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  • Organic Chemistry  (17)
  • Artificial photosynthesis  (1)
  • Electrophilic addition  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Supramolecular sensitizer-relay assemblies. An evaluation of binding constants from non-linear stern-volmer plotsDedicated to Professor K. Schaffner on the occasion of his 60th birthday. Electron Transfer Reactions, Part 9. For Part 8, see Ref. 2A. (1992)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 5 (1992), S. 63-73 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A novel technique for determining the binding constants of host-guest complexes, viz. the bis-cationic electron relays methylviologen and octylviologen in the macrocyclic host of novel (bisheteroleptic) crown ether-ruthenium sensitizers, is described. This technique allows the separation of the quenching effects of bound and free electron relays. It can be used to calculate binding constants in non-covalently linked supramolecular systems evaluating the electron transfer process between guest and host. High binding constants comparable to those in many natural enzymes and the photosynthetic reaction centre were found. As an explanation for the behaviour of the sensitizers bound to the bipyridinium cations it is suggested that photoelectron transfer affects the binding between the excited sensitizer and the bound acceptor.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610050202
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  • 2
    Electronic Resource
    Electronic Resource
    Modellsysteme zur artifiziellen Photosynthese - Synthese und Elektronentransferstudien neuartiger Sensibilisator-Relais-EinheitenHerrn Prof. Dr. C. W. Jefford zum 65. Geburtstag gewidmet. (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 407-413 
    Details
    ISSN: 0947-3440
    Keywords: Artificial photosynthesis ; Electron transfer ; Sensitizer-relais assemblies ; Photophysical properties ; Hydrogen production ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Modell Systems for an Artificial Photosynthesis - Synthesis and Electron Transfer Studies of Novel Sensitizer-Relais AssembliesSyntheses and determination of electron transfer rates between sensitizers and electron acceptors for a novel class of bis(4,4′-dimethyl-2,2′-bipyridine)[4,4′-bis(alkoxymethyl)-2,2′-bipyridin]ruthenium(II) complexes 6-8 are described. We report on the formation of supramolecular complexes between the dialkoxybenzene-tethered bisheteroleptic Ru(II)-bipyridine complexes 5, 8 and 1,1′-dimethyl-4,4′-bypiridinium (MV2+) and cyclo-[bis(1,1′-p-xylylene-4,4′-bipyridinium)] (BXV4+), respectively. Evidence for the formation of supramolecular sensitizer-relais assemblies is taken from the viologen radical and hydrogen production rates in sacrificial model systems for artificial photosynthesis.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199519950249
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  • 3
    Electronic Resource
    Electronic Resource
    4,5-Diazafluorenylidene: Preparation, Reactivity, Multiplicity, and Selectivity StudiesDedicated to Professor H. D. Scharf on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1611-1618 
    Details
    ISSN: 0947-3440
    Keywords: Carbenes ; Cycloadditions ; Diazo compounds ; Styrene ; Electrophilic addition ; Nitrogen heterocycles ; Photolysis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chemistry of 4,5-diazafluorenylidene (3), generated from the diazo compound 3a by photolysis, has been studied with regard to reactivity, multiplicity and selectivity. Reaction of 3 in 2,3-dimethylbutene gave exclusively ketazine 24. The [1 + 2] cycloaddition with styrenes 5-11 afforded cyclopropanes 16-23 in 25-54% yields and 24 as a side product. In these reactions no diazirine intermediate was involved. Irradiation of 3a in methanol afforded the ether 26 (25% yield). The stereoselectivity of 3 was studied by its addition to (E)- and (Z)-β-methylstyrene. A mixture of the (E)- and (Z)-cyclopropanes 22 and 23, respectively, was detected. Thus for 3, triplet multiplicity was concluded. The results of competition experiments with singlet/triplet scavengers (methanol/dimethylbutadiene) demonstrated that an equilibrium between singlet and triplet manifold of 3 exists at room temperature. Selectivity studies with carbene 3 were carried out by evaluating the competition experiments of the cycloaddition of 3 with differently substituted styrenes. A plot of the krel values from the competition studies versus Hammett σ constants gave ρ = -0.65 indicating that carbene 3 reacts as an electrophile.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970745
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  • 4
    Electronic Resource
    Electronic Resource
    Zum Mechanismus der Photoreduktion von Wasser mit Ruthenium-trisbipyrazil als Sensibilisator (1983)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 66 (1983), S. 2652-2655 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Mechanism of the Photoreduction of Water with Ruthenium-trisbipyrazil as SensitizerOxidative and reductive primary steps can be differentiated in using Ru(bipy)32+ and Ru(bipz)32+, respectively, as sensitizers in a photochemically induced, Pt-catalyzed sacrificial water reduction. Experimental evidence for the reductive primary step and kinetic data are given for the electron transfer to methylviologen as relay compound.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19830660833
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  • 5
    Electronic Resource
    Electronic Resource
    Dehydrobenzol und acyclische DieneKarl Ziegler zum 65. Geburtstag gewidmet (1964)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 672 (1964), S. 55-62 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Von acyclischen Dienen wurden Butadien, Isopren und 2.3-Dimethyl-butadien verwendet. Neben der stets zu beobachtenden Diels-Alder-Reaktion mit Dehydrobenzol wurde beim Isopren und beim Dimethylbutadien eine indirekt substituierende Addition festgestellt. Dimethylbutadien vereinigte sich mit Dehydrobenzol zusätzlich zum Benzocyclobuten-Derivat III, dessen Struktur wahrscheinlich gemacht wurde. Bei Einwirkung von Isobutylen konnten keine Anzeichen für eine diskutierte Biscarben-Form des Dehydrobenzols beobachtet werden.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.19646720105
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  • 6
    Electronic Resource
    Electronic Resource
    Über Cycloalken-carbene, VI1) Spiro-Konjugation bei Spiro[2.4]heptatrienenHerrn Prof. Dr. B. Eistert zum 70. Geburtstag gewidmet. (1973)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1973 (1973), S. 214-220 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On Cycloalkene Carbenes, VI1). Spiro Conjugation of Spiro[2.4]heptatrienesPhotolysis of diazocyclopentadienes 4 in alkynes or alkenes leads to spiro[2.4]heptatrienes 1 and spiro[2.4]heptadienes 5, respectively. The presence of spiro conjugation in compounds of type 1 can be proved by comparing the UV spectra of 1 and 5.
    Notes: Die Photolyse von Diazocyclopentadienen 4 in Alkinen oder Alkenen ergibt die Spiro[2.4]-heptatriene 1 bzw. die Spiro[2.4]heptadiene 5. Aus dem Vergleich der UV-Spektren von 1 und 5 läßt sich das Auftreten der Spiro-Konjugation bei den Verbindungen 1 nachweisen.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197319730207
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  • 7
    Electronic Resource
    Electronic Resource
    Photochemie kleiner Ringe, XXVIII1) Dibenzo[2.4]spirene und deren Umlagerungsprodukte durch Photofragmentierung und Thermolyse von Spiropyrazolen (1974)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1974 (1974), S. 1132-1139 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Photochemistry of Small Rings, XXVIII1). - Dibenzo[2.4]spirenes and Their Derivatives via Photofragmentation and Thermolysis of SpiropyrazolesPhotofragmentation of the spiropyrazoles 3 leads to the dibenzo[2.4]spirenes 4 in good to average yields. Thermolysis of 3 at lower temperatures also gives 4. At higher temperature, however, the pentalene derivatives 9 are formed. This rearrangement involves spirenes 4. The vinylcarbene 11 or the diradical 13 are intermediates in the reaction 3 → 4. Rearrangement 4 → 9 can proceed synchronously or via the diradical 15.
    Notes: Die Photofragmentierung der Spiropyrazole 3 ergibt in guten bis mittleren Ausbeuten die Dibenzo[2.4]spirene 4. Die Thermolyse von 3 führt bei tieferen Temperaturen ebenfalls zu 4, bei höheren Temperaturen werden die Pentalen-Derivate 9 gebildet. Bei dieser Umlagerung treten die Spirene 4 als Zwischenprodukte auf. Die Reaktion 3 → 4 dürfte über das Vinylcarben 11 oder das Diradikal 13 als Zwischenstufen verlaufen. Die Umlagerung 4 → 9 kann entweder synchron oder über ein Diradikal 15 formuliert werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197419740709
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  • 8
    Electronic Resource
    Electronic Resource
    Photochemie kleiner Ringe, IX1) Direkte oder in situ-Photodimerisierung von Triphenyl-cyclopropen (1969)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 723 (1969), S. 102-110 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Photochemistry of Small Rings, IX1). Director in situ-Photodimerisation of Triphenyl-cyclopropeneThe sensitized photodimerisation of triphenyl-cyclopropene (1) led to two stereoisomeric tricyclo-hexanes 2 and 3. The in situ-photodimerisation of 1 generated from 1,2,3-triphenylpropenone-tosylhydrazone (alkaline salt) gave also 2 and 3. These could be dehydrogenated thermally or catalytically to hexaphenyl- or hexaphenyl- and pentaphenyl-benzene. The cyclodimerisation of 1 can be sensitized. Using sensitizers of different phosphorescence energy the excited state of 1 was established to be a triplet and its energy was estimated.
    Notes: Triphenyl-cyclopropen (1) ergab bei der sensibilisierten Photodimerisierung die beiden stereoisomeren Tricyclo-hexane 2 und 3. Die in situ-Photodimerisierung des aus 1.2.3-Triphenylpropenon-tosylhydrazon (Alkalisalz) erzeugten Triphenyl-cyclopropens lieferte analog 2 und 3. Diese ließen sich thermisch oder durch katalytische Dehydrierung in Hexaphenyl- bzw. Hexaphenyl- und Pentaphenyl-benzol überführen. Die Cyclodimerisierung von 1 ist sensibilisierbar. Durch Sensibilisatoren verschiedener Phosphoreszenzenergie konnte der Anregungszustand von 1 als Triplett-Zustand bewiesen und seine Energie abgeschätzt werden.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.19697230112
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  • 9
    Electronic Resource
    Electronic Resource
    N-Heterocyclen durch 1,3-dipolare Cycloaddition und 1,5-sigmatrope Verschiebungen (1974)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1974 (1974), S. 1140-1149 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: N-Heterocycles via 1,3-DipolarAddition and 1,5-Sigmatropic Shifts1,3-Dipolar cycloaddition of diazofluorene (1a) to the alkynes 2 affords the diaza[4.4]spirenes 3. With the other diazocyclopentadienes 1b-e the primary adduct 3 undergoes a 1,5-sigma- tropic shift to give the azaindolizines 4 or the 3aH-indazoles 5. Acid-catalyzed rearrangement of 3 produces the 1H-indazoles 6. Substituent effects on cycloaddition and 1,5-rearrangement are discussed. An alternative mechanism is proposed for the van Alphen rearrangement 3 → 6.
    Notes: Die 1,3-dipolare Cycloaddition von Diazofluoren (1a) an die Alkine 2 ergibt die Diazat[4.4]spirene 3. Bei den anderen Diazocyclopentadienen 1b-e geht das primär gebildete 3 eine 1,5-sigmatrope Umlagerung zu den Azaindolizinen 4 oder den 3aH-Indazolen 5 ein. Die säurekatalysierte Umlagerung von 3 liefert die 1H-Indazole 6. Substituenteneffekte der Cycloaddition und der 1,5-Umlagerungen werden diskutiert. Für die van-Alphen-Umlagerung 3 → 6 wird ein alternativer Mechanismus vorgeschlagen.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197419740710
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  • 10
    Electronic Resource
    Electronic Resource
    Photochemie kleiner Ringe, VIII. Synthese, Photolyse und Thermolyse von p-disubstituierten Tetraphenyl-bicyclo[3.1.0]-hexenonen (1968)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 716 (1968), S. 212-215 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Titelsubstanzen (3a-d) werden photolytisch und thermolytisch zu den tetrasubstituierten Phenolen 4 aromatisiert.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.19687160132
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