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461.
462.
Dr. Jan-Henrik Weddeling Paul Lukas Waltersmann Beate Neumann Dr. Hans-Georg Stammler Prof. Dr. Norbert W. Mitzel 《ChemistryOpen》2021,10(10):1059-1066
Several rigid 1,3,5-tris(phenylethynyl)benzenes with different fluorination patterns were synthesized through selective Sonogashira-Hagihara coupling reactions to analyze the packing behavior in solid-state structures. The aggregation is dominated by various intermolecular interactions between aryl substituents, triple bonds, C−H bonds and H⋅⋅⋅F contacts. Co-crystallization experiments for the analysis of preferred aryl-aryl-interactions led to 1 : 1 complexes. Intermolecular phenyl-perfluorophenyl interactions with short centroid-centroid distances are dominating these co-crystal structures. They lead to melting point increases of up to 49 °C for the co-crystals compared to the pure substances. 相似文献
463.
M. Sc. Benedikt Waerder Dipl.‐Chem. Simon Steinhauer Beate Neumann Dr. Hans‐Georg Stammler Dr. Andreas Mix Dr. Yury V. Vishnevskiy Prof. Dr. Berthold Hoge Prof. Dr. Norbert W. Mitzel 《Angewandte Chemie (International ed. in English)》2014,53(43):11640-11644
Lithium carbenoids are versatile compounds for synthesis owing to their intriguing ambiphilic behavior. Although this class of compounds has been known for several years, few solid‐state structures exist because of their high reactivity and often low thermal stability. Using cryo X‐ray techniques, we were now able to elucidate the first solid‐state structure of a Li/F alkyl carbenoid, pentafluoroethyllithium (LiC2F5), finally yielding a prototype for investigating structure—reactivity relationships for this class of molecules. The compound forms a diethyl ether‐solvated dimer bridged by a rare C–F–Li link. Complementary NMR spectroscopy studies in solution show dynamic processes and indicate rapid exchange of starting material and product. Theoretical investigations help to understand the formation of the observed unusual structural motif. 相似文献
464.
Beate Fuchs 《Analytical and bioanalytical chemistry》2014,406(5):1291-1306
Many diseases such as arthritis or atherosclerosis are accompanied by inflammatory processes. Inflammation is characterized by the infiltration of cells such as neutrophilic granulocytes and (a) the release of phospholipases [particularly phospholipase A2 (PLA2)] and (b) the generation of reactive oxygen as well as nitrogen species (ROS and RNS). While PLA2 leads to defined lyso products (lacking one acyl residue), lipid oxidation is characterized by much more complex product patterns, including lipid peroxides, aldehydes (by double bond cleavage), and many others. Nevertheless, oxidation processes are highly important under in vivo conditions because molecules with regulatory functions are generated by the oxidation of lipids and/or free fatty acids. Therefore, lipid oxidation products as well as lysolipids are increasingly assumed to represent important disease (bio)markers. Consequently, there is also increasing interest in methods to characterize these products qualitatively and quantitatively. Mass spectrometry (MS) seems to be the method of choice to study (phospho)lipids changed under inflammatory conditions: nowadays, soft ionization MS methods are regularly used to study oxidative lipid modifications because of their high sensitivities and the tremendous mass resolutions that are achievable by using modern mass spectrometers. However, experimental care is required to be able to detect all relevant products. Although electrospray ionization (ESI) MS is so far most popular, applications of matrix-assisted laser desorption and ionization (MALDI) MS are continuously increasing. This review aims to summarize the so far available data on MS analyses of oxidized lipids as well as lysolipids. In addition to model systems, special attention will be paid to the monitoring of oxidized lipids and lysolipids under in vivo conditions. It is the aim of this review to provide a critical survey of the advantages and drawbacks of the different MS methods, with the focus on MALDI and ESI. Figure
Scheme of mass spectrometric analysis to study oxidation and enzyme-modified phospholipids changed under inflammatory conditions 相似文献
465.
Simon Steinhauer Dr. Hans‐Georg Stammler Beate Neumann Nikolai Ignat'ev Prof. Dr. Berthold Hoge 《Angewandte Chemie (International ed. in English)》2014,53(2):562-564
The research area of perfluoroalkylsilanes is still in its infancy. Although there are already many examples of difluorotriorganylsilicates, the first example of a completely characterized trifluorotriorganylsilicate is presented, the dianion [Si(C2F5)3F3]2?. The strongly electron‐withdrawing influence of the pentafluoroethyl groups appears to be a fundamental cause of the stability of this compound. This dianion is also the first structurally characterized example of a tris(pentafluoroethyl)silicon compound. The synthesis and complete characterization of [PPh4]2[Si(C2F5)3F3] and [PPh4][Si(C2F5)3F2] along with the precursor [H(OEt2)2][Si(C2F5)3F2] was achieved from SiCl4 and LiC2F5. 相似文献
466.
Crystal Structures of the Carborane Dianions [1,4‐(PhCB10H10C)2C6H4]2− and [1,4‐(PhCB10H10C)2C6F4]2− and the Stabilizing Role of the para‐Phenylene Unit on 2 n+3 Skeletal Electron Clusters 下载免费PDF全文
Dr. Jan Kahlert Dr. Hans‐Georg Stammler Beate Neumann Dr. Rachel A. Harder Prof. Dr. Lothar Weber Dr. Mark A. Fox 《Angewandte Chemie (International ed. in English)》2014,53(14):3702-3705
While carboranes with 2 n+2 and 2 n+4 (n=number of skeletal atoms) skeletal electrons (SE) are widely known, little has been reported on carboranes with odd SE numbers. Electrochemical measurements on two‐cage assemblies, where two C‐phenyl‐ortho‐carboranyl groups are linked by a para‐phenylene or a para‐tetrafluorophenylene bridge, revealed two well separated and reversible two‐electron reduction waves indicating formation of stable dianions and tetraanions. The salts of the dianions were isolated by reduction with sodium metal and their unusual structures were determined by X‐ray crystallography. The diamagnetic dianions contain two 2 n+3 SE clusters where each cluster has a notably long carborane C–carborane C distance of ca 2.4 Å. The π conjugation within the phenylene bridge plays an important role in the stabilization of these carboranes with odd SE counts. 相似文献
467.
Back Cover: Synthesis and Reactivity of New Functionalized Perfluoroalkylfluorophosphates (Chem. Eur. J. 25/2014) 下载免费PDF全文
468.
Dr. Benedikt Waerder Martin Pieper Leif A. Körte Timo A. Kinder Dr. Andreas Mix Beate Neumann Dr. Hans‐Georg Stammler Prof. Dr. Norbert W. Mitzel 《Angewandte Chemie (International ed. in English)》2015,54(45):13416-13419
Frustrated Lewis pairs (FLPs) have a great potential for activation of small molecules. Most known FLP systems are based on boron or aluminum atoms as acid functions, few on zinc, and only two on boron‐isoelectronic silicenium cation systems. The first FLP system based on a neutral silane, (C2F5)3SiCH2P(tBu)2 ( 1 ), was prepared from (C2F5)3SiCl with C2F5 groups of very high electronegativity and LiCH2P(tBu)2. 1 is capable of cleaving hydrogen, and adds CO2 and SO2. Hydrogen splitting was confirmed by H/D scrambling reactions. The structures of 1 , its CO2 and SO2 adducts, and a decomposition product with CO2 were elucidated by X‐ray diffraction. 相似文献
469.
Mapping of spikes, slow waves, and motor tasks in a patient with malformation of cortical development using simultaneous EEG and fMRI 总被引:1,自引:0,他引:1
We report on the simultaneous and continuous acquisition of EEG and functional MRI data in a patient with a left hemiparesis and focal epilepsy secondary to malformation of cortical development in the right hemisphere. EEG-triggered fMRI localization was previously demonstrated in this patient. In the experiments reported here, 322 spikes maximum at electrode C4 and 126 focal slow waves were identified offline. A hierarchy of models was explored in order to assess the relative contributions of each type of EEG event. Modeling the BOLD response to C4 spikes alone showed an area of activation within the large malformation, adjacent to the area of infolding cortex. However, also modeling slow-waves gave rise to a broader and stronger activation, suggesting that the generators overlap. Motor mapping of the right hand showed activation in the left sensorimotor cortex; left-hand tapping led to a more diffuse area of activation, displaced superiorly into the superior frontal gyrus, and a small area of activation within the lesion. In conclusion, continuous EEG-fMRI is useful to compare the functional mapping of epileptiform activity and eloquent cortices in individual patients. 相似文献
470.