Pushing the Energy-Sensitivity Balance with High-Performance Bifuroxans

Several energy-rich bifuroxans incorporating nitro and azido functionalities have been synthesized and thoroughly characterized by IR and multinuclear NMR spectroscopy, elemental analyses, single-crystal X-ray diffraction, and differential scanning calorimetry. N-oxide regiochemistry was employed to design the tunable azido(nitro)bifuroxans with different physicochemical and energetic properties. All synthesized compounds have high enthalpies of formation (449–777 kJ mol–1) and attractive performances, as evidenced by the high detonation velocities (8.95–9.75 km s–1) and Champan–Jouguet pressures (35–45 GPa). The most powerful energetic material in this series is 4,4′-dinitro-3,3′-bifuroxan. This hydrogen-free molecule (C4N6O8) exhibits an outstanding heat of explosion value of 15.3 kJ cm–1, far exceeding the top energetic material hexanitrohexaazaisowurtzitane CL-20. At the same time, the impact and friction sensitivities of 4,4′-dinitro-3,3′-bifuroxan were deemed acceptable for practical use. Overall, 4,4′-dinitro-3,3′-bifuroxan breaks a general trend called the “energy-sensitivity rule”, which describes a linear increase of the mechanical sensitivity with a growth of the energetic content of the molecule, and, thus, offers great promise for future applications.