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991.
Hetero‐tri‐spin [2p‐3d‐4f] Chain Compounds Based on Nitronyl Nitroxide Lanthanide Metallo‐Ligands: Synthesis,Structure, and Magnetic Properties 下载免费PDF全文
Mei Zhu Peng Hu Yungai Li Xiufeng Wang Prof. Licun Li Prof. Daizheng Liao V. M. L. Durga Prasad Goli Prof. S. Ramasesha Dr. Jean‐Pascal Sutter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13356-13365
Employing nitronyl nitroxide lanthanide(III) complexes as metallo‐ligands allowed the efficient and highly selective preparation of three series of unprecedented hetero‐tri‐spin (Cu?Ln‐radical) one‐dimensional compounds. These 2p–3d–4f spin systems, namely [Ln3Cu(hfac)11(NitPhOAll)4] (LnIII=Gd 1Gd , Tb 1Tb , Dy 1Dy ; NitPhOAll=2‐(4′‐allyloxyphenyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide), [Ln3Cu(hfac)11(NitPhOPr)4] (LnIII=Gd 2Gd , Tb 2Tb , Dy 2Dy , Ho 2Ho , Yb 2Yb ; NitPhOPr=2‐(4′‐propoxyphenyl)‐4,4,5,5‐tetramethyl‐imidazoline‐1‐oxyl‐3‐oxide) and [Ln3Cu(hfac)11(NitPhOBz)4] (LnIII=Gd 3Gd , Tb 3Tb , Dy 3Dy ; NitPhOBz=2‐(4′‐benzyloxyphenyl)‐4,4,5,5‐tetramethyl‐imidazoline‐1‐oxyl‐3‐oxide) involve O‐bound nitronyl nitroxide radicals as bridging ligands in chain structures with a [Cu‐Nit‐Ln‐Nit‐Ln‐Nit‐Ln‐Nit] repeating unit. The dc magnetic studies show that ferromagnetic metal–radical interactions take place in these hetero‐tri‐spin chain complexes, these and the next‐neighbor interactions have been quantified for the Gd derivatives. Complexes 1Tb and 2Tb exhibit frequency dependence of ac magnetic susceptibilities, indicating single‐chain magnet behavior. 相似文献
992.
Following Solid‐Acid‐Catalyzed Reactions by MAS NMR Spectroscopy in Liquid Phase—Zeolite‐Catalyzed Conversion of Cyclohexanol in Water 下载免费PDF全文
Aleksei Vjunov Mary Y. Hu Dr. Ju Feng Dr. Donald M. Camaioni Dr. Donghai Mei Dr. Jian Z. Hu Dr. Chen Zhao Prof. Dr. Johannes A. Lercher 《Angewandte Chemie (International ed. in English)》2014,53(2):479-482
A microautoclave magic angle spinning NMR rotor is developed enabling in situ monitoring of solid–liquid–gas reactions at high temperatures and pressures. It is used in a kinetic and mechanistic study of the reactions of cyclohexanol on zeolite HBEA in 130 °C water. The 13C spectra show that dehydration of 1‐13C‐cyclohexanol occurs with significant migration of the hydroxy group in cyclohexanol and the double bond in cyclohexene with respect to the 13C label. A simplified kinetic model shows the E1‐type elimination fully accounts for the initial rates of 1‐13C‐cyclohexanol disappearance and the appearance of the differently labeled products, thus suggesting that the cyclohexyl cation undergoes a 1,2‐hydride shift competitive with rehydration and deprotonation. Concurrent with the dehydration, trace amounts of dicyclohexyl ether are observed, and in approaching equilibrium, a secondary product, cyclohexyl‐1‐cyclohexene is formed. Compared to phosphoric acid, HBEA is shown to be a more active catalyst exhibiting a dehydration rate that is 100‐fold faster per proton. 相似文献
993.
Jinfa Chang Dr. Ligang Feng Prof. Dr. Changpeng Liu Prof. Dr. Wei Xing Prof. Dr. Xile Hu 《Angewandte Chemie (International ed. in English)》2014,53(1):122-126
The direct formic acid fuel cell is an emerging energy conversion device for which palladium is considered as the state‐of‐the‐art anode catalyst. In this communication, we show that the activity and stability of palladium for formic acid oxidation can be significantly enhanced using nickel phosphide (Ni2P) nanoparticles as a cocatalyst. X‐ray photoelectron spectroscopy (XPS) reveals a strong electronic interaction between Ni2P and Pd. A direct formic acid fuel cell incorporating the best Pd–Ni2P anode catalyst exhibits a power density of 550 mW cm?2, which is 3.5 times of that of an analogous device using a commercial Pd anode catalyst. 相似文献
994.
Rhodium(III)‐Catalyzed ortho Alkenylation of N‐Phenoxyacetamides with N‐Tosylhydrazones or Diazoesters through CH Activation 下载免费PDF全文
Fangdong Hu Ying Xia Fei Ye Zhenxing Liu Prof. Dr. Chen Ma Prof. Dr. Yan Zhang Prof. Dr. Jianbo Wang 《Angewandte Chemie (International ed. in English)》2014,53(5):1364-1367
A coupling reaction of N‐phenoxyacetamides with N‐tosylhydrazones or diazoesters through RhIII‐catalyzed C? H activation is reported. In this reaction, ortho‐alkenyl phenols were obtained in good yields and with excellent regio‐ and stereoselectivity. Rh–carbene migratory insertion is proposed as the key step in the reaction mechanism. 相似文献
995.
Tunable Oxygen Activation for Catalytic Organic Oxidation: Schottky Junction versus Plasmonic Effects 下载免费PDF全文
Ming Gong Shan Zhou Jiahua Hu Min Zhi Yang You Song Bai Prof. Jun Jiang Prof. Qun Zhang Prof. Xiaojun Wu Prof. Yujie Xiong 《Angewandte Chemie (International ed. in English)》2014,53(12):3205-3209
The charge state of the Pd surface is a critical parameter in terms of the ability of Pd nanocrystals to activate O2 to generate a species that behaves like singlet O2 both chemically and physically. Motivated by this finding, we designed a metal–semiconductor hybrid system in which Pd nanocrystals enclosed by {100} facets are deposited on TiO2 supports. Driven by the Schottky junction, the TiO2 supports can provide electrons for metal catalysts under illumination by appropriate light. Further examination by ultrafast spectroscopy revealed that the plasmonics of Pd may force a large number of electrons to undergo reverse migration from Pd to the conduction band of TiO2 under strong illumination, thus lowering the electron density of the Pd surface as a side effect. We were therefore able to rationally tailor the charge state of the metal surface and thus modulate the function of Pd nanocrystals in O2 activation and organic oxidation reactions by simply altering the intensity of light shed on Pd–TiO2 hybrid structures. 相似文献
996.
Hollow Spheres of Iron Carbide Nanoparticles Encased in Graphitic Layers as Oxygen Reduction Catalysts 下载免费PDF全文
M.Sc. Yang Hu Dr. Jens Oluf Jensen Dr. Wei Zhang Dr. Lars N. Cleemann Prof. Wei Xing Prof. Niels J. Bjerrum Dr. Qingfeng Li 《Angewandte Chemie (International ed. in English)》2014,53(14):3675-3679
Nonprecious metal catalysts for the oxygen reduction reaction are the ultimate materials and the foremost subject for low‐temperature fuel cells. A novel type of catalysts prepared by high‐pressure pyrolysis is reported. The catalyst is featured by hollow spherical morphologies consisting of uniform iron carbide (Fe3C) nanoparticles encased by graphitic layers, with little surface nitrogen or metallic functionalities. In acidic media the outer graphitic layers stabilize the carbide nanoparticles without depriving them of their catalytic activity towards the oxygen reduction reaction (ORR). As a result the catalyst is highly active and stable in both acid and alkaline electrolytes. The synthetic approach, the carbide‐based catalyst, the structure of the catalysts, and the proposed mechanism open new avenues for the development of ORR catalysts. 相似文献
997.
Catalytic Asymmetric Functionalization of Aromatic CH Bonds by Electrophilic Trapping of Metal‐Carbene‐Induced Zwitterionic Intermediates 下载免费PDF全文
Shikun Jia Dr. Dong Xing Dan Zhang Prof. Dr. Wenhao Hu 《Angewandte Chemie (International ed. in English)》2014,53(48):13098-13101
Asymmetric functionalization of aromatic C? H bonds of N,N‐disubstituted anilines with diazo compounds and imines is reported for the efficient construction of α,α‐diaryl benzylic quaternary stereocenters in good yields with high diastereoselectivities and excellent enantioselectivities. This RhII/chiral phosphoric acid cocatalyzed transformation is proposed to proceed through a metal‐carbene‐induced zwitterionic intermediate which undergoes electrophilic trapping. To the best of our knowledge, this is the first asymmetric example of metal carbene‐induced intermolecular functionalization of aryl C? H bonds. 相似文献
998.
An Ylide Transformation of Rhodium(I) Carbene: Enantioselective Three‐Component Reaction through Trapping of Rhodium(I)‐Associated Ammonium Ylides by β‐Nitroacrylates 下载免费PDF全文
Xiaochu Ma Dr. Jun Jiang Siying Lv Wenfeng Yao Yang Yang Dr. Shunying Liu Dr. Fei Xia Prof. Dr. Wenhao Hu 《Angewandte Chemie (International ed. in English)》2014,53(48):13136-13139
The chiral RhI–diene‐catalyzed asymmetric three‐component reaction of aryldiazoacetates, aromatic amines, and β‐nitroacrylates was achieved to obtain γ‐nitro‐α‐amino‐succinates in good yields and with high diastereo‐ and enantioselectivity. This reaction is proposed to proceed through the enantioselective trapping of RhI‐associated ammonium ylides by nitroacrylates. This new transformation represents the first example of RhI‐carbene‐induced ylide transformation. 相似文献
999.
Rhodium(III)‐Catalyzed Transannulation of Cyclopropenes with N‐Phenoxyacetamides through CH Activation 下载免费PDF全文
Hang Zhang Kang Wang Bo Wang Heng Yi Fangdong Hu Dr. Changkun Li Dr. Yan Zhang Prof. Dr. Jianbo Wang 《Angewandte Chemie (International ed. in English)》2014,53(48):13234-13238
An efficient rhodium(III)‐catalyzed synthesis of 2H‐chromene from N‐phenoxyacetamides and cyclopropenes has been developed. The reaction represents the first example of using cyclopropenes as a three‐carbon unit in rhodium(III)‐catalyzed C(sp2)? H activations. 相似文献
1000.
Fabrication of Predominantly Mn4+‐Doped TiO2 Nanoparticles under Equilibrium Conditions and Their Application as Visible‐Light Photocatalyts 下载免费PDF全文
Lijie Wang Jiajie Fan Zetan Cao Dr. Yichao Zheng Zhiqiang Yao Prof. Guosheng Shao Prof. Junhua Hu 《化学:亚洲杂志》2014,9(7):1904-1912
The chemical state of a transition‐metal dopant in TiO2 can intrinsically determine the performance of the doped material in applications such as photocatalysis and photovoltaics. In this study, manganese‐doped TiO2 is fabricated by a near‐equilibrium process, in which the TiO2 precursor powder precipitates from a hydrothermally obtained transparent mother solution. The doping level and subsequent thermal treatment influence the morphology and crystallization of the TiO2 samples. FTIR spectroscopy and X‐ray photoelectron spectroscopy analyses indicate that the manganese dopant is substitutionally incorporated by replacing Ti4+ cations. The absorption band edge can be gradually shifted to 1.8 eV by increasing the nominal manganese content to 10 at %. Manganese atoms doped into the titanium lattice are associated with the dominant 4+ valence oxidation state, which introduces two curved, intermediate bands within the band gap and results in a significant enhancement in photoabsorption and the quantity of photogenerated hydroxyl radicals. Additionally, the high photocatalytic performance of manganese‐doped TiO2 is also attributed to the low oxygen content, owing to the equilibrium fabrication conditions. This work provides an important strategy to control the chemical and defect states of dopants by using an equilibrium fabrication process. 相似文献