Chemical and electrochemical redox behavior of 9-anthrylmethyl-functionalized η5-cyclopentadienyl derivatives of rhodium(I) and iridium(I):: Generation and EPR characterization of the corresponding cation radicals

The study of the electrochemical behavior (CV) of 9-anthrylmethylcyclopentadienyl (AnCH(2)C(5)H(4)) derivatives of rhodium(I) and iridium(I) of formula [M(eta(5)-AnCH(2)C(5)H(4))L-2] (M = Rh or Ir; L = eta(2)-C2H4, eta(1)-CO, eta(2)-C8H14, PPh3; L-2 = eta(4)-C8H12), 1-8, in strictly aprotic conditions, allows a satisfactory interpretation of the observed electrode processes and gives information about the location of the redox sites along with the thermodynamic characterization of the corresponding redox processes. These data show that the occurrence of an intramolecular charge-transfer process between the photoexcited 9-anthryl group and the cyclopentadienylmetal unit is a possible route for the observed anthracenic fluorescence quenching in the compounds 1-8. Moreover, a study was carried out on the redox behavior of these complexes under chemical activation. The one-electron oxidation of compounds 1-8 by thallium(III) trifluoroacetate leads to the formation of the corresponding cation radicals, whose highly resolved X-band EPR spectra were fully interpreted by computer simulation as well as by semiempirical and DFT calculations of spin density distribution.