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排序方式: 共有998条查询结果,搜索用时 31 毫秒
1.
Yu Zhang Dr. Novruz G. Akhmedov Prof. Jeffrey L. Petersen Prof. Carsten Milsmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(12):3042-3052
Luminescent seven-coordinated zirconium and hafnium complexes bearing three mono-anionic 2,2′-pyridylpyrrolide ligands and one chloride were synthesized. Solid-state structures and the dynamic behaviors in solution were probed by X-ray crystallography and variable temperature 1H NMR experiments, respectively. Absorption spectroscopy and time-dependent density functional theory (TD-DFT) calculations supported a hybrid of ligand-to-metal charge transfer (LMCT)/ligand-to-ligand charge transfer (LLCT) for the visible light absorption band. The complexes (MePMPMe)3MCl (M=Zr, Hf, MePMPMe=3,5-dimethyl-2-(2-pyridyl)pyrrolide) are emissive in solution at room temperature upon irradiation with visible light due to a combination of phosphorescence and fluorescence characterized by excited state lifetimes in the μs and low to sub-ns timescale, respectively. Electrochemical experiments revealed that the zirconium complex possesses a reversible redox event under highly reducing condition (−2.29 V vs. Fc+/0). 相似文献
2.
3.
Ping Chen Yanhong Hao Xinxin Wang Prof. Dr. Dan Yuan Prof. Dr. Yingming Yao Prof. Dr. Lutz Ackermann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(30):7292-7297
Highly position selective alkylations of N-alkylindoles at C7-positions have been enabled by cationic zirconium complexes. The strategy provides a straightforward access to install alkyl groups at C7-positions of indoles without a complex directing group. Mechanistic studies provided support for the importance of Brønsted acids in the catalytic manifold. 相似文献
4.
Dr. Cédric Boulho Dr. Harmen S. Zijlstra Alexander Hofmann Prof. Dr. Peter H. M. Budzelaar Prof. Dr. Sjoerd Harder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(48):17450-17459
Reaction of (TBBP)AlMe ? THF with [Cp*2Zr(Me)OH] gave [(TBBP)Al(THF)?O?Zr(Me)Cp*2] (TBBP=3,3’,5,5’‐tetra‐tBu‐2,2'‐biphenolato). Reaction of [DIPPnacnacAl(Me)?O?Zr(Me)Cp2] with [PhMe2NH]+[B(C6F5)4]? gave a cationic Al/Zr complex that could be structurally characterized as its THF adduct [(DIPPnacnac)Al(Me)?O?Zr(THF)Cp2]+[B(C6F5)4]? (DIPPnacnac=HC[(Me)C=N(2,6‐iPr2?C6H3)]2). The first complex polymerizes ethene in the presence of an alkylaluminum scavenger but in the absence of methylalumoxane (MAO). The adduct cation is inactive under these conditions. Theoretical calculations show very high energy barriers (ΔG=40–47 kcal mol?1) for ethene insertion with a bridged AlOZr catalyst. This is due to an unfavorable six‐membered‐ring transition state, in which the methyl group bridges the metal and ethene with an obtuse metal‐Me‐C angle that prevents synchronized bond‐breaking and making. A more‐likely pathway is dissociation of the Al‐O‐Zr complex into an aluminate and the active polymerization catalyst [Cp*2ZrMe]+. 相似文献
5.
Detoxification of Chemical Warfare Agents Using a Zr6‐Based Metal–Organic Framework/Polymer Mixture 下载免费PDF全文
Dr. Su‐Young Moon Emmanuel Proussaloglou Gregory W. Peterson Dr. Jared B. DeCoste Morgan G. Hall Dr. Ashlee J. Howarth Prof. Joseph T. Hupp Prof. Omar K. Farha 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(42):14864-14868
Owing to their high surface area, periodic distribution of metal sites, and water stability, zirconium‐based metal–organic frameworks (Zr6‐MOFs) have shown promising activity for the hydrolysis of nerve agents GD and VX, as well as the simulant, dimethyl 4‐nitrophenylphosphate (DMNP), in buffered solutions. A hurdle to using MOFs for this application is the current need for a buffer solution. Here the destruction of the simulant DMNP, as well as the chemical warfare agents (GD and VX) through hydrolysis using a MOF catalyst mixed with a non‐volatile, water‐insoluble, heterogeneous buffer is reported. The hydrolysis of the simulant and nerve agents in the presence of the heterogeneous buffer was fast and effective. 相似文献
6.
Monika Szufla Aleksandra Choroś Dr. Wojciech Nitek Prof. Dariusz Matoga 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(37):e202200835
By using the strategy of pre-assembly chlorosulfonation applied to a linker precursor, the first sulfonated zirconium metal–organic framework ( JUK-14 ) with two-dimensional (2D) structure, was synthesized. Single-crystal X-ray diffraction reveals that the material is built of Zr6O4(OH)4(COO)8 oxoclusters, doubly 4-connected by angular dicarboxylates, and stacked in layers spaced 1.5 nm apart by the presence of sulfonic groups. JUK-14 exhibits excellent hydrothermal stability, permanent porosity confirmed by gas adsorption studies, and shows high (>10−4 S/cm) and low (<10−8 S/cm) proton conductivity under humidified and anhydrous conditions, respectively. Post-synthesis inclusion of imidazole improves the overall conductivity increasing it to 1.7×10−3 S/cm at 60 °C and 90 % relative humidity, and by 3 orders of magnitude at 160 °C. The combination of 2D porous nature with robustness of zirconium MOFs offers new opportunities for exploration of the material towards energy and environmental applications. 相似文献
7.
Dr. Minglu Huang Dr. Jiazhen Chen Dr. Binghao Wang Dr. Wei Huang Dr. Haibo Chen Dr. Yanshan Gao Prof. Tobin J. Marks 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(46):20703-20709
Polar functionalized isotactic and syndiotactic polypropylenes (PPs) are synthesized by direct, masking-reagent-free propylene and amino–olefin (AO, CH2=CH(CH2)xNnPr2, x=2, 3, 6) copolymerizations using the activated precatalysts rac-[Me2Si(indenyl)2]ZrMe2 and [Me2C(Cp)(fluorenyl)]ZrMe2, respectively. Polymerization activities at 25 °C are as high as 4208 and 535 kg/(mol h atm) with AO incorporation up to 4.0 mol % and 1.6 mol %, respectively. Remarkably, introducing the amino-olefin comonomers significantly enhances stereoselection for both isotactic (mmmm: 59.5 %→91.0 %) and syndiotactic (rrrr: 66.3 %→81.3 %) products. 相似文献
8.
Aida Contreras-Ramirez Dr. Bryan E. Tomlin Gregory S. Day Prof. Dr. Abraham Clearfield Prof. Dr. Hong-Cai Zhou 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(28):6185-6194
Nanosized α-zirconium phenylphosphonate particles were successfully prepared by the reaction between different zirconium sources and molten phenylphosphonic acid in the absence of solvent. The resultant nanoplates exhibit particle sizes in the range of 15 to 30 nm. The use of a topotactic anion exchange method starting from α-zirconium phosphate instead resulted in the generation of 15 to 180 nm plates, while also resulting in nanoparticles with a higher degree of crystallinity. The topotactic anion exchange of the phosphate groups by phenylphosphonate groups could be performed to completion when performed in molten phenylphosphonic acid. Characterization of both the final products as well as the individual steps in the anion exchange were performed by powder XRD, fast neutron activation analysis, TGA, FTIR spectroscopy, TEM, solid-state NMR and XPS. 相似文献
9.
Vladimir I. Bakhmutov Aida Contreras-Ramirez Hannah Drake Hong-Cai Zhou 《Magnetic resonance in chemistry : MRC》2022,60(6):541-553
Solid-state NMR experiments on 2H, 31P, 13C, and 1H nuclei, including 31P T1, 1H T1, and 1H T1ρ measurements, as well as on the kinetics of proton-phosphorus cross-polarization have been performed to characterize the crystalline and amorphous α-zirconium phosphates, which were intercalated with D2O and/or CD3OD. The 13C{1H} CP MAS NMR experiment performed for compound 1-CD 3 OD (Zr (HPO4)2 . 0.2CD3OD) with carbon cross-polarization via protons of phosphate groups has provided a prove that the methanol was intercalated into the interlayer spaces of this compound. The variable-temperature 2H solid-echo MAS NMR spectra of intercalated compounds demonstrated that the methanol molecules, in contrast to the mobile water, were immobile, keeping, however, free CD3 rotations around the C3-axis. It has been demonstrated that the intercalated species, D2O and CD3OD, do not affect the high-frequency motions of the phosphate groups. By utilizing local structural models that satisfy the constraints of the experimental data, it has been suggested that the immobile methanol molecules are located in the cavity between two neighboring layers of the zirconium phosphates. Thus, the present work illustrates the reliable criteria in a comprehensive NMR approach to structural and dynamic studies of such systems. 相似文献
10.
Dr. Ida Ritacco Dr. Maria Voccia Dr. Salvatore Impemba Dr. Matteo Farnesi Camellone Prof. Stefano Milione Prof. Lucia Caporaso 《欧洲无机化学杂志》2023,26(8):e202200588
In this work the mechanism of L-lactide polymerization promoted by NSSN zirconium complexes was investigated through DFT methods with the aim to understand as the electronic and steric features of the ligand affect the energy reaction. It was observed that the rate determining step of the process is the opening of the L-lactide ring and that by increasing the steric hindrance, evaluated by changing geometric parameters and topographic steric maps, or the electron-withdrawing properties of the ligand, the corresponding energy barrier increases. On the other hand, calculations foresee that a small and electron-releasing substituent on the nitrogen atom of the ligand, such as the methyl group, is desirable in order to obtain NSSN zirconium based catalysts with improved activity in the ROP of the L-lactide. 相似文献