Vanadium K‐edge XANES in vanadium‐bearing model compounds: a full multiple scattering study

A systematic study is presented on a set of vanadium‐bearing model compounds, representative of the most common V coordination geometries and oxidation states, analysed by means of vanadium K‐edge X‐ray absorption near‐edge spectroscopy calculations in the full multiple scattering (FMS) framework. Analysis and calibration of the free parameters of the theory under the muffin‐tin approximation (muffin‐tin overlap and interstitial potential) have been carried out by fitting the experimental spectra using the MXAN program. The analysis shows a correlation of the fit parameters with the V coordination geometry and oxidation state. By making use of this correlation it is possible to approach the study of unknown V‐bearing compounds with useful preliminary information.     

One-step bioengineering of magnetic nanoparticles via a surface diazo transfer/azide-alkyne click reaction sequence

We have developed an efficient conversion of amino iron oxides to carbohydrate and protein derived nanoparticles with highly conserved bioactivity through a combination of diazo transfer and azide-alkyne click technology.     

Comparative kinetic study of decomposition of some diazepine derivatives under isothermal and non-isothermal conditions

Thermal analysis is one of the most widely used methods for studying the solid state of pharmaceutical substances. TG/DTG and DSC curves provide important information regarding the physical properties of the pharmaceutical compounds (stability, compatibility, polymorphism, kinetic analysis, phase transitions etc.). The purpose of a kinetic investigation is to calculate the kinetic parameters and the kinetic model for the studied process. The results are further used to predict the system’s behaviour in various circumstances. A kinetic study regarding the diazepam, nitrazepam and oxazepam thermal decomposition was performed, under non-isothermal and isothermal conditions and in a nitrogen atmosphere, for the temperature steps: 483, 498, 523, 538 and 553 K. The TG/DTG data were processed by three methods: isothermal model-fitting, Friedman’s isothermal-isoconversional and Nomen-Sempere non-parametric kinetics. In the model-fitting methods the kinetic triplets (f(α), A and E _a) that defines a single reaction step resulted in being at variance with the multi-step nature of diazepines decomposition. The model-free approach represented by isothermal and non-isothermal isoconversional methods, gave dependences of the activation energies on the extent of conversion. It is very difficult to obtain an accord with the similar data which resulted under non-isothermal conditions from a previous work. The careful treatment of the kinetic parameters obtained in different thermal conditions was confirmed to be necessary, as well as a different strategy of experimental data processing.     

2-Arylhydroxytyrosol derivatives via Suzuki-Miyaura cross-coupling

2-Arylhydroxytyrosol derivatives, a new class of hydroxytyrosol derivatives, have been prepared in high to excellent yields from the corresponding 2-chloro precursors via Suzuki-Miyaura cross-coupling with arylboronic acids containing electron-donating, electron-withdrawing, as well as ortho substituents. A remarkable halide effect has been observed. 2-Iodo- and 2-bromohydroxytyrosol derivatives have been found to be ineffective cross-coupling partners in many cases. The acetonide and carbonate protecting groups can be readily removed.     

Enzymatic Oxy- and Amino-Functionalization in Biocatalytic Cascade Synthesis: Recent Advances and Future Perspectives

Biocatalytic cascades are a powerful tool for building complex molecules containing oxygen and nitrogen functionalities. Moreover, the combination of multiple enzymes in one pot offers the possibility to minimize downstream processing and waste production. In this review, we illustrate various recent efforts in the development of multi-step syntheses involving C−O and C−N bond-forming enzymes to produce high value-added compounds, such as pharmaceuticals and polymer precursors. Both in vitro and in vivo examples are discussed, revealing the respective advantages and drawbacks. The use of engineered enzymes to boost the cascades outcome is also addressed and current co-substrate and cofactor recycling strategies are presented, highlighting the importance of atom economy. Finally, tools to overcome current challenges for multi-enzymatic oxy- and amino-functionalization reactions are discussed, including flow systems with immobilized biocatalysts and cascades in confined nanomaterials.     

LC–MS–MS Determination of Stabilizers and Explosives Residues in Hand-Swabs

The contribution of explosive trace detection in samples from the hands of suspects has been fundamental in several forensic cases involving terrorists. This paper describes a method for the rapid extraction and unequivocal confirmation of some high potential explosives (trinitrotoluene, cyclotrimethylenetrinitramine, pentaerythritol tetranitrate, nitroglycerin) and two stabilizer (diphenylamine and ethylcentralite) residues in hand-swabs using liquid chromatography–tandem mass spectrometry. The extraction procedure of the analytes from the swabs is realized by solvent elution and the extracts are directly analyzed. Recoveries from spiked swabs range from 78 to 96%; the limits of quantification are between 0.04 and 1.8 ng injected and the inter-day method precision is less than 15%. The developed procedure was applied to the detection of explosives traces in samples after handling tests.     

Synthesis and characterization of tribenzyltin(IV) and dibenzyltin(IV) complexes of 2-{[(2Z)-3-hydroxy-1-methyl- 2-butenylidene]amino}acetic acid: Crystal structure of tribenzyl{2-{[(2Z)-3-hydroxy-1-methyl-2-butenylidene] amino}acetato}tin(IV)

Reactions of equimolar quantities of potassium 2-{[(2Z)-3-hydroxy-1-methyl-2-butenylidene]amino}acetate, with R _n SnX_4?n (R: benzyl– and n=2 or 3) in methanol yielded products of compositions LHSn(PhCH₂)₃ and LSn(PhCH₂)₂, respectively. The complexes were characterized by microanalysis, IR, NMR (¹H, ¹³C, ¹¹⁹Sn) and ^119mSn Mössbauer spectroscopy. A full characterization of the structure of the complex, tribenzyl{2-{[(2Z)-3-hydroxy-1-methyl-2-butenylidene]amino}acetato}tin(IV), was carried out by single crystal X-ray crystallography. The compound exists as centrosymmetric dimers in which two ligand molecules bridge the two tin centres. Each of the tin atoms in the dimeric unit is five coordinate in an approximately trigonal bipyramidal configuration, with carbon atoms in the equatorial positions and oxygen atoms arranged axially.     

Conformational analysis of 2-substituted 1-nitro-and 1-bromo-1-nitroethenes

Conformational analysis of 2-trichloromethyl(ethoxycarbonyl)-1-nitro-and 2-trichloromethyl-(ethoxycarbonyl)-1-bromo-1-nitroethenes was performed using the dipole moment method, IR spectroscopy, and DFT quantum-chemical calculations (B3LYP/6-31G*). The nitro and ester (or trichloromethyl) groups in the molecules of these compounds were found to occupy trans positions with respect to the double C=C bond, i.e., the nitroalkenes have E, and their bromine-containing analogs, Z configuration; the compounds having an ethoxycarbonyl group are characterized by s-cis orientation of the C=C and C=O bonds.     

Flavonoids: chemical properties and analytical methodologies of identification and quantitation in foods and plants

Flavonoids have been recognised as one of the largest and most widespread groups of plant secondary metabolites, with marked antioxidant properties. The general name flavonoid refers to a class of more than 6500 molecules based upon a 15-carbon skeleton. In this paper a general overview of flavonoids, their classification, structures and analytical methods for their determination is presented.     

Poly[[tetra‐μ3‐acetato‐hexa‐μ2‐acetato‐diaqua‐μ2‐oxalato‐tetrapraseodymium(III)] dihydrate]

The title complex, {[Pr₄(C₂H₃O₂)₁₀(C₂O₄)(H₂O)₂]·2H₂O}_n, was synthesized under hydrothermal conditions from praseodymium acetate and the ionic liquid 1‐butyl‐3‐methylimidazolium chloride via an in situ oxalate‐ligand synthesis. The compound is a two‐dimensional polymer and in the structure presents tightly bound planes parallel to (100), which are in turn linked into a three‐dimensional network by hydrogen bonds involving both coordinated and solvent water molecules. The oxalate anion lies across an inversion centre and acts as a bridge between pairs of Pr atoms within a tetranuclear segment of the polymer.