Quantum chemical study on the weak intermolecular interaction between 3,4-bis(3-nitrofurazan-4-yl) furoxan (DNTF) and microcrystalline wax

Context

Compatibility is a key factor restricting the engineering applications of 3,4-Bis(3-nitrofurazan-4-yl) furoxan (DNTF). To establish a scientific criterion for the compatibility of DNTF with other substances, this study uses the DNTF/WAX system as the research subject. By applying computational chemistry methods, it reveals the interactions and incompatibility mechanism between DNTF andMicrocrystalline Wax (MW). Molecular surface electrostatic potential studies indicate that electrostatic interactions exist between the side of DNTF away from the oxygen atom on the furazan ring and the side of MW containing alcoholic hydroxyl groups. IGMH analysis further reveals that these weak interactions consist of hydrogen bonding and van der Waals forces. AIM calculations reveal that the weak interactions at the bond critical points (BCPs) in the DNTF/MW system are primarily "weak"-level hydrogen bonds of the N···H-O type and hydrogen-bond-like interactions of the O···H-C type. Frontier molecular orbital (FMO) analysis reveals that compared with pure DNTF, the molecular orbital energy level difference ΔE of the DNTF/MW composite structure decreases by 21%. This indicates enhanced reactivity of the composite structure. Mayer bond order analysis verifies the accuracy of the FMO results: in the DNTF/MW composite structure, the bond orders of both the key pyrolysis initiation bond (O6-N3) and secondary initiation bonds decrease to varying degrees compared to the single-component DNTF. This study provides a theoretical basis for screening DNTF-based mixed explosive formulations and helps improve the safety of DNTF in practical applications.

Methods

The initial molecular structures of DNTF and MW used in this study were retrieved from the Cambridge Crystallographic Data Centre (CCDC) and optimized using Gaussian16 software at the B3LYP-D3/6-311G(d,p) computational level. To obtain the optimal bimolecular conformations of DNTF and MW, a conformational search method was employed: first, the Genmer package was used to generate 500 bimolecular configurations of DNTF/MW composites; then, the Molclus program was employed to invoke XTB software for structural optimization at the GFN2-xTB level, with five configurations of lower energy retained; subsequently, Gaussian16 software was called to perform optimization and frequency calculations for these structures at the B3LYP-D3(BJ)/6-31G* level; finally, the ORCA software was used to perform single-point energy calculations at the PWPB95-D3(BJ)/def2-TZVPP level for the structures optimized by Gaussian, thereby obtaining the free energy of each configuration, and the configuration with the lowest energy was selected based on the free energy for subsequent weak interaction analysis. Additionally, the counterpoise (CP) method was also used to correct for basis set superposition error (BSSE).