Low-lying electronic states and molecular structure of Fe2O2

Abstract

The structure, bonding and relative stabilities of the ground and low-lying excited states of Fe₂O₂ have been studied by the hybrid B3LYP density-functional and coupled-cluster molecular orbital methods. Calculations indicate that the (µ-O)₂ rhombic ⁷B_2u state is the ground state for Fe₂O₂. Stable molecular diiron oxo Fe₂-O₂ complexes in distorted tetrahedral and planar side-on modes have been also located on the potential-energy hypersurfaces of Fe₂O₂. The calculated IR-active frequencies corresponding to two in-plane deformations of the rhombic ring agree well with the observed values. The bonding features of the (µ-O)₂ rhombic Fe₂O₂ have been discussed based on natural bond orbital and Bader topological analyses. These analyses show that an effective Fe–Fe bonding across the ring exists in the ⁷B_2u ground state.