Nitrogen finally joins the elite tier of elements like carbon that can form neutral allotropes—different structural forms of a single chemical element. Researchers from Justus Liebig University, Giessen, Germany, have synthesized neutral hexanitrogen (N₆)—the first neutral allotrope of nitrogen since the discovery of naturally occurring dinitrogen (N₂) in the 18th century that is cryogenically stable and can be prepared at room temperature.

This new study, published in Nature, synthesized hexanitrogen (N₆) via gas-phase reaction, with the main ingredients being chlorine (Cl₂) or bromine (Br₂) and an extremely reactive and explosive solid silver azide (AgN₃), under reduced pressure.

The researchers spread AgN₃ on the inner surface, and a gaseous halogen (Cl₂ or Br₂) was passed through the solid under reduced pressure at room temperature. The reaction triggered by the process produced N₆ alongside byproducts chloronitrene (ClN) and hydrazoic acid (HN₃).