Electronic structures, bonding, and spin state energetics of biomimetic mononuclear and bridged dinuclear iron complexes: a computational examination

Mononuclear and dinuclear iron complexes are found as key intermediates in many synthetic and biocatalytic reactions, since many of these species are transient and have high catalytic abilities. However, there is still demanding and challenging to theoretical study on structures, bonding, magnetic interactions and reactivity of iron species. Here, we have discussed a detailed computational study on Fe(III/IV/V)–O/O2 and Fe(IV)–μ-O/O2–Fe(IV) species using a dispersion-corrected (B3LYP-D2) density functional method. By computing all the possible spin states for these species, we have predicted the ground state and structure-function relationships in their ground states and analyzed the bonding aspects of these species on employing MO analysis. We have also discussed the shifting of iron centers out of the plane and magnetic coupling between iron and iron/oxygen centers. A computed significant spin density on the oxygen can be a witness for reactivity during the C–H and O–H bond activation. Our DFT studies are also in general agreement with the available experimental data.