Coordination Polymerization of 5,5'-Dinitro-2H,2H'-3,3'-bi-1,2,4-triazole Leads to a Dense Explosive with High...

High-energy coordination polymers (CPs) based on nitrogen-rich ligands are an emerging class of explosives. However, modulation of the energetic properties of high-energy CPs and the establishment of their structure-function relationship remain in their infancy. In the present study, the utility of coordination polymerization as a technique to modulate the application of critical energetic properties, such as density and thermal stability, of a secondary explosive, 5,5'-dinitro-2H,2H'-3,3'-bi-1,2,4-triazole (DNBT), is presented. Ni-DNBT is a discrete octahedral complex with density lower than that of DNBT. Cu-DNBT also contains octahedral metal coordination, similar to that in Ni-DNBT, as the building unit; however, the partial reduction of Cu^II to Cu^I ions during the reaction and their unique geometrical preferences lead to linking of the octahedral Cu^II complexes by tetrahedral Cu^I ions and render the resultant material a one-dimensional polymer with high density. In fact, Cu-DNBT has the highest density among all of the DNBT-based energetics. Furthermore, Cu-DNBT exhibits thermal stability superior to that of both Ni-DNBT and DNBT. Cu-DNBT is one of the two DNBT-based energetic materials and one of the few energetics that are stable at temperatures higher than 300 °C.