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161.
M.Sc. Johannes E. M. N. Klein Dr. Burkhard Miehlich Dr. Michael S. Holzwarth Prof. Dr. Matthias Bauer Dipl.‐Chem. Magdalena Milek Dr. Marat M. Khusniyarov Dr. Gerald Knizia Prof. Dr. Hans‐Joachim Werner Prof. Dr. Bernd Plietker 《Angewandte Chemie (International ed. in English)》2014,53(7):1790-1794
During the past 10 years iron‐catalyzed reactions have become established in the field of organic synthesis. For example, the complex anion [Fe(CO)3(NO)]?, which was originally described by Hogsed and Hieber, shows catalytic activity in various organic reactions. This anion is commonly regarded as being isoelectronic with [Fe(CO)4]2?, which, however, shows poor catalytic activity. The spectroscopic and quantum chemical investigations presented herein reveal that the complex ferrate [Fe(CO)3(NO)]? cannot be regarded as a Fe?II species, but rather is predominantly a Fe0 species, in which the metal is covalently bonded to NO? by two π‐bonds. A metal–N σ‐bond is not observed. 相似文献
162.
M. Sc. Shih‐Fan Hsu Dipl.‐Chem. Susanne Rommel M. Sc. Philipp Eversfield Dr. Keven Muller Prof. Dr. Elias Klemm Prof. Dr. Werner R. Thiel Prof. Dr. Bernd Plietker 《Angewandte Chemie (International ed. in English)》2014,53(27):7074-7078
Apart from energy generation, the storage and liberation of energy are among the major problems in establishing a sustainable energy supply chain. Herein we report the development of a rechargeable H2 battery which is based on the principle of the Ru‐catalyzed hydrogenation of CO2 to formic acid (charging process) and the Ru‐catalyzed decomposition of formic acid to CO2 and H2 (discharging process). Both processes are driven by the same catalyst at elevated temperature either under pressure (charging process) or pressure‐free conditions (discharging process). Up to five charging–discharging cycles were performed without decrease of storage capacity. The resulting CO2/H2 mixture is free of CO and can be employed directly in fuel‐cell technology. 相似文献
163.
M. Sc. Isabel T. Alt Prof. Dr. Bernd Plietker 《Angewandte Chemie (International ed. in English)》2016,55(4):1519-1522
The nucleophilic iron complex Bu4N[Fe(CO)3(NO)] (TBA[Fe]) catalyzes the direct intramolecular C?H amination of α‐azidobiaryls and (azidoaryl)alkenes into the corresponding carbazoles and indoles, respectively, under mild conditions and with low catalyst loadings. These features and the broad functional‐group tolerance render this method a particularly attractive alternative to established noble‐metal‐based procedures. 相似文献
164.
Nitrogen‐Doped Ordered Mesoporous Carbon Supported Bimetallic PtCo Nanoparticles for Upgrading of Biophenolics 下载免费PDF全文
Dr. Guang‐Hui Wang Dr. Zhengwen Cao Dr. Dong Gu Norbert Pfänder Ann‐Christin Swertz Bernd Spliethoff Hans‐Josef Bongard Dr. Claudia Weidenthaler Dr. Wolfgang Schmidt Dr. Roberto Rinaldi Prof. Dr. Ferdi Schüth 《Angewandte Chemie (International ed. in English)》2016,55(31):8850-8855
Hydrodeoxygenation (HDO) is an attractive route for the upgrading of bio‐oils produced from lignocellulose. Current catalysts require harsh conditions to effect HDO, decreasing the process efficiency in terms of energy and carbon balance. Herein we report a novel and facile method for synthesizing bimetallic PtCo nanoparticle catalysts (ca. 1.5 nm) highly dispersed in the framework of nitrogen‐doped ordered mesoporous carbon (NOMC) for this reaction. We demonstrate that NOMC with either 2D hexagonal (p6m) or 3D cubic (Im m) structure can be easily synthesized by simply adjusting the polymerization temperature. We also demonstrate that PtCo/NOMC (metal loading: Pt 9.90 wt %; Co 3.31 wt %) is a highly effective catalyst for HDO of phenolic compounds and “real‐world” biomass‐derived phenolic streams. In the presence of PtCo/NOMC, full deoxygenation of phenolic compounds and a biomass‐derived phenolic stream is achieved under conditions of low severity. 相似文献
165.
Interface Engineering of MoS2/Ni3S2 Heterostructures for Highly Enhanced Electrochemical Overall‐Water‐Splitting Activity 下载免费PDF全文
Dr. Jian Zhang Dr. Tao Wang Dr. Darius Pohl Dr. Bernd Rellinghaus Dr. Renhao Dong Dr. Shaohua Liu Dr. Xiaodong Zhuang Prof. Xinliang Feng 《Angewandte Chemie (International ed. in English)》2016,55(23):6702-6707
To achieve sustainable production of H2 fuel through water splitting, low‐cost electrocatalysts for the hydrogen‐evolution reaction (HER) and the oxygen‐evolution reaction (OER) are required to replace Pt and IrO2 catalysts. Herein, for the first time, we present the interface engineering of novel MoS2/Ni3S2 heterostructures, in which abundant interfaces are formed. For OER, such MoS2/Ni3S2 heterostructures show an extremely low overpotential of ca. 218 mV at 10 mA cm?2, which is superior to that of the state‐of‐the‐art OER electrocatalysts. Using MoS2/Ni3S2 heterostructures as bifunctional electrocatalysts, an alkali electrolyzer delivers a current density of 10 mA cm?2 at a very low cell voltage of ca. 1.56 V. In combination with DFT calculations, this study demonstrates that the constructed interfaces synergistically favor the chemisorption of hydrogen and oxygen‐containing intermediates, thus accelerating the overall electrochemical water splitting. 相似文献
166.
Agarwal V Diehl A Skrynnikov N Reif B 《Journal of the American Chemical Society》2006,128(39):12620-12621
MAS solid-state NMR experiments applied to biological solids are still hampered by low sensitivity and resolution. In this work, we employ a deuteration scheme in which individual methyl groups are selectively protonated. This labeling scheme allows the acquisition of proton carbon correlation spectra with a resolution comparable to that in solution-state NMR experiments. We observe an increase in resolution by a factor of 10-15 compared to standard heteronuclear correlation experiments using PMLG for 1H,1H dipolar decoupling in the indirect dimension. At the same time, the full sensitivity of the proton-based experiment is retained. In comparison to the heteronuclear detected version of the experiment, a gain in sensitivity of a factor of approximately 4.7 is achieved. 相似文献
167.
Self-assembling cyclic peptides: molecular dynamics studies of dimers in polar and nonpolar solvents
Khurana E Nielsen SO Ensing B Klein ML 《The journal of physical chemistry. B》2006,110(38):18965-18972
The self-assembly of cyclic D,L-alpha-peptides into hollow nanotubes is a crucial mechanistic step in their application as antibacterial and drug-delivery agents. To understand this process, molecular dynamics (MD) simulations were performed on dimers of cyclic peptides formed from cyclo [(-L-Trp-D-N-MeLeu-)4-]2 and cyclo [(-L-Trp-D-Leu-)4-]2 subunits in nonpolar (nonane) and polar (water) solvent. The dimers were observed to be stable only in nonpolar solvent over the full 10 ns length of the MD trajectory. The behavior of the dimers in different solvents is rationalized in terms of the intersubunit hydrogen bonding, hydrogen bonding with the solvent, and planarity of the rings. It is shown that the phi and psi dihedral angles of a single uncapped ring in nonane lie in the beta-sheet region of the Ramachandran plot, and the ring stays in a flat conformation. Steered MD (SMD) simulations based on Jarzynski's equality were performed to obtain the potential of mean force as a function of the distance between the two rings of the capped dimer in nonane. It is also shown that a single peptide subunit prefers to reside close to the nonane/water interface rather than in bulk solvent because of the amphiphilic character of the peptide ring. The present MD results build the foundation for using MD simulations to study the mechanism of the formation of cyclic peptide nanotubes in lipid bilayers. 相似文献
168.
Hartke B 《Physical chemistry chemical physics : PCCP》2006,8(31):3627-3635
A simple quantum wavepacket propagation algorithm is presented, designed to produce a very compact, non-direct product representation in higher-dimensional cases. Instead of moving basis functions around, localized basis functions at pre-defined centers are added to and deleted from the representation, generating an active basis function set strictly localized to the region where the moving wavepacket has significantly non-zero values. Simple one-dimensional examples prove this property, as well as the ability of the algorithm to accommodate splitting and rejoining of an arbitrary number of wavefunction pieces, and tunnelling through potential energy barriers. It is argued that future applications to higher-dimensional examples will be less expensive than with traditional direct-product bases, since making the basis adaptive has a lower scaling than the elementary steps necessary for any propagation algorithm itself. 相似文献
169.
Based on torsion angle distributions of frequently occurring substructures, conformation preferences of druglike molecules are presented, accompanied by a review of the relevant literature. First, the relevance of the Cambridge Structural Database (CSD) for drug design is demonstrated by comparing substructures present in compounds entering clinical trials with those found in the CSD and protein-bound ligands in the Protein Data Bank (PDB). Next, we briefly highlight preferred conformations of elementary acyclic systems, followed by a discussion of sulfonamide conformations. Due to their central role in medicinal chemistry, we discuss properties of aryl ring substituents in depth, including biaryl systems and systems of two aryl rings connected by two acyclic bonds. For a subset of torsion motifs, we also compare torsion angle histograms derived from CSD structures with those derived from ligands in the PDB. Furthermore, selected properties of some six- and seven-membered ring systems are discussed. The article closes with a section on attractive sulfur-oxygen contacts. 相似文献
170.