Energetic salts based on dipicrylamine and its amino derivative

Article abstract of DOI:10.1002/chem.201101411

Energetic salts based on dipicrylamine and its amino derivative were synthesized. All salts were fully characterized by multinuclear NMR spectroscopy (¹H, ¹³C), vibrational spectroscopy (IR), and elemental analysis. Ethylenediammonium di-DPA (DPA=dipicrylamine) and 1,3- diaminoguanidinium DPA were further confirmed by single-crystal X-ray diffraction. These salts exhibit reasonable physical properties, such as high densities (1.71-1.81gcm^-3), good thermal stabilities (T _d=155-285°C), and low solubilities in water. The impact sensitivity of 1-methyl-3,4,5-triamino-1,2,4-triazolium DPA is lower than that of 2,4,6-trinitrotoluene (TNT), and for some other energetic salts their impact sensitivities are comparable to that of TNT. Based on experimental densities and theoretical calculations carried out by using the Gaussian03 suite of programs, all the salts have calculated detonation pressures (22.5-27.8GPa) and velocities (7226-7917ms^-1) that exceed those of conventional TNT. The toxicities of these salts measured by luminescent bacteria toxicity tests are much lower than that of TNT, and two binary eutectic mixtures with melting points that fall between 70 and 100°C were identified. A salty solution: Energetic salts based on dipicrylamine and its amino derivative (see figure) exhibit high density, good thermal stability, and low solubility in water. Predicted detonation pressures (22.5-27.8GPa) and velocities (7226-7917ms ^-1) are higher than that of 2,4,6-trinitrotoluene (TNT); measured toxicities are lower than that of TNT. Copyright

Full text of DOI:10.1002/chem.201101411

FULL PAPER
DOI: 10.1002/chem.201101411
Energetic Salts Based on DipicrylACTHNUGRTNEUNGamine and Its Amino Derivative
Haifeng Huang,[a] Zhiming Zhou,*[a, b] Jinhong Song,[a] Lixuan Liang,[a] Kai Wang,[a]
Dan Cao,[a] Wenwen Sun,[a] Xuemin Dong,[a] and Min Xue[a]
Abstract: Energetic salts based on dipi-
crylamine and its amino derivative
were synthesized. All salts were fully
characterized by multinuclear NMR
spectroscopy (1H, 13C), vibrational
spectroscopy (IR), and elemental anal-
ysis. Ethylenediammonium di-DPA
(DPA=dipicrylamine) and 1,3-diami-
noguanidinium DPA were further con-
firmed by single-crystal X-ray diffrac-
tion. These salts exhibit reasonable
physical properties, such as high densi-
ties (1.71–1.81 gcmꢀ3), good thermal
stabilities (Td =155–2858C), and low
solubilities in water. The impact sensi-
tivity of 1-methyl-3,4,5-triamino-1,2,4-
triazolium DPA is lower than that of
2,4,6-trinitrotoluene (TNT), and for
some other energetic salts their impact
sensitivities are comparable to that of
TNT. Based on experimental densities
and theoretical calculations carried out
by using the Gaussian 03 suite of pro-
grams, all the salts have calculated det-
onation pressures (22.5–27.8 GPa) and
velocities (7226–7917 msꢀ1) that exceed
those of conventional TNT. The toxici-
ties of these salts measured by lumines-
cent bacteria toxicity tests are much
lower than that of TNT, and two
binary eutectic mixtures with melting
points that fall between 70 and 1008C
were identified.
Keywords: density functional calcu-
lations · detonation performance ·
dipicrylamine
explosives
· energetic salts ·
Introduction
necessary to search for replacements for TNT that are
usable in melt-castable explosives.
After World War Two, composite B (composed of 60% cy-
clotrimethylenetrinitramine (RDX) and 40% 2,4,6-trinitro-
toluene (TNT)) replaced TNT as a kind of castable explo-
sive in large-diameter ammunition, which increased the de-
structiveness of weapons remarkably. However, several
drawbacks of composite B were found later, such as exuda-
tion of an oily liquid under normal storage conditions,[1] and
cracks that formed in the process of filling the explosives.[2]
Exudation is caused by the low-melting-point isomers gener-
ated during the manufacture of TNT. These isomers tend to
exude under the high storage temperature requirements of
about 748C.[3] Additionally, TNT has several disadvantages
(e.g., carcinogenic and mutagenic and toxic to microbes,
algae, fish, and other organisms).[4] Red water is also pro-
duced in the manufacturing process, which is hazardous to
workers and the environment.[5] Therefore, it is absolutely
Energetic salts have been the focus of high-energy-density
materials (HEDMs) in recent years.[6–9] They often possess
the advantages of lower vapor pressure (less toxic vapor in
handling), higher density, and better thermal stability over
nonionic molecules. Brand and co-workers investigated the
possibility of replacing TNT with energetic salts for use in
melt-castable explosives, and established that 1-amino-3-
methyl-1,2,3-triazolium nitrate has the potential to be a
TNT replacement.[10] However, its high solubility in water
may limit its application in melt-castable explosives. The or-
ganic anions of many energetic salts synthesized are usually
nitrogen-rich heterocyclic species such as 2-methyl-5-nitra-
minotetrazolate,[9g]
nitroaminodiazidoACTHNGUTERNNU[G 1,3,5]triazine-based
salts,[11] bis[3-(5-nitroimino-1,2,4-triazolate)]-based salts,[12] 5-
nitroguanidyltetrazolate,[13] salts based on the mono anion of
N,N-bis[1(2)H-tetrazol-5-yl]amine,[14]
3,4,5-trinitropyrazo-
late,[15] and carbonyl- and oxalylbis(aminotetrazolate).[16]
Nitroaromatic compounds have also played an important
role in the area of energetic materials (e.g., TNT, picric
acid, 2,4,6-trinitroanisole, and 1,3,5-triamino-2,4,6-trinitro-
benzene (TATB)). To our knowledge, only a few nitro-aro-
matic anion-based energetic salts have been reported: ener-
getic salts of nitrophenol,[17a] picric acid,[17b] and trinitro-
phloroglucinol.[18] Conventionally, the energy of traditional
nitro compounds such as TNT and 1,3,5,7-tetranitro-1,3,5,7-
tetraazacyclooctane (HMX) results primarily from the com-
bustion of the carbon backbone, which consumes oxygen
provided by the nitro groups.[19] Because nitrogen-rich com-
pounds derive most of their energy from their high positive
heats of formation, it is therefore valuable to introduce ni-
[a] H. Huang, Prof. Dr. Z. Zhou, J. Song, L. Liang, K. Wang, D. Cao,
W. Sun, X. Dong, Dr. M. Xue
School of Chemical Engineering and the Environment
Beijing Institute of Technology
Beijing, 100081 (P.R. China)
Fax : (+86)10-68918982
E-mail: zzm@bit.edu.cn
[b] Prof. Dr. Z. Zhou
State Key Laboratory of Explosion Science
and Technology, Beijing Institute of Technology
Beijing, 100081 (P.R. China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201101411.
Chem. Eur. J. 2011, 17, 13593 – 13602
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
13593

trogen-rich cations into nitro-aromatic compounds that are
acidic.
products, which exhibit low solubility in water. The synthesis
of energetic salts 1–7 was accomplished by treating Na-
Dipicrylamine (DPA; detonation velocity (vD)=
7150 msꢀ1; density (d)=1.67 gcmꢀ3) was used as a booster
and for making cast-composition explosives with TNT and
NH4NO3. But the use of this kind of explosive has ceased
because of its toxicity. Also, DPA has been used as a reagent
for the selective precipitation of alkali metal cations (K+,
Cs+, Rb+),[20] and a number of DPA derivatives with potas-
sium, sodium, ammonium, and silver cations have been re-
ported.[20,21] It is known that the toxicity of compounds is
usually caused by the electrophilicity of the corresponding
groups.[22] Therefore it is presumed that the toxicity of the
DPA anion will be lower than the parent by lowering the
electrophilicity of the aromatic ring through delocalization
of the negative charge.
3,3’-Diamino-2,2’,4,4’,6,6’-hexanitrodiphenylamine
(DAHNDPA)—the amino derivative of DPA—and its po-
tassium salt were reported as thermally stable energetic
compounds.[23–25] The introduction of an amino group onto
the benzene rings should not only increase the nitrogen con-
tent and thus increase the heat of formation of the energetic
salt, it should also improve the possibility for hydrogen
bonding, and as a consequence increase its density and
therefore the performance, as in the case of 1,3-diamino-
2,4,6-trinitrobenzene (DATB; d=1.84 gcmꢀ3) to TATB (d=
1.94 gcmꢀ3).
ACHTUNGTREN(NUGN DPA) prepared in situ with stoichiometric amounts of 1-
amino-3-methyl-1,2,3-triazolium iodide, 1-methyl-3,4,5-tria-
mino-1,2,4-triazolium iodide or imidazolium, hydrazinium,
ammonium, ethylenediammonium, and diaminoguanidinium
chloride salts (Scheme 1). They were fully characterized by
multinuclear NMR spectroscopy, IR spectroscopy, and ele-
mental analyses. Salts 4a and 6a were further confirmed by
single-crystal X-ray diffraction. The NMR spectroscopic
data of all the salts were collected in [D6]DMSO. For DPA-
based salts, 1H NMR spectroscopic signals assigned to the
anion occurred at d=8.75 ppm, and those at d=142.1,
138.6, 131.9, and 124.3 ppm in the 13C NMR spectrum. For
DAHNDPA-based salts, signals at d=8.80 and 7.94 ppm in
1
the H NMR spectrum and signals at d=144.1, 142.1, 128.0,
127.8, 127.6, and 121.1 ppm in the 13C NMR spectrum were
assigned to the anion. We also tried to prepare 4-amino-
1,2,4-triazolium DPA by mixing NaACTHNUTRGNEUNG(DPA) with 4-amino-
1,2,4-triazolium chloride in water, but it only led to the for-
mation of DPA as precipitate, which suggests the lower acid-
ity of DPA with respect to the 4-amino-1,2,4-triazolium
cation. Compounds 1a and 4a–7a were recrystallized from
ethanol, whereas 2a and 3a were recrystallized from water.
The procedure for the synthesis of energetic salts 1b–7b
was similar to the preparation of energetic salts 1a–7a. The
solubility of Na
Na(DPA). It easily crystallized from solution when the tem-
perature of the solution decreased. Therefore, the Na-
AHCTUNGTREG(NNUN DAHNDPA) solution has to be kept hot to prevent its pre-
ACHTUNGTRENN(UNG DAHNDPA) in water is lower than that of
Herein we report the synthesis, the calculated detonation
performance, and the toxicity test of DPA-based and
DAHNDPA-based energetic salts.
ACHTUNGTRENNUNG
cipitation before adding halogenated salts.
The hygroscopicity and water solubility of explosives are
two of the key dominants in melt-castable explosive manu-
facturing. The new salts are stable in air (insensitive to mois-
ture and no decomposition) and they are nearly insoluble in
water, whereas the solubility of 2a and 3a in water increases
sharply at elevated temperatures.
Results and Discussion
DPA and DAHNDPA were synthesized according to litera-
ture procedures.[24–26] Initially the salt formation was per-
formed with the reaction of BaACHTNUTRGNEUNG(DPA)2 and 1-amino-3-
methyl-1,2,3-triazolium sulfate in water, but the yield ob-
tained was very low on account of the low solubility of 1-
amino-3-methyl-1,2,3-triazolium DPA in water. An alterna-
tive synthesis of DPA-based salts was based on the metathe-
sis reactions of the sodium salt of DPA with the halides. The
driving force of these reactions is the precipitation of the
All of the salts were studied using differential scanning
calorimetry (DSC). As shown in Table 1, 1a, 3a, 6a, 1b, 5b,
and 6b melt prior to decomposition. Among the DPA-based
salts, diaminoguanidinium salt 6a shows the lowest melting
point (1358C), whereas the melting points of imidazolium
salt 1a and ammonium salt 3a are higher than 2008C.
Scheme 1. Synthesis of DPA and DAHNDPA salts.
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Chem. Eur. J. 2011, 17, 13593 – 13602

Energetic Salts Based on Dipicrylamine
FULL PAPER
Table 1. Properties of energetic salts 1a–7a and 1b–7b.
[a]
[b]
[d]
[e]
[f]
[g]
[i]
[l]
Compound
Tm
Td
d[c]
DfHL
DfH
DfHanion
DfHsal
P[h]
vD
IS[j]
OB[k]
LC50
cation
1a
2a
3a
4a
5a
6a
7a
1b
2b
3b
4b
5b
6b
7b
232
decomp
254
decomp
decomp
135
decomp
230
decomp
decomp
decomp
137
184
dec
282
185
269
232
261
233
285
241
155
261
177
235
219
235
275
264
295
1.72
1.78
1.72
1.71
1.71
1.71
1.69 (1.71)
1.75
1.80
1.80
1.81
1.75
1.71
1.73 (1.75)
1.79
1.85
406.4
417.3
417.1
1199.0
400.2
401.6
394.9
402.4
415.2
412.1
1197.6
397.2
396.3
392.2
–
720.2[m]
770.0[n]
626.4[n]
1630.5[m]
963.2[o]
769.0[p]
913.7
ꢀ125.2
ꢀ125.2
ꢀ125.2
ꢀ125.2
ꢀ125.2
ꢀ125.2
ꢀ125.2
ꢀ123.8
ꢀ123.8
ꢀ123.8
ꢀ123.8
ꢀ123.8
ꢀ123.8
ꢀ123.8
–
188.6
227.5
84.1
180.5
437.8
242.2
393.6
194.0
231.0
90.5
325.6
442.2
248.9
397.7
–
22.5
27.2
24.6
23.6
23.4
24.3
23.4
23.6
27.8
27.1
27.0
24.7
24.4
24.6
–
7226
7848
7551
7414
7384
7520
7376
7347
7917
7815
7787
7525
7528
7510
–
16
56
36
32
20
36
8
60
64
20
24
20
56
16
64
92
14
ꢀ71.0
ꢀ56.0
ꢀ56.1
ꢀ63.1
ꢀ70.0
ꢀ60.6
ꢀ69.1
ꢀ70.0
ꢀ55.9
ꢀ55.9
ꢀ62.5
ꢀ69.1
ꢀ60.2
ꢀ68.3
ꢀ52.8
ꢀ52.9
ꢀ74.0
6.7
4.7
2.7
8.7
3.5
6.5
12.0
–
6.0
10.0
–
–
10.9
–
720.2[m]
770.0[n]
626.4[n]
1630.5[m]
963.2[o]
769.0[p]
913.7
DPA
DAHNDPA
TNT
254
248
81
–
–
–
3.5
58.0
0.3
–
–
–
–
–
–
–
19.5
–
6881
1.65
[a] Melting point (peak) [8C]. [b] Thermal degradation (peak) [8C]. [c] Measured density (gas pycnometer) [gcmꢀ3]. Values in the parentheses were cor-
rected by subtracting the volume of a water molecule [VACTHNUTRGNEUNG
(H2O)=25 ꢁ3]. [d] Calculated molar lattice energy [kJmolꢀ1]. [e] Calculated molar enthalpy of
formation of cation [kJmolꢀ1]. [f] Calculated molar enthalpy of formation of anion [kJmolꢀ1]. [g] Calculated molar enthalpy of formation of salts
[kJmolꢀ1]. [h] Detonation pressure [GPa]. [i] Detonation velocity [msꢀ1]. [j] Impact sensitivity: firing rate (H=25 cm) [%]. [k] Oxygen balance (OB) is
an index of the deficiency or excess amount of oxygen in a compound required to convert all C into CO2 and all H into H2O for the compound with the
molecular formula of CaHbNcOd, OB(%)=1600CAHTUNGTRNENNUG
[o] From Ref. [8h]. [p] From Ref. [13].
Among the DAHNDPA-based salts 1-amino-3-methyl-1,2,3-
triazolium salt 5b shows the lowest melting point (1378C).
Symmetry of the cations is an important factor in determin-
ing the melting points of salts.[27] As shown in Table 1, the
cations with high symmetry are capable of showing endo-
thermic peaks that correspond to their melting points on
DSC curves (e.g., the imidazolium salts 1a and 1b, and the
diaminoguanidinium salts 6a and 6b). For 1-methyl-3,4,5-tri-
amino-1,2,4-triazolium salts 7a and 7b, their DSC curves
show a very small endotherm at 130 and 1378C, respectively,
which corresponds to the loss of water. Most of the salts ex-
hibit excellent thermal stability. The decomposition temper-
ature of DPA-based salt is higher than the DAHNDPA-
based salt with the same cation. The hydrazinium salts show
the lowest decomposition temperature among the salts with
the same anion. Compound 7a possesses the highest thermal
degradation temperature (Td =2858C). The decomposition
temperatures of this family of salts fall in the range 219–
2858C except 2a (Td =1858C), 2b (Td =1558C), and 4b
(Td =1778C), which are comparable to those of RDX (Td =
2308C) and HMX (Td =2878C). Decomposition of explo-
sives may be caused by the reactions in or between mole-
cules at a certain temperature. The decomposition of ener-
getic salts composed of cations and anions is possibly related
to the nucleophilic reactions of anions or electrophilic reac-
tions of cations. As can be seen from Table 1, the salts
paired with the conjugated ring-based cation that can deloc-
alize the positive charge on the cation usually possess better
thermal stability (1a,b, 5a,b, and 7a,b). It is probable that
delocalized positive charge lowers the nucleophilicity of the
anion and consequently results in higher thermal stability.
Oxygen balance (OB) is an expression that is used to indi-
cate the degree to which an explosive can be oxidized. The
sensitivity, strength, and brisance of an explosive are all
somewhat dependent upon oxygen balance and tend to ap-
proach their maximum values as the oxygen balance ap-
proaches zero. Although all of the salts described in this
paper have negative OB values, all have better oxygen bal-
ance than TNT (ꢀ74%). As shown in Table 1, 2–3b exhibit
the least negative oxygen balance of ꢀ55.9%. The
DAHNDPA-based salts have better oxygen balances than
the DPA-based salts with the same anion.
Density is one of the most important physical properties
of energetic compounds. According to the Kamlet–Jacobs
equations [Eq. (4) and (5), see below],[28] density (d) affects
detonation performance, that is, detonation pressure (P) is
dependent on the square of the density, and the detonation
velocity (vD) is proportional to the density. As shown in
Table 1, the densities of DPA-based salts and DAHNDPA-
based salts are in the range of 1.69–1.78 gcmꢀ3 and 1.71–
1.81 gcmꢀ3, respectively, which are lower than that of the
parent compounds DPA (1.79 gcmꢀ3) and DAHNDPA
(1.85 gcmꢀ3). Nevertheless, they are much higher than the
density of TNT (1.65 gcmꢀ3).
The single-crystal structures of 4a and 6a indicate that
various cations cause different dihedral angles of the two
benzene rings in the DPA anion (4a: 28.8088, 6a: 82.3168).
A larger dihedral angle will cause the DPA anion to occupy
greater space and result in a lower density. The volume of
the cation may be another factor that affects the density of
the salt. It seems that the cation with smaller volume will
result in a higher density. As shown in Table 1, hydrazinium
and ammonium salts usually possess higher densities except
3a. Not surprisingly, the DAHNDPA-based salts have
higher densities than the DPA-based salts when paired with
a common cation because the two extra amino groups in
Chem. Eur. J. 2011, 17, 13593 – 13602
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13595

Z. Zhou et al.
DAHNDPA-based salts will result in more extensive hydro-
gen bonding.
Impact sensitivities of the synthesized salts were measured
by using a fall hammer HGZ-19Z0991 apparatus with
50.0 mg samples. The firing rate (probability of explosion)
was recorded based on 25 measurements when a 10 kg drop
hammer was dropped from 25 cm. Listed in Table 1 are
impact sensitivities of the salts with firing rates that range
from 8 to 64%. The firing rates of DPA-based salts and
DAHNDPA-based salts are in the range of 8–56% and 20–
64%, respectively. Compound 7a has a lower impact sensi-
tivity than TNT (14%), and the sensitivities of 1a, 5a, 2b,
4b, 5b, and 7b are comparable to that of TNT. The differen-
ces in impact sensitivities between the salts paired with
common anions probably come from the different dihedral
angles of the nitro groups and the benzene rings connected
to them. It was interesting to find that most of the DAHND-
PA-based salts are even more sensitive than the correspond-
ing DPA-based salts except 3b and 4b. Kamlet and Adolph
suggested that the impact sensitivities of nitro compounds
increase when their oxygen balances are enhanced.[29] As
can be seen in Table 1, all the salts are less sensitive than
their parents. We can conclude that salt formation is an ef-
fective method to desensitize energetic compounds. 1-
Methyl-3,4,5-triaminotriazolium salts (7a and 7b) were ex-
ceptionally insensitive when paired with a common anion.
The heats of formation are another important parameter
to be considered in the design of energetic salts. Recently,
significant progress has been made in the theoretical predic-
tion of thermal properties of energetic salts.[30] Heats of for-
mation can be calculated for the salts with good accuracy
(including the heats of formation of the cation and anion
and the lattice energy of the salts).[30d] The calculated heats
of formation of the DPA and DAHNDPA anions and of the
1-methyl-3,4,5-triamino-1,2,4-triazolium cation were ob-
tained on the basis of isodesmic reactions (Scheme 2) and
protonation reactions (Scheme 3). The values for the other
cations are available in the literature.[8h,k,13,31] The heats of
formation of DPA and DAHNDPA anion are ꢀ125.2 and
ꢀ123.8 kJmolꢀ1, respectively. As shown in Table 1, all of the
salts exhibit positive heats of formation. The 1-amino-3-
Scheme 3. Protonation reactions for calculations of heats of formation.
methyl-1,2,3-triazolium salts possess the highest heats of
formation when paired with
a common anion (5a:
437.8 kJmolꢀ1, 5b: 442.2 kJmolꢀ1). The effect of cations on
the heat of formation is in the following order: 1-amino-
3-methyl-1,2,3-triazolium>1-methyl-3,4,5-triamino-1,2,4-tri-
azolium>diaminoguanidinium>hydrazinium>imidazoli-
um>ammonium>ethylenediammonium. Calculation by
Huang et al.[8f] and Gao et al.[30d] showed that the heat of
formation of a cation or anion increases as the number of
ꢀ
nitrogen atoms increases and nitrogen nitrogen bonds usu-
ally contribute more to a positive heat of formation than
ꢀ
does a nitrogen carbon bond. 1,2,3-Triazole has a higher
positive heat of formation (267.6 kJmolꢀ1) than 1,2,4-tria-
zole (194.0 kJmolꢀ1). As 1-amino-3-methyl-1,2,3-triazolium
and 1-methyl-3,4,5-triamino-1,2,4-triazolium have more ni-
ꢀ
trogen nitrogen bonds, they possess higher positive heats of
formation than the remaining cations. We can see from
Equation (1) (below) that the heat of formation of a salt is
related to the heats of formation of the cation and the anion
and the lattice energy of the salt. As shown in Table 1, there
is no large difference in the lattice energies between the
salts for which the cations bear a single positive charge.
Therefore, the heats of formation of cations dominate those
of salts. Although ethylenediammonium possesses very high
positive heats of formation, the large lattice energies of 4a,b
lead to low positive heats of formation of the salts.
The performance of energetic compounds is measured by
their detonation velocity vD [msꢀ1], and detonation pressure
P [GPa]. These parameters are directly related to the densi-
ty and heat of formation. They were obtained by calculation
using Kamlet–Jacobs equations [Eqs. (4) and (5), see
below]. As shown in Table 1, for the DPA-based and
DAHNDPA-based salts, the calculated detonation pressures
lie in the range of 22.5–27.2 and 23.6–27.8 GPa, respectively,
which are higher than that of TNT (19.5 GPa). The detona-
tion pressures of the salts are higher than or equal to that of
ammonium dinitramide (ADN;
23.7 GPa) except 1a, b, 4–5a,
and 7a. For the DPA-based and
DAHNDPA-based salts, the
calculated detonation velocities
fall in the range of 7226–7848
and 7347–7917 msꢀ1, respective-
ly, which are better than that of
TNT (6881 msꢀ1).
Toxicity test: The luminescent
bacteria toxicity test (LBT) was
developed as an alternative to
animal testing[32] and has
become a basic test for ecotoxi-
cological testing of chemicals,
Scheme 2. Isodesmic reactions for calculations of heats of formation.
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Chem. Eur. J. 2011, 17, 13593 – 13602

Energetic Salts Based on Dipicrylamine
FULL PAPER
waste water, and eluates from soil and sediment.[33] Herein
we employed this method to measure the toxicities of ener-
getic salts and the results are shown in Table 1. The LC50 of
all the new salts are much higher than that of TNT, which
suggests lower toxicities of the new salts relative to TNT.
For the DPA-based salts, their LC50 are higher than that of
their parent DPA except salt 3a, whereas for the DAHND-
PA-based salts the opposite is true. We have inferred in the
introductory section that the toxicity of a compound is usu-
ally caused by the electrophilicity of certain groups. For
DPA-based salts, the deprotonation of DPA presumably
lowers the electrophilicity of the aromatic rings because the
charge density increases through delocalization of the nega-
tive charge on the bridge nitrogen, which results in a lower
toxicity. Substitution of the hydrogen atoms on the DPA
anion by an electron-donating amino group will decrease
the electrophilicity of the aromatic rings. Therefore, it is rea-
sonable that the toxicity of the DAHNDPA-based salt is
lower than the DPA-based salt paired with a common
cation. Interestingly, the toxicities of the DAHNDPA-based
salts are higher than that of their parent DAHNDPA. It is
probable that the electrophilicity of the bridge nitrogen
anion in the DAHNDPA-based salts dominates the toxicities
of the salts.
Table 2. Crystallographic data and structure refinement parameters for
DPA, 4a, and 6a.
DPA
4a
6a
formula
Mr
C12H5N7O12
439.23
C26H18N16O24
938.56
C13H12N12O12
528.35
crystal system
space group
a [ꢁ]
b [ꢁ]
c [ꢁ]
orthorhombic
P212121
7.3398(8)
11.6240(14)
18.734(2)
90.00
monoclinic
P21/n
monoclinic
P21/c
11.5630(10)
12.9980(12)
11.9190(11)
96.560(5)
1779.6(3)
2
19.3010(14)
10.4600(7)
19.7250(14)
90.9130(10)
3981.7(5)
8
b [8]
V [ꢁ3]
Z
1598.3(3)
4
T [K]
113(2)
113(2)
113(2)
l [ꢁ]
0.71075
1.825
0.17
0.71075
1.751
0.16
0.71075
1.763
0.157
1calcd [mgmꢀ3
]
m [mmꢀ1
(000)
]
F
A
888
956
2160
crystal size [mmꢀ3
q range [8]
]
0.24ꢂ0.20ꢂ0.20 0.22ꢂ0.20ꢂ0.18 0.32ꢂ0.22ꢂ0.18
1.8–27.9
ꢀ9ꢁhꢁ9
ꢀ15ꢁkꢁ15
ꢀ24ꢁlꢁ24
16769
2.3–27.9
1.10–28.10
ꢀ25ꢁhꢁ24
ꢀ13ꢁkꢁ13
ꢀ26ꢁlꢁ26
38030
index ranges
ꢀ15ꢁhꢁ15
ꢀ13ꢁkꢁ17
ꢀ15ꢁlꢁ15
16903
reflns collected
indep reflns
data/restraints/
params
2186
N
4227
N
9532ACTHNGUTERNN[UG 0.0365]
9532/0/716
2186/0/284
4227/0/310
GOF
1.028
0.0312
0.0690
1.020
0.0364
0.0959
1.111
0.051
0.1377
R (F2 >2s(F2))
wR(F2)[a]
X-ray crystallography: X-ray-quality crystals of DPA, 4a,
and 6a were obtained by slow evaporation of ethanol
(Table 2). Their structures are shown in Figures 1, 2, and 3,
and crystallographic data are summarized in Table 2. DPA
crystallizes in orthorhombic P212121 space group with four
sets of cations and their anions in the unit cell and with a
calculated density of 1.825 gcmꢀ3.
[a] w=1/[s2(Fo2)+(0.0767P)+2.4159P], in which P=(Fo2 +2F2c)/3.
Compound 4a is monoclinic P21/n with two sets of cations
and their anions in the unit cell and with a calculated densi-
ty of 1.751 gcmꢀ3. The transfer of each proton from the NH
group of DPA to 1,2-ethylenediamine and diaminoguanidine
is confirmed in Figures 2a and 3a. As shown in Figure 2b,
the nitrogen atoms on the cation and the oxygen atoms of
the nitro groups on the anion in compound 4a form strong
ii
ꢀ
ꢀ
hydrogen bonds [N(8) H(8A)···O(6) 2.901(2), N(8)
H(8B)···O(11)iii 2.946(2), N(8) H(8B)···O(9)
N(8) H(8C)···O(3) 2.948(2), N(8) H(8C)···O(1) 2.864(2),
2.998(2),
iv
ꢀ
v
ꢀ
ꢀ
ꢀ
N(8) H(8C)···O(4) 3.205(2) ꢁ; symmetry codes: ii) xꢀ1, y,
z; iii) ꢀx+1, ꢀy+1, ꢀz+1; iv) ꢀx+3= , y+1= , ꢀz+1= ;
2
2
2
1
1
v) xꢀ = , ꢀy+1= , zꢀ = ].
2
2
2
Compound 6a is monoclinic P21/c with 8 sets of cations
and their anions in the unit cell and with a calculated densi-
ty of 1.763 gcmꢀ3. Since the amino groups in the cation are
excellent hydrogen-bonding donors, and the nitro groups in
salt 6a are hydrogen-bonding acceptors, the intermolecular
interactions were formed in salt 6a. As shown in Figure 3b,
the discrete diaminoguanadinium and DPA anion are linked
into a 3D network by the extensive hydrogen-bonding inter-
i
ꢀ
actions between cation and anion [N(8) H(8A)···O(16)
Figure 1. a) Displacement ellipsoid plot (30%) of DPA. The hydrogen
atoms are included but unlabeled for clarity. b) Ball-and-stick packing di-
agram of DPA viewed down the a axis. The dashed lines indicate hydro-
gen bonding.
ii
iii
ꢀ
ꢀ
2.888(4), N(8) H(8B)···O(5) 2.866(3), N(9) H(9)···O(21)
iii
ꢀ
ꢀ
2.947(4), 3.270(4),
N(9) H(9)···O(22)
N(10) H-
(10A)···O(8)iv 3.220(4), N(10) H(10A)···O(3)i 2.953(3),
ACTHNGUTERNNUG
ꢀ
Chem. Eur. J. 2011, 17, 13593 – 13602
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13597

Z. Zhou et al.
Figure 2. a) Displacement ellipsoid plot (30%) of 4a. The hydrogen
atoms are included but unlabeled for clarity. b) Ball-and-stick packing di-
agram of 4a viewed down the a axis. The dashed lines indicate hydrogen
bonding.
Figure 3. a) Displacement ellipsoid plot (30%) of 6a. The hydrogen
atoms are included but unlabeled for clarity. b) Ball-and-stick packing di-
agram of 6a viewed down the b axis. The dashed lines indicate hydrogen
bonding.
i
N(10) H
3.319(4),
T
(10B)···O(14)v
3.259(3),
(12A)···O(4)vi
N(11) H(11)···O(15)
ꢀ
ꢀ
ꢀ
ꢀ
N(12) H
U
3.146(3),
N(12) H-
(12A)···O(11)vi 3.136(4), N(12) H
(12B)···O(1)iv 3.145(4),
ꢀ
(20A)···O(9)iii 3.903(4), N(20) H
T
alization of the nitrogen lone pair on N(1) of salts 4a and
ꢀ
ꢀ
N(20) H
i
i
ꢀ
ꢀ
ꢀ
2.894(4), N(21) H(21)···O(4) 2.943(3), N(21) H(21)···O(3)
6a to stabilize the anions by strengthening N(1) C(1) and
ꢀ
ꢀ
ꢀ
3.342(3),
N(22) H
N
3.141(3),
N(22) H-
N(1) C(7) bonds.
(22A)···O(22)vii 2.989(3), N(22) H
(22B)···O(11)ii 3.230(3),
ꢀ
iii
ꢀ
ꢀ
N(23) H(23)···O(23)
3.048(4),
N(23) H(23)···O(10)
Theoretical study: Calculations were carried out by using
the Gaussian 03 (Revision E.01) suite of programs.[34] The
geometric optimization of the structures and frequency anal-
yses were carried out by using the B3LYP functional with
the 6-31+G** basis set,[35] and single-point energies were
ꢀ
ꢀ
3.320(4),
N(24) H
U
3.110(4),
N(24) H-
(24B)···O(14)v 3.108(4) ꢁ; symmetry codes: i) ꢀx, yꢀ =,
1
2
ꢀz+1= ; ii) x, ꢀy+3/2, zꢀ = ; iii) ꢀx+1, yꢀ =, ꢀz+1= ; iv) x,
1
1
2
2
2
2
yꢀ1, z; v) x, ꢀy+1= , zꢀ = ; vi) ꢀx, yꢀ =, ꢀz+1= ; vii) ꢀx+1,
1
3
2
2
2
2
y+1= , ꢀz+1= ].
calculated at the MP2ACTHUGNTERN(UNG full)/6-311++G** level. All of the
2
2
The benzene rings in the DPA anion have a dihedral
angle of 28.808 and 82.3168 in compounds 4a and 6a, re-
spectively, whereas the dihedral angle in the DPA molecule
is 49.8368. We can deduce that the cation affects the dihe-
dral angle of the two benzene rings in the DPA anion. The
dihedral angles of the benzene rings further differentiate the
dihedral angles between the nitro groups and their connect-
ed benzene rings, among which the two largest dihedral
angles are 38.914 and 35.4448 in DPA, 76.924 and 65.4118 in
4a, and 25.212 and 22.5638 in 6a, respectively.
optimized structures were characterized to be true local-
energy minima on the potential-energy surface without
imaginary frequencies.
Based on the Born–Haber energy cycle (Scheme 4), the
heat of formation of a salt can be simplified according to
Equation (1), in which DHL is the lattice energy of the salt.
DHAf ðionic salt, 298 KÞ ¼DHAf ðcation, 298 KÞþ
ð1Þ
DHAf ðanion, 298 KÞꢀDHL
ꢀ
ꢀ
The bond lengths of the N(1) C(1) and N(1) C(7) in
DPA, 4a, and 6a are 1.375 and 1.373 ꢁ, 1.338 and 1.324 ꢁ,
and 1.281 and 1.311 ꢁ, respectively, which indicates a deloc-
The DHL value could be predicted by the formula suggested
by Jenkins et al. [Eq. (2)],[36] in which UPOT is the lattice po-
13598
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 13593 – 13602

Energetic Salts Based on Dipicrylamine
FULL PAPER
gases [gmolꢀ1]; Q, the heat of detonation [Jgꢀ1]; M, molecu-
lar weight of the compound [gmolꢀ1]; and 1, the loaded
density of explosives [gcmꢀ3]. The measured density was
used for the calculation here.
Eutectic identification: To identify mixtures with the melting
points (70–1008C) suitable for TNT replacements, binary eu-
tectic mixtures were explored. The mixtures were made by
grinding method. Salts 6a and 5b, which possess the lowest
melting points, were chosen as the components of the mix-
tures. As shown in Figure 4, the melting point of the mixture
approached to the lowest one when the percentage of 6a in-
creased to 40% (988C) and 60% (968C), whereas the melt-
ing point was 1028C when the percentage of 6a was 50%.
Continuing by increasing the percentage of 6a led to melt-
ing points above 1008C. For the mixtures with the percent-
age of 6a of 80 and 90%, the DSC plots exhibited double
peaks, which indicated they did not act as single materials.
In conclusion, we found two mixtures (40 and 60%) with
melting points in the range of 70–1008C. Although the melt-
ing points of these two mixtures are in the target range,
more work is needed to judge if these eutectic mixtures can
be used as TNT replacement in terms of, for example,
safety/sensitivity properties, detonation performance, and
compatibility with other explosive compositions (e.g.,
RDX).
Scheme 4. Born–Haber cycle for the formation for energetic salts.
tential energy, and nM and nX depend on the nature of the
ions Mp+and Xqꢀ, respectively, and are equal to three for
monatomic ions, five for linear polyatomic ions, and six for
nonlinear polyatomic ions.
DHL ¼ UPOT þ ½pðnM=2ꢀ2Þ þ qðnX=2ꢀ2ÞꢂRT
ð2Þ
The equation for the lattice potential energy, UPOT, takes the
form of Equation (3), in which 1m is the density [gcmꢀ3],
Mm is the chemical formula mass of the ionic material [g],
and the coefficients g [kJmolꢀ1 cm] and d [kJmolꢀ1] are as-
signed literature values.[36]
1
=
UPOT ½kJ molꢀ1ꢂ ¼ gð1m=MmÞ þ d
3
ð3Þ
The remaining task was the determination of the heats of
formation of the cations and anions, which were computed
by using the method of isodesmic reactions (Scheme 2). The
sources of the energies of the parent ions in the isodesmic
reactions were calculated from protonation reactions
(DHAf (H+)=1530.1 kJmolꢀ1; Scheme 3). The enthalpy of an
isodesmic reaction (DHAf 298) is obtained by combining the
MP2ACHTUNGTRENNUNG(full)/6-311++G** energy difference for the reaction
with the scaled zero-point energies (B3LYP/6-31+G**).
The heats of formation of the cations and anions being in-
vestigated can then be extracted readily.
Detonation pressures (P) and detonation velocities (D)
were calculated according to the Kamlet–Jacobs equations
[Eqs. (4) and (5)]:[28,30d]
1
1
ꢀ 1
=
2
=
2
=
2
ð4Þ
ð5Þ
D ¼ 1:01ðNM Q Þ ð1 þ 1:301Þ
Figure 4. DSC curves (endo down) of different weight percentage of 6a
in the mixture.
1
ꢀ 1
2
=
2
=
2
P ¼ 1:5581 M Q
For the compound with the molecular formula of CaHbOcNd,
2a+b/2>cꢃb/2 (suitable for all the salts in this study), Q
can be calculated according to Equation (6):
Conclusion
Energetic salts 1a–7a and 1b–7b were successfully synthe-
sized and fully characterized. All the salts exhibit reasonable
physical properties, such as high density (1.71–1.81 gcmꢀ3)
and good thermal stability (Td =155–2858C), and they also
have low solubility in water. The impact sensitivity of 7a is
lower than that of TNT, and the impact sensitivities of 1a,
5a, 2b, 4b, 5b, and 7b are comparable to that of TNT.
Based on experimental densities and theoretical calculations
carried out by using Gaussian 03 suite of programs, all the
ꢀ
ꢁ
c
b
28:9b þ 94:05 2 ꢀ 4 þ 0:239DHf0
ð6Þ
Q ¼
ꢄ 103
M
in which each term in Equations (4), (5), and (6) is defined
as follows: D, the detonation velocity [kmsꢀ1]; P, the deto-
nation pressure [GPa]; N, the moles of detonation gases per
¯
gram explosive; M, the average molecular weight of these
Chem. Eur. J. 2011, 17, 13593 – 13602
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13599

Z. Zhou et al.
497 cmꢀ1; elemental analysis calcd (%) for C15H9N9O12 (507.29): C 35.51,
H 1.79, N 24.85; found: C 35.27, H 1.84, N 24.80.
salts have calculated detonation pressures (22.5–27.8 GPa)
and velocities (7226–7917 msꢀ1) that exceed those of con-
ventional TNT. The toxicities of the salts measured by lumi-
nescent bacteria toxicity tests were much lower than that of
TNT. Two binary eutectic mixtures with melting points that
fall between 70–1008C were identified. The aforementioned
property parameters meet the requirements as continuous-
phase ingredients for melt-castable explosives, which render
them promising as a TNT replacement.
Hydrazinium DPA (2a): Red solid; yield: 1.20 g (93%); 1H NMR: d=
8.75 ppm (s, 4H); 13C NMR: d=142.1, 138.6, 131.9, 124.3 ppm; IR (KBr
pellet): n˜ =3352, 3185, 3083, 1676, 1587, 1540, 1436, 1382, 1344, 1296,
1160, 932, 917, 884, 824, 766, 741, 719, 546, 510 cmꢀ1; elemental analysis
calcd (%) for C12H9N9O12 (471.25): C 30.58, H 1.92, N 26.75; found: C
30.60, H 1.90, N 26.67.
Ammonium DPA (3a): Red solid; yield: 1.20 g (96%); 1H NMR: d=
8.75 (s, 4H), 7.06 ppm (t, J=51 Hz, 4H); 13C NMR: d=142.1, 138.6,
131.9, 124.3 ppm; IR (KBr pellet): n˜ =3238, 3087, 1677, 1586, 1568, 1503,
1432, 1383, 1291, 1158, 1087, 936, 911, 881, 825, 767, 741, 718, 630, 549,
514 cmꢀ1; elemental analysis calcd (%) for C12H8N8O12 (456.24): C 31.59,
H 1.77, N 24.56; found: C 31.34, H 1.86, N 24.25.
Experimental Section
Ethylenediammonium di-DPA (4a): Red solid; yield: 1.10 g (86%);
1H NMR: d=8.75 (s, 8H), 7.73 (s, 6H), 2.99 ppm (s, 4H); 13C NMR: d=
142.1, 138.6, 131.9, 124.3, 36.7 ppm; IR (KBr pellet): n˜ =3172, 3097, 1674,
1583, 1503, 1421, 1380, 1299, 1160, 1087, 1034, 1013, 918, 887, 824, 786,
740, 721, 548, 516 cmꢀ1; elemental analysis calcd (%) for C26H18N16O24
(938.51): C 33.27, H 1.93, N 23.88; found: C 33.33, H 2.00, N 23.95.
General methods: 1H and 13C NMR spectra were recorded using
a
400 MHz nuclear magnetic resonance spectrometer operating at 400.18
and 100.63 MHz, respectively. Chemical shifts are reported relative to
tetramethylsilane. The solvent was [D6]DMSO unless otherwise specified.
The melting and decomposition points were recorded using a differential
scanning calorimeter at a scan rate of 108Cminꢀ1, respectively. Infrared
spectra were recorded by using KBr pellets. Densities were measured at
room temperature using a Micromeritics Accupyc II 1340 gas pycnome-
ter. Elemental analyses were obtained using an Elementar Vario MICRO
CUBE (Germany) elemental analyzer. Toxicity was measured by using a
BHP9511 Water Quality Toxicity Analysis System (luminescent bacteria
test).
1-Amino-3-methyl-1,2,3-triazolium DPA (5a): Red solid; yield: 1.31 g
1
(89%); H NMR: d=8.75 (s, 4H), 8.72 (s, 1H), 8.58 (s, 1H), 8.26 (s, 2H),
4.21 ppm (s, 3H); 13C NMR: d=142.1, 138.6, 134.5, 131.9, 131.7, 126.9,
124.28 ppm; IR (KBr pellet): n˜ =3342, 3279, 3219, 3138, 3085, 1729, 1560,
1491, 1429, 1378, 1310, 1262, 1225, 1156, 1080, 910, 880, 824, 719, 767,
740, 718, 545, 517, 479 cmꢀ1
; elemental analysis calcd (%) for
C15H11N11O12 (537.31): C 33.53, H 2.06, N 28.67; found: C 33.29, H 2.11,
N 28.65.
1-Amino-3-methyl-1,2,3-triazolium iodide,[37] 1-methyl-3,4,5-triamino-
1,2,4-triazolium iodide,[38] DPA,[26] and DAHNDPA[24,25] were synthesized
by using previously reported methods.
1,3-Diaminoguanidinium DPA (6a): Red solid; yield: 1.40 g (97%);
1H NMR: d=8.75 (s, 4H), 8.53 (brs, 2H), 7.13 (s, 2H), 4.58 ppm (s, 4H);
13C NMR: d=159.9, 142.1, 138.6, 131.9, 124.3 ppm; IR (KBr pellet): n˜ =
3450, 3377, 3321, 3087, 1678, 1583, 1498, 1636, 1380, 1278, 1157, 1084,
913, 880, 824, 769, 740, 719, 649, 549, 512 cmꢀ1; elemental analysis calcd
(%) for C13H12N12O12 (528.31): C 29.55, H 2.29, N 31.81; found: C 29.32,
H 2.31, N 31.71.
X-ray crystallography: Crystals of DPA, 4a, and 6a were removed from
the flask and covered with a layer of hydrocarbon oil. A suitable crystal
was selected, attached to a glass fiber, and placed in the low-temperature
nitrogen stream. Data for DPA, 4a, and 6a were collected at 113(2) K
using a Rigaku Saturn 724 CCD diffractometer equipped with graphite-
monochromatized MoKa radiation (l=0.71075 ꢁ) with omega scans.
Data collection and reduction were performed and the unit cell was ini-
tially refined by using CrystalClearSM Expert 2.0 r2[39] software. The re-
flection data were also corrected for Lorentz-polarization (Lp) factors.
The structure was solved by direct methods and refined by least squares
method on F2 using the SHELXTL-97 system of programs.[40] Structures
were solved in the space group P212121 for DPA, P21/n for 4a, and P21/c
for 6a by analysis of systematic absences. In this all-light-atom structure,
the value of the Flack parameter did not allow the direction of the polar
axis to be determined, and Friedel reflections were then merged for the
final refinement. Details of the data collection and refinement are given
in Table 2.
1-Methyl-3,4,5-triamino-1,2,4-triazolium DPA monohydrate (7a): Red
1
solid; yield: 1.41 g (88%); H NMR: d=8.76 (s, 4H), 7.94 (s, 2H), 6.49 (s,
2H), 5.62 (s, 2H), 3.42 ppm (s, 3H); 13C NMR: d=151.0, 148.0, 142.4,
138.9, 132.2, 124.6, 34.7 ppm; IR (KBr pellet): n˜ =3605, 3543, 3424, 3364,
3281, 3169, 3087, 1714, 1671, 1643, 1589, 1554, 1530, 1515, 1498, 1439,
1381,1305, 1239, 1164, 1085, 924, 884, 847, 826, 782, 764, 742, 719, 554,
527 cmꢀ1; elemental analysis calcd (%) for C15H13N13O12·H2O (585.09): C
30.78, H 2.58, N 31.11; found: C 30.78, H 2.68, N 31.03.
1
Imidazolium DAHNDPA (1b): Red solid; yield: 1.04 g (76%); H NMR:
d=14.25 (brs, 2H), 9.09 (s, 1H), 8.80 (s, 4H), 7.95 (s, 4H), 7.07 (t,
4H) ppm; 13C NMR: d=143.9, 142.2, 134.8, 128.1, 127.9, 127.6, 121.3,
119.8 ppm; IR (KBr pellet): n˜ =3291, 3161, 3081,3005, 1751, 1578, 1489,
1443, 1381, 1318, 1244, 1204, 1096, 1047, 957, 918, 902, 775, 752, 693, 620,
CCDC-822227 (DPA), 822225 (4a), and 822226 (6a) contain the supple-
mentary crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
521, 489, 463 cmꢀ1
; elemental analysis calcd (%) for C15H11N11O12
(537.31): C 33.53, H 2.06, N 28.67; found: C 33.78, H 2.18, N 28.75.
Hydrazinium DAHNDPA (2b): Red solid; yield: 1.13 g (88%);
1H NMR: d=8.80 (s, 2H), 7.94 ppm (s, 4H); 13C NMR: d=144.1, 142.1,
128.0, 127.8, 127.6, 121.1 ppm; IR (KBr pellet): n˜ =3387, 3277, 3089,
1759, 1571, 1478, 1464, 1414, 1378, 1318, 1249, 1195, 1135, 1099, 1042,
922, 821, 775, 746, 698, 639, 488 cmꢀ1; elemental analysis calcd (%) for
C12H11N11O12 (501.28): C 28.75, H 2.21, N 30.74; found: C 29.08, H 2.30,
N 30.87.
Ammonium DPA (3b): Red solid; yield: 1.09 g (88%); 1H NMR: d=
8.80 (s, 2H), 7.94 (s, 4H), 7.06 ppm (t, J=51 Hz, 4H); 13C NMR: d=
144.1, 142.1, 128.0, 127.8, 127.6, 121.1 ppm; IR (KBr pellet): n˜ =3396,
3286, 3090, 1607, 1560, 1524, 1476, 1443, 1410, 1371, 1306, 1219, 1033,
890, 830, 781, 713, 695, 622, 480, 456 cmꢀ1; elemental analysis calcd (%)
for C12H10N10O12 (486.27): C 29.64, H 2.07, N 28.80; found: C 29.66, H
2.16, N 29.13.
General procedures for the preparation of DPA-based salts (1a–7a) and
DAHNDPA-based salts (1b–7b): Sodium hydroxide (1 equiv) was added
to a suspension of DPA (1.200 g, 2.7 mmol) or DAHNDPA (1.200 g,
2.6 mmol) in H2O (10 mL). The resulting mixture was stirred at 808C for
30 min until all of the solid was dissolved followed by adding 1 equiv imi-
dazolium chloride, hydrazine monohydrochloride, ammonium chloride, 1-
amino-3-methyl-1,2,3-triazolium iodide, 1,3-diaminoguanidine hydrochlo-
ride, 1-methyl-3,4,5-triamino-1,2,4-triazolium iodide, or 0.5 equiv ethyle-
nediamine hydrochloride, respectively. After stirring at room tempera-
ture for 1 h, the red precipitate was filtered off and dried in an oven at
658C for 2 h.
Imidazolium DPA (1a): Red solid; yield: 1.21 g (87%); 1H NMR: d=
14.16 (brs, 2H), 9.07 (s, 1H), 8.75 (s, 4H), 7.69 ppm (s, 2H); 13C NMR:
d=142.1, 138.6, 134.5, 131.9, 124.3, 119.5 ppm; IR (KBr pellet): n˜ =3232,
3185, 3077, 3004, 1734, 1586, 1566, 1493, 1431, 1380, 1319, 1300, 1273,
1156, 1083, 1046, 945, 906, 877, 824, 796, 741, 719, 625, 551, 515,
Ethylenediammonium di-DAHNDPA (4b): Red solid; yield: 1.05 g
(82%); 1H NMR: d=8.80 (s, 4H), 7.94 (s, 8H), 7.68 (br, 6H), 2.98 ppm
(s, 4H); 13C NMR: d=144.1, 142.1, 128.0, 127.8, 127.6, 121.2, 31.1 ppm;
13600
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Chem. Eur. J. 2011, 17, 13593 – 13602

Energetic Salts Based on Dipicrylamine
FULL PAPER
IR (KBr pellet): n˜ =3427, 3325, 3091, 1715, 1586, 1496, 1380, 1325, 1254,
1047, 922, 821, 776, 746, 697, 559 cmꢀ1; elemental analysis calcd (%) for
C26H22N20O24 (998.57): C 31.27, H 2.22, N 28.05; found: C 31.05, H 2.11,
N 27.74.
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1-Amino-3-methyl-1,2,3-triazolium DAHNDPA (5b): Red solid; yield:
1.27 g (88%); 1H NMR: d=8.79 (s, 2H), 8.73 (s, 1H), 8.59 (s, 1H), 8.27
(s, 2H), 7.93 (s, 6H), 4.21 ppm (s, 3H); 13C NMR: d=144.1, 142.1, 132.0,
128.0, 127.8, 127.5,127.3, 121.1 ppm; IR (KBr pellet): n˜ =3407, 3295,
3195, 3145, 3111, 1740, 1587, 1488, 1374, 1323, 1246, 1196, 1092, 1047,
942, 923, 822, 776, 735, 702, 635, 599 cmꢀ1; elemental analysis calcd (%)
for C15H13N13O12 (567.34): C 31.76, H 2.31, N 32.09; found: C 31.78, H
2.37, N 31.96.
1,3-Diaminoguanidinium DAHNDPA (6b): Red solid; yield: 1.03 g
(72%); 1H NMR: d=8.79 (s, 2H), 8.53 (brs, 2H), 7.92 (s, 2H), 7.12 (s,
2H), 4.57 ppm (s, 4H); 13C NMR: d=160.2, 144.1, 142.1, 128.0, 127.8,
127.6, 121.1 ppm; IR (KBr pellet): n˜ =3456, 3329, 3267, 3085, 1729, 1684,
1570, 1493, 1374,1323, 1255, 1196, 1022, 964, 944, 922, 822, 776, 746, 693,
590 cmꢀ1; elemental analysis calcd (%) for C13H14N14O12 (558.34): C
27.97, H 2.53, N 35.12; found: C 27.80, H 2.44, N 34.99.
1-Methyl-3,4,5-triamino-1,2,4-triazolium DAHNDPA monohydrate (7b):
Red solid; yield: 1.40 g (89%); 1H NMR: d=8.80 (s, 2H), 7.93 (s, 6H),
6.48 (s, 2H), 5.62 (s, 2H), 3.42 ppm (s, 3H); 13C NMR: d=151.0, 148.0,
144.1, 142.1, 128.0, 127.8, 127.6, 121.1, 34.7 ppm; IR (KBr pellet): n˜ =
3580, 3377, 3331, 3165, 3088, 1709, 1669, 1574, 1494, 1378, 1327, 1306,
1219, 1139, 1103, 1049, 942, 922, 901, 822, 776, 745, 797, 527 cmꢀ1; ele-
mental analysis calcd (%) for C15H15N15O12·H2O (615.11): C 29.28, H
2.78, N 34.14; found: C 29.36, H 2.82, N 34.29.
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The authors gratefully acknowledge the support of the Specialized Re-
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20091101110033) and the Pre-Research Foundation of China North
Chemical Industries (Group) Co. (no. 3100021021002), the National Nat-
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Received: May 8, 2011
Published online: October 31, 2011
13602
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Chem. Eur. J. 2011, 17, 13593 – 13602