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排序方式: 共有120条查询结果,搜索用时 444 毫秒
21.
Sankaranarayanan J Bort LN Mandel SM Chen P Krause JA Brooks EE Tsang P Gudmundsdottir AD 《Organic letters》2008,10(5):937-940
Solid-state photolysis of 1a,b yields selectively cis-3a,b. X-ray analysis of 1a,b reveals the molecules adopt an extended structure and as such the crystal packing arrangement consists of planar, pi-stacked molecules. The shortest intermolecular distance between adjacent N-atoms is approximately 3.76 A and would lead to formation of trans-3a,b, whereas cis-3a,b is formed by dimerization between N-atoms that are approximately 3.9 A apart. We propose that the molecular orbital alignment of the adjacent nitrenes controls the solid-state reactivity. 相似文献
22.
Using integer and noninteger n-Slater type orbitals in single- and double-zeta approximations, the Hartree-Fock-Roothaan calculations were performed for the ground states of first ten cationic members of the isoelectronic series of He atom. All the noninteger parameters and orbital exponents were fully optimized. In the case of noninteger n-Slater type orbitals in double zeta basis sets, the results of calculations obtained are more close to the numerical Hatree-Fock values and the average deviations of our ground state energies do not exceed 2×10-6 hartrees of their numerical results. 相似文献
23.
An insight into the effect of composition for enhance catalytic performance of biogenic Au/Ag bimetallic nanoparticles
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A comprehensive knowledge of composition‐activity property relationship of nanoparticulate materials is highly desirable for applications in various catalysis reactions. We have addressed a facile green aqueous approach for preparation of Au, Ag monometallic, Au/Ag alloy as well as core‐shell bimetallic nanoparticles. The phytochemicals present in lemon grass leaves extract were employed both as natural reducing and capping agents at room temperature. X‐ray diffraction pattern, UV‐Vis spectroscopy, and energy dispersive X‐ray studies confirmed the formation of bimetallic system. The ensuing Au core/Ag shell and Au/Ag alloy bimetallic nanoparticles were crystalline and spherical in nature with identical average diameter of ~ 18 nm as measured via transmission electron microscopy. The bimetallic systems incredibly display higher catalytic potential than their monometallic counterparts which were vividly reckoned on structural effect, lattice compression, and synergistic electronic effect. 相似文献
24.
Sankaranarayanan SK Subbaraman R Ramanathan S 《Physical chemistry chemical physics : PCCP》2012,14(10):3360-3368
Atomistic simulations employing dynamic charge transfer between atoms are used to investigate ultra-thin oxide growth on Al(100) metal substrates in the presence of an ac electric field. In the range of 1-10 GHz frequencies, the enhancement in oxidation kinetics by ~12% over natural oxidation can be explained by the Cabrera-Mott mechanism. At field frequencies approaching 0.1-1 THz, however, we observe a dramatic lowering of the kinetics of oxygen incorporation by ~35% compared to the maximum oxidation achieved, which results in oxygen non-stoichiometry near the oxide-gas interface (O/Al ≈ 1.0). This is attributed to oxygen desorption from the oxide surface. These results suggest a general strategy to tune oxygen concentration at oxide surfaces using ac electric fields that could be of interest in diverse fields related to surface chemistry and applications such as tunnel barriers, thin dielectrics and oxide interfaces. 相似文献
25.
Hoong‐Kun Fun R. Sankaranarayanan D. Velmurugan S. Shanmuga Sundara Raj G. Babu P. T. Perumal 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(4):475-476
In the title compound, C26H22N2O2S, the tetrahydropyridine ring has a conformation intermediate between half‐chair and sofa. The tetrahydroquinoline mean plane makes a dihedral angle of 73.3 (1)° with the cyclopentene ring, which adopts an envelope conformation, and an angle of 45.45 (4)° with the indole best plane. The dihedral angle between the benzene and pyrrole rings is 2.6 (1)°. The orientations of the phenyl ring on the sulfonyl group and of the indole are governed by weak C—H?O interactions. The packing of the molecule in the solid state is stabilized by C—H?O and C—H?N hydrogen bonds. 相似文献
26.
Sankaranarayanan Jayashree 《合成通讯》2018,48(14):1805-1815
An efficient one-pot protocol for the synthesis of 2-((substituted amino)(4-phenyl)methyl)-3-hydroxy-naphthalene-1,4-dione derivatives has been developed by the three-component reaction of 2-hydroxy-naphthalene-1,4-dione, aromatic aldehydes and anilines/heterocyclic amines using montmorillonite K-10 as a catalyst. The advantages of this method include short reaction time, excellent yield and easy work-up. 相似文献
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29.
ÜMMÜHAN OCAK HALIT KANTEKIN YAŞAR GÖK H. BASIR ŞENTÜRK 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(1-2):87-91
The selective liquid–liquid extraction of various transition metal cations from the aqueous phase to the organic phase was carried out using a 14-membered N2O2S2-macrobicycle. Metal picrates such as Pb2+, Co2+, Zn2+, Ni2+,Cu2+ and Cd2+ were used in this extraction studies. It was found that the ligand showed moderate selectivity towards Pb2+ only among the other metals. The extraction constant (log K
ex) was determined to be 13.8 for Pb2+ complex. 相似文献
30.
Lakshmi Sankaranarayanan Erin O. Semmens Curtis W. Noonan 《International journal of environmental analytical chemistry》2016,96(2):137-147
As part of a randomised controlled residential intervention study, levoglucosan (LG) was investigated as a biomarker for wood smoke exposure. This study was conducted among 33 children living in homes that used wood stoves for residential heating. Indoor fine particulate matter (PM2.5) concentrations and corresponding urine samples from participants were collected during pre- and a post-intervention winter sampling periods. Interventions included the installation of an air filtration unit and a wood stove change out. Homes and children assigned to a placebo filter served as the control condition. Results showed a strong reduction in indoor PM2.5 among the air filter homes (≈58% reduction), whereas the wood stove change out homes did not have a significant PM2.5 reduction from pre- to post-intervention observations. Children living in the air filter homes did not show a corresponding reduction in urinary LG concentrations. Further analysis did not show an association between overall changes in indoor PM2.5 concentrations and changes in urinary LG concentrations. These findings suggest that urinary LG is not a reliable indicator of wood smoke exposure in residential wood heating settings. 相似文献