Nitrogen-rich bis-1,2,4-triazoles - A comparative study of structural and energetic properties

Article abstract of DOI:10.1002/chem.201202483

In this contribution, the synthesis and full structural and spectroscopic characterization of five bis-1,2,4-triazoles in combination with different energetic moieties like amino, nitro, nitrimino, azido, and dinitromethylene groups is presented. The main goal is a comparative study on the influence of those energetic moieties on the structural and energetic properties. A complete characterization including IR, Raman, and multinuclear NMR spectroscopy of all compounds is presented. Additionally, X-ray crystallographic measurements were performed and deliver insight into structural characteristics as well as inter- and intramolecular interactions. The standard enthalpies of formation were calculated for all compounds at the CBS-4M level of theory, the detonation parameters were calculated by using the EXPLO5.05 program. Additionally, the impact as well as the friction sensitivities and the sensitivity against electrostatic discharge were determined. The potential application of the synthesized compounds as energetic material will be studied and evaluated by using the experimentally obtained values for the thermal decomposition, the sensitivity data, and the calculated performance characteristics. Bang, boom, bang: In this contribution the synthesis and full structural and spectroscopic characterization of five bis-1,2,4-triazoles in combination with different energetic moieties like amino, nitro, nitrimino, azido, and dinitromethylene groups is presented (see figure). The main goal is a comparative study on the influence of those energetic moieties on structural and energetic properties. Copyright

Full text of DOI:10.1002/chem.201202483

DOI: 10.1002/chem.201202483
Nitrogen-Rich Bis-1,2,4-triazoles—A Comparative Study of Structural and
Energetic Properties
Alexander A. Dippold and Thomas M. Klapçtke*[a]
Abstract: In this contribution, the syn-
thesis and full structural and spectro-
scopic characterization of five bis-1,2,4-
triazoles in combination with different
energetic moieties like amino, nitro, ni-
trimino, azido, and dinitromethylene
groups is presented. The main goal is a
comparative study on the influence of
those energetic moieties on the struc-
tural and energetic properties. A com-
plete characterization including IR,
Raman, and multinuclear NMR spec-
troscopy of all compounds is presented.
Additionally, X-ray crystallographic
measurements were performed and de-
liver insight into structural characteris-
tics as well as inter- and intramolecular
interactions. The standard enthalpies of
formation were calculated for all com-
pounds at the CBS-4M level of theory,
the detonation parameters were calcu-
lated by using the EXPLO5.05 pro-
gram. Additionally, the impact as well
as the friction sensitivities and the sen-
sitivity against electrostatic discharge
were determined. The potential appli-
cation of the synthesized compounds as
energetic material will be studied and
evaluated by using the experimentally
obtained values for the thermal decom-
position, the sensitivity data, and the
calculated performance characteristics.
Keywords: energetic materials
·
heterocycles · nitrogen · NMR spec-
troscopy · X-ray diffraction
Introduction
1,2,4-triazoles.[6] Bridged compounds like 5,5’-dinitro-3,3’-
azo-1,2,4-triazole (DNAT)[7] or the analogue nitrimino com-
pound (DNAAT)[8] have already been investigated and
show remarkably high decomposition temperatures and ex-
cellent energetic properties.
The synthesis of energetic materials that combine high per-
formance and low sensitivities has attracted worldwide re-
search groups over the last decades.[1] Nitrogen-rich hetero-
cycles are promising compounds that fulfill many require-
ments in the challenging field of energetic-materials re-
search.[1f,2] A prominent family of novel high energy density
materials (HEDMs) are azole-based compounds, because
they are generally highly endothermic with high densities
and low sensitivities towards outer stimuli. Owing to the
ꢀ
Bis-1,2,4-triazoles connected through a C C bond are ex-
pected to show similar energetic properties in comparison to
azo-bridged 1,2,4-triazole compounds and with regard to the
outstanding properties of 5,5’-bistetrazoles.[9] Different syn-
thetic pathways towards 5,5’-dinitrimino-3,3’-bis-1,2,4-tria-
zole have been intensively investigated by Russian scien-
tists,[10] the sensitivities (time to explosion delay, impact sen-
sitivity) were first investigated by Astachov et al.[11] Shreeve
and co-workers determined the energetic properties of ni-
trogen-rich salts and the crystal structure of the neutral
compound.[12] 3,3’-Dinitro-5,5’-bis-1,2,4-triazole has been
mentioned in literature before, but was only characterized
by means of ultraviolet absorption and infrared spectrosco-
py.[13]
high positive heats of formation resulting from the large
[3]
ꢀ
ꢀ
number of N N and C N bonds and the high level of en-
vironmental compatibility, those compounds have been stud-
ied in our group over the last couple of years with growing
interest. Especially 1,2,4-triazoles show a perfect balance be-
tween thermal stability and high positive heats of formation,
required for applications as prospective HEDMs.
Many energetic compounds that combine the 1,2,4-tria-
zole backbone with energetic moieties have been synthe-
sized over the last decades. Examples for these kind of mol-
ecules are 5-amino-3-nitro-1,2,4-triazole (ANTA),[4] 2-azido-
5-nitramino-1,2,4-triazole,[5] or trinitromethyl-substituted
The focus of this contribution is on the full structural and
spectroscopic characterization of five different bis-1,2,4-tria-
zoles carrying energetic moieties like amino, nitro, nitrami-
no, azido, and dinitromethyl groups. We present a compara-
tive study on the influence of those energetic moieties on
the structural and energetic properties. The potential appli-
cation of the synthesized compounds as energetic material
will be studied and evaluated by using the experimentally
obtained values for the thermal decomposition and the sen-
sitivity data, as well as the calculated performance charac-
teristics.
[a] A. A. Dippold, Prof. Dr. T. M. Klapçtke
Department of Chemistry, Ludwig Maximilian Universitꢀt Mꢁnchen
Butenandstr. 5–13, Haus D, D-81377 Munich (Germany)
Fax: (+49)89-2180-77492
E-mail: tmk@cup.uni-muenchen.de
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201202483.
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FULL PAPER
Results and Discussion
using concentrated sulfuric and nitric acid in a ratio of 3:1
resulting in a yield of 77%.
Synthesis: The starting material 3,3’-diamino-5,5’-bis(1H-
1,2,4-triazole) (DABT, 1) was first synthesized with a moder-
ate yield of 56% by Shreve and Charlesworth.[14] We devel-
oped a straightforward synthetic procedure yielding DABT
as elemental analysis pure compound in yields of up to
70%. The modified procedure starts with the reaction of
oxalic acid and aminoguanidinium bicarbonate in concen-
trated hydrochloric acid at 708C, followed by isolation of
the intermediate product by filtration. While heating to
reflux in basic media, the molecule undergoes cyclization,
which leads to the formation of DABT (Scheme 1).
The azido compound 4 was synthesized through diazotiza-
tion in sulfuric acid and subsequent reaction with an excess
of sodium azide. After recrystallisation from water, com-
pound 4 can be isolated as the insensitive dihydrate.
The synthesis of the dinitromethyl-bis1,2,4-triazole
5
(DNMBT) was achieved through a completely different syn-
thetic pathway (Scheme 3). The chlorination of sodium cya-
Scheme 1. Synthesis of DABT (1).
Scheme 3. Synthetic pathway towards DNMBT (5).
As shown in Scheme 2, oxidation of DABT (1) was ach-
ieved by the well-known Sandmeyer reaction through diazo-
tization in sulfuric acid and subsequent reaction with
nide in ethanol and subsequent reaction with hydrazine
leads to the formation of the oxalimidohydrazide.[16] This in-
termediate product was reacted with the commercially avail-
able 3-ethoxy-3-iminopropionic acid ethyl ester hydrochlo-
AHCTUNGERTGrNNUN ide to form the 3,3’-(diethyl acetate)-5,5’-bis-1,2,4-triazole.
Introduction of the NO2 moieties was accomplished by ni-
tration with nitric acid in a mixture of sulfuric acid and
oleum (1:1). The ethyl ester hydrolyses rapidly, whereas stir-
ring the nitrated intermediate product in basic media and
subsequent acidification with concentrated hydrochloric acid
leads to the release of CO2 and the formation of 3,3’- dini-
tromethyl-5,5’-bis-1,2,4-triazole (5).
All nitrogen-rich bis-1,2,4-triazoles, that is, compounds 1–
5 were fully characterized by IR and Raman spectroscopy as
well as multinuclear NMR spectroscopy, mass spectrometry,
and differential scanning calorimetry (DSC). Additional X-
ray crystallographic measurements deliver insight into inter-
and intramolecular interactions.
Scheme 2. Synthesis of the energetic bis-1,2,4-triazole derivatives 2–4
based on DABT (1).
sodium nitrite.[15] The formation of 3,3’-dinitro-5,5’-bis(1H-
1,2,4-triazole) (DNBT, 2) was first mentioned by Russian
scientists with a low yield of 31%.[13b] We were able to opti-
mize the process by adding a suspension of DABT in aque-
ous sulfuric acid (20%) to a solution of sodium nitrite in
water at 408C, which leads to a remarkable increase of the
yield up to 82%.
Crystal structures: Single-crystal X-ray measurements were
accomplished for compounds 1, 2, 4, and 5 and are discussed
in detail. The crystal structure of the nitrimino compound 3
has already been described in literature.[12] All compounds
could only be recrystallized from water resulting in the for-
mation of the dihydrate as crystalline species, only com-
pound 2 could be obtained water free.
The nitrimino compound 3 was first synthesized by Metel-
kina et al. by using oxalic acid dihydrazide and 2-nitroguani-
dine,[10a] by using 1-amino-2-nitroguanidine with oxalic
acid,[10b] or by using 1-methyl-2-nitro-1-nitrosoguanidine and
oxalic acid dihydrazide.[10c] We followed the most efficient
method first mentioned by Astachov et al.[11] starting from
the amino compound 1. The nitration was optimized by
By detailed examination of the crystal structures of all
compounds, no difference is observed for the 1,2,4-triazole
system in comparison to other triazole ring systems.[7,17] The
bond lengths within the 1,2,4-triazole ring in the molecular
ꢀ
structures are all in between the length of formal C N and
ꢀ
ꢀ
ꢀ
N N single and double bonds (C N: 1.47, 1.22 ꢃ; N N:
1.48, 1.20 ꢃ).[18]
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16743

T. M. Klapçtke and A. A. Dippold
Due to the very low solubility in any solvent, crystals of
5,5’-diamino-3,3’-bis-(1H-1,2,4-triazole) (1) could only be
obtained by recrystallisation from DMSO. Compound 1
crystallizes as DMSO adduct in the monoclinic space group
P21/c with a cell volume of 750.55(14) ꢃ3 and two molecular
moieties in the unit cell, the crystal structure together with
the labeling scheme is displayed in Figure 1.
Figure 1. Crystal structure of DABT (1), only one orientation of the dis-
ordered DMSO molecules is shown. Thermal ellipsoids are set to 50%
probability. Symmetry: i) 2ꢀx, ꢀy, 1ꢀz.
Figure 2. Hydrogen bonding within the crystal structure of DABT (1).
DMSO molecules are omitted for clarity because they do not participate
in hydrogen bonds in the bc plane. Thermal ellipsoids are set to 50%
probability. Symmetry: i) x, 1/2ꢀy, ꢀ1/2+z; ii) 2ꢀx, ꢀ1/2+y, 1/2ꢀz; iii) x,
1/2ꢀy, 1/2+z; iv) 2ꢀx, 1/2+y, 1/2ꢀz.
As expected, the bis-triazole moiety shows a completely
planar assembly. In relation to the planar 1,2,4-triazole ring,
the protons of the amine groups are twisted out of plane by
only 26.18. The angles surrounding the N4 atom are larger
than expected for a sp3 atom in the range of 116(1) (C2-N4-
H5a) to 118(1)8 (C2-N4-H5b), which could be a reason for
the low nucleophilicity observed in reactions with compound
1.
The formula unit of compound 2 together with the atom la-
beling is presented in Figure 3.
It is remarkable to note that all nitrogen atoms of the
1,2,4-triazole ring as well as the amine group participate in
hydrogen bonds. All contacts are short with a D···A length
of 2.890(2) and 3.055(2) ꢃ (D=donor, A=acceptor), but
Figure 3. Crystal structure of compound 2. Thermal ellipsoids are set to
50% probability. Symmetry operators: i) ꢀx, 1ꢀy, 2ꢀz.
ꢀ
only the hydrogen bond N1 H1···N3 is strongly directed
ꢀ
with a D H···A angle of 170.8(17)8 (Table 1).
In contrast to compound 1, the structure is build up by
Table 1. Hydrogen bonds present in compound 1.
ꢀ
ꢀ
only one individual hydrogen bond N1 H1···O1. The D
H···A angle is close to 1808 with 171.9(2)8 and the D···A
length is shorter than the sum of the van der Waals radii
(rw(O)+rw(N)=3.07 ꢃ)[18a] with 2.902(2) ꢃ (Figure 4a). In
contrast to compound 1, the nitrogen atoms N2 and N3 do
not participate as acceptor in any hydrogen bond. As shown
in Figure 4, the crystal structure of compound 2 consists of
infinite zigzag rows along the b axis including an angle of
60.58. The layers are stacked above each other with a layer
distance of d=2.96 ꢃ. The layers are connected by two
ꢀ
ꢀ
ꢀ
ꢀ
D H···A
d
G
d
E
d
U
]ACTHNGUTERN(UNG D H···A)
[8]
[a]
ꢀ
N1 H1···N3(i)
ꢀ
0.881(18) 2.017(19) 2.890(2)
0.867(19) 2.25(2) 3.055(2)
170.8(17)
154.9(18)
[a]
N4 H5a···N2(ii)
[a] Symmetry operators: i) x, 3/2ꢀy, 1/2+z; ii) ꢀx, 1/2+y, 1/2ꢀz.
All hydrogen-bond lengths lie well within the sum of the
van der Waals radii (rw(N)+ rw(N)=3.20 ꢃ),[18a] resulting in
a strong network of hydrogen bonds in the bc plane
(Figure 2). The DMSO molecules do not participate in hy-
drogen bonds within this plane, but connect the layers
through interaction with the free hydrogen atoms of the
amine groups.
3,3’-Dinitro-5,5’-bis-(1H-1,2,4-triazole) (2) crystallizes in
the monoclinic space group P21/n with a cell volume of
394.73(8) ꢃ3 and one molecular moiety in the unit cell. The
calculated density at 173 K is 1.902 gcmꢀ3 and hence above
the density of the dihydrate (1.764 gcmꢀ3).[17c] Again, the
molecule shows a completely planar assembly with a torsion
angle of the nitro group towards the triazole ring of 2.9(2)8.
short contacts, N2···N4(ii) and C1···O1ACTHNUTRGNEUNG(iii) (symmetry opera-
tors: ii) 3/2ꢀx, 1/2+y, 1/2ꢀz; iii) 3/2ꢀx, ꢀ1/2+y, 1/2ꢀz).
Both contacts are shorter than the sum of the van der Waals
radii,[18a] with N2···N4 being the shortest (2.922(2) ꢃ) and
C1···O1 being the longest (3.051(2) ꢃ) contact. The stacking
of the layers is displayed in Figure 4b together with the dis-
tance d between the layers.
The azido compound 4 crystallizes in the triclinic space
3
¯
group P1 with a cell volume of 256.34(9) ꢃ and one molec-
ular moiety in the unit cell, the calculated density for the di-
hydrate is 1.646 gcmꢀ3. As shown in Figure 5, the proton is
located at the N1 atom next to the azido group and not next
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Nitrogen-Rich Bis-1,2,4-triazoles
FULL PAPER
Figure 5. Crystal structure of compound 4. Thermal ellipsoids are set to
50% probability. Symmetry operators: i) 1ꢀx, 1ꢀy, 2ꢀz; ii) ꢀx, 1ꢀy, 1ꢀz.
Table 2. Hydrogen bonds present in compound 4.
ꢀ
ꢀ
ꢀ
D H···A
d
[ꢃ]
(D H)
d
[ꢃ]
(H···A)
d
[ꢃ]
(D H···A)
]ACHTUNGTRENNUNG(D-H···A)
[8]
[a]
ꢀ
N1 H1···O1(i)
ꢀ
0.98(2)
0.92(2)
1.70(2)
1.98(2)
2.676(2)
2.892(2)
174(2)
174(2)
[a]
O1 H1b···N2(ii)
Figure 4. a) Hydrogen-bonding scheme in the crystal structure of com-
pound 2. b) Wave-like arrangement of the infinite rows in the crystal
structure of compound 2 (layer distance d=2.96 ꢃ). Thermal ellipsoids
are set to 50% probability. Symmetry operators: i) 1/2+x, 1/2ꢀy, 1/2+z.
[a] Symmetry operators: i) x, 1+y, z; ii) 2ꢀx, 1ꢀy, ꢀz.
son to all other bis-1,2,4-triazoles, the density of compound
5 is remarkably high with 1.951 gcmꢀ3.
ꢀ
to the C C bond as it is the case for the nitro compound 2.
In contrast to the previously described 3,3’-bis(dinitro-
methyl)-5,5’-azo-1H-1,2,4-triazole,[19] the proton of the dini-
tromethyl moiety is not located at the C3 atom but at the
The three nitrogen atoms of the azido group exhibit a slight-
ly bent arrangement with a N4-N5-N6 angle of 172.34(17)8.
Both azido moieties are assembled parallel and point in the
opposite direction.
N3 atom within the triazole ring. This leads to a completely
2
ꢀ
planar assembly typical for sp carbon atoms and a C2 C3
The crystal structure of compound 4 is build up by two in-
dividual hydrogen bonds including the nitrogen atoms N1
and N2 as well as two water molecules (Figure 6). Two mol-
ecules of compound 4 form pairs through the strong hydro-
gen bond N1 H1···O1(i). As shown in Table 2, the D H···A
angle is close to 1808 with
174(2)8 and the D···A length is
considerably shorter than the
sum of the van der Waals radii
(rw(O)+rw(N)=3.07 ꢃ).[18a]
distance in the range of a C=C double bond (1.440(2) ꢃ).[18a]
ꢀ
For comparison, the C C bond length in the similar 5-dini-
tromethylene-4,5-dihydro-1H-tetrazole is 1.418(2) ꢃ.[20] The
nitro groups are twisted out of the triazole plane by only
6.5(2) (O1-N4-C3-C2) and 0.9(2)8 (O3-N5-C3-C2), respec-
ꢀ
ꢀ
The individual pairs are as-
sembled coplanar, which re-
sults in the formation of a lay-
ered structure within the bc
plane. The azido moieties do
not participate in any hydrogen
bond but are connected
through
a
short contact
N6···N6(i) with a distance of
3.067(2) ꢃ (symmetry code:
i) 1ꢀx, ꢀy, 1ꢀz).
3,3’-Dinitromethyl-5,5’-bis-
1,2,4-triazole (5) crystallizes as
a dihydrate in the monoclinic
space group P21/c. The formula
unit of compound 5 together
with the atom labeling is pre-
sented in Figure 7. In compari-
Figure 6. Hydrogen-bonding scheme in the crystal structure of compound 4. Thermal ellipsoids are set to 50%
probability. Symmetry operators: i) ꢀx, 1ꢀy, 1ꢀz; ii) ꢀx, ꢀy, 2ꢀz; iii) x, ꢀ1+y, 1+z.
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16745

T. M. Klapçtke and A. A. Dippold
volved as donor atoms in further hydrogen bonds, that is,
ꢀ
ꢀ
N1 H1···O2 and N3 H3···O5, resulting in strong interac-
tions with the surrounding molecules (Figure 8).
Spectroscopic data
Vibrational spectroscopy: The IR and Raman spectra of all
compounds were recorded and the frequencies were as-
signed according to the literature.[21] The Raman spectrum
of compound 1 is dominated by the deformation mode of
the amino groups at n˜ =1579 cmꢀ1. The valence stretching
Figure 7. Crystal structure of compound 5. Thermal ellipsoids are set to
50% probability. Symmetry operators: i) 1ꢀx, 1ꢀy, ꢀz.
ꢀ
mode of the N H bond is observed in the range of n˜ =3116
to 3107 cmꢀ1. The nitro groups of compounds 2 and 5 are
observed with both, their symmetric and asymmetric stretch-
ing modes. The vibrational frequencies for the asymmetric
stretching mode of the nitro group are observed in the
range of n˜ =1550 (2) to 1568 cmꢀ1 (5). The symmetric
stretching modes are located at lower energy at n˜ =1410 (2)
and 1403 cmꢀ1 (5). The signals of the nitrimino moiety of
tively. The planar assembly is encouraged by the formation
ꢀ
of two intramolecular hydrogen bonds, that is, N1 H1···O1
ꢀ
ꢀ
and N3 H3···O3. Both interactions show rather small D
H···A angles of 117.9(16) and 113(2)8, respectively, but con-
ꢀ
siderably short D H···A distances of 2.558(2) and
2.603(2) ꢃ, respectively.
The hydrogen bonds within the crystal structure of com-
pound 5 are summarized in Table 3.
compound
3
can be observed at n˜ =1565 (nasym
)
and
ꢀ
1298 cmꢀ1 (nsym). The valence stretching mode of the N H
bond of the 1,2,4-triazole ring can be observed for all com-
pounds in the range of n˜ =3154 (3) to 3190 cmꢀ1 (2). In addi-
tion, as for any heterocyclic compound, many combined
stretching and deformation as well as torsion stretching
modes can be observed in the fingerprint region between
n˜ =1500 and 600 cmꢀ1.[21b]
Table 3. Hydrogen bonds present in compound 5.
ꢀ
ꢀ
ꢀ
ꢀ
D H···A
d
[ꢃ]
(D H)
d
E
d
G
]ACTHNGUTERN(UNG D H···A)
[8]
ꢀ
N1 H1···O1
0.79(2)
0.79(2)
0.92(3)
0.92(3)
0.80(3)
2.090(18) 2.558(2)
117.9(16)
152.6(18)
113(2)
160(2)
173(3)
[a]
ꢀ
N1 H1···O2(i)
2.11(2)
2.10(3)
1.83(3)
2.09(3)
2.839(2)
2.603(2)
2.711(2)
2.883(2)
ꢀ
N3 H3···O3
As shown in Figure 9, the Raman as well as the IR spec-
trum of the azido compound 4 exhibits two signals for the
individual asymmetric stretching modes of the azide groups
in the expected range.[21c] The bands for the different “in-
phase” and “out-of-phase” stretching vibrations can be ob-
served at n˜ =2171 and 2142 cmꢀ1 in the Raman spectrum
and at n˜ =2156 and 2137 cmꢀ1 in the IR spectrum.
[a]
ꢀ
N3 H3···O5(ii)
[a]
ꢀ
O5 H5b···O3(iii)
[a] Symmetry operators: i) ꢀx, 1/2+y, 1/2ꢀz; ii) 1ꢀx, 1ꢀy, ꢀz; iii) ꢀ1+x,
1+y, z.
In addition to the intramolecular hydrogen bonds, three
intermolecular interactions including the crystal water as
well as the oxygen atoms O2 and O3 of the nitro groups
could be observed. Both nitrogen atoms N1 and N3 are in-
Multinuclear NMR spectroscopy: All compounds were inves-
tigated by using H, 13C and 14N NMR spectroscopy. Addi-
1
tional 13C{1H} and 1H NMR
spectra of compound 5 were
recorded at elevated tempera-
tures to give insight into the
equilibrium between both pos-
sible isomers and will be dis-
cussed in the following para-
graph. Due to insufficient solu-
bility of compounds 1, 3, and 5
in DMSO or any other solvent,
the 15N NMR spectra could
only be obtained for com-
pounds 2 and 4.
All compounds show two
signals for the 1,2,4-triazole
carbon atoms in the expected
range.[7–8] One singlet for the
bridging carbon atom can be
Figure 8. Surroundings and hydrogen bonds of a DNMBT molecule in the crystal structure of compound 5.
Thermal ellipsoids are set to 50% probability. Symmetry operators: i) 1ꢀx, 1ꢀy, ꢀz; ii) 1+x, ꢀ1+y, z; iii) ꢀx,
ꢀ1/2+y, 1/2ꢀz; iv) ꢀx, 1/2+y, 1/2ꢀz.
found at chemical shifts of d=
142.1 (3) to 149.3 ppm (1). The
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Chem. Eur. J. 2012, 18, 16742 – 16753

Nitrogen-Rich Bis-1,2,4-triazoles
FULL PAPER
atom (C3) is the thermodynamically most stable configura-
tion. However, the signals of both isomers could be ob-
1
served in both the 13C{1H} and H NMR spectrum at room
temperature, indicating a small energy difference between
both isomers. Of course there is another possible isomer in
which one ring is a 1,2,4-triazole and the other is a 1,2,4-tri-
AHCTUNGTREGaNNNU zoline. This isomer could not be detected in any spectra at
any temperature. Apparently, this transition state is not an
energetic minimum and could therefore not be observed ex-
perimentally. Figure 10 shows a comparison of the experi-
mentally obtained 1H NMR spectra at different tempera-
tures.
Figure 9. Comparison of the IR and Raman spectra of compound 4. The
individual stretching modes for the azide groups are expanded in the el-
lipse.
signal of the carbon atom connected to the energetic moie-
ACHTUNGTRENNUNGties is shifted in all cases to lower field and is observed in
the range of d=151.1 (5) to 162.7 ppm (2). In the
14N{1H} NMR spectra, the nitro group of compounds 2, 3,
and 5 can be identified as a broad singlet at d=ꢀ21 (3) to
ꢀ26 ppm (2). The azido moiety in compound 4 can be ob-
served as a broad singlet at d=ꢀ145 ppm in the 14N NMR
spectrum, well-resolved resonances could only be observed
in the 15N NMR spectrum (as discussed below). The NMR
signals of all compounds are summarized in Table 4.
Table 4. NMR signals of compounds 1–5 in [D6]DMSO.
d [ppm]
13C{1H}
14N{1H}
1H
6.46
9.68
5.19
14.86
13.45, 8.91, 3.90
1
2
3
4
5
157.3, 149.3
162.7, 145.6
153.1, 142.1
157.7, 145.9
151.1, 149.3[a]
–
ꢀ26
ꢀ21
ꢀ145
ꢀ23
[a] Recorded at 608C, CACHTUNGTRENNUNG(NO2)2: d=124.3 (5a), 106.5 ppm (5b).
As mentioned before, the existence of different isomers
of compound 5 (see Scheme 4) could be demonstrated by
1
recording the 13C{1H} and H NMR spectra at elevated tem-
peratures. Additionally, quantum chemical calculations at
the B3LYP/aug-cc-pVDZ level of theory were performed.
Because isomer 5a is obtained in the solid state (as dis-
cussed in the previous section), in this case a sp2 carbon
Figure 10. Comparison of 1H NMR spectra of DNMBT (5) at room tem-
perature and at elevated temperatures in [D6]DMSO.
At room temperature, isomer 5a is the dominant species
resulting in a broad signal for both protons at d=9.03 ppm
(for comparison: protons of the similar 5-dinitromethylene-
4,5-dihydro-1H-tetrazole appear at d=11.09 ppm).[20] The
signals of the bis-1,2,4-triazoline isomer 5b can also be ob-
ꢀ
Scheme 4. Equilibrium between the two isomers 5a and 5b.
tained at room temperature at d=8.70 (Ntriazole H) and
Chem. Eur. J. 2012, 18, 16742 – 16753
ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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16747

T. M. Klapçtke and A. A. Dippold
ꢀ
3.87 ppm (Csp3 H). Owing to the fact that compound 5 is
spectra, especially with the exclusive appearance of isomer
5b in the NMR spectrum above 908C.
The calculated optimized gas-phase structure of isomer 5a
is in good agreement with the experimentally obtained crys-
tal structure of compound 5 (Figure 12). The planar assem-
very acidic and was used as dihydrate (as obtained after re-
crystallisation), the constant signal at d=6.85 ppm was as-
signed to the protons of the water molecules.
With raising temperature, the signal of isomer 5a decreas-
es and the two signals of isomer 5b gain intensity. The con-
version is completed at about 908C, the signal of 5a has dis-
appeared completely. Simultaneously, the compound starts
to decompose, resulting in small signals at about d=8.60–
8.70 ppm.
As shown in Figure 11, the signals of the carbon atoms of
the 1,2,4-triazole in the 13C{1H} NMR spectrum at room
temperature interfere with each other resulting in a broad
Figure 12. Comparison of the calculated gas-phase structures of the iso-
mers 5a and 5b.
bly of the dinitromethylene moiety is the thermodynamical-
ly most stable configuration. In addition, the C3’ atom of
isomer 5b shows the expected tetrahedral coordination as it
is the case for the sp3 carbon atoms in the similar bis(dini-
tromethylene)-5,5’-azo-1H-1,2,4-triazole.[19]
Due to insufficient solubility, 15N NMR spectra could only
be obtained for compounds 2 and 4. Four well-resolved res-
onances are observed in the 15N NMR spectrum for the four
nitrogen atoms of the dinitro compound 2 (Figure 13). The
Figure 11. Comparison of the 13C{1H} NMR spectra of DNMBT (5) at
room temperature and at elevated temperatures in [D6]DMSO.
multiplet at d=150.0 ppm. The sp2 carbon atom of isomer
5a (C3) appears at d=124.3 ppm, the sp3 carbon atom of
isomer 5b (C3’) could be found at d=106.5 ppm. For com-
parison, similar sp2 carbon atoms appear at d=124.9 (3,3’-
bis(dinitromethylene)-5,5’-azo-1H-1,2,4-triazole)[19] and at
121.5 ppm (5-dinitromethylene-4,5-dihydro-1H-tetrazole)[20]
.
At 608C, only the signals of isomer 5b could be observed.
The triazole carbon atoms now show two well-resolved reso-
nances at d=151.1 and 149.3 ppm, the sp3 carbon atom C3’
can be found at the identical chemical shift of d=106.5 ppm
(in comparison to the RT measurement) as a broad singlet.
Quantum chemical calculations at the B3LYP/aug-cc-
pVDZ level of theory reveal an energy difference between
both isomers of 30.4 kJmolꢀ1 (Table 5). The calculated
values go well with the experimentally obtained 1H NMR
Figure 13. 15N NMR spectra of 5,5’-diazido-3,3’-bis-1H-1,2,4-triazole (4,
top) and 3,3’-dinitro-5,5’-bis-1H-1,2,4-triazole (2, bottom) recorded in
[D6]DMSO.
signals were assigned by comparison to literature val-
AHCTUNGTRENNUNG
ues.[21a,22] The signals of the nitrogen atoms N1 and N2 of
Table 5. Calculations on the isomers of DNMBT (5) at the B3LYP/aug-
cc-pVDZ level of theory.
the diazido compound 4 appear in the same range as for
compound 2, but are rather broad in comparison to the
sharp signals of compound 2. The three signals of the azido
moiety are well resolved and can be found in the expected
range with the signal of N4 being shifted to highest field
with a chemical shift of Dd=ꢀ295.2 ppm.
Isomer 5a
Isomer 5b
point group
C2h
C1
ꢀE [Hartree]
1380.136812
0.0
0.0
1380.125222
+7.3
+30.4
Erel [kcalmolꢀ1
]
Erel [kJmolꢀ1
]
16748
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Chem. Eur. J. 2012, 18, 16742 – 16753

Nitrogen-Rich Bis-1,2,4-triazoles
FULL PAPER
Theoretical calculations, performance characteristics, and
stabilities: All calculations regarding energies of formation
were carried out by using the Gaussian G09W Version 7.0
program package.[23] Because very detailed descriptions of
the calculation process have been published earlier[8] and
can be found in specialized books,[1b] only a short summary
of the computational methods will be given. The enthalpies
(H) and Gibbs free energies (G) were calculated by using
the complete basis set method (CBS) of Petersson et al. in
order to obtain very accurate energies. In this contribution,
we used the modified CBS-4M method with M referring to
the use of minimal population localization, which is a repa-
program is based on the chemical equilibrium, steady state
model of detonation. It uses the Becker–Kistiakowsky–
Wilson equation of state (BKW EOS) for gaseous detona-
tion products together with the Cowan–Fickett equation of
state for solid carbon.[30] The calculation of the equilibrium
composition of the detonation products is performed by ap-
plying a modified White, Johnson, and Dantzig free energy
minimization technique. The program was designed to
enable calculations of detonation parameter at the Chap-
man–Jouguet point. The BKW equation as implemented in
the EXPLO5.05 program was used with the BKW-G set of
parameters (a, b, k, q) given below in Equation (4), in
which Xi is the mol fraction of the ith gaseous detonation
product, whereas ki is the molar co-volume of the ith gas-
eous detonation product.[29,30]
ACHTUNGTRENNUNGramACHTUNGTRENNUNGeterized version of the original CBS-4 computational
method and also includes additional empirical calcula-
tions.[24] The enthalpies of formation for the gas-phase spe-
cies were computed according to the atomization energy
method, by using NIST[25] values as standardized values for
the atoms standard heats of formation (DfH0) according to
Equation (1).[26]
pV=RT ¼ 1þxebx
x ¼ ðkSXikiÞ=½VðTþqÞꢁ
a
ð4Þ
a ¼ 0:5, b ¼ 0:096, k ¼ 17:56, q ¼ 4950
X
X
DfH0
¼ HðMoleculeÞ
ꢀ
H0ðAtomsÞ þ
DfH0
ðAtoms, NISTÞ
ðg, Molecule 298Þ
The results of the detonation runs, together with the cal-
culated energies of formation and the corresponding sensi-
tivities, are compiled in Table 6.
ð1Þ
The solid-state enthalpy of formation for neutral com-
pounds is estimated from the computational results by using
the rule of Trouton,[27] where Tm was taken equal to the de-
composition temperatures [Eq. (2)].
As shown in Table 6, the physicochemical properties were
calculated for the energetic compounds 2–5. For the starting
material 3,3’-diamino-5,5’-bis(1H-1,2,4-triazole) (DABT, 1),
only the sensitivities and the decomposition temperature
was determined. Compound 1 is insensitive towards friction
and impact and shows no decomposition below 4508C.
Compound 2 as well shows a remarkably high thermal sta-
bility of 2518C together with an insensitivity towards friction
and a moderate sensitivity towards impact (10 J). The bene-
ficial detonation parameters of DNBT with vdet =8413 msꢀ1
DHm ¼ DfH0ðg, Molecule, 298ÞꢀDHsub
ð2Þ
¼ DfH0ðg, Molecule, 298Þꢀðð188 J molꢀ1 Kꢀ1ÞTmÞ
The solid-state enthalpies of formation for the ionic com-
pounds are derived from the calculation of the correspond-
ing lattice energies (UL) and
Table 6. Physicochemical properties of compounds 2–5 in comparison to hexogen (RDX).
the lattice enthalpies (HL), cal-
culated from the corresponding
molecular volumes, by using
the equations provided by Jen-
kins et al.[28] The derived molar
standard enthalpies of forma-
tion for the solid state (DHm)
were used to calculate the
solid-state energies of forma-
tion (DUm) according to Equa-
tion (3), with Dn being the
change of moles of the gaseous
components.[1b]
DNBT (2)
DNABT (3)
DAzBT (4)
DNMBT (5)
RDX[n]
formula
C4H2N8O4
226.1
10
360
0.1
49.45
ꢀ35.4
251
C4H4N10O4
256.1
3
108
0.5
54.68
ꢀ37.5
194
C4H2N12
218.2
3
C6H4N10O8
344.2
20
360
0.2
40.70
ꢀ27.9
121
C3H6N6O6
222.1
7
molecular mass [gmolꢀ1
impact sensitivity [J][a]
friction sensitivity [N][b]
ESD test [J]
]
48
120
–
0.04
77.05
ꢀ66.0
201
1.70
971
N [%][c]
37.8
ꢀ21.6
210
1.80
70
W [%][d]
Tdecomp [8C][e]
1 [gcmꢀ3
]
1.90
285
1338
1.80
405
1667
1.95
298
946
[f]
DfHm0 [kJmolꢀ1
]
[g]
DfU0 [kJkgꢀ1
]
4532
417
[h]
Expos5 values
ꢀDEU0 [kJkgꢀ1
TE [K][j]
[i]
]
4888
3890
320
8413
642
4973
3814
300
8355
670
4639
3670
250
7944
653
4977
3862
341
8499
641
6125
4236
349
8748
739
pC–J [kbar][k]
VDet. [msꢀ1
]
[l]
DUm ¼ DHmꢀDnRT
ð3Þ
gas volume [Lkgꢀ1
]
[m]
The calculated standard en-
ergies of formation were used
to perform predictions of the
detonation parameters with
[a] Bundesanstalt fꢁr Materialforschung (BAM) drop hammer. [b] BAM friction tester. [c] Nitrogen content.
[d] Oxygen balance. [e] Temperature of decomposition by DSC (b=58C, onset values). [f] Derived from the
X-ray structure. [g] Molar enthalpy of formation. [h] Energy of formation. [i] Energy of explosion. [j] Explo-
sion temperature. [k] Detonation pressure. [l] Detonation velocity. [m] Assuming only gaseous products.
[n] Values based on reference [31] and the EXPLO5.05 database. The density values of compounds 3, 4, and 5
are based on the X-ray densities of the dihydrate species and additional pycnometer measurements of the an-
hydrous compounds.
the
program
package
EXPLO5, Version 5.05.[29] The
Chem. Eur. J. 2012, 18, 16742 – 16753
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16749

T. M. Klapçtke and A. A. Dippold
mainly stem from the high positive heat of formation
(285 kJmolꢀ1) and the remarkably high density of
1.902 gcmꢀ3 (X-ray measurement).
As it is characteristically for nitramino- and nitrimino-
1,2,4-triazoles,[8,32] the nitrimino compound 3 is very sensi-
tive towards impact (3 J) and sensitive towards friction
(108 N). As expected, the decomposition temperature
(1948C) is lower in comparison to the nitro-derivative 2.
However, the decomposition temperature was found to be
repeatable higher in comparison to the value determined by
Shreeve and co-workers (1658C[12] at a heating rate of 108C
minꢀ1). The calculated detonation parameters are well
below the commonly used explosive RDX and in the same
range compared to compound 2.
The azido compound 4 is the most sensitive compound
with a friction sensitivity of 48 N, an impact sensitivity of
3 J, and a sensitivity towards electrical discharge of 40 mJ.
The compound can, therefore, be classified as primary ex-
plosive and shows outstanding energetic properties for this
class of energetic materials.
Figure 14. DSC plots of DNBT (2), DAzBT (4), DNABT (3), and
DNMBT (5) in order of the decreasing decomposition temperature
Compound 5 shows the best performance of all com-
pounds with a detonation velocity of 8499 msꢀ1, a detona-
tion pressure of 341 kbar, and an oxygen balance of
ꢀ27.9%, which is in the range of RDX. Unfortunately, the
introduction of the dinitromethyl group leads to a decrease
of the decomposition temperature to 1218C in comparison
to the nitro compound 2 (2518C). 3,3’-Dinitromethyl-5,5’-
bistriazole could therefore only be of interest for ionic de-
rivatives in combination with nitrogen-rich cations, because
the deprotonation increases the thermal stability as it is
known for the previously described 3,3’-bis(dinitromethyl)-
5,5’-azo-1H-1,2,4-triazole.[19] The thermal stabilities of all
compounds are illustrated in Figure 14.
(onset). The DSC plots were recorded with a heating rate of 58C minꢀ1
.
moderate sensitivity towards impact (10 J). As expected, the
nitrimino compound 3 as well as the azido compound 4 are
the most sensitive derivatives with an impact sensitivity of
3 J and friction sensitivities of 108 (compound 3) and 48 N
(compound 4) and can therefore be classified as primary ex-
plosives.
The introduction of the dinitromethyl group in compound
5 leads to the best detonation parameters with a detonation
velocity of 8499 msꢀ1, a detonation pressure of 341 kbar,
and an oxygen balance of ꢀ27.9%. Unfortunately, the ther-
mal stability is decreased to 1218C, which limits the poten-
tial applications to ionic derivatives in combination with ni-
trogen-rich cations. In summary, compounds 2, 3, and 5 are
able to compete with commonly used trinitrotoluene (TNT),
however, the performance data for RDX are not reached.
Those three compounds can be considered as nitrogen-rich
starting materials for new energetic ionic derivatives in com-
bination with nitrogen-rich cations, as it has already been
shown by Shreeve and co-workers.[12] Because nitrogen-rich
salts of energetic compounds tend to be more stable com-
pared to the uncharged compounds and often show per-
formance characteristics in the range of modern secondary
explosives, those ionic derivatives could find application as
high-nitrogen energetic materials.
Conclusion
The starting material DABT (1) was synthesized following a
modified literature-known procedure[14] resulting in an in-
crease of the yield from 56 up to 70%. The optimization of
the reaction conditions for the formation of 3,3’-dinitro-5,5’-
bis(1H-1,2,4-triazole)[13] (DNBT, 2) and 5,5’-dinitrimino-3,3’-
bis(1H-1,2,4-triazole)[12] (DNABT, 3) resulted in excellent
yields and high purities. The previously unknown syntheses
of 3,3’-diazido-5,5’-bis(1H-1,2,4-triazole) (DAzBT, 4) as well
as 3,3’-dinitromethyl-5,5’-bis(1H-1,2,4-triazole) (DNMBT, 5)
are presented and reveal synthetic pathways towards numer-
ous novel energetic 1,2,4-triazole derivatives. All compounds
have been fully characterized by means of vibrational and
multinuclear NMR spectroscopy, mass spectrometry, and
differential scanning calorimetry. Single-crystal X-ray meas-
urements were accomplished for compounds 1, 2, 4, and 5
and deliver insight into structural characteristics as well as
inter- and intramolecular interactions.
Experimental Section
Caution: Although all presented bis-1,2,4-triazoles are rather stable
against outer stimuli, proper safety precautions should be taken, when
handling the dry materials. Especially derivatives of 3,3’-diazido-5,5’-
bis(1H-1,2,4-triazole) (DAzBT, 4) are energetic primary materials and
tend to explode under the influence of impact or friction. Lab personnel
and the equipment should be properly grounded and protective equip-
Regarding the stability values and the energetic parame-
ters, compound 2 shows the highest thermal stability of
2518C together with an insensitivity towards friction and a
16750
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Chem. Eur. J. 2012, 18, 16742 – 16753

Nitrogen-Rich Bis-1,2,4-triazoles
FULL PAPER
ment like earthed shoes, leather coat, Kevlar gloves, ear protection, and
face shield is recommended for the handling of any energetic material.
3,3’-Dinitro-5,5’-bis(1H-1,2,4-triazole) (DNBT, 2): A solution of 1 (11.9 g,
72 mmol) in 20% sulfuric acid (140 mL) was added dropwise to a solu-
tion of sodium nitrite (98.8 g, 1.4 mol, 10 equiv) in water (140 mL) at
408C. The mixture was stirred at 508C for one hour. After cooling down
to room temperature the mixture was acidified with sulfuric acid (20%)
until no evolution of nitrogen dioxide could be observed. The precipitate
was collected by filtration and dissolved in boiling water. The hot solu-
tion was filtrated and allowed to cool to room temperature. Collection of
the pale green precipitate affords 2·2H2O (15.5 g, 59 mmol, 82%) as a
crystalline solid. 1H NMR (400 MHz, [D6]DMSO): d=9.68 ppm (s, 2H;
General: All chemical reagents and solvents were obtained from Sigma–
Aldrich or Acros Organics (analytical grade) and were used as supplied
without further purification. 1H, 13C{1H}, 14N{1H}, and 15N NMR spectra
were recorded on a JEOL Eclipse 400 instrument in [D6]DMSO at 258C.
The chemical shifts are given relative to tetramethylsilane (1H, 13C) or ni-
tromethane (14N, 15N) as external standards and coupling constants are
given in Hertz (Hz). Infrared (IR) spectra were recorded on a Perkin–
Elmer Spectrum BX FT-IR instrument equipped with an ATR unit at
258C. Transmittance values are qualitatively described as “very strong”
(vs), “strong” (s), “medium” (m), “weak” (w), and “very weak” (vw).
Raman spectra were recorded on a Bruker RAM II spectrometer equip-
ped with a Nd:YAG laser (200 mW) operating at l=1064 nm and a re-
flection angle of 1808. The intensities are reported as percentages of the
most intense peak and are given in parentheses. Elemental analyses
(CHNO) were performed with a Netzsch Simultaneous Thermal Ana-
lyzer STA 429. Melting and decomposition points were determined by
differential scanning calorimetry (Linseis PT 10 DSC, calibrated with
standard pure indium and zinc). Measurements were performed at a
heating rate of 58Cminꢀ1 in closed aluminum sample pans with a 1 mm
hole in the lid for gas release to avoid an unsafe increase in pressure
under a nitrogen flow of 20 mLminꢀ1 with an empty identical aluminum
sample pan as a reference.
H
Triazole); 13C NMR (100 MHz, [D6]DMSO): d=162.7, 145.6 ppm;
14N NMR (28.9 MHz, [D6]DMSO): d=ꢀ26 ppm ( NO2); 15N NMR
(40.5 MHz, [D6]DMSO): d=ꢀ27.8 (N4), ꢀ88.8 (N2), ꢀ141.7 (N3),
ꢀ156.1 ppm (N1); IR: n˜ =3599 (m), 3499 (m), 3052 (w), 2849 (w), 2747
(w), 2670 (m), 2621 (m), 2574 (m), 2530 (m), 2488 (m), 2419 (m), 1844
(w), 1609 (m), 1532 (vs), 1466 (w), 1416 (vs), 1314 (vs), 1245 (m), 1183
(m), 1024 (m), 953 (s), 837 (s), 690 (w), 690 cmꢀ1 (w); Raman (200 mW):
n˜ (rel. intensity)=3192 (3), 1641 (100), 1546 (28), 1519 (5), 1485 (75),
1468 (43), 1458 (95), 1413 (18), 1393 (97), 1365 (6), 1362 (6), 1345 (13),
1325 (27), 1306 (35), 1172 (58), 1062 (67), 1015 (31), 855 (4), 774 (8), 744
(5), 619 (4), 511 (4), 452 (5), 452 (5), 399 (9), 297 (9), 203 cmꢀ1 (6); MS
(FABꢀ): m/: 225.1 [C4HN8O4]ꢀ; elemental analysis (%) calcd for
C4H2N8O4: C 21.25, H 0.89, N 49.56; found: C 21.44, H 0.95, N 49.19;
sensitivities (grain size<100 mm): friction=360 N, impact=10 J, ESD=
0.1 J; DSC (onset, 58C minꢀ1): Tdecomp =2518C.
ꢀ
For initial safety testing, the impact and friction sensitivities as well as
the electrostatic sensitivities were determined. The impact sensitivity
tests were carried out according to STANAG 4489,[33] modified according
to the WIWEB instruction 4-5.1.02[34] by using a BAM[35] drop hammer.
The friction sensitivity tests were carried out according to
STANAG 4487[36] and modified according to the WIWEB instruction 4-
5.1.03[37] by using the BAM[35] friction tester. The electrostatic sensitivity
tests were accomplished according to STANAG 4490[38] by using an elec-
tric spark testing device ESD 2010EN (OZM Research).
3,3’-Dinitrimino-5,5’-bis(1H-1,2,4-triazole) (DNABT, 3): Compound
3
was synthesized according to a modified literature-known procedure:[12]
Nitric acid (100%, 3.0 mL) was added slowly to a solution of 1 (1.0 g,
6.0 mmol) in concentrated sulfuric acid (9.0 mL) at 08C. The mixture was
allowed to warm to room temperature and stirred for one hour. The
clear solution was poured on ice, the precipitate was collected by filtra-
tion and recrystallized from boiling water to yield 3·2H2O (1.35 g,
4.6 mmol, 77%) as yellow crystalline solid. 1H NMR (400 MHz,
[D6]DMSO): d=5.52 ppm (s, 2H; HTriazole); 13C NMR (100 MHz,
[D6]DMSO): d=153.1, 142.1 ppm; 14N NMR (28.9 MHz, [D6]DMSO):
Crystallographic measurements: The single-crystal X-ray diffraction data
of compounds 1, 2, 4, and 5 were collected by using an Oxford Xcalibur3
diffractometer equipped with a Spellman generator (voltage=50 kV, cur-
rent=40 mA) and a Kappa CCD detector. The data collection was un-
dertaken by using the Crysalis CCD software,[39] whereas the data reduc-
tion was performed with the Crysalis Red software.[40] Crystals of com-
pound 3c were investigated by using a Bruker–Nonius Kappa CCD dif-
fractometer equipped with a rotating molybdenum anode and Montel-
graded multilayered X-ray optics. The structures were solved with SIR-
92[41] or SHELXS-97[42] and refined with SHELXL-97[43] implemented in
the program package WinGX[44] and finally checked by using
PLATON.[45] CCDC-887530 (1), 864398 (2), 887531 (4), and 887532 (5)
contain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallograph-
ic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
ꢀ
d=ꢀ21 ppm ( NO2); IR: n˜ =3165 (m), 3154 (m), 1565 (vs), 1508 (s),
1463 (s), 1446 (s), 1380 (m), 1298 (vs), 1229 (vs), 1140 (m), 1085 (m),
1054 (s), 989 (m), 947 (s), 849 (m), 778 (s), 766 (s), 751 (s), 708 cmꢀ1 (vs);
Raman (200 mW): n˜ (rel. intensity)=1655 (100), 1592 (60), 1568 (81),
1527 (14), 1288 (2), 1224 (7), 1123 (26), 1072 (2), 1019 (25), 992 (35), 851
(11), 764 (26), 691 (2), 558 (6), 520 (2), 440 (2), 417 (3), 407 (3), 226 cmꢀ1
(6); elemental analysis (%) calcd for C4H2N8O4: C 16.44, H 2.76, N
47.94; found: C 16.73, H 2.69, N 47.73; sensitivities (water-free com-
pound, grain size<100 mm): friction=108 N, impact=3 J, ESD=0.5 J;
DSC (onset, 58C minꢀ1): Tdecomp =1948C.
3,3’-Diazido-5,5’-bis(1H-1,2,4-triazole) (DAzBT, 4): A solution of sodium
nitrite (0.37 g, 5.4 mol, 3 equiv) in water (2.0 mL) was added dropwise to
a suspension of 1 (0.3 g, 1.8 mmol) in 20% sulfuric acid (20 mL,) at 08C.
The mixture was allowed to warm to room temperature and subsequently
stirred at 408C for one hour. After cooling down to room temperature, a
solution of sodium azide (5.9 g, 9.0 mmol, 5 equiv) in water (2.0 mL) was
added dropwise. (DANGER: EVOLUTION OF HN3!). The suspension
was stirred over night at room temperature to remove the excess of
sodium azide and extracted with ethyl acetate (3ꢄ20 mL). The solvent
was evaporated and the resulting solid was recrystallized from water.
Collection of the colorless precipitate affords 4·2H2O (0.25 g, 1.0 mmol,
56%) as crystalline needles. 1H NMR (400 MHz, [D6]DMSO): d=
14.86 ppm (s, 2H; HTriazole); 13C NMR (100 MHz, [D6]DMSO): d=157.7,
3,3’-Diamino-5,5’-bis(1H-1,2,4-triazole) (DABT, 1): Hydrochloric acid
(60 mL) was added to a stirred mixture of oxalic acid (20.0 g, 159 mmol)
and aminoguanidinium bicarbonate (45.4 g, 332 mmol). The reaction was
stirred at 708C for one hour and the precipitate was collected by filtra-
tion. The colorless solid was dissolved in water (240 mL) and alkalized
with sodium hydroxide to pH 14. The reaction mixture was heated to
reflux for one hour and subsequently acidified with acetic acid to pH 4.
The resulting precipitate was collected by filtration, washed with water
(ꢂ200 mL) and dried in air to yield 1 (18.6 g, 112 mmol, 70%) as a color-
less solid.1H NMR (400 MHz, [D6]DMSO): d=6.46 ppm (s, 2H; NH2);
13C NMR (100 MHz, [D6]DMSO): d=157.3, 149.3 ppm; IR: n˜ =3325 (m),
3116 (m), 2863 (m), 2784 (m), 1706 (s), 1668 (s), 1654 (s), 1618 (m), 1606
(m), 1484 (m), 1457 (m), 1267 (m), 1104 (vs), 1061 (s), 987 (w), 956 (w),
769 (w), 721 cmꢀ1 (s); Raman (200 mW): n˜ (rel. intensity)=1636 (62),
1614 (100), 1591 (67), 1575 (57), 1495 (13), 1439 (21), 1432 (21), 1361 (9),
1152 (24), 1143 (23), 1059 (23), 1042 (34), 1022 (22), 980 (27), 772 (18),
554 (7), 413 (11), 328 (12), 249 cmꢀ1 (16); MS (DEI+): m/z: 166.1
[C4H7N8]+; elemental analysis (%) calcd for C4H6N10: C 28.92, H 3.64, N
67.44; found: C 28.72, H 3.58, N 66.11.
145.9 ppm (C N3); 14N NMR (28.9 MHz, [D6]DMSO): d=ꢀ145 ppm
ꢀ
( N3); 15N NMR (40.5 MHz, [D6]DMSO): d=ꢀ115.3 (N2), ꢀ141.9 (N3),
ꢀ
ꢀ146.2 (N5), ꢀ153.0 (N6), ꢀ173.2 (N1), ꢀ295.2 ppm (N4); IR: n˜ =3141
(s), 3042 (s), 2876 (s), 2710 (s), 2655 (s), 2630 (m), 2571 (m), 2435 (m),
2362 (m), 2240 (m), 2228 (m), 2156 (vs), 2138 (vs), 2137 (vs), 1541 (vs),
1518 (s), 1483 (vs), 1457 (s), 1420 (vs), 1418 (vs), 1391 (s), 1333 (s), 1299
(m), 1299 (m), 1275 (s), 1241 (m), 1218 (m), 1188 (s), 1142 (s), 1122 (s),
1033 (vs), 1014 (m), 980 (vs), 958 (m), 846 (m), 799 (s), 780 (m), 729 (s),
714 (m), 661 (m), 532 cmꢀ1 (m); Raman (200 mW): n˜ (rel. intensity)=
2171 (14), 2142 (17), 1620 (56), 1605 (100), 1551 (17), 1551 (16), 1549
(17), 1548 (17), 1547 (17), 1515 (44), 1503 (24), 1501 (26), 1500 (27), 1423
Chem. Eur. J. 2012, 18, 16742 – 16753
ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
16751

T. M. Klapçtke and A. A. Dippold
(16), 1422 (16), 1421 (15), 1399 (15), 1335 (20), 1298 (5), 1228 (10), 1168
(6), 1148 (17), 1147 (17), 1147 (17), 1066 (16), 1065 (17), 1039 (22), 1038
(22), 1024 (31), 817 (7), 705 (3), 629 (3), 577 (9), 436 (6), 423 (7), 397 (9),
380 (21), 326 (24), 262 (9), 247 cmꢀ1 (16); MS: (DEI+): m/z: 218.1
[C4H2N12]+; elemental analysis (%) calcd for C4H6N12O2: C 18.90, H 2.38,
N 66.13; found: C 19.41, H 2.14, N 65.75; sensitivities (grain size<
100 mm): friction=48 N, impact=3 J, ESD=0.04 J; DSC (onset, 58C
minꢀ1): Tdecomp =2028C.
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3,3’-Dinitromethyl-5,5’-bis(1,2H-1,2,4-triazole) (DNMBT, 5): The precur-
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concentrated sulfuric acid (6 mL) and cooled to 08C. Subsequently, con-
centrated nitric acid (4 mL) and 60% oleum (SO3, 2 mL) were added
slowly, the mixture was allowed to warm to room temperature and stirred
at for 2 h. The mixture was poured on ice, alkalized with sodium hydrox-
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1
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a yellow solid (0.27 g, 0.79 mmol, 49%). H NMR (400 MHz, [D6]DMSO,
608C): d=8.94 (s, 2H; NH), 3.91 ppm (s, 2H; CH); 13C NMR (100 MHz,
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ꢀ
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1163 (15), 1101 (4), 1025 (4), 967 (46), 834 (16), 783 (10), 753 (2), 699 (3),
475 (7), 435 (4), 435 (4), 379 (2), 326 (3), 209 cmꢀ1 (4); MS: (FABꢀ):
m/z: 343 [MꢀH]ꢀ; sensitivities: (grain size<100 mm): friction=360 N,
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Financial support of this work by the Ludwig-Maximilian University of
Munich (LMU), the U.S. Army Research Laboratory (ARL) under grant
no. W911NF-09-2-0018, the Armament Research, Development and En-
gineering Center (ARDEC) under grant no. R&D 1558-TA-01, and the
Office of Naval Research (ONR) under grant nos. ONR.N00014-10-1-
0535 and ONR.N00014-12-1-0538 is gratefully acknowledged. The au-
thors acknowledge collaborations with Dr. Mila Krupka (OZM Research,
Czech Republic) in the development of new testing and evaluation meth-
ods for energetic materials and with Dr. Muhamed Sucesca (Brodarski
Institute, Croatia) in the development of new computational codes to
predict the detonation and propulsion parameters of novel explosives.
We are indebted to and thank Dr. Betsy M. Rice and Dr. Brad Forch
(ARL, Aberdeen, Proving Ground, MD). We are also indebted to and
thank Stefan Huber for measuring all sensitivity values and Dr. Burkhard
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Published online: November 14, 2012
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ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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16753