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91.
92.
The determination of the phase diagram of the binary system sodium perchlorate – water is reported. Beside the eutectic point, two polymorph crystal structures of sodium perchlorate dihydrate were determined. The two crystal structures are discussed, compared to each other and to other known sodiumhalide dihydrate crystal structures. The two polymorphs of the perchlorate dihydrate represent the two variants of connected octahedra in the layer structure found for sodium halide dihydrates. 相似文献
93.
Abstract The title trisaccharides were synthesized from a common trisaccharide thioglycoside derivative, which was, in turn, prepared from monosaccharide thioglycoside precursors. An acyclic analogue, methyl 3-O-(α-D-galacto-pyranosyl)-6-O-[(2′-hydroxyethyl)oxymethyl]-α-D-glucopyranoside, which carries a 2′-hydroxyethyloxymethyl group in place of the 6-O-galactosyl residue, was also synthesized. 相似文献
94.
Dr. Christoph Hirschhäuser Dr. Juraj Velcicky Dr. Daniel Schlawe Dr. Erik Hessler Dr. André Majdalani Dr. Jörg‐Martin Neudörfl Dr. Dr. Aram Prokop Dr. Thomas Wieder Prof. Dr. Hans‐Günther Schmalz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(39):13017-13029
The synthesis and stereochemical assignment of two classes of iron‐containing nucleoside analogues, both of which contain a butadiene? Fe(CO)3 substructure, is described. The first type of compounds are Fe(CO)3‐complexed 3′‐alkenyl‐2′,3′‐dideoxy‐2′,3′‐dehydro nucleosides (2,5‐dihydrofuran derivatives), from which the second class of compounds is derived by formal replacement of the ring oxygen atom by a CH2 group (carbocyclic nucleoside analogues). These compounds were prepared in a stereoselective manner through the metal‐assisted introduction of the nucleobase. Whilst the furanoid intermediates were prepared from carbohydrates (such as methyl‐glucopyranoside), the carbocyclic compounds were obtained by using an intramolecular Pauson–Khand reaction. Stereochemical assignments based on NMR and CD spectroscopy were confirmed by X‐ray structural analysis. Biological investigations revealed that several of the complexes exhibited pronounced apoptosis‐inducing properties (through an unusual caspase 3‐independent but ROS‐dependent pathway). Furthermore, some structure–activity relationships were identified, also as a precondition for the design and synthesis of fluorescent and biotin‐labeled conjugates. 相似文献
95.
Dr. Antoine Demont Dr. Carmelo Prestipino Dr. Olivier Hernandez Dr. Erik Elkaïm Serge Paofai Prof. Nikolaï Naumov Dr. Bruno Fontaine Prof. Régis Gautier Dr. Stéphane Cordier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(38):12711-12719
The crystal structure of Cs2BaTa6Br15O3 has been elucidated by using synchrotron X‐ray powder diffraction and absorption experiments. It is built from edge‐bridged octahedral [(Ta6${{\rm Br}{{{\rm i}\hfill \atop 9\hfill}}}$ ${{\rm O}{{{\rm i}\hfill \atop 3\hfill}}}$ )${{\rm Br}{{{\rm a}\hfill \atop 6\hfill}}}$ ]4? cluster units with a singular poor metallic electron (ME) count equal to thirteen. This leads to a paramagnetic behaviour related to one unpaired electron. The arrangement of the Ta6 clusters is similar to that of Cs2LaTa6Br15O3 exhibiting 14‐MEs per [(Ta6${{\rm Br}{{{\rm i}\hfill \atop 9\hfill}}}$ ${{\rm O}{{{\rm i}\hfill \atop 3\hfill}}}$ )${{\rm Br}{{{\rm a}\hfill \atop 6\hfill}}}$ ]5? motif. The poorer electron‐count cluster presents longer metal–metal distances as foreseen according to the electronic structure of edge‐bridged hexanuclear cluster. Density functional theory (DFT) calculations on molecular models were used to rationalise the structural properties of 13‐ and 14‐ME clusters. Periodic DFT calculations demonstrate that the electronic structure of these solid‐state compounds is related to those of the discrete octahedral units. Oxygen–barium interactions seem to prevent the geometry of the octahedral cluster to strongly distort, allowing stabilisation of this unprecedented electron‐poor Ta6 cluster in the solid state. 相似文献
96.
Liang‐Hua Zou Dr. Adam Johannes Johansson Dr. Erik Zuidema Prof. Dr. Carsten Bolm 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(25):8144-8152
An efficient catalytic system for Sonogashira–Hagihara‐type reactions displaying ligand acceleration in the copper‐catalyzed formation of C(sp2)? C(sp) bonds is described. The structure of the ligand plays a key role for the coupling efficiency. Various copper sources show excellent catalytic activity, even in sub‐mol % quantities. A wide variety of substituents is tolerated in the substrates. Mechanistic details have been revealed by kinetic measurements and DFT calculations. 相似文献
97.
Poul Erik Hansen Fadhil S. Kamounah Diana Zhiryakova Yana Manolova Liudmil Antonov 《Tetrahedron letters》2014
It has recently been suggested that 1,1′,1′′-(2,4,6-trihydroxybenzene-1,3,5-triyl)triethanone may be tautomeric. Using 13C NMR chemical shifts and deuterium isotope effects on 13C chemical shifts, it is demonstrated that this is not the case. This compound occurs as a strongly hydrogen bonded benzene structure with hydrogen bonds between OH groups and the acetyl groups in both non-polar and hydrogen donating solvents. Quantum-chemical calculations using MP2 and M06-2X methods show substantial preference for the phenol structure in both the gas phase, and in cyclohexane and methanol. In addition, conventional UV–vis spectroscopy data suggest not tautomeric, but aggregation behaviour of the molecule in methanol and acetonitrile. 相似文献
98.
Jingbo Chang Guihua Zhou Erik R. Christensen Robert Heideman Junhong Chen 《Analytical and bioanalytical chemistry》2014,406(16):3957-3975
Graphene (G) is attracting significant attention because of its unique physical and electronic properties. The production of graphene through the reduction of graphene oxide (GO) is a low-cost method. The reduction of GO can further lead to electrically conductive reduced GO. These graphene-based nanomaterials are attractive for high-performance water sensors due to their unique properties, such as high specific surface areas, high electron mobilities, and exceptionally low electronic noise. Because of potential risks to the environment and human health arising from heavy-metal pollution in water, G-/GO-based water sensors are being developed for rapid and sensitive detection of heavy-metal ions. In this review, a general introduction to graphene and GO properties, as well as their syntheses, is provided. Recent advances in optical, electrochemical, and electrical detection of heavy-metal ions using graphene or GO are then highlighted. Finally, challenges facing G/GO-based water sensor development and outlook for future research are discussed. 相似文献
99.
Daniel F. Kienle João V. de Souza Erik B. Watkins Tonya L. Kuhl 《Analytical and bioanalytical chemistry》2014,406(19):4725-4733
The thickness and refractive index of 1,2-dipalmitoyl-sn-glycero-3-phosphatidyl choline (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) monolayers Langmuir--Blodgett (LB) deposited on mica were measured in dry air and bulk water using multiple-beam interferometry (MBI). Measurements of thickness using atomic force microscopy (AFM) of identical monolayers, and X-ray reflectivity (XRR) of the monolayers on quartz were taken for comparison. The measurement of the properties of solid-supported monolayers in dry air allows lipid optical properties to be determined free from solvent effects. The thickness and refractive index measured by MBI were 25.5?±?0.6 Å and 1.485?±?0.007 for DPPE monolayers, and 23.9?±?0.5 Å and 1.478?±?0.006 for DPPC monolayers in dry air. These thicknesses are consistent with the other techniques used in this work as well as other measurements in the literature. The refractive indices of solid-supported lipid monolayers have not been previously measured. The values are higher than previous measurements on black lipid films done by reflectometry, which is attributed to increased lipid packing density and the absence of hydrocarbon solvents. Applying water to the monolayers had no measurable effect on their properties, indicating that any change in hydration was below detection. Figure
? 相似文献
100.
Pierre Gras Nicolas Ratel‐Ramond Sbastien Teychn Christian Rey Erik Elkaim Batrice Biscans Stphanie Sarda Christle Combes 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(9):862-866
Calcium pyrophosphate hydrate (CPP, Ca2P2O7·nH2O) and calcium orthophosphate compounds (including apatite, octacalcium phosphate etc.) are among the most prevalent pathological calcifications in joints. Even though only two dihydrated forms of CPP (CPPD) have been detected in vivo (monoclinic and triclinic CPPD), investigations of other hydrated forms such as tetrahydrated or amorphous CPP are relevant to a further understanding of the physicochemistry of those phases of biological interest. The synthesis of single crystals of calcium pyrophosphate monohydrate (CPPM; Ca2P2O7·H2O) by diffusion in silica gel at ambient temperature and the structural analysis of this phase are reported in this paper. Complementarily, data from synchrotron X‐ray diffraction on a CPPM powder sample have been fitted to the crystal parameters. Finally, the relationship between the resolved structure for the CPPM phase and the structure of the tetrahydrated calcium pyrophosphate β phase (CPPT‐β) is discussed. 相似文献