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81.
82.
Roberto Rossi Andrea Marchi Adriano Duatti Luciano Magon Plinio Di Bernardo 《Transition Metal Chemistry》1985,10(4):151-153
Summary The rhenium(V) imido-complexes [Re(NR)Cl3(PPh3)2] have been obtained by heating the rhenium(V) derivative [ReOCl3(PPh3)2] with RNHCHNR R = Ph (1a), p-MeC6H4 (1b), p-ClC6H4 (1c) andp-FC6H4 (1d) in THF under reflux. [Re(NR)Cl3(PPh3)2] (R =p-MeQ6H4) has also been obtained by heating the rhenium(III)-triazenido complex [ReCl2(RN
N
NR)(PPh3)2] in CCl4 under reflux. 相似文献
83.
84.
Several π-excessive heteropolyaromatic compounds, which contain furan and thiophen ring and are possible antifungal agents, have been synthesized in good yields according to two general methods. The first method has been used to prepare compounds possessing thiophens linked by their 2- and 5-positions, such as the ter-aryls , and . Two precursors of these compounds have been obtained either by the Glaser reaction, or using a novel Pd-mediated reaction. The second method,which consists of the Ni-or Pd-catalyzed heteroarylation of heteroarene halides via cross-coupling with heteroaryl Grignard reagents or zinc halides,has been used to prepare the bi-aryls , which contain two heteroaromatic units, and the ter-aryl . Compound has been also prepared starting from 2-(2-thienyl) furan () by selective lithiation, followed by bromination.The 13C NMR signals of and have been assigned on the basis of the literature data and by relaxation measurements. Relaxation data have been also used to obtain qualitative informations on the conformational equilibria of the bi-aryls , and the ter-aryls . 相似文献
85.
L. Benedetti R. Andreoli G. Battistuzzi Gavioli G. Grandi 《Journal of Electroanalytical Chemistry》1976,68(2):243-255
The electrochemical reduction of ØSO2NH2 and its ortho, para and meta amino derivatives was examined in aprotic medium (CH3CN) with varying experimental conditions, i.e. drop time, concentration and temperature. It has been shown that the reduction process is irreversible and controlled by diffusion at small values of concentration and low drop times, while the whole process is controlled by an adsorption step at larger values of concentration and drop times. The reduction mechanism, proposed by Horner for sulphonamides of the type XØSO2NR1R2, was confirmed and shown always to involve the S-N bond cleavage. Half-wave potentials and electrokinetic parameters were correlated with some theoretical and experimental structural indexes. Even if the correlation is fairly good and confirms the validity of the theoretical model assumed, it does not enable the pharmacological behaviour of the three isomers to be differentiated. 相似文献
86.
Adriano B. Pangelinan R. L. McCullough Michael J. Kelley 《Journal of Polymer Science.Polymer Physics》1994,32(14):2383-2394
An analytic model based on a random-walk formulation for absorbing barriers is presented. The range of applicability of the model is established from results derived from Monte Carlo simulations. The model takes into account the influences of neutral, repulsive, and attractive polymer-surface interactions on the spatial variation of species concentrations in the vicinity of a surface. The model predicts that the lower molecular weight species of a polydisperse mixture will accumulate in the vicinity of a surface to create an interphase region. The extent of this surface-perturbed interphase region is on the order of three times the radius of gyration of the longest species of the mixture. The degree of molecular weight segregation is dependent upon the breadth of the molecular weight distribution. © 1994 John Wiley & Sons. Inc. 相似文献
87.
We consider, for maps in H1/2(S1;S1), a family of (semi)norms equivalent to the standard one. We ask whether, for such a norm, there is some map in H1/2(S1;S1) of prescribed topological degree equal to 1 and minimal norm. In general, the answer is no, due to concentration phenomena. The existence of a minimal map is sensitive to small perturbations of the norm. We derive a sufficient condition for the existence of minimal maps. In particular, we prove that, for every given norm, there are arbitrarily small perturbations of it for which the minimum is attained. In case there is no minimizer, we determine the asymptotic behavior of minimizing sequences. We prove that, for such minimizing sequences, the energy concentrates near a point of S1. We describe this concentration in terms of bubbling-off of circles. 相似文献
88.
89.
90.
Liquid hydrogen in protonic chabazite 总被引:2,自引:0,他引:2
Zecchina A Bordiga S Vitillo JG Ricchiardi G Lamberti C Spoto G Bjørgen M Lillerud KP 《Journal of the American Chemical Society》2005,127(17):6361-6366
Due to its fully reversible nature, H(2) storage by molecular adsorption could represent an advantage with respect to dissociative processes, where kinetic effects during the charging and discharging processes are present. A drawback of this strategy is represented by the extremely weak interactions that require low temperature and high pressure. High surface area materials hosting polarizing sites can represent a viable way toward more favorable working conditions. Of these, in this contribution, we have studied hydrogen adsorption in a series of zeolites using volumetric techniques and infrared spectroscopy at 15 K. We have found that in H-SSZ-13 zeolite the cooperative role played by high surface area, internal wall topology, and presence of high binding energy sites (protons) allows hydrogen to densify inside the nanopores at favorable temperature and pressure conditions. 相似文献