Syntheses, crystal structures, thermal behaviors, and sensitivities of new initiator compositions: Rubidium salts of trinitrophenol and trinitroresorcinol

Article abstract of DOI:10.1080/00958972.2014.932353

Three new polymeric Rb(I) salts of trinitrophenol and trinitroresorcinol, rubidium trinitrophenol ([RbTNP]_n), bi-substituted rubidium salt of trinitroresorcinol ([Rb₂TNR·H₂O]_n), and mono-substituted rubidium sal

Full text of DOI:10.1080/00958972.2014.932353

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Syntheses, crystal structures, thermal
behaviors, and sensitivities of new
initiator compositions: rubidium salts
of trinitrophenol and trinitroresorcinol
a
a
b
a
Zhi-Min Li , Tong-Lai Zhang , Hui-Sheng Huang , Jian-Guo Zhang ,
a
a
c
Li Yang , Zun-Ning Zhou & Kai-Bei Yu
a
State Key Laboratory of Explosion Science and Technology,
Beijing Institute of Technology, Beijing, PR China
b
Chongqing Key Laboratory of Inorganic Special Functional
Materials, College of Chemistry and Chemical Engineering,
Yangtze Normal University, Chongqing, PR China
Click for updates
c
Chengdu Branch, Chinese Academy of Sciences, Chengdu, PR
China
Accepted author version posted online: 09 Jun 2014.Published
online: 08 Jul 2014.
To cite this article: Zhi-Min Li, Tong-Lai Zhang, Hui-Sheng Huang, Jian-Guo Zhang, Li Yang, Zun-
Ning Zhou & Kai-Bei Yu (2014) Syntheses, crystal structures, thermal behaviors, and sensitivities
of new initiator compositions: rubidium salts of trinitrophenol and trinitroresorcinol, Journal of
Coordination Chemistry, 67:11, 1923-1937, DOI: 10.1080/00958972.2014.932353
To link to this article: http://dx.doi.org/10.1080/00958972.2014.932353
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Journal of Coordination Chemistry, 2014
Vol. 67, No. 11, 1923–1937, http://dx.doi.org/10.1080/00958972.2014.932353
Syntheses, crystal structures, thermal behaviors, and
sensitivities of new initiator compositions: rubidium salts of
trinitrophenol and trinitroresorcinol
¶
ZHI-MIN LI† , TONG-LAI ZHANG*†, HUI-SHENG HUANG*‡, JIAN-GUO ZHANG†,
LI YANG†, ZUN-NING ZHOU† and KAI-BEI YU§
†State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology,
Beijing, PR China
‡Chongqing Key Laboratory of Inorganic Special Functional Materials, College of Chemistry and
Chemical Engineering, Yangtze Normal University, Chongqing, PR China
§Chengdu Branch, Chinese Academy of Sciences, Chengdu, PR China
(Received 19 January 2014; accepted 4 May 2014)
Three rubidium salts of trinitrophenol and trinitroresorcinol were obtained and characterized in
this article. Thermal behaviors and sensitivities investigation confirmed them to be promising
heat-resistant flame sensitive eco-friendly initiator composition.
Three new polymeric Rb(I) salts of trinitrophenol and trinitroresorcinol, rubidium trinitrophenol
(
[RbTNP]
n
2 2 n
), bi-substituted rubidium salt of trinitroresorcinol ([Rb TNR·H O] ), and mono-substi-
tuted rubidium salt of trinitroresorcinol ([RbHTNR]
n
) were synthesized and characterized by X-ray
single-crystal diffraction, elemental analysis, and IR spectroscopy. The central Rb(I) cations are 10
or 11-coordinated by oxygens from nitro group, phenolic hydroxyl and coordinated water, and the
multidentate ligands bridged different Rb(I) centers. Coordination bonds, electrostatic interaction,
and intermolecular hydrogen bonds assemble the ions into 3-D polymeric network structures.
Thermal decomposition behaviors of the compounds were studied by applying differential scanning
*
Corresponding authors. Email: ztlbit@bit.edu.cn (T.-L. Zhang); h.s.huang@hotmail.com (H.-S. Huang)
¶
Present address: Beijing Key Laboratory of Ionic Liquids Clean Process, Institute of Process Engineering, Chinese
Academy of Sciences, Beijing, PR China.
©
2014 Taylor & Francis

1
924
Z.-M. Li et al.
calorimetry under various linear heating rates. Sensitivities measurements revealed that these com-
pounds are sensitive to flame, insensitive to impact and friction stimulates. All properties show that
the compounds are promising to be an eco-friendly initiating composition, especially [RbTNP] .
n
Keywords: Rubidium salts; Trinitrophenol; Trinitroresorcinol; Crystal structure; Properties
1. Introduction
Initiator composition as the primary energy to ignite a secondary explosive has been widely
applied [1–3]. Lead trinitroresorcinol is one of the most famous initiator compositions and
is widely used in military and civilian areas since it was identified in 1907 [4–7], due to its
excellent properties, especially the sensitivity to flame. But, lead trinitroresorcinol is very
sensitive to electrostatic discharge, which caused many terrible accidents. Deleterious envi-
ronmental impacts and effects on human health have made replacement essential. Many
works on energetic coordination compounds as the replacement of lead trinitroresorcinol
have been accomplished [8–14].
Trinitro-substituted phenol compounds (2,4,6-trinitrophenol, HTNP; 2,4,6-trinitroresor-
cinol, H TNR; 2,4,6- trinitrophloroglucinol, H TNPG) are well-known explosives, and their
2
3
metallic salts and complexes are promising ingredients of primary explosives and propel-
lants [15–23]. To obtain eco-friendly initiator compositions, interests are focused on alkali
salts of tri-nitro hydroxybenzenes. Potassium salt of trinitrophenol (KTNP) was studied by
Shao et al. [24], then, Sheng et al. [19] investigated synthesis, properties, and applications,
and confirmed it as an initiator composition. The structures and thermal decomposition
mechanisms of di-substituted (K TNR) and mono-substituted (KHTNR) potassium salts of
2
trinitroresorcinol were reported by Li et al. [25, 26]. Chen et al. investigated the structures
and performances of mono-substituted (KH TNPG), di-substituted (K HTNPG), and tri-
2
2
substituted (K TNPG) potassium salts of trinitrophloroglucinol and recommended them as
3
components of clean initiating compositions and ignition [27, 28]. Energetic Rb salts have
aroused attention in recent years. Chen et al. [29] reported the crystal structure and thermal
behavior of mono-substituted rubidium salt of trinitrophloroglucinol (RbH TNPG).
2
Klapötke et al. [30, 31] investigated the structures and energetic properties of rubidium salts
of 5-(5-nitrotetrazole-2-ylmethyl)-tetrazolate and 5-nitrotetrazole. Luo et al. [32] investi-
gated the synthesis and thermal behaviors of Rb salt of 1,1-diamino-2,2-dinitroethylene.
The present article focused on Rb salts of trinitrophenol and trinitroresorcinol. Three new
energetic Rb salts were synthesized, the crystal structures were studied, and their thermal
decomposition behaviors and sensitivities were determined to assess their potential applica-
tion as energetic materials.
2
2
. Experimental
.1. Materials and instruments
All the reagents and solvents were of analytical grade and used without purification as com-
mercially obtained. Elemental analyses (C, H, and N) were performed on the Elementar Va-
rio MICROCUBE (Germeny) full-automatic trace element analyzer. IR spectra were
recorded on a Bruker Equinox 55 infrared spectrometer (KBr pellets, Germany) from 4000
−
1
−1
to 400 cm
with a resolution of 4 cm . Thermal behaviors were investigated by

Rubidium trinitrophenol and trinitroresorcinol
1925
differential scanning calorimeter (DSC) (CDR-4, Shanghai Precision & Scientific
Instrument Co., Ltd); about 0.5 mg sample was placed in aluminum pans in static air at
−
1
various heating rates (5, 10, 15, and 20 K min ) from room temperature to 873 K.
2
.2. Synthesis of [RbTNP]n
5.8 g (0.025 M) HTNP and 0.5 g (0.0125 M) MgO were put into 100 mL deionized water
with strong stirring at 343 K and a few minutes later, clear aqueous solution of Mg(TNP)2
was obtained. RbNO aqueous solution (3.7 g (0.025 M) RbNO dissolved in 40 mL deion-
3
3
ized water) was poured into the Mg(TNP) solution at 343 K. The mixture was stirred at
2
this temperature for 10 min, then cooled to room temperature rapidly, and filtered. The
product was obtained and washed with ethanol twice, and dried in a water bath oven at
3
23 K for 6 h, yield 86%. Anal. Calcd (%) for C H N O Rb: C, 22.94; H, 0.64; N, 13.38.
6 2 3 7
−
1
Found: C, 23.12; H, 0.66; N, 13.25. IR (KBr) ν (cm ): 3028, 1669, 1541, 1395, 1283,
9
41, 874, 763. The synthetic route of [RbTNP] is shown in scheme 1.
n
2
.3. Synthesis of [Rb TNR·H2O]n
2
6
.1 g (0.025 M) H TNR and 1 g (0.025 M) MgO were put into 100 mL deionized water with
2
strong stirring at 343 K and a few minutes later, clear aqueous solution of MgTNR was
obtained. RbNO aqueous solution (7.4 g (0.05 M) RbNO dissolved in 80 mL deionized
3
3
water) was poured into the MgTNR solution at 343 K. The mixture was stirred at this tem-
perature for 10 min, then cooled to room temperature rapidly and filtered. The product was
obtained and washed with ethanol twice, and dried in a water bath oven at 323 K for 6 h,
yield 72%. Anal. Calcd (%) for C H N O Rb : C, 16.67; H, 0.69; N, 9.72. Found: C,
6
3
3
1
9
2
−
1
6.85; H, 0.74; N, 9.57. IR (KBr) ν (cm ): 3428, 2913, 1643, 1495, 1382, 1311, 895, 723.
The synthetic route of [Rb TNR·H O] is shown in scheme 2.
2
2
n
2
.4. Synthesis of [RbHTNR]n
6
.1 g (0.025 M) H TNR and 1 g (0.025 M) MgO were put into 100 mL deionized water with
2
strong stirring at 343 K and a few minutes later, clear aqueous solution of MgTNR was
n
Scheme 1. The synthetic route of [RbTNP] .
2 2 n
Scheme 2. The synthetic route of [Rb TNR·H O] .

1
926
Z.-M. Li et al.
n
Scheme 3. The synthetic route of [RbHTNR] .
obtained. The pH of the solution was adjusted to 3–4 by adding dilute nitric acid. RbNO3
aqueous solution (3.7 g (0.025 M) RbNO dissolved in 40 mL deionized water) was poured
3
into the MgTNR solution at 343 K. The mixture was stirred at this temperature for 10 min,
then cooled to room temperature rapidly and filtered. The product was obtained and washed
with ethanol twice, and dried in a water bath oven at 323 K for 6 h, yield 78%. Anal. Calcd
(
(
[
%) for C H N O Rb: C, 21.85; H, 0.61; N, 12.74. Found: C, 21.78; H, 0.69; N, 12.91. IR
6 2 3 8
KBr) ν (cm ): 3476, 2932, 1651, 1478, 1409, 1288, 916, 843. The synthetic route of
−
1
RbHTNR] is shown in scheme 3.
n
2
.5. X-ray crystallography
+
The X-ray diffraction data collections were performed on a Rigaku AFC-10/Saturn 724
CCD diffractometer with graphite-monochromated Mo K radiation (λ = 0.71073 Å) using
α
the multi-scan technique. The structures were solved by direct methods using SHELXS-97
2
and refined by full-matrix least-squares procedures on F with SHELXL-97 [33–35]. All
non-hydrogen atoms were obtained from the difference Fourier map and subjected to aniso-
2
tropic refinement by full-matrix least squares on F . Hydrogens were obtained geometrically
and treated as riding on the parent atoms or were constrained in the locations during refine-
ments. Detailed information of crystallographic data collection and structures refinement is
summarized in table 1.
2
.6. Sensitivity measurements
Impact sensitivity (50% firing height, H ) was measured by Bruceton staircase method,
5
0
1
0 kg drop hammer, and 50 mg sample mass. Friction sensitivity (probability of
explosion, P) was measured by 1.5 kg pendulum hammer fixed on 66° tilt angle, 2.45 MPa
gage pressure, and 20 mg sample mass. For flame sensitivity (50% firing height, H ), 20
5
0
mg sample was compacted into a copper cap under 58.8 MPa and was ignited with a
standard black powder pellet. The 5 s delay explosive temperature (T ) was measured with
5
a copper detonator shell, wood’s alloy bath, and 30 mg sample mass.
3
3
. Results and discussion
.1. Crystal structures
The crystals of [RbTNP] and [RbHTNR] belong to the monoclinic system, P2(1)/c and
n
n
P2(1)/n space groups, respectively, whereas [Rb TNR·H O] belongs to the triclinic system,
2
2
n

Rubidium trinitrophenol and trinitroresorcinol
1927

1
928
Z.-M. Li et al.
P-1 space group. The crystal density of [RbTNP] , [Rb TNR·H O] , and [RbHTNR] are
n
2
2
n
n
−
3
2
.337, 2.512, and 2.302 g cm , respectively. The molecular unit and labeling scheme of
[
RbTNP] , [Rb TNR·H O] , and [RbHTNR] are shown in figure 1. The asymmetric unit
n
2
2
n
n
–
of [RbTNP] is comprised of one Rb(I) and one TNP , [Rb TNR·H O] is comprised of
two Rb(I) centers, one TNR , and one coordinated H O, and [RbHTNR] is comprised of
one Rb(I) and one HTNR . Selected bond lengths and angles for [RbTNP] ,
n
2
2
n
2
–
2
n
–
n
[
Rb TNR·H O] , and [RbHTNR] are given in table 2. The hydrogen bond parameters are
2 2 n n
summarized in table 3.
Figure 2 shows the coordination environment of TNP ligand and Rb(I), as well as the
–
packing diagram of [RbTNP] viewed along the b-axis. In [RbTNP] , the central Rb(I) is
n
n
–
coordinated by 11 oxygens from seven different TNP ligands. The bond lengths of Rb–O
are 2.89–3.38 Å, bigger than K–O lengths (2.74–2.92 Å) in KTNP [24] and shorter than
Cs–O lengths (3.03–3.54 Å) in CsTNP [36]. This can be attributed to the radius of K(I), Rb
–
(
I), and Cs(I). As shown in figure 2(a), TNP is coordinated with seven different Rb(I) cen-
–
ters. The 3-D polymeric network was formed by multidentate TNP ligands bridging adja-
cent Rb(I) ions, as shown in figure 1(c).
Figure 3 shows the coordination environment of TNR and two Rb(I) centers, as well as
2
–
the packing diagram of [Rb TNR·H O] viewed along the a-axis. Both Rb(I) centers are
2
2
n
2
–
coordinated by 10 oxygens, coordinated to Rb1 from seven different TNR ligands, and
for Rb2 from six different TNR ligands. Rb–O bond lengths are 2.76–3.42 Å, also
2
–
between the K–O lengths (2.64–3.19 Å) of K TNR [26] and Cs–O lengths (3.03–3.58 Å) of
2
2
–
Cs TNR [37]. TNR coordinated with 12 different Rb(I) centers, including six Rb1 and six
Rb2. H O bridged one Rb1 and one Rb2. The multidentate TNR ligands and H O mole-
2
2
–
2
2
cules joined various Rb(I) centers to form a 3-D polymeric structure. Furthermore, two kind
of hydrogen bonds were formed between O9 (water) and O5 (nitro group) and O6 (phenolic
xiii
ix
hydroxyl), O9–H9A···O5 and O9–H9B···EO6 .
–
Figure 4 shows the coordination environment of HTNR ligand and Rb(I), as well as the
packing diagram of [RbHTNR] viewed along the a-axis. In [RbHTNR] , the central Rb(I)
n
n
–
is coordinated by 10 oxygens from seven different HTNR ligands. The bond lengths of
n 2 2 n n
Figure 1. Molecular unit and labeling scheme of [RbTNP] , [Rb TNR·H O] , and [RbHTNR] .

Rubidium trinitrophenol and trinitroresorcinol
1929

1
930
Z.-M. Li et al.
2 2 n n
Table 3. Hydrogen bond lengths (Å) and bond angles (°) for [Rb TNR·H O] and [RbHTNR] .
D–H⋯A
Rb TNR·H
O9–H9A⋯O5
O9–H9B⋯O6
D–H(Å)
H⋯A (Å)
D–A (Å)
D–H⋯A (°)
[
2
2
O]
n
xiii
ix
0.82(2)
0.82(5)
2.39(2)
2.10(6)
3.159(6)
2.921(6)
158(4)
173(8)
[
RbHTNR]
n
O1–H10⋯O8
O1–H10⋯N3
O1–H10⋯O3
0.84(2)
0.84(2)
0.84(2)
1.85(3)
2.45(4)
2.21(4)
2.570(3)
2.895(4)
2.710(3)
144(3)
114(3)
119(3)
iv
2 2 n n
Note: Symmetry codes: [Rb TNR·H O] : (xiii) x−1, y, z−1; (ix) −x + 1, −y + 2, −z + 1. [RbHTNR] : (iv) −x + 3/2, y + 1/2, −z + 1/2.
–
+
n
Figure 2. Coordination environment of (a) TNP and (b) Rb center, (c) the packing diagram of [RbTNP] viewed
along the b-axis.
Rb–O are 2.85–3.29 Å, similar to mono-substituted rubidium salt of trinitrophloroglucinol
(
[
RbH TNPG, 2.94–3.22 Å) [29], also between the K–O lengths (2.77–2.92 Å) of KHTNR
2
–
35] and Cs–O lengths (3.00–3.76 Å) of CsHTNR [38]. HTNR coordinated with seven dif-
–
ferent Rb(I) centers. The multidentate HTNR ligands joined various Rb(I) centers to form
a stable 3-D polymeric structure. Due to the un-substituted H atom from phenolic hydroxyl,
three kinds of hydrogen bonds were formed between O1 (phenolic hydroxyl) and O8 (nitro
iv
group), O3 (nitro group) and N3 (nitro group): O1–H10···O8, O1–H10···O3 and
O1–H10···N3. The hydrogen bonds make an important contribution to the stability of the
compound.
3
.2. Thermal behaviors
DSC was applied to assess the thermal decomposition behaviors of the compounds. Figure 5
shows the DSC curves of [RbTNP] , [Rb TNR·H O] , and [RbHTNR] at a heating rate of
n
2
2
n
n

Rubidium trinitrophenol and trinitroresorcinol
1931
2
–
+
Figure 3. Coordination environment of (a) TNR and (b), (c) Rb center, (d) the packing diagram of
[
Rb
2
TNR·H
2
n
O] viewed along the a-axis.
−
1
1
0 K min . The peak temperatures (T ) of the exothermic process of the studied com-
p
−
1
pounds at heating rates of 5, 10, 15, and 20 K min are listed in table 4.
Kissinger’s [39] (equation (1)) and Ozawa’s [40] (equation (2)) methods were used to
determine the apparent activation energy and the pre-exponential factor of the exothermic
process from the multiple non-isothermal peak temperatures,
2
d lnðb=T Þ
Ea
R
p
¼
ꢀ
(1)
(2)
dð1=T Þ
p
0
:4567Ea
lg b þ
¼ C
RTp
−
1
−1
where T is the peak temperature, K; R is the gas constant, 8.314 J M K ; β is the lin-
p
−
1
ear heating rate, K min ; and C is a constant. The obtained apparent activation energy E
K
and E , pre-exponential factor A , and linear correlation coefficient R and R of the exo-
O
K
K
O
thermic decomposition process are shown in table 4; subscripts K and O denoted calcula-
tion results by Kissinger’s method and Ozawa’s method, respectively.
In figure 5, sharp exothermic peaks were found in the DSC curves of [RbTNP]n,
[
Rb TNR·H O] , and [RbHTNR] at 587–621 K, 489–556 K, and 495–522 K, respectively.
2 2 n n
Furthermore, a small endothermic peak from 380 to 402 K was observed in the DSC curve
of [Rb TNR·H O] due to the presence of coordinated water.
2
2
n

1
932
Z.-M. Li et al.
–
+
Figure 4. Coordination environment of (a) HTNR and (b) Rb center, (c) the packing diagram of [RbHTNR]
n
viewed along the a-axis.
0
[RbHTNR]n
-5
513 K
0
5
390 K
[
Rb TNR·H O]
2 2 n
-
518 K
0
5
[RbTNP]n
-
606 K
-10
400
500
600
700
Temperature (K)
n 2 2 n n
Figure 5. DSC curves of [RbTNP] , [Rb TNR·H O] , and [RbHTNR] .

Rubidium trinitrophenol and trinitroresorcinol
1933

1
934
Z.-M. Li et al.
The peak temperature of the exothermic process of [RbTNP] at a heating rate of
n
−
1
1
0 K min is 606 K, higher than that of [Rb TNR·H O] (518 K) and [RbHTNR] (513 K).
2 2 n n
KTNP and K TNR are more stable than the corresponding rubidium salts, with the peak
2
temperature of 612 and 592 K [19, 41]. Wang et al. [28] confirmed the acidic potassium
salts of trinitrophloroglucinol (H TNPG) are thermally more sensitive than normal salt; ther-
3
mal decomposition peak temperature of KH TNPG, K HTNPG, and K TNPG are 462,
2
2
3
5
33, and 568, respectively. The peak temperature of the intense exothermic process of
RbH TNPG is 480 K [29], lower than that of [RbHTNR] . The sensitivity for both potas-
2
n
sium and rubidium salts of nitro-phenol are trinitrophenol < trinitroresorcinol < trinitrophl-
oroglucinol, ascribed to the active nitro group. The structure of normal salt of
trinitroresorcinol is closer than that of acidic salt and Rb–O coordinate bonds are stronger
than H-bonds, resulting in [Rb TNR·H O] being more stable than [RbHTNR] . The calcu-
2
2
n
n
lated results using Kissinger’s and Ozawa’s methods are similar and in the normal range of
kinetic parameters for thermal decomposition of solid materials [42]. Using the values of
apparent activation energy (the average of EK and E ) and pre-exponential constant, the
O
Arrhenius equation of the exothermic process of [RbTNP] , [Rb TNR·H O] , and
n
2
2
n
[
RbHTNR] can be expressed as follows:
n
3
ln k ¼ 25:65 ꢀ 315:5 ꢁ 10 =RT;
ln k ¼ 21:06 ꢀ 226:0 ꢁ 103=RT;
ln k ¼ 12:10 ꢀ 139:3 ꢁ 103=RT:
The values of the peak temperature of the exothermic process corresponding to β → 0
T ) of [RbTNP] , [Rb TNR·H O] , and [RbHTNR] obtained according to equation (3)
43] are 596, 516, and 497 K, respectively, where b and c are coefficients. The correspond-
(
[
p0
n
2
2
n
n
ing critical temperature of thermal explosion (T ) obtained from following equation (4)
bp
[
44, 45] of [RbTNP] , [Rb TNR·H O] , and [RbHTNR] are 606, 526, and 513 K, respec-
n 2 2 n n
tively. The values of Tp0 and Tbp also confirmed the order of thermal stability of the title
compounds as:
½
RbTNPꢂ [ ½Rb2TNR ꢃ H2Oꢂ [ ½RbHTNRꢂ
n
n
n
2
i
Tpi ¼ Tp0 þ bb þ cb
(3)
(4)
i
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
2
EO ꢀ
E
O
ꢀ 4E RT
O
p0
Tbp
¼
2
R
≠
≠
The entropy of activation (ΔS ), enthalpy of activation (ΔH ), and free energy of activa-
≠
tion (ΔG ) of the exothermic decomposition process of the compounds corresponding to T
=
T , E = E , and A = A obtained by equations (5)–(7) [44, 45] are listed in table 4. The
p0 a K K
≠
positive values of ΔG indicate that the exothermic decomposition reaction of the studied
initiator compounds must proceed under the heating condition, and [RbHTNR] is easier to
n
decompose than [Rb TNR·H O] and [RbTNP] ,
2
2
n
n

Rubidium trinitrophenol and trinitroresorcinol
Table 5. The sensitivities of [RbTNP] , [Rb TNR·H O] , and [RbHTNR]
1935
n
2
2
n
n
.
Compounds
[RbTNP]
n
[Rb
2
TNR·H
2
O]
n
[RbHTNR]
n
KTNP [12]
K
2
TNR [34]
PbTNR [7]
T
H
P (%)
H
5
(K)
50(F) (cm)
641
50
no fire
no fire
556
39
no fire
no fire
542
36
no fire
no fire
664
38
2
645
12
–
596
47
68
50(I) (cm)
28
–
12
5
Note: T : 5 s delay explosion temperature; H50(F): 50% firing height for flame; P: probability of fire from friction; H50(I): 50% fir-
ing height for impact.
k T
6¼
=R
B
eDS
A ¼
(5)
h
6¼
DH ¼ Ea ꢀ RT
(6)
(7)
6
6
6¼
DG ¼ DH ꢀ TDS
−
23
−1
where k is the Boltzmann constant (1.3807 × 10 J K ) and h is the Plank constant
6.626 × 10 J s ).
B
−
34
−1
(
3
.3. Sensitivities
The 5s delay explosive temperature, flame, impact, and friction sensitivities of [RbTNP]n,
Rb TNR·H O] , and [RbHTNR] were determined and the results contrasted with the
[
2
2
n
n
potassium and lead salts (table 5). All the studied compounds are sensitive to heat and
flame stimulus, but not fire to impact and friction under the testing conditions. The 50%
firing thresholds toward flame of [RbTNP] is 50 cm, higher than lead trinitroresorcinol
n
(
PbTNR, 47 cm) [7]. [Rb TNR·H O] and [RbHTNR] are also sensitive to flame as KTNP
2 2 n n
[
19], with the H (F) of 39, 36, and 38 cm, respectively. The 5 s delay explosive tempera-
5
0
ture of [RbTNP] is 641 K, higher than that of [Rb TNR·H O] (556 K), [RbHTNR]
n
n
2
2
n
(
542 K), and PbTNR (596) [7], but a little lower than that of KTNP (664 K) and K TNR
2
(645 K) [19, 41].
The Rb salts are more sensitive than K salts to flame, salts based on trinitrophenol are
more sensitive than salts based on trinitroresorcinol to flame, and the heat sensitivities of
trinitrophenol salts are lower than that of trinitroresorcinol salts.
4
. Conclusion
Reaction of rubidium nitrate with the magnesium salts of trinitrophenol and trinitroresorcin-
ol aqueous solutions gave three coordination polymers, [RbTNP] , [Rb TNR·H O] , and
n
2
2
n
[
RbHTNR] . The products were characterized by elemental analysis, IR spectroscopy, and
n
X-ray single-crystal diffraction. Thermal behaviors of the three compounds were investi-
gated by DSC and the decomposition temperatures are higher than 473 K, meeting the
requirement of stable energetic material [2]. The kinetic parameters were obtained by non-
isothermal reaction kinetics, and the Arrhenius equations of [RbTNP] , [Rb TNR·H O] ,
n
2
2
n

1
936
Z.-M. Li et al.
3
3
and [RbHTNR] can be expressed as lnk = 25.65–315.5 × 10 /RT, lnk = 21.06–226.0 × 10 /
n
3
≠
RT, and lnk = 12.10–139.3 × 10 /RT, respectively. Thermal parameters of T , T , ΔS ,
ΔH , and ΔG were also obtained. Sensitivities of the compounds to heat, flame, impact,
p0
bp
≠
≠
and friction were tested. The 50% firing threshold toward flame of [RbTNP] is 50 cm and
n
the 5 s delay explosion temperature of [RbTNP] is 641 K. Herein, [RbTNP] was sug-
n
n
gested as a heat-resistant, flame sensitive eco-friendly initiator composition with a great
application prospect.
Supplementary material
CCDC 979638, 979639, and 979640 contain the supplementary crystallographic data of
[
RbTNP] , [Rb TNR·H O] , and [RbHTNR] , respectively. These data can also be obtained
n 2 2 n n
free of charge from the Cambridge Crystallographic Data Center via http://www.ccdc.cam.
ac.uk/data_request/cif.
Acknowledgements
This work was supported by the National Basic Research Program of China, the Natural
Science Foundation of Chongqing (cstc2011jjA50013) and the Doctoral Candidate Innova-
tion Research Support Program by Science & Technology Review (kjdb201001-2).
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