High Energy Density Materials Incorporating 4,5-Bis(dinitromethyl)-Furoxanate and 4,5-Bis(dinitromethyl)-3-Oxy-Furoxanate

Article abstract of DOI:10.1002/cplu.201600287

3-Oxy-furoxanate is immobilized in a heterometallic energetic metal–organic framework (MOFs). Two furoxan-based MOFs ([Ag₂K₄(BDOFO)(BDFO)₂(H₂O)₆]_n, [K₂(BDFO)]_n) and a salt ([(BDFO^2?)(NH₂NH₃ ⁺)₂(H₂O)]_n (BDOFO^2?=4,5-bis(dinitromethyl)-3-oxy-furoxanate, BDFO^2?=4,5-bis(dinitromethyl)-furoxanate) are synthesized and their energetic performance evaluated. This study outlines the systematic investigation of detonation performance of 3-oxy-furoxan and its derivatives.

Full text of DOI:10.1002/cplu.201600287

Accepted Article
Title: High-energy-density
Materials
Incorporating
4,5-Bis(dinitromethyl)-
Furoxanate and 4,5-Bis(dinitromethyl)-3-oxy-furoxanate with Improved
Oxygen Balance
Authors: Lianjie Zhai; Xiaoni Qu; Bozhou Wang; Fuqiang Bi; Sanping Chen; Xu-
ezhong Fan; Gang Xie; Qing Wei; Shengli Gao
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ChemPlusChem
10.1002/cplu.201600287
High-energy-density Materials Incorporating 4,5-Bis(dinitromethyl)-Furoxanate
and 4,5-Bis(dinitromethyl)-3-oxy-furoxanate
Lianjie Zhai,‡a Xiaoni Qu, ‡b Bozhou Wang, Fuqiang Bi,a Sanping Chen,*b Xuezhong Fan,*a
Gang Xie,a Qing Wei,a and Shengli Gaoa
a
State Key Laboratory of Fluorine & Nitrogen Chemicals, Xi’an Modern Chemistry Research Institute, Xi’an
b
710065, China; Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of
Education, College of Chemistry and Materials Science, Northwest University, Xi’an, Shaanxi 710069, China.
‡ These authors have equal contribution to this work.
* E-mail: sanpingchen@126.com
Abstract: Furoxan and its derivatives have been extensively favored in the field of energetic
materials. The synthesis of 3-oxy-furoxan is extremely challenging. In this work, we successfully
structurally immobilized 3-oxy-furoxanate in a heterometallic energetic MOF. Two furoxan-based
energetic MOFs ([Ag2K4(BDOFO)(BDFO)2(H2O)6]n, [K2(BDFO)]n) and an energetic salt
+
([(BDFO2-)(NH2NH3 )2(H2O)]n (BDOFO2- = 4,5- bis(dinitromethyl)-3-oxy-furoxanate, BDFO2- =
4,5-bis(dinitromethyl)-furoxanate) are reported, including synthesis, structure and energetic
performance. This work would shed potential insights into the systematic investigation of
detonation performance of 3-oxy-furoxan and its derivatives.
Keywords:
Energetic
MOFs/
4,5-Bis(dinitromethyl)-3-oxy-furoxanate
/
4,5-Bis(dinitromethyl)-furoxanate / Energetic performance/ Oxygen Balance
Energetic metal-organic frameworks (EMOFs) are a fascinating class of energetic materials
which have already demonstrated potential as propellants, explosives and pyrotechnics because of
their structural reinforcement, high thermal ability and lower sensitivity toward external stimuli. [1]
The investigation and development of the nitrogen-rich energetic ligands is still a current research
interest in the field of energetic materials.
Furoxan and its derivatives are superior candidates for energetic materials and have been used
to construct energetic MOFs because of their positive heat of formation and good oxygen balances
[2]
(Scheme 1). Theoritical calculations show that 3-oxy-furoxan has a higher heat of formation,
better oxygen balance, and improved detonation performance compared to furazan and furoxan. It
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10.1002/cplu.201600287
is conceivable that 3-oxy-furoxan-based energetic materials could have outstanding detonation
performance.
O
O
O
O
O
O
N
N
N
N
N
N
Furazan
3-oxy-furoxan
Furoxan
Heat of formation (kJ mol-1): 147.3
144.7
7521.1
23.3
155.5
8259.2
Detonation velocity (m s-1):
6479.8
Detonation pressure (GPa):
Oxygen balance (CO2, %):
Oxygen balance (CO, %):
16.4
-91.3
28.9
-31.3
0
-55.8
-45.7
-18.6
Scheme 1. Comparison of properties of furazan, furoxan and 3-oxy-furoxan.
O
O
O
O
3
O
O
O
O
N
N
O
N
N
O
O
1
N
N
N
N
CF3COOH / HNO3
N
N
NH2OH / H2
EtOH
O
NaNO2 / HCl
N2O5
NO2
Cl
NO2
NO2
Cl
NO2
NC
COOH
HON
O2N
NOH
NH2
O2
Cl
N
+
HON
NOH
40
- 50 ¡æ
NH2
2
NC
CN
Cl
Cl
Cl
NO2
5
NO2
4
KI / MeOH
[Ag2K4(BDOFO)(BDFO)2(H2O)6]n
8
O
O
O
O
O
N
N
N
N
NO2
NO2
O2N
AgNO3
O2
N
+
4
K+
NO2
NO2
NO2
NO2
O
O
7 (BDOFO2-
)
6 (BDFO2-
)
N
N
1. H2SO4
[(BDFO2-)(NH2NH3+)2(H2O)]n
9
2
K+
NO2
NO2
O2
N
2. Base / MeOH
NO2
6 (BDFO2-
)
Scheme 2. Syntheses of compounds BDFO and BDOFO.
Recently, Shreeve and co-workers synthesized potassium 4,5-bis(dinitromethyl)furoxanate
[3]
possessing high sensitivity and remarkable detonation performance.
We have simultaneously
performed the synthesis of furoxan/3-oxy-furoxan and their derivatives, as shown in Scheme 2. In
contrast to Shreeve's work, where trifluoroacetic anhydride and 100 % HNO3 was used, we chose
N2O5 as the nitration reagent due to its strong oxidizing potential under mild reaction conditions.[4]
Herein,
we
present
the
experimental
procedure
for
the
synthesis
of
4,5-bis(dinitromethyl)-furoxanate and 4,5-bis(dinitromethyl)-3-oxy-furoxanate, the structures of
intermediate product 4,5-bis(chlorodinitromethyl)furoxan (4), two furoxan-based energetic MOFs
([K2(BDFO)]n (6) and [Ag2K4(BDOFO)(BDFO)2(H2O)6]n (8)) and an energetic salt
+
([(BDFO2-)(NH2NH3 )2(H2O)]n (9)) (BDOFO2-
=
4,5-bis(dinitromethyl)-3-oxy-furoxanate,
BDFO2-
=
4,5-bis(dinitromethyl)-furoxanate). Most importantly, we have structurally
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characterized the first example of a 3-oxy-furoxan by trapping it as its metal salt in the form of a
MOF.
Compounds 1-3 were synthesized according to previous methods (Scheme 2).[3,4] Similarly, 4
and 5 were obtained using N2O5. Compound 4 was structurally characterized by single crystal
X-ray diffraction, even though it was unstable upon standing. Treatment of 4 and 5 with KI in
methanol, however, we were unable to obtain X-ray quality crystals upon repeated efforts.
Accidentally, to the aqueous solution system of the mixture 6 and 7 which AgNO3 aqueous
solution was added, a few pale yellow crystals 8 yielded at room temperature. To our surprise,
there is only one peak in the filtered solution checked by HPLC, and fortunately, compound 6
crystallized from the solution above. It is followed that, to the solution of 6 acidified with 50 %
H2SO4 which hydrazine was added, an energetic salt 9 was produced with a yield of 61.5 % (based
on 6).
Compounds 4, 6, 8 and 9 have been characterized by IR, elemental analysis, 13C NMR
spectroscopy and single crystal X-ray diffraction. The crystal data and structure refinement details
of compounds 4, 6, 8 and 9 are summarized in Table S5, and the selected bond lengths and angles
data are presented in Table S6. The X-ray diffraction analysis has confirmed the structure of
compound 4 (Fig. S1).
Fig. 1. a) Coordination environment of K1(I) ion, b) coordination environment of K2(I) ion, c)
coordination model of ligand of 6. (Hydrogen atoms are omitted for clarity).
Compound 6 crystallizes in the monoclinic P2(1)/c space group with two independent K(I) ions
and one BDFO2- ligand in the asymmetric unit.[3] The K1(I) ion is coordinated to eight oxygen
atoms (O1, O6, O7, O8, O9, O10, O8A, O9A) from five different BDFO2- ligands (Fig. 1a). The
K2(I) ion is coordinated to eight oxygen atoms and one nitrogen atom (O1, O2, O3, O4, O7, O2A,
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10.1002/cplu.201600287
O3A, O4A, N3) from five different BDFO2- ligands (Fig. 1b). The bond lengths of K-O and bond
o
angles of O-K-O are within 2.6562(16) Å-3.1530(16) Å and 41.68(4) -173.26(5) o, respectively.
The BDFO2- ligands (Fig. 1c) and K(I) ions are linked each other to generate a 3D EMOF (Fig.
S2).
Fig. 2. a) Coordination environment of K1(I) ion, b) coordination environment of K2(I) ion, c) coordination
environment of Ag(I) ion, d) coordination model of BDFO2- ligand, e) coordination model of BDOFO2- ligand of 8.
(Hydrogen atoms are omitted for clarity).
Compound 8 is a 3D heterometallic metal-organic framework and crystallizes in the
orthorhombic Iba2 space group with an asymmetric unit consisting of two crystallographically
independent Ag(I) ions, four K(I) ions, one BDOFO2- ligand, two BDFO2- ligands and six
coordinated water molecules. K1(I) ion is nine-coordinated with nine oxygen atoms from three
BDFO2- ligands (O4, O8, O9, O10, O11, O12), one BDOFO2- ligand (O14, O15) and one water
molecule (O13) (Fig. 2a). K2(I) ion is coordinated to ten oxygen atoms from four BDFO2- ligands
(O4, O8, O9, O10, O11, O12), two BDOFO2- ligands (O14, O15, O16) and one water molecule
(O1) (Fig. 2b). The Ag1(I) ion is five-coordinated to four oxygen atoms from two BDFO2- ligands
(O6, O7), and two water molecules (O1, O2), and one nitrogen atom from one BDFO2- ligand (N1)
(Fig. 2c). The bond lengths of K-O and Ag-O in compound 8 are in the range of 2.701(11)
Å-3.252(12) Å and 2.161(11) Å-2.479(11) Å, respectively. And the bond angles of O-K-O and
o
o
o
o
O-Ag-O fall into the range of 42.2(3) -177.5(3) and 90.0(4) -156.6(6) , respectively. The
detailed bond lengths and bond angles are listed in Table S6 in Supporting Information. The
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BDFO2- ligand adopts both bridging and chelating coordination modes to K1, K2 and Ag atoms
(Fig. 2d). The BDOFO2- ligand also features bridging and chelating coordination modes, but only
to the K1 and K2 atoms (Fig. 2e) resulting in a compacted 3D framework (Fig. S3). Compound 9
crystallizes in the monoclinic P2(1)/c space group. The asymmetric unit is composed of one
+
+
BDFO2- anion, two NH2NH3 cations and one water molecule. Both the BDFO2- and NH2NH3
ions participate in extensive hydrogen bonding, leading to a 3D hydrogen bond network that
incorporates the free water molecules (Fig. 3).
Fig. 3. a) The asymmetric unit of 9 showing the atom-numbering scheme, b) 3D structural network of 9.
In 6 and 8, the BDFO2- ligand exhibits different coordination modes to the metal ions
generating 3D structural frameworks, which has a crucial effect on the thermal stability and
detonation performance.
By comparing the structures of 6 and 8, it is reasonable to conclude that compound 7 has been
formed by oxidation with N2O5 followed by metathesis with KI. Since compound 4 is the
precursor for 6, we may deduce that compound 5 is the precursor to compound 7. This is the first
report that 3-oxy-furoxan was structurally characterized by trapping it as its anion in a metal
complex. Quantum chemical calculations were carried out using the Gaussian 09 (Revision A.02)
program package and visualized by GaussView 5.05,[5] and the detonation properties were
evaluated by the commercial program EXPLO5 v6.01.[6] The calculated parameters of the related
energetic compounds are listed in Table 1. As shown in Table 1, the calculated detonation
pressures of the compounds range from 27.3 GPa (6) to 38.4 GPa (9). The calculated detonation
velocities are from 7759 m s−1 (6) to 9294.7 m s−1 (9). Noteworthily, the calculated detonation
properties of hydrazinium salt (9) are higher than those of potassium
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10.1002/cplu.201600287
4,4’-bis(dinitromethyl)-3,3’-azofurazanate (P = 30.1 GPa, D = 8138 m s−1) [7]. And the impact and
friction sensitivities of are less insensitive than and potassium
9
6
4,4’-bis(dinitromethyl)-3,3’-azofurazanate, possibly due to the extensive hydrogen-bonding
interaction between the cations and anions.
Table 1. Calculated parameters of compounds 4, 6, 8 and 9.
Compounds
Empirical formula
M a (g mol-1)
Ρ b (g cm-3)
Tdecc (oC)
4
C4Cl2N6O10
363.0
1.97
6
K2C4N6O10
370.3
2.13
8
9
C4H12N10O11
376.2
1.81
C12H12Ag2K4N18O37
1372.5
2.31
231.3
18.7
4.7
67.8
218.9
21.3
120.8
12.3
ΩCOd (%)
30.9
ΩCO2e (%)
13.2
4.3
-4.47
37.24
84.03
180.6
38.4
Nf (%)
23.2
22.7
18.40
61.5
--
N+Og (%)
ΔfHmh (kJ mol-1)
P i (GPa)
67.23
-55.6
30.3
65.9
-421.0
27.3
--
D j (m s-1)
ISk (J)
8057.2
5
7759.0
2
--
9294.7
9
--
FSl (N)
76
5
--
170
a Molecular weight. b From X-ray diffraction. c Decomposition temperature. d Oxygen balance for CaHbOcNd:
1600(c-a-b/2)/M. e Oxygen balance for CaHbOcNd: 1600(c-2a-b/2)/M. f Nitrogen content. g Nitrogen and oxygen
h
i
j
content. Heat of formation. Detonation velocity calculated with EXPLO5 V6.01.[6] Detonation pressure
calculated with EXPLO5 V6.01.[6] k Impact sensitivity. l Friction sensitivity.
In summary, we have trapped the anion of 3-oxy-furoxan in a heterometallic energetic MOF and
characterized the complex by IR, elemental analysis, and X-ray crystallography. This finding
provides insight in the search for new high energy densitiy materials. Future efforts will focus on
the development of 3-oxy-furoxan based compounds.
Experimental Section
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10.1002/cplu.201600287
General caution: The related furazan-based compounds in this work are seriously hazardous
materials and may explode under certain external conditions. The compound should be handled
with proper safety precautions such as safety glasses, face shields, and plastic spatulas,
particularly when they are prepared on a large scale.
The detailed synthetic processes of compounds 1-9 are depicted in Scheme 2 and described in
Supporting Information.
Acknowledgements
This work was financially supported by the National Natural Science Foundation of China
(Grant Nos. 21373162, 21203149, 21473135, 21173168 and 21373157).
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Table-of-Contents
3-oxy-furoxan was first caught in a hereometallic 3D energetic MOF, which would
provide a ray of light in searching for High-energy-density-materials.
9