Isomeric energetic biocidal compounds derivates from methylene bridged nitro-iodopyrazoles

Fourteen oxatriazoles have been investigated computationally as potential energetic compounds. They include the two isomeric parent compounds, their amino and nitro derivatives, four N‐oxides and four amino‐N‐oxides. Densities and solid state heats of formation were calculated for all of these compounds, and used to determine their detonation velocities and detonation pressures by means of the Kamlet‐Jacobs equations. Four of the compounds, all N‐oxides, surpass or essentially equal Klapötke's criteria for detonation velocity and detonation pressure. Three other N‐oxides meet just the detonation velocity criterion. Impact sensitivity was addressed in terms of three factors that are known to affect it: the free space per molecule in the crystal lattice, the electrostatic potential on the molecular surface, and the detonation heat release of the compound. Three of the N‐oxides with the highest detonation velocities and detonation pressures have undesirably large heats of detonation, a warning of possible impact sensitivity. However 5‐amino‐1,2,3,4‐oxatriazole‐3‐oxide combines good detonation properties with a moderate heat release; its free space per molecule in the crystal lattice and molecular surface electrostatic potential are also consistent with low sensitivity. Overall, we believe that the results of this work should encourage further investigation of oxatriazole derivatives as energetic compounds.

Although the isomeric energetic compounds DTDA and T‐N10B share high sensitivity, DTDA possesses superior thermal stability. Investigations reveal that DTDA's enhanced thermal stability originates from stronger trigger bonds (resulting in a higher initial decomposition energy barrier), greater π ‐electron delocalization capability, and an effective hydrogen bonding network in the crystal. On the other hand, their shared high sensitivity stems from similar crystal packing imperfections: irregular Hirshfeld surfaces, anisotropic molecular arrangement, and inhomogeneous intermolecular interactions. These structural features collectively restrict energy dissipation under external stimuli, thereby explaining their high sensitivity.

Transforming the energy storage structure is an effective approach to achieve a balance between the detonation performance and the sensitivity of energetic compounds, with a goal of high energy and low sensitivity. Building upon previous work, this study employed an isomeric compound 1H-pyrazole-3-carbohydrazide (3-PZCA) as a ligand and creatively designed the energetic coordination compound (ECC) Ag(3-HPZCA)2(ClO4)3 (ECC-1). It is a novel material with a dual structure of ionic salts and coordination compounds, which represents the first report of such a structure in Ag(I)-based ECCs. With its unique structures, ECC-1 exhibits a larger [ClO4-] content, a higher oxygen balance constant (OB = 0%), and superior mechanical sensitivity (IS = 13 J and FS = 40 N). Theoretical calculations indicate that ECC-1 has a higher detonation performance compared to previous work. Furthermore, the explosive experiment testing results demonstrate that it can be ignited by lower-threshold lasers and possesses excellent initiation capability and explosive power, making it suitable not only as a primary explosive but also as a secondary explosive.

For a very long time, frequent occurrences of biocrises have wreaked havoc on human beings, animals, and the environment. As a result, it is necessary to develop biocidal agents to destroy or neutralize active agents by releasing large amounts of strong biocides which are obtained upon detonation. Iodine is an efficient biocidal agent for bacteria, fungi, yeasts, viruses, spores, and protozoan parasites, and it is the sole element in the periodic table that can destroy microbes without contaminating the environment. Based on chemical biology, the mechanism of iodine as a bactericide may arise from oxidation and iodination reactions of cellular proteins and nucleic acids. However, because of the high vapor pressure causing elemental iodine to sublime readily at room temperature, it is inconvenient to use this material in its normal solid state directly as a biocidal agent under ambient conditions. Iodine-rich compounds where iodine is firmly bonded in molecules as a C-I or I-O moiety have been observed to be among the most promising energetic biocidal compounds. Gaseous products comprised of large amounts of iodine or iodine-containing components as strong biocides are released in the decomposition or explosion of iodine-rich compounds. Because of the detonation pressure, the iodine species are distributed over a large area greatly improving the efficacy of the system and requiring considerably less effort compared to traditional biocidal methods. The commercially available tetraiodomethane and tetraiodoethene, which possess superb iodine content also have the disadvantages of volatility, light sensitivity, and chemically reactivity, and therefore, are not suitable for use directly as biocidal agents. It is absolutely critical to synthesize new iodine-rich compounds with good thermal and chemical stabilities.In this Account, we describe our strategies for the syntheses of energetic iodine-rich compounds while maintaining the maximum iodine content with concomitant stability and routes for the synthesis of oxygen-containing iodine-rich compounds to improve the oxygen balance and achieve both high-energy and high-iodine content. In the other work, which involves cocrystals, iodine-containing polymers were also summarized. It is hoped that this Account will provide guidelines for the design and syntheses of new iodine-rich compounds and a route for the development of inexpensive, more efficient, and safer iodine-rich antibiological warfare agents of the future.

While the effect of isomerism on the properties of energetic molecules has long been recognized, the use of this phenomenon to deliberately improve the performance of energetic materials has now been approached. Here, we report the development of effective protocols for the preparation of isomeric energetic compounds with a furazan-triazole-pyrazole framework, which differ in the binding points of these subunits and in the position of the nitro group. The two synthesized isomers readily form X-ray quality crystals of solvates with DMSO and water, but only one isomer was able to give unsolvated crystals. Significant differences in molecular geometry and noncovalent interactions due to the effect of the solvent incorporated into the crystal lattice are highlighted. The ambiguity of evaluating structure–property relationships for a single compound from the X-ray data of its solvate is demonstrated. The isomer synthesized for the first time, 3-(5-(5-(3,4-dinitro-1H-pyrazol-5-yl)-1H-1,2,4-triazol-3-yl)-4-nitrofurazan (6), is of greater interest because, unlike the other isomer, it is not hygroscopic and has a higher density. Isomer 6 has a shock sensitivity and detonation velocity similar to those of RDX, but it is more thermally stable and insensitive to friction.

Tuning energy properties via N-NH2 strategy: Construction of two isomeric energetic compounds based on nitro-substituted pyrazoles