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11.
Oleg V. Mikhailov Marina A. Kazymova Tatyana A. Shumilova Galina A. Chmutova Svetlana E. Solovieva 《Transition Metal Chemistry》2005,30(3):299-304
The complexing process proceeding in the NiII–thiocarbohydrazide (H2N–H–NC(=S)–NH–NH2)–propanone triple system in EtOH solution and nickel(II)hexacyanoferrate(II) gelatin-immobilized matrix has been studied. It has been found that in the first case, template synthesis leading, as a minimum, to formation of three coordination compounds of NiII with (N,N,S,S)-donor tetradentate ligands having NiL1, NiL2 and NiL3compositions where L1 is 4,6,6-trimethyl-2,3,7,8-tetraazanonen-3-di(thiohydrazide)-1,9, L2 is 4,6,6,12-tetrametyl-1,9-dithio-2,3,7,8,10,11-hexaazatridekadien-3,11-hydrazide-1 and L3 is 2,8,10,10,16-pentamethyl-5,13-dithio-3,4,6,7,11,12,14,15-octaazaheptadekatrien-2,7,15 is observed, whereas in the gelatin-immobilized matrix, a complexing process in the system considered does not occur. 相似文献
12.
Svetlana B. Lyubchik Irene I. Perepichka Olga L. Galushko Andrey I. Lyubchik Elena S. Lygina Isabel M. Fonseca 《Adsorption》2005,11(5-6):581-593
In order to understand the patterns of the adsorption equilibrium of Cr (III) on activated carbon, the adsorption process
was studied by two different ways: classical batch experiments on commercial Norit and Merck activated carbons and their oxidized
forms in a wide range of pHs; and extended time-based tests at the same pH values on the same adsorbents. This approach allowed
us to understand the role of texture, chemical carbon surface functionality and experimental conditions (initial pH of the
solution, contact time and adsorbate/adsorbent ratio) on the effectiveness of Cr (III) removal. The adsorption process of
Cr (III) at (24 ± 1∘C) on Merck and Norit activated carbons and their oxidized forms were studied at pH values between 1.5 and 5 (either adjusted
or buffered). Chromium concentration was fixed at 200 ppm. The carbon loading ranged from 1.2 to 20 g/l. The carbon/Cr (III)
solution contact time was varied from 0.5–1 month to 5 months, to ensure that the saturation of the carbon level was reached.
According to the data obtained, the presence of carboxylic groups on carbon surface seems to enhance Cr (III) uptake at initial
pH of the solution in the range between 2 and 4. Depending on the nature of the adsorbent surface chemistry, the contact time
to reach equilibrium may range from 3 to 5 months. There is an optimum carbon loading which limits the Cr (III) uptake/removal
at given pH value. In order to understand the adsorption process, an ion exchange, surface complex and surface precipitation
were considered.
This paper was presented in the 5th Brazilian Meeting on Adsorption, held at Natal, Brazil, 18-21 July, 2004. 相似文献
13.
Viktor A. Sipachev Lyudmila N. Reshetova Yurii S. Nekrasov Svetlana Yu. Sil'vestrova 《Journal of mass spectrometry : JMS》1980,15(4):192-194
The electron impact mass spectrum of Zn4O(CH3CO2)6 isostructural to Be4O(CH3CO2)6 studied earlier is reported. The principal fragmentation paths of both compounds involve the elimination of M(CH3CO2)2 where M is Zn, Be, or (CH3CO)2O. Further fragmentations proceed by the losses of CH2CO and H2O. The spectrum of Zn4O(CH3CO2)6 contains intense doubly charged ions. The results obtained are interpreted in terms of stereochemical considerations. 相似文献
14.
Rudnev AV Aleksenko SS Semenova O Hartinger CG Timerbaev AR Keppler BK 《Journal of separation science》2005,28(2):121-127
A CE method has been developed to evidence and quantitatively characterize the interaction between platinum-based antitumor drugs and human serum proteins. This method is a variant of affinity CE modified regarding both experimental setup and data treatment so as to measure the peaks (or vacancies) that correspond to the bound drug when it slowly binds to the protein. Using the formalism of the Hummel-Dreyer method and cisplatin and oxaliplatin as test compounds, a protocol for determining albumin and transferrin binding constants and stoichiometries, including (and distinguished by) 48 hours of incubation of the reaction mixture, was elaborated. Relative affinities of drugs toward different proteins in aqueous solution at physiological pH, chloride concentration, and temperature were compared in terms of overall binding constants and numbers of drug molecules attached to the protein. The results indicate that both platinum drugs bind to albumin more strongly than to transferrin, supporting the concept that the albumin fraction is a major drug supply route for chemotherapeutical needs. From a comparison with the binding parameters measured previously for cisplatin by other methods, conclusions were drawn about the validity of CE as a simple and convenient method for assaying protein-drug reactions with slow kinetics. 相似文献
15.
Iliyana V. Berlinova Aissa Amzil Svetlana Tsvetkova Ivan M. Panayotov 《Journal of polymer science. Part A, Polymer chemistry》1994,32(8):1523-1530
Amphiphilic graft copolymers were synthesized via activated ester substitution of derivatives of fumaric acid with amino-functionalized methoxypoly (oxyethylene)s (MPEO-NH2) of different molecular weights. The monomeric activated esters, isopropyl pentachlorophenyl fumarate (PCPFA) and isopropyl succinimido fumarate (SIFA), were copolymerized with styrene (St) or N-vinyl pyrrolidone (VP) at equimolar ratio. The polymeric-activated esters proved to be good precursors for grafting of definite amounts of MPEO-NH2. The aminolysis of the succinimide esters and VP-containing copolymers proceeded with gel formation due to extensive hydrogen bonding. The hydrodynamic behavior, the emulsifying ability, the thermal properties, and crystallinity of the graft copolymers were studied as a function of their molecular characteristics. The length of the PEO grafts and the degree of grafting are the factors which affect the melting parameters and the crystallinity of the side chains. © 1994 John Wiley & Sons, Inc. 相似文献
16.
Svetlana Ya. Jitomirskaya 《Communications in Mathematical Physics》1995,168(3):563-570
We prove that for any >2 and a.e. , the pure point spectrum of the almost Mathieu operator (H())
n
=
n-1
+
n+1
+ cos(2( +n))
n
contains the essential closure
of the spectrum. Corresponding eigenfunctions decay exponentially. The singular continuous component, if it exists, is concentrated on a set of zero measure which is nowhere dense in
. 相似文献
17.
Vladimir Leskovac Svetlana Trivi? Draginja Peric?in Julijan Kandra? 《Monatshefte für Chemie / Chemical Monthly》2004,53(4):1359-1372
The primary kinetic isotope effects of deuterium were investigated in 22 hydrogen and deuterium transfer reactions, including enzymatic and nonenzymatic hydride transfer reactions, elimination reactions, and reactions catalyzed by enzymes lipooxygenase, amine dehydrogenase, and methylmalonyl-CoA mutase. In each case, the Saunders-Bell analysis was applied to calculate the tunnel effects and the corresponding thermodynamic parameters. The Saunders-Bell analysis was effective in 14 cases out of 22. A high degree of correlation was found between the barrier factor, the tunnel factor, and the entropy factor among all reactions studied. From this, a general relationship between the three factors was derived, based on the Saunders-Bell analysis of the Bell equation; the Saunders-Bell analysis is valid within certain limits of the barrier factor. This general relationship is universally valid for all hydrogen/deuterium transfer reactions in nature with moderate tunneling, when the Saunders-Bell analysis applies. 相似文献
18.
Spin-unrestricted calculations and time-dependent DFT were used to characterize structure and reactivity of 1-methyl-8-nitronaphthalene (1) in the triplet state. Four hybrid models (B3LYP, PBE0, MPW1K, BHLYP) with significantly different amount of the exact exchange were employed. The triplet potential energy surface of 1 was mapped by using the UB3LYP and UMPW1K techniques. Both hybrid models provided qualitatively consistent pictures for the potential energy landscape. Thirty-one stationary points, of which 15 were minima, were found at the UB3LYP level of theory. Three minima corresponding to the nitro form of 1 were located on the triplet surface; just one was found for the singlet ground state. Two reaction paths leading from 1 either to a nitrite-type intermediate (2) or to the aci-form (3) were characterized. For both paths, reaction products were of diradical nature. The lower activation energy was obtained for the triplet-state tautomerization affording 3. The ground state of triplet multiplicity was predicted for two isomers of the aci-form. The triplet diradical 3 is expected to react through the thermal population of a close-lying singlet excited state. The results are discussed in relation to mechanisms of photoinduced rearrangements of peri-substituted nitronaphthalenes that can be used to develop novel photolabile protecting groups. 相似文献
19.
Kollmar M Steinhagen H Janssen JP Goldfuss B Malinovskaya SA Vázquez J Rominger F Helmchen G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(14):3103-3114
All possible (eta(3)-allyl)palladium complexes (1-4) of the ligand (4S)-[2-(2'-diphenylphosphanyl)phenyl]-4,5-dihydro-4-(2-propyl)-oxazole (L 1) and eta(3)-allyl ligands with one to three phenyl substituents at the terminal allylic centers were synthesized and characterized by X-ray crystal structure analysis and, with respect to allylic isomers, by NMR investigations. Equilibrium geometries, electronic structures, and relative energies of isomeric complexes were computed by restricted Hartree-Fock (RHF) and density functional theory (DFT) calculations; experimentally determined isomer ratios could be reproduced. The results allowed important conclusions to be drawn regarding the mechanism of Pd-catalyzed asymmetric allylic substitutions. 相似文献
20.
Abdeloihid Mellouki Robert Georges Michel Herman Deanne L. Snavely Svetlana Leytner 《Chemical physics》1997,220(3):443-322
We have recorded the infrared absorption spectrum of pyrrole at 0.005 cm−1 spectral resolution using a Fourier transform interferometer. The rotational analysis of the fundamental N---H stretch (110) at 3530.811343(82) cm−1 was performed. A set of 13 upper state rovibrational parameters was determined, allowing the 2715 assigned rovibrational lines to be reproduced with a standard deviation of 1.3 10−3 cm−1. An attempt to record the fundamental band under slit-jet conditions is reported. The role of hot bands accompanying the series of the N---H stretch excitation is investigated. Effective vibrational parameters — ω01, X011, Y111, X1,24 — are obtained. The lower level in the hot band series is unambiguously identified as the V24 = 1 level, by retrieving X1,24 independently, from other spectral data. The observation of the complex band pattern accompanying the N---H series in the higher overtone range is discussed with the help of new data, recorded around the 150 band at different temperatures using intracavity laser optoacoustic spectroscopy. 相似文献