Ruthenium cluster compounds containing 1,1′-bis(diphenylphosphino)ferrocene (dppf): an electrochemical analysis and the crystal structure of [Ru3(CO)11]2(μ-dppf)

The electrochemistry of 1,1′-bis(diphenylphosphino)ferrocene (dppf) derivatives of Ru₃(CO)₁₂ was investigated. Two known compounds [Ru₃(CO)₈(μ-dppf)₂ (1) and Ru₃(CO)₁₀dppf (2)] and a new compound [Ru₃(CO)₁₁(μ-dppf)Ru₃(CO)₁₁ (3)] were prepared. Compound 3 was characterized spectroscopically and an X-ray crystal structure was obtained. The reductive electrochemistry of 1 and 2 showed an irreversible reduction and a follow-up oxidation, similar to Ru₃(CO)₁₂. The electrochemistry of compound 3 showed two irreversible waves and a follow-up oxidation. A trend in the reduction potential vs. the number of coordinated phosphorus atoms was noted. The oxidative electrochemistry of 1-3 showed a dppf-based chemically reversible wave, and an irreversible wave similar to that of Ru₃(CO)₁₂. Trends were also noted between the oxidation potential and the number of coordinated phosphorus atoms.     

Structural and Chemical Analysis of Materials with High Spatial Resolution

 An understanding of the correlation between microstructures and properties of materials require the characterization of the material on many different length scales. Often the properties depend primarily on the atomistics of defects, such as dislocations and interfaces. The different techniques of transmission electron microscopy allow the characterization of the structure and of the chemical composition of materials with high spatial resolution to the atomic level: high resolution transmission electron microscopy allows the determination of the position of the columns of atoms (ions) with high accuracy. The accuracy which can be achieved in these measurements depends not only on the instrumentation but also on the quality of the transmitted specimen and on the scattering power of the atoms (ions) present in the analyzed column. The chemical composition can be revealed from investigations by analytical microscopy which includes energy dispersive X-ray spectroscopy, mainly quantitatively applied for heavy elements, and electron energy-loss spectroscopy. Furthermore, the energy-loss near-edge structure of EELS data results in information on the local band structure of unoccupied states of the excited atoms and, therefore, on bonding. A quantitative evaluation of convergent beam electron diffraction results in information on the electron charge density distribution of the bulk (defect-free) material. The different techniques are described and applied to different problems in materials science. It will be shown that nearly atomic resolution can be achieved in high resolution electron microscopy and in analytical electron microscopy. Recent developments in electron microscopy instrumentation will result in atomic resolution in the foreseeable future.     

Synthesis and Crystal Structure of an (N-Protected amino)-β-lactam Derivative of 1,5-Benzothiazepine

1 INTRODUCTION 1,5-Benzothiazepines are a kind of compounds which have important biological activitives[1, 2]. Cycloaddition reactions of their active C=N bond with ketene permit the construction of new -lactam ring. The -lactam moiety is the main part of the antibiotics such as penicillins. So the product of this reaction possesses two active centers and can be beneficial to pharmaceutical research. In this paper we have achieved the asymmetric ketene-imine cycloadditions employing the…     

Hemocompatibility of poly(acrylonitrile-co-N-vinyl-2-pyrrolidone)s: swelling behavior and water states

Hemocompatibility is an essential aspect of blood contacting polymers. Knowledge of the relationship between polymer structure and hemocompatibility is important in designing such polymers. In this work, the effect of swelling behavior and states of water on the hemocompatibility of poly(acrylonitrile-co-N-vinyl-2-pyrrolidone) (PANCNVP) films was studied. Platelet adhesion and plasma recalcification time tests were used to evaluate the hemocompatibility of the films. Considering the importance of surface properties on the hemocompatibility of polymers, static water contact angles were measured by both sessile drop and captive bubble methods. It was found that, on the film surface of PANCNVP with a higher NVP content, adhered platelets were remarkably suppressed and the recalcification time was longer. The total water content adsorbed on the PANCNVP film was determined through swelling experiments performed at temperatures of interest. Differential scanning calorimetry and thermogravimetric analysis were used to probe the states of water in the films. Based on the results from these experiments, it was hypothesized that the better hemocompatibility of PANCNVP films with higher NVP contents was due to their higher free water content, because water molecule exchange at the polymer/liquid interface, facilitated by a high free water content, is unfavorable for the formation of surface bound water, which causes poor hemocompatibility. [diagram in text].     

Synchrotron X-ray absorption of LaCoO3 perovskite

LaCoO₃ perovskite was prepared at 700°C using citrate precursors. The product was then characterized with X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). The powder XRD pattern indicates rhombohedral or its monoclinic I2/a subgroup symmetry. The electronic configuration and the short-range atomic structure of the LaCoO₃ perovskite at room temperature were investigated using synchrotron near-edge X-ray absorption spectroscopy (XANES) and extended X-ray absorption spectroscopy (EXAFS). From the XANES region of the XAS we conclude that Co(III) is at least partly in its intermediate- or high-spin state, which is in accordance with most of the published literature on LaCoO₃ perovskite. The EXAFS region of the LaCoO₃ perovskite spectrum, which up to now was almost not investigated, was simulated satisfactorily for the first two radial structure peaks in terms of the dominant scattering contributions generated with the FEFF8 code and the structural information available from crystallographic data. The best simulation results were obtained with I2/a symmetry. The obtained amplitude reduction factor, zero-energy shift and Debye-Waller factors are useful reference values for data analyses of similar compounds like partly substituted LaCoO₃ perovskite, such as La_1−xCa_xCoO₃ or La_1−xSr_xCoO₃, which are materials of technical interest in catalyst and other applications.     

Strukturen ladungsgestörter oder räumlich überfüllter Moleküle. 15. Tetracyanethen-Natrium-Dimethoxyethan

Structures of Charge-Perturbed or Sterically Overcrowded Molecules. 16. Tetracyanoethylene Sodium Dimethoxyethane The Single crystal structure of [(NC)₂C? C(CN)₂?·Na⊕(H₃CO? CH₂CH₂? OCH₃)]∞ reveals two formula units within the triclinic (P1 ) unit cell. The tetracyanoethylene radical anions are arranged along parallel double layers, which are shifted relative to each other, and in between which are interspersed the sodium counter cations and their dimethoxyethane ligands. The distances within the double layers amount to 300 pm and the ones between them to 385 pm. The six-fold coordinated Na⊕ centers are surrounded by four radical anions with contact distances Na…?N between 250 and 254 pm as well as by a twofold solvent ligand with Na…?O of 238 and 241 pm. Due to the electron transfer to the acceptor molecule, its (NC)₂C-halves twist by 8° and the bond lengths of the N?C? C subunits, bent by each 3°, are shortened up to 2 pm. The structural parameters are compared to those of the analogous potassium salt [TCNE^?K^⊕DME], of the dianion , of the sodium salts [(NC)₃C^?Na^⊕]∞ as well as [(NC)₂C? C(CHCH)₂? C(CN)₂^?Na^⊕]_∞ and, in addition, are discussed based on geometry-optimized MNDO calculations.     

结构相角二阶代数式的应用：Ⅱ.正交空间群二阶式及其应用

以作者在前文中提出的单相角二阶代数式的推导方法为依据,在完成三斜、单斜空间群推导结果的基础上,进而又完成了正交晶系59个空间群二阶式的推导,从而提供了低级晶系(三斜、单斜和正交)全部74个空间群的简明、完备的二阶代数式运算用表。对三个晶体结构进行了相角估算,结果较好。文中提出了代数法应用的新特点,即“一种类型相角可用多种二阶式求得,多种类型相角也可用一种二阶式求算”。     

Structural Study of C-undecylcalix[4]resorcinarene Solvate with Dioxane

The crystal structure of the molecular complex of C-undecylcalix[4]resorcinarene with dioxane has been determined by X-ray analysis. The asymmetric unit contains one host and four guest molecules. The calix[4]resorcinarene moiety adopts a bowl conformation with C_4v symmetry. Four undecyl chains are axially oriented. Calix molecules are packed in a bowl-to-bowl fashion with alternating hydrophilic and hydrophobic layers. One of the hydrophilic dioxane molecules is located at the rim of the calix moiety and is hydrogen bonded to the other one. There is no interaction to attract, or direct the dioxane molecule into the interior of the cavity. There is an exo complex formed. The dioxane molecules – located in the hydrophobic part – are highly disordered.     

SYNTHESIS AND PROPERTIES OF POLYSTYRENE／LAPONITE NANOCOMPOSITES

Exfoliated polystyrene (PS)/laponite nanocomposites were prepared successfully. The characteristic doo1 diffraction peak of organo-laponite disappeared in the XRD patterns of nanocomposites, indicating that the laponite layers were exfoliated and the ordered crystal structure of laponite was destroyed because of the styrene polymerization. TEM observations showed that the exfoliated laponite primary particles were dispersed randomly in the PS matrix with lateral dimensions from 1 nm to 10 rim. SEM results showed that the PS/laponite nanocomposite particles were almost monodispersed spheres with the size of about 120 rim. Because of the interaction between PS and laponite nanolayers, the nanocomposites exhibited higher thermal stability and glass transition temperature when compared to pure PS.     

高分子合金分离膜材料及结构研究进展

膜材料液相共混制备高分子合金分离膜不但可以调节膜材料与被分离物的亲和性，也在一定程度上改变了膜的结构。本文介绍高分子材料浓相共混对膜材料的亲水性、耐污染性及其它理化性能的影响和对膜结构的调节作用，同时指出高分子材料间的相容性是影响合金膜结构的重要因素。