Zeitschrift für Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie

Publisher: Max-Planck-Gesellschaft zur Förderung der Wissenschaften

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Other titles Zeitschrift für Naturforschung. B, Chemie, Biochemie, Biophysik, Biologie und verwandte Gebiete (Max-Planck-Gesellschaft zur Förderung der Wissenschaften: 1962), Zeitschrift für Naturforschung. Teil b, Chemie, Biochemie, Biophysik, Biologie und verwandte Gebiete, Chemie, Biochemie, Biophysik, Biologie und verwandte Gebiete
ISSN 0044-3174
OCLC 9321722
Material type Periodical
Document type Journal / Magazine / Newspaper

Publications in this journal

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    ABSTRACT: Heteroleptic ate complexes of the type K[M{N(SiMe3)2}2{OSi(OtBu)3}] (M = Cr, Mn, Co) were synthesized by adding one equivalent of the potassium salt KOSi(OtBu)3 to the bis(trimethylsilyl)amide precursors [Cr{N(SiMe3)2}2(thf)2], [Mn{N(SiMe3)2}2(thf)] and [Co{N(SiMe3)2}2(thf)], respectively. Surprisingly, the reaction of CrCl3(thf)3 with only two equivalents of KOSi(OtBu)3 yielded the homoleptic ate complex K[Cr{OSi(OtBu)3}4]. The compounds were characterized by elemental analysis and DRIFT spectroscopy as well as X-ray crystallography.
    No preview · Article · Dec 2014 · Zeitschrift für Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie
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    ABSTRACT: The transsilylation reaction between allyltrichlorosilane and 8-trimethylsiloxyquinoline in the molar ratio 1 : 3 yields the hexacoordinated silicon tris-chelate (oxinate)2Si(adho) ("oxinate" = 8-oxyquinolinate, "adho" = di-anion of 2-allyl-1,2-dihydro-8-oxyquinoline) comprising an SiO3N3 skeleton. The identity of this complex was established by single-crystal X-ray diffraction analysis and 29Si CP/MAS NMR spectroscopy of its chloroform solvate. Benzyltrichlorosilane and dibenzyldichlorosilane, comprising benzyl (Bn) as an "aromatically stabilized allyl moiety" did not undergo such rearrangement. Instead, the complexes (oxinate)2SiBnCl and (oxinate)2 SiBn2 were obtained even upon using three molar equivalents of 8-trimethylsiloxyquinoline. We determined the crystal structure of a non-disordered bis-chelate (oxinate)2SiBnCl with Sibound hydrocarbyl and halogen substituents (the previously published (oxinate)2SiMeCl was disordered with alternative Me/Cl site occupancies). (Oxinate)2SiBnCl exhibits surprisingly poor response of the N-Si bonds to the different trans-disposed Si-X (X = Bn, Cl) bonds. For comparison and deeper insights into the coordination chemistry of oxinato silicon complexes with halide substituents, we determined the crystal structures of (oxinate)2SiPhCl·CHCl3, (oxinate)2SiCl2, (oxinate)2SiF2·1.5(CHCl3), and (8-oxyquinaldinate)2SiF2. Furthermore, the crystal structures of BnSiCl3 and Bn2SiCl2 (and its dibromo analog) are reported. The influence of the Si-C-C-C torsion angles of the benzyl group on the 29Si NMR shift of benzylsilanes (which is noticeably upfield with respect to analogous methyl silanes) was analyzed by quantum-chemical calculations.
    No preview · Article · Dec 2014 · Zeitschrift für Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie
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    ABSTRACT: The first enantioselective synthesis of a photoreactive (R)-beta-phenylalanine is described. In the key step, m-diazirinyl-substituted benzaldehyde is converted to a chiral sulfinimine in a Ti(OEt)(4)-mediated reaction, followed by diastereoselective enolate addition. The absolute configuration of photo (R)-beta-phenylalanine was confirmed by Mosher analysis. The photo amino acid proved to be thermally stable under standard laboratory conditions. Irradiation in toluene afforded cycloheptatriene/norcaradiene valence tautomers, together with carbene benzylation. Quantum-chemical calculations indicate a small triplet-singlet gap.
    No preview · Article · Dec 2014 · Zeitschrift für Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie
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    ABSTRACT: The series of Li3Ba2(La1-xSmx)3 (MoO4)8 (0 ≤ x ≤ 1) compounds for phosphor-converted LEDs is prepared by solid state reaction of stoichiometric amounts of Li2CO3, BaCO3, La2O3, MoO3, and Sm2O3 (porcelaine crucibles, air, 800 °C, 10 h).
    No preview · Article · Jun 2014 · Zeitschrift für Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie
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    ABSTRACT: Herein we report on the syntheses, crystal structures and first electrochemical characterizations of ternary zirconium transition metal (poly)antimonides Zr2TSb3 (with T = Cu, Pd) and Zr3TSb7 (with T = Ni, Pd). The compounds were synthesized by arc-melting, followed by an annealing procedure at elevated temperatures. Phase analysis and structure analysis were performed by powder and single-crystal measurements. The electrochemical properties of all compounds were measured in half cells against lithium to test their potential as anode materials for Li batteries. The Zr3TSb7 phases show metallic behavior with conductivities of 10(-1) S cm(-1) within a temperature range of 324 to 428 K.
    No preview · Article · Nov 2013 · Zeitschrift für Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie
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    ABSTRACT: The lanthanoid(III) oxide fluoride sulfides M6O2F8S3 (M = La–Nd, Sm, Gd) can be obtained by reacting the rare-earth metals, their trifluorides and sesquioxides with elemental sulfur in appropriate molar ratios at 850 °C flux-assisted by NaCl in gas-tightly sealed niobium or tantalum ampoules. All compounds are colorless, except for those containing M = Pr with green, M = Nd with lilac and M = Sm with yellow color. They form transparent single crystals as needles or rods. The M6O2F8S3 representatives crystallize in a hexagonal structure (space group: P63/m; a ≈ 1382–1326, c ≈ 398–376 pm, c/a ≈ 0.288–0.284; Z = 2) with two different crystallographic M3+ positions. The (M2)3+ cations reside in ninefold coordination of anions arranged as tricapped trigonal prisms formed by three F−, four mixed-occupied O2−/F− and two S2− anions, resembling the unique M3+ coordination sphere of the M3OF5S-type oxide fluoride sulfides. The (M1)3+ cations are surrounded by square antiprisms built of four O2−/F− and S2− anions each, which are capped by one F− anion each, again resulting in a ninefold coordination similar to that of the A-MFS-type fluoride sulfides. While the crystallographically unique S2− anions have six cationic neighbors arranged in trigonal prisms, there are four different light-anion positions. Two of them, representing only fluoride anions, are situated in a triangular environment of cations ((F1)−: planar, (F2)−: non-planar). The mixed-occupied light-anion positions (F3)−/(O3)2− and (F4)−/(O4)2− exhibit tetrahedral coordination spheres with a ratio F− : O2−= 2:1. The M6O2F8S3 arrangement is characterized by an empty hexagonal channel structure created by (F1)− anions with a potential of accommodating alkali-metal cations like Na+. All single-crystal X-ray structure investigations did not indicate any ordering of the O2− and F− anions, but MAPLE calculations revealed a slightly favored oxygen occupation for the (F4)−/(O4)2− rather than for the (F3)−/(O3)2− position. Electron-beam microanalyses gave no evidence for the incorporation of either Na+ or Cl− ions stemming from NaCl used as the flux.
    No preview · Article · Jul 2013 · Zeitschrift für Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie
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    ABSTRACT: Small single crystals of the Sm5Ge4-type (space group Pnma) germanides RE2Nb3Ge4 (RE = Sc, Y, Gd–Er, Lu) and Sc2Ta3Ge4 were synthesized by arc-melting of the respective elements. The samples were characterized by powder and single-crystal X-ray diffraction. In all structures, except for Sc2:04Nb2:96Ge4 and Sc2:19Ta2:81Ge4, the rare earth and niobium atoms show full ordering on the three crystallographically independent samarium sites of the Sm5Ge4 type. Two sites with coordination number 6 are occupied by niobium, while the slightly larger site with coordination number 7 is filled with the rare earth element. Small homogeneity ranges with RE=Nb and RE=Ta mixing can be expected for all compounds. The ordered substitution of two rare earth sites by niobium or tantalum has drastic effects on the coordination number and chemical bonding. This was studied for the pair Y5Ge4/Y2Nb3Ge4. Electronic structure calculations show larger charge transfer from yttrium to germanium for Y5Ge4, contrary to Y2Nb3Ge4 which shows stronger covalent bonding due to the presence of Nb replacing Y at two sites
    No preview · Article · Jan 2013 · Zeitschrift für Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie
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    ABSTRACT: The reaction behavior of HF-HNO 3-H 2O etching mixtures, which are frequently used for texturing silicon surfaces, is significantly influenced by the addition of sulfuric acid. For high concentrations of sulfuric acid, nitronium ions NO 2 + ions have been detected by means of 14N NMR spectroscopy, and results of Raman spectroscopic investigation have allowed the quantification of the nitronium ions. Maximum etching rates of 4000 - 5000 nm s -1 are reached for HF (40 %)-HNO 3 (65%)-H2SO 4 (97%) mixtures with w (40%-HF)/w (65%-HNO 3) ratios of 2 to 4 and w (97%-H 2SO 4)<0.3. For higher concentrations of sulfuric acid, H 2SO 4 can be considered as a diluent. In order to investigate the influence of the sulfuric acid at constant HF and HNO 3 quantities, fuming HNO 3 (100 %) was used and the water in the mixtures successively replaced by H 2SO 4. A sudden increase of etching rates was found for sulfuric acid concentrations around 6 mol L?1 correlating with the characteristic color of the etching solutions. Decreased reaction rates at > 7 molL 1 H 2SO 4 are attributed to high solution viscosities and the formation of fluorosulfuric acid. Generally, in HF-HNO 3-H 2SO 4/H 2O etching mixtures a reduced dissociation of nitric acid, the formation of nitronium ions, the solubility of neutral nitrogen intermediates (e. g. NO 2, N 2O 3), as well as other effects influence the attack of silicon surfaces. The structure of etched silicon surfaces was investigated by means of scanning electron (SEM) and laser scanning microscopy (LSM). The morphologies are influenced most significantly by the relative amounts of sulfuric acid. Unexpectedly, in nitronium ion-containing mixtures rough surfaces with pore-like etching pits are generated.
    Full-text · Article · Feb 2011 · Zeitschrift für Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie
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    ABSTRACT: The bisoxazoles 1a – 1c that feature structures with two oxazole moieties connected to a 2,6-pyridylene central linker and contain different aryl substituents in 4- and 5-positions of the oxazole rings have been synthesized. Single-crystal X-ray structure determinations of the free ligand 1a, containing the NiCl2 complex of 1c as the CH3COOH solvate as well as the 1,4-dioxane-solvated diester intermediate 2a are reported, which show specific molecular conformations and packings in the crystals. The conformation of 1a is syn with reference to the oxazole nitrogen atoms and anti with reference to the oxazole and pyridine nitrogen atoms. In the Ni2+ complex, the metal ion is in an octahedral coordination environment with the nitrogens of 1c and an oxygen of an acetic acid molecule in the basal plane, while two chloride ions occupy the axial positions. Of three additional acetic acid molecules one is hydrogen-bonded to a chloride and two form a carboxylic dimer, thus giving rise to a 1 : 1 : 4 (1c : NiCl2 : HOAc) stoichiometric ratio. The crystalline 1 : 1 inclusion compound of 2a with 1,4-dioxane suggests a typical clathrate owing to the bulkyness of the host molecule.
    Full-text · Article · Feb 2011 · Zeitschrift für Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie
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    ABSTRACT: In a Henry-type reaction nitromethane reacts with N-(2-pyridylmethylidene)-methylamine (1) yielding 1-methylamino-1-(2-pyridyl)-2-nitromethane (2) in nearly quantitative yield. This orange compound decomposes slowly in an inert gas atmosphere and fast in contact with air. Therefore 2 has to be stored at −78 ◦C as a methanol solution. Reduction of 2 with hydrogen in the presence of a Pd/C catalyst leads to the formation of 1,4-dinitro-2,3-di(2-pyridyl)butane (3) in the rather poor yield of 12 %. The major product is the meso-isomer, meso-3, whereas only traces of (R,R)- and (S,S)- isomers of 3 are formed. A conversion of the nitro groups into amino functionalities succeeds with hydrazine hydrate in the presence of a Pd/C catalyst yielding meso-1,4-diamino-2,3-di(2-pyridyl)butane (4). Recrystallization from an aqueous solution gives 4・2H
    No preview · Article · Jul 2009 · Zeitschrift für Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie
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    ABSTRACT: The first total synthesis of annomuricatin B (8) is described via coupling of the tripeptide Boc-L-asparaginyl(benzhydryl)-L-alanyl-L-tryptophan-OH and the tetrapeptide L-leucyl-glycyl-L-thryl-L-proline-OMe followed by cyclization of the linear heptapeptide fragment. On pharmacological investigation, it was observed that the cycloheptapeptide 8 displays moderate cytotoxicity against Dalton’s lymphoma ascites and Ehrlich’s ascites carcinoma cell lines with cytotoxic inhibitory concentration (50 %) values of 11.6 and 14.1 μM, in addition to potent antidermatophyte activity against Trichophyton mentagrophytes and Microsporum audouinii with a minimum inhibitory concentration of 6 μg/mL. Moreover, Gram-negative bacteria and Candida albicans were found to be moderately sensitive towards the newly synthesized peptide.
    Full-text · Article · Feb 2009 · Zeitschrift für Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie
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    ABSTRACT: Solutions consisting of HF - NOHSO4 - H2SO 4 exhibit a strong reactivity towards crystalline silicon which is controlled by the concentrations of the reactive species HF and NO+. Selective isotropic and anisotropic wet chemical etching with these solutions allows to generate a wide range of silicon surface morphology patterns. Traces of Ag+ ions stimulate the reactivity and lead to the formation of planarized (polished) silicon surfaces. Analyses of the silicon surface, the etching solution and the gas phase were performed with scanning electron microscopy (SEM), DR/FT-IR (diffusive reflection Fourier transform infra-red), FT-IR, Raman and NMR spectroscopy, respectively. It was found that the resulting silicon surface is hydrogen-terminated. The gas phase contains predominantly SiF4, NO and N2O. Furthermore, NH4+ is produced in solution. The study has confirmed the crucial role of nitrosyl ions for isotropic wet chemical etching processes. The novel etching system is proposed as an effective new way for selective surface texturing of multi- and monocrystalline silicon. A high etching bath service lifetime, besides a low contamination of the etching solution with reaction products, provides ecological and economical advantages for the semiconductor and solar industry.
    No preview · Article · Nov 2007 · Zeitschrift für Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie

  • No preview · Article · Jan 2007 · Zeitschrift für Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie
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    ABSTRACT: DFT-calculations (RB3LYP/LANL2DZp) show that the migration of a proton inside [1.1.1]- and [2.2.2]-cryptand from one nitrogen atom to the other follows different paths. While the proton in [H⊂1.1.1]-cryptand moves via an ether oxygen atom (activation energy: 19.2 kcal/mol), the proton in [H⊂2.2.2]-cryptand moves directly from one nitrogenatom to the other (activation energy: 16.1 kcal/mol). Our calculations rule out the application of doubly protonated [2.2.2]-cryptands as anion hosts.
    No preview · Article · Jan 2006 · Zeitschrift für Naturforschung. Teil B. Anorganische Chemie, organische Chemie, Biochemie, Biophysik, Biologie