The synthesis of the first fluorine-containing iron porphycenes, 2,7,12,17-tetraethyl-3,6,13,16-tetrakis(trifluoromethyl)porphycen-atoiron(Ill) chloride [FePc(EtioCF(3))]Cl and its mu-oxo dimer [FePc(EtioCF(3))](2)O and their characterizations are reported. The crystal structure of [FePc(EtioCF(3))](2)O displays a severe saddled distortion of the porphycene framework due to the steric and electronic effects of the CF3 substituents. The oxidation and reduction potentials for the mu-oxo dimer are significantly more positive compared to those observed for the reference mu-oxo dimer of the iron porphycenes and porphyrins having no electron-withdrawing substituent. Moreover, the H-1 and F-19 NMR spectra of [FePc(EtioCF(3))](2)O demonstrated that the mu-oxo dimer is readily converted into the monomeric ferrous complex in pyridine-d(5) through autoreduction for 1 day, although the reduction of the reference iron porphycenes and porphyrins are not observed in pyridine. These results indicate that the trifluoromethylated iron porphycene is a highly electron-deficient complex with a pyrrolic macrocycle ligand.