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-(1 H-tetra-zol-1-olate) with five different cations

Abstract

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) (2N₂H₅⁺·C₆N₁₂O₄^2-), hydroxyl-ammonium (2) 2NH₄O⁺·C₆N₁₂O₄^2- [Pagoria et al.. (2017). Chem. Heterocycl. Compd, 53, 760-778; included for comparison], di-methyl-ammonium (3) (2C₂H₈N⁺·C₆N₁₂O₄^2-), 5-amino-1H-tetra-zol-4-ium (4) (2CH₄N₅⁺·C₆N₁₂O₄^2-·4H₂O), and amino-guanidinium (5) (2CH₇N₄⁺·C₆N₁₂O₄^2-). 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.

Keywords: 5-amino-1H-tetra­zol-4-ium; amino­guanidinium; crystal structure; energetic materials; hydrazinium; hydroxyl­ammonium; oxa­diazole; tetra­zole; tri­amino­guandidinium.