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101.
The preparation and the properties of the hexacyanopalladium(IV) acid (H3O)2[Pd(CN)6] and of a number of metal hexacyanopalladates(IV) are described. UV, IR and Raman spectra are reported, force constants have been calculated and the bonding properties are discussed. K2[Pd(CN)6] crystallizes in a hexagonal lattice; a = 7.42, c = 6.65 Å, Z = 1. 相似文献
102.
Rigler R 《Electrophoresis》2002,23(5):805-808
The behavior of negatively charged single rhodamine-labeled molecules excited to fluorescence in confocal volume elements has been investigated in oscillating voltage gradients between 1 and 15 kV/cm. The effective charge of rhodamin labeled deoxy-uridine triphosphate (Rh-dUTP) is dependent on the field strength applied and likely is due to differences in the screening by counter ions. It can be shown that the attractive forces generated by an oscillating dipole can increase the concentration of Rh-dUTP by a factor 2. Likewise a substantial increase of concentration can be obtained for Rh-labeled DNA molecules when linear voltage gradients are applied. The importance for diagnostic analysis at the single molecule level is discussed. 相似文献
103.
104.
Berry JF Cotton FA Daniels LM Murillo CA 《Journal of the American Chemical Society》2002,124(13):3212-3213
The molecule Ni(3)(dpa)(4)Cl(2) (1) can be oxidized by AgPF(6) to give crystalline Ni(3)(dpa)(4)(PF(6))(3) (2) (dpa is the anion of di(2-pyridyl)amine). This reversible oxidation occurs at a potential of 0.908 V vs Ag/AgCl electrochemically. The X-ray structure of 2 shows that the oxidation causes a major structural change (even though it is reversible), namely, a contraction of the Ni-Ni distances from ca. 2.43 A to 2.284[1] A. In addition, the electronic structure changes so that from four unpaired electrons in 1 there is only one in 2. From these remarkable results, it is inferred that while 1, and all higher homologues with 5, 7, 9,... nickel atoms are poor electronic conductors, the cations obtainable from them may be much better ones. This in turn means that by controlling the oxidation state electrochemically, these molecules may be able to function as nanoscale diodes. 相似文献
105.
The ZnCl2 catalyzed reaction of p-methoxybenzyl chloride with alkenes yields the 1:1 addition products 3, which are converted into the γ-lactones 4 via Ru(VIII) catalyzed oxidative degradation of the aromatic ring. 相似文献
106.
Albert Lévai Gábor Tóth Áron Szőllősy Tibor Timár 《Monatshefte für Chemie / Chemical Monthly》1990,121(5):403-411
Summary Arylsulfonyloxy-2,2-dimethyl-2H-chromenes (26–35) have been synthesized by reduction of arylsulfonyloxy-2,2-dimethyl-4-chromanones (6–15) followed by dehydration.
Synthese von Benzopyranderviaten. 15. Mitt.: Darstellung von Arylsulfonyloxy-2,2-dimethyl-2H-chromenen
Zusammenfassung Reduktion von Arylsulfonyloxy-2,2-dimethyl-4-chromanonen (6–15) und anschließende Dehydratisierung liefert Arylsulfonyloxy-2,2-dimethyl-2H-chromene (26–35).相似文献
107.
Four new stationary phases for HPLC were prepared by modifying silica gel with a trifrnctional aminoalkyl silane. A conjugated π-electron system was linked to the amino group either directly or with a carboxylic anhydride as a spacer in between. Characterization and dynamic measurements of the new stationary phases were performed by solid state NMR spectroscopy. The results of the 29si and 13C CP/MAS techniques were compared with the recently developed 1H MAS-only technique. Despite strong homonuclear dipole-dipole interactions it was possible to obtain well resolved 1H MAS spectra of those stationaru phases with a high degree of crosslinking. Limited mobility of the aromatic ligand fragments is common for all examined stationaryu phases. The chromatographic properties of the new phases were tested by their ability tio sepatate a mixture of eight PAHS. It could be shown that the π-π interaction mechanism is responsible for the separation of the eight PAHs, because the elution order of the PAHs did not changem despite the use of both a nonpolar mobile phase (n-heptane) and a polar mobile phase (methanol/ water mixture). 相似文献
108.
Contribution to the study of the behaviour of catechin in alkaline medium When catechin ( 1 ) is warmed with aqueous alkali it first undergoes rapid epimerisation. After some time a novel bridged carbocyclic enol, catechinic acid ( 3 ) separates out and may be isolated in excellent yield. Eventually catechinic acid isomerises to 2-(3′,4′-dihydroxyphenyl)-3,9-epoxy-6-oxo-bicyclo[3,3,1]-non-7-en-8,9-diol ( 4 ) via an open chain anion ( 5 ) which is also involved in the epimerisation of catechin. Assignments of structure are given and the equilibria observed are discussed. 相似文献
109.
110.
The model of two interacting ethylene molecules having D
2h symmetry was studied using generalized Hückel method. The validity of - separation was tested on this model. The general character of the ground state and lower lying excited states of the model was discussed and the implications drawn concerning transannular interaction and excimer formation. The values obtained for the dissociation energy of the first excited state of our model and corresponding equilibrium intermolecular distance are of right order of magnitude.
Zusammenfassung Mittels der verallgemeinerten Hückel-Methode wurde das Modell von zwei Äthylenmolekülen mit der Symmetrie D 2h studiert. An diesem Modell wurde die Gültigkeit der - -Separation geprüft. Der allgemeine Charakter des Grundzustandes und der niedriger liegenden angeregten Zustände des Modells wird erörtert und die Folgerungen in Bezug auf transannulare Wechselwirkung und Excimer-Entstehung diskutiert. Die erhaltenen Werte für die Dissoziationsenergie des ersten angeregten Zustandes von unserem Modell und den entsprechenden intermolekularen Gleichgewichtsabstand haben die richtige Größenordnung.
Résumé Le modèle à symétrie D 2h de deux molécules d'éthylène en interaction a été étudié en utilisant la méthode généralisée de Hückel. On a examiné la validité de la séparation - sur ce modèle. Le caractère général de l'état fondamental et celui des états excités inférieurs du modèle furent discutés et on a fait des déductions sur l'interaction transannulaire et sur la formation d'«excimères». Les valeurs obtenues pour l'énergie de dissociation du premier état excité de notre modèle et la distance intermoléculaire d'équilibre corréspondante ont l'ordre de magnitude correct.相似文献