Unraveling the Exotic Chemistry of High-Pressure Nitrogen Compounds

• Applicant: Professorin Dr. Natalia Dubrovinskaia, since 2/2022
• Subject Area: Solid State and Surface Chemistry, Material Synthesis ; Inorganic Molecular Chemistry - Synthesis and Characterisation ; Experimental Condensed Matter Physics
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 456543021

Nitrogen compounds are one of the most compelling class of solids. As nitrides (N3-), they are known to exhibit outstanding mechanical and electronic properties. As homoatomic poly-bonded species they can store the highest amount of chemical energy and have ultra-stiff bonds. Despite their outstanding potential as technological materials, nitrogen compounds are still strikingly uncommon, accounting for a mere 4% of all solids in the ICSD database. Their synthesis through classical chemical methods is severely hindered by the extreme stability of the N2 molecule, exhibiting one of the strongest covalent bonds. In recent years however, the rapid development of the nitrogen chemistry lead to the discovery of novel nitrogen species. These achievements are credited to the innovative use of the thermodynamic parameter pressure—imposing itself as one of the most important tools to discover, develop and exploit the chemistry of nitrogen. Through high pressure investigations of nitrogen in binary mixtures with alkali metal, alkaline earth and transition metal elements, a first generation of novel nitrogen entities were realized. Indeed, the pressure-induced formation of anionic nitrogen dimers ([N2]x-), polydiazenediyls ([N4]2-), cis-tetranitrogens ([N4]4-) and pentazolates (N5-) unprecedently exposed the nitrogen chemistry’s flexibility enabled by high densities. Moreover, with the exception of polydiazenediyls, all polynitrogen species were recovered at ambient conditions, forcing a revision of the chemical capabilities of nitrogen at atmospheric pressure and of its potential for technological materials. Still, given that solely anionic polynitrogen entities were thus far discovered strongly suggests that these initial investigations only scratched the surface of nitrogen’s high pressure chemistry. This research project aims at studying the high pressure behavior of nitrogen with pnictogen (As, Sb), chalcogen (O) and halogen (F) elements, as of now largely unexplored. In particular, the chosen elements are especially well-adapted to uncover novel nitrogen homoatomic cations (O, F) and covalently-bonded heteroatomic species (As, Sb), both of which are thus far singularly absent at high densities. The objectives of this experimental research project are to 1) investigate the high pressure chemistry of nitrogen with arsenic, antimony, oxygen and fluorine to discover novel compounds composed of nitrogen homoatomic cations and heteroatomic species; 2) characterize at high pressure the compounds’ crystal structure and electronic properties; 3) formulate crystal chemical principals governing their synthesis under extreme conditions; and 4) establish a direct link between their crystal chemistry and their physical properties, revealing their potential for the design of next-generation technological materials.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Dr. Dominique Laniel, until 1/2022