An iodine effect in ambipolar organic field-effect transistors based on indigo derivatives

Article abstract of DOI:10.1039/c5tc01023c

5,5′-Diiodoindigo (4) exhibits excellent ambipolar transistor properties with hole/electron mobilities of μ_h/μ_e = 0.42/0.85 cm² V^-1 s^-1. The halogen substituted indigos show decreasing tilt angles from F to I in the crystals. In addition, the iodine-iodine interaction provides extraordinarily large interchain interaction. However, the X-ray diffraction suggests that the indigo molecules are arranged approximately perpendicular to the substrate in the thin films, probably due to the extra iodine-iodine interaction. The remarkable performance is ascribed to this characteristic supramolecular interaction.

Full text of DOI:10.1039/c5tc01023c

View Article Online
View Journal
Journal of
Materials Chemistry C
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: O. Pitayatanakul,
K. Iijima, M. Ashizawa, T. Kawamoto, H. Matsumoto and T. Mori, J. Mater. Chem. C, 2015, DOI:
10.1039/C5TC01023C.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/materialsC

Page 1 of 8
Journal of Materials Chemistry C
View Article Online
DOI: 10.1039/C5TC01023C
Journal Name
RSCPublishing
ARTICLE
Iodine Effect in Ambipolar Organic Field-Effect
Transistors Based on Indigo Derivatives
Cite this: DOI: 10.1039/x0xx00000x
Oratai Pitayatanakul,*a Kodai Iijima,a Minoru Ashizawa,a Tadashi
Kawamoto,a Hidetoshi Matsumoto,a and Takehiko Mori*ab
Received 00th January 2012,
Accepted 00th January 2012
5,5’ꢀDiiodoindigo (
4
) exhibits excellent ambipolar transistor properties with the hole/electron
0.42/0.85 cm2 V−1 s−1.
The halogen substituted indigos show
mobilities of µh µe
/
=
DOI: 10.1039/x0xx00000x
systematically decreasing energy gaps from F to I due to the spreading highest occupied
molecular orbitals, and decreasing tilt angles in the crystals. In addition, the iodineꢀiodine
www.rsc.org/
interaction provides extraordinarily large interchain interaction.
However, the Xꢀray
diffraction suggests that the indigo molecules are arranged approximately perpendicular to the
substrate in the thin films, probably due to the extra iodineꢀiodine interaction. The remarkable
performance is ascribed to this characteristic supramolecular interaction.
withdrawing and an origin of the acceptor ability. However, it
is surprising that such a minimal molecule shows ambipolar
properties.11ꢀ13 In addition, the intermolecular interaction
Introduction
Ambipolar organic semiconductors, which exhibit both
pꢀtype
and ꢀtype transport, have attracted a great deal of attention due
n
mediated by the hydrogen bonding (ꢀNH
…O=Cꢀ) plays an
important role in determining the molecular packing.11,13,14 It
has been reported that Tyrian purple (6,6’ꢀdibromoindigo)
to the potential application to organic photovoltaic devices and
organic lightꢀemitting transistors.1ꢀ3 In particular, diketopyrrolo
pyrrole (DPP)ꢀbased polymers have afforded excellent
ambipolar materials, which show hole and electron fieldꢀeffect
mobilities (µh and µe) exceeding 1 cm2 V−1 s−1.2,3 It has been
recently reported that even the smallꢀmolecule DPP derivatives
shows improved ambipolar transport with ꢀh
V−1 s−1.6,7 We have reported that 5,5’ꢀdibromoindigo (
Scheme 1) and 5,5’ꢀdiphenylindigo exhibit excellent mobilities,
µh
µe = 0.21/0.35 and 0.56/0.95 cm2 V−1 s−1, respectively.9
Compound has oneꢀdimensional stacks basically similar to
/
ꢀe = 0.4/0.4 cm2
3
,
/
show ambipolar transport with µh
Similarly to the DPP derivatives, indigo shows high
ambipolar performance.5ꢀ10
Indigo is a plantꢀorigin dye
/
µe = 0.01~0.06 cm2 V−1 s−1.4
3
the parent indigo.14 In contrast, the diphenyl derivative has a
characteristic structure where the phenyl parts are not coplanar
to the indigo core to form a herringbone packing, but the indigo
core constructs a twoꢀdimensional brickwork packing. Owing
to this characteristic structure, the indigo cores are standing
perpendicular to the substrate. We have previously reported in
naphthalene diimide (NDI) series compounds that the charge
mobility attains the maximum when the molecular long axis is
perpendicular to the substrate.15 In this respect, the diphenyl
indigo has an ideal structure to realize high mobility, and this is
considered to be the origin of the actually observed high
produced from Indigofera tinctoria and Isatis tintora, which
have been cultivated for at least four thousand years for
coloring textiles.6
interaction, indigo shows
Because of the strong intermolecular
very high melting point
a
(390~392°C) and an extremely low solubility in common
organic solvents together with the ambipolar transport with
wellꢀbalanced mobilities ꢀh/
ꢀe = 0.01/0.01 cm2 V−1 s−1.5 The
amine (ꢀNH) group is electron donating and an origin of the
donor ability, and the carbonyl group (ꢀC=O) is electron
Scheme 1. Synthesis of indigo derivatives.
This journal is © The Royal Society of Chemistry 2013
J. Name., 2013, 00, 1-3 |
1

Journal of Materials Chemistry C
Page 2 of 8
ARTICLE
VJieowuArrtnicalelONnlainme e
DOI: 10.1039/C5TC01023C
performance.
Recently, several halogenꢀsubstituted indigo derivatives
have been reported, where the introduction of the halogen
atoms (F, Cl, and Br) to the 5ꢀpositions (1ꢀ3) induces the
bathochromic shifts to reduce the energy gaps.10 In the present
work, we show that introduction of iodine atoms, namely 5,5’ꢀ
diiodoindigo (4), remarkably improves the transistor properties.
The electrochemical properties, transistor characteristics,
crystal structures, and thinꢀfilm properties are compared with
other halogenꢀsubstituted compounds
(1ꢀ3), and the
characteristic role of the iodine atom is demonstrated.
Polarizability of a halogen atom increases in the order of F < Cl
< Br < I, and iodine shows particularly large polarizability
among the halogen atoms. Accordingly, iodine atoms mediate
halogenꢀhalogen interactions and halogen bonds, and
sometimes construct supramolecular architecture.16 Halogen
bonds have been extensively investigated in the conducting
cationꢀradical salts based on tetrathiafulvalene (TTF)
derivatives.17 In the chargeꢀtransfer salts, a halogen atom
substituted on the TTF skeleton makes a close contact with
such an anion as Cl−, Br−, and CN− to form characteristic
molecular packing. It has been also attempted to include the
Fig. 1. Energy levels of 1ꢀ4 estimated from the redox potentials and from
the Gaussian 09 calculation at the B3LYP/CEPꢀ31G level in the
parentheses. The energy gaps are evaluated from the redox potentials
(EgCV) and the absorption edges (EgUV).
Au
Au
Indigo derivatives
Passivation layer, TTC
Insulator, SiO2
third component such as diiodoacethylene and
pꢀbis(iodo
ethynyl)benzene, where the iodine atom makes a contact with
Cl− and Br− anions to construct supramolecular assembly.17f,g In
the crystals of neutral TTF, it has been demonstrated that the
halogenꢀhalogen contact gives a significant effect on the
molecular packing.17a In this analogy, here we show the iodine
substitution produces remarkable supramolecular interaction
that improves the transistor performance.
nꢀdoped Si Substrate
Fig. 2. Structure of an indigo fieldꢀeffect transistor in bottomꢀ
gate topꢀcontact geometry, where length (L) and width (W) are
100 and 1000 µm, respectively. A 20 nm of TTC and a 45 nm
of indigo derivatives are deposited by vacuum evaporation.
Energy levels
Results and discussion
Fig. 1 lists the highest occupied molecular orbital (HOMO)
levels and the lowest unoccupied molecule orbital (LUMO)
levels estimated from the redox potentials (Supporting
Information). The energy gaps (Eg) are estimated from the
absorption edges of the ultravioletꢀvisible spectra (UVꢀVis)
measured in about 20 nm of thin films evaporated on a glass
substrate (Fig. S2). HOMO and LUMO of 1-4 are calculated
by Gaussian 09 package at B3LYP/CEPꢀ31G level as shown in
Fig. 1. In comparison with the parent indigo, the halogen
substitution at the 5,5’ꢀpositions tends to induce slight
bathchromic shifts of the absorption spectra (Table S1).10,12,21
It has been reported that using gold (Au) source and drain
electrodes, ambipolar transport is realized when the HOMO
level is > −5.6 eV and the LUMO level is < −3.2 eV.22 The
LUMO levels of these compounds satisfy this condition, but the
HOMO levels are located near the boarder of the range.
Preparation of the indigo derivatives
Although the preparation of
we have prepared these compounds following a different route
(Scheme 1). Compound has been also previously reported
through another different route.18
1 ꢀ 2
has been recently reported,10
4
Compounds
1
ꢀ
4
were
prepared by starting iodination of 5ꢀhalogenoindole (
X
= F, Cl,
Br, and I),19,20 followed by acetoxy substitution with silver
acetate (AgOAc) in acetic acid (AcOH), to afford 5ꢀhalogenoꢀ
acetoxyindole (Scheme 1).
coupling reaction in a basic condition gave the target
compounds. All compounds were purified by repeated
temperature gradient sublimation in the range of 270~350°C, to
afford dark blue powders. The blue color came from the small
energy gap, and the resulting longꢀwavelength absorption was
closely related to the ambipolar transport.
Subsequently, the standard
2
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

Page 3 of 8
Journal Name
Journal of Materials Chemistry C
View ArticAle ROnTliInCeLE
DOI: 10.1039/C5TC01023C
10ꢀ6
10ꢀ7
10ꢀ8
10ꢀ9
10ꢀ10
6x10ꢀ4
4
10ꢀ5
3x10ꢀ3
2
1.0
0.8
0.6
0.4
0.2
0
0.004
0.002
0
a
b
c
d
1
2
120 V
=
VGS
1
2
VGS =100 V
10ꢀ6
10ꢀ7
10ꢀ8
10ꢀ9
VDS = 80 V
VDS = 80 V
100 V
80 V
80 V
2
1
60 V
40 V
60 V
40 V
0
0
ꢀ80 ꢀ40
0
40 80 120
0
40
80
VDS (V)
120 160
ꢀ120 ꢀ80 ꢀ40
0
40 80 120
0
20
40
VDS (V)
60
VGS (V)
VGS (V)
10ꢀ2
10ꢀ4
10ꢀ6
12x10ꢀ3
8
100
0
ꢀ4
e
f
g
4
–120 V
120 V
=
VDS = –80 V
VDS = 80 V
–40 V
4
80
–60 V
–20 V
0 V
VGS
80 V
40 V
60
40
20
0
10ꢀ8
4
ꢀ8
20 V
–80 V
10ꢀ10
10ꢀ12
–80 V
=
VGS
ꢀ80
4
–40 V
0
ꢀ12
ꢀ120 ꢀ80 ꢀ40
0
40 80 120
0
40
80
120
ꢀ120
ꢀ40
VDS (V)
0
VDS (V)
VGS (V)
Fig. 3. (a) Transfer characteristics, and (b) output characteristics at VDS > 0 of thinꢀfilm transistors based on 1. (c) Transfer characteristics, and (d) output
characteristics at VDS > 0 of thinꢀfilm transistors based on 2. (e) Transfer characteristics, (f) output characteristics at VDS < 0, and (g) output characteristics at
VDS > 0 of thinꢀfilm transistors based on 4. All measurements are done under vacuum.
Table 1. Summary of transistor performance of 1ꢀ4.
Compound
Maximum mobilities under vacuum
[cm2 V–1 s–1]
Average mobilities under vacuum
[cm2 V–1 s–1]
Threshold Voltage
[V]
Hole
ꢀ
Electron
1.7×10–3
0.022
0.04
Hole
Electron
7.6×10–4
0.012
0.03
Hole
Electron
1 (F)
ꢀ
ꢀ
19
33
71
15
ꢀ
2 (Cl)
3 (Br)9
4 (I)
ꢀ
ꢀ
ꢀ
0.07
0.42
0.01
0.02
0.16
ꢀ
−31
−34
ꢀ
0.85
0.48
Indigo5
0.01
ꢀ
0.56/0.95 cm2 V−1 s−1).9 There have been recently reported a
few donorꢀacceptor polymers in which both electron and hole
mobilities exceeding 1 cm2 V−1 s−1,3 and a pentacene ambipolar
transistor whose electron and hole mobilities are 3 cm2 V−1
s−1.27 However, mobilities of other smallꢀmolecule ambipolar
transistors are still lower than 1 cm2 V−1 s−1, and the present
Transistor characteristics
The transistors were fabricated on a heavily doped
nꢀtype
silicon substrate (300 nm of SiO2 as a gate dielectric) with a 20
nm passivation layer of tetratetracontane (TTC, C44H90, Fig. 2).
Long alkylꢀchain molecules like TTC were advantageous in
ambipolar transport due to the low dielectric constant, reduced
polarlization effect, and the improved crystallinity of the
semiconductor layer.23ꢀ26 The indigo derivatives of about 45
nm thickness were deposited by vacuum evaporation, on which
gold source and drain electrodes were formed to complete the
bottom gate – top contact devices. The transfer and output
characteristics were measured under vacuum (Fig. 3).
The transfer characteristics of
ambipolar characteristics, which affords very high and wellꢀ
balanced mobilities of µh
µe = 0.42/0.85 cm2 V−1 s−1 (Table 1).
The mobilities are extracted from the square root of the drain
current (ID) in the transfer characteristics. These mobilities are
even larger than µh/ 3, and amount
µe = 0.21/0.35 cm2 V−1 s−1 of
values of
4 are one of the highest among the smallꢀmolecular
ambipolar materials.3 The electron and hole threshold voltages
are estimated to be 15 V and −34 V, respectively (Table 1).
These values are also consistent with the flat regions of the
output characteristics (Fig. 3f and g).9,28 Since the difference
usually exceeds 100 V, the small difference (49 V) is
characteristic of the present ambipolar transistor.
Compounds
1 and 2 show only nꢀtype transport, where the
maximum mobilities are µe = 1.7×10−3 and 0.022 cm2 V−1 s−1,
4 (Fig. 3e) shows clear
respectively. This is in agreement with the electronegative
and 2 10
.
VTH of
1
and
2
are estimated to be 19 V and
/
nature of
33 V, respectively. The mobility decreases in the order of
(Br) > (Cl) > (F), which is opposite to the
electronegativity, but equal to the halogen size and the
1
4
(I)
>
3
2
1
to as large as those of the diphenyl compound (µh/µe =
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 |
3

Journal of Materials Chemistry C
Page 4 of 8
VJieowuArrtnicalelONnlainme e
ARTICLE
DOI: 10.1039/C5TC01023C
By contrast, no interaction is found in
long axis. However, short halogenꢀhalogen contacts with the
distances of 3.611 Å and 3.875 Å are observed in and along
the molecular long axis (Fig. 4b). These values are 2 4% and
2% shorter than the sum of the van der Waals radius (3.70 Å
for Br Br and 3.96 Å for I that
I).17,33 In comparison with
shows one intermolecular Br Br contact, has two
intermolecular I I contacts (Fig. 4d and 4e). These halogenꢀ
halogen contacts connect molecules of different conducting
layers along the axis. Along the axis, the adjacent stacks
are alternately tilted in the opposite directions (Fig. 4b). The
dihedral angle between the adjacent molecules ( ) and the tilt
angle of the molecular long axis from the direction vertical to
the stack direction ( , Fig. 4c) are summarized in Table 2.
These angles monotonously decrease from to Since the
molecules are slightly inclined from the stacking direction
2 along the molecular
polarizing power. The order of mobility also coincides with the
decreasing order of Eg (Fig. 1).
3
4
.
Crystal structures
2
.
Crystal structures of
Here, we show our data of crystal structures of
investigated by singleꢀcrystal Xꢀray structure analyses for
comparison with the crystal structures of and . Due to the
1 and 3
have been recently reported.9,10
and that are
…
…
3
2
4
…
4
…
1
3
poor solubility of these compounds in organic solvents, the
crystals were grown by the sublimation method. Although all
a
c
crystals belong to the same monoclinic space group
(Table S2), only and are strictly isostructural, and
P
and
21/
c
α
2
3
1
4
are different from these structures. In all cases, the stacking
direction corresponds to the crystallographic axis, and the
molecular long axis is basically parallel to the axis. However,
β
b
1
4.
a
the arrangements of the stacks are obviously different (Fig. 4).
The interplanar spacing ꢁ increases as the size of the halogen
substituent increases (Table 2); the difference is very slight
along the molecular short axis,
The molecular lengths
crystallographic
2). The lattice constant
and , 6.0281 Å > 4.54025 Å > 4.462 Å > 4.38905 Å. This
, hydrogen implies that the molecule in
is most close to perpendicular to
α
= 2
β
does not hold except for
1
.
l
of
1
ꢀ
4
are estimated from the
a
and the tilt angle
β from l = a / cos β (Table
from
1
to
3
, but
4
has a significantly large ꢁ. The stacks are
O distance of 2.9 Å
O distance of 2.1 Å in 4 14,29ꢀ32
For
H with the distance of 2.464 Å is found between
b
also decreases in the same order as
α
connected by hydrogen bonds with the N
and the H
bonding F
…
β
…
…
.
1
4
the stacking direction. The lattice constants
considerably smaller than the parent indigo,
b
b
of
2 to 4 are
= 5.77ꢀ5.88 Å
the adjacent molecules along the molecular long axis (Fig. 4a).
Fig. 4. Crystal structures of 1ꢀ4 viewed along the (a) c and (b) b axes. (c) Schematic illustration of the stacking structure. Halogenꢀhalogen contacts of (d)
3 and (e) 4. The distances are 3.611 Å and 3.875 Å, respectively.
4
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

Page 5 of 8
Journal Name
Journal of Materials Chemistry C
View ArticAle ROnTliInCeLE
DOI: 10.1039/C5TC01023C
(depending on the polymorphism),9,11,29ꢀ32 indicating that the thin film (β’, Fig. 5f) is calculated from l = d / cos β’, where l is the
molecular long axis is less tilted from the stacking direction,
and this is an origin of the enhanced mobility. However, the
molecules of
molecule length estimated from the crystal structure (Table 2). β’
decreases in the same order as and β. The β’ values for 2 and 3 are
α
4
are still by 34o tilted from the stacking direction,
not largely different from the β values in the crystals. However, the
values for 1 and 4 are significantly smaller than those in the crystals.
In particular, 4 shows nearly perpendicular arrangement (β’ = 0°).
Correlation of β’ and the maximum electron mobility (Table 1) is
depicted in Fig. 5f.5,7,9 Mobilities of not only the present compounds
but also the parent indigo, 5,5’ꢀdiphenylindigo, and 6,6’ꢀ
dibromoindigo show satisfactory correlation with the tilt angle in the
thin films. This reminds us the naphthalene diimide (NDI) series
compounds, where the charge mobility attains the maximum when
the molecular long axis is exactly perpendicular to the substrate.9,15
in contrast to the exactly perpendicular packing in the diphenyl
indigo. Nonetheless, the mobilities are not much different from
those of the diphenyl derivative. The high performance of
4 is
not entirely attributable to the preferable crystal packing, and
we have to assume a special effect of the iodine atoms.
The transfer integrals in the stacking (
HOMO and LUMO (tHOMO tLUMO) are estimated from the
molecular orbital calculation as shown in Table 2. In , the
LUMO affords a large transfer, whereas the HOMO gives a
small transfer. In addition, has a particularly large transfer
b) direction for
/
4
4
integral between halogenꢀhalogen atoms, tX , HOMO = 6.89 meV It has been recently reported that the tilt angle of unsubstituted
ꢀ
X
along the molecular long axis (Fig. 4e). This is obviously due indigo is much reduced in a thin film on an inert layer.35 Without
to the I I interaction; the HOMO is most seriously influenced assuming the thinꢀfilm structure different from the crystal structure,
…
we have to attribute the high performance of 4 to the anomalous
iodineꢀiodine electronic interaction coming from tXꢀX, HOMO It is,
however, more plausible that the iodineꢀiodine interaction changes
the thinꢀfilm structure, and the resulting perpendicular molecular
arrangement realizes the high ambipolar performance comparable to
the diphenyl derivative.
because the HOMO spread to the iodine atoms considerably
(Fig. 1). Since this interstack interaction is comparable to the
intrastack interaction in magnitude, there is a possibility that the
.
charge transport of
direction.
4 is not confined in the stacking (b)
Thin film properties
c
Atomic force microscopy (AFM) images and Xꢀray diffraction
(XRD) peaks of the thin films deposited on a TTC layer are shown
in Fig. 5. The thin films of 1ꢀ4 consist of highly crystalline domains
due to the strong intermolecular interactions, although the domain
size is comparatively small. The crystalline nature is enhanced by
the TTC passivation layer, because it has been reported in a wide
variety of organic semiconductors that the crystallinity is improved
on TTC. Accordingly, TTC plays a crucial role in the high mobility
as well as the ambipolar charge transport. In particular, the thin
film of 4 is densely and smoothly packed.
Fig. 5e shows Xꢀray diffraction (XRD) peaks. Several peaks
coming from TTC appear below 5o, which prove highly crystalline
and standing alignment of the TTC molecules.34 The 2θ value
coming from the indigo derivatives decreases systematically from 1
to 4, and the corresponding dꢀvalue increases as shown in Table 2.
d
3
a
e
b
1
2
4
4 ꢁm
4 ꢁm
4 ꢁm
4 ꢁm
46.48 nm
31.32 nm
49.27 nm
67.08 nm
101
f
d
4=17.1 Å
4
3
2
4
100
10ꢀ1
10ꢀ2
10ꢀ3
5,5'ꢀdiphenylindigo
6,6'ꢀdibromoindigo
d
3 =13.6 Å
3
d2
=13.0 Å
2
Indigo
d
1 =11.2 Å
1
1
0
10 20 30 40 50 60
Tilt angle ' (°)
5
6
7
8
9
10
β
Angle 2θ (º)
Fig. 5. AFM images of thin films of a) 1, b) 2, c) 3, and d) 4. e)
XRD patterns of 1ꢀ4. f) Correlation of the maximum electron
mobility with the tilt angle of the molecule long axis to the
substrate (β’) of 1ꢀ4, indigo, 6,6’ꢀdibromoindigo, and 5,5’ꢀ
diphenylindigo.
The dꢀvalues of
2 and 3 approximately coincide with the
crystallographic a axis. Thus the thinꢀfilm molecular packing is
considered to be the same as the crystal structure. However, the dꢀ
values of 1 and 4 are larger than the crystallographic axes (8.249 Å
and 14.0666 Å), indicating the molecules are less tilted from the
vertical direction in the thin films than in the crystals. In order to
discuss this point more quantitatively, the molecular tilt angle in the
Conclusion
In summary, we have investigated iodine introduction effect at
the 5ꢀposition of indigo. The diiodoꢀindigo
4 shows excellent
Compound
ꢁ (Å)
1 (F)10
2 (Cl)
3.38
84
3 (Br)9
3.39
81
4 (I)
3.42
78
ambipolar transistor properties, µh
/
µe = 0.42/0.85 cm2 V−1 s−1,
3.37
which are comparable to those of the diphenyl derivative. The
iodineꢀiodine interaction affords an extra interchain transfer
integral as large as 6.89 meV in the crystal, which is
α (°)
112
Table 2. Parameters extracted from the crystal and thinꢀfilm structures
β (°)
l (Å)
56
37
36
34
14.8
16.7
17.1
17.0
comparable to the intrachain interaction.
However, the
tHOMO/ tLUMO (meV)
tXꢀX, HOMO (meV)
2θ (°)
d (Å)
β’ (°)
11.8/39.2
0.040
7.85
11.2
41
12.2/12.6
1.16
12.4/21.0
1.83
2.96/35.3
6.89
5.17
17.1
0
systematic change of the thinꢀfilm ꢀvalue suggests a nearly
d
perpendicular molecular arrangement achieved in the thin film.
In this case, the iodineꢀiodine interaction is suspected to play an
important role. Since iodineꢀiodine contacts are universally
6.79
13.0
39
6.49
13.6
37
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 |
5

Journal of Materials Chemistry C
Page 6 of 8
ARTICLE
VJieowuArrtnicalelONnlainme e
DOI: 10.1039/C5TC01023C
observed in organic crystals, such supramolecular assembling
power is indispensable to achieve the exceptional packing
8
9
E. D. Głowacki, D. H. Apaydin, Z. Bozkurt, U.
Monkowius, K. Demirak, E. Tordin, M. Himmelsbach, C.
Schwarzinger, M. Burin, R. T. Lechner, N. Demitri, G.
Voss, and N. S. Sariciftci, J. Mater. Chem. C, 2014, 2,
8089.
O. Pitayatanakul, T. Higashino, T. Kadoya, M. Tanaka, H.
Kojima, M. Ashizawa, T. Kawamoto, H. Matsumoto, K.
Ishikawa, and T. Mori, J. Mater. Chem. C, 2014, 2, 9311.
pattern in the indigo derivative.
The present finding
demonstrates that supramolecular engineering mediated by
halogenꢀhalogen interaction has great possibilities in organic
semiconductors.
Acknowledgements
10 V. Klimovich, L. I. Leshanskaya. S. I. Troyanov, D. V.
Anokhin, D. V. Novikov, A. A. Piryazev, D. A. Ivanov, N.
N. Dremova, and P. A. Troshin, J. Mater. Chem. C, 2014,
2, 7621.
The authors are grateful to Tokyo Institute of Technology
Center for Advanced Materials Analysis for XRD measurement
and Prof. Kakimoto for NMR and AFM measurements.
11 H. Kojima and T. Mori, Chem. Lett., 2012, 42, 68.
12 L. SerranoꢀAndrés and B. O. Roos, Chem. Eur. J., 1997, 3,
Notes and references
717.
a
Department of Organic and Polymeric Materials, Tokyo Institute of
13 (a) G. R. Desiraju, Cryst. Growth Des., 2011, 11, 896. (b)
J. Mizuguchi, J. Phys. Chem. A., 2000, 104, 1817.
14 F. Kettner, L. Hüter, J. Schäfer, K. Röder, U. Purgahn, and
H. Krautscheid, Acta Crystallogr. sect E, 2011, 67, 2867.
15 T. Kakinuma, H. Kojima, M. Ashizawa, H. Matsumoto, and
Technology, Oꢀokayama, Meguroꢀku, Tokyo, 152ꢀ8552, Japan.
b ACTꢀC, JST, Honcho, Kawaguchi, Saitama 332ꢀ0012, Japan.
Eꢀmail:, mori.t.ae@m.titech.ac.jp
†
Electronic supporting information (ESI) available: CCDC 1042518
contains the supplementary crystallographic information for
4
.
T. Mori, J. Mater. Chem. C, 2013, 1, 5395.
Additional information of synthesis, redox properties, UVꢀvis spectra,
single crystal structures, and device fabrication.
16 (a) H. M. Yamamoto, J. Yamaura, and R. Kato, J. Am.
Chem. Soc., 1998, 120, 5905. (b) H. M. Yamamoto, R.
Maeda, J. Yamaura, and R. Kato, J. Mater. Chem., 2001,
11, 1034.
1
2
(a) J. Zaumseil and H. Sirringhaus, Chem. Rev., 2007, 107,
1296. (b) S. Z. Bisri, C. Piliego, J. Gao, and M. A. Loi,
Adv. Mater., 2014, 26, 1176.
(a) J. D. Yuen and F. Wudl, Energy Environ., Sci. 2013, 6,
17 (a) M. Fourmigué and P. Batail, Chem. Rev., 2004, 104
,
5379. (b) M. Fourmigué, Struct. Bonding, 2008, 126, 181.
(c) J. Lieffrig, R. L. Pennec, O. Jeannin, P. AubanꢀSenzier,
and M. Fourmigué, CrystEngComm, 2013, 15, 4408. (d) T.
392. (b) Y. Zhao, Y. Guo, and Y. Liu, Adv. Mater., 2013,
25, 5372. (c) N. Olivier, D. Niedzialek, V. Lemaur, W.
Pisula, K. Mullen, U. Koldemir, J. R. Reynolds, R.
Lazzaroni, J. Cornil, and D. Beljonne, Adv. Mater., 2014,
26, 2119. (d) E. Wang, W. Mammo, and M. R. Andersson,
Adv. Mater., 2014, 26, 1801.
Imakubo, H. Sawa, and R. Kato, Synth. Met., 1997, 86
,
1883. (e) H. Shirahata, M. Kibune, M. Maesato, T.
Kawashima, G. Saotp, and T. Imakubo, J. Mater. Chem.,
2006, 16, 3381. (f) H. M. Yamamoto, J. Yamaura, and R.
Kato, J. Am. Chem. Soc. 1998, 120, 5905. (g) H. M.
Yamamoto, R. Maeda, J. Yamaura, and R. Kato, J. Mater.
Chem. 2001, 11, 1034.
3
(a) J. D. Yuen, J. Fan, J. Seifter, B. Lim, R. Hufschmid, A.
J. Heeger, and F. Wudl, J. Am. Chem. Soc., 2011, 133
,
20799. (b) Z. Chen, M. J. Lee, R. S. Ashraf, Y. Gu, S.
AlbertꢀSeifried, M. M. Nielsen, B. Schroeder, T.
Anthopoulos, M. Heeney, I. McCulloch, and H.
Sirringhaus, Adv. Mater., 2012, 24, 647. (c) B. He, A. B.
Pun, D. Zherebetskyy, Y. Liu, F. Liu, L. M. Klivansky, A.
M. McGough, B. A. Zhang, K. Lo , T. P. Russell , L. Wang,
and Y Liu, J. Am. Chem. Soc. 2015, 136, 15093.
18 K. C. Tsou, K. W. Lo, S. L. Ledis, and E. E. Miller, J. Med.
Chem., 1972, 15, 1221.
19 Y. Tanoue, A. Terada, K. Sakata, M. Hashimoto, S.
Morishita, M. Hamada, N. Kai, and T. Nagai, Fish. Sci.
2001, 67, 726.
,
20 Y. Tanoue, K. Sakata, M. Hashimoto, M. Hamada, N. Kai,
and T. Nagai, Dye and Pigments, 2004, 62, 101.
21 P. W. Sadler, J. Org. Chem., 1955, 21, 316.
22 M. L. Tang, A. D. Reicharrdt, P. Wei, and Z. Bao, J. Am.
Chem. Soc., 2009, 131, 5264.
23 M. Kraus, S. Richler, A. Opitz, W. Brütting, S. Haas, T.
Hasegawa, A. Hinderhofer, and F. Schreiber, J. Appl. Phys.,
2010, 107, 094503.
24 M. Kraus, S. Haug, W. Brütting, and A. Opitz, Org.
Electron., 2011, 12, 731.
25 A. Opitz, M. Horlet, M. Kiwull, J. Wagner, M. Kraus, and
W. Brütting, Org. Electron., 2012, 13, 1614.
4
5
E. D. Głowacki, H. Coskun, M. A. BloodꢀForsythe, U.
Monkowius, L. Leonat, M. Grzybowski, D. Gryko, M. S.
White, A. AspuruꢀGuzik, and N. S. Sariciftci, Org.
Electron., 2014, 15, 3521.
M. IrimiaꢀVlada, E. D. Głowacki, P. A. Troshin, G.
Schwabegger, L. Leonat, D. K. Susarova, O. Krystal, M.
Ullah, Y. Kanbur, M. A. Bodea, V. F. Razumov, H. Sitter,
S. Bauer, and N. S. Sariciftci, Adv. Mater., 2012, 24, 375.
6
7
E. D. Głowacki, G. Voss, and N. S. Sariciftci, Adv. Mater.
2013, 25, 6783.
E. D. Głowacki, L. Lenonat, G. Voss, M. A. Bodea, Z.
Buzkurt, A. M. Ramil, M. IrimiaꢀVlada, S. Bauer, and N. S.
,
26 E. D. Głowacki, M. IrimiaꢀVladu, S. Bauer, and N. S.
Sariciftci, J. Mater. Chem. B., 2013, 1, 3742.
Sariciftci, AIP Advances, 2011,
1, 042132.
6
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

Page 7 of 8
Journal Name
Journal of Materials Chemistry C
View ArticAle ROnTliInCeLE
DOI: 10.1039/C5TC01023C
27 L.ꢀY. Chiu, H.ꢀL. Cheng, H.ꢀY. Wang, W.ꢀY. Chou, and F.ꢀ
C. Tang, J. Mater. Chem. C 2014 , 1823.
28 T. Higashino, J. Cho, and T. Mori, Appl. Phys. Exp., 2014,
, 121602.
,
, 2
7
29 H. von Eller, Bull. Soc. Chim. France, 1955, 1433.
30 H. von Eller, Bull. Soc. Chim. France, 1958, 316.
31 R. Süss, and A. Wolf, Naturwissenschaften E, 1980, 67
2867.
,
32 R. Süss, M. Steins, and V. Kupcik, Z. Kristallogr., 1988,
184, 269.
33 M. Yamada, R. Kanazawa, and F. Hamada,
CrystEngComm, 2014, 16, 2605.
34 (a) J.ꢀP. Gorce, S. J. Spells, X.ꢀB. Zeng and G. Ungar, J. Phys.
Chem. B, 2004, 108, 3130. (b) A. FilatreꢀFurcate, T.
Higashino, D. Lorcy, and T. Mori, J. Mater. Chem. C, 2015, 3,
3569.
35 D. V. Anokhin, L. I. Leshanskaya. A. A. Piryazev, D. K.
Susarova, N. N. Dremova, E. V. Shcheglov, D. A. Ivanov, V.
F. Racumov, and P. A. Troshin, Chem. Commun, 2014, 50,
7639.
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 |
7

Journal of Materials Chemistry C
Page 8 of 8
View Article Online
DOI: 10.1039/C5TC01023C
The table of contents entry
Title
Iodine effect in ambipolar organic field-effect transistors based on indigo derivatives
Text
5,5’ꢀDiiodoindigo exhibits excellent ambipolar transistor properties with the
hole/electron mobilities of µh/µe = 0.42/0.85 cm2 V−1 s−1.
Keywords
organic transistor, organic semiconductor, ambipolar
Authors
Oratai Pitayatanakul, Kodai Iijima, Minoru Ashizawa, Tadashi Kawamoto, Hidetoshi Matsumoto,
and Takehiko Mori
ToC figure (maximum size 8 cm x 4 cm)
µh/µe : 0.42/0.85 cm2 V–1 s–1