A promising cation of 4-aminofurazan-3-carboxylic acid amidrazone in desensitizing energetic materials

Article abstract of DOI:10.1039/c9ra09555a

For the development of energetic materials, insensitive compounds have attracted considerable attention due to their improved safety and lower cost than those of sensitive energetic compounds during production, transportation, and application. In this study, insensitive 4-aminofurazan-3-carboxylic acid amidrazone was used as a cation to obtain four derivatives which were determined by X-ray single crystal diffraction. It is interesting to note that all four derivatives are insensitive to impact and friction, while the velocities of detonation for derivatives are superior to that of insensitive TATB (1,3,5-triamino-2,4,6-trinitrobenzene). Multi-factors analysis shows that the cation of 4-aminofurazan-3-carboxylic acid amidrazone is a promising furazan-based cation in desensitizing energetic compounds.

Full text of DOI:10.1039/c9ra09555a

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A promising cation of 4-aminofurazan-3-
carboxylic acid amidrazone in desensitizing
Cite this: RSC Adv., 2020, 10, 2519
energetic materials†
Jichuan Zhang,‡ac Zhenyuan Wang,‡b Yunhao Hsieh,b Binshen Wang,b
a
a
bc
*
*
Haifeng Huang,
Jun Yang
and Jiaheng Zhang
For the development of energetic materials, insensitive compounds have attracted considerable attention
due to their improved safety and lower cost than those of sensitive energetic compounds during
production, transportation, and application. In this study, insensitive 4-aminofurazan-3-carboxylic acid
amidrazone was used as a cation to obtain four derivatives which were determined by X-ray single
crystal diffraction. It is interesting to note that all four derivatives are insensitive to impact and friction,
while the velocities of detonation for derivatives are superior to that of insensitive TATB (1,3,5-triamino-
2,4,6-trinitrobenzene). Multi-factors analysis shows that the cation of 4-aminofurazan-3-carboxylic acid
amidrazone is a promising furazan-based cation in desensitizing energetic compounds.
Received 15th November 2019
Accepted 24th December 2019
DOI: 10.1039/c9ra09555a
rsc.li/rsc-advances
Hydrogen bonds (H-bonds) are divided into two categories,
intramolecular and intermolecular H-bonds,4 which play
Introduction
a signicant role in desensitization of energetic compounds. In
general, intramolecular H-bonds are the stronger one, this is
due to (1) intramolecular H-bonds connect donator and
acceptor in a molecule, which can make the molecule consid-
erably more rm than those contain intramolecular H-bonds;
and (2) intramolecular H-bonds could enhance the conjuga-
tion effect of the molecule, and result in a planar molecule,
which are usually less sensitive than nonplanar energetic
compounds, such as the classic insensitive compounds, TATB,
LLM-116, and FOX-7, which are obviously less sensitive than
their derivatives.3b,5 However, for energetic materials, most of
the reported strong intramolecular H-bonds are N–H/O, the
intramolecular H-bonds of N–H/N are reported rarely.4a In
addition, intermolecular H-bonds help form innite networks
as it may also cause denser packing which reduces the amount
of free space in the crystal lattice, and thereby decreasing
sensitivity.6
Since the discovery of dynamite by Alfred Bernhard Nobel,
energetic compounds with a considerable amount of stored
chemical energy have played a crucial role in the civil and
military defence industries.1 During the development and
investigation of new-generation energetic compounds, insen-
sitive energetic materials have attracted extensive attention as it
can decrease the cost and risk greatly compared to those of less
sensitive or sensitive compounds during the production,
transportation, and application.2 Several strategies were
employed to design insensitive compounds, such as intro-
ducing insensitive groups (NH2, CH3) to energetic backbone,
assembly of energetic metal–organic frameworks, layer–layer
packing, forming strong hydrogen bonds, as well as the
combination of the above multi-factors.3
aCAS Key Laboratory of Energy Regulation Materials, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, 200032,
China. E-mail: yangj@sioc.ac.cn
Nitrogen-rich heterocyclic rings have drawn extensive
interest in the past two decades due to their high heat of
formation and nitrogen content.7 Comparing with these general
known heterocyclic rings, 1,2,5-oxadiazole ring (furazan)
exhibits promising performance due to its higher density, and
better oxygen balance than pyrazole and 1,2,4-triazole. In
addition, furazan also displays higher heat of formation than
1,2,4-oxadiazole ring.8 Some derivatives with furazan ring show
huge potential as new generation energetic materials.9 The
cations of furazan based energetic salts are inorganic cations,
such as ammonium, hydronium, and hydroxylammonium.
Although some azole rings have been employed as energetic
bSchool of Material Sciences and Engineering, Harbin Institute of Technology,
Shenzhen, 518055, China. E-mail: zhangjiaheng@hit.edu.cn
cBiomaterials Research Center, Zhuhai Institute of Advanced Technology, Chinese
Academy of Sciences, Zhuhai, 519003, China
† Electronic supplementary information (ESI) available: Details of X-ray
crystallography, including additional gures, crystallographic data, and bond
lengths and angles data for 1, 1a$H2O, 1b–1c. Details of hydrogen-bonding
interactions for 1, 1a$H2O, 1b–1c. CCDC 1916325–1916328. For ESI and
crystallographic data in CIF or other electronic format see DOI:
10.1039/c9ra09555a
‡ These authors contributed equally to this work, and they did the majority of this
work.
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cations while the furazan ring as energetic cation has been
studied rarely.
4-Aminofurazan-3-carboxylic acid amidrazone which is
insensitive to impact and friction was synthesized and charac-
terized in this work. Single crystal structure shows that it
contains not only intermolecular H-bonds, but also strong
N/H–N intramolecular H-bonds. If these H-bonds were still in
its derivatives, the sensitivities of its derivatives would possibly
be decreased greatly. Now, four derivatives (1a: nitrate; 1b:
1H,1H-5,5-bitetrazole-1,1-diolate;
1c:
3-nitramino-4-
tetrazolefurazanate; 1d: 3,4-dinitramino-furazanate) of 4-
aminofurazan-3-carboxylic acid amidrazone were synthesized
and characterized (Scheme 1). Their crystal structures, energetic
properties, and sensitivities were investigated comprehensively.
Results and discussion
Synthesis and single crystal X-ray structures
Fig. 1 Synthetic route of compounds 1 and 1a–1d.
Based on the previous study10 and the synthetic route shown in
Fig. 1, 4-(1,2,4-oxadiazol-3-yl)furazan-3-amine,
a luminous
yellow solid, was synthesized in high yield (85%), followed by
treatment with 80% of hydrazine hydrate in methanol at 50 C
1 (Fig. 4a and Tables S1 and S2†). Apart from intramolecular H-
bonds, ve intermolecular H-bonds were also observed, with
ꢀ
for 1 h while 4-aminofurazan-3-carboxylic acid amidrazone (1)
exhibits as a brown solid. Compound 1 was recrystallized from
water, and then it reacted with dilute HNO3 in methanol, aer
the solvent was removed, affording 1a$H2O. 1 reacted with HCl,
affording an amidrazone of 4-aminofurazan-3-carboxylic acid
chloride salt and then chloride salt of 1 react with the corre-
sponding silver salts of 1b–1d in water for 30 min, 1b–1d were
obtained aer ltration, evaporation. Finally, these four salts
were obtained aer recrystallization from mixture of water and
methanol, and drying, respectively.
Compound 1 was crystalized from water in the monoclinic
space group P121/c1 with a density of 1.627 g cmꢁ3 at 173 K
(Table S1†), as well as eight molecules in a unit cell (Z ¼ 8,
Fig. 2a). Five intramolecular H-bonds were observed in 1: N9–
H9B/N11, N4–H4A/N1, N3–H3B/N5, N10–H10A/N12 and
N10–H10B/N7. The corresponding hydrogen/acceptor (H/
˚
lengths of 2.209, 2.219, 2.335, 2.425, and 2.465 A, respectively
(Table S6†). Finally, the crystal structure was connected by these
intermolecular H-bonds, forming an innite three-dimensional
(3D) network (Fig. S6 and 7†).
Compound 1a$H2O was crystalized as a colourless block
crystal in the orthorhombic Pbca space group, with eight NO3
anions, eight amidrazone of 4-aminofurazan-3-carboxylic acid
cations, and eight water molecules in each unit cell (Z ¼ 8,
Fig. 2b). The crystal density of 1a$H2O was 1.64 g cmꢁ3 at room
temperature. It is interesting that the intramolecular H-bonds
still exist in 1a$H2O, and two intramolecular H-bonds (N3–
H3B/N4) and (N6–H6A/N1) are observed. The hydrogen/
˚
˚
acceptor (H/A) distance are 2.295 A and 2.382 A, respectively.
The intramolecular H-bonds make the atoms of cation and
oxygen from water molecules close to coplanar (Fig. 4b and
Table S3†). In addition, seven intermolecular H-bonds were
observed in a unit cell, and the lengths of their H/A were 1.881,
˚
˚
˚
˚
˚
A) distances were 2.215 A, 2.332 A, 2.410 A, 2.425 A and 2.410 A
(Table 1), respectively. Comparing to the reported N–H/N
˚
2.010, 2.077, 2.082, 2.198, 2.203 and 2.209 A, respectively. These
4a
˚
intramolecular H-bonds (H/A > 2.52 A), the intramolecular
intermolecular H-bonds connect NO3 anions, water molecules
as well as amidrazone of 4-aminofurazan-3-carboxylic acid
cations forming an innite 3D network structure (Fig. S8 and
9†).
H-bonds in 1 are shorter and stronger while the amount of
intramolecular H-bonds is greater. The intramolecular H-bonds
resulted in coplanar structure of all the non-hydrogen atoms of
Fig. 2 Single crystal structures and hydrogen bonds of 1 (a) and
1a$H2O (b) (hydrogen bonds: green dash line).
Scheme 1 Energetic salts based on furazan-ring.
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Table 1 Intramolecular hydrogen bonding distances (A˚) and angle (ꢀ)
for compounds 1, 1a$H2O and 1b–1c
D–H (A) H/A (A) D–H/A (A) <DHA (ꢀ)
˚
˚
˚
Comp
D–H/A
1
N3–H3B/N5
N9–H9/N11
N4–H4A/N1
N10–H10B/N7 0.886
N10–H10A/N12 0.886
0.883
0.881
0.884
2.410
2.215
2.332
2.425
2.419
2.295
2.382
2.269
2.168
2.250
2.455
2.491
2.471
2.930
2.814
2.798
2.799
2.699
2.847
2.771
2.826
2.855
2.828
2.770
2.727
2.794
118.06
124.91
112.97
105.78
98.72
126.37
107.89
122.54
134.36
123.02
102.31
95.12
1a$H2O N3–H3B/N4
N6–H6A/N1
1b
1c
0.805
0.861
0.859
0.882
0.880
0.880
0.910
N7–H7B/N8
N3–H3B/N5
N9–H9B/N11
N4–H4B/N2
N6–H6A/N4
Fig. 4 Coplanar structures of 1 and cations in various compounds ((a):
compound 1; (b): compound 1a; (c): compound 1b; (d): compound 1c).
N10–H10B/N8 0.880
102.30
structure was connected by these 13 intermolecular H-bonds,
forming an innite 3D network (Fig. S12 and 13†).
To conclude, these N–H/N intramolecular H-bonds caused
all of the non-hydrogen atoms in the neutral compound and
cations coplanar (Fig. 4). The hydrogen/acceptor (H/A)
1b was crystalized as a colourless block in the monoclinic
P21/c space group accompanied by four anions and eight
cations in a unit cell (Fig. 3a). Its density was 1.70 g cmꢁ3 at
room temperature. The structure of 1b is similar to 1a as 1b
contains intramolecular H-bond (N7–H7B/N8) in the cation
˚
distance of these intramolecular H-bonds ranged from 2.168 A
˚
while the hydrogen/acceptor (H7B/N8) distance was 2.275 A.
˚
to 2.491 A; they are not only shorter than those reported
The intramolecular H-bonds cause all the non-hydrogen atoms
of the cation to coplanar (Fig. 4c and Table S4†). Moreover,
a large amount of intermolecular H-bonds was observed
throughout the intermolecular H-bonds connected 3D crystal
structure (Fig. S10 and 11†), with lengths of 1.892, 2.048, 2.119,
˚
N–H/N intramolecular H-bonds (>2.52 A), but also shorter
than most of those N–H/N intermolecular H-bonds (H/A:
2.187–2.345 A).4a,11 Hence, these strong intramolecular H-bonds
˚
permit the close stacking of these compounds. Additionally, the
existing large amounts of intermolecular H-bonds of the cor-
responding compounds allow compounds to pack closely and
further led to innite 3D networks, particularly 1c, which dis-
played rm structure as 13 intermolecular H-bonds were
observed throughout the crystal.
˚
2.303, 2.271, and 2.489 A, respectively.
1c was crystalized in the monoclinic P1n1 space group, with
two anions and four cations in a unit cell (Z ¼ 2, Fig. 3b). Similar
to 1, ve intramolecular H-bonds (N3–H3B/N5, N9–H9B/
N11, N4–H4B/N2, N6–H6A/N4 and N10–H10B/N8 respec-
tively) were observed in two neighbouring cations, and their
corresponding hydrogen/acceptor (H3B/N5, H9B/N11)
Thermal stability and sensitivity
˚
˚
˚
˚
˚
lengths were 2.168 A, 2.250 A, 2.455 A, 2.471 A and 2.491 A,
respectively, which are more stronger than those in 1. The
intramolecular H-bonds make cation almost coplanar (Fig. 4d
and Table S5†). Further, as many as 13 intermolecular H-bonds
throughout the crystal were observed, and the hydrogen/
acceptor (H/A) lengths of these intermolecular H-bonds were
1.928, 1.983, 2.030, 2.060, 2.120, 2.183, 2.193, 2.295, 2.311,
Thermal stability is a crucial factor for energetic compounds:
the higher the decomposition temperature, the safer the ener-
getic compounds. Thermogravimetric analysis-differential
scanning calorimetry (DSC, 5 ꢀC minꢁ1) was employed to
characterize the thermal stability of all ve compounds
prepared in this stꢀudy. The decomposition temperatures (on
set) of 1 was 183.4 C, while the disintegration temperature of
1a–1d were 133.0, 184.9, 183.3, and 198.5 ꢀC (Fig. S1–S5†),
respectively. The decomposition temperatures of four
˚
2.355, 2.457, 2.491 and 2.499 A, respectively. The crystal
ꢀ
compounds, 1, 1b, 1c and 1d, were greater than 180 C.
All ve samples were examined by the Fall-hammer and
Friction apparatus and all of them exhibited insensitivity (IS >
Table 2 The percentage of O–H and N–H week interactions in 1 and
1a$H2O, 1b–1c
Crystal
1
1a$H2O
1b
1c
O–H (%)
N–H (%)
13.2
35.0
53.1
15.4
23.4
38.4
15.7
38.2
Fig. 3 Single crystal structures and hydrogen bonds of 1b (a) and 1c (b)
(hydrogen bonds: green dash line).
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40 J, FS > 360 N) to stimulation via impact and friction.19 Hence, interactions is higher than O–H weak interactions except
it is benecial to investigate the insensitivity of these 1a$H2O, which may due to more O atoms provided by NO3
compounds. In this study, all crystals prepared contain N–H/N anion and H2O in 1a$H2O. The strength of N–H weak interac-
intramolecular H-bonds. As comparing examples with 1a, 3,5- tions in the case of 1 and 1c are also higher than the strength of
diamino-1,2,4-triazole,
4,40,5,50-tetraamino-3,30-bis-1,2,4- O–H weak interactions as shown in Fig. 5 (Fig. S14†). The
triazole and 3-methyl-1-amino-1,2,3-triazole are insensitive. investigation of weak interactions displays that the large
The impact and friction sensitivities of 3,5-diamino-1,2,4- portions of N–H weak interactions are possibly also helpful in
triazole nitrate salts are 40 J and 288 N, respectively, and the decreasing sensitivities.
impact sensitivities of 3-methyl-1-amino-1,2,3-triazole nitrate
and 4,40,5,50-tetraamino-3,30-bis-1,2,4-triazole nitrate are 28.9 J
and 15 J, respectively, which are obviously more sensitive than
Detonation properties
those of 1a,12 which would possibly result from the strong
intramolecular H-bonds, and large amount of intermolecular H-
bonds in the structures. Similarly, compounds 1b and 1c were
less sensitive than the energetic compounds based on 5,50-
dihydrobistetrazole and 3-nitramino-4-tetrazolefurazan.9d,13
Thus far, all compounds based on 3,4-di(nitramino)furazan
were sensitive; hence, 1d can offer a new route to desensitize
compounds of 3,4-di(nitramino)furazan.9a
In general, the “so” O–H and N–H interactions are condu-
cive to stabilizing the crystal structure by absorbing the
mechanic stimuli.14 In this study, Hirshfeld surfaces15 were
employed to analyse the weak interactions of the obtained
compounds. As shown in Table 2, the percentage of O–H weak
interactions in 1 and 1a$H2O, 1b–1c are 13.2%, 53.1%, 23.4%
and 15.7%, respectively, while the percentage of N–H weak
interactions in 1, 1a$H2O and 1b–1c are 35.0%, 15.4%, 38.4%,
and 38.2%, respectively. The proportion of N–H weak
To examine the energetic properties of 1 and its derivatives, the
heat formation for 1 and its corresponding anion were deter-
mined by the isodesmic reaction approach (see ESI†). The
computation was performed using the Gaussian 03 suite of
programs.17 The heat formation for 1 and 1a–1d were 329.1,
208.2, 1507.2, 1432.5, and 1206.1 kJ molꢁ1, respectively (Table
3). The detonation properties of all new compounds were
calculated by EXPLO5 6.01 code with the calculated enthalpies
of formation and the measured densities.18 The detonation
velocities and pressures of 1 and 1a–1d were 7999, 8455, 8680,
8249, and 8541 m sꢁ1 and 22.20, 27.73, 28.77, 25.57, and
28.42 GPa (Table 2), respectively. The detonation properties of
all the compounds were greater than that of TNT; especially, the
detonation velocity of 1b, which exhibited the best detonation
performance, was 8680 m sꢁ1. This was greater than LLM-116
and comparable to that of RDX. The detonation velocity of 1d
was greater than that of TATB and comparable to that of LLM-
116. Samples 1a, 1b, and 1d demonstrated immense
Fig. 5 (a) The total weak interactions of 1; (b) the N–H weak interactions of 1; (c) the O–H weak interactions of 1; (d) the total weak interactions of
1c; (e) the N–H weak interactions of 1c; (f) the O–H weak interactions of 1c.
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Table 3 Physical properties of all compounds based on the amidrazone of 4-aminofurazan-3-carboxylic acid
Comp.
db c (g cmꢁ3
)
DfHc d (kJ molꢁ1
)
Vdd e (m sꢁ1
)
Pe f (Gpa)
ISf g (J)
FSg h (N)
a
Tm (ꢀC)
a b
Td (ꢀC)
1
1a
1b
1c
167.3
128.5
81.6
85.7
106.4
—
—
—
81
198.4
133
184.9
183.3
198.5
360
178
205
295
1.60
1.68
1.70
1.64
1.68
1.93
1.90
1.81
1.65
329.05
208.2
1507.2
1432.5
1206.06
ꢁ154.2/ꢁ0.60
96.3/0.56
80/0.36
7999
8455
8680
8249
8541
8114
8573
8795
6881
22.20
27.73
28.77
25.57
28.42
31.2
34.2
34.9
19.5
>40
>40
>40
>40
>40
>40
>40
7.4
>360
>360
>360
>360
>360
>360
>360
120
1d
TATBi
LLM-116i
RDXi
TNTi
ꢁ67.0/ꢁ0.30
15
353
a
Melting point. b Temperature of decomposition (onset). c Density measured by using a gas pycnometer at 25 ꢀC. d Calculated molar enthalpy of
formation in the solid state. e Calculated detonation velocity. f Calculated detonation pressure. g Impact sensitivity. h Friction sensitivity. i Ref. 3a
and 16.
applications as alternatives to traditional classic compounds as 13C and 15N spectrums were showed from Fig. S15–S20.† Except
they exhibited moderate detonation velocities at an insensitive for single crystal structure determination, before all character-
level.
izations (such as thermal stability, sensitivities, element anal-
ysis and density, etc.), the samples were dried in 60 ꢀC for 6 h, in
order to remove the water or moisture of the samples. The
melting and decomposition points were recorded on
Conclusions
a NETZSCH STA 449F3 equipment at a scan rate of 5 ꢀC minꢁ1
,
Insensitive 4-aminofurazan-3-carboxylic acid amidrazone (1)
was synthesized, and then its four derivatives (1a–1d) were
prepared and characterized. It is interesting that all four
derivatives are insensitive to impact and friction, which were
resulted from the combination of strong N–H/N intra-
molecular H-bonds, a large amount of intermolecular H-bonds,
and high percentage of weak N–H interactions in these deriva-
tives. In addition, the detonation velocity of compound 1b is
higher than that of LLM-116 and comparable to that of RDX.
The detonation velocity of 1d is greater than that of TATB and
comparable to that of LLM-116 demonstrating their promising
for applications. In a word, combining multi-stabilizing factors,
4-aminofurazan-3-carboxylic acid amidrazone cation is prom-
ising in desensitizing energetic materials.
respectively. Infrared spectra were recorded by using KBr
pellets. Densities were measured at room temperature using
a Micromeritics Accupyc II 1340 gas pycnometer. Elemental
analyses were obtained on an Elementar Vario MICRO CUBE
(Germany) elemental analyser. Impact and friction-sensitivity
measurements were tested by employing a standard BAM Fall-
hammer and a BAM friction tester. The acknowledgements
come at the end of an article aer the conclusions and before
the notes and references.
X-ray crystallography
The single-crystal X-ray diffraction data of 1 and 1a–1c were
collected at 293 K using graphite-monochromated MoKa radi-
˚
ation (l ¼ 0.71073 A) using omega scans from a Bruker CCD
Experimental
Safety precautions
area detector diffractometer. Data collection and reduction were
performed, and the unit cell was initially rened using Bruker
SMART soware.20 The reection data were also corrected for LP
factors. The structure was solved by direct methods and rened
by a least-squares method on F2 using the Bruker SHELXTL
program.21 In these structures, the value of the Flack parameter
did not allow the direction of the polar axis to be determined
and Friedel reections were then merged for the nal rene-
ment. Details of the data collection and renement are given in
Table S1.†
Although we experienced no difficulties in synthesis and char-
acterization of these materials, proper protective procedures
should be followed. All the experiments were carried out in
a hood behind a safety shield and face shield, and leather gloves
were worn at all times. Caution was exercised at all times during
the synthesis, characterization, and handling of any of these
materials.
Materials and methods
Computational method
1H spectra were recorded on a 300 MHz nuclear magnetic
resonance spectrometer operating at 300 MHz. 13C NMR spectra The gas phase heats of formation for all new neutral
were recorded on a 400 MHz nuclear magnetic resonance compounds and anions were obtained using isodesmic reac-
spectrometer. The solvent were [D6]dimethylsulfoxide ([D6] tions. The geometric optimization and frequency analysis of the
DMSO) and [D4]methanol ([D4]CH3DO) unless otherwise spec- structures were calculated using B3LYP function with 6-31+G**
ied. 15N NMR spectra was recorded on a 400 MHz nuclear basis set. All of the optimized structures were checked to be true
magnetic resonance spectrometer operating at 40.5 MHz, the local energy minima on the potential energy surface without
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Amidrazone of 4-aminofurazan-3-carboxylic acid 5,50-
bistetrazole-1,10-diolate (1b)
imaginary frequencies. Single-point energies based on the
optimized structures were calculated at the MP2/6-311++G* set.
Atomization energies for the frame molecules or ions were ob-
tained by employing the G2 ab initio method. The conversion of
gas phase enthalpies to solid phase values for the neutral
compounds was done by subtracting the empirical heat of
sublimation obtained based on Trouton's rule. Detonation
properties of new compounds were calculated by using EXPLO5
program. More calculation details can be found in the ESI.†
1
Yellow solid (0.42 g, 93.1%); H NMR (DMSO-d6): d 6.92 (NH3,
3H), 6.39 (NH2, 2H), 5.91 (NH2, 2H) ppm; 13C NMR (DMSO-d6):
d 155.26, 144.56, 140.71, 135.59 ppm; IR (KBr): n 3064, 1692,
1545, 1481, 1449, 1351, 1222, 1215, 1150, 1065, 1036, 955, 802,
760, 739, 548 cmꢁ1
; elemental analysis, calcd (%) for
C8H14N20O4 (454.15): C: 21.15; H: 3.11; N: 61.66; found, C: 20.83;
H: 2.76; N: 61.55.
Amidrazone of 4-aminofurazan-3-carboxylic acid 3-nitramino-
4-tetrazolefurazanate (1c)
Syntheses
According to the literature10 and synthesis route depicted in
Fig. 1, 4-(1,2,4-oxadiazol-3-yl) furazan-3-amine (1.53 g, 10
mmol), a luminous yellow solid, was synthesized with high
yield and then treated with 80% hydrazine hydrate in methanol
1
Yellow solid (0.44 g, 91.0%); H NMR (DMSO-d6): d 7.02 (NH2–
NH3, 5H), 6.39 (NH2, 2H) ppm; 13C NMR (DMSO-d6): d 158.06,
155.34, 147.64, 145.50, 141.87, 140.72 ppm; IR (KBr): n 3343,
3287, 3074, 2992, 2887, 1725, 1628, 1575, 1508, 1250, 1140,
1102, 1080, 966, 746 cmꢁ1; elemental analysis, calcd (%) for
C9H14N20O5 (482.15): C: 22.41; H: 2.93; N: 58.08; found, C: 22.07;
H: 3.17; N: 57.89.
ꢀ
at 50 C for 30 min. Hence, amidrazone of 4-aminofurazan-3-
carboxylic acid (1) was obtained as brown solid with high
yield, compound 1 was recrystallized from water, the brown
needle-like crystal was obtained, which were used for the
synthesis of salts. Yellow solid (1.35 g, 95.3%); 1H NMR (DMSO-
d6): d 6.39 (NH2, 2H), 5.86 (NH2, 2H), 569 (NH2, 2H) ppm; 13C
NMR (DMSO-d6): d 155.01, 141.10, 137.13 ppm; 15N NMR ([D4]
Amidrazone of 4-aminofurazan-3-carboxylic acid 3,4-
dinitraminofurazanate (1d)
1
CH3DO):
d
17.04, ꢁ21.67, ꢁ122.26, ꢁ282.99, ꢁ316.14,
Yellow solid (0.43 g, 91.5%); H NMR (DMSO-d6): d 7.12 (NH3,
3H), 6.92 (NH2, 2H), 6.41 (NH2, 2H) ppm; 13C NMR (DMSO-d6):
d 155.69, 155.24, 147.65, 141.85, 140.01 ppm; IR (KBr): n 3466,
3414, 3349, 3269, 3206, 1723, 1647, 1494, 1452, 1361, 1219,
1134, 1072, 962 cmꢁ1; elemental analysis, calcd (%) for
C8H14N18O7 (474.13): C: 20.26; H: 2.98; N: 53.13; found, C: 20.15;
H: 2.63; N: 53.40.
335.19 ppm; IR (KBr): n 3469, 3415, 3353, 3335, 2918, 2848,
1662, 1611, 1555, 1466, 1440, 1405, 1323, 1194, 1144, 1050, 992,
870, 841, 787, 754, 721, 574 cmꢁ1; elemental analysis, calcd (%)
for C3H6N6O (142.06): C: 25.35; H: 4.26; N: 59.13; found, C:
25.18; H: 3.98; N: 58.73.
General procedure for the preparation of salts 1a
Author contributions
Compound 1 (0.142 g, 1 mmol) was added to methanol (20 ml)
with stirring. HNO3 (5%, 1.23 ml, 1 mmol) was added into the
above methanol. The reaction mixture was stirred at room
temperature for 30 min followed by evaporation in vacuo. The
precipitate was collected and recrystalized in the methanol and
water. Colourless crystal contains one molecular water on each
crystal unit cell (0.18 g, 80.7%), aer drying in 60 ꢀC for 6 h, the
water in molecular were removed. The 1H NMR (DMSO-d6):
d 9.29 (NH3, 3H), 8.08 (NH2, 2H), 6.42 (NH2, 2H) ppm; 13C NMR
(DMSO-d6): d 155.49, 152.77, 140.23 ppm; IR (KBr): n 3064, 1692,
1545, 1481, 1449, 1351, 1222, 1215, 1150, 1065, 1036, 955, 802,
760, 739, 548 cmꢁ1; elemental analysis, calcd (%) for C3H7N7O4
(204.13): C: 17.65; H: 2.96; N: 48.03; found, C: 17.29; H: 3.06; N:
47.83.
Yunhao Hsieh polished this paper. Binshen Wang and Haifeng
Huang helped do some calculations for this job. Jun Yang and
Jiaheng Zhang provide the idea of this paper together.
Conflicts of interest
The authors declare no competing nancial interest.
Acknowledgements
The authors acknowledge nancial support from the National
Natural Science Foundation of China (NSFC, Grant. No.
21602241), Shenzhen Science and Technology Innovation
Committee (JCYJ20151013162733704), Economic, Trade and
Information Commission of Shenzhen Municipality through
the Graphene Manufacture Innovation Center (201901161514),
and the Thousand Talents Plan (Youth).
General procedure for the preparation of salts 1b–1d
To a stirring solution of 1$HCl (0.353 mg, 2.0 mmol), the silver
compounds (1.0 mmol) of 1b, 1c and 1d were added to the above
solutions, respectively. Then, the reaction mixture was stirred at
room temperature for 30 min followed by ltration, evapora-
tion. The precipitates were recrystalized from the mixture of
methanol and water, respectively. Then dried at 60 ꢀC for 6 h for
the next characterisations.
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