220
A.A. Kocaeren / Organic Electronics 24 (2015) 219–226
Chemical Co. (USA). 18-Crown-6 was used as phase transfer catal-
ysis. Boron trifluoride ethyl etherate (BF3EtE) was supplied from
Fluka Chemical Co.
LiClO4/acetonitrile (AN:BF3EtE) (1:1, v/v) and LiClO4/acetonitrile
(AN) without BF3EtE solvent mixture at room temperature during
200 s [30]. The electropolymerization reactions involved dissolving
B1 (0.1 M) in 10 ml of supporting electrolyte in AN, and placing the
resulting solution into the CV cell. Next, the solution was repeat-
edly scanned between À0.1 and 1.2 V. The resulting polymer films
were washed with AN to remove LiClO4 and BF3EtE [31]
(Scheme 3).
2.2. Synthesis of 4-(9H-carbazol-9-yl) phenol (A1)
Firstly, carbazole (1.672 g, 0.01 mol), KOH (0.842 g, 0.015 mol),
18-Crown-6 (0.01 g, 0.04 mmol) as phase transfer catalysis were
dissolved in toluene (20 mL) and this reaction mixture was vigor-
ously stirred at 110 °C under argon for 1 h. A solution of 4-iodo
phenol (3.3 g, 0.015 mol) in toluene (10 mL) was slowly added to
this reaction mixture, and it was refluxed at 110 °C under argon
and stirred for 16 h (Scheme 1). The reaction mixture was then
cooled to room temperature. Then, the reaction mixture poured
into the 150 ml of ethanol and stripped off by a rotary evaporator.
The product was recrystallized from methanol and dried in a vac-
uum desiccator [28]. (Yield: 60%).
2.5. Structural characterization
The FT-IR spectra of the compounds were recorded on a Perkin
Elmer RX I FT-IR spectrometer with KBr pellets in the range 4000–
400 cmÀ1. 1H NMR spectra (Bruker AC FT-NMR spectrometer oper-
ating at 400 and 100.6 MHz) were also recorded using DMSO-d6 as
the solvent at 25 °C. Tetramethylsilane was used as an internal
standard. An Ivium potentiostat was used to supply a constant
potential during the electrochemical syntheses and cyclic voltam-
metry experiments. An Agilent 8453 UV–vis spectrophotometer
was used for the spectroelectrochemical studies and characteriza-
tion of the compounds.
A1: FT-IR (cmÀ1): v (OAH, phenolic) 3170 m, v (C@C phenyl)
1560, 1475 s, v (CAN) 1450 s, v (CAO) 1236 s. 1H NMR (DMSO):
dH ppm, 7.512, 7.492 (d, 2H, Ha), 7.411, 7.391, 7.374 (t, 2H, Hb),
7.183, 7.164, 7.144 (t, 2H, Hc), 7.271, 7.249 (d, 2H, Hd), 8.129,
8.110 (d, 4H, He, Hf), 11.486 (s, 1H, AOH). Calculated: C, 83.40; H,
5.02; N, 5.41. Found: C, 84.70; H, 4.85; N, 5.39.
2.6. Spectroelectrochemical characterization
2.3. Synthesis of B1 via HBr elimination
The polymer films, which had been electrochemically deposited
onto ITO-coated glass slides, were used to perform the spectroelec-
trochemical experiments. Spectroelectrochemical and elec-
The
synthesis
reaction
of
bis-4-(9H-carbazol-9-yl)
phenyl-3,4-diyloxy thiophene (B1) had a two-stage process. In
the first stage, K2CO3 (0.552 g, 0.004 mol) and A1 (0.518 g,
0.002 mol) were dissolved in THF (20 ml) and stirred for 1 h. In
the second stage, 3,4-dibromo thiophene (0.242 g, 0.001 mol)
was added to this reaction mixture. The reaction mixture was stir-
red with a magnetic stirring bar for 16 h under argon atmosphere.
This reaction solution was poured into 200 ml of water and the
precipitated crude product was collected and filtered. The obtained
compound was dried in a vacuum oven at 60 °C [29] (Yield ꢀ50%).
B1 was obtained as a light yellow colored powder. Additionally, the
chemical structure of the compound was shown in Scheme 2.
B1: FT-IR (cmÀ1): v (C@C phenyl) 1627, 1598, 1490 s, v (CAN)
1450 s, v (CAOAC) 1238, v (CAS) 746, 725 s. 1H NMR (DMSO): dH
ppm, 7.518, 7.497 (d, 4H, Ha, Hd), 7.419, 7.399, 7.381 (t, 2H, Hb),
7.189, 7.170, 7.150 (t, 2H, Hc), 8.133, 8.114 (d, 4H, He, Hf), 7.885
(s, 1H, Hg). Calculated: C, 80.17; H, 4.34; N, 4.68. S, 5.34. Found:
C, 79.84; H, 5.24; N, 5.01; S, 5.30.
trochromic measurements were conducted in a LiClO4/AN
solution using an Ag wire as the reference and a Pt wire as the aux-
iliary electrode. The data obtained from the cyclic voltammetry
measurements were used for the spectroelectrochemical measure-
ments of the polymer film [32]. These measurements were per-
formed to account for the absorption spectra of the polymer film
under the applied potentials. The spectroelectrochemical cell
included a quartz cuvette, an Ag wire (RE), a Pt wire counter elec-
trode (CE) and the polymer film on ITO/glass as a transparent
working electrode (WE). These measurements were performed in
a 0.05 M LiClO4 supporting electrolyte in both AN/BF3EtE and only
LiClO4/AN without BF3EtE. Cycle number was chosen as 5 for each
CV measurements [33].
3. Results and discussion
3.1. NMR spectra and FT-IR spectra
2.4. Electrochemical polymerization
Synthesized compounds have different colors like light yellow
and violet. While A1 has a violet color, B1 has a light yellow.
Additionally, when A1 is a crystalline structured, B1 is a powder
form.
The FT-IR spectra of the synthesized compounds are recorded.
4-(9H-carbazol-9-yl) phenol (A1), which possesses a phenolic
AOH stretching peak, CAN and CAO peaks at 3170, 1450 and
1236 cmÀ1, respectively [34]. The FT-IR spectrum from A1 shows
that the ANH peak belong to carbazole unit disappears after the
reaction [35]. This indicates that the reaction takes place and that
the target product form. The results of these FT-IR studies clearly
indicate that polymerization is successfully achieved.
Cyclic voltammetry (CV) measurements were performed using
an Ivium potentiostat at different potential scan rates. CV was
employed to assay the electrical activity of the compounds and
determine their oxidation–reduction peak potentials. The system
consists of a CV cell containing an indium tin oxide (ITO)-coated
glass plate as the working electrode, platinum wire as the counter
electrode and Ag wire as the reference electrode. The CV measure-
ments were separately performed using both
a (0.05 M)
The FT-IR spectrum from B1 shows the following absorption
peaks: 1627, 1598 and 1490 cmÀ1 (from the aromatic C@C stretch-
ing), 1238 cmÀ1 (from the CAO stretching), 1450 cmÀ1 (from the
CAN stretching) and 746, 725 cmÀ1 (from the CAS stretching)
[20,34]. Due to thiophene groups in the structure of B1, the peak
related to CAS bonding is observed at 746 and 725 cmÀ1, as
expected [36]. Moreover, the presence of these peaks confirms that
the reaction successfully occurs.
I
N
18- Crown-6, KOH
Toluene, 110 oC, 16 h
N
H
OH
OH
Scheme 1. Synthesis of 4-(9H-carbazol-9-yl) phenol (A1).