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151.
Stefan Müllegger Kathrin H?nel Thomas Strunskus Christof W?ll Adolf Winkler 《Chemphyschem》2006,7(12):2552-2558
Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy has been applied to reveal the molecular arrangement of ultrathin oligophenyl films [p-quaterphenyl (4P) and p-hexaphenyl (6P)] on Au(111). In the half-monolayer films the molecules lie flat on the surface but still have a considerable inter-ring twist of 30 degrees -40 degrees , similar to the gas-phase conformation. In the saturated monolayer film the second half of the molecules is side-tilted by an angle of less than 66 degrees with respect to the surface. This arrangement is already similar to that in bulk net planes of thicker films parallel to the surface, that is, the 4P(211) and 6P(21-3) planes, respectively. 相似文献
152.
153.
Molecular routes to metal oxides has become an area of intensescientific interest due to the technological relevance of thesematerials. Molecular routes are proving important as a result ofthe possibility to control the physical and chemical propertiesof the final materials.We have chosen to study non-hydrolytic methods, namely esterelimination reactions between two prototypical molecularprecursors metal alkoxides, M(OR)n, and metal carboxylates, M(O2CR)n, to synthesize metal oxides:
This method allows for the synthesis of pure metal oxides bycomplete elimination of the organic supporting ligands withconcomitant formation of M-O-M bridges.Furthermore, incomplete esterelimination can lead to isolation of molecular clusters asintermediates which can also be used as building blocks for theformation of metal oxides with controlled microstructure.Here we report a series of reactions between Sn and Si alkoxidesand carboxylates designed to gain further insight into thefactors governing ester elimination reactions. By choosingcompounds with varying coordination environments and stericaccessibility we have devised a set of criteria which shouldallow for successful ester elimination between metal alkoxide andcarboxylate compounds. Furthermore we have also shown theability of ester elimination derived molecular clusters withspecific microstructure to be used in the synthesis of bulkmaterials retaining the structural attributes of the precursor cluster. 相似文献
154.
An amperometric detector with a small thin mercury film electrode is described. The device demonstrates advantageous operational
characteristics such as small dispersion (D<2) and “memory effect” (me<0.6%), extensive maximum sample frequency (msf −200
samples/h), and high sensitivity. It has been proven useful in flow-injection analysis at a constant potential under hydrodynamic
conditions. 相似文献
155.
Saeed Yousefinejad Fatemeh Honarasa Samira Akbari Mohsen Nekoeinia 《液相色谱法及相关技术杂志》2020,43(15-16):580-588
AbstractSeparation of amino acids (AAs) and their simple and inexpensive determination/identification is an interesting topic in biological and protein science, different food industries, and drug factories. Also, the presentation of the chromatographic behavior of compounds in a predictive model can be effective to estimate the structural/chemical properties of analyte and mobile phases. In this work for the first time, retardation factor (RF) of 42 AAs in reversed-phase thin layer chromatography (RP-TLC) was modeled. Acetonitrile-sodium azide solution and 1,2 dioxane-sodium azide solution were two mobile phases which have been studied in this work. Results showed that the values of RF are correlated with the structural properties of AAs and these properties had some similarities and differences in two noted mobile phases. For the TLC data in two mobile phases, five parametric linear models were suggested (R2train = 0.93 and 0.97; R2test = 0.93 and 0.99). The models were also evaluated with different statistical approaches. It was shown that increasing the sum of geometrical distances between N and O in AAs causes decreasing their RF in RP-TLC using both mobile phases. Other structural effects of AAs on their separation in the desired RP-TLC system were also discussed. 相似文献
156.
V. V. Dunina O. A. Zatevskaya S. P. Palii D. V. Zagorevskii Yu. S. Nekrasov 《Russian Chemical Bulletin》1996,45(3):694-701
Synthesis of acetylacetonate derivatives of a series ofortho-palladated complexes based on secondary and tertiary -arylalkylamines was described. Their structures and stereochemistry were elucidated by IR, UV,1H NMR, and CD spectra. Fragmentation processes of these complexes and some model compounds were studied by mass spectrometry (EI). An unusual rearrangement of a molecular ion involving migration of the hydrogen atom from the alkylaminoalkyl group to the palladium atom to form a hydride intermediate followed by the elimination of PdH was observed. The rearrangement occurs through isomerization of the 2-O,O-coordinated -diketonate ligand to the 1-C-bonded diketonyl form to give the coordinationally unsaturated metal center.Translated fromIsvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 733–740. March, 1996. 相似文献
157.
Liping Heng Jin Zhai Yong Zhao Jinjie Xu Xianliang Sheng Lei Jiang 《Chemphyschem》2006,7(12):2520-2525
A light-emitting poly (distyryldimethylbenzene-co-triethylene glycol) rod-coil block copolymer was used to fabricate films with three-dimensionally ordered honeycomb structures by the breath-figure method. Photocurrent generation and photovoltaic performance are studied, and the dependence of photocurrent on applied electric field is investigated. Introducing the ordered porous structure significantly improves the photoelectric conversion behavior, because porous structures not only enhance the light-harvesting efficiency but also benefit charge separation and charge transfer. This phenomenon may have great prospects for enhancing the photovoltaic behavior of organic thin-film devices. 相似文献
158.
159.
Acetonitrile and [D3]acetonitrile in the vicinal region of a planar AgX fiber contain linear dipole–dipole linked oligomers as shown by 1) comparison of infrared band intensity ratios in the gaseous and condensed phases and 2) remarkable plots of absorbance (C? N stretch) versus time during evaporation from an AgX planar fiber element. The plots (CH3CN 2252 cm?1, CD3CN 2262 cm?1) reveal the presence of octamers, hexamers, tetramers, and dimers along with some heptamer, trimer, and monomer structures. A novel isotope effect arises from the somewhat smaller size of the CD3CN resulting in an increase in the CN band intensity. The organized oligomers may be termed pseudocrystals and are the main components responsible for absorption intensity in the infrared spectrum of acetonitrile, on the AgX planar fiber or in an IR cell. 相似文献
160.
Solution-cast films of the major isomer of Dy@C(82) (Dy@C(82)(I)) have been studied by cyclic voltammetry (CV) in acetonitrile. The films are found to display pronounced and stable redox responses in solution. The reduction/reoxidation processes exhibit large splittings between the first two reduction and reoxidation waves. However, a pair of reversible oxidation and rereduction waves is observed after the reoxidation of a reduced film. The characteristics and the inter-relationship of these waves are uncovered by the CV technique, scanning electron microscopy (SEM), and UV/Vis-NIR spectra. A possible mechanism is proposed for the film electrode processes, which emphasizes the redox-induced structural reorganization of the metallofullerene film by the incorporation and expulsion of electrolyte ions into and out of the film. The influence of the counter ion diffusivity and the ion-pair stability on the electrochemical activity of the metallofullerene film has also been indicated. 相似文献