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91.
Markus Hecht Dr. Pawaret Leowanawat Tabea Gerlach Dr. Vladimir Stepanenko Dr. Matthias Stolte Prof. Dr. Matthias Lehmann Prof. Dr. Frank Würthner 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(39):17232-17238
A new perylene bisimide (PBI), with a fluorescence quantum yield up to unity, self-assembles into two polymorphic supramolecular polymers. This PBI bears four solubilizing acyloxy substituents at the bay positions and is unsubstituted at the imide position, thereby allowing hydrogen-bond-directed self-assembly in nonpolar solvents. The formation of the polymorphs is controlled by the cooling rate of hot monomer solutions. They show distinctive absorption profiles and morphologies and can be isolated in different polymorphic liquid-crystalline states. The interchromophoric arrangement causing the spectral features was elucidated, revealing the formation of columnar and lamellar phases, which are formed by either homo- or heterochiral self-assembly, respectively, of the atropoenantiomeric PBIs. Kinetic studies reveal a narcissistic self-sorting process upon fast cooling, and that the transformation into the heterochiral (racemic) sheetlike self-assemblies proceeds by dissociation via the monomeric state. 相似文献
92.
Markus Suta Flavie Lavoie‐Cardinal Claudia Wickleder 《Angewandte Chemie (International ed. in English)》2020,59(27):10949-10954
Inorganic hosts, such as SrB4O7 or certain nitrides, intrinsically stabilize Eu2+ even when the dopant is an Eu3+‐based precursor and reducing conditions are not employed in the synthesis. Although this concept is well known in the synthesis of phosphorescent materials, the mechanistic details are scarcely understood. Herein, we demonstrate that trapped charge carriers, such as color centers, can also act as redox partners to stabilize certain oxidation states of activators. Eu‐activated CsMgCl3 and CsMgBr3 are used as examples. Upon doping with EuCl3 and in the absence of reducing conditions during the synthesis, dominant cyan or green luminescence from Eu2+ ions was observed. Photoluminescence spectroscopy at 10 K revealed that the reduction is correlated to color centers localized at defects. Although defects are typically undesired in phosphors, we have shown that their role may be underestimated and they could be used on purpose in the preparation of selected inorganic phosphors. 相似文献
93.
Bhuvanesh Gupta Felix N. Büchi Markus Staub D. Grman Günther G. Scherer 《Journal of polymer science. Part A, Polymer chemistry》1996,34(10):1873-1880
The structure and some physico-chemical properties of radiation grafted FEP-g-polystyrenesulfonic acid proton exchange membranes were studied as a function of the degree of grafting. The distribution of grafted polymer across the membrane thickness was obtained from microprobe measurements. It was found that for low levels of grafting (ca. 3%), polystyrene chains are located near the membrane surface only, and the interior of the membrane remains ungrafted. With the increasing degree of grafting, polystyrene chains were incorporated into the interior of the membrane as well. An almost homogeneous distribution of grafts in the membrane was obtained at a graft level of > 13%. The influence of the degree of grafting on membrane properties, such as ion exchange capacity, swelling, and specific resistivity was studied. Three different states of water, viz., freezing free, freezing bound, and nonfreezing water have been identified in noncrosslinked membranes. However, the nature and the amount of crosslinker had a profound influence on the states of water in a membrane. © 1996 John Wiley & Sons, Inc. 相似文献
94.
The formation and consumption of CH radicals during shock-induced pyrolysis of a few ppm ethane diluted in argon was measured by a ring-dye laser spectrometer. Absorption-over-time profiles, measured at a resonance line in the Q-branch of the A2Δ − X2Π band of CH at λ = 431.1311 nm, were recorded and transformed into CH concentrations by known absorption coefficients. By adding some hundred ppm of CO2 or O2 to the initial mixtures, the CH concentration profiles were significantly perturbed. Both the perturbed and unperturbed CH concentration profiles have been compared with calculations based on a reaction kinetic model. A sensitivity analysis revealed that the perturbation process was dominated by direct reactions of CH with the added molecules. By fitting calculated to observed CH profiles the following rate coefficients were obtained The experiments were performed in the temperature range between 2500 K and 3500 K. © 1996 John Wiley & Sons, Inc. 相似文献
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97.
The changes in the local and global dynamics of azide-labelled lysozyme compared with that of the wild type protein are quantitatively assessed for all alanine residues along the polypeptide chain. Although attaching -N to alanine residues has been considered to be a minimally invasive change in the protein it is found that depending on the location of the alanine residue, the local and global changes in the dynamics differ. For Ala92, the change in the cross-correlated motions are minimal, whereas attaching -N to Ala90 leads to pronounced differences in the local and global correlations as quantified by the cross-correlation coefficients of the C atoms. We also demonstrate that the spectral region of the asymmetric azide stretch distinguishes between alanine attachment sites, whereas changes in the low frequency, far-infrared region are less characteristic. 相似文献
98.
M. Sc. Stephanie Kindt Karina Wicht Prof. Dr. Markus R. Heinrich 《Angewandte Chemie (International ed. in English)》2016,55(30):8744-8747
The radical carbohydroxylation of styrenes with aryldiazonium salts has been achieved under mild thermal conditions. A broad range of aryldiazonium salts was tolerated, and the reaction principle based on a radical–polar crossover mechanism could be extended to carboetherification as well as to a two‐step, metal‐free variant of the Meerwein arylation leading to stilbenes. 相似文献
99.
100.
A kicked quantum nondemolition measurement is introduced, where a qubit is weakly measured by pumping current. Measurement statistics are derived for weak measurements combined with single-qubit unitary operations. These results are applied to violate a generalization of the Leggett-Garg inequality. The violation is related to the failure of the noninvasive detector assumption, and may be interpreted as either intrinsic detector backaction, or the qubit entangling the microscopic detector excitations. The results are discussed in terms of a quantum point contact kicked by a pulse generator, measuring a double quantum dot. 相似文献