Variety of [Fe, N, O] Isomers. A Theoretical Study

Abstract

Stationary points on the potential energy hypersurfaces of triatomic [Fe, N, O] have been systematically studied using an economic combination of a density functional/Hartree−Fock hybrid method, i.e., the B3LYP functional and the multireference-averaged quadratic coupled cluster approach. The global minimum is linear FeNO(2Δ), which is not adiabatically connected to the neutral ground-state fragments Fe and NO. Side-on and oxygen-bound isomers have low barriers for rearrangement; however, they might be stabilized because of ligand effects. Inserted OFeN(4A‘‘) is kinetically stable, although it lies considerably higher in energy than the other isomers. The calculations indicate near-degenerate ground states for all isomers. We discuss the implications for the reported experimental observations. Furthermore, the findings are rationalized using valence bond and molecular orbital theories.