Synthesis and structure of a novel alkynyl-containing disulfide compound as cathode materials for secondary lithium batteries

Article abstract of DOI:10.1080/00397911.2013.789526

A novel alkynyl-containing disulfide compound, 5,8-dihydro-1H,4H-2,3,6,7- tetrathia-anthracen (TMSEDTTA), was synthesized. The structures of the target compound and the intermediates have been identified by ¹H NMR, ¹³C NMR, mass spectrometry, Fourier-transform infrared, Raman spectra, X-ray photoelectron spectroscopy, and elemental analysis. In addition, the structure of (Z)-(1,2-dibromo-2-(2,3,5,6-tetrakis(bromomethyl)phenyl)vinyl) trimethylsilane (5) was determined by single X-ray analysis. Taylor and Francis Group, LLC.

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Synthesis and Structure of a Novel
Alkynyl-Containing Disulfide Compound
as Cathode Materials for Secondary
Lithium Batteries
a
a
a
a
Zuxi Jin , Yunguo Lu , Shixi Li & Zaoying Li
a
College of Chemistry and Molecular Sciences , Wuhan University ,
Wuhan , China
Accepted author version posted online: 15 Aug 2013.Published
online: 11 Oct 2013.
To cite this article: Zuxi Jin , Yunguo Lu , Shixi Li & Zaoying Li (2014) Synthesis and Structure of a
Novel Alkynyl-Containing Disulfide Compound as Cathode Materials for Secondary Lithium Batteries,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 44:1, 82-88, DOI: 10.1080/00397911.2013.789526
To link to this article: http://dx.doi.org/10.1080/00397911.2013.789526
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Synthetic Communications , 44: 82–88, 2014
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2013.789526
SYNTHESIS AND STRUCTURE OF A NOVEL
ALKYNYL-CONTAINING DISULFIDE COMPOUND
AS CATHODE MATERIALS FOR SECONDARY
LITHIUM BATTERIES
Zuxi Jin, Yunguo Lu, Shixi Li, and Zaoying Li
College of Chemistry and Molecular Sciences, Wuhan University,
Wuhan, China
GRAPHICAL ABSTRACT
Abstract
7
A novel alkynyl-containing disulfide compound, 5,8-dihydro-1H,4H-2,3,6,
-tetrathia-anthracen (TMSEDTTA), was synthesized. The structures of the target
1
13
compound and the intermediates have been identified by H NMR, C NMR, mass
spectrometry, Fourier-transform infrared, Raman spectra, x-ray photoelectron spec-
troscopy, and elemental analysis. In addition, the structure of (Z)-(1,2-dibromo-2-(2,3,5,
6-tetrakis(bromomethyl)phenyl)vinyl)trimethylsilane (5) was determined by single x-ray
analysis.
Received January 28, 2013.
Address correspondence to Zaoying Li, College of Chemistry and Molecular Sciences, Wuhan
University, Wuhan 430072, China. E-mail: zyliwuc@whu.edu.cn
8
2

ALKYNYL-CONTAINING DISULFIDE COMPOUND
83
[Supplementary materials are available for this article. Go to the publisher’s online
1
edition of Synthetic Communications for the following free supplemental resource(s):
Full experimental and spectral details.]
Keywords Alkylbromination; disulfide; synthesis; thioesterification
INTRODUCTION
Since the 1980s, organodisulfide compounds have attracted research interest as
positive active materials that have large energy density and are lightweight, low cost,
and environmentally benign for high-power and lightweight lithium secondary bat-
[
1]
teries. The disulfide bond (S-S), providing a reversible two-electron reaction during
ꢀ
ꢀ
oxidation and reduction (RS-SR þ 2e ¼ 2RS ), is the key moiety contributing high
[
2,3]
specific capacity to the organodisulfide compounds in the batteries.
At the same
time polyphenylacetylene, one of the most promising intrinsically conducting poly-
mers because of its straightforward polymerization, chemical and environmental
stability, and relatively high conductivity, has been widely studied for applications
[
4,5]
in electronic and optical devices.
6,7]
According to our previous studies and related
the most effective approach for increasing practical specific capacity
[
reports,
and cycling stability is to combine the S-S bond with the side chain of some kind
of conducting polymer. The modification in the structure not only enables the cata-
lysis of the backbone chain on the redox process of disulfides, it also brings about an
effective inhibition of the loss of sulfur in the electrolyte during charging and
[
8]
discharging. The depolymerized ‘‘monomer’’ after discharge was in fact a polymer
and thus could provide an improved recombination efficiency of the S-S bond to
enhance the cycling stability of this cathode material.
In this article, we designed, synthesized, and characterized a new phenylacety-
lene derivative, which has two condensed aliphatic rings containing two disulfur
bonds. Its high disulfide density and intramolecular S-S bonds can lead to the
promise of high effectivity as a potential battery material.
DISCUSSION
The total synthesis for the target compound 9-trimethyl silane ethynyl-5,
-dihydro-lH,4H-2,3,6,7-tetrathia-anthracene (7) were achieved in four steps starting
8
from 1,2,4,5-tetramethyl-benzene (1) as outlined in Scheme 1. First, the starting
material 1 was converted to 3-iodo-1,2,4,5-tetramethylbenzene (2) in 90% yield,
which was modified from the general method of iodination of aromatic substrates
[
9]
under solvent-free conditions using the I =AgNO combination in a solid state.
2
3
Thus we avoided the difficulty of eliminating the disubstituted by-product and
obtained the highly pure monoiodination 2.
Next, a direct Sonogashira cross-coupling reaction of iodo-durene with
[
10]
terminal acetylenes has been achieved under the optimized conditions. This trans-
ꢁ
formation was performed in diethylamine solvent at 60 C, affording good isolated
yield (95%), but yield was only moderate in the case when triethylamine was used
as solvent, despite the prolonged reaction time.

84
Z. JIN ET AL.
Scheme 1. Synthesis of compound 7.
Silylated alkyne 3 was brominated to 4 by N-bromosuccinimide (NBS) in
the presence of benzoyl peroxide (BPO) in 30% yield. Not only tetrabromination
compound 4 but also the addition product 5 were synthesized in one pot, which has
not been reported in the literature under similar reaction circumstances. We success-
fully grew a single crystal of 5 from CHCl =petroleum ether (PE) and submitted it to
3
x-ray crystallography. The ORTEP drawing of compound 5 is shown in Fig. 1, and it
can be seen that the molecule has a Z-olefin structure, which provides a possible syn-
thetic method from alkynyl to bromination addition olefin. The relative crystal data
are presented in the Supporting Material. To suppress the generation of compound
5
, we diluted the concentration of reaction mixtures by increasing the amount of sol-
vent; meanwhile N-bromosuccinimide (NBS) was added in small portion at mild
reflux.
Finally, the benzylic bromide 4 was then converted to sodium alkylthiosulfate 6
ꢁ
(Na S O , EtOH=H O, 80 C) as an intermediate, which, without purification, was
directly used to generate tricyclic structure 7 by the oxidation of I . This process
2
2
3
2
2
can be more efficiently carried out in one pot without the necessity of isolating the
thioesterification product. Sodium alkylthiosulfate (Bunte salts) has been reported
[
11]
as a generally used regent to form disulfide compound by reaction with I
or
2
[12]
hydrogen peroxide. In this case, we completed the reaction with iodine but failed
with hydrogen peroxide. Furthermore, to prove the existence of compound 6, this
reaction was interrupted before the addition of iodine. After evaporating solvents,
the residue was recrystallized with EtOH=H O to afford the analytically pure
2
product, which subsequently has been characterized by Fourier transform (FT)–
Raman, NMR, and mass spectrometry (MS). Based on its water solubility and

ALKYNYL-CONTAINING DISULFIDE COMPOUND
85
Figure 1. ORTEP drawing of the molecular structure of 5. CCDC reference number 920770. (Figure is
provided in color online.)
characterization data, it is indeed confirmed that the Bunte salts was formed in the
procedure of cyclization.
Sulfur-rich compounds give very intense Raman spectra because the valence
[
13]
electrons in S-S bonds are highly polarizable Therefore, Raman spectroscopy
has always been a powerful research tool to characterize these compounds. In this
work, the S-S stretching vibrations of compound 7 in Raman spectra were observed
ꢀ
1
[14]
at 521 cm , which was similar to the character of other disulfide compounds. To
confirm that the disulfide groups were well protected from further oxidation to sulf-
oxide or sulfone, X-ray photoelectron spectroscopy (XPS) spectra have been carried
out to prove the preservation of S-S bonds. The bonding energy of S2p is located at
163.7 eV, indicating the existence of disulfide bonds in compound 7. The S2p spectra
also shows that sulfur in the target compound has only one valence state, in
[
15]
agreement with its structure.
5
The charge–discharge tests on the Li=LiClO4=
,8-dihydro-1H,4H-2,3,6,7-tetrathia-anthracen (TMSEDTTA) battery showed that
ꢀ
1
the initial discharge capacity reached 330 mAh g , which should include both
contributions of phenylethynyl and S-S bonds of TMSEDTTA. However, the spe-
cific capacity of TMSEDTTA decreased dramatically, due to a rapid escape of the
monomer from the cathode during the charge–discharge process. Nevertheless, the
greater capacity and better cycle stability could be enhanced when the phenylethynyl
polymer of unit TMSEDTTA was used as the cathode material.
In conclusion, the four-step synthesis of a novel alkynyl-containing disulfide
compound, TMSEDTTA, has been developed. During the synthesis of target
compounds, we utilized the solid-phase reaction to obtain monoiodination 2 with
satisfactory conversion yield. Furthermore, three new compounds, 4, 5, and 7, were

86
Z. JIN ET AL.
first prepared, and the single-crystal x-ray analysis of 5 confirmed its structure. The
designed molecular is a potential material when polymerized and used as the cathode
material of the secondary lithium batteries. The corresponding research work on
polymerization is under way.
EXPERIMENTAL
Trimethyl((2,3,5,6-tetrakis(bromomethyl)phenyl)ethynyl)silane (4)
and (Z)-(1,2-Dibromo-2-(2,3,5,6-tetrakis(bromomethyl)phenyl)vinyl)-
trimethylsilane (5)
N-Bromosuccinimide (15.7 g, 88.4 mmol) was alternately added in small
portions under nitrogen protection to a round-bottom Schlenk flask containing 3
(2.8 g, 12.3 mmol) and the benzoyl peroxide (0.6 g, 2.5 mmol) in CCl (90 mL). The
4
mixture was stirred at mild reflux for 12 h. After filtration of succinimide and
removal of the solvent, the residue was purified by column chromatography. The
resulting solid (R ¼ 0.3) was recrystallized from petroleum ether (PE) to give pure
f
ꢁ
as white solid (30%). Mp: 128–129 C. H NMR (300 MHz, CDCl ) d 7.32
3
s, 1H), 4.86 (s, 4H), 4.57 (s, 4H), 0.34 (s, 9H). C NMR (75 MHz, CDCl ) (139.4,
3
1
4
(
1
1
1
3
þ
37.6, 132.8, 126.3, 108.3, 98.2, 28.9, 27.2, ꢀ0.38. GC-MS (EI, m=z): 546 (M ,
ꢀ
) cm . The resulting solid
C-Br
1
00). FT-IR (KBr) 2161 (n
), 1250 (n ), 680 (n
CꢂC
C-Si
1
(
(
(
(
R ¼ 0.5) was recrystallized from PE to obtain 5 as white solid (20%). H NMR
f
1
3
300 MHz, CDCl ) d 7.43 (s, 1H), 4.62–4.73 (m, 8H), ꢀ0.01 (s, 9H). C NMR
3
75 MHz, CDCl ) (141.7, 138.9, 137.4, 135.1, 134.6, 125.4, 28.9, 25.4, ꢀ0.38. FT-IR
3
ꢀ
) cm .
C
1
KBr) 1630 (nC
=
Characterization Data of Compound 6
ꢁ
1
Mp: >300 C. H NMR (D O, 300 MHz): d=ppm 7.45 (s, 1H, ph-H), 4.55
2
1
s, 4H, o-ph-CH ), 4.38 (s, 4H, m-ph-CH ), 0.20 [s, 9H, -Si(CH ) ]. C NMR
3
(
2 2 3 3
(
D O, 75 MHz): 137.4, 135.6, 133.8, 125.5, 109.1, 100.6, 36.3, 34.9, ꢀ0.76.
ꢀ
C-Si C-S S-S
2
1
FT-Raman: 2147 (n
m=z): 743 (M-Na, 100).
), 1301 (n ), 722, 679 (n ), 415 (n ) cm . MS (ESI,
CꢂC
9-Trimethyl Silane Ethynyl-5,8-dihydro-1H,4H-
2,3,6,7-tetrathia-anthracene (TMSEDTTA, 7)
The compound 4 (1.67 g, 3.06 mmol) and sodium thiosulphate (3.34 g,
3.5 mmol) were dissolved in 30 mL of anhydrous EtOH=H O (1:1). The mixture
1
2
was refluxed with stirring until the solution was homogeneous. Iodine (1.61 g,
.34 mmol) was then added in small portions until the color remained. Next,
a sodium bisulfite solution was added to remove the excess iodine. After filtration,
6
ꢁ
the brown precipitation was washed with water, dried in vacuum at 60 C, and then
extracted by 100 mL of boiling CHCl . Evaporation of solvent left the crude product,
3
which was purified using silica-gel chromatography (PE=chloroform 3:0.2) to give
0
ꢁ
1
.20 g (total yield 20%) of 7 as a white solid. Mp: 175–176 C. H NMR
1
3
(
300 MHz, CDCl ) d 6.80 (s, 1H), 4.16 (s, 4H), 3.99 (s, 4H), 0.28 (s, 9H). C NMR
3

ALKYNYL-CONTAINING DISULFIDE COMPOUND
87
(
(
75 MHz, CDCl ) (133.8, 131.7, 131.1, 124.5, 108.7, 99.6, 34.9, 32.6, ꢀ0.04. FT-IR
ꢀ ꢀ1
C-S S-S
3
1
KBr) 758, 678 (n ) cm . FT-Raman 521 (n ) cm . Elem. anal.: Calcd. for
C H S Si (%): C, 50.80; H, 5.12; S, 36.17; Found(%): C, 50.84; H, 5.06; S, 36.50.
þ
1
5
18 4
ESI HRMS for C H S Si[MþH] : Found 352.9989. Calcd. 352.9977.
1
5
18 4
SUPPORTING INFORMATION
Full experimental detail, characterization data of compound 2 and 3, copies of
NMR spectra, crystallographic structure parameters, x-ray crystallographic infor-
mation files (CIF) for compound 5 (CCDC 920770), S2p of XPS, and the cycling
specific capacity of TMSEDTTA can be found via the Supplementary Content
section of this article’s Web page.
ACKNOWLEDGMENT
We gratefully acknowledge financial support by the National Natural Science
Foundation of China (No. 20872114).
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