Combining the furoxanylhydrazone framework with various energetic functionalities to prepare new insensitive energetic materials with 3D-cube layer stacking

Article abstract of DOI:10.1039/d0nj00541j

A series of furoxanylhydrazone-derived energetic compounds including salts and neutral compounds were systematically studied using 3-methyl-4-furoxancarbaldehyde as a versatile starting material. Target compounds present a 3D-cube layer crystal packing style due to the special structure of furoxanylhydrazone and vast hydrogen bonds. This configuration breaks through the limitation of the 2D-plane layer structure. Target compounds, which feature such characteristics, exhibit excellent sensitivities toward impact and friction (IS > 24 J; FS > 180 N) and acceptable energetic performance. Moreover, the detonation velocities and pressures of all ionic compounds (6-9, 11-13) were both increased relative to their corresponding neutral compounds. Compared with 5-(3′-methylfuroxanyl)methyleneamino-tetrazole (10), the sensitivities to impact and friction of its anion salts (11-13) were also lowered to some extent. The structure-property relationship was studied using theoretical calculations, crystal structure analysis and energetic properties. It is noted that five types of crystal packing have been analyzed, which may be useful for the further understanding of crystal and chemical phenomena in energetic materials. The results obtained demonstrate that this study enriches future prospects for the design of energetic materials.

Full text of DOI:10.1039/d0nj00541j

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Combining the Furoxanylhydrazone Framework with Various
Energetic Functionalities to Prepare New Insensitive Energetic
Materials with a 3D-cube Layer Stacking
Received 00th January 20xx,
Accepted 00th January 20xx
Jie Tang,a Hongwei Yang,a Hualin Xiong,a Wei Hu,a Caijin Lei,a Guangbin Cheng*,a
DOI: 10.1039/x0xx00000x
Abstract: A series of furoxanylhydrazone-derived energetic compounds including salts and neutral compounds were
systematically studied using 3-methyl-4-furoxancarbaldehyde as a versatile starting material. Target compounds present a
3D-cube layer crystal packing style due to the special structure of furoxanylhydrazone and vast hydrogen bonds. This
configuration breaks through the limitation of the 2D-plane layer structure. Target compounds, which feature such
characteristics, exhibit excellent sensitivities toward impact and friction (IS > 24 J; FS > 180 N) and acceptable energetic
performance. Moreover, the detonation velocities and pressures of all ionic compounds (6-9, 11-13) were both increased
relative to their corresponding neutral compounds. Compared with 5-(3’-methylfuroxanyl)methyleneamino-tetrazole (10),
the sensitivities to impact and friction of its anion salts (11-13) were also lowered to some extent. The structure-property
relationship was studied by theoretical calculation, crystal structure analysis and energetic property. It is noted that five
types of crystal packing have been analyzed, which may be useful for the further understanding of crystal and chemical
phenomena in energetic materials. These desire results demonstrate that this study enriches future prospects for the design
of energetic materials.
applications of HEDMs.7 Therefore, the combination of the
formation of energetic salts and crystal engineering will be
worthy of investigation.
Introduction
In the past decades, the design and development of high energy
density materials (HEDMs) played an important role in civilian
and military such as propellants, explosives, pyrotechnics and
gas generating agents.1 The demands of modern HEDMs are
getting higher and higher, in addition to high energetic
performance (detonation velocity and pressure) and low
As known, furoxan (1,2,5-oxadiazole-2-oxide) is a N-oxide
derivative of furazan, which has a “latent” nitro group within
one side of its ring. The density and detonation velocity of
energetic molecule can be increased by ca. 0.06-0.08 g cm-3 and
ca. 300 m s-1 through introducing a furoxan ring into the
molecule, respectively.8 Some energetic salts containing
sensitivity (sensitivity to spark, impact and friction), furoxan ring and other backbones have been investigated.9
There are four known stacking types of classic energetic
environmentally friendly decomposition products should be
considered.2 However, the contradiction between these
requirements is often a huge challenge, especially energy and
safety, because the enhanced properties come mostly at the
expense of molecular stability.3 Therefore, the combination of
physics, crystallography and chemistry should be considered to
prepare modern HEDMs.4 There are four promising routes to
obtain modern HEDMs: crystal engineering, constructing
energetic metal organic frameworks, designing polynitrogen
compounds and forming energetic salts.5 As an important cross-
branch of chemistry and physics in energetic materials, the
design and synthesis of energetic salts have received significant
interests due to better detonation performances and stabilities
than their precursors.6 While the crystal engineering of HEDMs
mainly aims to obtain the most stable form to realize the
molecules: face-to-face, wavelike, crossing, and mixing.10
Figure 1. Several types of 2D-plane and 3D-cube crystal packing.
a.School of Engineering, Nanjing University of Science and Technology. Nanjing,
210094, China. Email: gcheng@mail.njust.edu.cn
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
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Scheme 1. Synthesis of furoxanyl functionalized derivatives.
Recently, a 3D-cube layer stacking type has been reported by M.
Lu’s group, which overcomes the limitation of the 2D-plane
layer structure (Figure 1).11 However, the great potential of
developing 3D-cube layer stacking in energetic materials has
not fully exploited yet. To our best knowledge, few energetic
salts based on furoxan-functioned nitrogen-rich heterocycle
cations have been reported. With our continuing interest to the 3D supramolecular structure of
explore the relation between properties and structures of
energetic materials, herein, the reactions of hydrazine groups in
Figure 3. a) The molecular structure of compound
supramolecular interaction between chloridion and nearby
energetic cation; c) the ”Z” shaped unit cell contained in ; d)
. (Green lines represent
hydrogen bonds; red ellipsoid indicates furoxanyl framework;
blue column presents triazoleyl group, green plot is chloridion).
5; b) the
5
5
nitrogen-rich
heterocyclic
rings
with
3-methyl-4-
furoxancarbaldehyde are further studied. The synthesis,
structure, and energetic performance of 3-(3’-methylfuroxanyl)
product
amino-3-hydrazino-1,2,4-triazole
furoxancarbaldehyde with a catalytic amount of hydrochloric
acid at 78 °C. Subsequently, the energetic cation salts of were
synthesized by means of Bronsted acid-base reaction. When
was treated with an equivalent of acid, energetic salts based on
4
can be precipitated from the reaction mixture of 4-
and 3-methyl-4-
methyleneamino-4-amino-1,2,4-triazole
(
4
),
5-(3’-
methylfuroxanyl)methyleneamino-tetrazole (10) and a series of
energetic salts based on furoxanylhydrazone functionalized
cation(5-10) and anion (11-13) were reported. Importantly,
these crystals of furoxanylhydrazone derivatives exhibit five
different 3D-cube layer stacking forms: “Z” shaped, spring
shaped, stair shaped, sandwich shaped and face-to-face layer.
And the relation between crystal phenomenon and properties
of some target compounds were discussed. All these results
indicated that the design of furoxan-derived energetic salts and
the exploration of their microstructures may open new avenues
in the following research on HEDMs.
4
4
furoxanyl functionalized
synthesized protonated salts
5
,
6
8
and
and
7
9
were prepared. We
by using ammonium
dinitramide with hydrochloric acid and 5-nitro-tetrazole,
respectively. In addition, in order to systematically study on
furoxanyl functionalized derivatives, the compound 10 and its
furoxanyl functionalized salts (11
series of energetic salts from compounds
-
13) were also synthesized. A
and 10 were
4
prepared by dissolving the neutral compounds in ethanol,
followed by the addition of the corresponding Bronsted acid or
base (Figure 2). The desired energetic salts were precipitated
almost quantitatively with high purities due to the poor
solubility of the target ionic molecules.
Results and discussion
Synthesis
Single-crystal X-ray analysis
The synthetic pathway is shown in Scheme 1. Compounds 1-3
were synthesized according to the literature.12 First, the desired
Single crystals of
5, 7 and cocrystal 8/4 suitable for X-ray
diffraction studies were all obtained from methanol by slow
evaporation of the solvents at ambient temperature, whereas
crystals 10 and 11 were re-crystallized from the hot water
solution. The crystallographic data and CCDC numbers of these
compounds are summarized in Table S1 (ESI†).
Compound
5 crystallizes in the monoclinic space group P21/n
with four molecules per unit cell (Z = 4) and a calculated density
of 1.602 g cm-3 based on crystal data. The furoxan ring and
triazole ring of
5 are noncoplanar, which is clearly confirmed
from torsion angles of C1-C3-C4-N3 (24.5 (4)°) and N2-C3-C4-N3
(-153.0 (3)°) (Figure 3a). The adjacent molecules are interacted
with each other through hydrogen bonds (N–H⋯O) and halogen
bonds (N–H Cl) (Figure 3b). The “Z” shaped unit cell is formed
⋯
through these interactions between two furoxanyl cations and
a chloridion (Figure 3c). Then several unit cells arrange side by
side to form a layer, finally these layers are further stacked to
Figure 2. The process of salts (5-9, 11-13) based on Bronsted
acid-base reaction.
form the 3D-cube layer stacking type of 5 (Figure 3d).
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Figure 6. a) The molecular structure of compound 10·H2O; b) the
supramolecular interaction of 10; c) the sandwich shaped unit
Figure 4. a) The molecular structure of compound 7; b) the
supramolecular interaction between perchlorate anion and
nearby energetic cation; c) the spring shaped unit cell contained
in 7; d) the 3D supramolecular structure of 7. (Green lines
represent hydrogen bonds; red ellipsoid indicates perchlorate
anion; blue column presents furoxanyl functionalized cation.)
cell contained in 10; d) the 3D supramolecular structure of 10
.
(Green lines represent hydrogen bonds; blue ellipsoid indicates
10; red column presents water molecule.)
Cocrystal 8/4 (compound 8: compound 4, 1:1) crystallizes in the
triclinic space group P-1 consists of two molecules per unit cell
(Z = 2) and a calculated density of 1.630 g cm-3. All the non-
Compound
four molecules per unit cell (Z = 4) and a crystal density of 1.745
g cm-3. The furoxanyl functionalized cation in compound
is
7 belongs to the monoclinic space group P21/c with
7
hydrogen atoms in 8/4 are almost in a plane confirmed by the
nearly coplanar supported by torsion angles (C2-N5-N6-C3,
167.70 (16)° and N7-C4-C3-N6, -6.9 (3°) (Figure 4a). There are
abundant intermolecular and intramolecular hydrogen bonds
torsion angles (C9-C10-N17-N16, 178.7 (2)° and C10-N17-N16-
C11, 171.2 (2)°). The molecular structure is shown in Figure 5, a
stair shaped layer structure is constructed by supramolecular
(N–H⋯O) in compound 7 (Figure 4b). Figure 4c presents a spring
interaction between dinitramide anion, compound
4 and 3-(3’-
shaped layer, which can be interpreted as two adjacent
perchlorate anions serving as the connection point of the
network. Then, the layers stack into a stratiform structure to
form the 3D-cube packing system (Figure 4d). It is notably that
abundant hydrogen bonds exist between layers which enhances
the strength of crystal packing as well as the stability of
explosive crystal.
methylfuroxanyl) methyleneamino-4-amino-1,2,4-triazolium
cation. And then, the layers are stacked in a face-to-face mode
to build the 3D supramolecular structure of cocrystal 8/4. The
closed 3D-cube system is held by the inter- and intra-molecular
hydrogen bonds between unit cells and layers (green lines in
Figure 5b and 5d represent hydrogen bonds), which contributes
to low sensitivity to impact and friction.
Compound 10·H 2O belongs to the monoclinic space group P21/c
with four molecules per unit cell (Z = 4) and a crystal density of
1.593 g cm-3. This molecular structure is also planar confirmed
by torsion angles (C2-C4-N3-N4, 179.7 (3)° and C4-N3-N4-C5, -
178.0 (3)°) (Figure 6a). The sandwich shaped layer structure was
stacked by two 10 molecules and a H2O molecule due to
hydrogen bonds (Figure 6b, 6c). Such layer units are repeated in
an infinite stack, which classifies the whole crystal as having a
sandwich stacking (Figure 6d). The 3D network of 10 is formed
through hydrogen bonding of inter- and intra-molecular. It is
notably that the sandwich-type stacking can protect the energy
moieties in the interlayer and enhance the molecular stability
when encountering external stimuli.13
Compound 11·3H2O crystallizes in monoclinic P21/n space group
with a density of 1.421 g cm-3, and consists of four molecules
per unit cell (Z = 4).As shown in Figure 7, the planar structure is
identified by torsion angles (C1-N5-N6-C2, 179.28 (15)° and N5-
N6-C2-C3, 179.88 (14)°). The extensive hydrogen bonds
between H2O, ammonium and furoxanyl functionalized anion
result in the face-to-face layer stacking. The 3D supramolecular
structure of 11 is dominated by an infinite face-to-face
arrangement to form a 3D-cube layer stacking (Figure 7d).
Figure 5. a) The molecular structure of cocrystal
supramolecular interaction between dinitramide anion
compound and energetic cation; c) the stair shaped unit cell
contained in ; d) the 3D supramolecular structure of 8/4.
8/4; b) the
,
4
8
/4
(Green lines represent hydrogen bonds; red ellipsoid indicates
dinitramide anion; blue (yellow) column presents furoxanyl
functionalized cation (compound 4).)
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Figure 7. a) The molecular structure of compound 11·3H2O; b)
the supramolecular interaction of 11; c) the face-to-face layer
structure of 11; d) the 3D supramolecular structure of 11
.
(Green lines represent hydrogen bonds; blue ellipsoid indicates
11; red (blue) pot presents water (ammonium) molecule.)
Figure 9. DSC plots of compound 10 and its energetic salts 11-
13
.
Moreover, the hydrogen bond and π−π stacking exist among
layers and lead to the maximum external stimuli layers
sustained.14
Based on these analyses of crystal structure, furoxanyl
functionalized energetic materials own planar structure due to
the special structural characteristic of furoxanylhydrazone
detonation performance were evaluated. The thermal stability
of all synthesized compounds was obtained by differential
scanning calorimetry (DSC) with a linear heating rate of 5 °C min-
1
under a nitrogen atmosphere. All the compounds own
acceptable decomposition temperature (Tdec > 160 °C) due to
the extensive hydrogen-bonding interaction. As shown in Figure
except compound 5. In this work, it is interesting to note that
8, compound
bit higher than its energetic salts. Except for salt
all other salts of compound decomposed above 190 °C.
4
starts to decompose at 208 °C, which is quite a
five packing styles present 3D-cube layer stacking because of
the planar structure molecule, inter- and intramolecular
interaction between molecules, unit cells, and layers. The 3D-
cube layer stacking can effectively dissipate the external
mechanical energy into intermolecular and interlayer slide,
avoiding too big potential increases to decay molecules, which
leads to high safety.15 Moreover, all these stacking types may
contribute to further understanding and analysis of chemical
and physical phenomena in energetic materials.
8
(Tdec = 175 °C),
4
Interestingly, the decomposition temperature of ammonium
salt (11, Tdec = 160 °C ), hydrazinum salt (12, Tdec = 165 °C ) and
hydroxylammonium salt (13, Tdec = 186 °C ) are slightly lower
than that of neutral compound 10 (Tdec = 191 °C ) (Figure 9). And
the decomposition temperature of cocrystal 8/4 is 189 °C (DSC
plot of 8/4 was showed in Supporting Information, Figure S19).
The impact sensitivity (IS) and friction sensitivity (FS) were
determined using the standard BAM fall hammer and BAM
friction tester, respectively.16 As given in Table 1, all of those
compounds in anhydrous powder were very insensitive with
low impact sensitivity (> 24 J) and low friction sensitivity (> 280
N). Recently, the relationship between crystal stacking and
sensitivity has been widely concerned. External mechanical
stimuli on energetic material can lead to a certain degree of
shape change of energetic material to store mechanical energy.
Hot spots are formed once this energy exceed the limit of the
energetic material stored, then decomposition will be activated
and trigger final detonation.17 As known, the stacking mode-
sensitivity relationships of common 2D-plane stackings have
been studied through quantum chemical and empirical
Physicochemical and energetic properties
To investigate whether 3D-cube layer stacking and formation of
energetic salts could improve the properties of energetic
materials, their thermal stability, mechanical sensitivities and
Figure 8. DSC plots of compound 4 and its energetic salts 5-9.
Figure 10. Green arrows showing sliding allowed; x and z
represent the sliding along right/left and front/back.
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potential calculations. And steric hindrance caused by interlayer
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sliding is usually thought to be a crucial factor in impact
sensitivity.18 However, the stacking mode-sensitivity
relationships of 3D-cube layer stacking have rarely been
reported. As shown in Figure 10, the aforementioned 3D-cube
layer stacking will cause the two-steps slide. First, the sliding is
limited to intralayer of 2D plane, which have been reported
according to the literature.18c Then, the slide occurs along the
layer plane both in front/back and right/left direction, resulting
9
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in low sensitivity (4, 6-13, IS > 24 J; FS > 280 N). It is obvious that
3D-cube layer stacking possesses much more sliding orientation
relative to 2D-plane stacking.
Figure 12. Hirshfeld surfaces (a and b), fingerprint plots (c and
d) and individual atomic contacts percentage contribution to
the Hirshfeld surface (e and f) of 10 and 11, respectively.
To better understand the structure-property relationship, two-
dimensional (2D) fingerprint and Hirshfeld surfaces were
employed to analyse the weak interactions and hydrogen bonds
of furoxanylhydrazone derivatives. Generally, the sensitivity can
be demonstrated by the shape of Hirshfeld surfaces as it
represents conjugated molecular structure. Furthermore, the
red and blue regions on the Hirshfeld surfaces represent high
and low close contact populations, respectively.19 The
that π−π interactions exist in both 10 and 11. In a word, π−π
interactions and multi hydrogen-bonding interactions as well as
the 3D-cube packing contribute to the insensitivity of energetic
salts.
To further investigate the interactions among target
compounds, the non-covalent interaction (NCI) plots of
molecules of 7 and 8 present an approximately planar structure
and a plate shape, and most of the red dots (intermolecular
interactions) are located on the surface edges (Fig 11a cf. Fig
11b). O…H and N…H are close contacts, and a pair of spikes at
the bottom left of Figure 11c, 11d are the dominant interactions
compounds 7, 8, 10 and 11 were performed to analyse the real
spatial structure based on electron density.20 As shown in Figure
13, the π-π interactions were abundant in these compounds,
which could be easily observed as larger green isosurfaces.
Extensive π−π interactions observed in target compounds result
in the low sensitivity of those compounds.
in the 2D fingerprint plots of both
7 and 8, indicating the
hydrogen bonds between adjacent molecules and layers in the
3D-cube system. There are many hydrogen-bonding
All compounds own positive heats of formation in the rage of
565.9 kJ mol-1 to 1290.1 kJ mol-1 (1.74 kJ g-1 to 3.84 kJ g-1). Based
on their heats of formation and measured densities at 298 K,
the detonation properties including detonation velocity and
pressure were calculated with EXPLO5 (version 6.0221). As
shown in Table 1, the detonation velocities and pressures are in
range from 7058 m s-1 to 8332 m s-1 and 19.9 GPa to 28.5 GPa,
respectively. All compounds exhibit higher detonation velocity
and detonation pressure than TNT (D = 6881 m s-1, P = 19.5 GPa).
interactions (O…H and N…H contacts, 62.0% for
) and π−π interactions exist in and (C…N and N…O contacts,
13.1% for and 10.4% for ).
Remarkably, the formation of the nitrogen-rich salts (11-13
7 and 57.2% for
8
7
8
7
8
)
leads to a significant improvement in mechanical sensitivity
compared with that of neutral compound 10. In Figure 12,
compound 11 exhibits a more planar shape and red dots
(intermolecular interactions) on the surface edges than 10 (Fig
12a cf. Fig 12b). Moreover, these interactions can also be
demonstrated by 2D fingerprint plot (Figure 12c, 12d).
Compound 11 possesses more O…H and N…H interactions
(about 59.3%) than that in 10 (about 50.7%), which indicates
stronger hydrogen bonds in 11 results in more stable
mechanical stability. C…N and N…O possess 15.9% of total
interactions for 10 and 8% for 11 (Figure 12e, 12f), suggesting
Experimental
Caution: Although we experienced no difficulties in handling
these energetic materials, small scale and best safety practices
(leather gloves, face shield) are strongly encouraged. All
chemical reagents, solvents were obtained by purchase and
were used as supplied without further purification.
Figure 11. Hirshfeld surfaces (a and b), fingerprint plots (c and
d) and individual atomic contacts percentage contribution to Figure 13. NCI plots of gradient isosurfaces for
7 (a), 8 (b), 10 (c),
the Hirshfeld surface (e and f) of
7
and
8
, respectively.
11 (d).
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Table 1. Energetic properties of the title compounds.
5
6
Compound
Tda [°C ]
ΔfHb[kJ mol-1/kJ g-1]
Dc [m s-1]
Pd [GPa]
de [g cm-3]
ISf [J]
FSg [N]
7
8
9
4
208
190
196
175
195
191
160
165
186
295
686.3/3.06
602.4/2.09
565.9/1.74
965.3/2.91
949.4/2.80
760.2/3.62
796.6/3.51
930.9/3.84
856.1/3.54
-67.3/-0.30
7058
7614
8213
8110
8145
7991
8040
8270
8332
6881
19.9
24.1
28.5
24.8
27.6
23.5
23.0
24.5
25.9
19.5
1.61
1.62
1.75
1.64
1.63
1.60
1.61
1.62
1.65
1.65
>40
28
25
24
27
35
>40
37
36
15
360
336
280
280
324
330
>360
360
336
353
10
11
12
13
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15
16
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58
59
60
6
7
8
9
10
11
12
13
TNTh
[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 determined by gas pycnometer at 25 °C. [f] Impact
sensitivity (BAM method). [g] Friction sensitivity (BAM method). [h] Ref.22
Synthesis of 3-(3’-Methylfuroxanyl) methyleneamino-4- mixed in portions. The mixture became clear immediately, then
amino-1,2,4-triazole (4)
A solution of amino-3-hydrazino-1,2,4-triazole (5.0 mmol, 0.57 filtrate was left for crystallization at room temperature as a
the solution was stirred for another 0.5 h and filtered. The
1
g) and 3-methyl-4-furoxancarbaldehyde (5.0 mmol, 0.64 g) in 20 colorless crystalline solid (
ml ethanol, a catalytic amount of hydrochloric acid was added MHz, DMSO-d6):
and stirred for 12 h at 60 °C . The reaction mixture was cooled to 2.40 (s, 3H). 13C NMR (125 MHz, DMSO-d6):
0 °C and the white precipitate was formed. Then the 143.2, 137.9, 111.7, 9.2. IR (KBr): 3363.39, 3099.21, 2706.74,
precipitated solid was filtered off, washed with cold ethanol and 1693.81, 1592.69, 1461.57, 1087.62, 1063.59, 1036.98, 930.54,
dried in vacuo to afford 1.02 g of
of 91%. 1H NMR (500 MHz, DMSO-d6):
(s, 1H), 6.32 (b, 1H), 5.85 (b, 2H), 2.38 (s, 3H). 13C NMR (125 MHz, 22.54, H 2.17, N 34.03.
DMSO-d6): (ppm) 161.2, 155.1, 140. 8, 125.8, 112.0, 9.5. IR General procedures for preparation of energetic salts 8-9.
(KBr): 3244.91, 2646.85, 1686.73, 1599.82, 1459.39, 1358.60, A suspension of (5.0 mmol, 1.12 g) in deionized water (15 ml)
1114.58, 993.92, 974.06, 843.52, 816.87, 783.17, 692.04, was stirred at ambient temperature while an energetic acid was
644.68 cm-1. C, H, N analysis (%): C6H9N8O2 (224.08), calculated added. The reaction mixture was stirred for another 1 h at 60-
result: C 32.15, H 3.60, N 49.98; found: C 32.28, H 3.46, N 49.33. 70 °C . Then, the precipitate for
Synthesis of 6. A suspension of (5.0 mmol, 1.12 g) in deionized air.
water (15 ml) and nitric acid (5.5 mmol) were mixed in portions. Synthesis of 8
7
), yield, 1.45g, 90%. H NMR (500
δ
(ppm) 8.81 (s, 1H), 8.59 (s, 1H), 6.45 (b, 2H),
(ppm) 153.3, 148.9,
δ
1
as a white powder in a yield 853.10, 776.05, 618.68 cm-1. C, H, N analysis (%): C6H9ClN8O6
(ppm) 8.33 (s, 1H), 8.17 (323.03), calculated result: C 22.27, H 2.49, N 34.62; found: C
δ
δ
4
8 and 9 was filtered and dried in
4
.
Ammonium dinitramide (5.0 mmol, 0.62 g) and
Then the mixture was stirred and then filtered, washed with 1ml 1M hydrochloric acid were added to suspension, 1.47g of
water and dried in vacuo. 1.19 g of
solid in a yield of 83%. H NMR (500 MHz, DMSO-d6):
9.68 (s, 1H), 8.92 (s, 1H), 8.37 (s, 2H), 2.40 (s, 3H). 13C NMR (125 2.39 (s, 3H). 13C NMR (125 MHz, DMSO-d6):
8
1
6
was obtained as a yellow was obtained as a white solid in a yield of 89%. H NMR (500
1
δ
(ppm) MHz, DMSO-d6):
δ
(ppm) 8.51 (s, 1H), 8.42 (s, 1H), 6.20 (b, 2H),
(ppm) 157.0, 155.2,
(ppm) 155.9, 154.9, 150.7, 142.7, 111.8, 11.9. 153.3, 137.2, 110.2, 9.2. IR (KBr): 3334.36, 3120.50, 1690.48,
δ
MHz, DMSO-d6):
δ
IR (KBr): 3245.75, 3151.45, 2778.65, 2647.03, 1686.24, 1612.26, 1582.70, 1501.58, 1459.66, 1170.54, 1109.42, 1002.10, 851.44,
1598.29, 1459.79, 1114.85, 994.28, 843.45, 693.44 cm-1. C, H, N 663.82 cm-1. C, H, N analysis (%): C6H8N12O6 (337.21), calculated
analysis (%): C6H9N9O5 (286.07), calculated result: C 25.18, H result: C 21.82, H 2.44, N 46.66; found: C 21.53, H 2.17, N 46.88.
2.82, N 44.05; found: C 25.03, H 2. 71, N 44.38.
Synthesis of 7. A suspension of
Synthesis of 9. 5-nitrotetrazole (5.0 mmol, 0.58 g) was added to
4
(5.0 mmol, 1.12 g) in deionized suspension, 1.49 g of
9
was obtained as a yellow solid in a yield
(ppm) 12.79 (s, 1H),
1
water (15 ml) and perchloric acid (70 wt%, 5.0 mmol) were of 88%. H NMR (500 MHz, DMSO-d6):
δ
6 | J. Name., 2012, 00, 1-3
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8
9.78 (b, 1H), 8.81 (s, 1H), 8.36 (s, 1H), 2.40 (s, 3H). 13C NMR (125 characterized by NMR spectra, IR spectroscopy and differential
View Article Online
DOI: 10.1039/D0NJ00541J
MHz, DMSO-d6):
δ (ppm) 162.3, 156.7, 154.5, 153.2, 145.0, scanning calorimetry (DSC). The structures of compounds 5, 7,
107.1, 9.2. IR (KBr): 3367.23, 1606.80, 1565.05, 1491.75,
8, 10 and 11 were further determined by single crystal X-ray
1456.22, 1375.15, 1174.54, 1060.06, 1022.16, 821.87, 636.21 diffraction. All ionic compounds 6-9 and 11-13 showed a
cm-1. C, H, N analysis (%): C7H9N13O4 (338.08), calculated result: positive influence on the detonation performance, such as
C 24.86, H 2.38, N 53.84; found: C 24.55, H 2.17, N 54.21.
detonation velocities and pressures relative to their
Synthesis of 10. A solution of 5-hydrazino-tetrazole (5.0 mmol, corresponding neutral compounds. Compared with 10, the
0.50 g) and 3-methyl-4-furoxancarbaldehyde (5.0 mmol, 0.64 g) anion salts (11-13) exhibit increases of exceeding 5 J and 6 N in
in 20 ml ethanol, a catalytic amount of hydrochloric acid was impact and friction sensitivity due to more hydrogen bonds in
added and stirred for 12 h at 60 °C . The reaction mixture was 3D-cube layer stacking system, respectively. Furthermore, the
cooled to 0 °C and the white precipitate was formed. Then the combination of experimental results, theoretical calculations
precipitated solid was filtered off, washed with cold ethanol and and crystal structure analysis was employed to better
9
10
11
12
13
14
15
16
17
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22
23
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26
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dried in vacuo to afford 0.98 g of 10 as a white powder in a yield understand the structure-property relationship. All these desire
1
of 91%. H NMR (500 MHz, DMSO-d6):
δ (ppm) 15.68 (b, 1H), results demonstrate that a 3D-cube layer stacking structure
12.48 (s, 1H), 8.08 (s, 1H), 2.39 (s, 3H). 13C NMR (125 MHz, features can improve impact, and friction stability of energetic
DMSO-d6): (ppm) 154.8, 153.6, 131.9, 111.6, 9.3. IR (KBr): material. And these different crystal stacking forms would
δ
2979.00, 2843.10, 1634.53, 1598.18, 1533.51, 1458.11, 1376.73, contribute to further understanding of chemical and physical
1155.11, 1043.36, 848.99 cm-1. C, H, N analysis (%): C5H6N8O2 phenomena in energetic materials. Therefore, the combination
(210.06), calculated result: C 28.58, H 2.88, N 53.32; found: C of energetic salts and crystal engineering could be a promising
28.64, H 2.37, N 53.77.
strategy for design of energetic materials.
General procedures for the preparation of energetic salts 11-
13.
Conflicts of interest
There are no conflicts to declare.
Ammonia (25 wt% in water, 5.0 mmol), hydrazine hydrate (80
wt% in water, 5.0 mmol) or hydroxylamine (50 wt% in water, 5.0
mmol) was added to a solution of 12 (5.0 mmol, 1.05 g) in
methanol (5 ml). After stirring for 2h at ambient temperature,
the precipitate was collected by filtration and washed with
MeOH.
Acknowledgements
This work was supported by the Science Challenge Project
1
11 (White solid), 0.77 g, in a 65% yield. H NMR (500 MHz,
(TZ2018004)
， the National Natural Science Foundation of
DMSO-d6):
NMR (125 MHz, DMSO-d6):
δ
(ppm) 8.54 (s, 1H), 3.85 (b, 2H), 2.36 (s, 3H). 13C
China (No. 21676147, 21875110).
δ
(ppm) 160.4, 154.9, 126.5, 111.8,
9.4. IR (KBr): 2948.71, 2873.79, 1600.62, 1497.03, 1458.21,
1417.63, 1377.53, 1315.01, 1167.15, 1126.71, 1013.91, 912.35,
844.59, 652.51 cm-1. C, H, N analysis (%): C5H9N9O2 (227.09),
calculated result: C 26.43, H 3.99, N 55.49; found: C 26.03, H
4.12, N 55.16.
Notes and references
1
2
3
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(ppm) 160.4, 154.9,
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1490.34, 1452.35, 1376.14, 1163.03, 893.65, 845.44, 653.00 cm-
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Conclusions
,
−
A new series of energetic salts and neutral compounds
containing furoxanylhydrazone with a 3D-cube layer stacking
were designed and synthesized based on 3-methyl-4-
furoxancarbaldehyde. All target compounds were well
6
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−
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(c) G. Zhang, Y. Chen, L. Liao, H. Lu, Z. Zhang, Q. Ma, H. Yang
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We provide a new series of energetic salts and neutral compounds containing
furoxanylhydrazone with a 3D-cube layer stacking.