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171.
Liang Yue Verena Wulf Shan Wang Itamar Willner 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(35):12366-12373
The evolution of networks is a fundamental unresolved issue in developing the area of systems chemistry. We introduce a versatile rewiring mechanism that leads to the emergence of nucleic‐acid‐based constitutional dynamic networks (CDNs). A two‐component constituent AA′ functionalized with a Mg2+‐ion‐dependent DNAzyme activator unit forms a complex with an intact hairpin HBB′ composed of B and B′ sequences. Cleavage of HBB′ leads to the two‐component constituent BB′, and its rewiring with AA′ yields CDN X composed of the equilibrated constituents AA′, AB′, BA′, and BB′. In analogy, subjecting AA′ to an intact hairpin HCC′ leads to the formation of CDN Y consisting of AA′, AC′, CA′, and CC′. Subjecting AA′ to the mixture of HBB′ and HCC′ evolves the [3×3] CDN Z, composed of nine constituents, thus demonstrating hierarchical adaptive properties. Furthermore, the DNAzyme units associated with the constituents are applied to tailor emerging catalytic functions from the different CDNs. 相似文献
172.
Vapour pressure is an important parameter for predicting the distribution of a substance in the environment. Therefore, the vapour pressure of the herbicide Triallate was determined using the Knudsen effusion technique. At least two polymorphic phases of Triallate were identified employing thermooptical and calorimetric methods. 相似文献
173.
Wolfgang Walter Wulf Ruback Claus O. Meese 《Magnetic resonance in chemistry : MRC》1978,11(12):612-616
The 13C NMR shifts of the E/Z mixtures of twelve, mainly ortho substituted, methyl N-methylthio-benzimidates have been completely assigned. The angles of twist about the aryl-imino-carbon bond were determined by means of the C-1 aryl shifts. Depending on the bulk of the ortho substituents the values vary from 18° in methyl 2-fluoro-N-methylthiobenzibenzimidate (Z) to 73° in methyl 4-bromo-N,2,6-trimethylthio-benzimidate (E). An explanation for the 13C-E/Z-N-alkyl and -S-alkyl resonances is facilitated by a new model which is initially based on the influence of electric fields. As this model is derived from amides, thioamides etc. it is possible to interpret the 13C-E/Z shifts in all related classes of compounds. The role of steric compression does not seem to be as important as was previously assumed. 相似文献
174.
175.
Ya. I. Isakov Kh. M. Minachev R. Tome A. Tissle G. Oehlmann V. P. Kalinin T. A. Isakova 《Russian Chemical Bulletin》1994,43(12):2004-2010
It is found that zeolite-like crystalline aluminophosphates VPI-5, Si-VPI-5, and Mn-VPI-5 as well as those dirived from them, AlPO{in4}-8, SAPO{in4}-8, and MnAPO{in4}-8, are capable of catalyzing aldol condensation and crotonization of butyraldehyde (BA). Pd/AlPO{in4}-8 is catalytically active in hydrocondensation of BA with H{in2} at atmospheric pressure. The activities in BA conversion to 2-ethylhexane-3-ol-1-al increase in the following order: Mn-VPI-5 < Si-VPI-5 < VPI-5. The same order of activities is also found for AlPO{in4}-8, SAPO{in4}-8, and MnAPO{in4}-8. These catalysts are characterized by a lower initial activity in crotonization of BA than M{su+}NaX (CsNaX), but they are much more stable. Pd/AlPO{in4}-8 catalyzes BA conversion to 2-ethylhexanal even in the absence of H{in2} feed to the reaction zone. The influence of catalyst pretreatments and experimental conditions on the catalyst structures and catalytic activities is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khmicheskaya, No. 12, pp. 2123–2129, December, 1994. 相似文献
176.
Siemensmeyer K Wulf E Mikeska HJ Flachbart K Gabáni S Mat'as S Priputen P Efdokimova A Shitsevalova N 《Physical review letters》2008,101(17):177201
We investigate the phase diagram of TmB4, an Ising magnet on a frustrated Shastry-Sutherland lattice, by neutron diffraction and magnetization experiments. At low temperature we find Néel order at low field, ferrimagnetic order at high field, and an intermediate phase with magnetization plateaus at fractional values M/M_(sat)=1/7,1/8,1/9,... and spatial stripe structures. Using an effective S=1/2 model and its equivalent two-dimensional fermion gas we suggest that the magnetic properties of TmB4 are related to the fractional quantum Hall effect of a 2D electron gas. 相似文献
177.
178.
Wang S Alekseev EV Depmeier W Albrecht-Schmitt TE 《Chemical communications (Cambridge, England)》2011,47(39):10874-10885
The use of molten boric acid as a reactive flux for synthesizing actinide borates has been developed in the past two years providing access to a remarkable array of exotic materials with both unusual structures and unprecedented properties. [ThB(5)O(6)(OH)(6)][BO(OH)(2)]·2.5H(2)O possesses a cationic supertetrahedral structure and displays remarkable anion exchange properties with high selectivity for TcO(4)(-). Uranyl borates form noncentrosymmetric structures with extraordinarily rich topological relationships. Neptunium borates are often mixed-valent and yield rare examples of compounds with one metal in three different oxidation states. Plutonium borates display new coordination chemistry for trivalent actinides. Finally, americium borates show a dramatic departure from plutonium borates, and there are scant examples of families of actinides compounds that extend past plutonium to examine the bonding of later actinides. There are several grand challenges that this work addresses. The foremost of these challenges is the development of structure-property relationships in transuranium materials. A deep understanding of the materials chemistry of actinides will likely lead to the development of advanced waste forms for radionuclides present in nuclear waste that prevent their transport in the environment. This work may have also uncovered the solubility-limiting phases of actinides in some repositories, and allows for measurements on the stability of these materials. 相似文献
179.
G. Gesekus I. Dierking Corresponding author S. Gerber M. Wulf V. Vill 《Liquid crystals》2013,40(2):145-152
This paper describes the synthesis and physical properties of a chiral bent-core liquid crystal containing the chiral non-aromatic central ring system 1,5-anhydro-2-desoxy-D-arabino-hexitol. The preparation involved a stepwise construction of the mesogenic side chains via a selective diesterification of glucal at positions three and six with 4-O-acetylbenzoyl chloride followed by selective deacetylation. Repeated esterification of the aromatic hydroxy group with a substituted benzoic acid and hydrogenation of the double bond resulted in the desired product. To our knowledge, this is the first banana shaped liquid crystal synthesized containing a sugar derivative as a chiral core. Investigation of the mesogenic properties and electro-optic experiments showed traditional calamitic phases along with banana phases. 相似文献
180.
The hydrothermal treatment of UO3, Cd(CH3CO2)2·2H2O, and triethyl phosphonoacetate results in the formation of Cd2[(UO2)6(PO3CH2CO2)3O3(OH)(H2O)2]·16H2O (CdUPAA-1), [Cd3(UO2)6(PO3CH2CO2)6(H2O)13]·6H2O (CdUPAA-2), and Cd(H2O)2[(UO2)(PO3CH2CO2)(H2O)]2 (CdUPAA-3). CdUPAA-1 adopts a cubic three-dimensional structure constructed from planar uranyl oxide clusters containing both UO7 pentagonal bipyramids and UO8 hexagonal bipyramids that are linked by Cd(II) cations and phosphonoacetate to yield large cavities approximately 16 Å across that are filled with disordered water molecules. CdUPAA-2 forms a rhombohedral three-dimensional channel structure that is assembled from UO7 pentagonal bipyramids that are bridged by phosphonoacetate. CdUPAA-3 is layered with the hydrated Cd(II) cations incorporated directly into the layers linking one-dimensional uranyl phosphonate substructures together. In this structure, there are complex networks of hydrogen bonds that exist within the sheets, and also stitch the sheets together. 相似文献