Showing papers in "Zeitschrift für anorganische und allgemeine Chemie in 2014"

The Zintl-Klemm Concept – A Historical Survey†

Abstract: The Zintl-Klemm concept (ZKC) is a combination of a valence electron counting rule and a set of structure-chemical considerations which works well for a continuously growing class of compounds between classical salts and classical covalent compounds on the on hand, and intermetallic phases on the other. In this historical article the lines of development of the ZKC are reviewed. They originate from Eduard Zintl in Darmstadt and were carried on and extended by Wilhelm Klemm in Munster, early on. After World War II different schools developed their own points of view on the ZKC which converged in the 1990s, backed by blossoming quantum mechanical schemes of treating complex solids. The limits of applicability of the ZKC are subject of ongoing investigations, still, and it seems that the concept has reached a state of quite general acceptance in solid state sciences.

Recent Discoveries of Polyhalogen Anions – from Bromine to Fluorine

Abstract: In this review we discuss the recent discoveries in polyhalide anion chemistry with the main focus on polybromide, -chloride, and -fluoride anions. Based on novel synthetic strategies either in ionic liquids or in neat halogens several new polyhalides of bromine and chlorine were synthesized. Beyond these discoveries the chemistry of polyfluoride monoanions is reviewed. Such species were investigated under cryogenic conditions at 4 K in conjunction with quantum-chemical calculations. In addition to these bonding and structural discussions, an overview of possible applications of such polyhalide anions is provided.

In situ X-ray Diffraction Studies of Cation and Anion Inter­calation into Graphitic Carbons for Electrochemical Energy Storage Applications

Abstract: Graphite is a redox-amphoteric intercalation host and thus capable to incorporate various types of cations and anions between its planar graphene sheets to form so-called donor-type or acceptor-type graphite intercalation compounds (GICs) by electrochemical intercalation at specific potentials. While the LiCx/Cx donor-type redox couple is the major active compound for state-of-the-art negative electrodes in lithium-ion batteries, acceptor-type GICs were proposed for positive electrodes in the “dual-ion” and “dual-graphite” cell, another type of electrochemical energy storage system. In this contribution, we analyze the electrochemical intercalation of different anions, such as bis(trifluoromethanesulfonyl) imide or hexafluorophosphate, into graphitic carbons by means of in situ X-ray diffraction (XRD). In general, the characterization of battery electrode materials by in situ XRD is an important technique to study structural and compositional changes upon insertion and de-insertion processes during charge/discharge cycling. We discuss anion (X–) and cation (M+) intercalation/de-intercalation into graphites on a comparative basis with respect to the Mx+Cn– and Cn+Xn– stoichiometry, discharge capacity, the intercalant gallery height/gallery expansion and the M–M or X–X in-plane distances.

Coloring, Distortions, and Puckering in Selected Intermetallic Structures from the Perspective of Group‐Subgroup Relations

Abstract: Group-subgroup relations are a compact and concise tool for structure systemization. The present review summarizes the use of Barnighausen trees for classification of intermetallic structures into structural families. The overview starts with group-subgroup relationships between the structures of the metallic elements (W, In, α-Po, β-Po, Pa, α-Sn, β-Sn) followed by examples for ordered close-packed arrangements that derive from fcc, hcp, and bcc subcells (e.g. CuAu, Cu3Au, MoNi4, ZrAl3, FeAl, MoSi2). The main focus lies on more complex structures that derive from aristotypes with comparatively high space group symmetry: AlB2, Fe2P, U3Si2, BaAl4, La3Al11, NaZn13, CaCu5, and Re3B. The symmetry reductions arise from coloring of sites with different atoms or from distortions / puckering due to size restrictions (different radii of atoms). The resulting superstructures are discussed along with the consequences for diffraction experiments, chemical bonding, and physical properties.

MCX: a Synchrotron Radiation Beamline for X-ray Diffraction Line Profile Analysis

Abstract: The potential of modern methods for X-ray diffraction Line Profile Analysis can be fully exploited with data collected at synchro- tron radiation beamlines, provided that optics and experimental set-up are suitably designed and characterized. The Material Characterization by X-ray Diffraction beamline, MCX, at Elettra-Sincrotrone Trieste,

Two Lanthanide(III) Complexes based on the Schiff Base N,N′-Bis(salicylidene)-1,5-diamino-3-oxapentane: Synthesis, Characterization, DNA-binding Properties, and Antioxidation

Abstract: The Schiff base N,N′-bis(salicylidene)-1,5-diamino-3-oxapentane (H2L) and its lanthanide(III) complexes, PrL(NO3)(DMF)(H2O) (1) and Ho2L2(NO3)2·2H2O (2), were synthesized and characterized by physicochemical and spectroscopic methods. Single crystal X-ray structure analysis revealed that complex 1 is a discrete mononuclear species. The PrIII ion is nine-coordinate, forming a distorted capped square antiprismatic arrangement. Complex 2 is a centrosymmetric dinuclear neutral entity in which the HoIII ion is eight-coordinate with distorted square antiprismatic arrangement. The DNA-binding properties of H2L and its LnIII complexes were investigated by spectrophotometric methods and viscosity measurements. The results suggest that the ligand H2L and its LnIII complexes both connect to DNA in a groove binding mode; the complexes bind more strongly to DNA than the ligand. Moreover, the antioxidant activities of the LnIII complexes were in vitro determined by superoxide and hydroxyl radical scavenging methods, which indicate that complexes 1 and 2 have OH· and O2–· radical scavenging activity.

Synthesis and Properties of Cobalt Sulfide Phases: CoS2 and Co9S8

Abstract: Single phase cobalt disulfide (CoS2) nanoparticles were prepared by thermal decomposition of cobalt-thiourea complex at a low temperature (400 °C). CoS2 nanoparticles exhibit ferromagnetic ordering at 122 K below which the temperature dependent resistivity of cold pressed nanoparticles deviates from metallic behavior and shows a broad maximum. Just below TC, it also exhibits a large magnetoresistance effect (6.5 %). A mixture of CoS and Co9S8 phases were obtained between the temperature interval 400 °C < T < 1000 °C. At 1000 °C, a pure bulk Co9S8 phase was obtained. It exhibits magnetic hysteresis typical of a ferromagnet at room temperature and a peak in magnetization at low temperature with a strong relaxation indicating possible spin glass state.

New Mn2-based Heusler Compounds†

Abstract: Mn2-based Heusler compounds have attracted a great deal of interest as half-metallic ferri- and ferromagnets and as materials for spintronic applications. In this paper, we report the synthesis, crystal structure, and disorder type of the new Heusler compounds Mn2RuGe, Mn2RhGa, and the redetermination of the crystal structure of Mn2RuSn. They crystallize cubic with L21b structure type in Fmm, which is an inverse Heusler structure with a transition metal disorder of the type (Mn0.5,Y0.5)2MnZ (Y = Ru or Rh and Z = Ge, Ga or Sn). It is shown that an inverse Heusler structure can generally gain stability through the configurational part of the entropy of mixing at elevated temperatures without loosing too much enthalpy in the configurational part of the enthalpy of mixing owing to a special bond arrangement in the inverse type structure. The enthalpy of formation of transition-metal-based Heusler compounds and Al, Ga, and Ge as the main group metals obtained from DFT calculations and experimental data are used to confirm Burch's rule, which predicts the stability of transition-metal-based inverse Heusler compounds. Alloying tendencies as manifested in binary phase diagrams and the enthalpies obtained from the Miedema model are correlated with the stability of Heusler compounds. Burch's rule is in excellent agreement with the current available experimental data. The DFT data and general alloying tendencies show that deviations are expected from this rule. Miedema's model allows the estimation of the enthalpy of formation for the transition- and main group metal-based Heusler compounds, except for those having period 6 elements and Pd.

Vertically-aligned Mesoporous Silica Films

Abstract: Mesoporous silica thin films with mesochannels oriented perpendicularly to the underlying support have attracted a great deal of attention over past years because of their potential applications as novel functional materials and hosts to confine guest molecules or catalysts, with advantageous features (such as favorable mass transport issues) with respect to other silica films exhibiting large surface area and uniform pore size, due to the vertical alignment of mesopore channels. However, the preparation of such vertically-aligned mesoporous silica films still remains extremely challenging. Here, we give an overview of the various synthetic approaches that have been proposed to date for the generation of vertically-aligned mesoporous silica films. We also present briefly the methods used for their characterization and some of their applications, especially their use as hard templates for getting other nanostructures.

Chemical Reactions followed by in situ Neutron Powder Diffraction

Abstract: In situ neutron powder diffraction is a very convenient tool for the investigation of chemical reactions, whenever crystalline solids are involved. It may give insight into reaction pathways, thus allowing for strategic synthesis planning, revealing particular intermediate steps and quantifying the reaction kinetics. Although the method is rather straightforward, one is bound to a small number of available neutron sources and the few sufficiently high intensity powder diffractometers there, most of which are briefly described herein. The high penetration depth of thermal neutrons allows for a large range of complex sample environments; however neutron absorption and parasitic scattering have to be carefully considered in the construction of dedicated in situ equipment. Some specific types of sample environment, specially designed for in situ neutron powder diffraction will be discussed such as electrochemical cells, autoclaves for the study of solvothermal reactions, and gas-solid reaction cells. Several examples from inorganic chemistry are being presented, ranging from metal hydrides, nitrides, oxides, and halides, to intermetallic compounds or metal organic frameworks, many of them of importance in applications, e.g. in lithium ion batteries, as magnetic or hard materials, high strength alloys, hydrogen storage, ferroelectric or superconducting materials, or as solid catalysts. In situ neutron powder diffraction often paves the way to a better reaction control in chemical synthesis, to the discovery of metastable compounds or gives insight into technologically relevant processes. These successful applications in inorganic chemistry demonstrate the usefulness of the method of in situ neutron powder diffraction and may encourage the reader to consider neutron diffraction in the repertoire of analytic tools.

Inverse Opal SiO2 Photonic Crystals as Structurally-Colored Pigments with Additive Primary Colors

Abstract: Porous silica, structured as three-dimensionally ordered macroporous (3DOM) photonic crystal particles, is investigated as a pigment material with structural color. Brightly and uniformly colored 3DOM SiO2 powders were obtained by templating of a tetraethoxysilane-containing precursor in polymeric colloidal crystals, pyrolysis in an inert atmosphere to maintain a small amount (ca. 5–8 wt %) of residual carbon as a background absorber, and particle size reduction. The color depended on placing optical stop bands in the appropriate range of the visible spectrum. This was achieved through selection of the polymer sphere diameter in the colloidal crystal template and fine-tuning by the pyrolysis temperature, which controls the extent of condensation and shrinkage of the 3DOM SiO2 structure. The stop bands shifted to shorter wavelengths, and the chroma of these pigments increased with increasing pyrolysis temperature in the range from 475 to 900 °C. Using this temperature control, it was possible to obtain materials with a variety of colors and chroma using a single template sphere size. In addition, the assortment of spectral colors could be extended by mixing 3DOM SiO2 pigments with primary colors (red, green, blue) via a unique additive color-mixing mechanism, which distinguishes these pigments from most conventional pigments that rely on subtractive color mixing. These approaches enable the preparation of pigments with multiple colors using a single material composition, providing opportunities to replace potentially harmful dyes and pigments with nontoxic and relatively inert silica.

Synthesis and Crystal Growth of Tetragonal β-Fe1.00Se

Abstract: Single crystals of tetragonal β-Fe1.00Se were grown from polycrystalline material by chemical vapor transport reaction at temperatures below 723 K using AlCl3 as transport additive. The plate-shaped single crystals have edge lengths up to 4 mm. The single crystals display complete diamagnetic shielding 4πχ ≈ –1 below the superconducting transition.

Further New Borosulfates: Synthesis, Crystal Structure, and Vibrational Spectra of A[B(SO4)2] (A = Na, K, NH4) and the Crystal Structures of Li5[B(SO4)4] and NH4[B(S2O7)2]

Abstract: The reaction of alkali sulfates and boron oxide in oleum yielded the complexes A[B(S2O7)2] (A = Li, Na, K, NH4). This way we obtained the first ammonium-containing borosulfate and we determined the crystal structure. NH4[B(S2O7)2] [Cc, Z = 8, a = 11.4403(2), b = 14.9439(2) c = 13.8693(2) A] crystallizes isotyp to K[B(S2O7)2]. Thermal decomposition or treatment in vacuo resulted in compounds with composition A[B(SO4)2]. One-dimensional chain structures are obtained for A = Na, K, NH4. NH4[B(SO4)2] [P4/ncc, Z = 4, a = 9.1980(1), c = 7.4258(1) A] and K[B(SO4)2] [P4/ncc, Z = 4, a = 8.9739(3), c = 7.4114(3) A] are isotyp with H3O[B(SO4)2]. The chains of edge-sharing “BS4 super tetrahedra” have symmetry. In Na[B(SO4)2] [P2/c, Z = 2, a = 5.434(5), b = 7.570(7) c = 7.766(8) A, β = 108.56(3)°] the chain is twisted. Li5[B(SO4)4] [P21/c, Z = 4, a = 8.0191(1), b = 10.1211(1) c = 15.0401(2) A, β = 104.033(1)°] contains isolated pentameric unit and represents a new structure type. Li5[B(SO4)4] was obtained from Li[B(S2O7)2] with additional Li2SO4/SO3. Vibrational spectra of A[B(S2O7)2] (A = Na, K, NH4) are presented and force constants calculated. In all structures BO4 and SO4 tetrahedra are connected by common apices forming BS4 super tetrahedra.

Mitochondria targeting Photocytotoxic Oxidovanadium(IV) Complexes of Curcumin and (Acridinyl)dipyridophenazine in Visible Light

Abstract: Oxidovanadium(IV) complexes, VO(acac)(L)Cl] (1), VO(cur)(L)Cl] (2), and VO(scur)(L)Cl] (3) {acac = acetylacetonate, cur = curcumin monoanion, scur = diglucosylcurcumin monoanion, L = 11-(9-acridinyl)dipyrido3, 2-a:2',3'-c]phenazine (acdppz)}, were prepared and characterized. The complexes are non-electrolytic in DMF and 1:1 electrolytic in aqueous DMF. The one-electron paramagnetic complexes showed a d-d band near 725 nm in aqueous DMF and green emission near 520 nm in aqueous DMSO. The complexes exhibited an irreversible V-IV/V-III redox response near -0.85 V versus SCE in aqueous DMF. The complexes showed good binding strengths to calf thymus DNA (K-b: 3.1x10(5)-9.6x10(5) M-1) and efficient pUC19 DNA photocleavage activity in red light of 705 and 785 nm by singlet oxygen (O-1(2)) pathway. Complexes 1 and 2 exhibited significant photocytotoxicity (IC50: 0.1-1.0 M) in visible light (400-700 nm) with low dark toxicity (IC50: >20 M) in HeLa and HaCaT cells. Complex 3 was cytotoxic in both light and dark. DNA ladder formation experiments indicated cell death via apoptotic pathway. Confocal microscopy done with 1 and 2 revealed primarily cytosolic localization of the complexes with significant presence of the complex in the mitochondria as evidenced from the imaging data using mitotracker red.

Formation and Decomposition of Iron Nitrides Observed by in situ Powder Neutron Diffraction and Thermal Analysis

Abstract: In order to gain more information on the formation and decomposition behavior of various iron nitrides from different starting materials in situ neutron diffraction and thermal analysis under application of different gas atmospheres and heating rates were carried out. The following phases were observed during these investigations: crystalline α-Fe, γ-FeNz, γ′-Fe4Ny, ϵ-Fe3N1+x, ζ-Fe2N, FeCl2, [Fe(NH3)6]Cl2, Fe(NH3)2Cl2, and amorphous Fe(NH3)Cl2. In situ neutron diffraction data were collected in high quality, due to an optimized experimental setup with a time resolution of two minutes on D20 (Institut Laue-Langevin) allowing for detailed Rietveld analyses. For all phase transitions, decomposition and formation temperatures a strong dependency from the heating rate, thermal history of the sample, gas flow conditions, and particle size exists. The nitrogen contents observed during thermal decomposition of ζ-Fe2N were related to the binary phase diagram Fe-N. At low temperatures (< 400 °C) ϵ- and ζ-phase are non-equilibrated. However, through annealing equilibrium state is reached. For γ′-Fe4Ny formed in situ at higher temperatures an expansion of the homogeneity range towards lower nitrogen content is observed above 600 °C. For the formation of ϵ-Fe3N1+x from FeCl2 and NH3 a previously proposed reaction sequence involving different ammoniates was confirmed. This reaction occurs via formation of amorphous Fe(NH3)Cl2. The therein observed in situ formed ammoniates were additionally characterized by IR spectroscopy.

Synthesis, Structure, and SOD‐like Activity of a Copper(II) Complex Containing a Bistriazole Group

Abstract: The dinuclear complex [Cu2(HL)2(H2O)2](ClO4)2 (1) [H2L = 5′-(pyridin-2-yl)-1-H,2′-H-3, 3′-bis(1, 2,4-triazole)] was obtained and fully characterized. It exhibits a centrosymmetry configuration, in which each copper(II) ion is pentacoordinate with four nitrogen atoms of two triazole ligands and one oxygen atom from a water molecule. The net atomic charges distribution and atomic orbital contribution to frontier molecular orbitals were obtained using the Gaussian 98 program with Hartree-Fock method at LANL2DZ level, indicating that the copper(II) ion has the potential to accept the electron of O2·–. The complex showed quasi-reversible one-electron CuII/CuI redox waves with redox potentials of –0.034 V. The SOD-like activity (IC50) of 1 was measured to be 0.18 ± 0.01 μM by xanthine/xanthine oxidase-NBT assay at pH 7.8. The relatively high SOD activity suggests that the positive charge of protonated triazole can effectively steer O2·– to and from the active copper ion.

Three New Coordination Compounds with Neodymium Based on Tetrazole Containing Carboxylic Acid Ligands

Abstract: Reactions of three tetrazole containing carboxylic acid ligands, namely, Hpztza, Htzpya, and Hpytza [Hpztza = 5-(2-pyrazinyl)tetrazole-2-acetic acid, Htzpya = 3-(5-tetrazolyl)pyridine-1-acetic acid, Hpytza = 5-(3-pyridyl)tetrazole-2-acetic acid] with NdCl3·6H2O under hydrothermal conditions, afforded the complexes [Nd(pztza)2(H2O)6]·pztza·3H2O (1), [Nd2(tzpya)2(H2O)12]Cl4·2H2O (2), and [Nd(pytza)2Cl(H2O)2] (3). The compounds were structurally characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. X-ray diffraction analyses revealed that compound 1 displays a mononuclear structure, 2 shows a dinuclear structure, and 3 features a 1D polymeric chain structure via pytza as linker. Furthermore, the luminescent properties investigated at room temperature in the solid state show that compound 2 has an obvious decrease in its luminescence, when compared to the ligand.

The Energetic Nitrocarbamate O2NN(H)CO[OCH2C(NO2)3] Derived from Phosgene

Abstract: A new simple synthesis route for 2,2,2-trinitroethyl chloroformate (1), from easily available starting materials 2,2,2-trinitroethanol and phosgene is presented. 2,2,2-Trinitroethyl carbamate (2) was obtained by the reaction of 1 with aqueous ammonia. The nitration of 2 with anhydrous nitric acid and sulfuric acid yields 2,2,2-trinitroethyl nitrocarbamate (3), which has potential as a perchlorate free high energetic dense oxidizer with a high oxygen balance of Ω(CO2) = +14.9 %. The thermal stability was studied using differential scanning calorimetry and the energies of formation were calculated on the CBS-4M level of theory, as well as several detonation parameters and propulsion properties were determined. In addition to full spectroscopic characterization, X-ray diffraction studies were performed for 2 and 3.

Synthesis and Structural Characterization of the Alkali Thiophosphates Na2P2S6, Na4P2S6, K4P2S6, and Rb4P2S6

Abstract: The hitherto unknown, but expected title compounds are synthesized from stoichiometric mixtures of the elements (973—1120 K, 10 h) and characterized by single crystal XRD.

The First Neutral Dinuclear Vanadium Complex Comprising VO and VO2 Cores: Synthesis, Structure, Electrochemical Properties, and Catalytic Activity

Abstract: A neutral dinuclear vanadium complex containing both oxido and dioxidovanadium cores with hydrazone based ligand, [VO(OCH3)(CH3OH)(HL)VO2] (1) {H4L = bis[(E)-N′-(5-bromo-2-hydroxybenzylidene)]-carbohydrazide}, was synthesized and fully characterized by X-ray crystallography and spectroscopic methods (IR, UV/Vis, NMR). The ligand acts as a trinegative hexadentate N3O3 donor ligand to form a dinuclear complex and during the reaction V4+ is oxidized to V5+. The coordination polyhedra are a VO5N distorted octahedron for the mono-oxidovanadium core and a VO3N2 trigonal bipyramid for the dioxidovanadium core. The results of catalytic reactions indicate that 1 is a highly active catalyst in the clean epoxidation reaction of cis-cyclooctene using aqueous hydrogen peroxide in acetonitrile. Cyclic voltammetric experiments of 1 in DMSO reveal two quasi-reversible peaks due to the VO3+–VO2+ and VO2+–VO2 couples.

Characterization of Gas-Solid Reactions using In Situ Powder X-ray Diffraction

Abstract: X-ray diffraction is a superior technique for structural char- acterization of crystalline matter. Here we review the use of in situ powder X-ray diffraction (PXD) mainly for real-time studies of solid- gas reactions, data analysis and the extraction of valuable knowledge of structural, chemical and physical properties. Furthermore, the dif- fraction data may also provide knowledge on reaction mechanisms, kinetics and thermodynamic properties. Thus, in situ PXD simulta- neously provides properties as a function of pressure, temperature and/ or time at different length scales, i.e. nanoscale structural data and bulk

On The Steric Hindrance of Bulky Substituents – Determination of Their Cone Angles

Abstract: A series of simple halogen compounds was studied with respect to steric hindrance by means of quantum mechanical methods utilizing the M062X/aug-cc-pvdz level of theory. The maximal cone angles of the halogen compounds R–E were computed for a series of different substituents (R carbon or silyl based substituents, E = halogen). Depending on the substitution pattern and the bulkiness of the substituent R a correlation between the cone angle and structural parameters is discussed. Estimates for the cone angles of any element attached to R are provided, that allows comparison of cone angles of different substituents at different distances, which can facilitate synthesis. Additionally, the bonding situation was assessed by natural bond orbital (NBO) analysis indicating that significant electronic effects should be considered when changing from silyl to carbon based substituents. Silyl based substituents display a considerably larger charge transfer to E compared to carbon based once.

Role of Annealing Atmosphere on Structure, Dielectric and Magnetic Properties of La2CoMnO6 and La2MgMnO6 †‡

Abstract: Polycrystalline samples of La2MMnO6 (M = Co and Mg) were prepared by a combined gel-combustion and high temperature reaction method. The samples were annealed in different oxygen partial pressure (pO2) and characterized by powder XRD, SQUID magnetometry, ac impedance spectroscopy, and electron paramagnetic resonance techniques. Monoclinic (P21/n) and rhombohedral (R) lattices were observed for La2CoMnO6 and La2MgMnO6, respectively. On annealing in inert atmosphere, La2MgMnO6 partially converted to monoclinic La2CoMnO6 type structure, whereas no structural change was observed in La2CoMnO6. Dielectric studies of La2CoMnO6 indicated relaxor like behavior with polaronic conduction, which systematically decreased with the increase in pO2 of the annealing atmosphere. Magnetic studies indicated multiple ferromagnetic phase transitions in La2CoMnO6 and a spin-glass like phase transition in La2MgMnO6. The fraction of ferromagnetic phases of La2CoMnO6 was significantly dependent on the annealing environments. The variations of magnetic and dielectric properties of samples were related to the fluctuation of oxidation state of transition metal ions and oxygen vacancies in the samples.

Metal‐Centered Zintl Ions Isolated by Direct Extraction from Endohedral Intermetallic Precursor: [Co1–x@Sn9]4– (x ≈ 0.32) and [Co2@Sn17]5–

Abstract: Two new compounds with Co-centered Sn9 clusters were obtained by the extraction directly from the intermetallic precursor K4.79Co0.79Sn9 in ethylenediamine with addition of cryptand [2.2.2]. The anions [Co0.68@Sn9]4– in K[K([2.2.2]crypt)]3[Co0.68@Sn9] (1) consisting of overlaying [Co@Sn9]4– and [Sn9]4– cluster anions are connected by K atoms to form infinite K[Co0.68@Sn9] chains. The anions [Co2@Sn17]5– in [K([2.2.2]crypt)]5[Co2@Sn17]·en·tol (2) are built from two [Co@Sn9] sharing one common Sn atom, with the same composition but a different conformation as in the previously reported [K([2.2.2]crypt)]5[Co2@Sn17]. Quantum chemical calculations for the different conformers of [Co2@Sn17]5– reveal that both conformers are rather close in energy and that the short intercluster Sn–Sn distance in 2 does not originate from attractive interactions.

In-situ Stabilization of Tin Nanoparticles in Porous Carbon Matrix derived from Metal Organic Framework: High Capacity and High Rate Capability Anodes for Lithium-ion Batteries

Abstract: It is a formidable challenge to arrange tin nanoparticles in a porous matrix for the achievement of high specific capacity and current rate capability anode for lithium-ion batteries. This article discusses a simple and novel synthesis of arranging tin nanoparticles with carbon in a porous configuration for application as anode in lithium-ion batteries. Direct carbonization of synthesized three-dimensional Sn-based MOF: K2Sn2(1,4-bdc)(3)](H2O) (1) (bdc = benzenedicarboxylate) resulted in stabilization of tin nanoparticles in a porous carbon matrix (abbreviated as Sn@C). Sn@C exhibited remarkably high electrochemical lithium stability (tested over 100 charge and discharge cycles) and high specific capacities over a wide range of operating currents (0.2-5 Ag-1). The novel synthesis strategy to obtain Sn@C from a single precursor as discussed herein provides an optimal combination of particle size and dispersion for buffering severe volume changes due to Li-Sn alloying reaction and provides fast pathways for lithium and electron transport.

[Th10(μ-F16)(μ3-O4)(μ4-O4)(NH3)32](NO3)8·19.6 NH3 – the Largest Thorium Complex from Solution known to Date

Abstract: . The reaction of K2Th(NO3)6 and UF4 with liquid ammonia as a solvent leads on air to planar colorless crystals of ditriakontaammine hexadeca-μ-fluorido tetra-μ3-oxido tetra-μ4-oxido decathorium(IV) octanitrate ammonia (1/19.6), [Th10F16O8(NH3)32](NO3)8·19.6 NH3 (1). The compound crystallizes in the tetragonal space group P21c (no. 114) with a = 18.4167(2), c = 14.7920(4) A, and V = 5017.1(2) A3 at 123 K with Z = 2. The crystal structure shows the presence of a decanuclear thorium core [Th10O4]32+ similar to an “inverse” P4O10 or like 1,3,5,7-tetramethyladamantane. Such a complex seems to be the largest thorium complex reported so far – a finding that is of great importance for the knowledge of actinoid speciation in solutions.

Periodic Mesoporous Organosilicas as Adsorbents of Toxic Trace Gases out of the Ambient Air

Abstract: New periodic mesoporous organosilicas were synthesized using (bis(triethoxysilyl)vinyl)aniline (BTEVA) and (bis(triethoxysi- lyl)vinyl)benzene (BTEVB) as precursors and by functionalizing the BTEVA PMO with aminopropyl groups. All PMO materials showed a high degree of hexagonal order in the respective P-XRDs as well as high surface areas with narrow pore size distributions. The PMOs to- gether with activated carbon were investigated with regards to their hexanal adsorption capacity in a gravimetric apparatus with an at- tached GC-MS. For the amine PMOs two different regions during ad- sorption were found. In the first region loadings in the range of 30 wt% were reached by a fast adsorption process. In the second region the

Investigation of the Microstructure of Disordered, Non‐graphitic Carbons by an Advanced Analysis Method for Wide‐Angle X‐ray Scattering

Abstract: The analysis of the wide-angle X-ray scattering (WAXS) data of non-graphitic carbons is challenging due to the broad and overlapped (hk)- and (00l)-reflections. A recently developed advanced analysis method developed by Ruland and Smarsly allows for the fitting of the WAXS data by a continuous model function, providing a detailed insight into the sp2-carbon microstructure. Obtaining parameters like the graphene layer extent La, the average stack height Lc and disorder effects permits the quantification of microstructural features. Firstly, this publication gives a brief review over historical und recent developments regarding the evaluation of the WAXS of disordered carbons. Secondly, the applicability of this algorithm to carbon samples possessing a substantial degree of disorder is tested by investigating activated carbons, heat treated coal tar pitch and furfuryl alcohol. It is seen that several structural parameters are determined with reasonable accuracy and thereby the influence of the precursor and the temperature on the resulting carbon microstructure is identified. The decrease in disorder within the 2D graphene lattice and in the stacking of the layers at higher synthesis temperatures is quantified. Moreover, this study reveals that the graphene layer extent La is only about a few nanometers in size, showing that typical non-graphitic carbons used for diverse applications possess quite small dimensions of graphene stacks.

Eco‐friendly Trifoliate Stable Energetic Zinc Nitrate Co­ordination Compounds: Synthesis, Structures, Thermal and Explosive Properties

Abstract: Three trifoliate environmental friendly coordination compounds, [Zn(SCZ)3](NO3)2 (1) (SCZ = semicarbazide), [Zn(CHZ)3](NO3)2 (2) (CHZ = carbohydrazide), and [Zn(MCZ)3](NO3)2·H2O (3) (MCZ = methyl carbazate), were synthesized by the reaction of zinc nitrate with its corresponding ligands. The products were characterized by elemental analysis and FT-IR spectroscopy. Furthermore, compound 1 and 2 were characterized by X-ray single crystal diffraction. The crystal structures of both 1 and 2 belong to the monoclinic P21/c space group. Remarkably, in all the three compounds, the central zinc cations are six-coordinated with three oxygen atoms of carbonyl groups and three terminal nitrogen atoms of the hydrazine groups from three SCZ / CHZ / MCZ molecules, which can form three five-member (Zn–O–C–N–N) rings and exhibit a distorted octahedron. Thermal stabilities of 1 to 3 were studied by differential scanning calorimetry (DSC) and showed that they are all thermostable. The non-isothermal kinetics parameters were calculated by the Kissinger's method and Ozawa's method, respectively. The energies of combustion, enthalpies of formation, critical temperature of thermal explosion, entropies of activation (ΔS≠), enthalpies of activation (ΔH≠), and free energies of activation (ΔG≠) were measured and calculated. Sensitivity tests revealed that 1–3 are insensitive to mechanical stimuli. The studies of all these three zinc compounds showed that they have potential applications as heat-stable insensitive energetic materials, especially the semicarbazide coordination compound 1, which has higher crystal density.