Bioinspired Energetic Materials: A Co-Crystal of Explosophore-Functionalized Nucleobase Analogs

A new class of bio-inspired insensitive energetic materials has been designed, synthesized, and comprehensively characterized. Co-crystal of 2,8-diazidoadenine and 8-nitrotetrazolo[1,5-c]pyrimidine-5,7(1H,6H)-dione was formed upon simple suspension in EtOAc. The crystalline phases were characterized by powder x-ray diffractograms, which unambiguously confirmed the formation of new crystalline species, and were supported by electron diffraction, solid-state NMR, and infrared spectroscopy. The crystal structures of 2,8-diazidoadenine and 8-nitrotetrazolo[1,5-c]pyrimidine-5,7(1H,6H)-dione were determined by single-crystal x-ray analysis. The detonation performance of the designed energetic materials was calculated, yielding detonation pressures of 15.9‒20.4 GPa and detonation velocities of 6284‒7423 m/s, placing the materials among the competitive candidates in the class of insensitive high-energy density materials. The impact sensitivities confirmed the insensitivity of 2,8-diazidoadenine, 8-nitrotetrazolo[1,5-c]pyrimidine-5,7(1H,6H)-dione, and their co-crystal. Co-crystallization induced a conformational rotation of the azido group in 2,8-diazidoadenine, resulting in improved crystal packing and a higher material density. Furthermore, the low thermal stability of 8-nitrotetrazolo[1,5-c]pyrimidine-5,7(1H,6H)-dione was significantly improved in the formed co-crystal. Besides, the energetic properties of 2,6,8-triazidopurine revealed its sensitivity to impact and friction, and it was identified as a high-performance energetic compound in the class of primary explosives, with a calculated detonation pressure of 19.8 GPa and a detonation velocity of 7423 m/s.