Search results for "acetonitrile"
showing 10 items of 1007 documents
Head-to-tail connected double calix[4]arenes
1997
New macrotricyclic compounds consisting of two calix[4]arene substructures connected by aliphatic chains of various length (three to five carbon atoms) between two oppositep-positions and two distal phenolic oxygens have been synthesized. Starting withp-tert-butyl-calix[4]arene, two O-protected phenolic units are attachedvia ether links in 1,3-position by reaction with the corresponding tosylates. After deprotection, the new calix[4]arene is formed by fragment condensation with 2,6-bisbromomethylated 4-alkylphenols. The structure of one example (8c) has been confirmed by single crystal X-ray analysis. Both calixarene parts assume the cone conformation, a molecule of acetonitrile being inclu…
Crystal Structures and Thermal Behavior of Isostructural Bis(dibenzyldimethylammonium) Tetrachlorometallate [M = Mn(II), Co(II), Ni(II) and Zn(II)] S…
2007
Five isostructural bis(dibenzyldimethylammonium) tetrachlorometallate solvate complexes [M = Mn(II), Co(II), Ni(II) or Zn(II)] were crystallized from acetonitrile and/or methanol solutions. The crystal structures are compared to those of the analogous, isostructural copper compounds (X = Cl or Br) reported earlier. The complexes crystallize in the monoclinic space group P21/n with Z = 4, and unit cell dimensions of a ≈ 14.1, b ≈ 16.1, c ≈ 15.7 °A and β ≈ 108 - 109°. The asymmetric unit of these compounds contains one MCl4 2− anion, two Bz2Me2N+ cations in theW-conformation and one half of a disordered solvent molecule (acetonitrile or methanol). The geometry of the MCl4 2− anion is close to…
Synthesis, crystal structure and magnetic properties of novel heterobimetallic malonate-bridged MIIReIV complexes (M = Mn, Fe, Co and Ni).
2008
Five novel ReIV-MII bimetallic complexes of formula [ReCl4(mu-mal)M(dmphen)2].MeCN [M = Co (1), Fe (2) and Ni (3)], [ReCl4(mu-mal)Ni(dmphen)(MeCN)2(H2O)].(MeCN)0.5(H2O)0.5 (4), and [ReCl4(mu-mal)Mn(dmphen)(H2O)2].dmphen.MeCN.H2O (5) (mal = malonate dianion, dmphen = 2,9-dimethyl-1,10-phenanthroline) have been synthesized, and the structures of 1, 2, 4, and 5 determined by single-crystal X-ray diffraction. The structures of 1 and 2 consist of neutral [ReCl4(mu-mal)M(dmphen)2] dinuclear units where the metal ions are linked through a malonate ligand which adopts simultaneously the bidentate (at ReIV) and monodentate (at MII) coordination modes. The bridging carboxylate-malonate group in them …
4,2-Ribbon like ferromagnetic cyano-bridged FeIII2NiII chains: a magneto-structural study
2007
The low-spin iron(III) complex AsPh(4)[Fe(III)(bpy)(CN)(4)].CH(3)CN (1) [AsPh(4) = tetraphenylarsonium cation] and the heterobimetallic chains [{Fe(III)(L)(CN)(4)}(2)Ni(II)(H(2)O)(2)].4H(2)O with L = bpy (2) and phen (3) [bpy = 2,2'-bipyridine and phen = 1,10-phenanthroline] have been prepared and their structures determined by X-ray diffraction methods. The structure of 1 consists of mononuclear [Fe(bpy)(CN)(4)](-) anions, tetraphenylarsonium cations and acetonitrile molecules of crystallization. The iron(III) is hexacoordinated with two nitrogen atoms of the bidentate bpy and four carbon atoms of four terminal cyanide groups building a distorted octahedral surrounding around the metal ato…
Coordination versatility of 1,3-bis[3-(2-pyridyl)pyrazol-1-yl]propane: Co(II) and Ni(II) complexes
2006
Abstract The ligand 1,3-bis[3-(2-pyridyl)pyrazol-1-yl]propane (L8) has afforded six-coordinate monomeric and dimeric complexes [(L8)CoII(H2O)2][ClO4]2 (1), [(L8)NiII(MeCN)2][BPh4]2 (2), [(L8)NiII(O2CMe)][BPh4] (3), and [ ( L 8 ) 2 Co 2 II ( μ - O 2 CMe ) 2 ] [ BPh 4 ] 2 ( 4 ) . The crystal structures of 1, 2 · MeCN, 3, and 4 revealed that the ligand L8 is flexible enough to expand its coordinating ability by fine-tuning the angle between the chelating fragments and hence folds around cobalt(II)/nickel(II) centers to act as a tetradentate chelate, allowing additional coordination by two trans-H2O, cis-MeCN, and a bidentate acetate affording examples of distorted octahedral Co II N 2 ( pyridy…
Study of passive sampling of polycyclic aromatic hydrocarbons in gas phase using Amberlite XAD resins as filling materials of semipermeable membranes
2013
Abstract In this work, a study was performed to evaluate the use of Amberlite XAD resins (XAD-2, XAD-4 and XAD-16), for the first time, as filling materials for low-density polyethylene membranes, which will be inserted as passive samplers for polycyclic aromatic hydrocarbons (PAHs) in gas phase. The use of samplers deployed for 48 h evidenced a relative capability to retain the compounds under study. A detailed study was performed to evaluate the recovery of analytes from the sampler through microwave-assisted extraction by using acetonitrile. A clean-up step using alumina-C18 cartridges was necessary before determination of the PAHs by high performance liquid chromatography with fluoresce…
Fast Separation and Determination of Sterols in Vegetable Oils by Ultraperformance Liquid Chromatography with Atmospheric Pressure Chemical Ionizatio…
2010
A method for the determination of sterols in vegetable oils by ultraperformance liquid chromatography (UPLC) with atmospheric pressure chemical ionization mass spectrometry detection has been developed. The separation of sterols was optimized in terms of mobile phase composition, column temperature and flow rate. The optimal conditions were achieved using an Acquity UPLC BEH C18 column (50 x 2.1 mm, 1.7 microm) with a mobile phase consistent of acetonitrile/water (0.01% acetic acid) using a linear gradient, at a flow rate of 0.8 mL min(-1) and column temperature of 10 degrees C, giving a total analysis time below 5 min. The determination was performed in selective ion recording mode. The li…
Automated Fourier Transform near Infrared Determination of Buprofezin in Pesticide Formulations
2005
An automated procedure has been developed for Fourier transform near infrared (FT-NIR) determination of buprofezin in pesticide formulations. This methodology is based on on-line pesticide extraction with acetonitrile from solid samples and its determination by using peak area absorbance measurements between 2147 and 2132 nm, corrected with a horizontal baseline established at 2091 nm. The repeatability, as a relative standard deviation of five independent analyses of 18.9 mg g−1 of buprofezin, was 0.06% and the limit of detection 5 mg L−1. The reagent consumption was clearly reduced compared with a chromatographic reference procedure from 40.4 mL acetonitrile per sample, required by high …
Near infrared determination of Diuron in pesticide formulations
2005
Abstract A simple, fast and environmentally friendly near infrared (NIR)-based methodology was developed for Diuron determination in pesticide formulations. This methodology was based on the pesticide extraction with acetonitrile and subsequent transmittance measurement determination by peak area measurement between 2021 and 2047 nm, corrected with a single point baseline established at 2071 nm. The repeatability, as relative standard deviation of five independent analysis of a 15.3 mg g −1 Diuron standard was 0.03% and the limit of detection 0.013 mg g −1 . The reagent consumption was clearly reduced in front of a chromatographic reference procedure from 39.1 ml acetonitrile per sample, re…
Mid- and near-infrared determination of metribuzin in agrochemicals
2008
Abstract Two infrared-based methodologies were developed for metribuzin determination in pesticide formulations after extraction with acetonitrile. Fourier transform mid infrared (MIR) procedure was based on peak area measurements between 1692 and 1670 cm −1 corrected with a baseline fixed at 1877 cm −1 . Fourier transform near infrared (NIR) determination was made by measuring the peak area between 6498 and 6332 cm −1 corrected using a two points baseline defined between 6570 and 6212 cm −1 . Repeatability, as relative standard deviation, of 5 independent measurements at mg g −1 concentration level was 0.3% and 0.03% for MIR and NIR, respectively, and limit of detection values of 9 and 17 …