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  • Chemistry  (16)
  • Inorganic Chemistry  (4)
  • calorimetry  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 13 (1998), S. 295-298 
    ISSN: 1573-4846
    Keywords: precursor chemistry ; calorimetry ; enzyme immobilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Using the sol-gel process, the enzyme glucose-oxidase was immobilized in modified SiO2 layers. The tetraethoxysilane based sol was varied by veratrylaldehyde, aminopropyltriethoxysilane and an azomethine compound, which was synthesized from both molecules. Changes in reaction kinetics of the sol-gel process by addition of veratrylaldehyde were observed by 29Si NMR measurements. The fixation of this additive in the final gel was clarified by FTIR spectroscopy. The influence of inserted functional groups on the enzyme activity was determined by calorimetry. The Enzyme Thermistor is a fast and uncomplicated method to obtain comparative results of sol-gel immobilized enzyme activity. Differences in immobilization effects were found dependent on structure and concentration of additives.
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  • 2
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Efficiency of the Photochemical Co-C-Bond Cleavage in σ-Alkyl-Co(III)(salen)-and-Co(III)(salphen)-Complexes.The photodealkylation rate of RCoIII(chel) X complexes (R = methyl, ethyl; chel = salen, salphen; X = H2O, py, PPh3) depends on the nature of ligands and solvents as well as on the concentration of oxygen and scavengers for alkyl radicals. The rapid recombination of the fragments R. and Co(chel)X is responsible for the low quantum yields of the anaerobic dealkylation. The quantum yields may reflect the H-donating ability of the solvents used. Lewis bases X in the trans position generally cause a decrease of quantum yields relative to the pentacoordinated species RCo (chel). The anaerobic photolysis can be accelerated by the addition of scavengers for alkyl radicals (e. g. Koelsch radical, nitrosodurene, styrene). The quantum yield also increases in the presence of oxygen, preventing the recombination of the fragments of the cobalt-carbon bond scission by forming alkyl-peroxocomplexes ROOCo(chel)X.α-Hydroxyalkylradicals arising from the decomposition of the ROOCo(chel)X complexes via secondary reactions probably react with the starting σ-alkyl complexes and cause the dependence of quantum yields on the light intensity.
    Additional Material: 7 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 323 (1981), S. 864-868 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photolysis of Ternary Fe(III)-Complexes with Oxalate and Phenolate LigandsThe overall iron(II) quantum yields of the photolysis of mixed ligand complexes [Fe(C2O4)3-nLn]3- (L = salicylate, sulfosalicylate or the dianion of catechol, sodium 3,5-sulfocatechol, tetrachlorcatechol) in aqueous solution within the spectral region 436 nm ≤ λirr. ≤ 546 nm are much smaller than those of the complexes [Fe(C2O4)3-n(H2O)2n]3-2n (n = 0; 1; 2). This means that the intramolecular photoredoxreaction between iron(III) and the oxalate ligand is not sensitized by the L→Fe(III) charge transfer excitation. Moreover, filter effects through photoinactive complexes [FeL2(H2O)2]- or [FeL(H2O)4]+ probably give rise to the strong decrease of the quantum yields.
    Additional Material: 2 Ill.
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  • 4
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 5
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The partially diethylamino substituted phenyl-chloromono- and -disilanes Cl2Ph(NEt2)Si(2) Cl2Ph(NEt2)2Si(3), [ClPh(NEt2)Si-]2 (7) and Cl(NEt2)PhSi—SiPh(NEt2)2 (8) were synthesized. 3 and 8 are able to react with lithium powder to form the corresponding silyllithium compounds. The resulting species were characterized in solution by 13C and 29Si NMR spectroscopy. To prove the expected substitution patterns of the silyllithium compounds some coupling reactions with chlorosilanes were carried out and the resulting new oligosilanes were characterized by means of NMR spectroscopy and MS.
    Additional Material: 3 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 339 (1997), S. 603-606 
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparation and Characterization of Oligomeric as well as Polymeric Ethynylsilanes Containing Si2—Si4 UnitsThe treatment of methylchlorodisilanes with ethynyldigrignard (BrMgC≡CMgBr) resulted in oligomeric as well as polymeric ethynyldisilanes. The kind of this products is related to the chloro functionality of the starting disilane. The reaction of SiClMe(SiCl2Me)2 as well as SiMe(SiCl2Me)3 yielded polymers beside small amounts of the monomeric products (HC≡C)MeSi[SiMe(C≡CH)2]2 and MeSi[SiMe(C≡CH)2]3.
    Additional Material: 5 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 319 (1977), S. 1031-1035 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Electron Spin Resonance Studies of the Photolysis of σ-Methyl-cobalt-ComplexesThe anaerobic photolysis with visible light of the complexes [CH3CoIII(salen)Y] and [CH3CoIII(salphen)Y] in the solvents chloroform, methanol, isopropanol and dimethylformamide proceeds by a mechanism involving a homolytic cleavage of the Co—C bond. Resulting low spin complexes were identified by EPR spectra. They react with oxygen in dimethylformamide forming the superoxid cobalt complexes \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm YCo}^{{\rm III}} \left({{\rm salen}} \right){\rm O}_{\rm 2} }^{\scriptstyle {{\relbar}\kern-3pt {.} }} \right] $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm YCo}^{{\rm III}} \left({{\rm salphen}} \right){\rm O}_{\rm 2} }^{\scriptstyle {{\relbar}\kern-3pt {.} }} \right] $\end{document} respectively. The methyl radicals were detected using the technique of spin trapping with nitroso-tert.-butane. In the aerobic photolysis of the methyl-Co(III) complexes CH3· as well as CH3O· radicals could be trapped.
    Notes: Die anaerobe Photolyse der Komplexe [CH3CoIII(salen)Y] und [CH3CoIII(salphen)Y] mit sichtbarem Licht in den Lösungsmitteln Chloroform, Isopropanol, Methanol und DMF verläuft unter homolytischer Spaltung der Co—C-Bindung. Die resultierenden low spin Co(II)-Komplexe sind direkt ESR-spektroskopisch identifizierbar. Sie reagieren in DMF mit Sauerstoff unter Bildung von Superoxidkomplexen [\documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm YCo}^{{\rm III}} \left({{\rm salen}} \right){\rm O}_{\rm 2} }^{\scriptstyle {{\relbar}\kern-3pt {.} }} \right] $\end{document}] bzw. \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm YCo}^{{\rm III}} \left({{\rm salphen}} \right){\rm O}_{\rm 2} }^{\scriptstyle {{\relbar}\kern-3pt {.} }} \right] $\end{document}. Das Methyl-radikal kann mit tert.-Nitrosobutan abgefangen werden. Bei der aeroben Photolyse der Methyl-Co(III)-Komplexe sind sowohl das Methyl- als auch das Methoxyradikal nachweisbar.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 319 (1977), S. 123-132 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Fixation of Cupric Ions in Matrices from Polyamide- and Polyhydrazide AcidsOn polymerisation of pyromellitic dianhydride with 4,4′-diamino-diphenyl ether and the dihydrazides of oxalic acid, malonic acid, adipic acid and terephthalic acid, respectively, filmforming polyamide-hydrazide-acids result. It is possible to control the reducing and mechanical properties of the polymers by variation of the mole ratio of 4,4′-diamino-diphenyl ether and acid hydrazide. Polymers with 0.3 moles of acid hydrazide and 0.7 moles of 4,4′-diamino-diphenyl ether do not reduce cupric ions, but co-ordinate them. EPR and absorption spectra show the cupric ions to co-ordinate with the hydrazide but not with the amide groups if the stoichiometric ratio polymer/Cu(II) is greater then 12. Only in foils prepared with the hydrazide of terephthalic acid the co-existence of Cu(II) complexes of the amide and hydrazide groups, respectively, is observed. Both these complex polyeders exhibit axial geometry.
    Notes: Bei der Polymerisation von Pyromellitsäureanhydrid mit 4,4′-Diaminodiphenyläther und den Dihydraziden von Oxalsäure, Malonsäure, Adipinsäure oder Terephthalsäure entstehen koordinationsaktive filmbildende Polyamidhydrazidsäuren. Das Reduktionsvermögen gegenüber Cu2+-Ionen und die mechanischen Eigenschaften der Polymeren lassen sich durch die Variation des Konzentrationsverhältnisses von 4,4′-Diaminodiphenyläther und Säurehydrazid steuern. Polymere mit 0,3 Mol Säurehydrazid und 0,7 Mol 4,4′-Diaminodiphenyläther pro Mol Pyromellitsäureanhydrid sind bei Zimmertemperatur gegenüber Cu2+-Ionen redoxstabil und fixieren diese unter Komplexbildung. Die Auswertung der ESR- und Absorptionsspektren der Cu(II)-haltigen Polymermatrizen zeigt, daß bei Stöchiometrieverhältnissen Polymer: Cu(II) ≥ 12 die Cu2+-Ionen generell von der Hydrazidsäure- und nicht von der Amidsäuregruppierung komplexiert werden. Lediglich in den Folien mit Terephthalsäuredihydrazid liegen Cu(II)-Amidsäure- und Cu(II)-Hydrazidsäure-Komplexpolyeder nebeneinander vor. Sie besitzen jeweils eine axiale Geometrie.
    Additional Material: 1 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 317 (1975), S. 675-681 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Durch Chlormethylierung von schwach vernetztem Polystyrol gelingt die Ankettung von Hydrazid- und Verdazylgruppierungen. Die Polymeren werden dadurch koordinationsaktiv gegenüber Cu2+-Ionen. Eine Fixierung der Cu(II)-Verbindungen an den Polymeren wird ESR-spektroskopisch bewiesen.Polymere Verdazyle aus 1,3,5-Triphenylformazan und chlormethyliertem Polystyrol können Cu(II)-Salze reduzieren. Ihre Reaktivität wird vom Lösungsmittel (Äthanol 〉 Acetonitril 〉 Dimethylformamid 〉 Dimethylsulfoxid) und vom Anion (Cl- 〉 SO42-, NO3-) beeinflußt.
    Additional Material: 2 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 321 (1979), S. 75-85 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fe(III)-Complexes with Mixed Ligands Consisting of Oxalate and Phenolate LigandsThe formation of mixed-ligand complexes between iron(III) ion, potassium oxalate and potassium salts of salicylic acid, sulfosalicylic acid, catechol, sodium 3,5-sulfocatechol („tiron“) and tetrachlorocatechol, respectively, has been investigated. There were obtained solid products with the approximate composition K3[Fe(C2O4)3-xLx] · n H2O (L = phenolat; x = 1; 2). For the synthesis of the above compounds ligand exchange reactions as well as addition-technique of oxalic acid followed by potassium phenolat to Fe2O3 · aq has been used. Through spectroscopic examination of the obtained products was found, that Fe3+-ion is simultaneously coordinated by oxalat and phenolat. Probably the products consist of at least two components as Fe(III) was found in two different bond states.
    Additional Material: 2 Ill.
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