Power of sulfur-Chemistry, properties, laser ignition and theoretical studies of energetic perchlorate-free 1,3,4-thiadiazole nitramines

The chemistry of lead-, azide- and perchlorate-free photosensitive energetic materials suitable for laser-ignition systems is an emerging field of research with a broad range of applications. To develop less toxic materials that would be sufficiently thermostable, safe, and sensitive enough to be ignited by low-power laser, is a formidable challenge. In this work, we designed, prepared, and studied properties of new sulfur-containing energetic molecules (SEMols), based on novel N-(1,3,4-thiadiazol-2-yl)nitramide explosophore. Newly synthesized energetic compounds N-(5-nitro-1,3,4-thiadiazol-2(3H)-ylidene)-nitramide (L1) and N5,N5 '-dinitro-[2,2 '-bi(1,3,4-thiadiazole)]-5,5 '(4H,4 ' H)-diimine (L4) were found to be more thermostable than their sulfur-free 1,3,4-oxadiazole analogues. In small-scale detonation experiments, L1, L4, and C7 showed better brisance than TNT. Perchlorate-free complex C7 was found to have low-power laser igniting properties, showing an ignition delay time of 11 ms and threshold ignition energy of 12.0 mJ (at 915 nm irradiation). Extensive crystal-level (328-atom super-cell) ab-initio molecular dynamics and TD-DFT calculations were performed to study the laser ignition mechanism of C7. Based on our hypothesis, this photo-thermal ignition is taking place via sequential multiphoton absorption, with energy transfer to vibrational motions in this molecule. We suggest that SEMols, such as C7, can open a new platform for the development of novel energetic materials that have a potential for integration into laser-based safe energetic components in civil, aerospace, and defense applications.

Automated summary

The chemistry of lead-, azide- and perchlorate-free photosensitive energetic materials is an emerging field of research with wide applications. In this study, new sulfur-containing energetic molecules were designed, synthesized, and their properties were studied. These molecules showed good thermostability and brisance, and one of them exhibited laser igniting properties. Extensive calculations were performed to study the laser ignition mechanism.