pubs.acs.org/IC Article A Duo and a Trio of Triazoles as Very Thermostable and Insensitive Energetic Materials Yongxing Tang,*,∥ Zhaoyang Yin,∥ Ajay Kumar Chinnam, Richard J. Staples, and Jean’ne M. Shreeve* Cite This: https://dx.doi.org/10.1021/acs.inorgchem.0c03014 Downloaded via SAN FRANCISCO STATE UNIV on November 17, 2020 at 09:24:23 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles. ACCESS Metrics & More Read Online Article Recommendations sı Supporting Information * ABSTRACT: The triazole moiety with a high heat of formation and a high nitrogen content has been investigated for decades in combination with other nitrogen-rich heterocyclic rings in the field of energetic materials. A novel strategy for the construction of both thermally stable and mechanically insensitive energetic materials using a multi-aminotriazole system is now described. Using this methodology, two series of energetic materials were created on the basis of a duo of triazoles, 5-amino-3-(3,4-diamino-1,2,4-triazol-5-yl)-1H-1,2,4-triazole (TT), and a trio of triazoles, 4,5-di(3,4-diamino-1,2,4-triazol-5-yl)-2H-1,2,3triazole (TTT). Their nitrogen-rich salts were also synthesized. Compound TT exhibits an excellent onset decomposition temperature (Td = 341 °C), which is superior to that of the conventional heat-resistant explosive hexanitrostilbene (HNS) (Td = 318 °C). The nitrogen-rich salt 4,5-di(3,4-diamino-1,2,4-triazol-5yl)-2H-1,2,3-triazolium 3,4,5-trinitropyrazol-1-ide (TTT-1) exhibits both remarkable detonation properties and low sensitivities (Dv = 8715 m s−1; P = 32.6 GPa; IS > 40 J; FS > 360 N), which are superior to those of the traditional explosive LLM-105 (Dv = 8639 m s−1; P = 31.7 GPa; IS = 20 J; FS = 360 N). Therefore, this methodology of building a multi-aminotriazole system could effectively assist in the design of thermally stable and mechanically insensitive energetic materials in future exploration. formation, triazole-based energetic materials can be used to construct high-performance explosives with low sensitivity as well as good thermal stability. For example, the triazole derivatives 4-amino-5-nitro-1,2,3-2H-triazole and 3,5-dinitro1H-1,2,4-triazole19,20 possess both good detonation performances and satisfactory safety properties. Previous studies have shown that amino-substituted energetic compounds may exhibit low sensitivity arising from inter- and intramolecular interactions.21−24 Thus, the 3,4-diamino-1,2,4triazole moiety was regarded as promising in the formation of thermally stable and mechanically insensitive compounds. Studies on compounds containing this species, such as 3amino-4-(4,5-diamino-1,2,4-triazol-3-yl)furazan25,26 and 1,2bis(3,4-diamino-1,2,4-triazol-5-yl)ethene,27 were attempted previously. These compounds show low sensitivities with impact sensitivities (IS) of >40 J and friction sensitivities (FS) of >360 N. To improve the thermal stability and energy level of triazole-based energetic materials further, it was envisioned that a combination of multi-aminotriazoles might enable a good INTRODUCTION Since the discovery of nitroglycerin (NG), energetic materials such as explosives, propellants, and pyrotechnics rapidly accelerated the development of military force and civilian construction.1−4 However, safety problems arising from thermoinstability, high sensitivity to external stimuli, and electrostatic discharge occurred frequently over the past several decades, arousing the attention of many scientists. Therefore, improving the safety properties of energetic materials is today one of the most urgent issues in research.5−9 Generally, enhanced insensitivity is accompanied by the sacrifice of detonation performance for, e.g., 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), 4-amino-3,5-dinitropyrazole (LLM-116), and 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105)10−15 (Scheme 1), where, although they have exhibit insensitivities, their detonation performances are not comparable to that of the traditional explosive RDX. Therefore, searching for energetic materials with outstanding safety properties and good detonation performances is ongoing. The use of azoles as precursors has offered a promising solution for the preparation of novel energetic materials in recent years. It has been found that pyrazole and its derivatives show low sensitivity but low energy, making them unable to supply sufficient energy output.16 On the contrary, pentazole and its derivatives meet the requirements of high energy but also high sensitivity, which present an extremely high potential risk.17,18 Due to the high nitrogen content and high heats of ■ © XXXX American Chemical Society Received: October 10, 2020 A https://dx.doi.org/10.1021/acs.inorgchem.0c03014 Inorg. Chem. XXXX, XXX, XXX−XXX Inorganic Chemistry pubs.acs.org/IC Article Scheme 1. Typical Insensitive Energetic Compounds (TATB, LLM-116, and LLM-105) and the Multi-triazole Studied in This Work Scheme 2. Synthesis of TTT and Its Energetic Salts (TTT-1−5) unless otherwise stated. The IR spectra were recorded by using KBr plates on a Thermo Nicolet AVATAR 370 spectrometer. Densities were measured at room temperature by using a Micromeritics AccuPyc II 1340 gas pycnometer. Elemental analyses (C, H, and N) were carried out by a Vario Micro cube Elementar Analyzer. The impact sensitivity was determined with a standard BAM Fallhammer, and friction sensitivity by using a BAM friction apparatus. Synthesis of TTT. A well-stirred mixture of 1 (6.28 g, 40.0 mmol, 1.0 equiv) and diaminoguanidine monohydrochloride (13.08 g, 104 mmol, 2.6 equiv) was added slowly to a solution of phosphorus pentoxide (16 g) in phosphoric acid (56 g) at 45 °C. The reaction mixture was heated slowly to 120 °C and stirred for an additional 4 h. After the mixture had cooled to room temperature, ice−water (150 mL) was poured into the mixture and then a solution of NaOH (10 M, 50 mL) was added to neutralize the reaction mixture; the precipitate was collected and washed repeatedly with water (100 mL). The product was purified by being recrystallized from glacial acetic acid (200 mL). TTT. White solid. Yield: 7.37 g, 70%. Td (onset): 290 °C. 1H NMR: δ 6.01 (s, 4H), 5.98 (s, 4H). 13C NMR: δ 156.0, 141.9, 131.5. IR (KBr): ν̃ balance between energy and sensitivity. In this work, TTT and TT (Scheme 2 and Scheme 3) were selected as target compounds on the basis of this methodology, and all of them are well characterized. ■ EXPERIMENTAL SECTION Caution! All of the materials described in this work are potentially energetic compounds, which could lead to explosion in same cases such as impact, friction, or electric discharge. Appropriate safety precautions, including safety goggles, face shields, and gloves, are strongly recommended at all times. General. All chemicals were purchased in analytical grade and used without further purification. Decomposition temperatures (onset) were performed with a differential scanning calorimeter (DSC, TA Instruments Q2000) at a heating rate of 5 °C min−1. The 1H and 13C NMR spectra were recorded on a Bruker AVANCE 300 instrument with frequencies of 300 and 75 MHz, respectively. Chemical shifts are given relative to (CH3)4Si. [D6]DMSO was used as a locking solvent B https://dx.doi.org/10.1021/acs.inorgchem.0c03014 Inorg. Chem. XXXX, XXX, XXX−XXX Inorganic Chemistry pubs.acs.org/IC Article Scheme 3. Synthesis of TT and Its Energetic Salts (TT-1−9) 142.2, 131.8. IR (KBr): ν̃ 3588, 3412, 3315, 1698, 1655, 1637, 1541, 1457, 1415, 1402, 1375, 138, 1288, 1132, 1055, 1032, 987, 972, 947, 815, 792, 777, 746, 694, 626, 597 cm−1. Elemental analysis for C10H13N23O7 (567.37). Calcd: C, 21.17%; H, 2.31%; N, 56.78%. Found: C, 21.15%; H, 2.35%; N, 56.49%. TTT-5·H2O. Yellow solid. Yield: 0.53 g, 90%. Td (onset): 244 °C. 1H NMR: δ 7.38 (s, 4H), 6.02 (s, 4H). 13C NMR: δ 155.1, 155.0, 153.9, 153.7, 151.3, 142.4, 131.5. IR (KBr): ν̃ 3469, 3400, 3349, 3107, 1701, 1661, 1561, 1518, 1498, 1473, 1436, 1405, 1385, 1279, 1176, 1099, 1076, 1043, 991, 967, 949, 923, 859, 821, 795, 777, 750, 734, 706 cm−1. Elemental analysis for C10H13N23O8 (583.37). Calcd: C, 20.59%; H, 2.25%; N, 55.22%. Found: C, 20.62%; H, 2.38%; N, 55.64%. Synthesis of TT. A well-stirred mixture of 2 (5.12 g, 40.0 mmol, 1.0 equiv) and diaminoguanidine monohydrochloride (6.54 g, 52 mmol, 1.3 equiv) was added slowly to a solution of phosphorus pentoxide (16 g) in phosphoric acid (56 g) at 45 °C. The reaction mixture was slowly heated to 120 °C and stirred for an additional 4 h. After the mixture had cooled to room temperature, ice−water (150 mL) was poured into the mixture and then a solution of NaOH (10 M, 50 mL) was used to neutralize the reaction mixture; the precipitate was collected and washed repeatedly with water (50 mL). The crude product was purified by being recrystallized with glacial acetic acid (200 mL). TT. White solid. Yield: 5.43 g, 75%. Td (onset): 341 °C. 1H NMR: δ 12.33 (s, 1H), 6.18 (s, 2H), 5.79 (s, 2H), 5.67 (s, 2H). 13C NMR: δ 156.8, 155.0, 150.1, 142.1. IR (KBr): ν̃ 3426, 3314, 3163, 2851, 1673, 1638, 1558, 1518, 1483, 1409, 1372, 1310, 1127, 1062, 990, 910, 754, 711 cm−1. Elemental analysis for C4H7N9 (181.16). Calcd: C, 26.52%; H, 3.89%; N, 69.59%. Found: C, 26.44%; H, 4.09%; N, 69.12%. Synthesis of TT-1. TT (0.36 g, 2.0 mmol) was added to diluted nitric acid (15 mL, 10%), and the reaction mixture was heated to 50 °C and stirred for 30 min. After the nitric acid had been removed, the residue was recrystallized in a water/ethanol mixture to give TT-1. TT-1. White solid. Yield: 0.52 g, 85%. Tm: 116 °C. Td (onset): 211 °C. 1 H NMR: δ 8.33 (s, 2H), 6.82 (br, 4H). 13C NMR: δ 156.1, 151.4, 3335, 3149, 1707, 1647, 1578, 1548, 1400, 1340, 1284, 1228, 1176, 1037, 976, 796, 753, 721, 693, 585 cm−1. Elemental analysis for C6H9N13 (263.23). Calcd: C, 27.38%; H, 3.45%; N, 69.18%. Found: C, 27.58%; H, 3.27%; N, 69.98%. Synthesis of TTT-1. A mixture of 3,4,5-trinitropyrazole (0.40 g, 2.0 mmol) and TTT (0.26 g, 1.0 mmol) in water (50 mL) was heated at reflux and stirred for 30 min. The precipitate was collected by filtration to give TTT-1. TTT-1. White solid. Yield: 0.61 g, 91%. Td (onset): 241 °C. 1H NMR: δ 7.92 (s, 4H), 6.00 (s, 4H). 13C NMR: δ 152.7, 146.9, 142.3, 131.6, 122.0. IR (KBr): ν̃ 3449, 3358, 1707, 1638, 1542, 1522, 1461, 1366, 1321, 1299, 1088, 1029, 972, 927, 850, 804, 782, 717, 618 cm−1. Elemental analysis for C12H11N23O12 (669.36). Calcd: C, 21.53%; H, 1.66%; N, 48.13%. Found: C, 21.14%; H, 2.27%; N, 49.27%. General Procedure for the Synthesis of TTT-2−5. A mixture of energetic acid (1.0 mmol for 4,4′,5,5′-tetranitro-1H,1′H-2,2′-biimidazole, 5,5′-bistetrazole-1,1′-diol, 3,3′-dinitroamino-4,4′-azofurazan, or 3,3′-dinitroamino-4,4′-azoxyfurazan) and TTT (0.26 g, 1.0 mmol) in water (50 mL) was heated to reflux and stirred for 30 min. The precipitate was collected by filtration to give products. TTT-2. Yellow solid. Yield: 0.51 g, 89%. Td (onset): 213 °C. 1H NMR: δ 8.42 (s, 4H), 6.06 (s, 4H). 13C NMR: δ 151.9, 142.2, 142.0, 139.5, 131.7. IR (KBr): ν̃ 3362, 1702, 1637, 1541, 1389, 1304, 1274, 1221, 1113, 991, 972, 854, 753, 709 cm −1. Elemental analysis for C12H11N21O8 (577.35). Calcd: C, 24.96%; H, 1.92%; N, 50.95%. Found: C, 24.67%; H, 2.00%; N, 49.29%. TTT-3·H2O. White solid. Yield: 0.42 g, 92%. Tm: 182 °C. Td (onset): 195 °C. 1H NMR: δ 7.31 (s, 4H), 6.01 (s, 4H). 13C NMR: δ 153.8, 142.3, 135.1, 131.4. IR (KBr): ν̃ 3116, 1696, 1637, 1597, 1409, 1355, 1297, 1234, 1169, 1026, 998, 968, 793, 733, 702, 602, 502 cm−1. Elemental analysis for C8H13N21O3 (451.33). Calcd: C, 21.29%; H, 2.90%; N, 65.17%. Found: C, 21.60%; H, 2.93%; N, 66.00%. TTT-4·H2O. Orange solid. Yield: 0.52 g, 92%. Td (onset): 174 °C. 1H NMR: δ 8.42 (s, 4H), 5.99 (s, 4H). 13C NMR: δ 160.0, 152.4, 151.8, C https://dx.doi.org/10.1021/acs.inorgchem.0c03014 Inorg. Chem. XXXX, XXX, XXX−XXX Inorganic Chemistry pubs.acs.org/IC 145.1, 141.8. IR (KBr): ν̃ 3336, 3134, 1702, 1609, 1551, 1515, 1384, 1313, 1222, 1044, 979, 984, 820, 792, 747, 692. Elemental analysis for C4H9N11O6 (307.19). Calcd: C, 15.64%; H, 2.95%; N, 50.16%. Found: C, 15.72%; H, 3.02%; N, 50.32%. General Procedure for the Synthesis of TT-2−5. Energetic acid (2.0 mmol for 3,4,5-trinitropyrazole, 2,4-dinitroimidazole, 4,5-dinitroimidazole, or 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one) was added to a suspension of TT (0.36 g, 2.0 mmol) in water (50 mL). The reaction mixture was heated to reflux and stirred for 30 min. The precipitate was collected by filtration to give products. TT-2. White solid. Yield: 0.68 g, 89%. Td (onset): 187 °C. 1H NMR: δ 12.70 (br), 7.66 (s, 2H), 6.36 (s, 2H), 6.04 (s, 2H). 13C NMR: δ 157.4, 151.9, 147.8, 146.9, 142.5, 122.0. IR (KBr): ν̃ 3426, 3343, 1702, 1648, 1518, 1489, 1456, 1400, 1363, 1321, 1302, 1257, 1132, 1056, 976, 850, 805, 689 cm−1. Elemental analysis for C7H8N14O6 (384.23). Calcd: C, 21.88%; H, 2.10%; N, 51.04%. Found: C, 21.73%; H, 2.23%; N, 51.53%. TT-3. Yellow solid. Yield: 0.61 g, 90%. Td (onset): 268 °C. 1H NMR: δ 12.79 (br), 8.18 (s, 2H), 7.71 (s, 1H), 6.42 (s, 2H), 6.11 (s, 2H). 13C NMR: δ 157.3, 153.9, 151.2, 147.5, 146.8, 142.7, 130.0. IR (KBr): ν̃ 3471, 3431, 3404, 3323, 1708, 1648, 1589, 1513, 1481, 1432, 1402, 1354, 1304, 1253, 1232, 1156, 1042, 1002, 978, 840, 824, 758, 680 cm−1. Elemental analysis for C7H9N13O4 (339.23). Calcd: C, 24.78%; H, 2.67%; N, 53.68%. Found: C, 24.48%; H, 2.80%; N, 53.26%. TT-4·2H2O. Light-yellow crystals. Yield: 0.69 g, 92%. Tm: 92 °C (without H2O). Td (onset): 178 °C. 1H NMR: δ 13.01 (br), 8.14 (s, 2H), 6.97 (s, 1H), 6.42 (s, 2H), 6.11 (s, 2H). 13C NMR: δ 157.4, 151.3, 147.5, 142.7, 140.2, 139.3. IR (KBr): ν̃ 1705, 1637, 1525, 1477, 1452, 1385, 1358, 1307, 1259, 1176, 1126, 1099, 1065, 974, 814, 670 cm−1. Elemental analysis for C7H13N13O6 (375.26). Calcd: C, 22.40%; H, 3.49%; N, 48.52%. Found: C, 22.15%; H, 3.47%; N, 48.91%. TT-5·H2O. Yellow solid. Yield: 0.59 g, 90%. Tm: 161 °C. Td (onset): 202 °C. 1H NMR: δ 6.73 (s, 2H), 6.30 (s, 2H), 5.93 (s, 2H). 13C NMR: δ 159.9, 157.5, 154.1, 153.8, 148.6, 142.1. IR (KBr): ν̃ 3440, 1702, 1654, 1599, 1521, 1388, 1314, 1253, 1128, 1095, 1055, 1015, 781, 745, 714, 612, 502 cm−1. Elemental analysis for C6H11N13O4 (329.24). Calcd: C, 21.89%; H, 3.37%; N, 55.31%. Found: C, 21.94%; H, 3.69%; N, 56.30%. General Procedure for the Synthesis of TT-6−9. Energetic acid (1.0 mmol for 4,4′,5,5′-tetranitro-1H,1′H-2,2′-biimidazole, 5,5′-bistetrazole-1,1′-diol, 3,3′-dinitroamino-4,4′-azofurazan, or 3,3′-dinitroamino4,4′-azoxyfurazan) was added to a suspension of TT (0.36 g, 2.0 mmol) in water (50 mL). The reaction mixture was heated to reflux and stirred for 30 min. The precipitate was collected by filtration to give products. TT-6. Orange-red solid. Yield: 0.60 g, 88%. Td (onset): 282 °C. 1H NMR: δ 12.89 (br), 8.16 (s, 2H), 6.42 (s, 2H), 6.10 (s, 2H). 13C NMR: δ 157.4, 151.2, 147.4, 143.9, 142.6, 140.3. IR (KBr): ν̃ 3465, 3358, 3211, 1716, 1655, 1611, 1525, 1494, 1478, 1379, 1353, 1300, 1206, 1111, 1068, 1022, 964, 904, 859, 814, 770, 754, 702, 676 cm−1. Elemental analysis for C14H16N26O8 (676.45). Calcd: C, 24.86%; H, 2.38%; N, 53.84%. Found: C, 24.95%; H, 2.53%; N, 53.13%. TT-7. White crystals. Yield: 0.45 g, 85%. Td (onset): 257 °C. 1H NMR: δ 7.05 (s, 2H), 6.29 (s, 2H), 5.97 (s, 2H). 13C NMR: δ 157.4, 153.0, 148.3, 142.3, 135.1. IR (KBr): ν̃ 3443, 1702, 1638, 1509, 1483, 1406, 1385, 1307, 1235, 1176, 1043, 981, 793, 737, 713 cm−1. Elemental analysis for C10H16N26O2 (532.42). Calcd: C, 22.56%; H, 3.03%; N, 68.40%. Found: C, 22.75%; H, 3.17%; N, 68.87%. TT-8·2H2O. Brown solid. Yield: 0.64 g, 94%. Td (onset): 226 °C. 1H NMR: δ 12.84 (br), 8.24 (s, 2H), 6.25 (s, 2H), 6.10 (s, 2H). 13C NMR: δ 160.0, 157.4, 152.4, 151.2, 147.3, 142.7. IR (KBr): ν̃ 3420, 3318, 1693, 1644, 1595, 1532, 1491, 1463, 1419, 1392, 1366, 1307, 1130, 1095, 1059, 1005, 949, 829, 792, 769, 738, 710, 689, 644, 592 cm−1. Elemental analysis for C12H20N28O8 (684.47). Calcd: C, 21.06%; H, 2.95%; N, 57.30%. Found: C, 21.03%; H, 2.97%; N, 56.53%. TT-9·2H2O. Yellow solid. Yield: 0.64 g, 92%. Td (onset): 187 °C. 1H NMR: δ 12.82 (br), 8.22(s, 2H), 6.42 (s, 2H), 6.11 (s, 2H). 13C NMR: δ 157.4, 155.1, 155.0, 154.0, 151.3, 147.4, 142.8. IR (KBr): ν̃ 3523, 3416, 3315, 3168, 1701, 1640, 1604, 1567, 1531, 1485, 1459, 1423, 1395, 1294, 1191, 1124, 1086, 1053, 998, 958, 948, 831, 813, 797, 775, 747, 735, 719, 707, 687 cm−1. Elemental analysis for C12H20N28O9 (700.47). Calcd: C, 20.58%; H, 2.88%; N, 55.99%. Found: C, 20.44%; H, 2.92%; N, 55.18%. Article Computational Methods. The gas phase heats of formation were computed using isodesmic reactions (Supporting Information). The enthalpy of reaction is obtained by combining the MP2/6-311++G** energy difference for the reactions, the scaled zero-point energies (ZPE), values of thermal correction (HT), and other thermal factors. The solid-state heats of formation for neutral compounds (TT and TTT) were estimated by subtracting gas phase enthalpies with the corresponding enthalpy of sublimation (ΔHsub). In eq 1, T represents either the melting point or the decomposition temperature when no melting occurs prior to decomposition.28 ΔHsub = 188/J mol−1 K−1 × T (1) For salts, the solid-state enthalpy of formation is obtained using a Born−Haber energy cycle.29 For compounds that are hydrates (TTT3·H2O, TTT-4·H2O, TTT-5·H2O, TT-4·2H2O, TT-5·H2O, TT-8· 2H2O, and TT-9·2H2O), the solid-state enthalpy of formation is calculated by adding the solid phase heat of formation of the anhydrous compound to that of water (−241.8 kJ mol−1).30 Single-Crystal X-ray Diffraction Determination. A suitable yellow needle crystal (TTT-3·2.667H2O) with dimensions of 0.21 mm × 0.07 mm × 0.02 mm, a suitable colorless block crystal (TT-1·H2O) with dimensions of 0.10 mm × 0.06 mm × 0.02 mm, a suitable colorless plate crystal (TT-4·2H2O) with dimensions of 0.11 mm × 0.10 mm × 0.03 mm, or a suitable colorless needle crystal (TT-7·2H2O) with dimensions of 0.12 mm × 0.03 mm × 0.03 mm was selected and mounted on a nylon loop with paratone oil on an XtaLAB Synergy, Dualflex, HyPix diffractometer. The crystal was kept at a steady tenperature of 100.00(10) K during data collection. The structure was determined with the ShelXT solution program using dual methods and by using Olex2 as the graphical interface.31,32 The model was refined with ShelXL using full matrix least-squares minimization on F2.33 In TT-1, TT-4, and TT-7, all hydrogen atoms were found by difference Fourier methods and refined isotropically. TT-4 also was shown to be a twin crystal (all crystals tested) where the Twin Law was to have component 2 rotated by 179.99° around the [0 0 1] reciprocal axis and the [0.15 −0.46 0.87] direct axis with the BASF component refined to 0.5498(12) using the TWIN5 file. TTT-3 was found to contain water molecules in disordered locations in the cell, and this prevented us from finding and refining the hydrogen atoms so they were placed in calculated positions. RESULTS AND DISCUSSION Synthesis. As shown in Scheme 2, compound TTT was synthesized using a one-step reaction from the commercially available reactant 2H-1,2,3-triazole-4,5-dicarboxylic acid (1), which was mixed with diaminoguanidine monohydrochloride and then added to a mixture of phosphorus pentoxide and phosphoric acid. The reaction mixture was stirred at 120 °C for 4 h. Then it was poured into ice−water, and a solution of NaOH (20%) was added until the pH was ∼7. The precipitate was collected and washed with hot water to give TTT. A series of its nitrogen-rich salts TTT−1−5 were synthesized by neutralization reactions. These products were isolated in high yields and are stable in air. As shown in Scheme 3, compound TT was synthesized in a similar manner. Reactant 2 and diaminoguanidine monohydrochloride were added to a mixture of phosphorus pentoxide and phosphoric acid preheated to 45 °C. The reaction mixture was stirred at 120 °C for 4 h to give TT in a high yield (75%). The nitrogen-rich salts TT-1−9 were synthesized through neutralization reactions of TT with a variety of energetic acids. It should be noted that both triazole rings were protonated with nitric acid to give the dinitrate salt (TT-1), which was studied by singlecrystal X-ray diffraction analysis. Analysis of NMR Spectra. All of the compounds were determined by 1H and 13C NMR spectroscopy. The spectra are ■ D https://dx.doi.org/10.1021/acs.inorgchem.0c03014 Inorg. Chem. XXXX, XXX, XXX−XXX Inorganic Chemistry pubs.acs.org/IC Article Table 1. Crystallographic Data and Structure Determination Details for TTT-3·2.667H2O, TT-1·H2O, TT-4·2H2O, and TT-7· 2H2O CCDC number Dcalc (g cm−3) T (K) crystal system space group a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) V (Å3) Z θmin (deg) θmax (deg) GoF wR2 (all data) wR2 [I > 2σ(I)] R1 (all data) R1 [I > 2σ(I)] TTT-3·2.667H2O TT-1·H2O TT-4·2H2O TT-7·2H2O 2036212 1.647 100(10) orthorhombic Pccn 8.04136(18) 31.8342(6) 22.7569(4) 90 90 90 5825.5(2) 12 2.776 77.205 1.052 0.1390 0.1332 0.0619 0.0529 2036210 1.793 100(10) triclinic P1̅ 6.6380(3) 7.2931(3) 13.9010(6) 75.379(3) 81.775(4) 67.925(4) 602.57(5) 2 3.290 76.955 1.044 0.1068 0.0980 0.0491 0.0392 2036211 1.698 100(10) triclinic P1̅ 6.9595(2) 7.8226(2) 14.9928(5) 75.838(3) 88.924(3) 68.491(2) 734.03(4) 2 3.049 77.229 1.081 0.1097 0.1088 0.0406 0.0395 2036213 1.663 100(10) triclinic P1̅ 7.8161(9) 8.4093(9) 9.5265(6) 97.240(7) 107.014(8) 104.038(10) 567.62(10) 2 4.968 76.870 1.074 0.1558 0.1463 0.0652 0.0539 Figure 1. (a) Molecular structure of TTT-3·2.667H2O. Water molecules have been omitted for the sake of clarity. (b) Packing diagram of TTT-3· 2.667H2O. given in Figures S1−S32. In the 1H NMR spectrum of TTT, there are two signals at 6.01 and 5.98 ppm assigned to the two amino groups on the 3,4-diaminotriazole rings. The -NH on the 1,2,3-triazole ring was not detected. For the salts (TTT-1−5), one signal was observed around 6.00 ppm while the other signal for the amino group was downshifted to 7.31−8.42 ppm due to the protonation of the 1,2,4-triazole rings and the effects of different energetic anions. However, the NH signals were not detected here either. In the 1H NMR spectrum of TT, three signals for the three amino groups were observed and the signal for NH on the triazole were also found at 12.33 ppm. For TT-1− 9, it is worth noting that N−H protons were detected in TT-2− 4, TT-6, TT-8, and TT-9, while in the other cases, they were not. This may be caused by rapid proton exchange between the TT cation and deuterated reagent as well as different attractions of the anions. In the 13C NMR spectra, all of the signals are found as expected. Single-Crystal X-ray Structure Analysis. The crystal structures of compounds TTT-3·2.667H2O, TT-1·H2O, TT-4· 2H2O, and TT-7·2H2O were determined. The crystallographic data and structure determination details are listed in Table 1. Detailed information, including bond lengths and bond angles, is available in the Supporting Information. TTT-3·2.667H2O crystallizes in orthorhombic space group Pccn with 12 chemical formula units per unit cell, and the molecular structure is shown in Figure 1a. The calculated crystal density is 1.647 g cm−3 at 100 K. The two protonating hydrogen atoms are located on N14 and N22, respectively. A variety of intermolecular and intramolecular hydrogen bonds (N···H and O···H) ranged in length from 1.38 to 2.21 Å (Figure 1b). Rings A and B are nearly coplanar with a N(15)−C(1)−C(3)−C(4) torsion angle of 172.7° and a N(15)−C(1)−C(3)−N(18) torsion angle of −4.1°. However, ring C is twisted out of the plane of ring B with a C(3)−C(4)−C(5)−N(23) torsion angle E https://dx.doi.org/10.1021/acs.inorgchem.0c03014 Inorg. Chem. XXXX, XXX, XXX−XXX Inorganic Chemistry pubs.acs.org/IC Article Figure 2. (a) Molecular structure of TT-1·H2O. (b) Packing diagram of TT-1·H2O. Figure 3. (a) Molecular structure of TT-4·2H2O. (b) Packing diagram of TT-4·2H2O. triazole rings have a N(7)−C(5)−C(6)−N(10) torsion angle of 6.0° and a N(7)−C(5)−C(6)−N(12) torsion angle of 174.8°. The bicyclic cation shows good coplanar characteristics compared to that of TT-1·H2O. The C5−C6 bond length is 1.45 Å, which is a somewhat shorter than that in TT-1·H2O. TT-7·2H2O crystallizes in triclinic space group P1̅ with two chemical formula units per unit cell. The molecular structure is shown in Figure 4a. The crystal density is 1.663 g cm−3 at 100 K. The protonating hydrogen atom is located on N(10). An abundance of hydrogen bonds such as N10−H10···N4 (2.03 Å) and N6−H6···O1W (2.08 Å) hydrogen bonds formed between the bicyclic cation and 5,5-bistetrazole-1,1-diolate anion as well as water molecules (Figure 4b). The two triazole rings have a N(5)−C(3)−C(4)−N(11) torsion angle of 7.4° and a N(7)− C(3)−C(4)−N(9) torsion angle of 7.8°. In addition to this, the 5,5-bistetrazole-1,1-diolate also shows good coplanar characteristics, which lead to tightness of the coplanar packing of the molecule. The C3−C4 bond length is 1.46 Å, which is equal to that in TT-1·H2O. of 59.8° and a C(3)−C(4)−C(5)−N(21) torsion angle of −117.9°. Compound TT-1·H2O crystallizes in triclinic space group P1̅ with two chemical formula units per unit cell, and the molecular structure is shown in Figure 2a. The calculated crystal density is 1.793 g cm−3 at 100 K. One molecule of TT consists of two nitrates and one bicyclic cation with two protonating hydrogen atoms on N2 and N7. Due to the presence of the nitrate anions and water molecules, many strong intramolecular and intermolecular hydrogen bonds (N···H and O···H) ranged in length from 1.76 to 2.43 Å (Figure 2b). The two triazole rings have a N(1)−C(1)−C(3)−N(6) torsion angle of −166.2° and a N(1)−C(1)−C(3)−N(8) torsion angle of 14.8°. The C1−C3 bond length is 1.46 Å. TT-4·2H2O crystallizes in triclinic space group P1̅ with two chemical formula units per unit. The molecular structure is shown in Figure 3a. The calculated crystal density is 1.698 g cm−3 at 100 K. The protonating hydrogen atom is located on N(6). Several hydrogen bond interactions are present with lengths ranging from 1.85 to 2.30 Å (Figure 3b). The two F https://dx.doi.org/10.1021/acs.inorgchem.0c03014 Inorg. Chem. XXXX, XXX, XXX−XXX Inorganic Chemistry pubs.acs.org/IC Article Figure 4. (a) Molecular structure of TT-7·2H2O. (b) Packing diagram of TT-7·2H2O. Table 2. Energetic Properties and Detonation Parameters of TTT and Its Salts compound ρa (g cm−3) Dvb (m s−1) Pc (GPa) Ωd (%) Ne (%) ΔHff (kJ mol−1/kJ g−1) Tdg (°C) ISh (J) FSi (N) TTT TTT-1 TTT-2 TTT-3·H2O TTT-4·H2O TTT-5·H2O TNTj RDXj 1.65 1.75 1.77 1.68 1.72 1.74 1.65 1.80 7806 8715 7889 7859 8101 8264 6881 8795 20.7 32.6 23.7 21.9 24.8 26.6 19.5 34.9 −63.83 −13.15 −26.33 −40.77 −26.79 −23.31 −24.66 0 69.18 48.13 50.95 65.17 56.78 55.22 18.50 37.84 763.0/2.90 1930.8/2.88 457.2/0.79 770.3/1.71 884.0/1.56 922.4/1.58 −59.3/−0.26 70.3/0.32 290 241 213 195 174 244 300 204 >40 >40 >40 30 28 25 15 7.4 >360 >360 >360 >360 >360 >360 353 120 a Density measured by a gas pycnometer at 25 °C. bCalculated detonation velocity. cCalculated detonation pressure. dOxygen balance assuming the formation of CO. eNitrogen content. fCalculated molar enthalpy of formation in the solid state. gTemperature of decomposition (onset). hImpact sensitivity. iFriction sensitivity. jData from ref 34. Table 3. Energetic Properties and Detonation Parameters of TT and Its Salts compound ρa (g cm−3) Dvb (m s−1) Pc (GPa) Ωd (%) Ne (%) ΔHff (kJ mol−1/kJ g−1) Tdg (°C) ISh (J) FSi (N) TT TT-1 TT-2 TT-3 TT-4·2H2O TT-5·H2O TT-6 TT-7 TT-8·2H2O TT-9·2H2O TNTj HNSj RDXj 1.68 1.78 1.75 1.73 1.70 1.71 1.78 1.74 1.74 1.69 1.65 1.74 1.80 7818 8235 8698 7994 7887 7884 8252 8519 8456 8273 6881 7612 8795 20.4 26.5 31.3 23.6 22.9 22.2 26.0 26.7 27.3 25.8 19.5 24.3 34.9 −66.24 −13.02 −20.82 −35.37 −31.98 −36.45 −33.11 −48.08 −32.73 −29.69 −24.66 −17.77 0 69.59 50.16 51.04 53.68 48.52 55.31 53.84 68.40 57.30 55.99 18.50 18.67 37.84 396.8/2.19 −219.7/−0.72 1108.9/2.89 429.0/1.26 −16.3/−0.04 126.8/0.39 1067.8/0.39 1602.8/3.01 1726.2/2.66 1315.2/1.88 −59.3/−0.26 78.2/0.17 70.3/0.32 341 211 187 268 178 202 282 257 226 187 300 318 204 >40 30 >40 >40 >40 >40 >40 30 22 20 15 5 7.4 >360 >360 >360 >360 >360 >360 >360 360 360 360 353 240 120 a Density measured by a gas pycnometer at 25 °C. bCalculated detonation velocity. cCalculated detonation pressure. dOxygen balance assuming the formation of CO. eNitrogen content. fCalculated molar enthalpy of formation in the solid state. gTemperature of decomposition (onset). hImpact sensitivity. iFriction sensitivity. jData from ref 34. The heats of formation were calculated by using Gaussion 03 software.35 Due to the high nitrogen content of the multiaminotriazoles, TTT and its salts display high positive heats of formation. With the measured densities and calculated heats of formation, detonation velocities (Dv) and detonation pressures (P) were calculated with EXPLO5 software.36 These com- Physicochemical and Energetic Properties. Density is an important parameter in the field of energetic materials. The higher the density of a compound, the better the detonation properties. Densities were measured by using a gas pycnometer at 25 °C. The densities of TTT and its nitrogen-rich salts range from 1.65 to 1.77 g cm−3 (Table 2). G https://dx.doi.org/10.1021/acs.inorgchem.0c03014 Inorg. Chem. XXXX, XXX, XXX−XXX Inorganic Chemistry pubs.acs.org/IC pounds exhibit good detonation velocities and detonation pressures (Dv = 7806−8715 m s−1, and P = 20.7−32.6 GPa). Among them, TTT-1 possesses remarkable detonation properties (Dv = 8715 m s−1, and P = 32.6 GPa), which are superior to those of TNT (Dv = 6881 m s−1, and P = 19.5 GPa) and almost the same as those of RDX (Dv = 8795 m s−1, and P = 34.9 GPa). The thermal behavior was determined by differential scanning calorimetry (DSC) at a rate of 5 °C min−1. The onset decomposition temperature of TTT is 290 °C, which is superior to that of RDX (Td = 204 °C) and comparable to that of TNT (Td = 300 °C). In addition to thermal stability, mechanical sensitivities to impact and friction were determined.37 All of the compounds exhibit good mechanical sensitivities (IS > 25 J, and FS > 360 N). Furthermore, TTT and its nitrogen-rich salts, TTT-1 and TTT-2, are very insensitive explosives with IS values of >40 J and FS values of >360 N. The energetic parameters and detonation properties of TT and its salts were also measured or calculated (Table 3). The densities of TT and its nitrogen-rich salts are in the range of 1.68−1.78 g cm−3. The Dv and P of TT and its salts fall between 7818 and 8698 m s−1 and between 20.4 and 31.3 GPa, respectively. TT-2 has good detonation properties (Dv = 8698 m s−1, and P = 31.3 GPa), which are comparable to those of RDX (Dv = 8795 m s−1, and P = 34.9 GPa). Compound TT and most of its salts possess high positive heats of formation. More importantly, TT with two aminotriazoles has an ultrahigh decomposition temperature of 341 °C, which is superior to that of HNS (Td = 318 °C). Therefore, it has a very good potential application in heat-resistant explosives. In addition to the prominent thermal stability, TT is also mechanically insensitive with an IS of >40 J and an FS of >360 N, which supports high safety guarantees for future applications. In contrast to polyamino-substituted furazan-triazole,24,25 TTT and TT have higher nitrogen contents (∼70%) due to the incorporation of triazole moieties. Most of their derivatives also have high nitrogen contents of >50%. The high nitrogen contents might allow them to find applications in gas generators. Article Crystal structure analysis of TTT-3·2.667H2O, TT-1· H2O, TT-4·2H2O, and TT-7·2H2O, isodesmic reactions, NMR spectra, and DSC plots (PDF) Accession Codes CCDC 2036210−2036213 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033. ■ AUTHOR INFORMATION Corresponding Authors Yongxing Tang − Nanjing University of Science and Technology, Nanjing 210094, China; Department of Chemistry, University of Idaho, Moscow, Idaho 83844-2343, United States; orcid.org/0000-0002-9549-9195; Email: yongxing@njust.edu.cn Jean’ne M. Shreeve − Department of Chemistry, University of Idaho, Moscow, Idaho 83844-2343, United States; orcid.org/0000-0001-8622-4897; Email: jshreeve@ uidaho.edu Authors Zhaoyang Yin − Nanjing University of Science and Technology, Nanjing 210094, China Ajay Kumar Chinnam − Department of Chemistry, University of Idaho, Moscow, Idaho 83844-2343, United States; orcid.org/0000-0001-8643-5694 Richard J. Staples − Department of Chemistry, Michigan State University, East Lansing, Michigan 48825, United States; orcid.org/0000-0003-2760-769X Complete contact information is available at: https://pubs.acs.org/10.1021/acs.inorgchem.0c03014 Author Contributions ∥ Y.T. and Z.Y. contributed equally to this work. Notes CONCLUSION In summary, two novel thermally stable and insensitive energetic materials based on multi-aminotriazoles (TTT and TT) were explored and synthesized. Their energetic salts were synthesized, as well. TT, based on two triazoles, displays an ultrahigh decomposition temperature of 341 °C, which is superior to that of HNS (Td = 318 °C) and those of most triazole-containing explosives. It has great potential as a heat-resistant explosive. TTT-1 based on three triazoles shows both outstanding detonation properties (Dv = 8715 m s−1, and P = 32.6 GPa) and good thermal stability as well as satisfactory sensitivities (Td = 290 °C, IS > 40 J, and FS > 360 N), indicating it could be used as a secondary explosive. Importantly, utilizing the “multiaminotriazole system” methodology could accelerate the process of exploring more high-performance energetic materials with desirable detonation properties, thermostabilities, and insensitivities. ■ ■ The authors declare no competing financial interest. ACKNOWLEDGMENTS Financial support of the Office of Naval Research (N00014-161-2089) and the Defense Threat Reduction Agency (HDTRA 115-1-0028) is gratefully acknowledged. The Rigaku Synergy S Diffractometer was purchased with support from the National Science Foundation MRI program (1919565). This work was supported by the National Natural Science Foundation of China (21905135), the Natural Science Foundation of Jiangsu Province (BK20190458), and the Large Equipment Open Funding of Nanjing University of Science and Technology. ■ ■ REFERENCES (1) Fischer, D.; Gottfried, J. L.; Klapötke, T. M.; Karaghiosoff, K.; Stierstorfer, J.; Witkowski, T. G. Synthesis and Investigation of Advanced Energetic Materials Based on Bispyrazolylmethanes. Angew. Chem., Int. Ed. 2016, 55, 16132−16135. (2) Sabatini, J. J. A Review of Illuminating Pyrotechnics. Propellants, Explos., Pyrotech. 2018, 43, 28−37. (3) Pang, W.; Fan, X.; Zhao, F.; Xu, H.; Zhang, W.; Yu, H.; Li, Y.; Liu, F.; Xie, W.; Yan, N. Effects of Different Metal Fuels on the Characteristics for HTPB-based Fuel Rich Solid Propellants. Propellants, Explos., Pyrotech. 2013, 38, 852−859. ASSOCIATED CONTENT * Supporting Information sı The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.inorgchem.0c03014. H https://dx.doi.org/10.1021/acs.inorgchem.0c03014 Inorg. Chem. XXXX, XXX, XXX−XXX Inorganic Chemistry pubs.acs.org/IC (4) Ma, J.; Tang, Y.; Cheng, G.; Imler, G. H.; Parrish, D. A.; Shreeve, J. M. Energetic Derivatives of 8-Nitropyrazolo[1,5-a][1,3,5]triazine2,4,7-triamine: Achieving Balanced Explosives by Fusing Pyrazole with Triazine. Org. Lett. 2020, 22, 1321−1325. (5) Zhang, J.; Mitchell, L. A.; Parrish, D. A.; Shreeve, J. M. Enforced Layer-by-Layer Stacking of Energetic Salts towards High-Performance Insensitive Energetic Materials. J. Am. Chem. Soc. 2015, 137, 10532− 10535. (6) Yin, P.; Zhang, J.; Imler, G. H.; Parrish, D. A.; Shreeve, J. M. Polynitro-Functionalized Dipyrazolo-1,3,5-triazinanes: Energetic Polycyclization toward High Density and Excellent Molecular Stability. Angew. Chem., Int. Ed. 2017, 56, 8834−8838. (7) Witkowski, T. G.; Sebastiao, E.; Gabidullin, B.; Hu, A.; Zhang, F.; Murugesu, M. 2,3,5,6-Tetra(1H-tetrazol-5-yl)pyrazine: A Thermally Stable Nitrogen-Rich Energetic Material. ACS Appl. Energy Mater. 2018, 1, 589−593. (8) Yuan, J.; Long, X.; Zhang, C. Influence of N-Oxide Introduction on the Stability of Nitrogen-Rich Heteroaromatic Rings: A Quantum Chemical Study. J. Phys. Chem. A 2016, 120, 9446−9457. (9) Snyder, C. J.; Wells, L. A.; Chavez, D. E.; Imler, G. H.; Parrish, D. A. Polycyclic N-oxides: High Performing, Low Sensitivity Energetic Materials. Chem. Commun. 2019, 55, 2461−2464. (10) Tang, Y.; He, C.; Imler, G. H.; Parrish, D. A.; Shreeve, J. M. Aminonitro Groups Surrounding a Fused Pyrazolotriazine Ring: A Superior Thermally Stable and Insensitive Energetic Material. ACS Appl. Energy Mater. 2019, 2, 2263−2267. (11) Cady, H. H.; Larson, A. C. The Crystal Structure of 1,3,5Triamino-2,4,6-trinitrobenzene. Acta Crystallogr. 1965, 18, 485−496. (12) Zhao, X.; Qi, C.; Zhang, L.; Wang, Y.; Li, S.; Zhao, F.; Pang, S. Amination of NitroazolesA Comparative Study of Structural and Energetic Properties. Molecules 2014, 19, 896−910. (13) Zhang, J.; Zhang, J.; Parrish, D. A.; Shreeve, J. M. Desensitization of the Dinitromethyl Group: Molecular/crystalline Factors that Affect the Sensitivities of Energetic Materials. J. Mater. Chem. A 2018, 6, 22705−22712. (14) Pagoria, P. F.; Mitchell, A. R.; Schmidt, R. D.; Simpson, R. L.; Garcia, F.; Forbes, J. W.; Swansiger, R. W.; Hoffman, D. M. Synthesis, Scale-up, and Characterization of 2,6-Diamino-3,5-dinitropyrazine-1oxide (LLM-105). Report UCRL-JC-130518; Lawrence Livermore National Laboratory: Livermore, CA, 1998. (15) Tran, T. D.; Pagoria, P. F.; Hoffman, D. M.; Cutting, J. L.; Lee, R. S.; Simpson, R. L. Characterization of 2,6-Diamino-3,5-dinitropyrazine1-oxide (LLM-105) as an Insensitive High Explosive Material. Propellants, Explos., Pyrotech. 1995, 20, 38−−42. (16) Xia, H.; Zhang, W.; Jin, Y.; Song, S.; Wang, K.; Zhang, Q. Synthesis of Thermally Stable and Insensitive Energetic Materials by Incorporating the Tetrazole Functionality into Fused Ring 3,6Dinitropyrazolo-[4,3-c]Pyrazole Framework. ACS Appl. Mater. Interfaces 2019, 11, 45914−45921. (17) Xu, Y.; Wang, Q.; Shen, C.; Lin, Q.; Wang, P.; Lu, M. A Series of Energetic Metal Pentazolate Hydrates. Nature 2017, 549, 78−81. (18) Zhang, W.; Wang, K.; Li, J.; Lin, Z.; Song, S.; Huang, S.; Liu, Y.; Nie, F.; Zhang, Q. Stabilization of the Pentazolate Anion in a Zeolitic Architecture with Na20N60 and Na24N60 Nanocages. Angew. Chem., Int. Ed. 2018, 57, 2592−2595. (19) Zhang, Y.; Parrish, D. A.; Shreeve, J. M. Derivatives of 5-Nitro1,2,3−2H-triazole − High Performance Energetic Materials. J. Mater. Chem. A 2013, 1, 585−593. (20) Haiges, R.; Bélanger-Chabot, G.; Kaplan, S. M.; Christe, K. O. Preparation and Characterization of 3,5-Dinitro-1H-1,2,4-triazole. Dalton Trans. 2015, 44, 7586−7594. (21) Zeng, Z.; Wang, R.; Twamley, B.; Parrish, D. A.; Shreeve, J. M. Polyamino-Substituted Guanyl-Triazole Dinitramide Salts with Extensive Hydrogen Bonding: Synthesis and Properties as New Energetic Materials. Chem. Mater. 2008, 20, 6176−6182. (22) Tao, G.; Twamley, B.; Shreeve, J. M. A Thermally Stable Nitrogen-rich Energetic Material − 3,4,5-Triamino-1-tetrazolyl-1,2,4triazole (TATT). J. Mater. Chem. 2009, 19, 5850−5854. Article (23) Geng, W.; Ma, Q.; Chen, Y.; Yang, W.; Jia, Y.; Li, J.; Zhang, Z.; Fan, G.; Wang, S. Structure−Performance Relationship in Thermally Stable Energetic Materials: Tunable Physical Properties of Benzopyridotetraazapentalene by Incorporating Amino Groups, Hydrogen Bonding, and π−π Interactions. Cryst. Growth Des. 2020, 20, 2106− 2114. (24) Mathpati, R. S.; Dharavath, S.; Kumar, N.; Ghule, V. D.; Paul, A. K.; Tittal, R. K. Design, Synthesis and Investigations of a Series of Energetic Salts Through the Variation of Amines and Concentration of Picrate Anions. CrystEngComm 2020, 22, 4842−4852. (25) Xiong, H.; Yang, H.; Cheng, G.; Zhang, Z. Energetic Furazan and Triazole Moieties: A Promising Heterocyclic Cation. ChemistrySelect 2019, 4, 8876−8881. (26) Liu, Y.; Xu, Y.; Yang, F.; Dong, Z.; Sun, Q.; Ding, L.; Lu, M. Achieving Good Molecular Stability in Nitrogen-rich Salts Based on Polyamino Substituted Furazan-triazole. Cryst. Growth Des. 2020, 20, 6084. (27) Ma, Q.; Chen, Y.; Liao, L.; Lu, H.; Fan, G.; Huang, J. Energetic πConjugated Vinyl Bridged Triazoles: a Thermally Stable and Insensitive Heterocyclic Cation. Dalton Trans. 2017, 46, 7467−7479. (28) Westwell, M. S.; Searle, M. S.; Wales, D. J.; Williams, D. H. Empirical Correlations Between Thermodynamic Properties and Intermolecular Forces. J. Am. Chem. Soc. 1995, 117, 5013−5015. (29) Gao, H.; Ye, C.; Piekarski, C. M.; Shreeve, J. M. Computational Characterization of Energetic Salts. J. Phys. Chem. C 2007, 111, 10718− 10731. (30) Linstrom, P. J., Mallard, W. G., Eds. NIST Chemistry WebBook, NIST Standard Reference Database Number 69, June 2005; National Institute of Standards and Technology: Gaithersburg, MD (http:// webbook.nist.gov). (31) Sheldrick, G. M. ShelXT-Integrated Space-group and Crystalstructure Determination. Acta Crystallogr., Sect. A: Found. Adv. 2015, A71, 3−8. (32) Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.; Puschmann, H. Olex2: A Complete Structure Solution, Refinement and Analysis Program. J. Appl. Crystallogr. 2009, 42, 339−341. (33) Sheldrick, G. M. Crystal Structure Refinement with ShelXL. Acta Crystallogr., Sect. C: Struct. Chem. 2015, C71, 3−8. (34) Mayer, R.; Köhler, J.; Homburg, A. Explosives, 6th ed.; WileyVCH: Weinheim, Germany, 2007. (35) Frisch, M. J.; Trucks, G. W.; Schlegel, H. G.; Scuseria, G. E.; Robb, M. A.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, A. L. G.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M.; Gonzalez, C.; Pople, J. A. Gaussian 03, rev. D.01; Gaussian, Inc.: Wallingford, CT, 2004. (36) Sućeska, M. EXPLO5, version 6.01; Brodarski Institute: Zagreb, Croatia, 2013. (37) (a) United Nations. Recommendations on the transport of dangerous goods. Manual of Tests and Criteria, 5th revised ed.; 2009. (b) 13.4.2 Test 3 (a) (ii) BAM Fallhammer, pp 75. (c) 13.5.1 Test 3 (b) (i) BAM friction apparatus, pp 104. I https://dx.doi.org/10.1021/acs.inorgchem.0c03014 Inorg. Chem. XXXX, XXX, XXX−XXX