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61.
Horst Kunkely 《Journal of organometallic chemistry》2004,689(18):2940-2943
The electronic spectra of solid MgCp2 (Cp = cyclopentadienyl) show features which indicate the presence of intramolecular interligand interactions. The fluorescence of MgCp2 (λmax = 363 nm) undergoes a considerable Stokes shift which is apparently caused by a bonding attraction between both Cp rings in the excited state. An additional phosphorescence of the (Cp−)2 fragment (λmax = 535 nm) appears at 77 K. 相似文献
62.
W. Wojnowski J. Pikies K. Peters E.-M. Peters D. Thiery H. G. Von Schnering 《无机化学与普通化学杂志》1994,620(2):377-384
Formation and Structures of N-(tri-t-butoxysilyl)aniline Compounds Para-substituted N-(tri-t-butoxysilyl)anilines (t-BuO)3SiNRC4H4X-p, R = H, CH3, with substituents of high electron affinity (X = CN, NO2) were prepared by a one-pot reaction of tri-t-butoxychlorsilane, potassium t-butanolate and substituted anilines. Corresponding compounds with substituents of low electron affinity (X = OMe, H) preferably were prepared by metalation of anilines with sodium amide. Four crystal structures were determined. N-(tri-t-butoxysilyl)-p-nitro-aniline, N-methyl-(N-tri-t-butoxysilyl)-p-nitroaniline and N-(tri-t-butoxysilyl)-p-cyanoaniline crystallize at 298 K monoclinically, N-(tri-t-butoxysilyl)aniline crystallizes orthorhombically. 相似文献
63.
Zusammenfassung Polyäthyleniminzellulosen sorbieren Cu2+ durch koordinative Bindung als Zentralion des sekundären Stickstoffs des Polyäthylenimins im PH-Bereich 3,5 bis 4,5 selektiv aus verd. Lösungen. 10g Kupfer können von 105fachen Überschüssen anderer Übergangsmetalle separiert, mit verd. Salzsäure eluiert und mit Diäthyldithiocarbamat photometrisch bestimmt werden. Das Verfahren eignet sich zur Erfassung von 0,001% Kupfer in Zink, Mangan, Kobalt, Nickel, Cadmium und Aluminium sowie aus Lösungen, deren Kupfergehalt 0,02 ppm beträgt.
Selectivation of small amounts of copper with polyethyleneimine-cellulose
Summary Polyethyleneimine celluloses selectively sorb Cu2+ from dilute solutions through coordinative bonding as central ion of the secondary nitrogen of polyethyleneimine in the pH-range of 3.5–4.5. 10g of copper may be separated from 105-fold excesses of other transition metals, then eluted with dilute hydrochloric acid and determined photometrically with diethyldithiocarbamate. The method is suitable for determining 0.001% copper in zinc, manganese, cobalt, nickel, cadmium, and aluminium as well as in solutions whose coppercontent is 0.02 ppm.相似文献
64.
Horst Müller 《Analytical and bioanalytical chemistry》1969,247(3-4):145-149
The ions ReBrnCl 6?n 2? (0?n?6) and OsBrnCl 6?n 2? , respectively, ReO4 ? and Br? have been separated on cellulose using the thin-layer chromatographic technique with 3.2 M sulphuric acid as the mobile phase. 相似文献
65.
The synthesis of glycopeptides carrying tumour-associated antigens is of interest for cancer diagnosis and treatment. Here, a very efficient route lo disaccharide threonine building block 8 is presented which allows the introduction of the sialyl-Tn antigen into a peptide. The syntheses of the undecapeptide and the sialyl-Tn-containing glycoundecapeptide, which are a part of the repeating unit of MUC1, were performed by solid-phase synthesis with an allylic anchor cleavable under neutral conditions. After detachment from the resin, the peptide and the glycopeptide arc completely deprotected giving the target compounds 13 and 15 , respectively. 相似文献
66.
Johanna Sabine Becker Jochen Westheide Anatolij I. Saprykin Horst Holzbrecher Uwe Breuer Hans -Joachim Dietze 《Mikrochimica acta》1997,125(1-4):153-160
For the determination of trace impurities in ceramic components of solid oxide fuel cells (SOFCs), some mass spectrometric methods have been applied such as spark source mass spectrometry (SSMS), laser ionization mass spectrometry (LIMS), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and inductively coupled plasma mass spectrometry (ICP-MS). Due to a lack of suitable standard reference materials for quantifying of analytical results on La
x
Sr
y
MnO3 cathode material a matrix-matched synthetic standard-high purity initial compounds doped with trace elements-was prepared in order to determine the relative sensitivity coefficients in SSMS and LA-ICP-MS. Radiofrequency glow discharge mass spectrometry (rf-GDMS) was developed for trace analysis and depth profiling of thick non-conducting layers. Surface analytical techniques, such as secondary ion mass spectrometry (SIMS) and sputtered neutral mass spectrometry (SNMS), were used to determine the element distribution on surfaces (homogeneity) and the surface contaminants of SOFC ceramic layers.Dedicated to Professor Dr. rer. nat. Hubertus Nickel on the occasion of his 65th birthday 相似文献
67.
Ren Traber Camilla Keller-Jusln Hans-Rudolf Loosli Max Kuhn Albert Von Wartburg 《Helvetica chimica acta》1979,62(4):1252-1267
Cyclopeptide antibiotics from Aspergillus species. Structure of echinocandins C and D The echinocandins B, C and D are antifungal antibiotics produced by a strain of Aspergillus rugulosus. All three metabolites are closely related representing cyclic oligopeptides composed of six amino acids and a linolic acid residue in an amide linkage. The complete structure of echinocandin B ( 1 ) has recently been established by X-ray analysis. Structural assignments to the new minor metabolites C and D have now been made by hydrolytic and oxidative cleavage reactions, formation of N-acyl-α-aminoethers as well as by chemical correlations and extensive NMR. examinations. Echinocandin C ( 2 ), C52H81N7O15, contains 3-hydroxyhomotyrosine in the place of 3, 4-dihydroxyhomotyrosine present in 1 . Echinocandin D ( 3 ), C52H81N7O13, differs in two amino acids: 3, 4-dihyroxyhomotyrosine and 4, 5-dihydroxyornithine, unusual units of 1 being replaced by 3-hydroxyhomotyrosine and ornithine. 相似文献
68.
On the Temperature Dependence of the 13C-NMR.-Spectra of Tetracarbonyl (η-( Z )-cyclooctene)iron and of ( Z )-Cyclooctene Reaction of (Z)-cyclooctene (1) with Fe2(CO)9 in pentane at 0° yielded tetracarbonyl(η-(Z)-cyclooctene)iron (2) as a yellow oil which can be stored over a longer period only at ?78°. It is shown that the title compounds ( 1 and 2 , respectively) are fluxional. The activation parameters for the conformational C-atom site exchange of (Z)-cyclooctene (1) and tetracarbonyl (η-(Z)-cyclooctene)iron (2) (in CCl2F2) have been determined between 113 K and 151 K for 1 and between 151 K and 205 K for 2 , respectively, by a complete line shape analysis of the temperature dependent proton noise-decoupled 13C-NMR. signals of the olefinic C-atom. The kinetic data and activation parameters are given in Tables 1 and 2. 相似文献
69.
Kraus RM Lagoudakis PG Müller J Rogach AL Lupton JM Feldmann J Talapin DV Weller H 《The journal of physical chemistry. B》2005,109(39):18214-18217
We study the interplay between Auger effects and ionization processes in the limit of strong electronic confinement in core/shell CdSe/ZnS semiconductor nanocrystal quantum dots. Spectrally resolved fluorescence decay measurements reveal a monotonic increase of the photoluminescence decay rate on excitation density. Our results suggest that Auger recombination accelerates ionization processes that lead to the occupation of dark, nonemissive nanocrystal states. A model is proposed in the quantized Auger regime describing these experimental observations and providing an estimate of the Auger assisted ionization rates. 相似文献
70.
Larry I. Amstutz Horst Meyer Samuel M. Myers
Robert L. Mills
《Journal of Physics and Chemistry of Solids》1969,30(12):2693-2697Measurements of T1 in the hep phase of H2, over the temperature range 2°–12°K and the ortho concentration range between 0.5 and 0.97 are presented. At temperatures below 10°K, the thermally activated self-diffusion is negligible and the mechanism for nuclear relaxation is that attributed by Moryia and Motizuki and by Harris to intramolecular dipolar interaction, modulated by intennolecular electric quadrupole-quadrupole (EQQ) interaction. The gaussian approximation for the correlation function was used by these authors to predict T1. From the comparison between experiment and theory, we determine the EQQ parameter Γ/kB to be 0.67°K. Above 10°K the effect of diffusion influences T1, and the experimental results for an 88 per cent ortho H2 sample up to the melting point suggest that the relaxation mechanisms resulting from EQQ interaction and diffusion are not independent of one another. 相似文献