Hexanitrogen (diazide, hexaaza-1,2,4,5-tetraene) is an allotrope of nitrogen with the formula N6. The six nitrogen atoms are all covalently bonded in a single molecule: two azide units linked to each other. Its stability and structure were theorized in 2016[1] and its synthesis was reported in 2025.[2] It is stable at cryogenic temperatures.[2] The higher symmetry analogue, the benzene-like cyclic hexazine, has remained only theoretically hypothesized.
Its synthesis has been regarded as highly significant, as higher allotropes of nitrogen have potential application as propellants, explosives or energy storage.[3][4][5]
Computational analysis predicts that the bond lengths in the molecule vary significantly, indicating a complex electronic distribution, and a trans geometry in the central part of the structure. The terminal double bonds (N1=N2 and N5=N6) are about 1.138 Å. The adjacent double bonds (N2=N3 and N4=N5) are slightly longer, about 1.251 Å, and the central single bond (N3–N4) is the longest, about 1.460 Å. Each azide-like unit is approximately linear, with bond angles of about 172.5° at N2 and N5, and distinctly bent geometry of about 107° at N3 and N4.[2]
↑Greschner, Michael J.; Zhang, Meng; Majumdar, Arnab; Liu, Hanyu; Peng, Feng; Tse, John S.; Yao, Yansun (2016). "A New Allotrope of Nitrogen as High-Energy Density Material". The Journal of Physical Chemistry A120 (18): 2920–2925. doi:10.1021/acs.jpca.6b01655. PMID27088348. Bibcode: 2016JPCA..120.2920G.
