Novel carbazole-pyridine copolymers by an economical method: Synthesis, spectroscopic and thermochemical studies

Article abstract of DOI:10.3762/bjoc.7.75

The synthesis, as well as spectroscopic and thermochemical studies of a novel class of carbazole-4-phenylpyridine co-polymers are described. The synthesis was carried out by a simple and cheaper method compared to the lengthy methods usually adopted for the preparation of carbazole-pyridine copolymers which involve costly catalysts. Thus, two series of polymers were synthesized by a modified Chichibabin reaction, i.e., by the condensation of diacetylated N-alkylcarbazoles with 3-substituted benzaldehydes in the presence of ammonium acetate in refluxing acetic acid. All the polymers were characterized by FTIR, ¹H NMR, ¹³C NMR, UV-vis spectroscopy, fluorimetry, TGA and DSC. The weight average molecular masses (M_w) of the polymers were estimated by the laser light scattering (LLS) technique.

Full text of DOI:10.3762/bjoc.7.75

Novel carbazole–pyridine copolymers by an
economical method: synthesis, spectroscopic and
thermochemical studies
Aamer Saeed*1, Madiha Irfan1 and Shahid Ameen Samra1,2
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2011, 7, 638–647.
1Department of Chemistry, Quaid-i-Azam University, Islamabad,
Pakistan and 2Kohat University of Science and Technology (KUST),
Kohat, 26000, NWFP, Pakistan
doi:10.3762/bjoc.7.75
Received: 02 November 2010
Accepted: 12 April 2011
Published: 19 May 2011
Email:
Aamer Saeed* - aamersaeed@yahoo.com
Associate Editor: H. Ritter
* Corresponding author
© 2011 Saeed et al; licensee Beilstein-Institut.
License and terms: see end of document.
Keywords:
carbazole–pyridine copolymers; fluorescent materials; organic light
emitting diode (OLED); photoluminescence spectra; UV spectra
Abstract
The synthesis, as well as spectroscopic and thermochemical studies of a novel class of carbazole-4-phenylpyridine co-polymers are
described. The synthesis was carried out by a simple and cheaper method compared to the lengthy methods usually adopted for the
preparation of carbazole–pyridine copolymers which involve costly catalysts. Thus, two series of polymers were synthesized by a
modified Chichibabin reaction, i.e., by the condensation of diacetylated N-alkylcarbazoles with 3-substituted benzaldehydes in the
presence of ammonium acetate in refluxing acetic acid. All the polymers were characterized by FTIR, 1H NMR, 13C NMR, UV–vis
spectroscopy, fluorimetry, TGA and DSC. The weight average molecular masses (Mw) of the polymers were estimated by the laser
light scattering (LLS) technique.
Introduction
An immense research effort has been focused on organic semi- electron-donating properties together with intense lumines-
conductors, including polymers, oligomers, dendrimers, small cence, high thermal stability and excellent photoconductivity.
molecules and heavy-metal complexes, after the discovery by Furthermore, the functionalization of the carbazole nucleus can
Burroughes et al. in 1990 [1-6] that they can be used for fabri- easily be carried out at the 3-, 6- and 9-positions to afford a
cating organic light emitting diodes (OLEDs). A number of great diversity of structures [16]. Carbazole containing poly-
criteria exist for employing organic materials as LEDs [7] and mers have been greatly explored during the last few years for
carbazole containing polymers are the most studied group their applications in organic electronic devices [8]. New conju-
amongst the different polymers intended for OLED applica- gated, fully aromatic poly-2,7-carbazole derivatives have been
tions [8-15]. Carbazole containing polymers exhibit excellent synthesized that exhibit high glass transition temperatures, high
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Beilstein J. Org. Chem. 2011, 7, 638–647.
molecular weights and stability, and that have excellent power
efficiency with low bandgaps [17,18]. Alternating poly-2,7-
carbazole polymers show good thermoelectric properties [19].
Carbazole–pyridine alternate copolymers are a fascinating class
of polymers on account of the fact that they take advantage of
the combination of the electron-donating properties of carbazole
and electron-withdrawing properties of the pyridine ring [20].
Zheng et al. have prepared a new class of copolymers that
incorporate pyridine and N-alkyl carbazole alternatively into the
main chain by oxidative-coupling copolymerization. These
polymers are thermostable, highly soluble, and processable, and
Scheme 1: Synthesis of the monomers. i) R–Br, 50% KOH, benzene,
TBAB, 80 °C, 2 h; ii) AcCl, AlCl3, CHCl3, 0 °C then rt, 3 h.
the fluorescence spectra of the polymers display blue light emit- tion at the active positions of carbazole, viz. 3 and 6, with anhy-
ting properties [21]. drous aluminum chloride in dry chloroform [26].
In view of the above literature reports, it was thought to be of The monomers were purified by recrystallization. The diacetyl-
considerable interest to synthesize carbazole–pyridine copoly- ated carbazole monomers were heated under reflux with various
mers by a route that involved the synthesis of the pyridine units 3-substituted benzaldehydes and ammonium acetate in glacial
as a polymer analogous reaction. To the best of our knowledge, acetic acid in a modified Chichibabin reaction to assemble the
there is no previous report of such a synthesis; the nearest pyridine ring in situ and afford the desired polymers (Scheme 2)
precedent is the use of a Friedländer synthesis to prepare [27].
polyquinolines by Jenekhe [22]. Herein, we report a cost-effec-
tive synthesis of carbazole–pyridine copolymers in contrast to The construction of the pyridine ring in situ by reaction of di-
the protracted and costly methods which involve expensive acetylated carbazole monomers with different benzaldehydes
catalysts.
and ammonium acetate may be envisaged by the complex
sequence shown in Scheme 3 which involves protonation,
enolization, deprotonation, dehydration, the nucleophilic addi-
Results and Discussion
The synthetic pathway employed to prepare the monomers is tion of ammonia, intramolecular cyclization and aromatization.
outlined in Scheme 1. N-Butyl and N-octylcarbazoles were
synthesized by heating a mixture of carbazole and the respec- The polymers were obtained by pouring the reaction mixture
tive alkyl halide in a two phase system of aqueous KOH (50%) into distilled water, followed by filtration and washing of the
and benzene in the presence of tetrabutylammonium bromide residue with copious quantities of distilled water to remove
(TBAB) as a phase-transfer catalyst [23-25]. The N-alkylcar- completely acetic acid and salts. Finally, the polymers were
bazoles were subsequently subjected to Friedel–Crafts acetyla- dissolved in THF and re-precipitated thrice in methanol to
Scheme 2: Synthesis of poly[3,6-N-alkylcarbazole-4-(3-substituted phenyl)pyridine-2,5-diyl]. i) CH3COONH4, CH3COOH, reflux, 18 h.
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Beilstein J. Org. Chem. 2011, 7, 638–647.
Scheme 3: Proposed mechanism of pyridine ring formation.
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Beilstein J. Org. Chem. 2011, 7, 638–647.
remove oligomers. The polymers were obtained as yellow to
brown powders which were then dried in a vacuum oven. The
polymers were readily soluble, at room temperature, in a variety
of common solvents such as tetrahydrofuran, dichloromethane,
chloroform and acetone.
All polymers were characterized on the basis of FTIR, 1H NMR
and 13C NMR spectroscopic analysis. The IR spectral data of all
polymers showed the characteristic peaks of C=N stretching at
1590–1584 cm−1, aromatic tertiary C–N stretching at
1354–1340 cm−1, and C–N stretching at 1153–1143 cm−1
showing the formation of the pyridine ring. The peaks at 3415
and 1523 cm−1 indicating the presence of OH- and NO2- groups
respectively, were also observed in the corresponding polymers.
Figure 1b shows the 1H NMR spectrum of the polymer
P1a whilst that of corresponding monomer is shown in
Figure 1a.
A comparison of the 1H NMR spectra of the monomer to that of
the polymer indicates the disappearance of a peak due to acetyl
protons at δ 2.75 ppm in addition to the appearance of a number
of new peaks in the aromatic region. A complex pattern of split-
ting in the aromatic region and the characteristic peak broad-
ening was also observed consistent with the in situ formation of
the pyridine ring and polymerization. Polymer solutions in THF
were subjected to GPC using polystyrene standards for the
determination of the molecular weights, however, no elution
was observed for any of the polymers. Therefore, molecular
weights could not be determined by GPC, because no standard
column was found to be compatible with this type of polymer.
Consequently, it was decided that the molecular weights would
be determined by the LLS technique, and the results are given
in Table 1.
Figure 1: 1H NMR spectra of (a) monomer 2a and (b) polymer P1a.
In the static laser light scattering (LLS) technique, the angular
dependence of the excess absolute time-average scattered inten- By measuring Rvv(q) at a set of C and θ, Mw, <Rg>z and A2 can
sity, the so-called Raleigh ratio Rvv(q) at a scattering angle θ is be determined from a conventional Zimm plot which incorpo-
measured. The molecular weights of the polymers in a dilute rates q and C extrapolation on a single grid. There are experi-
solution at a concentration C can then be obtained on the basis mental points at all grid points except along the lower line (the
of the following equation:
θ = 0 line) and the left-most line (the C = 0) line. The values of
Mw and <Rg>z were calculated from the slopes of [KC/Rvv
(q)]C→0 vs q2 and [KC/Rvv (q)]q→0 vs C and the intercept of
[KC/Rvv (q)]q→0,C→0, respectively. Figure 2 shows the Zimm
plot of P2a in THF at room temperature.
where K = 4π2n2(dn/dC)2/(NAλ04), q = (4πn/λ0)sin(θ/2) and NA,
dn/dC, n, λ0, and θ being Avogadro's number, the specific Thermochemical properties of the polymers
refractive index increment, the solvent refractive index, the The thermal properties of the two series of polymers, P1 and P2
wavelength of the light in vacuo, and the scattering angle, res- were investigated by thermogravimetric analysis (TGA) and
pectively. Mw is the weight average molar mass, A2 is the differential scanning calorimetry (DSC). For TGA the samples
second virial coefficient, and <Rg2>z1/2 is the root-mean square were heated (PerkinElmer Thermal Analysis System 409) from
Z-average radius of gyration of the polymer chain.
25 °C to 85 °C at a rate of 10 °C/min and at a nitrogen gas flow
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Beilstein J. Org. Chem. 2011, 7, 638–647.
Figure 3: Thermogravimetric analysis curve of P1a.
Figure 2: Zimm plot for P2a in THF at room temperature.
grams for polymers P1 and P2 are shown in Figure 4 and the
results of the thermal analysis are shown in Table 1.
rate of 80 mL/min. Polymers P1 and P2 lost weight gradually
during the early phase of the experiment. A thermal gravi- For DSC, the samples were first heated to melting, then cooled
metric analysis curve of P1a is shown in Figure 3.
to the glassy state and reheated to determine the glass transition
temperature (Tg). A representative DSC graph is shown for P1a
The thermal analysis results indicated that polymers P1 and P2 in Figure 5. Tg is calculated from the second heating curve. As
have a high decomposition temperature Td and good thermal it can be seen from the graph, Tg for the polymer is 154 °C. All
stability above 300 °C, which is very attractive for the fabrica- the polymers show glass transition temperatures above 150 °C
tion of stable organic electroluminescent devices. TGA thermo- (Table 1).
Table 1: Thermal data and molecular weights for polymers P1 and P2.
P1a
P1b
P1c
P1d
P2a
P2b
P2c
P2d
(Mw) 105 (g/mol)a
Td (°C)b
0.57
380
154
0.56
300
165
0.75
265
161
0.12
300
170
1.28
376
158
2.43
295
160
1.73
400
158
1.29
295
164
Tg (°C)c
aMolecular weights of polymers of series P1 and P2 by static LLS. bDecomposition temperature Tg determined by TGA at a heating rate of 10 °C/min
under a N2 atmosphere. cGlass transition temperature Tg determined by DSC at a heating rate of 10 °C/min under a N2 atmosphere, 2nd run.
Figure 4: TGA curves of polymers (a) P1 and (b) P2.
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Beilstein J. Org. Chem. 2011, 7, 638–647.
for polymers of P2 series. The λmax values were 291, 284, 291
and 289 nm for P2a, P2b, P2c and P2d, respectively, along
with distinct shoulders. The main peaks on the spectra are
attributed to a π→π* transition, and the shoulders correspond to
n→π* transitions in the respective materials. A comparison of
the photophysical properties of the synthesized polymers may
be made with structurally related polymers previously synthe-
sized by Zheng et al. [21,28]. The observed differences in the
absorption spectra of both polymer series arise due to the differ-
ence in alkyl chain lengths. As the chain length increases, there
is a marked decrease in the bandwidth of the absorption and
emission bands [29]. By comparing both series of polymers, the
absorption maxima shifts to an upper limit with increasing
chain length [30]. Furthermore, polymers with similar groups in
both series show similar absorption maxima, but the apparent
differences from one another are due to the difference in the
Figure 5: DSC graph for polymer P1a.
Photophysical properties of the polymers
The photophysical properties of the polymer, including absorp- electron-donating and electron-withdrawing nature of the
tion and emission spectral studies, were determined from solu- substituents. The additional peak in the absorption spectrum of
tions in chloroform. A summary of the measured spectroscopic P1c is due to the optical transition attributed to the presence of
data is given in Table 2.
the auxochromic OH group, which increases the conjugation
length [31] and becomes part of extended chromophore. This
Figure 6 shows the absorption spectra for the two series of poly- effect is absent in the other compounds.
mers. The solution of P1a exhibited an absorption maximum at
301 nm along with a shoulder at a higher wavelength. Similarly, The photoluminescence spectra of the polymer solutions of
P1b, P1c and P1d had λmax values of 282, 285 and 300 nm, res- series P1 and P2 in CHCl3 are shown in Figure 7. Polymers
pectively. Distinct shoulders are observed for all of the four P1a, P1b, P1c and P1d show emission maxima at 417, 424,
polymers at higher wavelengths. Similar spectra were obtained 397 and 421 nm, respectively, whereas polymers P2a, P2b, P2c
Table 2: Absorption and emission spectroscopic data for polymers P1 and P2.
P1a
P1b
P1c
P1d
P2a
P2b
P2c
P2d
λabs,max [nm]
λem,max [nm]
301
417
282
424
285
300
421
291
426
284
435
291
289
431
397 (491)
400 (524)
Figure 6: UV–vis spectra of the polymers of (a) series P1 and (b) series P2.
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Beilstein J. Org. Chem. 2011, 7, 638–647.
Figure 7: Photoluminescence spectra of polymers P1and P2 in CHCl3 solution.
and P2d show maxima at 426, 435, 400 and 431 nm, respective- 1H and 13C NMR spectra were determined in deuterochloro-
ly. Polymers P1c and P2c having hydroxyl functionality show form solutions using a Bruker AM-300 spectrophotometer.
an extra emission band at 491 and 524 nm, respectively. These FTIR spectra were recorded on an FTS 3000 MX spectropho-
suggest that the polymer solutions in CHCl3 should emit tometer. Mass spectra (EI, 70eV) were obtained on a GC–MS
blue–green light.
instrument of Agilent technologies. UV–vis and fluorescence
spectra were recorded on a Perkin Elmer Lambda 20
The emission colors of dilute solutions of the polymer samples UV–visible spectrophotometer and a Perkin Elmer LS 55 fluo-
were also observed under UV light and are shown in Figure 8.
rescence spectrophotometer, respectively.
Conclusion
Molecular weights of the polymers were determined by
A new class of polymeric materials that contain alternating hole the laser light scattering (LLS) technique using a commercial
transporting and electron transporting moieties of carbazole and light-scattering spectrometer (ALV/SP-150 equipped with
pyridine, respectively, has been synthesized by a simple and an ALV-5000 multi-τ digital time correlator) with a
inexpensive method. The polymers are highly soluble in most solid-state laser (ADLAS DPY 425II, output power ≈ 400 mW
common solvents, which makes them easily to process by spin at λ = 532 nm) as the light source. Thermogravimetric
coating methods. These materials can be considered as poten- analysis (TGA) was performed with a PerkinElmer Thermal
tial candidates for application as OLEDs. The synthesis of analysis System 409. Differential scanning calorimetry (DSC)
further polymers of this novel class is underway.
measurements were performed using Bruker Reflex II ther-
mosystem. The TGA and DSC measurements were recorded
under a nitrogen atmosphere at a heating rate of 10 °C/min.
Experimental
Melting points were recorded using a digital Gallenkamp Elemental analyses were performed on CHNS 932 LECO
(Sanyo) model MPD BM 3.5 apparatus and are uncorrected. instrument.
Figure 8: (a) Polymers of P2 series in visible light; (b) observed fluorescence (CHCl3 dilute solutions) under UV irradiation (254 nm).
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Beilstein J. Org. Chem. 2011, 7, 638–647.
Carbazole, 1-bromobutane, 1-bromooctane, tetrabutylammo- solid which was recrystallized from ethanol to afford 2a (85%)
nium bromide (TBAB) and aluminum chloride were commer- as dull green crystals with a moldy bread smell. Mp 145 °C; IR
cial products from Fluka; acetyl chloride, benzaldehydes and (KBr, υ/cm−1): 2907, 1718, 1655, 1348, 1145; 1H NMR
ammonium acetate were purchased from the Aldrich Chemical (CDCl3, 300 MHz): δ 8.79 (s, 2H), 8.18 (dd, J = 8.7 Hz, 2H),
Company. Glacial acetic acid was purchased from Riedel 7.45 (d, J = 8.4 Hz, 2H), 4.35 (t, J = 7.2 Hz, 2H), 2.75 (s, 6H),
de-Haën.
1.87 (m, 2H), 1.42 (m, 2H), 0.97 (t, J = 7.2 Hz, 3H); 13C NMR
(CDCl3, 75 MHz): δ 197.4, 143.9, 129.6, 127.0, 122.8, 122.0,
108.9, 43.3, 31.0, 26.6, 20.4, 13.8; GC–MS (m/z): 307 (M.+),
Synthesis of 9-butylcarbazole (1a)
A mixture of carbazole (8.35 g, 50 mmol), 1-bromobutane 264 (100%), 221, 178, 43, 29.
(7.13 g, 52 mmol), benzene (25 mL), 50% KOH aqueous solu-
tion (60 mL), tetrabutylammonium bromide (TBAB, 0.4 g, 3,6-Diacetyl-9-octylcarbazole (2b)
1.25 mmol) was stirred at 80 °C for 2 h. The reaction mixture The compound 1b was synthesized by the same procedure as
was cooled to room temperature. The benzene layer was sep- for 2a from AlCl3, 4.00 g (3 mmol), acetyl chloride, 2.35 g
arated, diluted with 20 mL of ethyl acetate, washed with three (3 mmol) to afford 1b 5.58 g (2 mmol) in 88% yield as dull
50 mL portions of water and dried over anhydrous MgSO4. green crystals. Mp 139 °C; IR (KBr, υ/cm−1): 2939, 1715, 1640,
Solvents were removed in vacuo to give a viscous oil, which 1350, 1140; 1H NMR (CDCl3, 300 MHz): δ 8.75 (s, 2H,
solidified on standing at room temperature to afford a white Ar-1,1’), 8.18 (dd, 2H, J = 8.4 Hz, Ar-2,2’), 7.45 (d, 2H, J =
solid. Recrystallization from ethanol gave 1a as white needles 8.7 Hz, Ar-3,3’), 4.34 (t, 2H, J = 7.2 Hz, H-a), 2.75 (s, 6H,
(92%). Mp 54–56 °C; IR (KBr, υ/cm−1): 1640, 1350, 1153; COCH3), 1.86 (m, 2H, H-b), 1.30 (m, 10H, H-c,d,e,f,g), 0.86 (t,
1H NMR (CDCl3, 300 MHz): δ 8.16 (d, J = 7.8 Hz, 2H), 7.51 3H, J = 6.9 Hz, H-h); 13C NMR (CDCl3, 75 MHz): δ 198.1,
(m, 4H), 7.28 (d, J = 7.6 Hz, 2H), 4.35 (t, J = 7.2 Hz, 2H), 1.90 142.4, 128.9, 127.0, 121.8, 120.3, 109.9, 43.1, 31.0, 29.3, 28.9,
(m, 2H), 1.45 (m, 2H), 0.99 (t, J = 7.2 Hz, 3H); 13C NMR 27.2, 22.4, 13.8; GC–MS (m/z): 363 (M.+), 264 (100%), 348,
(CDCl3, 75 MHz): δ 140.7, 125.5, 122.8, 120.3, 118.7, 108.6, 221, 178, 43, 29.
42.8, 31.17, 20.62, 13.95; Elemental analysis: Calcd C: 86.0%,
H: 7.6%, N: 6.2%; found C: 85.8%, H: 7.5%, N: 6.1%.
General procedure for the synthesis of polymers P1
and P2 (a–d)
9-Octylcarbazole (1b)
Ammonium acetate (10 mmol) was added portionwise to a
The compound 1b was synthesized by the same procedure as stirred equimolar mixture of 3,6-diacetyl-N-alkylcarbazole
for 1a using carbazole (8.35 g, 50 mmol), 1-bromooctane and benzaldehyde in acetic acid (10 mL). The reaction mixture
(10.0 g, 52 mmol), benzene (25 mL), and TBAB (0.4 g, was heated under reflux for 18 h. Upon completion of reaction
1.25 mmol). The product was obtained as a light-yellow (TLC monitoring), the reaction mixture was cooled to room
oil (87%). IR (NaCl cell, υ/cm−1): 1630, 1340, 1147; 1H NMR temperature, poured into distilled water (20 mL) and stirred
(CDCl3, 300 MHz): δ 8.35 (d, J = 7.8 Hz, 2H), 7.69 (m, 4H), for 5 min. The precipitated solid was filtered and washed
7.59 (d, J = 8.1 Hz, 2H), 4.41 (t, J = 7.2 Hz, 2H), 2.03 (m, 2H), well with copious quantities of distilled water to remove acetic
1.51 (m, 5H), 1.14 (t, J = 7.2 Hz, 3H); 13C NMR (CDCl3, acid and salts completely. The resulting solid was dissolved in
75 MHz): δ 140.5, 125.8, 123.0, 120.5, 118.9, 108.9, 43.1, 32.1, THF and precipitated by adding methanol to remove the
29.6, 29.4, 29.2, 27.5, 22.9, 14.4; Elemental analysis: Calcd C: oligomers. The precipitation process was repeated three times
85.9%, H: 9.0%, N: 5.0%; found C: 85.8%, H: 8.9%, N: 5.0%. and the polymers obtained were dried in a vacuum oven at
70 °C overnight.
3,6-Diacetyl-9-butylcarbazole (2a)
Aluminum chloride, (4.0 g, 3 mmol) and acetyl chloride, Poly{[N-butylcarbazole-3,6-diyl][4-phenylpyridine-
(2.35 g, 3 mmol) were added successively to 10 mL of dry chlo- 2,6-diyl]} (P1a)
roform. The mixture was stirred for 10 min at 0 °C to obtain a Yellow solid; yield: 44%; IR (KBr, υ/cm−1): 3055, 2930, 2860,
clear solution. A solution of (4.46 g, 2 mmol) of 1a in 10 mL of 1658, 1584, 1326, 1153; 1H NMR (CDCl3, 300 MHz): δ 8.94
dry chloroform was added dropwise to the above solution at (s, Ar-1), 8.55 (dd, J = 8.4 Hz, Ar-2), 8.28 (d, J = 8.4 Hz,
0 °C during 15 min. The reaction mixture was stirred at room Ar-H), 8.0–7.5 (m, Ar H), 4.4 (t, 2H, J = 6.9 Hz, H-a), 1.7 (m,
temperature for 3 h. After the completion of the reaction (TLC 4H, H-b,c), 1.0 (t, 3H, J = 6.9 Hz, H-d); 13C NMR (CDCl3,
monitoring), the reaction mixture was poured into a stirred solu- 75 MHz): δ 148.6, 146.2, 144.1, 142.3, 139.8, 137.2, 129.0,
tion of 10% HCl (50 mL). The organic layer was separated, 128.7, 127.5, 120.5, 119.1, 116.7, 109.5, 33.2, 29.9, 29.2, 28.7,
washed with distilled water three times and dried over anhy- 27.2, 21.9, 14.8; Elemental analysis: Calcd C: 86.6%, H: 5.8%,
drous Na2SO4. The solvent was removed in vacuo to give a N: 7.4%; found C: 84.3%, H: 5.9%, N: 7.1%.
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Beilstein J. Org. Chem. 2011, 7, 638–647.
Poly{[N-butylcarbazole-3,6-diyl][4-(3-nitrophenyl)-
pyridine-2,6-diyl]} (P1b)
Poly{[N-octylcarbazole-3,6-diyl][4-(3-nitrophenyl)-
pyridine-2,6-diyl]} (P2b)
Yellow powder; yield: 49%; IR (KBr, υ/cm−1): 3035, 2930, Yellow powder; yield: 46%; IR (KBr, υ/cm−1): 3070, 2950,
2890, 1656, 1585, 1523, 1345, 1145, 800; 1H NMR (CDCl3, 2840, 1654, 1586, 1345, 1145, 802; 1H NMR (CDCl3, 300
300 MHz): δ 8.96 (s, Ar-8), 8.58 (s, Ar-7), 8.27 (m, Ar-H), 8.0 MHz): δ 8.96 (s, Ar-8), 8.58 (s, Ar-7), 8.33–8.22 (m, Ar-H), 8.0
(d, J = 7.8 Hz, Ar-5), 7.92 (s, Ar-4), 7.66 (d, J = 8.1 Hz, Ar-3), (d, J = 7.8 Hz, Ar-H), 7.92 (s, Ar-H), 7.66 (at, Ar-H), 7.5 (d, J =
7.54 (m, Ar-H), 4.4 (t, 2H, J = 7.1 Hz, H-d), 1.9 (m, 2H, H-c), 8.7 Hz, Ar-H), 4.4 (t, 2H, J = 6.9 Hz, H-a), 1.93 (m, 12H,
1.46 (m, 2H, H-b), 1.0 (t, 3H, J = 7.2 Hz, H-a); 13C NMR H-b,c,d,e,f,g), 0.86 (t, 3H, J = 6.9 Hz, H-h); 13C NMR (CDCl3,
(CDCl3, 75 MHz): δ 148.9, 144.5, 142.0, 137.1, 134.3, 130.5, 75 MHz): δ 148.7, 144.1, 141.0, 136.9, 134.3, 130.1, 130.0,
130.0, 127.8, 124.9, 124.5, 123.3, 122.1, 108.7, 33.5, 29.3, 27.6, 127.6, 124.6, 124.5, 123.1, 122.4, 109.5, 31.7, 29.3, 29.1, 28.4,
22.6, 14.8; Elemental analysis: Calcd C: 77.3%, H: 5.0%, N: 27.2, 22.6, 14.0; Elemental analysis: Calcd C: 78.3%, H: 6.1%,
10.0%; found C: 76.9%, H: 4.7%, N: 9.8%.
N: 8.8%; found C: 77.1%, H: 5.9%, N: 8.2%.
Poly{[N-butylcarbazole-3,6-diyl][4-(3-hydroxy-
phenyl)pyridine-2,6-diyl]} (P1c)
Poly{[N-octylcarbazole-3,6-diyl][4-(3-hydroxy-
phenyl)pyridine-2,6-diyl]} (P2c)
Dark brown powder; yield: 40%; IR (KBr, υ/cm−1): 3415, 3110, Brownish-black solid; yield: 42%; IR (KBr, υ/cm−1): 3345,
2955, 2860, 1663, 1584, 1354, 1146; 1H NMR (CDCl3, 300 3085, 2925, 2840, 1640, 1589, 1350, 1152; 1H NMR (CDCl3,
MHz): δ 8.79 (s, Ar-1), 8.21 (dd, J = 1.9, 9.0 Hz, Ar-2), 300 MHz): δ 8.94 (s, Ar-H), 8.89 (m, Ar-H), 8.84–8.81 (m,
7.47–7.41 (m, Ar-H), 7.31–7.18 (m, Ar-H), 7.02–6.99 (m, Ar-H), 8.22–8.17 (m, Ar-H), 7.49–7.46 (m, Ar-H), 5.31 (s,
Ar-H), 5.10 (s, OH), 4.34 (t, 2H, J = 9.0 Hz, H-a), 1.93–1.79 OH), 4.36 (t, 2H, J = 7.1 Hz, H-a), 2.20 (m, 2H, H-b),
(m, 2H, H-b), 1.44–1.35 (m, 2H, H-c), 0.97 (t, 3H, J = 9.0 Hz, 1.45–1.34 (m, 10H, H-c,d,e,f,g), 0.87 (t, 3H, J = 7.2 Hz, H-h);
H-d); 13C NMR (CDCl3, 75 MHz): δ 150.1, 147.1, 144.3, 13C NMR (CDCl3, 75 MHz): δ 153.1, 145.2, 144.3, 141.1,
141.6, 139.7, 137.8, 134.4, 131.1, 129.3, 126.2, 125.4, 122.9, 139.0, 137.2, 134.4, 132.1, 129.3, 127.2, 125.3, 122.6, 120.2,
120.4, 117.1, 109.3, 36.2, 29.3, 28.5, 28.1, 25.5, 22.2, 14.6; 117.3, 108.2, 39.2, 29.4, 28.6, 28.2, 26.3, 22.5, 15.1; Elemental
Elemental analysis: Calcd C: 83.0%, H: 5.6%, N: 7.1%; found analysis: Calcd C: 83.4%, H: 6.7%, N: 6.2%; found C: 82.1%,
C: 82.6%, H: 5.3%, N: 6.8%.
H: 6.4%, N: 6.0%.
Poly{[N-butylcarbazole-3,6-diyl][4-(3-bromophenyl)-
pyridine-2,6-diyl]} (P1d)
Poly{[N-octylcarbazole-3,6-diyl][4-(3-bromophenyl)-
pyridine-2,6-diyl]} (P2d)
Yellow precipitate; yield: 66%; Rf: 0.45; IR (KBr, υ/cm−1): Dark yellow precipitates; yield: 40%; Rf: 0.47; IR (KBr,
3065, 2960, 2890, 1652, 1596, 1340, 1143, 664; 1H NMR υ/cm−1): 3020, 2960, 2855, 1651, 1587, 1343, 1144, 668;
(CDCl3, 300 MHz): δ 8.91 (s, Ar-1), 8.28 (dd, J = 8.7 Hz, 1H NMR (CDCl3, 300 MHz): δ 8.92 (s, Ar-1), 8.28 (d, J =
Ar-2), 7.78 (d, J = 4.2 Hz, Ar-H), 7.55 (m, Ar-H), 7.33 (at, 7.5 Hz, Ar-H), 7.92–7.88 (m, Ar-H), 7.63–7.49 (m, Ar-H), 7.33
Ar-H), 4.38 (t, 2H, J = 7.2 Hz, H-a), 1.91 (m, 2H, H-b), 1.42 (at, Ar-H), 4.37 (t, 2H, J = 6.6 Hz, H-a), 1.92 (m, 2H, H-b),
(m, 2H, H-c), 0.98 (t, 3H, J = 7.2 Hz, H-d); 13C NMR (CDCl3, 1.36–1.26 (m, 10H, H-c,d,e,f,g), 0.87 (t, 3H, J = 6.9 Hz, H-h);
75 MHz): δ 145.6, 143.2, 136.5, 134.1, 133.7, 131.4, 130.5, 13C NMR (CDCl3, 75 MHz): δ 144.0, 142.2, 137.2, 133.1,
130.3, 127.5, 126.2, 123.2, 123.0, 122.6, 109.1, 32.7, 29.1, 27.3, 130.8, 130.4, 130.4, 130.3, 127.5, 127.3, 123.2, 123.1, 123.0,
22.4, 14.8; Elemental analysis: Calcd C: 71.5%, H: 4.6%, N: 122.2, 109.3, 31.7, 29.3, 29.1, 28.9, 27.3, 22.6, 14.1; Elemental
6.1%; found C: 69.3%, H: 4.3%, N: 6.0%.
analysis: Calcd C: 73%, H: 5.6%, N: 5.5%; found C: 70%, H:
5.4%, N: 5.2%.
Poly{[N-octylcarbazole-3,6-diyl][4-phenylpyridine-
2,6-diyl]} (P2a)
Acknowledgements
Yellow powder; yield: 39%; IR (KBr, υ/cm−1): 3060, 2950, The authors gratefully acknowledge a research grant from
2862, 1651, 1590, 1326, 1145; 1H NMR (CDCl3, 300 MHz): Quaid-i-Azam University, Islamabad, under the URF program.
δ 8.94 (s, Ar-1), 8.54–7.47 (m, Ar Hs), 4.38 (t, 2H, H-a), 1.93 M. I. gratefully acknowledges a research scholarship from
(m, 2H, H-b), 1.27 (m, 10H, H-c,d,e,f,g), 0.88 (t, 3H, H-h); HEC, Islamabad, under the HEC Indigenous PhD Scholarship
13C NMR (CDCl3, 75 MHz): δ 150.6, 148.3, 147.1, 144.4, 5000 Scheme.
139.8, 136.5, 129.0, 127.3, 126.2, 120.7, 118.1, 116.5, 110.5,
35.2, 30.1, 29.2, 28.7, 27.2, 21.9, 14.8; Elemental analysis:
Calcd C: 86.5%, H: 6.9%, N: 6.5%; found C: 83.3%, H: 6.7%,
N: 6.1%.
646

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