The Structure of Tris(trifluoromethyl)tellurium Fluoride Dimethylformamide, $\rm [Te(CF_{3})_{3} \times DMF(\mu-F)]{\infty}$

represents the first structurally characterized example of a trifluoromethyl main group element compound with more than 8‐N (where N is the main group number) perfluoroalkyl groups and also the first fluoro(triorgano)tellurium derivative. Its polymeric nature is caused by asymmetric bridging fluorine atoms forming infinite chains.     

Reactions of Co2(CO)8 and of Co2(CO)6L (L = 3-pentyn-1-ol, 1,4-butyn-diol or 2-methyl-3-butyn-2-ol) with 2(diphenylphosphino)ethyl-trietoxysilane and tris(hydroxymethyl)phosphine for applications to new sol-gel materials

The complex Co₂(CO)₆[μ-η²-(H₃CCCCH₂CH₂OH)] (1) with the ligand 3-pentyn-1-ol (pol) has been synthesized following established procedures. Its structure has been determined by X-ray analysis. The complex Co₂(CO)₆(mbo) (mbo = 2-methyl-3-butyn-2-ol, HCCC(CH₃)₂OH), (3), along with the already known Co₂(CO)₆(bud) (bud = 1,4-butyn-diol, HOCH₂CCCH₂OH) (2), and Co₂(CO)₈ were reacted with 2(diphenylphosphino)ethyl-triethoxysilane [Ph₂PCH₂CH₂Si(OCH₂CH₃)₃] (dpts) and tris(hydroxymethyl)phosphine [P(CH₂OH)₃] (thp). With dpts, mono- and di-substituted complexes were obtained: these were characterized by analytical and spectroscopic techniques. The structures of Co₂(CO)₆(dpts)₂ (5) and of Co₂(CO)₄(pol)(dpts)₂ (8) have been determined by X-ray analysis.Complex (1) was reacted with 3-(triethoxysilyl)propyl isocyanate [(H₃CCH₂O)₃Si(CH₂)₃NCO] (tsi): the new complex Co₂(CO)₆[H₃CCCCH₂CH₂OC(O)NH(CH₂)₃Si(OCH₂CH₃)₃] (9) was obtained and spectroscopically characterized. The complex has also been reacted with tetraethyl orthosilicate (teos); a new inorganic-organometallic material was obtained. Complex (5) has been grafted on the mesoporous material SBA-15. The hybrid inorganic-organometallic materials obtained have been characterized by inductively coupled plasma-mass spectrometry (ICP-MS), infrared spectroscopy (FT-IR) under vacuum conditions, X-ray diffraction (XRD) and scanning electron microscopy coupled to EDS probe (SEM-EDS).     

Microstructure evolution and dielectric properties of Ba<Subscript>5-x</Subscript>Na<Subscript>2x</Subscript>Nb<Subscript>10</Subscript>O<Subscript>30</Subscript> ceramics with different Ba–Na Ratios

The tetragonal tungsten bronzes of Ba5−xNa_2x Nb₁₀O₃₀ (BNN, 0.5≤ x≤1.3) ceramics were synthesized using the solid state reaction method. The sintering behavior and dielectric characteristics of the BNN ceramics, as a function of the Ba-Na ratio, were examined. Densification of the samples with excess compositions of Ba and Na was higher than that of the stoichiometric BNN sample. The maximum dielectric constant and the Curie temperature showed highest values at the stoichiometric composition and decreased as the composition shifted away from the stoichiometry. in order to obtain a quantitative evaluation of the diffuse phase transition (DPT) behavior of the BNN ceramics, γ and C/κ_max were calculated. The weakest DPT behavior was observed in the stoichiometric composition. An increase in the DPT is in correlation with the increase in the number of ways of cation distribution by the disordered occupation of Ba and Na and the vacancies in the A1 and A2 sites of the tungsten bronze structure.     

Synthesis and Characterization of the Isocyanide Ligated Centered Zirconium Halide Cluster [(Zr6Be)Cl12(CNXyl)6]

The first isocyanide ligated hexanuclear zirconium halide cluster is reported. The unoxidized [(Zr₆Be)Cl₁₂(CNXyl)₆] (CNXyl = 2,6-dimethylphenyl isocyanide) was obtained from the solid state precursor K₃Zr₆Cl₁₅Be by dissolution in CH₃CN in the presence of CNXyl. The CNXyl ligands occupy all the axial positions on the cluster. The compound was recrystallized from CH₂Cl₂ and Et₂O. [(Zr₆Be)Cl₁₂(CNXyl)₆].2CH₂Cl₂ crystallizes in the space group (#2) with a = 12.092(5) Å, b=12.728(5) Å, c = 14.102(8) Å, = 104.98(4)°, =107.11°, = 100.94°, V = 1919(2) ų, Z = l, R = 11.3% and R _W = 27.0%. For the bound isocyanide ligands, v _CN increases to 2140 cm^–1.     

Molecular and crystal structure of quinoline-2-aldehyde thiosemicarbazone

The molecular and crystal structure of quinoline-2-aldehyde thiosemicarbazone is determined. The thiosemicarbazide fragment has cis-arrangement of terminal nitrogen atoms relative to the central N-C bond. The structure is based on a centrosymmetric dimer formed by hydrogen bonds between NH groups and sulfur atoms of thiosemicarbazide fragments of the neighboring molecules. In the crystal, the dimers are joined with each other through a system of hydrogen bonds and intermolecular π-π interactions.     

Segregated self-assembly and pillaring action of aliphatic dicarboxylic acids in the super structure of Cu–picolinate complexes

Three new supramolecular assemblies of co-crystallized metal complexes and aliphatic dicarboxylic acids, {[Cu(pic)₂(H₂O)₂](H₂mal)}_n (1), {[Cu(pic)₂(H₂O)₂](H₂mal)₂(H₂O)₂}_n (2) and {[Cu(pic)₂(MeOH)](H₂succ)}_n (3) {Hpic = 2-picolinic acid, H₂mal = malonic acid and H₂succ = succinic acid} have been synthesized and characterized by X-ray single-crystal structure determination. The crystal packings of the complexes reveal that supramolecular associations of the monomeric complex units lead to the formation of layers through hydrogen bonding. In all the complexes, the dicarboxylic acid units connect the 2-D layers to act as pillars. The interaction between water molecules and the dicarboxylic acid plays an important role in the overall supramolecular assembly.     

Molecular and crystalline structure of the enol form of (dimorpholinophosphoryl)chloroacetaldehyde and (dimorpholinophosphoryl)-dibromomethane

The crystal and molecular structures of the products of the halogenation of the dimorpholide of ethoxyvinylphosphonic acid were determined by the method of x-ray structure analysis. It was established that (dimorpholinophosphoryl)chloroacetaldehyde only exists in the crystals as the Z-enol [(Z)-1-hydroxy-2-(dimorpholinophosphoryl)-2-chloroethene] with intra- and intermolecular H-bonds (=CH...O=P and OH...O=P). The (dimorpholinophosphoryl)dibromomethane forms centrosymmetric eight-membered cyclic dimers in the crystals due to intermolecular CH...O=P H-bonds. The structure of the morpholine and phosphoryl groups in both compounds was discussed.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan' Scientific Center, Russian Academy of Sciences, 420083 Kazan'. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 12, pp. 2730–2737, December, 1992.     

Synthesis, X-ray structure and properties of a new nitrite-bound copper(II) complex with 2-(3,5- dimethylpyrazol-1-ylmethyl)pyridine in a CuN4(O) coordination

Synthesis and characterization of a nitrite-bound copper(II) compound [CuL⁴)₂(ONO)]ClO₄ have been achieved (L⁴ = 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine]. The bidentate ligand L⁴ provides a pyridine and a pyrazole donor site; however, they are separated by a methylene spacer. The complex has been structurally characterized and it belongs to only a handful of complexes having nitrito-bound mononuclear copper(II) centre. The metal atom has a distorted square pyramidal geometry with the copper atom displaced from the equatorial plane by 0.25 Å. In MeCN solution the green complex exhibits a broad ligand-field transition at 655 nm with a shoulder at 675 nm and in dichloromethane-toluene glass (80 K) it exhibits an EPR spectral feature characteristic of the unpaired electron in the d_x²−y² orbital. Variable-temperature (80–300 K) magnetic susceptibility measurements in the solid state as well as room temperature measurement in MeCN solution reveal mononuclear magnetically dilute copper(II) centre. When examined by cyclic voltammetry (MeCN solution) it displays electrochemically irreversible Cu^II---Cu^I response [cathodic peak potential, E_pc (V vs saturated calomel electrode (SCE)): −0.32]. An oxidative response is observed at 1.14 V, probably due to bound-nitrite oxidation and is partially removed to generate a solvated complex at the electrode surface. The latter species gives rise to reversible Cu^II---Cu^I redox response [ ].     

Waugh-型镍钼杂多酸的量子化学计算

采用半经验INDO法，完成了Waugh-型镍钼杂多酸（NH44）6〔NIMO9O32〕·6H2O的量子化学计算，得到146个成键轨道和78个反键轨道，轨道能级，电荷和键序等数据。通过对这些数据的分析，表明杂多酸分子中端氧和Ni都可能为化学活性中心，各原子轨道在分子轨道中都占有一定比例，其HOMO和LUMO能级皆为负值，其体系具有进一步接受电子的能力。这些结论与实验事实一致。     

Variable predictive model based classification algorithm for effective separation of protein structural classes

Variable predictive model based class discrimination (VPMCD) algorithm is proposed as an effective protein secondary structure classification tool. The algorithm mathematically represents the characteristics amino acid interactions specific to each protein structure and exploits them further to distinguish different structures. The new concept and the VPMCD classifier are established using well-studied datasets containing four protein classes as benchmark. The protein samples selected from SCOP and PDB databases with varying homology (25-100%) and non-uniform distribution of class samples provide challenging classification problem. The performance of the new method is compared with advanced classification algorithms like component coupled, SVM and neural networks. VPMCD provides superior performance for high homology datasets. 100% classification is achieved for self-consistency test and an improvement of 5% prediction accuracy is obtained during Jackknife test. The sensitivity of the new algorithm is investigated by varying model structures/types and sequence homology. Simpler to implement VPMCD algorithm is observed to be a robust classification technique and shows potential for effective extensions to other clinical diagnosis and data mining applications in biological systems.