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排序方式: 共有606条查询结果,搜索用时 171 毫秒
1.
Philipp Dabringhaus Marcel Schorpp Dr. Harald Scherer Prof. Dr. Ingo Krossing 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22207-22211
The potential of a dicationic strontium ansa-arene complex for Lewis acid catalysis has been explored. The key to its synthesis was a simple salt metathesis from SrI2 and 2 Ag[Al(ORF)4], giving the base-free strontium-perfluoroalkoxyaluminate Sr[Al(ORF)4]2 (ORF=OC(CF3)3). Addition of an ansa-arene yielded the highly Lewis acidic, dicationic strontium ansa-arene complex. In preliminary experiments, the complex was successfully applied as a catalyst in CO2-reduction to CH4 and a surprisingly controlled isobutylene polymerization reaction. 相似文献
2.
Single Crystal to Single Crystal (SC‐to‐SC) Transformation from a Nonporous to Porous Metal–Organic Framework and Its Application Potential in Gas Adsorption and Suzuki Coupling Reaction through Postmodification 下载免费PDF全文
Dr. Rupam Sen Debraj Saha Dr. Subratanath Koner Dr. Paula Brandão Dr. Zhi Lin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5962-5971
A new amino‐functionalized strontium–carboxylate‐based metal–organic framework (MOF) has been synthesized that undergoes single crystal to single crystal (SC‐to‐SC) transformation upon desolvation. Both structures have been characterized by single‐crystal X‐ray analysis. The desolvated structure shows an interesting 3D porous structure with pendent ?NH2 groups inside the pore wall, whereas the solvated compound possesses a nonporous structure with DMF molecules on the metal centers. The amino group was postmodified through Schiff base condensation by pyridine‐2‐carboxaldehyde and palladium was anchored on that site. The modified framework has been utilized for the Suzuki cross‐coupling reaction. The compound shows high activity towards the C?C cross‐coupling reaction with good yields and turnover frequencies. Gas adsorption studies showed that the desolvated compound had permanent porosity and was microporous in nature with a BET surface area of 2052 m2 g?1. The material also possesses good CO2 (8 wt %) and H2 (1.87 wt %) adsorption capabilities. 相似文献
3.
采用玻璃微米管支撑的液/液界面通过循环伏安法(CV)研究了二环己基-18冠6(DCH18C6)加速Sr2+在水/1,2-二氯乙烷(W/DCE)界面上的转移反应,考察了DCH18C6加速Sr2+在W/DCE界面转移的影响因素,如DCH18C6和Sr2+浓度等,并求算其络合物的稳定常数。实验结果表明,Sr2+与DCH18C6发生的是一个1:1的扩散控制的界面络合转移过程,其络合常数β为5.31×1023。本研究可为理解溶剂萃取Sr2+行为提供基础理论数据。 相似文献
4.
Synthesis,Structure, and Properties of SrC(NH)3, a Nitrogen‐Based Carbonate Analogue with the Trinacria Motif 下载免费PDF全文
M. Sc. Ronja Missong M. Sc. Janine George Dr. Andreas Houben Dr. Markus Hoelzel Prof. Dr. Richard Dronskowski 《Angewandte Chemie (International ed. in English)》2015,54(41):12171-12175
Strontium guanidinate, SrC(NH)3, the first compound with a doubly deprotonated guanidine unit, was synthesized from strontium and guanidine in liquid ammonia and characterized by X‐ray and neutron diffraction, IR spectroscopy, and density‐functional theory including harmonic phonon calculations. The compound crystallizes in the hexagonal space group P63/m, constitutes the nitrogen analogue of strontium carbonate, SrCO3, and its structure follows a layered motif between Sr2+ ions and complex anions of the type C(NH)32?; the anions adopt the peculiar trinacria shape. A comparison of theoretical phonons with experimental IR bands as well as quantum‐chemical bonding analyses yield a first insight into bonding and packing of the formerly unknown anion in the crystal. 相似文献
5.
《Current Applied Physics》2020,20(5):611-618
Pure BST and doped BSTF (with BSTF2: Fe2O3 2 wt % and BSTF4: Fe2O3 4 wt %) ceramics were prepared by solid state reaction. XRD pattern showed the different phases were formed depend on the weight percent of Fe2O3. The crystal size and lattice parameters increased while the lattice strain decreased. The topography of the sintered samples shows increase of the grain size with increasing Fe2O3 ratio and hence enhances the compaction of ceramics. Broadband dielectric spectroscopy was employed to investigate the effect of magnetite nanoparticle on the dielectric properties of the pure BST ceramic. The interfacial polarization and the conductivity contribution reflect the high values of permittivity and its gradual increase as frequency decreases. The two BSTF samples show relaxation peak dynamic originated from presence of immobile species/electrons at low temperatures and defects/vacancies results from the formation of oxygen vacancies originates from the spontaneous change in oxidation states of Fe ions (Fe 3+/Fe2+) at high temperatures. The relaxation rate obeys Arrhenius law at high temperatures in case of BST sample with activation energy 225 kJ/mol. This high value of activation energy at higher temperatures reflects and confirms the slowed down of the dynamics at the interphase and the decoupling nature of the OH-dynamic and the interfacial polarization. 相似文献
6.
It was studied the effect of ultrasonic processing (22 kHz) of the aqueous suspension of metakaolin, sodium hydroxide and alumina with a molar ratio 2Al2Si2O7:12NaOH:2Al2O3 on the low-modulus zeolite synthesis processes. To investigate the XRD, SEM, IR, EDS had been used. It was shown that after ultrasonic processing, sodium aluminates are formed, what leads to a change in process of further synthesis. It was found that without ultrasonic processing on the stage of thermal treatment at 650 °C, SOD zeolite (|Na6|[Al6Si6O24]) and sodium aluminosilicate (Na6Al4Si4O17) are synthesized. In the sample after ultrasound during thermal treatment, only sodium aluminosilicates of cubic syngony (Na6Al4Si4O17 and Na8Al4Si4O18) are formed. It was demonstrated that sodium aluminosilicates are precursors for the formation of LTA zeolite (|Na12|[Al12Si12O48]). As a result zeolitization of sodium aluminosilicates after the hydrothermal crystallization in alkaline solution, the sonicated sample contained 97 wt% LTA. Without ultrasonic processing, the product of synthesis contained 50 wt% SOD and 40 wt% LTA. 相似文献
7.
B. Gorski Nguyen Za Hung N. Ya Ljubman 《Isotopes in environmental and health studies》2013,49(3):275-282
Abstract Possibilities of using a new generation of sorbents have been investigated. Polymers of spatial-globular (spherulitic) structure (RGS polymers) have been tested to separate Cs, Sr and rare earth elements – which can also be radioactive contaminants – from different waters. RGS polymers are both, solids and highly-disperse systems being extremely permeable to fluids and gases with low pressure decline. They were currently used to clean industrial waste-water. It is shown that these polymers can be used successfully to separate radionuclides. Polymers RGS-81 and RGS-112 have high distribution coefficients for CS, Sr, Sc, the lanthanide series and Hf in weakly acid solutions. In HF solutions, Sc and Hf can be separated from Cs, Sr and the lanthanides. 相似文献
8.
H. Herzmann 《Isotopes in environmental and health studies》2013,49(2):45-52
Radioaktiv markierte Präparate haben in denletzten Jahren in schnell zunehmendem Maße Eingang in die klinische Medizin gefunden. Sie sind beieiner Reihe von Indikationen schon jetzt außerordentlich wertvolle Hilfsmittel bei der Diagnose, besonders bei der Prüfung von Organfunktionen. 相似文献
9.
Fabian Ebner Philipp Mainik Dr. Lutz Greb 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5120-5124
Structural constraint represents an attractive tool to modify p-block element properties without the need for unusual oxidation or valence states. The recently reported methyl-calix[4]pyrrolato aluminate established the effect of forcing a tetrahedral aluminum anion into a square-planar coordination mode. However, the generality of this structural motif and any consequence of ligand modification remained open. Herein, a systematic ligand screening was launched, and the class of square-planar aluminum anions was extended by two derivatives that differ in the meso-substitution at the calix[4]pyrrolato ligand. Strikingly, this modification provoked opposing trends in the preference for a Lewis acidic binding mode with σ-donors versus the aluminum-ligand cooperative binding mode with carbonyls. Insights into the origin of these counterintuitive experimental observations were provided by computation and bond analysis. Importantly, this rationale might allow to exploit mode-selective binding for catalytic rate control. 相似文献
10.
Jingyi Cai Haoshan Wei Prof. Yong Zhang Rui Cai Dr. Xueru Zhang Prof. Yan Wang Prof. Jiaqin Liu Prof. Hark Hoe Tan Prof. Ting Xie Prof. Yucheng Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(25):7300-7306
Efficient separation of photogenerated electron–hole pairs is a crucial factor for high-performance photocatalysts. Effective electron–hole separation and migration could be achieved by heterojunctions with suitable band structures. Herein, a porous SrTiO3/SrSO4 heterojunction is prepared by a sol-gel method at room temperature followed by an annealing process. XRD characterization suggests high crystallinity of the heterostructure. A well-defined interface between the two phases is confirmed by high-resolution (HR)TEM. The photocatalytic H2 evolution productivity of the SrTiO3/SrSO4 heterojunction with Pt as co-catalyst reaches 396.82 μmol g−1 h−1, which is 16 times higher than that of SrTiO3/Pt. The boosted photocatalytic activity of SrTiO3/SrSO4/Pt can be ascribed to the presence of SrSO4, which promotes the transfer and migration of photogenerated carriers by forming the heterojunction and porous structure, which provides a large amount of active sites. This novel porous heterostructure brings new ideas for the development of high-efficiency photocatalysts for H2 release. 相似文献