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61.
Teresa Borowiak Maciej Kubicki Grzegorz Dutkiewicz Marek Pietraszkiewicz Oksana Pietraszkiewicz 《Journal of inclusion phenomena and macrocyclic chemistry》2005,51(3-4):181-189
Two newly identified supramolecular structures arise from self-assembly of the macrocyclic 1,5,9,18,22,26- hexaaza[11.11]-p-cyclophane salts with o-nitrophenol (C28H50N6)4+·4(C6H4NO2O)− (1) and with HCl (C28H52N6)6+·6Cl-·4H2O (2). In both cases two-dimensional supramolecular sheets are formed. 相似文献
62.
Roland Boese Dieter Bläser Michael Nussbaumer Tadeusz Marek Krygowski 《Structural chemistry》1992,3(5):363-368
The crystal and molecular structure of nitrobenzene was determined at 103 K by X-ray diffraction, yieldingR=0.034 and a highly precise geometry of the molecule (esds of bond lengths 0.001 Å and bond angles 0.1°). The bond angles in the ring agree very well with additive scheme based on angular substituent parameters. X-X electron density maps support the view that the C-N bond does not exhibit-character, and, hence, the nitro group interacts with the ring mostly by inductive effects. 相似文献
63.
Marek Trojanowicz Joanna Szpunar-Łobińska Zdzislaw Michalski 《Mikrochimica acta》1991,103(3-4):159-169
An original computer-controlled solid-state photometer has been developed and its potential for simultaneous multicomponent flow-injection analysis of binary and ternary mixtures is demonstrated. The device is simple in construction. Its principle of operation is based on rapid sequential measurements of the absorbance of the complexes formed by the analytes with chromogenic reagents at the wavelengths corresponding to the emission maxima of three light emitting diodes (563, 580 and 638 nm). 相似文献
64.
Lestage DJ Schleis DJ Urban MW 《Langmuir : the ACS journal of surfaces and colloids》2004,20(17):7027-7035
These studies focus on the effect of phospholipids in the presence of ionic surfactants on the behavior of poly(methylmethactrylate/n-butyl acrylate) (p-MMA/nBA) colloidal particles during film formation. With the presence of two surfactants, it is possible to obtain particles that exhibit two distinct particle sizes. The presence of hydrogenated soybean phosphatidylcholine (HSPC) and sodium dioctyl sulfosuccinate (SDOSS), which stabilize these bimodal colloidal dispersions, has a significant effect on the mobility of individual components during coalescence. Specifically, the presence of HSPC inhibits migration of SDOSS to the film-air (F-A) interface. Furthermore, the presence of electrolyte species such as aqueous CaCl2 has a very pronounced effect on film formation. When the Ca2+/HSPC ratio is 0.1/1.0, SDOSS is released to the F-A interface during coalescence. At 2.0/1.0 Ca2+/HSPC, HSPC diffuses to the F-A interface and crystalline domains consisting of HSPC are formed. This stimuli-responsive behavior is confirmed using IRIR imaging that ultimately exhibits different surface morphologies. These studies illustrate for the first time that it is possible to control the release of two different surface-active species during coalescence that form crystalline domains. 相似文献
65.
The electronic absorption spectrum for the dibiphenylene-ethene radical anion (
), generated electrochemically in dimethylsulfoxide solutions, is reported. Based on calculations by the LCAO-MO method in theHückel approximation and on the analysis of the band positions it is suggested that in the
molecule two planar fluorenylidene fragments are twisted (60°) about the central C=C bond.
Das Elektronenabsorptionsspektrum des Dibiphenylen-Radikalanions (Kurze Mitteilung)
Zusammenfassung Das Dibiphenylenethen-Radikalanion ( ) wurde elektrochemisch hergestellt und das Elektronenabsorptionsspektrum aufgenommen. Auf Grund von LCAO-MO Berechnungen in derHückel-Annäherung und der Analyse der Bandenlagen wird nahegelegt, daß im -Molekül zwei planare Fluorenyliden-Fragmente ca. 60° um die zentrale C=C-Bindung verdrillt angeordnet sind.相似文献
66.
M. Marek L. Toman J. Pila 《Journal of polymer science. Part A, Polymer chemistry》1975,13(7):1565-1573
ESR spectra of Lewis acids (VCl4, TiCl4, TiBr4, SnCl4, and AlBr3) and their mixtures with isobutylene were investigated in a n-heptane solution in the dark and under irradiation at 400–480 nm at ?80 to ?150°C. A signal was observed only upon irradiating mixtures of VCl4, TiCl4, or TiBr4 and isobutylene. The signal was identified as an isobutylene radical-cation by comparison with a simulated spectrum. A signal indicating the presence of peroxy radicals were recorded in measurements carried out in the presence of oxygen; these radicals originated from reaction of the isobutylene radical-cation with oxygen. Radical-cation initiation by visible light is indicated by the polymerization of isobutylene by VCl4, TiCl4, and TiBr4 and by ESR spectra. The inhibiting effect of oxygen in photochemically initiated polymerization of isobutylene was also elucidated. 相似文献
67.
Fluorescence quenching of aromatic molecules by inorganic anions has been the subject of many investigations, yet the nature of the quenching mechanism is not fully understood. The fluorescence-quenching rate constants correlate with electrochemical data, but the radicals expected to form upon transfer of an electron to the excited aromatic molecules have escaped observation. We report the first observation of radical-ion species formed by electron-transfer quenching with inorganic anions in acetonitrile. A decisive step leading to formation of separated radical ions is the trapping of the primary charge-transfer complex by a second inorganic ion. 相似文献
68.
Flow-injection single-point titration of acids is based on biamperometric measurement of iodine formed quantitatively in the reaction of iodide with iodate. Results are presented for determination of sulphuric, hydrofluoric, monochloroacetic, formic and acetic acids. The slopes of the calibration plots, which are linear for about 1–10 rum acid, depend on the strength of the acid, decreasing from sulphuric acid to acetic acid. With microcomputer on-line data processing, relative standard deviations were about 0.2%. 相似文献
69.
Jaromir Dmytrzyk Andrzej Kotarba Hanna Grabowska Roman Klimkiewicz 《Research on Chemical Intermediates》2004,30(3):337-342
The influence of gas-phase methylation of phenol on the state of the Fe-Si-Cr-K oxide catalyst surface was investigated by thermodesorption of K atoms and ions. Changes in potassium desorption energies, as determined from Arrhenius-like plots, varied from 3.07 eV to 1.21 eV for the atoms and from 2.59 eV to 2.89 eV for ion desorption from the active and deactivated samples, respectively. The results were discussed in terms of transformation of the catalyst surface and formation of β-ferrite. 相似文献
70.
Lucjan Chmielarz Piotr Kustrowski Marek Michalik Barbara Dudek Magdalena Czajka Roman Dziembaj 《Reaction Kinetics and Catalysis Letters》2007,91(2):369-378
Natural phlogophite, pre-treated with acids and intercalated with alumina pillars, was used as catalytic support. Transition
metals (Fe, Cu) were deposited on the surface of the modified clay materials by an ion-exchange method. The obtained samples
were characterized with respect to structure (XRD), texture (BET), composition (EPMA) and chemical nature of the deposited
transition metals species (UV-vis-DRS). The phlogophite based materials have been found to be active and selective catalysts
of the DeNOx process. The Fe-containing samples were catalytically active at lower temperatures than the clays modified with
copper. A competitive ammonia oxidation by oxygen decreased the effectiveness of the DeNOx process in the high temperature
range. 相似文献