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991.
992.
Mahmoud Al‐Ktaifani Mwaffak Rukiah 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(9):m246-m250
In order to explore the potential propensity of the 1,1′‐methylenedipyridinium dication to form organic–inorganic hybrid ionic compounds by reaction with the appropriate halide metal salt, the organic–inorganic hybrid salts 1,1′‐methylenedipyridinium tetrachloridocuprate(II), (C11H12N2)[CuCl4], (I), and 1,1′‐methylenedipyridinium bis[tetrachloridoaurate(III)], (C11H12N2)[AuCl4]2, (II), were obtained by treatment of 1,1′‐methylenedipyridinium dichloride with CuCl2 and Na[AuCl4], respectively. Both hybrid salts were isolated as pure compounds, fully characterized by multinuclear NMR spectroscopy and their molecular structures confirmed by powder X‐ray diffraction studies. The crystal structures consist of discrete 1,1′‐methylenedipyridinium dications and [CuCl4]2− and [AuCl4]− anions for (I) and (II), respectively. As expected, the dications form a butterfly shape; the CuII centre of [CuCl4]2− has a distorted tetrahedral configuration and the AuIII centre of [AuCl4]− shows a square‐planar coordination. The ionic species of (I) and the dication of (II) each have twofold axial symmetry, while the two [AuCl4]− anions are located on a mirror‐plane site. Both crystal structures are stabilized by intermolecular C—H...Cl hydrogen bonds and also by Cl...π interactions. It is noteworthy that, while the average intermolecular centroid–centroid pyridinium ring distance in (I) is 3.643 (8) Å, giving strong evidence for noncovalent π–π ring interactions, for (II), the shortest centroid–centroid distance between pyridinium rings of 5.502 (9) Å is too long for any significant π–π ring interactions, which might be due to the bulk of the two [AuCl4]− anions. 相似文献
993.
994.
995.
Dr. Marta E. Plonska‐Brzezinska Dr. Mikołaj Lewandowski Dr. Małgorzata Błaszyk Dr. Agustin Molina‐Ontoria Prof. Dr. Tadeusz Luciński Prof. Dr. Luis Echegoyen 《Chemphyschem》2012,13(18):4134-4141
Composites of unmodified or oxidized carbon nano‐onions (CNOs/ox‐CNOs) with poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are prepared with different compositions. By varying the ratio of PEDOT:PSS relative to CNOs, CNO/PEDOT:PSS composites with various PEDOT:PSS loadings are obtained and the corresponding film properties are studied as a function of the polymer. X‐ray photoelectron spectroscopy characterization is performed for pristine and ox‐CNO samples. The composites are characterized by scanning and transmission electron microscopy and differential scanning calorimetry studies. The electrochemical properties of the nanocomposites are determined and compared. Doping the composites with carbon nanostructures significantly increases their mechanical and electrochemical stabilities. A comparison of the results shows that CNOs dispersed in the polymer matrices increase the capacitance of the CNO/PEDOT:PSS and ox‐CNO/PEDOT:PSS composites. 相似文献
996.
Li‐Wei Zhao Hui‐Min Shi Jiu‐Zhao Wang Prof. Jing He 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(48):15323-15329
An efficient ligand design strategy towards boosting asymmetric induction was proposed, which simply employed inorganic nanosheets to modify α‐amino acids and has been demonstrated to be effective in vanadium‐catalyzed epoxidation of allylic alcohols. Here, the strategy was first extended to zinc‐catalyzed asymmetric aldol reaction, a versatile bottom‐up route to make complex functional compounds. Zinc, the second‐most abundant transition metal in humans, is an environment‐friendly catalytic center. The strategy was then further proved valid for organocatalyzed metal‐free asymmetric catalysis, that is, α‐amino acid catalyzed asymmetric aldol reaction. Visible improvement of enantioselectivity was experimentally achieved irrespective of whether the nanosheet‐attached α‐amino acids were applied as chiral ligands together with catalytic ZnII centers or as chiral catalysts alone. The layered double hydroxide nanosheet was clearly found by theoretical calculations to boost ee through both steric and H‐bonding effects; this resembles the role of a huge and rigid substituent. 相似文献
997.
998.
The polymerization kinetics of acrylamide (AAM) in water initiated by a ternary enzymatic system of horseradish peroxidase (HRP)/H2O2/acetylacetone (ACAC) was investigated. Conversion–time plots were obtained by dilatometry under different conditions of reaction temperatures and initial concentrations of HRP, ACAC, H2O2, and AAM. The results showed that the effect of the initial concentration of ACAC on the inhibition period was significant. The inhibition period decreases with increasing the initial concentration of ACAC. The inhibition period can be even eliminated by the use of a comparatively large amount of ACAC. From the conversion–time plots, the polymerization rate equation was obtained. Some kinetic features were explained on the basis of analysis of the reaction mechanism. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 475–481, 2012 相似文献
999.
In this study, we successfully studied water‐soluble extract from Radix isatidis. Optimized conditions of MAE were listed, the sample can be extracted completely in 10 minutes under microwave power of 400W and solid/liquid ratio of 1:80. Active compounds in water‐soluble extract from R. isatidis were identified with HPLC‐DAD/ESI‐MS, these compounds followed by cytidine, uridine, guanosine, (R,S)‐goitrin and adenosine. RODWs–HPLC as a new sensitive chromatography were also first proposed and investigated, we favoringly used this method for simultaneous determination of these active constitutents in water‐soluble R. isatidis extract. Chromatographic separation was performed on a Diamonsil C18 column (5 μm, 150 mm × 4.6 mm) with a mobile phase gradient consisting of methanol and water at a flow‐rate of 1.0 mL/min, detection wavelengths 240, 250, 260 and 270 nm, the retention times of the tested five compounds were about 4.2, 5.8, 11.1, 14.2 and 20.8 min respectively, the limits of detection were 15, 12, 20, 5.8 and 24 ng/mL for cytidine, uridine, guanosine, (R,S)‐goitrin and adenosine respectively, their linear ranges were between 0.045 and 350 μg/mL with correlation coefficient (R) of 0.9998‐0.9999. The relative standard deviations (RSDs) of intra‐day and inter‐day assays were 0.30‐2.36% and 0.86‐2.54% respectively. Extraction recoveries were 94.25‐106.21%. This novel analytical method was shown to be simple, low‐cost, sensitive and reliable for multiple components in complex or undeveloped materials via MAE, ESI‐MS and RODWs‐HPLC. 相似文献
1000.
Fen Ran Yong‐tao Tan Ji Liu Lei zhao Ling‐bin Kong Yong‐chun Luo Long Kang 《先进技术聚合物》2012,23(9):1297-1301
This article reports the preparation and self‐assembly of polyaniline (PANI) nanotubes, which were chemically synthesized by using in situ doping polymerization in the presence of ammonium persulfate (APS; (NH4)S2O8) as the oxidant without the use of an external template. The synthesized hierarchically nanotubes with a shape of a single nanotube with a length of 0.6 to 0.8 µm and an average with of 100 nm assembled from nanoparticles. The effects of the [salicylic acid]/[aniline] ratio on the size and capacitance of PANI nanotubes were studied. The specific capacitance behavior of the PANI nanotubes was also investigated by using cyclic voltammogram and galvanostatic charge–discharge tests. A maximum discharge‐specific capacitance of 422.5 F/g could be achieved, suggesting its potential application in electrode material for electrochemical capacitors. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献