Abstract
Density, detonation property, and sensitivity may be the most valued features when evaluating an energetic material. By reasoning structure–property relationships, a nitro-free planar energetic material with high nitrogen and oxygen content, 7-hydroxy-difurazano[3,4-b:3′,4′-f]furoxano[3″,4″-d]azepine (4), was synthesized using a unique and facile approach. The structure was fully characterized by IR and NMR spectra, elemental analysis, differential scanning calorimetry (DSC), and single-crystal X-ray diffraction. The expected properties of 4, including a high density of 1.92 g cm−3, high detonation velocity of 8,875 m s−1, and low mechanical sensitivities (impact sensitivity, 21 J and friction sensitivity, >360 N), confirm our strategy. Interestingly, the single-crystal structures of 4 reveal expected face-to-face and edge-to-face π-interactions in the crystal stacking. The remarkable differences in crystal stacking of 4 provide unequivocal evidence that face-to-face π-π interactions contribute significantly to closer assembly and higher density.
Highlights
At the early stages of energetic materials, chemists mainly focused on designing and synthesizing the polynitro compounds, such as 1,3,5-trinitro-1,3,5-triazinane (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), 2,4,6,8,10,12-hexanitro-2,4,6,8,10, 12-hexaazaisowurtzitane (CL-20), and octanitrocubane (ONC) (Badgujar et al, 2008; Klapötke, 2012)
Nitro group has been playing a critical role in the developing of energetic materials since nitroglycerin (NG) and 2,4,6-trinitrotoluene (TNT) were widely used for the purpose of military and civilization
The contributions of nitro group primarily consist of enhancing the oxygen balance and density, leading to an increase in the detonation performances
Summary
At the early stages of energetic materials, chemists mainly focused on designing and synthesizing the polynitro compounds, such as 1,3,5-trinitro-1,3,5-triazinane (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), 2,4,6,8,10,12-hexanitro-2,4,6,8,10, 12-hexaazaisowurtzitane (CL-20), and octanitrocubane (ONC) (Badgujar et al, 2008; Klapötke, 2012). Based on the analysis above, we are aimed at designing and synthesizing high-performance insensitive materials that have the following structure characteristics: (1) a nearperfect planar molecular being able to form face-to-face stacking to achieve a high density; (2) high nitrogen and oxygen content leading to high heat of formation and good oxygen balance; (3) no nitro within it to achieve a low sensitivity. With these in mind, we were interested in some furazan/furoxan-based planar compounds containing Nhydroxy group. We report the results on the ingenious synthesis, full characterization, energetic properties of 4
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