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排序方式: 共有1462条查询结果,搜索用时 140 毫秒
1.
Povarov I. G. Shilenkov N. A. Peterson I. V. Suboch G. A. Tovbis M. S. 《Russian Journal of Organic Chemistry》2019,55(5):730-733
Russian Journal of Organic Chemistry - Dimethyl 5-amino-2-hydroxy-4,6-dimethylisophthalate and dimethyl 5-amino-2-hydroxy-4,6-dimethylisophthalate were obtained in the free form for the first time.... 相似文献
2.
Anna Peterson Mari-Liis Ludvig Jevgenija Martõnova Sandra Kaabel Paul Kerner Merle Uudsemaa 《Supramolecular chemistry》2020,32(5):313-319
ABSTRACT We demonstrate that Ullman fragment-coupling can be used to synthesise an oxacalix[4]arene monocarboxylic acid, which provides easy access to its water-soluble carboxylato derivatives. Crystallographic and computational data suggest that the new carboxyl-substituted oxacalix[4]arene adopts a 1,3-alternate conformation both in the solid-state and in methanol solution. Its water-soluble tetrabutylammonium derivate can detect the herbicide paraquat at neutral pH in aqueous media (K a = 111 ± 3 M–1) and in methanol (K a = 2020 ± 70 M–1). 相似文献
3.
Dr. Haixiang Han Jesse C. Carozza Audra P. Colliton Yuxuan Zhang Dr. Zheng Wei Dr. Alexander S. Filatov Prof. Dr. Yu-Sheng Chen Melisa Alkan Prof. Dr. Andrey Yu. Rogachev Prof. Dr. Evgeny V. Dikarev 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(24):9711-9717
A known trinuclear structure was used to design the heterobimetallic mixed-valent, mixed-ligand molecule [CoII(hfac)3−Na−CoIII(acac)3] ( 1 ). This was used as a template structure to develop heterotrimetallic molecules [CoII(hfac)3−Na−FeIII(acac)3] ( 2 ) and [NiII(hfac)3−Na−CoIII(acac)3] ( 3 ) via isovalent site-specific substitution at either of the cobalt positions. Diffraction methods, synchrotron resonant diffraction, and multiple-wavelength anomalous diffraction were applied beyond simple structural investigation to provide an unambiguous assignment of the positions and oxidation states for the periodic table neighbors in the heterometallic assemblies. Molecules of 2 and 3 are true heterotrimetallic rather than a statistical mixture of two heterobimetallic counterparts. Trinuclear platform 1 exhibits flexibility in accommodating a variety of di- and trivalent metals, which can be further utilized in the design of molecular precursors for the NaMM′O4 functional oxide materials. 相似文献
4.
Matthew L. Gettings Michael T. Thoenen Dr. Edward F. C. Byrd Dr. Jesse J. Sabatini Dr. Matthias Zeller Prof. Dr. Davin G. Piercey 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(64):14530-14535
This work reports the first compound containing both a tetrazole and an azasydnone ring, a unique energetic material. Several energetic salts of the tetrazole azasydnone were synthesized and characterized, leading to the creation of new secondary and primary explosives. Molecular structures are confirmed by 1H and 13C NMR, IR spectroscopy, and X-ray crystallographic analysis. The high heats of formation, fast detonation velocities, and straight-forward synthesis of energetic azasydnones should capture the attention of future energetics research. 相似文献
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7.
Dr. Igor V. Pimkov Dr. Barbara Serli‐Mitasev Antoinette A. Peterson Stephen C. Ratvasky Dr. Bernd Hammann Prof. Partha Basu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(47):17057-17072
Molybdopterin is an essential cofactor for all forms of life. The cofactor is composed of a pterin moiety appended to a dithiolene‐functionalized pyran ring, and through the dithiolene moiety it binds metal ions. Different synthetic strategies for dithiolene‐functionalized pyran precursors that have been designed and synthesized are discussed. These precursors also harbor 1,2‐diketone or osone functionality that has been condensed with 1,2‐diaminobenzene or other heterocycles resulting in several quinoxaline or pterin derivatives. Use of additives improves the regioselectivity of the complexes. The molecules have been characterized by 1H and 13C NMR and IR spectroscopies, as well as by mass spectrometry. In addition, several compounds have been crystallographically characterized. The geometries of the synthesized molecules are more planar than the geometry of the cofactor found in proteins. 相似文献
8.
Dr. Michael Georg Hoesl M. Sc. Stefan Oehm Dr. Patrick Durkin Dr. Elise Darmon Dr. Lauri Peil Dr. Hans‐Rudolf Aerni Prof. Dr. Juri Rappsilber Prof. Dr. Jesse Rinehart Prof. Dr. David Leach Prof. Dr. Dieter Söll Prof. Dr. Nediljko Budisa 《Angewandte Chemie (International ed. in English)》2015,54(34):10030-10034
We have changed the amino acid set of the genetic code of Escherichia coli by evolving cultures capable of growing on the synthetic noncanonical amino acid L ‐β‐(thieno[3,2‐b]pyrrolyl)alanine ([3,2]Tpa) as a sole surrogate for the canonical amino acid L ‐tryptophan (Trp). A long‐term cultivation experiment in defined synthetic media resulted in the evolution of cells capable of surviving Trp→[3,2]Tpa substitutions in their proteomes in response to the 20 899 TGG codons of the E. coli W3110 genome. These evolved bacteria with new‐to‐nature amino acid composition showed robust growth in the complete absence of Trp. Our experimental results illustrate an approach for the evolution of synthetic cells with alternative biochemical building blocks. 相似文献
9.
This paper presents measurements in the turbulent wake of a circular cylinder rotating with its axis normal to the free-stream velocity; in other words, the axis of rotation was parallel to the streamwise direction. All three mean velocities and six Reynolds stresses were obtained at three positions downstream of the cylinder, with and without rotation of the free-stream. Most emphasis is given to the latter results because of the better flow quality. The ratio of the circumferential velocity of the cylinder to the free-stream velocity — the swirl number — had a maximum value of 0.6. Measurements for two combinations of the free-stream and angular velocities showed the velocity deficit in the wake to be a multi-valued function of the swirl number, implying that the rotation affected the separation of the cylinder's boundary layer in a complex manner. In the turbulent wake, the rotation did not significantly alter the magnitudes of the normal stresses, but caused large changes to the shape of the profiles of the axial and cross-stream normal stresses. Eventually, the primary (cross-stream) shear stress became almost entirely positive, but there was no corresponding change to the (cross-stream) gradient of the streamwise mean velocity. Despite these alterations to the turbulence, the rotationally-activated generation terms in the Reynolds transport equations never dominated the terms that are common to the wakes of rotating and non-rotating cylinders.This work was supported by the Australian Research Council. Most of the data acquisition software was written by Mr J. J. Smith. 相似文献
10.
In this study, a coupled regional air quality modeling system is applied to investigate the time spatial variations in airborne particulate matters (PM10), originating from Mentougou to Beijing municipal area in the period of April 1-7, 2004, and the influences of complex terrain and meteorological conditions upon boundary layer structure and PM10 concentration distributions. An intercomparison of the performance with CALPUFF against the observed data is presented and an examination of scatter plots is provided. The statistics show that the correlation coefficient and STD between the modeled and observed data are 0.86 and 0.03, respectively. Analysis of model results illustrates that the pollutants emitted from Mentougou can be transported to Beijing municipal area along certain transport pathways, and PM10 concentration distributions show heterogeneity characteristics. Contributions of the Mentougou sources to the PM10 concentrations in Beijing municipal area are up to 0.1-15 μg/m^3. 相似文献