Amazing stuff! Justus von Liebig is smiling!
"The first neutral nitrogen molecule – other than dinitrogen – has been isolated and characterised by researchers in Germany. The molecule, the most energetic ever synthesised, is effectively stable at liquid nitrogen temperatures, which could make it attractive as an energy storage material. ...
While the dinitrogen molecule is low in energy, other nitrogen-containing molecules such as trinitrotoluene (TNT) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane, octogen (HMX) are the world’s most powerful non-nuclear explosives. ...
In the new work, organic chemists Weiyu Qian, Artur Mardyukov and Peter Schreiner at Justus Liebig University Giessen calculated that a hexanitrogen molecule could be relatively long lived because it contained no discernible dinitrogen units.
They synthesised the molecule by flowing chlorine gas through solid silver azide under reduced pressure. Silver azide is an excellent reagent for the synthesis of both halogen azides and polyazides. The chlorine therefore reacted with the silver azide to produce chloroazide, which reacted further with more silver azide to produce silver chloride and hexanitrogen. The weakest point of the structure – the ‘Achilles heel’ – is the bond between the two azide units. ‘It’s more like two times N3 than three times N2,’ ... This increases the molecule’s lifetime at room temperature to around 36 milliseconds – long enough for it to be trapped and cooled to liquid nitrogen temperatures, where the researchers calculate its half life to be over 100 years. ...
When hexanitrogen does break down, it releases double the energy per unit mass of HMX – currently the most powerful chemical explosive known. ..."
From the abstract:
"Compounds consisting only of the element nitrogen (polynitrogens or nitrogen allotropes) are considered promising clean energy-storage materials owing to their immense energy content that is much higher than hydrogen, ammonia or hydrazine, which are in common use, and because they release only harmless nitrogen on decomposition. However, their extreme instability poses a substantial synthetic challenge and no neutral molecular nitrogen allotrope beyond N2 has been isolated.
Here we present the room-temperature preparation of molecular N6 (hexanitrogen) through the gas-phase reaction of chlorine or bromine with silver azide, followed by trapping in argon matrices at 10 K.
We also prepared neat N6 as a film at liquid nitrogen temperature (77 K), further indicating its stability. Infrared and ultraviolet–visible (UV-Vis) spectroscopy, 15N-isotope labelling and ab initio computations firmly support our findings. The preparation of a metastable molecular nitrogen allotrope beyond N2 contributes to our fundamental scientific knowledge and possibly opens new opportunities for future energy-storage concepts."
Chemiker der JLU stellen erstmals Hexastickstoff her (original news release) "Künftige Anwendung als umweltfreundlicher Energiespeicher denkbar – „Nature“-Veröffentlichung des Teams um den Chemiker Prof. Dr. Peter R. Schreiner"
Preparation of a neutral nitrogen allotrope hexanitrogen C2h-N6 (open access)
Fig. 1: All known neutral molecular nitrogen allotropes and preparation of N6. [a timeline]
Contour line map of the electron density of hexanitrogen (top) with an electron localisation map (bottom) showing the molecule’s weak point
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