Unlocking the ultrafast laser response and low initiation energy of perchlorate-free tetrazine-based energetic coordination compounds

Abstract

Laser ignition technology holds significant and diverse applications in the domains of weapon equipment, aerospace and engineering blasting because of its exceptional resistance to electromagnetic interference, outstanding ignition efficiency and flexible controllability. However, the commercial initiation material B/KNO3 still suffers the high minimum laser initiation energy (Emin = 723.2 mJ) and lengthy ignition delay time (ID=160 ms). In this study, we have successfully synthesized two perchlorate-free energetic coordination compounds (ECCs): [Cu(DHT)(NO3)(H2O)](NO3) 1 and [Ni(DHT)(H2O)2](NO3)22 (DHT=3,6-dihydrazine-1,2,4,5-tetrazine). Though two compounds with similar structures show high explosion parameter values, the behaviors of laser responsive ignition are different. Noteworthy, laser ignition tests demonstrate that Cu-based 1 exhibits excellent laser response characteristics with an ultra-low Emin value of 4.2 mJ and a short ID time of 20 ms, while Ni-based 2 shows extremely insensitivity to laser under identical conditions. Furthermore, theoretical calculations reveal that the higher sensitivity of 1 towards laser response activity might be attributed to the narrower band gap (Eg = 0.44 eV) resulting from Cu centers in contrast with 2. In addition, mechanical sensitivities between 1 and 2 are discussed sufficiently by theoretical and structural studies. Compared to the commercial B/KNO3, compound 1 has promise to serve as a competitive laser ignition material.