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View Journal | View Issue“Disrupt and induce” intermolecular interactions torationally design organic semiconductor crystals:
from herringbone to rubrene-like pitched pstacking†Chengyuan Wang, *a Daisuke Hashizume, b Masahiro Nakano,Takuya Ogaki, a Hiroyuki Takenaka,c Kohsuke Kawabata cand Kazuo Takimiya *ac

aThe packing structures of organic semiconductors in the solid state play critical roles in determining theperformances of their optoelectronic devices, such as organic ﬁeld-eﬀect transistors (OFETs). It is
a formidable challenge to rationally design molecular packing in the solid state owing to the diﬃculty ofcontrolling intermolecular interactions. Here we report a unique materials design strategy based on theb-methylthionation of acenedithiophenes to generally and selectively control the packing structures ofmaterials to create organic semiconductors rivalling rubrene, a benchmark high-mobility material witha characteristic pitched p-stacking structure in the solid state. Furthermore, the eﬀect of the bmethylthionation on the packing structure was analyzed by Hirshfeld surface analysis together withtheoretical calculations based on symmetry-adapted perturbation theory (SAPT). The results clearlyReceived 21st November 2019
Accepted 15th December 2019

demonstrated that the b-methylthionation of acenedithiophenes can universally alter the intermolecularinteractions by disrupting the favorable edge-to-face manner in the parent acenedithiophenes and

DOI: 10.1039/c9sc05902d

simultaneously inducing face-to-face and end-to-face interactions in the b-methylthionatedacenedithiophenes. This “disrupt and induce” strategy to manipulate intermolecular interactions canrsc.li/chemical-science

open a door to rational packing design based on the molecular structure.

Introduction
In the past few decades, both theoretical and experimental
studies have proven that the packing of organic semiconductors
in the solid state plays a critical role in determining the properties, in particular, the charge carrier transport properties, ofvarious optoelectronic devices, such as organic eld-eﬀect
transistors (OFETs).1–6 Organic semiconductors including theones based on small molecules are packed through intermolecular interactions, in which diﬀerent intermolecular forces,
e.g., electrostatics, exchange repulsion, induction, and dispersion, act as attractive or repulsive forces in the packing process
to reach a certain balance that denes the packing structure ofaEmergent Molecular Function Research Team, RIKEN Center for Emergent Matter
Science (CEMS), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. E-mail: chengyuan.
wang@riken.jpbMaterials Characterization Support Team, RIKEN Center for Emergent Matter Science(CEMS), 2-1 Hirosawa, Wako, Saitama 351-0198, Japanc
Department of Chemistry, Graduate School of Science, Tohoku University, 6-3 Aoba,
Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan† Electronic supplementary information (ESI) available. CCDC 1899660, 1899661,
1899662. For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/c9sc05902d

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molecules in the solid state. For this reason, it is extremely
diﬃcult to design and predict the packing structure of a given
semiconducting molecule, and even a tiny molecular modication could break the existing balance of intermolecularinteractions and thus result in the change of the packing in an
unpredictable manner.7,8 In this respect, Anthony et al. havebeen highly successful in selectively changing the packing
structures of linear acenes and acenedithiophenes (a family ofhigh-performance thienoacene-based organic semiconductors
in OFETs) (Fig. 1a and b) from a typical herringbone to a twodimensional (2D) brickwork packing by attaching [(trialkyl)silyl]
ethynyl groups at their peri-positions.9–11 In sharp contrast, mostof the studies on the control of packing structures are still in thetrial-and-error stage, and therefore, the rational design ofpacking structures has remained a challenging issue in thedevelopment of organic semiconductors.
The importance of the packing structures of organic semiconductors in the solid state is attributed to the fact that thepacking of molecules critically determines the electronic
structures of the organic semiconducting materials.6,12 This
correlation is well illustrated by rubrene (Fig. 1c), a benchmark
organic semiconductor in OFETs. Rubrene packing features thecharacteristic “pitched p-stacking”,13 where the intermolecular

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Chemical ScienceFig. 1 Molecular structures of (a) linear acenes, (b) linear acenedithiophenes,(c)rubrene,and(d)b-methylthionatedacenedithiophenes.

electronic coupling between the HOMOs of the p-stacking
molecules is very large (0.1 eV). As a result, the single-crystal
OFETs (SC-OFETs) of rubrene show reproducible high mobilities of 15–20 cm2 V1 s1.14–16 Tremendous eﬀorts have been
devoted to realizing organic semiconductors with a rubrene-like
pitched p-stacking in the solid state, which, however, have
hardly succeeded.17–20 More generally, establishing rational
materials design strategies to control the packing structure bymanipulating molecular structures is highly desired. However,they remain ambitious tasks.21–23
We have recently found that methylthionation at the bposition of benzo[1,2-b:4,5-b0 ]dithiophene (BDT, Fig. 1b), thesmallest linear acenedithiophene, can selectively alter thepacking from the BDT's herringbone24 to the rubrene-like
pitched p-stacking.13,25,26 Thanks to its packing structure, b-

Scheme 1

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methylthionated BDT (b-MT-BDT) realizes large intermolecularelectronic coupling between the HOMOs of the p-stacking
molecules. Accordingly, its SC-OFETs yield a moderately highmobility of 0.38 cm2 V1 s1 despite having a small p-conjugated system with only 14 p-electrons. Enlightened by theseresults, we were curious about whether b-methylthionation isjust a successful example particularly of BDT to selectively alter
the packing or if it can be a general strategy to widely realize therubrene-like pitched p-stacking. If the latter is the case, thegeneral questions then arise: what is the origin of this selectivity
and generality, and furthermore, with the strategy, is it possible
to create materials rivalling rubrene? Inspired by these questions, we designed a series of b-methylthionated (b-MT)-acenedithiophenes with a gradually extended molecular pbackbone from BDT to naphtho[2,3-b:6,7-b0 ]dithiophene (NDT)
and anthra[2,3-b:6,7-b0 ]dithiophene (ADT) (Fig. 1d). Here we
report the synthesis, packing structure, electronic structure in
the solid state, and OFET performance of a series of b-MT-acenedithiophenes. We also discuss the origin of the general andselective packing control through b-methylthionation and thepotential of this materials design strategy in the development ofhigh performance organic semiconductors in OFETs.

Results
Synthesis of molecules
Scheme 1 shows the synthesis of b-methylthionated NDT (b-MTNDT) and ADT (b-MT-ADT). In our previous study on b-MT-BDT,
we developed a straightforward method to directly introduce
sulphur functional groups at the b-position of BDT by utilizing
disulphur dichloride (S2Cl2) as the electrophilic reagent in
Larock cyclization.25,27 This method is convenient and versatilefor the b-alkylthionation of the BDT core,26 but results in only

Synthetic route to the b-MT-acenedithiophenes.

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moderate yields, possibly because of the formation of oligomers
as byproducts. In this work, we employed methyl thiohypochlorite (methylsulfenyl chloride, MeSCl) as the electrophilic
reagent instead of S2Cl2 to avoid the formation of oligomers.28,29
Starting from the functionalized naphthalene derivative (1), bMT-NDT could be readily synthesized by the reaction of 1 with
MeSCl followed by treatment with tetrabutylammonium uoride (TBAF). In contrast, a similar reaction of functionalized
anthracene (3) with MeSCl aﬀorded 5,11-dichlorinated ADT
derivative (4) instead of the precursor (5). These unexpected
results could be explained as follows: MeSCl was unstable under
the reaction conditions and decomposed to liberate chlorine,
which reacted with in situ formed 5 at the reactive 5,11-positions
to aﬀord 4 as the major product. Fortunately, the chlorine
substituents were readily removed by the treatment withlithium aluminium hydride (LAH) to give 5, which was thenconverted into b-MT-ADT in a similar manner to the synthesisof b-MT-NDT. b-MT-NDT and b-MT-ADT were fully characterized by means of spectroscopic analysis (see the ESI†) andsingle-crystal X-ray structural analysis (vide infra). Their opticaland electrochemical properties were evaluated and are fully
discussed in the ESI† with the aid of theoretical calculations.
Packing structures in the solid stateFig. 2 shows the packing structures of b-MT-acenedithiophenes.25 Intriguingly, with the extension of the molecular p-

Chemical Science
backbone, b-MT-NDT (with one more central benzene ring) andb-MT-ADT (two additional central benzene rings) are of isostructure with b-MT-BDT (monoclinic with P21/c space group),
and all the three structures have the same pitched p-stacking(Fig. 2). This indicates that the b-methylthionation of linear
acenedithiophenes is a universal strategy to tune the packing
into the rubrene-like pitched p-stacking. Note that all the corresponding parent acenedithiophenes, i.e., BDT,24 NDT, and space group with the
ADT,30 are crystallized into the triclinic P1
herringbone packing, similar to those of linear acenes.
One distinct feature of the pitched p-stacking is that thedisplacement of neighbouring molecules occurs along the longmolecular axis direction while maintaining substantial face-toface overlap, whereas only marginal displacement is observed
along the short molecular axis direction. The other feature isthat the neighbouring p-stacking columns are inclined in
opposite directions to each other with certain dihedral angles(68–90 ) between the molecules in the adjacent stacks, whichinteract with each other in an end-to-face mode (Fig. 2a, c ande). As a result, the molecular network with the face-to-face andend-to-face modes in the pitched p-stacking forms a layered
structure (Fig. 2b, d and f). These features are signicantly
diﬀerent from those of the herringbone packing, where thedisplacement of neighbouring molecules occurs along the shortmolecular axis direction without face-to-face overlap, resulting

Fig. 2 Packing structures of molecules projected along short and long molecular axes: (a and b) b-MT-BDT, (c and d) b-MT-NDT (CCDC:
1899661), and (e and f) b-MT-ADT (CCDC: 1899662). Red dashed lines represent intermolecular S–S contacts shorter than the sum of van der
Waals (vdW) radii. ta, ta0 , tb, and tc (meV) are calculated values of the intermolecular electronic coupling between the HOMOs of neighbouringmolecules in each crystallographic axis direction.

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in diﬀerent layered structures with the face-to-edge and edge-toedge modes.13
Intermolecular electronic coupling between the HOMOs ofmolecules in the solid state
One advantage of the pitched p-stacking is that large intermolecular electronic coupling between the HOMOs (or transfer
integral, t) in the stacking columns likely occurs. This is well
represented by the packing of b-MT-BDT, where the maximum
electronic coupling is as large as 78 meV (tc) in the p-stacking
direction (or the crystallographic c-axis direction) (Fig. 2a). In
contrast, tb in the end-to-face direction (crystallographic b-axis
direction) is only 14 meV, indicating the anisotropic nature of
the electronic structure in each layer. Interestingly, moderately
large electronic coupling is observed between the layers (or in
the edge-to-edge direction of molecules) (ta, up to 31 meV),
implying that three-dimensional (3D) electronic communication is possible (Fig. 2b).
With the same packing structure and extended p-backbone,b-MT-NDT (with 18 p-electrons) is expected to have larger
electronic coupling than b-MT-BDT. However, the largest electronic coupling (tc) in b-MT-NDT is only 45 meV in the face-toface direction, which is signicantly smaller than that in b-MTBDT (Fig. 2c). The electronic couplings in the other directions
are also small for b-MT-NDT. This may be because in b-MT-NDT
crystals, the neighbouring dimers have disadvantageous mutual
positions to achieve eﬃcient electronic coupling, which is discussed in detail in the ESI.†In the packing structure of b-MT-ADT with 22 p-electrons,
the maximum electronic coupling in the stacking column (tc) is
90 meV (Fig. 2e), which is the highest among the three b-MTacenedithiophenes, and is very close to the corresponding one
in rubrene (96 meV) (Fig. S4†). Furthermore, the electronic
coupling in the end-to-face direction (tb) in b-MT-ADT is also thelargest and even larger than that of rubrene (33 meV for b-MTADT, 19 meV for rubrene), indicating that the anisotropic
nature of b-MT-ADT in the semiconducting layer is mitigated.
These features of the electronic structure of b-MT-ADT aremostly identical to those of rubrene, indicating that b-MT-ADT
can be a rubrene-like semiconducting material. Especially, inthe t vs. displacement plots (Fig. S5†), the actual mutual positions of neighbouring molecules along the p-stacking direction
in rubrene and b-MT-ADT are both located at the extrema.
Furthermore recent studies pointed out that small dynamic
disorder of rubrene in the solid state is crucial to achieve highperformance in SC-OFETs. The similarities of b-MT-ADT in thesolid state to those of rubrene may suggest the possibility of thatbenet to achieve high performance as semiconducting materials in SC-OFETs (discussed in the ESI†).31–33

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ADT single crystals on the substrates show similar diﬀraction
peaks, which can be indexed as 1 0 0 and 2 0 0 diﬀractions bycomparison with the simulated powder patterns from thesingle-crystal X-ray data (Fig. S8†). This indicates that both bMT-NDT and b-MT-ADT adopt the edge-on molecular orientation on the substrates (Fig. 2d and f), consistent with the case of
rubrene and b-MT-BDT (Fig. S9†).25 Such an edge-on molecularorientation is reported to be advantageous to enhance carrier
mobility by reducing the coupling between molecular polarization and charge carriers.36
The b-MT-BDT-based SC-OFETs were reported to show
mobilities of up to 0.38 cm2 V1 s1 (Table 1).19 We noticed thatthe crystals of b-MT-BDT were very thick (500–800 nm), which
could increase the contact resistance between the top electrodes
and the transistor channel at the substrate/crystal interface,likely limiting empirical mobility values. In the case of b-MTNDT and -ADT, on the other hand, the single crystals preparedby the PVT method were much thinner (100–300 nm thickness) than those of b-MT-BDT, and thus the eﬀects of thecontact resistance could be reduced.
SC-OFETs based on b-MT-NDT showed mobilities of up to
0.35 cm2 V1 s1 (Table 1), which are similar to those of b-MTBDT-based devices, although the intermolecular electronic
couplings in b-MT-NDT are much smaller than those in b-MTBDT, as mentioned above (see also Fig. 2). In contrast, single
crystals of b-MT-ADT acted as an excellent transistor channel,
showing mobilities of up to 4.08 cm2 V1 s1 (average 3.44 cm2V1 s1, Table 1), which are almost one order of magnitude
higher than those of b-MT-BDT and -NDT.
Fig. 3 shows the transfer and output curves of the SC-OFETs
based on b-MT-NDT and b-MT-ADT, respectively. It has beenreported that rubrene-based SC-OFETs usually show mobilitiesof 3–6 cm2 V1 s1 on Si/SiO2 substrates,37–39 and in fact, similarvalues (average mobility: 3.79 cm2 V1 s1, 100–300 nm
thickness) were also reproduced by our group (Table 1). The
reliability factor of the SC-OFETs is discussed in the ESI.†40
To conrm the experimental carrier motilities, theoreticalmobilities of b-MT-acenedithiophenes and rubrene were
calculated in the hopping regime utilizing the Marcus/Hushmodel based on the electronic structure in the solid state. The
calculations show that b-MT-ADT can have the highest mobilities (0.65–12.38 cm2 V1 s1) among the b-MT-

Table 1 Performances of SC-OFETs based on b-MT-acenedithiophenes and rubrenea

CompoundMobility (cm2 V1 s1)

Vth (V)On/oﬀ ratio

SC-OFETs of b-MT-acenedithiophenes

b-MT-BDTb-MT-NDT
b-MT-ADT
Rubrene0.22 (0.38)
0.25 (0.35)
3.44 (4.08)
3.79 (4.73)

21.5
11.8
4.5
5.1

105 to 106
105 to 106
104 to 106
106 to 107

SC-OFETs of b-MT-BDT, -NDT, and -ADT with the bottom-gate/
top-contact device conguration were fabricated with single
crystals grown directly on octadecyltrichlorosilane (ODTS)modied Si/SiO2 substrates by the physical vapour transport(PVT) method.34,35 The XRD patterns of b-MT-NDT and b-MT-a
The charge transport directions in the SC-OFETs are along the pstacking directions (crystallographic b-axis for rubrene and c-axis forb-MT-acenedithiophenes, Fig. S7). The mobilities were extracted fromthe saturation regime of the transfer curves. The average mobilities
and Vths are based on more than 10 devices, and values withinparentheses are the highest mobilities.

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Fig. 3Chemical Science

Transfer (top) and output (bottom) curves of SC-OFETs (a) b-MT-NDT and (b) b-MT-ADT.

acenedithiophenes (0.014–1.62 cm2 V1 s1 for b-MT-BDT,
0.010–2.81 cm2 V1 s1 for b-MT-NDT), which are even higher
than those of rubrene (0.024–7.68 cm2 V1 s1), suggesting its
great potential in the application of OFETs (see the ESI for
details†). From both the experimental (SiO2 as the dielectric
layer) and theoretical investigations, it is safe to say that b-MTADT is a superior organic semiconducting material rivallingrubrene.

Table 2

Discussion
Molecular factors that dictate packing structures
As described in the section of packing structures, it is concluded
that the b-methylthio group on the linear acenedithiophenes isa reliable controller that selectively alters the packing structurefrom the herringbone of the parent acenedithiophenes to thepitched p-stacking of the b-MT-acenedithiophenes.

Intermolecular interaction energies (kcal mol1) of dimers in the packing structures of parent and b-MT-acenedithiophenesa

CompoundBDT
b-MT-BDT

NDT
b-MT-NDT

ADT
b-MT-ADT

CH–p (edge-to-face)p-stacking
p-stacking (w/o MT)b
CH–p (end-to-face)
S–H w/S–S contact (edge-to-edge)
S–H w/o S–S contact (edge-to-edge)
CH–p (edge-to-face)p-stacking
p-stacking (w/o MT)b
CH–p (end-to-face)
S–H w/S–S contact (edge-to-edge)
S–H w/o S–S contact (edge-to-edge)
CH–p (edge-to-face)p-stacking
p-stacking (w/o MT)b
CH–p (end-to-face)
S–H w/S–S contact (edge-to-edge)
S–H w/o S–S contact (edge-to-edge)

Ees

Eex

Eind

Edisp

Etotal

2.83
7.05
4.07
2.48
4.12
2.49
4.06
10.58
6.23
2.32
5.36
1.03
5.63
10.47
6.70
2.94
6.56
2.00

5.48
14.59
9.26
5.76
5.97
3.92
7.99
21.07
15.66
5.64
8.84
3.49
11.15
22.30
17.59
6.62
11.78
4.22

0.83
1.69
0.87
0.98
0.71
0.60
1.18
2.28
1.40
0.95
1.12
0.55
1.66
2.53
1.75
1.10
1.45
0.65

9.15
21.31
12.93
7.35
3.91
5.20
13.67
30.80
21.93
7.23
8.03
5.66
18.8932.16
24.39
9.63
9.68
6.68

7.33
15.46
8.60
5.06
2.77
4.36
10.92
22.5913.91
4.88
5.68
3.75
15.03
22.86
15.26
7.06
5.91
5.11

a

Obtained from zeroth-order symmetry-adapted perturbation theory (SAPT0) calculations with the jun-cc-pVDZ basis. Ees, Eex, Eind, Edisp, and Etotal
are electrostatic, exchange, induction, dispersion, and total intermolecular interaction energy, respectively. Etotal ¼ Ees + Eex + Eind + Edisp. b The rows
highlight the intermolecular interaction energies in the p-stacking dimers without (w/o) methylthio groups.

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The herringbone packing is known to be a dispersion-driven
packing structure.41 In fact, zeroth-order symmetry-adapted
perturbation theory (SAPT0) calculations with the jun-cc-pVDZ
basis42,43 for the parent acenedithiophenes clearly show that thedispersion term in the edge-to-face dimer (9.15 kcal mol1 for
BDT, 13.67 kcal mol1 for NDT, and 18.89 kcal mol1 for
ADT) is the largest one among the decomposed intermolecularinteraction energies (see Table 2). The presence of the favourable edge-to-face intermolecular interaction is further
conrmed by the Hirshfeld surface mapped with de (distancefrom the Hirshfeld surface to the nearest nucleus outside thesurface),44,45 which shows close contacts between the perihydrogen atoms and the p-clouds of the adjacent molecule in
the edge-to-face manner (top of Fig. 4a, b and c). Furthermore,
the intermolecular C–H contact accounts for up to 40–50% of
the total intermolecular short contacts in the packing structure(bottom of Fig. 4a, b and c). From these analyses, we canEdge Article
conrm that the herringbone packing of the parent acenedithiophenes is a dispersion-driven packing structure.
The b-methylthio groups on acenedithiophenes, on the other
hand, can have drastic eﬀects on the intermolecular interactions. First, the stabilizing eﬀect induced by the edge-to-faceinteraction in the parent acenedithiophenes does not work
owing to the steric bulkiness of the b-methylthio groups; inother words, the b-methylthio group disrupts the contacts
between the peri-hydrogen atoms and the p-cloud of the adjacent molecules. As a result, instead of the edge-to-face interaction in the parent system, the face-to-face (p–p) interaction,
which is largely stabilized by dispersion (21.31 kcal mol1 forb-MT-BDT, 30.80 kcal mol1 for b-MT-NDT, and 32.16 kcal
mol1 for b-MT-ADT) and electrostatic interactions (7.05 kcal
mol1 for b-MT-BDT, 10.58 kcal mol1 for b-MT-NDT, and10.47 kcal mol1 for b-MT-ADT) is manifested in the packing
structure of b-MT-acenedithiophenes (Table 2). The change ofintermolecular interaction caused by b-methylthionation isFig. 4 Hirshfeld surface analysis of (a) BDT, (b) NDT (CCDC: 1899660), (c) ADT, (d) b-MT-BDT, (e) b-MT-NDT, and (f) b-MT-ADT, which illustrates
the distance (de) from the surface to the nucleus of external atoms in the adjacent molecules in a red-green-blue colour scheme.

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consistent with the ratio of intermolecular contacts; the CH–pcontacts decrease from 40–50% in the parent system to 15–20%
of all the intermolecular contacts, whereas the C–C contacts
corresponding to the face-to-face (p–p) interaction increase toaround 6–12% relative to the parent system that has less than
1% contribution (Fig. 4d, e and f).
Second, the b-methylthio group induces other intermolecular interactions in a diﬀerent manner; in the face-to-facedimer, the methyl moiety in the b-methylthio group is immediately above/beneath the p-face, facilitating a CH–p interaction between the p-face of the acenedithiophene core and the
methyl hydrogen atom. This is clearly visualized by the Hirshfeld surface, where a large red depression directly beneath themethyl moiety shows close contact, which can be described asa “methyl-on–p” interaction. To conrm the net eﬀect of the“methyl-on–p” interaction, we calculated the interaction energyof the face-to-face dimer without the methylthio groups. The
diﬀerence of the interaction energies with and without the
methylthio groups is substantially large (approximately 7–9 kcal
mol1 for the total interaction energy, including a dispersion
energy of approximately 7–9 kcal mol1 and an electrostatic
energy of approximately 3–4 kcal mol1, Table 2), indicatingthat the “methyl-on–p” interaction contributes to the stabilization of the face-to-face dimer. Another intermolecular interaction induced by the methylthio groups is observed in the endto-face dimer; one of the methyl hydrogen atoms and the phydrogen atoms in the thiophene moiety cooperatively comeinto contact with the p-face of a neighbouring molecule,enabling an “end-to-face” CH–p interaction, as visualized fromthe Hirshfeld surface mapped with de (top of Fig. 4d, e and f).
The SAPT calculations also support this attractive interaction
with relatively large interaction energies (5.06 kcal mol1 forb-MT-BDT, 4.88 kcal mol1 for b-MT-NDT, and 7.06 kcal
mol1 for b-MT-ADT, Table 2) contributed mainly by thedispersion term. In addition, the b-methylthio group participates in the intermolecular contacts in the edge-to-edge direction through S–H and S–S contacts (bottom of Fig. 4d, e and f)that energetically stabilize the present pitched p-stacking.
From the above analyses, it can be summarized that the bmethylthio groups play two key roles in altering the packing
structure. One is to disrupt the favourable CH–p interaction
along the molecular edge in the parent system and the other is
to induce new intermolecular interactions in diﬀerent molecular faces, i.e., methyl-on–p in the face-to-face dimer, CH–p in
the end-to-face dimer, and S–S and S–H in the edge-to-edge
dimers. The “disrupt and induce” eﬀects caused by the bmethylthio groups would be a possible scenario that dictates
the structural change from the herringbone in the parent
system to the pitched p-stacking in b-MT-acenedithiophenes.

that of rubrene, up to 4.1 cm2 V1 s1, in SC-OFETs with SiO2 as
the dielectric layer. Taking these aspects, including the packing
structure, the electronic structure in the solid state, and theexcellent empirical and theoretical transport properties, into
account, it can be said that b-MT-ADT is a material rivallingrubrene.
The most important knowledge obtained from this study isthat such a simple molecular modication as b-methylthionation is a powerful strategy to generally and selectively control
the packing structure of molecules in the solid state. The key tothe generality and selectivity in the packing design is to “disrupt
and induce” intermolecular interactions along diﬀerent directions of the molecular backbone. In particular, the major
driving force is changed from the dispersion in the CH–pinteraction along the edge-to-face direction in the parent acenedithiophenes to the dispersion together with electrostatic
terms in the p–p interactions along the face-to-face direction in
the b-MT-acenedithiophenes. Overall, our results strongly imply
that the rational control of intermolecular interactions by the“bottom–up approach” i.e., molecular modication, enables
developing new superior organic semiconductors with welldesigned packing structures. We hope that the present study
will open the door to the possibility of a rational design ofpacking structures of organic semiconductors through themanipulation of intermolecular interactions with molecularmodications.

Conclusion

1 V. Coropceanu, J. Cornil, D. A. da Silva Filho, Y. Olivier,
R. Silbey and J.-L. Brédas, Chem. Rev., 2007, 107, 926–952.
2 H. Huang, L. Yang, A. Facchetti and T. J. Marks, Chem. Rev.,
2017, 117, 10291–10318.
3 H. Sirringhaus, Adv. Mater., 2014, 26, 1319–1335.
4 J. Mei, Y. Diao, A. L. Appleton, L. Fang and Z. Bao, J. Am.
Chem. Soc., 2013, 135, 6724–6746.

We have demonstrated that b-methylthionation of a series ofacenedithiophenes can control the packing of molecules into
rubrene-like pitched p-stacking. b-MT-ADT with a large pbackbone realizes large electronic couplings between neighbouring molecules, which yield high mobility comparable toThis journal is © The Royal Society of Chemistry 2020

Conﬂicts of interest
There are no conicts to declare.

Acknowledgements
We thank Dr Takemichi Nakamura of the Molecular Structure
Characterization Unit, RIKEN Center for Sustainable Resource
Science (CSRS), for high-resolution mass spectral (HR-MS)
measurements. We acknowledge the Supercomputer System in
the Advanced Center for Computing and Communication(ACCC) of RIKEN and the Center for Computational Materials
Science, Institute for Materials Research, Tohoku University, for
the use of MASAMUNE-IMR (MAterials science Supercomputing
system for Advanced MUlti-scale simulations towards NExtgeneration – Institute for Materials Research) for support intheoretical calculations. This work was nancially supported by
JSPS KAKENHI Grant Numbers 15H02196, 17K14478 and
19H00906, the Strategic Promotion of Innovative Research andDevelopment from JST, and the Mitsubishi Foundation.

Notes and references

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Chemical Science
5 H. Dong, X. Fu, J. Liu, Z. Wang and W. Hu, Adv. Mater., 2013,25, 6158–6183.
6 C. Wang, H. Dong, W. Hu, Y. Liu and D. Zhu, Chem. Rev.,
2012, 112, 2208–2267.
7 Y. Tsutsui, G. Schweicher, B. Chattopadhyay, T. Sakurai,
J.-B. Arlin, C. Ruzié, A. Aliev, A. Ciesielski, S. Colella,
A. R. Kennedy, V. Lemaur, Y. Olivier, R. Hadji,
L. Sanguinet, F. Castet, S. Osella, D. Dudenko, D. Beljonne,
J. Cornil, P. Samorı̀, S. Seki and Y. H. Geerts, Adv. Mater.,
2016, 28, 7106–7114.
8 C. Sutton, C. Risko and J.-L. Brédas, Chem. Mater., 2016, 28,
3–16.
9 J. E. Anthony, Chem. Rev., 2006, 106, 5028–5048.
10 J. E. Anthony, Angew. Chem., Int. Ed., 2007, 47, 452–483.
11 M. Klues and G. Witte, CrystEngComm, 2018, 20, 63–74.
12 K. Takimiya, S. Shinamura, I. Osaka and E. Miyazaki, Adv.
Mater., 2011, 23, 4347–4370.
13 M. D. Curtis, J. Cao and J. W. Kampf, J. Am. Chem. Soc., 2004,
126, 4318–4328.
14 V. C. Sundar, J. Zaumseil, V. Podzorov, E. Menard,
R. L. Willett, T. Someya, M. E. Gershenson and
J. A. Rogers, Science, 2004, 303, 1644–1646.
15 V. Podzorov, E. Menard, A. Borissov, V. Kiryukhin,
J. A. Rogers and M. E. Gershenson, Phys. Rev. Lett., 2004,
93, 086602.
16 X. Ren, M. J. Bruzek, D. A. Hani, A. Schulzetenberg, Y. Wu,
C.-H. Kim, Z. Zhang, J. E. Johns, A. Salleo, S. Fratini,
A. Troisi, C. J. Douglas and C. D. Frisbie, Adv. Electron.
Mater., 2017, 3, 1700018.
17 K. A. McGarry, W. Xie, C. Sutton, C. Risko, Y. Wu,
V. G. Young, J.-L. Brédas, C. D. Frisbie and C. J. Douglas,
Chem. Mater., 2013, 25, 2254–2263.
18 M. Mamada, H. Katagiri, T. Sakanoue and S. Tokito, Cryst.
Growth Des., 2015, 15, 442–448.
19 Y. Sakamoto and T. Suzuki, J. Org. Chem., 2017, 82, 8111–
8116.
20 G. Xie, S. Hahn, F. Rominger, J. Freudenberg andU. H. F. Bunz, Chem. Commun., 2018, 54, 7593–7596.
21 Z. Chen, P. Müller and T. M. Swager, Org. Lett., 2006, 8, 273–
276.
22 H. Moon, R. Zeis, E.-J. Borkent, C. Besnard, A. J. Lovinger,
T. Siegrist, C. Kloc and Z. Bao, J. Am. Chem. Soc., 2004, 126,
15322–15323.
23 T. Kimoto, K. Tanaka, M. Kawahata, K. Yamaguchi,
S. Otsubo, Y. Sakai, Y. Ono, A. Ohno and K. Kobayashi, J.
Org. Chem., 2011, 76, 5018–5025.
24 K. Takimiya, Y. Konda, H. Ebata, N. Niihara and T. Otsubo, J.
Org. Chem., 2005, 70, 10569–10571.
25 C. Wang, H. Nakamura, H. Sugino and K. Takimiya, Chem.
Commun., 2017, 53, 9594–9597.

1580 | Chem. Sci., 2020, 11, 1573–1580

Edge Article
26 C. Wang, H. Nakamura, H. Sugino and K. Takimiya, J. Mater.
Chem. C, 2018, 6, 3604–3612.
27 D. Yue and R. C. Larock, J. Org. Chem., 2002, 67, 1905–1909.
28 J. K. Son and R. W. Woodard, J. Am. Chem. Soc., 1989, 111,
1363–1367.
29 H. Takenaka, T. Ogaki, C. Wang, K. Kawabata andK. Takimiya, Chem. Mater., 2019, 31, 6696–6705.
30 M. Mamada, H. Katagiri, M. Mizukami, K. Honda,
T. Minamiki, R. Teraoka, T. Uemura and S. Tokito, ACS
Appl. Mater. Interfaces, 2013, 5, 9670–9677.
31 S. Fratini, D. Mayou and S. Ciuchi, Adv. Funct. Mater., 2016,
26, 2292–2315.
32 S. Fratini, S. Ciuchi, D. Mayou, G. T. de Laissardière and
A. Troisi, Nat. Mater., 2017, 16, 998.
33 S. Illig, A. S. Eggeman, A. Troisi, L. Jiang, C. Warwick,
M. Nikolka, G. Schweicher, S. G. Yeates, Y. H. Geerts,
J. E. Anthony and H. Sirringhaus, Nat. Commun., 2016, 7,10736.
34 R. A. Laudise, C. Kloc, P. G. Simpkins and T. Siegrist, J. Cryst.
Growth, 1998, 187, 449–454.
35 C. Kloc, P. G. Simpkins, T. Siegrist and R. A. Laudise, J. Cryst.
Growth, 1997, 182, 416–427.
36 N. A. Minder, S. Ono, Z. Chen, A. Facchetti andA. F. Morpurgo, Adv. Mater., 2011, 24, 503–508.
37 H. T. Yi, Y. Chen, K. Czelen and V. Podzorov, Adv. Mater.,
2011, 23, 5807–5811.
38 A. F. Stassen, R. W. I. de Boer, N. N. Iosad andA. F. Morpurgo, Appl. Phys. Lett., 2004, 85, 3899–3901.
39 I. N. Hulea, S. Fratini, H. Xie, C. L. Mulder, N. N. Iossad,
G. Rastelli, S. Ciuchi and A. F. Morpurgo, Nat. Mater.,
2006, 5, 982.
40 H. H. Choi, K. Cho, C. D. Frisbie, H. Sirringhaus and
V. Podzorov, Nat. Mater., 2017, 17, 2.
41 G. Gryn’ova and C. Corminboeuf, J. Phys. Chem. Lett., 2016, 7,
5198–5204.
42 B. Jeziorski, R. Moszynski and K. Szalewicz, Chem. Rev., 1994,
94, 1887–1930.
43 R. M. Parrish, L. A. Burns, D. G. A. Smith, A. C. Simmonett,
A. E. DePrince, E. G. Hohenstein, U. Bozkaya, A. Y. Sokolov,
R. Di Remigio, R. M. Richard, J. F. Gonthier, A. M. James,
H. R. McAlexander, A. Kumar, M. Saitow, X. Wang,
B. P. Pritchard, P. Verma, H. F. Schaefer, K. Patkowski,
R. A. King, E. F. Valeev, F. A. Evangelista, J. M. Turney,
T. D. Crawford and C. D. Sherrill, J. Chem. Theory Comput.,
2017, 13, 3185–3197.
44 J. J. M. M. J. Turner, S. K. Wolﬀ, D. J. Grimwood,
P. R. Spackman, D. Jayatilaka and M. A. Spackman,
CrystalExplorer17, University of Western Australia, 2017,
http://hirshfeldsurface.net.
45 J. J. McKinnon, M. A. Spackman and A. S. Mitchell, Acta
Crystallogr., Sect. B: Struct. Sci., 2004, 60, 627–668.

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