Evidence for cobalt-cobalt bond homolysis and wavelength-dependent CO loss in (μ2-alkyne)Co2(CO)6 complexes

Time-resolved infrared spectroscopy was used to probe the photochemistry of three (μ(2)-alkyne)Co(2)(CO)(6) complexes. The data indicate the formation of a triplet diradical species, with lifetimes in the range 38-71 ps. Theoretical calculations support these experimental findings. No evidence for the CO loss species, (μ(2)-alkyne)Co(2)(CO)(5), was observed, and this is rationalized by the low quantum yield for this process at the excitation wavelengths used.     

A bis(amine–carboxylate) copper(II) coordination compound forms a two‐dimensional metal–organic framework when crystallized from water and methanol

When {2,2′‐[(2‐methyl‐2‐nitropropane‐1,3‐diyl)diimino]diacetato}copper(II), [Cu(C₈H₁₃N₃O₆)], (I), was crystallized from a binary mixture of methanol and water, a monoclinic two‐dimensional water‐ and methanol‐solvated metal–organic framework (MOF) structure, distinctly different from the known orthorhombic one‐dimensional coordination polymer of (I), was isolated, namely catena‐poly[[copper(II)‐μ₃‐2,2′‐[(2‐methyl‐2‐nitropropane‐1,3‐diyl)diimino]diacetato] methanol 0.45‐solvate 0.55‐hydrate], {[Cu(C₈H₁₃N₃O₆)]·0.45CH₃OH·0.55H₂O}_n, (II). The monoclinic structure of (II) comprises centrosymmetric dimers stabilized by a dative covalent Cu₂O₂ core and intramolecular N—H...O hydrogen bonds. Each dimer is linked to four neighbouring dimers via symmetry‐related (opposing) pairs of bridging carboxylate O atoms to generate a `diamondoid' net or two‐dimensional coordination network. Tight voids of 166 ų are located between these two‐dimensional MOF sheets and contain a mixture of water and methanol with fractional occupancies of 0.55 and 0.45, respectively. The two‐dimensional MOF sheets have nanometre‐scale spacings (11.2 Å) in the crystal structure. Hydrogen‐bonding between the methanol/water hydroxy groups and a Cu‐bound bridging carboxylate O atom apparently negates thermal desolvation of the structure below 358 K in an uncrushed crystal of (II).     

Flow-injection in-line complexation for ion-pair reversed phase high performance liquid chromatography of some metal-4-(2-pyridylazo) resorcinol chelates

Flow injection (FI) was coupled to ion-pair reversed phase high performance liquid chromatography (IP-RPHPLC) for the simultaneous analysis of some metal-4-(2-pyridylazo) resorcinol (PAR) chelates. A simple reverse flow injection (rFI) set-up was used for in-line complexation of metal-PAR chelates prior to their separation by IP-RPHPLC. The rFI conditions were: injection volume of PAR 85 μL, flow rate of metal stream 4.5 mL min⁻¹, concentration of PAR 1.8 × 10⁻⁴ mol L⁻¹ and the mixing coil length of 150 cm. IP-RPHPLC was carried out using a C₁₈ μBondapak column with the mobile phase containing 37% acetonitrile, 3.0 mmol L⁻¹ acetate buffer pH 6.0 and 6.2 mmol L⁻¹ tetrabutylammonium bromide (TBABr) at a flow rate of 1.0 mL min⁻¹ and visible detection at 530 and 440 nm. The analysis cycle including in-line complexation and separation by IP-RPHPLC was 16 min, which able to separate Cr(VI) and the PAR chelates of Co(II), Ni(II) and Cu(II).     

The effect of cationic disorder on the optical and electrochemical behavior of nanocrystalline ZnO preparedfrom peroxide precursors

The relation between particle size and the optical and electrochemical behavior of nanocrystalline ZnO was studied on materials prepared by the thermal decomposition of zinc peroxide. The formation of zinc oxide starts at 180°C and yields particles of characteristic size bigger than 10 nm. Smaller particles (r∼2–5 nm) may be prepared at reduced pressure and at a temperature of 150°C. The particle radius of synthesized nanocrystals increases proportionally to synthesis temperature. Regardless of actual particle size, synthesized ZnO samples show cationic disorder, with Zn distributed between 2b and 2a sites. The fraction of “octahedrally” coordinated Zn in 2a position decreases with increasing synthesis temperature. Zn disorder causes a narrowing of band gap, which results in the “red shift” of the absorption edge in the UV–Vis spectra of prepared samples with respect to bulk ZnO. The effect of the disorder on the band gap width is partially compensated by quantum size effects when the characteristic particle size drops below 5 nm. A decrease in particle size results in an asymmetric shift of valence and conduction band edges, which can be assigned to uneven effective masses of electrons and holes in nanocrystalline ZnO. Prepared nanocrystalline samples were (photo)electrochemically active; their activity, however, decreases with particle size.

Coated wire thorium ion selective electrode: Part I

Coated wire ion selective electrode for thorium ion selective potentiometry was developed. Thorium ion selective coated wire electrodes were prepared by depositing a membrane comprising of Aliquat-336 loaded with Th(NO₃)₆²⁻ ions and poly vinyl chloride in varying proportion. A linear near-Nernstian response with a slope of −29.5 ± 0.3 mV over thorium concentration range of 1 × 10⁻¹–3 × 10⁻⁵ M in constant total nitrate concentration of 6 M was obtained for the electrodes of almost all the composition studied. In spite of small drift in response potential from composition to composition, day to day as well as from electrode to electrode, the slope of potential response line was constant within experimental error. Moreover, the electrode once prepared could be conveniently used over a period of one and half month.     

Testing of the influenza virus purification by CIEF

In virological practice, the pre‐concentration, purification and subsequent determination of the purity and concentration of the viruses from the cultural medium and/or from the real sample are required. The conventional techniques used today are equipment demanding, time‐consuming and laborious. In this study, the CIEF of influenza viruses with UV detection has been developed and subsequently used to test the purification of the virus from the biological samples. The equine and swine influenza viruses present in infected allantoic fluid of specific pathogen free embryonated chicken eggs were precipitated by using PEG 6000 and sodium chloride. The precipitated viruses were centrifuged at 14 000×g, and the impurities of different densities were removed by using the sucrose gradients. The efficiency of the virus purification technique was examined by the CIEF and compared to the results of real‐time PCR. The pIs of both influenza viruses were determined. Simultaneously, the CIEF was found to be a suitable method for the rapid testing of the efficiency of the virus purification.     

An evaluation of primary water standards by TG/DTA and vapor sorption analysis

The thermal behavior of [Ca(H₂O)₃(2,3-pydcH)₂] _n (I), [Cd(H₂O)₃(2,3-pydc)] _n (II), and [Cd(H₂O)₆][Cd(2,3-pydcH)₃]₂ (III) complexes with pyridine-2,3-dicarboxylic acid was monitored by TG, DTG, and DSC analysis, where 2,3-pydcH—mono deprotonated pyridine-2,3-dicarboxylic acid and 2,3-pydc—doubly deprotonated dicarboxylate anion. Thermal decomposition of these compounds go through one or two dehydratation stages, followed by the loss of organic matter. The final decomposition products are found to be the corresponding metal oxides. The possible scheme of destruction of the complexes have been used to reveal the relationships between stability and molecular structure.     

Binding abilities of copper to phospholipids and transport of oxalate

Monatshefte für Chemie - Chemical Monthly - Cu(II) creates complexes with dipalmitoylphosphatidylcholine (lecithin), which are detectable using electrospray ionization mass spectrometry....     

Characterization and use of a Raman liquid-core waveguide sensor using preconcentration principles

A novel Raman sensor using a liquid-core optical waveguide is reported, implementing a Teflon-AF 2400 tube filled with water. An aqueous analyte mixture of benzene, toluene and p-xylene was introduced using a 1000 μl sample loop to the liquid-core waveguide (LCW) sensor and the analytes were preconcentrated on the inside surface of the waveguide tubing. The analytes were then eluted from the waveguide using an acetonitrile-water solvent mixture injected via a 30 μl eluting solvent loop. The preconcentration factor was experimentally determined to be 14-fold, in reasonable agreement with the theoretical preconcentration factor of 33 based upon the sample volume to elution volume ratio. Raman spectra of benzene, toluene and p-xylene were obtained during elution. It was found that analytically useful Raman signals for benzene, toluene and p-xylene were obtained at 992, 1004 and 1206 cm⁻¹, respectively. The relative standard deviation of the method was 3% for three replicate measurements. The limit of detection (LOD) was determined to be 730 ppb (parts per billion by volume) for benzene, exceptional for a system that does not resort to surface enhancement or resonance Raman approaches. The Raman spectra of these test analytes were evaluated for qualitative and quantitative analysis utility.