Isolation of Hypervalent Group-16 Radicals and Their Application in Organic-Radical Batteries

Article abstract of DOI:10.1021/jacs.5b10774

Using a newly prepared tridentate ligand, we isolated hypervalent sulfur and selenium radicals for the first time and characterized their structures. X-ray crystallography, electron spin resonance spectroscopy, and density functional theory calculations r

Full text of DOI:10.1021/jacs.5b10774

Subscriber access provided by CMU Libraries - http://library.cmich.edu
Communication
Isolation of hypervalent group-16 radicals and
their application in organic-radical batteries
Yasuyuki Imada, Hideyuki Nakano, Ko Furukawa, Ryohei Kishi, Masayoshi Nakano, Hitoshi Maruyama,
Masaaki Nakamoto, Akira Sekiguchi, Masahiro Ogawa, Toshiaki Ohta, and Yohsuke Yamamoto
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.5b10774 • Publication Date (Web): 31 Dec 2015
Downloaded from http://pubs.acs.org on January 3, 2016
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Journal of the American Chemical Society is published by the American Chemical
Society. 1155 Sixteenth Street N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 16
Journal of the American Chemical Society
1
2
3
4
5
6
Isolation of hypervalent group-16 radicals and their applica-
tion in organic-radical batteries
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
†
‡
ǁ
§
§
Yasuyuki Imada, Hideyuki Nakano, Ko Furukawa, Ryohei Kishi, Masayoshi Nakano, Hitoshi
#
#
#
¶
¶
Maruyama, Masaaki Nakamoto, Akira Sekiguchi, Masahiro Ogawa, Toshiaki Ohta, Yohsuke
Yamamoto
*,†
†
Department of Chemistry, Graduate School of Science, Hiroshima University, 1ꢀ3ꢀ1 Kagamiyama, Higashiꢀhiroshima 739ꢀ
8
‡
526, Japan
TOYOTA CENTRAL R&D LABS., INC., Nagakute, Aichi 480ꢀ1192, Japan
ǁ
Center for Instrumental Analysis, Institute for Research Promotion, Niigata University, Niigata 950ꢀ2181, Japan
§
Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaꢀ
ka 560ꢀ8531, Japan
#
Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305ꢀ
8
¶
571, Japan
SR Center, Ritsumeikan University, 1ꢀ1ꢀ1 NojiꢀHigashi, Kusatsu, Shiga, 525ꢀ8577, Japan
Supporting Information Placeholder
6
C) and have not been isolated and structurally characterized by
ABSTRACT: Using a newly prepared tridentate ligand, we isoꢀ
lated hypervalent sulfur and selenium radicals for the first time
and subsequently characterized their structures. Xꢀray crystallogꢀ
raphy, electron spin resonance spectroscopy, and density funcꢀ
tional theory calculations revealed a threeꢀcoordinate hypervalent
structure. Then, utilizing the reversible redox reactions between
Xꢀray analysis. To the best of our knowledge, these radicals are
the only examples of stable sulfuranyl radicals, and no further
attempts to stably isolate these species have been reported.
Chart 1. Bonding types and examples of sulfuranyl radi-
cals.
+
hypervalent radicals and the corresponding anions bearing Li , we
developed organic radical batteries with these compounds as
cathodeꢀactive materials. Furthermore, an allꢀradical battery, with
these compounds as the cathode and a silyl radical as the anode,
was developed and the cell exhibited a practical discharge potenꢀ
tial of approximately 1.8 V and stable cycle performance, demonꢀ
strating the potential of these materials for use in metalꢀfree batꢀ
teries that can replace conventional Liꢀion batteries where Li is
used in the metal form.
Sulfurꢀcentered radicals are recognized as key intermediates in
1
many biological processes and organic syntheses. Among them,
sulfuranyl radicals are considered intermediates in displacement
2
reactions. They have nine formal valence electrons in their neuꢀ
tral threeꢀcoordinate state, giving them a hypervalent structure.
The structures of sulfuranyl radicals are categorized into three
Scheme 1. Thermally stable sulfuranyl radicals (R = H,
tBu).
3
types: pyramidal σ*, Tꢀshaped σ, and Tꢀshaped π (Chart 1a). The
first structure has a twoꢀcenter, threeꢀelectron (2cꢀ3e) bond,
whereas the latter two have a threeꢀcenter, threeꢀelectron (3cꢀ3e)
bond and a threeꢀcenter, fourꢀelectron (3cꢀ4e) bond, respectively.
These structures are experimentally supported by ESR and UVꢀ
3,4
vis results (Chart 1b). However, no detailed structure elucidaꢀ
tion has been reported because they are usually unstable under
ambient conditions. In 1986, Martin et al. reported thermally staꢀ
ble sulfuranyl radicals stabilized by a tridentate ligand (Scheme 1,
A). Although these sulfuranyl radicals were reported to be persisꢀ
tent in solution, they existed in equilibrium with dimers (B and
We have extensively explored the chemistry of hypervalent
compounds containing mainꢀgroup elements by utilizing various
multidentate ligands. In our study of the fluxional behavior of
5
7
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 2 of 16
pentacoordinated phosphorus compounds, we observed that the
barrier of isomerization was increased through the use of a bidenꢀ
neutral species. The crystal structures of 6 and 7 exhibit similar
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
structural features and have slightly asymmetric apical bonds. In 6,
the apical S–O bond lengths are 1.723(2) and 2.395(2) Å, which
are longer than the sum of the covalent bond radii of sulfur and
oxygen atoms (1.71 Å) and shorter than the sum of the van der
7b
tate ligand bearing C F groups instead of CF groups. These
2
5
3
results prompted us to examine the synthesis of stable sulfuranyl
radicals stabilized by a bulky tridentate ligand. We envisioned
that if a tridentate ligand with C F groups instead of CF groups
9
Waals (vdW) radii of sulfur and oxygen atoms (3.32 Å). No inꢀ
2
5
3
was used, dimerization could be inhibited by steric hindrance;
thus, sulfuranyl radicals could be isolated as stable monomers,
thereby enabling their structural characterization.
termolecular interactions between sulfur atoms were observed in
6; the closest intermolecular S···S distance is 6.026 Å, far larger
9
than the sum of the vdW radii of two sulfur atoms (3.70 Å).
However, the intermolecular O···O distance is 2.806 Å, which is
equivalent to the sum of the vdW radii of two oxygen atoms (2.80
Herein, we report the first isolation and structural characterizaꢀ
tion of stable sulfuranyl radicals and their selenium analogs; these
radicals are stabilized by a new tridentate ligand bearing C2F5
groups. Furthermore, utilizing the reversible redox reactions beꢀ
tween the hypervalent radicals and the corresponding anions,
organic radical batteries using these compounds as cathodeꢀactive
materials were developed. An allꢀradical battery, with these comꢀ
pounds as the cathode and a silyl radical as the anode, was also
developed.
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Å), suggesting that intermolecular interactions affect the asymꢀ
metric S–O distance (Figure S6, SI). The O1–S1–O2 angle of
1
67.80(9)° is slightly smaller than the ideal angle between the
apical bonds, i.e., 180°. Similarly, in 7, the two apical Se–O bond
lengths are nonꢀequivalent; Se1–O1 and Se1–O2 are 1.969(4),
1
.886(4) and 2.297(5), 2.382(4) Å (two independent molecules),
respectively, which are longer than the sum of the covalent bond
radii of selenium and oxygen atoms (1.83 Å) and shorter than the
Martin’s tridentate ligand was synthesized via a long and comꢀ
9
8
sum of their vdW radii (3.40 Å). The smallest Se···Se distance is
plicated synthetic route , which prevented us from modifying this
6.100 Å, far larger than the sum of the vdW radii of two selenium
route to prepare a new C F ꢀtype tridentate ligand. Thus, we deꢀ
2
5
9
atoms (4.00 Å) ; however, the intermolecular O···O distance is
signed and established the simple and efficient synthetic route
2
.752, 2.747 Å, indicating intermolecular interactions (Figure S7,
shown in Scheme 2. Ester 1 was treated with C F Li, generated in
2
5
SI).
situ from C F I and MeLi, followed by the addition of an excess
2
5
amount of I to give iodinane 2, a tridentate ligand precursor, in
2
7
9% yield. The trimetallization of 2 was achieved using nꢀBuLi
(
3.3 equivalents), which was then reacted with electrophiles (S or
8
SeCl ) to give hypervalent anions 4-Et N and 5-Et N in yields of
4
4
4
7
5% and 49%, respectively. Cyclic voltammograms of 4-Et N
4
and 5-Et N showed reversible redox peaks at E = 0.83 and 0.81
4
1/2
V (vs. SCE), respectively (Figure S8 and S9, Supporting Inforꢀ
mation (SI)). The oxidation of sulfur anion 4-Et N with one
4
•+
−
equivalent of aminium salt ([4ꢀBrC H ] N SbCl ) in dichloroꢀ
6
4 3
6
methane at room temperature gave a red crystalline solid of hyꢀ
pervalent sulfur radical 6 in 61% yield. Similarly, selenium radiꢀ
cal 7 was obtained from selenium anion 5-Et N as an orange crysꢀ
4
talline solid in 28% yield.
Scheme 2. Synthesis of hypervalent radical 6 and 7.
Figure 1. Crystal structures of 6 (a) and 7 (b). Thermal ellipsoids
are drawn at the 30% probability level. Hydrogen atoms and disꢀ
orders are omitted for clarity. For 7, two independent molecules
exist in the unit cell, but only one is shown. Selected bond lengths
C2F5
O
C2F5
MeO
C2F5
C2F5
O
Br
O
1) C F I, MeLi
OLi
2
5
2
) I2
nBuLi
I
Li
Et2O
THF
8 °C, 1 h
(
Å) and angles (deg) for 6: S1–O1 = 1.723(2), S1–O2 = 2.395(2),
S1–C1 = 1.738(3), O1–S1–O2 = 167.80(9), C1–S1–O1 =
1.98(12), C1–S1–O2 = 75.82(11). Selected bond lengths (Å) and
angles (deg) for 7: Se1–O1 = 1.969(4), 1.886(4), Se1–O2 =
7
O
OLi
C2F5
C2F5
C2F5
MeO
C2F5
C2F5
3
9
1
2
7
9%
2
1
.297(5), 2.382(4), Se1–C1 = 1.870(5), 1.874(5), O1–Se1–O2 =
61.29(15), 161.28(16), C1–Se1–O1 = 84.8(2), 86.6(2), C1–Se1–
C2F5
O
C2F5
O
1
) S8
) tBuOCl
) KOH, Et4NBr
C2F5
2
3
(4-BrC6H4)3N•+ SbCl6
O2 = 76.5(2), 74.7(2).
S
Et4N
S
CH2Cl2
r.t., 2 h
Theoretical calculations were carried out to gain further insight
into the structure of these radicals. The optimized structure of 6,
calculated at the UB3PW91/ccꢀpVTZ level, is symmetric, with
two equivalent S–O bond lengths of 1.819 Å (Figure S12, SI).
The differences in the symmetry and the S–O bond lengths of the
optimized geometry from those of the Xꢀray data are considered
to originate from packing effects in the crystal. In the atomsꢀinꢀ
O
O
C2F5
C2F5
C2F5
C2F5
C2F5
4
7
-Et4N
5%
6
61%
C2F5
O
C2F5
1
2
) SeCl4
) KOH, Et4NBr
C2F5
O
3) PPh3
(4-BrC6H4)3N•+ SbCl6
Se Et4N
O
Se
10
CH2Cl2
r.t., 2 h
molecules (AIM) analysis , bond paths are observed between
O
each S–O bond, and the electron density and Laplacian at the
C2F5
C2F5
2
C2F5
-Et4N
9%
C2F5
bond critical point (bcp) of the S–O bonds (ρbcp and ∇ ρbcp) are
7
5
3
5
28%
0
(
.1472, 0.1475 e/a0 and −0.0713, −0.0726 e/a , respectively
0
2
4
Figure S15, SI). Because negative values of ∇2 ρbcp imply covaꢀ
The molecular structures of radicals 6 and 7 in the solid state
were determined by Xꢀray analysis (Figure 1). No counterꢀions
are contained in the unit cells of 6 and 7, indicating that they are
lent bond character, the observed negative ∇ ρbcp of the S–O
bonds suggest that they exhibit covalent character, indicating
associative interactions. Xꢀray structure of 6 was also analyzed
ACS Paragon Plus Environment

Page 3 of 16
Journal of the American Chemical Society
and shows bond paths between each S–O bond (ρbcp = 0.1797,
(oxidation) and lithiation (reduction) processes that are not obꢀ
served in the curves for the oneꢀelectron redox process (Figure
S25, SI). The similar situation was observed in the selenium anion
3
2
5
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
.0439 e/a0 and ∇
ρ
bcp
2
= −0.2313, 0.1072 e/a ), though small
0
ρbcp and the positive ∇ ρbcp are observed at the longer S–O bond,
indicating weak ionic interaction (Figure S16, SI). Furthermore
the spin density distribution of the optimized structure of 6 was
calculated (Figure S19, SI), and the largest spin density of +0.56
observed at the sulfur atom suggests that 6 is a sulfurꢀcentered
radical. The similar calculation results were obtained for 7, sugꢀ
gesting that 7 is a threeꢀcoordinated seleniumꢀcentered radical
5
-Li cell (Figure 3b and S26). The plateaus were observed at 3.7
V in the first charge process and at approximately 3.0 and 2.3 V in
the subsequent discharge process. In this case, the first discharge
–1
capacity of 76.7 mAh g is similar to the theoretical capacity of a
twoꢀelectron redox process between the anion and cation (77.4
–1
mAh g ). These larger capacities suggest the involvement of
cationic species. For both materials, the plateaus practically disꢀ
appeared after the second cycle, indicating a structural change to
(see SI).
The ESR spectrum of 6 in dichloromethane at room temperaꢀ
16
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
the amorphous phase during the initial oxidation.
ture shows a complicated pattern (Figure 2a). That radical 6 reꢀ
mains the sole species in solution was confirmed by comparison
with a standard radical substance (SI, Figure S21). This spectrum
is reproduced by the hyperfine coupling constant, A, of the proton,
1
3
the fluorine, and the C atoms, as defined in Figure 2b. These
hyperfine coupling constants indicate that 6 has a C symmetric
2
(
1)
structure along the C –S axis. The spectra observed in the lower
temperature (Figure S23, SI) also show the similar coupling patꢀ
tern, suggesting that 6 has the same symmetry in the ground state.
On the other hand, only broad signals were observed in the specꢀ
trum of selenium radical 7 (Figure S24, SI).
Figure 3. Galvanostatic charge–discharge curves of the 4-Li (a)
and 5-Li (b) cells at 0.10 A g between 2.0 and 4.2 V vs. Li/Li .
–1
+
To investigate the redox mechanism during the electrochemical
reactions, we performed ex situ S Kꢀedge XAFS measurements of
the electrode of the 4-Li cell upon cycling (Figure S28, SI). In the
chargeꢀdischarge process, the consecutive spectral changes were
observed and they were in good agreement with the simulated
spectra (see SI). On the basis of these results, we concluded that a
cationic species exists and that a stepwise twoꢀelectron redox
reaction between anion 4-Li (appeared at 2.4 V in Figure 3a) and
the corresponding cation 8 (appeared at 3.7 V in Figure 3a) ocꢀ
curs, as shown in Scheme 3.
Figure 2. Observed ESR spectrum of 6 in CH Cl at room temperꢀ
2
2
Scheme 3. Redox mechanism on the electrode.
ature and the simulated ESR spectrum with parameters g =
2.0089, A H(1) = 0.17 mT, A H(2) = 0.07 mT, A F(1) = 0.08 mT, A F(2)
=
0.06 mT, A C(1) = 1.27 mT.
We subsequently used these hypervalent compounds as cathꢀ
odeꢀactive materials for radical batteries. The Liꢀion batteries
most commonly employed today use an electrode combination
1
1
12
based on a graphite negative electrode and a LiCoO2
,
1
3
14
Figures 4a and 4b show the discharge of 4-Li and 5-Li at variꢀ
ous rates after the cells were slowly charged and maintained at 4.2
V to fully charge the material. A rate of nC corresponds to a full
discharge in 1/n h. At a 1.2C rate, 4-Li and 5-Li achieve 78% and
LiMn O , or LiFePO4 positive electrode. Recently, highꢀ
2
4
performance organic cathode materials for Liꢀion batteries have
attracted extensive research interest because of their sustainabilꢀ
1
5
ity, flexibility, and versatile molecular design. However, their
use in more demanding applications such as sustainable transport
is prevented mainly by the lack of a Li source for use in their
cathode materials. To overcome this drawback, as cathodeꢀactive
materials, we chose anions with a lithium cation (4-Li and 5-Li),
which were prepared from 4-Et N and 5-Et N by countercation
9
9% of their theoretical capacities, respectively (calculated on the
basis of a twoꢀelectron redox process). Even at the highest rate
tested (12C), corresponding to a time of 300 s to fully discharge
the capacity, these materials achieved 53% and 66% of their theoꢀ
retical capacities, respectively. After 50 full charge–discharge
cycles at 1.2C and 12C, approximately 90% of the initial disꢀ
charge capacities were maintained. In the 4-Li cell, 65% of the
discharge capacity at 1.2C was maintained at 12C, whereas 75%
was maintained in the 5-Li cell. The differences in these rate
properties are attributed to the rate of the redox reaction. With
respect to the redox reaction, the selenium anion 5-Li, which exꢀ
hibited better capacity retention, had a faster reaction rate than the
sulfur anion 4-Li.
4
4
exchange (see SI). To investigate their utility as cathodeꢀactive
materials, we initially made a coinꢀtype cell composed of a cathꢀ
ode containing 50 wt% of an active material and a Liꢀmetal anode
with a porous polymer film separator in an electrolyte solution of
1
M LiPF in 1:1 (v/v) ethylene carbonate/diethyl carbonate.
6
Figure 3a shows the galvanostatic charge–discharge profiles of
the sulfur anion 4-Li cell. The first charge curve exhibited a single
+
voltage plateau at 3.9 V vs. Li/Li , and the subsequent discharge
curve exhibited two sloped plateaus at approximately 3.7 and 2.4
–1
V. The first discharge capacity of 64.4 mAh g is surprisingly
larger than the theoretical capacity of a oneꢀelectron redox process
–
1
between the anion and the radical (41.5 mAh g ) and is similar to
–
1
that of a twoꢀelectron redox process (83.0 mAh g ). The differenꢀ
tial capacity curves show two broad peaks during the delithiation
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 4 of 16
as the anode exhibited a practical discharge potential of approxiꢀ
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
mately 1.8 V and stable cycle performance, demonstrating the
potential of these materials for use in metalꢀfree batteries that can
replace conventional Liꢀion batteries where Li is used in the metal
form.
ASSOCIATED CONTENT
Supporting Information
The synthetic, experimental, and calculation procedures, characꢀ
terization data including crystallographic measurements, geomeꢀ
try optimization and calculation results, cyclic voltammograms,
the XAFS measurements and the simulated spectra, differential
capacity curve of the cells. This material is available free of
charge via the Internet at http://pubs.acs.org.
Figure 4. The cycle performance of the discharge processes of the
-Li (a) and 5-Li (b) cells measured at 1.2C, 2.4C, 4.8C, and 12C
for 50 cycles between 2.0 and 4.2 V.
4
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
For more practical use, we decided to replace the Liꢀmetal anꢀ
ode with organic materials. Examples of fully organicꢀbased batꢀ
teries in the literature are limited. Nishide and coworkers emꢀ
ployed a bipolar radical polymer for both electrodes to create a
AUTHOR INFORMATION
Corresponding Author
17
fully organicꢀbased battery with a working potential of 1.3 V.
To develop a fully organicꢀbased battery for our system, we chose
18
yyama@sci.hiroshimaꢀu.ac.jp
Notes
The authors declare no competing financial interests.
a stable persilylꢀsubstituted silyl radical (tBu MeSi) Si·(9) as an
2
3
anodeꢀactive material (Scheme 4). Cyclic voltammograms of
sulfur anion 4-Li and silyl radical 9 display reversible redox proꢀ
+
cesses at E1/2 = 3.7 and 1.7 V (vs. Li/Li , Figure S10 and S11, SI),
ACKNOWLEDGMENT
respectively, and a working potential of approximately 2 V was
expected. Figure 5a shows the charge–discharge curves for the
cell with 4-Li and 9. The charge curve shows a plateau at 2.1 V,
and the discharge curve shows a sloped plateau at approximately
This work was supported by a Grantꢀin Aid for Science Research
on Innovative Areas (No. 24109002, Stimuliꢀresponsive Chemical
Species) from the Ministry of Education, Culture, Sports, Science
and Technology, Japan. The authors are grateful to Central Glass
Co., Ltd., for the generous gift of the iodopentafluoroethane.
1
.8 V, in good agreement with the potential gap between 4-Li and
9
. As shown in Figure 5b, the first discharge capacity at the 1C
–
1
rate was 27.8 mAh g , which corresponds to 67% of the theoretiꢀ
–
1
cal capacity of 4-Li (41.5 mAh g ). The discharge capacity gradꢀ
ually decreased and maintained 50% of the initial value after 50
cycles. However, at 12C, though the first discharge capacity was
REFERENCES
(1) (a) Gara, W. B.; Roberts, B. P. J. Organomet. Chem. 1977, 135, C20–
–
1
C22. (b) Schoneich, C.; Zhao, F.; Madden, K. P.; Bobrowski, K. J. Am.
Chem. Soc. 1994, 116, 4641ꢀ4652. (c) Signor, L.; Knuppe, C.; Hug, R.;
Schweizer, B.; Pfaltz, A.; Jaun, B. Chem.—Eur. J. 2000, 6, 3508ꢀ3516.
2
3.0 mAh g , the discharge capacity after 50 cycles was 89% of
the initial value. The decrease in the capacity was caused by the
dissolution of the sulfur radical into the electrolyte solution. In the
case of the cell cycled at 12C, the sulfur radicals were exposed to
the electrolyte solution for a shorter time than in the case of the
cell cycled at 1C, resulting in better cycle performance.
(d) Faucitano, A.; Buttafava, A.; Mariani, M.; Chatgilialoglu, C. Chem.
Phys. Chem. 2005, 6, 1100ꢀ1107. (e) Kampmeier, J. A.; Hoque, A. M.;
Saeva, F. D.; Wedegaertner, D. K.; Thomsen, P.; Ullah, S.; Krake, J.;
Lund, T. J. Am. Chem. Soc. 2009, 131, 10015ꢀ10022.
(2) (a) Pryor, W. A.; Guard, H. J. Am. Chem. Soc. 1964, 86, 1150ꢀ1152.
Scheme 4. Schematic description of an allꢀradical battery.
(b) Kampmeier, J. A.; Evans, T. R. J. Am. Chem. Soc. 1966, 88, 4096ꢀ
4
5
097. (c) Franz, J. A.; Roberts, D. H.; Ferris, K. F. J. Org. Chem. 1987,
2, 2256ꢀ2262.
(3) (a) Perkins, C. W.; Martin, J. C.; Arduengo, A. J.; Lau, W.; Alegria,
A.; Kochi, J. K. J. Am. Chem. Soc. 1980, 102, 7753ꢀ7759. (b) Chatgiliꢀ
aloglu, C.; Castelhano, L.; Griller, D. J. Org. Chem. 1985, 50, 2516ꢀ2518.
(4) (a) Gara, W. B.; Giles, J. R. M.; Roberts, B. P. J. Chem. Soc. Perkin
Trans. II 1979, 1444ꢀ1450. (b) Chapman, J. S.; Cooper, J. W.; Roberts, B.
P. J. Chem. Soc., Chem. Commun. 1976, 835.
(
5) Perkins, C. W.; Clarkson, R. B.; Martin, J. C. J. Am. Chem. Soc. 1986,
08, 3206ꢀ3210.
6) Perkins, C. W.; Martin, J. C. J. Am. Chem. Soc. 1986, 108, 3211ꢀ
1
(
3
214.
(7) (a) Akiba, K.ꢀy.; Yamashita, M.; Yamamoto, Y.; Nagase, S. J. Am.
Chem. Soc. 1999, 121, 10644ꢀ10645. (b) Jiang, X. D.; Kakuda, K.ꢀi.;
Matsukawa, S.; Yamamichi, H.; Kojima, S.; Yamamoto, Y. Chem. Asian J.
2
007, 2, 314ꢀ323. (c) Yamaguchi, T.; Yamamoto, Y.; Kinoshita, D.;
Akiba, K.ꢀy.; Zhang, Y.; Reed, C. A.; Hashizume, D.; Iwasaki, F. J. Am.
Chem. Soc. 2008, 130, 6894ꢀ6895. (d) Matsukawa, S.; Yamamichi, H.;
Yamamoto, Y.; Ando, K. J. Am. Chem. Soc. 2009, 131, 3418ꢀ3419.
Figure 5. Galvanostatic charge–discharge profiles (a) and cycle
performance (b) of the allꢀradical battery.
(8) Nguyen, T. T.; Amey, R. L.; Martin, J. C. J. Org. Chem. 1982, 47,
1
024ꢀ1027.
(9) Emsley, J. The Elements, 3rd ed.; Oxford University Press: Oxford,
1998.
(10) Bader, R. F. W. Atoms in Molecules―A Quantum Theory; Oxford
University Press: Oxford, 1990.
In summary, we have synthesized, isolated, and structurally
characterized hypervalent sulfur and selenium radicals. The reꢀ
versible redox reaction of the radicals enabled us to apply them in
radical batteries. Their useful properties as cathodeꢀactive materiꢀ
als were confirmed by electrochemical measurements. An allꢀ
radical battery with sulfur anions as the cathode and silyl radicals
(11) (a) Aurbacha, D.; Markovskya, B.; Weissmana, I.; Levia, E.; EinꢀEli,
Y. Electrochim. Acta 1999, 45, 67ꢀ86. (b) Aurbach, D.; Markovsky, B.;
Shechter, A.; EinꢀE1i, Y.; Cohen, H. J. Electrochem. Soc. 1996, 143,
ACS Paragon Plus Environment

Page 5 of 16
Journal of the American Chemical Society
3
809ꢀ3820. (c) Yoshio, M.; Wang, H.; Fukuda, K.; Hara, Y.; Adachi, Y. J.
(14) (a) Malik, R.; Zhou F.; Ceder, G. Nat. Mater. 2011, 10, 587ꢀ590.
Electrochem. Soc. 2000, 147, 1245ꢀ1250.
(b) Yamada, A.; Chung, S. C.; Hinokuma, K. J. Electrochem Soc. 2001,
148, A224ꢀA229.
(15) (a) Armand, M.; S. Grugeon, S.; Vezin, H.; Laruelle, S.; Ribière, P.;
Poizot, P.; Tarascon, J.ꢀM. Nat. Mater. 2009, 8, 120ꢀ125. (b) Morita, Y.;
Nishida, S.; Murata, T.; Moriguchi, M.; Ueda, A.; Satoh, M.; Arifuku, K.;
Sato. K.; Takui, T. Nat. Mater. 2011, 10, 947ꢀ951.
(16) Kim, J.; Manthiram, A. Nature 1997, 390, 265ꢀ267.
(17) Suga, T.; Sugita, S.; Ohshiro, H.; Oyaizu, K.; Nishide, H. Adv. Ma-
ter. 2011, 23, 751ꢀ754.
(18) Maruyama, H.; Nakano, H.; Nakamoto, M; Sekiguchi, A. Angew.
Chem. Int. Ed. 2014, 53, 1324ꢀ1328.
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(
12) (a) Cho, J.; Kim, Y. J.; Park, B. Chem. Mater. 2000, 12, 3788ꢀ3791.
b) Amatucci, G.G.; Tarascon, J. M.; Klein, L. C. Solid State lonics 1996,
3, 167ꢀ173. (c) Okubo, M.; Hosono, E.; Kim, J.; Enomoto, M.; Kojima,
N.; Kudo, T.; Zhou, H.; Honma, I. J. Am. Chem. Soc. 2007, 129, 7444ꢀ
452.
13) (a) Tarascon, J. M.; Wang, E.; Shokoohi, F. K.; McKinnon, W. R.;
(
8
7
(
Colson, S. J. Electrochem. Soc. 1991, 138, 2859ꢀ2864. (b) Kim, D. K.;
Muralidharan, P.; Lee, H.ꢀW.; Ruffo, R.; Yang, Y.; Chan, C. K.; Peng, H.;
Huggins, R. A.; Cui, Y. Nano Lett. 2008, 8, 3948ꢀ3952.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 6 of 16
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Table of content
33x39mm (300 x 300 DPI)
1
ACS Paragon Plus Environment

Page 7 of 16
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Crystal structures of 6 (a) and 7 (b). Thermal ellipsoids are drawn at the 30% probability level. Hydrogen
atoms and disorders are omitted for clarity. For 7, two independent molecules exist in the unit cell, but only
one is shown. Selected bond lengths (Å) and angles (deg) for 6: S1–O1 = 1.723(2), S1–O2 = 2.395(2), S1–
C1 = 1.738(3), O1–S1–O2 = 167.80(9), C1–S1–O1 = 91.98(12), C1–S1–O2 = 75.82(11). Selected bond
lengths (Å) and angles (deg) for 7: Se1–O1 = 1.969(4), 1.886(4), Se1–O2 = 2.297(5), 2.382(4), Se1–C1 =
1
.870(5), 1.874(5), O1–Se1–O2 = 161.29(15), 161.28(16), C1–Se1–O1 = 84.8(2), 86.6(2), C1–Se1–O2 =
6.5(2), 74.7(2).
45x90mm (300 x 300 DPI)
7
1
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 8 of 16
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Observed ESR spectrum of 6 in CH2Cl2 at room temperature and the simulated ESR spectrum with
parameters g = 2.0089, A H(1) = 4.7 MHz, A H(2) = 2.1 MHz, A F(1) = 2.3 MHz, A F(2) = 1.8 MHz, A C(1)
= 35.5 MHz.
1
39x74mm (300 x 300 DPI)
ACS Paragon Plus Environment

Page 9 of 16
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Galvanostatic charge–discharge curves of the 4-Li (a) and 4-Li (b) cells at 0.10 A g–1 between 2.0 and 4.2 V
vs. Li/Li+.
1
74x64mm (300 x 300 DPI)
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 10 of 16
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
The cycle performance of the discharge processes of the 4-Li (a) and 5-Li (b) cells measured at 1.2C, 2.4C,
4.8C, and 12C for 50 cycles between 2.0 and 4.2 V.
173x65mm (300 x 300 DPI)
ACS Paragon Plus Environment

Page 11 of 16
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Galvanostatic charge–discharge profiles (a) and cycle performance (b) of the all-radical battery.
171x64mm (300 x 300 DPI)
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 12 of 16
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Bonding types and examples of sulfuranyl radicals.
130x81mm (300 x 300 DPI)
ACS Paragon Plus Environment

Page 13 of 16
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Thermally stable sulfuranyl radicals (R = H, tBu).
1
34x38mm (300 x 300 DPI)
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 14 of 16
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Synthesis of hypervalent radical 6 and 7.
1
38x134mm (300 x 300 DPI)
ACS Paragon Plus Environment

Page 15 of 16
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Redox mechanism on the electrode.
1
17x38mm (300 x 300 DPI)
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 16 of 16
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Scheme 4
133x37mm (300 x 300 DPI)
ACS Paragon Plus Environment