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Friedlein R Crispin X Suess C Pickholz M Salaneck WR 《The Journal of chemical physics》2004,121(5):2239-2245
Lithium intercalation compounds of alpha- and beta-perylene are investigated by photoelectron spectroscopy. Spectroscopic data together with a Born-Haber cycle provide information on the formation enthalpy of those materials. This approach allows understanding the amount of charge transferred from the alkali metal atoms to the pi system, and illuminates the role of molecular versus solid-state properties in the formation of the intercalation compounds. In the bulk of alpha-perylene material, molecular dimerization survives upon intercalation which reduces the Madelung energy of the intercalation compound but increases the electron-accepting capability of the organic system and facilitates the ionization of lithium atoms in the molecular solid environment. The lower ionization potential results in a larger charge transfer (about two electrons per molecule) in alpha-perylene compared to the monomeric system, beta-perylene. 相似文献
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Anna Hanft Dr. Krzysztof Radacki Priv.-Doz. Dr. Crispin Lichtenberg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(20):6230-6239
The behavior of the redox-active aminotroponiminate (ATI) ligand in the coordination sphere of bismuth has been investigated in neutral and cationic compounds, [Bi(ATI)3] and [Bi(ATI)2Ln][A] (L=neutral ligand; n=0, 1; A=counteranion). Their coordination chemistry in solution and in the solid state has been analyzed through (variable-temperature) NMR spectroscopy, line-shape analysis, and single-crystal X-ray diffraction analyses, and their Lewis acidity has been evaluated by using the Gutmann–Beckett method (and modifications thereof). Cyclic voltammetry, in combination with DFT calculations, indicates that switching between ligand- and metal-centered redox events is possible by altering the charge of the compounds from 0 in neutral species to +1 in cationic compounds. This adds important facets to the rich redox chemistry of ATIs and to the redox chemistry of bismuth compounds, which is, so far, largely unexplored. 相似文献
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Crispin Lichtenberg 《Journal of organometallic chemistry》2010,695(17):2000-2006
Ph2P(C5HMe4) (1) was found to undergo a prototropic rearrangement contrary to previous reports. The first detailed investigation of a cyclopentadienylphosphane to undergo such a reaction is presented. One of the two tautomers of 1 which were observed represents the kinetic product, the other one is the thermodynamic product. The two isomers exhibit pronounced differences with respect to their chemical reactivity. Thermodynamic and kinetic data of the isomerisation process were determined. A novel, electron rich cyclopentadienylphosphane, the phosphorus diamide (Me2N)2P(C5HMe4) (2), was synthesised and was also found to undergo a prototropic rearrangement. The characteristics of the isomerisation process are fully consistent with the findings on 1. The molecular structure of the kinetic product of 2 was established by means of single crystal X-ray diffraction analysis. Me2P(C5H4tBu) (3) is presented as another novel cyclopentadienylphosphane. The mixture of isomers of 3 in thermodynamic equilibrium was investigated in detail with respect to the molecular structures of the tautomers. The results of this study suggested a reinvestigation of the parent compound Ph2P(C5H4tBu) (4) and findings differing from an earlier report in some details are presented. 相似文献
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Quantum annealing extends simulated annealing by introducing artificial quantum fluctuations. The path-integral Monte Carlo version chosen is population-based and designed to be implemented on a classical computer. Its first application to the graph coloring problem is presented in this paper. It is shown by experiments that quantum annealing can outperform classical thermal simulated annealing for this particular problem. Moreover, quantum annealing proved competitive when compared with the best algorithms on most of the difficult instances from the DIMACS benchmarks. The quantum annealing algorithm has even found that the well-known benchmark graph dsjc1000.9 has a chromatic number of at most 222. This is an improvement on its best upper-bound from a large body of literature. 相似文献
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Lizbet Le��n Angel Bustamante Ana Osorio G. S. Olarte Luis De Los Santos Valladares Crispin H. W. Barnes Yutaka Majima 《Hyperfine Interactions》2011,202(1-3):131-137
In this work we report the preparation of magnetic hematite hollow sub-micron spheres (??-Fe2O3) by colloidal suspensions of ferric nitrate nine-hydrate (Fe(NO3)3·9H2O) particles in citric acid solution by following the sol?Cgel method. After the gel formation, the samples were annealed at different temperatures in an oxidizing atmosphere. Annealing at 180°C resulted in an amorphous phase, without iron oxide formation. Annealing at 250°C resulted in coexisting phases of hematite, maghemite and magnetite, whereas at 400°C, only hematite and maghemite were found. Pure hematite hollow sub-micron spheres with porous shells were formed after annealing at 600°C. The characterization was performed by X-ray diffraction (XRD), Mössbauer spectroscopy (MS) and scanning electron microscopy (SEM). 相似文献
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Ek M Borgstr?m MT Karlsson LS Hetherington CJ Wallenberg LR 《Microscopy and microanalysis》2011,17(5):752-758
The twin interface structure in twinning superlattice InP nanowires with zincblende structure has been investigated using electron exit wavefunction restoration from focal series images recorded on an aberration-corrected transmission electron microscope. By comparing the exit wavefunction phase with simulations from model structures, it was possible to determine the twin structure to be the ortho type with preserved In-P bonding order across the interface. The bending of the thin nanowires away from the intended 110 axis could be estimated locally from the calculated diffraction pattern, and this parameter was successfully taken into account in the simulations. 相似文献
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