscopic evidence for the carbonyl complex of the ferrocene dication [Fc(CO)]2+, the [P9]+ cation from white phosphorus, the solvent-free copper(I) salt starting from copper metal and the dicationic Fe(IV)-scorpionate complex [Fe(sc)2]2+.

Nutzung des Perfluornaphthalin‐Radikalkations als selektiver Deelektronierer zur Erzeugung einer Vielzahl stark oxidierender reaktiver Kationen

AbstractEin selektives Deelektronierungsreagenz mit einem sehr hohen Potential von +2.00 V (Lösung)/+2.41 V (Festkörper) vs. Fc+/0 wurde entwickelt und angewendet, welches auf einem raumtemperaturstabilen Perfluornaphthalin(NaphthalinF)‐Radikalkationsalz basiert. Durch die Deelektronierung von kommerziellem NaphthalinF durch [NO]+[F{Al(ORF)3}2]− im Festkörper kann [NaphthalinF]+⋅[F{Al(ORF)3}2]− (ORF=OC(CF3)3) in Gramm‐Maßstäben erhalten werden. Durch eine Thermodynamikanalyse wurde das Festkörperpotential des [NO]+‐Edukts zu +2.34 V vs. Fc+/0 mit [F{Al(ORF)3}2]− als Gegenion ermittelt, welches sich von +1.14 V vs. Fc+/0 für das kleinere [SbF6]−‐Anion stark unterscheidet. In selektiven Reaktionen wurde die Selektivität von [NaphthalinF]+⋅ in der Deelektronierung einer Vielzahl von organ(ometall)ischen Molekülen und Elementen in Lösung demonstriert: So wurden die Molekülstrukturen der Acen‐Dikationen [Tetracen]2+ und [Pentacen]2+ erhalten und der Carbonylkomplex des Ferrocen‐Dikations [Fc(CO)]2+ spektroskopisch nachgewiesen, sowie das [P9]+‐Kation aus weißem Phosphor, lösungsmittelfreies Kupfer(I)‐Salz aus Kupfermetall und der dikationische Fe(IV)‐Scorpionatkomplex [Fe(sc)2]2+ hergestellt.

Reactivity Manipulation of Ionic Liquid Based on Alkyl Primary Ammonium: Protonation Control Using 4‐tert‐Butylpyridine Additive for Effective Spontaneous Passivation of Perovskite via Hole Transport Material Deposition

Alkyl‐primary‐ammonium‐based room‐temperature ionic liquids (RTILs) designed to exhibit specific reactivities allowing functions that cannot be achieved by other RTILs have recently emerged. The archetype of the reactive RTILs is n‐octylammonium bis(trifluoromethanesulfonyl)imide (OA‐TFSI), which has promising functions as an additive for hole transport materials (HTMs) in perovskite solar cells (PSCs); the high reactivity of the OA cations on the perovskite surface allows spontaneous perovskite passivation via HTM deposition, effectively improving the photovoltaic (PV) performance. However, although the reactivity manipulation of the reactive RTILs is instrumental for exploiting their potential functions and exploring their application scope, methods for reactivity control have not been developed. Herein, it is proposed that the coaddition of a pyridine derivative (4‐tert‐butylpridine: TBP) can effectively manipulate the reactivity of OA‐TFSI by controlling the protonation between OA and the 2,2′,7,7′‐tetrakis‐(N,N‐di‐4‐methoxyphenylamino)‐9,9′‐spirobifluorene (Spiro‐OMeTAD) HTM. The TBP prevents OA deprotonation presumably via stabilization of the OA cation, thus retaining its ammonium form, which allows efficient spontaneous perovskite passivation, effectively enhancing the PV performance. This reveals the protonation preference in the OA‐TFSI system, which is opposite to that in conventional RTILs. This first proposal of a method in manipulating reactivity of the reactive RTILs will contribute to the development of materials science.

On the Role of the Solvent in the Synthesis of Spirocycles from Alkyne Cations Catalyzed by Triflic Acid: A DFT Study

The role of discrete solvent molecules in the reactivity of alkyne cations has been analyzed computationally. Analysis of the possible reaction mechanisms towards competitive cyclization and elimination processes including a molecule of solvent show the crucial role of dichloromethane (DCM) and tetrahydrofuran (THF). In the presence of DCM, a strong intramolecular p‐cation interaction between the electrophilic center and the triple bond favors the [5‐exo‐dig] cyclization route, with no direct participation of the solvent in the reaction path. On the contrary, in the presence of a discrete molecule of THF, a strong solvent–cation interaction via formation of a dative C(+)–O(THF) bond drastically modifies the energy profile, thus promoting the elimination pathway.

High-Energy Earth-Abundant Cathodes with Enhanced Cationic/Anionic Redox for Sustainable and Long-Lasting Na-Ion Batteries.

Layered iron/manganese-based oxides are a class of promising cathode materials for sustainable batteries due to their high energy densities and earth abundance. However, the stabilization of cationic and anionic redox reactions in these cathodes during cycling at high voltage remain elusive. Here, an electrochemically/thermally stable P2-Na0.67Fe0.3Mn0.5Mg0.1Ti0.1O2 cathode material with zero critical elements is designed for sodium-ion batteries (NIBs) to realize a highly reversible capacity of ≈210mAhg-1 at 20mAg-1 and good cycling stability with a capacity retention of 74% after 300 cycles at 200mAg-1, even when operated with a high charge cut-off voltage of 4.5V versus sodium metal. Combining a suite of cutting-edge characterizations and computational modeling, it is shown that Mg/Ti co-doping leads to stabilized surface/bulk structure at high voltage and high temperature, and more importantly, enhances cationic/anionic redox reaction reversibility over extended cycles with the suppression of other undesired oxygen activities. This work fundamentally deepens the failure mechanism of Fe/Mn-based layered cathodes and highlights the importance of dopant engineering to achieve high-energy and earth-abundant cathode material for sustainable and long-lasting NIBs.