Nitroimino as an energetic group in designing energetic materials for practical use, a tautomerism from nitroamino

Energetic materials are widely used as energy components in military and civilian applications, which require high energy, and good safety, and are inexpensive and environmentally friendly. As an easily synthesized high-energy group, nitroamino can provide excellent energetic properties to a system. Compared with other energetic groups, nitroamino itself has the ability to form intermolecular hydrogen bonds (HB). The nitroamino undergoes a hydrogen transfer process to generate nitroimino, which forms intramolecular HBs unexpectedly, resulting in a larger conjugated system. The generation of secondary bonds promotes the stability and planarity of the system, thus favoring a series of important parameters such as density, thermal stability, and sensitivity, providing a theoretical basis for the design of nitroamino-substituted explosives with balanced energy and safety. This facilitates the development of high energy density materials (HEDMs) for aerospace, military and civilian applications. The hydrogen transfer process of the nitroamino system can be understood as one in which the nitroamino moiety becomes stable by changing the structure of the backbone or other substituent groups. However, the construction strategies and properties of nitroimino energetics have attracted little attention and are far from being fully exploited. The summarization of views and possible construction ideas will provide new opportunities. In this review, some important nitroimino-substituted explosives have been included to confirm the guiding role of hydrogen transfer strategy by capturing their structural features. Through comprehensive analysis of the skeleton structure, synthesis method, and performance characteristics, we strive to provide a macroscopic view of nitroimino explosives including the mechanism of the self-stabilizing hydrogen transfer, the improved performance, and the blueprint for the future design of HEDMs based on these characteristics.