Design, preparation, characterization and formation mechanism of a novel kinetic CL-20-based cocrystal

Abstract

2,4,6,8,10,12-Hexanitrohexaazaisowurtzitane (CL-20)-based cocrystals have gained increasing attention as a means of obtaining insensitive high explosives. However, the design of ideal candidates for these cocrystals remains difficult. This work compares the crystal energies of the CL-20–dinitrobenzene (DNB) and CL-20–2,4,6-trinitrotoluene (TNT) cocrystals with those of the respective pure coformers. The results indicate that the cocrystal formation is driven by the differences in the energies of the cocrystals and the coformers. Furthermore, analysis via Hirshfeld surfaces and two-dimensional fingerprint plots confirms that the O...O, O...H, O...N and C...O interactions were the main force for stabilizing the CL-20-based cocrystal structure. Based on these findings, a novel energetic–energetic cocrystal of CL-20–2,4,6-trinitrophenol (TNP) was designed and prepared by means of a rapid method for solvent removal. The crystal structure was investigated via powder X-ray diffraction methods, solid-state nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy. The results revealed that the O—H...O hydrogen bonding interaction between the phenolic hydroxyl group of TNP and nitro groups of CL-20, as well as nitro...π, nitro...nitro and ONO2...π(N)NO2 interactions, based on the benzene ring and nitro groups, are the main interactions occurring in the cocrystal.