Arrangement Of Anions Research Articles

Comparative study of the phase stability in SrTaO2N

Recently, ferroelectric behavior was observed in compressed SrTaO2N thin films epitaxially grown on SrTiO3 substrates. Piezoresponse force microscopy measurements revealed small domains (101–102nm) that exhibited classical ferroelectricity, a behavior not previously observed in perovskite oxynitrides. The surrounding matrix region exhibited relaxor ferroelectric-like behavior. Bulk SrTaO2N samples do not show ferroelectricity, thus suggesting that the origin of it may be related with the strain induced by the substrate. Ab-initio calculations reported that the small domains and the surrounding matrix had trans-type and a cis-type anion arrangements, respectively, but do not describe the experimentally observed equilibrium phase, nor the strain dependent polarization. In this work, we present high accurate all-electron first-principles calculations on the different possible local structures that can explain the ferroelectric-like properties of the strained material. The determined local structure and oxygen/nitrogen ordering has been related with polarization and epitaxial strain. The potential energies and polarization as functions of the in-plane lattice constant are reported.

Nanosheet-enhanced efficiency in amine-catalyzed asymmetric epoxidation of α, β-unsaturated aldehydes via host-guest synergy

Amine-catalyzed asymmetric epoxidation of α, β-unsaturated aldehydes has been promoted by attaching the nanosheets of layered double hydroxides (LDHs), a natural and/or synthetic anionic layered compound. 76% of epoxide yield and 93% ee of major diastereomer have been afforded in the asymmetric epoxidation of cinnamaldehyde. The amine sites employed here are the amino group in α-amino acid anion intercalated in the interlayer space of LDHs. The nanosheets of LDHs have been revealed to play key role in the enhancement of catalytic activity by affording the desired basicity and the boost of enantioselectivity by serving as the rigid substituent of amino acids. The hydrophobic interlayer microenvironment and ordered arrangement of intercalated amino acid anions additionally contribute to the catalytic efficacy. Stronger interlayer hydrophobicity favors the conversion and epoxide yield and better arrangement of interlayer anions favors the ee.

Computational Prediction and Evaluation of Solid-State Sodium Superionic Conductors Na7P3X11 (X = O, S, Se)

Inorganic solid-state ionic conductors with high ionic conductivity are of great interest for their application in safe and high-energy-density solid-state batteries. Our previous study reveals that the crystal structure of the ionic conductor Li7P3S11 contains a body-centered-cubic (bcc) arrangement of sulfur anions and that such a bcc anion framework facilitates high ionic conductivity. Here, we apply a set of first-principles calculations techniques to investigate A7P3X11-type (A = Li, Na; X = O, S, Se) lithium and sodium superionic conductors derived from Li7P3S11, focusing on their structural, dynamic and thermodynamic properties. We find that the ionic conductivity of Na7P3S11 and Na7P3Se11 is over 10 mS cm–1 at room temperature, significantly higher than that of any known solid Na-ion sulfide or selenide conductor. However, thermodynamic calculations suggest that the isostructural sodium compounds may not be trivial to synthesize, which clarifies the puzzle concerning the experimental problems in t...

Stepwise Synthesis and Crystal Structure of an AuI4CoIII2 Hexanuclear Complex with d-Penicillaminate and Bis(dicyclohexylphosphino)ethane

Abstract The stepwise synthesis of AuI4CoIII2 complex with d-penicillaminate and 1,2-bis(dicyclohexylphosphino)ethane, [2]2+, via metalloligand approach, together with single-crystal X-ray analysis of nitrate salt, [2](NO3)2, is reported. [2](NO3)2 adopts normal alternate arrangement of cations and anions in crystal, which is different from non-alternate arrangement in corresponding AuI4CoIII2 complex with d-penicillaminate and 1,2-bis(diphenylphosphino)ethane.

Comparative Evaluation of Synthetic Routes and Antibacterial/Antifungal Properties of Zn–Al Layered Double Hydroxides Containing Benzoate Anion

Abstract With variation in synthetic routes, properties of the as-obtained products also vary. Three synthetic routes are opted such as coprecipitation (CP), ion exchange (IE), and rehydration (RH) to form an antibacterial/antifungal composite of Zn–Al layered double hydroxide with benzoate (BZ) anion in the interlayer space. X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectrum, and thermogravimetric analyses are used to characterize the samples. In case of composite obtained by CP route, the molecular arrangement of the BZ anion is bilayer with both the molecules are arranged along their y-axis. Similarly, in case of IE route, the arrangement is also bilayer but the molecules are arranged along the y-axis of one molecule and along the x-axis of another. In the RH route, the arrangement is monolayer. The three novel nanocomposites showed different performance in terms of liberation factor and antibacterial activity toward both Gram-positive (Staphylococcus au...

Crystal structure, Hirshfeld surface analysis, vibrational, thermal behavior and UV spectroscopy of (2,6-diaminopyridinium) dihydrogen arsenate

A new organic dihydrogenomonoarsenate (C5H8N3)H2AsO4 was synthesized by slow evaporation method at room temperature and characterized by X-ray single crystal diffraction. This compound crystallizes in the monoclinic system with the centro-symmetric space group P21/n. Unit cell parameters are a = 10.124 (5)Ǻ, b = 6.648 (5)Ǻ, c = 13.900 (5)Ǻ, β = 105.532° with Z = 4. The crystal structure was solved and refined to R = 0.038 with 2001 independent reflections. Hirshfeld surfaces analysis were used to visualize the fidelity of the crystal structure which has been determined by X-ray data collection on single crystals (C5H8N3)H2AsO4. Due the strong hydrogen OH⋯O bond network connecting the H2AsO4 groups, the anionic arrangement must be described as infinite (H2AsO4)nn-of dimers chains spreading, in a zig zag fashion, parallel to the b direction. The organic groups (C5H8N3)+ are anchored between adjacent polyanions through multiple hydrogen bonds NH⋯O. The thermal decomposition of precursors studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), indicate the existence of two mass loss regions correspond to degradation of the title compound. The existence of vibrational modes correspond to the organic and inorganic groups are identified by the infrared and Raman spectroscopy in the frequency ranges 500–4000 and 25-4000 cm−1, respectively.

Computational perspectives on structure, dynamics, gas sorption, and bio-interactions in deep eutectic solvents

We present a snapshot of the current status of understanding structure, dynamics, and molecular interactions within deep eutectic solvents (DESs) gained from a computational perspective. The simulations reported thus far have been largely aimed at unravelling the relationship between the molecular features within a DES and the depressed melting temperature at its eutectic composition. Computational efforts consistently reveal that the addition of hydrogen bond donors significantly disrupts long-range ordering of the cation–anion arrangement in choline chloride, resulting in significant moderation of the interaction energies between the components of the DES. These studies paint a picture of DES formation being accompanied by hydrogen-bond directed charge transfer processes yielding transient cage-like formation and nanoscale ordering entailing segregation of the ionic and molecular domains. Computational insights further uncover how unique solvation features present within DESs may lead to enhanced biomolecular (e.g., protein, nucleic acid, polysaccharide) stability and/or activity while also offering advantages as environmentally-responsible gas sorbents.

Column anion arrangements in chemically zoned ternary chlorapatite and fluorapatite from Kurokura, Japan

The substitution of F, OH, and Cl in apatite has recently gained increased attention due to the complex nature of incorporation of these three constituents and the implications of apatite column anion chemistry, such as apatite’s contribution to the water budget of the Moon and Mars and the use of apatite anion chemistry as an indicator of halogen and water activities. The solid solutions among F, OH, and Cl are complex because the end-member atomic arrangements cannot fully explain the ternary and binary substitutions of these constituents due to differing atomic radii and the resulting steric constraints in the structure. Three structural variations have recently been reported for the OH-Cl binary solid solution in synthetic samples. This study elucidates column anion arrangements in a chemically zoned ternary apatite from Kurokura, Japan. The structures of the compositionally different core and rim were solved (R1 = 0.0158 and R1 = 0.0143, respectively) in space group P 6 3 /m using single-crystal X-ray diffraction data. The chemistry of these apatites was analyzed using electron microprobe analysis and crystal structure refinement. The core of the Kurokura crystal is a naturally occurring example of the OH ≈ Cl apatite structural variation in a ternary chlorapatite, with four column anion sites (one for F, two for Cl and one for both OH and Cl). The rim exhibits a previously unseen apatite structural variation in a ternary OH-rich fluorapatite (with only a trace Cl component) with three column anion sites (one each for F, OH, and Cl). Both structural variations show a splitting of the Ca2 site that enables reasonable column anion bond distances with Ca2 atoms. A sequence of anions that provides reasonable anion-anion distances while simultaneously enabling reversal of the anion sites relative to the mirror planes at z = ¼ and z = ¾ exists for both structure variations. This study demonstrates the structural complexity of natural ternary apatites, and that a structural variety of OH-Cl apatite occurs over a wider range of chemistry than initially anticipated. The results have implications regarding the poorly understood (and potentially complex) crystallization history of apatite from Kurokura, Japan.

Strain Engineering for Anion Arrangement in Perovskite Oxynitrides.

Mixed-anion perovskites such as oxynitrides, oxyfluorides, and oxyhydrides have flexibility in their anion arrangements, which potentially enables functional material design based on coordination chemistry. However, difficulty in the control of the anion arrangement has prevented the realization of this concept. In this study, we demonstrate strain engineering of the anion arrangement in epitaxial thin films of the Ca1-xSrxTaO2N perovskite oxynitrides. Under compressive epitaxial strain, the axial sites in TaO4N2 octahedra tend to be occupied by nitrogen rather than oxygen, which was revealed by N and O K-edge linearly polarized X-ray absorption near-edge structure (LP-XANES) and scanning transmission electron microscopy combined with electron energy loss spectroscopy. Furthermore, detailed analysis of the LP-XANES indicated that the high occupancy of nitrogen at the axial sites is due to the partial formation of a metastable trans-type anion configuration. These results are expected to serve as a guide for the material design of mixed-anion compounds based on their anion arrangements.

New Dmit-Based Organic Magnetic Conductors (PO-CONH-C2H4N(CH3)3)[M(dmit)2]2 (M = Ni, Pd) Including an Organic Cation Derived from a 2,2,5,5-Tetramethyl-3-pyrrolin-1-oxyl (PO) Radical

We have prepared two dmit-based salts with a stable organic radical-substituted ammonium cation, (PO-CONH-C2H4N(CH3)3)[Ni(dmit)2]2·CH3CN and (PO-CONH-C2H4N(CH3)3)[Pd(dmit)2]2 where PO is 2,2,5,5-Tetramethyl-3-pyrrolin-1-oxyl and dmit is 2-Thioxo-1,3-dithiol-4,5-dithiolate. The salts are not isostructural but have similar structural features in the anion and cation packing arrangements. The acceptor layers of both salts consist of tetramers, which gather to form 2D conducting layers. Magnetic susceptibility measurements indicate that the Ni salt is a Mott insulator and the Pd salt is a band insulator, which has been confirmed by band structure calculations. The cationic layers of both salts have a previously unreported polar structure, in which the cation dipoles order as ➚➘➚➘ along the acceptors stacking direction to provide dipole moments. The dipole moments of nearest neighbor cation layers are inverted in both salts, indicating no net dipole moments for the whole crystals. The magnetic network of the [Ni(dmit)2] layer of the Ni salt is two-dimensional so that the magnetic susceptibility would be expected to obey the 1D or 2D Heisenberg model that has a broad maximum around T ≈ θ. However, the magnetic susceptibility after subtraction of the contribution from the PO radical has no broad maximum. Instead, it shows Curie–Weiss behavior with C = 0.378 emu·K/mol and θ = −35.8 K. The magnetic susceptibility of the Pd salt obeys a Curie–Weiss model with C = 0.329 emu·K·mol−1 and θ = −0.88 K.

α‐RbO3, a Low Temperature Polymorph of Rubidium Ozonide

Applying the known procedure for synthesis of alkali metal ozonides, just at a lower temperature, has yielded a new polymorph of rubidium ozonide, α‐RbO3 [P21; a = 436.3(2), b = 595.3(3), c = 548.7(3) pm, β = 99.680(7), R = 0.0400, 1184 reflections]. Like previously reported β‐RbO3, the basic structural arrangement of anions and cations corresponds to the CsCl type of structure, however, the mutual orientation of the ozonide ions is different, in as much as one of the two terminal oxygen atoms is pointing to the adjacent bridging oxygen atom, forming a chain running along the b axis.

Noncovalent interactions underlying binary mixtures of amino acid based ionic liquids: insights from theory

Mixtures of ionic liquids formed by blending a common 1-methyl-3-butylimidazolium [Bmim] cation with the dicarboxylic amino acid anions viz., aspartic acid [Asp], asparagine [Asn], glutamic acid [Glu], and glutamine [Gln], have been investigated by employing dispersion corrected density functional theory. Binary mixtures of [Bmim]2[Asp][Asn] and [Bmim]2[Glu][Gln] ionic liquids emerge with distinct structural patterns. Competition between the constituting anions towards cationic binding sites in acidic and basic (polar) amino acid binary mixtures engenders diverse noncovalent interactions, viz., C-HO hydrogen bonding, π-π stacking, and lpπ and CHπ interactions, which impart local liquid structure to these systems governing the structural and physicochemical properties of such double salt ionic liquids (DSILs). The DSIL conformers reveal distinct structural features arising from the middle, normal and front arrangements of anions combined with parallel, antiparallel, rotated or displaced orientations of the cations. The inclusion of dispersion corrections through the D3 method affects their binding energies significantly bringing forth alteration in their energy rank order. Molecular insights accompanying the ion aggregates provide directives for the use of DSILs with improved performance in tribological applications.

Ideal wollastonite and the structural relationship between the pyroxenoids and pyroxenes

A hypothetical ideal wollastonite with regular octahedra and T3 tetrahedron is presented and used to compare and contrast the pyroxenes and pyroxenoids. While clinopyroxenes have close-packed arrangements of oxygen anions, several lines of evidence demonstrate that pyroxenoids do not. One such line is the number of tetrahedra in a single tetrahedral chain per octahedra in a single associated octahedral chain (interior to the octahedral band), referred to as the “single-chain T:O ratio,” which is 1:1 in pyroxenes but 3:2 in wollastonite and always greater than 1:1 in other MSiO3 pyroxenoids. Because the Si-tetrahedron is extremely resistant to distortion, this forces marked distortion in at least one pyroxenoid octahedral site. The octahedral layers in pyroxenes and pyroxenoids are compared by placing them in the context of a fully occupied, closest-packed sheet of idealized octahedra, and it is shown that they are fundamentally different. The new mineral yangite is analyzed from the perspective developed in this study. It is structurally similar to the pyroxenoids, but the structure is a new type because it contains double tetrahedral chains and mixed polyhedral layers containing double chains of tetrahedra and bands of octahedra of width two. The tetrahedral chains are wollastonite-type chains and the wollastonite-type double chain is shown to have important differences from the amphibole double chain. A possible explanation for the existence of this crystal structure based on a hydrogen bond between Pb and O is presented.

Crystal Structures and Phase Sequences of Metallocenium Salts with Fluorinated Anions: Effects of Molecular Size and Symmetry on Phase Transitions to Ionic Plastic Crystals.

Sandwich compounds often exhibit various phase transitions, including those to plastic phases. To elucidate the general features of the phase transitions in metallocenium salts, the thermal properties and crystal structures of [Fe(C5 Me5 )2 ]X ([1]X), [Co(C5 Me5 )2 ]X ([2]X), and [Fe(C5 Me4 H)2 ]X ([3]X) have been investigated, where the counter anions (X) are Tf2 N (=(CF3 SO2 )2 N- ), OTf (=CF3 SO3- ), PF6 , and BF4 . The Tf2 N salts commonly undergo phase transitions from an ordered phase at low temperatures to an anion-disordered phase, followed by a plastic phase and finally melt at high temperatures. All these salts exhibit a phase transition to a plastic phase, and the transition temperature generally decreases with decreasing cation size and increasing anion size. The crystal structures of these salts comprise an alternating arrangement of cations and anions. About half of these salts exhibit phase transitions at low temperatures, which are mostly correlated with the order-disorder of the anion.

Assessment of the U3O7 Crystal Structure by X-ray and Electron Diffraction.

Polycrystalline U3O7 powder was synthesized by oxidation of UO2 powder under controlled conditions using in situ thermal analysis, and by heat treatment in a tubular furnace. The O/U ratio of the U3O7 phase was measured as 2.34 ± 0.01. The crystal structure was assessed from X-ray diffraction (XRD) and selected-area electron diffraction (SAED) data. Similar to U4O9-ε (more precisely U64O143), U3O7 exhibits a long-range ordered structure, which is closely related to the fluorite-type arrangement of UO2. Cations remain arranged identical to that in the fluorite structure, and excess anions form distorted cuboctahedral oxygen clusters, which periodically replace the fluorite anion arrangement. The structure can be described in an expanded unit cell containing 15 fluorite-like subcells (U15O35), and spanned by basis vectors A = ap - 2bp, B = -2ap + bp, and C = 3cp (lattice parameters of the subcell are ap = bp = 538.00 ± 0.02 pm and cp = 554.90 ± 0.02 pm; cp/ap = 1.031). The arrangement of cuboctahedra in U3O7 results in a layered structure, which is different from the well-known U4O9-ε crystal structure.

Synthesis and H- Conductivity of Ba2LiH3-2x O1+X

Hydride ions are attractive as charge carriers because these have an ionic radius appropriate for fast ionic conduction and also show strong reducing properties with a standard redox potential of H–/H2 (–2.25 V vs. SHE), which is close to that of Mg/Mg2+ (–2.38 V vs. SHE). Therefore, H– conductors may be applied in energy storage and conversion devices with high energy densities. Recently, we have found La2-x-y Sr x +y LiH1-x+y O3-y (LSLHO) oxyhydride system possessing pure H– conductivity, and have confirmed the capability of the oxyhydride to act as an H– solid electrolyte by demonstrating the battery reaction of an all-solid-state Ti/LSLHO/TiH2 cell [1]. The LSLHO system shows H– conductivity of 10-4 S·cm–1 at 300 ºC. However, a higher H– conductivity will be required to make novel electrochemical devices using H– conduction phenomenon. In this study, we attempted to synthesize a new H– conductive oxyhydride, Ba2LiH3-2x O1+x (BLHO), in order to achieve a higher H– conductivity than that of LSLHO [2]. BLHO was designed on the basis of LSLHO with the K2NiF4-type structure. La/Sr in LSLHO was substituted by Ba to expand the bottleneck size for H– diffusion in the crystal lattice. Furthermore, H– vacancies were introduced into the structure by controlling H/O ratio in the composition of BLHO. Crystal structure of BLHO was determined by X-ray and neutron diffraction. The X-ray diffraction peak of the sample could be indexed as the K2NiF4-type structure. The crystal structure of Ba2LiH3O (BLHO: x = 0) and Sr2LiH3O (LSLHO: x = 0, y = 2) determined by the Rietveld analysis are compared in Figure 1. The anion arrangement of Ba2LiH3O is basically same with Sr2LiH3O. The two apical anion sites in Li-octahedra are preferentially occupied by oxide ions. Oxide and hydride ions randomly occupy the apical site. In contrast, the four axial anion sites of the Li-anion octahedra prefer to be occupied by only hydride ions. As a result, square-planar LiH4 is formed in the Li-octahedra. When the A-site cation in the composition of A 2LiH3O changed from Sr to Ba, the lattice volume expand depending on the difference of ionic radii between Sr2+ (1.58 Å) and Ba2+ (1.75 Å). In particular, influences of the volume expansion mainly appeared to ab plane in the crystal lattice. The details of H– conduction properties for BLHO will be discussed in our presentation.

Synthesis, identification and in vitro drug release of layered zinc hydroxide-gemifloxacin nanohybrids

The intercalation of fluoroquinolone antibiotic, Gemifloxacin (GEM) anions, into layered zinc hydroxide (LZH) has been achieved by using ion-exchange method. The GEM-LZH/Chitosan nanocomposite coating Chitosan nanocomposite was prepared in alkaline aqueous solution. Powder X-ray diffraction studies confirmed a basal spacing of 25.54 A, showing that the GEM was successfully intercalated into the LZH interlayer. The arrangement of GEM anions was in a monolayer form between the LZH interlayers. Fourier transform infrared spectroscopy results exhibited the formation of the host–guest nanohybrid without any change in the structure of the GEM. The increased thermal stability of nanohybrid was confirmed by thermal analyses. The in vitro release study of GEM from nanohybrid and nanocomposite was investigated in phosphate buffer saline solution of pH 4.8 and 7.4 using ultraviolet–Visible spectroscopy.

Materials Design Guidelines for All-Solid-State Batteries

All-solid-state batteries with non-flammable solid-state electrolytes have significant advantages over Li-ion or Na-ion batteries with liquid electrolytes. In this poster we will present our recent advances in understanding the fundamental relationship between crystal structure and ionic transport in fast Li-ion conductors [1]. We find that the topology of the sites along the lithium hopping path, and the volume per anion, largely control the activation energy for Li motion. This topology is more favorable in compounds where the anions form a bcc lattice than in the typical close-packed fcc and hcp anion arrangements, explaining why most compounds are not fast-ion conductors. Furthermore, an accurate and efficient first-principles computational methodology has been developed to evaluate thermodynamic stability of the solid-state electrolyte against battery electrodes [2]. These findings not only provide valuable insights towards the understanding of materials behaviors in discovered ionic conductors, but also serve as design principles for new Li and Na conducting materials and all-solid-state batteries. We will also report a few novel Li and Na ionic conductors that are predicted based on our design principles and experimentally confirmed by our collaborators. [1] Y. Wang, et al., “Design principles for solid-state lithium superionic conductors,” Nat. Mater., 14, 1026-1031, (2015). [2] W. Richards, et al., “Interface stability in solid-state batteries”, Chem. Mater., 28, 266-273, (2016).

In situ synthesis of polystyrene nanocomposites with layered double hydroxide with an unusual anion arrangement: Morphology and thermal and mechanical properties

ABSTRACTToday, the steady advance of technology and society makes the development of materials with improved properties of paramount importance. In this article, we contribution to this area by presenting an in situ bulk synthesis of polystyrene (PS) nanocomposites with layered double hydroxide (LDH) as a reinforcement. The LDH that we adopted presented an unusual arrangement of anions and had ZnAl cations intercalated with laurate and palmitate anions. The nanocomposites were analyzed by X‐ray diffraction and transmission electron microscopy to characterize their morphologies. The thermal properties, including the glass‐transition temperature and thermal stability, were measured by differential scanning calorimetry and thermogravimetric analysis, respectively. The mechanical properties and flexural fracture morphologies were also determined, with a bending test. The results demonstrate that the synthesized nanocomposites showed considerable improvements in their thermal stability and mechanical properties compared with the neat PS. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 132, 42856.

Design principles for solid-state lithium superionic conductors.

Lithium solid electrolytes can potentially address two key limitations of the organic electrolytes used in today's lithium-ion batteries, namely, their flammability and limited electrochemical stability. However, achieving a Li(+) conductivity in the solid state comparable to existing liquid electrolytes (>1 mS cm(-1)) is particularly challenging. In this work, we reveal a fundamental relationship between anion packing and ionic transport in fast Li-conducting materials and expose the desirable structural attributes of good Li-ion conductors. We find that an underlying body-centred cubic-like anion framework, which allows direct Li hops between adjacent tetrahedral sites, is most desirable for achieving high ionic conductivity, and that indeed this anion arrangement is present in several known fast Li-conducting materials and other fast ion conductors. These findings provide important insight towards the understanding of ionic transport in Li-ion conductors and serve as design principles for future discovery and design of improved electrolytes for Li-ion batteries.