Theoretical study of the electronic properties of peroxohexaniobate, [H3Nb6O13(O2)6]5−, by DFT

Abstract

Calculations based on density functional theory (DFT) have been carried out to investigate the geometric structures, electronic properties, redox potential, and electronic spectrum of the peroxohexaniobate species [H3Nb6O13(O2)6]5−. The segments in the terminal positions effectively modify the electronic properties. The HOMO of [H3Nb6O13(O2)6]5− is mainly concentrated on the η2 oxygen atoms in the terminal positions. The LUMO delocalizes over the niobium atoms and bridging oxygens, but η2 oxygen atoms in the terminal positions contribute. The LUMO energy and the HOMO–LUMO energy gap (E g) of [H3Nb6O13(O2)6]5− are lower than those of [H3Nb6O19]5−, therefore [H3Nb6O13(O2)6]5− is readily reduced and the electron transition between the HOMO and LUMO is much easier. Furthermore, theoretical prediction of the redox potential of [H3Nb6O13(O2)6]5− confirms that the first reduction step of [H3Nb6O13(O2)6]5− becomes easier as all six terminal oxygen atoms are replaced by . In addition, calculation of the electronic spectrum shows that the nature of the transition for [H3Nb6O13(O2)6]5− and [H3Nb6O19]5− is also different and the photochemical activity of the terminal oxygen (Ot) of [H3Nb6O13(O2)6]5− is significant.