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441.
Lara C. Spencer Shu A. Yao John F. Berry Ilia A. Guzei 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(7):m197-m199
The title compound, [Ni(C45H28N4O)], crystallizes in the space group I2d and resides on a crystallographic fourfold rotoinversion axis with only a quarter of the complex in the asymmetric unit. The complex displays positional disorder as the one aldehyde group on the ligand can be located at four different positions. It was necessary to model this as compositional disorder to obtain a correct model and refinement. The practical approach to the refinement is explained. 相似文献
442.
Campbell AN White PB Guzei IA Stahl SS 《Journal of the American Chemical Society》2010,132(43):15116-15119
Pd-catalyzed C-H oxidation reactions often require the use of oxidants other than O(2). Here we demonstrate a ligand-based strategy to replace benzoquinone with O(2) as the stoichiometric oxidant in Pd-catalyzed allylic C-H acetoxylation. Use of 4,5-diazafluorenone (1) as an ancillary ligand for Pd(OAc)(2) enables terminal alkenes to be converted to linear allylic acetoxylation products in good yields and selectivity under 1 atm O(2). Mechanistic studies have revealed that 1 facilitates C-O reductive elimination from a π-allyl-Pd(II) intermediate, thereby eliminating the requirement for benzoquinone in this key catalytic step. 相似文献
443.
Ilia A. Guzei Lara C. Spencer Michael K. Ainooson James Darkwa 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(11):m336-m338
The title compound, [CoCl2(C11H20ClN2)2], forms two intramolecular hydrogen bonds [graph set S(5)] between the N atoms of the pyrazole ligands and the chloride ligands. This hydrogen‐bonding motif is uncommon among related compounds but occurs here because of the bulk of tert‐butyl substituents on the pyrazole ligands which shield the central metal atom to a significantly larger extent than pyrazole ligands with smaller 3,5‐substituents. 相似文献
444.
Polyna V. Anikina Alexey A. Markov Mikhail V. Patrakeev Ilia A. Leonidov Victor L. Kozhevnikov 《Solid State Sciences》2009,11(6):1156-1162
The conductivity is measured in the series of solid solutions SrFe1 ? xNbxO3 ? δ, where x = 0.05, 0.1, 0.2, 0.3, 0.4, within the oxygen partial pressure limits 10?18–0.5 atm and temperature range 650–950 °C. The contributions to the total conductivity from oxygen ions, electrons and electron holes are obtained based on their different pressure dependences. The doped derivative with x = 0.1 is found to be a singular composition where ion conductivity attains a maximal value while activation energy for ion transport is minimal. This peculiar behavior is attributed to formation of favorable microstructure in the oxide. The deeper doping results in deterioration of ion transport, which is explained by oxygen vacancy filling. It is shown that replacement of iron for niobium favors enhanced thermodynamic stability towards reduction. The oxygen permeability is evaluated from the conductivity data, and it achieves rather high values in the doped derivatives. These oxides can, therefore, be recommended for further evaluation as oxygen separating membrane materials for partial oxidation of natural gas. 相似文献
445.
G. Vlase T. Vlase N. Doca M. Perţa G. Ilia N. Plesu 《Journal of Thermal Analysis and Calorimetry》2009,97(2):473-478
Samples of an organic–inorganic hybrid were prepared by solvolysis and polycondensation in formic acid of tetraethoxysilane
and diethylbenzyl phosphonate, simultaneous with the oxidative polymerization of aniline. The thermal behavior of the samples
in dynamic air atmosphere and non-isothermal conditions was determined by a coupled thermogravimetric/evolved gas analysis.
Two significant thermal events were established: the elimination from the polymeric matrix of low mass molecules, respectively
the thermooxidative degradation of the organic part of the matrix. The kinetic analysis was performed with the Flynn-Wall-Ozawa,
Friedman and modified Non-Parametric-Kinetic methods. Only the last one allowed an objective analysis of the first process
as a process of two simultaneous thermally induced phenomena with the kinetic functions of the type αm(1 − α)n. 相似文献
446.
447.
Aurelia Visa Maria Mracec Bianca Maranescu Valentin Maranescu Gheorghe Ilia Adriana Popa Mircea Mracec 《Chemistry Central journal》2012,6(1):1-8
Background
Biosensors have attracted increasing attention as reliable analytical instruments in in situ monitoring of public health and environmental pollution. For enzyme-based biosensors, the stabilization of enzymatic activity on the biological recognition element is of great importance. It is generally acknowledged that an effective immobilization technique is a key step to achieve the construction quality of biosensors.Results
A novel disposable biosensor was constructed by immobilizing laccase (Lac) with silica spheres on the surface of multi-walled carbon nanotubes (MWCNTs)-doped screen-printed electrode (SPE). Then, it was characterized in morphology and electrochemical properties by scanning electron microscopy (SEM) and cyclic voltammetry (CV). The characterization results indicated that a high loading of Lac and a good electrocatalytic activity could be obtained, attributing to the porous structure, large specific area and good biocompatibility of silica spheres and MWCNTs. Furthermore, the electrochemical sensing properties of the constructed biosensor were investigated by choosing dopamine (DA) as the typical model of phenolic compounds. It was shown that the biosensor displays a good linearity in the range from 1.3 to 85.5 ??M with a detection limit of 0.42 ??M (S/N = 3), and the Michaelis-Menten constant (Km app) was calculated to be 3.78 ??M.Conclusion
The immobilization of Lac was successfully achieved with silica spheres to construct a disposable biosensor on the MWCNTs-doped SPE (MWCNTs/SPE). This biosensor could determine DA based on a non-oxidative mechanism in a rapid, selective and sensitive way. Besides, the developed biosensor could retain high enzymatic activity and possess good stability without cross-linking reagents. The proposed immobilization approach and the constructed biosensor offer a great potential for the fabrication of the enzyme-based biosensors and the analysis of phenolic compounds. 相似文献448.
Lara C. Spencer Ilia A. Guzei Tebogo V. Segapelo James Darkwa 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(11):m317-m319
The title compound, [PdCl2(C21H17N3)], is a member of a sequence of Pd, Pt and Co dichloride complexes bearing polysubstituted (pyrazol‐1‐ylmethyl)pyridine ligands. It is shown that there is a correlation between the steric bulkiness of the bidentate (pyrazol‐1‐ylmethyl)pyridine ligands and the Pd—Npyrazole distances, i.e. the larger the ligand, the longer the bond. In contrast, no trend is observed between the steric properties of the ligand and the Pd—Npyridine bond lengths. 相似文献
449.
An efficient asymmetric synthesis of the 22nd amino acid L-pyrrolysine has been accomplished. The key stereogenic centers were installed by an asymmetric conjugate addition reaction. A Staudinger/aza-Wittig cyclization was used to form the acid-sensitive pyrroline ring. Pyrrolysine was synthesized in 13 steps in 20% overall yield. 相似文献
450.
Ilia Rodushkin Emma Engström Douglas C. Baxter 《Analytical and bioanalytical chemistry》2010,396(1):365-377
In theory, state of the art inductively coupled plasma mass spectrometry (ICP–MS) instrumentation has the prerequisite sensitivity
to carry out multi-elemental trace analyses at sub-ng L−1 to sub-pg L−1 levels in solution. In practice, constraints mainly imposed by various sources of contamination in the laboratory and the
instrument itself, and the need to dilute sample solutions prior to analysis ultimately limit detection capabilities. Here
we review these sources of contamination and, wherever possible, propose remedial strategies that we have found efficacious
for ameliorating their impact on the results of multi-elemental trace analyses by ICP–MS. We conclude by providing a list
of key points to consider when developing methods and preparing the laboratory to routinely meet the demands of multi-elemental
analyses at trace analytical levels by ICP–MS. 相似文献