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Frontispiece: Dendronized Hyperbranched Macromolecules: Soft Matter with a Novel Type of Segmental Distribution
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Introducing a Hydrogen‐Bond Donor into a Weakly Nucleophilic Brønsted Base: Alkali Metal Hexamethyldisilazides (MHMDS,M=Li,Na, K,Rb and Cs) with Ammonia
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Dr. Roman Neufeld Reent Michel Dr. Regine Herbst‐Irmer Ralf Schöne Prof. Dr. Dietmar Stalke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(35):12340-12346
Alkali metal 1,1,1,3,3,3‐hexamethyldisilazide (MHMDSs) are one of the most utilised weakly nucleophilic Brønsted bases in synthetic chemistry and especially in natural product synthesis. Like lithium organics, they aggregate depending on the employed donor solvents. Thus, they show different reactivity and selectivity as a function of their aggregation and solvation state. To date, monomeric LiHMDS with monodentate donor bases was only characterised in solution. Since the first preparation of LiHMDS in 1959 by Wannagat and Niederprüm, all efforts to crystallise monomeric LiHMDS in the absence of chelating ligands failed. Herein, we present ammonia adducts of LiHMDS, NaHMDS, KHMDS, RbHMDS and CsHMDS with unprecedented aggregation motifs: 1) The hitherto missing monomeric key compound in the LiHMDS aggregation architectures. Monomeric crystal structures of trisolvated LiHMDS ( 1 ) and NaHMDS ( 2 ), showing unique intermolecular hydrogen bonds, 2) the unprecedented tetrasolvated KHMDS ( 3 ) and RbHMDS ( 4 ) dimers and 3) the disolvated CsHMDS ( 5 ) dimer with very close intermolecular Si?CH3???Cs s‐block “agostic” interactions have been prepared and characterised by single‐crystal X‐ray structure analysis. 相似文献
998.
Copper‐Based Photosensitisers in Water Reduction: A More Efficient In Situ Formed System and Improved Mechanistic Understanding
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Dr. Alastair J. J. Lennox Steffen Fischer Mark Jurrat Dr. Shu‐Ping Luo Dr. Nils Rockstroh Dr. Henrik Junge Prof. Dr. Ralf Ludwig Prof. Dr. Matthias Beller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1233-1238
The reduction of water has been achieved through a non‐noble‐metal‐based homogeneous catalyst system that is formed in situ. Optimisation of the ligand quantities increased catalyst turnover numbers compared to preformed complexes. Mechanistic studies confirm a heteroleptic Cu complex as the active photosensitiser (PS) and an in situ formed Fe–phosphido dimer complex as the water reduction catalyst. The in situ method has been used to screen a range of ligands for the active PS, which has led to the identification a number of structural features important to longevity and performance. 相似文献
999.
Edgar Fuentes Kamila Boháčová Ana M. Fuentes-Caparrós Dr. Ralf Schweins Dr. Emily R. Draper Dr. Dave J. Adams Dr. Silvia Pujals Dr. Lorenzo Albertazzi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(44):9869-9873
Self-assembly of fluorenylmethoxycarbonyl-protected diphenylalanine (FmocFF) in water is widely known to produce hydrogels. Typically, confocal microscopy is used to visualize such hydrogels under wet conditions, that is, without freezing or drying. However, key aspects of hydrogels like fiber diameter, network morphology and mesh size are sub-diffraction limited features and cannot be visualized effectively using this approach. In this work, we show that it is possible to image FmocFF hydrogels by Points Accumulation for Imaging in Nanoscale Topography (PAINT) in native conditions and without direct gel labelling. We demonstrate that the fiber network can be visualized with improved resolution (≈50 nm) both in 2D and 3D. Quantitative information is extracted such as mesh size and fiber diameter. This method can complement the existing characterization tools for hydrogels and provide useful information supporting the design of new materials. 相似文献
1000.
NNP‐Type Pincer Imidazolylphosphine Ruthenium Complexes: Efficient Base‐Free Hydrogenation of Aromatic and Aliphatic Nitriles under Mild Conditions
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Dr. Rosa Adam Dr. Elisabetta Alberico Dr. Wolfgang Baumann Dr. Hans‐Joachim Drexler Dr. Ralf Jackstell Dr. Henrik Junge Prof. Dr. Matthias Beller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(14):4991-5002
A series of seven novel NImNHP‐type pincer imidazolylphosphine ruthenium complexes has been synthesized and fully characterized. The use of hydrogenation of benzonitrile as a benchmark test identified [RuHCl(CO)(NImNHPtBu)] as the most active catalyst. With its stable Ru?BH4 analogue, in which chloride is replaced by BH4, a broad range of (hetero)aromatic and aliphatic nitriles, including industrially interesting adiponitrile, has been hydrogenated under mild and base‐free conditions. 相似文献