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861.
Metal‐Catalyzed Reductive Coupling Reactions of Organic Halides with Carbonyl‐Type Compounds 下载免费PDF全文
Dr. Toni Moragas Dr. Arkaitz Correa Prof. Dr. Ruben Martin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(27):8242-8258
Metal‐catalyzed reductive coupling reactions of aryl halides and (pseudo)halides with carbonyl‐type compounds have undergone an impressive development within the last years. These methodologies have shown to be a powerful alternate strategy, practicality aside, to the use of stoichiometric, well‐defined, and, in some cases, air‐sensitive organometallic species. In this Minireview, the recent findings in this field are summarized, with particular emphasis on the mechanistic interpretation of the results and future aspects of this area of expertise. 相似文献
862.
Oligosiloxane Functionalized with Pendant (1,3‐Bis(9‐carbazolyl)benzene) (mCP) for Solution‐Processed Organic Electronics 下载免费PDF全文
Dr. Dianming Sun Dr. Zhaomin Yang Dr. Zhongjie Ren Dr. Huihui Li Prof. Martin R. Bryce Prof. Dongge Ma Prof. Shouke Yan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(49):16233-16241
A new oligosiloxane derivative (ODCzMSi) functionalized with the well‐known 1,3‐bis(9‐carbazolyl)benzene (mCP) pendant moiety, directly linked to the silicon atom of the oligosiloxane backbone, has been synthesized and characterized. Compared to mCP, the attachment of the oligosiloxane chain significantly improves the thermal and morphological stabilities with a high decomposition temperature (Td=540 °C) and glass transition temperature (Tg=142 °C). The silicon–oxygen linkage of ODCzMSi disrupts the backbone conjugation and maintains a high triplet energy level (ET=3.0 eV). A phosphorescent organic light‐emitting diode (PhOLED) using iridium bis(4,6‐difluorophenyl)pyridinato‐N,C2 picolinate (FIrpic) as the emitter and ODCzMSi as the host shows a relatively low turn‐on voltage of 5.0 V for solution‐processed PhOLEDs, maximum external quantum efficiency of 9.2 %, and maximum current efficiency of 17.7 cd A?1. The overall performance of this device is competitive with the best reported solution‐processed blue PhOLEDs. Memory devices using ODCzMSi as an active layer exhibit non‐volatile write‐once read‐many‐times (WORM) characteristics with high stability in retention time up to 104 s and a low switch on voltage. This switching behaviour is explained by different stable conformations of ODCzMSi with high or low conductivity states which are obtained under the action of electric field through a π–π stacking alignment of the pendant aromatic groups. These results with both PhOLEDs and memory devices demonstrate that this oligosiloxane–mCP hybrid structure is promising and versatile for high performance solution‐processed optoelectronic applications. 相似文献
863.
Effects of Quantum Nuclear Delocalisation on NMR Parameters from Path Integral Molecular Dynamics 下载免费PDF全文
Dr. Martin Dračínský Dr. Paul Hodgkinson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(8):2201-2207
The influence of nuclear delocalisation on NMR chemical shifts in molecular organic solids is explored using path integral molecular dynamics (PIMD) and density functional theory calculations of shielding tensors. Nuclear quantum effects are shown to explain previously observed systematic deviations in correlations between calculated and experimental chemical shifts, with particularly large PIMD‐induced changes (up to 23 ppm) observed for carbon atoms in methyl groups. The PIMD approach also enables isotope substitution effects on chemical shifts and J couplings to be predicted in excellent agreement with experiment for both isolated molecules and molecular crystals. An approach based on convoluting calculated shielding or coupling surfaces with probability distributions of selected bond distances and valence angles obtained from PIMD simulations is used to calculate isotope effects. 相似文献
864.
A Novel Bismuth‐Based Metal–Organic Framework for High Volumetric Methane and Carbon Dioxide Adsorption 下载免费PDF全文
Mathew Savage Dr. Sihai Yang Dr. Mikhail Suyetin Prof. Dr. Elena Bichoutskaia Dr. William Lewis Prof. Dr. Alexander J. Blake Sarah A. Barnett Prof. Dr. Martin Schröder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(26):8024-8029
Solvothermal reaction of H4L (L=biphenyl‐3,3′,5,5′‐tetracarboxylate) and Bi(NO3)3 ? (H2O)5 in a mixture of DMF/MeCN/H2O in the presence of piperazine and nitric acid at 100 °C for 10 h affords the solvated metal–organic polymer [Bi2(L)1.5(H2O)2] ? (DMF)3.5 ? (H2O)3 (NOTT‐220‐solv). A single crystal X‐ray structure determination confirms that it crystallises in space group P2/c and has a neutral and non‐interpenetrated structure comprising binuclear {Bi2} centres bridged by tetracarboxylate ligands. NOTT‐220‐solv shows a 3,6‐connected network having a framework topology with a {4 ? 62}2{42 ? 65 ? 88}{62 ? 8} point symbol. The desolvated material NOTT‐220a shows exceptionally high adsorption uptakes for CH4 and CO2 on a volumetric basis at moderate pressures and temperatures with a CO2 uptake of 553 g L?1 (20 bar, 293 K) with a saturation uptake of 688 g L?1 (1 bar, 195 K). The corresponding CH4 uptake was measured as 165 V(STP)/V (20 bar, 293 K) and 189 V(STP/V) (35 bar, 293 K) with a maximum CH4 uptake for NOTT‐220a recorded at 20 bar and 195 K to be 287 V(STP)/V, while H2 uptake of NOTT‐220a at 20 bar, 77 K is 42 g L?1. These gas uptakes have been modelled by grand canonical Monte Carlo (GCMC) and density functional theory (DFT) calculations, which confirm the experimental data and give insights into the nature of the binding sites of CH4 and CO2 in this porous hybrid material. 相似文献
865.
Chemical Probing of the Human Sirtuin 5 Active Site Reveals Its Substrate Acyl Specificity and Peptide‐Based Inhibitors 下载免费PDF全文
Claudia Roessler Theresa Nowak Martin Pannek Dr. Melanie Gertz Giang T. T. Nguyen Michael Scharfe Dr. Ilona Born Prof. Dr. Wolfgang Sippl Prof. Dr. Clemens Steegborn Prof. Dr. Mike Schutkowski 《Angewandte Chemie (International ed. in English)》2014,53(40):10728-10732
Sirtuins are NAD+‐dependent deacetylases acting as sensors in metabolic pathways and stress response. In mammals there are seven isoforms. The mitochondrial sirtuin 5 is a weak deacetylase but a very efficient demalonylase and desuccinylase; however, its substrate acyl specificity has not been systematically analyzed. Herein, we investigated a carbamoyl phosphate synthetase 1 derived peptide substrate and modified the lysine side chain systematically to determine the acyl specificity of Sirt5. From that point we designed six potent peptide‐based inhibitors that interact with the NAD+ binding pocket. To characterize the interaction details causing the different substrate and inhibition properties we report several X‐ray crystal structures of Sirt5 complexed with these peptides. Our results reveal the Sirt5 acyl selectivity and its molecular basis and enable the design of inhibitors for Sirt5. 相似文献
866.
Shira D. Halperin Hope Fan Stanley Chang Dr. Rainer E. Martin Prof. Robert Britton 《Angewandte Chemie (International ed. in English)》2014,53(18):4690-4693
Fluorination reactions are essential to modern medicinal chemistry, thus providing a means to block site‐selective metabolic degradation of drugs and access radiotracers for positron emission tomography imaging. Despite current sophistication in fluorination reagents and processes, the fluorination of unactivated C? H bonds remains a significant challenge. Reported herein is a convenient and economic process for direct fluorination of unactivated C? H bonds that exploits the hydrogen abstracting ability of a decatungstate photocatalyst in combination with the mild fluorine atom transfer reagent N‐fluorobenzenesulfonimide. This operationally straightforward reaction provides direct access to a wide range of fluorinated organic molecules, including structurally complex natural products, acyl fluorides, and fluorinated amino acid derivatives. 相似文献
867.
Bertrand Schweitzer‐Chaput Joachim Demaerel Hauke Engler Dr. Martin Klussmann 《Angewandte Chemie (International ed. in English)》2014,53(33):8737-8740
Based on a mechanistic study, we have discovered a Brønsted acid catalyzed formation of ketone radicals. This is believed to proceed via thermally labile alkenyl peroxides formed in situ from ketones and hydroperoxides. The discovery could be utilized to develop a multicomponent radical addition of unactivated ketones and tert‐butyl hydroperoxide to olefins. The resulting γ‐peroxyketones are synthetically useful intermediates that can be further transformed into 1,4‐diketones, homoaldol products, and alkyl ketones. A one‐pot reaction yielding a pharmaceutically active pyrrole is also described. 相似文献
868.
M. Sc. Moritz C. Baier Dr. Martin A. Zuideveld Prof. Dr. Stefan Mecking 《Angewandte Chemie (International ed. in English)》2014,53(37):9722-9744
Research on “post‐metallocene” polymerization catalysis ranges methodologically from fundamental mechanistic studies of polymerization reactions over catalyst design to material properties of the polyolefins prepared. A common goal of these studies is the creation of practically useful new polyolefin materials or polymerization processes. This Review gives a comprehensive overview of post‐metallocene polymerization catalysts that have been put into practice. The decisive properties for this success of a given catalyst structure are delineated. 相似文献
869.
Martin Heise Bertold Rasche Dr. Anna Isaeva Dr. Alexey I. Baranov Prof. Dr. Michael Ruck Konrad Schäfer Prof. Dr. Rainer Pöttgen Jens‐Peter Eufinger Prof. Dr. Jürgen Janek 《Angewandte Chemie (International ed. in English)》2014,53(28):7344-7348
Nanoparticles of Bi3Ir, obtained from a microwave‐assisted polyol process, activate molecular oxygen from air at room temperature and reversibly intercalate it as oxide ions. The closely related structures of Bi3Ir and Bi3IrOx (x≤2) were investigated by X‐ray diffraction, electron microscopy, and quantum‐chemical modeling. In the topochemically formed metallic suboxide, the intermetallic building units are fully preserved. Time‐ and temperature‐dependent monitoring of the oxygen uptake in an oxygen‐filled chamber shows that the activation energy for oxide diffusion (84 meV) is one order of magnitude smaller than that in any known material. Bi3IrOx is the first metallic oxide ion conductor and also the first that operates at room temperature. 相似文献
870.
Dr. Yann Gloaguen Christophe Rebreyend Dr. Martin Lutz Pravin Kumar Dr. Martina Huber Dr. Ir. Jarl Ivar van der Vlugt Prof. Dr. Sven Schneider Prof. Dr. Bas de Bruin 《Angewandte Chemie (International ed. in English)》2014,53(26):6814-6818
Photochemical activation of [(PNNH)Rh(N3)] (PNNH=6‐di‐(tert‐butyl)phosphinomethyl‐2,2′‐bipyridine) complex 2 produced the paramagnetic (S=1/2), [(PNN)Rh?N.‐Rh(PNN)] complex 3 (PNN?=methylene‐deprotonated PNNH), which could be crystallographically characterized. Spectroscopic investigation of 3 indicates a predominant nitridyl radical (.N2?) character, which was confirmed computationally. Complex 3 reacts selectively with CO, producing two equivalents of [(PNN)RhI(CO)] complex 4 , presumably by nitridyl radical N,N‐coupling. 相似文献