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排序方式: 共有406条查询结果,搜索用时 15 毫秒
151.
Dr. Eberhardt Herdtweck Tobias Kornprobst Roland Sieber Leo Straver Johann Plank 《无机化学与普通化学杂志》2011,637(6):655-659
From hydrothermal synthesis needle‐shaped crystals of [Ca3(C6H5O7)2(H2O)2] · 2H2O were obtained. The crystal structure was determined by single‐crystal X‐ray experiments and confirmed by powder data (P$\bar{1}$ (no. 2) a = 5.9466(4), b = 10.2247(8), c = 16.6496(13) Å, α = 72.213(7)°, β = 79.718(7)°, γ = 89.791(6)°, V = 947.06(13) Å3, Z = 2, R1 = 0.0426, wR2 = 0.1037). The structure was obtained from pseudo merohedrically polysynthetic twinned crystals using a combined data collection approach and refinement processes. The observed three‐dimensional network is dominated by eightfold coordinated Ca2+ cations linked by citrate anions and hydrogen bonds between two non‐coordinating crystal water molecules and two coordinating water molecules. 相似文献
152.
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154.
F Kniep L Rout SM Walter HK Bensch SH Jungbauer E Herdtweck SM Huber 《Chemical communications (Cambridge, England)》2012,48(74):9299-9301
Bi- and tridentate polycationic halogen bond donors based on 5-iodo-1,2,3-triazolium groups have been synthesized by 1,3-dipolar cycloaddition reactions. These halogen-based Lewis acids have been evaluated as activators in a halide-abstraction benchmark reaction. 相似文献
155.
Canella D Hock SJ Hiltner O Herdtweck E Herrmann WA Kühn FE 《Dalton transactions (Cambridge, England : 2003)》2012,41(7):2110-2121
Nine new complexes of the type fac-[(CO)(3)ReBr(L)], where L represents a chelating bis-NHC ligand consisting of two alkylene (propylene and butylene) bridged (R') N-substituted (R) imidazoline moieties (1,1'-di-R-3,3'-R'-diimidazolin-2,2'-diylidene), were synthesized. Spectroscopic methods, elemental analysis, mass spectrometry and X-ray crystallography were employed to characterize the complexes both in solution and in solid state. The complexes were compared to the analogous complexes with smaller bridge lengths in order to reveal differences and similarities. Depending on the bridge length and the ligand size in some cases dinuclear complexes were obtained as small scale side products. 相似文献
156.
The title compounds were prepared by aldol reaction of anisaldehyde and the respective N,N‐dibenzyl glycinates. Deprotection of the nitrogen atom with Pearlman’s catalyst delivered the unprotected β‐hydroxytyrosine esters, which were further N‐protected as N,N‐phthaloyl (Phth) and N‐fluorenylmethylcarbonyloxy (Fmoc) derivatives. The Friedel–Crafts reaction with various arenes was studied employing these alcohols as electrophiles. It turned out that the facial diastereoselectivitiy depends on the nitrogen protecting group and on the ester group. The unprotected substrates (NH2) gave preferentially syn‐products but the anti‐selectivity increased when going from NHFmoc over NPhth to NBn2. If the ester substituent was varied the syn‐preference increased in the order Me <Et <iPr. The reactions were shown to be fully stereoconvergent and proceeded under kinetic product control. A model is suggested to explain the facial diastereoselectivity based on a conformationally locked benzylic cation intermediate. The reactions are preparatively useful for the N‐unprotected isopropyl ester, which gave Friedel–Crafts alkylation products with good syn‐selectivity (anti/syn=21:79 to 7:93), and for the N,N‐dibenzyl‐protected methyl ester, which led preferentially to anti‐products (anti/syn=80:20 to >95:5). Upon acetylation of the latter compound to the respective acetate, Bi(OTf)3‐catalyzed alkylation reactions became possible, in which silyl enol ethers served as nucleophiles. The respective alkylation products were obtained in high yield and with excellent anti‐selectivitiy (anti/syn≥95:5). 相似文献
157.
Dvorak J Brüchle W Chelnokov M Dressler R Düllmann ChE Eberhardt K Gorshkov V Jäger E Krücken R Kuznetsov A Nagame Y Nebel F Novackova Z Qin Z Schädel M Schausten B Schimpf E Semchenkov A Thörle P Türler A Wegrzecki M Wierczinski B Yakushev A Yeremin A 《Physical review letters》2006,97(24):242501
Theoretical calculations predict 270Hs (Z=108, N=162) to be a doubly magic deformed nucleus, decaying mainly by alpha-particle emission. In this work, based on a rapid chemical isolation of Hs isotopes produced in the 26Mg+248Cm reaction, we observed 15 genetically linked nuclear decay chains. Four chains were attributed to the new nuclide 270Hs, which decays by alpha-particle emission with Qalpha=9.02+/-0.03 MeV to 266Sg which undergoes spontaneous fission with a half-life of 444(-148)(+444) ms. A production cross section of about 3 pb was measured for 270Hs. Thus, 270Hs is the first nucleus for which experimental nuclear decay properties have become available for comparison with theoretical predictions of the N=162 shell stability. 相似文献
158.
J. Ketelaer K. Blaum M. Block K. Eberhardt M. Eibach R. Ferrer S. George F. Herfurth J. Ketter Sz. Nagy J. Repp L. Schweikhard C. Smorra S. Sturm S. Ulmer 《The European Physical Journal A - Hadrons and Nuclei》2009,42(3):311-317
The highest precision in the determination of nuclear and atomic masses can be achieved by Penning trap mass spectrometry. The mass value is obtained through a measurement of the cyclotron frequency of the stored charged particle. Two different approaches are used at the Penning trap mass spectrometer TRIGA-TRAP for the mass determination: the destructive Time-Of-Flight Ion Cyclotron Resonance (TOF-ICR) technique and the non-destructive Fourier Transform Ion Cyclotron Resonance (FT-ICR) method. New developments for both techniques are described, which will improve the detection efficiency and the suppression of contaminations in the case of TOF-ICR. The FT-ICR detection systems will allow for the investigation of an incoming ion bunch from a radioactive-beam facility on the one hand, and for the detection of a single singly charged ion in the Penning trap on the other hand. 相似文献
159.
André Boltjes Dr. Annadka Shrinidhi Kees van de Kolk Dr. Eberhardt Herdtweck Prof. Dr. Alexander Dömling 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(22):7352-7356
A simple Ugi tetrazole multicomponent reaction allows the synthesis of a novel macrocyclic cyclen derivative with four appendant tetrazole arms in just two steps in excellent yields. This ligand, called TEMDO, turns out to have a high complexation affinity with lanthanoid metals. Here we describe the design, synthesis, solid‐state structure, binding constant, and some MRI applications of the Gd‐TEMDO complex as the first example of a congeneric family of oligo‐amino tetrazoles. 相似文献
160.