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991.
992.
A novel 14-membered macrocyclic Schiff base derived from 3-cinnamalideneacetoacetanilide and o-phenylenediamine acts as a tetradentate and strongly conjugated ligand to form a cationic solid complex with CuCl2/NiCl2/CoCl2/ZnCl2. The ligand and the complexes were characterized by the usual spectral and analytical techniques. The main i.r. band of the macrocyclic Schiff base was compared to that of its metal complexes. The C=N bands are shifted to the lower wave number. The cyclic voltammogram of the copper complex shows that the macrocyclic ligand is able to stabilize the copper(III) oxidation state. The e.s.r. spectra of the copper complex in DMSO solution at room temperature and liquid N2 temperature were recorded and their salient features thoroughly discussed. The antimicrobial screening tests were also recorded and gave good results in the presence of metal ions in the ligand system. 相似文献
993.
Jaime González Velasco 《Central European Journal of Chemistry》2005,3(3):470-481
The analytical treatment of a model considering the electrooxidation of p-porous silicon layers under galvanostatic conditions
is able to give account of experimental facts such as the shape and location of the electroluminescence peak as well as of
the spectral shift of the electroluminescence peak produced by oxidation. The proposed model considers electroluminescence
to be the result of electron injection into the conduction band by an adsorbed intermediate produced by electrooxidation of
the surface coverage with hydrogen or siloxene of the silicon nanocrystallites. The access of holes to the surface is made
possible by low accumulation layer conditions and is the rate determining step in the electroluminescence mechanism. In this
way it is possible to give a satisfactory explanation to the shift towards the blue experimented by the electroluminiscence
emission maximum as a consequence of electrooxidation. 相似文献
994.
Christoph Kratky Heinz Falk Ulrich Zrunek 《Monatshefte für Chemie / Chemical Monthly》1985,116(5):607-623
The molecular and crystal structures of the two racemic diastereomeric 3,4-dihydropyrromethenone derivatives1 and2 of configurations (Z) and (E) were determined at 93 K (1, 2) and at room temperature (1). From an analysis of the crystallographically observed temperature coefficients a pseudorotation flexibility of the pyrrolidinone ring in the crystal is deduced. In both compounds a nearly orthogonal arrangement between the two heterocyclic ring systems is observed, which is ascribed to the steric bulk of the substituents in positions 1 and 3 of the pyrrolidinone ring.Herrn Prof.Josef Schurz zum 60. Geburtstag gewidmet. 相似文献
995.
Novel Inorganic Ring Systems. 34. Derivatives of the Cyclo-1-thiaIV- and of the Cyclo-1-thia VI-3,4-disila-2,5-diazane Variations of fivemembered “hetero” cyclosilazanes of the type Si2N2El could be enlarged to the systems with El = SO and SO2. They are obtained by the formation principles 4 + 1 and 2 + 3 respectively, according to the equation (1), (4) and (5). The prepared compound are described in their properties and confirmed in their structure (Tables 1–2). 相似文献
996.
V. V. Barbakadze E. P. Kemertelidze I. Targamadze K. Mulkidzhanyan J. Kemink A. J. J. van den Berg K. J. Beukelman A. I. Usov 《Chemistry of Natural Compounds》2005,41(4):374-377
Two high-molecular-weight (>1000 kDa) water-soluble preparations were isolated from stems of Symphytum asperum and S. caucasicum. Their basic component was established as poly[hydroxy-1-carboxy-2-(3,4-dihydroxyphenyl)ethylene], analogous to that of high-molecular-weight
(>1000 kDa) preparations from roots of these same plants, using IR and NMR spectral data.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 303–305, July–August, 2005.
An erratum to this article is available at . 相似文献
997.
Ulrich Jordis 《Monatshefte für Chemie / Chemical Monthly》1988,119(10):1179-1184
Carbophilic reaction of 1,3-benzodithiole-2-thione (1) with trideuteroborane · dimethylsulfide, synthesized from NaBD4 and BF3 ·Me
2S inTHF, gave 2,2-dideutero-1,3-benzodithiole (5 b) as well as the minor side-products7 b,8 and9 b. 相似文献
998.
Ulrich Heber 《Fresenius' Journal of Analytical Chemistry》1958,161(6):409-421
Zusammenfassung Es wird ein neues, leicht herstellbares Gerät beschrieben, mit dem Transmissions- und Remissionsmessungen an papierchromatographischen Flecken zur quantitativen Auswertung durchgeführt werden können. Das Gerät ist auch für andere Zwecke brauchbar, ist aber vor allen Dingen für genaue Serienuntersuchungen an biologischem Material entwickelt worden. Die Fehlergrenze liegt bei etwa ± 3% (bei 100 g Galaktose und Anilinphthalatentwicklung). Theoretische Grundlagen werden aufgezeigt und diskutiert. An Stelle des Lambert-Beerschen Gesetzes wird eine Beziehung mit weiterem Gültigkeitsbereich für die Auswertung von Transmissionsmessungen an Papieren erörtert.Für reges Interesse an der Arbeit und stete Förderung bin ich den Herren Prof. Dr. H. Ullrich vom Institut für Landwirtschaftliche Botanik und Prof. Dr. B. Helferich vom Chemischen Institut der Universität Bonn zu außerordentlichem Dank verpflichtet. Die Untersuchungen sind zum Teil aus Mitteln der Deutschen Forschungsgemeinschaft bestritten worden, wofür hier noch besonders gedankt sei. 相似文献
999.
Stephen de Mora Jean-Pierre Villeneuve Eric Wyse 《Accreditation and quality assurance》2007,12(11):587-592
Aspects of the International Atomic Energy Agency (IAEA) Analytical Quality Control Services (AQCS) for marine environmental
studies are discussed, focusing on recent laboratory performance studies (LPS) and the production of reference materials for
trace metals and organic compounds in various marine matrices. The IAEA has organized seventeen global interlaboratory studies
for a range of organic contaminants. Of note has been the inclusion of numerous polychlorinated biphenyl congeners (PCBs)
and some sterols of anthropogenic origin. Concurrently, there have been eleven worldwide intercomparison exercises for trace
metals in the marine environment, most of which included methylmercury. Although such interlaboratory studies can help improve
performance in individual laboratories and regional laboratory networks, the results reveal that problems remain in the determination
of some metals and many organic contaminants. 相似文献
1000.
Summary. An efficient direct conversion of THP ethers into the corresponding acetates was achieved with acetic anhydride in the presence of CuSO4 · 5H2O as an available and green catalyst in high yields. 相似文献