爆轰波面轮廓及其旋转对称性的同时观测

利用间隙技术并靠一个专用模板,就能仅通过一次试验而对爆轰波面轮廓进行记录,辽河对其不同对称程度和旋转对称性加以详细分析.     

The state of iron in andalusite

Iron in andalusite (Al₂SiO₅) with concentrations of 1.5 … 4.3 wt-% has been reported in the literature to occupy mainly Al1 sites as Fe³⁺, and only small portions occupy Al2 sites as Fe³⁺ and Fe²⁺. In no case a magnetic hyperfine splitting has been found at temperatures above 77 K. We have studied natural samples of andalusite containing 0.3 and 0.5 wt-% only. Mössbauer spectra recorded at 80 and 300 K show magnetically split spectra and, for the 0.5% sample, an additional doublet can be seen. The spectra are interpreted as being due to a slow paramagnetic relaxation resulting in Fe³⁺ and Fe²⁺ hyperfine multiplets. An increase in the Fe concentration reduces the paramagnetic relaxation time. It seems that the andalusite structure can contain a limited number of Fe²⁺ only, and a similar limitation does not exist for Fe³⁺ ions.     

Siliciumverbindungen mit starken intramolekularen sterischen wechselwirkungen: XXI. 2,4,6-Tri-t-Butylphenyl-substituierte silane

Trifluoro(2,4,6-tri-t-butylphenyl)silane (ArSiF₃, 2), the first silicon compound containing the very bulky 2,4,6-tri-t-butylphenyl group, has been prepared by treatment of ArLi with silicon tetrafluoride. Reaction of 2 with several organolithium compounds gives the corresponding diorganyl derivatives Ar(R)SiF₂, R = Me, t-Bu, and Ar, respectively. The fluorosilanes are easily converted into the air-stable hydrosilanes ArSiH₃ and Ar(R)SiH₂.     

The accreditation of reference material producers — EUROLAB's position

A third-party assessment of reference materials (RMs) and their production is not of the highest priority for RM users. But if RM producers do want a third-party involvement this should be realised within the frame of existing conformity assessment schemes. Nevertheless, the right and responsibility of the laboratories to select the most appropriate RMs for their tasks must not be restricted by accreditation bodies or other interested parties.     

Orientation modulation of a synthetic polypeptide in self-assembled monolayers: a TOF-SIMS study

Structure and orientation of molecules are key properties of functionalized surfaces. Using time-of-flight secondary ion mass spectrometry (TOF-SIMS), here we investigate how to modulate these parameters upon the immobilization process varying the conditions of self-assembly. The molecule of interest, a template-assembled synthetic protein (TASP), consists of a central peptide ring with orthogonally arranged residues. Thioalkane chains allow the directed self-assembly of the molecule on a gold surface; four serine residues on the opposite side of the ring can be used as anchoring sites for various functional sensing molecules. The TASP conformation and its orientation in self-assembled monolayers (SAMs) play a central role for the accessibility of these serine residues. To study the influence of the self-assembly conditions, two series of samples were prepared. Pure TASP monolayers of different surface densities are compared to mixed TASP/alkanethiol monolayers prepared by sequential adsorption varying sequence and particular incubation times as well as by coadsorption modifying incubation times and TASP/alkanethiol mass ratios. Switching the TASP orientation from a state where the molecules are lying flat on the surface to an upright orientation turned out to be possible by inserting the TASP into a preformed alkanethiol monolayer of an appropriate surface density. This study demonstrates that TOF-SIMS is an excellent tool not only to investigate the surface composition, but also the molecular structure of functionalized surfaces.     

Wasserstoffbrückenbindungen mit Cyanidionen? Die Strukturen von 1,3‐Diisopropyl‐4,5‐dimethylimidazoliumcyanid und 1‐Isopropyl‐3,4,5‐trimethylimidazoliumcyanid

Hydrogen Bonds with Cyanide Ions? The Structures of 1,3‐Diisopropyl‐4,5‐dimethylimidazolium Cyanide and 1‐Isopropyl‐3,4,5‐trimethylimidazolium Cyanide 1,3‐Diisopropyl‐4,5‐dimethylimidazolium cyanide ( 2a ) and 1‐isopropyl‐3,4,5‐trimethylimidazolium cyanide ( 2b ) are obtained from the reaction of the corresponding 2,3‐dihydrodimethylimidazol‐2‐ylidenes ( 1 ) and hydrogen cyanide in excellent yield. Their crystal structure analyses reveal the presence of ion pairs linked by hydrogen bonds. The crystal structure analysis of 2a reveals a near colinear orientation of the C(1)‐H bond axis and the cyanide ion while in 2b this orientation is perpendicular. In both cases, the interionic distances are in the expected range for hydrogen bonds. Ab‐initio calculations of the total energy of the salts 2 indicate small differences in energy between the colinear and perpendicular orientation of the ions as well as between the colinear C‐H···C‐N and C‐H···N‐C orientations. The comparison of calculated and measured ¹³C and ¹⁵N NMR chemical shifts does not allow the distinction between the possible orientations.     

A radical mechanism for the photochemical iron pentacarbonyl catalyzed hydrogenation of octenes

A high pressure IR and UV spectroscopic study of the catalysis of hydrogenation of 1-octene by Fe(CO)₅ under UV irradiation reveals that Fe(CO)₅ and (olefin)Fe(CO)₄ are the light absorbing species. The primary photolysis product Fe(CO)₄ reacts with H₂Fe(CO)₄ to give HFe(CO)₄ radicals, which are suggested to be the active hydrogenation promoters.     

Synthesis,Structure and Isomerism of the [Fe<Subscript>3</Subscript>Pt(μ<Subscript>4</Subscript>-Q)(CO)<Subscript>9</Subscript>(dppm)] Clusters (Q = Se,Te; dppm = Ph<Subscript>2</Subscript>PCH<Subscript>2</Subscript>PPh<Subscript>2</Subscript>)

The reaction of K₂[Fe₃(μ₃-Q)(CO)₉] (Q = Se (K₂[1a]), Te (K₂[1b])) with [(dppm)PtCl₂] leads to the addition of a [(dppm)Pt]²⁺ unit to a Fe₂Q face of the initial cluster. By this way new heteronuclear clusters [Fe₃Pt(μ₃-Q)(CO)₉(dppm)] were obtained possessing a butterfly-shaped cluster core bridged by a μ₄-Q unit. It has been found that the resulting Fe-Pt clusters exist as equilibrium mixtures of two isomeric forms in solution differing by the dppm coordination mode: as a chelate ligand coordinated to Pt or as a bridging ligand coordinated to Pt and Fe atoms. The mixtures of isomers can be separated by chromatography and the pure isomers can be isolated as stable crystalline phases. Solutions of both isomers attain equilibrium at normal conditions in about 1 month as found by NMR. Dedicated to Professor Dieter Fenske in the occasion of his 65th birthday.