Structure, Physicochemical Properties, and Density Functional Theory Calculation of High-Energy-Density Materials Constructed with Intermolecular Interaction: Nitro Group Charge Determines Sensitivity

Four nitro-containing energetic compounds,
cocrystal of AT·DNBA (1), salt of MA·DNSA (2), salt of AG·DNBA·H2O (3), and salt of DAT·DNSA H2O (4), are
synthesized and structurally characterized based on supramolecular
interactions (AT, 4-amino-1,2,4-triazole; DNBA, 3,5-dinitrobenzoic
acid; MA, melamine; DNSA, 3,5-dinitrosalicylic acid; AG, amino guanidine;
DAT, 3,5-diamino-1,2,4-triazole). The physicochemical properties of
the compounds are theoretically and experimentally investigated in
detail. The optimized structures, molecular total energies, frontier
orbit energies, and charge densities of 1–4 are calculated by theoretical methods. The experimental
results indicate that all compounds exhibit good thermostability and
low sensitivity. It is worth noting that the values of impact sensitivity
are measured to be 30, >40, 38, and >40 J for 1, 2, 3, and 4, respectively,
which correspond well to the order of nitro group charge (QNitro) calculated by density functional theory.
The detonation performances of 1–4 are discussed; in particular, 1 and 2 exhibit
heats of detonation (2.191 kcal g–1 for 1 and 2.214 kcal g–1 for 2) superior to those of classical nitro-rich compounds. In addition,
the nonisothermal thermokinetic parameters are obtained by Kissinger
and Ozawa methods, and the standard molar enthalpies of formation
are calculated from the determination of constant volume combustion
energies.