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1.
This review summarizes recent progress in understanding the oxygen reduction and evolution reactions at the lanthanum strontium manganite electrode of a high-temperature solid oxide cell. Information provided here is put into the perspective of the defect chemistry of lanthanum strontium manganite and its impact on the electrode reaction mechanisms itself. After summarizing recent views on the oxygen reduction reaction mechanism, the focus turns to the oxygen evolution reaction, which is significantly less treated in the literature. A combination of the information in the literature on both reactions was the basis for modified reaction mechanism of the oxygen evolution reaction to be proposed under consideration of recent experimental observations and theoretical findings. 相似文献
2.
This study reports the structural and spectroscopic characterization of a novel metal organic compound formulated as [Fe (bpy)3] [Fe (dipic)2]2.7H2O ( 1 ) (dipic = pyridine‐2,6‐dicarboxylate and bpy = 2,2′‐bipyridine). 1 was investigated by elemental analysis, FT‐IR spectroscopy, powder X‐ray diffraction and single crystal X‐ray diffraction (SC‐XRD), which revealed a triclinic structure of expected composition. Thermal degradation of 1 was also investigated. Complex 1 was used as a precursor to prepare superparamagnetic nanoparticles of Fe3O4 by thermal analysis. The obtained Fe3O4 was characterized by Fourier transformed infrared spectroscopy (FT‐IR), powder X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Fe3O4 nanoparticles were used as a nano‐adsorbent to remove Cd2+ from water at room temperature. The results showed that this nano‐adsorbent is effective in removing Cd2+ from contaminated water sources, and that the maximal effectivity of adsorption occurs at pH = 6. Magnetic measurements of complex 1 and Fe3O4 nanoparticles at room temperature revealed paramagnetic and superparamagnetic behavior, respectively. 相似文献
3.
Lubomír Havlk Jan Fbry Margarida Henriques Michal Duek 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(7):623-630
The title structures of KScS2 (potassium scandium sulfide), RbScS2 (rubidium scandium sulfide) and KLnS2 [Ln = Nd (potassium neodymium sufide), Sm (potassium samarium sulfide), Tb (potassium terbium sulfide), Dy (potassium dysprosium sulfide), Ho (potassium holmium sulfide), Er (potassium erbium sulfide), Tm (potassium thulium sulfide) and Yb (potassium ytterbium sulfide)] are either newly determined (KScS2, RbScS2 and KTbS2) or redetermined. All of them belong to the α‐NaFeO2 structure type in agreement with the ratio of the ionic radii r3+/r+. KScS2, the member of this structural family with the smallest trivalent cation, is an extreme representative of these structures with rare earth trivalent cations. The title structures are compared with isostructural alkali rare earth sulfides in plots showing the dependence of several relevant parameters on the trivalent cation crystal radius; the parameters thus compared are c, a and c/a, the thicknesses of the S—S layers which contain the respective constituent cations, the sulfur fractional coordinates z(S2−) and the bond‐valence sums. 相似文献
4.
Efficient Synthesis of Diaryl Ketones by Nickel‐Catalyzed Negishi Cross‐Coupling of Amides by Carbon–Nitrogen Bond Cleavage at Room Temperature Accelerated by a Solvent Effect 下载免费PDF全文
Shicheng Shi Prof. Dr. Michal Szostak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10420-10424
The first Negishi cross‐coupling of amides for the synthesis of versatile diaryl ketones by selective C?N bond activation under exceedingly mild conditions is reported. The cross‐coupling was accomplished with bench‐stable, inexpensive precatalyst [Ni(PPh3)2Cl2] that shows high functional‐group tolerance and enables the synthesis of highly functionalized diaryl ketone motifs. The coupling occurred with excellent chemoselectivity favoring the ketone (cf. biaryl) products. Notably, this process represents the mildest conditions for amide N?C bond activation accomplished to date (room temperature, <10 min). Considering the versatile role of polyfunctional biaryl ketone linchpins in modern organic synthesis, availability, and excellent functional‐group tolerance of organozinc reagents, this strategy provides a new platform for amide N?C bond/organozinc cross‐coupling under mild conditions. 相似文献
5.
Structures of Highly Twisted Amides Relevant to Amide N−C Cross‐Coupling: Evidence for Ground‐State Amide Destabilization 下载免费PDF全文
Dr. Vittorio Pace Prof. Dr. Wolfgang Holzer Guangrong Meng Shicheng Shi Prof. Dr. Roger Lalancette D.Sc. Roman Szostak Prof. Dr. Michal Szostak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(41):14494-14498
Herein, we show that acyclic amides that have recently enabled a series of elusive transition‐metal‐catalyzed N?C activation/cross‐coupling reactions are highly twisted around the N?C(O) axis by a new destabilization mechanism of the amide bond. A unique effect of the N‐glutarimide substituent, leading to uniformly high twist (ca. 90°) irrespective of the steric effect at the carbon side of the amide bond has been found. This represents the first example of a twisted amide that does not bear significant steric hindrance at the α‐carbon atom. The 15N NMR data show linear correlations between electron density at nitrogen and amide bond twist. This study strongly supports the concept of amide bond ground‐state twist as a blueprint for activation of amides toward N?C bond cleavage. The new mechanism offers considerable opportunities for organic synthesis and biological processes involving non‐planar amide bonds. 相似文献
6.
Tiribilli Chiara Sokolová Romana Giannarelli Stefania Valášek Michal 《Monatshefte für Chemie / Chemical Monthly》2015,146(5):807-812
Monatshefte für Chemie - Chemical Monthly - The electrochemical reduction of diflunisal was studied in dimethyl sulfoxide on static mercury drop electrode. Diflunisal yields one irreversible... 相似文献
7.
8.
Highly Chemoselective Synthesis of Indolizidine Lactams by SmI2‐Induced Umpolung of the Amide Bond via Aminoketyl Radicals: Efficient Entry to Alkaloid Scaffolds 下载免费PDF全文
Shicheng Shi Prof. Dr. Roger Lalancette D.Sc. Roman Szostak Prof. Dr. Michal Szostak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(34):11949-11953
Samarium(II) iodide enables a wide range of highly chemoselective umpolung radical transformations proceeding by electron transfer to carbonyl groups; however, cyclizations of important nitrogen‐containing precursors have proven limited due to their prohibitive redox potential. Herein, we report the first reductive cyclizations of unactivated cyclic imides onto N‐tethered olefins using SmI2/H2O. This new umpolung protocol leads to the rapid synthesis of nitrogen‐containing heterocycles that are of particular significance as precursors to pharmaceutical pharmacophores and numerous classes of alkaloids. The reaction conditions tolerate a wide range of functional groups. Excellent chemoselectivity is observed in the cyclization over amide and ester functional groups. Such unconventional reactivity has important implications for the design and optimization of new bond‐forming reactions by umpolung radical processes. The reaction advances the SmI2 cyclization platform to the challenging unactivated N‐tethered acyl‐type radical precursors to access nitrogen‐containing architectures. 相似文献
9.
Pham The Anh Artur Babiarz Adam Czornik Michal Niezabitowski Stefan Siegmund 《Mathematical Methods in the Applied Sciences》2020,43(13):7815-7824
In this paper, we establish some criteria for boundedness, stability properties, and separation of solutions of autonomous nonlinear nabla Riemann-Liouville scalar fractional difference equations. To derive these results, we prove the variation of constants formula for nabla Riemann-Liouville fractional difference equations. 相似文献
10.
Dr. Jan Vícha Dr. Petr Švec Dr. Zdeňka Růžičková Dr. Maksim A. Samsonov Kateřina Bártová Prof. Aleš Růžička Dr. Michal Straka Dr. Martin Dračínský 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(40):8698-8702
Spin-orbit (SO) heavy-atom on the light-atom (SO-HALA) effect is the largest relativistic effect caused by a heavy atom on its light-atom neighbors, leading, for example, to unexpected NMR chemical shifts of 1H, 13C, and 15N nuclei. In this study, a combined experimental and theoretical evidence for the SO-HALA effect transmitted through hydrogen bond is presented. Solid-state NMR data for a series of 4-dimethylaminopyridine salts containing I−, Br− and Cl− counter ions were obtained experimentally and by theoretical calculations. A comparison of the experimental chemical shifts with those calculated by a standard DFT methodology without the SO contribution to the chemical shifts revealed a remarkable error of the calculated proton chemical shift of a hydrogen atom that is in close contact with the iodide anion. The addition of the relativistic SO correction in the calculations significantly improves overall agreement with the experiment and confirms the propagation of the SO-HALA effect through hydrogen bonds. 相似文献