Fully C/N-Polynitro-Functionalized 2,2'-Biimidazole Derivatives as Nitrogen- and Oxygen-Rich Energetic Salts

Article abstract of DOI:10.1002/chem.201504407

Through the use of a fully C/N-functionalized imidazole-based anion, it was possible to prepare nitrogen- and oxygen-rich energetic salts. When N,N-dinitramino imidazole was paired with nitrogen-rich bases, versatile ionic derivatives were prepared and fully characterized by IR, and ¹H, and ¹³C NMR spectroscopy and elemental analysis. Both experimental and theoretical evaluations show promising properties for these energetic compounds, such as high density, positive heats of formation, good oxygen balance, and acceptable stabilities. The energetic salts exhibit promising energetic performance comparable to the benchmark explosive RDX (1,3,5-trinitrotriazacyclohexane). The combination of a fully C/N-functionalized biimidazole-based anion with nitrogen-rich cations gives rise to a series of nitrogen- and oxygen-rich energetic salts. Some of them show excellent detonation properties with acceptable thermal stabilities and sensitivities, which are comparable to the benchmark explosive RDX (1,3,5-trinitrotriazacyclohexane).

Full text of DOI:10.1002/chem.201504407

DOI: 10.1002/chem.201504407
Full Paper
&
Energetic Materials
Fully C/N-Polynitro-Functionalized 2,2’-Biimidazole Derivatives as
Nitrogen- and Oxygen-Rich Energetic Salts
Ping Yin, Chunlin He, and Jean’ne M. Shreeve*[a]
Abstract: Through the use of a fully C/N-functionalized imi-
dazole-based anion, it was possible to prepare nitrogen- and
oxygen-rich energetic salts. When N,N-dinitramino imidazole
was paired with nitrogen-rich bases, versatile ionic deriva-
perimental and theoretical evaluations show promising
properties for these energetic compounds, such as high den-
sity, positive heats of formation, good oxygen balance, and
acceptable stabilities. The energetic salts exhibit promising
energetic performance comparable to the benchmark explo-
sive RDX (1,3,5-trinitrotriazacyclohexane).
1
tives were prepared and fully characterized by IR, and H,
and 13C NMR spectroscopy and elemental analysis. Both ex-
Introduction
Nitrogen-rich heterocycles are one of the most important
structural motifs in the design of high energy density materials
(HEDMs).[1] Due to practical application demands, the interest
of researchers is focused mainly on density, heat of formation,
oxygen balance, detonation properties, thermal stability, and
sensitivity toward destructive stimuli.[2] However, investigation
involving diverse HEDMs continues to demonstrate the contra-
dictory nature of energetic performance and molecular stabili-
ty. As such, understanding of rational molecular design is cru-
cial to achieve an ideal balance for different criteria. In general,
introduction of highly energetic functionalities (for example
nitro, azido, diazo, N-oxide, and trinitromethyl) are capable of
improving density and detonation properties.[2c,3] Meanwhile,
clever formation of versatile interactions between different en-
ergetic moieties are conducive in retaining a certain molecular
stability.[4]
Scheme 1. Thermal stability of fully C-nitrated azoles and their N-methyl
functionalized derivatives.
to good decomposition temperatures ranging from 100 to
2648C.[8] In contrast N-methyl functionalization of fully C-nitrat-
ed azoles enhances greatly the thermal stability where the N-
methyl-2,4,5-trinitro-1H-imidazole at 3108C has the highest de-
composition temperature of the N-methyl functionalized deriv-
atives;[9] furthermore, ammonium trinitroimidazolate is more
thermally stable than other ammonium azolates.[10]
Recently, the development of N-heterocyclic chemistry has
led to an upsurge of five membered azole-based energetic ma-
terials.[5] The advanced energetic properties benefit not only
from the positive heat of formation of the nitrogen-rich back-
bone, but also from the electron-rich features that are compat-
ible with multiple energetic functionalities. Reflecting on the
progress in azole-based energetic materials, fully C-nitrated
functionalization appears to be the mainstream strategy
toward high energetic performance (Scheme 1).
This unique structure–property feature indicates that it is
possible to balance energetic performance and stability by
virtue of both C- and N- functionalizations. Despite unsuccess-
ful attempts to stabilize a form of TNI, research enthusiasm is
still increasing in the search for imidazole-based HEDMs.[11] Re-
cently, a multifunctionalized strategy to improve the energetic
performance of various heterocyclic backbones, such as pyra-
zole, triazole, and imidazole, was demonstrated. Of these, rep-
resentative compounds include 5-nitramino-3,4-dinitropyrazole
(NADNP) and N,N’-dinitramino-4,4’,5,5’-tetranitro-bisimidazole
(4) with excellent detonation properties that are superior to
those of cyclo-1,3,5,7-tetramethylenene-2,4,6,8-tetranitramine
(HMX).[4e,f] However, their relatively high sensitivities may pre-
clude practical application. In the continuing research interest
in exploring energetic materials, various energetic bisimida-
Among these analogues, 2,4,5-trinitro-1H-imidazole (TNI),
albeit with a high predicted density of 1.905 gcmÀ3,[6] is not
isolable neat and can only be stored in ether solution.[7] In
comparison, the other fully C-nitrated azoles exhibit moderate
[a] Dr. P. Yin, Dr. C. He, Prof. Dr. J. M. Shreeve
Department of Chemistry, College of Science, University of Idaho
P.O. Box 442343, Moscow, 83844-2342 ID (USA)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201504407.
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zole-based energetic salts were synthesized and further study
associated with physicochemical properties indicate that they
have favorable detonation properties with enhanced stabilities.
Additionally, single-crystal X-ray crystallographic analysis was
employed to acquire insight into structural features of the en-
ergetic salts.
and IR spectroscopy, thermal stability, elemental analyses, and
impact and friction sensitivity.
For the N,N’-diamino compound (3), the characteristic IR ab-
sorption bands of NH2 were observed as sharp double peaks
at 3337 and 3325 cmÀ1. Typically for polynitro compounds, the
characteristic IR absorption bands of the nitro groups ap-
peared in the 1300–1600 cmÀ1 region. The chemical shifts of
the imidazole ring in the 13C NMR spectra of 4 were found at
135.8, 132.4, and 129.0 ppm, which are very similar to those of
ammonium salt (6) at 133.5, 132.1, and 128.7 ppm. Although
the synthesis of 4 and 8 was studied previously, the detail data
of 14N and 15N NMR spectra were not illustrated.[4f] The 14N
NMR spectra of the dinitroamino compound (4) and hydroxy-
lammonium salt (8) were measured in [D6]acetone and
[D6]DMSO, respectively (Figure 1). In the case of compound 4,
the resonance at À30.04 ppm can be assigned to the N-NO2
group, whereas the resonances at À34.59 ppm and
À38.49 ppm were attributed to the C-NO2 groups on the basis
of comparison with previously reported data.[4e]
Results and Discussion
The precursor 1H,1’H-2,2’-biimidazole (1) was prepared from
glyoxal and ammonium acetate in water (Scheme 2). Employ-
ing sodium nitrate and concentrated sulfuric acid, nitration of
carbon was accomplished.[12] Although N-nitro-functionalized
biimidazole has been predicted as a high-performance com-
pound exceeding HMX,[13] a stable form cannot be isolated
Although the neat compound (4) can be stored for an ex-
tended period, a concentrated solution of 4 in [D6]acetone was
unstable for 24 h, precluding the acquisition of 15N spectro-
scopic data. In the 14N NMR spectrum of hydroxylammonium
salt (8), three broad peaks are found at À5.20 (N4), À34.60
(N6), and À304.23 (N7). Whereas in the 15N NMR spectrum of 8
five signals at À6.14 (N4), À26.66 (N5), À34.70 (N6), À128.06
(N3), À135.26 (N2) are seen.
Aiming for structural insight, 12 was further characterized by
single-crystal X-ray diffraction (Figure 2).[15] A crystal of 12 was
obtained by dissolving 12 in methanol and allowing chloro-
Scheme 2. Synthesis of N,N’-nitroamino 4,4’,5,5’-tetranitro-2,2’-biimidazole
(4) and its energetic salts (6–14).
due to the high sensitivity. In contrast, N-nitramino functional-
ized biimidazole was readily obtained by N-amination of 2 fol-
lowed by the nitration of 3 using O-tosylhydroxylamine and
H2SO4/HNO3, respectively. A modified workup procedure by re-
crystallization of the crude N-amino product resulted in a good
yield of highly pure 3 and precluded chromatographic column
separation.[14] Because of the highly reactive nature of the N-
amino groups, the nitration reaction of 3 in mixed acid was
carried out at À15 to À108C to prevent NÀN bond cleavage.
Treated with potassium carbonate and silver nitrate, 4 was
converted into the disilver salt, 5. The following metathesis re-
actions with corresponding chloride salts gave rise to diammo-
nium (6), dihydrazinium (7), and dihydroxylammonium (8)
salts. Similarly, reaction of 4 with versatile nitrogen-rich bases
yielded ionic derivatives, 9–14. All of the new biimidazole-
based energetic compounds were fully characterized by NMR
Figure 1. 14N and 15N NMR spectra of 4 and 8.
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Figure 2. Single-crystal X-ray structure of 12.
form to diffuse into the solution. With a calculated density of
1.813 gcmÀ3 at 100 K, 12 crystallizes in the monoclinic space
group P21/c with two molecules in the unit cell (Figure 3).
Compared to some reported guanidinium salts, for example
guanidinium nitrate (15) and guanidinium dinitramide (16),
salt 12 shows a higher density arising from the C/N- fully poly-
nitro functionalized anion (12, 1.813 gcmÀ3 at 100 K,
1.75 gcmÀ3 at 298 K; 15, 1.369 gcmÀ3 at 291 K; 16,
1.673 gcmÀ3 at 293 K).[16] The CÀN bond lengths of four C-nitro
groups are similar (N4ÀC2 1.441(2) Š, N5ÀC3 1.438(2) Š). Gen-
erally, nitro groups play a role as hydrogen-bond acceptors.
Hydrogen-bond interactions of 12 are found between the gua-
Figure 3. Packing diagram of 12 along the a axis.
ranging between 113 8C and 2038C. When 3,6,7-triamino-7H-
[1,2,4]triazolo[5,1-c][1,2,4]triazole was utilized as a nitrogen-rich
base, the resulting salt (11) is the most thermally stable of
these energetic salts (2038C).
As a pivotal evaluation, densities of these new energetic
compounds were measured with a gas pycnometer at room
temperature. The measured densities (d) of these energetic
salts (6–14) fall between 1.75 and 1.85 gcmÀ3 (Table 1). Impact
and friction sensitivities of biimidazole-based energetic com-
nidinium cations and N-nitramino anions (N7ÀH7A···O2, N8À pounds were measured using a BAM drop hammer apparatus
H8A···O2, N7ÀH7A···O6, and N9ÀH9A···O2).
and a BAM friction tester, respectively. Compound 3 shows
moderately sensitive parameters with an impact sensitivity (IS)
of 15 J and a friction sensitivity (FS) of 160 J. In spite of the rel-
atively sensitive characteristics of 4 (IS, 3 J; FS, 20 N), its ionic
derivatives exhibit lower impact and friction sensitivities (IS, 5-
30 J; FS, 60-240 N).
To evaluate the thermal stability, differential scanning calori-
metric (DSC) measurements were used for the biimidazole-
based energetic compounds (3, 4, and 6–14) (Table 1). The
N,N-diamino compound 3 has a decomposition temperature
(Td) of 2178C comparable to that of RDX (Td, 2058C). In spite of
the low decomposition temperature of the N,N-dinitroamine
(4) (Td, 1168C), the energetic salts of 4 (6–14) have moderate
to good thermal stabilities with decomposition temperatures
Theoretical computations associated with the heats of for-
mation (DHf) were performed by using the Gaussian03 (Revi-
sion D.01) suite of programs.[17] As seen in Table 1, energetic
Table 1. Properties of biimidazole-based energetic compounds 3, 4, and 6–14.
[a]
[e]
Comp
Td [oC]
d[b] [gcmÀ3
]
DHf[c] [kJgÀ1
]
P[d] [GPa]
vD [msÀ1
]
IS[f] [J]
FS[g] [N]
OB[h] [%]
3
217
116
135
128
135
113
133
203
158
141
140
205
1.93
1.94
1.78
1.79
1.85
1.78
1.80
1.85
1.75
1.81
1.77
1.81
0.90
1.11
0.75
1.33
0.90
1.19
2.45
1.96
0.59
0.95
1.55
0.36
36.6
40.1
33.6
35.7
38.2
30.4
35.4
33.8
29.5
33.0
32.8
34.9
9012
9350
8715
8916
9169
8499
8996
8899
8409
8786
8898
8748
15
3
8
5
6
30
5
10
30
25
9
160
20
80
80
80
240
60
120
240
160
80
0
18.4
4.71
3.21
4[i]
6
7
8[i]
9
12.8
À12.7
À2.52
À15.1
À5.80
À8.25
À12.5
0
10
11
12
13
14
RDX
7.4
120
[a] Decomposition temperature. [b] Density measured by gas pycnometer (258C). [c] Heat of formation. [d] Detonation pressure (calculated with Explo5
v6.01). [e] Detonation velocity (calculated with Explo 6.01). [f] Impact sensitivity. [g] Friction sensitivity. [h] Oxygen balance (based on CO) for CaHbOcNd,
1600(cÀaÀb/2)/MW, MW=molecular weight. [i] Ref. [4f].
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13C, 14N, and 15N NMR spectra were recorded on a 300 MHz (Bruker
AVANCE 300) or 500 MHz (Bruker AVANCE 500) nuclear magnetic
resonance spectrometer. Chemical shifts are reported relative to
Me4Si or deuterated solvents. Elemental analyses (C, H, N) were
performed on a CE-440 Elemental Analyzer. Impact and friction
sensitivity measurements were made using a standard BAM Fall-
hammer and a BAM friction tester. IR spectra were recorded using
KBr pellets with a Biorad Model 3000 FTS spectrometer. Densities
were determined at 258C by employing a Micromeritics AccuPyc
1330 gas pycnometer.
biimidazoles and ionic derivatives are endothermic compounds
with positive heats of formation ranging from 0.59 kJgÀ1 to
2.45 kJgÀ1, which exceed those of RDX (0.36 kJgÀ1) and HMX
(0.36 kJgÀ1). Incorporating experimental densities and theoreti-
cally calculated heats of formation, the detonation pressures
(P) and velocities (vD) were calculated based on the EXPLO5
v6.01 program.[18] With high densities and favorable heats of
formation, the detonation properties of 3 (P=36.6 GPa; vD =
9012 msÀ1) and 4 (P=40.1 GPa; vD =9350 msÀ1) suggest their
potential use as high explosives. Further to molecular com-
pounds 3 and 4, the ionic derivatives also show promising det-
onation parameters (P=29.5–38.2 GPa; vD =8409–9169 msÀ1).
Among them, 11 exhibits favorable overall properties, such as
density, detonation properties, and molecular stabilities, which
are comparable to the benchmark explosive RDX (11: d=
1.85 gcmÀ3, P=33.8 GPa, vD =8899 msÀ1, Td =2038C, IS=10 J,
Theoretical study
Based on the method of isodesmic reactions, the gas-phase enthal-
pies of formation were computed and the enthalpy of reaction is
obtained by combining the MP2/6–311+ +G** energy difference for
the reactions, the scaled zero point energies (ZPE), values of ther-
mal correction (HT), and other thermal factors.[17] Thus, the gas
phase enthalpy of the species can be extracted. Solid-state heats
of formation of the resulting compounds were calculated with
Equation (1) (Tm is the melting temperature).[19]
FS=120 N; RDX: d=1.81 gcmÀ3, P=34.9 GPa, vD =8748 msÀ1
Td =2058C, IS=7 J, FS=120 N).
,
Oxygen balance (OB) is a significant index to indicate the de-
ficiency or excess of oxygen in energetic ingredients. While 4,
6, 7, and 8 have positive oxygen balances (3.21 to 18.4), 3 has
an OB value of zero, and the other compounds show negative
values (À2.52 to À15.1). Arising from fully C- and N-polynitro
functionalization, the nitrogen- and oxygen-rich compounds 4
and 8 exhibit promising OB values of 18.4 and 12.8, respective-
ly, which suggests use as potential energetic oxidizers to im-
prove the overall performance in multiple energetic ingredi-
ents.
DHf ¼ DHfðgÞÀDHsub ¼ DHfðgÞÀ188 ½J molÀ1 KÀ1Š  Tm
ð1Þ
Based on the Born–Haber energy cycle (Scheme 3), the solid phase
heat of formation of energetic salts can be simplified by Equa-
tion (2).
DHfo ðsalt, 298 KÞ ¼
ð2Þ
DHfo ðcation, 298 KÞ þ DHfo ðanion, 298 KÞÀDHL
Conclusion
A reasonable assembly of C-nitro and N-nitroamino functionali-
ties gave rise to a family of new high-density energetic biimi-
dazoles. All biimidazole-based compounds were fully character-
ized by elemental analysis and IR and NMR spectroscopy. Com-
pared to the instability of the fully C-nitrated monocyclic imi-
dazole TNI, polynitro functionalized biimidazole 4 and its ener-
getic salts exhibit enhanced molecular stability and
performance parameters, such as density, oxygen balance, and
detonation properties, are superior to those of TNI. Based on
both experimental and calculated methods, some representa-
tive energetic salts exhibit promising properties, such as good
densities, high detonation parameters, and moderate sensitivi-
ties. By incorporating a conventional C-nitro functionality and
a novel N-nitroamino functionality into biimidazole rings, this
enriches the design strategy of polynitro introduction and
demonstrates a promising pathway to high-density energetic
heterocycles.
Scheme 3. Born–Haber cycle for the formation of biimidazole compounds. a,
b, c, d are the number of moles of the respective products.
In Equation (2), the lattice energy (DHL) could be predicted by
using the formula suggested by reported methods [Equation
(3)].[20]
DHL ¼ UPOT þ ½pðnM=2À2Þ þ qðnX=2À2ފRT
ð3Þ
in which nM and nX depend on the nature of the ions Mp+ and
XqÀ, respectively, and are equal to three for monoatomic ions, five
for linear polyatomic ions, and six for nonlinear polyatomic ions.
The equation for lattice potential energy UPOT has the form [Equa-
tion (4)]:
Experimental Section
General methods
All chemicals were pure analytical grade materials obtained from
Aldrich, Acros Organics, or AK Scientific and used as received. De-
composition points were recorded on a differential scanning calo-
rimeter (DSC, TA Instruments Q10) at a scan rate of 58C minÀ1
UPOT ½kJ molÀ1Š ¼ gð1=MÞ1=3 þ d
ð4Þ
.
1 H,
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4,4’,5,5’-tetranitro-1H,1’H-[2,2’-biimidazole]-1,1’-diamine
(3):
1H NMR ([D6]DMSO): d=7.00 ppm (br, 8H); 13C NMR ([D6]DMSO):
d=152.8, 135.5, 132.1, 128.7 ppm; IR (KBr pellet): u˜ =3310, 1765,
1695, 1655, 1418, 1292, 1111, 1057, 1015, 850, 804, 776 cmÀ1; ele-
mental analysis (%) calcd for C10H12N22O12 (632.35): C 18.99, H 1.91,
N 48.73; found: C 18.62, H 1.89, N 47.51.
Preparation of 4,4’,5,5’-tetranitro-1H,1’H-2,2’-biimidazole dihydrate
(2) was based on the modified method.[14] A mixture of 2 (4 mmol,
1.4 g) and 1,8-diazabicycloundec-7-ene (8 mmol, 1.22 g) in CH3CN
(20 mL) was stirred at room temperature for 1 h. To this orange
suspension, freshly prepared O-tosylhydroxylamine (ca. 15 mmol)
in chloroform solution (30 mL) was added in 2 min. The final mix-
ture was stirred for 3 h and then was filtered, washed by CH3CN
(3”5 mL). The combined filtrate was concentrated and the final
crude product was recrystallized in ethanol and water to yield 3
(orange solid, 63% yield). 1H NMR (CD3CN): d=6.30 ppm (s, 4H);
13C NMR (CD3CN): d=137.0, 134.8, 131.6 ppm; elemental analy-
sis (%) calcd for C6H4N10O8 (344.16): C 20.94, H 1.17, N 40.70; found:
C 21.14, H 1.21, N 39.97.
Di(1,5-diamino-tetrazolium) N,N’-(4,4’,5,5’-tetranitro-1H,1’H-[2,2’-
biimidazole]-1,1’-diyl)dinitramide (10): red solid, 91% yield.
1H NMR ([D6]DMSO): d=5.25 ppm (br, 8H); 13C NMR ([D6]DMSO):
d=153.0, 135.6, 132.2, 128.8 ppm; IR (KBr pellet): u˜ =3433, 3154,
2745, 2155, 1759, 1701, 1649, 1542, 1425, 1383, 1298, 1043, 864,
809, 781 cmÀ1; elemental analysis (%) calcd for C8H10N24O12 (634.32):
C 15.15, H 1.59, N 53.00; found: C 14.72, H 1.67, N 50.93.
Di[3,6,7-triamino-7H-[1,2,4]triazolo[5,1-c][1,2,4]triazol-2-ium]
N,N’-(4,4’,5,5’-tetranitro-1H,1’H-[2,2’-biimidazole]-1,1’-diyl)dini-
tramide (11): yellow solid, 85% yield. 1H NMR ([D6]DMSO): d=
13.32 (br, 1H), 8.16 (s, 2H), 7.21 (s, 2H), 5.76 ppm (s, 2H); 13C NMR
([D6]DMSO): d=153.0, 135.6, 132.2, 128.8 ppm; IR (KBr pellet): u˜ =
3429, 3364, 3297, 3158, 1699, 1645, 1542, 1414, 1299, 1042, 852,
Disilver
N,N’-(4,4’,5,5’-tetranitro-1H,1’H-[2,2’-biimidazole]-1,1’-
diyl)dinitramide (5): The dinitramino compound 4 was prepared
according to our previous method.[4f] Potassium carbonate
(138 mg, 1 mmol) was added to a solution of 4 (434 mg, 1 mmol)
in distilled water (2 mL) and the mixture was stirred at room tem-
perature for 10 min. Then silver nitrate (340 mg, 2 mmol) was
added to the suspension and stirred at room temperature for 1 h.
The precipitate 5 was collected by filtration and dried in vacuum
(orange solid, 95%). Elemental analysis (%) calcd for C6N12O12Ag2
(647.87): C 11.12, H 0.00, N 25.94; found: C 11.47, H 0.26, N 26.40.
810, 702 cmÀ1
(742.43): C 19.41, H 1.90, N 52.83; found: C 19.12, H 1.86, N 52.13.
; elemental analysis (%) calcd for C12H14N28O12
Di(guanidinium)
N,N’-(4,4’,5,5’-tetranitro-1H,1’H-[2,2’-biimida-
zole]-1,1’-diyl)dinitramide (12): yellow solid, 81% yield. 1H NMR
([D6]DMSO): d=6.90 ppm (s, 12H); 13C NMR ([D6]DMSO): d=158.0,
135.5, 132.1, 128.8 ppm; IR (KBr pellet): u˜ =3455, 3353, 1655, 1524,
1427, 1379, 1349, 1302, 1154, 1061, 1000, 850, 806 cmÀ1; elemental
analysis (%) calcd for C8H12N18O12 (552.30): C 17.40, H 2.19; N 45.65;
found: C 17.48; H 2.19; N 45.05.
General procedure for salts 6–8: Compound 5 (648 mg, 1 mmol)
was added to an ice-cold methanol solution (10 mL) of ammonium
chloride (107 mg, 2 mmol), hydrazinium chloride (137 mg, 2 mmol),
or hydroxylammonium chloride (139 mg, 2 mmol). After stirring 1 h
at 0–58C, silver chloride was removed by filtration and washed
with a small amount of methanol. The filtrate was concentrated
under reduced pressure and dried in vacuo to yield 6–8.[4f]
Di(aminoguanidinium) N,N’-(4,4’,5,5’-tetranitro-1H,1’H-[2,2’-bi-
imidazole]-1,1’-diyl)dinitramide (13): yellow solid, 75% yield.
1H NMR ([D6]DMSO): d=8.54 (s, 2H), 7.20 (br, 4H), 6.75 (br, 4H),
4.67 ppm (s, 4H); 13C NMR ([D6]DMSO): d=158.7, 135.4, 132.0,
128.6 ppm; IR (KBr pellet): u˜ =3439, 3362, 1672, 1549, 1427, 1382,
1359, 1290, 1197, 1059, 951, 916, 849, 806, 774, 664 cmÀ1; elemen-
tal analysis (%) calcd for C8H14N20O12 (582.33): C 16.50, H 2.42,
N 48.11; found: C 16.48, H 2.51, N 47.97.
Diammonium N,N’-(4,4’,5,5’-tetranitro-1H,1’H-[2,2’-biimidazole]-
1,1’-diyl)dinitramide dihydrate (6): red solid, 86% yield. 1H NMR
([D6]DMSO): d=7.08 ppm (br, 8H); 13C NMR ([D6]DMSO): d=135.5,
132.1, 128.7 ppm; IR (KBr pellet): u˜ =3554, 1631, 1536, 1440, 1413,
1302, 1279, 1109, 853, 810, 717 cmÀ1; elemental analysis (%) calcd
for C6H12N14O14 (504.25): C 14.29, H 2.40, N 38.89; found: C 14.60,
H 2.16, N 37.23.
Di(triaminoguanidinium) N,N’-(4,4’,5,5’-tetranitro-1H,1’H-[2,2’-bi-
imidazole]-1,1’-diyl)dinitramide (14): yellow solid, 63% yield.
1H NMR ([D6]DMSO): d=8.57 (s, 6H), 4.48 ppm (s, 12H); 13C NMR
([D6]DMSO): d=159.0, 135.4, 132.0, 128.6 ppm; IR (KBr pellet): u˜ =
3360, 3213, 3147, 3071, 1527, 1442, 1371, 1348, 1304, 1285, 1272,
1208, 1136, 1051, 1017, 989, 964, 927, 863, 848, 811, 777, 757, 639,
616 cmÀ1; elemental analysis (%) calcd for C8H18N24O12 (642.39):
C 14.96, H 2.82, N 52.33; found: C 14.52, H 3.13, N 53.07.
Dihydrazinium N,N’-(4,4’,5,5’-tetranitro-1H,1’H-[2,2’-biimidazole]-
1,1’-diyl)dinitramide (7): red solid, 82% yield. H NMR (CD3CN): d=
1
4.43 ppm (br, 10H); 13C NMR ([D6]DMSO): d=135.5, 132.1,
128.7 ppm; IR (KBr pellet): u˜ =3375, 3303, 3159, 2154, 1626, 1546,
1422, 1279, 1090, 928, 851, 806, 768 cmÀ1; elemental analysis (%)
calcd for C6H10N16O12 (498.25): C 14.46, H 2.02, N 44.98; found:
C 15.09,H 2.17, N 42.70.
General procedure for salts 9–14: Compound 4 (434 mg, 1 mmol)
was added to a mixture of 3,5-diaminotriazole (198 mg, 2 mmol) in
MeOH (10 mL), 1,5-diaminotetrazole (200 mg, 2 mmol) in MeOH
Acknowledgements
We are grateful to the Office of Naval Research (N00014-12-1-
0536) and the Defense Threat Reduction Agency (HDTRA 1-11-
1-0034). The authors acknowledge Dr. Orion Berryman (NSF-
CHE1337908 and CoBRE NIGMS P20M103546) for considerable
assistance with crystal structures.
(10 mL),
3,6,7-triamino-7H-[1,2,4]triazolo[5,1-c][1,2,4]triazole
(308 mg, 2 mmol) in H2O (15 mL), guanidinium carbonate (180 mg,
1 mmol) in MeOH (10 mL), aminoguanidinium carbonate (272 mg,
2 mmol) in MeOH (10 mL), or triaminoguanidinium chloride
(280 mg, 2 mmol) in EtOH (20 mL) and H2O (5 mL). After stirring
1 h at 508C, the product was obtained by filtration or concentra-
tion.
Keywords: biimidazoles · detonation properties · energetic
salts · explosives
Di(3,5-Diamino-triazolium) N,N’-(4,4’,5,5’-tetranitro-1H,1’H-[2,2’-
biimidazole]-1,1’-diyl)dinitramide (9): red solid, 93% yield.
Chem. Eur. J. 2016, 22, 2108 – 2113
www.chemeurj.org
2112
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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Received: November 2, 2015
Published online on January 12, 2016
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