Synthesis and Crystal Structures of Bis(tetraethylammonium)(2-oxo-1,3-dithiole-4,5-dithiolato)zincate(II) and Bis(tetra-n-butylammonium)(2-oxo-1,3-dithiole-4,5-dithiolato)zincate(II)

The title compounds were prepared from 1,3,4,6-tetrathiapentalene-2,5-dione ( 1 ) in one step via the in situ generated intermediate 2-oxo-1,3-dithiole-4,5-dithiolate (dmid; 2 ). The X-ray single crystal structure of (Et₄N)₂[Zn(dmid)₂] ( 3 a ) gave the tetragonal space group P4₃2₁2 with a = b = 13.810(2) Å, c = 16.480(3) Å, and Z = 4. (n-Bu₄N)₂[Zn(dmid)₂] ( 3 b ) gave the triclinic space group P 1 with a = 11.947(4) Å, b = 14.665(5) Å, c = 16.662(8) Å, α = 100.21(3)°, β = 104.46(3)°, γ = 110.73(3)°, and Z = 2.     

Crystal structure of radical cation salt (BEDT-TTF)4(GaCl4)2 · C6H5CH3

A new radical cation salt based on bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) with the tetrahedral anion GaCl ₄ ^? , namely, (BEDT-TTF)₄(GaCl₄)₂ · C₆H₅CH₃, has been synthesized. The crystal structure of this salt is determined by X-ray diffraction analysis [a = 31.757(2) Å, b = 6.8063(3) Å, c = 34.879(2) Å, β = 90.453(4)°, V = 7538.8(7) ų, space group I2/c, and Z = 4]. In the structure, the radical cation layers alternate with the anion layers along the c-axis. The anion layers consist of the GaCl ₄ ^? tetrahedra and solvent molecules. The packing of BEDT-TTF molecules in the radical cation layer differs from that in the structure of the known salt (BEDT-TTF)₂GaCl₄, even though both compounds exhibit semiconductor properties.     

Hexafluoroacetone as a Protecting and Activating Reagent. Regioselective Esterification of Aspartic, Malic, and Thiomalic Acid

Hexafluoroacetone reacts with -functionalized ,-dicarboxy acids like aspartic, malic, and thiomalic acid to give exclusively five-membered lactones. The -carboxylic groups remain unaffected and can be derivatized separately. They can be linked i.a. to orthogonal protecting groups or multivalent alcohols like pentaerythritol to give synthetically valuable building blocks.     

LC-MS/MS determination of potential endocrine disruptors of cortico signalling in rivers and wastewaters

A targeted analytical method was established to determine a large number of chemicals known to interfere with the gluco- and mineralocorticoid signalling pathway. The analytes comprise 30 glucocorticoids and 9 mineralocorticoids. Ten out of these corticosteroids were primary metabolites. Additionally, 14 nonsteroids were included. These analytes represent a broader range of possible adverse modes of action than previously reported. For the simultaneous determination of these structurally diverse compounds, a single-step multimode solid-phase extraction and pre-concentration was applied. Extracts were separated by a short linear HPLC gradient (20 min) on a core shell RP column (2.7 μm particle size) and compounds identified and quantified by LC-MS/MS. The method provided excellent retention time reproducibility and detection limits in the low nanograms per litre range. Untreated hospital wastewater, wastewater treatment plant influent, treated effluent and river waters were analysed to demonstrate the applicability of the method. The results show that not all compounds were sufficiently eliminated by the wastewater treatment, resulting in the presence of several steroids (～20 ng/L) and nonsteroids in the final effluent, some of them at high concentrations up to 200 ng/L. Most of the detected mono-hydroxylated steroidal transformation products were found at significantly higher concentrations than their parent compounds. We therefore recommend to include these potentially bioactive metabolites in environmental toxicity assessment.     

Electronic structure and spectroscopy of nucleic acid bases: ionization energies, ionization-induced structural changes, and photoelectron spectra

We report high-level ab initio calculations and single-photon ionization mass spectrometry study of ionization of adenine (A), thymine (T), cytosine (C), and guanine (G). For thymine and adenine, only the lowest-energy tautomers were considered, whereas for cytosine and guanine we characterized the five lowest-energy tautomeric forms. The first adiabatic and several vertical ionization energies were computed using the equation-of-motion coupled-cluster method for ionization potentials with single and double substitutions. Equilibrium structures of the cationic ground states were characterized by DFT with the ωB97X-D functional. The ionization-induced geometry changes of the bases are consistent with the shapes of the corresponding molecular orbitals. For the lowest-energy tautomers, the magnitude of the structural relaxation decreases in the following series, G > C > A > T, the respective relaxation energies being 0.41, 0.32, 0.25, and 0.20 eV. The computed adiabatic ionization energies (8.13, 8.89, 8.51-8.67, and 7.75-7.87 eV for A, T, C, and G, respectively) agree well with the onsets of the photoionization efficiency (PIE) curves (8.20 ± 0.05, 8.95 ± 0.05, 8.60 ± 0.05, and 7.75 ± 0.05 eV). Vibrational progressions for the S(0)-D(0) vibronic bands computed within double-harmonic approximation with Duschinsky rotations are compared with previously reported experimental photoelectron spectra and differentiated PIE curves.     

Phenolic compounds extracted from spruce (Picea abies) by supercritical carbon dioxide as antimicrobial agents against gram-positive bacteria assessed by isothermal calorimetry

Journal of Thermal Analysis and Calorimetry - Antimicrobial agents are substances that, when present at low concentrations, can delay microbial growth. For many years, several powerful...     

Electrochemical Methods to Evaluate the Antioxidant Activity and Capacity of Foods: A Review

Antioxidants are an important class of food additives playing the fundamental role of retarding oxidation reactions in food. Although their functional role is well-established, less clear is their mechanism of action. Electrochemical methods based on cyclic, differential pulse, square wave voltammetry and coulometry allow direct and rapid screening of antioxidant activity. Their main advantages are sensitivity, rapidity, simplicity and the capacity to directly measure the number of electrons transferred by an antioxidant offer advantage over conventional spectrophotometric assays. This review aims to summarize the most recent efforts towards the use of electrochemical methods to evaluate the antioxidant activity of foods.     

Synthesis of 3-(N-arylthiocarbamoyl)chromones from 2-hydroxyaryl amino enones and isothiocyanates

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Modification of laser gain properties through local-field effects and nanostructuring

We have recently developed a simple phenomenological model that allows one to account for the modifications of the gain characteristics of nanocomposite optical materials with specific geometries. Here we give a generalized formulation of our model to show that it can be applied to a broad variety of composite geometries. We demonstrate the application of our model using the Maxwell Garnett composite geometry with the resonant molecules in its host, which represent a practically important case that has not been treated earlier. We also give numerical examples for the Maxwell Garnett composite geometry with the resonances in either host or inclusions, and find the conditions under which it is possible to achieve an enhancement or suppression of the small-signal gain coefficient compared to its value in a bulk material. Using our simple model, one can identify the set of parameters, exhibiting the desired changes to the gain characteristics, prior to or instead of performing a more precise computationally intensive analysis.