Tricarbonylrhenium(I) complexes with thiosemicarbazone derivatives of 2-acetylpyridine and 2-pyridine formamide showing two unusual coordination modes of tridentate thiosemicarbazone ligands

[NEt(4)](2)[Re(CO)(3)Br(3)] reacts with 2-acetylpyridine phenylthiosemicarbazone (HL(1)) and 2-pyridine formamide thiosemicarbazone (HL(2)) under formation of air-stable, neutral rhenium(I) complexes of the compositions [Re(CO)(3)(L(1)-N,N,S)] and [Re(CO)(3)Br(HL(2)-N,N)]. Spectroscopic studies and X-ray crystallography show that the potentially tridentate thiosemicarbazones adopt unusual coordination modes. Whereas HL(1) deprotonates and binds to the metal in a nonplanar fashion, HL(2) acts as neutral N,N donor ligand. The bond lengths inside the chelate rings are almost uninfluenced by the overall bonding situation.     

Synthesis,crystal structure determination and pharmacological activity of 7,8,3′,4′-tetramethoxyisoflavone

7 The8,3′,4′-tetramethoxyisoflavone 2 was synthesized and its structure confirmed by X-ray crystallographic analysis. Pharmacological screening was carried out with this compound in order to assess its pharmacological profile. Isoflavone 2 possessed antiinflamatory activity in the carrageenan oedema test, with a dose-effect relationship comparable to that of hydroxylated flavonoids. It is noteworthy that 2 is one of the few isoflavones efficient as antiinflammatory with complete alkylation of hydroxyl groups.     

Synthesis of 4,4-diphenyl-7-oxodibenzodihydro-1,4-diazepinium salts

Conclusions The salt of a new completely aromatic ammonium cation, namely 4, 4-diphenyl-7-oxodibenzo-1, 4-dihydrodiazepinium iodide, was obtained, the structure of which was confirmed by qualitative tests with silver hydroxide, aqueous NaOH solution, and nitrosylsulfuric acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1096–1101, May, 1973.     

The very-low-pressure study of the kinetics and equilibrium: Cl + CH4 ⇄ CH3 + HCl at 298 K. The heat of formation of the CH3 radical

The bimolecular rate constant for the direct reaction of chlorine atoms with methane was measured at 25°C by using the very-low-pressure-pyrolysis technique. The rate constant was found to be In addition, the ratio k₁/k_?1 was observed with about 25% accuracy: K₁₍₂₉₈₎ = 1.3 ± 0.3. This gives a heat of formation of the methyl radical ΔH° _{f 298}(CH₃) = 35.1 ± 0.15 kcal/mol. A bond dissociation energy BDE (CH₃ ? H) = 105.1 ± 0.15 kcal/mol in good agreement with literature values was obtained.     

(Schiff base) divalent group 14 element species: manganese and iron complexes (Salen)M=Mn(Co)2(eta 5-C5H5) (M14 = Ge, Sn, Pb) and (Salen)Sn=Fe(CO)4

Syntheses of the (divalent group 14 species)dicarbonyl(cyclopentadienyl)manganese (Salen)M=Mn(CO)2(eta 5-C5H5) [M = Ge (1), Sn (2), Pb (3)] and [(Salen)tin(II)]tetracarbonyliron (Salen)Sn=Fe(CO)4 (4) are reported. The structures of 2 and 4 were determined by X-ray crystallography. The observed Sn-Mn bond length, 2.4428(7) A, is the shortest distance observed for this type of bond and corresponds to considerable multiple bonding between these atoms. In complex 4, the iron atom has a slightly distorted trigonal-bipyramidal coordination sphere; the (Salen)tin(II) ligand occupies an axial site, indicating that it functions in this complex as a strong sigma-donor and weak pi-acceptor ligand. Crystal data for 2: orthorhombic, P2(1)2(1)2(1), a = 6.972(1) A, b = 15.678(2) A, c = 19.032(2) A, alpha = beta = gamma = 90 degrees, V = 2080.3(5) A3, T = 173(2) K, Z = 4. Crystal data for 4: triclinic, P1, a = 8.465(2) A, b = 9.795(3) A, c = 13.213(4) A, alpha = 105.55(3) degrees, beta = 105.15(3) degrees, gamma = 100.84(3) degrees, V = 978.7(5) A3, T = 173(2) K, Z = 2.     

Determination of 40 currently used pesticides in airborne particulate matter (PM 10) by microwave-assisted extraction and gas chromatography coupled to triple quadrupole mass spectrometry

A confirmatory and sensitive procedure has been developed for the determination of 40 currently used pesticides (CUPs) in airborne particulate matter (PM 10) at trace level. The proposed method includes extraction of PM 10-bound pesticides by microwave-assisted extraction (MAE) followed by a gel permeation chromatography (GPC) clean-up and determination by GC-MS/MS. The injection mode and the main parameters in MS/MS were optimized. The matrix effect was also evaluated. Recoveries ranged from 70 to 120% except for pyrimethanil and pirimicarb. The limit of quantification (LOQ) ranged from 1.32 to 39.47 pg m(-3), when air volumes of 760 m(3) were collected. The method was applied to 38 samples collected from a rural station belonging to the atmospheric monitoring network of the Regional Valencia Government (Spain) during April-June 2010. Eighteen out of 40 pesticides investigated were found in at least one sample (bifenthrin, chlorothalonil, chlorpyriphos-e, chlorpyriphos-m, clorpropham, diazinon, dicofol, diphenylamine, fipronil, fludioxonil, folpet, malathion, metalaxyl, penconazole, quinoxyfen, triadimefon, trifluralin, and vinclozoline), with concentrations ranging from 1.32 to 625.80 pg m(-3).     

A survey of the parallel performance and accuracy of Poisson solvers for electronic structure calculations

We present an analysis of different methods to calculate the classical electrostatic Hartree potential created by charge distributions. Our goal is to provide the reader with an estimation on the performance—in terms of both numerical complexity and accuracy—of popular Poisson solvers, and to give an intuitive idea on the way these solvers operate. Highly parallelizable routines have been implemented in a first‐principle simulation code (Octopus ) to be used in our tests, so that reliable conclusions about the capability of methods to tackle large systems in cluster computing can be obtained from our work. © 2013 Wiley Periodicals, Inc.     

Polymorph of {2‐[(2‐hydroxyethyl)iminiomethyl]phenolato‐κO}dioxido{2‐[(2‐oxidoethyl)iminomethyl]phenolato‐κ3O,N,O′}molybdenum(VI)

A second polymorphic form (form I) of the previously reported compound {2‐[(2‐hydroxyethyl)iminiomethyl]phenolato‐κO}dioxido{2‐[(2‐oxidoethyl)iminomethyl]phenolato‐κ³O,N,O′}molybdenum(VI) (form II), [Mo(C₉H₉NO₂)O₂(C₉H₁₁NO₂)], is presented. The title structure differs from the previously reported polymorph [Głowiak, Jerzykiewicz, Sobczak & Ziółkowski (2003). Inorg. Chim. Acta, 356 , 387–392] by the fact that the asymmetric unit contains three molecules linked by O—H...O hydrogen bonds. These trimeric units are further linked through O—H...O hydrogen bonds to form a chain parallel to the [11] direction. As in the previous polymorph, each molecule is built up from an MoO₂²⁺ cation surrounded by an O,N,O′‐tridentate ligand (O⁻C₆H₄CH=NCH₂CH₂O⁻) and weakly coordinated by a second zwitterionic ligand (O⁻C₆H₄CH=N⁺HC₂H₄OH). All complexes are chiral with the absolute configuration at Mo being C or A. The main difference between the two polymorphs results from the alternation of the chirality at Mo within the chain.     

Investigation of the asymmetric Birch reduction-alkylation of a chiral 5-arylbenzamide containing a carbamate group

The synthesis and asymmetric Birch reduction-alkylation of chiral benzamide 17 are described. Birch reductive alkylation of benzamide 17 was optimized to give the corresponding cyclohexa-1,4-diene products in 66-78% isolated yield and with high diastereoselectivity (dr: >98:2). The effects of performing the reduction in the presence and in the absence of tert-butyl alcohol are discussed.