Effect of counter-ion on packing and crystal density of 5,5'-(3,3'-bi[1,2,4-oxa-diazole]-5,5'-di-yl)bis-(1H-tetra-zol-1-olate) with five different cations.

In energetic materials, the crystal density is an important parameter that affects the performance of the material. When making ionic energetic materials, the choice of counter-ion can have detrimental or beneficial effects on the packing, and therefore the density, of the resulting energetic crystal. Presented herein are a series of five ionic energetic crystals, all containing the dianion 5,5'-(3,3'-bi[1,2,4-oxa-diazole]-5,5'-di-yl)bis-(1H-tetra-zol-1-olate), with the following cations: hydrazinium (1) (2N(2)H(5)(+)·C(6)N(12)O(4)(2-)), hydroxyl-ammonium (2) 2NH(4)O(+)·C(6)N(12)O(4)(2-) [Pagoria et al.. (2017). Chem. Heterocycl. Compd, 53, 760-778; included for comparison], di-methyl-ammonium (3) (2C(2)H(8)N(+)·C(6)N(12)O(4)(2-)), 5-amino-1H-tetra-zol-4-ium (4) (2CH(4)N(5)(+)·C(6)N(12)O(4)(2-)·4H(2)O), and amino-guanidinium (5) (2CH(7)N(4)(+)·C(6)N(12)O(4)(2-)). Both the supra-molecular inter-actions and the sterics of the cation play a role in the density of the resulting crystals, which range from 1.544 to 1.873 Mg†m(-1). In 5, the tetra-zolate ring is disordered over two positions [occupancy ratio 0.907†(5):0.093†(5)] due to a 180° rotation in the terminal tetra-zole rings.