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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.
Acknowledgements
This work was supported by the National Natural Science Foundation of China (No. 20701005/20701006), the Science and Technology Development Project Foundation of Jilin Province (No. 20060420), the Postdoctoral Station Foundation of the Ministry of Education (No. 20060200002), the Testing Foundation of Northeast Normal University, and the Program for Changjiang Scholars and the Innovative Research Team. We would like to thank Prof. Zhongmin Su for discussions and support.