Enhancing chemical stability of tetranitro biimidazole-based energetic materials through co-crystallization

Abstract

<jats:p> Co-crystallization technology was employed as a way of solving two problems hampering the usefulness of 4,4′,5,5′-tetranitro-2,2′biimidazole (TNBI) as a viable energetic material, namely hygroscopicity and corrosiveness (high acidity). Co-crystal screening was carried out with 15 co-formers containing nitrogen or oxygen as the primary hydrogen-bond acceptor site. Formation of co-crystals was confirmed by IR spectroscopy and DSC, and suitable co-crystals were then analysed via single-crystal X-ray diffraction. In each case, the formation of a co-crystal was driven by the formation of multiple N–H···N or N–H···O hydrogen bonds between TNBI and the co-former. The N-oxide based acceptors produce better energetic materials due to a more optimal oxygen balance. Hygroscopicity evaluations and corrosion tests revealed that the unavailability of N–H protons in the co-crystals of TNBI reduce hygroscopicity and suppress the chemical acidity of the free parent compound thereby making it substantially easier to handle, store, and transport. </jats:p>

Recent Progress on Synthesis, Characterization, and Performance of Energetic Cocrystals: A Review

“…The shelf life and stability of these ECCs is also improved due to their imperviousness to humidity and, therefore, these ECCs can substitute for TNBI materials in industrial applications [ 67 ]. The absence of N—H protons in the resulting ECC lowers the hygroscopicity and chemical acidity of the parent compound thereby enhancing its handling, storage, and transport [ 68 ].…”

Challenging the Limitations of Tetranitro Biimidazole through Introducing a gem-Dinitromethyl Scaffold

“…17−19 In addition, cocrystallization technology was also employed to conquer the limitations of TNBI. 13,20 These excellent works greatly promote the practical applications of TNBI. However, the key parameters for energetic materials, including oxygen balance and detonation properties, should be further improved.…”

“…Many strategies have been tried to solve the hygroscopicity and corrosiveness (high acidity) of TNBI. Difunctionalization of N–H bonds in imidazole rings with amino and alkyl groups − or deprotonation of imidazole rings and further transformation into energetic salts were the most investigated. − In addition, cocrystallization technology was also employed to conquer the limitations of TNBI. , These excellent works greatly promote the practical applications of TNBI. However, the key parameters for energetic materials, including oxygen balance and detonation properties, should be further improved.…”

Syntheses, Structures, and Properties of Polynitro-Substituted 5,6-Dihydrodiimidazo[1,2-a:2′,1′-c]pyrazine Energetic Compounds

“…7−9,12−20 In addition, co-crystallization technology has been employed recently as a way of solving hygroscopicity and corrosiveness (high acidity) problems of TNBI. 21 In 2018, an ingenious method to fine-tune the properties of energetic molecules by the ring closure of polynitroazoles with N,N′-ethylene bridges was developed by Shreeve and coworkers. 22 The N,N′-ethylene bridge can connect two nitrogen atoms on the azoles that were originally protonated to form a tricyclic fused structure.…”

“…One strategy utilized to overcome the inherent hygroscopicity of TNBI is the substitution of hydrogen atoms attached to the imidazole ring with covalently bound N -amino and N -methyl groups. − Another approach to solve the hygroscopicity issues associated with TNBI have focused on the ability of this compound to co-ordinate with metals or metalloids (for use in pyrotechnic applications) and form the deprotonated energetic di-anion in nitrogen-rich energetic salts. − ,− In addition, co-crystallization technology has been employed recently as a way of solving hygroscopicity and corrosiveness (high acidity) problems of TNBI …”