Energy Storage in Cubane Derivatives and Their Real-Time Decomposition: Computational Molecular Dynamics and Thermodynamics

Cubane features one of the highest densities of covalent bonds among all known compounds. Kinetically stable, it constitutes an excellent candidate for efficient storage of large amounts of energy. We employ ab initio and semiempirical quantum-chemical methods to investigate systematically the amounts of energy that can be stored in cubane and its two derivatives known synthetically, octanitrocubane (8-CUB) and heptanitrocubane (7-CUB). Using nonequilibrium molecular dynamics, we establish the energy liberation pathways and molecular decomposition mechanisms. The reaction starts with spontaneous isomerizations of nitrocubanes into nitroannulenes and nitrosooxycubanes, subsequently producing NO and octaone C 8 O 8 . Unstable C 8 O 8 decomposes within a picosecond, producing 8 CO molecules. All reactions are exothermic, giving rise to a sharp temperature increase. Ultimately, CO and NO recombine into CO 2 and N 2 . According to the thermochemical calculations, 8-CUB stores 4145 kJ mol –1 of free energy, while 7-CUB stores 4346 kJ mol –1 . The reported results foster consideration of cubanes for energy storage.