Photolytic Generation of Radicals from [η-C5R5Fe+Arene]* Complexes. Implications for Electron Transfer Catalysis and Radical Reactions

  • Enrique Roman
  • Mauricio Barrera
  • Sergio Hernandez
  • Charles Giannotti
Part of the NATO ASI Series book series (ASIC, volume 257)

Abstract

Visible irradiation of [η-C5R5Fe+Arene] in polar solvents leads to generation of (C5R5)° radicals, (R=H, CH3), which are identified as their spin-trapped adducts. Photophysical studies show that the excited triplet state, a 3 E 1, of these organometallic complexes can be efficiently quenched by classical redox quenchers such as methylviologen or dimethylaniline. The excited state of [η-C5R5Fe+Arene]* complexes can also be quenched by hexamethyl (Dewar) benzene, HMDB. In this case two decay types have been determined: (i) a photochemical path occuring in the excited state surface, where simultaneous regioisomerization of HMDB and photoligand exchange take place, affording the hexamethylbenzene derivative-[η-C5R5Fe + HMB], and (ii) a photoinduced radical chainmechanism (detected on the e.s.r. time scale) for HMDB isomerization, caused by an ET photoprimary process between HMDB (an electron donor molecule) and the [η-C5R5Fe+Arene]* complex. Electrocatalytic studies suggest that in the decay of [η-C5R5Fe+Arene]* complexes, two kinds of transient species (17 or 19 electron) are photogenerated depending on the redox-potentials of the quenchers.

Keywords

Visible Irradiation Radical Adduct Arene Ligand Photophysical Study Excited Surface 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Kluwer Academic Publishers 1989

Authors and Affiliations

  • Enrique Roman
    • 1
  • Mauricio Barrera
    • 1
  • Sergio Hernandez
    • 1
  • Charles Giannotti
    • 2
  1. 1.Catholic University of Chile Faculty of ChemistrySantiago-ChileFrance
  2. 2.Institut de Substances Naturelles, CNRSGif-sur-YvetteFrance

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