Synthesis and characterization of energetic compounds based on N-oxidation of 5-Nitroso-2,4,6-triaminopyrimidine

Article abstract of DOI:10.1016/j.molstruc.2021.130732

The N-oxidation of 5-Nitroso-2,4,6-triaminopyrimidine leads to the successful synthesis of 5-Nitro-2,4,6 triaminopyrimidine-1,3-Dioxide (NTAPDO) 1 and 5-Nitro-2,4,6-triaminopyrimidine-1-oxide (NTAPMO) 2 by using mild oxidation reactions and the NTAPMO (2)

Full text of DOI:10.1016/j.molstruc.2021.130732

Journal of Molecular Structure 1242 (2021) 130732
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstr
Synthesis and characterization of energetic compounds based on
N-oxidation of 5-Nitroso-2,4,6-triaminopyrimidine
Saira Manzoora, Piao Heb, Jun-Qing Yang c, Qamar-un-nisa Tariq a, Li Jing-Rua, Yong Hua,
Wenli Caoa, Jian-Guo Zhanga,∗
a State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081, China
b College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan 410083, China
c School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
a r t i c l e i n f o
a b s t r a c t
Article history:
The N-oxidation of 5-Nitroso-2,4,6-triaminopyrimidine leads to the successful synthesis of 5-Nitro-2,4,6
triaminopyrimidine-1,3-Dioxide (NTAPDO) 1 and 5-Nitro-2,4,6-triaminopyrimidine-1-oxide (NTAPMO) 2
by using mild oxidation reactions and the NTAPMO (2) based energetic salts (3–5) were prepared ef-
fectively by reacting 2 with the related acids following neutralization reaction. The single-crystal X-ray
diffraction, differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA) techniques
were applied to manifest the structures and thermal stability of compounds respectively. The compounds
1–5 exhibited high densities in the range of 1.76 -1.87 g.cm−3 and mechanically insensitive towards im-
pact and friction. The heat of formation (HOF) of these compounds was found high positive between the
ranges of 207.7 to 768.4 kJ.mol−1. The energetic salts 3, 4, and 5 demonstrated high detonation perfor-
Received 5 April 2021
Revised 14 May 2021
Accepted 16 May 2021
Available online 23 May 2021
Keywords:
5-Nitroso-2,4,6-triaminopyrimidine
Crystal structures
Detonation properties
Oxidation
mance (velocity and pressure) and high volumes of explosion gasses (789.77, 733.85, and 730.61 L•kg−1
,
Thermal stability
respectively). Hence, compounds 1–5 displayed good thermal stability, high positive HOFs, and good deto-
nation performance as well as low sensitivity suggesting their potential to be used as energetic materials
in the field of high-performance explosives.
X-ray diffraction technique
© 2021 Elsevier B.V. All rights reserved.
1. Introduction
HOF, oxygen balance, and safety remain a big challenge for chemi-
cal researchers [19–21].
Energetic Materials (EMs), a distinctive family of compounds
that can rapidly release a big quantity of chemical energy have
gained enormous attention since the nitroglycerin reported in 1863
by Alfred Nobel [1–3]. The EMs are playing a significant role in
both civilian and military operations as explosives, propellants, and
pyrotechnics [4–6]. In the past few decades, several researchers
have been focusing on and participating in the quick development
of EMs [7–10]. As a result a large number of EMs were established
based on a variety of backbones such as aromatics, strain-caged
heterocyclic, alkanes, and nitrogen-rich heterocycle [11–14]. How-
ever, the EMs that retain high energy usually showed less stabil-
ity toward heat, friction, and impact which consequently leads to
the safety risk as applied on TNT (2,4,6-trinitrotoluene) and TATB
(1,3,5-triamino-2,4,6-trinitro benzene) [15–18]. Ultimately, these
safety threats marked EMs hazardous for manufacturing, handling,
and usage in civilian and military operations. Therefore, the design
and synthesis of potent EMs having good detonation performance,
The synthesis of EMs based on N-oxides is considered a recent
methodology due to the presence of high-nitrogen contents, source
of oxygen, and possible replacement for the nitro group. [22,23]
The N-O bond of N-oxide relatively proves a strong bond owing to
its significant double-bond character and π-back-bonding by the
–
lone pair of oxygen [24]. The additional oxygen atom of N O not
only improves the density, HOF, and detonation performance but
also stabilizes the whole molecule by increasing aromaticity of the
ring system and reduce mechanical sensitivity towards impact and
friction [24,25]. Therefore, in recent years a large number of N-
oxide-based reactions have been described such as the develop-
ment of the furoxan ring, azoxy link, and N-oxidation on nitrogen-
rich heterocyclic compounds [26–30].
Energetic salts possess high density and stability due to high
lattice energy as compared to their neutral analogues [31]. The
synthesis of energetic salts based on N-heterocyclic compounds
which have been further N-oxygenated proves to be beneficial over
traditional molecules due to low vapor pressures, less possibility
of exposure by inhalation, high HOF, and high nitrogen content
[32,33]. Moreover, the properties of these compounds could be
∗
Corresponding author.
E-mail address: zjgbit@bit.edu.cn (J.-G. Zhang).
https://doi.org/10.1016/j.molstruc.2021.130732
0022-2860/© 2021 Elsevier B.V. All rights reserved.

S. Manzoor, P. He, J.-Q. Yang et al.
Journal of Molecular Structure 1242 (2021) 130732
Scheme 1. Synthesis of NTAPDO (1) and NTAPMO (2).
readily improved by the suitable combination of cation and anion
components. In addition, these molecules have gained considerable
attention for the synthesis of energetic salts because the energy of
these molecules originates from the ring strain, which makes them
versatile in comparison to the aromatic molecules to be used for
practical applications such as propellants, explosives, and pyrotech-
nics [34–36].
formation of di-N-oxides (1) requisite more time in comparison to
mono-N-oxides (2). The colorless single crystals of 1 and 2 reason-
able for a single-crystal x-ray diffraction technique were grown in
the water at room temperature and pressure.
The NTAPMO (2) reacts more efficiently with strong acids to
carry out acid-base neutralization reactions due to its weak ba-
sic nature. Therefore, the preparation of energetic salts 3, 4, and
5 was carried out in a simple way using a neutralization reaction
method as illustrated in Scheme 2. To carry out the synthesis of
a nitrate salt, we first reacted NTAPMO (2) with 15% nitric acid
(HNO3) but it contains water of crystallization (3). Therefore, in ef-
forts to get pure nitrate salt NTAPMO (2), the reaction was carried
out with 65% HNO3 to attained compound 4. Whereas, the syn-
thesis of energetic salt 5 was accomplished with 60% perchlorate
acid (HClO4). The solutions of nitrate salts (3 and 4) were kept at
room temperature and pressure for 2–3 days to get colorless crys-
tals, while yellow crystals of 5 were attained after slow evapora-
tion of mother liquid in two weeks at low temperature. The ob-
tained crystals of 3, 4, and 5 were appropriate for single-crystal
x-ray diffraction analysis. All the energetic salts were attained in
good yield and high purity. Moreover, the amino group present at
position 6 of the NTAPMO (2) oxidized readily to enhance the oxy-
gen balance of energetic salts due to the strong oxidizing nature of
nitric and perchlorate acids.
Hence, in continuing efforts to develop high-performing explo-
sives with better detonation properties than traditional explosives,
we have done mono and di N-oxidation of 5-Nitrosopyrimidine-
2,4,6-triamine and further prepared energetic salts (3–5) in this
work. The oxidation of 5-Nitrosopyrimidine-2,4,6-triamine is al-
ready reported, however, the individual synthesis of compounds di
N-oxygenated (1) and mono N-oxygenated (2) compounds follows
the complex procedure, and their physiochemical and energetic
properties were also not discussed in detail [37,38]. Therefore, in
our work, a mild oxidation reaction approach was adopted for the
synthesis of compounds 1 and 2 individually. Furthermore, the ni-
trate and perchlorate salts (3, 4, and 5) of compound 2 were also
synthesized, using 15, 65% nitric acid (HNO3), and 60% perchlo-
rate acid (HClO4) respectively. The single crystals of prepared com-
pounds 1–5 were characterized using the X-ray diffraction tech-
nique. In addition, the HOF and detonation performance (velocity
and pressure) of targeted compounds were calculated by the DFT
method, Gaussian 09 suites of programs, and EXPLO5 6.04 program
respectively. Results suggested that all of the synthesized com-
pounds exhibit reasonable decomposition temperatures, low sen-
sitivities (> 40 J, > 360 N), and high detonation performances.
2.2. X-ray crystallography
The single crystals of compounds 1–5 were grown by slow
evaporation of respective solutions at room temperature and pres-
sure except compound 5 that is crystallized at a lower tempera-
ture. The molecular structures of compounds 1–5 were character-
ized by the X-ray single-crystal diffraction technique. Compound 1
crystallizes in the orthorhombic crystal system with a space group
of Pca21 (Fig. 1) four molecular moieties in the unit cell, and a
density of 1.85 g.cm−3. Compound 2 crystallizes in the monoclinic
crystal system with a space group of P21/c, and four molecules in
the unit cell (Fig. 2). The density of compound 2 is 1.76 g.cm−3
at 163.15 K. Both of the compounds were crystallized with the
molecule of water in the crystals. The N-O bond lengths of the
2. Result and discussions
2.1. Synthesis
The synthesis of compounds (NTAPDO) 1 and (NTAPMO) 2 was
described by the groups of Delia, Hollins, and Millar in 1960,
1995, and 2004 respectively followed by complicated, less pro-
ductive, and containing scale-up issues methods [37–39]. These
methods of preparations were convoluted owing to the develop-
ment of di-N-oxides (1) and mono-N-oxides (2) mixture, one prod-
uct in higher concentration, and hydrolysis of products. Therefore,
we prepared NTAPDO (1) and NTAPMO (2) by adopting a unique
and improved approach of mild oxidation reactions, as depicted
in Scheme 1. The designated method was acceptable to develop 1
and 2 distinctly with good yield. The commercially available and
economically cheap 5-Nitroso-2,4,6-triaminopyrimidine was used
as a starting reagent, which was oxidized by trifluoroacetic acid
and 30% hydrogen peroxide (H2O2) to yield 1 and 2. The most
important factors observed to reach the synthesis of 1 and 2 in-
dependently were precipitating solvents and reaction time. Thus,
we used two different solvents for the purification which were
dichloromethane and diethyl ether respectively Furthermore, the
˚
six-membered aromatic di-N-oxides (1) are 1.351(4) A between
the N5-O3 and N6-O3. Whereas, in the case of mono-N-oxides
(2) this bond length is slighter larger than di-N-oxides (1) which
˚
is 1.356 (4) A between the connected bond N5-O3.These bond
lengths which typically represented the acyclic type bond between
the N-O, confirm the di-oxygenated (1) and mono-oxygenated (2)
products of the 5-Nitroso-2,4,6-triaminopyrimidine. Additionally,
the oxygen atom in the pyrimidine mono N-oxide acts as a more
operational Lewis-type base to react with strong Lewis acids to
give neutralized salts.
Compound 3 (Fig. 3) crystallizes in the triclinic crystal system
with a P-1 space group, two water molecules of crystallization, and
2

S. Manzoor, P. He, J.-Q. Yang et al.
Journal of Molecular Structure 1242 (2021) 130732
Scheme 2. Synthesis of NTAPMO (2) based energetic salts 3, 4, and 5.
Fig. 1. Molecular structure and labeling scheme of 1 thermal ellipsoid represented at the 50% probability level. (Hydrogen atoms are included but labeling omitted for
clarity).
˚
˚
four molecules in the unit cell. The calculated density of compound
3 was 1.77 g.cm−3 at 163.15 K. whereas, compound 4 crystallizes
in the orthorhombic P2121 space group as illustrated in Fig. 4. The
density of energetic salt 4 was 1.86 g.cm−3 with four molecular
moieties in the unit cell at 163.15 K. The crystallographic infor-
mation and structure refinements of compounds 1–5 are given in
Table 1. The presence of bond angles 118.5° (3), 122.3° (3), and 119°
(3) confirmed the slightly bent and trigonal planar geometry of -
NO3 in both compounds 3 and 4. Whereas, the O-N (pyrimidine
N-oxide) bond lengths are different in both compounds, which
are 1.381(6) A (O8-N8) and 1.374 (3) A (N5-O3). The O-N bond
lengths are greater due to the nitrogen atom participation in ring
pi-electron resonance. The large variations in N-oxide bond length
demonstrate that the N-oxide group is generally involved in the
intermolecular interaction of N-oxide. Therefore, the presence of
extended hydrogen bond interactions between the O…N…O and
N…O…H practice a reticular framework of 3 and 4 which can be a
significant influence on thermal stability.
Furthermore, the energetic salt 5 crystallized in monoclinic
P21/n1 space group (Fig. 5), with twelve molecular moieties in the
3

S. Manzoor, P. He, J.-Q. Yang et al.
Journal of Molecular Structure 1242 (2021) 130732
Table 1
X-ray crystallographic information and structure refinement details of 1, 2, 3, 4, and 5.
Compound
1
2
3
4
5
CCDC
1,975,142
C4H6N6O4
202.13
1,975,156
C4H6N6O3
186.13
1,975,140
C4H10N6O9
286.18
1,975,159
2,010,114
C4H6ClN5O8
287.59
Empirical Formula
C4H6N6O7
250.15
−1
•
Mw (g mol
)
Crystal system
Space group
Orthorhombic
Pca21
Monoclinic
P21/c
Triclinic
P1
Orthorhombic
P21212
Monoclinic
P21/n1
˚
a [A]
13.043(3)
3.9867(8)
29.200(6)
1518.36(5)
90
6.4294(13)
15.066(3)
16.198(3)
1537.96(6)
90
8.6729(17)
10.326(2)
12.857(3)
1073.62(4)
98.10 (3)
104.42 (3)
100.86 (3)
4
8.5559(17)
20.660(4)
5.050(10)
892.66(3)
90
11.0205 (2)
12.4216 (2)
22.734 (2)
3053.26(5)
90
˚
b [A]
˚
c [A]
3
˚
V (A )
α (°)
β (°)
ᵧ (°)
Z
90
101.42 (3)
90
90
101.16(3)
90
90
90
4
4
4
12
−3
•
Crystal density(g cm
Crystal size
)
1.85
1.76
1.77
1.86
1.88
0.21×0.13×0.11
0.166
0.13×0.12×0.04
0.155
0.15×0.12×0.1
0.172
0.18×0.17×0.12
0.177
0.45×0.40×0.24
0.427
μ (mm−1
)
F(000)
872
848
592
512
1752
˚
λMoKα(A)
0.71073
0.0508
0.71073
0.1319
0.71073
0.1299
0.71073
0.0410
0.71073
0.1158
R1 (all data)
wR2 (all data)
Refl. coll.
0.1081
0.2332
0.2973
0.1001
0.3449
3261
3490
4819
2017
5277
Max. and min. transmission
1.00 & 0.694
1.119
0.8126 & 1.00
1.219
0.8123 & 1.00
1.121
0.7799 & 1.00
1.054
0.831 & 0.905
1.199
GOF
−3
˚
largest differential peak and hole [e A
]
0.25 & −0.22
1.39 - 27.47
163.15 (2)
Colorless
Block
0.36 & 0.35
1.35 - 27.48
163.15(2)
Colorless
Block
0.93 & −0.61
1.67 - 27.39
163.15(2)
Colorless
Block
0.24 & −0.22
3.092- 27.48
163.15(2)
Colorless
Block
0.899 & 0.645
2.25–25.020
298.15(2)
Colorless
Block
θ (°)range
T (K)
Crystal color
Crystal habit
bonding between the perchlorate ion and mono-N oxide (2) in the
form of N…O…N and O…N…O interactions.
2.3. Thermal analysis
High Thermal stability is required for energetic materials aimed
at safe handling during transportation, usage, and storage. The
thermal behavior of prepared compounds 1, 2, 3, and 4, studied us-
ing differential scanning calorimetry (DSC) and thermo-gravimetric
(TG) measurements. The DSC and TGA results are shown in Fig. 6a
and b. For compounds 1, 2, and 4, melting points were not ob-
served, exhibiting exothermic decomposition. The compounds 1,
2, and 4 have decomposition peaks at 276 °C, 337 °C, and 180
°C respectively, as illustrated in Fig. 6a. Whereas, in the case of
compound 3 first the process of dehydration occurred leading to
the decomposition of the compounds exhibiting sharp exothermic
peaks at 168 °C. These results show that Compounds 1 and 2 have
high thermal stability as compared to 4. The thermal stability of
nitrate salts (3 and 4) decreases as compared to the neutral com-
pounds (1 and 2), which is due to the intermolecular hydrogen
bond. The thermo-grams mass loss percentage (%) of compounds 1,
2, 3, and 4, are presented in Fig. 6b. For compound 1 the mass loss
percentage has been found 84%, having decomposition temperature
at 276 °C. Compound 2 shows a mass loss percentage value of 97%,
at decomposition peak. Compound 3 has one endothermic peak
(>95 °C) and one exothermic process (168 °C), in which the first
is a process of dehydration as confirmed from TG with a mass loss
of 36%. Whereas, the thermo-gravimetric analysis curve for com-
pound 4 shows a 73% mass loss percentage at a decomposition
temperature of 180 °C. Hence, for compounds 1, 2, 3, and 4 the
temperature range of mass-loss processes agreed with the exother-
mic processes as suggested by DSC. Therefore, compounds 1 and 2
have a good decomposition temperature which is greater than 200,
while 4 has reasonable (180 °C) as compared to the standard dis-
Fig. 2. Molecular structure and labeling scheme of 2 thermal ellipsoids represented
at the 50% probability level. (Hydrogen atoms are included but labeling omitted for
clarity).
unit cell and a density of 1.87 g.cm−3 at 163.15 K. The bond angles
between O13-Cl1- O14, O13-Cl1- O15, O13-Cl1- O16, O14-Cl1- O15,
and O14-Cl1- O16, are 113.2° (4), 109.5° (4), 113.5° (4) 103.9° (4),
109.1° (4), which confirmed the tetrahedral geometry of four oxy-
gen molecules surrounding the chlorine atom (-ClO4). Whereas, the
O-N (pyrimidine N-oxide) bond length is 1.380(5) between the N1-
O1 connected bonds. Therefore, this extended bond length could
be involved in intermolecular interaction in the form of hydrogen
4

S. Manzoor, P. He, J.-Q. Yang et al.
Journal of Molecular Structure 1242 (2021) 130732
Fig. 3. Molecular structure and labeling scheme of 3 thermal ellipsoids represented at the 50% probability level (hydrogen atoms are included but labeling omitted for
clarity).
Fig. 4. Molecular structure and labeling scheme of 4 thermal ellipsoids represented at the 50% probability level (hydrogen atoms are included but labeling omitted for
clarity).
integration temperature (>200) for energetic materials. However,
compound 5 was found thermally unstable at room temperature.
used to calculate the HOF of the energetic salts [43].
ꢀHof ionic salt, 298K
(
)
= ꢀHof cation, 298K + ꢀHo anion, 298K − ꢀH
(1)
(
)
(
)
L
f
2.4. HOFs and lattice energies of energetic salts (3–5)
The HOFs of the new EMs were calculated theoretically to avoid
the synthesis of these compounds on a large scale and the associ-
ated experimental obstacles. The HOFs of energetic salts 3–5 (all
cations and anions) were calculated by the Gaussian 09 suites of
programs using the isodesmic reaction method [40,41]. The lat-
tice energy (ꢀHL) was calculated by Jenkins and Glasser equation
[42] and according to the Born-Haber energy cycle, Eq. (1) was
The results displayed in Table 2 indicated that the energetic
salts 3–5 are all formed endothermically and show a highly pos-
itive value of HOFs and lattice energies. The energetic salt 4 has
the lowest value (207.7 kJ.mol−1) due to its high lattice energy
(495.5 kJ.mol−1). The highest positive value is originated for the
energetic salt 3 (230.8 kJ.mol−1) which has a lower value of lattice
energy (472.4 kJ.mol−1).
5

S. Manzoor, P. He, J.-Q. Yang et al.
Journal of Molecular Structure 1242 (2021) 130732
Fig. 5. Molecular structure and labeling scheme of 5 thermal ellipsoids represented at the 50% probability level (hydrogen atoms are included but labeling omitted for
clarity).
Fig. 6. Thermal analysis curves of compounds 1, 2, 3, and 4 with the heating rate of 10 °C min−1 (a) Curves of differential scanning calorimetry (b) Thermo-gravimetric
analysis curves.
Table 2
ditional explosives TNT and RDX. These compounds possess high
HOFs and Lattice energies of energetic salts 3–5.
nitrogen content (about 45%) and negative oxygen balances in the
case of compounds 1 and 2. While, energetic salts 3, 4, and 5 ex-
hibited zero and positive oxygen balances respectively. The ener-
getic compounds (NTAPDO) 1 and (NTAPMO) 2 show good ther-
mal stability with high decomposition temperatures of 276 °C and
337 °C as compared to the salts (3, 4, and 5) as well as RDX.
Whereas, energetic salt 4 has a higher decomposition temperature
(180 °C) among all the other synthesized salts. The calculated den-
sities of these compounds range from 1.76 to 1.87 g•cm3. The com-
pounds 2 and 3 have a higher density as compared to TNT, while
1, 4, and 5 have even higher than RDX. The HOFs of (NTAPDO) 1
and (NTAPMO) 2 were calculated by DFT method using atomiza-
tion reaction [44] which were found 768.4 and 623.3 kJ.mol−1 re-
spectively greater than TNT and RDX. All of the salts scrutinized,
show positive HOFs varying between 207.7 (4) and 230.8 kJ.mol−1
(3) and are significantly superior to those of TNT, and RDX. The
HOFs of energetic salts were calculated using Gaussian 09 suites
Compound
3
4
5
Density (g.cm−3
Cation
)
1.77
NTAPMO+
1.86
NTAPMO+
1.87
NTAPMO+
−
−
−
Anion
NO3
NO3
ClO4
ꢀHf (cation) [kJ.mol−1
]
1011.1
−307.9
472.4
1011.1
−307.9
495.5
966.0
−277.8
479.0
209.2
a
ꢀHf (anion) [kJ.mol−1
]
b
ꢀHL [kJ.mol−1
]
c
298
d
ꢀfHm
K[kJ.mol−1
]
230.8
207.7
a
b
Heats of formation for the cation. Heats of formation for the an-
c
ion. Lattice energy calculated by the equations of Jenkins and Glasser.
d
Standard solid-state heats of formation.
2.5. Energetic properties
The physiochemical and energetic properties of synthesized
compounds 1–5 are depicted in Table 3 and compare with the tra-
6

S. Manzoor, P. He, J.-Q. Yang et al.
Journal of Molecular Structure 1242 (2021) 130732
Table 3
Physicochemical and energetic properties of synthesized compounds 1, 2, 3, 4, and 5.
Compound
1
2
3
4
5
TNT [47–49]
RDX [49–52]
a
T
( °C)
276
337
168
180
–
295
204
Dec
3
b
•
ρ (g cm )
1.84
1.76
1.77
1.86
1.87
209.2
−13.95
2.77
44.66
24.44
69.10
–
1.65
1.80
70
HOF (kJ.mol−1
Ω Co2 [%]d
Ω Co [%]e
O (%)f
)
768.4
−43.53
−23.75
31.66
41.58
73.24
>40
623.3
−47.27
−34.38
25.79
45.15
70.94
>40
230.8
−22.37
0.00
207.7
−25.58
0.00
−59.4
−74.0
−24.7
42.26
18.5
c
−21.6
0.00
43.2
37.8
81.00
5.6
50.32
29.37
79.69
>40
44.77
33.60
78.37
>40
N (%)g
N+O (%)h
60.76
36.6
Is (J)i
Fs (N)j
Tdet [K]k
>360
–
>360
–
>360
4253.6
789.77
9021
37.09
>360
4021.5
733.85
8969
36.65
–
353
120
4451.7
730.61
8762
36.44
–
3745.0
711.00
8724
33.60
−1
l
•
VO [L kg
]
–
–
825.00
6881
19.50
−1
m
•
D (m
P (GPa)n
s
)
8560
29.88
7970
23.88
a
b
c
d
decomposition temperature. crystal density. heat of formation (calculated by DFT method). Oxygen
e
f
balance for CaHbOcNd : 1600(c-2a-b/2)/MW. Oxygen balance for CaHbOcNd: 1600(c-a-b/2)/MW. Oxygen
g
h
i
j
content. Nitrogen content percentage. Combined nitrogen and oxygen contents. Impact sensitivity. Fric-
k
l
tion sensitivity. Detonation temperature. (Calculated with EXPLO5). Volume of detonation gasses (assuming
m
n
only gaseous products) (calculated with EXPLO5).
tion pressure (calculated with EXPLO5).
detonation velocity (calculated with EXPLO5). Detona-
between the ranges of 207.7 to 768.4 kJ.mol−1. The differential
scanning calorimetry (DSC) and thermal gravimetric analysis (TGA),
have shown good thermal stability for compounds 1, 2, and 4.
The detonation performances (velocity and pressure) and sensitiv-
ities (impact and friction) of the compounds were obtained by the
EXPLO5 6.04 code and BAM methods, respectively. Therefore, the
metal-free energetic salts 3 and 4 have superior detonation proper-
ties (velocity 9021 and 8969 m.s−1, pressure 37.09 and 36.65 Gpa
respectively) and insensitive than RDX and can be considered as
potentially fascinating compounds for applications in the area of
high-performance explosives.
of programs by the isodesmic reaction method [40,41]. Further-
more, the detonation properties of compounds 1–5 were calculated
by the EXPLO5 6.04 code [45] based on the calculated densities
and HOFs. The detonation velocities of energetic salts 3, 4, and
5 are 9021, 8969, and 8762 m.s−1 respectively, which are higher
than RDX (8724 m.s−1). Whereas, the detonation velocities of com-
pounds 1 and 2 are 8560 and 7970 m.s−1 respectively which are
greater than TNT for the former and comparable to RDX for later
respectively. The detonation pressures of energetic salts 3–5 are
in the range from 36.44 (5) to 37.09 (3) GPa, which are superior
to RDX (33.6 GPa). While, compounds 1 and 2 have detonation
pressure 29.8 and 23.88 respectively, which is higher than TNT
(19.3 Gpa). It is worth mentioning that the synthesized energetic
salts of NTAPMO (3, 4, and 5) possess a high volume of detona-
tion gasses of 789.77, 733.85, and 730.61 L•kg−1, respectively, ap-
proaching other reported explosives. The sensitivities (Impact and
friction) of these compounds were evaluated using standard BAM
techniques and classified according to the “U.N. Recommendations
on the transport of Hazardous materials [46]. All the synthesized
compounds excluding 5 are found insensitive towards impact and
friction. All the compounds (1–5) synthesized in this work exhibit
superior detonation properties to TNT. The energetic salt 5 dis-
played high density and higher detonation properties as compared
to RDX however it is thermally unstable and contains perchlorate.
Therefore, among all of these synthesized compounds, the metal-
free energetic salts 3 and 4 which have superior detonation and
physicochemical properties than RDX can be considered as poten-
tial energetic materials.
4. Experimental section
4.1. Caution
During the synthesis of these compounds, we observed no ex-
plosions or hazards. The use of leather gloves, fume hoods, face
shields, and careful handling are highly recommended throughout
the preparation of targeted compounds.
4.2. General methods
All reagents and solvents were of analytical grade and used
without purification as commercially obtained and reactions were
performed in an oven-dried round-bottomed flask. IR spectra were
obtained from KBr pellets using a Bruker Equinox 55. Elemen-
tal analysis was measured with a Flash EA 1112 fully automatic
trace element analyzer. Differential scanning calorimeter (DSC) and
thermo-gravimetric analysis (TG) measurements were recorded on
a METTLER TOLEDO differential scanning calorimeter (DSC) and
METTLER TOLEDO thermo-gravimetric analyzer with the heating
rate of 10 °C min−1 under dry nitrogen atmosphere. The collec-
tion of XRD data was performed on a Rigaku Saturn 724+ CCD
3. Conclusion
In summary, the synthesis of 5-nitro-2,4,6 triaminopyrimidine-
1,3-Dioxide (NTAPDO) 1 and 5-nitro-2,4,6-triaminopyrimidine-1-
oxide (NTAPMO) 2 were performed successfully using mild oxida-
tion reactions. Additionally, the energetic salts (3–5) of NTAPMO
(2) were also synthesized effectively by using a neutralization re-
action. The single-crystal X-ray diffraction technique was used to
analyze the structures of all compounds (1–5). The crystal densities
diffractometer equipped with graphite monochromatized Mo K
α
radiation. The structure was solved with the SHELXS-97 program
[53] and refined with the SHELXL-97 program [54]. The non-
hydrogen atoms were refined anisotropically and the hydrogen
atoms were located and freely refined. Furthermore, the heat of
formation and detonation properties of compounds 1, 2, 3, 4, and
5 were calculated by using the DFT method based on atomization
reaction [44], Gaussian 09 suites of programs by the isodesmic re-
action method [40,41], and EXPLO5 6.04 program respectively [45].
of compounds (1–5) were found in the range of 1.76–1.87 g.cm−3
.
The heats of formation (HOFs) of energetic salts (3–5) and N-
oxygenated compounds (1–2) were calculated by using the Born-
Haber energy cycle and DFT method respectively. All the com-
pounds reported in this work have high positive values of HOFs
7

S. Manzoor, P. He, J.-Q. Yang et al.
Journal of Molecular Structure 1242 (2021) 130732
5-Nitro-2,4,6-triaminopyrimidine-1,3dioxide (NTAPDO) (1).
1 g (7 mmol) of 5-Nitroso-2,4,6-triaminopyrimidine was dissolved
into the trifluoroacetic acid (15 ml) at room temperature. Added
dropwise this solution to the 30% hydrogen peroxide (30 mmol)
and 5 ml of trifluoroacetic acid, maintain the temperature below
20 °C. Stirred this solution at room temperature for a further
4 h, until the yellow precipitate appears in the mixture. Added
dichloromethane (20 ml), filtered, washed with dichloromethane,
warm n-propanol, dry, and get the dark orange solid as a required
product. Yield 61%, (DSC 10 °C min−1), 276 °C (Dec), crystal density,
1.84 g.cm−3, IR (KBr, cm−1): 3402, 3219, 2975, 1643, 1517, 1398,
1304, 1205, 1105, 1055, 883, 767, 610, 545. Elemental Analysis:
calculated for C, H, & N (%) C4H6N6O4 (202.13) C, 23.77; H, 2.99;
N, 41.58; Found; C, 23.30; H, 3.58; N, 40.76. BAM drop hammer:
40 J; friction tester: 360 N.
the MP2/6–311++G∗∗ level [55–57]. The optimized structures were
characterized as true local energy minima on the potential energy
surface without imaginary frequencies. All computations were per-
formed by using the Gaussian 09 suites of programs [40,41].
Declaration of Competing Interest
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared to
influence the work reported in this paper.
CRediT authorship contribution statement
Saira Manzoor: Writing – original draft, Investigation, Formal
analysis. Piao He: Writing - review & editing, Validation. Jun-Qing
Yang: Methodology, Investigation, Formal analysis. Qamar-un-nisa
Tariq: Formal analysis, Resources, Software. Li Jing-Ru: Validation,
Visualization, Resources. Yong Hu: Writing - review & editing, For-
mal analysis. Wenli Cao: Validation, Writing - review & editing.
Jian-Guo Zhang: Conceptualization, Project administration, Fund-
ing acquisition, Supervision.
5-Nitro-2,4,6-triaminopyrimidine-1-oxide (NTAPMO) (2) 1 g
(7 mmol) of 5-Nitroso-2,4,6-triaminopyrimidine was dissolved into
the trifluoroacetic acid (15 ml) at room temperature. Added drop-
wise this solution to the 30% hydrogen peroxide (15 mmol) and
5 ml of trifluoroacetic acid, maintain the temperature below 20
°C. Stirred this solution at room temperature for a further 3 h.
Added diethyl ether (40 ml), filtered, washed with diethyl ether,
warm isopropyl alcohol, dry, and get the light orange solid as a re-
quired product. Yield 78%, (DSC 10 °C min−1), 337 °C (Dec), crystal
density, 1.76 g.cm−3, IR (KBr, cm−1): 3421, 3300, 3163, 1650, 1606,
1563, 1492, 1384, 1291, 1212, 1183, 1076, 889, 769, 717, 610. Ele-
mental Analysis: calculated for C, H, & N (%) C4H6N6O3 (186.13) C,
25.81; H, 3.25; N, 45.15; Found; C, 22.52; H, 3.56; N, 38.51. BAM
drop hammer: 40 J; friction tester: 360 N.
Acknowledgment
We are thankful to the NSAF (U1830134), NSFC (21905023 and
21911530096) and SKLEST YBKB21-02 for their generous financial
support and Open Research Fund Program of CAS Key Laboratory
of Energy Regulation Materials (ORFP2020–01)
6-amino-1–hydroxy-5-nitro-4-oxo-3,4-dihydropyrimidin-
2(1H)-iminium nitrate salt (3) C4H6N5O4 (NO3).2H2O; Take 1 g of
NTAPMO (2) and dissolve into the 10 ml of 15% nitric acid. After
2–3 days colorless crystals are formed appropriate for x-ray single
diffraction technique. Yield 85%, (DSC 10 °C min−1), 168 °C (Dec),
crystal density, 1.77 g.cm−3. IR (KBr, cm−1): 3409, 3263, 2894,
2830, 1778, 1680, 1617, 1527, 1374, 1304, 1234, 1220, 1101, 1038,
969, 773, 707, 627. Elemental Analysis: calculated for C, H, & N (%)
C4H10N6O9 (286.18) C, 19.21; H, 3.42; N, 33.60; Found; C, 16.79; H,
3.52; N, 29.37. BAM drop hammer: 40 J; friction tester: 360 N.
6-amino-1–hydroxy-5-nitro-4-oxo-3,4-dihydropyrimidin-
2(1H)-iminium nitrate salt (4) C4H6N5O4 (NO3); Added 1 g of
NTAPMO (2) into the 3 ml of 65% nitric acid and stirred well until
the solid was appropriately dissolved. After 2–3 days colorless
crystals were collected suitable for x-ray single diffraction tech-
nique. Yield 80%, (DSC 10 °C min−1), 180 °C (Dec), crystal density,
1.86 g.cm−3, IR (KBr, cm−1): 3387, 3256, 2824, 1770, 1680, 1604,
1534, 1388, 1297, 1241, 1220, 1115, 1038, 975, 759, 704, 641, 523.
Elemental Analysis: calculated for C, H, & N (%) C4H6N6O7 (250.03)
C, 19.21; H, 2.42; N, 33.60; Found; C, 19.20; H, 2.52; N, 33.59. BAM
drop hammer: 40 J; friction tester: 360 N.
Supplementary materials
Supplementary material associated with this article can be
found, in the online version, at doi:10.1016/j.molstruc.2021.130732.
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