Wittig olefination “baking powder”: a hexameric halogen-bonded phosphonium salt cage for encapsulation and mechanochemical transformation of small-molecule carbonyl compounds

We report a hexameric supramolecular cage assembled from the components of a Wittig-type phosphonium salt, held together by charge-assisted R-Br· · ·Br-· · ·Br-R halogen bonds. The cage reliably encapsulates small polar molecules, including aldehydes and ketones, to provide host-guest systems in which components are pre-formulated in a near-ideal stoichiometry for a base-activated Wittig olefination in the solid-state. These pre-formulated solids enable a molecular-level “baking powder” approach for solvent-free Wittig reactions, based on a design of solid-state reactivity in which the host for molecular inclusion also acts as a complementary reagent for the chemical transformation of an array of guests. These host-guest solid-state complexes can also act as supramolecular surrogates to their Wittig olefination vinylbromide products, in a Sonogashira-type coupling that enables one-pot mechanochemical conversion of an aldehyde to an enediyne.

The Effect of Stoichiometry, Mg-Ca Distribution, and Iron, Manganese, and Zinc Impurities on the Dolomite Order Degree: A Theoretical Study

The determination of the degree of Mg-Ca order in the dolomite structure is crucial to better understand the process or processes leading to the formation of this mineral in nature. I01.5/I11.0 intensity ratios in the X-ray powder diffractograms are frequently measured to quantify dolomite cation order in dolomites. However, the intensity of diffraction peaks can be affected by factors other than the Mg-Ca distribution in the dolomite structure. The most relevant among these factors are (i) deviations from the ideal dolomite stoichiometry, and (ii) the partial substitution of Mg and Ca atoms by Fe, Mn, and Zn impurities. Using the VESTA software, we have constructed crystal structures and calculated I01.5/I11.0 ratios for dolomites with Mg:Ca ratios ranging from 0.5 to 1.5, and with Fe, Mn, and Zn contents up to 30%. Our results show that both deviations from dolomite ideal stoichiometry and the presence of impurities in its structure lead to a significant decrease in I01.5/I11.0 intensity ratios, an effect which must be considered when cation orders of natural dolomites from different origins are compared.

Topology modulation of 2D covalent organic frameworks via “two-in-one” strategy

Topology modulation of covalent organic frameworks (COFs) still remains barely explored, probably due to the lack of appropriate building blocks. “Two-in-one” strategy applies bifunctional monomers to endow ideal stoichiometry, and...

Urbach’s tail in the absorption spectra of Cu2GeSe3 semiconducting compound

In the present work we report on the analysis of the Urbach’s tail in pure and Mn-doped Cu2GeSe3 samples having small deviation from its ideal stoichiometry. It is found that the high values of the phonon energy hnp involved in the electrons/excitons-phonon interaction in the formation of this tail are due to structural disorder caused by deviation from ideal stoichiometry. Values of hnp for pure and doped samples were found to be 48, 60 and 81 meV, respectively, whereas the phonon energy for an entirely ordered Cu2GeSe3 sample was estimated to be about 25 meV.

Dellagiustaite: A Novel Natural Spinel Containing V2+

Dellagiustaite, ideally Al2V2+O4, is a new spinel-group mineral from Sierra de Comechingones, San Luis, Argentina, where it is found associated with hibonite (containing tubular inclusions, 5–100 μm, of metallic vanadium), grossite, and two other unknown phases with ideal stoichiometry of Ca2Al3O6F and Ca2Al2SiO7. A very similar rock containing dellagiustaite has been found at Mt Carmel (northern Israel), where super-reduced mineral assemblages have crystallized from high-T melts trapped in corundum aggregates (micro-xenoliths) within picritic-tholeiitic lavas ejected from Cretaceous volcanoes. In the holotype, euhedral grains of dellagiustaite are found as inclusions in grossite. The empirical average chemical formula of dellagiustaite is (Al1.09 V 0.91 2 + V 0.87 3 + Mg0.08 Ti 0.04 3 + Mn0.01)Σ3O4, but it may show limited replacement of V2+ by Mg and of V3+ by Al. As Al is the dominant trivalent cation, the ideal formula is Al2V2+O4 according to the current IMA rules. Dellagiustaite shows the usual space group of spinel-group minerals (Fd 3 ¯ m, R1 = 1.46%) with a = 8.1950(1) Å. The observed mean bond lengths <T–O> = 1.782(2) Å and <M–O> = 2.0445(9) Å, the observed site scattering (T = 13.3 eps, M = 22.5 eps), and the chemical composition show that dellagiustaite is an inverse spinel: T tetrahedra are occupied by Al3+, whereas M octahedra are occupied by V2+ and V3+, leading to the site assignment as TAlM( V 0.91 2 + V 0.88 3 + Al 0.09 3 + Mg0.08 Ti 0.03 3 + Mn0.01)O4.

Assembly of dicobalt and cobalt–aluminum oxide clusters on metal–organic framework and nanocast silica supports

NU-1000, a mesoporous metal–organic framework (MOF) featuring hexazirconium oxide nodes and 3 nm wide channels, was infiltrated with a reactive dicobalt complex to install dicobalt active sites onto the MOF nodes. The anchoring of the dicobalt complex onto NU-1000 occurred with a nearly ideal stoichiometry of one bimetallic complex per node and with the cobalt evenly distributed throughout the MOF particle. To access thermally robust multimetallic sites on an all-inorganic support, the modified NU-1000 materials containing either the dicobalt complex, or an analogous cobalt–aluminum species, were nanocast with silica. The resulting materials feature Co2or Co–Al bimetallated hexazirconium oxide clusters within a silica matrix. The cobalt-containing materials are competent catalysts for the selective oxidation of benzyl alcohol to benzaldehyde. Catalytic activity depends on the number of cobalt ions per node, but does not vary significantly between the NU-1000 and silica supports. Hence, the multimetallic oxide clusters remain site-isolated and substrate-accessible within the nanocast materials.

Characterization and Vertical Elements Distribution of ZnGeP2 Single Crystals

A large, crack-free ZnGeP2 single crystal with size of Φ26 mm×70 mm was grown in a vertical three-zone tubular furnace by modified vertical Bridgman method, i.e. real-time temperature compensation technique with small temperature gradient in double-wall quartz ampoule. The as-grown single crystal was characterized by X-ray diffractometer (XRD), energy dispersive spectrometer (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). It was found that there is a face of (100) and its second-order XRD peaks were observed. The vertical elements distribution of the main part of the grown crystal has a stoichiometric ratio which is close to the ideal stoichiometry of 1:1:2. The IR transmittance of a sample of 2.5 mm thickness is above 58% in the range from 3500 to 800 cm-1. All these results demonstrate that the quality of the ZnGeP2 single crystal grown by the modified method is good, and could be used in the preparation of devices.

Klajite, MnCu4(AsO4)2(AsO3OH)2(H2O)10, from Jáchymov (Czech Republic): the second world occurrence

Klajite, MnCu4(AsO4)2(AsO3OH)2(H2O)10, the Mn-Cu-bearing member of the lindackerite group, was found in Jáchymov, Czech Republic, as the second world occurrence. It is associated with ondrušite and other arsenate minerals growing on the quartz gangue with disseminated primary sulfides, namely tennantite and chalcopyrite. Electron-microprobe data showed klajite aggregates to be chemically inhomogeneous at larger scales, varying from Mn-Ca-rich to Cu-rich domains. The chemical composition of the the Mn-rich parts of aggregates can be expressed by the empirical formula (Mn0.46Ca0.22Cu0.07Mg0.02)∑0.77(Cu3.82Mg0.14Ca0.03Zn0.01)∑4.00(As1.94Si0.06)∑2.00O8[AsO2.73(OH)1.27]2(H2O)10 (mean of seven representative spots; calculated on the basis of As + Si + P = 4 a.p.f.u. (atoms per formula unit) and 10 H2O from ideal stoichiometry), showing a slight cationic deficiency at the key Me-site. According to single-crystal X-ray diffraction, klajite from Jáchymov is triclinic, P , with a = 6.4298(8), b = 7.9716(8), c = 10.707(2) Å, α = 85.737(12)°, β = 80.994(13)°, γ = 84.982(10)°, and V = 538.85(14) Å3, Z = 1. The crystal structure was refined to R1 = 0.0628 for 1034 unique observed reflections (with Iobs > 3σ(I)), confirming that klajite (Mn-Cu member) and ondrušite (Ca-Cu member) are isostructural. The current data-set allowed determination of the positions of several hydrogen atoms. Discussion on hydrogen bonding networks in the structure of klajite as well as detailed bond-valence analysis are provided.

Effect of Deposition Conditions on the Characterization of Cu(In,Ga)Se2 Precursor Films by Sputtering Process

In this study, Cu(In,Ga)Se2 (CIGS) thin films were deposited onto bi-layer Mo coated soda-lime glass by sputtering a chalcopyrite CIGS quaternary alloy target. The influence of sputtering power and substrate temperature on the characterization of CIGS precursor films was investigated. Experimental results demonstrate that the CIGS quaternary target has the characteristics of chalcopyrite structures. The samples deposited at a sputter power of 1.5 W/cm2 (both as-deposited and after annealing) exhibited superior uniformity, and the phenomenon of composition loss resulting from annealing was not drastic. The composition distribution of as-deposited film produced at a substrate temperature 373 K approached that of ideal stoichiometry.

Structures of the pseudo-trigonal polymorphs of Cu2(OH)3Cl

The crystal structure of Cu2(OH)3Cl has been determined using two natural samples with almost ideal stoichiometry. While one of the samples exhibits a twinned clinoatacamite structure, the other sample is characterized by the appearance of additional weak diffraction maxima at half integer positions of h and k. Structure refinement was carried out with the space group P\bar 1. The relationship between the triclinic phase, clinoatacamite, paratacamite and the herbertsmithite structure is discussed in terms of symmetry as a function of Cu concentration.