Pentacene precursors for solution-processed OFETs

Article abstract of DOI:10.1016/j.tet.2010.06.051

15-Acetoxy- and 15-hydroxy-6,13-dihydro-6,13-ethanopentacenes sublimed over 300 °C and no pentacene was formed below the temperature. The precursors bearing chlorinated epithiomethano bridges suffered complicated decomposition to give oligomeric pentacene derivatives. The precursor bearing an epithio-oxomethano bridge underwent smooth and clean conversion to pentacene by heat or light. An organic field-effect transistor fabricated by the spin-coating method of the precursor followed by light irradiation at 120 °C showed a good FET performance of μ=2.5×10^-2 cm² V ^-1 s^-1 and on/off ratio=3.8×10⁴.

Full text of DOI:10.1016/j.tet.2010.06.051

Tetrahedron 66 (2010) 6889e6894
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Pentacene precursors for solution-processed OFETs
Hiroki Uoyama, Hiroko Yamada, Tetsuo Okujima, Hidemitsu Uno *
Department of Chemistry and Biology, Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577, Japan
a r t i c l e i n f o
a b s t r a c t
ꢀ
Article history:
Received 10 May 2010
Received in revised form 17 June 2010
Accepted 18 June 2010
Available online 25 June 2010
15-Acetoxy- and 15-hydroxy-6,13-dihydro-6,13-ethanopentacenes sublimed over 300 C and no pen-
tacene was formed below the temperature. The precursors bearing chlorinated epithiomethano
bridges suffered complicated decomposition to give oligomeric pentacene derivatives. The precursor
bearing an epithioeoxomethano bridge underwent smooth and clean conversion to pentacene by heat
or light. An organic field-effect transistor fabricated by the spin-coating method of the precursor
ꢀ
ꢂ2
2
ꢂ1 ꢂ1
s and
followed by light irradiation at 120 C showed a good FET performance of
m
¼2.5ꢁ10 cm V
Keywords:
Pentacene
Retro-DielseAlder reaction
Photochemical cycloreversion
Organic field-effect Transistor
Thermolysis
4
on/off ratio¼3.8ꢁ10 .
Ó 2010 Elsevier Ltd. All rights reserved.
1
. Introduction
(460 nm). Its solution-processed OFET showed high performance
2
ꢂ1 ꢂ1
6 12
(mobility: 0.34 cm V
s
; on/off ratio: 2.0ꢁ10 ). In order to make
Organic field-effect transistors (OFETs) have attracted much at-
high performance OFETs of pentacene by the solution process, we
started to explore new precursors of pentacene. In this paper, we
discuss our results on behavior of such pentacene precursors.
1
tention as a flexible and low-costdevice. Pentacene-OFETsfabricated
byavacuum deposition method showed high mobilityand a large on/
off ratio. However, the vacuum deposition method has some disad-
2
vantages. For an example, the preparation of large-area devices re-
quires very high cost. A solutionprocess such as a spin- or dip-coating
method is relatively unexpensive and thought to be alternative.
However, this method hardly used for the preparation of pentacene
2
2
. Results and discussion
.1. Synthesis of pentacene precursors
3
devices due to its low solubility in common solvents. Müllen and co-
Preparation of pentacene precursors was shown in Scheme 1.
workers overcame this problem by use of a soluble precursor of
pentacene, which was converted to pentacene directly on a substrate
Acetoxyethylene-bridged pentacene 1 was prepared by the
DielseAlder reaction of pentacene and vinyl acetate in 66% yield
according to the literature. Hydrolysis of 1 with sodium meth-
oxide gave hydoxyethylene-bridged derivative 2 in 87% yield.
Oxidation of 2 with the DesseMartin reagent afforded 3 in 72%
yield. Thiophosgene adduct 4 and its hydrolized derivative 5 were
4
by the retro-DielseAlder reaction. The fabricated pentacene OFET
13
2
ꢂ1 ꢂ1 4b
s . Since then,
was reported to have a high mobility of 0.1 cm V
14
several pentacene OFETs using its DielseAlder adducts as precursors
5
have been reported: (N-sulfinylacetamide adduct: 0.89; N-sulfinyl-
6
n-butylcarbamate adduct: 0.068; N-sulfinylbenzamide adduct:
15
prepared according to the literatures. Contrary to the liter-
ature,
7
8
0
.05, N-sulfinylmethacryl-amide adduct: 0.021; N-sulfinyl-tert-
15a
adduct 4 was easily isolated by recrystallization in 57%
9
butylcarbamate adduct: 0.25; and bis(ethylenedioxo)methano ad-
yield. Hydrolysis of 4 with silica gel afforded hydrolized derivative
in 79% yield. Oxidation of adduct 4 was carried out by one
equivalent of m-CPBA to give sulfoxide 6 in 78% yield.
ꢂ6
2
ꢂ1 ꢂ1 10
s ). PentaceneOFETsbasedonthesolution
duct:7.9ꢁ10 cm V
5
process using photo precursors were reported. Chow and co-workers
prepared the OFET devices based on thermal and photo pentacene
formation from 6,13-dihydro-6,13-methanopentacen-15-one (ther-
ꢂ3
ꢂ3
2
ꢂ1 ꢂ1 11
s ). 6,13-Dihydro-6,13-
2
.2. Thermal conversion of the precursors
mal: 8.8ꢁ10 ; photo: 2.4ꢁ10 cm V
ethanopentacene-15,16-dione was shown to give pentacene by light
We examined thermal behaviors of the pentacene derivatives by
thermogravimetric (TG) analyses. In order to know the molecular
composition of the obtained pentacene precursors, elemental
analyses were carried out by using samples recrystallized from an
*
Corresponding author. E-mail address: uno@dpc.ehime-u.ac.jp (H. Uno).
0
040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.06.051

6890
H. Uoyama et al. / Tetrahedron 66 (2010) 6889e6894
OR
(i)
Pentacene
iv)
1
: R = Ac
: R = H
(ii)
2
(
(
iii)
O
Cl
S
Cl
4
3
(vi)
(v)
O
Cl
Cl
O
S
S
5
6
Scheme 1. Preparation of pentacene adducts. Reagents, conditions, and yields: (i) vinyl
ꢀ
acetate, chlorobenzene, autoclave, 220 C, 66%; (ii) MeONa, MeOH, THF, reflux, 87%;
ꢀ
(
iii) DesseMartin reagent, CH
2
Cl
Cl
2
, rt, 72%; (iv) thiophosgene, 65 C, 57%; (v) silica gel,
, 78%.
CH Cl , 79%; (vi) m-CPBA, CH
2
2
2
2
appropriate solvent system (dichloromethane or dichloromethane/
isopropanol) followed by evacuation (ca. 0.05 mm Hg) overnight at
room temperature. Elemental analysis of the sample of 4 gave
variable results by sampling. The sample of 4 consisted of powdery
white solid and fine colorless block crystals. X-ray analysis of the
block crystal revealed the absence of co-crystallized solvent. We
concluded that the recrystallization of 4 from dichloromethane
gave two or more kinds of crystals. In order to obtain a uniform
composition of the sample of 4, several recrystallization solvents
2 4 2
were examined. Among them, the crystals of 4 from C H Cl were
stable and contained uniformly one molecule of dichloroethane,
which was unambiguously proved by the elemental and X-ray
analyses. In other samples, some solvent molecules were involved
and the sample compositions were as follows: 2 with a quarter
molecule of water, 3 with a quarter molecule of isopropanol, 5 with
one eighths of water, and 6 with a quarter molecule of dichloro-
Figure 1. TG curves (a) 1 (solid line) and 2 (broken line); (b) 3 (solid line) and 5
(broken line); (c) 4 (solid line) and 6 (broken line).
ꢀ
of residues remained even at 400 C (41.4% for 4 and 64.0% for 6). In
the case of 4, additional steep weight loss (19.3%) corresponding to
ꢀ
methane. The TG experiments were performed by a heating rate of
one C
2
H
4
Cl
2
molecule (20.1%) was observed around 90 C. The
ꢀ
1
0 C/min under N
2
. The TG curves are shown in Figure 1.
amounts in the steep weight losses of 4 and 6 were 39.6% and
25.9%, respectively. These values were roughly close to the sums of
two chlorine atoms and solvents (34.5% for 4 and 23.7% for 6). If the
retro-DielseAlder reaction would occur in 4 and 6, 44.5% (di-
chloroethane and thiophosgene) and 35.4% (thiophosgene S-oxide
and a quarter molecule of dichloromethane) of the initial weights
would be lost. In the case of 6, gentle weight loss was observed in
In the cases of vinyl alcohol adducts 1 and 2, the extensive
ꢀ
weight loss started around 300 C (Fig. 1a). As pentacene started to
ꢀ
sublime around 300 C under the same conditions (see Fig. S1 in
the ESI), we concluded that adducts 1 and 2 did not undergo the
retro-DielseAlder reaction below the sublimation temperature of
pentacene. TG curves of 3 and 5 are shown in Figure 1b. There were
two obvious steep slopes and a flat step in the TG curve of 5. The
ꢀ
the temperature range of 290e350 C, which would be corre-
ꢀ
first weight loss observed between 193 and 225 C (17.1%) was
sponding to the sublimation of pentacene. In the case of 4, no ob-
corresponding to the calculated value of thiocarbonyl and a quarter
molecule of water (18.3%), and the entire weight loss corresponding
to the pentacene sublimation started around 300 C. Therefore, we
vious weight was lost in the temperature range of pentacene
sublimation, but additional weight loss started at 350 C.
ꢀ
ꢀ
In order to clarify the thermal degradation pathways, bulk de-
composition experiments were carried out at each beginning
temperature of the first steep slop. As volatile materials were re-
moved under the gentle flow of nitrogen in the TG experiments, we
performed the experiments under a reduced pressure in order to
remove the volatile materials generated. Precursors 3, 4, 5, and 6
concluded that precursor 5 underwent the clean retro-DielseAlder
conversion to pentacene. On the other hand, one steep slope and
another moderate slope were observed in the TG curve of 3 at the
ꢀ
temperature ranges of 227e243 and 306e355 C, respectively. No
step was observed and the weight was gently lost between these
ranges. Moreover, a considerable amount of a residue remained
ꢀ
were heated at 230, 250, 190, and 270 C for 1 h under a reduced
ꢀ
even over 400 C (26.9%). The first weight loss was 28.8%, which
pressure (ca. 30 mm Hg) by a glass tube oven, respectively. Black
residues and sublimed materials at the rim part of the glass tube
were obtained except for 3. In the case of 3, the color of residue was
brown. From the CHN elemental analysis of the residues from 3, 4,
was far more than the calculated value of ketene and a quarter
molecule of isopropanol (17.8%). In the cases of chlorinated pre-
ꢀ
cursors 4 and 6, a steep slope was observed around 250 C and a lot

H. Uoyama et al. / Tetrahedron 66 (2010) 6889e6894
6891
5
, and 6, the compositions were C, 92.12, H, 4.63; C, 84.93, H, 4.00;
C; 95.17, H; 5.19; and C, 83.65, H, 3.96%, respectively. In the cases of
, 5, and 6, pentacene was identified in the sublimed materials. The
composition of the thermal degradation residue from 5 was well in
accord with that of pentacene (Calcd for C22 14: C, 94.93; H, 5.07%).
the spectrum of degradation residue from 3, the peaks of m/z¼278
and 291 were found in addition to many higher-mass peaks up to
800 (Fig. 2a). As the pentacene chromophore did not exist in this
residue due to no characteristic absorption in the UV spectrum,
the peaks were derived from degradation of the polymeric ma-
terial. In the case of the residue from thiophosgene adduct 4,
strong peaks of m/z¼321, 597, 640, and 959 was observed in ad-
dition to a small peak of pentacene (Fig. 2b). Judging from the
isotopic pattern, there was no chlorine atom in these peaks, and
4
H
On the other hand, other compositions were between pentacene
and the precursors.
Next, we examined the MALDI-TOF Mass spectra of the residual
materials from 3, 4, and 6. The results are shown in Figure 2. From
the compositions of m/z¼321, 597, 640, and 959 were assigned as
þ
pentacene-6-thiocarbonyl cation (C22
H
13CS ), dipentacenyl thio-
ketone derivative, dimeric pentacenethiocarbonyl derivative, and
trimeric pentacenethio-carbonyl species, respectively. On the
other hand, new peaks of m/z¼278 (pentacene), 323, 325, and 567
as well as many higher-mass peaks were observed in the spectrum
of the residue from 6 in addition to the same four strong peaks of
m/z¼321, 597, 640, and 959 as 4 (Fig. 2c). The new peaks were
thought to be derived from pentacenyl chlorocarbene. Pausible
decomposition pathways of the precursors containing the epi-
thiomethano moieties are illustrated in Scheme 2, where the
possible species and intermediates are shown with the observed
mass numbers.
In the thermal decomposition of 4, 5, and 6, the weakest bond of
C eS would be first broken to give diradical 7. There would be two
6
possible fates in the decomposition of the radical. In the case of 5,
retro-DielseAlder-like decomposition pathway a would only occur
to give pentacene, because no weak
exists. In the cases of 4 and 6, the weak
b
bond to the thiyl radical
bond of CeCl would be
b
cleaved in addition to the pathway a, and the resulted chloro radical
would abstract the adjacent hydrogen atom to form thiocarbonyl
and thiocarbonyl S-oxide derivatives 8 and 9. The thiocarbonyl
chloride 8 would undergo some bond-forming reactions such as
the FriedeleCrafts reaction giving dimeric compounds 11, 12, 13,
and so on. In the case of thiocarbonyl S-oxide 9,1 1,3-dipolar
cyclodimerization would occur to give dioxadithiol 14, which
would then decompose to give thiocarbonyl chloride 8, sulfur di-
oxide, and pentacenyl chlorocarbene 15. The last intermediate
species would undergo the insertion reaction with pentacene to
give dipentacenylmethyl chloride (16).
6
Figure 2. MALDI-TOF MS spectra of residues from 3 (a), 4 (b), and 6 (c).
X
X
X
b
X
S
O n
Route a
H
a
On
S
retro-Diels-Alder
6
X
4
5
6
: n = 0, X
: n = 0, X
2
2
= Cl
= O
2
2
S
On
Pentacene: 278
7
X
Route b
: n = 1, X = Cl
2
X = Cl
O
Cl
S
C+
n S
S+
8
pentacene
S
10: 321
8: n = 0: 355
: n = 1: 371
1
2: 597
9
1
1
9
Dimerize
Dimerize
S
C
8
S=(O)
n
SO2
Cl
S
O
S
C
Cl
-pentacenyl
S
6
-pentacenyl
Cl
Cl
O
6
14
-
-
1
5: M-H : 323
16: M-Cl : 567
13: 640
Scheme 2. Pausible decomposition pathways of the precursors containing epithiomethano moieties.

6892
H. Uoyama et al. / Tetrahedron 66 (2010) 6889e6894
2
.3. Photo conversion of pentacene derivative to pentacene
suggested the complete conversion of 5 to pentacene by light
irradiation.
Pentacene derivatives 1e6 in acetonitrile were irradiated with
54-nm light roughly corresponding to the transition of
nitrogen atmosphere. Only epi-
2
pep
*
2.4. Device preparation
naphthalene under
a
thioeoxomethano-bridged derivative 5 underwent the photo
conversion to pentacene. The progress was monitored by UV/vis
measurement (Fig. 3). As the strong absorption peak at 238 nm
decreased, the absorption peaks at 296, 495, 527, and 571 nm due
to pentacene increased until 30 s. After 30 s, the absorptions due to
pentacene decreased quickly due to precipitation of pentacene
from the super-saturated solution.
Only epithioeoxomethano-bridged precursor 5 is a candidate
for the solution-processed OFET. When the pentacene devices were
ꢀ
annealed at higher temperatures than 150 C, holes due to sub-
limation of pentacene were generated and their device perfor-
12c
mance was reduced. As the conversion temperature of 5 by heat
ꢀ
(>180 C) was higher than the temperature limitation, we decided
to use the light conversion method. The epithioeoxomethano
precursor 5 was fairly soluble in halogenated and carbonyl solvents
such as chloroform, dichloromethane, dichloroethane, chloroben-
zene, acetone, and ethyl acetate, slightly soluble in alcoholic and
aromatic hydrocarbon solvents, and hardly soluble in non-aromatic
hydrocarbon and ethereal solvents. We made field-effect transis-
tors (FETs) in the top-contact fashion by deposition of pentacene
with the visible-light irradiation to the thin-layered precursor as
2
follows. Heavily n-doped SiO (500-nm thickness)/Si substrates
were spin-coated with a 0.25% MSQ EtOH/BuOH (v/v¼1/1) solution
ꢀ
(
5000 rpm, 50 s) and then dried at 220 C for 30 min. The precursor
5
in a 1.0% solution of chloroform containing 7.8-molar equivalents
of ethanol was spin-coated (1000 rpm, 30 s) on the SiO
2
/Si sub-
ꢀ
strate, and the film was dried at 60 C on a hot plate for 5 min. In
order to avoid the undesirable side reactions of deposited penta-
cene caused by irradiation of high-energy light and existence of
1
2a,12b,18
oxygen,
the thin-layered precursor was converted on a hot
ꢀ
plate (30e140 C) by irradiation (1 min) with a lamp (HOYA-
SCHOTT EX250) in a glove box under an inert atmosphere. The
thickness of the precursor film was ca. 100 nm. Then gold elec-
Figure 3. UV/vis spectra during photo conversion of 5 (broken bold line) to pentacene.
trodes were installed (channel length: 0.05 mm, channel width:
ꢂ3
0
.3 cm) at room temperature by vapor deposition (1.3ꢁ10 Pa).
We next examined the photo conversion of 5 in acetonitrile by IR
spectroscopy (Fig. 4). The carbonyl stretching of 5 was observed at
First, we tested the deposition temperature during the light ir-
radiation, since the temperature was the most significant factor for
ꢂ1
1
693 cm . When epithiooxomethano-bridged precursor 5 was
the OFET performance of the device from 6,13-ethano-6,13-dihy-
ꢂ1
irradiated for 2 min, a new absorption at 2040 cm due to the
cumulenic C]O stretching appeared and increased at the expense
of the carbonyl absorption at 1693 cm . After five min, the ab-
sorption at 1693 cm completely disappeared and the absorption
12c
dropentacene-15,16-dione.
The mobility increased from
s , as the temperature increased
17
ꢂ5
ꢂ1
2
ꢂ1 ꢂ1
m
¼6.2ꢁ10 to 1.0ꢁ10 cm V
ꢂ1
ꢀ
from 30 to 140 C (Table 1). The on/off ratio, however, reached
ꢂ1
3
ꢀ
a maximum of 1.9ꢁ10 at 120 C and then decreased. We decided
ꢂ1
at 2040 cm became very strong. It is worthy to note that no ob-
ꢀ
that the best conversion temperature was 120 C, which was the
vious carbonyl stretching except for the mentioned stretching of
carbonyl sulfide was observed in the IR spectra. This fact also
same as the case of 6,13-ethano-6,13-dihydropentacene-15,16-
12c
dione. As a polar solvent additive in the spin-coating process of
the precursor was also important in the fabrication of the solution-
1
2c
processed pentacene OFET,
we next tested the solvent system.
3
Complete removal of ethanol improved the on/off ratio to 9.6ꢁ10 ,
ꢂ3
ꢂ1 ꢂ1
2
ꢂ1 ꢂ1
although the mobility
m
slightly decreased to 2.3ꢁ10 cm V
s
.
ꢂ2
2
The best performance of
m
¼2.5ꢁ10 cm V
s
and on/off
4
ratio¼3.8ꢁ10 was obtained by substitution of ethanol with ace-
tone (Table 1, entry 5).
Table 1
FET performance of the device using 5
2
ꢂ1 ꢂ1
s
Entry
Solvent
Annealing
temperature/ C
Mobility/cm V
On/off
ratio
ꢀ
ꢂ5
ꢂ2
ꢂ2
ꢂ1
ꢂ2
ꢂ2
1
2
3
4
5
6
EtOH/CHCl
EtOH/CHCl
EtOH/CHCl
EtOH/CHCl
3
3
3
3
30
120
130
140
120
120
6.2ꢁ10
29
3
2
2
4
3
5.0ꢁ10
1.9ꢁ10
1.3ꢁ10
1.4ꢁ10
3.8ꢁ10
9.6ꢁ10
9.0ꢁ10
1.0ꢁ10
a
Acetone/CHCl
3
2.5ꢁ10
b
CHCl
3
2.3ꢁ10
a
Acetone was used instead of ethanol.
Without an additive.
b
In conclusion, we prepared 6,13-bridged pentacenes based on
the DielseAlder reaction of pentacene with vinyl acetate or thio-
Figure 4. IR spectra in CH
3
CN during light irradiation of 5.
phosgene and studied thermal and photo reactions of the

H. Uoyama et al. / Tetrahedron 66 (2010) 6889e6894
6893
pentacene derivatives. 15-Acethoxy-6,13-dihydro-6,13-ethano-
washed with water and brine, dried over Na
2
SO
4
, and concentrated
pentacene (1) and 6,13-dihydro-15-hydroxy-6,13-ethanopenta-
cene (2) were not converted to pentacene below the sublimation
temperature of pentacene. Thermal reaction of 16,16-dichloro-6,13-
dihydro-6,13-epithiomethanopentacene (4) and 16,16-dichloro-
in vacuo. The residue was chromatographed on silica gel (CHCl
3
) to
ꢀ
give 2 (149 mg, 87%) as colorless powder: mp 223e226 C, R
f
¼0.25
1
(CHCl
3
); H NMR
d
7.95 (1H, s), 7.81 (2H, s), 7.75e7.85 (4H, m), 7.71
(1H, s), 7.42 (4H, m), 4.62 (1H, m), 4.51 (1H, m), 4.36 (1H, m), 2.52
13
6
,13-dihydro-15-oxo-6,13-epithiomethano-pentacene (6) gave
(1H, m), 1.59 (1H, m),1.31 (1H, br s); C NMR d 141.01, 140.65,
mainly polymeric materials derived from pentacene-6-thocarbonyl
species in addition to a small amount of pentacene. 6,13-Dihydro-
138.05, 136.04,132.83,132.64,132.39,132.32,127.58,127.48, 125.66,
125.47, 125.33, 125.23, 123.35, 123.25, 121.75, 121.65, 121.61, 121.51,
6
,13-epithiomethanopentacen-16-one (5) was quantitatively
69.80, 52.33, 43.78, 39.77; IR (KBr):
885, 756 cm ; EIMS: m/z (rel int.) 322 (M , 23), 278 (100). Anal.
n
max 3554, 1444, 1389, 1022,
ꢀ
ꢂ1
þ
converted to pentacene by heat (220 C) and light (254 nm). The
pentacene OFET fabricated by spin-coating of 5 followed by light
Calcd for C24
5.85%.
H
18Oþ1/4H
2
O: C, 88.18; H, 5.70. Found: C, 88.15; H,
ꢀ
irradiation at 120 C showed good performance of
m
¼2.5ꢁ
ꢂ2
2
ꢂ1 ꢂ1
4
1
3
3
0
cm V
s
and on/off ratio¼3.8ꢁ10 .
3.1.3. 6,13-Dihydro-6,13-ethanopentacen-15-one (3). To a stirred
. Experimental
.1. General
solution of 2 (129 mg, 0.400 mmol) in CH Cl (8.0 mL) was added the
DesseMartin reagent (254 mg, 0.600 mmol) at room temperature.
The mixture was stirred for 6 h. The reaction was quenched with
2
2
a saturated aqueous NaHCO
with EtOAc. The organic extract was washed with water and brine,
dried over Na SO , and concentrated in vacuo. The residue was
3
solution and the mixture was extracted
Melting points were measured on a Yanagimoto micromelting
point apparatus and are uncorrected. NMR spectra were obtained
with a JEOL AL-400 or EX-400 spectrometer at the ambient tem-
2
4
purified by recrystallization with CHCl
3
/isopropanol to give 3
¼0.7 (CHCl );
ꢀ
perature by using CDCl
internal standard for H and C. IR spectra were measured with
a Horiba FT-720 infrared spectrophotometer. Mass spectra (EI,
3
as a solvent, and tetramethylsilane as an
(109 mg, 72%)aswhite powder: mp 216 C (decomp.), R
f
3
1
13
1
HNMR
d7.85(4H, m), 7.80(4H, m), 7.45(4H, m), 5.08(1H,s), 4.81(1H,
13
m), 2.58 (2H, m); C NMR
d
205.75, 139.79, 134.63, 133.23, 132.77,
7
0 eV) were measured with a JEOL JMS-700. The MALDI-TOF MS
128.03, 127.92, 126.59, 126.35, 124.64, 122.71, 63.10, 44.93, 40.84; IR
ꢂ1
spectra were measured with a Voyager DE Pro instrument. Ele-
mental analyses were performed with a Yanaco MT-5 elemental
analyzer. UV/vis spectra were measured in acetonitrile with
a HITACHI U-2810 spectrophotometer. TG measurements were
performed with Seiko Instruments EXSTAR 6000. The photo con-
(KBr)
n
max 1722,1608,1560,1439,1340, 742 cm ; EIMS: m/z (rel int.)
þ
320 (M , 2), 292 (7), 278 (100),139 (24). Anal. Calcd for C24
isopropanol: C, 88.63; H, 5.41. Found: C, 88.38; H, 5.74%.
H16Oþ1/4
3.1.4. 16,16-Dichloro-6,13-dihydro-6,13-epithiomethanopentacene
version experiments were performed by using a UV lamp (AS ONE
(4). A suspension of pentacene (1.11 g, 4.00 mmol) and thio-
phosgene (6.0 mL) was heated at 65 C for 6 h. After cooling to
2
ꢀ
SLUV-4: 614
mW/cm ). All solvents and chemicals were reagent
grade quality, obtained commercially and used without further
purification except as noted. Acetonitrile for spectroscopy was
purchased from Nacalai Tesque Co. Solvents for chromatography
were purified by distillation. Thin-layer and column chromatogra-
phy was performed on Art. 5554 (Merck KGaA) and Silica Gel 60N
2 2
room temperature, CH Cl was added to the reaction mixture and
unreacted pentacene was removed by filtration. Toluene (40 mLꢁ2)
was added and the mixture was evaporated to remove excess thi-
ophosgene completely. The product was recrystallized with 1,2-
dichloroethane to give the title compound (1.13 g, 57%) as colorless
ꢀ
1
(
Kanto Chemical Co.), respectively. Other commercially available
crystals: mp 252 C (decomp.); H NMR
d 8.00 (2H, s), 7.84 (4H, m),
13
materials were used without further purification.
7.79 (2H, s), 7.47 (4H, m), 5.52 (1H, s), 5.39 (1H, s); C NMR
d
137.07,
135.11, 132.85, 132.37, 128.95, 127.92, 127.10, 126.73, 126.41, 120.77,
3
.1.1. 15-Acetoxy-6,13-dihydro-6,13-ethanopentacene (1). Penta-
64.19, 51.03, 43.42; IR (KBr)
1230 cm ; EIMS: m/z (rel int.) 392 (M , 10), 357 (7), 321 (6), 278
(100), 139 (12). Anal. Calcd for C23
3.69. Found: C, 61.29; H, 3.67%.
n
max 3057, 1498, 1446, 1398, 1338,
ꢂ1
þ
cene (278 mg, 1.00 mmol), vinyl acetate (0.37 mL, 4.0 mmol), hy-
droquinone (5 mg, 0.05 mmol), and chlorobenzene (20 mL) were
placed in a stainless steel cylinder equipped with a magnetic stir-
ring bar. The cylinder was screw-capped and heated at 220 C for
2
and the cap was carefully unscrewed. The mixture was filtered to
remove pentacene and the filtrate was concentrated. The residue
was chromatographed (silica gel, 60% CHCl
tallized (CHCl /MeOH) to give 1 (241 mg, 66%) as colorless crystals:
mp 186e189 C, R
H14Cl
2
SþC
2 4 2
H Cl : C 60.99; H,
ꢀ
4 h with stirring. The cylinder was cooled to room temperature
3.1.5. 6,13-Dihydro-6,13-epithiomethanopentacen-16-one (5)15a. To
a solution of 4 (789 mg, 2.00 mmol) in CH Cl (20 mL) was added
silica gel. After the solvent was removed, the silica gel was washed
with CH Cl . The organic extract was concentrated and dried under
a reduced pressure to give 5 (546 mg, 79%) as colorless powder: mp
2
2
3
/hexane) and recrys-
2
2
3
ꢀ
1
ꢀ
1
f
¼0.3 (60% CHCl
3
/hexane); H NMR
d
7.70e7.81
193 C (decomp.), R
s), 7.82 (4H, m), 7.49 (4H, m), 5.82 (1H, s), 5.46 (1H, s); C NMR
201.89, 137.73, 134.34, 132.55, 132.28, 127.88, 127.81, 126.83,
f
¼0.75 (CHCl
3
); H NMR d 7.91 (2H, s), 7.89 (2H,
13
(
(
1
8H, m), 7.41 (4H, m), 5.23 (1H, m), 4.78 (1H, m), 4.52 (1H, m), 2.53
13
1H, m), 1.91 (3H, s), 1.75 (1H, m); C NMR
37.12, 136.82, 132.70, 132.65, 132.49, 132.33, 127.64, 127.57, 127.55,
27.48, 125.81, 125.55, 125.52, 125.38, 124.18, 123.75, 121.62, 121.43,
d
170.90, 140.86, 140.81,
d
126.69, 125.23, 121.75, 64.66, 52.19; IR (KBr):
n
max 3003, 1668, 1604,
ꢂ1
þ
1
1500, 1336, 1205 cm ; MS (EI): m/z (rel int.) 338 (M , 10), 278
7
2.29, 48.45, 43.49, 36.14, 21.20; IR (KBr):
n
max 1738, 1371, 1242,
(100), 139 (17);
l
max (log
3) 232 (4.90), 250 (4.66) nm. Anal. Calcd
ꢂ1
þ
1028, 891, 752 cm ; EIMS: m/z (rel int.) 364 (M , 6), 278 (100).
for C23H14OSþ1/8H
2
O: C, 81.09; H, 4.22. Found: C, 81.14; H, 4.35%.
20 2
Anal. Calcd for C26H O : C, 85.69; H, 5.53. Found: C, 85.39; H,
5
.71%.
3.1.6. 16,16-Dichloro-6,13-dihydro-15-oxo-6,13-epithio-meth-
anopentacene (6). To a stirred solution of 5 (108 mg, 0.275 mmol)
3
.1.2. 6,13-Dihydro-15-hydroxy-6,13-ethanopentacene (2). To a so-
in CH
2
Cl
2
(10 mL) was added m-CPBA (64.8 mg, 0.274 mmol) at
ꢀ
lution of 1 (190 mg, 0.521 mmol) in THF (20 mL) and MeOH (5 mL)
was added a 28% solution of MeONa in MeOH (1.0 mL, 5.7 mmol) at
room temperature. The mixture was refluxed for 18 h. The mixture
was cooled to room temperature and quenched with 1.0 M aqueous
HCl. The mixture was extracted with EtOAc. The organic extract was
0 C. After the mixture had been stirred for 1 h at room tempera-
ture, a saturated aqueous NaHCO
was extracted three times with CH
washed with water and brine, dried over Na
in vacuo. The residue was washed with ether to give 6 (92.2 mg,
3
solution was added. The mixture
Cl . The organic extract was
SO , and concentrated
2
2
2
4

6894
H. Uoyama et al. / Tetrahedron 66 (2010) 6889e6894
ꢀ
1
7
NMR
s); C NMR
1
1
1
(
C
8%) as white powder: mp 273 C (decomp.), R
f
¼0.3 (CHCl
3
); H
205e239; Di, C.-A.; Liu, Y.; Yu, G.; Zhu, D. Acc. Chem. Res. 2009, 42, 1573e1583;
Liu, S.; Wang, W. M.; Briseno, A. L.; Mannsfeld, S. C. B.; Bao, Z. Adv. Mater. 2009,
d
7.85e8.03 (8H, m), 7.50e7.55 (4H, m), 5.76 (1H, s), 5.29 (1H,
134.06, 133.38, 133.29, 133.04, 132.16, 128.46, 128.44,
28.14, 128.03, 127.99, 127.90, 127.53, 127.35, 127.24, 127.10, 127.07,
26.97, 126.94, 126.93, 126.92, 101.88, 69.12, 61.48; IR (KBr):
21, 1217e1232; Yamashita, Y. Sci. Technol. Adv. Mater. 2009, 10 024313/1-9;
13
d
Hasegawa, T.; Takeya. J. Sci. Technol. Adv. Mater. 2009, 10 2024314/1-16; Allard,
S.; Forster, M.; Souharce, B.; Thiem, H.; Scherf, U. Angew. Chem., Int. Ed. 2008, 47,
4
2
070e4098; Yamada, H.; Okujima, T.; Ono, N. Chem. Commun. 2008,
957e2974; Mas-Torrent, M.; Rovira, C. Chem. Soc. Rev. 2008, 37, 827e838.
n
max
ꢂ1
500, 1331, 1188, 1095, 897, 837, 756 cm ; EIMS: m/z (rel int.) 408
2
. Zhang, X.-H.; Domercq, B.; Wang, X.; Yoo, S.; Kondo, T.; Wang, Z. L.; Kippelen, B.
Org. Electron 2007, 8, 718e726; Oyama, T.; Ye, R.; Baba, M.; Ohta, K. Mol. Cryst.
Liq. Cryst. 2007, 471, 205e211.
. Natsume, Y.; Minakata, T.; Aoyagi, T. Org. Electron 2009, 10, 107e114.
. (a) Brown, A. R.; Pomp, A.; de Leeuw, D. M.; Klaassen, D. B. M.; Havinga, E. E.;
Herwig, P.; Müllen, K. J. Appl. Physiol. 1996, 79, 2136e2138; (b) Herwig, P. T.;
Müllen, K. Adv. Mater. 1999, 11, 480e483.
þ
M , 5) 360 (11), 325 (20), 278 (100). Anal. Calcd for
H14Cl
23 2
OSþ1/4CH
2 2
Cl : C, 64.86; H, 3.39. Found C, 64.74; H, 3.37%.
3
4
3
.2. X-ray analysis
5
. Aflzali, A.; Dimitrakopoulos, C. D.; Breen, T. L. J. Am. Chem. Soc. 2002, 124,
8
Determination of cell parameters and collection of reflection
intensities were performed on Rigaku Mercury-8 (3-kW sealed
tube) instrument equipped with graphite monochromated Mo K
812e8813.
6. Afzali, A.; Kagan, C. R.; Traub, G. P. Synth. Met. 2005, 155, 490e494.
. Zander, Z.; Hoffmann, N.; Lmimouni, K.; Lemfan, S.; Peit, C.; Vuillaume, D.
7
a
Microelectron. Eng. 2005, 80, 394e397.
. Afzali, A.; Dimitrakopoulos, C. D.; Graham, T. O. Adv. Mater. 2003, 15,
2066e2069.
. Weidkamp, K. P.; Afzali, A.; Tromp, R. M.; Hamers, R. J. J. Am. Chem. Soc. 2004,
126, 12740e12741.
radiation. The data were corrected for Lorentz, polarization, and
absorption effects. X-ray data were processed by CrystalClear SM
Ver. 1.3.6.19 The processed data were treated with the Crystal-
8
9
1
9
20
Structure 3.8.2 or WinGX 1.80.03. Structures were solved by
10. Haung, H.-H.; Hsieh, H.-H.; Wu, C.-C.; Lin, C.-C.; Chou, P.-T.; Chuang, T.-H.; Wen,
21
22
SIR-97 and then refined by SHELXL-97. The structure was vali-
dated by Platon cif check. The X-ray analysis results in cif format
were deposited at the Cambridge Crystallographic Data Centre. The
Y.-S.; Chow, T. J. Tetrahedron Lett. 2008, 49, 4494e4497.
2
3
11. Chen, K.-Y.; Hsieh, H.-H.; Wu, C.-C.; Hwang, J.-J.; Chow, T. J. Chem. Commun.
2007, 1065e1067; Chuang, T.-H.; Hsieh, H.-H.; Chen, C.-K.; Wu, C.-C.; Lin, C.-C.;
Chou, P.-T.; Chao, T.-H.; Chow, T. J. Org. Lett. 2008, 10, 2869e2872.
CCDC numbers of 1þCHCl
3
, 4, and 4þC
2 4 2
H Cl are 771012, 771013,
1
2. (a) Uno, H.; Yamashita, Y.; Kikuchi, M.; Watanabe, H.; Yamada, H.; Okujima, T.;
Ogawa, T.; Ono, N. Tetrahedron Lett. 2005, 46, 1981e1983; (b) Yamada, H.; Ya-
mashita, Y.; Kikuchi, M.; Watanabe, H.; Okujima, T.; Uno, H.; Ogawa, T.; Ohara,
K.; Ono, N. Chem.dEur. J. 2005, 11, 6212e6220; (c) Masumoto, A.; Yamashita, Y.;
Go, S.; Kikuchi, T.; Yamada, H.; Okujima, T.; Ono, N.; Uno, H. Jpn. J. Appl. Phys.
and 771014, respectively.
Acknowledgements
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009, 48 051505/1-5.
3. Alder, K.; Rickert, H. F. Ann. 1939, 543, 1e27.
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1
1
1
This work was partially supported by Grant-in-Aid for the Sci-
entific Research (20550047) from the Japanese Ministry of Educa-
tion, Culture, Sports, Science and Technology and by a grant for the
Research for Promoting Technological Seeds B (14-B02) from the
Japan Science and Technology Agency. Miss Akane Masumoto
1
1
2
(
Canon Co.) is greatly appreciated for her measurement of FET
6
performance. X-ray, elemental analysis, IR, NMR, FAB MS, and TG
measurements were performed at Integrated Center for Sciences,
Ehime University.
1
H.; Lee, H. K.; Wang, Y. M.; Fu, N. Y.; Chen, X. M.; Cai, Z. W.; Wong, H. N. C.
Chem. Commun. 2005, 66e68; Coppo, P.; Yeates, S. G. Adv. Mater. 2005, 17,
3
001e3005.
9. Diffraction Data Reduction And Crystal Structure Analysis Packages; Rigaku (3-9-
2 Akishima, Tokyo, Japan) and Rigaku/MSC (9009 New Trails Dr.: The Wood-
lands, TX 77381 USA), 2000e2004.
1
Supplementary data
1
Supplementary data associated with this article can be found in
online version at doi:10.1016/j.tet.2010.06.051. These data include
MOL files and InChIKeys of the most important compounds
described in this article.
20. Wingx 1.80.03 suite for small-molecule single-crystal crystallography, Univer-
sity of Glasgow, Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837e838.
21. SIR-97: A package for crystal structure solution and refinement, Istituto di
Gristallografia, Italy. Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R. J. Appl.
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2. SHELXL-97: Program for the refinement of crystal structures from diffraction
data, University of Gottingen, Gottingen, Germany; ‘A short history of SHELX’
Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112e122.
References and notes
€
€
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