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21.
Nils Metzler 《Nachrichten aus der Chemie》1994,42(12):1254-1256
„First International Conference on the Chemistry of the Alkali and Alkaline Earth Metals”︁ - die unter diesem Titel Ende September in Cambridge (UK) abgehaltene Tagung zeigte, daß sich die Chemie der Elemente der ersten beiden Hauptgruppen von einem esoterischen Spiel mit hochempfindlichen Verbindungen zu einem aktuellen und vielseitigen Zweig der Chemie entwickelt hat. 相似文献
22.
Chevallier Eloïse Demazy Nils Cuenca Amandine Chabert Max 《Transport in Porous Media》2020,131(1):43-63
Transport in Porous Media - The optimization of foam injection in porous media for enhanced oil recovery or soil remediation requires a large screening of surfactant formulations. Tests of foam... 相似文献
23.
In this contribution recent results on selective and precise tailoring of triangular gold nanoparticles (NPs) using ns-pulsed laser light are presented. The NPs were prepared by nanosphere lithography and subsequently tailored with ns-pulsed laser light using different fluences and wavelengths. The method is based on the size and shape dependent localized surface plasmon polariton resonance (SPR) of the NPs. We will demonstrate that the gap size between triangular NPs can be tuned from approximately 102±14 nm to 122±11 nm, due to a shape change of the NP from triangular to oblate. These morphological changes are accompanied by a significant shift of the surface plasmon resonance from λSPR=730 nm to λSPR=680 nm. Most importantly if the laser wavelength is chosen such that the dipolar SPR is excited, the hexagonal order of the NPs remains intact after irradiation, in contrast to excitation via the quadrupole SPR or within the interband transition. A tuneable gap size and the conservation of the hexagonal order of the NP array is the precondition for applications, where the NPs should serve as anchor points, e.g. for functional molecular nanowires, which can be used to utilize molecular devices. 相似文献
24.
With more and more organometallic compounds receiving attention for applications in medicinal organometallic chemistry, the need arises for stereoselective syntheses of more complicated structures containing organometallic moieties, for example as isosteric substitutes for organic drug candidates. Herein, the synthesis and characterization of both diastereomers of a planar chiral (η(6)-arene)Cr(CO)(3) containing carboxylic acid derivative, namely, 3-{η(6)-(1, 2, 3, 4-tetrahydro-1-endo/exo-methyl-2-oxonaphthalen-1-yl)-tricarbonylchromium(0)}propanoic acid (7 and 8) is reported. The molecular structures of both were confirmed by single crystal X-ray diffraction. The degree of diastereoselectivity in Cr(CO)(3) complexation with methyl/tert-butyl-3-(1,2,3,4-tetrahydro-1-methyl-2-oxonaphthalen-1-yl)propanoate (4a/4b) vs. the Michael addition of methyl/tert-butyl acrylate to (η(6)-1-methyl-2-tetralone)Cr(CO)(3) (9) was also examined. In the latter case the alkylation was found to be completely diastereoselective and gave methyl/tert-butyl-3-{η(6)-(1, 2, 3, 4-tetrahydro-1-endo-methyl-2-oxonaphthalen-1-yl)-tricarbonylchromium (0)}propanoate (5a and 5b) in excellent yield. Both the carboxylic acids 7 and 8 were coupled with the aminoresorcyclic acid core to achieve diastereomeric bioorganometallics 15a and 15b based on the naturally occurring antibiotic platensimycin lead structure (1a, see Fig. 1). The newly synthesized bioorganometallics were tested against various Gram-positive and Gram-negative bacterial strains but show no promising antibacterial activity. 相似文献
25.
Nils G. A. Ekelund Christer Sundqvist Peter H. Quail Richard D. Vierstra 《Photochemistry and photobiology》1985,41(2):221-223
Abstract— From light-induced changes in linear dichroism, we have calculated the rotation of the long-wavelength-absorbing transition moment that occurs during phototransformation of 124-kilodalton Avena sativa phytochrome. Phytochrome was purified to homogeneity and immobilized onto Sepharose beads covalently coated with antibodies against A. sativa phytochrome. Changes in linear dichroism were induced by plane-polarized red or far-red light and measured by the absorbance differences at 660 and 730 nm using a dual-wavelength spectrophotometer equipped with polarizing filters in the measuring beams. From such measurements, we calculate a rotation angle of 31o (or 149o ) during photoconversion of Pr to Pfr and 30o (or 150o ) during photoconversion of Pfr to Pr. These values are similar to the value of 32o (or 148o ) reported earlier for the rotation of the transition moment of "large" A. sativa phytochrome (∽ 120 kilodalton) isolated under conditions that did not preclude post homogenization proteolysis of the 124 kilodalton molecule. 相似文献
26.
Parmish Kaur Lukas Mai Arbresha Muriqi David Zanders Ramin Ghiyasi Dr. Muhammad Safdar Nils Boysen Manuela Winter Prof. Michael Nolan Prof. Maarit Karppinen Prof. Anjana Devi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(15):4913-4926
Owing to the limited availability of suitable precursors for vapor phase deposition of rare-earth containing thin-film materials, new or improved precursors are sought after. In this study, we explored new precursors for atomic layer deposition (ALD) of cerium (Ce) and ytterbium (Yb) containing thin films. A series of homoleptic tris-guanidinate and tris-amidinate complexes of cerium (Ce) and ytterbium (Yb) were synthesized and thoroughly characterized. The C-substituents on the N-C-N backbone (Me, NMe2, NEt2, where Me=methyl, Et=ethyl) and the N-substituents from symmetrical iso-propyl (iPr) to asymmetrical tertiary-butyl (tBu) and Et were systematically varied to study the influence of the substituents on the physicochemical properties of the resulting compounds. Single crystal structures of [Ce(dpdmg)3] 1 and [Yb(dpdmg)3] 6 (dpdmg=N,N'-diisopropyl-2-dimethylamido-guanidinate) highlight a monomeric nature in the solid-state with a distorted trigonal prismatic geometry. The thermogravimetric analysis shows that the complexes are volatile and emphasize that increasing asymmetry in the complexes lowers their melting points while reducing their thermal stability. Density functional theory (DFT) was used to study the reactivity of amidinates and guanidinates of Ce and Yb complexes towards oxygen (O2) and water (H2O). Signified by the DFT calculations, the guanidinates show an increased reactivity toward water compared to the amidinate complexes. Furthermore, the Ce complexes are more reactive compared to the Yb complexes, indicating even a reactivity towards oxygen potentially exploitable for ALD purposes. As a representative precursor, the highly reactive [Ce(dpdmg)3] 1 was used for proof-of-principle ALD depositions of CeO2 thin films using water as co-reactant. The self-limited ALD growth process could be confirmed at 160 °C with polycrystalline cubic CeO2 films formed on Si(100) substrates. This study confirms that moving towards nitrogen-coordinated rare-earth complexes bearing the guanidinate and amidinate ligands can indeed be very appealing in terms of new precursors for ALD of rare earth based materials. 相似文献
27.
Dr. Kai-Stephan Feichtner Dr. Lennart T. Scharf Dr. Thorsten Scherpf Dr. Bert Mallick Nils Boysen Prof. Dr. Viktoria H. Gessner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(69):17351-17360
The use of iminophosphoryl-tethered ruthenium carbene complexes to activate secondary phosphine P−H bonds is reported. Complexes of type [(p-cymene)-RuC(SO2Ph)(PPh2NR)] (with R = SiMe3 or 4-C6H4−NO2) were found to exhibit different reactivities depending on the electronics of the applied phosphine and the substituent at the iminophosphoryl moiety. Hence, the electron-rich silyl-substituted complex undergoes cyclometallation or shift of the imine moiety after cooperative activation of the P−H bond across the M=C linkage, depending on the electronics of the applied phosphine. Deuteration experiments and computational studies proved that cyclometallation is initiated by the activation process at the M=C bond and triggered by the high electron density at the metal in the phosphido intermediates. Consistently, replacement of the trimethylsilyl (TMS) group by the electron-withdrawing 4-nitrophenyl substituent allowed the selective cooperative P−H activation to form stable activation products. 相似文献
28.
Sebastian Wöllner Timothy Nowak Dr. Gui-Rong Zhang Dr. Nils Rockstroh Dr. Hanadi Ghanem Prof. Dr. Stefan Rosiwal Prof. Dr. Angelika Brückner Prof. Dr. Bastian J. M. Etzold 《ChemistryOpen》2021,10(5):600-606
Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) offers a renewable approach to produce the value-added platform chemical 2,5-furandicarboxylic acid (FDCA). The key for the economic viability of this approach is to develop active and selective electrocatalysts. Nevertheless, a reliable catalyst evaluation protocol is still missing, leading to elusive conclusions on criteria for a high-performing catalyst. Herein, we demonstrate that besides the catalyst identity, secondary parameters such as materials of conductive substrates for the working electrode, concentration of the supporting electrolyte, and electrolyzer configurations have profound impact on the catalyst performance and thus need to be optimized before assessing the true activity of a catalyst. Moreover, we highlight the importance of those secondary parameters in suppressing side reactions, which has long been overlooked. The protocol is validated by evaluating the performance of free-standing Cu-foam, and CuCoO modified with NaPO2H2 and Ni, which were immobilized on boron-doped diamond (BDD) electrodes. Recommended practices and figure of merits in carefully evaluating the catalyst performance are proposed. 相似文献
29.
30.
Olena Dobrovolska
yvind Strmland
rjan Sele Handegrd Martin Jakubec Morten L. Govasli ge Aleksander Skjevik Nils ge Frystein Knut Teigen
yvind Halskau 《Molecules (Basel, Switzerland)》2021,26(12)
The driving forces and conformational pathways leading to amphitropic protein-membrane binding and in some cases also to protein misfolding and aggregation is the subject of intensive research. In this study, a chimeric polypeptide, A-Cage-C, derived from α-Lactalbumin is investigated with the aim of elucidating conformational changes promoting interaction with bilayers. From previous studies, it is known that A-Cage-C causes membrane leakages associated with the sporadic formation of amorphous aggregates on solid-supported bilayers. Here we express and purify double-labelled A-Cage-C and prepare partially deuterated bicelles as a membrane mimicking system. We investigate A-Cage-C in the presence and absence of these bicelles at non-binding (pH 7.0) and binding (pH 4.5) conditions. Using in silico analyses, NMR, conformational clustering, and Molecular Dynamics, we provide tentative insights into the conformations of bound and unbound A-Cage-C. The conformation of each state is dynamic and samples a large amount of overlapping conformational space. We identify one of the clusters as likely representing the binding conformation and conclude tentatively that the unfolding around the central W23 segment and its reorientation may be necessary for full intercalation at binding conditions (pH 4.5). We also see evidence for an overall elongation of A-Cage-C in the presence of model bilayers. 相似文献