NO^2- Created

The periodic table has once again yielded a new form of a diatomic molecule—the radical dianion of nitrogen oxide, NO^2– (Nat. Chem., DOI: 10.1038/nchem.701). Nitric oxide, NO, is a hybrid of N₂ and O₂ and exhibits extensive biochemical, industrial, and atmospheric chemistry. The unpaired electron on NO makes it highly reactive and easy to oxidize to NO⁺ and reduce to NO^– , which are electronically analogous to N₂ and O₂, respectively. A year ago, William J. Evans of the University of California, Irvine, and colleagues isolated the reactive triply reduced N₂ ^3– radical between two yttrium atoms in a diyttrium complex, expanding the collection of N₂ species (C&EN, July 27, 2009, page 13). N₂ ^3– is electronically analogous to the superoxide radical O₂ ^– , an ion that plays important roles in immune system biochemistry. The discovery prompted Evans and his colleagues to try to make NO^2– , the hybrid-species analog. The researchers knew the diyttrium N₂ ^3– complex is a very strong reducing agent, which gave them the idea to react it with NO. When they did, the NO^2– complex shown formed immediately. “After all the decades of research on NO, it is quite surprising to find a new oxidation level for this simple diatomic molecule,” Evans says.