Energetic multifunctionalized nitro/nitramino isomeric pyrazole-tetrazole hybrids: enhancing density and detonation properties through hydrogen bonding and π-π interactions

Abstract

This study focuses on synthesizing high-density isomeric pyrazole-tetrazoles and their energetic salts, with a particular emphasis on improving detonation performance. First synthesized was 5-(3,4-dinitro-1H-pyrazol-5-yl)-1H-tetrazole (H2DNP-5T, 3), an isomer of 5-(3,4-dinitro-1H-pyrazol-4-yl)-1H-tetrazole (H2DNP-4T) followed by synthesis of the nitramine derivative N-(4-nitro-5-(1H-tetrazol-5-yl)-1H-pyrazol-3-yl)nitramide (H3NANP-5T, 11) to further enhance detonation properties. Crystal packing and NCI analysis were used to gain insight into the impact of significant interactions such as hydrogen bonding and π-π interactions on density enhancement. Isomeric pyrazole-tetrazole (H2DNP-5T) demonstrated high density and superior detonation properties compared to its 4-substituted derivative, H2DNP-4T, attributed to increased inter-hydrogen bonding interactions, a high packing coefficient (73.1%), and π-π interactions. All substances were characterized spectroscopically using NMR, IR, and elemental analyses. The structures of compounds H2DNP-5T, H3NANP-5T, and 4 were further confirmed by single-crystal X-ray diffraction. Using EXPLO5 software, the detonation parameters of energetic materials based on experimental density and computed heat of formation were determined. Furthermore, the nitramine derivative H3NANP-5T (Dv: 8846 m s−1; P: 33.2 GPa) and its energetic salts 13 (Dv: 9414 m s−1; P: 34.5 GPa) and 14 (Dv: 9088 m s−1; P: 33.9 GPa) exhibit outstanding detonation properties comparable to RDX. Comprehensive molecular and crystal-level insights into the impact of positional isomerism which hold significance for the design and development of new energetic materials.