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  • 1
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Photoinduced Electron Transfer-Reactions of Arenediazonium Ions Complexed with Crown EthersThe photolysis (full light of a medium pressure Hg-lamp) of p-methylbenzenediazonium-tetrafluoroborate in the presence of the crown ether 18-crown-6 (1) yields mainly the products of a heterolytic dediazoniation via arene cations as intermediates. The quantum yield ϕges of the photolysis from p-methoxybenzenediazonium-tetrafluoroborat in CH2Cl2 decreases in the presence of 18- crowns-6 (1) from 0.66 to 0.08. In contrast to 1, the photolysis of arenediazonium salts in the presence of dibenzo-18-crown-6 (3) yields mainly the products of a homolytic dediazoniation as a consequence of an electron transfer from 3 to the diazonium ion. ϕges of this reaction increases with decreasing wavelength of the exciting light from 0.09 (436 nm) to 0.32 (366 nm). this wavelength dependence is explained by formation of a correlated radical pair after excitation. In agreement with this situation a photo-CIDNP-effect is observed in the 15N-n.m.r.-spectra of isotopically labeled arenediazonium salts complexed by 3 and benzo-18-crown-6(2). No photo-CIDNP-effect is observed in the presence of 1. This different behaviour of the EDA-complexes formed by arenediazonium salts with the two different groups of crown ethers 1 and 2, 3 is discussed as a control of the electron transfer-reaction by the structure of the frontier orbitals.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 327 (1985), S. 399-410 
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Photoinduced Electron Transfer between Arenediazonium Cations and AnionsAnions X⊖ can act as donors in electron transfer reactions to photoexcited arenediazonium ions. The yield of the arene formed in this reaction increases with decreasing electrochemical oxidation potential EoxD of X⊖ (X⊖ = BPh4⊖, Br⊖, HOOC—COO⊖, Cl⊖, BF4⊖). The oxidized donor X· (Cl·, ·COO⊖) and aryl radicals Ar· benig intermediates of the reductive dediazoniation of ArN2⊖ can be detected by spin trapping with nitrosodurene (ND) and phenyl-tert-butylnitrone (PBN). A solvent effect in the electron transfer reaction is interpreted in terms of ion pairing, where the electron transfer is favored by preorientation and a short distance between the electron donor and the acceptor previous to excitation of ArN2⊖ by light.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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