Dinitrogen dioxide is an inorganic compound having molecular formula N2O2. Many structural isomers are possible. The covalent bonding pattern O=N–N=O (a non-cyclic dimer of nitric oxide (NO)) is predicted to be the most stable isomer based on ab initio calculations and is the only one that has been experimentally produced. In the solid form, the molecules have C2v symmetry: the entire structure is planar, with the two oxygen atoms cis across the N–N bond. The O–N distance is 1.15 Å, the N–N distance is 2.33 Å, and the O=N–N angle is 95°.

• East, Allan L. L. (August 8, 1998). "The 16 valence electronic states of nitric oxide dimer (NO)2". Journal of Chemical Physics. 109 (6): 2185–2193. Bibcode:1998JChPh.109.2185E. doi:10.1063/1.476786.
• Harcourt, Richard D. (April 1990). "The origin of the long N–N bond in N2O2: an ab initio valence bond study". Journal of Molecular Structure: THEOCHEM. 206 (3–4): 253–264. doi:10.1016/0166-1280(90)85140-I.[1]
• Dkhissi, Ahmed; Soulard, Pascale; Perrin, Agnès; Lacome, Nelly (May 1997). "The NO Dimer". Journal of Molecular Spectroscopy. 183 (1): 12–17. Bibcode:1997JMoSp.183...12D. doi:10.1006/jmsp.1996.7249.