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991.
Different Complexation Behavior of P‐Functionalized Ferrocene Derivatives Towards SnCl2, SnCl4 and SnPh2Cl2: Auto‐ionization and Redox‐Type Reactions 下载免费PDF全文
Dipl.‐Chem. Matthias Gawron Dr. Christina Dietz Michael Lutter Dr. Andrew Duthie Prof. Dr. Viatcheslav Jouikov Prof. Dr. Klaus Jurkschat 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16609-16622
The novel phosphonyl‐substituted ferrocene derivatives [Fe(η5‐Cp)(η5‐C5H3{P(O)(O‐iPr)2}2‐1,2)] ( Fc1,2 ) and [Fe{η5‐C5H4P(O)(O‐iPr)2}2] ( Fc1,1′ ) react with SnCl2, SnCl4, and SnPh2Cl2, giving the corresponding complexes [(Fc1,2)2SnCl][SnCl3] ( 1 ), [{(Fc1,1′)SnCl2}n] ( 2 ), [(Fc1,1′)SnCl4] ( 3 ), [{(Fc1,1′)SnPh2Cl2}n] ( 4 ), and [(Fc1,2)SnCl4] ( 5 ), respectively. The compounds are characterized by elemental analyses, 1H, 13C, 31P, 119Sn NMR and IR spectroscopy, 31P and 119Sn CP‐MAS NMR spectroscopy, cyclovoltammetry, electrospray ionization mass spectrometry, and single‐crystal as well as powder X‐ray diffraction analyses. The experimental work is accompanied by DFT calculations, which help to shed light on the origin for the different reaction behavior of Fc1,1′ and Fc1,2 towards tin(II) chloride. 相似文献
992.
Strongly Coupled Pt–Ni2GeO4 Hybrid Nanostructures as Potential Nanocatalysts for CO Oxidation 下载免费PDF全文
Zhuo Wang Shuang Yao Jing Feng Dapeng Liu Shuyan Song Prof. Hongjie Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14768-14771
A facile and low‐cost method has been developed to successfully fabricate 3D flower‐like and sphere‐like Ni2GeO4 nanostructures with tunable sizes and shapes. It is found that the hard template, polymethyl methacrylate (PMMA) nanopsheres, is essential to the formation of the final products. The as‐prepared nanostructures can serve as an outstanding support for Pt nanoparticles after surface modification with L ‐lysine. In the catalytic test of CO oxidation, Pt–Ni2GeO4 nanoflowers exhibited much higher catalytic performance compared with Pt–Ni2GeO4 nanospheres, representing a typical size‐dependent catalytic property. 相似文献
993.
Activation of Strong Boron–Fluorine and Silicon–Fluorine σ‐Bonds: Theoretical Understanding and Prediction 下载免费PDF全文
Dr. Hajime Kameo Prof. Shigeyoshi Sakaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(39):13588-13597
The oxidative addition of BF3 to a platinum(0) bis(phosphine) complex [Pt(PMe3)2] ( 1 ) was investigated by density functional calculations. Both the cis and trans pathways for the oxidative addition of BF3 to 1 are endergonic (ΔG°=26.8 and 35.7 kcal mol?1, respectively) and require large Gibbs activation energies (ΔG°≠=56.3 and 38.9 kcal mol?1, respectively). A second borane plays crucial roles in accelerating the activation; the trans oxidative addition of BF3 to 1 in the presence of a second BF3 molecule occurs with ΔG°≠ and ΔG° values of 10.1 and ?4.7 kcal mol?1, respectively. ΔG°≠ becomes very small and ΔG° becomes negative. A charge transfer (CT), F→BF3, occurs from the dissociating fluoride to the second non‐coordinated BF3. This CT interaction stabilizes both the transition state and the product. The B?F σ‐bond cleavage of BF2ArF (ArF=3,5‐bis(trifluoromethyl)phenyl) and the B?Cl σ‐bond cleavage of BCl3 by 1 are accelerated by the participation of the second borane. The calculations predict that trans oxidative addition of SiF4 to 1 easily occurs in the presence of a second SiF4 molecule via the formation of a hypervalent Si species. 相似文献
994.
Asymmetric Synthesis of Furo[3,4‐b]indoles by Catalytic [3+2] Cycloaddition of Indoles with Epoxides 下载免费PDF全文
Dr. Lili Lin Xiao Yuan Songsong Guo Prof. Dr. Xiaohua Liu Prof. Dr. Xiaoming Feng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(43):15104-15107
A highly efficient N,N′‐dioxide–NiII catalyst system for the catalytic [3+2] cycloaddition of indoles with epoxides through C?C cleavage of oxiranes was accomplished under mild conditions. It provided a promising approach for chiral furo[3,4‐b]indoles in up to 98 % yield with up to 91 % enantiomeric excess (ee) and >95:5 diastereomeric ratio (d.r.). 相似文献
995.
Coating Platinum Nanoparticles with Methyl Radicals: Effects on Properties and Catalytic Implications 下载免费PDF全文
Dr. Ronen Bar‐Ziv Dr. Israel Zilbermann Dr. Michael Shandalov Prof. Dr. Vladimir Shevchenko Prof. Dr. Dan Meyerstein 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(52):19000-19009
It was recently reported that the reaction of methyl radicals with Pt0 nanoparticles (NPs), prepared by the reduction of Pt(SO4)2 with NaBH4, is fast and yields as the major product stable (Pt0‐NPs)?(CH3)n and as side products, in low yields, C2H6, C2H4, and some oligomers. We decided to study the effect of this coating on the properties of the Pt0‐NPs. The results show that the coating can cover up to 75 % of the surface Pt0 atoms. The rate constant of the reaction, k( . CH3+Pt0‐NPs), decreases with the increase in the surface coverage, leading to competing reaction paths in the solution, which gradually become dominant, affecting the composition of the products. The methyl coating also affects the zeta potential, the UV spectra, and the electrocatalytic reduction of water in the presence of the NPs. Thus, the results suggest that binding alkyl radicals to Pt0 surfaces might poison the NPs catalytic activity. When the Pt0‐NPs are prepared by the reduction of a different precursor salt, PtCl62?, nearly no C2H4 and oligomers are formed and the methyl coating covers a larger percentage of the surface Pt0 atoms. The difference is attributed to the morphology of the Pt0‐NPs: those prepared from Pt(SO4)2 are twinned nanocrystals, whereas those prepared from PtCl62? consist mostly of single crystals. Thus, the results indicate that the side products, or most of them at least, are formed on the twinned Pt0 nanocrystal edges created between (111) facets. In addition, the results show that Pt0‐NPs react very differently compared with other noble metals, for example, Au0 and Ag0; this difference is attributed in part to the difference in the bond strength, (M0‐NP)?CH3, and should be considered in heterogeneous catalytic processes involving alkyl radicals as intermediates. 相似文献
996.
Unmasking the Action of Phosphinous Acid Ligands in Nitrile Hydration Reactions Catalyzed by Arene–Ruthenium(II) Complexes 下载免费PDF全文
Dr. Eder Tomás‐Mendivil Dr. Victorio Cadierno Dr. María I. Menéndez Dr. Ramón López 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(47):16874-16886
The catalytic hydration of benzonitrile and acetonitrile has been studied by employing different arene–ruthenium(II) complexes with phosphinous (PR2OH) and phosphorous acid (P(OR)2OH) ligands as catalysts. Marked differences in activity were found, depending on the nature of both the P‐donor and η6‐coordinated arene ligand. Faster transformations were always observed with the phosphinous acids. DFT computations unveiled the intriguing mechanism of acetonitrile hydration catalyzed by these arene–ruthenium(II) complexes. The process starts with attack on the nitrile carbon atom of the hydroxyl group of the P‐donor ligand instead of on a solvent water molecule, as previously suggested. The experimental results presented herein for acetonitrile and benzonitrile hydration catalyzed by different arene–ruthenium(II) complexes could be rationalized in terms of such a mechanism. 相似文献
997.
Catalytic Asymmetric Michael Reaction of 5H‐Oxazol‐4‐Ones with α,β‐Unsaturated Acyl Imidazoles 下载免费PDF全文
Bangzhi Zhang Fengxia Han Linqing Wang Dan Li Dongxu Yang Xiaoli Yang Junxian Yang Xiaofang Li Dr. Depeng Zhao Prof. Dr. Rui Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(48):17234-17238
The asymmetric Michael reaction between 5H‐oxazol‐4‐ones and α,β‐unsaturated acyl imidazoles is reported. A novel 2‐benzo[b]thiophenyl‐modified chiral ProPhenol species is synthesized and used as a ligand, leading to good enantioselectivities in this asymmetric conjugate addition reaction. Furthermore, the introduction of phenol additives as achiral co‐ligands is found to improve the reaction’s chemical yields, diastereoselectivities, and enantioselectivities. 相似文献
998.
Light‐Controlled Histone Deacetylase (HDAC) Inhibitors: Towards Photopharmacological Chemotherapy 下载免费PDF全文
Dr. Wiktor Szymanski Maria E. Ourailidou Dr. Willem A. Velema Prof. Dr. Frank J. Dekker Prof. Dr. Ben L. Feringa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16517-16524
Cancer treatment suffers from limitations that have a major impact on the patient’s quality of life and survival. In the case of chemotherapy, the systemic distribution of cytotoxic drugs reduces their efficacy and causes severe side effects due to nonselective toxicity. Photopharmacology allows a novel approach to address these problems because it employs external, local activation of chemotherapeutic agents by using light. The development of photoswitchable histone deacetylase (HDAC) inhibitors as potential antitumor agents is reported herein. Analogues of the clinically used chemotherapeutic agents vorinostat, panobinostat, and belinostat were designed with a photoswitchable azobenzene moiety incorporated into their structure. The most promising compound exhibits high inhibitory potency in the thermodynamically less stable cis form and a significantly lower activity for the trans form, both in terms of HDAC activity and proliferation of HeLa cells. This approach offers a clear prospect towards local photoactivation of HDAC inhibition to avoid severe side effects in chemotherapy. 相似文献
999.
Fluorescent Coumarin–Artemisinin Conjugates as Mitochondria‐Targeting Theranostic Probes for Enhanced Anticancer Activities 下载免费PDF全文
Dr. Xu Zhang Qian Ba Zhanni Gu Dr. Diliang Guo Prof. Yu Zhou Prof. Yungen Xu Prof. Hui Wang Prof. Deju Ye Prof. Hong Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(48):17415-17421
Mitochondria‐targeting theranostic probes that enable the simultaneously reporting of and triggering of mitochondrial dysfunctions in cancer cells are highly attractive for cancer diagnosis and therapy. Three fluorescent mitochondria‐targeting theranostic probes have been developed by linking a mitochondrial dye, coumarin‐3‐carboximide, with a widely used traditional Chinese medicine, artemisinin, to kill cancer cells. Fluorescence images showed that the designed coumarin–artemisinin conjugates localized mainly in mitochondria, leading to enhanced anticancer activities over artemisinin. High cytotoxicity against cancer cells correlated with the strong ability to accumulate in mitochondria, which could efficiently increase the intracellular reactive oxygen species level and induce cell apoptosis. This study highlights the potential of using mitochondria‐targeting fluorophores to selectively trigger and directly visualize subcellular drug delivery in living cells. 相似文献
1000.
Small‐Sized Tungsten Nitride Particles Strongly Anchored on Carbon Nanotubes and their Use as Supports for Pt for Methanol Electro‐oxidation 下载免费PDF全文
Yuan Liu Dr. Haijing Yan Dr. Xiaoguang Zhou Dr. Mingxia Li Prof. Honggang Fu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18345-18353
The anchoring of small‐sized WN (tungsten nitride) nanoparticles (NPs) with good dispersion on carbon nanotubes (CNTs) offers an effective means of obtaining promising materials for use in electrocatalysis. Herein, an effective method based on grinding treatment followed by a nitridation process is proposed to realize this goal. In the synthesis, a solution containing H4[SiO4(W3O9)4] (SiW12) and CNTs modified with polyethylenimine (PEI‐CNTs) was ground to dryness. Small‐sized WN NPs were anchored onto the CNTs with good dispersion after calcination under NH3. Under hydrothermal assembly conditions (absence of grinding), WN particles of larger size and with inferior dispersion were obtained, demonstrating the important role of the grinding process. The benefit of the small‐sized WN has been demonstrated by using WN/CNTs as a support for Pt to catalyze the methanol electro‐oxidation reaction. The mass activity of Pt‐WN/CNTs‐G‐70 (where G denotes the grinding treatment, and 70 is the loading amount (%) of WN in the WN/CNTs) was evaluated as about 817 mA mg?1Pt, better that those of commercial Pt/C (340 mA mg?1Pt) and Pt/CNTs (162 mA mg?1Pt). The Pt‐WN/CNTs‐G also displayed good CO tolerance. In contrast, Pt‐WN/CNTs prepared without the grinding process displayed an activity of 344 mA mg?1Pt, verifying the key role of grinding treatment in the preparation of WN/CNTs with good co‐catalytic effect. 相似文献