Three structural isomers of dinaphthothieno[3,2-b]thiophenes: Elucidation of physicochemical properties, crystal structures, and field-effect transistor characteristics

Article abstract of DOI:10.1246/bcsj.20090230

In order to gainan insight into the relationship between the molecular structure and the semiconductor characteristics of highly π-extended heteroarene-based organic semiconductors, three structural isomers of dinaphthothieno[3,2-b]thiophenes with C₂

Full text of DOI:10.1246/bcsj.20090230

120 Bull. Chem. Soc. Jpn. Vol. 83, No. 2, 120–130 (2010)
© 2010 The Chemical Society of Japan
BCSJ Award Article
Three Structural Isomers of Dinaphthothieno[3,2-b]thiophenes:
Elucidation of Physicochemical Properties, Crystal Structures,
and Field-Effect Transistor Characteristics
Tatsuya Yamamoto,1,³ Shoji Shinamura,1 Eigo Miyazaki,1 and Kazuo Takimiya*1,2
1Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University,
Higashi-Hiroshima 739-8527
2Institute for Advanced Materials Research, Hiroshima University, Higashi-Hiroshima 739-8530
Received September 1, 2009; E-mail: ktakimi@hiroshima-u.ac.jp
In order to gain an insight into the relationship between the molecular structure and the semiconductor
characteristics of highly ³-extended heteroarene-based organic semiconductors, three structural isomers of
dinaphthothieno[3,2-b]thiophenes with C2h symmetry were investigated. Of these, two isomers, dinaphtho[2,1-b:2¤,1¤-
f]thieno[3,2-b]thiophene (2) and dinaphtho[1,2-b:1¤,2¤-f]thieno[3,2-b]thiophene (3), were newly synthesized, charac-
terized, and utilized as active semiconducting layers in organic field-effect transistors (FETs). Detailed investigation of the
physicochemical properties of 2 and 3, together with another isomer, dinaphtho[2,3-b:2¤,3¤-f]thieno[3,2-b]thiophene (1),
indicated that the electronic structures of the three isomers are fairly different from each other despite having the same
molecular formula and the same aromatic constituents. Comparison of the molecular arrangements in the crystals
elucidated by X-ray structural analysis implied that the molecular shape and the thus-induced favorable intermolecular
interactions play important roles in determining the entire molecular arrangement. The characteristics of 2- and 3-based
FETs with maximum field-effect mobilities (®FETs) of 10¹3-10¹2 cm2 V¹1 s¹1 were inferior to those of 1-based FETs with
®
FETs up to 3.0 cm2 V¹1 s¹1. The inferior characteristics of 2- and 3-based devices were due to film morphology as
elucidated by atomic force microscopy (AFM) and supported by theoretical calculations of electronic structure in the
solid state. Together, the results indicate that the molecular structure and shape, even for similar heteroarenes with the
same molecular formula and symmetry, are important parameters to determine the solid-state properties of organic
semiconductors.
Pentacene, a representative oligoacene consisting of five
benzene rings fused in a linear manner, is widely utilized as a
standard organic semiconductor for high-performance thin-
3.0 cm2 V¹1 s¹1.4 The stabilization of the heteroarene can be
understood by lowering the energy levels of the highest
occupied molecular orbital (HOMO) and raising the energy
levels of the lowest unoccupied molecular orbital (LUMO),
resulting in a large HOMO-LUMO energy gap.5 The high
stability and good performances of DNTT-based OFETs
indicate that the introduction of the thieno[3,2-b]thiophene
substructure into the acene framework is beneficial for the
development of new organic semiconductors based on highly
³-extended aromatic compounds.
The molecular structure of 1 can be viewed as a benzo-fused
[1]benzothieno[3,2-b][1]benzothiophene (BTBT) or a naphtho-
fused thieno[3,2-b]thiophene with C2h symmetry. Using the
same aromatic constituents, one can draw two structural
isomers while keeping the same symmetry, namely, dinaphtho-
[2,1-b:2¤,1¤-f ]thieno[3,2-b]thiophene (2) and dinaphtho[1,2-
b:1¤,2¤-f ]thieno[3,2-b]thiophene (3)6 (Figure 1). Although the
isomers have the same aromatic constituents, their molecular
shapes and electronic structures are expected to differ.
film-based organic field-effect transistors (OFETs) showing
¹1 1
field-effect mobilities (®FETs) higher than 1.0 cm2 V¹1 s
.
Higher oligoacenes than pentacene, e.g., hexacene that has
six fused benzene rings, are promising candidates for the
development of superior organic semiconductors that show
better performance than pentacene.2 However, the instability of
such large oligoacenes has hindered their practical use as an
organic semiconductor.3
In sharp contrast, we recently reported that a newly
developed highly ³-extended heteroarene, dinaphtho[2,3-
b:2¤,3¤-f ]thieno[3,2-b]thiophene (DNTT, 1), which possesses
six aromatic rings fused in a linear manner, is stable and its
evaporated thin-film-based OFETs show ®FETs as high as
³ Present address: Research Center for Composite Device
Technology, Iwate University, Hanamaki 025-0312
Published on the web January 20, 2010; doi:10.1246/bcsj.20090230

T. Yamamoto et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
121
pentacene
hexacene
S
S
S
S
S
S
2
3
DNTT (1)
Figure 1. Chemical structures of highly extended acenes and heteroarenes.
Li
N
1)
N
CHO
CHO
(1.1 equiv)
/ꢀTHF
H3CS
SCH3
S
TiCl4 /Zn
THF
I2
2) n-BuLi (3 equiv)
3) CH3S-SCH3
4) HCl aq.
CHCl3
S
4a
5a (62%)
SCH3
6a (49%)
2 (23%)
Li
N
1)
N
H3CS
SCH3
CHO
(1.6 equiv)
/ THF
S
CHO
TiCl4 /Zn
THF
I2
CHCl3
2) n-BuLi (3 equiv)
3) CH3S-SCH3
4) HCl aq.
S
SCH3
4b
5b (15%)
6b (26%)
3 (33%)
Scheme 1. Synthesis of 2 and 3.
Furthermore, the difference in molecular shape will bring about
different molecular arrangements in the solid state, and this will
have a significant impact on the electrical properties in the solid
state, including the FET characteristics of thin-film-based
devices. Keeping these expectations in mind, we carried out
the syntheses, characterization, and elucidation of the crystal
structures of isomers 2 and 3, as well as the evaluation of FET
characteristics of evaporated thin-film-based OFET devices.
Comparison of 1-3 in terms of molecular factors, i.e., molecular
and electronic structure, frontier orbitals, reorganization energy,
and intermolecular factors, i.e., molecular arrangement in the
solid state and intermolecular transfer integrals, will give an
insight into understanding molecular design strategies for
superior organic semiconductors. We here report the synthesis,
characterization, crystal structures, and FET characteristics of
evaporated thin-film-based OFETs, together with theoretical
studies of the electronic structures of 1-3 in the solid state.
hyde (4a) was the substrate, the same procedure applied to 2-
naphthaldehyde (4b) gave a mixture of isomers consisting of
desired 1-methylthio-2-naphthaldehyde9 (5b, 15% yield) and
3-methylthio-2-naphthaldehyde (58% yield), the latter of which
is the intermediate for 1. Aldehydes 5a and 5b were readily
converted into olefinic intermediates 6a and 6b in moderate
yields by low-valent titanium-mediated olefination.10 The
conversion of 6a and 6b into 2 and 3, respectively, which
was accomplished by the action of I2 in refluxing CHCl3, was
readily achieved, although the conversion yields were low.
Compounds 2 and 3 were fully characterized by spectroscopic
and combustion elemental analyses, and the selective formation
of 2 and 3 was unambiguously confirmed by X-ray single
crystal analyses (vide infra).
Electrochemical and Spectroscopic Properties.
The
oxidation potentials of isomers 1-3 determined by cyclic
voltammetry are summarized in Table 1, together with spec-
troscopic data extracted from UV-vis spectra (Figure 2).
The first oxidation potentials of 2 (+0.83 V, vs. ferrocene/
ferrocenium) and 3 (+0.87 V) are slightly higher than that of 1
(+0.75 V), which means that the HOMO energy levels of 2 and
3 are lower than that of 1. The HOMO energy levels estimated
from the oxidation onsets are 5.44 eV for 1, 5.54 eV for 2, and
5.58 eV for 3 below the vacuum level,11 and are higher than
that of BTBT (5.74 eV) that corresponds to the common central
core structure of 1-3, indicating that the ³-system extension
contributes to the elevation of HOMO energy level, although
the perturbation effect depends on the position of attachment of
the outermost benzene rings.
Results and Discussion
Synthesis.
DNTT isomers 2 and 3 were synthesized
following a three-step procedure similar to that reported for the
synthesis of 1 (Scheme 1).4a Commercially available 1- or 2-
naphthaldehyde as starting material was first ortho-lithiated
using excess butyllithium in the presence of N,N,N¤-trimethyl-
ethylenediamine in THF,7 and the resulting lithium naph-
thalenide intermediates were reacted with dimethyl disulfide to
give corresponding naphthaldehyde with a methylthio group at
the ortho-position. Although the desired 2-methylthio-1-naph-
thaldehyde (5a)8 was selectively obtained when 1-naphthalde-

122
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010) BCSJ AWARD ARTICLE
In accordance with the elevation of HOMO energy levels
caused by the addition of two benzene rings to the BTBT core,
HOMO-LUMO gaps optically estimated as well as the LUMO
energy levels of 1-3 are decreased. However, the extent
of LUMO energy level lowering is not consistent in 1-3:
pronounced lowering of LUMO energy level and the HOMO-
LUMO gap is noticeable in 1, in which the additional benzene
ring is fused in a linear manner.
MO Calculations. To elucidate the dependence of the
perturbation effect of the outermost benzene rings on the
annulated positions in the BTBT core structure, we carried out
MO calculations with the DFT method at the B3LYP/6-31G(d)
level using Gaussian03 program.12 HOMO and LUMO of 1-3
and BTBT are depicted in Figure 3, and the calculated energy
levels of their frontier orbitals are listed in Table 2. The
experimentally estimated energy levels listed in Table 1
are qualitatively reproduced by the theoretical calculations,
indicating that the calculations are useful to understand the
difference in electronic structure among the isomers.
Regardless of the isomer, the coefficients (charge densities)
of both HOMO and LUMO spread over the entire molecular
framework. In other words, effective conjugation is extended to
the outermost benzene rings. The distribution of coefficients of
HOMO, on the other hand, is quite different among the isomers
(Figure 3). Focusing on the central BTBT core structure in 1-3,
HOMO of 1 can be understood as a linear combination of
HOMOs of BTBT and 1,3-butadiene, resulting in a partially
acene-like electronic structure, i.e., half of the molecule, the
naphtho[3,2-b]thiophene moiety, is isoelectronic with anthra-
cene. In sharp contrast, HOMOs of 2 and 3 do not preserve the
features of the BTBT core structure, thereby resulting in a very
different electronic system from that of 1, which may be
reflected by the fact that the naphthothiophene moieties in these
compounds are isoelectronic with phenanthrene. These con-
siderations based on MO calculations indicate that the
perturbation effect of the outermost benzene rings is not just
a simple ³-extension, and that the properties of 2 and 3 as a
p-channel organic semiconductor will be different from those
of 1.
Table 1. Electrochemical and UV-Vis Data of 1-3 and
Thus-Estimated HOMO and LUMO Energy Levels
d)
Eoxa)/V
-
b)/nm HOMOc) Eg
LUMO
max
E1/2/onset
peak/edge
/eV
/eV
/eV
1
2
3
+0.75/+0.64 401/420
+0.83/+0.74 367/380
+0.87/+0.78 351/370
¹5.44
¹5.54
¹5.58
¹5.74
2.95 ¹2.49
3.26 ¹2.28
3.35 ¹2.23
3.59 ¹2.15
BTBTe) +1.02/+0.94 332/345
a) Versus Fc/Fc+. b) Absorption spectra. c) Estimated from the
onset of the oxidation peak. d) Determined from the absorption
edge. e) [1]Benzothieno[3,2-b][1]benzothiophene.
We also computed the internal reorganization energy for hole
(-h) for 1-3, since the internal reorganization (-) and the
intermolecular transfer integral (t) are important factors for the
carrier transport under the hopping transport mechanism, which
is believed to be important for thin-film OFETs.13 According to
Marcus theory,13,14 the rate of charge transfer between two
identical molecules, ket, depends on - and t:
1 × 105
8 × 104
1
2
3
6 × 104
Table 2. Calculated HOMO and LUMO Energy Levels and
Reorganization Energy for Hole of 1-3 and BTBT with the
DFT Method at the B3LYP/6-31G(d) Level
4 × 104
2 × 104
h
HOMO
LUMO
-
/eV
/eV
/eV
1
2
3
¹5.18
¹5.32
¹5.47
¹5.58
¹1.81
¹1.61
¹1.46
¹1.26
0.130
0.199
0.192
0.226
250
300
350
400
450
wavelength / nm
BTBT
Figure 2. UV-vis spectra of 1-3 in CH2Cl2.
LUMO
HOMO
1
2
3
BTBT
Figure 3. Calculated frontier orbitals of 1-3 and BTBT.

T. Yamamoto et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
123
(a)
c
a
d1
d1
d2
d2
d1
d1
Figure 4. Molecular structures of 2 (left) and 3 (right).
ket ¼ ðt2=hÞð³=-kBTÞ1=2 expðꢀ-=4kBTÞ
where h is Planck constant, kB Boltzmann constant, and T the
temperature.
o
a
b
c
o
ð1Þ
As summarized in Table 2, all 1-3 molecules have smaller
-hs than that of BTBT. This agrees well with the general
tendency between the extension of ³-conjugation system and
the reorganization energies: with extension of ³-conjugation
system, smaller - is realized.15 On the other hand, comparison
of 1-3 indicates that 1 has apparently smaller -h than those of 2
and 3 by more than 60 meV. This can be qualitatively explained
by the electronic structure of their HOMOs. As discussed
above, only 1 has a partially acene-like electronic structure,
whereas 2 and 3 have a phene-like one. The phene-substructure
can be energetically stabilized by localized aromatic nature at
the neutral state, whereas injection of cationic charge requires
large deformation of molecular structure, which results in
large -h for 2 and 3. On the other hand, the acene-like
electronic structure in 1 receives little stabilization effect from
the localized aromaticity at the neutral state, and thus the
deformation of molecular structure at the cationic state is rather
smaller than those of 2 and 3.
(b)
d1
d2
d1
a
d1
c
d1
b
a
o
c
o
Figure 5. Crystal structures of 2 (a) and 3 (b). Inter-
molecular distances: d1(S£H) = 3.037 ¡, d2(³£³) =
3.536 ¡ for 2; d1(C£H) = 2.861 and 2.866 ¡, d2(³£³) =
3.434 ¡ for 3.
tions may play a critical role.17 For linear isomer 1 with a
partially acene-like structure, the herringbone packing is
favorable as seen in the crystal structures of oligoacenes. In
contrast, for markedly bent, S-shaped 2, the herringbone
structure seems to be less favorable because of the lack of
hydrogen atoms suitable for the face-to-edge CH-³ interaction.
Thus, the optimal intermolecular interaction of 2 is the face-to-
face manner, resulting in the ³-stack structure. In contrast, 3
with a slightly bent molecular structure corresponds to an
intermediate between 1 and 2: the crystal structure of 3 is
understood from the coexistence of two different intermolec-
ular interactions, the face-to-face ³-stacking forming the dimer
structure and the face-to-edge CH-³ interactions resulting in
the sandwich herringbone.
Detailed inspection of the crystal structures of 2 and 3
suggests that the above consideration may be adequate. In the
crystal structure of 2, the intermolecular face-to-face distance in
the ³-stacks is 3.536 ¡, which is almost the same as the
reported value of the sum of van der Waals radii of ³-electrons
(3.536 ¡).18 However, no close contact between the ³-stacks is
noted, indicating that the structure of 2 is highly one-dimen-
sional (1D). In contrast, very short face-to-face distances were
observed for the dimer of 3 (d2 in Figure 5, 3.434 ¡), and the
inter-dimer C-H distances are 2.861 and 2.866 ¡, shorter than
the sum of van der Waals radii of carbon and hydrogen atoms
(2.90 ¡).18 It is reasonable to consider that these two kinds of
close intermolecular interactions play a substantial role in 3 to
take the sandwich herringbone structure.
X-ray Single Crystal Analysis.
Since the molecular
arrangement in the solid state influences the electronic proper-
ties of organic semiconductors in the condensed phase,
elucidation of the exact molecular and crystal structures by
means of X-ray single crystal analysis is vital. As we already
reported, the molecular arrangement in the crystal of 1 is
characterized by herringbone packing (Figure S1),4a which is
known to be the optimal molecular arrangement for high-
performance OFET materials, as can be seen for pentacene.16
The molecular and crystal structures of 2 and 3 determined in
the present work are depicted in Figure 4 and Figure 5,
respectively. Both molecules are almost completely planar with
maximum deviation from the mean plane of 0.0179 ¡ for 2 and
0.0458 ¡ for 3 (Figure 4).
As in the case of 1, both 2 and 3 assume a layer-by-layer
crystal structure, although the crystallographic axis that the
layers pile up along is different: the crystallographic c axis
direction for 1 (Figure S1), and the a axis direction for 2 and 3
(Figure 5). The molecular arrangement of 2 and 3 in their
respective layers however, is strikingly different from that of 1
and also different from each other. 2 takes a simple ³-stack
structure (Figure 5a), whereas 3 assumes the so-called sand-
wich herringbone in which dimers of 3 are packed in a
herringbone manner (Figure 5b).
Although it is difficult to rationalize the crystal structure
differences among the isomers, we speculate that the molecular
shape and the thus-induced preferred intermolecular interac-

124
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010) BCSJ AWARD ARTICLE
Vapor-Deposited Thin Films. Homogeneous thin films of
2 and 3 with metallic luster were prepared by physical vapor
deposition on n-doped Si wafer with 200 nm thermally grown
SiO2 that was surface-modified with octyltrichlorosilane
(OTS)19 or hexamethyldisilazane (HMDS).20 The deposition
of thin films of 3 was successful at any substrate temperatures
during deposition (Tsub, rt, 60 or 100 °C), whereas no thin film
of 2 was obtained at Tsub = 100 °C, probably owing to the high
volatility of 2, which causes re-sublimation on the surface of
the substrate at 100 °C.
grains with needle-like shape, whereas at Tsub = 60 °C
relatively large grains (ca. 1 ¯m in size) were observed. The
surface morphology of the thin film of 3 was also affected by
Tsub: at Tsub = rt, the film consisted of small crystalline grains
of sub-micrometer size. In contrast, in the film deposited at
Tsub = 100 °C, plate-like crystalline grains larger than 1 ¯m in
size were observed. This may be related to the crystalline phase
at Tsub = 100 °C determined by XRD measurements, as we will
discuss later.
The size of crystalline grains in the thin films of 2 and 3
depended markedly on Tsub, and a similar Tsub dependence of
grain size was also observed for the vapor-deposited films of 1
(Figure S2). However, the shape of the crystalline grains was
primarily dependent on the type of compound. Needle-like
and plate-like crystalline grains were observed for 2 and 3,
respectively, whereas a dendritic texture reminiscent of
pentacene thin films21 was observed for 1-based thin film at
Figures 6 and 7 show AFM images of vapor-deposited thin
films of 2 and 3 on HMDS-modified substrates, respectively.
The surface morphology of the thin film of 2 was fairly affected
by Tsub: at Tsub = rt, the film consisted of small crystalline
Tsub = 100 °C on the HMDS-treated substrate (Figure S2).
From these observations, we speculate that the effects of the
number of grain boundaries are similar to each other, although
the nature of the grain boundaries, in other words, connectivity
between grains, may be different for each compound.
XRDs of Evaporated Thin Films. Figure 8 shows the
X-ray diffraction (XRD) patterns of the thin films on HMDS-
modified Si/SiO2 substrates. Irrespective of Tsub, the XRD
patterns of the thin films of 2 are identical and can be well
characterized by the simulated powder pattern of bulk single
crystal (Figure 9a). Two intense peaks (2ª = 6.5 and 19.5°) are
assigned to (100) and (300) diffractions, indicating that the
crystallographic a axis is perpendicular to the substrate. Thus,
the crystallographic bc plane (Figure 5a) is expected to be
parallel to the substrate, that is, the molecular arrangement is
closely related to carrier transport in FET devices.
The XRD patterns of the thin films of 3 show the coexistence
of two different phases, the major phase in each pattern
depending on Tsub. By comparing the simulated powder
patterns of 3 based on the single crystal structure (Figure 9b),
the major phase at Tsub = 100 °C with monolayer thickness
Figure 6. AFM images of evaporated thin films of 2:
Tsub = rt (left) and 60 °C (right).
Figure 7. AFM images of evaporated thin films of 3: Tsub = rt (left), 60 °C (center), and 100 °C (right).

T. Yamamoto et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
125
(a)
(b)
100 °C
60 °C
60 °C
sub = rt
30
Tsub = rt
T
0
5
10
15
20
25
0
5
10
15
20
25
30
2θ / degree
2θ / degree
Figure 8. XRD patterns of 2-based (a) and 3-based (b) thin films on HMDS-modified substrates.
(a) (b)
(1 0 0)
(1 0 0)
(3 0 0)
(3 0 0)
20
0
5
10
15
25
30
0
5
10
15
20
25
30
2
θ
/ degree
2θ / degree
Figure 9. Simulated powder patterns of 2 (a) and 3 (b) based on X-ray single crystal structures.
(d-spacing) of 12.6 ¡ was assigned to the bulk single crystal
phase. Two intense peaks at 2ª = 7.0 and 21.0° correspond to
(100) and (300) reflections, respectively, showing that the
crystallites of 3 in the thin film perpendicular orient with the
crystallographic a axis to the substrate. The crystallographic bc
plane (Figure 5b) is thus parallel to the substrate, which is
actually the channel direction in FET devices as seen in the thin
film of 2.
107,4 the performance of 2- and 3-based OFETs is rather
inferior. For 2-based devices, ®FETs are in the order of
10¹2 cm2 V¹1 s¹1, and for 3-based devices, they are in the order
¹1
of 10¹3 cm2 V¹1 s
.
The present devices showed not only mobilities that were
lower by two or three orders of magnitude than those of
1-based OFETs, but higher threshold voltages (Vths) as well.
Although Vth is not purely a molecular property but one of the
device characteristics influenced by both factors in the device
configuration and properties of the materials used, the high Vth
of 2- and 3-based OFETs can be related to the lower HOMO
energy levels of 2 and 3 than that of 1 (ca. 9 « 4 V).
In contrast, the other phase detected as the major phase at
Tsub = rt has longer d-spacing (15.0 ¡) than that of the bulk
single crystal phase, which is close to the molecular length of 3
(ca. 14.9 ¡). Thus, in the present phase (thin-film phase), the
molecules of 3 are nearly perpendicular to the substrate,
different from the bulk single crystal phase. However, the FET
characteristics of devices fabricated from the thin film of 3
deposited at Tsub = rt are more or less similar to those deposited
at different Tsub (vide infra).
Another point that should be addressed is the weak Tsub
dependence of FET characteristics. For 3-based devices, in
particular, the existence of different phases depending on Tsub
s
was confirmed by XRD analyses. However, the ®FETs of
devices fabricated at Tsub = 100 °C, in which the bulk single
crystal phase is dominant, are almost the same as those of
devices fabricated at lower Tsub. The reasons for the weak Tsub
dependence of FETcharacteristics are not known at the moment.
Electronic Structures of 1-3 in the Solid State. The FET
characteristics of the devices are affected by several factors,
including the electronic structure of an individual molecule, the
molecular arrangement in the thin-film state, grain boundaries
in the channel, and interfacial morphology between the organic
semiconductor and the gate dielectric. Among such factors, the
effects from the molecular arrangement in the thin-film state, in
OFET Devices.
Fabrication of OFET devices was
completed by the deposition of source and drain electrodes
on top of evaporated thin films of 2 or 3 through a shadow
mask. Thus-obtained devices having a “top-contact” config-
uration with W/L = ca. 30 were evaluated in ambient con-
ditions and found to exhibit typical p-channel FET character-
istics, as shown in Figure 10. Table 3 summarizes the FET
characteristics of 2- and 3-based OFET devices. In contrast to
the impressive performance of 1-based OFETs showing ®FET
s
as high as 3.0 cm2 V¹1 s¹1 with current on/off ratio (Ion/Ioff) of

126
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010) BCSJ AWARD ARTICLE
0.0001
0.0035
0.003
0.0025
0.002
0.0015
0.001
0.0005
0
Vd = -60 V
-8 × 10-6
10-5
Vg = -60 V
10-6
10-7
10-8
10-9
10-10
-6 × 10-6
-4 × 10-6
-2 × 10-6
0
Vg = -50 V
Vg = -40 V
Vg = 0, -10, -20, -30 V
0
-10 -20 -30 -40 -50 -60
-50
-30
-60
-40
-20 -10
Vg / V
0 10
Vd / V
-1.8 × 10-6
-1.5 × 10-6
-1.2 × 10-6
-9 × 10-7
-6 × 10-7
-3 × 10-7
0
0.0001
10-5
0.0035
0.003
0.0025
0.002
0.0015
0.001
0.0005
0
Vd = -60 V
Vg = -60 V
Vg = -50 V
10-6
10-7
10-8
Vg = -40 V
10-9
Vg = 0, -10, -20, -30 V
10-10
0
-10 -20 -30 -40 -50 -60
-60 -50 -40 -30 -20 -10
0
Vd / V
Vg / V
Figure 10. Output (left) and transfer characteristics (right) of 2-based (upper) and 3-based (lower) devices with OTS modification
and Tsub = rt.
Table 3. FET Characteristics of 2- and 3-Based Devices
Fabricated on Si/SiO2 Substrates with Different Surface
Treatments and under Different Substrate Temperatures
integrals between HOMOs are shown in Figure 11. For 1 that
gives superior FET performance (Figure 11a), both the transfer
integral along the stacking direction designated as ta and those
in the side-by-side direction (designated as tp and tq) are large up
to 91 meV, clearly indicating that a two-dimensional (2D),
strongly interactive electronic structure is realized. On the other
hand, the calculated transfer integrals of 2 (Figure 11b) indicate
that the electronic structure is highly one-dimensional (1D): the
transfer integral along the stacking direction (designated as tb) is
large (ca. 35 meV), but that in the side-by-side direction (tp) is
less than one-tenth (ca. 2.0 meV) of tb. It is thus understood that
the lack of a 2D interactive structure is one of the reasons for the
inferior transport characteristics of 2-based FETs compared to
those of 1-based devices.
The distribution of the calculated transfer integrals of 3
with the sandwich herringbone structure (Figure 11c) is rather
complicated, and it shows characteristic features of the
structural type. The transfer integral between HOMOs in the
dimers is very large (tp = 172 meV) compared to those of other
inter-dimer modes. Small but similar magnitude of inter-dimer
transfer integrals both in the crystallographic a (tq2 = 6.0 meV).
and b (tb = 2.0 meV) directions suggests that weakly interactive
2D electronic structure is plausible for the molecular packing
of 3 in the crystal. Thus, the poor transport characteristics of
3-based FETs can be explained by the weak orbital coupling
between the dimers, although the intra-dimer orbital coupling is
very strong.
(Tsub
)
a)
FET
/cm2 V¹1 s
Surface-treatment Tsub
®
Ion/Ioff
Vth/V
¹1
reagent
HMDS
/°C
¹2
2
3
rt
1.0-1.2 © 10
60 0.92-1.1 © 10
1.2-2.3 © 10
60 0.95-2.6 © 10
104
103
¹12 « 2
¹13 « 4
¹2
¹2
OTS
rt
5 © 104 ¹14 « 3
104
103
¹15 « 5
¹2
¹3
HMDS
OTS
rt
60
3.2-3.6 © 10
2.8-3.1 © 10
100 4.8-7.4 © 10
3.8-7.4 © 10
2.2-8.6 © 10
100 1.4-2.6 © 10
¹14 « 3
5 © 103 ¹13 « 2
¹3
¹3
¹3
¹3
¹2
104
105
¹27 « 3
¹24 « 2
rt
60
5 © 103 ¹28 « 5
5 © 104 ¹33 « 5
a) Data from more than 10 devices.
particular, the intermolecular electronic coupling is one of the
most important, according to Marcus theory.13,14
In order to evaluate intermolecular electronic coupling more
quantitatively, calculation of transfer integrals between HOMOs
of molecules 1-3 in the semiconducting layer elucidated by X-
ray analyses were carried out using the Amsterdam Density
Functional (ADF) program package.13e,22,23 Calculated transfer

T. Yamamoto et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
127
(a)
very different from that of 1-based devices. In contrast to the
impressive performance of 1-based OFETs with ®FETs as
high as 3.0 cm2 V¹1 s¹1, the FET performance of 2- and
¹3
3-based OFETs was inferior with ®FETs of the order of 10
-
ta
10¹2 cm2 V¹1 s¹1. In order to clarify such large differences,
we focused on the surface morphology of the thin films, the
molecular orientation on the substrates, and the molecular
arrangements in the solid state. It turned out that the substrate
temperatures during thin-film deposition (Tsubs) had a similar
influence on the grain sizes of the thin films of 1-3, whereas the
shapes of crystalline grains largely depended on the compound,
which may affect the connectivity between crystalline grains.
Among the three isomers, the thin film of 1 with dendrite-like
morphology reminiscent of the thin-film morphology of
pentacene seems to be most suitable for use in the fabrication
of high-performance OFETs.
tp
tp
tq
tq
a
ta
tp = 14 meV
ta = 71 meV
tq = 91 meV
(b)
XRD studies of both thin films and single crystals indicated
that the molecular arrangements in both states are basically the
same and that in the thin-film state, the molecules stand on the
surface with their molecular long axes in the surface normal
direction. Comparison of the electronic structures of 1-3 in the
solid state using the single crystal structure indicated that the
calculated electronic structures largely depend on the molecular
arrangements in the solid state: 2D with large transfer integrals
for 1, 1D with small transfer integrals for 2, and 2D with small
intermolecular transfer integrals for 3. The FET characteristics
of devices based on 1-3 were consistent with the electronic
structures in the solid state. These experimental as well as
theoretical results clearly show that 1 having a highly 2D
structure with large intermolecular overlap is most suitable for
use in the fabrication of high-performance OFET devices.
The present results indicate that molecular structure and
shape, even for molecules with the same molecular formula
and symmetry, are crucial parameters to determine the solid-
state properties of organic semiconductors. Therefore, careful
molecular design taking into account molecular ordering
parameters arising from the molecular structure and shape is
necessary for the further development of far superior organic
semiconductors.
tb
tp
tp
tp
tb
tp
b
tb = 35 meV
tp = 2.0 meV
(c)
tb
tq1
tq2
tq2
tq1
tq1
tp
tq2
tq1
tq2
tb
b
tp = 172 meV
tb = 2.0 meV
q1 = 0.10 meV
tq2 = 6.0 meV
t
Experimental
General. All chemicals and solvents are of reagent grade
unless otherwise indicated. THF was distilled from sodium
benzophenone ketyl prior to use. Nuclear magnetic resonance
spectra were obtained in deuterated chloroform with a JEOL
Lambda 400 spectrometer operating at 400 MHz for 1H with TMS
as internal reference; chemical shifts (¤) are reported in parts per
million. EI-MS spectra were obtained on a Shimadzu QP-5050A
spectrometer using an electron impact ionization procedure
(70 eV). The molecular ion peaks of the compounds showed a
typical isotopic pattern, and all the mass peaks are reported based
on 32S, unless otherwise stated. Cyclic voltammograms (CVs)
were recorded on a Hokuto Denko HA-301 potentiostat and
a Hokuto Denko HB-104 function generator in benzonitrile
Figure 11. Molecular arrangements and calculated transfer
integrals in the semiconducting layer viewed along the
molecular long axes of 1 (a), 2 (b), and 3 (c).
Conclusion
In summary, we have synthesized two isomers 2 and 3 of
DNTT (1), thereby completing the synthesis of all members of
the dinaphthothieno[3,2-b]thiophene family with C2h symme-
try. In the selective synthesis of 2 and 3, we employed a unique
three-step synthesis from naphthaldehyde originally developed
for the synthesis of 1. Characterization of 1-3 by means of
cyclic voltammetry and UV-vis absorption spectra with the
aid of DFT calculations clearly indicated that the molecular
electronic structures of the three isomers are different, although
they have the same aromatic substructures.
containing tetrabutylammonium hexafluorophosphate (Bu4NPF6,
¹1
0.1 M) as supporting electrolyte at a scan rate of 100 mV s
.
Counter and working electrodes were made of Pt, and the reference
electrode was Ag/AgCl. All the potentials were calibrated with the
standard ferrocene/ferrocenium redox couple (E1/2 = +0.46 V
measured under identical conditions). UV-vis spectra in CH2Cl2
Evaporated thin-film-based OFET devices of 2 and 3 showed
typical p-channel FET characteristics but their performance was

128
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010) BCSJ AWARD ARTICLE
solution were recorded on a Shimadzu UV-3100 spectrometer.
2-Methylthio-1-naphthaldehyde (5a).8 Caution! This pro-
cedure involves use of dimethyl disulfide, which emits a powerful
stench. Therefore, this must be carried out in a well-ventilated
fume hood with disposable gloves.
After cooling to room temperature, a solution of 5a (0.405 g,
2.0 mmol) in THF (5 mL) was added to the mixture, and zinc
powder (0.392 g, 6.0 mmol) was added slowly. The resulting
mixture was then refluxed for 18 h. After cooling to room
temperature, the mixture was diluted with saturated aqueous
sodium hydrogen carbonate solution (10 mL) and chloroform
(30 mL) and stirred for 1 h. Concentrated HCl solution (10 mL)
was added to the mixture, and the mixture was filtered through a
filter paper, and the filtrate was separated into an organic and an
aqueous layer. The aqueous layer was extracted with chloroform
(20 mL © 3), and the combined organic layer was dried (MgSO4)
and concentrated in vacuo. The residue was purified by column
chromatography on silica gel eluted with hexane-ethyl acetate
(9:1, v/v, Rf = 0.6) to give 6a as a pale yellow solid (0.182 g, 49%
isolated yield). Analytical sample was obtained by recrystallization
from dichloromethane. Pale yellow needles; mp 159.0-160.0 °C;
1H NMR (400 MHz, CDCl3): ¤ 2.59 (s, 6H, SMe), 7.28 (s, 2H,
CH=CH), 7.46 (brdd, 2H, J = 8.3, 7.0 Hz, ArH), 7.51 (d, 2H,
J = 9.3 Hz, ArH), 7.55 (brdd, 2H, J = 8.3, 7.0 Hz, ArH), 7.81 (d,
2H, J = 9.3 Hz, ArH), 7.84 (brd, 2H, J = 8.3 Hz, ArH), 8.59 (d,
2H, J = 8.3 Hz, ArH); 13C NMR (100 MHz, CDCl3): ¤ 16.7, 123.8,
125.2, 125.6, 126.7, 128.0, 128.2, 131.7, 132.0, 132.5, 133.6,
134.8; IR (KBr): ¯ 1503, 1134, 811, 803, 778, 743 cm¹1; EIMS
(70 eV): m/z = 372 (M+), 357 (M+ ¹ Me), 325 (M+ ¹ SMe);
Anal. Calcd for C24H20S2: C, 77.37; H, 5.41%. Found: C, 77.57; H,
5.52%.
To a solution of N,N,N¤-trimethylethylenediamine (2.80 mL,
22.0 mmol) in THF (50 mL) was added butyllithium (13.84 mL
of 1.59 M solution in hexane, 22.0 mmol) at ¹20 °C. After the
mixture was stirred for 15 min at the same temperature, a solution
of 1-naphthaldehyde (4a, 2.72 mL, 20.0 mmol) in THF (20 mL)
was slowly added over a period of 15 min, and then additional
butyllithium (37.74 mL of 1.59 M solution in hexane, 60.0 mmol)
was added, and the resulting mixture was stirred for 22 h at
¹20 °C. Excess dimethyl disulfide (7.97 mL, 90.0 mmol) was then
added, and after stirring at room temperature for 1 h, 1 M hydro-
chloric acid (20 mL) was added. The resulting mixture was stirred
for 10 h and was extracted with dichloromethane (20 mL © 3). The
combined extracts were dried (MgSO4) and concentrated in vacuo.
The residue was purified by column chromatography on silica gel
eluted with hexane-ethyl acetate (9:1, v/v, Rf = 0.4) to give 5a as
a yellow solid (2.498 g, 62% isolated yield). Mp 52.0-53.0 °C;
1H NMR (400 MHz, CDCl3): ¤ 2.62 (s, 3H, SMe), 7.52 (brdd, 1H,
J = 8.7, 8.5 Hz, ArH), 7.56 (d, 1H, J = 8.7 Hz, ArH), 7.64 (brdd,
1H, J = 8.7, 8.5 Hz, ArH), 7.84 (brd, 1H, J = 8.5 Hz, ArH), 7.99
(d, 1H, J = 8.7 Hz, ArH), 8.71 (brd, 1H, J = 8.5 Hz, ArH), 11.04
(s, 1H, CHO); 13C NMR (100 MHz, CDCl3): ¤ 16.7, 123.0, 123.7,
125.9, 127.2, 128.5, 129.1, 131.0, 132.1, 134.1, 145.7, 190.8; IR
trans-1,2-Bis(1-methylthio-2-naphthyl)ethene (6b).
To an
¹1
(KBr): ¯ 1668 (C=O), 1544, 1437, 1354, 1191, 1120, 745 cm
;
ice-cooled suspension of zinc powder (0.392 g, 6.0 mmol) in THF
(10 mL), titanium tetrachloride (0.66 mL, 6.0 mmol) was slowly
added, and the resulting mixture was refluxed for 1.5 h. After
cooling to room temperature, a solution of 5b (0.405 g, 2.0 mmol)
in THF (10 mL) was slowly added to the mixture, and the mixture
was then refluxed for 20 h. After cooling to room temperature, the
mixture was diluted with saturated aqueous sodium hydrogen
carbonate solution (30 mL) and chloroform (30 mL) and stirred
for 3.5 h. The mixture was filtered through a Celite pad, and the
filtrate was separated into an organic and an aqueous layers. The
aqueous layer was extracted with chloroform (20 mL © 3), and the
combined organic layer was dried (MgSO4) and concentrated in
vacuo. The resulting reside was purified by passing through a silica
gel pad eluted with dichloromethane to give 6b as pale yellow
crystals (0.097 g, 26%). Analytical sample was obtained by
recrystallization from dichloromethane. Pale yellow crystals; mp
EIMS (70 eV): m/z = 202 (M+); Anal. Calcd for C12H10OS: C,
71.25; H, 4.98%. Found: C, 71.44; H, 4.96%.
1-Methylthio-2-naphthaldehyde (5b).9 Caution! This pro-
cedure involves use of dimethyl disulfide, which emits a powerful
stench. Therefore, this must be carried out in a well-ventilated
fume hood with disposable gloves.
To a solution of N,N,N¤-trimethylethylenediamine (2.87 mL,
21.0 mmol) in THF (35 mL) was added butyllithium (13.2 mL of
1.59 M solution in hexane, 21.0 mmol) at ¹30 °C. After the
mixture was stirred for 15 min at the same temperature, a solution
of 2-naphthaldehyde (4b, 2.0 g, 12.8 mmol) in THF (10 mL) was
slowly added over a period of 5 min, and then additional
butyllithium (24.15 mL of 1.59 M solution in hexane, 38.4 mmol)
was added, and the resulting mixture was stirred for 3.5 h at
¹30 °C. Excess dimethyl disulfide (5.67 mL, 64 mmol) was then
added, and after stirring at room temperature for 2 h, 1 M
hydrochloric acid (20 mL) was added. The resulting mixture was
stirred for 10 h and was extracted with dichloromethane
(20 mL © 3). The combined extracts were dried (MgSO4) and
concentrated in vacuo. The residue was purified by column
chromatography on silica gel eluted with hexane-ethyl acetate
(9:1, v/v, Rf = 0.4) to give 5b as a colorless solid (0.38 g, 15%
1
178.0 °C; H NMR (400 MHz, CDCl3): ¤ 2.37 (s, 6H, SMe), 7.51
(dd, 2H, J = 6.9, 6.9 Hz, ArH), 7.61 (dd, 2H, J = 6.9, 6.9 Hz,
ArH), 7.86 (d, 2H, J = 8.7 Hz, ArH), 7.88 (d, 2H, J = 8.7 Hz,
ArH), 8.03 (d, 2H, J = 8.3 Hz, ArH), 8.40 (s, 2H, CH=CH), 8.78
(d, 2H, J = 8.3 Hz, ArH); 13C NMR (100 MHz, CDCl3): ¤ 20.0,
123.9, 126.2, 126.8, 127.2, 128.5, 129.3, 130.6, 133.0, 133.6,
135.2, 139.3; IR (KBr): ¯ 1503, 1309, 1267, 971, 819, 812,
756 cm¹1; EIMS (70 eV): m/z = 372 (M+), 357 (M+ ¹ Me), 325
(M+ ¹ SMe); Anal. Calcd for C24H20S2: C, 77.37; H, 5.41%.
Found: C, 77.39; H, 5.27%.
Dinaphtho[2,1-b:2¤,1¤-f ]thieno[3,2-b]thiophene (2). A solu-
tion of trans-1,2-bis(2-methylthio-1-naphthyl)ethene (6a, 0.062 g,
0.166 mmol) and iodine (1.348 g, 5.312 mmol) in chloroform
(5 mL) was refluxed for 27 h. After cooling to room temperature,
saturated aqueous sodium hydrogen sulfite solution (10 mL) was
added, and the aqueous layer was extracted with chloroform
(20 mL © 3), and the combined organic layer was dried (MgSO4)
and concentrated in vacuo. The residue was purified by column
chromatography on silica gel eluted with hexane-dichloromethane
1
isolated yield). Mp 105.0-106.0 °C; H NMR (400 MHz, CDCl3):
¤ 2.45 (s, 3H, SMe), 7.67 (ddd, 1H, J = 6.8, 6.8, 2.0 Hz, ArH),
7.70 (ddd, 1H, J = 7.0, 7.0, 2.6 Hz, ArH), 7.88-7.92 (m, 2H, ArH),
7.98 (d, 1H, J = 8.7 Hz, ArH), 8.82-8.85 (m, 1H, ArH), 11.08 (brs,
1H, CHO); 13C NMR (100 MHz, CDCl3): ¤ 21.6, 123.3, 126.8,
127.7, 128.8, 129.1, 129.7, 134.4, 135.9, 136.6, 141.6, 193.5; IR
(KBr): ¯ 1675 (C=O), 1653, 1423, 1315, 1259, 825, 782, 763
cm¹1; EIMS (70 eV): m/z = 202 (M+); Anal. Calcd for C12H10OS:
C, 71.25; H. 4.98%. Found: C, 71.28; H, 4.87%.
trans-1,2-Bis(2-methylthio-1-naphthyl)ethene (6a). To ice-
cooled THF (10 mL), titanium tetrachloride (0.66 mL, 6.0 mL) was
slowly added, and the resulting mixture was refluxed for 30 min.

T. Yamamoto et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
129
(2:1, v/v, Rf = 0.7) and recrystallization with dichloromethane-
hexane to give 2 as an off-white solid (0.013 g, 23% isolated
yield). Analytical sample was obtained by vacuum sublimation
(source temperature: 230 °C under ca. 10¹3 Pa). Colorless solid;
mp >300 °C; 1H NMR (400 MHz, CDCl3): ¤ 7.66 (brdd, 2H,
J = 8.3, 8.3 Hz, ArH), 7.81 (brdd, 2H, J = 8.3, 8.3 Hz, ArH), 7.90
(d, 2H, J = 8.9 Hz, ArH), 8.06 (d, 2H, J = 8.9 Hz, ArH), 8.07 (brd,
2H, J = 8.3 Hz, ArH), 8.59 (brd, 2H, J = 8.3 Hz, ArH); IR (KBr):
¯ 1364, 1225, 903, 790, 732 cm¹1; EIMS (70 eV): m/z = 340
(M+), 170 (M+/2); Anal. Calcd for C22H12S2: C, 77.61; H, 3.55%.
Found: C, 77.66; H, 3.56%.
2 © 10¹3 Pa. On top of the organic thin film, gold films (80 nm) as
drain and source electrodes were deposited through a shadow
mask. For a typical device, the drain-source channel length (L) and
width (W) are 50 ¯m and ca. 1.5 mm, respectively. The character-
istics of the OFET devices were measured at room temperature
in air with a Keithley 6430 subfemtoammeter and a Keithley
2400 source meter, operated by a LabTracer program and GPIB
interface. Field-effect mobility (®FET) was calculated in the
saturation regime (Vd = ¹60 V) of Id using the following equation,
2
Id ¼ ðWCi=2LÞ®FETðVg ꢀ VthÞ
ð2Þ
Dinaphtho[1,2-b:1¤,2¤-f ]thieno[3,2-b]thiophene (3).5 A solu-
tion of trans-1,2-bis(3-methylthio-2-naphthyl)ethene (6b, 0.0814
g, 0.218 mmol) and iodine (1.7706 g, 6.976 mmol) in chloroform
(6 mL) was refluxed for 11 h. After cooling to room temperature,
saturated aqueous sodium hydrogen sulfite solution (10 mL) was
added, and the resulting precipitate was collected by filtration
and was washed with water and chloroform to give 3 as a colorless
solid (0.0245 g, 33%). Analytical sample was obtained by vacuum
sublimation (source temperature: 200 °C under ca. 10¹3 Pa).
Colorless solid; mp >300 °C; 1H NMR (400 MHz, CDCl3): ¤
7.56-7.59 (m, 2H, ArH), 7.64-7.68 (m, 2H, ArH), 7.90 (d, 2H, J =
8.7 Hz, ArH), 7.98-8.01 (m, 4H, ArH), 8.20 (d, 2H, J = 7.9 Hz,
ArH); IR (KBr): ¯ 1380, 1322, 1257, 806, 745 cm¹1; EIMS
(70 eV): m/z = 340 (M+), 170 (M+/2); Anal. Calcd for C22H12S2:
C, 77.61; H, 3.55%. Found: C, 77.65; H, 3.64%.
where Ci is the capacitance of the SiO2 insulator, and Vg and Vth are
the gate and threshold voltages, respectively. Current on/off ratio
(Ion/Ioff) was determined from Id at Vg = 0 V (Ioff) and Vg = ¹60 V
(Ion). The ®FET data appearing in Table 3 are values from more
than 10 different devices.
Theoretical Calculations. Geometry optimization and normal
mode MO calculations of 1-3 were carried out by the DFT method
at the B3LYP/6-31G(d) level using the Gaussian03 program.12
The transfer integrals (t) for neighboring molecules in the crystal
structures were calculated using the fragment analysis method
embedded in Amsterdam Differential Functional (ADF) program
with the PW91 functional and Slater-type triple-¦ plus polarization
(TZP) basis sets, following the procedure described by Siebbeles
et al.23 and Chao et al.25
X-ray Crystallographic Analysis.
Single crystals were
This work was partially supported by a Grant-in-Aid for
Scientific Research from the Ministry of Education, Culture,
Sports, Science and Technology, Japan. Combustion elemental
analyses were carried out at the Natural Science Center for
Basic Research and Development (N-BARD), Hiroshima
University. Computation in the present study was performed
with the HPC system PC Grid/Cluster of the Information
Media Center, Hiroshima University. We also thank Mr. K.
Chiba, Ryoka Systems Inc., Japan for help in the electronic
structure calculations with ADF program.
obtained by recrystallization from m-dichlorobenzene for 2 and
from chloroform for 3. The X-ray crystal structure analysis was
made on a Rigaku Rapid-S imaging plate (Mo K¡ radiation,
- = 0.71069 ¡, graphite monochromator, T = 296 K, 2ªmax
=
55.0°). The structure was solved by the direct method SHELXS.
The non-hydrogen atoms were refined anisotropically. Hydrogen
atoms were included but not refined. All calculations were
performed using the SHELXL-97 package program.24 Crystallo-
graphic data for 2 and 3 have been deposited at the Cambridge
Dada Centre: Deposit numbers CCDC-734667 and -734668,
respectively.
Crystal data for 2: C22H12S2, Mr = 340.46, colorless needle,
0.75 © 0.10 © 0.05 mm3, Monoclinic, space group P21/c
(No. 14), a = 14.3186(16), b = 3.9269(4), c = 13.882(2) ¡, ¢ =
105.092(6)°, V = 753.63(16) ¡3, Z = 2,
Supporting Information
Molecular arrangement of 1 in the bulk single crystal, AFM
images of vapor-deposited films of 1. This material is available
free of charge on the web at http://www.csj.jp/journals/bcsj/.
¹3
Dcalcd = 1.500 g cm ,
R = 0.044 for 1712 observed reflections (I > 2·(I)) and 109
variable parameters, Rw = 0.1392 for all data.
References
Crystal data for 3: C22H12S2, Mr = 340.46, colorless prism,
0.20 © 0.15 © 0.10 mm3, Monoclinic, space group P21/c
1
a) D. J. Gundlach, Y. Y. Lin, T. N. Jackson, S. F. Nelson,
D. G. Schlom, IEEE Electron Device Lett. 1997, 18, 87. b) T. W.
Kelley, L. D. Boardman, T. D. Dunbar, D. V. Muyres, M. J.
Pellerite, T. P. Smith, J. Phys. Chem. B 2003, 107, 5877.
(No. 14), a = 13.0500(8), b = 8.8641(3), c = 13.6026(6) ¡, ¢ =
¹3
103.239(2)°, V = 1531.68(13) ¡3, Z = 4, Dcalcd = 1.476 g cm
,
R = 0.051 for 3519 observed reflections (I > 2·(I)) and 265
variable parameters, Rw = 0.1399 for all data.
2
a) M. M. Payne, S. R. Parkin, J. E. Anthony, J. Am. Chem.
Soc. 2005, 127, 8028. b) J. E. Anthony, Chem. Rev. 2006, 106,
Device Fabrication.
Si/SiO2 substrates were modified as
5028.
follows. Si/SiO2 substrate with OTS (octyltrichlorosilane)-SAM
(self-assembled monolayer) was obtained by immersing the
substrate in 0.1 M OTS in toluene at 60 °C for 20 min.19 Treatment
with HMDS (hexamethyldisilazane) was carried out by exposing
silicon wafers to HMDS vapor at room temperature in a closed
desiccator under nitrogen for 12 h.20 OFETs were fabricated in the
“top-contact” configuration on a heavily doped n+-Si(100) wafer
with a 200 nm-thick thermally grown SiO2 (Ci = 17.3 nF cm¹2). A
thin film (50 nm thick) of DNTT as the active layer was vacuum-
3
R. Mondal, R. M. Adhikari, B. K. Shah, D. C. Neckers,
Org. Lett. 2007, 9, 2505.
4
a) T. Yamamoto, K. Takimiya, J. Am. Chem. Soc. 2007,
129, 2224. b) T. Yamamoto, K. Takimiya, J. Photopolym. Sci.
Technol. 2007, 20, 57.
5
K. Takimiya, T. Yamamoto, H. Ebata, T. Izawa, Sci.
Technol. Adv. Mater. 2007, 8, 273.
The synthesis of 3 was already reported, see: M. T.
6
Srinivasa, L. J. Pandya, B. D. Tilak, J. Sci. Ind. Res., Sect. B 1961,
20B, 169.
deposited on the Si/SiO2 substrate maintained at various temper-
¹1
atures (Tsub) at a rate of 1-2 ¡ s
under a pressure of ca.
7
D. L. Comins, J. D. Brown, J. Org. Chem. 1984, 49, 1078.

130
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010) BCSJ AWARD ARTICLE
8
M. S. Korobov, L. E. Nivorozhkin, V. I. Minkin, J. Org.
14 R. A. Marcus, Rev. Mod. Phys. 1993, 65, 599.
Chem. USSR 1973, 9, 1739.
15 a) V. Coropceanu, O. Kwon, B. Wex, B. R. Kaafarani, N. E.
Gruhn, J. C. Durivage, D. C. Neckers, J.-L. Brédas, Chem.®Eur. J.
2006, 12, 2073. b) G. R. Hutchison, M. A. Ratner, T. J. Marks,
J. Am. Chem. Soc. 2005, 127, 16866.
16 a) J. Cornil, J. P. Calbert, J. L. Brédas, J. Am. Chem. Soc.
2001, 123, 1250. b) H. Yoshida, N. Sato, Appl. Phys. Lett. 2006,
89, 101919. c) H. Yoshida, K. Inaba, N. Sato, Appl. Phys. Lett.
2007, 90, 181930. d) S. Schiefer, M. Huth, A. Dobrinevski, B.
Nickel, J. Am. Chem. Soc. 2007, 129, 10316.
17 Similar analyses of the crystal structures of polycyclic
aromatic hydrocarbons were reported: G. R. Desiraju, A.
Gavezzotti, J. Chem. Soc., Chem. Commun. 1989, 621.
18 A. Bondi, J. Phys. Chem. 1964, 68, 441.
19 B. S. Ong, Y. Wu, P. Liu, S. Gardner, J. Am. Chem. Soc.
2004, 126, 3378.
20 M.-H. Yoon, S. A. DiBenedetto, A. Facchetti, T. J. Marks,
J. Am. Chem. Soc. 2005, 127, 1348.
21 C. D. Dimitrakopoulos, P. R. L. Malenfant, Adv. Mater.
2002, 14, 99.
22 ADF2008.01, Scientific Computing & Modeling (SCM),
Theoretical Chemistry, Vrije Universiteit, Amsterdam, The Neth-
erlands, http://www.scm.com.
23 a) K. Senthilkumar, F. C. Grozema, F. M. Bickelhaupt,
L. D. A. Siebbeles, J. Chem. Phys. 2003, 119, 9809. b) P. Prins, K.
Senthilkumar, F. C. Grozema, P. Jonkheijm, A. P. H. J. Schenning,
E. W. Meijer, L. D. A. Siebbeles, J. Phys. Chem. B 2005, 109,
18267.
9
N. P. Buu-Hoï, N. Hoán, D. Lavit, J. Chem. Soc. 1953, 485.
10 a) T. Mukaiyama, T. Sato, J. Hanna, Chem. Lett. 1973,
1041. b) J. E. McMurry, Chem. Rev. 1989, 89, 1513. c) D. Lenoir,
Synthesis 1989, 883.
11 J. Pommerehne, H. Vestweber, W. Guss, R. F. Mahrt, H.
Bässler, M. Porsch, J. Daub, Adv. Mater. 1995, 7, 551.
12 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr., T. Vreven,
K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi,
V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R.
Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross,
V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann,
O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski,
P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J.
Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C.
Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari,
J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J.
Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I.
Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham,
C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M. W. Gill,
B. Johnson, W. Chen, M. W. Wong, C. Gonzalez, J. A. Pople,
Gaussian 03, Revision C.02, Gaussian, Inc., Wallingford CT, 2004.
13 a) K. Sakanoue, M. Motoda, M. Sugimoto, S. Sakaki,
J. Phys. Chem. A 1999, 103, 5551. b) J.-L. Brédas, D. Beljonne, V.
Coropceanu, J. Cornil, Chem. Rev. 2004, 104, 4971. c) E. F.
Valeev, V. Coropceanu, D. A. da Silva Filho, S. Salman, J.-L.
Brédas, J. Am. Chem. Soc. 2006, 128, 9882. d) V. Coropceanu, J.
Cornil, D. A. da Silva Filho, Y. Olivier, R. Silbey, J.-L. Brédas,
Chem. Rev. 2007, 107, 926. e) E.-G. Kim, V. Coropceanu, N. E.
Gruhn, R. S. Sánchez-Carrera, R. Snoeberger, A. J. Matzger, J.-L.
Brédas, J. Am. Chem. Soc. 2007, 129, 13072.
24 G. M. Sheldrick, SHELX-97-Program for the Refinement of
Crystal Structures, University of Göttingen, Germany, 1997.
25 a) M.-Y. Kuo, H.-Y. Chen, I. Chao, Chem.®Eur. J. 2007,
13, 4750. b) Y.-C. Chang, Y.-D. Chen, C.-H. Chen, Y.-S. Wen, J. T.
Lin, H.-Y. Chen, M.-Y. Kuo, I. Chao, J. Org. Chem. 2008, 73,
4608.