3,3'-Bicarbazolyl-containing oxirane and its reaction products as new glass-forming electroactive materials

Article abstract of DOI:10.1080/15421400802462938

Low-molar-mass oxiranyl-substituted 3,3'-bicarbazolyl derivatives were synthesized by the reaction of 3,3'-bicarbazolyl-containing oxirane with dimercapto compounds as linking agents. The cationic ring opening polymerization of oxirane monomers was performed using ytterbium (III) trifluoromethanesulfonate [Yb(OTf)3] as a cationic initiator to obtain polyether. The full characterization of the compounds by mass spectrometry, IR, 1H NMR, and 13C NMR is presented. All the compounds represent amorphous materials with glass transition temperatures ranging from 28C to 112C and with 5%-weight-loss temperatures exceeding 308C. The electron photoemission spectra of the materials were recorded, and the ionization potentials of ca. 5.5eV were established. Time-of-flight hole drift mobilities of the amorphous films of some synthesized compounds exceed 10-5cm2/Vs at high electric fields.

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3,3′-Bicarbazolyl-Containing
Oxirane and its Reaction
Products as New Glass-Forming
Electroactive Materials
a
b
V. Vaitkeviciene , J. V. Grazulevicius & V.
c
Jankauskas
a
Nuclear Engineering Laboratory, Lithuanian Energy
Institute, Breslaujos, Kaunas, Lithuania
b
Department of Organic Technology, Kaunas
University of Technology, Kaunas, Lithuania
c
Department of Solid State Electronics, Vilnius
University, Vilnius, Lithuania
Version of record first published: 10 Jun 2010.
To cite this article: V. Vaitkeviciene , J. V. Grazulevicius & V. Jankauskas (2008):
3
,3′-Bicarbazolyl-Containing Oxirane and its Reaction Products as New Glass-Forming
Electroactive Materials, Molecular Crystals and Liquid Crystals, 497:1, 241/[573]-253/
585]
[
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Mol. Cryst. Liq. Cryst., Vol. 497, pp. 241=[573]–253=[585], 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400802462938
0
Products as New Glass-Forming Electroactive Materials
3
,3 -Bicarbazolyl-Containing Oxirane and its Reaction
1
2
V. Vaitkeviciene , J. V. Grazulevicius ,
3
and V. Jankauskas
Nuclear Engineering Laboratory, Lithuanian Energy Institute,
1
Breslaujos, Kaunas, Lithuania
2
Department of Organic Technology, Kaunas University of Technology,
Kaunas, Lithuania
3
Department of Solid State Electronics, Vilnius University,
Vilnius, Lithuania
0
Low-molar-mass oxiranyl-substituted 3,3 -bicarbazolyl derivatives were synthesized
0
by the reaction of 3,3 -bicarbazolyl-containing oxirane with dimercapto compounds
as linking agents. The cationic ring opening polymerization of oxirane monomers
was performed using ytterbium (III) trifluoromethanesulfonate [Yb(OTf)
3
] as a catio-
nic initiator to obtain polyether. The full characterization of the compounds by mass
1
13
spectrometry, IR, H NMR, and C NMR is presented. All the compounds represent
ꢀ
ꢀ
amorphous materials with glass transition temperatures ranging from 28 C to 112 C
ꢀ
and with 5%-weight-loss temperatures exceeding 308 C. The electron photoemission
spectra of the materials were recorded, and the ionization potentials of ca. 5.5 eV were
established. Time-of-flight hole drift mobilities of the amorphous films of some synthe-
ꢁ5
2
sized compounds exceed 10 cm =Vs at high electric fields.
Keywords: bicarbazolyl; glass transition; hole drift mobility; ionization potential; oxiranyl
1. INTRODUCTION
Poly[9-(2,3-epoxypropyl)carbazole] (PEPK) is apparently one of the
most thoroughly studied and most widely used compounds among
Financial support of this research by the Lithuanian State Science and Studies
Foundation is gratefully acknowledged. Habil. Dr. V. Gaidelis from the Department of
Solid State Electronics, Vilnius University is thanked for the data of ionization potential
measurements.
Address correspondence to J. V. Grazulevicius, Department of Organic Technology,
Kaunas University of Technology, 19, Radvilenu Pl., Kaunas LT-50254, Lithuania.
E-mail: juozas.grazulevicius@ktu.lt
241=[573]

2
42=[574]
V. Vaitkeviciene et al.
carbazolyl-containing photoconductors [1,2]. High-molar-mass PEPK
exhibits one of the highest hole mobilities among the photoconductive
polymers with pendant photoactive groups [3,4]. Synthesis of low-
molar-mass organic glass-forming photoconductors by the reactions of
carbazolyl-containing glycidyl ethers with different bifunctional com-
pounds such as aromatic diols, dimercaptanes, and the derivatives of ani-
line has been reported in the literature [5,6]. Till recently, no such work
0
has been done with 3,3 -bicarbazolyl-containing oxiranes. The aim of this
work was the synthesis and investigation of properties of the oxiranyl-
0
substituted 3,3 -bicarbazolyl derivative and of the compounds prepared
by the reaction of oxirane with dimercapto compounds as linking
agents. The cationic ring opening polymerization of 9-(2-ethylhexyl)-3-
[9-(oxiran-2-ylmethyl)carbazol-3-yl]carbazole using ytterbium (III) tri-
fluoromethanesulfonate [Yb(OTf) ] as a cationic initiator is reported as
3
well. Lanthanide triflates are commercially available cationic initiators
and have many advantages over BF derivatives and other Lewis acids,
3
since they do not require expensive anhydrous solvents [7,8].
2. EXPERIMENTAL
2.1. Instrumentation
1
13
H NMR and C NMR spectra were recorded, by using Varian Unity
Inova and JOEL JNM- FX 250 apparatus. Mass spectra were obtained
on a Waters ZQ 2000 spectrometer. FTIR spectra were recorded using
a Perkin Elmer FT-IR System. UV spectra were measured with a
TM
Spectronic Genesys 8 spectrometer. Fluorescence (FL) spectra were
recorded with an MPF-4 spectrometer. Differential scanning calori-
metry (DSC) measurements were carried out using a Perkin Elmer
Pyris Diamond calorimeter. Thermogravimetric analysis (TGA) was
performed on a Netzsch STA 409. The TGA and DSC curves were
ꢀ
recorded in a nitrogen atmosphere at a heating rate of 20 C=min
and 10 C=min, respectively.
ꢀ
The ionization potentials of layers of the compounds synthesized
were measured by the electron photoemission method in air, as was
described earlier [9,10]. The samples for the ionization potential
measurement were prepared as described previously [11].
The charge drift mobilities were measured by the xerographic time-
of-flight technique [12]. The samples for the charge carrier mobility
measurements were prepared by casting the pure material or mix-
tures in the weight proportion 1:1 with polycarbonate-Z (PC-Z) on
polyester films with an Al layer. The thickness of the charge transport
layer varied in an interval of 5–9 mm.

0
Oxiranyl-Substituted 3,3 -Bicarbazolyl and its Reaction Products
243=[575]
2.2. Materials
Carbazole, 3-chloro-1,2-epoxypropane, 1-bromo-2-ethylhexane, 1,3-
0
benzenedithiol, 4,4 -thiobisbenzenethiol and [Yb(OTf)3] were
purchased from Aldrich and used as-received.
0
9
-(2-Ethylhexyl)-3,3 -bicarbazolyl (2) and 9-(2-ethylhexyl)-3-[9-(2-
ethylhexyl)-9H-carbazol-3-yl]-9H-carbazole (Di(EtHexCz)) were pre-
0
pared by alkylation of 3,3 -bicarbazolyl (1) in the presence of a phase
transfer catalyst [13]. The key starting material 1 was obtained by
chemical oxidation of carbazole in the presence of FeCl [14].
3
9-(2-Ethylhexyl)-3-[9-(oxiran-2-ylmethyl)carbazol-3-yl]carbazole (3)
(
FW ¼ 500 g=mole) was prepared by the procedure similar to that ear-
lier described in the literature [5]. Compound 2 (2.0 g, 4.51 mmole) was
dissolved in 15.31 g of 3-chloro-1,2-epoxypropane under mild heating.
Potassium hydroxide (1.0 g, 17.82 mmole) was added to the reaction
mixture in three portions. Sodium sulfate (1.2 g, 8.45 mmole) was
added additionally before every addition of potassium hydroxide into
ꢀ
the flask. The reaction mixture was stirred for 3 h at 30 C. It was fil-
trated and then 3-chloro-1,2-epoxypropane was removed by vacuum
distillation. After the distillation, the product was subjected to chro-
matography using the mixture of ethyl acetate and hexane in a volume
ratio of 15:1 as an eluent. The yield of 1.52 g (68%) of brownish
þ
þ
material was obtained. MS (APCI , 20 V), m=z: 501 ([M þ H] ,
1
1
2
00%). H NMR (300 MHz, CDCl , d, ppm): 8.46 (split s, J ¼ 1.5 Hz,
3
0
0
H, H-4, H-4 ), 8.26 (d, J ¼ 2.4 Hz, 1H, H-5 ), 8.23 (d, J ¼ 2.4 Hz, 1H,
0
0
H-5), 7.92–7.85 (m, 2H, H-2, H-2 ), 7.62–7.45 (m, 6H, H-1, H-1 , H-7,
0
0
0
3
H-7 , H-8, H-8 ), 7.37–7.28 (m, 2H, H-6, H-6 ), 4.72 (dd, J ¼ 3.3 Hz,
cis
2
JAB ¼ 15.3 Hz, 1H, one of >NꢁCH -protons, >CH ), 4.48 (dd,
2
B
3
2
J
¼ 4.8 Hz, J ¼ 16.2 Hz, 1H, another >NꢁCH -proton, >CH ),
trans
AB
2
A
3
2
4
1
.26 (dd, J ¼ 7.5 Hz, J ¼ 2.1 Hz, 2H, >NꢁCH ꢁ), 3.48–3.40 (m,
3 2
0
HH
HH
2
H, >NꢁCH ꢁCHꢁOꢁ), 2.88 (dd, J ¼ 3.9 Hz, J
¼ 4.8 Hz, 1H,
2
cis
A M
3
one of ꢁOꢁCH -protons, >CH ), 2.65 (dd,
J
¼ 2.4 Hz, J
0
A M
¼
2
M
trans
4
.8 Hz, 1H, ꢁOꢁCH -another proton, >CH
0
), 2.24–2.12 (m, 1H,
2
A
>
NꢁCH ꢁCH<), 1.56–1.28 (m, 8H, ꢁ(CH ꢁCH ) ꢁCH ꢁCH ꢁCH ꢁ
2
2
3
2
2
2
13
CH ), 1.04–0.9 (m, 6H, ꢁCH ). C NMR (75.4 MHz, CDCl , d, ppm):
3
3
3
1
1
1
4
1
1
41.65, 141.42, 140.06, 140.35, 134.29, 133.36, 126.26, 126.10, 125.93,
25.74, 123.87, 123.61, 123.51, 123.25, 120.75, 120.66, 119.68, 119.52,
19.13, 119.01, 109.45, 109.35, 109.29, 109.16, 50.95, 47.78, 45.64,
4.95, 39.75, 31.29, 29.15, 24.69 ( >CHꢁ(CH ꢁCH )), 23.39, 14.38,
2
3
ꢁ1
1.24. IR (KBr window), (in cm ): 3052, 2958, 2922, 2856, 1601,
489, 1379, 1290, 1256, 970, 851, 799, 746, 727. Elemental analysis
for C H N O: % Calc.: C 83.96, H 7.25, N 5.59, O 3.20; % Found:
3
5
36
2
C 84.02, H 7.26, N 5.60.

2
44=[576]
V. Vaitkeviciene et al.
Poly{oxy[2-({[9-(2-ethylhexyl)carbazol-3-yl]carbazol-9-yl}methyl)
ethylene]} (4). Compound 3 (0.5 g, 0.999 mmole) was polymerized in 3 ml
of CH Cl in the presence of the catalyst ytterbium(III) trifluoro-
2
2
methane sulfonate (Yt(TfO) ) (0.06 g, 0.1 mmole) at reflux temperature
3
under nitrogen atmosphere during 72 h. Polymer 4 was purified by sev-
eral reprecipitations into methyl alcohol, recovered by filtration, and
1
dried. We obtained 0.13 g (26%) of white powder. H NMR (300MHz,
CDCl , d, ppm): 8.5–7.7 (m, 4H, H-4, H-5), 7.6–7.0 (m, 10H, Ht), 4.6–
3
3
2
.95 (m, 4H, >NꢁCH ꢁ), 3.85–3.4 (m, 2H, ꢁOꢁCH ꢁ), 2.2–1.9 (m,
2
2
H, >NꢁCH ꢁCHꢁ), 1.56–1.10 (m, 8H, ꢁ(CH ꢁCH )ꢁCH ꢁCH ꢁ
2
2
3
2
2
1
3
CH ꢁCH ), 1.04–0.8 (m, 6H, ꢁCH ). C NMR (75.4 MHz, CDCl , d,
2
3
3
3
ppm): 141.49, 140.36, 134.26, 133.35, 126.21, 126.14, 125.93, 125.78,
1
7
23.90, 123.56, 123.50, 123.28, 120.69, 119.66, 119.15, 109.50, 109.37,
5.02, 69.24, 47.80, 39.76, 31.32, 29.16, 24.71, 23.41, 14.41, 11.25. IR
ꢁ1
(
KBr window), (in cm ): 3551, 3049, 2956, 2927, 2870, 1600, 1459,
1
379, 1330, 1216, 1204, 799, 746, 727.
Bis[4-({3-[9-(2-ethylhexyl)carbazol-3-yl]carbazol-9-yl}-2-hidroxyprop-1-
yl-thio)phenyl]sulfide (5) (FW ¼ 1250 g=mole). Three drops of triethy-
lamine were added to the solution of 3 (0.9 g, 1.798 mmole) and
0
4
,4 -thiobisbenzenethiol (0.21 g, 0.84 mmole) in 10 ml of dry THF
under the nitrogen atmosphere. The reaction mixture was kept below
ꢀ
6
0 C over night. After evaporation of the solvent, the residue was
subjected to chromatography using the mixture of ethyl acetate
and hexane in a volume ratio of 1:7 as an eluent. The yield of yel-
þ
lowish powder was 0.52 g (50%). MS (APCI , 20 V), m=z: 1251
þ
1
(
[M þ H] , 98%). H NMR (300 MHz, CDCl , d, ppm): 8.43 (s, 4H,
3
0
0
H-4, H-4 ), 8.21 (d, J ¼ 7.8 Hz, 4H, H-5, H-5 ), 7.83 (dd,
3
4
0
JHH ¼ 8.4 Hz, JHH ¼ 1.5 Hz, 4H, H-2, H-2 ), 7.55 ꢁ 7.4 (m, 12H,
0
0
0
0
H-1, H-1 , H-7, H-7 , H-8, H-8 ), 7.34 ꢁ 7.25 (m, 4H, H-6, H-6 ),
7
4
4
.21 (d, J ¼ 3 Hz, 8H, Ph), 4.58–4.4 (m, 4H, >NꢁCH ꢁCHOHꢁ),
3 2
2
.36–4.26 (m, 2H, >CHꢁOH), 4.22 (dd, J ¼ 6 Hz, J ¼ 2.1 Hz,
HH
HH
H, >NꢁCH ꢁCH<), 3.2–2.98 (m, 4H, ꢁSꢁCH ꢁ), 2.44 (d, 2H,
2
2
J ¼ 3.6 Hz, >CHꢁOH), 2.2–2.08 (m, 2H, >NꢁCH ꢁCH<), 1.52–
2
1
1
1
1
1
6
1
2
7
6
.24 (m, 16H, ꢁ(CH ꢁCH )ꢁCH ꢁCH ꢁCH ꢁCH ), 1.02–0.88 (m,
2
3
2
2
2
3
13
2H, ꢁCH ). C NMR (75.4 MHz, CDCl , d, ppm): 141.62, 141.40,
3
3
40.34, 140.00, 139.94, 134.34, 134.21, 133.23, 131.87, 130.54,
26.26, 126.07, 125.94, 125.71, 123.90, 123.61, 123.54, 123.22,
20.79, 120.66, 119.72, 119.24, 119.14, 119.01, 109.49, 109.36,
9.38, 48.14, 47.74, 39.72, 39.10, 31.29, 29.12, 24.68, 23.36, 14.39,
ꢁ1
1.21. IR (KBr window), (in cm ): 3535, 3049, 2956, 2925, 2870,
855, 1628, 1600, 1575, 1472, 1459, 1330, 1256, 1214, 798, 745,
27. Elemental analysis for C H N O S : % Calc.: C 78.68, H
8
2
82
4
2 3
.60, N 4.48, O 2.56, S 7.68; % Found: C 78.57, H 6.57, N 4.53.

0
Oxiranyl-Substituted 3,3 -Bicarbazolyl and its Reaction Products
245=[577]
1,3-Bis(4-{3-[9-(2-ethylhexyl)carbazol-3-yl]carbazol-9-yl}-2-hydroxy-
prop-1-yl-thio)benzene (6) (FW ¼ 1142 g=mole) was synthesized by the
same procedure as compound 5, only 1,3-benzenethiol (0.06 g,
0
0
.42 mmole) was used instead of 4,4 -thiobisbenzenethiol. After evap-
oration of the solvent, the residue was subjected to chromatography
using the eluent mixture of ethyl acetate and hexane in a volume ratio
þ
of 1:5. The yield of yellowish powder was 0.29 g (60%). MS (APCI ,
þ
0
1
2
0 V), m=z: 1143 ([M þ H] , 97%). H NMR (300 MHz, CDCl , d,
3
0
ppm): 8.43 (s, 4H, H-4, H-4 ), 8.20 (d, J ¼ 7.2 Hz, 4H, H-5, H-5 ), 7.76
3
4
0
(
dd,
J
¼ 8.0 Hz,
J
¼ 1.5 Hz, 4H, H-2, H-2 ), 7.60 ꢁ 7.35 (m,
HH
HH
0
0
0
0
1
7
4
2
2
2H, H-1, H-1 , H-7, H-7 , H-8, H-8 ), 7.30 ꢁ 7.25 (m, 4H, H-6, H-6 ),
.24–7.10 (m, 4H, Ph), 4.48–4.25 (m, 4H, >NꢁCH ꢁCHOHꢁ), 4.25–
2
.15 (m, 2H, >CHꢁOH), 4.16 (d, J ¼ 6.2 Hz, 4H, >NꢁCH ꢁCH<),
2
.90–2.40 (m, 4H, ꢁSꢁCH ꢁ), 2.52 (d, J ¼ 3.6 Hz, 2H, ꢁOH), 2.16–
2
.04 (m, 2H, >NꢁCH ꢁCH<), 1.56–1.24 (m, 16H, ꢁ(CH ꢁCH )ꢁ
2
2
3
13
CH ꢁCH ꢁCH ꢁCH ), 1.04–0.80 (m, 12H, ꢁCH ).
C
NMR
2
2
2
3
3
(
75.4 MHz, CDCl , d, ppm): 141.35, 140.07, 139.72, 133.94, 132.87,
3
1
1
2
3
1
29.60, 125.95, 125.77, 125.37, 123.56, 123.34, 122.96, 120.36, 119.41
18.75, 109.19, 109.06, 69.19, 48.00, 47.49, 39.43, 36.62, 31.02,
ꢁ
1
9.68, 28.83, 24.40, 23.06, 14.04, 10.90. IR (KBr window), (in cm ):
370?, 3050, 2957, 2927, 2871, 2858, 1628, 1575, 1560, 1488, 1472,
459, 1342, 1323, 1297, 798, 745, 727. Elemental analysis
for C H N O S : % Calc.: C 79.82, H 6.87, N 4.9, O 2.8, S 5.61;
7
6
78
4
2 2
%
Found: C 79.77, H 6.93, N 4.68.
2
. RESULTS AND DISCUSSION
The synthetic routes to monomer (3), polymer (4), and twin compounds
5 and 6) are shown in Scheme 1. Compound 3 was synthesized by the
(
reaction of 2 with 3-chloro-1,2-epoxypropane in the presence of KOH.
The cationic polymerization of 3 initiated with ytterbium (III)
trifluoromethanesulfonate ([Yt(OTf) ] ¼ 0.1 M) was carried out in a
3
1
,2-dichloroethane solution ([3] ¼ 1.0 M) at the reflux temperature
under nitrogen during 72 h.
The average molecular weights of 4 were estimated by GPC. The
obtained values were M ¼ 1220, M ¼ 2090, with the polydispersity
n
w
index 2.
0
Compound 2 was prepared by alkylation of 3,3 -bicarbazolyl (1). The
key starting material 3,3 -bicarbazolyl (1) was obtained by chemical
0
oxidation of carbazole in the presence of FeCl [14].
3
The reactions of 3 in THF solutions with 1,3-benzenedithiol and
0
ꢀ
4
,4 -thiobisbenzenethiol at 60–65 C in the presence of a catalytic
amounts of TEA yielded twin molecules 5 and 6. In search for the

2
46=[578]
V. Vaitkeviciene et al.
SCHEME 1 Synthetic route to compounds 3, 4, 5, and 6.
optimal solvent for these reactions, they were carried out in the
solvents with different dipole moments, i.e. in 2-butanone and THF
(
Table 1). It was found that the rate of the reaction in THF was higher,
and the higher yields of product 6 were obtained during the shorter
periods of time. In addition, the solubility of 3 in 2-butanone was
very poor.
TABLE 1 Influence of Solvents and Temperature on the Yield of Twin
Compound 6
Reaction
Dipole moment
(25 C), [D]
Product yield,
ꢀ
ꢀ
Solvent
-Butanone
THF
time, [h]
36
temperature, [ C]
[%]
2
2.80
1.74
40
40
40
65
38
40
58
76
4
8
26
8

0
Oxiranyl-Substituted 3,3 -Bicarbazolyl and its Reaction Products
247=[579]
Compounds 5 and 6 were purified by column chromatography. Their
1
structures were confirmed by H NMR-, IR-, and mass spectrometries.
Since a 1,2-epoxypropan-3-yl group was attached, the characteristic
NH stretches were not observed in the IR spectrum of 3. In the synthesis
ꢁ
1
of compounds 4, 5, and 6, the strong IR absorption at 968 cm due to
the 1,2-epoxypropan-3-yl group which is observed in the IR spectrum
of compound 3 disappears completely. The broad IR absorption at
ꢁ
1
3
370–3535 cm due to the hydroxyl group stretching appears in the
spectra of twin compounds 5 and 6. Compounds 3, 4, 5, and 6 show
ꢁ
1
the characteristic absorption of aromatic groups at 3050 cm (CꢁH
ꢁ
1
ꢁ1
stretches), at 1575–1600 cm
and 1459–1488 cm
(CꢁC stretches),
ꢁ
1
and absorption at 1290–1350 cm due to CꢁN stretching.
1
The structures of the synthesized compounds were confirmed by H
NMR spectrometry. The split singlet at 8.46 ppm, ascribed to H-4 of
0
1
3
,3 -bicarbazolyl fragment [14] is observed in the H NMR spectrum
of all the newly synthesized compounds (Fig. 1). The doublets of H-5
0
and H-5 are at 8.26 ppm and 8.23 ppm. It is possible to distinguish
0
the 4th, 5th, and 5 th proton signals not only in the spectrum of the
monomer, but also in the spectrum of polymer 4, where the peaks
1
FIGURE 1 Proton signals in the H NMR spectra (300 MHz, CDCl
of 5, 3, and 4.
3
, d, ppm)

2
48=[580]
V. Vaitkeviciene et al.
0
are broadened due to the side-to-side interaction of 3,3 -bicarbazolyl
monomeric units in macromolecules.
0
The signals of characteristic A MX and ABX systems due to different
CH groups in the 1,2-epoxypropane ring and out of it, respectively,
2
1
appear in the H NMR spectrum of 3. The signals in the 2.85–2.58-ppm
region in the spectra of compound 3 confirm the existence of the character-
0
istic A MX (Dn=J
0
> 12) system in the oxirane ring. The proton signals of
A M
0
A MX and ABX systems of a 1,2- epoxypropan-3-yl group observed in the
spectrum of 3-[9-(2-ethylhexyl)carbazol-3-yl]-9-(oxiran-2-ylmethyl)carba-
zole (3) disappear in the spectrum of oligomer 4 completely.
The signals of protons of a flexible aliphatic bridge connecting
photoconductive fragments are well recognizable in the spectra of 5
1
and 6. As an example, the H NMR spectrum of 5 is given in Figure
1
. Consequently, the above-mentioned protons appear after the reac-
tion of oxirane with dithiol, forming the different environment for
every proton in the alkyl spacer. The signals of the protons which
are near the more electronegative nitrogen atom are shifted towards
the lower fields to the 4.58–4.25-ppm region. The signals of the protons
situated near the sulphur atom appear in the higher fields in the 3.2–
1
2
2
.98-ppm region of the H NMR spectrum of compound 5 and in the
1
.90–2.40-ppm region of the H NMR spectrum of compound 6. The
doublet of O-H groups at 2.37 ppm in the spectrum of 5 shows that
the desirable product was isolated. The signals confirming the exist-
0
ence of the characteristic A MX system in the oxirane ring in the spec-
trum of compound 3 disappear in the spectra of compounds 5 and 6
completely, confirming the nucleophilic opening of the oxirane ring.
The thermal properties of the low-molar-mass compounds and the
oligomer were examined using the DSC and TGA techniques. The
ꢀ
ꢀ
glass transition (T , C) and 5% weight loss (T , C) temperatures of
g
ID
the materials are summarized in Table 2.
TABLE 2 Thermal Characteristics of 3, 4, 5, and 6
ꢀ
a
ꢀ
b
Compound
T
g
, [ C]
T
ID, [ C]
3
4
5
6
28
112
70
308
387
348
351
62
a
Determined by DSC during the 1st and the 2nd heating, scan rate
ꢀ
2
0 C=min, N atmosphere.
2
b
The 5% weight loss temperature determined by TGA, heating
ꢀ
rate 20 C=min, N
2
atmosphere.

0
Oxiranyl-Substituted 3,3 -Bicarbazolyl and its Reaction Products
249=[581]
0
All the synthesized 3,3 -bicarbazolyl-based compounds and even
monomer (3) are capable of the glass formation. Neither melting nor
crystallization peaks were observed in the DSC curves of these com-
pounds. The presence of a relatively bulky bicarbazolyl fragment in
these compounds apparently enhances their inclination to the glass
formation. The influence of the rigidity of a linking spacer in twin com-
pounds 5 and 6 on the value of their T is evident. The metasubstituted
g
benzene spacer apparently allows the twisting of the molecules, and
the numbers of conformers and modes of packing increase by leading
to a lower T of 6 as compared to that of 5. The increase in the molecular
g
size due to the ring-opening polymerization leads to an increase of T .
g
ꢀ
Oligoether 4 shows T higher by 85 C than that of the corresponding
g
monomer (3). TGA experiments in nitrogen atmosphere revealed that
all the synthesized compounds exhibit a high thermal stability. Their
ꢀ
5
% weight loss temperatures range from 308 to 387 C.
Optical, photophysical and photoelectrical properties of dilute
solutions and films of compounds were investigated. The graphical
representation of the absorption and emission spectra of dilute solutions
of monomer 3, polyether 4, and the derivatives 5 and 6 are given in
FIGURE 2 UV absorption and fluorescence spectra of the dilute THF
ꢁ5
solutions (10 mole=l) of 3, 4, 5, and 6 (kex ¼ 310 nm).

2
50=[582]
V. Vaitkeviciene et al.
TABLE 3 Optical Characteristics of Dilute Solutions in
ꢁ
5
THF (10 mole=l) of Di(EtHexCz), 3, 4, 5 and 6
a
Compound
kabs, [nm]
kem, [nm]
3
4
5
6
241, 302, 345, 356
247, 308, 348, 360
242, 265, 303, 345, 356
242, 303, 345, 356
412
437
430
428
408
Di(EtHexCz)
242, 299, 344, 355
a
k ¼ 310 nm.
Figure 2. The wavelengths of the absorption (kabs) and emission (kem
)
maxima of dilute solutions in THF are summarized in Table 3.
The absorption spectra of monomer 3, oligomer 4, and twin com-
pounds 5, 6 are similar to that of Di(EtHexCz). They shows character-
istic bands in the regions of 241–247, 299–308, and 325–375 nm. The last
ꢂ
low-energy absorption bands are attributed to p ! p transitions.
The absorption bands of oligomer (4) exhibit small bathochromic
shifts ranging from 4 to 9 nm with respect of the absorption bands of
Di(EtHexCz). Such shifts of absorption bands could occur due to
the interaction between monomer units in the macromolecule.
The UV spectra of compound 5 revealed a additional small absorp-
0
tion band with the maximum at 265 nm due to 4,4 -dimercaptobisben-
zenethiol functionality present in the molecule.
The emission spectra of the dilute solution of twin compounds (5, 6)
and oligoether (4) exhibit considerable bathochromic shifts of 16–25
nm with respect of the spectrum of monomer (3). This is apparently
due to the presence of intermolecular excimer-forming sites in oligo-
mer 4 and twin compounds (5, 6). The excited polymeric species occupy
lower energy levels due to the formation of excimers. Therefore, the
emission bands of dilute solutions of monomer 3, on the one hand,
and of oligomer 4, as well as of twin compounds (5, 6) on the other
hand, are in different regions. These facts show that the behavior of
0
the 3,3 -bicarbazolyl-containing oligoether is different from that of
the earlier reported carbazolyl-containing oligoethers [15]. Carbazo-
lyl-containing derivatives showed only the monomer emission, which
means that excimer formation centers do not exist in such macromole-
0
cules. In the case of 3,3 -bicarbazolyl-containing twins 5 and 6, the
formed excimers are higher in energy as compared with the excimers
of oligoether 4 (cf. the data in Table 3). One of the possible explana-
0
tions of the different photophysical behavior of 3,3 -bicarbazolyl-
containing oligoether and the twin molecules can be the possibility

0
Oxiranyl-Substituted 3,3 -Bicarbazolyl and its Reaction Products
251=[583]
TABLE 4 Ionization Potentials of the Films of Compounds 3, 4, 5, 6 and
PEPK
Compound
, [eV]
Di(EtHexCz)
3
4
5
6
PEPK
I
p
5.5
5.5
5.5
5.5
5.5
5.9
0
for relatively bulky 3,3 -bicarbazolyl species linked by relatively
flexible spacers to overlap.
The values of I of the materials described in this section are given
p
in Table 4. For the comparison, the values of I of Di(EtHexCz) and
p
PEPK [16] are given as well.
Compounds 3–6 demonstrate the same values of I as Di(EtHexCz)
p
and lower than that of PEPK. From the viewpoint of Ip values,
the reported compounds are applicable as hole transport materials
in electrophotographic photoreceptors.
The time-of-flight technique was used to study the charge transport
properties of compounds 3, 5, and 6. The linear dependences of hole
FIGURE 3 Electric field dependences of the drift mobility of holes for 50%
solid solutions in PCZ of compounds 3, 5, and 6 and for the amorphous film
of pure 3.

2
52=[584]
V. Vaitkeviciene et al.
TABLE 5 Hole Drift Mobility Data for an Amorphous Film of 3 and the Solid
Solutions of 3, 5, 6 in PC-Z
2
2
Transport material: host polymer
m
0
, [cm =Vs]
m, [cm =Vs]
ꢁ8
ꢁ8
ꢁ9
ꢁ9
ꢁ6
3
3
5
6
þ Al
4.6 ꢃ 10
3.6 ꢃ 10
2 ꢃ 10
5.0 ꢃ 10
ꢁ7
þ PC-Z, 1:1
þ PC-Z, 1:1
þ PC-Z, 1:1
4.7 ꢃ 10
ꢁ8
7 ꢃ 10
ꢁ7
1.5 ꢃ 10
1.1 ꢃ 10
drift mobilities on the square root of the electric field strength were
observed for all the systems under study (Fig. 3).
The zero field mobilities (m ) and the mobilities at a field of
0
5
6
.48 ꢃ 10 V=cm (l) are given in Table 5. The hole mobility values for
compounds 3, 5, and 6 molecularly doped in the PC-Z range from
ꢁ
7
ꢁ6
2
1
0
to 1.16 ꢃ 10 cm =Vs at high electric fields and are a little lower
than those for the systems based on carbazole-containing compounds
6]. Rather low charge mobilities in molecularly doped polymers con-
taining 3, 5, and 6 can apparently be explained by the unfavourable
non-planar) configuration of the relatively big molecules which causes
[
(
an increase of the molecular or energy disorder in the molecular mix-
ture of these materials with the polymer host.
The charge mobility of the amorphous film of pure 3 was
ꢁ
5
2
5
1
.26 ꢃ 10 cm =Vs at 9.0 ꢃ 10 V=cm electric fields, i.e. by one order
of magnitude higher than that of the molecular mixture with PC-Z
cf. the data presented in Fig. 3).
In conclusion, we have synthesized new oxiranyl-substituted 3,3 -
(
0
bicarbazolyl derivatives which exhibit a good thermal stability with
ꢀ
5
% weight loss temperatures exceeding 308 C and form amorphous
ꢀ
films with glass transition temperatures ranging from 28 to 112 C.
The electron photoemission spectra of the materials revealed the
ionization potentials of ca. 5.5 eV for the synthesized compounds.
Time-of-flight hole drift mobilities of the amorphous films of
9
1
-(2-ethylhexyl)-3-[9-(oxiran-2-ylmethyl)carbazol-3-yl]carbazole exceed
ꢁ
5
2
0
cm =Vs at high electric fields.
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