Development of Polynitrogen and Halogen‐Containing Bishomocubane‐Based High Energy Density Materials: Synthetic, Theoretical, and Thermogravimetric Studies

Highly strained bishomocubane-based molecules bearing energetic functionalities have been synthesized from readily available dicyclopentadiene and cyclopentanone in a minimum number of steps. Due to their high density, thermal stability, and superior propulsive characteristics and burn rate, these compounds are potential replacements for conventional binders in solid propellants and additives to liquid propellants, especially for applications in volume-limited environments.

Novel nitro, tetrazole, and halo-substituted 1,3-bishomocubanes have been successfully synthesized and characterized by various spectroscopic and analytical techniques, including single-crystal X-ray analysis. According to Density Functional Theory (DFT) calculations, performed at B3LYP/6-311++G(d, p) level of theory, the densities and heats of formation of the newly synthesized compounds are in the range of 1.52–2.26 g cm⁻³ and −70.8–111.4 kcal mol⁻¹, respectively. These compounds are predicted to exhibit enhanced propulsive properties in terms of density-specific impulse (ρIsp), compared to that of conventional liquid propellant RP1 and solid propellant binder hydroxy-terminated polybutadiene (HTPB), which makes them potential candidates for volume-limited propulsion systems. However, two derivatives have exceptional calculated figures of merit for volume-limited propulsion systems, a dibromoester (ρIsp 415.8 s), and a dibromonitroalcohol (ρIsp 421.3 s). Though its detonation properties indicate low explosive potential, the dibromonitroalcohol possesses the highest detonation pressure (20.1 GPa) and velocity (6.3 Km s⁻¹), which are closer to the detonation performance of trinitrotoluene (TNT). Stability parameters, including Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energy gaps, thermogravimetric analysis, and differential thermal analysis, confirm the robust kinetic and thermal stability of our compounds.

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