Formation and Characterization of Two FeO3 Isomers in Solid Argon

Two FeO3 isomers were prepared and characterized using matrix isolation infrared spectroscopy and theoretical calculations. The iron monoxide molecules produced from laser evaporation of the bulk iron oxide target react with dioxygen in solid argon to form the (eta(2)-O-2)FeO complex spontaneously on annealing. The (eta O-2-(2))FeO complex was predicted to have a B-5(2) ground state with a planar C-2v structure, in which the O-2 fragment is side-on bonded to the iron center. The (eta(2)-O-2)FeO complex rearranges to the more stable iron trioxide isomer upon visible light (lambda > 500 nm) irradiation. The iron trioxide molecule was predicted to have a closed-shell singlet ground state with a planar D-3h Symmetry, in which the iron possesses a +6 oxidation state.