Searching for Neutralisers of Energetic Organic Compounds: A Theoretical Approach from the Perspective of Quantum Chemistry

Abstract

Neutralising energetic molecules is a valuable approach to minimize the risks of unpredictable explosions and associated tragic events. Quantum chemical methods offer highly efficient and effective tools for studying these compounds. The main objective of this dissertation is to quantify the impact of intermolecular interactions on the sensitivity of energetic compounds. Concerning the cyclic compounds RDX (1,3,5- trinitro-1,3,5-triazinane) and HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane), a quantitative analysis with MEP evidenced anomalies arising from the marked depletion of negative charge distribution. The EDA-NOCV results reveal that the electrostatic and orbital contributions are the dominant factors driving the assembly of the M = {Ti, Zr, Hf}-based complexes. The chemical nature of the O· · ·M = {Ti, Zr, Hf} bonding has been investigated by using the QTAIM theory. Additionally, the topological properties of the N–NO2 trigger bonds were quantified before and after the O· · ·M interaction. These intermolecular interactions strengthens the trigger bonds, revealing an increased stability to decomposition. The IRI-based analysis was carried out to further investigate the electronic properties of group 4 transition metals in coordination environments. With regard to the aliphatic compound FOX-7 (1,1-diamino-2,2-nitroethylene), we examined three types of interactions: oxygen and nitrogen from a nitro group interacting with the metal atom, as well as nitrogen from an amino group interacting with the same metal atom. The local chemical reactivity of FOX-7 was elucidated through a quantitative study of MEP. Results derived from QTAIM showed that the C–NO2 bonds are influenced by the O· · ·M = {Ti, Zr, Hf} bonding. Furthermore, this interaction rules the complex formation when a nitro group interacts with MMCs. The interaction energies calculated by EDA-NOCV revealed that the (H2N)2C=C(NO2)- (O)NO· · · Cp2MCH+3 complexes are significantly more structurally stable (by about 21.8 kcal/mol) than the (O2N)2C=C(NH2)-H2N· · · Cp2MCH+3 complexes. This work is crucial to validate the proposal of using MMCs (metallocene methyl cations) as a neutraliser of energetic molecules.