An integrated quantum chemical and experimental approach for exploring the structures and properties of insensitive munitions interacting with ions in bulk water

Abstract

Alternatives to legacy munitions and explosives, materials that feature increased stability against external stimuli without compromising their energetic yields are currently being developed. The environmental interactions of such energetic materials need to be addressed, especially as their use becomes more widespread. In order to explore such compounds with environmental influences in mind, we assess the electronic structure and properties of these insensitive munitions (IMs) compounds in modeled hard water using both theory and experiment. To model the IMs in hard water, we have used density functional theory with the M06-2X functional and the 6-311 + G(d,p) basis set with explicit water molecules to capture features like hydrogen bonding, implicit solvent to incorporate bulk water effects, and select ions that would be present in natural water. We ensured the nature of the potential energy surfaces of optimized geometries through vibrational frequency calculations under the harmonic approximation. Several electronic properties, such as oxidation and reduction potentials and electron affinity and ionization potential, for each system are presented. Additionally, cyclic voltammetry experiments were performed, and obtained results were compared with quantum chemical predictions. The experimental reduction potentials are found to be in good agreement with the predicted results. Overall, the reduction potentials predicted by density functional theory for the IM-ion-water complexes are shifted compared with the corresponding isolated munition such that reduction or oxidation would be more facile in the presence of water and ions.