3‑Methylazasydnone: First Energetic Mesoionic Liquid

Energetic ionic liquids (EILs) have drawn considerable attention as potential liquid propellant components. However, most known EILs are oxygen-deficient and can be used only with external oxidizer. Herein, we report the first example of energetic mesoionic liquid, 3-methylazasydnone, that can function both as a monopropellant and in bipropellant systems. Methylazasydnone has the highest density among the methylated five-membered aromatic heterocycles in the liquid and solid state (1.49 and 1.60 g cm–3, respectively), shows moderate volatility, good thermal stability, and is insensitive to impact. The computed performance of liquid propellant’s combustion is superior to that of the benchmark energetic ionic liquid, 2-hydroxyethylhydrazinium nitrate (428 vs 424 g·s cm–3). Overall, methylazasydnone is a promising advanced functional material for application in green liquid mono- and bipropellants.