Thermostable and insensitivity furazan energetic complexes: Syntheses, structures and modified combustion performance for ammonium perchlorate

Article abstract of DOI:10.1016/j.poly.2019.02.051

It is an important issue to balance energy and sensitivity in the construction of high energy materials. Herein, two furozacycline energetic complexes ([Zn(HTZF)(H₂O)₃]·H₂O (1) and [Co(HTZF)(H₂O)₃]·2H₂O (2) (HTZF = 3-hydroxyl-4-(tetrazol-5-yl)furazan)) were hydrothermally synthesized. Single crystal X-ray diffraction shows that in 1, energetic ligand adopting bidentate chelating coordination mode coordinates to Zn²⁺. The coordinated units Zn(HTZF)₂(H₂O)₂ and Zn(H₂O)₄ are alternatively linked to an infinite chain through nitrogen atom in furazan group, and with the aid of hydrogen bonding interaction, forming 3D supramolecule structure. Different in 2, ligand coordinates to Co²⁺ in bidentate chelating coordination and bridging coordination modes. π?π interaction further supports 3D framework stabilization. The thermal decomposition temperature of 1 and 2 are up to 293.0 °C and 295.8 °C, respectively. The heat of detonation (Q), detonation velocity (D), and detonation pressure (P), were evaluated to be, for 1: 1.123 kcal·g^?1, 7.971 km·s^?1 and 30.8 GPa; for 2: 2.165 kcal·g^?1, 8.846 km·s^?1 and 35.3 GPa. 1 and 2 are insensitive to impact and friction. As combustion promoter, both of complexes can effectively accelerate the thermal decomposition of ammonium perchlorate (AP).

Full text of DOI:10.1016/j.poly.2019.02.051

Accepted Manuscript
Thermostable and Insensitivity Furazan Energetic Complexes: Syntheses,
Structures and Modified Combustion Performance for Ammonium Perchlorate
Shuai Chang, Shilong Wei, Junlong Zhao, Lianjie Zhai, Zhengqiang Xia,
Bozhou Wang, Qi Yang, Sanping Chen, Shengli Gao
PII:
S0277-5387(19)30152-4
https://doi.org/10.1016/j.poly.2019.02.051
POLY 13795
DOI:
Reference:
Polyhedron
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Received Date:
Revised Date:
Accepted Date:
4 February 2019
23 February 2019
27 February 2019
Please cite this article as: S. Chang, S. Wei, J. Zhao, L. Zhai, Z. Xia, B. Wang, Q. Yang, S. Chen, S. Gao,
Thermostable and Insensitivity Furazan Energetic Complexes: Syntheses, Structures and Modified Combustion
Performance for Ammonium Perchlorate, Polyhedron (2019), doi: https://doi.org/10.1016/j.poly.2019.02.051
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Thermostable and Insensitivity Furazan Energetic Complexes:
Syntheses, Structures and Modified Combustion Performance
for Ammonium Perchlorate
Shuai Chang[a]‡, Shilong Wei[a]‡, Junlong Zhao[a], Lianjie Zhai[b]*, Zhengqiang Xia[a]*,
Bozhou Wang[b], Qi Yang, Sanping Chen[a]*, Shengli Gao[a]
[a]Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of
Education, College of Chemistry and Materials Science, Northwest University, Xi’an,
Shaanxi 710127, China.
[b]Xi'an Modern Chemistry Research Institute, Xi'an Shaanxi 710069, China.
‡These authors contribute equally to this work
*S Supporting Information
Corresponding author
Prof. Sanping Chen
E−mail address: sanpingchen@126.com

Abstract
It is an important issue to balance energy and sensitivity in the construction of high
energy
materials.
Herein,
two
furozacycline
energetic
complexes
([Zn(HTZF)(H2O)3]·H2O (1) and [Co(HTZF)(H2O)3]·2H2O (2) (HTZF
=
3-hydroxyl-4-(tetrazol-5-yl) furazan)) were hydrothermally synthesized. Single
crystal X-ray diffraction shows that in 1, energetic ligand adopting bidentate chelating
coordination mode coordinates to Zn2+. The coordinated units Zn(HTZF)2(H2O)2 and
Zn(H2O)4 are alternatively linked to an infinite chain through nitrogen atom in furazan
group, and with the aid of hydrogen bonding interaction, forming 3D supramolecule
structure. Different in 2, ligand coordinates to Co2+ in bidentate chelating coordination
and bridging coordination modes. π···π interaction further supports 3D framework
o
stabilization. The thermal decomposition temperature of 1 and 2 are up to 293.0 C
o
and 295.8 C, respectively. The heat of detonation (Q), detonation velocity (D), and
detonation pressure (P), were evaluated to be, for 1: 1.123 kcal·g−1, 7.971 km·s−1 and
30.8 GPa; for 2: 2.165 kcal·g−1, 8.846 km·s−1 and 35.3 GPa. 1 and 2 are insensitive to
impact and friction. As combustion promoter, both of complexes can effectively
accelerate the thermal decomposition of ammonium perchlorate (AP).

1. INTRODUCTION
Energetic materials play an irreplaceable role in military, aerospace, civil and
others [1-8]. In the past few decades, heterocyclic ring explosives based on
conventional PETN, nitramine (RDX and HMX) [9] and nitroaromatic group (TNT
and TATB) [10-12] have constantly been synthesized. High-nitrogen heterocyclic
systems are one of useful and promising structures for the design and synthesis of
energetic materials because of the inherently energetic N-N, N=N and C-N bonds, and
high ring strain, such as azoles, azines, furazans and their derivatives [13-18].
The inherent contradiction between high energy and insensibility is a major
problem in constructing energetic materials. In order to keep the balance of energy
and sensibility, energetic complexes have caused close attention in recent years. As an
insensitive energetic unit, furazan ring is focused on. Because large π bonds and
approximate coplanar atoms, the structure is denser when forming crystals [19]. At
known, the oxygen atom in the ring is highly active and can act as an oxidizing agent
[20-24]. For these considerations above, it seems attractive enough to construct
energetic complexes with furazan group as energy carrier. Unfortunately,
furazacycline is of non-liable coordination group, and only a few complexes directly
coordinate with N atoms in furazan [25-27]. In order to improve the activity of N
atoms, an electron-rich group hydroxyl group is introduced in its ortho carbon atom.
3-nitro-4-(tetrazol-5-yl) furazan (NTZF: N = 53.60%), which was used as the
starting materials for synthesis. [28] In aqueous solution, the hydroxyl group from
water molecule can attack the carbon cation to replace the nitro group, producing
hydroxyl-4-(tetrazol-5-yl) furazan (HTZF). Compared with NTZF, HTZF is apt to
participates in coordination to form complexes with the activated ortho nitrogen atom
in the one-pot reaction (Scheme 1). In the present work, we obtained cobalt(II) and
zinc(II) energetic complexes with HTZF and structurally characterized. TG analysis
reveals that two 3D surpramolecule complexes have good thermal stability.
Detonation property reveals that 2 has better performance. Their thermodynamic
parameter ΔG≠, ΔH≠ and ΔS≠, detonation properties and sensitivities were also

investigated. Moreover, the performances of the two complexes thermal
decomposition of AP were explored.
Scheme 1
Syntheses of complexes 1 and 2.
2. EXRERIMENTAL SECTION
Caution: Ligands and the target complexes are hazardous materials, which
explosion may occur under certain conditions. The necessary safety precautions
should be used during the experiment, especially when the complexes are prepared on
a large scale.
2.1. Materials and instruments
All starting materials are commercially available and were used without any
purification. Elemental analyses were carried out with an Elementar Vario EL III
analyzer. IR spectra were recorded with a Tensor 27 spectrometer (Bruker Optics,
Ettlingen, Germany). TG and DSC analyses were conducted on a Netzsch STA 449C
instrument using nitrogen gas as atmosphere. About 0.7 mg of samples was used for
each measurement. The specific procedures are described as follows: the standard
o
weights were used for the calibration of the balance. In the range of 30-800 C, the
o
baseline was calibrated with an empty crucible at a heating rate of 10 C min-1 and a
flowing rate of 10 mL min-1 of nitrogen gas. X-ray powder diffraction measurements
were performed on a Rigaku RU200 diffractometer at 60 kV, 300 mA and Mo Kα

radiation (λ = 0.71073 Å).
2.2 Synthesis of complexes 1 and 2
2.2.1. Synthesis of 3-amino-4-(tetrazol-5-yl) furazan (ATZF)
ATZF
was
prepared
using
the
optimized
procedure
[28].
3-Amino-4-aminohydrazolyfurazan (AFAD) (2.00 g, 12.66 mmol) and 40 mL of 2.0%
hydrochloric acid were added into a three-necked round-bottomed flask fitted with a
mechanical stirrer and a dropping funnel. 10% NaNO2 solution (10 mL) was added
o
dropwise at 0 C. Upon complete addition, continuous stirring has been held for 2
o
hours at 15 C. The yellow precipitate was filtered and 1.65 g yellow solid was
collected with a yield of 76.7%. The product was crystallized from water with a
o
1
melting point of 210-211 C. H NMR (DMSO-d6, 500 MHz) δ: 6.59 (s, 2H, NH2);
13C NMR (DMSO-d6, 500 MHz) δ: 155.44, 147.49, 136.20; IR (KBr) v: 3458, 3357
(NH2), 3050 (N-H), 1641, 1622 (C=N) cm-1. Anal. calcd for C3H3N7O: C 23.53, N
64.05, H 1.961; found: C 23.84, N 64.06, H 1.956.
2.2.2. Synthesis of 3-nitro-4-(tetrazol-5-yl) furazan (NTZF)
NTZF was prepared using the optimized procedure [28]. The mixture of Na2WO4
(6.60 g, 0.011 mol) and 50% hydrogen peroxide solution (90.00 g, 1.32 mol) was
placed in a three-necked round-bottomed flask with a stirrer and dropping funnel in an
o
ice-salt bath at -10 C. To which sulfuric acid (88.0 g) was added dropwise under
o
stirring at 5 C. Then, the reaction mixture was warmed up to room temperature and
3-amino-4-cyanofurazan (1.6 g, 14.55 mmol) was added slowly. After
3-amino-4-cyanofurazan was added completely, the reaction mixture was kept stirring
at room temperature for another 3 hours and extracted with CH2Cl2 (50 mL × 4). The
combined extracts were washed with ice-water and dried on MgSO4. The yellow
precipitate obtained was concentrated on a rotary evaporator to leave 1.5 g solid with
a yield of 83.3%. The crude compound was crystallized from ethyl acetate with a
o
melting point of 123-124 C. 13C NMR (DMSO-d6, 500 MHz) δ: 159.62, 146.96,
140.93; IR (KBr) v: 3250 (broad, N-H), 1566, 1345 (NO2), 1622 (C=N) cm-1. Anal.
calcd for C3HN7O3: C 19.67, N 53.55, H 0.55; found: C 19.63, N 54.01, H 0.58

2.2.3. Synthesis of {[Zn(HTZF)(H2O)3]·H2O}n (1)
A mixture of Zn(NO3)2·6H2O (0.1 mmol, 0.030 g), NTZF (0.1 mmol, 0.015 g)
and distilled water (5 mL) were kept stirring for 2 hours, and sealed in a 15 mL
o
Teflon-lined stainless autoclave at 150 C for 3 days. After slowly cooling to room
o
temperature with a cooling rate of 5 C min-1. The mixture was filtrated and left at
room temperature with slow evaporation for several days. The colorless transparent
crystals of 1 were collected by filtration (yield: 82%, based on NTZF). Elemental
analysis (%) calcd for C3H8N6O6Zn: C, 12.45; H, 2.76; N, 29.02. Found: C, 12.50; H,
2.69; N, 29.08. IR (cm-1, KBr): 3212s, 3362m, 1625m, 1569s, 1470w, 1186w, 995m,
879m, 775m, 617w. PXRD patterns of 1 is given in Fig. S1.
2.2.4. Synthesis of {[Co(HTZF)(H2O)3]·2H2O}n (2)
2 was prepared according to the same synthetic procedure as that of 1. A mixture
of Co(ClO4)2·6H2O (0.1 mmol, 0.037 g), NTZF (0.1 mmol, 0.015 g) and distilled
water (8 mL) was kept stirring for 2 hours, and sealed in a 15 mL Teflon-lined
o
stainless autoclave at 120 C for 3 days. Upon cooling to room temperature with a
cooling rate of 5 oC min-1, the mixture was filtrated and left at room temperature with
slow evaporation for several days. The orange block-like crystals of 2 were collected
by filtration (yield: 70%, based on NTZF). Elemental analysis (%) calcd for
C3H10N6O7Co: C, 11.96; H, 3.32; N, 27.91. Found: C, 12.03; H, 3.30; N, 28.01. IR
(cm-1, KBr): 3349s, 1623m, 1567s, 1466w, 1396w, 1178m, 999m, 881m, 772w, 704w,
620w. PXRD patterns of 2 is given in Fig. S2.
2.3. X-ray crystallography
The single-crystal X-ray diffraction data of 1 and 2 were collected using a Bruker
Smart Apex CCD diffractometer equipped with a graphite monochromatized Mo Kα
radiation (λ = 0.71073 Å) using ω and φ scan modes. The single crystal structure was
solved by direct methods using SHELXS-97 [29] and refined by means of full-matrix
least-squares procedures on F2 and the SHELXL-97 [30] program. All non-H atoms
were located using subsequent Fourier-difference methods and refined anisotropically.

Experimental details for the structural determination of the complexes are
summarized in Table S1. Selected bond lengths and bond angles of 1 and 2 are listed
in Tables S2 and S3, respectively. Further information on the crystal structure
determination in crystallographic information framework (CIF) format is available in
the ESI.
3. RESULTS AND DISCUSSION
3.1 Structural description
Crystal structure of 1. X-ray structural analysis shows that crystallizes in the
monoclinic space group P21/c. One Zn2+ ion, one ligand, three coordinated water
molecules and one free water molecules are present in the asymmetric unit. As shown
in Fig.1a, Zn1 is coordinated in a slightly distorted octahedral geometry environment
in which the basal plane is formed by two nitrogen atoms and two oxygen atoms from
two ligands (oxygen is derived from the hydroxyl group, which is generated by the
attack of nitro-linked carbon cations from water.) (Zn1-N4=2.067 Å, Zn1-O2=2.126
Å) and two oxygen atoms from two water molecules (Zn1-O3 = 2.191 Å) in the axial
position. The ligands coordinate to Zn1 with bidentate chelating coordination modes
(Fig. 1a). Zn2 is also coordinated in octahedral geometry environment in which the
basal plane is formed by four oxygen atoms from two water molecules (Zn2-O4 =
2.103 Å, Zn2-O5 = 2.135Å) and two nitrogen atoms from two ligands (Zn2-N6 =
2.114 Å) in the axial position, and the ligands coordinate to Zn2 with bridging
coordination mode. Each ligand links two Zn2+ ions to generate a 1D infinite chain.
The interaction of the coordination waters through hydrogen bonds makes the 1D
chains form a 3D supramolecular structure. Lattice waters are also involved in the
formation of hydrogen bonds, making 3D structure more compact. (N-H···O,
O-H···O, O-H···N). The detailed hydrogen bond interaction information is shown in
Table S4.
Crystal structure of 2. X-ray structural analysis reveals that crystallizes in the
monoclinic space group P21/c. The asymmetric unit of 2 contains one Co2+ ion, two

ligands, three coordinated water molecules and two free water. As shown in Fig. 2a,
Co2+ is coordinated in a slightly distorted octahedral geometry environment in which
the basal plane is formed by four oxygen atoms from one ligand (Oxygen is derived
from the hydroxyl group, which is generated by the attack of nitro-linked carbon
cations from water.) and three coordinated water molecules (Co-O2 = 2.055 Å, Co-O3
= 2.090 Å, Co-O4 = 2.089 Å, Co-O5 = 2.074 Å), respectively. The axial position is
defined by two nitrogen atoms (Co-N1 = 2.112 Å, Co-N6 = 2.172 Å) which belongs
to two ligands. Each ligand links two Co(II) ions to form a 1D infinite chain, where
the ligands coordinate to Co(II) with bidentate chelating coordination and bridging
coordination modes. The 1D infinite chains are further fabricated into a 3D
supramolecular structure just through π···π stacking and coordination waters. Like 1,
lattice waters play a significant role in stabilizing structure (Fig. 2c-2d).
Fig. 1. (a) The coordination environment of the Zn2+ ion and ligand HTZF, (b) The 1D chain in 1,
and (c) 3D supramolecular structure of 1, where the green dashed lines represent hydrogen bonds.

3.2. Thermal stability
The themodecomposition reactions of crystalline samples of 1 and 2 were
o
measured with a linear heating rate of 10 C min-1 in nitrogen atmosphere. As shown
in Fig. 3a, there are one endothermic peak and one exothermic peak for 1. The range
of endothermic progress starts from 76 oC to 140 oC with the peak temperature of 106
oC, which confirms that loss part of water molecules. The exothermic peak
o
temperature of 293.0 C shows the partial collapse of the framework. It isn’t
completely collapsed until 800 oC. For 2, there are two peaks in DSC curve. One is an
o
endothermic peak with a peak temperature of 148.7 C, which is ascribed to a
dehydration process. The exothermic peak is the main decomposition process with the
peak temperature of 295.8 oC.
Fig. 2. (a) The coordination environment of the Co2+ ion and ligand HTZF, (b) The 1D chain
structure of 2, and (c) The 3D supramolecular structure of 2. (d) Adjacent tetrazolyl and furazan
rings showing the π···π stacking interactions.

o
For both 1 and 2, decomposition temperatures are above 290 C, revealing their
good thermal stabilities, which is presumably attributed to extensive intermolecular
interactions. As noticed, TG curve is more gently and DSC curve emits less heat for 1,
which is ascribed to the existence of hydrogen bonds in 1. To our surprise, 2 (2 mg)
o
was heated in nitrogen atmosphere at temperature above 150 C, there was a violent
explosion, which indicates that lattice water plays an important role in reducing
complexes sensitivity.
3.3. Non-isothermal kinetics analysis
The thermokinetic parameters of decomposition processes of 1 and 2 were
discussed by Kissinger's method [31] and Ozawa's method [32,33]. The equations can
be used to estimate the rate constants of the thermal decomposition processes of 1 or 2.
The Kissinger (1) and Ozawa (2) equations are as follows, respectively:

Tp
AR
E
E
ln
 ln

2
RTp
(1)
0.4567E
log 
 C
RTp
(2)
where E is the apparent activation energy; A is the pre-exponential factor; Tp is
the peak temperature; R is the gas constant, 8.314 J mol-1 K-1; β is the linear heating
rate and C is a constant. The exothermic peak temperature was measured from DSC
o
curves at heating rates of 2, 5, 8 and 10 C min-1. The apparent activation energies Ek
and Eo, pre-exponential factor Ak and linear correlation coefficients Rk and Ro were
determined and are shown in Table 1. The calculate results are similar with both
methods and within the normal range of deviation allowed. The Arrhenius equations
can be expressed by using Ea (the average of Ek and EO) and lnA values, as follows: ln
k = 23.57 - 272.05 × 103/RT for 1, and ln k = 23.52 - 272.88 × 103/RT for 2.
Additionally, the entropies of activation (ΔS≠), enthalpies of activation (ΔH≠), and free
energies of activation (ΔG≠) of 1 and 2 were calculated and listed in Table 2. The
thermokinetic analysis shows that the initial thermal decomposition reaction is
kinetically inert. The thermodynamic data reveals that thermodecomposition reactions
are of non-spontaneous enthalpy-driven process.

Fig. 3. (a) DSC curves of 1 and 2, and (b) TG curves of 1 and 2.
Table 1
Thermokinetic parameters of decomposition reactions for 1 and 2.
Complex
1
2
Heating rates (oC min-1)
Peak temperature (oC)
Peak temperature (oC)
2
278.0
285.9
290.0
293.0
278.0
286.0
290.1
295.8
5
8
10
Kissinger’s method
Ek (kJ mol-1)
lnAk (s-1)
274.36
23.5692
0.9980
275.19
23.5170
0.9982
Rk
Ozawa–Doyle’s method
Eo (kJ mol-1)
Ro
269.73
0.9981
270.56
0.9983
Table 2
Thermodynamic parameters of decomposition reactions for 1 and 2.
Complex
ΔG≠ (KJ·mol-1)
302.79
ΔH≠ (KJ·mol-1)
267.34
ΔS≠ (J·mol-1·K-1)
-62.62
1
2
304.06
268.15
-63.12

3.4. Heat of detonation
The heat of detonation (Q), detonation velocity (D) and detonation pressure (P)
are significant parameters for energetic materials. We obtained Q, D and P of
complexes by density functional theory (DFT) and Kamlet-Jacobs equations. The
energy of detonation (ΔEdet) was computed by the equation: ΔEdet
=
=
θ
θ
-[ΔfHm (detonation products) - ΔfHm (explosive)]. Using a linear correlation (ΔHdet
1.127ΔEdet + 0.046, r = 0.968) to estimate the heat of detonation (ΔHdet), which is
widely used in the evaluation of the heat of detonation of explosives [34,35]. For both
1 and 2, water, carbon dioxide, nitrogen and carbon were considered to be the
decomposition products of the organic components and all the nonmetallic products
are treated as gas. The detonation reactions are described using the following
equations:
ZnC3N6O6H8 → ZnO + 4H2O + 1/2CO2 + 3N2 +5/2C
CoC3N6O7H10 → CoO + 5H2O + 1/2CO2 +3N2 +5/2C
(3)
(4)
The DFT calculate values for 1 and 2 are listed in Table S5.
3.5. Characterization of the detonation velocity and detonation pressure
The characteristics of energetic materials is evaluated by its detonation velocity
(D) and detonation pressure (P), and they can be estimated based on Kamlet-Jacobs
equations [35].
D 1.011/2 (11.30)
P 1.5582
  31.68N(MQ)1/2
(5)
where D is the detonation velocity (km s-1) and P is the detonation pressure (GPa), ρ
is the density of the explosive (g cm-3), N is the number of moles of detonation gases
per gram of explosive, M is the average molecular weight of these gases and Q is the
heat of detonation (kcal g-1). The detonation velocity and detonation pressure of 1 and
2 are shown in the Table 3.

3.6. Sensitivity tests
Sensitivity is the ability of an explosive substance to undergo an explosive
change under the influence of external energy. For safety testing, the impact and
friction sensitivities of 1 and 2 were measured by a Fall Hammer apparatus. Twenty
milligrams of sample 1 or 2 into a copper cap, and a 2 kg weight was dropped from a
set height in a 39.2 MPa press. The collected data are summarized in Table 3. The
results show that the impact sensitivity of 1 and 2 are 40 J and friction sensitivity of 1
and 2 was observed at up to 36 kg (360 N).
3.7. Discussion
The physical properties of 1 and 2 compared with the properties of furozan
complexes and traditional energetic materials are summarized in Table 3. For 1 and 2,
heat of formation and explosive parameters are obtained by theoretical calculations. Q,
D and P are calculated by the DFT (density functional theory) and Kamlet-Jacobs
equation (1: 1.123 kcal·g−1, 7.971 km·s−1 and 30.8 GPa; 2: 2.165 kcal·g−1, 8.846
km·s−1 and 35.3 GPa). Compared with furazan compounds, 3 and 4 show the pretty
good detonation performance, but its impact and friction sensitivity are unacceptable.
The detonation performance and stability of 2 are better than 5. Compared with the
complexes with triazole and tetrazole as energy units, furazan complexes perform
better in detonation performance. Obviously, the impact and friction sensitivities of
the complexes show excellent results. The detonation performance of 2 is superior to
RDX, and the safety is higher than TNT. And its decomposition temperature reaches
295.8 oC. Obviously, 2 presents a good balance between energy and sensitivity.
Table 3
The physicochemical properties of 1, 2 and some energetic materials.
d
Complex
ρa
(g cm-3)
2.11
Nb
Ωc
Td
Qe
Df
Pg
ISh
(J)
FSi
(N)
(%)
(%)
(℃)
(kcal g-1) (km s-1) (GPa)
29.02 -19.11
27.91 -17.27
39.44 -11.30
293.0
295.8
183.6
1.123
2.165
－
7.971
8.846
8.480
30.8
35.3
31.0
>40
>40
13.0
>360
>360
240
1
1.85
2
3,4-Bis(4'-aminofuroxan
o-3')furoxan(3) [36]
1.79

3,4-Bis(4'-nitrofuroxano-
3')furoxan(4) [36]
LLM-191(5) [37]
[Co(HATT)2(H2O)2]
(ClO4)3·4H2O(6) [38]
[Co(AZT)2(H2O)4](PA)2
(7) [39]
1.91
32.56 +18.60 146.5
－
9.503
40.8
3.0
40
1.89
2.02
37.81 -27.00
283
176
1.48
8.85
36.0
－
148
－
－
－
－
－
－
－
－
－
－
－
>40
>360
－
31.32
20.38
45.23
－
208
238
－
－
－
－
35.9
3
Co(TO)2(DNBA)2(H2O)
2(8) [40]
1.684
1.726
1.322
7.834
7.92
－
26.13
3
35.3 >360
{[Cu(tztr)]·H2O}n (9)
[41]
325
31.99
>40
>40
>40
>40
>360
>360
>360
>360
2.316
1.94
[Cd(HTRTR)2(H2O)4]
(HTNR)2(10) [42]
[PbCu(bta)2(H2O)5]·2H2
O(11) [43]
195.9
231
－
0.247
36.07
58.5
8.751
8.120
39.61
22.83
2.415
1.706
1.507
0.99
[Na(H2BTT)(H2O)2]n
336
(
Ta
) [44]
12
TNT [34]
HMX [34]
RDX [34]
1.65
1.91
1.80
18.50 -24.67
37.84 -21.61
295
275
205
1.0
7.303
8.900
8.795
21.3
38.4
34.9
15.0
7.0
353
112
120
－
37.84 -21.61
－
7.5
a
b
c
Density from X-ray diffraction analysis.
Nitrogen content.
Oxygen balance {ΩCO = nO − xC −
d
e
f
g
yH/2(1600/FW)}. Temperature of decomposition by DSC. Heat of detonation. Detonation velocity.
h
I
Detonation pressure.
Impact sensitivity.
Friction sensitivity. Abbreviations: HATT
=
5-(4-Amino-1,2,4-triazol-3-on-5-yl) tetrazole; AZT = 3-azido-1,2,4-triazole; TO = 1,2,4-triazole-5-one; HDNBA =
3,5-dinitrobenzoic acid; H2tztr = 3-(1H-tetrazol-5-yl)-1H-triazole; HTRTR = 4-[3-(1,2,4-triazol-yl)-1,2,4-triaozle;
HTNR–
4,5-bis(tetrazol-5-yl)-2H-1,2,3-triazole.
=
styphnic
acid
anion;
H2bta
=
N,N-bis(1H-tetrazole-5-yl)-amine;
H3BTT
=
3.7. Catalytic Effect on the Decomposition of Ammonium Perchlorate
AP is the most widely-used component of high-energy oxidant in solid
propellants. The combustion process of the composite solid propellant is strongly
dependent on the thermal decomposition behavior of AP. In general, the catalytic
performances of burning rate catalysts in the solid propellant are often evaluated by
their effects on the thermal decomposition of AP by DSC techniques. The DSC curve
for thermal decomposition of AP shows one endothermic peak and two exothermic
o
peaks. The endothermic peak at 242 C corresponds to the morphological transition
o
from an orthorhombic to a cubic phase of AP. The first exothermic peak at 337 C
corresponds to the low-temperature decomposition (LTD). The second exothermic

o
peak at 442 C corresponds to the high-temperature decomposition (HTD). In the
experiment, that mass ratio of 1 and 2 to AP is 1:3. In Fig. 4, there exhibit no effect on
the morphological transition peaks for 1 and 2. 1 has two peaks with LDT peak and
HDT peak, they shift downwards about 11.2 oC and 92.3 oC, respectively. 2 combines
o
two exothermic peaks into one intense exothermic peak at 323.5 C. The LDT peak
decreases about 13.5 oC compared with pure AP and HDT peak decreases about 118.5
oC. In summary, both 1 and 2 show good performance for the thermodecomposition of
AP. Although the carbon content of 1 (12.45%) is slightly higher than 2 (12.03%), the
heat release and peak temperature of 2 are better than 1. It is possible that different
metal centers will have different effects on combustion modifier. In this work, the
catalytic effect of cobalt is better than that of zinc. In order to further confirm this
conclusion, some published compounds of Co and Zn used as AP combustion
catalysts are summarized in Table S6. As can be seen from the data, the catalytic
effects of Co-centered compounds are significantly better than that of Zn.
Fig. 4. DSC curves of AP, 1+AP and 2+AP.
4. Conclusions
In conclusion, two furazan energetic complexes, {[Zn(HTZF)(H2O)3]·H2O}n (1)
and {[Co(HTZF)(H2O)3]·2H2O}n (2) were synthesized and structurally characterized.
o
Both complexes feature excellent thermostability and insensitivity (Td,1 = 293 C, Td,2

o
= 295.8 C). The non-isothermal kinetics analysis of the complexes indicates that the
thermal decomposition process is inert and thermodynamic data reveals that is a
non-spontaneous enthalpy-driven process. For 2, the detonation performance (2.165
kcal·g−1, 8.846 km·s−1 and 35.3 GPa) is superior to RDX and the safety (IS>40 J,
FS>360 N) is higher than TNT. As combustion rate modifier, the energetic complexes
of cobalt with furazan demonstrate the promising development prospect. 2 would be
potentially applied for energetic materials.
Conflicts of interest
There are no conflicts to declare.
Acknowledgments
This work was financially supported by the National Natural Science Foundation
of China (Nos. 21703135, 21727805, 21673180, 21803042 and 21473135), the
Natural Science Foundation of Shaanxi Province (Nos. 2017JZ002 and 2018JM5180),
the Natural Science Foundation of the Department of Education of Shaanxi Province
(Nos. 15JF030 and 17JS034).
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Two energetic complexes were synthesized based on the furazan derivative,
3-hydroxyl-4-(tetrazol-5-yl) furazan (HTZF). They show well-balance between
sensitivity and detonation performance. The detonation performance of 2 is superior
to RDX, and the safety is higher than TNT.