Chemical and Electrochemical Redox Behavior of 9-Anthrylmethyl-Functionalized h 5 -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(AnCH2C5H4) derivatives of rhodium(I) and iridium(I) of formula [M(è 5 -AnCH2C5H4)L2](M) Rh or Ir; L ) è 2 -C2H4, è 1 -CO, è 2 -C8H14, PPh3;L2 ) è 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 characteriza-tion 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.