Synthesis and promising properties of a new family of high-nitrogen compounds: Polyazido- and polyamino-substituted N,N′-Azo-1,2,4-triazoles

Article abstract of DOI:10.1002/chem.201202428

A new family of high-nitrogen compounds, that is, polyazido- and polyamino-substituted N,N'-azo-1,2,4-triazoles, were synthesized in a safe and convenient manner and fully characterized. The structures of 3,3′,5,5′-tetra(azido)-4,4′-azo-1,2,4-triazole (15) and 3,3′,5,5′-tetra(amino)-4,4′-azo-1,2,4-triazole (23) were also confirmed by X-ray diffraction. Differential scanning calorimetry (DSC) was performed to determine their thermal stability. Their heats of formation and density, which were calculated by using Gaussian03, were used to determine the detonation performances of the related compounds (EXPLO 5.05). The heats of formation of the polyazido compounds were also derived by using an additive method. Compound 15 has the highest heat of formation (6933kJ kg^-1) reported so far for energetic compounds and a detonation performance that is comparable to that of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), while compound 23 has a decomposition temperature of up to 290 °C. Showing some backbone: The N,N'-azo heteroaromatic backbone could be used to develop new high-nitrogen compounds with promising properties. Polyazido and polyamino compounds 1 and 2, respectively, were efficiently synthesized in a safe and convenient manner (see figure).

Full text of DOI:10.1002/chem.201202428

DOI: 10.1002/chem.201202428
Synthesis and Promising Properties of a New Family of High-Nitrogen
Compounds: Polyazido- and Polyamino-Substituted N,N’-Azo-1,2,4-triACTHNUTRGNEaNUG zoles
Cai Qi,[a] Sheng-Hua Li,[a] Yu-Chuan Li,[a] Yuan Wang,[a] Xiu-Xiu Zhao,[a] and
Si-Ping Pang*[a, b]
Abstract: A new family of high-nitro-
gen compounds, that is, polyazido- and
polyamino-substituted N,N’-azo-1,2,4-
triazoles, were synthesized in a safe
and convenient manner and fully char-
acterized. The structures of 3,3’,5,5’-
determine their thermal stability. Their
heats of formation and density, which
were calculated by using Gaussian 03,
were used to determine the detonation
performances of the related com-
pounds (EXPLO 5.05). The heats of
formation of the polyazido compounds
were also derived by using an additive
method. Compound 15 has the highest
heat of formation (6933 kJkgꢀ1) report-
ed so far for energetic compounds and
a detonation performance that is com-
parable to that of octahydro-1,3,5,7-tet-
tetra
ACHTUNGTRENNUNG
and 3,3’,5,5’-tetra
G
ranitro-1,3,5,7-tetrazocine
while compound 23 has a decomposi-
tion temperature of up to 2908C.
(HMX),
Keywords: azo compounds · ener-
getic materials · heats of formation ·
heterocycles · nitrogen
triazole (23) were also confirmed by X-
ray diffraction. Differential scanning
calorimetry (DSC) was performed to
Introduction
tro-1,5-diazocine (HNFX, Scheme 1),[3] is composed of two
parts, backbones (or skeletons) and functional groups, which
always act as fuels and oxidizers, respectively. By combining
Energetic materials represent an important class of materi-
als because they can store large amounts of chemical energy
that can be released by rapid decomposition, accompanied
by the production of large quantities of hot gaseous prod-
ucts; as such, the design and synthesis of new energetic ma-
terials has been a long-standing tradition in the chemical sci-
ences.[1] New energetic materials must meet increasing per-
formance requirements, that is, propellants must transport
ever-increasing payloads and explosives must become more
powerful; therefore, energetic compounds with higher
energy are a keen concern of many researchers.[1f,2] The
amount of energy that is contained in a compound is direct-
ly determined by its chemical structure. In general, the
structure of classical energetic compounds, such as octani-
trocubane (ONC),[2c] hexanitrohexaazaisowurzitane (CL-
20),[2a] and 3,3,7,7-tetrakis(difluoramino)octahydro-1,5-dini-
[a] Dr. C. Qi, Dr. S.-H. Li, Dr. Y.-C. Li, Dr. Y. Wang, Dr. X.-X. Zhao,
Prof. Dr. S.-P. Pang
School of Materials Science & Engineering
Beijing Institute of Technology
5 South Zhongguancun Street, Haidian District
Beijing 100081 (P. R. China)
Fax : (+86)010-68913038
Scheme 1. Examples of the synthesis of some classical energetic com-
pounds.
E-mail: pangsp@bit.edu.cn
[b] Prof. Dr. S.-P. Pang
State Key Laboratory of Explosion Science and
Technology, Beijing Institute of Technology
5 South Zhongguancun Street, Haidian District
Beijing 100081 (P. R. China)
Supporting information for this article, including the H and 13C spec-
tra of compounds 17–19, is available on the WWW under http://
the right backbone with the right functional groups, the en-
ergetic properties of these compounds could be tuned and
improved. Strained backbones are appreciated because of
their increased energy and density that is derived from ring
and cage strain; for example, cubane is an exceptionally
dense (1.29 gcmꢀ3) energetic molecule that has a surprising-
1
dx.doi.org/10.1002/chem.201202428.
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FULL PAPER
ly kinetic stability in spite of its tremendous strain energy of
161 kcalmolꢀ1.[1e] By introducing eight nitro groups onto this
backbone, ONC can be obtained, which has improved
energy performance (the predicted performance of ONC is
15–30% better than HMX).[1e] Compared with traditional
simple energetic compounds like TNT, new energetic com-
pounds have relatively complicated molecular structures
that make them difficult to synthesize in a simple and
straightforward manner. As shown in Scheme 1, their back-
bone must usually be synthesized first and then the energet-
ic functional groups are introduced by multi-step functional-
group transformations. On the other hand, many energetic
compounds with astonishingly high predicted energy, such as
2,4,6,8-tetranitro-1,3,5,7-tetraazacubane, have not yet been
synthesized, even though its structure was first predicted a
long time ago,[4] partly owing to the difficulties in building
up the backbone in the initial stage of the synthesis. There-
fore, a good backbone is of paramount importance for the
synthesis of new energetic compounds.
linkage not only desensitizes but also dramatically increases
the heats of formation of high-nitrogen compounds.[13] For
example, in Scheme 3, 3,3’-azobis(6-amino-1,2,4,5-tetrazine)
(5, DAAT, N 76.35%) is thermally stable up to 2528C and
insensitive to mechanical stimulus,[14] while 4,4’,6,6’-tetra-
AHCTUNGTREG(NNNU azido)azo-1,3,5-triazine (6, TAAT, N 79.55%) has a high
heat of formation of 6168 kJkgꢀ1 (2171 kJmolꢀ1).[13]
Scheme 3. Examples of high-nitrogen compounds with an azo linkage.
High-nitrogen compounds, which derive their energy from
their inherently high heats of formation, have attracted sig-
nificant recent attention from many researchers.[1d,2g,5] To-
gether with their high positive heats of formation and high
thermal stability, nitrogen-rich heterocycles, such as tri-
In a continuing effort to seek more powerful high-nitro-
gen compounds with good stability, we expanded C,C’-azo
linkages to include a new N,N’-azo linkage.[15] Compared
with the C,C’-azo linkage, the N,N’-azo linkage results in
high-nitrogen compounds with a long chain of catenated ni-
trogen atoms, which will increase the energy more effective-
ly and result in compounds with higher densities.[15b,c,16]
These new compounds are also potential backbones, owing
to their more tunable ring positions of the carbon atoms. In
particular, 4,4’-azo-1,2,4-triazole (7) is very thermally stable,
with a decomposition temperature of up to 3138C, and its
heat of formation (878 kJmolꢀ1) is also relatively high. In
addition, there are four carbon atoms in the molecule that
can be modified; therefore, it is possible to further control
the properties of compound 7 by judicious selection of the
substituent on the carbon atoms, as in analogues 5 and 6.
These above-mentioned properties make compound 7 an
ideal backbone for the development of new energetic com-
ACHTUNGTRENNUNG
azole,[6] tetrazole,[1f,2g,7] triazine,[8] and tetrazine,[9] offer good
backbones for the development of new energetic com-
pounds. Such heterocycles are often modified by functional
groups, like NH2 and N3, which further increase the overall
nitrogen content (Scheme 2). The incorporation of amino
Scheme 2. Examples of high-nitrogen compounds with amino and azido
groups.
pounds. Energetic compounds that contain
moiety are uncommon in scientific literature. Although Bot-
taro et al. reported some N,N’-azobisnitroazoles in
a N,N’-azo
groups is one of the simplest routes to enhance the thermal
stability of such compounds,[1a] while the introduction of
azido groups can rapidly increase their energy level. Cova-
lent polyazido heteroaromatic compounds have recently
been extensively studied for their use in applications in
either materials science or as high-density energetic materi-
als,[2f,6e,10] and this family of compounds is famous for their
extremely high heats of formation and nitrogen content. For
example, 3,6-diazido-1,2,4,5-tetrazine (4, DiAT, N 85.36%)
has the highest reported heat of formation of about
6709 kJkgꢀ1 (1101 kJmolꢀ1).[5a,11] In addition, both the
amino and azido heteroaromatic compounds are valuable
precursors or intermediates in the pharmaceutical indus-
try.[12]
a
patent,[17] no physical properties or proof of structure were
given for these compounds. Energetic derivatives that are
based on a N,N’-azo heteroaromatic backbone are practical-
ly nonexistent and the effect of functional groups, such as
NH2 and N3, on N,N’-azo moiety, as well as the reactivity of
the N,N’-azo heteroaromatic backbone are also unknown.
Beyond applications as energetic materials, N,N’-azo het-
eroaromatic derivatives also have great synthetic potential,
for example, as building blocks in spin-crossover systems.[18]
Herein, we report the synthesis of a series of poly-
azido- and polyamino-substituted N,N’-azo-1,2,4-triazoles
(Scheme 4), as well as their significant physical and energet-
ic properties. By comparison of these new compounds with
their analogues 5 (DAAT) and 6 (TAAT), we have demon-
strated the capability of N,N’-azo heteroaromatic backbones
to form high-performance energetic compounds.
By combining an azo group with nitrogen-rich heteroaro-
matic rings in which the azo group is bonded to a carbon
atom (C,C’-azo linkage), a new kind of high-nitrogen back-
bone is obtained. Moreover, it has been shown that the azo
Chem. Eur. J. 2012, 18, 16562 – 16570
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16563

S.-P. Pang et al.
All of the products were iso-
lated and characterized by IR
and NMR spectroscopy, MS,
and elemental analysis. Com-
pounds 15, 17, 18·4CH3OH,
and 23·2H2O[19] were also char-
acterized by X-ray crystallogra-
phy; selected data and parame-
ters from their X-ray structures
are given in Table 1.
Crystals of compound 15 that
were suitable for crystal-struc-
ture analysis were obtained
from a mixture of CH2Cl2 and
petroleum ether. Compound 15
crystallizes in a monoclinic crys-
tal system (space group C2/c,
Figure 1) and has a density of
Scheme 4. Synthesis of polysubstituted derivatives based on the N,N’-azo linkage.
Table 1. Crystallographic data for compounds 15, 17, 18·4CH3OH, and 23·2H2O.
Results and Discussion
15
17
18·4CH3OH
23·2H2O
formula
MW
crystal system monoclinic
space group
size [mm]
T [K]
l [ꢂ]
a [ꢂ]
b [ꢂ]
c [ꢂ]
C4N20
328.24
C40H32N10P2
714.70
monoclinic
P21/n
C62H62N11O4P3
1118.14
monoclinic
P21/n
C4H12N12O2
260.26
monoclinic
P21/c
To prepare their corresponding high-nitrogen deriv-
atives, compound 7 must be prefunctionalized, be-
cause it is difficult to introduce azido or amino
C2/c
0.58ꢁ0.10ꢁ0.07 0.50ꢁ0.40ꢁ0.20 0.55ꢁ0.18ꢁ0.12 0.43ꢁ0.27ꢁ0.13
groups onto heterocycles in
a straightforward
153(2)
0.71073
19.407(14)
4.211(3)
14.910(10)
90
94.625(10)
90
1214.4(14)
4
293(2)
0.71073
10.317(2)
14.406(3)
13.106(3)
90
105.60(3)
90
1876.1(7)
2
1.265
0.159
744
0.0486
0.1193
SHELXL-97
673984
293(2)
0.71073
13.735(3)
19.111(4)
22.320(5)
90
91.42(3)
90
5857(2)
4
1.268
0.159
2352
0.0594
0.0726
SHELXL-97
673985
293(2)
0.71073
9.874(3)
15.901(4)
6.7279(17)
90
95.750(4)
90
1051.0(5)
4
1.645
0.135
544
0.0384
0.0905
SHELXL-97
875777
manner. Therefore, the necessary chlorides 8–11
were produced by either using N-chlorosuccinimide
(NCS) or sodium dichloroisocyanurate (SDIC). The
solutions of compounds 8–11 in DMF were treated
with excess amounts of sodium azide. When the re-
actions were complete, the residues were washed
with acetone to obtain compounds 12–14 after the
removal of the solvent under reduced pressure. In
the case of compound 15, owing to its poor solubili-
ty in water and extremely high sensitivity, the reac-
tion mixture was poured into water and filtered to
obtain the product. The introduction of the amino
group was achieved by a mild Staudinger reaction.
a [8]
b [8]
g [8]
V [ꢂ3]
Z
1 [gcmꢀ3
]
]
1.795
0.144
656
0.0409
m [mmꢀ1
(000)
R1 [I>2s(I)]
F
A
wR2 [I>2s(I)] 0.0949
refinement
CCDC
SHELXL-97
875776
The combination of compounds 12–15 with
a
number
common reducing agent, triphenylphosphine
(PPh3), in acetone afforded iminophosphorane in-
termediates 16–19 that were then hydrolyzed in 1M
HCl to prepare amino derivatives 20–23. Meanwhile, a one-
pot method to synthesize compounds 16–19 was also devel-
oped. The reactions of compounds 8–11 with sodium azide
in DMF were monitored by TLC, and triphenylphosphine
was added when the chlorides had been completely con-
sumed. In this way, the iminophosphorane intermediates 16–
19 could be obtained more easily, without the need to
handle the dangerous azido compounds 12–15, thus enabling
the development of safer procedures for the preparation of
valuable molecules through halogenated heterocycles and
avoiding the need for the isolation, purification, and han-
dling of azido-heterocycles. Experimental details are sum-
marized in the Experimental Section.
1.795 gcmꢀ3 (at 153 K). Only one conformation of com-
pound 15 is observed, although its analogue (TAAT) was
previously reported to be polymorphous.[13] Both compounds
17 and 18 crystallize in the monoclinic space group P21/n
(Figures 2 and 3). Crystals of compound 23, which were ob-
tained from water, contain two molecules of water. Com-
pound 23·2H2O crystallizes in the monoclinic space group
P21/c (Figure 4) and has a density of 1.645 gcmꢀ3 (at 293 K).
Both compounds 15 and 23·2H2O have two almost planar
triazole rings and a planar N4 chain, which is the same as
that in compound 7. Moreover, the two triazole rings are co-
planar in compounds 7 and 15, while the dihedral angle of
ꢀ
ꢀ
ꢀ
C1 C2 C3 C4 (167.528) indicates that the structure of com-
pound 23·2H2O is slightly twisted. The four azido groups in
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Synthesis and Properties of High-Nitrogen Compounds
FULL PAPER
Table 2. Selected bond lengths [ꢂ] in compounds 7, 15, and 23·2H2O.
15
23·2H2O
7
ꢀ
N3 N4
ꢀ
C1 C3
1.385
1.384
1.376
1.294
1.292
1.403
1.362
1.401
1.389
1.298
1.294
1.424
1.384
1.373
1.369
1.305
1.298
1.406
ꢀ
C2 C3
ꢀ
C1 N1
ꢀ
C2 N2
ꢀ
N1 N2
ꢀ
ꢀ
ent. In addition, although both of the C1 N3 and C2 N3
bonds in compounds 15 and 23·2H2O are stretched, owing
to the effect of the substituent, all of the bond lengths of the
ꢀ
ꢀ
C N, N N, and C=N bonds within the triazole moiety are
ꢀ
still between the lengths of the standard single (C N 1.47 ꢂ,
ꢀ
N N 1.45 ꢂ) and double bonds (C=N 1.28 ꢂ, N=N 1.24 ꢂ),
which indicates that the molecule is aromatic. Moreover, ni-
trogen atoms from the triazole ring in compound 23·2H2O
ꢀ
are found to participate in hydrogen bonds (N9 H9a···N7
ꢀ
0.957, 1.973, 2.899, 162.3178; N9 H9a···N8 0.957, 2.723, 3.449,
133.1508), and hydrogen-bonding interactions between
oxygen atoms from water and hydrogen atoms from the
ꢀ
amino group (N10
H
10a···O1 0.814, 2.286, 3.018, 149.9418;
ꢀ
N10
H
10b···O2 0.812, 2.107, 2.918, 176.1658) can also be ob-
served.
The thermal stabilities of the related compounds were
studied by differential scanning calorimetry (DSC) at a
heating rate of 108Cminꢀ1 (Figures 5 and 6). All of the
azido derivatives decomposed between 135 and 1908C with-
out melting, and their thermal stability decreased as the
number of azido groups increased. The lowest decomposi-
tion temperature occurred at 1368C for compound 15, which
is a little higher than the value for DiAT (1308C). Not unex-
pectedly, compounds 20–23 are more stable than their azido
derivatives, with values in the range 245–2908C. The highest
value (2908C) for compound 23 is 408C higher than that of
DAAT, while compounds 20, 21, and 22 have values of 248,
245 and 2468C, respectively. Notably, although the decom-
position temperatures of the azido and amino derivatives
are lower than that of compound 7 (3138C), the N,N’-azo
linkage is still stable enough for normal operation because
all of the values are higher than 1358C, which means that
the synthesis, treatment, and characterization of these high-
nitrogen derivatives are possible under normal conditions,
without decomposition.
The electron-withdrawing group N3 is commonly used as
an effective ligand for increasing the heat of formation of an
energetic compound, because one azido group adds about
87 kcalmolꢀ1 (364 kJmolꢀ1) of endothermicity to a hydrocar-
bon compound, along with an increase in nitrogen con-
tent.[20] The heats of formation of compounds 12–15 are cal-
culated by using the method of isodesmic reactions
(Scheme 5).[21] All calculations were carried out by using the
Gaussian 03 program.[22] Geometries were optimized at the
B3LYP/6-31G* level by using the default convergence crite-
ria and were confirmed to be true local-energy minima on
potential-energy surfaces without imaginary frequencies.
The single-point energy was calculated at the B3LYP/6-311+
Figure 1. ORTEP of the molecular structure of compound 15; thermal el-
lipsoids are set at 50% probability.
compound 15 lie perfectly within the plane of the parent
ring. However, the hydrogen atoms of the amino groups in
compound 23·2H2O are slightly twisted out of the triazole
plane, with a maximum torsion angle of 378. Notably, there
ꢀ
is a difference in the N3 N4 distances between compounds
15 and 23·2H2O (1.385 versus 1.362 ꢂ; Table 2); the value
of this same bond in compound 7 is 1.384 ꢂ. This result is
probably attributed to the different properties of the two
kinds of substituents (the amino group is electron donating
whereas the azido group is electron withdrawing). Neverthe-
less, a comparison with the bond lengths of the N4 azo link-
age in compounds 15, 23·2H2O, 7, and N4H4 (2-tetrazene)
indicates that the strong delocalization of the azo p-bond
along the N4 moiety is not greatly affected by the substitu-
Chem. Eur. J. 2012, 18, 16562 – 16570
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16565

S.-P. Pang et al.
cluding the zero-point energy
(ZPE) and the thermal correc-
tion to the enthalpy (HT). As
shown in Table 3, the heats of
formation of compounds 12–15
are remarkably higher than that
of compound 7 and they in-
crease linearly with the number
of azido groups. The incremen-
tal contribution of each addi-
tional azido group to the heat
of formation in the sequence
7!12, 12!13, 13!14, and
14!15 is 344, 344, 340, and
356 kJmolꢀ1, respectively.
The high energy of high-ni-
trogen compounds is derived
from the larger number of in-
ꢀ
herently energetic N N and
Figure 2. ORTEP of the molecular structure of compound 17; thermal ellipsoids are set at 50% probability.
ꢀ
C N bonds that are contained
Figure 3. ORTEP of the molecular structure of compound 18·4CH3OH;
thermal ellipsoids are set at 50% probability.
Figure 4. ORTEP of the molecular structure of compound 23·2H2O; hy-
drogen atoms are shown as spheres and thermal ellipsoids are set at 50%
probability.
Scheme 5. Isodesmic reactions of polyazido and polyamino derivatives.
within the molecule;[13] thus, nitrogen content and the heat
of formation are important parameters in high-nitrogen
compounds. The higher the nitrogen content is, the higher
the heat of formation, and, concurrently, the better the ener-
getic performance. Unfortunately, such increased perform-
+G** level. The enthalpy of the isodesmic reaction was ob-
tained by combining the B3LYP/6-311++G** energy differ-
ence for the reaction with thermodynamic parameters, in-
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Synthesis and Properties of High-Nitrogen Compounds
FULL PAPER
1H-1,2,4-triazole.[24] Therefore, the change in the
heat of formation of compound 7 is predicted to be
+349 kJmolꢀ1 following the first introduction of N3.
This value is also confirmed by the theoretical pre-
dictions, as mentioned above. According to the ad-
ditive method, the value of compound 15 is estimat-
ed to be 6933 kJkgꢀ1(2274 kJmolꢀ1), which is
224 kJkgꢀ1 higher than that of DiAT and is the
highest reported heat of formation. Moreover, the
NDHf value (94.75 kJatomꢀ1) is also higher than
that of other known organic molecules (Scheme 7).
Compound 15 is superior to TAAT in terms of both
the heat of formation and the nitrogen content. Fur-
Table 3. Physical properties of azido and amino derivatives.
[b]
N
Tdecomp
1[c]
[gcmꢀ3
HOF[d]
[kJmolꢀ1
HOF[d]
[kJkgꢀ1
D[e]
[kmsꢀ1
P[f]
ACHTUNGTRENN[UNG GPa] [J]
IS[g]
[%][a] [8C]
G
]
G
]
U
]
R
]
12
13
14
15
75.1
79.7
82.9
85.4
189.7
185.7
136
1.63
1.66
1.74
1.76
1205
1549
1889
2245
5878
6297
6582
6845
8.28
8.54
8.95
9.37
27.18
29.62
34.09
38.43
12
(1227)
(5985)
8
<3
<3
A
(1.76)
A
136
A
E
ACHTUNGTRNE(NUNG 6933)
20
21
70.4
72.1
248
245
1.53
1.59
829.8
799.0
4636
4119
7.64
7.84
21.52
23.04
>40
>40
AHCTUNGTRENGN(UN 1.68)
22
23
73.7
75.0
246
290
1.57
1.57
774.3
748.9
3705
3343
7.73
7.70
22.08
21.70
>40
>40
thermore, it is probably
a good precursor to
AHCTUNGTRENGN(UN 1.64)
1.60
carbon-nitride nanomaterials, like DiAT and TAAT,
owing to its high nitrogen content (N 85.36%) and
binary C/N component.[5a,11]
The theoretical densities of compounds 7 and 12–
23 (Table 3) were obtained by using the statistical
averaging method reported by Xiao and co-work-
ers.[25] By using the calculated densities and heats of
formation of compounds 12–15, their detonation
performances were calculated with EXPLO pro-
gram (version 5.05). However, in the case of com-
7[h]
68.3
313.4
861
5250
7.97
24.42
14
A
ACHTUNGTRNE(NUNG 5354)
419
361
RDX[i] 37.8
HMX[i] 37.8
230
287
1.82
1.91
8.97
9.32
35.20
39.60
7.4
7.4
[a] The percentage of nitrogen content. [b] Temperature of thermal decomposition
under a nitrogen atmosphere (heating rate: 108Cminꢀ1). [c] Calculated density based
on the method reported in reference [25]; measured value is given in parentheses.
[d] Theoretical heat of formation (HOF) and derived heat of formation (in parenthe-
ses) based on the method reported in reference [5a]. [e] Detonation velocity. [f] Deto-
nation pressure. [g] Impact sensitivity (IS). [h] Data taken from reference [15c].
[i] Data from reference [6c].
Figure 6. DSC thermograms of compounds 20–23 (heating rate:
108Cminꢀ1); Tdecomp: 20=2488C, 21=2458C (Tmelt: 1528C), 22=2468C,
23=2908C.
Figure 5. DSC thermograms of compounds 12–15 (heating rate:
108Cminꢀ1); Tdecomp: 12=1908C, 13=1868C, 14=1368C, 15=1368C.
ance is always accompanied by poor stability, both thermally
and mechanically.[6c,10f,g] Studies on unstable high-nitrogen
compounds that are on the borderline of existence and non-
existence allows the elucidation of the fundamental proper-
ties that affect their chemical stability and bonding.[2f,16,23]
Therefore, it is of particular interest to compare the heat of
formation of 3,3’,5,5’-tetraACTHNURTGNEU(GN azido)azo-1,2,4-triazole (15) with
those of DiAT and TAAT, because of their relatively high
nitrogen content and similar polyazido structures. Thus, a
similar method to that used to derive the heat of formation
of DiAT was applied (Scheme 6).[5a] The heat of formation
of 3-azido-1,2,4-triazole is 349 kJmolꢀ1 larger than that of
Scheme 6. Additive method that was used to derive the heats of forma-
tion of compounds 12–15.
Chem. Eur. J. 2012, 18, 16562 – 16570
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16567

S.-P. Pang et al.
access to many new high-nitrogen compounds. We hope that
this work might also inspire others in shedding additional
light on this fundamental class of compounds.
Experimental Section
All materials were commercially available and used as received. Melting
points were determined on an XT4 microscope melting point apparatus
and are uncorrected. IR spectra were recorded on a Nicolet Magna IR
560 spectrophotometer (KBr pellets). NMR spectroscopy was performed
on an ARX-400 instrument with TMS as an internal standard. MS EI
were recorded on a GCTMS Micromass UK spectrometer and MS ESI
were recorded on an Agilent 6120 LCMS spectrometer. Elemental analy-
Scheme 7. Polyazido energetic compounds with high heats of formation.
pound 15, owing to the limitations of the program, the per-
formances of compounds with a binary CN form could not
be predicted. By using the formula of compound 14, the pa-
rameters of compound 15 were derived with its own calcu-
lated density and heat of formation. Although the detona-
tion performance of compound 15 that is derived in this way
must be lower than the actual value, the increasing trend is
still obvious, as shown in Table 3. Owing to the increased
density and heat of formation, the detonation parameters of
compound 15 are superior to those of RDX and comparable
to those of HMX. Impact-sensitivity measurements were
performed according to the Bruceton method on a type-12
tooling. The values of compounds 12–15 ranged from sensi-
tive (12: 12 J, 13: 8 J) to very sensitive (14, 15:<3 J).[26] Con-
sidering the hydrogen-bonding interactions that are formed
between the nitrogen atoms of the triazole rings and the hy-
drogen atoms of the amino groups in compounds 20–23, it is
no surprise that the impact sensitivities of these compounds
are greater than 40 J. Although the impact sensitivity can be
decreased by replacing the azido groups with amino groups,
the corresponding detonation performance is negatively im-
pacted. The calculated performances of compounds 20–23
are not excellent, but their good stability, especially for com-
pound 23, enable them to be further modified into their N-
oxide derivatives, like DAAT.[9b]
sis was performed on an Elementar Vario ELACTHNUTRGNE(NUG Germany). Crystal struc-
tures were determined on a Rigaku RAXIS IP diffractometer with the
SHELXTL crystallographic software package of molecular structure. To
determine the thermal stability of the described compounds, a TA-DSC
Q2000 differential scanning calorimeter (heating rate: 108Cminꢀ1) was
used.
Safety precautions: We encountered several unintended explosions were
we were working with these materials, so standard safety precautions
(leather gloves, face shield, and ear plugs) should be used at all times!
Preparation of compounds 8–11: The necessary chlorides (8–11) were
produced by either using NCS or, in a more direct way in which the oxi-
dation and chlorinated reactions occurred simultaneously, by the treat-
ment of 4-amino-1,2,4-triazole with SDIC under different reaction condi-
tions.[15a,27] The latter route afforded the chlorides products more effi-
ciently and in higher yields. This route is important, because it enabled
us to tune the properties of these compounds by controlling the number
of functional groups on their backbones.
General method for the preparation of compounds 8–11 from compound
7: Compound 7 was added to a solution of NCS in THF with molar
ratios of 1:1, 1:2, 1:3, and 1:4 for compounds 8--11, respectively. The mix-
ture was stirred at RT and, when the reaction was complete, the solvent
was removed under reduced pressure. The residue was washed succes-
sively with CH2Cl2 and acetone. The acetone solution was collected and
evaporated slowly to afford the corresponding products (Yield: 30% for
compound 8, 25% for compound 9, 15% for compound 10, and 8% for
compound 11).
3-Azido-4,4’-azo-1,2,4-triazole (12): NaN3 (0.25 g, 3.8 mmol) was added
to a solution of compound 8 (0.5 g, 2.5 mmol) in DMF (15 mL) at RT
and the reaction mixture was stirred for 2 h. After evaporation of the sol-
vent, the residue was dissolved in acetone, filtered, concentrated, and pu-
rified by recrystallization from acetone/petroleum ether. Yield: 0.26 g,
1908C (DSC, 108Cminꢀ1); 1H NMR (400 MHz,
Conclusion
50%; Tdecomp
:
[D6]DMSO): d=9.17 (s, 1H), 9.29 ppm (s, 2H); 13C NMR (400 MHz,
[D6]DMSO): d=135.0, 138.0, 147.2 ppm; IR (KBr): n˜ =2921, 2172, 1553,
1469, 1423, 1167, 1031 cmꢀ1; MS (ESI): m/z: 206 [M+H]+.
In summary, a series of polyazido- and polyamino-substitut-
ed high-nitrogen compounds that are based on a new back-
bone have been synthesized and fully characterized. The
physical and detonation properties of these polyazido and
polyamino compounds were also determined. 3,3’,5,5’-Tetra-
3,3’-DiACHTUNTGRNE(UGN azido)-4,4’-azo-1,2,4-triazole (13): NaN3 (0.18 g, 2.75 mmol) was
added to a solution of compound 9 (0.25 g, 1.1 mmol) in DMF (15 mL) at
RT and the reaction mixture was stirred for 4 h. After evaporation of the
solvent, the residue was dissolved in acetone, filtered, concentrated, and
purified by recrystallization from acetone. Yield: 0.12 g, 44%; Tdecomp
:
ACHTUNGTRENNUNG(azido)azo-1,2,4-triazole (15, N 85.36%) was found to have
1868C (DSC, 108Cminꢀ1); 1H NMR (400 MHz, [D6]DMSO): d=
9.90 ppm (s, 2H); 13C NMR (400 MHz, [D6]DMSO): d=135.1,
153.8 ppm; IR (KBr): n˜ =3090, 2145, 1500, 1417, 1180, 1095 cmꢀ1; MS
(ESI): m/z: 247 [M+H]+.
a relatively high decomposition temperature (1368C) and
the highest positive heat of formation of 6933 kJkgꢀ1
(2274 kJmolꢀ1) reported so far for energetic materials.
Moreover, its detonation values are comparable to those of
HMX. Meanwhile, the decomposition temperature of
3,3’,5-TriACHTNUTRGENNG(U azido)-4,4’-azo-1,2,4-triazole (14): NaN3 (0.45 g, 8 mmol) was
added to a solution of compound 10 (0.53 g, 2 mmol) in DMF (15 mL) at
RT and the reaction mixture was stirred for 12 h. After evaporation of
the solvent, the residue was dissolved in acetone, filtered, concentrated,
and purified by recrystallization from acetone/petroleum ether, as previ-
ously reported by our group.[28]
3,3’,5,5’-tetraACHTUNGTRENNUNG(amino)azo-1,2,4-triazole (23, N 74.97%) is up
to 2908C. The ease of these reactions, together with the high
stability of the N,N’-azo linkage, make this family of N,N’-
azo heteroaromatic compounds potential precursors for
many interesting subsequent transformations and may give
3,3’,5,5’-Tetra
ACHTUNGTREN(NNUG azido)-4,4’-azo-1,2,4-triazole (15): NaN3 (0.29 g, 4.5 mmol)
was added to a solution of compound 11 (0.30 g, 1.0 mmol) in DMF
16568
www.chemeurj.org
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2012, 18, 16562 – 16570

Synthesis and Properties of High-Nitrogen Compounds
FULL PAPER
(15 mL) at RT and the reaction mixture was stirred for 2 h. The mixture
was poured into water, stirred for a further 1 h, and then filtered. The
residue was dissolved in CH2Cl2 and purified by recrystallization from
3,3’,5-TriACTHNGUTERNNU(G amino)-4,4’-azo-1,2,4-triazole (22): Compound 18 (3.96 g,
4 mmol) was added to a stirring solution of 1m HCl (100 mL) and then
the mixture was heated at 508C, until no starting material remained
(TLC). The precipitate was filtered and washed with CHCl3/MeOH to
CH2Cl2/petroleum ether. Yield: 0.13 g, 40%; Tdecomp
: 1368C (DSC,
obtain compound 22. Yield: 0.50 g, 60%; Tdecomp
:
2468C; 13C NMR
108Cminꢀ1); 13C NMR (400 MHz, CD3COCD3): d=154.3 ppm; MS
(ESI): m/z: 301 [MꢀN2+H]+.
(100 MHz, D2O): d=131.2, 145.9, 148.7 ppm; IR (KBr): n˜ =3318, 3249,
3167, 3129, 2963, 2796, 2723, 1515, 1456, 1365, 1265, 1140 cmꢀ1; MS
(ESI): m/z: 210 [M+H]+; elemental analysis calcd (%) for C4H7N11:
C 22.97, H 3.35, N 73.68; found: C 23.15, H 3.30, N 73.43.
3,3’-Di(iminotriphenylphosphorane)-4,4’-azo-1,2,4-triazole (17): NaN3
(0.55 g, 8.5 mmol) was added to a solution of compound 9 (0.93 g,
4 mmol) in DMF (30 mL) at RT and the reaction mixture was stirred for
4 h. PPh3 (2.36 g, 9 mmol) was added to the solution and the reaction
mixture was stirred for a further 2 h before pouring into water. After fil-
tration and washing with acetone, the residue was purified by recrystalli-
zation from CHCl3/MeOH to obtain compound 17. Yield: 2.37 g, 83%;
m.p. 2558C; IR (KBr): n˜ =3050, 1578, 1534, 1482, 1437, 1339, 1173, 1112,
972, 721, 690 cmꢀ1; MS (FAB+): m/z: 715 [M+H]+; elemental analysis
calcd (%) for C40H32N10P2: C 67.23, H 4.48, N 19.27; found: C 66.96,
H 4.63, N 19.27.
3,3’,5,5’-TetraACTHNUGTRNEUNG(amino)-4,4’-azo-1,2,4-triazole (23): Compound 19 (5.06 g,
4 mmol) was added to stirring solution of 1m HCl (120 mL) and then the
mixture was heated to 508C, until no starting material remained (TLC).
The precipitate was filtered and washed with CHCl3/MeOH to obtain
compound 23. Yield: 0.49 g, 45%; Tdecomp: 2908C; 1H NMR (400 MHz,
[D6]DMSO): d=9.66 ppm (s); 13C NMR (400 MHz, D2O): d=145.2 ppm;
IR (KBr): n˜ =3462, 3295, 3265, 3174, 3112, 2943, 2658, 2742, 2695, 1515,
1456, 1365, 1265, 1140 cmꢀ1; MS (ESI): m/z: 225 [M+H]+; elemental
analysis calcd (%) for C4H8N12: C 21.43, H 3.57, N 75.00; found: C 21.21,
H 3.40, N 75.18.
3,3’,5-Tri(iminotriphenylphosphorane)-4,4’-azo-1,2,4-triazole (18): NaN3
(0.85 g, 13 mmol) was added to a solution of compound 10 (1.07 g,
4 mmol) in DMF (30 mL) at RT and the reaction mixture was stirred for
4 h. PPh3 (3.67 g, 14 mmol) was added to the solution and the reaction
mixture was stirred for a further 2 h before pouring into water. After fil-
tration and washing with acetone, the residue was purified by recrystalli-
zation from CHCl3/MeOH to obtain compound 18. Yield: 3.09 g, 78%;
m.p. 1608C; IR (KBr): n˜ =3055, 1580, 1530, 1480, 1438, 1331, 1112, 925,
720, 692 cmꢀ1; MS(MALDI-TOF): m/z: 990 [M+H]+; elemental analysis
calcd (%) for C58H46N11P3: C 70.37, H 4.65, N 15.57; found: C 69.98,
H 4.89, N 15.46.
Acknowledgements
The authors gratefully acknowledge the support of the National Natural
Science Foundation of China (No.11176004).
[1] a) J. P. Agrawal, Prog. Energy Combust. Sci. 1998, 24, 1–30;
b) A. K. Sikder, N. Sikder, J. Hazard. Mater. 2004, 112, 1–15;
c) High Energy Density Materials, Vol. 125 (Ed.: T. M. Klapçtke),
Springer, Berlin, 2007; d) D. M. Badgujar, M. B. Talawar, S. N. As-
thana, P. P. Mahulikar, J. Hazard. Mater. 2008, 151, 289–305; e) J. P.
Agrawal, High Energy Materials: Propellants, Explosives and Pyro-
technics, Wiley-VCH, Weinheim, 2010; f) M. Gçbel, K. Karaghios-
off, T. M. Klapçtke, D. G. Piercey, J. Stierstorfer, J. Am. Chem. Soc.
2010, 132, 17216–17226; g) D. I. A. Millar, H. E. Maynard-Casely,
D. R. Allan, A. S. Cumming, A. R. Lennie, A. J. Mackay, I. D. H.
Oswald, C. C. Tang, C. R. Pulham, Crystengcomm 2012, 14, 3742–
3749.
3,3’,5,5’-Tetra(iminotriphenylphosphorane)-4,4’-azo-1,2,4-triazole
(19):
NaN3 (1.11 g, 17 mmol) was added to a solution of compound 11 (1.21 g,
4 mmol) in DMF (30 mL) at RT and the reaction mixture was stirred for
1 h. PPh3 (4.45 g, 17 mmol) was added to the solution and the reaction
mixture was stirred for a further 2 h before pouring into water. After fil-
tration and washing with acetone, the residue was purified by recrystalli-
zation from CHCl3/MeOH to obtain compound 19. Yield: 2.53 g, 50%;
m.p. 2108C; IR (KBr): n˜ =3054, 1580, 1575, 1520, 1483, 1436, 1336, 1111,
942, 718 cmꢀ1; MS (FAB+): m/z: 1265 [M+H]+; elemental analysis calcd
(%) for C76H60N12P4: C 73.19, H 4.82, N 13.29; found: C 73.07, H 4.89,
N 13.46.
[2] a) A. T. Nielsen, A. P. Chafin, S. L. Christian, D. W. Moore, M. P.
Nadler, R. A. Nissan, D. J. Vanderah, R. D. Gilardi, C. F. George,
J. L. Flippen-Anderson, Tetrahedron 1998, 54, 11793–11812;
b) K. O. Christe, W. W. Wilson, J. A. Sheehy, J. A. Boatz, Angew.
Chem. 1999, 111, 2112–2118; Angew. Chem. Int. Ed. 1999, 38, 2004–
2009; c) P. E. Eaton, R. L. Gilardi, M. X. Zhang, Adv. Mater. 2000,
12, 1143–1148; d) M. X. Zhang, P. E. Eaton, R. Gilardi, Angew.
Chem. 2000, 112, 422–426; Angew. Chem. Int. Ed. 2000, 39, 401–
404; e) K. O. Christe, Propellants Explos. Pyrotech. 2007, 32, 194–
204; f) K. Banert, Y. H. Joo, T. Rꢃffer, B. Walfort, H. Lang, Angew.
Chem. 2007, 119, 1187–1190; Angew. Chem. Int. Ed. 2007, 46, 1168–
1171; g) T. M. Klapçtke, in High Energy Density Materials, Vol. 125
(Ed.: T. M. Klapçtke), Springer, Berlin, 2007, pp. 85–121; h) J. H.
Song, Z. M. Zhou, X. Dong, H. F. Huang, D. Cao, L. X. Liang, K.
Wang, J. Zhang, F. X. Chen, Y. K. Wu, J. Mater. Chem. 2012, 22,
3201–3209.
General method for the preparation of compounds 16–19 from com-
pounds 12–15: Triphenylphosphine (PPh3) was added to a solution of the
corresponding azido derivatives (12--15) in acetone with molar ratios of
1:1.5, 1:2.5, 1:3.5, and 1:4.5, respectively. The reaction mixture was stirred
for 4 h at RT. After filtration, the residue was purified by recrystallization
from CHCl3/MeOH to obtain compounds 16–19 (Yield: 72% for com-
pounds 16, 65% for compounds 17, 60% for compounds 18, and 20%
for compounds 19).
3-Amino-4,4’-azo-1,2,4-triazole (20): Compound 16 (1.75 g, 4 mmol) was
added to a stirring solution of 1m HCl (60 mL) and then the mixture was
heated at 508C for 3 h, until no starting material remained (by TLC).
The precipitate was filtered and washed with CHCl3/MeOH to obtain
compound 20. Yield: 0.54 g, 75%; Tdecomp: 2488C (DSC, 108Cminꢀ1);
1H NMR (400 MHz, [D6]DMSO): d=9.56 (s, 2H), 9.08 (s, 1H), 8.77 ppm
(s, 2H); 13C NMR (400 MHz, [D6]DMSO): d=131.0, 138.3, 149.4 ppm;
IR (KBr): n˜ =3039, 2960, 1703, 1503, 1470, 1361, 1222, 1175, 1062, 889,
617 cmꢀ1; MS (EI): m/z: 179 [M]+; elemental analysis calcd (%) for
C4H5N9: C 26.82, H 2.81, N 70.37; found: C 26.80, H 2.81, N 70.39.
[3] R. D. Chapman, R. D. Gilardi, M. F. Welker, C. B. Kreutzberger, J.
Org. Chem. 1999, 64, 960–965.
[4] F. Wang, H. C. Du, J. Y. Zhang, X. D. Gong, J. Phys. Chem. A 2011,
115, 11788–11795.
3,3’-DiACHTUNGTRENNUNG(amino)-4,4’-azo-1,2,4-triazole (21): Compound 17 (2.86 g, 4 mmol)
was added to a stirring solution of 1m HCl (80 mL) and then the mixture
was heated at 508C for 3 h, until no starting material remained (TLC).
The precipitate was filtered and washed with CHCl3/MeOH to obtain
compound 21. Yield: 0.59 g, 75%; Tdecomp: 2458C; 1H NMR (400 MHz,
[D6]DMSO): d=8.55 (s, 4H), 9.11 ppm (s, 2H); 13C NMR (400 MHz,
[D6]DMSO): d=131.2, 148.8 ppm; IR (KBr): n˜ =3292, 3209, 3144, 3123,
2957, 1685, 1642, 1531, 1462, 1328, 1224, 1117, 1062, 967 cmꢀ1. MS (EI):
m/z: 194 [M]+; elemental analysis calcd (%) for C4H6N10: C 24.74, H 3.09,
N 72.16; found: C 24.54, H 3.30, N 71.26.
[5] a) M. H. V. Huynh, M. A. Hiskey, D. E. Chavez, D. L. Naud, R. D.
Gilardi, J. Am. Chem. Soc. 2005, 127, 12537–12543; b) M. B. Tala-
war, R. Sivabalan, T. Mukundan, H. Muthurajan, A. K. Sikder, B. R.
Gandhe, A. S. Rao, J. Hazard. Mater. 2009, 161, 589–607; c) H. Gao,
J. M. Shreeve, Chem. Rev. 2011, 111, 7377–7436.
[6] a) Y. Huang, H. X. Gao, B. Twamley, J. M. Shreeve, Eur. J. Inorg.
Chem. 2008, 2560–2568; b) D. E. Chavez, B. C. Tappan, B. A.
Mason, D. Parrish, Propellants Explos. Pyrotech. 2009, 34, 475–479;
c) R. H. Wang, H. Y. Xu, Y. Guo, R. J. Sa, J. M. Shreeve, J. Am.
Chem. Eur. J. 2012, 18, 16562 – 16570
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
16569

S.-P. Pang et al.
Chem. Soc. 2010, 132, 11904–11905; d) V. Thottempudi, H. Gao,
J. M. Shreeve, J. Am. Chem. Soc. 2011, 133, 6464–6471; e) K. Wang,
D. A. Parrish, J. M. Shreeve, Chem. Eur. J. 2011, 17, 14485–14492;
f) Q. H. Lin, Y. C. Li, Y. Y. Li, Z. Wang, W. Liu, C. Qi, S. P. Pang, J.
Mater. Chem. 2012, 22, 666–674.
[15] a) S. H. Li, S. P. Pang, X. T. Li, Y. Z. Yu, X. Q. Zhao, Chin. Chem.
Lett. 2007, 18, 1176–1178; b) Y. C. Li, C. Qi, S. H. Li, H. J. Zhang,
C. H. Sun, Y. Z. Yu, S. P. Pang, J. Am. Chem. Soc. 2010, 132, 12172–
12173; c) C. Qi, S. H. Li, Y. C. Li, Y. A. Wang, X. K. Chen, S. P.
Pang, J. Mater. Chem. 2011, 21, 3221–3225.
[7] a) Y. B. Joo, J. M. Shreeve, Angew. Chem. 2009, 121, 572–575;
Angew. Chem. Int. Ed. 2009, 48, 564–567; b) T. M. Klapçtke, C. M.
Sabate, J. Stierstorfer, New J. Chem. 2009, 33, 136–147; c) T. M. Kla-
pçtke, F. A. Martin, J. Stierstorfer, Chem. Eur. J. 2012, 18, 1487–
1501.
[16] T. M. Klapçtke, D. G. Piercey, Inorg. Chem. 2011, 50, 2732–2734.
[17] J. C. Bottaro, R. J. Schmitt, P. E. Penwell (SRI International, Menlo
Park, CA), US 5889161, 1999.
[18] Y. C. Chuang, C. T. Liu, C. F. Sheu, W. L. Ho, G. H. Lee, C. C.
Wang, Y. Wang, Inorg. Chem. 2012, 51, 4663–4671.
[8] a) A. V. Shastin, T. I. Godovikova, B. L. Korsunskii, Usp. Khim.
2003, 72, 279; b) P. N. Simꢄes, L. M. Pedroso, A. M. M. Beja, M. R.
Silva, E. MacLean, A. A. Portugal, J. Phys. Chem. A 2007, 111, 150–
158; c) A. V. Shastin, T. I. Godovikova, B. L. Korsunskii, Russ.
Chem. Bull. 2011, 60, 1220–1222; d) Y. G. Huang, Y. Q. Zhang,
J. M. Shreeve, Chem. Eur. J. 2011, 17, 1538–1546.
[9] a) D. E. Chavez, M. A. Hiskey, J. Energ. Mater. 1999, 17, 357–377;
b) D. E. Chavez, M. A. Hiskey, D. L. Naud, Propellants Explos. Py-
rotech. 2004, 29, 209–215; c) D. E. Chavez, M. A. Hiskey, R. D. Gi-
lardi, Org. Lett. 2004, 6, 2889–2981; d) D. E. Chavez, R. D. Gilardi,
J. Energ. Mater. 2009, 27, 110–117; e) Z. D. Fu, C. He, F. X. Chen, J.
Mater. Chem. 2012, 22, 60–63.
[10] a) E. G. Gillan, Chem. Mater. 2000, 12, 3906–3912; b) D. R. Miller,
D. C. Swenson, E. G. Gillan, J. Am. Chem. Soc. 2004, 126, 5372–
5373; c) S. Brꢅse, C. Gil, K. Knepper, V. Zimmermann, Angew.
Chem. 2005, 117, 5320–5374; Angew. Chem. Int. Ed. 2005, 44, 5188–
5240; d) C. F. Ye, H. X. Gao, J. A. Boatz, G. W. Drake, B. Twamley,
J. M. Shreeve, Angew. Chem. 2006, 118, 7420–7423; Angew. Chem.
Int. Ed. 2006, 45, 7262–7265; e) Organic Azides: Syntheses and Ap-
plications (Eds.: S. Brꢅse, K. Banert), Wiley, Chichester, 2010;
f) T. M. Klapçtke, F. A. Martin, J. Stierstorfer, Angew. Chem. 2011,
123, 4313–4316; Angew. Chem. Int. Ed. 2011, 50, 4227–4229;
g) T. M. Klapçtke, B. Krumm, F. A. Martin, J. Stierstorfer, Chem.
Asian J. 2012, 7, 214–224.
[19] CCDC-875776
(15),
CCDC-673984
(17),
CCDC-673985
(18·4CH3OH), and CCDC-875777 (23·2H2O) contain the supple-
mentary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
[20] M. A. Petrie, J. A. Sheehy, J. A. Boatz, G. Rasul, G. K. S. Prakash,
G. A. Olah, K. O. Christe, J. Am. Chem. Soc. 1997, 119, 8802–8808.
[21] W. J. Hahre, L. Radom, P. V. R. Schleyer, J. A. Pople, Ab Initio Mo-
lecular Orbital Theory, Wiley, New York, 1986.
[22] Gaussian 03, Revision A.1., M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, V. G.Zakrzewski,
J. A. Montgomery, R. E. Stratmann, J. C. Burant, S. Dapprich, J. M.
Millam, A. D. Daniels, K. N. Kudin, M. C. Strain, O. Farkas, J.
Tomasi, V.Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli, C.
Adamo, S. Clifford, J. W. Ochterski, G. A. Petersson, P. Y. Ayala,
Q.Cui, K. Morokuma, D. K. Malick, A. D. Rabuck, K. Raghava-
chari, J. B. Foresman, J. Cioslowski, J. V. Ortiz, A. G. Baboul, B. B.
Stefanov, G. Liu, A. Liashenko, P.Piskorz, I. Komaromi, R. Gom-
perts, R. L. Martin, D. J. Fox, T. Keith, M. A. A.-L. C. Y. Peng,
A.Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W.
Chen, M. W. Wong, J. L. Andres, C. Gonzalez, M. Head-Gordon,
E. S. Replogle, J. A. Pople, Gaussian, Inc., Wallingford CT, 2004.
[23] V. V. Semenov, M. I. Kanischev, S. A. Shevelev, A. S. Kiselyov, Tetra-
hedron 2009, 65, 3441–3445.
[11] M. H. V. Huynh, M. A. Hiskey, J. G. Archuleta, E. L. Roemer, R.
Gilardi, Angew. Chem. 2004, 116, 5776–5779; Angew. Chem. Int.
Ed. 2004, 43, 5658–5661.
[12] a) H. S. Sutherland, A. Blaser, I. Kmentova, S. G. Franzblau, B. J.
Wan, Y. H. Wang, Z. K. Ma, B. D. Palmer, W. A. Denny, A. M.
Thompson, J. Med. Chem. 2010, 53, 855–866; b) A. Capes, S. Patter-
son, S. Wyllie, I. Hallyburton, I. T. Collie, A. J. McCarroll, M. F. G.
Stevens, J. A. Frearson, P. G. Wyatt, A. H. Fairlamb, I. H. Gilbert,
Bioorg. Med. Chem. 2012, 20, 1607–1615.
[24] H. Xue, Y. Gao, B. Twamley, J. M. Shreeve, Chem. Mater. 2005, 17,
191–198.
[25] G. X. Wang, X. D. Gong, Y. Liu, H. C. Du, X. J. Xu, H. M. Xiao, J.
Hazard. Mater. 2010, 177, 703–710.
[26] M. Gçbel, T. M. Klapçtke, Adv. Funct. Mater. 2009, 19, 347–365.
[27] a) S. H. Li, S. P. Pang, X. T. Li, Y. Z. Yu, X. Q. Zhao, Chin. J. Org.
Chem. 2008, 28, 727–731; b) S. H. Li, H. G. Shi, C. H. Sun, X. T. Li,
S. P. Pang, Y. Z. Yu, X. Q. Zhao, Chin. J. Energ. Mater. 2009, 17, 7–
10.
[13] M. H. V. Huynh, M. A. Hiskey, E. L. Hartline, D. P. Montoya, R. Gi-
lardi, Angew. Chem. 2004, 116, 5032–5036; Angew. Chem. Int. Ed.
2004, 43, 4924–4928.
[28] S. H. Li, H. G. Shi, C. H. Sun, X. T. Li, S. P. Pang, Y. Z. Yu, X. Q.
Zhao, J. Chem. Crystallogr. 2009, 39, 13–16.
[14] D. E. Chavez, M. A. Hiskey, R. D. Gilardi, Angew. Chem. 2000, 112,
1861–1863; Angew. Chem. Int. Ed. 2000, 39, 1791–1793.
Received: July 8, 2012
Published online: October 22, 2012
16570
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