Linear and star-shaped pyrazine-containing acene dicarboximides with high electron-affinity

Article abstract of DOI:10.1039/c2ob25680k

A series of linear and star-shaped pyrazine-containing acene molecules 1a-b, 2a-b and 3 substituted by dicarboximide groups are synthesized via condensation reactions between o-diamine and dione. High electron affinity (up to 4.01 eV) is achieved due to t

Full text of DOI:10.1039/c2ob25680k

View Article Online / Journal Homepage / Table of Contents for this issue
Dynamic Article Links
Organic &
Biomolecular
Chemistry
Cite this: Org. Biomol. Chem., 2012, 10, 7045
www.rsc.org/obc
PAPER
Linear and star-shaped pyrazine-containing acene dicarboximides with high
electron-affinity†
Jinjun Shao, Jingjing Chang and Chunyan Chi*
Received 6th April 2012, Accepted 2nd July 2012
DOI: 10.1039/c2ob25680k
A series of linear and star-shaped pyrazine-containing acene molecules 1a–b, 2a–b and 3 substituted by
dicarboximide groups are synthesized via condensation reactions between o-diamine and dione. High
electron affinity (up to 4.01 eV) is achieved due to the introduction of an electron-deficient pyrazine
moiety and the attachment of electron-withdrawing dicarboximide groups. Some of these molecules show
thermal liquid crystalline behavior and their space-charge limited current mobilities are measured. The
high electron affinity and liquid crystalline property qualify them as promising electron transporting
materials in organic optoelectronic devices.
Introduction
Organic semiconductors are of great importance and interest
from the viewpoint of their fundamental electronic and optoelec-
tronic properties and their potential applications, such as for
organic field-effect transistors (OFETs).1 After large success on
hole-transporting (p-type) organic semiconductors,2 recently
there is increasing interest in the development of high perform-
ance electron-transporting (n-type) semiconductors, which are
desirable for the fabrication of p–n junction diodes, bipolar tran-
sistors, and complementary integrated circuits.3 The general
Fig. 1 Chemical structures of nitrogen-rich dibenzohexacene diimides
(1a–b, 2a–b) and trinaphthylene trisimide (3).
design approaches to achieve n-type semiconductors include (1)
attachment of electron-withdrawing substituents (e.g. fluorine,4
carboximide,5 cyano-6) onto the traditional p-type semiconduc-
tors (e.g. acene, oligothiophene) and/or (2) replacement of the
carbon atoms in the framework by electron-deficient atoms (e.g.
imine nitrogen7). Following this guidance, some n-type semicon-
ductors have been successfully synthesized and used in
n-channel OFETs.8
Linear acene and star-shaped angularly fused acene (i.e., star-
phene) are good candidates for organic semiconductors and
recently electron-deficient n-type acenes4d,5f,g,6e,7a–f and starphe-
nes7m–o,9 have been reported by several groups including us. The
substitution by electron-withdrawing dicarboximide groups
stabilized the electron-rich acene molecules and also improved
their solubility.5 Replacement of one or more benzene rings in
acene and starphene with an electron-deficient pyrazine ring not
only increased the electron affinity, but also enhanced intermole-
cular interactions and improved their kinetic stability towards
H2O and O2.7a–e,10 To further increase the electron affinity,
herein we are interested in combining both approaches together
to design and synthesize new pyrazine-containing acene and star-
phene dicarboximide derivatives such as the dibenzo-tetraaza-
hexacene7m,11 bis(dicarboximide)s 1a–b and 2a–b, and
hexaazatrinaphthylene tris(dicarboximide) 3 (Fig. 1). High elec-
tron affinity is expected for these molecules which is a pre-requi-
site for a good n-type semiconductor. Different alkyl chains are
used to tune their solubility and thermal behavior in the solid
state.
Department of Chemistry, National University of Singapore, 3 Science
Drive 3, 117543, Singapore. E-mail: chmcc@nus.edu.sg;
Fax: +65 6779 1691; Tel: +65 6516 5375
Results and discussion
†Electronic supplementary information (ESI) available: Structural
characterization data for all new compounds; additional photophysical
and electrochemical data; TGA curves; additional DSC curves and POM
images; powder XRD data, and additional SCLC data. See DOI:
10.1039/c2ob25680k
Synthesis
The synthesis of these electron-deficient compounds is shown in
Scheme 1. The formation of pyrazine rings is based on a
This journal is © The Royal Society of Chemistry 2012
Org. Biomol. Chem., 2012, 10, 7045–7052 | 7045

View Article Online
12a–b in 85% and 90% yield, respectively. The tert-butyl group
was supposed to facilitate the solubility of 1a–b,18 however, to
our surprise, 2a (2b) have better solubility than 1a (1b). Conden-
sation between 13a–b and 12c gave insoluble materials. The
star-shaped hexaaza-trinaphthylene trisimide 3 was prepared in
86% yield by a similar condensation reaction between hexaketo-
cyclohexane octahydrate and 3.3 equivalents of 12c. Compound
3 showed excellent solubility, such as in DCM, THF, and even in
hexane, which allows us to perform various characterizations in
1
solution. H NMR, 13C NMR spectroscopy, mass spectrometry
(HR-EI MS and MALDI-TOF MS), and elemental analysis were
used to identify the chemical structure and purity of all the new
compounds (see ESI†).
Photophysical properties
The UV-vis absorption and photoluminescence (PL) spectra of
compounds 1a–b, 2a–b, and 3 were recorded in THF solution. It
was found that the alkyl chains had almost no effect on the
spectra profile (Fig. S1 in ESI†) and thus only the spectra for 1a,
2a, and 3 are shown in Fig. 2. All of the three compounds show
well-resolved UV-vis absorption and emission bands, with the
longest absorption maximum at 431, 429, and 399 nm and the
emission maxima at 457, 447, and 504 nm for 1a, 2a, and 3,
respectively. The absorption spectra of 1–3 in thin film showed a
similar profile to that in solution but with a 12–16 nm red-shift
and accompanied with a long tail to the near infrared region,
indicating strong intermolecular interactions in the solid state
(Fig. S2 in the ESI†).
Scheme 1 Synthetic scheme for 1a–b, 2a–b, and 3.
condensation reaction between o-diamine and dione. The key
intermediate compounds are the 1,2-diamino-4,5-phthalimides
12a–c with different alkyl chains which have never been
reported previously. The synthesis started from the protection of
o-phenylenediamine (4) with p-toluenesulfonyl chloride (TsCl)
in dry pyridine to afford 5 in 93% yield. Bromination of 5 with
Br2 in HOAc gave compound 6 in 89% yield, and subsequent
deprotection was conducted by heating 6 in 95% sulfuric acid at
110 °C for about 15 min to give the diamine 7 in 95% yield. Pro-
longation of the reaction time to 2 h as reported in the literature12
led to an unknown black solid without 7 at all. The diamine 7
was reacted with SOCl2–Et3N in DCM to give 5,6-dibromo-
benzo[c][1,2,5]thiadiazole 8 in 96% yield, which was refluxed
with CuCN–CuI in nitrobenzene for 6 h, followed by treatment
with FeCl3 in HCl solution to give compounds 9 and 10 in 60%
and 10% yield, respectively.13 9 could be hydrolyzed under acid
conditions (FeCl3–HCl) to give 10 in 28% yield. Alkylation of
10 with 1-bromo-3,7-dimethyloctane, 11-(bromomethyl)trico-
sane,14 and 1-bromododecane in the presence of K2CO3 afforded
compounds 11a, 11b, and 11c in 90%, 88%, and 90% yield,
respectively.15 In addition, 11 can also be prepared by treating 9
with the corresponding alkyl amine in o-DCB catalyzed by
ZnBr2 in around 50% yield. Reduction of 11 was first attempted
by using reducing agents such as NaBH4, Zn powder16 and tin
powder, however, all attempts failed to give the desired diamine
12. Alternatively, a mild reductant, Fe powder, turned out to be
an appropriate reductant and the diamines 12a–c were prepared
in 90–93% yields from 11a–c. Interestingly, all these diamine
compounds show good environmental stability in contrast to
many other electron-rich diamines.
Electrochemical properties
The electrochemical properties of 1a–b, 2a–b and 3 were inves-
tigated by cyclic voltammetry (CV) and differential pulse vol-
tammetry (DPV) in DCM solution. As shown in Fig. 3, three
quasi-reversible reduction waves were observed for 1a, 2a, and
3, with the onset reduction potential (Eredonset) at −1.37, −1.31,
and −0.79 V, respectively. Again, the different alkyl chains and
tert-butyl group have shown little effect on the redox behaviour
(Table 1 and Fig. S3 in the ESI†). No obvious redox waves were
observed upon oxidation up to 1.8 V. The LUMO energy level
The linear compounds 1a and 1b were then synthesized in
85% and 90% yield, respectively, by a condensation reaction
between 2,7-di-tert-butylpyrene-4,5,9,10-tetraone (13a)17 and
2.2 equivalents of 12a–b in refluxing o-DCB in the presence of
a catalytic amount of TsOH. Similarly, compounds 2a–b were
prepared under the same conditions from compounds 13b and
Fig. 2 Absorption and normalized emission spectra of compounds 1a,
2a, and 3 in THF.
7046 | Org. Biomol. Chem., 2012, 10, 7045–7052
This journal is © The Royal Society of Chemistry 2012

View Article Online
(electron-affinity) derived from the onset of reduction potential is
−3.43, −3.49 and −4.01 eV for 1a, 2a, and 3, respectively.19
Accordingly, the respective HOMO energy levels are deducted
as −6.22, −6.29, and −6.96 eV for 1a, 2a, and 3, respectively,
the crystalline phase to an isotropic phase (Fig. S5 in ESI†),
which was confirmed by POM measurements (Fig. S6 in ESI†).
The detailed packing structure at room temperature cannot be
simply concluded from their powder XRD patterns (Fig. S7 in
ESI†). DSC curves of 2a exhibited three endothermic transitions
at 127, 154 and 167 °C upon heating and three exothermic tran-
sitions at 165, 134 and 103 °C upon cooling (Fig. 4). POM
measurements disclosed that the compound entered an isotropic
phase at around 170 °C. Upon slow cooling, a typical fan-type
texture was observed at 160 °C (Fig. 5), indicating an ordered
columnar liquid crystalline phase. Upon further cooling below
135 °C, some defects were observed in the fan-type texture, cor-
responding to the second exothermic transition. Upon further
cooling below 103 °C, crystalline domains were observed. The
XRD pattern of 2a recorded at room temperature (Fig. S7 in
ESI†) revealed that 2a has an orthorhombic arrangement with
lattice parameter a = 2.68 nm and b = 1.05 nm and γ = 90°.
opt
based on the equation HOMO = LUMO − Egopt, where Eg is
the optical energy gap determined from the lowest energy
absorption onset. Compared with the trinaphthylene tris(dicar-
boximide)s,9 after the introduction of six N atoms, the LUMO
energy level of 3 was lowered by 0.33 eV from −3.68 eV to
−4.01 eV. The electron affinities of 1a–b and 2a–b are also
increased to ca. 0.20 eV compared to their analogs without
dicarboximide substituents.11c The low-lying LUMO energy
level (i.e., large electron affinity) of all compounds indicates that
they can serve as promising candidates for n-type devices with
good air stability.8,20
Thermal behavior and self-assembly in the solid state
The thermal behavior and self-assembly of 1a–b, 2a–b, and 3 in
the solid state were investigated by thermogravimetric analysis
(TGA), differential scanning calorimetry (DSC), polarizing
optical microscopy (POM) and X-ray diffraction (XRD). TGA
measurements revealed that all compounds were thermally stable
over 390 °C with 5% weight loss (see Fig. S4 in the ESI†). DSC
curves of 1a, 1b and 2b showed one endothermic transition from
Fig. 3 Cyclic voltammograms of compounds 1a, 2a, and 3 in dry
DCM with 0.1 M Bu4NPF6 as supporting electrolyte, a gold electrode
with a diameter of 2 mm, a Pt wire, and an Ag/AgCl electrode were
used as the working electrode, the counter electrode, and the reference
Fig. 4 DSC curves for compounds 2a and 3 with a heating–cooling
scan rate of 10 °C min−1 under nitrogen. (Cr = crystalline phase, I = iso-
tropic phase, Col = columnar liquid crystalline phase).
electrode, respectively, with a scan rate at 100 mV s−1
.
Table 1 Electrochemical data for compounds 1a–b, 2a–b, and 3
E1/2red(1)/V
E1/2red(2)/V
E1/2red(3)/V
Eredonset/V
Ega/V
HOMOb/eV
LUMOc/eV
1a
1b
2a
2b
3
−1.43
−1.42
−1.38
−1.39
−0.91
−1.56
−1.57
−1.54
−1.52
−1.29
−2.12
−2.10
−2.15
−2.03
−1.80
−1.37
−1.36
−1.31
−1.30
−0.79
2.79
2.79
2.80
2.81
2.95
−6.22
−6.23
−6.29
−6.31
−6.96
−3.43
−3.44
−3.49
−3.50
−4.01
a Eg was estimated from the absorption edge in solution. b LUMO was calculated according to the equation, LUMO = −(4.80 + Eredonset). c HOMO
was estimated according the equation, HOMO = Eg − LUMO.
This journal is © The Royal Society of Chemistry 2012
Org. Biomol. Chem., 2012, 10, 7045–7052 | 7047

View Article Online
Fig. 5 POM images of (a) 2a at 160 °C upon cooling and (b) 3 at
345 °C upon heating.
However, the broad reflection peaks in the XRD patterns
recorded at 160 °C and 130 °C (Fig. S8 in ESI†) limited detailed
analysis of the mesophases. Compound 3 entered into a colum-
nar liquid crystalline phase after 317 °C as demonstrated by the
bright focal conic texture recorded at 345 °C upon heating
(Fig. 5). XRD pattern of 3 at room temperature showed only one
major reflection peak at 2θ = 2.943° and thus the accurate
packing structure cannot be figured out.
Space-charge limited-current mobility
Charge carrier mobilities of 1a–b, 2a–b, and 3 in thin films were
estimated via space-charge limited-current (SCLC) technique by
using a diode device configuration of ITO–PEDOT : PSS–Al
(2 nm)–material–Al. The SCLC is described by J = 9/8ε0εrμV2/
d3, where ε0 is the permittivity of free space, εr is the relative
dielectric constant of the active material estimated from capaci-
tance measurements (assumed to be 3), d is the film thickness, μ
is electron mobility, V is the voltage drop across the device, V =
Vappl − Vr − Vbi, Vappl is the applied voltage to the device, Vr is
the voltage drop due to contact resistance and series resistance
across the electrodes, Vbi is the built-in voltage due to the differ-
ence in work function of the two electrodes. The resistance of
the device was measured using a blank configuration ITO–
PEDOT–Al and was found to be about 10–20 Ω. The Vbi was
determined from the transition between the ohmic region and
SCL region and is found to be about 1 V. The film thickness was
measured by surface profilometer. The fabricated device was
tested in a nitrogen filled glovebox and dark conditions. The
current density–voltage (J–V) curves were measured using a
Keithley 2400 source measurement unit.
Fig. 6 Double logarithmic plot of the current density (J) versus
applied voltage (V) curves for 1a, 2a, and 3.
attachment of electron-withdrawing carboximide groups and the
fusion of pyrazine rings, these new compounds showed high
electron affinities. Moderate electron mobilities in thin films
were also measured via the SCLC technique. The observed high
electron affinity of these molecules suggests that they can be
used as potential electron transporting materials in organic elec-
tronic devices.
The SCLC electron mobilities were found to be 3–7 × 10−4
cm2 V−1 s−1 for 1a–b, 2a–b, and 3.4 × 10−5 cm2 V−1 s−1 for 3
(Fig. 6 and Fig. S9 in ESI†). Unfortunately, our preliminary
results show that solution processed thin films of all these com-
pounds only show very weak field effect transistor activity which
was also observed for other imine nitrogen-containing
semiconductors.8
Experimental
General
Anhydrous tetrahydrofuran (THF) and dichloromethane (DCM)
were obtained by distillation over sodium and calcium hydride,
respectively. 2,7-Di-tert-butylpyrene-4,5,9,10-tetraone,17 pyrene-
4,5,9,10-tetraone,17 and 11-(bromomethyl)-tricosane14 were pre-
pared according to the literature procedures. All other chemicals
were purchased from commercial supplies and used without
further purification. All NMR spectra were recorded on Bruker
AMX500 at 500 MHz and Bruker ACF300 at 300 MHz
Conclusions
In summary, a series of electron-deficient pyrazine-containing
linear and star-shaped acene and starphene molecules end func-
tionalized with dicarboximide groups have been successfully
synthesized and their optical properties, electrochemical proper-
ties and thermal behavior were investigated. Due to the
7048 | Org. Biomol. Chem., 2012, 10, 7045–7052
This journal is © The Royal Society of Chemistry 2012

View Article Online
1
spectrometers. H NMR and 13C NMR spectra were recorded in
filtration, the precipitate gave a fine colorless powder of 6 (46 g,
89%). H NMR (500 MHz, CDCl3): δ ppm = 7.60 (d, J = 8.2
1
CDCl3 and DMSO-d6. All chemical shifts are quoted in ppm,
using the residual solvent peak as a reference standard. Mass
spectra were recorded in EI mode and high resolution mass
spectra were recorded with EI source. Matrix-assisted laser deso-
rption ionization time-of-flight (MALDI-TOF) analysis was per-
formed on a Bruker Autoflex II MALDI-TOF instrument by
using 1,8,9-trihydroxyanthracene as matrix and Pepmix as
internal standard or external standard. UV-vis absorption and flu-
orescence spectra were recorded on Shimadzu UV-1700 and
RF-5301 spectrometers in HPLC pure solvents. Cyclic voltam-
metry was performed on a CHI 620C electrochemical analyzer
with a three-electrode cell in a solution of 0.1 M tetrabutyl-
ammonium hexafluorophosphate (Bu4NPF6) dissolved in dry DCM
at a scan rate of 100 mV s−1. A gold electrode with a diameter
of 2 mm, a Pt wire and an Ag/AgCl electrode were used as the
working electrode, the counter electrode and the reference elec-
trode, respectively. The potential was calibrated against the ferro-
cene/ferrocenium couple. Thermogravimetric analysis was
carried out on a TA instrument 2960 at a heating rate of 10 °C
min−1 under N2 flow, differential scanning calorimetry was per-
formed on a TA instrument 2920 at a heating–cooling rate of
10 °C min−1 under N2 flow. The initial phase transitions and cor-
responding temperatures for these compounds were determined
by an OLYMPUS BX51 polarizing optical microscope equipped
with a Linkam TP94 programmable hot stage. VT X-ray diffrac-
tion studies were carried out on a Bruker-AXS D8 ADVANCE
Powder X-ray diffractometer with Anton Paar Model HTK 1200
High Temperature Chamber and room temperature XRD
measurements were performed on a Bruker-AXS D8 DIS-
COVER with GADDS Powder X-ray diffractometer, both with
Cu Kα radiation.
Hz, 4 H), 7.28 (d, J = 8.2 Hz, 4 H), 7.20 (s, 2 H), 6.75 (br, 2 H),
2.42 (s, 6 H). 13C NMR (125 MHz, CDCl3): δ ppm = 144.83,
135.34, 130.89, 130.09, 129.92, 127.64, 122.59, 21.55.
HR-EI-MS (m/z): calcd for C20H18Br2N2O4S2: 571.9075; found
571.9055. (error = −3.5 ppm).
4,5-Dibromobenzene-1,2-diamine (7). The preceding
6
(45.2 g, 78.7 mmol) was heated in concentrated sulphuric acid
(90.0 mL) at 110 °C for about 15 min. After cooling to room
temperature, the reaction mixture was poured into ice–water and
neutralized with 50% NaOH solution until the color of the solu-
tion is off-white and lots of precipitate was formed. After fil-
tration, the precipitate gave an off-white powder of 7 (19.3 g,
95%). 1H NMR (500 MHz, CDCl3): δ ppm = 6.92 (s, 2 H), 3.40
(br, 4 H). 13C NMR (125 MHz, CDCl3): δ ppm = 135.47,
120.65, 113.62. HR-EI-MS (m/z): calcd for C6H6Br2N2:
263.8898; found 263.8893 (error = −1.9 ppm).
5,6-Dibromobenzo[c][1,2,5]thiadiazole (8). To a solution of 7
(5.32 g, 20.0 mmol) and Et3N (4.15 eq, 12 mL, 83 mmol) in dry
DCM (60 mL) was added, in an ice-cooled condition, a solution
of thionyl chloride (2.55 eq, 3.80 mL, 51 mmol) in DCM
(10 mL). After addition was complete, the reaction mixture was
stirred for 5 h under reflux. After cooling to room temperature,
the reaction mixture was filtered, the filtrate was collected while
discarding the solid residue, and the solvent was removed under
vacuum. The residue was purified with column chromatography
using pure DCM as the eluent to give product 8 as a pink–white
solid (5.65 g, 96%). 1H NMR (300 MHz, CDCl3): δ ppm = 8.38
(s, 2 H). 13C NMR (125 MHz, CDCl3): δ ppm = 153.82, 127.14,
124.90. EI-MS (m/z): calcd for C6H2Br2N2S: 291.8305; found
291.8305 (error = 0 ppm).
Synthesis and characterizations of 1a–b, 2a–b, and 3
Compound 9 and 10. A mixture of nitrobenzene (40 mL) and
dry DMF (120 mL) was added to a stirred mixture of 8 (5.88 g,
20.0 mmol), CuCN (4.1 eq, 82.0 mmol, 7.30 g) and CuI (1.36 g,
7.2 mmol). The mixture was stirred under reflux for 6 h, cooled
and poured into a mixture of hydrated FeCl3 (6.8 g), 37% HCl
(1.7 mL) and water (10 mL). The suspension was heated at
70 °C for 1 h, and then the solvent removed under vacuum; the
residue was dissolved with DCM and water, and extracted with
DCM (100 mL). The combined organic phases were washed
with HCl (6 M, 200 mL), saturated NaCl (200 mL), and satu-
rated NaHCO3 (200 mL), and was finally dried over Na2SO4,
concentrated under reduced pressure to give a black residue,
which was purified with column chromatography using eluent
hexane–EA (5 : 1) to give 9 as a light yellow solid (2.23 g,
60%), and then THF–MeOH (1 : 1) to give 10 as a white solid
(0.41 g, 10%).
N,N′-(1,2-Phenylene)bis(4-methylbenzenesulfonamide)
(5).
o-Phenylenediamine (540 mmol, 58.5 g) was added slowly to a
solution of p-toluenesulfonyl chloride (2 eq, 1.080 mol, 205.9 g)
in dry pyridine (500 mL) which was cooled to −10 °C in a
NaCl–ice bath. The resulting mixture was stirred at room temp-
erature for 18 h. By slow addition of 15% aqueous HCl, a pre-
cipitate was formed. The solids were dissolved in EtOH
(1400 mL) and refluxed for 1 h, and then stored in a refrigerator
overnight for crystallization. After filtration, compound 5 was
obtained as a pale solid (210 g, 93%). 1H NMR (500 MHz,
CDCl3): δ ppm = 7.57 (d, J = 8.2 Hz, 4 H), 7.22 (d, J = 8.2 Hz,
4 H), 7.04–7.01 (m, 2 H), 6.98–6.94 (m, 2 H), 6.91 (br, 2 H),
2.39 (s, 6 H); 13C NMR (125 MHz, CDCl3): δ ppm = 144.15,
135.46, 130.76, 129.60, 127.53, 127.23, 125.96, 21.57.
HR-EI-MS (m/z): calcd for C20H20N2O4S2: 416.0864; found
416.0860 (error = −1.0 ppm).
1
Compound 9: H NMR (500 MHz, CDCl3): δ ppm = 8.61
(s, 2 H); 13C NMR (125 MHz, CDCl3): δ ppm = 153.94, 129.81,
114.65, 113.88. HR-EI-MS (m/z): calcd for C8H2N4S: 186.0000;
found 186.0008 (error = 4.3 ppm).
N,N′-(4,5-Dibromo-1,2-phenylene)bis(4-methylbenzenesulfon-
amide) (6). Bromine (19.2 g, 0.180 mol) was added drop-wise
to an ice-cooled and stirred suspension of 5 (37.5 g, 0.090 mol)
and anhydrous NaOAc (15.0 g) in glacial acetic acid (150 mL).
The mixture was stirred and heated at 110 °C for 3 h, then
cooled and poured into ice water (400 mL), and then stirred for
an additional 1 h, and EtOH (200 mL) was added. After
Compound 10: 1H NMR (300 MHz, DMSO-d6): δ ppm =
11.88 (br, 1 H), 8.56 (s, 2 H); 13C NMR (125 MHz, DMSO-d6):
δ ppm = 167.52, 156.16, 132.77, 117.42. HR-EI-MS (m/z):
calcd for C8H3N3O2S: 204.9946; found 204.9939 (error =
−3.4 ppm).
This journal is © The Royal Society of Chemistry 2012
Org. Biomol. Chem., 2012, 10, 7045–7052 | 7049

View Article Online
12b: Yield = 93%. Yellow powder. 1H NMR (500 MHz,
CDCl3): δ ppm = 7.09 (s, 2 H), 3.83 (br, 4 H), 3.62–3.59 (m,
2 H), 1.68–1.61 (m, 1 H), 1.53–1.10 (m, 9 H), 0.94 (d, J =
6.3 Hz, 3 H), 0.84 (d, J = 6.9 Hz, 6 H); 13C NMR (125 MHz,
CDCl3): δ ppm = 169.01, 139.29, 124.98, 110.26, 39.24, 37.06,
36.06, 35.70, 30.74, 27.91, 24.55, 22.64, 22.57, 19.40.
HR-EI-MS (m/z): calcd for C18H27N3O2: 317.2103; found
317.2102 (error = 0.3 ppm).
General procedure for alkylation of compound 10. A mixture
of 10 (8.0 mmol), K2CO3 (3.500 g, 24.0 mmol, 3.0 eq), and
alkyl bromide (8.4 mmol, 1.05 eq) was heated under argon
atmosphere to reflux in DMF (50 mL) for overnight. The reac-
tion was stopped upon complete consumption of the starting
material 10 at which point the reaction was cooled and diluted
with CH2Cl2 (100 mL) and washed with 10% aqueous HCl sol-
ution (100 mL × 2) and with saturated aqueous NaCl solution
(100 mL × 2), dried over Na2SO4 and the solvent was removed
under vacuum. The residue was purified by silica gel column
chromatography using hexane–CHCl3 (4 : 1–10 : 1) as the eluent
to give the title compound 11a–c.
12c. Yield = 93%. Golden yellow powder. 1H NMR
(500 MHz, CDCl3): δ ppm = 7.08 (s, 2 H), 3.83 (br, 4 H), 3.57
(t, J = 7.5 Hz, 2 H), 1.63–1.60 (q, 2 H), 1.30–1.24 (m, 18 H),
0.87 (t, J = 7.5 Hz , 3 H); 13C NMR (125 MHz, CDCl3): δ ppm
= 169.09, 139.30, 124.90, 110.28, 37.79, 31.90, 29.69, 29.60,
29.57, 29.51, 29.32, 29.24, 28.77, 26.89, 22.67, 14.09.
HR-EI-MS (m/z): calcd for C20H31N3O2: 345.2416; found
345.2421 (error = −1.4 ppm).
6-(2-Decyltetradecyl)-5H-[1,2,5]thiadiazolo[3,4-f]isoindole-5,7-
(6H)-dione (11a). 11a: Yield = 83%. Viscous oil. 1H NMR
(500 MHz, CDCl3): δ ppm = 8.49 (s, 2 H), 3.67 (d, J = 7.0 Hz,
2 H), 1.94 (br, 1 H), 1.45–1.23 (m, 40 H), 0.89–0.86 (m, 6 H);
13C NMR (125 MHz, CDCl3): δ ppm = 166.61, 156.66, 131.54,
118.04, 43.07, 40.51, 36.87, 31.85, 31.84, 31.51, 30.92, 29.86,
29.63, 29.61, 29.56, 29.51, 29.29, 26.86, 26.22, 22.61, 14.01.
HR-EI-MS (m/z): calcd for C32H51N3O2S: 541.3702; found
541.3708 (error = 1.1 ppm).
General procedure for diamine and dione condensation reac-
tion for 1a–b and 2a–b. Diamine 12a–b (0.22 mmol, 2.2 eq)
and 2,7-di-tert-butylpyrene-4,5,9,10-tetraone or pyrene-4,5,9,10-
tetraone (0.1 mmol) were suspended in o-DCB (8 mL). A cataly-
tic amount of p-toluenesulfonic acid (2 mg) was added. The pH
of the solution should be a little acidic at this stage. The resulting
solution was stirred and refluxed for overnight under Ar (g)
atmosphere. The o-DCB was removed under vacuum and the
residue was dissolved in DCM and saturated NaCl, extracted
with DCM. The combined organic phases were washed with
saturated NaHCO3 (200 mL), and then the solvent was removed
under reduced pressure to give a yellow residue. The solid
residue was purified with column chromatography using
hexane–CHCl3 (1 : 1–1 : 5) to give the final product 1a–b and
2a–b.
6-(3,7-Dimethyloctyl)-5H-[1,2,5]thiadiazolo[3,4-f]isoindole-5,7-
(6H)-dione (11b). 11b: Yield = 91%. White solid. 1H NMR
(500 MHz, CDCl3): δ ppm = 8.49 (s, 2 H), 3.83–3.76 (m, 2 H),
1.78–1.73 (m, 1 H), 1.54–1.49 (m, 4 H), 1.36–1.13 (m, 5 H),
1.00–0.85 (m, 9 H); 13C NMR (125 MHz, CDCl3): δ ppm =
166.27, 156.60, 131.62, 117.97, 39.09, 37.11, 36.86, 35.17,
30.73, 27.81, 24.45, 22.56, 22.49, 19.30. HR-EI-MS (m/z):
calcd for C18H27N3O2S: 345.1511; found 345.1513 (error =
0.6 ppm).
1a: Yield = 81%. Yellow powder. 1H NMR (500 MHz,
CDCl3): δ ppm = 9.66 (s, 4 H), 8.55 (s, 4 H), 3.46 (d, J = 5.2
Hz, 4 H), 1.88–1.82 (m, 20 H), 1.24–1.23 (m, 80 H), 0.87–0.84
(m, 12 H); 13C NMR (125 MHz, CDCl3): δ ppm = 166.88,
151.77, 144.03, 143.90, 130.80, 128.26, 126.33, 126.12, 125.67,
42.83, 36.97, 36.01, 31.91, 31.81, 31.57, 29.97, 29.68, 29.65,
29.59, 29.35, 26.28, 22.67, 14.09. MALDI-TOF MS: m/z =
1329.9659 ([M + H]+); calculated exact mass: 1329.9762. ([M +
H]+) Elemental Analysis: calcd for C64H76N6O4: C, 79.47; H
9.40; N, 6.32; found: C, 79.17; H 9.38; N, 6.30.
6-Dodecyl-5H-[1,2,5]thiadiazolo[3,4-f]isoindole-5,7(6H)-dione
(11c). 11c: Yield = 90%. White solid. 1H NMR (500 MHz,
CDCl3): δ ppm = 8.50 (s, 2 H), 3.78 (t, J = 7.3 Hz, 2 H),
1.76–1.70 (q, 2 H), 1.35–1.25 (m, 18 H), 0.87 (t, J = 7.0 Hz ,
3 H); 13C NMR (125 MHz, CDCl3): δ ppm = 166.49, 156.71,
131.66, 118.15, 38.93, 31.87, 29.58, 29.51, 29.43, 29.29, 29.13,
28.33, 26.87, 22.64, 14.06. HR-EI-MS (m/z): calcd for
C20H27N3O2S: 373.1824; found 373.1823 (error = −0.3 ppm).
General procedure for reduction of 11a–c to compound 12a–c.
A mixture of 11 (2.0 mmol), iron powder (1.344 g, 24.0 mmol,
12 eq), and glacial acetic acid (20 mL) was heated under reflux
for 15–30 min. It was then cooled to room temperature, basified
with a solution of NaOH, and extracted with ether. The com-
bined ether extract was washed with a solution of NaOH and
water, dried over anhydrous Na2SO4, and the solvent was
removed to afford a yellow residue which was purified with
column chromatography using hexane–THF (1 : 1–3 : 1) to give
the final product 12a–c.
1b: Yield = 86%. Yellow powder. 1H NMR (500 MHz,
CDCl3, 323K): δ ppm = 9.83 (s, 4 H), 8.81 (s, 4 H), 3.82 (d, J =
7.5 Hz, 4 H), 1.83–1.54 (m, 20 H), 1.42–1.19 (m, 8 H + 10 H),
1.04 (d, J = 6.3 Hz, 6 H), 0.90 (d, J = 6.9 Hz, 12 H); 13C NMR
(125 MHz, CDCl3, 323K): δ ppm = 166.96, 152.08, 144.51,
144.47, 131.45, 128.82, 126.69, 126.53, 125.97, 39.36, 37.20,
37.13, 36.07, 35.53, 31.79, 31.10, 28.00, 24.64, 22.65, 22.59,
19.49. MALDI-TOF MS: m/z = 937.5888 ([M + H]+); calculated
exact mass: 937.5380. ([M + H]+) Elemental Analysis: calcd for
C64H76N6O4: C, 76.89; H, 7.31; N, 8.97; found: C, 76.90; H,
7.29; N, 9.00.
12a: Yield = 92%. Yellow powder. 1H NMR (500 MHz,
CDCl3): δ ppm = 7.09 (s, 2 H), 3.83 (br, 4 H), 3.47 (d, J = 7.5
Hz, 2 H), 1.83–1.82 (br, 1 H), 1.33–1.23 (m, 40 H), 0.89–0.86
(m, 6 H); 13C NMR (125 MHz, CDCl3): δ ppm = 169.51,
139.40, 124.20, 109.98, 41.92, 37.06, 31.81, 31.42, 29.91,
29.59, 29.56, 29.53, 29.52, 29.24, 26.25, 22.57, 13.99.
HR-EI-MS (m/z): calcd for C32H55N3O2: 513.4294; found
513.4273 (error = 4.1 ppm).
2a: Yield = 88%. Yellow powder. 1H NMR (500 MHz,
CDCl3): δ ppm = 8.39 (d, J = 7.0 Hz, 4 H), 7.71(s, 4 H), 7.36 (t,
J = 7.0 Hz, 2H), 3.52 (d, J = 5.1 Hz, 4 H), 1.90 (br, 2 H),
1.40–1.26 (m, 80 H), 0.89–0.86 (m, 12 H); 13C NMR
(125 MHz, CDCl3): δ ppm = 166.35, 143.08, 141.45, 130.75,
128.01, 127.52, 127.07, 125.84, 124.56, 42.89, 37.08, 31.96,
7050 | Org. Biomol. Chem., 2012, 10, 7045–7052
This journal is © The Royal Society of Chemistry 2012

View Article Online
4 (a) Z. Bao, A. J. Lovinger and J. Brown, J. Am. Chem. Soc., 1998, 120,
207; (b) Y. Sakamoto, K. Shingo and T. Suzuki, J. Am. Chem. Soc.,
31.94, 31.89, 31.49, 30.12, 29.77, 29.72, 29.66, 29.63, 29.42,
29.39, 29.33, 26.28, 22.70, 22.68, 14.09. MALDI-TOF MS: m/z
= 1217.7934 ([M + H]+); calculated exact mass: 1217.8510.
([M + H]+) Elemental Analysis: calcd for C64H76N6O4: C,
78.90; H, 8.94; N, 6.90; found: C, 78.75; H, 8.93; N, 6.92.
2b: Yield = 87%. Yellow powder.1H NMR (500 MHz, CDCl3,
323 K): δ ppm = 8.48 (d, J = 7.5 Hz, 4 H), 7.77 (s, 4 H), 7.44
(t, J = 7.0 Hz, 2 H), 3.67 (t, J = 7.5 Hz, 4 H), 1.79–1.20 (m, 2 H +
2001, 123, 4643; (c) A. Facchetti, M. H. Yoon, C. L.
S tern,
G. R. Hutchison, M. A. Ratner and T. J. Marks, J. Am. Chem. Soc., 2004,
126, 13480; (d) H. Qu and C. Chi, Org. Lett., 2010, 12, 3360.
5 (a) H. E. Katz, A. J. Lovinger, J. Johnson, C. Kloc, T. Siegrist, W. Li,
Y.-Y. Lin and A. Dodabalapur, Nature, 2000, 404, 478; (b) B. A. Gregg
and R. A. Cormier, J. Am. Chem. Soc., 2001, 123, 7959; (c) B. A. Jones,
A. Facchetti, M. R. Wasielewski and T. J. Marks, J. Am. Chem. Soc.,
2007, 129, 15259; (d) Z. Wang, C. Kim, A. Facchetti and T. J. Marks,
J. Am. Chem. Soc., 2007, 129, 13362; (e) X. Guo, R. P. Ortiz, Y. Zheng,
Y. Hu, Y.-Y. Noh, K.-J. Baeg, A. Facchetti and T. J. Marks, J. Am. Chem.
Soc., 2011, 133, 1405; (f) H. Qu, W. Cui, J. Li, J. Shao and C. Chi,
Org. Lett., 2011, 13, 924; (g) Q. Ye, J. Chang, K.-W. Huang and C. Chi,
Org. Lett., 2011, 13, 5960; (h) C. Ramanan, A. L. Smeigh,
J. E. Anthony, T. J. Marks and M. R. Wasielewski, J. Am. Chem. Soc.,
2012, 134, 386.
6 (a) H. Usta, A. Facchetti and T. J. Marks, J. Am. Chem. Soc., 2008, 130,
8580; (b) X. Gao, C. Di, Y. Hu, X. Yang, H. Fan, F. Zhang, Y. Liu, H. Li
and D. Zhu, J. Am. Chem. Soc., 2010, 132, 3697; (c) Y. Hu, X. Gao,
C. Di, X. Yang, F. Zhang, Y. Liu, H. Li and D. Zhu, Chem. Mater., 2011,
23, 1204; (d) Y. Qiao, Y. Guo, C. Yu, F. Zhang, W. Xu, Y. Liu and
D. Zhu, J. Am. Chem. Soc., 2012, 134, 4084; (e) J. Li, J.-J. Chang,
H. S. Tan, H. Jiang, X. Chen, Z. Chen, J. Zhang and J. Wu, Chem. Sci.,
2012, 3, 848.
7 (a) Z. Liang, Q. Tang, R. Mao, D. Liu, J. Xu and Q. Miao, Adv. Mater.,
2011, 23, 5514; (b) Z. Liang, Q. Tang, J. Xu and Q. Miao, Adv. Mater.,
2011, 23, 1535; (c) S. Miao, A. L. Appleton, N. Berger, S. Barlow,
S. R. Marder, K. I. Hardcastle and U. H. F. Bunz, Chem.–Eur. J., 2009,
15, 4990; (d) J. U. Engelhart, B. D. Lindner, O. Tverskoy, F. Rominger
and U. H. F. Bunz, Org. Lett., 2012, 14, 1008; (e) C. Wang, Z. Liang,
Y. Liu, X. Wang, N. Zhao, Q. Miao, W. Hu and J. Xu, J. Mater. Chem.,
2011, 21, 15201; (f) C. Tong, W. Zhao, J. Luo, H. Mao, W. Chen,
H. S. O. Chan and C. Chi, Org. Lett., 2012, 14, 494; (g) Z. Liang,
Q. Tang, J. Liu, J. Li, F. Yan and Q. Miao, Chem. Mater., 2010, 22, 6438;
(h) U. H. F. Bunz, Chem.–Eur. J., 2009, 15, 6780; (i) U. H. F. Bunz, Pure
Appl. Chem., 2010, 82, 953; ( j) A. L. Appleton, S. M. Brombosz,
S. Barlow, J. S. Sears, J. L. Brédas, S. R. Marder and U. H. F. Bunz, Nat.
Commun., 2010, 1, 91; (k) O. Tverskoy, F. Rominger, A. Peters,
H. J. Himmel and U. H. F. Bunz, Angew. Chem., Int. Ed., 2011, 50, 3557;
(l) B. D. Lindner, J. U. Engelhart, O. Tverskoy, A. L. Appleton,
F. Rominger, A. Peters, H. J. Himmel and U. H. F. Bunz, Angew. Chem.,
Int. Ed., 2011, 50, 8588; (m) B. R. Kaafarani, T. Kondo, J. Yu, Q. Zhang,
D. Dattilo, C. Risko, S. C. Jones, F. Barlow, B. Domercq, F. Amy,
A. Kahn, J.-L. Brédas, B. Kippelen and S. R. Marder, J. Am. Chem. Soc.,
2005, 127, 16358; (n) T. Ishi-i, K. Yaguma, R. Kuwahara, Y. Taguri and
S. Mataka, Org. Lett., 2006, 8, 585; (o) H.-L. Yip, J. Zou, H. Ma,
Y. Tuan, N. M. Tucker and A. K.-Y. Jen, J. Am. Chem. Soc., 2006, 128,
13042.
18 H), 1.40 (d, J = 6.3 Hz, 6 H), 0.93 (d, J = 6.9 Hz, 12 H); 13
C
NMR (125 MHz, CDCl3, 323K): δ ppm = 166.09, 143.28,
141.73, 131.06, 128.21, 127.70, 127.33, 126.16, 124.63, 39.39,
37.13, 35.42, 31.18, 28.03, 24.68, 22.71, 22.64, 19.44. MALDI-
TOF MS: m/z = 825.4212 ([M + H]+); calculated exact mass:
825.4128 ([M
+
H]+). Elemental Analysis: calcd for
C64H76N6O4: C, 75.70; H, 6.35; N, 10.19; found: C, 75.57;
H, 6.34; N, 10.17.
Synthesis of compound 3. Diamine 12c (0.33 mmol, 114 mg,
3.3 eq) and hexaketocyclohexane octahydrate (0.1 mmol, 31 mg)
were suspended in o-DCB (8 mL). A catalytic amount of
p-toluenesulfonic acid (2 mg) was added. The pH of the solution
should be a little acidic at this stage. The resulting solution was
stirred and refluxed overnight under Ar (g) atmosphere. The
o-DCB was removed under vacuum and the residue was dis-
solved in DCM and saturated NaCl, extracted with DCM. The
combined organic phases were washed with saturated NaHCO3
(50 mL), and then the solvent was removed under reduced
pressure to give yellow residue, which was purified with column
chromatography using hexane–THF (1 : 3–1 : 1) to give the final
product 3 as a yellow green solid in 82% yield. 1H NMR
(500 MHz, CDCl3): δ ppm = 9.12 (s, 6 H), 3.86 (t, J = 7.5 Hz,
6 H), 1.83–1.77 (m, 6 H), 1.46–1.26 (m, 54 H), 0.87 (t, J = 7.0
Hz, 9 H); 13C NMR (125 MHz, CDCl3): δ ppm = 165.84,
145.76, 143.97, 133.77, 126.53, 39.15, 31.87, 29.60, 29.58,
29.56, 29.47, 29.30, 29.16, 28.40, 26.96, 22.63, 14.05. MALDI-
TOF MS: m/z = 1096.7280 ([M + H]+); calculated exact mass:
1096.6388. ([M
+
H]+. Elemental Analysis: calcd for
C64H76N6O4: C, 72.30; H, 7.45; N, 11.50; found: C, 72.51;
H, 7.44; N, 11.53.
8 C. Wang, H. Dong, W. Hu, Y. Liu and D. Zhu, Chem. Rev., 2012, 112,
2208.
9 J. Yin, H. Qu, K. Zhang, J. Luo, X. Zhang, C. Chi and J. Wu, Org. Lett.,
2009, 11, 3028.
Acknowledgements
10 (a) M. Winkler and K. N. Houk, J. Am. Chem. Soc., 2007, 129, 1805;
(b) M. M. Payne, S. A. Odom, S. R. Parkin and J. E. Anthony, Org. Lett.,
2004, 6, 3325; (c) M. M. Payne, S. R. Parkin, J. E. Anthony, C. Kuo and
T. N. Jackson, J. Am. Chem. Soc., 2005, 127, 8028.
11 (a) J. Hu, D. Zhang, S. Jin, S. Z. D. Cheng and F. W. Harris, Chem.
Mater., 2004, 16, 4912; (b) S. Miao, M. D. Smith and U. H. F. Bunz,
Org. Lett., 2006, 8, 757; (c) B. Gao, M. Wang, Y. Cheng, L. Wang,
X. Jing and F. Wang, J. Am. Chem. Soc., 2008, 130, 8297.
This work was financially supported by NUS start-up grant
R-143-000-486-133 and MOE AcRF Tier 1 grant R-143-000-
510-112.
Notes and references
12 G. W. H. Cheeseman, J. Chem. Soc., 1962, 1170.
13 E. H. Mørkved, S. M. Neset, O. Bjørlo, H. Kjøsen, G. Hvistendahl and
F. Mo, Acta Chem. Scand., 1995, 49, 658.
14 H. Qu, J. Luo, X. Zhang and C. Chi, J. Polym. Sci., Part A: Polym.
Chem., 2010, 48, 186.
15 (a) B. Zhao, B. Liu, R. Q. Png, K. Zhang, K. A. Lim, J. Luo, J. Shao,
P. K. H. Ho, C. Chi and J. Wu, Chem. Mater., 2010, 22, 435; (b) J. Shao,
Z. Guan, Y. Yan, C. Jiao, Q.-H. Xu and C. Chi, J. Org. Chem., 2011, 76,
780.
16 (a) L. J. Lindgren, F. Zhang, M. Andersson, S. Barrau, S. Hellstrom,
W. Mammo, E. Perzon, O. Inganas and M. R. Andersson, Chem. Mater.,
2009, 21, 3491; (b) D.-J. Hong, E. Lee, H. Jeong, J.-K. Lee, W.-C. Zin,
T. D. Nguyen, S. C. Glotzer and M. Lee, Angew. Chem., Int. Ed., 2009,
48, 1664.
1 For a recent review, see: (a) M. Bendikov, F. Wudl and D. F. Perepichka,
Chem. Rev., 2004, 104, 4891; (b) J. Wu, Curr. Org. Chem., 2007, 11,
1220; (c) J. Wu, W. Pisula and K. Müllen, Chem. Rev., 2007, 107, 718;
(d) A. R. Murphy and J. M. J. Fréchet, Chem. Rev., 2007, 107, 1066;
(e) J. Zaumseil and H. Sirringhaus, Chem. Rev., 2007, 107, 1296;
(f) M. Mas-Torrent and C. Rovira, Chem. Soc. Rev., 2008, 37, 827.
2 For a recent review, see: (a) H. E. Katz, Z. Bao and S. L. Gilat, Acc.
Chem. Res., 2001, 34, 359; (b) R. A. Pascal Jr, Chem. Rev., 2006, 106,
4809; (c) J. E. Anthony, Chem. Rev., 2006, 106, 5028; (d) J. E. Anthony,
Angew. Chem., Int. Ed., 2008, 47, 452.
3 (a) M.-H. Yoon, S. A. Dibeneddetto, A. Facchetti and T. J. Marks, J. Am.
Chem. Soc., 2005, 127, 1348; (b) Y. Sun, Y. Liu and D. Zhu, J. Mater.
Chem., 2005, 15, 53; (c) C. Di, G. Yu, Y. Liu and D. Zhu, J. Phys. Chem.
B, 2007, 111, 4083.
This journal is © The Royal Society of Chemistry 2012
Org. Biomol. Chem., 2012, 10, 7045–7052 | 7051

View Article Online
17 J. Hu, D. Zhang and F. W. Harris, J. Org. Chem., 2005, 70, 707.
18 (a) B. B. Jang, S. H. Lee and Z. H. Kafafi, Chem. Mater., 2006, 18, 449;
(b) J. L. Brusso, O. D. Hirst, A. Dadvand, S. Ganesan, F. Cicoira,
C. M. Robertson, R. T. Oakley, F. Rosei and D. F. Perepichka, Chem.
Mater., 2008, 20, 2484.
19 (a) C. Chi and G. Wegner, Macromol. Rapid Commun., 2005, 26, 1532;
(b) C. Chi, C. Im, V. Enkelmann, A. Ziegler, G. Lieser and G. Wegner,
Chem.–Eur.J., 2005, 11, 6833.
20 C. P. Constantinides, P. A. Koutentis and J. Schatz, J. Am. Chem. Soc.,
2004, 126, 16232.
7052 | Org. Biomol. Chem., 2012, 10, 7045–7052
This journal is © The Royal Society of Chemistry 2012