Silyl Modification of Biologically Active Compounds. 7. Synthesis, Structure, Physicochemical and Biological Properties of Some Silicon-containing “3+1” Oxorhenium(V) Complexes

With the aim of studying the structure-physicochemical properties-biological activity relation, we have synthesized a series of organosilicon neutral oxorhenium(V) complexes with mixed ligands and we have determined their lipophilicity. X-ray diffraction has been used to establish the molecular structure of (3-triphenylsiloxypropanethiolato)(3-thiapentane-1,5-dithiolato)oxorhenium(V), (2-trimethylsiloxy- and 2-hydroxyethanethiolato)[3-(N-methyl)azapentane-1,5-dithiolato]oxorhenium(V). We have studied the neurotropic properties and acute toxicity of the synthesized complexes in vivo and their dependence on the nature of the monodentate and tridentate ligands. We have established that all the studied compounds have pronounced sedative action (they prolong the life of mice under hypoxia conditions, they are phenamine antagonists, they exhibit anticonvulsive action and prevent retrograde amnesia).     

Steviosid aus Süßkraut

The diterpene glycoside stevioside is the most abundant among a group of sweet steviol glycosides, present in sweetleaf (Stevia rebaudiana), which is naturally occurring in Paraguay. It has already been used by the Guarani Indians as a sweetener. Since 2011 such “steviosides” have an EU approval as sweeteners E 960. They taste ca. 250 times sweeter than sucrose. Meanwhile, they have got a significant recognition, not least due to their use in Coca Cola life®. We describe the isolation of stevioside and rebaudioside A from dried leaves of the sweetleaf plant. The complete set of spectra for stevioside is reported. Based on students' laboratory work this project is a follow up of the book “Classics in Spectroscopy” by S. Berger und D. Sicker (Wiley‐VCH 2009).     

ChemInform Abstract: Structure and Conformational Properties of Azido(difluoro)phosphane,F2PN3.

The title compound is characterized by IR (gas phase, Ar matrix), Raman (liquid, amorphous, and crystalline solid), and ¹⁹F, ³¹P, ¹⁴N and ¹⁵N NMR spectroscopy, as well as by quantum chemical DFT calculations.     

Silver Coated Platinum Core–Shell Nanostructures on Etched Si Nanowires: Atomic Layer Deposition (ALD) Processing and Application in SERS

A new method to prepare plasmonically active noble metal nanostructures on large surface area silicon nanowires (SiNWs) mediated by atomic layer deposition (ALD) technology has successfully been demonstrated for applications of surface‐enhanced Raman spectroscopy (SERS)‐based sensing. As host material for the plasmonically active nanostructures we use dense single‐crystalline SiNWs with diameters of less than 100 nm as obtained by a wet chemical etching method based on silver nitrate and hydrofluoric acid solutions. The SERS active metal nanoparticles/islands are made from silver (Ag) shells as deposited by autometallography on the core nanoislands made from platinum (Pt) that can easily be deposited by ALD in the form of nanoislands covering the SiNW surfaces in a controlled way. The density of the plasmonically inactive Pt islands as well as the thickness of noble metal Ag shell are two key factors determining the magnitude of the SERS signal enhancement and sensitivity of detection. The optimized Ag coated Pt islands on SiNWs exhibit great potential for ultrasensitive molecular sensing in terms of high SERS signal enhancement ability, good stability and reproducibility. The plasmonic activity of the core‐shell Pt//Ag system that will be experimentally realized in this paper as an example was demonstrated in numerical finite element simulations as well as experimentally in Raman measurements of SERS activity of a highly diluted model dye molecule. The morphology and structure of the core‐shell Pt//Ag nanoparticles on SiNW surfaces were investigated by scanning‐ and transmission electron microscopy. Optimized core–shell nanoparticle geometries for maximum Raman signal enhancement is discussed essentially based on the finite element modeling.     

Characterization of Ascentis RP-Amide column: Lipophilicity measurement and linear solvation energy relationships

This study investigates lipophilicity determination by chromatographic measurements using the polar embedded Ascentis RP-Amide stationary phase. As a new generation of amide-functionalized silica stationary phase, the Ascentis RP-Amide column is evaluated as a possible substitution to the n  -octanol/water partitioning system for lipophilicity measurements. For this evaluation, extrapolated retention factors, log k^′_w$\text{log}{k^{\prime }}_w$, of a set of diverse compounds were determined using different methanol contents in the mobile phase. The use of n-octanol enriched mobile phase enhances the relationship between the slope (S  ) of the extrapolation lines and the extrapolated log k^′_w$\text{log}{k^{\prime }}_w$ (the intercept of the extrapolation), as well as the correlation between log P   values and the extrapolated log k^′_w$\text{log}{k^{\prime }}_w$ (1:1 correlation, r² = 0.966). In addition, the use of isocratic retention factors, at 40% methanol in the mobile phase, provides a rapid tool for lipophilicity determination. The intermolecular interactions that contribute to the retention process in the Ascentis RP-Amide phase are characterized using the solvation parameter model of Abraham. The LSER system constants for the column are very similar to the LSER constants of the n-octanol/water extraction system. Tanaka radar plots are used for quick visual comparison of the system constants of the Ascentis RP-Amide column and the n-octanol/water extraction system. The results all indicate that the Ascentis RP-Amide stationary phase can provide reliable lipophilic data.     

Oligomerization of 1,2‐Ethanedithiol: An Expedient Approach to Oligothiaethylenethioglycols

Reactions of ethylenedithioglycol (ETG) with Na₂CO₃, K₂CO₃, and Cs₂CO₃ provided the oligothiaethylenethioglycols (nETG): di‐ (DETG), tri‐ (TrETG), tetra‐ (TETG), and pentathiaethylenethioglycol (PETG), along with higher polymers. The most efficient carbonate was K₂CO₃ and reactions using DETG and TrETG as starting materials—or their mixtures—were also found to afford similar species. This largely unknown oligomerization process was thoroughly explored and potential pathways were put forward. A convenient conversion of ETG to laboratory quantities of the otherwise scarce and/or expensive DETG, TrETG, TETG, and PETG oligomers, in organic or aqueous media was achieved. Notably, this straightforward reaction takes place without the addition of expensive or toxic metal catalysts and with pure water as the solvent, thereby highlighting its potential as a green chemical reaction. Moreover, the process opens up new approaches to dynamic combinatorial libraries (DCLs) of oligomers and macrocycles with manifolded nETG [(SCH₂CH₂)_nS] bridges.     

Precise predictions for W+4-jet production at the large hadron collider

We present the next-to-leading order (NLO) QCD results for W+4-jet production at hadron colliders. This is the first hadron-collider process with five final-state objects to be computed at NLO. It represents an important background to many searches for new physics at the energy frontier. Total cross sections, as well as distributions in the jet transverse momenta, are provided for the initial LHC energy of √s = 7 TeV. We use a leading-color approximation, known to be accurate to 3% for W production with fewer jets. The calculation uses the BLACKHAT library along with the SHERPA package.