title: Is the FeO2(-) anion bent or linear?
abstract: FeO(2)(-) anions were produced by co-condensation of laser-ablated iron atoms and electrons with dioxygen in excess argon at 6 K. A photosensitive absorption at 870.6 cm(-1) is assigned to the antisymmetric OFeO stretching vibration (nu(3)) of the inserted FeO(2)(-) anion trapped in solid argon. On the basis of the observed nu(3) vibrational frequencies for Fe(16)O(2) and Fe(18)O(2), the anion is estimated to be linear. Due to the severe symmetry-breaking problems of the reference wave function, calculations with single-reference methods, including various DFT and post-HF methods, are unreliable for this molecule. However, the state-averaged multireference MRCI method, which incorporates both dynamical and nondynamical correlations, predicted that the anion has a linear doublet ground state, consistent with the experimental observations.
authors.affiliation: Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysts and Innovative Materials, Fudan University, Shanghai 200433, People's Republic of China. lizhenhua@fudan.edu.cn
authors.forename: Zhen Hua
authors.initials: ZH
authors.lastname: Li
authors.forename: Yu
authors.initials: Y
authors.lastname: Gong
authors.forename: Kangnian
authors.initials: K
authors.lastname: Fan
authors.forename: Mingfei
authors.initials: M
authors.lastname: Zhou