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排序方式: 共有185条查询结果,搜索用时 328 毫秒
61.
Dr. Emine Sager Dr. Pavleta Tzvetkova Dr. Alvar D. Gossert Philippe Piechon Prof. Dr. Burkhard Luy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(63):14435-14444
NMR-based determination of the configuration of complex molecules containing many stereocenters is often not possible using traditional NOE data and coupling patterns. Making use of residual dipolar couplings (RDCs), we were able to determine the relative configuration of a natural product containing seven stereocenters, including a chiral amine lacking direct RDC data. To identify the correct relative configuration out of 32 possible ones, experimental RDCs were used in three different approaches for data interpretation: by fitting experimental data based singular value decomposition (SVD) using a single alignment tensor and either (i) a single conformer or (ii) multiple conformers, or alternatively (iii) using molecular dynamics simulations with tensorial orientational constraints (MDOC). Even though in all three approaches one and the same configuration could be selected and clear discrimination between possible configurations was achieved, the experimental data was not fully satisfied by the methods based on single tensor approaches. While these two approaches are faster, only MDOC is able to fully reproduce experimental results, as the obtained conformational ensemble adequately covers the conformational space necessary to describe the molecule with inherent flexibility. 相似文献
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Bilge Taner Pervin Deveci Emine ?zcan Ali Osman Solak 《Journal of inclusion phenomena and macrocyclic chemistry》2012,74(1-4):391-396
A new calix[4]pyrrole functionalized vic-dioxime, 3-(4-methyl-9,9,14,14,19,19-hexaethylcalix[4]pyrrole)benzoaminoglyoxime (LH2) was synthesized from anti-chloroglyoxime and 3-aminophenyl-calix[4]pyrrole at room temperature. The mononuclear complexes {nickel(II), copper(II) and cobalt(II)} of this vic-dioxime ligand were prepared and their structures were confirmed by elemental analysis, IR and UV–Vis spectrophotometry, magnetic susceptibility; the MS, 1H and 13C NMR spectra of the LH2 ligand and its Ni(II) complex were also recorded. The experimental results indicated that the ligand:metal ratio was 2:1 in the cases of Ni(II), Cu(II) and Co(II) complexes as is with most vic-dioximes. Electrochemical properties of the ligand, and its complexes were investigated in DMSO solution by cyclic voltammetry at 200?mV?s?1 scan rate. 相似文献
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Let R be a noncommutative prime ring and I a nonzero left ideal of R. Let g be a generalized derivation of R such that [g(r k ), r k ] n = 0 for all r ∈ I, where k, n are fixed positive integers. Then there exists c ∈ U, the left Utumi quotient ring of R, such that g(x) = xc and I(c ? α) = 0 for a suitable α ∈ C. In particular we have that g(x) = α x, for all x ∈ I. 相似文献
65.
Diane Donovan James Lefevre Mary Waterhouse Emine Şule Yazıcı 《Graphs and Combinatorics》2009,25(6):825-839
A defining set of a t-(v, k, λ) design is a subcollection of its blocks which is contained in no other t-design with the given parameters, on the same point set. A minimal defining set is a defining set, none of whose proper subcollections is a defining set. The spectrum of minimal defining sets of a design D is the set {|M| | M is a minimal defining set of D}. We show that if a t-(v, k, λ) design D is contained in a design F, then for every minimal defining set d D of D there exists a minimal defining set d F of F such that \({d_D = d_F\cap D}\). The unique simple design with parameters \({{\left(v,k, {v-2\choose k-2}\right)}}\) is said to be the full design on v elements; it comprises all possible k-tuples on a v set. Every simple t-(v, k, λ) design is contained in a full design, so studying minimal defining sets of full designs gives valuable information about the minimal defining sets of all t-(v, k, λ) designs. This paper studies the minimal defining sets of full designs when t = 2 and k = 3. Several families of non-isomorphic minimal defining sets of these designs are found. For given v, a lower bound on the size of the smallest and an upper bound on the size of the largest minimal defining set are given. The existence of a continuous section of the spectrum comprising approximately v values is shown, where just two values were known previously. 相似文献
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Yiğit Murat Karaca Emine Özge Yiğit Beyhan Gürbüz Nevin Özdemir İsmail 《Transition Metal Chemistry》2019,44(6):565-573
Transition Metal Chemistry - New ruthenium(II) complexes with N-heterocyclic carbene ligand were synthesized by transmetalation reactions between silver(I) N-heterocyclic carbene complexes and... 相似文献
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The heterogeneous esterification reaction of acrylic acid with hexanol over three different cation‐exchange resins, Amberlyst 131, Amberlyst 15, and Dowex 50Wx‐400, was investigated. Surface area, pore volume, average pore diameter, and acid capacity analyses were carried out for these three catalysts. Amberlyst 131 gave the highest conversion, and therefore, further experiments were performed catalyzed by Amberlyst 131. The absence of external and internal mass transfer resistances was investigated for the esterification of acrylic acid with hexanol. Experiments showed that the reaction is controlled by chemical step rather than external and internal mass transfer steps. The effects of temperature, catalyst loading, and alcohol to acid molar ratio on the conversion of acrylic acid were determined. The activation energy and kinetic and adsorption constants were determined according to the Langmuir–Hinshelwood–Hougen–Watson mechanism. 相似文献