Room temperature liquid crystalline perylene diester benzimidazoles with extended absorption

Article abstract of DOI:10.1039/c0jm01626h

The synthesis, characterization and thermotropic properties of novel asymmetrically substituted discotic molecules, perylene diester benzimidazoles (PDBIs), are presented. PDBIs were designed with an imidazole unit at 3,4 positions and a bisester moiety a

Full text of DOI:10.1039/c0jm01626h

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PAPER
www.rsc.org/materials | Journal of Materials Chemistry
Room temperature liquid crystalline perylene diester benzimidazoles with
extended absorption†
*
ꢀ
Andre Wicklein, Mathis-Andreas Muth and Mukundan Thelakkat
Received 27th May 2010, Accepted 30th July 2010
DOI: 10.1039/c0jm01626h
The synthesis, characterization and thermotropic properties of novel asymmetrically substituted
discotic molecules, perylene diester benzimidazoles (PDBIs), are presented. PDBIs were designed with
an imidazole unit at 3,4 positions and a bisester moiety at 9,10 positions of the perylene tetracarboxylic
acid core. By attaching linear or branched aliphatic substituents at the ester moiety and two alkyl or
alkoxy substituents at the benzimidazole unit, sufficient solubility and the flexibility to obtain
mesophases was guaranteed. Thermotropic behaviour, which is strongly influenced by the nature of the
respective substituents at the diester and benzimidazole moiety, was investigated using differential
scanning calorimetry (DSC), polarization optical microscopy (POM) and X-ray diffraction
measurements (XRD). All PDBIs under investigation self-organize into liquid crystalline columnar
hexagonal phases (Colh), among them PDBI-3 even at room temperature. Also the formation of a room
temperature columnar plastic phase (Colhp) and the formation of a lamellar phase was observed. Due to
extension of the p-conjugation system, the absorption of these well soluble discogens is significantly
extended to longer wavelengths in the visible regime up to 680 nm.
is often gained at the expense of planarity and loss of strong p–p
Introduction
interactions, by incorporating substituents at the bay position,
which results in twisting of the perylene core. However strong p–
p interactions are required for intermolecular order and efficient
charge carrier transport. Very recently we reported on a series of
highly soluble discotic liquid crystalline PBIs carrying swallow-
tail N-substituents.18
Self-organizing organic semiconductor molecules like discotic
liquid crystals (LCs)1–3 have found increased interest as solution
processable materials for organic semiconductor applications in
areas like light emitting diodes,4 field effect transistors5 or
photovoltaic devices.6 The uniaxial conducting properties along
the p–p stacking axis in self-assembled columnar superstructures
of disc-like molecules, consisting of a rigid aromatic core with
flexible side-chains attached at the periphery of the mesogen,
provide the high charge carrier mobility within the bulk phase
which is decisive in organic electronics.7–9 In such materials
charge carrier mobilities up to 0.1–1.3 cm2 Vꢀ1$sꢀ1 in their liquid
crystalline mesophases have been measured.8,10–12 Liquid crys-
talline organization also increases the local order without
creating too many grain boundaries on the macroscopic level as
in the case of crystalline materials. It is also desirable to have
room temperature LC materials, so that devices can be processed
from isotropic melt at high temperatures and the LC order can be
maintained at room temperature. However, most discotic
semiconductor materials are good hole transporting materials (p-
type), while the number of suitable electron transporting mate-
rials (n-type) is still very limited.13–15 In this context discotic
mesogens derived from perylene bisimides16,17 (PBI) and related
molecules are a promising class of dyes. This is in view of their
high electron affinity making them highly attractive as n-type
semiconductors and their favourable absorption properties in the
visible wavelength regime. Unfortunately, high solubility of PBIs
Another class of liquid crystalline perylene dyes are tetraalkyl
esters of perylene tetracarboxylic acid (PTE).19 But PTEs absorb
only in the blue region and are less electron deficient compared to
PBIs.20 Therefore it is of fundamental interest to improve the
electron deficiency and extend the absorption to longer wave-
length region in this class of materials. One elegant way to ach-
ieve this is to introduce a fused benzimidazole moiety to the
perylene core. It was recently demonstrated for bisimides to get
a new class of n-type semiconductors.21 Taking these facts into
account, we decided to design new soluble asymmetric molecules
based on a perylene diester benzimidazole (PDBI) structure in
which liquid crystalline organization along with an extended
absorption in the red region of visible spectrum was realized. The
electron affinity could also be maintained close to that of PBI.18
A substitution at the bay positions of the perylene core was
avoided in all cases in order to maintain planarity and to
promote strong p–p interactions.
Results and discussion
Synthesis
Herein, we describe the synthesis of asymmetrically substituted
perylene diester benzimidazoles PDBIs 1–3 (Fig. 1) and their
structural, thermotropic, optical and electrochemical properties.
PDBIs were designed with an imidazole unit at 3,4 positions and
a bisester moiety at 9,10 positions of the perylene tetracarboxylic
acid core. We attached linear or branched aliphatic substituents
Department of Macromolecular Chemistry
I – Applied Functional
Polymers, University of Bayreuth, Universita€tsstrasse 30, 95440
Bayreuth, Germany; Web: http://afupo.de/index.php. E-mail: mukundan.
thelakkat@uni-bayreuth.de; Fax: (+49) 921-55-3206
† Electronic supplementary information (ESI) available: Synthesis and
characterization of intermediates. Additional figures. See DOI:
10.1039/c0jm01626h
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Optical and electronic properties
The UV-vis absorption spectra of PDBIs 1–3 and PTE-1 in
CHCl3 solution are presented in Fig. 2. Both tetraesters PTE-1
and PTE-2 exhibit similar absorption spectra as perylene bisi-
mide with characteristic vibronic bands, but with a blue shift of
54 nm (lmax ¼ 471 nm). The incorporation of the fused benz-
imidazole unit significantly extends the absorption of PDBIs 1–3
to longer wavelengths, up to 680 nm. This is almost 100 nm red-
shifted compared to perylene bisimides (PBIs). The alkoxy
substituted PDBIs 2 and 3 exhibit a better absorption range than
PDBI-1 carrying only alkyl substituents. All derivatives posses
high molar extinction coefficients (3) in the visible range; for
instance PDBI-2 3 ¼ 3.32 ꢁ 104 L$molꢀ1$cmꢀ1 at lmax ¼ 554 nm.
Thus the extended absorption range of these dyes can be used for
efficient light-harvesting in photovoltaic devices. PDBI-2 and 3
absorb in the same wavelength regime but have different fine
structures, for instance absorption maxima are located at 554 nm
for PDBI-2 and at 516 nm for PDBI-3. As expected the fluo-
rescence maxima are also red-shifted and compared to PDBI-1,
PDBI-3 exhibits a higher Stokes-shift (see ESI†). For PDBI-2 no
fluorescence could be observed in solution.
Fig. 1 Synthesis of asymmetric perylene diester benzimidazoles PDBIs
1–3 i) 1. KOH, H2O. 2. HCl, pH 8–9. 3. R1-Br, Aliquat 336, KI, 100 ꢂC ii)
pTsOH$H2O, n-dodecane/toluene (5 : 1), 95 ꢂC. iii) 2, Zn(OAc)2, DMAc,
300 Watt, 160 ꢂC, 20 Min.
at the ester moiety and two alkyl or alkoxy chains at the benz-
imidazole unit in order to guarantee sufficient solubility and
flexibility to obtain mesophases. All these molecules self-
assemble into discotic columnar structures also at low tempera-
tures and have an extended absorption range up to 680 nm.
The synthesis of PDBIs is carried out by partial hydrolysis of
symmetrically substituted perylene tetraesters PTEs with
pTosOH$H2O allowing access to diester-anhydrides 1a,
b (Fig. 1).22 The benzimidazole moiety was subsequently intro-
duced by condensation of 1,2-diaminophenyls 2a, b with the
respective anhydride 1a, b in DMAc using zinc acetate under
microwave irradiation conditions to afford highly soluble PDBIs
1–3 in good yields (> 60%). All three compounds were fully
characterized by means of 1H-, 13C-NMR spectroscopy, IR,
GPC, MS and microanalyses after thorough purification by
column chromatography (for details see Experimental Section).
The details of synthesis of perylene tetraesters, diester anhydrides
and aromatic ortho-diamines are given in ESI.†
Fig. 3 (a) Cyclic voltammograms of PDBIs 1–3, showing the first and
second reduction peaks. The measurements were conducted in CH2Cl2
containing 0.1 M Bu4NPF6 with respect to ferrocene–ferrocenium couple
(Fc/Fc+) at a scan rate of 50 mVsꢀ1. (b) Energy band level diagram
showing HOMO- and LUMO- energy levels with corresponding
bandgaps of perylene tetraester PTE-124 and perylene diester benzimid-
azoles PDBIs 1–3.
Fig. 2 UV-vis absorption spectra of PTE-1 and PDBIs 1–3 measured in
1.0 ꢁ 10ꢀ5 M CHCl3 solution. All PDBIs exhibit high molar extinction
coefficient values in the whole range from 450 to 600 nm.
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Fig. 4 (a) DSC thermograms of PDBIs 1–3 (scan rate 10 Kminꢀ1) showing the second heating (solid curves) and first cooling cycle (dashed curve). (b–e)
Optical microscopic images of textures of PDBIs 1–3 (under crossed polarizers). (b) Focal conic texture of Colh phase of PDBI-1 at 169 ꢂC. (c) Mosaic
texture of Colh phase of PDBI-3 at 175 ꢂC. (d) Mixture of mosaic and pseudo focal conic textures representing the Colh-phase of PDBI-2 at 220 ꢂC and
(e) same film region showing the Colhp phase of PDEBI-2 at 130 ꢂC.
Further the electrochemical stability and reversibility of redox
processes were studied using cyclic voltammetry (CV). All the
compounds exhibit two reversible reduction peaks. Fig. 3a shows
the cyclic voltamogramms of PDBIs 1–3 and Fig. 3b shows the
HOMO- and LUMO- energy levels with corresponding
bandgaps. In order to calculate the LUMO levels, the first
reduction potentials were calibrated with respect to ferrocene–
thermogravimetric analysis (TGA; see ESI†). Thermotropic
behaviour of PDBIs was analyzed by a combination of differ-
ential scanning calorimetry (DSC) and polarization optical
microscopy (POM). Additionally temperature dependent small
and wide angle X-ray scattering (SAXS and WAXS) experiments
were performed to unequivocally determine the structure of the
mesophases on the molecular level. All of the derivatives under
investigation exhibit thermotropic liquid crystalline mesophases;
two of them maintaining their liquid crystalline behavior even at
room temperature. DSC thermograms of all PDBIs are
summarized in Fig. 4a and phase transition temperatures with
corresponding transitions enthalpies are presented in Table 1.
ferrocenium couple Fc/Fc+, which has
a quasi-calculated
HOMO-energy level of 4.8 eV.23 The HOMO levels were esti-
mated from the optical band gap and the respective LUMO
values. The respective optical band gaps, were determined from
the absorption edges of absorption spectra of diluted CHCl3
solutions. The extension of the p-conjugation system between
the perylene core and the benzimidazole unit generally accounts
for a narrowing of the HOMO–LUMO gap of the PDBI dyes.
Moreover, the lowering of band-gap in PDBIs is mainly caused
by a positive shift in HOMO-value rather than a negative shift in
LUMO values. For PDBIs 2 and 3, the band-gap could further
be decreased by 0.2 eV by introduction of electron-donating
alkoxy substituents at the benzimidazole moiety. This is highly
desired if energy loss during charge transfer from donor mole-
cules to PDBI is to be minimized and can also contribute to high
open-circuit voltages in photovoltaic devices using PDBIs as
acceptors.
Table 1 Summary of the thermal behaviour, phase transition tempera-
tures with corresponding transitions enthalpies and phasesa of investi-
gated PDBIs 1–3
PDBI
phase transitionsb (T [ꢂC]/DH [kJmolꢀ1])
PDBI-1 CrL (120/49.4) / Colh (172/3.9) / I
I (168/ꢀ2.4) / Colh (89/ꢀ51.9) / CrL
PDBI-2 Cr (ꢀ16/18.8) / Colhp (165/2.1) / Colhd (235/4.5) / I
I (232/ꢀ4.6) / Colhd (160/ꢀ2.6) / Colhp (ꢀ23/ꢀ17.4) / Cr
PDBI-3 Colh (183/1.2) / I
I (168/ꢀ1.9) / Colh
a
Cr ¼ crystalline phase; CrL ¼ crystalline lamellar phase; Colh
¼
columnar hexagonal mesophase; Colhd
¼
disordered columnar
Thermotropic properties
hexagonal mesophase; Colhp ¼ columnar plastic phase; I ¼ isotropic
b
phase. Obtained from DSC measurements at a heating rate of
10 Kminꢀ1 under nitrogen atmosphere.
PDBIs are highly thermally stable as shown by the high onset
decomposition temperatures (Ton between 303 and 319 ꢂC) in
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The DSC heating curve of PDBI-1 shows two reversible
transitions at 120 ꢂC (49.4 kJ/mol) and 172 ꢂC (3.9 kJ/mol). The
corresponding transitions on cooling are observed at 168 ꢂC and
89 ꢂC (Fig. 4a). POM experiments upon cooling from the
isotropic melt (Fig. 4b) gave evidence for a columnar hexagonal
(Colh) ordering in the high temperature phase (ca. 120–172 ꢂC).
As can be seen, large focal conic textures were observed. Also
X-ray diffraction experiments are in accordance with a columnar
hexagonal ordering of the mesogens. The diffractogram of
PDBI-1 in the mesophase and at room temperature (dashed
curve) is presented in Fig. 5a. At 140 ꢂC, we observed a 2D
PDBI-2 carrying alkoxy substituents at the benzimidazole
moiety depicts a quite different thermotropic behaviour. Here
three reversible transitions can be observed in DSC measure-
ments, at ꢀ16 ꢂC (18.8 kJ/mol), 165 ꢂC (2.1 kJ/mol) and 235 ꢂC
(4.5 kJ/mol) during heating. From POM and XRD the transi-
tions can be assigned as Cr / Colhp / Colhd. Thus compared to
PDBI-1, PDBI-2 exhibits additionally a transition from a highly
27
ordered liquid crystalline columnar plastic phase (Colhp
)
to
a columnar hexagonal disordered phase (Colhd) at 165 ꢂC.
The fact that the enthalpy for the Colhp / Colhd transition is
small compared to the enthalpy of the Colhd / I transitionꢂat
ꢂ
ꢁ
hexagonal lattice with ahex ¼ 32.9 A which is in reasonable
235 C supports the existence of a Colhp phase between ꢀ16 C
agreement with the (100), (110) and (210) Bragg reflections with
the typical ratios of the d-values of 1:O3:O7 (For details see
ESI†). The relatively broad reflection at 25.3ꢂ in the wide angle
regime depicts a moderate intracolumnar long-range order with
and 165 ꢂC.3,28 This is in line with the loss of shear abiꢂlity of the
texture in POM when the sample is cooled under 165 C. In the
Colhd phase PDBI-2 features a mixture of mosaic and pseudo
focal conic textures under crossed polarizers (Fig. 4d) and only
negligible textural changes are observable for the transition at
165 ꢂC to the plastic phase (Fig. 4e). XRD measurements in the
Colhp phase (cf. Fig. 5b dashed curve) indicates that the cores of
the mesogen are regularly stacked as can be deduced from the
relatively sharp reflection peak at 24.5ꢂ. This corresponds to
ꢁ
a p–p stacking distance of dpp ¼ 3.52 A. Upon further cooling to
95 ꢂC, PDBI-1 forms spherulites under crossed polarizers (see
ESI†). This texture remains the same on cooling down to room
temperature. X-ray diffraction experiments at RT show (001) and
its corresponding higher-order reflections, up to (006) as shown in
Fig. 5a (dashed curve). This corresponds to one dimensional
ꢁ
a stacking distance of dpp ¼ 3.50 A. The absence of any peaks
translational order25,26 with a layer distance of 41.6 A. The
in the wide angle regime between 165 ꢂC and 235 ꢂC is char-
acteristic for a disordered nature of the columns in the Colhd
phase (solid curve). For both phases the Bragg reflections in the
small-angle regime correspond to a 2D hexagonal lattice (see
ESI†).
ꢁ
d-spacings estimated from the position of Bragg reflections are
exactly in the ratios 1: 1/2: 1/3: 1/4, etc. Thus PBBI-1 exhibits
a lamellar ordering below 95 ꢂC. Nevertheless the mixed reflexes in
the wide-angle regime could not yet be assigned.
Fig. 5 X-ray diffraction patterns of (a) PDBI-1 in Colh phase (140 ꢂC) and crystalline lamellar CrL phase (RT). (b) PDBI-2 in Colhd phase (200 ꢂC) and
Colhp phase (120 ꢂC). (c) PDBI-3 in Colh phase at 160 ꢂC and RT. (d) Schematic representation of 2D discotic columnar hexagonal packing.
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PDBI-3 with two branched alkyl chains at the ester groups
possess only one reversible phase transition at 183 ꢂC in DSC
Experimental section
ꢂ
Materials and methods
upon heating. Here mosaic textures can be observed at 175 C
in POM (Fig. 4c), indicating a Colh phase. Further charac-
teristic dendritic textures are given in ESI†. It is also worthy
to note that PDBI-3 shows a partial homeotropic alignment of
the columns as observed in POM micrographs employing
a l/4 plate (see ESI†). Here X-ray diffraction gave evidence
for the existence of a liquid crystalline columnar hexagonal
lattice in the whole temperature range below the transition to
the isotropic phase. Fig. 5c depicts the diffractograms at
160 ꢂC and at RT. It is obvious that the intracolmnar
ordering (see 001 reflection) increases with lowering of
The starting materials, perylenetetracarboxylic acid dianhydride
PTCDA, 1-bromododecane, 3-(bromomethyl)heptane, Aliquat
336, Catechol, dibenzo-18-crown-6, hydrazine monohydrate,
palladium on carbon (10% Pd), p-toluenesulfonic acid mono-
hydrate, zinc acetate and solvents were purchased from Aldrich,
Fluka, Acros or TCI and used without any further purification.
Solvents used for precipitation and column chromatography
were distilled under normal atmosphere. DMAc (anhydrous with
crowncap, 99.5%) and ortho-dichlorobenzene (anhydrous with
crowncap, 99.0%) were purchased from Fluka and Aldrich.
1H- and 13C-NMR spectra were recorded on a Bruker AC 300
spectrometer (300 MHz and 75 MHz, respectively). Chemical
shifts are reported in ppm at room temperature using CDCl3 as
solvent and tetramethylsilane as internal standard unless indi-
cated otherwise. Abbreviations used for splitting patterns are s ¼
singlet, d ¼ dublett, t ¼ triplet, qui ¼ quintet, m ¼ multiplet.
FTIR-spectra were recorded with a Perkin Elmer Spectrum 100
(FTIR) in the range of 400–4000 cmꢀ1. Oligomeric size exclusion
chromatography (Oligo-SEC) was used to determine the purity
of synthesized perylene bisimides. Oligo-SEC measurements
were performed utilizing a Waters 515-HPLC pump with stabi-
lized THF as eluent at a flow rate of 0.5 ml/min. 20 ml of
a solution with a concentration of approx. 1 mg/ml were injected
into a column setup, which consists of a guard column (Varian;
5 ꢁ 0.8 cm; mesopore gel; particle size 3 mm) and two separation
columns (Varian; 30 ꢁ 0.8 cm; mesopore gel; particle size 3 mm).
The compounds were monitored with a Waters 486 tunable UV
detector at 254 nm and a Waters 410 differential RI detector.
Mass spectroscopic (MS) data were obtained from a FIN-
NIGAN MAT 8500 instrument. UV-vis spectra were recorded
with a Perkin Elmer Lambda 900 spectrophotometer. Photo-
luminescence spectra were acquired on a Shimadzu RF 5301 PC
spectrofluorophotometer. The thermal degradation was studied
using a Mettler Toledo TGA/SDTA 851e with a heating rate of
10 Kminꢀ1 under N2 atmosphere. Differential scanning calo-
rimetry (DSC) was carried out with a Perkin Elmer differential
scanning calorimeter (Diamond) with heating and cooling rates
of 10 K/min under N2 atmosphere. The instrument was cali-
brated with indium standards before measurements. Phase
transitions were also examined by a polarization optical micro-
scope (POM) Nikon Diaphot 300 with a Mettler FP 90
temperature-controlled hot stage. X-ray diffraction measure-
ments were performed on a Huber Guinier Diffraktometer 6000
temperature. The fact that PDBIs
2 and 3 are liquid
crystalline even at RT is highly interesting for applications
requiring high order in molecular arrangement. 2D lattice
parameters and p–p stacking distances dpp of all PDBIs are
summarized in Table 2.
Conclusion
In summary, we synthesized three discotic molecules belonging
to a novel class of semiconductors, perylene diester benzimid-
azoles. All these molecules exhibit extended absorption up to
680 nm. Even compared to perylene bisimides, these materials
thus exhibit longer wavelength absorption with 130 nm red-shift
due to further extension of p-conjugation via the benzimidazole
group. The decrease in band gap energy was essentially achieved
by a shift of the HOMO value. All PDBIs self-organize into
liquid crystalline columnar hexagonal phases (Colh) at higher
temperatures below 250 ꢂC; PDBIs 2 and 3 even at room
temperature. Also the existence of a columnar plastic phase
(Colhp) for PDBI-2 and a lamellar ordering for PDBI-1 was
observed at room temperature. This self-assembling behaviour
should allow for an orientation of PDBIs 2 and 3 in the high
temperature liquid crystalline phase and for a transfer of the
orientation during cooling to a highly ordered phase at room
temperature. All of these properties make n-type semiconducting
PDBIs promising candidates for applications in organic
electronics.
Table 2 X-ray diffraction data of liquid crystalline mesophases of
PDBIs 1–3. 2D Lattice parameters and p–p stacking distance dpp as
determined from temperature dependent X-ray diffraction experiments
a
lattice parameters [A]
b
dpp [A]
ꢁ
ꢁ
PDBI
T [ꢂC]
phasec
equipped with a Huber quartz monochromator 611 with Cu-Ka1
:
PDBI-1
PDBI-2
PDBI-3
120
RT
200
120
160
RT
ahex ¼ 32.9
dL ¼ 41.6
3.52
-
-
3.50
3.49
3.49
Colh
CrL
Colhd
Colhp
Colh
Colh
ꢁ
1.54051 A. For cyclic voltammetry (CV) experiments, a conven-
tional three-electrode assembly using a Ag/AgNO3 reference
electrode was used. CH2Cl2 containing 0.1 M Bu4NPF6 was used
as solvent. All measurements were carried out under N2-atmo-
sphere at a scan rate of 0.05 Vsꢀ1 at 25 ꢂC and all redox potentials
were calibrated to ferrocene/ferrocenium couple (Fc/Fc+).
ahex ¼ 34.0
ahex ¼ 35.9
ahex ¼ 30.6
ahex ¼ 31.8
a
Hexagonal lattice parameter
rffiffiffiffiffiffiffiffiffiffi
d
2
ahex
¼
dp2p
:
a
General procedure for the preparation of perylene diester
benzimidazoles PDBI 1 to 3
b
c
From (001) reflex. Colho ¼ ordered columnar hexagonal; Colhd
disordered columnar hexagonal; Colhp ¼ columnar plastic; CrL
crystalline lamellar phase.
¼
¼
A mixture of the respective diester anhydride 1a, b (0.3 mmol)
and zinc acetate (0.5 mmol) were dissolved in dry DMAc (6 mL)
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in a microwave pressure tube and the respective ortho-diamine
2a, b (0.4 mmol) was added. The condensation was carried out
under microwave irradiation conditions for 25 min at 160 ꢂC and
300 W. The violet crude product was precipitated in methanol
(300 mL) and filtered. The residue was washed with H2O (2 ꢁ
30 mL) and methanol (3 ꢁ 30 mL) and dried over night at 60 ꢂC
in vacuo. The crude product was purified via column chroma-
tography.
Synthesis of bis(2-ethylhexyl)-perylene-3,4-(4,5-bisdodecyl-oxy-
1,2-benzimidazole)-9,10-dicarboxylate PDBI-3
1b (0.50 g, 0.8 mmol) and diamine 2b (0.80 g, 1.7 mmol) were
allowed to react according to the general procedure. Then,
CHCl3 (100 mL) was added to the mixture and the violet crude
product was washed with water (2 ꢁ 100 mL). The organic layer
was dried over Na2SO4 and the solvent was evaporated under
reduced pressure. The crude product was purified via column
chromatography (silica flashgel, eluent CHCl3:MeOH 95 : 5 v/v).
Freeze-drying from benzene gave the violet product PDBI-3.
Yield: 0.55 g (65%) as violet solid. Calcd. for C70H94N2O7: C
78.17, H 8.81, N 2.60. Found: C 77.26, H 8.93, N 2.46. EI-MS (70
eV): m/z 1074 ([M+], 29%). IR (ATR): n ¼ 2922 (s), 2853 (s), 1710
(s), 1687 (s), 1592 (m), 1455 (s), 1364 (w), 1290 (s), 1169 (s), 745
(m) cmꢀ1. 1H-NMR (300 MHz, CDCl3, 298 K) d ¼ 8.76–8.64 (m,
2H, HAr), 8.54–8.41 (m, 4H, HAr), 8.15–8.07 (m, 3H, HAr), 7.36
(s, 1H, HAr), 4.37–4.26 (m, 4H, O–CH2), 4.23–4.10 (m, 4H,
benzimidazole-O–CH2), 2.00–1.88 (m, 2H, OCH2–CH), 1.87–
1.77 (m, 4H, benzimidazole-CH2–CH2), 1.61–1.23 (m, 52H,
CH2), 1.05–0.86 (m, 18H, CH3) ppm. 13C-NMR (75 MHz,
CDCl3, 298 K) d ¼ 168.4 (2C, O–C]O), 159.9 (1C, N–C]O),
148.8 (1C, N–C]N), 147.1, 137.9, 136.4, 132.4, 132.3, 131.9,
131.3, 131.1, 130.2, 129.9, 129.2, 128.8, 127.4, 126.4, 126.1, 125.7,
122.6, 121.8, 120.6, 103.7, 100.1 (26C, CAr), 69.7, 69.5 (2C,
benzimidazole-O–CH2), 68.0 (2C, O–CH2), 38.8 (2C, O–CH2-
CH), 32.0, 30.5, 29.8, 29.7, 29.6, 29.5, 29.4, 29.3, 29.0, 26.1, 23.9,
23.0, 22.7 (28C, CH2), 14.1, 11.0 (6C, CH3) ppm.
Synthesis of bisdodecyl-perylene-3,4-(4,5-bisdodecyl-1,2-
benzimidazole)-9,10-dicarboxylate PDBI-1
1a (0.22 g, 0.3 mmol) and diamine 2a (0.20 g, 0.4 mmol) were
allowed to react according to the general procedure. The crude
product was purified via column chromatography (silica flashgel,
eluent CHCl3:acetone 20 : 1 v/v). Yield: 0.27 g (80%) as violet
solid. Calcd. for C78H110N2O5: C 80.06, H 9.59, N 2.42. Found:
C 80.58, H 9.66, N 2.16. EI-MS (70 eV): m/z 1155 ([M+], 8%). IR
(ATR): n ¼ 2915 (s), 2848 (s), 1714 (s), 1690 (s), 1596 (m), 1468
(s), 1358 (s), 1171 (s), 743 (s) cmꢀ1. 1H-NMR (300 MHz, CDCl3,
298 K) d ¼ 8.74–8.65 (m, 2H, HAr), 8.48–8.36 (m, 4H, HAr), 8.28–
8.24 (m, 1H, HAr), 8.12–8.06 (m, 2H, HAr), 7.61–7.57 (m, 1H,
3
H
Ar), 4.36 (t, J ¼ 6.9 Hz, 4H, O–CH2), 2.80–2.69 (m, 4H, ben-
zimidazol-CH2), 1.90–1.78 (m, 4H, OCH2-CH2), 1.76–1.62 (m,
4H, benzimidazole-CH2-CH2), 1.53–1.15 (m, 72H, CH2), 0.95–
0.84 (m, 12H, CH3) ppm. 13C-NMR (75 MHz, CDCl3, 298 K) d ¼
168.3 (2C, O–C]O), 159.4 (1C, N–C]O), 147.6 (1C, N–C]N),
142.1, 139.4, 139.0, 135.9, 132.5, 132.3, 131.8, 131.0, 130.3, 130.0,
129.8, 129.0, 128.6, 127.4, 126.6, 126.1, 122.4, 121.8, 120.3, 119.2,
115.1 (26C, CAr), 65.8 (2C, O–CH2), 32.8, 32.0, 31.3, 30.9,
30.0, 29.8, 29.7, 29.6, 29.4, 28.7, 26.1, 22.7 (42C, CH2), 14.1 (4C,
CH3) ppm.
Acknowledgements
Financial Support from SPP 1355 (DFG) is kindly acknowl-
edged.
Notes and references
Synthesis of bisdodecyl-perylene-3,4-(4,5-bisdodecyloxy-1,2-
benzimidazole)-9,10-dicarboxylate PDBI-2
1 S. Laschat, A. Baro, N. Steinke, F. Giesselmann, C. Haegele,
G. Scalia, R. Judele, E. Kapatsina, S. Sauer, A. Schreivogel and
M. Tosoni, Angew. Chem., Int. Ed., 2007, 46, 4832–4887.
2 S. Kumar, Chem. Soc. Rev., 2006, 35, 83–109.
3 C. Destrade, P. Foucher, H. Gasparoux, N. H. Tinh, A. M. Levelut
and J. Malthete, Mol. Cryst. Liq. Cryst., 1984, 106, 121–146.
€
4 G. LussemandJ. H. Wendorff, Polym. Adv. Technol., 1998, 9, 443–460.
5 H. E. Katz, A. J. Lovinger, J. Johnson, C. Kloc, T. Slegrist, W. Li,
Y. Y. Lin and A. Dodabalapur, Nature, 2000, 404, 478–481.
6 L. Schmidt-Mende, A. Fechtenkotter, K. Mullen, E. Moons,
R. H. Friend and J. D. MacKenzie, Science, 2001, 293, 1119–1122.
7 P. Wojciech, Z. Matthias, C. Ji Young, M. Klaus and Z. Rudolf,
Macromol. Rapid Commun., 2009, 30, 1179–1202.
8 S. Sergeyev, W. Pisula and Y. H. Geerts, Chem. Soc. Rev., 2007, 36,
1902–1929.
9 D. Adam, P. Schuhmacher, J. Simmerer, L. Haussling,
K. Siemensmeyer, K. H. Etzbachi, H. Ringsdorf and D. Haarer,
Nature, 1994, 371, 141–143.
10 J. M. Warman, M. P. de Haas, G. Dicker, F. C. Grozema, J. Piris and
M. G. Debije, Chem. Mater., 2004, 16, 4600–4609.
1a (0.30 g, 0.4 mmol) and diamine 2b (0.29 g, 0.6 mmol) were
allowed to react according to the general procedure. The crude
product was purified via column chromatography (silica flashgel,
eluent CHCl3:acetone 20 : 1 v/v). Freeze-drying from benzene
gave the violet product PDBI-2. Yield: 0.28 g (59%) as violet
solid. Calcd. for C78H110N2O7: C 78.88, H 9.33, N 2.36. Found:
C 78.75, H 9.32, N 2.30. EI-MS (70 eV): m/z 1187 ([M+], 5%). IR
(ATR): n ¼ 2917 (s), 2849 (s), 1720 (s), 1677 (s), 1592 (m), 1465
(s), 1364 (m), 1293 (s), 1170 (s), 746 (s) cmꢀ1. 1H-NMR (300MHz,
CDCl3, 298 K) d ¼ 8.69 (d, 3J ¼ 8.12 Hz, 2H, HAr), 8.50–8.38 (m,
4H, HAr), 8.13–8.05 (m, 3H, HAr), 7.34 (s, 1H, HAr), 4.36 (t, 3J ¼
6.8 Hz, 4H, O–CH2), 4.22–4.09 (m, 4H, benzimidazole-OCH2),
2.01–1.89 (m, 4H, OCH2–CH2), 1.89–1.78 (m, 4H, benzimid-
azole–CH2–CH2), 1.52–1.14 (m, 72H, CH2), 0.97–0.82 (m, 12H,
CH3) ppm. 13C-NMR (75 MHz, CDCl3, 298 K) d ¼ 168.3 (2C,
O–C]O), 159.5 (1C, N–C]O), 148.8 (1C, N–C]N), 147.0,
139.4, 137.8, 136.3, 132.5, 132.2, 131.9, 131.3, 131.0, 130.4, 130.2,
129.2, 128.7, 127.4, 126.4, 126.1, 125.6, 122.4, 121.8, 120.6, (26C,
€
€
11 B. A. Jones, M. J. Ahrens, M.-H. Yoon, A. Facchetti, T. J. Marks and
M. R. Wasielewski, Angew. Chem., Int. Ed., 2004, 43, 6363–6366.
€
€
€
12 M. Gsanger, J. H. Oh, M. Konemann, H. W. Hoffken, A.-M. Krause,
Z. Bao and F. Wurthner, Angew. Chem. Int. Ed., 2010, 49, 740–743.
€
13 Y.-D. Zhang, K. G. Jespersen, M. Kempe, J. A. Kornfield, S. Barlow,
B. Kippelen and S. R. Marder, Langmuir, 2003, 19, 6534–6536.
14 R. J. Chesterfield, J. C. McKeen, C. R. Newman, P. C. Ewbank,
D. A. da Silva Filho, J.-L. Bredas, L. L. Miller, K. R. Mann and
C. D. Frisbie, J. Phys. Chem. B, 2004, 108, 19281–19292.
CAr), 69.7, 69.5 (2C, benzimidazole-O–CH2), 65.8 (2C, O–CH2),
31.9, 31.3, 29.8, 29.7, 29.6, 29.5, 29.4, 29.3, 28.6, 26.1, 22.7 (40C,
CH2), 14.1 (4C, CH3) ppm.
This journal is ª The Royal Society of Chemistry 2010
J. Mater. Chem., 2010, 20, 8646–8652 | 8651

View Article Online
15 M. J. Sienkowska, J. M. Farrar, F. Zhang, S. Kusuma,
P. A. Heiney and P. Kaszynski, J. Mater. Chem., 2007, 17, 1399–
1411.
22 C. Xue, R. Sun, R. Annab, D. Abadi and S. Jin, Tetrahedron Lett.,
2009, 50, 853–856.
€
23 J. Pommerehne, H. Vestweber, W. Guss, R. F. Mahrt, H. Bassler,
16 H. Langhals, Helv. Chim. Acta, 2005, 88, 1309–1343.
€
M. Porsch and J. Daub, Adv. Mater., 1995, 7, 551–554.
24 X. Mo, H.-Z. Chen, Y. Wang, M.-M. Shi and M. Wang, J. Phys.
Chem. B, 2005, 109, 7659–7663.
25 K. Ohta, H. Muroki, A. Takagi, K.-I. Hatada, H. Ema, I. Yamamoto
and K. Matsuzaki, Mol. Cryst. Liq. Cryst., 1986, 140, 131–152.
26 H. Sakashita, A. Nishitani, Y. Sumiya, H. Terauchi, K. Ohta and
I. Yamamoto, Mol. Cryst. Liq. Cryst., 1988, 163, 211–219.
27 S. K. Prasad, D. S. S. Rao, S. Chandrasekhar and S. Kumar, Mol.
Cryst. Liq. Cryst., 2003, 396, 121–139.
17 F. Wurthner, Chem. Commun., 2004, 1564–1579.
18 A. Wicklein, A. Lang, M. Muth and M. Thelakkat, J. Am. Chem.
Soc., 2009, 131, 14442–14453.
19 S. Benning, H.-S. Kitzerow, H. Bock and M.-F. Achard, Liq. Cryst.,
2000, 27, 901–906.
20 M. Oukachmih, P. Destruel, I. Seguy, G. Ablart, P. Jolinat,
S. Archambeau, M. Mabiala, S. Fouet and H. Bock, Sol. Energy
Mater. Sol. Cells, 2005, 85, 535–543.
21 A. Wicklein, P. Kohn, L. Ghazaryan, T. Thurn-Albrecht and
M. Thelakkat, Chem. Commun., 2010, 46, 2328.
28 D. M. Collard and C. P. Lillya, J. Am. Chem. Soc., 2002, 113, 8577–
8583.
8652 | J. Mater. Chem., 2010, 20, 8646–8652
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