Hydrogen bonding distribution and its effect on sensitivity of planar tricyclic polyazole energetic materials

Abstract

• A series of insensitive planar tricyclic polyazole were effectively synthesized. • A novel method for preparing energetic cocrystal has also been presented. • Hydrogen bonding distribution is responsible for the differences of sensitivity. A series of planar tricyclic polyazole, energetic salts and energetic co-crystal were effectively synthesized via simple process from commercial materials. These structures of 5,5′-(2-nitro-1H-imidazole-4,5-diyl)bis(1H-tetrazole) (neutral compound 3) , Ammonium 5,5′-(2-nitro-1H-imidazole-4,5-diyl)bis(1H-tetrazole) (4) , Hydroxylammonium 5,5′-(2-nitro-1H-imidazole-4,5-diyl)bis(1H-tetrazole) (5) and Hydroxylamine . 2[5,5′-(2-nitro-1H-imidazole-4,5-diyl)bis(1H-tetrazole)] (co-crystal 7 ) which are combined with two neutral molecules 3 and one hyroxylamine were confirmed by X-ray diffraction analysis. Compared with the compounds 3 and 5 , energetic co-crystal 7 exhibit better thermal stabilities with an increase of 31 °C or 62 °C, respectively. Additionally, compound 3 (IS: > 60 J; FS > 360 N), 4 (IS: > 60 J; FS > 360 N) and 5 (IS = 39 J; FS > 360 N) are nearly insensitive toward mechanical stimuli, but co-crystal 7 (IS < 1 J) possesses extremely high impact sensitivities. Crystal and Hirschfeld analyses have demonstrated that the difference of hydrogen bonding distribution lead to the extremely difference of sensitivity between neutral compound 3 and co-crystal 7 , which will help to accelerate the creating of new nitrogen-rich energetic materials for different applications.