Effect of Counter-Ion on Packing and Crystal Density of 5,5′-(3,3′-bi[1,2,4-oxadiazole]-5,5′-diyl)bis(1h-tetrazol-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-oxadiazole]-5,5′-diyl)bis(1H-tetrazol-1-olate), with the following cations: hydrazinium (1) (2N2H5+·C6N12O42−), hydroxylammonium (2) 2NH4O+·C6N12O42− [Pagoria et al.. (2017). Chem. Heterocycl. Compd, 53, 760–778; included for comparison], dimethylammonium (3) (2C2H8N+·C6N12O42−), 5-amino-1H-tetrazol-4-ium (4) (2CH4N5+·C6N12O42−·4H2O), and aminoguanidinium (5) (2CH7N4+·C6N12O42−). Both the supramolecular interactions 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 tetrazolate ring is disordered over two positions [occupancy ratio 0.907 (5):0.093 (5)] due to a 180° rotation in the terminal tetrazole rings.