Boosting performance and safety of energetic materials by

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Boosting performance and safety of energetic materials by polymorphic transition jie tang, guangbin cheng, shenghua feng, xiao zhao, Zaichao Zhang, Xuehai Ju, and Hongwei Yang Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.9b00775 • Publication Date (Web): 15 Jul 2019 Downloaded from pubs.acs.org on July 18, 2019

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Crystal Growth & Design

Boosting performance and safety of energetic materials by polymorphic transition Jie Tang,a Guangbin Cheng,a Shenghua Feng,a Xiao Zhao,a Zaichao Zhang,b Xuehai Ju,a Hongwei Yang*,a a. School of Chemical Engineering, Nanjing University of Science and Technology, Xiaolingwei 200, Nanjing 210094, P. R. China. E-mail: [email protected] b. Jiangsu Key Laboratory for the Chemistry of Low-dimensional Materials, School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huai'an 223300, P. R. China. KEYWORDS: polymorph, structure, transition, energy, safety, indazole

ABSTRACT: An increasing attention have been witnessed to the field of crystal engineering of energetic materials very recently. This study revealed the synthesis, structure and energetic properties of 4,6-dinitro-1-(4-amino-1,2,4- triazole-2-yl)-1Hindazole(3) with two polymorphic forms, α-3 and β-3. The 4,6-dinitro-indazole derivative, α-3 with a wave-like stacking structure was synthesized by one-step reaction at room temperature. Interestingly, the β-3 could be formed at 78 °C. It is noteworthy

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Crystal Growth & Design 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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that plate-shaped α-3 crystals could transform to β-3 with needle-shaped crystals. The single-crystal diffraction data revealed that β-3 is nearly coplanar and features closer layer-by-layer package structure, thereby exhibiting increases of 0.08 g cm-3 (4.7%), 36.6 kJ mol-1 (6.1%), 667 m s-1 (9%) , 3.4 GPa (15.5%) , 88 °C (49%), 6 J (23%) and 97 N (43%) in density, heat of formation (ΔH), detonation velocity (D) and pressure (P), decomposition temperature (Tdec), impact sensitivity (IS) and friction sensitivity (FS) than α-3, respectively. Compared to TNT, the β-3 (D = 8061 m s-1, P = 25.4 GPa, IS = 32J, FS = 320N) possesses better detonation properties and sensitivities. Based on experimental results and theoretical analysis, this study provides an effective strategy for improving the performance of energetic materials in molecular design and crystal configuration.

Introduction Since Alfred Nobel has successfully improved the process of manufacturing explosives, the development of energy materials has been widely concerned in the military and civilian fields,1 such as propellants, explosives, pyrotechnics and gas generating agents.2 “Safer, greener, stronger…” are the keywords for many synthetic and theoretical researchers in the field of modern energetic material.3 However, to achieve a fine balance between these interrelated requirements remains a big challenging, especially for energy and safety, because the high energy is primarily at the expense of molecular stability.4 Molecular


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design cannot meet the needs of new high-energy-density materials (HEDMs). Therefore, a combination of physics, crystallography and chemistry must be considered to prepare high-level energy materials.5 In addition to energetic metal organic frameworks, the introduction of energetic groups and the formation of energetic salts, crystal engineering is another efficient and acceptable strategy to improve the performance of new HEDMs.6 Explosive crystals with minimal defects, ideal crystal shapes and a single polymorph with high packing density and stability have enhanced safety and increased applicability.7 Thus, the crystal engineering of HEDMs is mainly aimed at obtaining its most stable form, avoiding conversion to other less stable forms and finally realizing the applications.8, 9 There are four types of π-π stacking known as high classic energetic aromatic molecules: face-to-face, wavelike, crossing, and mixing.10 Several representative energetic compounds and their different crystal packings are shown in Figure 1. Among these, the face-to-face crystal stacking is desirable because the stacking geometries of HEDMs can absorb mechanical stimuli by converting kinetic energy into layer sliding which results in lower sensitivity.11 For instance, 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) with the face-to-face style is highly insensitive to impact, friction and heat (IS, 50J; FS, >360N; Tdec, 350°C).12


3


Face-to-face H 2N O 2N

NO2

NH2

Wavelike

NH2 NO2

TATB

O 2N

NH2

O 2N

NH2

Crossing

NH2

FOX-7

Mixing

NO2 O 2N

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NO2 NO2

TNA

O 2N

NO2 TNB

Figure 1. Four types of crystal packing and representative energetic compounds. The introduction of azole skeleton into HEDM is an effective strategy in view of the balance between high detonation performance and good mechanical sensitivity because of the relatively high formation of thermally and environmentally friendly decomposition products such as CO2, N2 and H2O.13 Triazole-based energetic materials combine heats of formation, energetic properties, and sensitivity in a fine balance.14 Owing to their wide variety of reactivity, indazole derivatives have attracted considerable interest, which inspired the developments of new syntheses, optimizations and functionalization of the indazole ring system.15 However, there is a lack of research on indazole derivatives in the literature. With our continuing efforts, herein we reported the synthesis, structure and energetic performance of 4,6-dinitro-1-(4-amino1,2,4- triazole-2-yl)-1H-indazole (3). Interestingly, two stable crystal forms of 3 (α, β) are obtained under different synthetic conditions. Polymorphic transition from α-3 crystals


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to β-3 was discussed. The target compounds were well characterized by NMR spectra, mass spectrometry, IR spectroscopy, powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and single crystal X-ray diffraction. In addition, some detonation performance tests and quantum chemical calculations were used to better understand the structure-property relationship. In view of these findings, the design of 4,6-dinitro-indazole derivatives and the exploration of their perfect microstructures may open new avenues in the following research on HEDMs. Results and discussion Synthesis. The synthesis route of 3 is shown in Scheme 1. First, the raw material 4amino-3-hydrazino-1,2,4-triazolelium chloride (2) was prepared according to the literature.16 The 2,4,6-trinitrobenzaldehyde(1) was obtained through a modified condition by raising 10 °C of the reaction temperature according to literature.17 Then, 1 and 2 were treated in ethanol to generate hydrazine intermediate with elimination of water molecule. Following that, 3 was synthesized in a 72% yield through cyclization of the intermediate due to intramolecular nucleophilic substitution for the nitro group. (Scheme 1).


5


O 2N

CHO NO2 +

NO2 1

NH2 N H N N N

2HCl

EtOH

O 2N

H 2N N H N N N N NO2

O 2N

NH2

2

NO2

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HN N 2 N N NN NO2

3

Room temperature

78oC

polymorph α

polymorph β

Scheme 1. Synthesis of compound 3

Figure 2. Preparation processes of α-3 and β-3 Obtaining an ideal polymorph is not an obvious task because the difference in free energy between polymorphs is relatively small, depending mainly on the contribution of entropy to free energy.18 The polymorphs of 4, 6-dinitro-indazole derivative 3 could be selectively formed in pure form by a finely control ling the temperature. The preparation process of α-3 and β-3 is shown in Figure 2. Powder α-3 was formed by one-step reaction of compounds 1 and 2 in ethanol at room temperature. Surprisingly,


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the β-3 was obtained if the temperature of the solution was raised to 78 °C. Inspired by this, the plate-shaped crystal of α-3 was dissolved in ethanol and then kept at 78 °C more than 5 h. To our delight, the needle-shaped crystals of β-3 were grown by slow evaporation of this solution (Figure 3). Significantly, the two polymorphs are stable at ambient pressure without solvent. The phase purity of two polymorphs was examined by comparing PXRD patterns with the simulated pattern from the single-crystal X-ray structural data. (Supporting Information, Figure S2, S3)

Figure 3. Photographs of single crystals for α-3 and β-3. Crystal Structure. Two polymorphs of 3 were further confirmed through singlecrystal X-ray diffraction and the potential relationship between molecular structures and configuration packing styles were studied. Polymorph β of 3 belongs to the monoclinic space group P21/c, which has four molecules per unit cell (Z=4) and a crystal density of 1.756 g cm-3 (Figure 4a). Polymorph α of 3 crystallizes in the orthorhombic space group Pbca, has eight molecules in each lattice cell (Z=8) and a crystal density of


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1.675 g cm-3 (Figure 4b). As shown in Figure 4c, 4d, the indazole ring belongs to the planar structure confirmed by the dihedral angle of benzene ring a and pyrazol ring b (1.029°) in α-3 or benzene ring a' and pyrazol ring b' (1.526°) in β-3. The planar structure is also supported by the torsion angles (C4-C3-N1-N2, -179.1(3)° and C1-C2-C3-C4, 179.0(3)° in β-3, C4-C3-N1-N2, -178.8(3)° and C1-C2-C3-C4, -178.8(3)° in α-3). The indazole ring and triazole ring c of α-3 are noncoplanar, which is clearly evident from the dihedral angles of plane a and plane c (40.717°) and the torsion angles (C3-N1-C8N4, 41.3(4)° and C3-N1-C8-N5, -136.5(3)° in α-3). In comparison to α-3, β-3 is more coplanar explained by the dihedral angles of plane a' and plane c' (11.265°) and the torsion angles (C3-N1-C8-N4, 10.2(5)° and C3-N1-C8-N5, -169.7(3)° in β-3). These differences give rise to the conformational difference between α-3 and β-3.


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Figure 4. a) Single-crystal X-ray structures of β-3. b) Single-crystal X-ray structures of α3. c) Planarity of β-3. d) Planarity of α-3. In addition, the crystal packing diagram of polymorphs of 3 is shown in Figure 5. Due to the close relation between the planarity of the molecules and their crystal stackings, they exhibit different behaviours in crystal stacking.19,20,10 In the α-3 molecule, the triazole ring is twisted out of the indazole plane in one molecule and stacked with triazole ring in another molecular to form an edge-to-face arrangement. This crystal unit is repeated in an infinite stack, which classifies the entire crystal as having wave-like stacking (Figure 5a). The 3D network of α-3 is formed by inter- and intra-molecular


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hydrogen bonding of monomers (Figure 5b). As for β-3, the triazole ring is slightly twisted out of the indazole plane. The crystal packing is dominated by an infinite faceto-face arrangement (Figure 5c). Furthermore, a large number of inter- and intramolecular hydrogen bond forms among the indazole rings, triazole rings, amino and nitro groups. The distance between the two indazole centroids of β-3 is less than 4.0 Å (3.350 Å, Figure 5c), indicating that two molecules are in the range of π−π interactions and packing more tightly.21 In β-3, a 3D network structure is formed by hydrogen bonding and π-π interaction (Figure 5d).

Figure 5. a) View of α-3 along a axis. b) Crystal packing diagram of α-3 along a axis. c) View of β-3 along b axis d) Crystal packing diagram of β-3 along b axis. Green lines represent HBs in crystal packing diagram.


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Energetic properties. To deeply study whether the conformational transition can improve the energetic properties. Sensitivities, thermal stabilities and detonation performances of α-3 and β-3 were determined (Table 1). The impact sensitivity (IS) and friction sensitivity (FS) of α-3, β-3 were measured to evaluate their safety against external stimuli.22 The IS and FS of α-3 were tested to be 26 J and 223 N respectively, higher than β-3 (IS, 32 J; FS, 320 N). The impact sensitivity of

Figure 6. Two-dimensional fingerprint plots in crystal stacking for α-3 and β-3 as well as the associated Hirshfeld surfaces. The fingerprint plots in crystal stacking for β-3 (a) and α-3 (b). Images (c) and (d) showing the Hirshfeld surfaces that use color coding to represent the proximity of close contacts around β-3 and α-3 molecules (white, distance d equals the van der Waals distance; blue, d exceeds the van der Waals distance; red, d is less than van der Waals distance). In images e and f, the individual atomic contacts


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percentage contribution to the Hirshfeld surface are shown in the pie graphs for β-3 and α-3, respectively. β-3 is lower than that of RDX (IS, 7 J) and TNT (IS, 15 J). To better understand the different sensitivity between α-3 and β-3, two-dimensional (2D) fingerprint and Hirshfeld surfaces were employed to analyse the weak interactions and hydrogen bonds of α-3 and β-3.23 In general, the plate shape indicates insensitivity because it represents a planar conjugated molecular structures.24 Furthermore, the red and blue regions on the Hirshfeld surfaces represent high and low close contact populations, respectively (Figure 6).25 The results can be demonstrated by 2D fingerprint plot. O−H, H−O, N−H and H−N are close contacts, and a pair of spikes at bottom left of Figure 6a, 6b are the dominant interactions in the 2D fingerprint plots of both α-3 and β-3, indicating the hydrogen bonds between adjacent molecules in the layer.26 As showed in Figure 6c, the molecule of β-3 presents an approximately planar structure and a plate shape, and most of the red dots (intermolecular interactions) are located on the surface edges. Therefore, π−π stacking exists among layers and leads to the maximum external stimuli layers can be maintained.26 While α-3 appears as uneven blocks with red dots dispersed in many orientations (Figure 6d). The value of C−N and O−C interactions (about 17%) in β-3 is higher than that in α-3 (about 14%), which indicates stronger π−π interactions in β-3 leads to more stable mechanical stability. O−H and N−H accounted for 55.1% of total interactions for β-3 and 46% for α-3 (Figure 6e, 6f), suggesting that


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hydrogen bonding is important characteristics of α-3 and β-3. These layers are formed through inter-layered intermolecular hydrogen bonds and these layers are further stacked to form the 3D supramolecular packing structure.27 In a word, π−π interactions and intramolecular hydrogen-bonding interactions, as well as the closer layer-by-layer packing, contribute to the insensitivity of β-3. To

obtain

further

information

on

inter-

and

intramolecular

effects

and

comprehensively study their influence on crystal packing, the non-covalent interaction (NCI) plots of α-3 and β-3 were performed to analyse real spatial structure based on electron density. The gradient was reduced using the method of Yang et al. In this method, analysis of the relationship between quantum-mechanical electron density (ρ) and the reduced density gradient (s= 1/2(3π2)1/3)|∇ρ|/ρ4/3) allows detection of and observation of the differences between hydrogen bonds, van der Waals interactions and repulsive steric clashes, etc.28, 29 As shown in Figure 7, more intramolecular hydrogen bonds in β-3 could be demonstrated by blue and elliptical surfaces, which theoretically were large accumulations of electron density. In addition, the π-π interaction in β-3 is more intense and abundant than α-3, which makes it easy to observe as a larger green isosurface. Overall, more π-π interaction and hydrogen bonding in β-3 results in the tighter packing and higher density, which result in reduced sensitivity to impact and friction.


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Figure 7. NCI plots of gradient isosurfaces for α-3 (b) and β-3 (a) unit cells. The surfaces are colored on a blue-green-red scale indicating strong attractive interactions, weak attractive, and strong nonbonded overlap, respectively. Thermal stability is an important property of energetic materials we concerned with, as unacceptably decomposition temperature will limit its application. Herein, differential scanning calorimetry (DSC) was carried out to determine the thermal stabilities of α-3 and β-3 with a linear heating rate of 5 °C min-1 under a nitrogen atmosphere. As shown in Figure 8, α-3 began to decompose at 179 °C and ended at 203 °C. The thermal stability of β-3 is much higher than α-3, and the initial decomposition temperature measured is 267 °C.


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Figure 8. DSC plots for α-3 and β-3 To further investigate the thermal stability, electrostatic potential surfaces (EPS) analysis for α-3 and β-3 were employed to explain the bond strength variation before and after polymorphic transition. The bond dissociation enthalpies (BDEs) for the possible trigger bond (the first bond to break) are the most important factor in pyrogenic decomposition.30 Therefore, the C8-N1 bond was found to be the trigger bond for both compounds by calculating the BDEs of α-3 and β-3. The β-3 possesses lower ESP values and more negative charge accumulation in the C8-N1 bond than α-3 (Figure 9). This negative charge accumulation will shorten and strengthen the C8-N1 bond, thus increasing the corresponding BDE and improving the thermal stability. Both compounds α-3 and β-3 exhibit positive heats of formation (ΔfH = 2.08 and 2.22 kJ g−1, respectively). The conformational transition from α-3 to β-3 increases ΔfH by 0.14 kJ g−1, leading to better detonation performance. The detonation characteristics of the


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detonation velocity and pressure were calculated using EXPLO5 (version 6.0231) based on their formation heat and crystal density. Compared with α-3 (D = 7394 m s-1, P = 22.0 GPa), β-3 (D = 8061 m s-1, P = 25.4 GPa) showed an increase of 667 m s-1, 3.4 GPa in detonation velocity and detonation pressure respectively, resulting from higher density and heat of formation (Table 1). β-3 has higher detonation velocity and detonation pressure than TNT (D = 6881 m s-1, P = 19.5 GPa). Moreover, β-3 exhibits lower impact sensitivity than the RDX and TNT, indicating that it is the potential candidate for applications requiring these properties.

Figure 9. Electrostatic potential surfaces of β-3 (a) and α-3 (b). Significant surface local minima and maxima of ESP are represented as orange and azure spheres, respectively. The maxima of ESP around C-nitro groups are labelled by brown-red texts, the units are in kcal mol-1.

Compound

Tda [°C]

ΔfHb[kJ mol-1/kJ g-1]

Dc [m s-1]

Pd [GPa]

de [g cm-3]

ISf [J]

FSg [N]


16

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α-3

179

605.8/2.08

7394

22.0

1.68

26

223

β-3

267

642.4/2.22

8061

25.4

1.76

32

320

TNTh

295

-67.3/-0.30

6881

19.5

1.65

15

353

RDXh

204

70.3/0.32

8795

34.9

1.80

7.4

120

Table 1. Energetic properties of α-3 and β-3 [a]Thermal decomposition temperature (onset) under nitrogen (determined by the DSC exothermal peak, 5 °C min-1). [b] Heat of formation. [c] Detonation velocity. [d] Detonation pressure. [e] Density (from X-ray diffraction) [f] Impact sensitivity (BAM method). [g] Friction sensitivity (BAM method). [h] Reference 32. Conclusions In conclusion, the 4,6-dinitro-1-(4-amino-1,2,4- triazole-2-yl)-1H-indazole (3) was synthesized based on the one-step reaction of 4-amino-3-hydrazino-1,2,4-triazolelium chloride (2) and 2,4,6-trinitrobenzaldehyde (1). The structure and energetic properties of the two polymorphic forms α-3 and β-3 were presented. Furthermore, the desirable β-3 can be formed directly through increasing reaction temperature as well as polymorphic transition from α-3. The two polymorphic forms were determined by single crystal X-ray diffraction. Compared with α-3, the β-3 exhibits closer layer-by-layer packing and the increases of 0.08 g cm-3 (4.7%), 36.6kJ mol-1(6.1%), 667 m s-1 (9%), 3.4 GPa (15.5%) in density, heat of formation detonation velocity and detonation pressure respectively contributed to π-π interactions and hydrogen bonds. As for thermal stability,


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sensitivities toward impact and friction, β-3 shows obvious increases of 88 °C (49%), 6 J (23%) and 97 N (43%) respectively relative to α-3. Meanwhile, a series of experimental tests and quantum chemical calculations were carried out to better study the structureproperty relationship. More π-π interaction and hydrogen bonding in β-3 were proved by two-dimensional fingerprint plots based on Hirshfeld surfaces, NIC plots of α-3 and β-3. The higher BDE for trigger bond in β-3 was confirmed by the EPSs of α-3 and β-3. All these desire results demonstrate that a close layer-by-layer structure features can improve density and thermal, impact, and friction stability of energetic material. Furthermore, polymorphic transition can enrich the methodology for development of new energetic materials. ASSOCIATED CONTENT Supporting Experimental

Information. section,

The

following

computational

files

details,

are

available

free

of

crystallographic

data

for

charge. target

compounds, and spectra AUTHOR INFORMATION Corresponding Author * E-mail: [email protected] Present Addresses


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School of Chemical Engineering, Nanjing University of Science and Technology, Xiaolingwei 200, Nanjing 210094, P. R. China Notes The authors declare no competing financial interest ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China (No. 21676147, 21875110, 21601061) and the Science Challenge Project (TZ2018004). REFERENCES 1

Agrawal, J. P.; Hodgson, R. D. Organic Chemistry of Explosives, John Wiley & Sons Ltd, Copyright 2007.

2

Mei, X.; Yang, H.; Li, X.; Li, Y.; Cheng, Y. Study of Some Low Temperature Gas-Generating Compositions. Propellants Explos. Pyrotech. 2015, 40, 526–530.

3

Fischer, D.; Gottfried, J. L. Synthesis and Investigation of Advanced Energetic Materials Based on Bispyrazolylmethanes. Angew. Chem. Int. Ed. 2016, 55, 16132-16135.

4

Thottempudi, V.; Gao, H.; Shreeve, J. M. Trinitromethyl-Substituted 5-Nitro- or 3-Azo-1,2,4-triazoles: Synthesis, Characterization, and Energetic Properties. J. Am. Chem. Soc. 2011, 133, 6464−6470.


19


5

Page 20 of 26

Bolton, O.; Matzger, A. J. Improved Stability and Smart-Material Functionality Realized in an Energetic Cocrystal. Angew. Chem., Int. Ed. 2011, 50, 8960−8963.

6

Landenberger, K. B.; Bolton, O.; Matzger, A. J. Two Isostructural Explosive Cocrystals with Significantly Different Thermodynamic Stabilities. Angew. Chem., Int. Ed. 2013, 52, 6468−6471.

7

Li, H.; Xu, R.; Kang, B.; Li, J. S.; Zhou, X.; Zhang, C.; Nie, F. Influence of Crystal Characteristics on the Shock Sensitivities of Cyclotrimethylene Trinitramine, Cyclotetramethylene Tetranitramine, and 2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12hexaazatetra-cyclo[5,5,0,03,1105,9]dodecane Immersed in Liquid. J. Appl. Phys. 2013, 113, 203-519.

8

Sivabalan, R.; Gore, G. M.; Nair, U. R.; Venugopalan, A. S.; Gandhe, B. R. Study on Ultrasound Assisted Precipitation of CL-20 and Its Effect on Morphology and Sensitivity. J. Hazard. Mater. 2007, 139, 199−203.

9

Wei, X.; Xu, J.; Li, H.; Long, X.; Zhang, C. Comparative Study of Experiments and Calculations on the Polymorphisms of 2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12hexaazaisowurtzitane (CL-20) Precipitated by Solvent/Antisolvent Method. J. Phys. Chem. C 2016, 120, 5042−5051.


20

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10 Yin, P.; Mitchell, L. A.; Parrish, D. A.; Shreeve, J. M. Energetic N ‐Nitramino ‐ N ‐Oxyl ‐Functionalized Pyrazoles with Versatile π–π Stacking: Structure– Property Relationships of High

‐ Performance Energetic Materials. Angew.

Chem., Int. Ed. 2016, 55, 14409−14411. 11 Zhang, J.; Zhang, Q.; Vo, T. T.; Parrish, D. A.; Shreeve, J. M. Energetic Salts with π-Stacking and Hydrogen-Bonding Interactions Lead the Way to Future Energetic Materials. J. Am. Chem. Soc. 2015, 137, 1697–1704. 12 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. 13 Gao, H.; Shreeve, J. M. Azole-Based Energrtic Salts. Chem. Rev. 2011, 111, 7377– 7436. 14 Dippold, A. A.; Klapotke, T. M. Nitrogen-Rich Bis-1,2,4

‐ triazoles—A

Comparative Study of Structural and Energetic Properties. Chem. Eur. J. 2012, 18, 16742–16753. 15 Schmidt, A.; Beutler, A.; Snovydovych, B. Recent Advances in the Chemistry of Indazoles. Eur. J. Org. Chem. 2008, 2008, 4073–4095.


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16 Cardillo, P.; Dellavedova, M.; Gigante, L.; Lunghi, A. Synthesis, Spectroscopic and Thermal Characterization of Azido-1, 2, 4-triazoles: A Class of Heteroarenes with a High Nitrogen Content. Eur. J. Org. Chem. 2012, 6, 11951201. 17 Wu, B.; Yang, H.; Wang, Z.; Lin, Q.; Ju, X.; Lu, C.; Cheng, G. Synthesis and Characterization of New Energetic Derivatives Containing a High Nitrogen Content Moiety and Picryl Group: a New Strategy for Incorporating the Picryl Functionality. RSC Adv. 2014, 4, 53282–53290. 18 Hang, H.; Fei, B.; Chen, X.; Tong, M.; Ksenofontov, V.; Gural’skiy, I. A.; Bao, X. Multiple Spin Phases in a Switchable Fe (II) Complex: Polymorphism and Symmetry Breaking Effects. J. Mater. Chem. C. 2018, 6, 3352-3361. 19 Zhang, C.; Xue, X.; Cao, Y.; Zhou, J.; Zhang, A.; Li, H.; Zhou, Y.; Xua, R.; Gao, T. Toward Low-sensitive and High-energetic Co-crystal II: Structural, Electronic and Energetic Features of CL-20 Polymorphs and the Observed CL-20-based Energetic–energetic Co-crystals. CrystEngComm. 2018, 16, 5905−5916. 20 Wei, X.F.; Zhang, A.; Ma, Y.; Xue, X.; Zhou, J; Zhu, Y.; Zhang, C. Toward Lowsensitive and High-energetic Cocrystal III: Thermodynamics of Energetic– energetic Cocrystal Formation. CrystEngComm. 2015, 17, 9037−9047.


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21 Zhang, J.; Zhang, J.; Parrishd, 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. 22 Tests were conducted according to: Recommendations on the Transport of Dangerous Goods: Manual of Tests and Criteria, 5th ed.; ST/SG/AC.10/11/Rev.5; United Nations: New York, 2009. 23 Spackman, M. A.; Jayatilaka, D. Hirshfeld Surface Analysis. CrystEngComm 2009, 11, 19−32. 24 Ma, Y.; Zhang, A.; Zhang, C.; Jiang, D.; Zhu, Y.; Zhang, C. Crystal Packing of Low-Sensitivity and High-Energy Explosives. Cryst. Growth. Des. 2014, 14, 4703 −4713. 25 Spackman, M. A.; McKinnon, J. J. Fingerprinting Intermolecular Interactions in Molecular Crystals. CrystEngComm 2002, 4, 378-392. 26 Zhang, C.; Xue, X.; Cao, Y.; Zhou, Y.; Li, H.; Zhou, J.; Gao, T. Intermolecular Friction Symbol Derived from Crystal Information. CrystEngComm 2013, 15, 6837−6844.


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27 Yan, C.; Yang, H.; Qi, X.; Jin, Y.; Wang, K; Liu, T.; Tian, J.; Nie, F.; Cheng, G.; Zhang, Q. A Simple and Versatile Strategy for Taming FOX-7. Chem. Commun 2018, 54, 9333-9336. 28 Politzer, P.; Murray, J. S. Some Molecular/crystalline Factors that Affect the Sensitivities of Energetic Materials: Molecular Surface Electrostatic Potentials, Lattice Free Space and Maximum Heat of Detonation per Unit Volume. J. Mol. Model. 2015, 21, 25–36. 29 Johnson, E. R.; Keinan, S.; Sanchez, P. M.; Garcıa, J. C.; Cohen, A. J.; Yang, W. Revealing Noncovalent Interactions. J. Am. Chem. Soc. 2010, 132, 6498–6506. 30 Yu, Z.; Bernstein, E. R. On the Decomposition Mechanisms of New ImidazoleBased Energetic Materials. J. Phys. Chem. A 2013, 117, 1756−1764. 31 Suceska, M. EXPLO5 Program, Croatia, Zagreb, 2011. 32 Xu, Z.; Cheng, G.; Yang, H.; Ju, X.; Yin , P.; Zhang, J.; Shreeve, J. M. A Facile and Versatile Synthesis of Energetic Furazan‐Functionalized 5‐Nitroimino‐ 1,2,4‐Triazoles. Angew. Chem. Int. Ed. 2017, 56, 5877 –5881. For Table of Contents Use Only


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We achieved an improvement in energy and safety of energetic materials by polymorphic transition.


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338x190mm (96 x 96 DPI)


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Boosting performance and safety of energetic materials by

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