Photooxidation and reproduction of pentacene derivatives substituted by aromatic groups

Article abstract of DOI:10.1016/j.tet.2007.07.021

Pentacene derivatives substituted by aromatic groups at the 6,13-positions were prepared and investigated for their electronic properties and the photoaddition reaction with oxygen. The pentacene derivatives substituted by 2-thienyl and phenyl groups reac

Full text of DOI:10.1016/j.tet.2007.07.021

Tetrahedron 63 (2007) 9699–9704
Photooxidation and reproduction of pentacene derivatives
substituted by aromatic groups
a
a
a
a
Katsuhiko Ono,a, Hiroaki Totani, Takao Hiei, Akihiro Yoshino, Katsuhiro Saito,
*
Katsuya Eguchi,b Masaaki Tomura,c Jun-ichi Nishidad and Yoshiro Yamashitad
aDepartment of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya 466-8555, Japan
bDow Corning Toray Co., Ltd, Chigusa, Ichihara 299-0108, Japan
cInstitute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan
dDepartment of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology,
Nagatsuta, Midori-ku, Yokohama 226-8502, Japan
Received 6 July 2007; accepted 9 July 2007
Available online 13 July 2007
Abstract—Pentacene derivatives substituted by aromatic groups at the 6,13-positions were prepared and investigated for their electronic
properties and the photoaddition reaction with oxygen. The pentacene derivatives substituted by 2-thienyl and phenyl groups reacted with
oxygen in solution under light and afforded their endoperoxides. These first-order kinetic constants were evaluated to be 1.5ꢀ10ꢁ3 sꢁ1
and 2.7ꢀ10ꢁ3 sꢁ1. The pentacene derivative with pentafluorophenyl groups was relatively stable in solution. The thermolysis and photolysis
of the endoperoxide with 2-thienyl groups in solution afforded the pentacene derivative with yields of 30 and 44%, respectively. In addition,
UV irradiation (254 nm) of the thin film of the endoperoxide was studied, which indicated the reproduction of the pentacene derivative.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
On the other hand, the Diels–Alder adducts of pentacene
were synthesized and investigated as pentacene precursors
in the study of solution-processed OFETs.8,9 The adducts
of pentacene with N-sulfinyl-tert-butylcarbamate,8a N-sulfi-
nylacetamide,8b and carbon monoxide8c formed the thin
films of pentacene after their thermal decomposition pro-
cesses. Their OFET properties were almost similar to those
observed in the devices using pentacene films formed by
vacuum deposition. Furthermore, the photolysis of the ad-
duct with a 1,2-diketone unit under argon formed the thin
film of pentacene.8d In the synthetic studies on pentacene
derivatives substituted by aromatic groups at the 6,13-
positions, we investigated the photooxidation of pentacenes
1b–d affording their endoperoxides and the reproduction of
the pentacene derivatives (Fig. 1). In this paper, we report the
preparation, properties, and photoreaction of pentacene
derivatives 1b–d and the deoxygenation reactions of an
endoperoxide.
Pentacene (1a) is one of the highly attractive compounds in
organic field-effect transistors (OFETs)1–3 since its thin
films formed by vacuum deposition show a good perfor-
mance of p-type semiconducting properties with mobilities
of 35 and 58 cm2 Vꢁ1 sꢁ1 at the temperatures of 290 and
225 K, respectively.2 These values are comparable to those
of the hydrogenated amorphous silicon devices.3 However,
the application of pentacene for preparing OFET films is
limited to the vacuum-deposition process since pentacene
is insoluble in common organic solvents and is unstable in
solution. Therefore, synthetic studies on various pentacene
derivatives have been conducted.4 Among these compounds,
6,13-functionalized pentacenes have been synthesized. The
introduction of ethynyl groups into the 6,13-positions of
pentacene led to the modification of molecular stacking,
resulting in high semiconducting properties.5 Recently, a
pentacene derivative with 2-thienyl groups (1b) was synthe-
sized and a hole mobility of 0.10 cm2 Vꢁ1 sꢁ1 was observed
in an OFET device using it.6 The synthesis and crystal
structures of bis(alkylthio)pentacenes were also reported.7
R
S
a
R = H
R =
b
R =
R =
F
F
F
F
c
d
F
R
Keywords: Pentacene; Photooxidation; Endoperoxide; Deoxygenation.
* Corresponding author. Tel./fax: +81 52 735 5407; e-mail: ono.
katsuhiko@nitech.ac.jp
1
Figure 1. Structure of pentacene derivatives 1a–d.
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.07.021

9700
K. Ono et al. / Tetrahedron 63 (2007) 9699–9704
2. Results and discussion
this result is due to the presence of the thienyl groups. The
cyclic voltammetry (CV) of pentacenes 1b–d in dichloro-
methane showed reversible oxidation and reduction waves.
The half-wave potentials are summarized in Table 1. The
oxidation potential of 1d is higher than those of 1b and 1c,
and the reduction potential of 1d is higher than those of 1b
and 1c. These results indicated that two pentafluorophenyl
groups increased the electron affinity of the pentacene
moiety of 1d.
Pentacene derivatives 1b–d were synthesized as shown in
Scheme 1.10 6,13-Pentacenequinone (2)11 reacted with aryl-
lithium reagents (3 mol equiv) to afford the corresponding
diarylpentacenediols (3b–d) with yields of 48–80%. Com-
pounds 3c and 3d were obtained as single isomers. Com-
pound 3b was identified as a mixture of two regioisomers
(1.7:1) and it was used for the following reaction. Pentacenes
1b–d with yields of 47–73% were prepared by the reaction
of compounds 3b–d with NaH2PO2$H2O (7 mol equiv)
and NaI (5 mol equiv) in refluxing acetic acid. The resulting
solids were purified by sublimation at 300–320 ꢂC under
10ꢁ3 Torr to provide deep purple or deep blue crystals (1b
and 1d: mp >300 ꢂC, 1c: mp 292–293 ꢂC). These com-
pounds were soluble in dichloromethane and chloroform.
The solutions of 1b and 1c were very sensitive to light in
air and the decolorization of the solutions was observed.
However, pentacene 1d was relatively stable in solution.
The structural determination of these compounds was per-
formed using spectral data and elemental analysis.
Pentacenes 1b–d were soluble in common organic solvents
in contrast to pentacene 1a. In order to investigate the behav-
ior of these compounds in solution, decolorization by irradi-
ation was studied. The solution of 1b with a concentration
of 10ꢁ5 M in dichloromethane gradually became colorless
by exposure to room light, and the color of pentacene disap-
peared after 20 min (Fig. 2). The decolarization of 1c as well
as 1b was observed.12 However, the decolarization of 1d was
very slow due to the bulky electron-withdrawing groups
substituted at the 6,13-positions of pentacene. The color of
the pentacene could still be observed 2 h later (Fig. 2). The
absorption spectrum of 1b was monitored depending on
the exposure time as shown in Figure 3. The absorption
bands gradually decreased, and this decay obeyed first-order
kinetics. The kinetic constant (k) was measured to be
1.5ꢀ10ꢁ3 sꢁ1. This value was comparable to that of 1c
The absorption bands based on the pentacene moieties were
observed in the range between 450 and 650 nm. The absorp-
tion maxima are listed in Table 1. The maxima of 1b are
slightly red-shifted as compared to those of 1c and 1d, and
O
HO
R
NaH2PO2
NaI
RLi
1
THF
AcOH
HO
R
O
2
3
F
F
F
F
S
,
,
F
R =
Scheme 1. Synthesis of pentacene derivatives 1b–d.
(k¼2.7ꢀ10ꢁ3 sꢁ1), which was reported as k¼
Table 1. Absorption maximaa and half-wave potentialsb of 1
2.32ꢀ10ꢁ3 s
.
ꢁ1 12 The kinetic constant of 1d was evaluated
ox
1/2
red
E /V
1/2
1
to be 3ꢀ10ꢁ5 sꢁ1. According to the H NMR analysis of
1b, the decolorization cleanly proceeded to yield endoperox-
ide 4 (Scheme 2). Therefore, the reaction was a photoaddi-
tion reaction of pentacene with oxygen.13 Thus, 100 mg of
pentacene 1b was dissolved in dichloromethane (100 mL),
and the solution filtered through a Pyrex filter was exposed
Compound
lmax/nm
E
/V
1b
1c
1d
605, 560, 521
600, 555, 517
595, 550, 512
+0.31
+0.23
+0.58
ꢁ1.72
ꢁ1.85
ꢁ1.53
a
In CH2Cl2.
nBu4NClO4 (0.1 M) in CH2Cl2, Pt electrode, V versus Fc/Fc+.
b
Figure 2. Color of the solutions of 1b (left), 1c (center), and 1d (right); (a) before irradiation and (b) after irradiation for 2 h.

K. Ono et al. / Tetrahedron 63 (2007) 9699–9704
9701
Figure 3. UV–vis absorption spectra of 1b under light.
to sunlight in air for 2 h. After removal of the solvent, the
residue was filtered and washed with hexane to yield
88 mg of the product (81% yield). The molecular structure
of endoperoxide 4 was investigated by X-ray crystallo-
graphic analysis. A single crystal of 4 was obtained by re-
crystallization from benzene. The molecule has a bridge
structure with an oxygen molecule, which bonds to penta-
cene at the 6,13-positions (Fig. 4). The oxygen moiety is
located between the S atoms of the thienyl groups. The intra-
molecular distances between the O atoms and the S atoms
Figure 4. Molecular structure of endoperoxide 4.
other types of decomposition reactions take place upon heat-
ing. UV irradiation (254 nm) of the solution of endoperoxide
4 in decalin-d18 under argon for 10 min produced pentacene
1b with a yield of 44%. After UV irradiation (254 nm) of the
thin film of endoperoxide 4 was carried out in air for 8 min,
the absorption bands on the pentacene moiety of 1b were ob-
served in the UV–vis spectrum (Fig. 5). This result indicated
that the deoxygenation reaction in the solid state proceeded
by the UV irradiation. Therefore, endoperoxide 4 is also a
candidate for the photopatternable pentacene precursors used
in OFETs. Further investigation on the UV irradiation of the
thin film of 4 is under progress. If the thin films of pentacene
1b prepared by the photolysis of endoperoxide 4 successfully
show semiconducting properties, the conversion between 1b
˚
are 2.71 and 2.78 A. These values are shorter than the sum
˚
of their van der Waals radii (3.32 A). The molecular struc-
ture is analogous to those of the photopatternable pentacene
precursors used in OFETs.8
The colorless solution of endoperoxide 4 in decahydronaph-
thalene (decalin) turned purple upon heating, indicating the
reproduction of pentacene 1b (Scheme 2). The absorption
bands based on the pentacene moiety were observed in the
UV–vis spectrum after the thermal decomposition. Accord-
1
ing to the H NMR analysis upon heating at 170 ꢂC for
10 min in decalin-d18, the thermal decomposition of 4
gave pentacene 1b with a yield of 30%. This value is higher
than those observed for the thermal decomposition of the en-
doperoxide of 1c (7–14% yields).14 During the melting point
measurement of endoperoxide 4, the white solid was tinged
with blue at around 130 ꢂC, and then this solid turned black
at 180 ꢂC. The thermogravimetric analysis (TGA) of endo-
peroxide 4 demonstrated a weight loss of 2.7% at 188 ꢂC.
This is corresponding to the change from a white solid to
a black one in the melting point measurement. The weight
loss is smaller than the theoretical O2 loss (6.8%) by thermal
decomposition [FW 474 (4)/FW 442 (1b)]. This result
may be attributed to the molecular packing in the solid and
Figure 5. UV–vis absorption spectrum after UV irradiation (254 nm) of the
film of endoperoxide 4.
S
S
O
O
sunlight in CH2Cl2
O2
+
or UV in decalin
UV in film
S
S
1b
Scheme 2. Photooxidation of 1b and deoxygenation of 4.
4

9702
K. Ono et al. / Tetrahedron 63 (2007) 9699–9704
and 4 is of interest as an ecological technology for the fabri-
cation of solution-processed OFETs.
7.97 (dd, J¼6.2, 3.2 Hz, 2.52H), 8.20 (s, 1.48H), 8.54 (s,
2.52H).Dataforthemajorproductareasfollows:Orangecrys-
tals. Decomp. >190 ꢂC. IR (KBr): 3513, 3436, 3057, 1231,
1092, 988, 955, 828, 748, 698 cmꢁ1 1H NMR (CDCl3,
.
3. Conclusions
300 MHz): d 3.10 (s, 2H), 5.76 (dd, J¼3.7, 0.9 Hz, 2H), 6.21
(dd, J¼5.0, 3.7 Hz, 2H), 6.84 (dd, J¼5.0, 0.9 Hz, 2H), 7.59
(dd, J¼6.2, 3.3 Hz, 4H), 7.90 (dd, J¼6.2, 3.3 Hz, 4H), 8.40
(s, 4H). 13C NMR (acetone-d6, 50 MHz): d 73.2, 125.5,
126.1, 126.5, 127.1, 127.4, 128.9, 133.8, 140.8, 151.8.
MS m/z (%): 458 (100) [M+ꢁH2O]. Anal. Calcd for
C30H20O2S2: C, 75.60; H, 4.23. Found: C, 75.45; H, 4.22.
We synthesized pentacene derivatives substituted by aro-
matic groups at the 6,13-positions (1b–d). The absorption
bands based on the pentacene moieties were observed in
a similar wavelength region. The electron-donating ability
and the electron affinity depended on the aromatic groups.
Although these compounds were more stable in solution
than pentacene 1a, compounds 1b and 1c were highly reac-
tive with oxygen under irradiation and afforded their endo-
peroxides. Pentacene 1d was relatively stable in solution.
The thermolysis and photolysis of endoperoxide 4 in
solution afforded pentacene 1b with yields of 30 and 44%,
respectively. UV irradiation of the thin film of endoperoxide
4 indicated the reproduction of pentacene 1b. These deoxy-
genation reactions are of interest for the film formation tech-
nology, which is of use in OFETs because pentacene 1b was
reported as a good semiconductor in the thin films formed by
vacuum deposition. Further investigation on the photolysis
of endoperoxide 4 in film is under progress.
Similar reaction conditions were applied to the synthesis of
compounds 3c6,15 and 3d. These compounds were obtained
as a single isomer.
Compound 3c: Yield 50%. Decomp. >244 ꢂC. IR (KBr):
1
3526, 3434, 3056, 1493, 1096, 868, 694 cmꢁ1. H NMR
(CDCl3, 300 MHz): d 3.04 (s, 2H), 6.72–6.89 (m, 10H),
7.56 (dd, J¼6.3, 3.2 Hz, 4H), 7.94 (dd, J¼6.3, 3.2 Hz,
4H), 8.40 (s, 4H). MS m/z (%): 464 (6) [M+], 446 (42),
430 (45), 341 (100). Anal. Calcd for C34H24O2: C, 87.90;
H, 5.21. Found: C, 87.89; H, 5.21.
Compound 3d: Yield 48%. Decomp. >200 ꢂC. IR (KBr):
3301, 1526, 1487, 993, 951 cmꢁ1 1H NMR (CDCl3,
.
4. Experimental
4.1. General
300 MHz): d 3.55 (s, 2H), 7.52 (dd, J¼6.2, 3.3 Hz, 4H),
7.73 (s, 4H), 7.78 (dd, J¼6.2, 3.3 Hz, 4H). MS m/z (%):
644 (31) [M+], 627 (30), 610 (100), 460 (37), 309 (31).
Anal. Calcd for C34H14F10O2: C, 63.37; H, 2.19. Found: C,
63.60; H, 2.23.
Melting points were measured with a Yanaco micro melting
point apparatus and are uncorrected. IR and UV–vis absorp-
tion spectra were obtained with JASCO FT/IR-5300 and
Hitachi U-3500 spectrometers, respectively. Mass spectra
(EI) were determined with a Hitachi M-2000S mass spectro-
meter operating at 70 eV by a direct inlet system. Elemental
analyses were performed with a Perkin–Elmer 2400II ana-
4.1.2. Preparation of 6,13-diarylpentacene (1b–d).10
A
solution of compound 3b (a mixture of two isomers)
(0.60 g, 1.26 mmol), NaH2PO2$H2O (1.00 g, 9.43 mmol),
and NaI (1.00 g, 6.67 mmol) in acetic acid (7 mL) was re-
fluxed for 30 min. A deep blue solid was precipitated. After
cooling, the precipitate was filtered and washed with water
to give a deep blue solid (0.56 g), which was sublimed at
320 ꢂC under 10ꢁ3 Torr to afford pentacene 1b6,10 (0.26 g,
47%) as deep blue crystals. Mp >300 ꢂC. IR (KBr): 3048,
1
lyzer. H and 13C NMR spectra were recorded with Varian
GEMINI (300 and 50 MHz) and Bruker AVANCE600 (600
and 150 MHz) spectrometers with tetramethylsilane as an
internal standard.
1364, 1321, 1221, 874, 828, 735, 696 cmꢁ1 1H NMR
.
4.1.1. Preparation of 6,13-dihydroxy-6,13-diarylpentacene
(3b–d).10 nBuLi in hexane (1.60 M, 2.43 mL, 3.89 mmol)
was added dropwise to a solution of 2-bromothiophene
(0.38 mL, 3.89 mmol) in dry THF (15 mL) at ꢁ78 ꢂC under
nitrogen. The solution was stirred for 30 min. After addition
of 6,13-pentacenedione (0.40 g, 1.30 mmol), the reaction
mixture was stirred at ꢁ78 ꢂC for 1 h and at room temperature
for 2 h. The mixture was poured into water (20 mL) and ethyl
acetate (40 mL) was added. The organic layer was separated
and the aqueous layer was extracted with ethyl acetate
(40 mLꢀ2). The combined organic solutions were washed
with water and dried over Na2SO4. After removal of the sol-
vent, the residue was chromatographed on silica gel (hexane/
CH2Cl2¼4:6/2:8) to afford compound 3b6,10 (0.49 g, 80%)
as a mixture of two isomers (1.7:1). 1H NMR (CDCl3,
300 MHz): d 2.93 (s, 0.74H), 3.11 (s, 1.26H), 5.85 (dd,
J¼3.7, 1.0 Hz, 1.26H), 6.26 (dd, J¼5.1, 3.7 Hz, 1.26H),
6.78 (dd, J¼3.6, 1.2 Hz, 0.74H), 6.89 (dd, J¼5.1, 1.0 Hz,
1.26H), 6.97 (dd, J¼5.1, 3.6 Hz, 0.74H), 7.34 (dd, J¼5.1,
1.2 Hz, 0.74H), 7.51 (dd, J¼6.2, 3.3 Hz, 1.48H), 7.59 (dd,
J¼6.2, 3.2 Hz, 2.52H), 7.87 (dd, J¼6.2, 3.3 Hz, 1.48H),
(CDCl3, 600 MHz): d 7.28 (dd, J¼6.7, 3.1 Hz, 4H), 7.40
(dd, J¼3.3, 1.1 Hz, 2H), 7.46 (dd, J¼5.3, 3.3 Hz, 2H),
7.77 (dd, J¼5.3, 1.1 Hz, 2H), 7.80 (dd, J¼6.7, 3.1 Hz,
4H), 8.50 (s, 4H). 13C NMR (CDCl3, 150 MHz): d 125.4,
125.5, 127.2, 127.4, 128.6, 130.0, 130.0, 130.1, 131.4,
139.5. MS m/z (%): 442 (100) [M+]. Anal. Calcd for
C30H18S2: C, 81.41; H, 4.10. Found: C, 81.41; H, 3.93.
Similar reaction conditions were applied to the synthesis of
pentacenes 1c6,15 and 1d.
Compound 1c: Yield 73%. Deep violet crystals. Mp 292–
293 ꢂC. IR (KBr): 3056, 1441, 1383, 1101, 1026, 878,
750 cmꢁ1. MS m/z (%): 430 (100) [M+]. Anal. Calcd for
C34H22: C, 94.85; H, 5.15. Found: C, 94.79; H, 5.00.
Compound 1d: Yield 69%. Deep violet crystals. Mp
>300 ꢂC. IR (KBr): 1495, 1364, 1098, 990, 781, 735 cmꢁ1
.
1H NMR (CDCl3, 600 MHz): d 7.37 (dd, J¼6.7, 3.0 Hz,
4H), 7.85 (dd, J¼6.7, 3.0 Hz, 4H), 8.22 (s, 4H). 13C NMR
(CDCl3, 150 MHz): d 112.7 (t, J¼20.2 Hz), 122.6, 123.9,

K. Ono et al. / Tetrahedron 63 (2007) 9699–9704
9703
126.5, 128.3, 128.6, 132.3, 138.2 (d, J¼252.6 Hz), 141.8 (d,
J¼252.8 Hz), 145.3 (d, J¼243.9 Hz). MS m/z (%): 610
(100) [M+]. Anal. Calcd for C34H12F10: C, 66.90; H, 1.98.
Found: C, 66.70; H, 1.95.
increasing temperature rate of 10 ꢂC minꢁ1. The profile re-
vealed a weight loss of 2.7% at 188 ꢂC. The weight loss
was smaller than the theoretical O2 loss (6.8%) by thermal
decomposition [FW 474 (4)/FW 442 (1b)].
4.2. Electrochemical measurements
4.7. Photolysis of endoperoxide 4
CV was performed with a Toho Technical Research polari-
zation unit PS-07 potentiostat/galvanostat. The CV studies
of compounds 1b–d were carried out in dichloromethane
with 0.1 M nBu4NClO4 using Pt and SCE electrodes. The
values are expressed in potentials versus Fc/Fc+.
UV irradiation of the solution of 4 in decalin-d18 was exam-
ined for 10 min under bubbling argon using UV lamps
(254 nm, 15 Wꢀ6). The conversion yield of pentacene 1b
was evaluated to be 44% by the 1H NMR spectra. UV irradi-
ation of the thin film of 4 was carried out in air for 8 min
using a UV lamp (254 nm, 610 mW cmꢁ2). The film was
dissolved in dichloromethane and the UV–vis spectrum of
the solution was measured. The spectrum of 4 without UV
irradiation was also measured as a reference.
4.3. Photooxidation reaction of pentacene 1b
A solution of pentacene 1b (100 mg, 0.23 mmol) in dichloro-
methane (100 mL) was exposed to sunlight through a Pyrex
filter in air for 2 h. After removal of the solvent, the residue
was washed with hexane to give endoperoxide 4 (88 mg,
81%). Decomp. >188 ꢂC. IR (KBr): 3430, 1609, 1233,
Acknowledgements
1
1171, 951, 878, 841, 750, 704 cmꢁ1. H NMR (CDCl3,
This work was supported by a Grant-in-Aid (Nos. 17750037,
17550033) from the Ministry of Education, Culture, Sports,
Science, and Technology, Japan. We would like to thank
Yazaki Memorial Foundation for Science and Technology
for their financial support. We thank Research Center
for Molecular-Scale Nanoscience, Institute for Molecular
Science, for the crystal analysis.
600 MHz): d 7.46 (dd, J¼6.2, 3.2 Hz, 4H), 7.50 (dd, J¼5.1,
3.6 Hz, 2H), 7.66 (dd, J¼3.6, 1.2 Hz, 2H), 7.68 (dd, J¼5.1,
1.2 Hz, 2H), 7.77 (dd, J¼6.2, 3.2 Hz, 4H), 7.84 (s, 4H). 13C
NMR (CDCl3, 150 MHz): d 84.7, 122.3, 126.3, 126.8,
126.9, 127.7, 128.3, 132.6, 134.0, 136.2. MS (EI) m/z (%):
475 (100) [M++1], 459 (74), 443 (57). UV (CH2Cl2): lmax
(log 3) 280 sh (4.29), 250 (4.93) nm. HRMS(EI) calcd for
C30H18O2S2 474.0748, found 474.0755.
References and notes
4.4. X-ray crystallographic analysis of 4
1. (a) Reese, C.; Roberts, M.; Ling, M.; Bao, Z. Mater. Today
2004, 7, 20; (b) Klauk, H.; Halik, M.; Zschieschang, U.;
Schmid, G.; Radlik, W.; Weber, W. J. Appl. Phys. 2002, 92,
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3. Lin, Y.-Y.; Gundlach, D. J.; Nelson, S. F.; Jackson, T. N. IEEE
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A single crystal was prepared by recrystallization from
benzene. Crystal data are as follows: 0.25ꢀ0.12ꢀ0.12 mm,
C30H18O2S2$6(H2O), M¼570.59 (C30H18O8S2), colorless
prism, tetragonal, space group I41/a, a¼29.20(2), b¼
3
˚
˚
29.20(2), c¼13.918(9) A, V¼11,866(14) A , Z¼16, Dc¼
1.242 g cmꢁ3, m¼0.222 mmꢁ1, F(000)¼4704. Reflection
data were collected with a Rigaku MSC Mercury CCD dif-
fractometer using graphite-monochromated Mo Ka radiation
˚
(l¼0.71070 A) at 173 K. No absorption correction was
4. Bendikov, M.; Wudl, F.; Perepichka, D. F. Chem. Rev. 2004,
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applied. The structure was solved using the direct method
(SHELXS-97).16 All non-hydrogen atoms were refined
anisotropically by the full-matrix least-squares (SHELXL-
97)17 and all hydrogen atoms were placed in geometrically
calculated positions and refined by using a rigid model.
The final values of R1¼0.1168, GOF¼1.012, and max./
5. (a) Payne, M. M.; Parkin, S. R.; Anthony, J. E.; Kuo, C.-C.;
Jackson, T. N. J. Am. Chem. Soc. 2005, 127, 4986; (b)
Sheraw, C. D.; Jackson, T. N.; Eaton, D. L.; Anthony, J. E.
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Parkin, S. R. Org. Lett. 2002, 4, 15; (d) Anthony, J. E.;
Brooks, J. S.; Eaton, D. L.; Parkin, S. R. J. Am. Chem. Soc.
2001, 123, 9482.
min. residual electron density¼0.474/ꢁ0.403 eAꢁ3 were ob-
˚
tained for 6756 unique reflections [I>2s(I)]. CCDC 613494.
6. Miao, Q.; Chi, X.; Xiao, S.; Zeis, R.; Lefenfeld, M.; Siegrist, T.;
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