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)


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.


Visible Irradiation Radical Adduct Arene Ligand Photophysical Study Excited Surface 
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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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