Creating Cyclo-N5+ Cations and Assembling N5+N5– Salts via Electronegativity Comatching in Tailored Ionic Compounds

The recent discovery of crystalline pentazolates marks a major advance in polynitrogen chemistry and raises prospects of making the long-touted potent propellant N5+N5– salt. However, despite the synthesis of cyclo-N5– anions in pentazolates, countercation cyclo-N5+ remains elusive due to the strong oxidizing power of the pentazole ion; moreover, pure N5+N5– salt is known to be unstable. Here, we devise a new strategy for making rare cyclo-N5+ cations and assembling the long-sought N5+N5– salt in tailored ionic compounds, wherein the negative/positive host ions act as oxidizing/reducing agents to form cyclo-N5+/N5– species. This strategy is implemented via an advanced computational crystal structure search, which identifies X N5N5F (X = Li, Na, and K) compounds that stabilize at high pressures and remain viable at ambient pressure–temperature conditions based on ab initio molecular dynamics simulations. This finding opens an avenue for creating and stabilizing the N5+N5– salt assembly in ionic compounds, where cyclo-N5 species are oxidized/reduced via comatching with host ions of high/low electronegativity. The present results demonstrate novel polynitrogen chemistry, and these findings offer new insights and prospects for the design and synthesis of diverse chemical species that exhibit unusual charge states, bonding structures, and superior functionality.