Chloromethane surface chemistry on Fe3O4(1 1 1)-(2 × 2): A thermal desorption spectrometry comparison of CCl4, CBr2Cl2, and CH2Cl2

The surface chemistry of CBr₂Cl₂ on the Fe₃O₄(1 1 1)-(2 × 2) selvedge of single-crystal α-Fe₂O₃(0 0 0 1) has been investigated using temperature programmed reaction and desorption (TPR/D) measurements. The spectra obtained in this case show that strong chemisorption occurs and that a series of adsorbed halogenated reaction products are present. By comparison, studies of the adsorbed phase of CH₂Cl₂ show that only physisorption occurs. The TPR/D spectra of CBr₂Cl₂ show that dissociative formation of CCl₂ followed by its reaction with lattice oxygen is central to the monolayer reaction chemistry in this chloromethane. The branching ratios of the various desorbed products are compared with those obtained from CCl₄ adsorbed on the same (2 × 2) surface.     

Crystal rigidifying strategy toward hybrid cadmium halide to achieve highly efficient and narrowband blue light emission

Highly efficient and narrowband blue light-emitting performance is extremely crucial for the optoelectronic applications of organic-inorganic hybrid perovskites. However, the not yet viable approach has been shown to simultaneously improve photoluminescence quantum yield (PLQY) and narrow linewidth of blue light emission. Herein, a new crystal rigidifying strategy is proposed as a viable dual-optimization avenue. Specifically, we perform a post-synthetic technique on hybrid cadmium halides and successfully convert zero-dimensional (0D) DMP-0-CdBr₄ to one-dimensional (1D) DMP-1-CdBr₃, accompanied by luminescent transformation from sky-blue (470 nm) to deep-blue (432 nm) emissions. The structural evolution from discrete block to infinite chain significantly enhances the crystal rigidity, which results in narrower emission linewidth (89 to 50 nm) and increased color purity (74.5% to 96.7%). Synchronously, the PLQY also realizes a notable enhancement from 14.0% to 52.3%. Systematical characterizations demonstrate that enhanced crystal rigidity simultaneously weakens the electron-phonon interaction and slows down nonradiative decay, which narrows the emission linewidth and boosts the PLQY. The highly efficient light-emitting performance enables them as excellent down-conversion blue phosphors to fabricate solid-state LED giving bright warm white light with high color rendering index of 95.4. This work paves a novel structural optimization way to rationally design or fine-tune high-performance blue-light emitting halides.     

Supported copper triflate as an efficient catalytic system for the synthesis of highly functionalized 2-naphthol Mannich bases under solvent free condition

Various heterogeneous catalysts (Lewis acid) have been prepared and screened for the synthesis of Betti bases in an attempt to reduce the environmental hazards associated with the conventional homogeneous Lewis acid system. And we found especially Cu(OTf)₂·SiO₂ catalyzes the three-component coupling of aldehyde, 2-naphthol, and alicyclic amine to generate Betti base with high efficiency under neat conditions without additional co-catalyst or additive in air. The reaction is not sensitive to water and occurs smoothly in water as well.     

Etching of hexagonal SiC surfaces in chlorine-containing gas media at ambient pressure

The modification of the silicon carbide (4H-SiC) single-crystal surface in a chlorine-containing gas mixture at high temperature (800-1000 °C) and ambient pressure was investigated. The results of silicon carbide chlorination are found to strongly depend on the hexagonal surface orientation. Due to the thermodynamically more favorable reaction of chlorine with silicon rather than carbon, the C-terminated side clearly undergoes considerable changes, resulting in coverage by a black-colored carbon film, whereas the Si-side (0 0 0 1) surprisingly remains visually untouched. With using X-ray photoelectron spectroscopy (XPS), angle-resolved XPS and SEM it is shown that this drastic change in behavior is associated with a different structure of oxicarbide/silicate adlayer formed on the C- and Si-terminated sides of silicon carbide surface during experimental pre-treatment and air exposure. The presence of oxygen bridges connecting the silicate adlayer with the bulk SiC in the case of Si-side inhibits the chlorination reaction and makes this surface strongly resistant to chlorine attack. Only some places on the Si-terminated side demonstrate traces of chlorine etching in the form of hexagonal-shaped voids, which are possibly initiated by distortion of the initial crystalline structure by micropipes. In contrast, a thin carbon layer resulted on the C-terminated side as a consequence of the chlorination process. XPS, ARXPS, SEM and Raman spectroscopy study of created film allows us to argue that it consists mainly of sp2-bonded carbon, mostly in the form of nanoscale graphene sheets. The absence of a protective oxygen bridge between the silicate adlayer and the bulk silicon carbide crystal leads to unlimited growth of carbon film on the side.     

Synthesis, crystal structure and thermal behavior of two hydrated forms of lanthanide phthalates Ln2(O2+C6H4-CO2)3(H2O) (Ln=Ce, Nd) and Nd2(O2C-C6H4-CO2)3(H2O)3

New hydrated lanthanide phthalates have been hydrothermally prepared with cerium and neodymium in different reaction media involving water or mixed water-ethanol solvent. The monohydrated Ln₂(1,2-bdc)₃(H₂O) (Ln=Ce or Nd) and dihydrated Nd₂(1,2-bdc)₃(H₂O)₂ forms have been characterized by single-crystal analysis. Their structures consist of infinite inorganic chains of lanthanide-centered polyhedra linked to each other through the phthalate ligands in order to generate mixed organic-inorganic layered structure. The two hydrated structures differ by the number of terminal water species attached to the lanthanide cations, which induce symmetry change from a triclinic (Nd₂(1,2-bdc)₃(H₂O)₂) to an orthorhombic (Nd₂(1,2-bdc)₃(H₂O)₂) cell for neodymium whereas the cerium-based phase only exists in the monohydrated form, with two distinct symmetries (orthorhombic or triclinic). Structural comparisons with the other members of the lanthanide phthalate series with identical chemical formula are also discussed. Thermal X-ray diffraction experiment indicates that the transformation from dihydrate form into the monohydrated form does not occur during a heating process.     

Synthesis, structure and magnetic properties of new phosphates K2Mn0.5Ti1.5(PO4)3 and K2Co0.5Ti1.5(PO4)3 with the langbeinite structure

New complex phosphates of the general formula K₂M_0.5Ti_1.5(PO₄)₃ (M=Mn, Co) have been obtained from the melting mixture of KPO₃, K₄P₂O₇, TiO₂ and CoCO₃·mCo(OH)₂ or Mn(H₂PO₄)₂ by means of a flux technique. The synthesized phosphates have been characterized by the single-crystal X-ray diffraction and the FTIR-spectroscopy. The compounds crystallize in the cubic system with the space group P2₁3 and cell parameters a=9.9030(14) Å for K₂Mn_0.5Ti_1.5(PO₄)₃ and a=9.8445(12) Å for K₂Co_0.5Ti_1.5(PO₄)₃. Both phosphates are isostructural with the langbeinite mineral and contain four formula unit K₂M_0.5Ti_1.5(PO₄)₃ per unit cell. The structure can be described using [M₂(PO₄)₃] framework composed of two [MO₆] octahedra interlinked via three [PO₄] tetrahedra. The Curie-Weiss-type behavior is observed in the magnetic susceptibility.     

Synthesis, structure, and physical properties of Ce2PdGa10

A new ternary compound, Ce₂PdGa₁₀, has been synthesized using Ga flux and characterized by single-crystal X-ray diffraction. Ce₂PdGa₁₀ adopts a tetragonal structure in the I₄/mmm space group and is isostructural to Ce₂NiGa₁₀. Lattice parameters are , , , and Z=2. The compound is metallic (dρ/dT>0), with the resistance decreasing roughly linearly with temperature from 300 to 175 K. The magnetic susceptibility of Ce₂PdGa₁₀ is consistent with local-moment paramagnetism and no long-range magnetic ordering occurs down to 2 K. A large positive magnetoresistance over 200% is observed at 2 K for fields of 9 T. In this paper, we present the structure and physical properties of Ce₂PdGa₁₀ and compared them to CePdGa₆.     

New mixed-halide, boron-centered zirconium cluster phases with different cation distributions within a cluster framework: syntheses and structures of A[(Zr6B)ClxI14−x] (A=Na or Cs, 0x4)

Two new mixed-halide zirconium cluster phases have been synthesized by solid-state reactions in sealed tantalum containers from the Zr(IV) halides, elemental Zr and B, and NaI or CsCl, respectively. Single-crystal X-ray data were used to determine the crystal structures of Na[(Zr₆B)Cl_3.9I_10.1], and Cs[(Zr₆B)Cl_2.2I_11.8]. Both phases crystallize in a stuffed version of the [Nb₆Cl₁₄] structure type, orthorhombic, space group Cmca (Na[(Zr₆B)Cl_3.87(5)I_10.13]: a=15.787(2) Å, b=14.109(2) Å, c=12.505(2) Å, Z=4, R1(F)=0.0322 and wR2(F²)=0.0842; Cs[(Zr₆B)Cl_2.16(5)I_11.84]: a=15.696(4) Å, b=14.156(4) Å, c=12.811(4) Å, Z=4, R1(F)=0.0404 and wR2(F²)=0.1031). This structure type is constructed of clusters which contain centered (Zr₆Z) octahedra of the type [(Zr₆Z)X₁₂ⁱX₆^a] with Z=B and X=Cl and/or I. In both structures, chlorine and iodine atoms are randomly (to X-rays) distributed on the inner non-cluster-interconnecting ligand positions, whereas those sites which bridge metal octahedra are solely occupied by iodine. The phase widths for both phases have been found to cover 0x4 for A^I[(Zr₆B)Cl_xI_14−x]. Whereas the sodium cations in Na[(Zr₆B)Cl_xI_14−x] occupy 25% of a site which is octahedrally surrounded by halogen atoms, the larger cations in the cesium-containing phase occupy a 12-coordinate site within the cluster network.     

New dammarane-type saponins from the leaves of Panax notoginseng

Two new triterpenoid saponins, notoginsenoside-Ng3 (1) and notoginsenoside-Ng4 (2), along with three known saponins (3-5), were isolated from a water extract of the leaves of Panax notoginseng. The absolute configuration of notoginsenoside Fa (3) with five sugars was confirmed by the single-crystal X-ray diffraction for the first time.     

An efficient one-pot synthesis of pyrazolyl-[1,2,4]triazolo[3,4-b][1,3,4] thiadiazin-6-yl)-2H-pyran-2-one derivatives via multicomponent approach and their potential antimicrobial and nematicidal activities

A series of simple or/and aryl, heteryl hydrazono pyrazolyl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazin-6-yl)-2H-pyran-2-one derivatives have been efficiently synthesized in excellent yields via one-pot, multi-component approach. The importance of this methodology is that in a one-pot operation four new bonds (3C–N and 1C–S) are generated. The structure of compound 5a was confirmed by single-crystal X-ray diffraction. The newly synthesized compounds were evaluated for their in vitro antimicrobial activity against gram-positive bacteria (Staphylococcusaureus and Bacillussubtilis), gram-negative bacteria (Escherichiacoli andKlebsiellapneumoniae), antifungal activity against Candida albicans, and nematicidal activity against Meloidogyneincognita. Among all the compounds 6f showed excellent antimicrobial and nematicidal activity against tested bacteria, fungi, and nematodes.