Adjacent N→O and C–NH₂ groups — a highly efficient amphoteric structure for energetic materials resulting from tautomerization proved by crystal engineering

Existing amphoteric energetic materials (EMs) are very scarce, and their amphoteric structures are difficult to reproduce and protonate. Herein, adjacent N→O and C–NH₂ groups (O←NC–NH₂) were found to be a highly efficient and fairly balanced amphoteric energetic structure for EMs by crystal engineering and are the first discovered amphoteric structure caused by tautomerization to the best of our knowledge. As the O←NC–NH₂ structure has existed in many synthesized nitrogen-rich EMs, our work will greatly enrich amphoteric EMs.