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21.
Andrew G. Tennyson Dr. Robert J. Ono Todd W. Hudnall Dr. Dimitri M. Khramov Dr. Joyce A. V. Er Justin W. Kamplain Dr. Vincent M. Lynch Dr. Jonathan L. Sessler Prof. Christopher W. Bielawski Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(1):304-315
Reaction of bromanil with N,N′‐dimesitylformamidine followed by deprotonation with NaN(SiMe3)2 afforded 1,1′,3,3′‐tetramesitylquinobis(imidazolylidene) ( 1 ), a bis(N‐heterocyclic carbene) (NHC) with two NHC moieties connected by a redox active p‐quinone residue, in 72 % yield of isolated compound. Bimetallic complexes of 1 were prepared by coupling to FcN3 ( 2 ) or FcNCS ( 3 ; Fc=ferrocenyl) or coordination to [M(cod)Cl] ( 4 a or 4 b , where M=Rh or Ir, respectively; cod=1,5‐cyclooctadiene). Treatment of 4 a and 4 b with excess CO(g) afforded the corresponding [M(CO)2Cl] complexes 5 a and 5 b , respectively. Analysis of 2 – 5 by NMR spectroscopy and X‐ray diffraction indicated that the electron‐deficient quinone did not significantly affect the inherent spectral properties or coordination chemistry of the flanking imidazolylidene units, as compared to analogous NHCs. Infrared spectroscopy and cyclic voltammetry revealed that decreasing the electron density at MLn afforded an increase in the stretching energy and a decrease in the reduction potential of the quinone, indicative of metal–quinone electronic interaction. Differential pulse voltammetry and chronoamperometry of the metal‐centered oxidations in 2 – 4 revealed two single, one‐electron peaks. Thus, the metal atoms bound to 1 are oxidized at indistinguishable potentials and do not appear electronically coupled. However, the metal–quinone interaction was used to increase the electron density at coordinated metal atoms. Infrared spectroelectrochemistry revealed that the average νCO values for 5 a and 5 b decreased by 14 and 15 cm?1, respectively, upon reduction of the quinone embedded within 1 . These shifts correspond to 10 and 12 cm?1 decreases in the Tolman electronic parameter of this ditopic ligand. 相似文献
22.
Daniel J. Coady Dr. Dimitri M. Khramov Dr. Brent C. Norris Andrew G. Tennyson Dr. Christopher W. Bielawski Prof. 《Angewandte Chemie (International ed. in English)》2009,48(28):5187-5190
A click by any other name : Coupling bis(N‐heterocyclic carbene)s with bis(azide)s afforded a novel class of conjugated polytriazenes. These polymers were rendered electrically conductive upon doping, and fluorene‐containing variants exhibited luminescence. This adaptation of N‐heterocyclic carbene (NHC)/azide coupling chemistry to polymer synthesis reveals the potential of NHCs as building blocks for accessing polymers having useful electronic properties.
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Treatment of N-heterocyclic carbenes (as their free carbenes or generated in situ) with alkyl, aryl, acyl or tosyl azides afforded the respective substituted triazenes in excellent yields. 相似文献
24.
N. I. Kuznetsova L. I. Kuznetsova N. V. Kirillova L. G. Detusheva V. A. Likholobov M. I. Khramov J.-E. Ansel 《Kinetics and Catalysis》2005,46(2):204-216
Cyclohexane, cyclohexene, and -pinene react with dioxygen in the liquid phase in the presence of catalysts based on platinum, heteropoly compounds (HPCs), metal-containing HPCs, and combinations of these components. In cyclohexane and -pinene oxidations occurring by an autooxidation mechanism at 160–170 and 80– 90°C, respectively, the catalysts serve to control free-radical processes. The simultaneous action of a Ru-containing phosphotungstate as a hydroperoxide decomposition catalyst and of a V-containing phosphotungstate as a scavenger of hydroxyl and alkoxyl radicals increases the cyclohexanol + cyclohexanone selectivity of cyclohexane oxidation without yielding a hydroperoxide. A Pt/C catalyst affords an increase in -pinene conversion in a fixed time. In combination with ammonia or tetrahexylammonium chloride admixtures, it retards side reactions and raises the yield of verbenol and verbenone, which are the most valuable products. During cyclohexane, cyclohexene, and -pinene oxidation with an O2-H2 mixture at room temperature, no free-radical chain reaction develops in the Pt-HPC system and reactive intermediates form and interact, involving the HPC, with hydrocarbons on the surface of the platinum catalyst. Analysis of reactivity and of the composition of substrate oxidation products suggests a mechanism for the conjugate oxidation of hydrocarbons in systems with various HPCs. In this mechanism, HPC composition determines, to a large extent, the nature of reactive intermediates, which may be peroxides or radicals bound to platinum or HPC. The properties of catalytic systems in oxidation with O2-H2 mixtures can be controlled by selecting an appropriate HPC as the modifying component.__________Translated from Kinetika i Kataliz, Vol. 46, No. 2, 2005, pp. 219–232.Original Russian Text Copyright © 2005 by N. Kuznetsova, L. Kuznetsova, Kirillova, Detusheva, Likholobov, Khramov, Ansel. 相似文献
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V. Bednyakov E. Khramov N. Russakovich A. Tonoyan 《Physics of Particles and Nuclei Letters》2007,4(6):491-496
We have investigated the possibility of reconstructing the top quark charge through measurement of its decay product charges
at the ATLAS detector. Verification of the hypothesis about alternative interpretation of top-quark experimental data has
been considered as well. The method of “semileptonic B-meson decay” was applied for reconstructing the b-jet charge. A statistical significance of more than 5σ can be achieved using this method after analyzing 1 fb−1 of the t̄t-pairs data. The analysis was carried out with HERWIG and PYTHIA generators and using the GEANT4 detector simulation software
package.
The text was submitted by the authors in English. 相似文献
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N. I. Kislyakov I. A. Piven' A. K. Rebrov G. A. Khramov 《Journal of Applied Mechanics and Technical Physics》1976,17(1):27-31
The presence of fluctuations in the intensity of radiation excited by electrons in a jet core was discovered using an electron beam and by studying the interaction of two low-density supersonic CO2 flows. The nature of the variation of the frequency and amplitude of the surges within the jet core as well as the region within which the surges exist depend on the parameters of the flow retardation.Translated from Zhurnal Prikladnoi Mekhaniki i Teknicheskoi Fiziki, No. 1, pp. 35–40, January–February, 1976.In conclusion, the authors wish to express their appreciation to R. G. Sharafutdinov and Yu. S. Kusner for participating in the discussion of the experimental results. 相似文献
30.
Ivanov VV Khramov A Hansen AH Dowd WH Münchow F Jamison AO Gupta S 《Physical review letters》2011,106(15):153201
We report on the realization of a stable mixture of ultracold lithium and ytterbium atoms confined in a far-off-resonance optical dipole trap. We observe sympathetic cooling of 6Li by 174Yb and extract the s-wave scattering length magnitude |a(6Li-174Yb)|=(13±3)a0 from the rate of interspecies thermalization. Using forced evaporative cooling of 174Yb, we achieve reduction of the 6Li temperature to below the Fermi temperature, purely through interspecies sympathetic cooling. 相似文献