ZnII and CuII complexes generated from 5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione

A new 1,3,4‐oxadiazole‐containing bispyridyl ligand, namely 5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione (L), has been used to create the novel complexes tetranitratobis{μ‐5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione}zinc(II), [Zn₂(NO₃)₄(C₁₄H₁₂N₄OS)₂], (I), and catena‐poly[[[dinitratocopper(II)]‐bis{μ‐5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione}] nitrate acetonitrile sesquisolvate dichloromethane sesquisolvate], {[Cu(NO₃)(C₁₄H₁₂N₄OS)₂]NO₃·1.5CH₃CN·1.5CH₂Cl₂}_n, (II). Compound (I) presents a distorted rectangular centrosymmetric Zn₂L₂ ring (dimensions 9.56 × 7.06 Å), where each Zn^II centre lies in a {ZnN₂O₄} coordination environment. These binuclear zinc metallocycles are linked into a two‐dimensional network through nonclassical C—H...O hydrogen bonds. The resulting sheets lie parallel to the ac plane. Compound (II), which crystallizes as a nonmerohedral twin, is a coordination polymer with double chains of Cu^II centres linked by bridging L ligands, propagating parallel to the crystallographic a axis. The Cu^II centres adopt a distorted square‐pyramidal CuN₄O coordination environment with apical O atoms. The chains in (II) are interlinked via two kinds of π–π stacking interactions along [01]. In addition, the structure of (II) contains channels parallel to the crystallographic a direction. The guest components in these channels consist of dichloromethane and acetonitrile solvent molecules and uncoordinated nitrate anions.     

A new three‐dimensional silver(I) coordination framework with a diamondoid topology constructed from 2‐(pyridin‐4‐yl)‐1H‐imidazole‐4,5‐dicarboxylic acid

The title compound, poly[[μ₄‐5‐carboxy‐4‐carboxylato‐2‐(pyridin‐4‐yl)‐1H‐imidazol‐1‐ido]disilver(I)], [Ag₂(C₁₀H₅N₃O₄)]_n, was synthesized by reacting silver nitrate with 2‐(pyridin‐4‐yl)‐1H‐imidazole‐4,5‐dicarboxylic acid (H₃PyIDC) under hydrothermal conditions. The asymmetric unit contains two crystallographically independent Ag^I cations and one unique HPyIDC²⁻ anion. Both Ag^I cations are three‐coordinated in distorted T‐shaped coordination geometries. One Ag^I cation is coordinated by one N and two O atoms from two HPyIDC²⁻ anions, while the other is bonded to one O and two N atoms from two HPyIDC²⁻ anions. It is interesting to note that the HPyIDC²⁻ group acts as a μ₄‐bridging ligand to link the Ag^I cations into a three‐dimensional framework, which can be simplified as a diamondoid topology. The thermal stability and photoluminescent properties of the title compound have also been studied.     

Characterization of Nineteen Impurities in Roxithromycin by HPLC/TOF and Ion Trap Mass Spectrometry

Nineteen impurities in roxithromycin drug substance made in China were separated and identified by HPLC–MSⁿ (TOF and TRAP) for the further improvement of official monographs in Pharmacopoeias. The fragmentation patterns and structural assignment of these impurities were studied. The column was Shim VP-ODS (250 × 4.6 mm, 5 μm). The mobile phase was 10 m mol L⁻¹ ammonium acetate and 0.1 % formic acid aqueous solution-acetonitrile (62.5:37.5). In positive mode, full scan LC–MS was first performed to obtain the m/z value of the protonated molecules and formulas of all detected peaks on Agilent 6538Q TOF high resolution mass spectrometer. LC–MS-MS and LC–MS-MS–MS were then carried out on the compounds of interest on AB SCIEX 4000 Q TRAP™ composite triple quadrupole/linear ion trap tandem mass spectrometer. The complete fragmentation patterns of nineteen impurities were studied and used to obtain information about the structures of these impurities. The structures of nineteen impurities in roxithromycin drug substance were deduced based on the HPLC–MSⁿ data, in which nine impurities were novel impurities.

     

Synthesis and Characterization of Iron Nanowires

The iron nanowires can be fabricated via the process in which sodium borohydride reduces iron salts in external magnetic field. The iron nanowires are found to be covered by passivated layers of iron oxide which prevent the oxidation of iron nanowires. In this process, the boron will include in iron nanowires. The average length and diameter of iron nanowires is around 1.2 micrometers and 60 nanometers, respectively. According to ICP results, the contents of B and Fe are about 1.98 wt% and 87.04 wt%, respectively, in iron nanowires. A wide variety of equipment is used to investigate the morphological, microchemical, and structural characteristics of the newly synthesized iron nanowires ––– e.g., XRD, FE‐SEM, HR‐TEM, VSM and XANES. XANES analysis indicates the boron in iron nanowires exists in the form of B₂O₃. The saturation magnetization and the coercive force of iron nanowires are 157.93 emu/g and 9.74 Oe, respectively. In‐situ images of synthesized iron nanowires during reduction process in magnetic field are observed by NSRRC transmission X‐ray microscope. Thus, this study develop a novel process to produce iron nanowires with large quantitates and can control its length and diameter by various the concentration of precursors for various applications.     

Design,Synthesis, and Antifungal Activities of New β‐Methoxyacrylate Analogues

Strobilurins have become one of the most important classes of agricultural fungicides. To search for new strobilurin derivatives with high activity against resistant pathogens, a series of new β‐methoxyacrylate analogues containing substituted pyrimidine in the side chain with strobilurin pharmacophore were synthesized and their biological activities were tested. The compounds were confirmed and characterized by ¹H‐NMR, elemental analysis and mass spectroscopy. The bioassays indicated that most of the compounds 1 exhibited potent antifungal activities against Colletotrichum orbiculare, Botrytis cinerea Pers and Phytophthora capsici Leonian at a concentration of 50 μg mL^?1. Notably, compound 1b (R = 2,5‐dimethylphenyl) showed better antifungal activity against all the tested fungi than the commercial strobilurin fungicide azoxystrobin.     

Graphene as Solid-Phase Extraction Adsorbent for CZE Determination of Sulfonamide Residues in Meat Samples

A solid-phase extraction (SPE) using graphene as adsorbent coupled with capillary zone electrophoresis method was developed for the determination of four sulfonamide residues (sulfadimidine, sulfadimethoxine, sulfathiazole and sulfadiazine) in meat sample. Several condition parameters, such as elution solvents and volumes, sample pH and sample volume were optimized to obtain high SPE recoveries and extraction efficiency. Intra-day precisions of sulfonamides were in the range of 2.5–2.6 % and the inter-day precisions of sulfonamides were in the range of 2.6–3.4 %. Recoveries were 60.9–66.6 % for sulfadiazine and 86.1–111.4 % for other three sulfonamides in spiked meat sample. The developed method was successfully applied for the determination of sulfonamides in meat samples.     

Two New Abietane Diterpenoids from the Roots of Tripterygium wilfordii Hook. f.

Two new abietane‐type diterpenoids, named triptobenzene R ( 1 ) and triptobenzene S ( 2 ), together with three known abietane‐type diterpenoids, triptophenolide ( 3 ), triptonodiol ( 4 ), and triptonoterpene methyl ether ( 5 ), were isolated from the roots of Tripterygium wilfordii Hook . f. Their structures and relative configurations were established by detailed spectral studies, including 1D‐ and 2D‐NMR (HSQC, HMBC, and NOESY), and HR‐ESI‐TOF‐MS, and by comparison with published data. Their absolute configurations were assigned by the CD technique, applied for the first time to abietane diterpenes from Tripterygium wilfordii. Compound 2 is the first abietane‐type norditerpenoid isolated from the genus Tripterygium.     

Atmospheric degradation mechanisms of a simulant organophosphorus pesticide isopropyl methyl methylphosphonate: A theoretical consideration

Calculations using density functional theory were performed to explore the mechanisms for atmospheric degradation of isopropyl methyl methylphosphonate (IMMP). The potential energy surface profiles for OH‐initiated reaction of IMMP were constructed, and all possible degradation channels were considered. Rate constants were further calculated using transition state theory. It was established from these calculations that H‐abstractions from alkyl groups have much lower energy barriers than substitutions of alkoxyl groups, and four possible H‐abstraction channels are competitive. Investigations into the secondary reactions under the presence of O₂/NO were also performed. It is shown that O₂ addition, reaction of peroxide radicals with NO to form RO radicals, and removal of ·RO are the major degradation pathways for alkyl radicals. Four selected products, CH₃OP(O)(CH₃)OC(O)CH₃, CH₃OP(O)(O)CH₃, (CH₃)₂CHOP(O)(CH₃)OH, and (CH₃)₂CHOP(O)(CH₃)OCH?O, are predicted to be the major products in this study. © 2013 Wiley Periodicals, Inc.     

Atom-Economic Route to Densely Functionalized Thiophenes via Base-Catalyzed Rearrangement of 5-Propargyl-2H-thiopyran-4(3H)-ones

An atom-economic route to densely functionalized thiophenes has been developed via base-catalyzed rearrangement of 5-propargyl-2H-thiopyran-4(3H)-ones involving tandem retro-thio Michael addition, propargyl isomerization, and intramolecular thio-addition to allenes.