DFT study of α-Keggin, lacunary Keggin, and ironII–VI substituted Keggin polyoxometalates: the effect of oxidation state and axial ligand on geometry, electronic structures and oxygen transfer

Abstract

Herein, the geometry, electronic structure, Fe–ligand bonding nature and simulated IR spectrum of α-Keggin, lacunary Keggin, iron(II/III)-substituted and the important oxidized high-valent iron derivatives of Keggin type polyoxometalates have been studied using the density functional theory (DFT/OPTX-PBE) method and natural bond orbital (NBO) analysis. The effects of different Fe oxidation states (II–VI) and H₂O/OH⁻/O²⁻ ligand interactions have been addressed concerning their geometry and electronic structures. It has been revealed that the d-atomic orbitals of Fe and 2p orbitals of polyoxometalate's oxygen-atoms contribute in ligand binding. Compared with other high valent species, the considered polyoxometalate system of [PW₁₁O₃₉(Fe^VO)]⁴⁻, possesses a high reactivity for oxygen transfer.