The Electrochemical Synthesis of Polycationic Clusters

Carbon-Based Weakly Coordinating Anions: Molecular Design, Synthesis and Applications

Although carbanions, which are usually regarded as reactive species and powerful metalation reagents, can be stabilized through choice of the substitution pattern, they have rarely been considered for the design of weakly coordinating anions (WCA). Here, we report on an evaluation of the potential of a series of differently substituted carbanions to serve as WCA by computational methods. This led us to the synthesis of the water- and air-stable allyl anion 1 with triflyl and 3,5-bis(trifluoromethyl)phenyl (ArF) moieties, which can be isolated in high yields even on a gram-scale. Single crystal X-ray crystallography and NMR studies confirmed the weak coordination ability of the anion by showing negligible or only weak interactions with different cations. This property enabled the application of 1 in the stabilization of reactive group 14 and 15 cations. In addition to the crystallization of a phosphenium cation, the first all-carbon salt with a non-aromatic carbanion is reported, which revealed to be a convenient reagent for hydride abstraction such as from silanes. Overall, this work demonstrates the so far untapped potential of carbanions as WCA, that are accessible with a variety of different cations for various applications.

Recent advances in atomic cluster synthesis: a perspective from chemical elements

Despite its potential significance, "cluster chemistry" remains a somewhat marginalized topic within the chemistry field. However, atomic clusters with their unusual and unique structures and properties represent a novel material group situated between molecules and nanoparticles or solid matter, judging from both scientific standpoints and historical backgrounds. Surveying an entire material group, including all substances that can be regarded as a cluster, is essential for establishing cluster chemistry as a more prominent chemistry field. This review aims to provide a comprehensive understanding by categorizing, summarizing, and reviewing clusters, focusing on their constituent elements in the periodic table. However, because numerous disparate synthetic processes have been individually developed to date, their straightforward and uniform classification is a challenging task. As such, comprehensively reviewing this field from a chemical composition viewpoint presents significant obstacles. It should be therefore noted that despite adopting a synthetic method-based classification in this review, the discussions presented herein could entail inaccuracies. Nevertheless, this unorthodox viewpoint unfolds a new scientific perspective which accentuates the common ground between different development processes by emphasizing the lack of a definitive border between their synthetic methods and material groups, thus opening new avenues for cementing cluster chemistry as an attractive chemistry field.

Construction of double reaction zones for long-life quasi-solid aluminum-ion batteries by realizing maximum electron transfer

Achieving high energy density and long cycling life simultaneously remains the most critical challenge for aluminum-ion batteries (AIBs), especially for high-capacity conversion-type positive electrodes suffering from shuttle effect in strongly acidic electrolytes. Herein, we develop a layered quasi-solid AIBs system with double reaction zones (DRZs, Zone 1 and Zone 2) to address such issues. Zone 1 is designed to accelerate reaction kinetics by improving wetting ability of quasi-solid electrolyte to active materials. A composite three-dimensional conductive framework (Zone 2) interwoven by gel network for ion conduction and carbon nanotube network as electronic conductor, can fix the active materials dissolved from Zone 1 to allow for continuing electrochemical reactions. Therefore, a maximum electron transfer is realized for the conversion-type mateials in DRZs, and an ultrahigh capacity (400 mAh g-1) and an ultralong cycling life (4000 cycles) are achieved. Such strategy provides a new perspective for constructing high-energy-density and long-life AIBs.

Recent advances in NMR spectroscopy of ionic liquids

This review presents recent developments in the application of NMR spectroscopic techniques in the study of ionic liquids. NMR has been the primary tool not only for the structural characterization of ionic liquids, but also for the study of dynamics. The presence of a host of NMR active nuclei in ionic liquids permits widespread use of multinuclear NMR experiments. Chemical shifts and multinuclear coupling constants are used routinely for the structure elucidation of ionic liquids and of products formed by their covalent interactions with other materials. Also, the availability of a multitude of NMR techniques has facilitated the study of dynamical processes in them. These include the use of NOESY to study inter-ionic interactions, pulsed-field gradient techniques for probing transport properties, and relaxation measurements to elucidate rotational dynamics. This review will focus on the application of each of these techniques to investigate ionic liquids.

Coexistence of Tellurium Cations and Anions in Phosphonium-Based Ionic Liquids

Elemental tellurium readily dissolves in ionic liquids (ILs) based on tetraalkylphosphonium cations even at temperatures below 100 °C. In the case of ILs with acetate, decanoate, or dicyanamide anions, dark red to purple colored solutions form. A study combining NMR, UV‐Vis and Raman spectroscopy revealed the formation of tellurium anions (Te_n)²⁻ with chain lengths up to at least n=5, which are in dynamic equilibrium with each other. Since external influences could be excluded and no evidence of an ionic liquid reaction was found, disproportionation of the tellurium is the only possible dissolution mechanism. Although the spectroscopic detection of tellurium cations in these solutions is difficult, the coexistence of tellurium cations, such as (Te₄)²⁺ and (Te₆)⁴⁺, and tellurium anions could be proven by cyclic voltammetry and electrodeposition experiments. DFT calculations indicate that electrostatic interactions with the ions of the ILs are sufficient to stabilize both types of tellurium ions in solution.

From polygons to polyhedra through intermediate structures. A shape measures study of six-atom inorganic rings and clusters

Among the wealth of well-established molecular structures, inorganic rings and clusters present an overwhelming variety of geometries that chemists try to describe with a limited assortment of regular polygons and polyhedra. In the case of six-atom structures we usually employ the hexagon, the pentagonal pyramid, the trigonal prism and the octahedron. More often than not, however, real world structures deviate from those ideal geometries, and we try to cope with non-ideality by adding adjectives such as distorted, twisted, puckered or flattened, additionally nuanced by adverbs such as slightly, significantly or severely. This contribution presents a systematic structural perspective of six-atom groups in molecules by means of a continuous shape measures (CShM) analysis. The shape of a group of N points is defined by all the sets of 3 N Cartesian coordinates that can be generated by rigid translation, rotation, or isotropic scale change. Among all possible arrangements of N points in space, we select as reference shapes the corresponding regular N-vertex polygons and polyhedra, together with univocally defined combinations thereof (e.g., two coplanar or perpendicular edge-sharing squares). The present CShM study allows us to classify most of the structures not only by their closeness to a particular regular shape, but also by quantifying their position along minimal distortion interconversion pathways between two regular shapes.

The crystal structure of trimethylsulfonium tris(trifluoromethylsulfonyl)methanide, C7H9F9O6S4

C7H9F9O6S4, orthorhombic, P212121 (no. 19), a = 8.80180(10) Å, b = 10.96580(10) Å, c = 16.91360(10) Å, V = 1632.48(3) Å3, Z = 4, R gt (F) = 0.0222, wRref (F 2) = 0.0604, T = 100 K.

Modern cluster design based on experiment and theory

For decades, chemists have explored cluster compounds according to theoretical models that have proved too simplistic to accurately predict cluster properties, stabilities and functions. By incorporating molecular symmetry into existing cluster models, we can better study real polyatomic molecules and have new guidelines for their design. This symmetry-adapted cluster model allows us to discover substances that shatter the conventional notion of clusters. Theoretical predictors will point to the viability of new clusters, whose syntheses can be realized with parallel advances in experimental methods. This Perspective describes these modern experimental and theoretical strategies for cluster design and how they may give rise to new fields in cluster chemistry.

TiCl4 Dissolved in Ionic Liquid Mixtures from ab Initio Molecular Dynamics Simulations

To gain a deeper understanding of the TiCl4 solvation effects in multi-component ionic liquids, we performed ab initio molecular dynamics simulations of 1-butyl-3-methylimidazolium [C4C1Im]+, tetrafluoroborate [BF4]−, chloride [Cl]− both with and without water and titanium tetrachloride TiCl4. Complex interactions between cations and anions are observed in all investigated systems. By further addition of water and TiCl4 this complex interaction network is extended. Observations of the radial distribution functions and number integrals show that water and TiCl4 not only compete with each other to interact mainly with [Cl]−, which strongly influences the cation-[BF4]− interaction, but also interact with each other, which leads to the fact that in certain systems the cation-anion interaction is enhanced. Further investigations of the Voronoi polyhedra analysis have demonstrated that water has a greater impact on the nanosegregated system than TiCl4 which is also due to the fact of the shear amount of water relative to all other components and its higher mobility compared to TiCl4. Overall, the polar network of the IL mixture collapses by including water and TiCl4. In the case of [Cl]− chloride enters the water continuum, while [BF4]− remains largely unaffected, which deeply affects the interaction of the ionic liquid (IL) network.

Rechargeable Nickel Telluride/Aluminum Batteries with High Capacity and Enhanced Cycling Performance

Rechargeable aluminum-ion batteries (AIBs) possess significant advantages of high energy density, safety performance, and abundant natural resources, making them one of the desirable next-generation substitutes for lithium battery systems. However, the poor reversibility, short lifespan, and low capacity of positive materials have limited its practical applications. In comparison with semiconductors, the metallic nickel telluride (NiTe) alloy with enhanced electrical conductivity and fast electron transmission is a more favorable electrode material that could significantly decrease the kinetic barrier during battery operation for energy storage. In this paper, the NiTe nanorods prepared through a simple hydrothermal routine enable an initial reversible capacity of approximately 570 mA h g^-1 (under the current density of 200 mA g^-1) to be delivered on the basis of the ionic liquid electrolyte, along with the average voltage platform of about 1.30 V. Moreover, the cycling performance could be easily enhanced using a modified separator to prevent the diffusion of soluble intermediate species to the negative electrode side. At a high rate of 500 mA g^-1, the NiTe nanorods could retain a specific capacity of about 307 mA h g^-1 at the 100th cycle. The results have important implications for the research of transition metal tellurides as positive electrode materials for AIBs.

Multi-Valent Group 14 Chalcogenide Architectures from Ionic Liquids: 0D-{[Cs@SnII4 (GeIV4 Se10 )4 ]7- } and 2D-{[SnII (GeIV4 Se10 )]2- }

In order to explore if and how salts comprising polycations and salts comprising polyanions might interact, the [AlBr₄ ]^- salt of the [Pt@Bi₁₀ ]⁴⁺ cluster cation was added to the reaction mixture for the synthesis of the supersphere cluster anion [Ge₂₄ Sn₃₆ Se₁₃₂ ]^24- from Cs₄ [Ge₄ Se₁₀ ]⋅H₂ O and SnCl₄ ⋅5 H₂ O under ionothermal conditions at 120 °C. Indeed, the reaction yields two new compounds, depending on the cation of the used ionic liquid. Apparently, the polycation is not retained under the given conditions, but it acts as a reductant affording Sn^II . In a (C₄ C₁ C₁ im)⁺ -based ionic liquid mixture, a unique supertetrahedral anion is obtained that embeds a Cs⁺ cation, 0D-{[Cs@Sn^II₄ (Ge^IV₄ Se₁₀ )₄ ]^7- }, while (C₄ C₁ im)⁺ cations stabilize an unprecedented ternary layered anion, 2D-{[Sn^II (Ge^IV₄ Se₁₀ )]^2- }. Test reactions with common sources of Sn^II did not afford the new compounds, indicating the necessity of an in situ reduction, for which the polycation seems appropriate.

Controlled Synthesis of Polyions of Heavy Main-Group Elements in Ionic Liquids

Ionic liquids (ILs) have been proven to be valuable reaction media for the synthesis of inorganic materials among an abundance of other applications in different fields of chemistry. Up to now, the syntheses have remained mostly “black boxes”; and researchers have to resort to trial-and-error in order to establish a new synthetic route to a specific compound. This review comprises decisive reaction parameters and techniques for the directed synthesis of polyions of heavy main-group elements (fourth period and beyond) in ILs. Several families of compounds are presented ranging from polyhalides over carbonyl complexes and selenidostannates to homo and heteropolycations.