Cage engineering via isomerism: a computational study of octanitrocuneane (C8N8O16) as a potential high-energy density material

The energy-safety dilemma in high-energy density materials (HEDMs) necessitates innovative molecular design strategies. Here, we report the first systematic computational investigation of octanitrocuneane (isoONC), a constitutional isomer of octaniotrocubane (ONC), as a model system for cage engineering via structural isomerism. Density functional theory calculations reveal that isoONC achieves comparable energetic properties (density = 2.07 g cm⁻³, detonation velocity = 9.8 km s⁻¹) to ONC (density = 2.06 g cm⁻³, detonation velocity = 9.8 km s⁻¹) while potentially offering enhanced safety performance. The cuneane framework has a 5.3% reduction in cage strain energy from 967.4 to 916 kJ mol⁻¹ and a 52% improvement in calculated impact sensitivity threshold from 3.2 cm to 4.9 cm (h₅₀). Enhanced safety originates from stronger trigger bonds (284.5 vs. 274.5 kJ mol⁻¹), more uniform electrostatic potential distribution, reduced steric frustration and enhanced intermolecular interactions. This computational study establishes structural isomerization as a promising molecular design strategy for cage-type energetic materials, though experimental validation remains essential.