Room-temperature discotic liquid-crystalline coronene diimides exhibiting high charge-carrier mobility in air

Article abstract of DOI:10.1039/b910898j

Six N,N′,5,11-tetrasubstituted coronene-2,3,8,9-tetracarboxydiimides have been synthesised incorporating 3,4,5-tri(n-dodecyloxy)phenyl or 2-(n-decyl)-n-tetradecyl groups in various positions. Differential scanning calorimetry, polarised optical microscopy, and X-ray diffraction indicate that all form columnar discotic mesophases from around room temperature to around 200 °C. Charge-carrier mobility values, which energetic considerations suggest are electron mobility values, have been determined in non-aligned samples cooled from the isotropic melt using the space-charge-limited current technique. The highest mobility, 6.7 cm² V^-1 s^-1, was found in N,N′-bis(n-2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecylfluorooctyl)-5,11- bis(3-[{3,4,5-tri(n-dodecyloxy)phenyl}carbonyloxy]-n-propyl)coronene-2,3,8, 9-tetracarboxydiimide, which X-ray diffraction suggests is the most highly ordered of the materials examined.

Full text of DOI:10.1039/b910898j

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Volume 19 | Number 37 | 7 October 2009 | Pages 6625–6916
ISSN 0959-9428
PAPER
Seth R. Marder et al.
Room-temperature discotic liquid-
FEATURE ARTICLE
crystalline coronene diimides exhibiting Uday Maitraet al.
0959-9428(2009)19:37;1-M
high charge-carrier mobility in air
Supramolecular gels‘in action’

PAPER
www.rsc.org/materials | Journal of Materials Chemistry
Room-temperature discotic liquid-crystalline coronene diimides exhibiting
high charge-carrier mobility in air†
a
Zesheng An, Junsheng Yu, Benoit Domercq, Simon C. Jones, Stephen Barlow, Bernard Kippelen
b
b
a
a
b
*
a
*
and Seth R. Marder
Received 3rd June 2009, Accepted 17th July 2009
First published as an Advance Article on the web 18th August 2009
DOI: 10.1039/b910898j
Six N,N0,5,11-tetrasubstituted coronene-2,3,8,9-tetracarboxydiimides have been synthesised
incorporating 3,4,5-tri(n-dodecyloxy)phenyl or 2-(n-decyl)-n-tetradecyl groups in various positions.
Differential scanning calorimetry, polarised optical microscopy, and X-ray diffraction indicate that all
form columnar discotic mesophases from around room temperature to around 200 ꢀC. Charge-carrier
mobility values, which energetic considerations suggest are electron mobility values, have been
determined in non-aligned samples cooled from the isotropic melt using the space-charge-limited current
technique. The highest mobility, 6.7 cm2 Vꢁ1 sꢁ1, was found in N,N0-bis(n-2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-
pentadecylfluorooctyl)-5,11-bis(3-[{3,4,5-tri(n-dodecyloxy)phenyl}carbonyloxy]-n-propyl)coronene-
2,3,8,9-tetracarboxydiimide, which X-ray diffraction suggests is the most highly ordered of the materials
examined.
been reported that for some series of compounds increased core
sizes lead to stronger intermolecular interactions and, hence, to
increased charge-carrier mobility.32 However, although coronene
diimides and related systems have been the subject of a number
of studies,33–42 there is little information available regarding
charge mobility in these materials. Indeed, to the best of our
knowledge, the only report of a charge-carrier in a coronene
imide derivative is for a 2,3-dicarboxymonoimide derivative, III
(Fig. 1), for which a 1D intrastack carrier mobility as high as
ca. 0.3 cm2 Vꢁ1 sꢁ1 was obtained using the PR-TRMC tech-
nique.34 Columnar coronene diimides previously reported by
Rohr et al.,33,34 IIa (Fig. 1), were found to form mesophases only
at rather high temperatures (>177 ꢀC) at which mobility
measurements were deemed impractical. No mobility data have
been reported for an example with long ‘‘swallow-tail’’ N,N0-
substituents, IIb (that forms a columnar phase, assigned to
a plastic crystalline phase) at temperatures between room
temperature and 285 ꢀC.39 Here, we report the synthesis and
characterisation of six 6,11,N,N0-substituted coronene-2,3:8,9-
tetracarboxydiimides, 1a–c, 2 and 3 (Scheme 1), in which 3,4,5-
tris(n-dodecyloxy)phenyl groups are linked to either N,N0 (1a–c)
or 6,11 (2) positions, or in which long branched alkyl groups are
attached to the N,N0 positions, with the aim of lowering the
phase-transition temperatures. We describe the synthesis of these
compounds, following the procedure previously reported by
Rohr et al.;33,34 characterisation of their mesophase behaviour
using optical polarised microscopy (OPM), differential scanning
calorimetry (DSC) and X-ray diffraction (XRD); and measure-
ments of charge-carrier mobility using the SCLC technique.
Introduction
Compounds that form columnar discotic liquid-crystalline (LC)
mesophases have attracted attention as possible hole- and elec-
tron-transport materials for applications in organic electronic
devices.1 These materials offer the possibility for high degrees of
order and extensive p-orbital overlap leading to high intrachain
charge-carrier mobilities, while potentially being more readily
processed from solution or from an isotropic melt than p-stacked
single-crystal materials, and are typically composed of molecules
in which a central planar redox-active p-delocalised core is sur-
rounded by flexible side chains.2 Therefore, extensive efforts have
been directed towards developing and studying columnar dis-
cotic materials as hole- and electron-transport materials;3–15
a few examples have been reported with charge-carrier mobility
values in the columnar phase exceeding 1 cm2 Vꢁ1 sꢁ1 16–18
.
Perylene-3,4:9,10-tetracarboxydiimides, I (Fig. 1), have attr-
acted interest as electron-transport materials;19–30 very high
electron mobility values of 1.7 and 1.3 cm2 Vꢁ1 sꢁ1 have been
obtained from field-effect measurements on polycrystalline films
of Ia31 and from space-charge-limited current (SCLC) measure-
ments on a columnar LC mesophase of Ib,18 respectively. The
related coronene-2,3:8,9-tetracarboxydiimides appear to be
interesting candidates for transport materials; while there is not
a universal correlation between core size and mobility,17 it has
aSchool of Chemistry and Biochemistry and Center for Organic Photonics
and Electronics, Georgia Institute of Technology, Atlanta, Georgia, 30332,
USA. E-mail: seth.marder@chemistry.gatech.edu
bSchool of Electrical and Computer Engineering and Center for Organic
Photonics and Electronics, Georgia Institute of Technology, Atlanta,
Georgia, 30332, USA. E-mail: kippelen@ece.gatech.edu
Results and discussion
† Electronic supplementary information (ESI) available: NMR spectra
showing isomer mixture present for 3; UV-vis absorption and emission
data; UV-vis data showing aggregation; examples of cyclic
voltammograms; polarised optical microscopy images; X-ray
diffraction patterns and indexing for all 6 compounds; diffraction
pattern for 2b at 100 ꢀC. See DOI: 10.1039/b910898j
Synthesis
As noted above, a series of N,N0,5,11-tetrasubstituted coronene-
2,3,8,9-tetracarboxydiimides,IIa, havepreviously beensynthesised
6688 | J. Mater. Chem., 2009, 19, 6688–6698
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Fig. 1 Structures of perylene diimide, I, coronene diimide, II, and a coronene monoimide, III, discussed in the text.
Scheme 1
by Rohr et al. and found to exhibit LC behaviour only at high
temperatures.34 The substituents used were generally straight chain
alkyl groups (with short branched substituents being used in the
5,11 positions of one example and 2,6-di(isopropyl)phenyl groups
being used as N,N0 substituents in another). In the hope of lowering
the LC transition temperatures, we chose to investigate the use of
3,4,5-tris(n-dodecyloxy)benzyl groups, attached either directly in
the N,N0 positions (1a–c) or through long linkers to the 5,11 posi-
tions (2a,b), or the long ‘‘swallow-tail’’ 2-(n-decyl)-n-tetradecyl
groups in the N,N0 positions (3). Indeed a similar long-chain
branched substituent in the N,N0 position to that in 3 was used by
Nolde and co-workers to obtain a coronene diimide, IIb, with
This journal is ª The Royal Society of Chemistry 2009
J. Mater. Chem., 2009, 19, 6688–6698 | 6689

a markedly lower isotropic melting point.39 Scheme 1 shows the
syntheses of the six coronene diimides discussed here, which are
closely analogous to those of the coronene diimides reported by
Rohr et al.34 Thus, 1,7-dibromoperylene-3,4:9,10-tetracarbox-
yanhydride, 4,43 is first converted to a 1,7-dibromoperylene-
3,4:9,10-tetracarboxydiimide (6, 10a,b, or14)using the appropriate
amine (5,44 the commercially available 9a,b, or 1345), which is then
coupled with the appropriate terminal alkyne (the commercially
available species 7a–c or the new compound 11) under Sonogashira
conditions.46 The resulting 1,7-dialkynyl perylene diimide deriva-
tives (8a–c, 12a,b, 15) are then cyclised to give the coronene dii-
mides using diazabicyclo[5.4.0]undec-7-ene (DBU). In some cases,
the intermediate dialkynyl species were not isolated, but were
converted in situ to the coronene diimides by addition of DBU to
thereactionmixture. Inthecaseof2b, some cyclisation of 12b tothe
final product was observed even prior to the addition of DBU.
It should be noted that bromination of perylene-3,4:9,10-tet-
racarboxydianhydride in concentrated sulfuric acid can give
1,6,7-tribromo and 1,6-dibromo derivatives in addition to the
1,7-dibromo compound, 4,47 with the isomer ratio depending
somewhat on the reaction conditions (we find that, generally, the
use of more bromine, higher temperature, or longer reaction time
tends to lead to formation of more of the 1,6 isomer). While any
tribrominated species are easily removed from soluble diimides
derived from the brominated dianhydride by column chroma-
tography, separation of the 1,6 and 1,7 isomers is less straight-
forward. Therefore, formation of all of the 1,7-substituted
perylene and 5,11-substituted coronene derivatives shown in
scheme 1 is accompanied by formation of small amounts of the
1,6- and 5,12-substituted derivatives, respectively. Thus, as in
previous work on LC coronene diimides,34 subsequent charac-
terisation was performed using isomer mixtures. While Rohr
et al. obtained a 96 : 4 isomer ratio, we found an 88 : 12 ratio
Perylene diimides typically exhibit two electrochemically
reversible molecular reductions; for example, we have previously
noted that Ib is successively reduced at ꢁ1.02 and ꢁ1.21 V vs.
n
ferrocenium/ferrocene in dichloromethane–0.1 M Bu4NPF6.18
Under the same conditions the present coronene diimides exhibit
less straightforward molecular reduction features in their vol-
tammograms; these are not electrochemically reversible (see
ESI†), perhaps in part due to complications related to aggrega-
tion. This hampers direct comparison with perylene diimides.
However, the first reduction potential appears to be ca. ꢁ1.4 V vs.
ferrocenium/ferrocene for 1a–c, 2a, and 3, suggesting the LUMO
for these species to be some 0.4 eV higher in energy than that of
perylene diimides (i.e. the EA for these species is ca. 3.7 eV using
a value of 4.1 eV for perylene diimides18,49), consistent with
quantum-chemical calculations which predict that the LUMO
and HOMO of coronene diimides are higher and lower, respec-
tively, in energy than those of perylene diimides.35 No molecular
oxidation is detected in the accessible potential range, but the IP
can be estimated from the estimated EA and the optical gap
(obtained from intersection of normalised absorption and fluo-
rescence spectra as 2.4 eV) to be in excess of 6.1 eV (this estimate
neglects the exciton binding energy and so represents a lower
limit). Compound 2b appears to be somewhat more easily
reduced than the other coronene diimides with a potential of
ca. ꢁ1.1 eV, suggesting that HOMO and LUMO both lie ca.
0.3 eV lower in this system. This effect is presumably due to the
inductive electron-withdrawing properties of the CH2C7F15
substituents. Similar effects on the electrochemical properties of
naphthalene and perylene diimides have previously been
observed upon partial fluorination of the N-alkyl groups.26,27,50
Thermal properties and mesophase structure
1
from a 500 MHz H NMR study of 3 (see ESI† for details).
A differential scanning calorimetry (DSC) trace for 2b is shown
as an example in Fig. 2; all six compounds show qualitatively
similar behaviour, with a transition at room temperature or
lower and an isotropic clearing point at ca. 180–250 ꢀC (Table 1).
Optical polarised microscopy and X-ray diffraction (discussed
below) are consistent with assignment of the phases stable
Optical and electrochemical properties
The UV-vis absorption spectra of coronene diimides 1a–c, 2a,b
and 3 in dilute dichloromethane solution (see ESI†) are essen-
tially identical to one another and to those previously reported
for other coronene diimides.33,34,38 The compounds are weakly
fluorescent in dichloromethane; the spectra (see ESI†) closely
resemble to those previously reported for annealed dilute
dispersions of coronene diimides in polystyrene.33 Although one
might naively anticipate that extension of the p-system from
perylene to coronene diimide would lead to a red shift in the
absorption, in fact a blue shift is observed and also predicted by
quantum-chemical calculations.35 In methylcyclohexane, a much
less polar solvent, there is evidence for significant aggregation,
with solutions of concentrations of ca. 10ꢁ5 M closely resembling
those of drop-cast films. Variable concentration studies for 1a–c
and 3 (see ESI†) suggest aggregation constants in the range
0.8–5.1 ꢂ 105 Mꢁ1, increasing in the order 3 < 1a < 1c < 1b. These
values suggest significant intermolecular interactions and fall
within the range of aggregation constants estimated in the same
way for perylene diimide discotic mesogens; values of 1.3 ꢂ 104
and ca. 107 Mꢁ1 have been reported for N,N0-bis[3,4,5-tri(n-
dodecyloxy)benzyl] and N,N0-bis[3,4,5-tri(n-dodecyloxy)phenyl]
derivatives, respectively.48
Fig. 2 Differential scanning calorimetry trace (10 ꢀC minꢁ1, second
heating–cooling cycle) for 2b.
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Table 1 Transition temperatures (ꢀC) with enthalpy changes (kJ molꢁ1
)
be indexed to a rectangular cell, the diffraction patterns can all
be indexed to hexagonal cells (see ESI† for indexing of
diffraction patterns). For 1a (Fig. 1a), only two diffraction
peaks, attributed to the (100) and (110) reflections of a hexag-
onal cell, are observed in the low-angle region. However, 1c,
which has longer side chains attached to the coronene core,
displays four diffraction peaks from (100) to (210), suggesting
a higher degree of molecular ordering than in the mesophase of
1a. Films of 2b show considerably more diffraction peaks than
2a and the crystal-to-mesophase transition occurs at higher
temperature for the former compound, suggesting that the
perfluoroalkyl group significantly enhances the ordering of
room temperature films, perhaps through improved alignment
of the molecules by fluorophobic interaction between the fluo-
roalkyl group and the hydrocarbon moieties. In all cases except
2b, a very broad ‘‘alkyl halo’’ is observed centred at a diffrac-
tion angle of ca. 20ꢀ. In 2b, the broad halo is seen at a slightly
lower value of 2q (ca. 17–18ꢀ), consistent with assignment to the
fluoroalkyl chains,51 while a relatively sharp feature within the
‘‘alkyl halo’’ region (2q ¼ ca. 21ꢀ) is perhaps indicative of
increased ordering of the alkyl side chains at room temperature;
on heating this peak is replaced by a broad feature at ca. 20ꢀ,
overlapping with the fluoroalkyl halo, suggesting melting of
the alkyl chains similar to that seen inꢀ the other compounds
(see ESI† for an X-ray pattern at 100 C). The X-ray patterns
of most of the films, including those of 1a and 2b shown in
Fig. 3, also exhibit a reasonably well-defined feature at ca. 25ꢀ,
attributable to the separation between neighbouring aromatic
cores along the column stacking direction; the distance of
ca. 3.5ꢀ is similar to that seen for other columnar mesophases,
such as those based on hexabenzocoronene52,53 and that formed
by the coronene diimide IIb,39 and indicates the possibility of
strong p–p overlap.
a
in parentheses for coronene diimides measured by DSC (10 ꢀC minꢁ1
)
2nd heating
2nd cooling
Compound
Cr / Col
Col / I
I / Col
Col / Cr
1a
1b
1c
2a
2b
3
27 (17)
16 (48)
19 (62)
28 (20)
36 (67)
188 (9.6)
182 (11)
181 (12)
205 (6.8)
189 (13)
254 (5.9)
179 (7.8)
175 (11)
174 (12)
201 (6.4)
184 (13)
250 (5.9)
0 (51)
9 (43)
11 (69)
11 (21)
19 (64)
ꢁ26 (7.2)
ꢁ13 (3.6)
a
Cr, Col, and I denote phases assigned to crystal, columnar discotic
liquid crystal, and isotropic liquid, respectively.
ꢀ
between ca. room temperature and ca. 200 C as columnar dis-
cotic LC phases. The low temperature transition is, therefore,
likely to be a Cr / Col transition, where Cr and Col denote
crystalline and columnar discotic LC phases, respectively,
although we cannot rule out the possibility that the lowest
temperature phase is in fact another LC phase. These transition
temperatures are considerably lower than those reported for
a range of N,N0,5,11-tetraalkyl coronene diimides IIa (the lowest
Cr / Col transition in the series was observed at 177 ꢀC),34 and
a little lower than for IIb (Cr / Col < 20 ꢀC; Col / I at 285 ꢀC,
where I denotes the isotropic phase).39
Polarised optical microscopy for films of all six compounds
obtained from cooling from the isotropic melt to room
temperature shows textures consistent with the presence of
columnar order. Micrographs 1a and 2b are shown in Fig. 3;
data for the other compounds are shown in the ESI†. X-Ray
diffraction (XRD) confirms the presence of columnar order in
all cases; with the exception of 1b, for which the reflections can
Fig. 3 Polarised optical microscopy images (top, image sizes are 615 ꢂ 460 mm in both cases) and room-temperature X-ray diffraction patterns (below)
for 1a (left) and 2b (right).
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J. Mater. Chem., 2009, 19, 6688–6698 | 6691

SCLC carrier mobilities
i.e., ohmic, dependence of J on V is observed at low voltages,
while at higher applied voltages there is a transition to a regime
assigned to SCLC in which the dependence can be fitted as
J f Vx where x is in the range 2.0–2.6. Based on the estimated IP
and EA of the coronene diimides, electron injection from Ag
(which has a work function of 4.2 eV) into the material is
anticipated to be more favourable than hole injection from ITO
(4.5 eV); therefore, electron injection is likely to be the dominant
process and the mobility values derived from these J–V data are
most likely those for electrons.
The charge-carrier mobility in 1a–c, 2a,b, and 3 was investigated
using the steady-state space-charge-limited current (SCLC)
technique, which has been widely used to investigate carrier
mobility in organic materials,54–62 including several materials
forming columnar discotic mesophases.14,18,63,64 This technique
uses the current–voltage characteristics of organic thin films
sandwiched between injecting electrodes. The current typically
exhibits a linear dependence on the voltage at low voltages and
depends on two unknowns, the carrier density and carrier
mobility. However, at high voltages, an approximately quadratic
SCLC regime can be observed with appropriate combinations of
sample geometry and electrode material; in this regime, if the
contacts are assumed to be ohmic and the materials to be trap-
free, the current depends only on the carrier mobility, m, and on
the capacitance of the sample, which can be measured indepen-
dently. SCLC values of m obtained neglecting the possibility of
imperfectly ohmic injection can vary depending on the work
function of the injecting electrodes and are, in general, similar to
or lower than values obtained for the same material from
(injectionless) time-of-flight measurements.14,64–68
As in our previous work,18,58,63,64 the approximately quadratic
portions of the J–V curves were fitted to a modified Mott–
Gurney equation:69
!
rffiffiffiffi
9
V
V2
d3
J ¼ q303rm0 exp 0:981g
(1)
8
d
where q # 1 (deviating from unity when the injection is non-
ohmic or the material contains charge-carrier traps), 30 is the
permittivity of free space, 3r is the relative dielectric constant of
the transport material (obtained from capacitance measure-
ments), m0 is the charge-carrier mobility in zero electric field, g is
a constant that is related to the field dependence of the mobility,
and d is the sample thickness.
Current density–voltage (J–V) characteristics were measured
under ambient conditions for devices with geometry (+) ITO–
coronene diimide (5 mm)–Ag (ꢁ) prepared by melting the coro-
nene diimides between glass-supported electrodes. Fig. 4 shows
data acquired for 2b and 3; in these and all other cases, a linear,
Values of m0 and g obtained from the best fits of the J–V
curves, assuming q ¼ 1, are compared in Table 2, along with
the maximum values of the mobility, mmax, obtained from
inserting these values and the maximum applied voltage into
the equation:70
!
rffiffiffiffi
V
mmax ¼ m0 exp g
(2)
d
The values of mobility, which are discussed in more detail
below, along with those of g (which are typical values for
organics), are collected in Table 2. Also in Table 2, we compare
values of the threshold voltage, VT, at which the J–V dependence
changes from ohmic to SCLC obtained directly from the J–V
plots, VT(exp), and estimated the parameters used to fit the
SCLC data to eqn (1), VT(calcd). At VT, the current density can
be described using either Ohm’s law or the Mott–Gurney
expression; equating these two expressions leads to:
8
VT ¼ enfb
9
d2
(3)
303r
where e is the electronic charge and nfb is the number of free
background carriers in the ohmic regime, which can be estimated
by extracting the carrier density for the linear regime using an
estimate of the mobility derived from eqn (1) and (2). We note
that the agreement between the experimental and calculated
values of the threshold voltage is not perfect; however, both
values remain within the same order of magnitude. Considering
that both the density of free carriers and the carrier mobility can
vary each by several orders of magnitude in materials tested with
SCLC experiments, this result constitutes an important self-
consistency test when performing these experiments.
Fig. 4 J–V characteristics of coronene diimide (a) 2b and (b) 3 in device
geometry: (+) ITO–coronene diimide 2b or 3 (5 mm)–Ag (ꢁ) under
ambient conditions.
With the exception of 3, the new coronene diimides all show
very high effective charge-carrier mobility. Moreover, as noted
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Table 2 SCLC charge-carrier mobility values and associated parameters for coronene diimides
Compound
3ra
gb/10ꢁ3 cm0.5 Vꢁ0.5
mmax /cm2 Vꢁ1 sꢁ1
VT(calcd)d/V
VT(exp)d/V
b
m0 /cm2 Vꢁ1 sꢁ1
c
1a
1b
1c
2a
2b
3
2.0
2.7
2.6
2.8
3.4
2.6
0.44
1.78
2.04
4.3
4.0
1.9 ꢂ 10ꢁ7
1.6
4.3
3.5
0.81
4.7
9.0
0.54 (at 7.5 V)
3.0 (at 7.5 V)
3.1 (at 7.5 V)
4.7 (at 6.6 V)
6.7 (at 6 V)
2.4
1.1
2.4
3.9
1.2
1.9
3
3
3
3
2
6
1.1 ꢂ 10ꢁ6
a
b
Relative dielectric constant from capacitance measurements. Determined by best fit of approximately quadratic portion of J–V curve to eqn (1),
c
d
assuming q ¼ 1. Determined from eqn (2) and the maximum voltage applied. VT(calcd) and VT(exp) are threshold voltages for SCLC transport
and are estimated from equating Ohm’s law and the Mott–Gurney expression, as described in the text, and determined from the intersection of
linear fits to the ohmic and SCLC regions in a log J–log V plot, respectively.
above, these mobility values were obtained by assuming ohmic
injection and trap-free transport (q ¼ 1) and, therefore, represent
lower limits for the mobility in these samples. Indeed, the effec-
tive mobility values for some of these species exceed those that we
have observed using the same technique in the columnar discotic
perylene diimide 1b,18 perhaps due to the increased core size of
the coronene compounds leading to more effective intermolec-
ular interactions, and are among the highest measured for
molecular materials.
It is worth pointing out that we encountered some variation in
electrical behaviour between different devices for a given
compound in the SCLC studies, with current densities varying
from those corresponding to the data summarised in Table 2 to
essentially immeasurable using our apparatus. Presumably this
variation is related to whether or not a suitable conduction
pathway of a correctly aligned domain is present between the
electrodes in a given device. Several previous reports have also
indicated that the ordering, alignment, and electrical behaviour
of columnar materials can be strongly dependent on processing
conditions and/or device geometries.18,39,63,71 These issues repre-
sent an obstacle to exploiting these materials for organic elec-
tronic applications. Indeed, to date we have been unsuccessful in
our attempts to fabricate field-effect transistors based on these
materials, for which the columns must be oriented parallel to the
gate dielectric surface along the source–drain axis to provide
charge-transport pathways. Of possible significance is the recent
report that the coronene diimide IIb tends to self-assemble ‘‘face
down’’ on surfaces with the columns improperly aligned for
transistor applications.39 On the other hand, while this type of
orientation might suggest the possibility of use in solar cell
applications, these will require the coronene diimides to be used
in combination with a hole-transport material, which raises
additional questions regarding the stability of the columnar
mesophases in the presence of this material and the nature of the
organic–organic interface in these blends.72
Several factors limit the extent to which structure–property
relationships within the series of coronene diimides examined can
be made. Firstly, it should be noted that carrier mobility in
columnar materials such as these are anticipated to be highly
anisotropic; however, as demonstrated by the POM textures (vide
supra), films of these materials cooled from the melt contain
a mixture of differently aligned domains, with the precise mixture
of alignments perhaps varying between samples and, potentially,
with the effect of domain boundaries upon the mobility varying
between samples. Thus, it is unlikely that our values approach
the maximum 1D mobility, m1D, along the columnar stacking
direction (i.e., the LC director) and it is also possible that the
trends we observe do not reflect those for m1D. Secondly, the
transition temperatures observed on heating and cooling for 2b
bracket room temperature and, accordingly, it is unclear whether
2b is actually in the LC phase under the measurement conditions,
although POM and XRD data indicate that it certainly retains
columnar order. In any case, several previous studies have shown
that mobility can be highly temperature dependent in the vicinity
of crystal–LC phase transitions.16,17 Given these caveats, it is
worth noting a number of trends. The compounds containing
[tri(n-dodecyloxy)phenyl]-based mesogens (1a–c, 2a,b) all show
considerably higher mobility than compound 3. Perhaps the
presence of long branched alkyl substituent of 3 introduces
additional disorder into the mesophase, although XRD does not
show any clear evidence for different degrees of order between 1a
(the least ordered [tri(n-dodecyphenyl]-based species) and 3.
However, the increased mobility in 1b and 1c vs. 1a may be
related to the increased order evident in their XRD pattern.
Similarly, 2b, which XRD suggests is the most ordered of any of
the species examined, shows the highest mobility. However, it
also worth noting that more facile electron injection into 2b, due
to the inductive electron-withdrawing effects of the fluoroalkyl
groups, may also play a role in the higher measured effective
mobility.
Conclusion
Introduction of tris(3,4,5-n-dodecyphenyl)-based groups into
either N,N0 or 5,11 positions of coronene diimides has proven
a successful strategy for lowering the temperature window of
stability for coronene diimide columnar discotic mesophases.
The use of a long-chain ‘‘swallow-tail’’ substituent in the N,N0
positions also leads to similar transition temperatures. We have
found that very high charge-carrier mobility—as high as 6.7 cm2
Vꢁ1 sꢁ1—can be achieved in the columnar structures formed by
these coronene diimides under ambient conditions. These
mobility values represent lower limits for the values of the
mobility in these materials due to assumptions (trap-free trans-
port and ohmic contact) used in the determination; moreover,
the 1D mobility along the columnar stacking direction is likely to
be higher still. However, significant challenges remain to be
This journal is ª The Royal Society of Chemistry 2009
J. Mater. Chem., 2009, 19, 6688–6698 | 6693

overcome before these high carrier mobility values can be
exploited in device applications.
mixture was then cooled again at 0 ꢀC and ice-cold water (40 mL)
and then 20% aqueous NaOH (40 mL) were added dropwise. The
mixture was extracted with ethyl acetate; the organic extracts
were washed with brine, dried over MgSO4, filtered, and evap-
orated under reduced pressure to give a solid which was recrys-
Experimental details
1
tallised from acetone to give a white solid (11.23 g, 90%). H
General
NMR (500 MHz, C6D6): d 7.08 (s, 2H), 4.21 (t, 2H), 3.67 (t, 4H),
1.87 (m, 2H), 1.63 (m, 6H), 1.37 (m, 56H), 0.92 (t, 9H). 13C{1H}
NMR (125 MHz, C6D6): d 190.4, 154.1, 144.4, 132.3, 108.1, 73.6,
69.1, 32.33, 32.32, 30.96, 30.22, 30.20, 30.19, 30.15, 30.12, 30.08,
30.02, 29.83, 29.82, 29.79, 29.66, 26.6, 26.5, 23.1, 14.3. HRMS
(EI) calcd for C43H81NO3 (M+): 659.6216. Found: 659.6209.
All chemicals, unless otherwise noted, were purchased from
Aldrich, Acros Organics, Alfa Aesar or Lancaster and were used
without further purification. The 1H and 13C NMR spectra were
acquired on Varian 300 MHz or Bruker 500 MHz spectrometers
using tetramethylsilane (TMS; d ¼ 0 ppm) as an internal stan-
dard. EI and FAB mass spectra were obtained on a VG 70SE
spectrometer and MALDI mass spectra were obtained on an
Applied Biosystems 4700 Proteomics Analyzer. Flash column
Compound 6. Compound 443 (1.07 g, 1.95 mmol) was sonicated
in nBuOH–H2O (160 mL, 1 : 1 v/v) for 10 min. 5 (3.86 g, 5.85 mmol)
was added and the reaction mixture was stirred at 80 ꢀC for 24 h.
Concentrated HCl (15 mL) was added; the resultant precipitate
was filtered and was purified by column chromatography eluting
with chloroform–hexane (1 : 1) to give a red solid (3.01 g, 84%).
1H NMR (500 MHz, CDCl3): d 9.43 (d, J ¼ 8.0 Hz, 2H), 8.90
(s, 2H), 8.67 (d, J ¼ 8.5 Hz, 2H), 6.79 (s, 4H), 5.26 (s, 4H), 3.94
(t, J ¼ 7.0 Hz, 8H), 3.87 (t, J ¼ 7.0 Hz, 4H), 1.75 (m, 8H), 1.68
(m, 4H), 1.5–1.1 (m, 108H), 0.85 (t, J ¼ 7.0 Hz, 18H). 13C{1H}
NMR (125 MHz, CDCl3): d 162.8, 163.4, 153.0, 138.2, 137.9,
132.1, 131.7, 130.2, 129.2, 128.5, 126.9, 123.2, 122.7, 120.8, 108.2,
73.4, 69.2, 44.0, 31.9, 30.3, 29.7, 29.6, 29.5, 29.4, 29.36, 26.1, 22.7,
14.1 (10 carbon resonances were not observed presumably due to
near equivalencies leading to overlap of resonances). HRMS
(MALDI) calcd for C110H165N2O10Br2 (MH+): 1832.0831.
Found: 1832.0824. Anal. Calcd for C110H164N2O10Br2: C, 72.03;
H, 9.01; N, 1.53. Found: C, 72.23; H, 9.30; N, 1.56.
˚
chromatography was performed on silica gel (32–63 mm, 60 A,
Sorbent Technologies). Elemental analyses were carried out by
Atlantic Microlabs using a LECO 932 CHNS elemental analyzer.
DSC traces were taken on a Mettler Toledo DSC 822e instru-
ment at 10 ꢀC minꢁ1. XRD data were collected on a Scintag X1
˚
diffractometer with a Cu Ka source (l ¼ 1.5406 A) in a contin-
uous scan mode with a step size of 0.02ꢀ. Optical textures were
obtained using an Olympus BX51 microscope equipped with an
Olympus U-TU1 X digital camera and an Instec STC200 hot
stage.
3,4,5-Tri(n-dodecyloxy)benzonitrile.73 A solution of BBr3 (9.3
mL, 98.34 mmol) in dichloromethane (10 mL) was added drop-
wise to a solution of 3,4,5-trimethoxybenzonitrile (4.88 g,
25.25 mmol) in 30 mL dry dichloromethane at ꢁ78 ꢀC under
nitrogen. The reaction mixture was allowed to warm to room
temperature and stirred for 12 h. The reaction mixture was
recooled to ꢁ78 ꢀC and ice-cold water was added dropwise. The
mixture was stirred at room temperature for 2 h and then
extracted with ethyl acetate; the organic solution was dried over
anhydrous MgSO4, filtered, and evaporated under reduced
pressure to give a pale yellow solid. K2CO3 (13.2 g, 95.51 mmol)
and 1-bromododecane (22.15 g, 88.89 mmol) were added to
a solution of this solid in DMF (100 mL); the reaction mixture
was then heated to 100 ꢀC and stirred at that temperature for
42 h. After cooling to room temperature, water was added and
the mixture was extracted with dichloromethane. The organic
extracts were dried over MgSO4, filtered, and evaporated under
reduced pressure to give solids which were recrystallised from
acetone to give a white solid (13.84 g, 84%). 1H NMR (500 MHz,
CDCl3): d 6.79 (s, 2H), 3.98 (t, J ¼ 6.5 Hz, 2H), 3.94 (t, J ¼ 6.5
Hz, 4H), 1.78 (m, 4H), 1.71 (m, 2H), 1.44 (m, 6H), 1.27 (m, 48H),
0.86 (t, J ¼ 7.0 Hz, 9H). 13C{1H} NMR (125 MHz, CDCl3):
d 153.4, 142.5, 119.3, 110.4, 106.1, 73.7, 69.4, 31.9, 30.3, 29.73,
29.70, 29.68, 29.65, 29.60, 29.52, 29.38, 29.35, 29.33, 29.2, 26.0,
22.7, 14.1. HRMS (EI) calcd for C43H77NO3 (M+): 655.5904.
Found: 655.5925. Anal. Calcd for C43H77NO3: C, 78.72; H,
11.83; N, 2.13. Found: C, 78.90; H, 11.96; N, 2.18.
Compound 8a. Pd(PPh3)4 (0.064 g, 0.055 mmol), CuI (0.012 g,
0.063 mmol), and 7a (0.4 mL, 2.20 mmol) were added succes-
sively to a deoxygenated suspension of 6 (1.02 g, 0.56 mmol) in
toluene (35 mL) and triethylamine (3.5 mL). After the reaction
mixture was heated at 65 ꢀC under nitrogen for 22 h, it was
poured into 2 N HCl solution. The solvent was removed under
reduced pressure and the residue was purified by column chro-
matography, eluting with chloroform–hexane (2 : 1), to give a red
solid (0.94 g, 87%). 1H NMR (500 MHz, CDCl3): d 10.05
(d, J ¼ 8.5 Hz, 2H), 8.72 (s, 2H), 8.59 (d, J ¼ 8.5 Hz, 2H), 6.79
(s, 4H), 5.27 (s, 4H), 3.95 (t, J ¼ 6.5 Hz, 8H), 3.87 (t, J ¼ 6.5 Hz,
4H), 2.62 (t, J ¼ 7.0 Hz, 4H), 1.8–1.6 (m, 16H), 1.53 (m, 4H),
1.5–1.1 (m, 124H), 0.85 (m, 24H). 13C{1H} NMR (125 MHz,
CDCl3): d 163.3, 163.1, 153.0, 138.2, 137.8, 134.3, 133.9, 132.0,
130.4, 127.5, 127.2, 127.0, 122.8, 121.8, 121.0, 108.1, 101.5, 82.2,
73.4, 69.1, 43.9, 31.9, 31.8, 30.3, 29.73, 29.70, 29.65, 29.61, 29.46,
29.44, 29.36, 29.23, 29.21, 29.13, 28.3, 26.1, 22.7, 22.6, 20.3, 14.1
(11 carbon resonances were not observed presumably due to near
equivalencies leading to overlap of resonances). HRMS
(MALDI) calcd for C130H198N2O10 (M+): 1947.5038. Found:
1947.5046. Anal. Calcd for C130H198N2O10: C, 80.11; H, 10.24;
N, 1.44. Found: C, 80.25; H, 10.26; N, 1.46.
Compound 5.44 A solution of 3,4,5-tri(n-dodecyloxy)benzoni-
trile (12.43 g, 18.95 mmol) in dry THF (200 mL) was added to
a suspension of LiAlH4 (1.57 g, 42.37 mmol) in dry THF
(100 mL) at 0 ꢀC. The reaction mixture was allowed to warm to
room temperature and then heated to reflux for 2 h. The reaction
Compound 1a. Compound 1a was obtained in a one-pot
process from 6 and 7a without isolation of 8a (although 8a was
obtained pure in a separate experiment, vide supra). Pd(PPh3)4
(0.12 g, 0.1 mmol) and CuI (0.02 g, 0.1 mmol) were added to
6694 | J. Mater. Chem., 2009, 19, 6688–6698
This journal is ª The Royal Society of Chemistry 2009

a deoxygenated suspension of 6 (1.47 g, 0.8 mmol) in toluene
(50 mL) and triethylamine (5 mL). After further deoxygenation,
7a (0.6 mL, 3.3 mmol) was added and the reaction mixture was
heated at 65 ꢀC under nitrogen for 24 h. DBU (0.5 mL) was
added to the crude reaction mixture containing 8a; the temper-
ature was raised to 110 ꢀC and the reaction mixture was stirred at
this temperature under nitrogen for 21 h. After cooling to room
temperature, the reaction mixture was poured into 2 N HCl
solution and was extracted with dichloromethane. The organic
extracts were dried over anhydrous MgSO4, filtered, evaporated
under reduced pressure, and purified by column chromatography
eluting with chloroform–hexane (2 : 1). After repeated chroma-
for C134H207N2O10 (MH+): 2004.5751. Found: 2004.5746. Anal.
Calcd for C134H206N2O10: C, 80.27; H, 10.36; N, 1.40. Found: C,
80.26; H, 10.35; N, 1.45.
Compound 8c. Pd(PPh3)4 (0.12 g, 0.1 mmol), CuI (0.02 g,
0.1 mmol), and 7c (1.2 mL, 4.3 mmol) were added successively to
a deoxygenated suspension of compound 6 (2.0 g, 1.1 mmol) in
toluene (70 mL) and triethylamine (10 mL). The resulting solu-
tion was further deoxygenated and heated to 70 ꢀC under
nitrogen for 42 h. After cooling, the mixture was poured into 2 N
HCl solution. The solvent was removed and the residue was
purified by column chromatography eluting with chloroform–
hexane (2 : 1) to give a red solid (1.96 g, 85%). 1H NMR
(500 MHz, CDCl3): d 9.95 (d, J ¼ 8.5 Hz, 2H), 8.57 (s, 2H), 8.49
(d, J ¼ 8.0 Hz, 2H), 6.79 (s, 4H), 5.28 (s, 4H), 3.95 (t, J ¼ 6.0 Hz,
8H), 3.86 (t, J ¼ 6.5 Hz, 4H), 2.61 (t, J ¼ 7.0 Hz, 4H), 1.8–1.6
(m, 16H), 1.6–1.1 (m, 152H), 0.85 (t, J ¼ 7.0 Hz, 24H). 13C{1H}
NMR (125 MHz, CDCl3): d 163.1, 162.9, 153.0, 138.1, 137.8,
134.0, 133.6, 131.9, 130.2, 127.3, 127.1, 126.8, 122.7, 121.7, 120.9,
108.0, 101.8, 82.2, 73.3, 69.1, 43.9, 31.9, 30.3, 29.71, 29.65, 29.57,
29.47, 29.45, 29.36, 29.3, 29.2, 28.3, 26.1, 22.7, 20.3, 14.1 (21
carbon resonances were not observed presumably due to near
equivalencies leading to overlap of resonances). MS (MALDI):
m/z 2116.8 (MH+). Anal. Calcd for C142H222N2O10: C, 80.55; H,
10.57; N 1.32. Found: C, 80.69; H, 10.68; N, 1.36.
1
tography, a yellow solid (0.75 g, 48%) was obtained. H NMR
(500 MHz, CD2Cl2): d 9.16 (s, 2H), 8.85 (s, 2H), 7.89 (s, 2H), 7.02
(s, 4H), 5.55 (s, 4H), 4.08 (br. s, 8H), 3.87 (t, J ¼ 6.5 Hz, 4H), 3.36
(br. s, 4H), 2.0–1.0 (m, 144H), 0.93 (t, 6H), 0.81 (m, 18H). HRMS
(MALDI) calcd for C130H198N2O10 (M+): 1947.5046. Found:
1947.5047. Anal. Calcd for C130H198N2O10: C, 80.11; H, 10.24;
N, 1.44. Found: C, 80.23; H, 10.24; N, 1.49.
Compound 8b. Pd(PPh3)4 (0.12 g, 0.10 mmol), CuI (0.02 g,
0.10 mmol), and 7b (0.76 mL, 3.48 mmol) were added succes-
sively to a deoxygenated suspension of 6 (1.60 g, 0.87 mmol) in
triethylamine (8 mL) and toluene (60 mL). After the reaction
mixture was heated at 70 ꢀC under argon for 24 h, it was cooled
to room temperature and washed twice with 2 N HCl. The
solvent was removed under reduced pressure and the residue was
purified by column chromatography eluting with chloroform–
Compound 1c. A solution of 8c (1.78 g, 0.84 mmol) and DBU
(1 mL) in toluene (50 mL) was heated at 110 ꢀC under argon for
42 h. After cooling, the reaction mixture was poured into 2 N
HCl and extracted with hexane. After removal of solvent under
reduced pressure, the material was purified by column chroma-
tography eluting with chloroform–hexane (1 : 1) to give a yellow
solid (0.65 g, 37%). 1H NMR (500 MHz, CDCl3): d 9.55 (s, 2H),
9.27 (s, 2H), 8.26 (s, 2H), 7.05 (s, 4H), 5.62 (s, 4H), 4.08 (br. s,
8H), 3.89 (t, J ¼ 6.5 Hz, 4H), 3.57 (br. s, 4H), 1.97 (br. m, 4H),
1.78 (m, 8H), 1.69 (m, 4H), 1.65 (m, 4H), 1.5–1.1 (m, 148H), 0.84
(m, 24H). 13C{1H} NMR (125 MHz, CDCl3): d 164.1, 163.9,
153.2, 140.7, 138.0, 132.4, 129.1, 128.1, 127.5, 127.1, 125.2, 121.4,
120.9, 120.7, 120.4, 120.2, 118.8, 108.4, 73.4, 69.3, 44.4, 33.6,
31.93, 31.88, 31.1, 30.4, 29.96, 29.79, 29.78, 29.76, 29.70, 29.68,
29.64, 29.63, 29.57, 29.53, 29.4, 29.3, 26.2, 26.1, 22.7, 22.6, 14.09,
14.06 (13 carbon resonances were not observed presumably due
to near equivalencies leading to overlap of resonances). HRMS
(MALDI) calcd for C142H222N2O10 (M+): 2115.6924. Found:
2115.6920. Anal. Calcd for C142H222N2O10: C, 80.55; H, 10.57;
N, 1.32. Found: C, 80.32; H, 10.50; N, 1.35.
1
hexane (2 : 1) to give a dark red solid (1.16 g, 73%). H NMR
(500 MHz, CDCl3): d 9.98 (d, J ¼ 8.0 Hz, 2H), 8.67 (s, 2H), 8.53
(d, J ¼ 8.0 Hz, 2H), 6.79 (s, 4H), 5.25 (s, 4H), 3.95 (t, J ¼ 6.5 Hz,
8H), 3.86 (t, J ¼ 6.5 Hz, 4H), 2.61 (t, J ¼ 2.61 Hz, 4H), 1.8–1.6
(m, 16H), 1.6–1.1 (m, 136H), 0.86 (m, 24H). 13C{1H} NMR
(125 MHz, CDCl3): d 163.2, 163.0, 153.0, 138.2, 137.8, 134.1,
133.7, 132.0, 130.3, 127.4, 127.2, 126.8, 122.7, 121.7, 120.9, 108.0,
101.7, 82.2, 73.4, 69.1, 43.9, 31.9, 30.3, 29.73, 29.72, 29.71, 29.67,
29.65, 29.61, 29.56, 29.47, 29.45, 29.4, 29.3, 29.26, 29.19, 28.3,
26.1, 22.7, 20.3, 14.1 (12 carbon resonances were not observed
presumably due to near equivalencies leading to overlap of
resonances). Anal. Calcd for C134H206N2O10: C, 80.27; H, 10.36;
N, 1.40. Found: C, 80.28; H, 10.39; N, 1.45.
Compound 1b. A solution of DBU (0.32 mL) and 8b (1.09 g,
0.54 mmol) in toluene (100 mL) was heated to 100 ꢀC under
argon. After 20 h, the mixture was allowed to cool to room
temperature and washed twice with 2 N HCl. The solvent was
removed under reduced pressure and the residue was purified by
column chromatography, eluting with dichloromethane, to give
a yellow solid (0.90 g, 83%). 1H NMR (500 MHz, CDCl3): d 9.56
(s, 2H), 9.29 (s, 2H), 8.28 (s, 2H), 7.05 (s, 4H), 5.62 (s, 4H), 4.08
(br. s, 8H), 3.88 (t, J ¼ 7.0 Hz, 4H), 3.58 (br. s, 4H), 1.98 (m, 4H),
1.78 (m, 8H), 1.68 (m, 4H), 1.59 (m, 4H), 1.5–1.1 (m, 136H), 0.85
(m, 24H). 13C NMR (125 MHz, CDCl3): d 163.8, 163.6, 153.2,
140.2, 138.0, 132.3, 128.7, 127.6, 127.0, 126.6, 124.8, 120.8, 120.4,
120.1, 119.8, 119.5, 118.1, 108.5, 73.3, 69.2, 44.26, 33.4, 32.0,
31.9, 30.8, 30.4, 30.0, 29.8, 29.71, 29.68, 29.64, 29.61, 29.53,
29.45, 29.4, 29.3, 26.2, 26.1, 22.7, 22.6, 14.1, 14.0 (11 carbon
resonances were not observed presumably due to near equiva-
lencies leading to overlap of resonances). HRMS (MALDI) calcd
Compound 10b. Compound 4 (0.93 g, 1.68 mmol) was soni-
cated in NMP (20 mL) for 30 min, and acetic acid (0.645 g, 11.80
mmol) followed by a solution of 9b (2.0 g, 4.86 mmol) in NMP
(15 mL) were added. After the reaction mixture was heated at
85 ꢀC under nitrogen for 8 h, it was allowed to cool to room
temperature. Methanol (150 mL) was added, the resulting
precipitate was collected by filtration and purified by column
chromatography, eluting with chloroform, to give a red solid
(1.25 g, 57%). 1H NMR (500 MHz, CDCl3): d 9.51 (d, J ¼ 8.0 Hz,
2H), 8.97 (s, 2H), 8.75 (d, J ¼ 8.0 Hz, 2H), 5.03 (m, 4H). HRMS
(MALDI) calcd for C40H10N2O4F30Br2 (M+): 1309.8528. Found:
This journal is ª The Royal Society of Chemistry 2009
J. Mater. Chem., 2009, 19, 6688–6698 | 6695

1309.8528. Anal. Calcd for C40H10Br2F30N2O4: C, 36.61; H,
0.77; N, 2.13. Found: C, 36.68; H, 0.66; N, 2.07.
a deoxygenated suspension of compound 10b (0.77 g, 0.59 mmol)
in toluene (40 mL) and triethylamine (10 mL). The reaction
mixture was heated at 65 ꢀC for 18 h. After cooling to room
temperature, the reaction mixture was poured into 2 N HCl
solution. The organic layer was separated and the solvent was
removed under reduced pressure. The residue was purified by
column chromatography, eluting with dichloromethane–chloro-
form, to afford a mixture of red and yellow compounds, presum-
ably 12b and 2b, respectively. This crude mixture was then
dissolved in toluene (90 mL) and was heated to 100 ꢀC under
nitrogen; DBU (0.35 mL) was added and the reaction was main-
tained at 100 ꢀC for 19 h under nitrogen. After cooling to room
temperature, the reaction mixture was poured into 2 N HCl
solution. The organic layer was separated and the solvent was
removed under reduced pressure. The residue was purified by
column chromatography eluting with chloroform, 0.62 g (37%) of
a yellow–brown solid was obtained. 1H NMR (500 MHz, CDCl3):
d 9.89(s, 2H),9.64(s, 2H),8.84(s,2H), 6.89(s, 4H),5.31(t, J ¼ 15.7
Hz, 4H), 4.60 (t, J ¼ 6.0 Hz, 4H), 3.94 (m, 4H), 3.75 (t, J ¼ 6.5 Hz,
4H), 3.69 (t, J ¼ 6.5 Hz, 8H), 2.66 (m, 4H), 1.8–1.55 (m, 12H), 1.5–
1.1 (m, 108H), 0.83 (m, 18H). Anal. Calcd for C136H176F30N2O14:
C, 62.04; H, 6.74; N, 1.06. Found: C, 61.98; H, 6.69; N, 1.10.
Compound 11. 4-Dimethylpyridine (0.44 g, 3.59 mmol) was
added to a solution of 3,4,5-tris(n-dodecyloxy)benzoyl chlo-
ride74,75 (1.56 g, 2.25 mmol). Pent-4-yn-1-ol (0.26 g, 3.10 mmol)
was added via a syringe under nitrogen and the reaction mixture
was stirred for 80 min at room temperature. The solvent was then
removed under reduced pressure; the residue was purified by
column chromatography eluting with ethyl acetate–hexane (1 :
1
19) to give a white solid (1.37 g, 82%). H NMR (300 MHz,
CDCl3): d 7.23 (s, 2H), 4.38 (t, J ¼ 6.3 Hz, 2H), 3.98 (m, 6H), 2.34
(dt, J ¼ 7.2, 2.4 Hz, 2H), 1.97 (m, 3H), 1.86–1.68 (m, 6H), 1.54–
1.16 (m, 59H), 0.86 (m, 9H). 13C{1H} NMR (75 MHz, CDCl3):
d 166.2, 152.7, 142.3, 124.6, 108.0, 83.0, 73.5, 69.2, 69.0, 63.5,
32.0, 30.4, 29.8, 29.73, 29.70, 29.6, 29.5, 29.4, 27.8, 26.2, 26.1,
22.8, 15.5, 14.2 (10 carbon resonances were not observed
presumably due to near equivalencies leading to overlap of
resonances). HRMS (MALDI) calcd for C48H85O5 (MH+):
741.6397. Found: 741.6392. Anal. Calcd for C48H84O5: C, 77.78;
H, 11.42. Found: C, 77.54; H, 11.47.
Compound 12a. Pd(PPh3)4 (0.06 g, 0.05 mmol) and CuI (0.015 g,
0.17 mmol) were added to a deoxygenated solution of 10a34
(0.42 g, 0.54 mmol) in toluene (30 mL) and triethylamine (6 mL).
A deoxygenated solution of 11 (1.20 g, 1.62 mmol) in toluene
(10 mL) was then added; the reaction mixture was heated to 60 ꢀC
under nitrogen for 14 h, after which it was allowed to cool to room
temperature and poured into 2 N HCl solution. The organic phase
was separated and was washed with water. The solvent was
removed under reduced pressure and the residue was purified by
column chromatography, eluting with dichloromethane, to give
Compound 14. Compound 14 was synthesised from 4 and 1345
as described previously.76
Compound 3. Compound 3 was obtained in a one-pot process
from 14 and 7a without isolation of 15. Pd(PPh3)4 (0.28 g, 0.24
mmol), CuI (0.034 g, 0.18 mmol), and 7a (1.3 mL, 7.20 mmol)
were added successively to a deoxygenated solution of 14 (2.2 g,
1.8 mmol) in toluene (50 mL) and ꢀtriethylamine (10 mL). The
reaction mixture was heated at 65 C under nitrogen for 24 h.
DBU (0.5 mL) was added and the reaction temperature was
1
a red solid (1.01 g, 89%). H NMR (500 MHz, CDCl3): d 10.07
ꢀ
(d, J ¼ 8.5 Hz, 2H), 8.65 (s, 2H), 8.61 (d, J ¼ 8.0 Hz, 2H), 7.21
(s, 4H), 4.55 (t, J ¼ 6.0 Hz, 4H), 4.16 (t, J ¼ 8.0 Hz, 4H), 3.88
(t, J ¼ 6.5 Hz, 8H), 3.82 (t, J ¼ 6.5 Hz, 4H), 2.86 (t, J ¼ 6.5 Hz, 4H),
2.25 (m, 4H), 1.8–1.6 (m, 16H), 1.5–1.1 (m, 128H), 0.87 (m, 24H).
Anal. Calcd for C136H206N2O14: C, 78.04; H, 9.92; N, 1.34.
Found: C, 77.82; H, 9.97; N, 1.50.
raised to 100 C and stirred for another 16 h. Additional DBU
(0.5 mL) was added and the reaction temperature was raised to
110 ꢀC and the reaction mixture was further stirred at this
temperature for 24 h. The reaction mixture was cooled to room
temperature, poured into 2 N HCl solution, and extracted with
dichloromethane. The organic extracts were evaporated under
reduced pressure and the residue was purified by column chro-
matography, eluting with chloroform–hexane (1 : 3) to give
a yellow solid (1.9 g, 86%). 1H NMR (500 MHz, CDCl3): d 9.32
(s, 2H), 9.10 (s, 2H), 8.25 (s, 2H), 4.42 (d, J ¼ 7.0 Hz, 4H), 3.52
(t, J ¼ 7.0 Hz, 4H), 2.15 (m, 2H), 2.00 (m, 4H), 1.63 (m, 4H),
1.55–1.0 (m, 104H), 0.91 (t, J ¼ 7.0 Hz, 6H), 0.80 (m, 12H).
13C{1H} NMR (125 MHz, CDCl3): d 164.9, 164.7, 141.1, 129.4,
128.7, 128.1, 127.5, 125.5, 122.1, 121.5, 121.0, 120.8, 120.7, 119.5,
45.5, 37.5, 34.0, 32.4, 32.3, 31.3, 30.64, 30.62, 30.4, 30.1, 30.07,
30.01, 29.9, 29.74, 29.70, 27.1, 23.2, 23.0, 14.6, 14.5 (11 carbon
resonances were not observed presumably due to near equiva-
lencies leading to overlap of resonances). HRMS (MALDI) calcd
for C9013C2H138N2O4 (M+): 1337.0724. Found: 1337.0807. Anal.
Calcd for C92H138N2O4: C, 82.70; H, 10.41; N, 2.10. Found: C,
82.82; H, 10.55; N, 2.21.
Compound 2a. DBU (0.2 mL) was added via syringe to
a solution of 12a (0.72 g, 0.34 mmol) in toluene (50 mL), and the
resulting solution was heated to 100 ꢀC under nitrogen for 20 h.
After cooling to room temperature, the reaction mixture was
poured into 2 N HCl solution. The organic layer was separated,
and the solvent was removed under reduced pressure. The
residue was purified by column chromatography, eluting first
with dichloromethane and then with 5% ethyl acetate–
dichloromethane (1 : 19), to give a yellow solid (0.58 g, 80%). 1H
NMR (500 MHz, CD2Cl2): d 9.61 (s, 2H), 9.34 (s, 2H), 8.60
(s, 2H), 6.89 (s, 4H), 4.60 (t, J ¼ 6.0 Hz, 4H), 4.44 (t, J ¼ 8.0 Hz,
4H), 3.87 (t, J ¼ 6.0 Hz, 4H), 3.64 (m, 12H), 2.62 (m, 4H), 1.94
(m, 4H), 1.7–1.1 (m, 140H), 1.0–0.7 (m, 24H). HRMS (MALDI)
calcd for C136H207N2O14 (MH+): 2092.5547. Found: 2092.5543.
Anal. Calcd for C136H206N2O14: C, 78.04; H, 9.92; N, 1.34.
Found: C, 77.85; H, 9.88; N, 1.47.
Sample preparation and mobility measurements
Compound 2b. Pd(PPh3)4 (0.075 g, 0.065 mmol), CuI (0.023 g,
0.12 mmol), and 11 (1.31 g, 1.77 mmol) were added successively to
The ITO-covered glass substrates were cleaned using ultrasonic
treatment in detergent water, water, DI water, acetone, ethanol,
6696 | J. Mater. Chem., 2009, 19, 6688–6698
This journal is ª The Royal Society of Chemistry 2009

and dried at 60 ꢀC in a vacuum oven overnight, and finally
treated with high-pressure N2 gas flow. Prior to the fabrication of
the device, ITO-covered glass substrates were plasma treated
(750 W) for 5 min. A small amount of the coronene diimide
compound was melted at a temperature above its isotropic
clearing point on an ITO-coated glass substrate on a digital hot
plate in air. Compounds 1a–c were melted at 210 ꢀC, compounds
6 H. Iino, J.-i. Hanna, R. J. Bushby, B. Movaghar, B. J. Whitaker and
M. J. Cook, Appl. Phys. Lett., 2005, 87, 132102.
7 H. Iino, Y. Takayashiki, J.-i. Hannaa, R. J. Bushby and D. Haarer,
Appl. Phys. Lett., 2005, 87, 192105.
8 Q. Zhang, P. Prins, S. C. Jones, S. Barlow, T. Kondo,
L. D. A. Siebbeles and S. R. Marder, Org. Lett., 2005, 7, 5019.
9 M. Kastler, W. Pisula, F. Laquai, A. Kumar, R. J. Davies,
ꢀ
S. Baluschev, M.-C. Garcia-Gutierrez, D. Wasserfallen, H.-J. Butt,
€
C. Riekel, G. Wegner and K. Mullen, Adv. Mater., 2006, 18, 2255.
ꢀ
ꢀ
2a and 2b at 220 C and 210 C, respectively, and compound 3
was processed at 285 ꢀC. While kept in the isotropic phase on the
first ITO substrate, the compounds were sandwiched using
a silver-coated glass substrate to form a device. Calibrated glass
spacers were used to ensure a uniform sample thickness of 5 mm.
The device with the compound in the isotropic phase was
removed from the hot plate and allowed to cool down in air to
room temperature. During the cooling process, a slight exterior
force without shear was applied in order to enhance the contact
between organic layer and the electrodes. The active area of each
device was in the range of 3 to 5 mm2. Prior to the current–
voltage characteristic measurement, devices were sealed with
quick-setting epoxy adhesive. The silver electrodes were fabri-
cated on glass substrates by thermal evaporation of silver using
a SPECTROS Kurt J. Lesker System at a vacuum of 10ꢁ7 Torr
through shadow masks. On each glass substrate four silver
electrodes with a thickness in the range of 150 to 350 nm were
formed. Prior to the silver deposition, the 100 ꢂ 100 glass slides
were cleaned using the same procedure as the cleaning of ITO-
coated glass slides. For SCLC experiments, the measurements of
J–V characteristics of all devices were performed at room
temperature in air and in the dark. The J–V characteristics were
measured using a Keithley 2400 Source Meter. Capacitance was
measured using Agilent 16048A Test Leads connected to an
Agilent 4284A Precision LCR Meter.
10 V. Duzhko, A. Semyonov, R. J. Twieg and K. D. Singer, Phys. Rev.
B: Condens. Matter, 2006, 73, 064201.
11 W. Pisula, M. Kastler, D. Wasserfallen, M. Mondeshki, J. Piris,
€
I. Schnell and K. Mullen, Chem. Mater., 2006, 18, 3634.
12 B. R. Kaafarani, L. A. Lucas, B. Wex and G. E. Jabbour, Tetrahedron
Lett., 2007, 48, 5995.
13 Y. Hirai, H. Monobe, N. Mizoshita, M. Moriyama, K. Hanabusa,
Y. Shimizu and T. Kato, Adv. Funct. Mater., 2008, 18, 1668.
´
14 M. Talarico, R. Termine, E. M. Garcıa-Frutos, A. Omenat,
J. L. Serrano, B. Gomez-Lor and A. Golemme, Chem. Mater.,
ꢀ
2008, 20, 6589.
15 R. Chaudhuri, M.-Y. Hsu, C.-W. Li, C.-I. Wang, C.-J. Chen,
C. K. Lai, L.-Y. Chen, S.-H. Liu, C.-C. Wu and R.-S. Liu, Org.
Lett., 2008, 10, 3053.
€
16 A. M. van de Craats, J. M. Warman, A. Fechtenkotter, J. D. Brand,
€
M. A. Harbison and K. Mullen, Adv. Mater., 1999, 11, 1469.
ˇ
17 M. G. Debije, J. Piris, M. P. de Haas, J. M. Warman, Z. Tomovic,
ꢀ
C. D. Simpson, M. D. Watson and K. Mullen, J. Am. Chem. Soc.,
2004, 126, 4641.
€
18 Z. An, J. Yu, S. C. Jones, S. Barlow, S. Yoo, B. Domercq, P. Prins,
L. D. A. Siebbeles, B. Kippelen and S. R. Marder, Adv. Mater.,
2005, 17, 2580.
19 G. Horowitz, F. Kouki, P. Spearman, D. Fichou, C. Nogues, X. Pan
and F. Garnier, Adv. Mater., 1996, 8, 242.
20 C. W. Struijk, A. B. Sieval, J. E. J. Dakhorst, M. van Dijk, P. Kimkes,
R. B. M. Koehorst, H. Donker, T. J. Schaafsma, S. J. Picken,
A. M. van de Craats, J. M. Warman, H. Zuilhof and
E. J. R. Sudholter, J. Am. Chem. Soc., 2000, 122, 11057.
21 P. R. L. Malenfant, C. D. Dimitrakopoulos, J. D. Gelorme,
L. L. Kosbar and T. O. Graham, Appl. Phys. Lett., 2002, 80, 2517.
22 B. J. Jones, M. J. Ahrens, M. H. Yoon, A. Facchetti, T. J. Marks and
M. R. Wasielewski, Angew. Chem., Int. Ed., 2004, 43, 6363.
23 Z. Chen, M. G. Debije, T. Debaedemaeker, P. Osswald and
€
F. Wurthner, ChemPhysChem, 2004, 5, 137.
24 R. Schmidt, M. M. Ling, J. H. Oh, M. Winkler, M. Konemann,
€
Acknowledgements
€
B. Zhenan and F. Wurthner, Adv. Mater., 2007, 19, 3692.
€
€
25 F. Wurthner, P. Osswald, R. Schmidt, T. E. Kaiser, H. mansikkamaki
This material is based upon work supported in part by the STC
Program of the National Science Foundation under Agreement
Number DMR-0120967. We also thank the NSF for funding
through CHE-0211419.
€
and M. Konemann, Org. Lett., 2006, 8, 3765.
26 B. J. Jones, A. Facchetti, M. R. Wasielewski and T. J. Marks, J. Am.
Chem. Soc., 2007, 129, 15259.
€
27 J. H. Oh, S. Liu, Z. Bao, R. Schmidt and F. Wurthner, Appl. Phys.
Lett., 2007, 91, 212107.
28 H. Z. Chen, M. M. Ling, X. Mo, M. M. Shi, M. Wang and Z. Bao,
Chem. Mater., 2007, 19, 816.
29 Y. Wang, Y. Chen, R. Li, S. Wang, W. Su, P. Ma, M. R. Wasielewski,
X. Li and J. Jiang, Langmuir, 2007, 23, 5836.
30 Y. Li, L. Tan, Z. Wang, H. Qian, Y. Shi and W. Hu, Org. Lett., 2008,
10, 529.
References
€
1 S. Laschat, A. Baro, N. Steinke, F. Giesselmann, C. Hagele, G. Scalia,
R. Judele, E. Kapatsina, S. Sauer, A. Schreivogel and M. Tosoni,
Angew. Chem., Int. Ed., 2007, 46, 4832.
31 R. J. Chesterfield, J. C. McKeen, C. R. Newman, P. C. Ewbank,
2 In some other examples of columnar discotic mesophases the redox
activity is associated with electroactive moieties located in arms
surrounding the core, rather than with the core itself, the arms
being either conjugated to the core (for example: Y.-D. Zhang,
K. G. Jespersen, M. Kempe, J. A. Kornfield, S. Barlow,
B. Kippelen and S. R. Marder, Langmuir, 2003, 19, 6534) or linked
through saturated bridging groups to the core (for example:
I. Paraschiv, K. de Lange, M. Giesbers, B. van Lagen,
F. C. Grozema, R. D. Abellon, L. D. A. Siebbeles,
ꢀ
D. A. da Silva Filho, J.-L. Bredas, L. L. Miller, K. R. Mann and
C. D. Frisbie, J. Phys. Chem. B, 2004, 108, 19281.
32 A. van de Craats and J. M. Warman, Adv. Mater., 2001, 13, 130.
€
33 U. Rohr, P. Schlichting, A. Bohm, M. Gross, K. Meerholz,
C. Brauchle and K. Mullen, Angew. Chem., Int. Ed., 1998, 37, 1434.
€
€
€
34 U. Rohr, C. Kohl, K. Mullen, A. van de Craats and J. Warman,
J. Mater. Chem., 2001, 11, 1789.
35 M. Adachi and Y. Nagao, Chem. Mater., 2001, 13, 662.
´
€
36 P. Samorı, N. Severin, C. D. Simpson, K. Mullen and J. P. Rabe,
€
E. J. R. Sudholter, H. Zuilhof and A. T. M. Marcelis, J. Mater.
Chem., 2008, 18, 5475).
3 I. Seguy, P. Destruel and H. Bock, Synth. Met., 2000, 111–112, 15.
J. Am. Chem. Soc., 2002, 124, 9454.
37 M. Franceschin, A. Alvino, G. Ortaggi and A. Bianco, Tetrahedron
Lett., 2004, 45, 9015.
€
€
4 L. Schmidt-Mende, A. Fechtenkotter, K. Mullen, E. Moons,
R. H. Friend and J. D. MacKenzie, Science, 2001, 293, 1119.
5 M. Lehmann, G. Kestemont, R. G. Aspe, C. Buess-Herman,
M. H. J. Koch, M. G. Debije, J. Piris, M. P. de Haas,
J. M. Warman, M. D. Watson, V. Lemaur, J. Cornil, Y. H. Geerts,
R. Gearba and D. A. Ivanov, Chem.–Eur. J., 2005, 11, 3349.
€
€
38 S. Muller and K. Mullen, Chem. Commun., 2005, 4045.
€
€
39 F. Nolde, W. Pisula, S. Muller, C. Kohl and K. Mullen, Chem.
Mater., 2006, 18, 3715.
40 S. Alibert-Fouet, I. Seguy, J.-F. Bobo, P. Destruel and H. Bock,
Chem.–Eur. J., 2007, 13, 1746.
This journal is ª The Royal Society of Chemistry 2009
J. Mater. Chem., 2009, 19, 6688–6698 | 6697

€ €
41 Y. Avlasevich, S. Muller, P. Erk and K. Mullen, Chem.–Eur. J., 2007,
13, 6555.
58 B. R. Kaafarani, T. Kondo, J. Yu, Q. Zhang, D. Dattilo, C. Risko,
S. C. Jones, S. Barlow, B. Domercq, F. Amy, A. Khan,
ꢀ
J. L. Bredas, B. Kippelen and S. R. Marder, J. Am. Chem. Soc.,
2005, 127, 16358.
42 M. Franceschin, A. Alvino, V. Casagrande, C. Mauriello, E. Pascucci,
M. Savino, G. Ortaggi and A. Bianco, Bioorg. Med. Chem., 2007, 15,
1848.
43 A. Boehm, H. Arms, G. Henning and P. Blaschka, German Patent,
DE 95–19547209, 1997.
44 J. van Herrikhuyzen, A. Syamakumari, A. P. H. J. Schenning and
E. W. Meijer, J. Am. Chem. Soc., 2004, 126, 10026.
45 M. Conrads, A. T. Herrmann, E. Scherf and A. Wagner, European
Patent 742199, 1996.
46 K. Sonogashira, Y. Tohda and N. Hagihara, Tetrahedron Lett., 1975,
50, 4467.
59 E. Zhou, Z. Tan, L. Huo, Y. He, C. Yang and Y. Li, J. Phys. Chem. B,
2006, 110, 26062.
60 J. E. Parmer, A. C. Mayer, B. E. Hardin, S. R. Scully,
M. D. McGehee, M. Heeney and I. McCulloch, Appl. Phys. Lett.,
2008, 92, 113309/1.
61 C. H. Woo, B. C. Thompson, B. J. Kim, M. F. Toney and
ꢀ
J. M. J. Frechet, J. Am. Chem. Soc., 2008, 130, 16324.
62 M. Giulianini, E. R. Waclawik, J. M. Bell and N. Motta, Appl. Phys.
Lett., 2009, 94, 083302.
€
€
47 F. Wurthner, V. Stepanenko, Z. Chen, C. R. Saha-Moller, N. Kocher
63 J.-Y. Cho, J. Yu, B. Domercq, S. C. Jones, S. Barlow, B. Kippelen and
S. R. Marder, J. Mater. Chem., 2007, 17, 2642.
64 B. Domercq, J. Yu, B. R. Kaafarani, T. Kondo, S. Yoo,
J. N. Haddock, S. Barlow, S. R. Marder and B. Kippelen, Mol.
Cryst. Liq. Cryst., 2008, 481, 80.
65 R. W. I. de Boer, M. Jochemsen, T. M. Klapwijk, A. F. Morpurgo,
J. Niemax, A. K. Tripathi and J. Pflaum, J. Appl. Phys., 2004, 95, 1196.
66 W. Xu, Khizar-ul-Haq, Y. Bai, X. Y. Jiang and Z. L. Zhang, Solid
State Commun., 2008, 146, 311.
and D. Stalke, J. Org. Chem., 2004, 69, 7933.
€
48 F. Wurthner, C. Thalacker, S. Diele and C. Tschierske, Chem.–Eur.
J., 2001, 7, 2245.
49 See discussion in ref. 18 (in footnote 12) of alternative estimates.
However, the estimate of 4.1 eV for perylene diimides is broadly in
line with an EA of 4.0 eV measured by inverse photoelectron
spectroscopy
for
films
of
perylene-3,4:9,10-dianhydride
(C. K. Chan, E.-G. Kim, J.-L. Bredas and A. Kahn, Adv. Funct.
ꢀ
Mater., 2006, 16, 831).
50 H. E. Katz, J. Johnson, A. J. Lovinger and W. Li, J. Am. Chem. Soc.,
2000, 122, 7787.
51 For example, see: C. P. Jariwal and L. J. Mathias, Macromolecules,
1993, 26, 5129; Y. Yanagimoto, Y. Takaguchi, Y. Sako, S. Tsuboi,
M. Ichihara and K. Ohta, Tetrahedron, 2006, 62, 8373;
N. Terasawa, H. Monobe and K. Kiyohara, Liq. Cryst., 2007, 34, 311.
67 C. H. Cheung, K. C. Kwok, S. C. Tse and S. K. So, J. Appl. Phys.,
2008, 103, 093705/1.
68 G. Schwartz, T.-H. Ke, C.-C. Wu, K. Walzer and K. Leo, Appl. Phys.
Lett., 2008, 93, 073304.
69 P. N. Murgatroyd, J. Phys. D: Appl. Phys., 1970, 3, 151.
€
70 P. M. Borsenberger, L. Pautmeier and H. Bassler, J. Chem. Phys.,
1991, 94, 5447.
71 V. De Cupere, J. Tant, P. Viville, R. Lazzaroni, W. Osikowicz,
W. R. Salaneck and Y. H. Geerts, Langmuir, 2006, 22, 7798.
€
€
€
52 A. Fechtenkotter, K. Saalwachter, M. A. Harbison, K. Mullen and
H. W. Spiess, Angew. Chem., Int. Ed., 1999, 38, 3099.
53 D. Adam, P. Schuhmacher, J. Simmerer, L. Haussling,
€
€
72 L. Schmidt-Mende, M. Watson, K. Mullen and R. H. Friend, Mol.
K. Siemensmeyer, K. H. Etzbach, H. Ringsdorf and D. Haarer,
Nature, 1994, 371, 141.
54 P. W. M. Blom, M. J. M. de Jong and M. G. van Munster, Phys. Rev.
B: Condens. Matter, 1997, 55, R656.
55 L. Bozano, S. A. Carter, J. C. Scott, G. G. Malliaras and P. J. Brock,
Appl. Phys. Lett., 1999, 74, 1132.
56 J. Reynaert, V. I. Arkhipov, G. Borghs and P. Heremans, Appl. Phys.
Lett., 2004, 85, 603.
Cryst. Liq. Cryst., 2003, 396, 73.
73 M. Lee, Y.-S. Yoo and M.-G. Choi, Bull. Korean Chem. Soc., 1997,
18, 1067.
74 V. Percec, D. Schlueter, J. C. Ronda, G. Johansson, G. Ungar and
J. P. Zhou, Macromolecules, 1996, 29, 1464.
75 D. J. P. Yeardley, G. Ungar, V. Percec, M. N. Holerca and
G. Johansson, J. Am. Chem. Soc., 2000, 122, 1684.
76 X. Zhan, Z. Tan, B. Domercq, Z. An, X. Zhang, S. Barlow, Y. Li,
D. Zhu, B. Kippelen and S. R. Marder, J. Am. Chem. Soc., 2007,
129, 7246.
57 P. W. M. Blom, C. Tanase, D. M. de Leeuw and R. Coehoorn, Appl.
Phys. Lett., 2005, 86, 092105.
6698 | J. Mater. Chem., 2009, 19, 6688–6698
This journal is ª The Royal Society of Chemistry 2009