Recently, iChEM Prof. Mingfei Zhou’s research group from FDU made a great breakthrough about the research on high oxidation states. The related paper of "Identification of an iridium-containing compound with a formal oxidation state of IX" was published on Nature on October 23, 2014. This work was carried out by Prof. Zhou's group and the other scientists from Freie Universität Berlin (Germany), Tsinghua University and McMaster University (Canda). Prof. Guanjun Wang, an associate professor of FDU, is the first author of this paper.

One of the most important classifications in chemistry and within the periodic table is the concept of formal oxidation states, which reflects the chemical state of an element in compound and the change during the chemical reaction. The highest experimentally known formal oxidation state of any chemical element is at present VIII. Compounds with oxidation state VIII include several xenon compounds (for example XeO₄ and XeO₃F₂) and the well-characterized species RuO₄ and OsO₄. These compounds with high oxidation states have high oxidizing ability, and widely apply as oxidizing agents and catalysts in industrial reactions.

Prof. Zhou's group has collaborated with Prof. Riedel from Freie Universität Berlin to carry out the preparation and investigation of high oxidation states compounds since 2009. In 2009, they characterized the IrO₄ as an isolated molecule in rare-gas matrices. The valence electron configuration of iridium in IrO₄ is 5d¹, with a formal oxidation state of VIII. The related paper was published in Angew. Chem. Int. Ed., and highlighted by C&EN entitled "Unprecedented Iridium (VIII) seen". Based on the work above, they proposed that removal of the remaining d electron from IrO₄ would lead to the iridium tetroxide cation ([IrO₄]⁺) in which iridium is in a formal oxidation state of IX. In order to confirm the assumption experimentally, Prof. Zhou's group prepared iridium oxide cations using a pulsed-laser vaporization/supersonic-expansion source. [IrO₄]⁺ was identified by mass spectra-infrared photodissociation spectroscopy. They demonstrate the first time that [IrO₄]⁺ has a T_d-symmetrical structure and iridium is in a formal oxidation state of IX, thus confirming the existence of compounds with IX oxidation state experimentally.

These results have great scientific significance for the expansion of oxidation states and the understanding of bonding features of compounds with high oxidation states. This paper also provided a basis for further synthesizing compounds with high oxidation states and its application in the chemical reaction systems.

Most importantly, the first affiliation of this paper is under iChEM.