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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*
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*
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
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© XXXX American Chemical Society
Received: October 10, 2020
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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.
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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
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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,
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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
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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
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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
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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
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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.
■
■
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