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1.
Summary New cyanato-copper(II) complexes with aminopyridines (ampy) were prepared and studied;viz. Cu(NCO)2(3-ampy)2 (- and -form), Cu(NCO)2(3-ampy)2(H2O), Cu(NCO)2(4ampy)2, and Cu(NCO)2(2-ampy). According to physical results, the Cu(NCO)2L2 complexes exhibitpseudo-octahedral structures with amine nitrogens or cyanate oxygens occupying axial sites. For - and -Cu(NCO)2(3-ampy)2 the crystal structure reorganization is connected with a change in axial distortion. The compound Cu(NCO)2(2-ampy) is square pyramidal or — more probably — rhombic octahedral and its strong antiferromagnetism reveals the N-bridging function of the NCO groups.Part XXII, Ref. 9. 相似文献
2.
From a series of antioxidants comprising 2,2′-biphenyldiols, 2,2′-thiobisphenols and 2,2′-dithiobisphenol, free phenoxyls were prepared by oxidation with tert-butylperoxyls co-ordinated to Co(III) in non-polar media at ambient temperature. Both the effect of extended conjugation as a consequence of the direct bond between the two aromatic nuclei and, also, the steric effect of alkyl substituents could be observed. In the presence of free tert-butylperoxyls in excess, primary phenoxyls are transformed into cyclohexadienonyloxyls, which form stable radical complexes with Co(III). A mechanism for the formation of the cyclohexadienonyloxyls is suggested. 相似文献
3.
An ESR method for studying the mechanism of H-transfer reactions between H-donors of different reactivity (A1H, A2H…) and their free radicals (A1; A2.…) in non-polar solvents at ambient temperature is presented. The new technique is based on a pulsed initiation of various secondary phenoxy or nitroxy radicals in binary mixtures of hindered phenols, unhindered phenols, partially hindered thiobisphenols and diphenylamine, employing a high concentration of free RO2. and coordinated (CoIII)RO2. tert-butyl peroxy radicals generated in the redox-reaction of Co(acac)2 with tert-butyl hydroperoxide. The consecutive H-transfer reactions proceed to equilibrium until the most stable radicals are formed. In this way criteria are obtained for ranking the compared free and coordinated phenoxy radicals according to their relative stabilities. The secondarily generated phenoxy radicals from unhindered phenols after coordination to CoIII are stabilized and cannot take part in further H-transfer reactions. 相似文献
4.
Marek Omelka Matías Salibián-Barrera 《Annals of the Institute of Statistical Mathematics》2010,62(5):897-927
In this paper we find verifiable regularity conditions to ensure that S-estimators of scale and regression and MM-estimators
of regression are uniformly consistent and uniformly asymptotically normally distributed over contamination neighbourhoods.
Moreover, we show how to calculate the size of these neighbourhoods. In particular, we find that, for MM-estimators computed
with Tukey’s family of bisquare score functions, there is a trade-off between the size of these neighbourhoods and both the
breakdown point of the S-estimators and the leverage of the contamination that is allowed in the neighbourhood. These results
extend previous work of Salibian-Barrera and Zamar for location-scale to the linear regression model. 相似文献
5.
Summary The oxidation of 2,2-Diacyl-1-arylhydrazines1a–l with the system Pb(OAc)4-CF3COOH-CH2Cl2 led to the formation of two types of radical products. Phenazinium cation radicals5a–h were formed from 2,2-diacyl-1-arylhydrazines1a–h, while hydrazyl radicals2i–l were observed to be the only radical products of the oxidation of1i–l. The generated radicals are characterized by their EPR parameters.
Radikalische Produkte der Oxidation von 2,2-Diacyl-1-arylhydrazinen mit dem System Pb(OAc)4-CF3COOH-CH2Cl2
Zusammenfassung Die Oxidation der 2,2-Diacyl-1-arylhydrazine1a–l mit dem System Pb(OAc)4-CF3COOH-CH2Cl2 führte zu zwei unterschiedlichen Typen von Radikalen. Aus den 2,2-Diacyl-1-arylhydrazinen1a–h werden die Phenaziniumkationenradikale5a–h gebildet, während nach Oxidation von1i–l die entsprechenden Hydrazyle2i–l als einzige Radikalprodukte nachweisbar waren. Die erzeugten Radikale wurden durch ihre EPR-Parameter charakterisiert.相似文献
6.
Renata Superatová Zoja Vlčková Ladislav Omelka Jan Světlík 《Monatshefte für Chemie / Chemical Monthly》2008,139(2):101-106
Summary. A series of coumarin derivatives containing substituents with an acidic CH2 group in 3-position was decomposed on the surface of PbO2. The radical intermediates were identified by EPR spectroscopy. Although the occurrence of several tautomeric forms is possible,
the application of the spin trapping technique confirmed the formation of only one radical product, namely the C-radical resulting
from the homolytic splitting of the C–H bond of the methylene group. 相似文献
7.
The phenoxy radicals obtained from 2,2′- and 4,4′-biphenyldiols show, in nonpolar solvents, symmetrization of the unpaired electron spin density on the two phenyl rings in the temperature range 290–410 K. Below 270 K the paramagnetic systems became diamagnetic. This para-diamagnetic conversion with temperature is reversible. According to INDO calculations the symmetrization of spin density is due to the formation of dimeric phenoxy radicals. The para-diamagnetic conversion at various temperatures is explained by the reversible conversion of the radical dimer to the quinone-hydroquinone pair. 相似文献
8.
9.
Ladislav Omelka Imrich Vrbel Katarína Erentov Jochen Dauth Bernward Deubzer Johann Weis 《Helvetica chimica acta》1996,79(3):663-669
The triazenols 4-R1? C6H4? N?N? N(OH)? R2 ( 1 ), oxidized with t-BuO radicals, produced nitroxide radicals R1? C6H4? N(O?)? N?N(R2) +O? ( 5 ). The suggested radical structure was confirmed by 15N-labeling. The reaction of triazenols 1 with PbO2 proceeded under N2 elimination, in which case nitroxides R1? C6H4? N(R2)? O?( 2 ) were observed as the final radical products. The intermediate R1? C6H radicals were identified by spin-trapping. 相似文献
10.
R. Kluge D. Ströhl L. Omelka M. T. da Silva M. Schulz 《Monatshefte für Chemie / Chemical Monthly》1997,128(3):261-270
Summary Substituted 3-anilino-1,5-diphenylpyrazoles1a–i were oxidized with Pb(OAc)4 in benzene or CH2Cl2 solution. The ESR measurements confirmed the formation of aminyl radicals3f–i frompara-CH3 substituted pyrazoles1f–i. The radical intermediates from unsubstituted pyrazoles1a–e were assigned to triarylaminium cation radicals These were generated by consecutive oxidation of the dimeric products4a–e whose structure was proven by NMR spectroscopy and15N labeling.
Radikalreaktionen von N-Heterocyclen, 15. Mitt. Intermediäre Radikale und Endprodukte der Oxidation von 3-Anilino-1,5-diphenylpyrazolen mit Pb(OAc)4
Zusammenfassung Die substituierten 3-Anilino-1,5-diphenylpyrazole1a–i wurden mit Pb(OAc)4 in Benzol oder CH2Cl2 oxidiert. Die intermediären Aminylradikale3f–i wurden ESR-spektroskopisch bei der Oxidation der im Anilinrest methylsubstituierten Pyrazole1f–i nachgewiesen. Die ESR-spektroskopisch nach Oxidation der Pyrazole1a–e beobachteten Radikalintermediate interpretieren wir als Kationradikale6a–e. Diese werden durch Weiteroxidation der Dimeren4a–e gebildet, deren Struktur durch NMR-Untersuchungen und15N-Markierung bewiesen wurde.相似文献