Synthesis and properties of carbazole-containing poly(aryleneethynylenes) and poly(aryleneimines)

Article abstract of DOI:10.1021/ma049391i

Novel poly(aryleneethynylenes) and poly(aryleneimines) containing carbazole units in the main chain were synthesized by polycondensation of diethynylcarbazoles with dihaloarenes, or diformylcarbazole with phenylenediamines, and their general properties we

Full text of DOI:10.1021/ma049391i

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7578
Macromolecules 2004, 37, 7578-7583
Synthesis and Properties of Carbazole-Containing
Poly(aryleneethynylenes) and Poly(aryleneimines)
Yosh ih ir o Ta k ih a n a , Ma sa sh i Sh iotsu k i, F u m io Sa n d a ,* a n d Tosh io Ma su d a *
Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University,
Kyoto 615-8510, J apan
Received March 26, 2004; Revised Manuscript Received J une 30, 2004
ABSTRACT: Novel poly(aryleneethynylenes) and poly(aryleneimines) containing carbazole units in the
main chain were synthesized by polycondensation of diethynylcarbazoles with dihaloarenes, or diformyl-
carbazole with phenylenediamines, and their general properties were studied. The polymers with Mw
)
2700-33 700 were obtained in 60-100% yields. Compared to carbazole, the UV-vis absorption of the
polymers was red-shifted, which indicates the extension of conjugation length. Excited at the absorption
maxima, the polymers containing ethynylene moieties showed blue or green emission with high
fluorescence quantum yields (6-86%) in the solution state, while in the film state, they exhibited
fluorescence at longer wavelength, which suggests the formation of excimers. On the contrary, the polymers
having imine moieties showed emission with low fluorescence quantum yields (<1%).
Sch em e 1
In tr od u ction
Carbazole is a conjugated unit that has interesting
optical and electronic properties such as photoconduc-
tivity and photorefractivity.1 In the field of electro-
luminescence, carbazole derivatives are often used as
the materials for hole-transporting layers, utilizing the
high charge mobility. Moreover, carbazole derivatives
are used as light-emitting layers because they are
thermally stable and show blue photo- and electrolu-
minescence due to the large band gap of the biphenyl
unit and planarity improved by the bridging nitrogen
atom.2 Meanwhile, poly(aryleneethynylenes) (PAEs)
are known as typical conjugated polymers, which pos-
sess conductivity, nonlinear optical properties, fluores-
cence, and so on.3 Especially with respect to lumines-
cence, the rigid structure reduces nonradiative decay,
leading to high fluorescence quantum yields. In fact,
some PAEs show almost quantitative fluorescence quan-
tum yields.4 Although PAEs containing carbazole units
in the main chain are expected as light-emitting poly-
mers, the reports concerning them5 are fewer than those
of poly(arylenevinylenes).6 This paper deals with the
synthesis of carbazole-containing PAEs and character-
ization of their basic properties, where the arylene units
are para- and meta-linked phenylene, biphenylene,
anthracenylene, thiazolylene, phenazinylene, and fer-
rocenylene (Scheme 1). We also describe the synthesis
and characterization of polymers whose carbazole is
linked by an imine group.7
Exp er im en ta l Section
Mea su r em en ts. 1H and 13C NMR spectra were recorded
on a J EOL EX-400 spectrometer using tetramethylsilane as
an internal standard. IR, UV-vis, and fluorescence spectra
were measured on Shimadzu FTIR-8100, J ASCO V-550, and
JASCO FP750 spectrophotometers, respectively. Melting points
were measured by a Yanaco micro-melting point apparatus.
Elemental analysis was carried out at the Kyoto University
Elemental Analysis Center. The sensitivity and detecting limit
of the elemental analysis is 0.3%. High-resolution mass spectra
were recorded on a J EOL J MS-HX110A or a J MS-SX102A
spectrometer. The number- and weight-average molecular
weights (Mn and Mw) of polymers were determined by gel
permeation chromatography on a J ASCO GULLIVER system
(PU-980, CO-965, RI-930, and UV-1570) equipped with poly-
styrene gel columns (Shodex columns K804, K805, and J 806),
using CHCl3 as an eluent at a flow rate of 1.0 mL/min,
calibrated by polystyrene standards at 40 °C. MALDI-TOF
mass spectrometry was performed on a PerSeptive Biosystems
Voyager DE-STR equipped with a 337 nm nitrogen laser.
* Corresponding authors. E-mail: sanda@adv.polym.kyoto-
u.ac.jp and masuda@adv.polym.kyoto-u.ac.jp. Telephone: +81-75-
383-2589. Fax: +81-75-383-2590.
10.1021/ma049391i CCC: $27.50 © 2004 American Chemical Society
Published on Web 09/03/2004

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Macromolecules, Vol. 37, No. 20, 2004
Poly(aryleneethynylenes) and Poly(aryleneimines) 7579
Ta ble 1. P olycon d en sa tion of N-Alk yld ieth yn ylca r ba zoles
Thermal gravimetric analysis was carried out with a Perkin-
Elmer Pyris 1 TGA.
w ith Dih a loa r en esa
Ma ter ia ls. Unless otherwise stated, reagents were pur-
chased and used as received. The solvents used for polymer-
ization were purified by standard methods. N-Dodecyl-3,6-
diformylcarbazole,8 1,4-dibutyl-2,5-diiodobenzene,9 1,4,6,9-
tetrahexyl-2,7-diiodophenazine,10 and 1,1′-diiodoferrocene11
were synthesized according to the literature.
monomer
polymer
c
c
run
1
2
3
yieldb (%)
Mw
Mw/Mn
1
1A
1B
1B
1B
1B
1B
1A
1A
1C
2a
2b
2c
2d
2e
2f
2g
2h
2h
3a
3b
3c
3d
3e
3f
3g
3h
3h ′
60
100
74
83
81
97
100
86
9200e
3100e
6500e
33700f
4500
5800
7800e
5600e
g
1.5e
2.8e
1.8e
3.4f
1.3
2d
3d
4d
5d
6d
7
N-Octyl-3,6-d ieth yn ylca r ba zole. The title compound was
synthesized according to the modified method referring to the
literature.12 3,6-Dibromocarbazole (7.0 g, 42 mmol) and 1-bro-
mooctane (8.1 g, 22 mmol) were dissolved in tetrahydrofuran
(THF)/N,N-dimethylformamide (DMF) (80 mL, 3:1, volume
ratio) at room temperature. After washed with hexane, NaH
(1.0 g, 42 mol) was slowly added to the solution. The resulting
mixture was stirred at room temperature for 1 day, and then
methanol (30 mL) was added to the mixture to quench the
reaction. The solvents were removed under reduced pressure,
CH2Cl2 was added to the residue, and then the mixture was
washed with 2 M HCl twice and water, dried over MgSO4, and
filtered. The obtained solution was concentrated by rotary
evaporation and poured into a large amount of methanol to
precipitate N-octyl-3,6-dibromocarbazole as a white solid. It
was collected by filtration and used in the next step without
further purification.
A mixture of N-octyl-3,6-dibromocarbazole (6.6 g, 15 mmol),
CuI (98 mg, 1.1 mmol), PdCl2(PPh3)2 (365 mg, 0.5 mmol), PPh3
(179 mg, 0.7 mmol), trimethylsilylacethylene (8.0 mL, 58
mmol), and i-Pr2NH (220 mL) was stirred with refluxing for
24 h. The solvent was distilled off by rotary evaporation, and
the residue was extracted with Et2O. The solution was dried
over MgSO4, filtered, and concentrated. The resulting solution
was subjected to silica gel column chromatography (eluent:
hexane/CH2Cl2 ) 8/1, volume ratio). From the third band,
N-octyl-3,6-bis(trimethylsilylethynyl)carbazole was obtained as
oil, which was used in the next step as it was.
1.6
1.4e
1.7e
g
8
9
100
a
[1]0 ) [2]0 ) 50 mM, [CuI] ) [Pd(PPh3)4] ) 2 mM, at 80 °C,
b
72 h in i-Pr2NH. MeOH-insoluble part. c Determined by GPC
d
(CHCl3, PSt). In i-Pr2NH/THF (1:2, volume ratio). e The polymer
was partly insoluble in CHCl3. The GPC data of the CHCl3-soluble
part are shown here. f Bimodal. Could not be determined.
g
Ta ble 2. P olycon d en sa tion of
N-Dod ecyl-3,6-d ifor m ylca r ba zole w ith
P h en ylen ed ia m in esa
monomer
polymer
c
c
run
1
2
3
yieldb (%)
Mw
Mw/Mn
1
2
1D
1D
2i
2j
3i
3j
82
79
2700
6600
1.8
2.1
a
[1]0 ) [2]0 ) 0.24 M, [LiCl] ) 0.5 M, at rt, 24 h in NMP/HMPA
(4:1). MeOH-insoluble part. c Estimated by GPC (CHCl3, PSt).
b
N-Octadecyl-3,6-diethynylcarbazole (117 mg, 0.25 mmol), 1,4-
diiodobenzene (83 mg, 0.25 mmol), CuI (2.2 mg, 0.01 mmol),
and Pd(PPh3)4 (13.3 mg, 0.01 mmol) were added to i-Pr2NH (5
mL), and the resulting mixture was stirred at 80 °C for 72 h.
i-Pr2NH was removed from the mixture by evaporation, and
then the obtained material was washed with water, dissolved
in a small amount of CHCl3, and poured into a large amount
of methanol to precipitate a polymer. It was filtered and dried
under reduced pressure. Yield 60%. Runs 2-9 in Table 1 were
conducted in a similar manner. The polycondensation of
diformylcarbazole with phenylenediamines was conducted as
follows.14 N-Dodecyl-3,6-diformylcarbazole (180 mg, 0.45 mmol),
para-phenylenediamine (49 mg, 0.45 mmol), and LiCl (40 mg,
0.95 mmol) were added to N-methylpyrrolidinone (NMP)/
hexamethylphosphoramide (HMPA) (2 mL, 4:1, volume ratio)
in a two-necked 50 mL glass flask under nitrogen, and the
resulting mixture was stirred at room temperature for 24 h.
A small amount of CHCl3 was added to the mixture, and it
was poured into a large amount of methanol/water (1:1, volume
ratio) to precipitate a polymer. It was filtered and dried under
reduced pressure. Yield 82%. Run 2 in Table 2 was conducted
in a similar manner.
A solution of N-octyl-3,6-bis(trimethylsilylethynyl)carbazole
(2.0 g, 4.1 mmol) in THF/methanol (24 mL, 3:1, volume ratio)
was added to a 1 M tetrabutylammonium fluoride solution (12
mL) at room temperature. The resulting solution was stirred
overnight, and water was added to the solution. It was
extracted with CH2Cl2, and the organic layer was concentrated
and purified by silica gel column chromatography (eluent:
hexane/CH2Cl2 ) 5/1, volume ratio) to obtain the title com-
pound, which solidified in 1 day. Yield 1.0 g (3.0 mmol); mp
69-70 °C. 1H NMR (CDCl3, δ): 060-0.80 (m, 15H) 3.06 (s,
2H), 4.05 (t, J ) 7.6 Hz, 2H), 7.17 (d, J ) 8.8 Hz 2H), 7.51 (d,
J ) 6.8 Hz, 2H), 8.11 (s, 2H). IR (neat): 3308, 2955, 2105,
1597, 808 cm-1
29.6, 29.8, 32.3, 43.8, 75.9, 85.2, 109.4, 113.1, 122.7, 125.2,
.
13C NMR (CDCl3, δ): 14.6, 23.1, 27.7, 29.4,
130.6, 141.1. Mass (m/z): Calcd for
C24H25N: 327.1987.
Found: 327.1989 [M+].
N-Dod ecyl-3,6-d ieth yn ylca r ba zole. It was synthesized in
a manner similar to the product mentioned above, starting
from 1-bromododecane instead of 1-bromooctane. Mp: 51-53
°C. 1H NMR (CDCl3, δ): 0.80-1.90 (m, 23H), 3.08 (s, 2H), 4.27
(t, J ) 7.2 Hz, 2H), 7.33 (d, J ) 26.4 Hz, 2H), 7.60 (d, J ) 8.8
Hz, 2H), 8.22 (s, 2H). 13C NMR (CDCl3, δ): 14.1, 22.7, 27.2,
28.8 29.3, 29.5, 29.5, 29.6, 31.9, 43.2, 75.4, 84.7, 108.9, 112.6,
122.1, 124.7, 130.0, 140.5. IR (KBr): 3274, 2923, 2105, 1597,
1483, 806 cm-1. Anal. Calcd for C28H33N: C, 87.68; H, 8.67;
N, 3.65. Found: C, 87.71; H, 8.74; N, 3.50.
Sp ectr oscop ic Da ta of th e P olym er s. 3a 1H NMR
(CDCl3, δ): 0.87 (t, J ) 8.0 Hz, 3H), 1.01-2.41 (m, 32H), 4.28
(s, 2H), 7.09-8.30 (m, 10H). IR (neat): 2924, 2853, 1597, 1510,
1485, 1286, 804 cm-1. 3b 1H NMR (CDCl3, δ): 0.77-1.90 (m,
23H) 4.30 (s, 2H), 6.85-8.37 (m, 14H). IR (KBr): 2920, 2849,
2105, 1593, 1480, 1283, 804 cm-1. 3c 1H NMR (CDCl3, δ):
0.65-1.97 (m, 23H), 3.82-4.35 (m, 2H), 6.65-8.86 (m, 14H).
IR (KBr): 2924, 2853, 2191, 1597, 1489, 804 cm-1. 3d 1H NMR
(CDCl3, δ): 0.80-2.30 (m, 37H), 3.06 (s, 2H), 4.35 (m, 2H),
7.17-8.60 (m, 8H. IR (neat): 2955, 2926, 2855, 1597, 1497,
1482, 804 cm-1. 3e 1H NMR (CDCl3, δ): 0.80-1.90 (m, 23H),
4.05 (m, 2H), 7.03-8.22 (m, 10H). IR (neat): 2924, 2853, 2208,
N-Octa d ecyl-3,6-d ieth yn ylca r ba zole. It was synthesized
in a manner similar to the product mentioned above, starting
from 1-bromooctadecane instead of 1-bromooctane. Mp: 53-
1
54 °C. H NMR (CDCl3, δ): 0.80-1.90 (m, 35H), 3.11 (s, 2H),
1
4.29 (t, J ) 6.8 Hz, 2H), 7.35 (d, J ) 8.8 Hz, 2H), 7.62 (d, J )
8.0 Hz, 2H), 8.21 (s, 2H). 13C NMR (CDCl3, δ): 13.8, 22.4, 26.9,
28.6, 29.0, 29.0, 29.1, 29.2, 29.3, 29.3, 29.3, 29.4, 31.6, 43.0,
75.1, 84.4, 108.6, 112.3, 121.8, 124.4, 129.7, 140.2. IR (KBr):
3312, 2924, 2853, 2106, 1597, 1482, 806 cm-1. Mass (m/z):
Calcd for C34H45N: 467.3552. Found: 467.3551 [M+].
2105, 1859, 1489,1215, 884, 806 cm-1. 3f H NMR (CDCl3, δ):
0.74-2.55 (m, 23H), 4.02-4.51 (m, 2H), 7.21-8.45 (m, 7H).
IR (KBr): 2924, 2853, 2205, 1595, 1483, 1287, 806 cm-1. 3g
1H NMR (CDCl3, δ): 0.80-1.90 (m, 69H), 3.20-3.65 (m, 8H),
4.30 (s, 2H), 7.18-8.19 (m, 8H). IR (KBr): 2955, 2924, 2853,
2201, 1595, 804 cm-1. 3h 1H NMR (CDCl3, δ): 0.51-2.62 (m,
35H), 3.15-4.95 (m, 10H), 6.61-8.70 (m, 6H). IR (KBr): 2924,
2853, 806 cm-1. 3h ′ IR (KBr): 2205, 1595, 804 cm-1. 3i 1H
NMR (CDCl3, δ): 0.80-1.92 (m, 23H), 4.35 (m, 2H), 6.50-8.74
P olycon d en sa tion (Typ ica l P r oced u r e). The polycon-
densation of diethynylcarbazoles with dihaloarenes was con-
ducted in a two-necked 50 mL glass flask under nitrogen.13

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7580 Takihana et al.
Macromolecules, Vol. 37, No. 20, 2004
Ta ble 3. Solu bility of th e P olym er sa
solventb
polymer acetone MeOH THF CH2Cl2 CHCl3 toluene hexane
3a
3b
3c
3d
3e
3f
3g
3h
3h ′
3i
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
+
+
+
+
-
-
-
-
-
-
-
-
-
-
-
+
+
+
+
+
+
+
+
++
++
++
+
++
++
++
+
++
++
++
+
++
++
++
+
+
-
++
++
+
-
++
++
+
-
++
++
+
-
++
++
3j
a
b
Polymer 1 mg in solvent 1 mL. Symbols: ++, soluble; +,
partly soluble; -, insoluble.
Ta ble 4. Op tica l P r op er ties of th e P olym er s Mea su r ed in
CHCl3
a
polymer
λAbs (nm)
320, 359
320, 357
461
λE,max (nm)
Φ (%)
3a
3b
3c
3d
3e
3f
3g
3h
3i
403b
409c
522
403
398d
466e
522
f
86
73
28
45
10
45
5.8
f
362
313, 344
319, 365, 382
310
308
388
F igu r e 1. MALDI-TOF mass spectrum of 3d .
(m, 11H). IR (KBr): 2923, 2851, 1612, 1595, 810 cm-1. 3j 1H
NMR (CDCl3, δ): 0.80-1.92 (m, 23H), 4.35 (m, 2H), 6.50-8.74
409
433
0.8
1.0
3j
351
(m, 11H). IR (KBr): 2924, 2853, 1612, 1593, 810 cm-1
.
a
b
Excited at the absorption maxima. Excited at 320 nm.
c Excited at 357 nm. Excited at 313 nm. e Excited at 365 nm.f Not
determined.
d
Resu lts a n d Discu ssion
P olycon d en sa tion . Table 1 summarizes the results
of the polycondensation of N-alkyldiethynylcarbazoles
with dihaloarenes catalyzed by a mixture of CuI and
Pd(PPh3)4. The proceeding of the Sonogashira coupling
was confirmed by disappearance of the signal at 3.1 ppm
(Table 3). This fact shows that the length of N-alkyl
group is important for solubility of the polymers.
Incorporation of butyl group on the phenylene moiety
was also effective in enhancing the solubility (3a vs 3d ).
The polymers with para-arylene structures, 3a , 3b, and
3c, were only partly soluble, while the polymers with
meta-arylene and thiazole structures, 3e and 3f, were
completely soluble. It seems that polymers with twisted
main chains are more soluble than those with straight
ones.
Table 4 summarizes the optical properties of the
polymers, and Figure 2 shows the UV-vis spectra of
ethynylene-type polymers 3a -h measured in CHCl3
solution. All the polymers exhibited absorption peaks
at 310-320 nm, which originate from the carbazole
units and are red-shifted compared to 1A (λ ) 290 nm).
This fact suggests the extension of conjugation length
of the polymers. The absorption at 461 nm of 3c is
attributable to the anthracene moiety.17 We can say that
3a with para-structure is more conjugated than 3e with
meta-structure judging from the UV-vis absorption
wavelength.
Figure 3 depicts the fluorescence spectra of ethy-
nylene-type polymers (3a -g) excited at the absorption
maxima. The concentrations of the sample solutions
were set so that the absorbance at the excited wave-
length stayed in the range from 0.05 to 0.1. Strong
emission was observed at the blue-green region. In
particular, para-phenylene polymer 3a and biphenylene
polymer 3b showed very high fluorescence quantum
yields (86 and 73%, respectively). On the contrary, the
quantum yield of phenazinylene polymer 3g was as low
as 6%, like other phenazine-containing polymers.10 The
emission at 522 nm of 3c seems to be based on the
anthracene unit.17 On the contrary to para-phenylene
1
in the H NMR spectrum and the peak at 3273 cm-1 in
the IR spectrum due to monosubstituted alkyne ob-
served in the corresponding monomers. Polymers with
Mw ) 3100-33 700 were obtained in good yields.15 The
molecular weight of the polymer in run 9 could not be
measured because it was insoluble in common organic
solvents. Polymer 3d exhibited a bimodal GPC trace,
whose peak top molecular weights were 30 000 and 3000
(run 4 in Table 1). We measured the MALDI-TOF mass
spectrum of 3d to reveal the component of the low-
molecular-weight peak as shown in Figure 1. The
signals at 1708.41, 2277.94, 2846.78, and 3415.51 m/z
can be assigned to cyclic trimer, tetramer, pentamer,
and hexamer, respectively, judging from the agreement
between the theoretical and observed values.16 The
signals at 1521.00, 2090.81, 2660.58, and 3228.46 m/z
can be assigned to linear oligomers, which have carba-
zole units in both ends. The halogen content of polymer
determined by elemental analysis was negligible, which
supports the formation of cyclic oligomers and linear
polymers with carbazole terminals.
Table 2 summarizes the results of the polycondensa-
tion of N-dodecyl-3,6-diformylcarbazole 1D with para-
and meta-phenylenediamines 2i and 2j using lithium
chloride as a dehydration agent. Polymers with Mw
2700 and 6600 were obtained in 82 and 79% yields,
respectively.
)
P olym er P r op er ties. Polymer 3h ′ having an N-octyl
group was insoluble in common organic solvents, in
contrast to 3h having an N-octadecyl group, which was
partly soluble in THF, toluene, CH2Cl2, and CHCl3

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Macromolecules, Vol. 37, No. 20, 2004
Poly(aryleneethynylenes) and Poly(aryleneimines) 7581
F igu r e 4. Excitation spectra of 3d monitored at 403 and 485
nm, measured in CHCl3.
F igu r e 2. UV-vis spectra of ethynylene-type polymers
measured in CHCl3 (c ) 8.0 × 10-7-1.7 × 10-5 M). (a) 3a -e,
(b) 3f-h .
F igu r e 5. UV-vis (a) and PL (b) spectra of 3d measured as
film and CHCl3 solutions.
F igu r e 3. PL spectra of ethynylene-type polymers 3a -g
measured in CHCl3 (c ) 8.0 × 10-7-2.1 × 10-6 M).
spectroscopic pattern on the sample concentration and
state. The relative intensity of the emission at longer
wavelength became larger with the sample concentra-
tion and especially obvious in the film state. There was
little difference in the absorption spectra between the
solution and film ones, which suggests the ground states
are almost the same (Figure 5). These findings lead to
the idea that the emission of longer wavelength is due
to the formation of excimers.18
The fluorescence spectra of other polymers 3b, 3e, and
3f were also measured in the film state (Figure 6). The
relative intensities of the peaks at 500-600 nm to those
at shorter wavelength were larger in film than in
solution like the case of 3d . It is assumed that these
polymers also form excimers in the solid state.
polymer 3a , the quantum yield of meta-phenylene
polymer 3e was as low as 10%. It is likely that the meta-
linked polymer 3e is less rigid than the para-linked 3a ,
resulting in the low quantum yield due to nonradiative
decay.
We paid attention to 3d because it showed two kinds
of fluorescence peaks: a sharp one at 403 nm and a
broad one at longer wavelength region. First, its excita-
tion spectra for the emissions at 403 and 485 nm were
measured in order to confirm whether the broad emis-
sion is due to a different fluorophore or not as shown in
Figure 4. Since both spectra were similar to each other,
we can conclude that the broad emission band is based
on carbazole. We next checked the dependence of the