Electrochemical polymerization of a new low-voltage oxidized thienylenepyrrole-derivative and its electrochromic device application

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Electrochemical polymerization of a new low-voltage oxidized

thienylenepyrrole derivative and its electrochromic device application

Buket Bezgin Carbas

⇑

, Arif Kivrak

1

_{, Ecem Teke, Metin Zora, Ahmet M. Önal}

⇑

Department of Chemistry, Middle East Technical University, 06800 Ankara, Turkey

a r t i c l e

i n f o

Article history: Received 18 March 2014

Received in revised form 6 June 2014 Accepted 3 July 2014

Available online 11 July 2014 Keywords: Multichromism Electrochemical polymerization Electrochromic device Thienylenepyrrole polymers

a b s t r a c t

Synthesis of a new monomer, 2,5-bis-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1-phenyl-1H-pyrrole (ENE), from pyrrole, iodobenzene and 3,4-ethylenedioxythiophene (EDOT), and its electropolymerization are reported. ENE was oxidized at a low oxidation potential (0.45 V vs. Ag/AgCl) and successfully elec-tropolymerized in acetonitrile containing 0.1 M NaClO4and LiClO4electrolyte mixture. The resulting

polymer, P(ENE), revealed five distinctive colors upon doping, which indicated that the polymer is mul-tichromic. P(ENE) has a coloration efficiency of 288 cm2_{/C at 422 nm with a specific optical band gap of}

2.0 eV. Furthermore, an electrochromic device (ECD) based on P(ENE) and poly(ethylene dioxythiophene) (PEDOT) was constructed and its switching was investigated by UV–vis spectroscopy.

Ó 2014 Published by Elsevier B.V.

1. Introduction

Functional conjugated polymers are still of great interest since they are promising candidates for a large number of advanced technological applications including solar cells[1,2], light emitting diodes[3–5], optical displays and sensors[6–8]. Although the ﬁrst generation electrochromic materials have been mostly inorganic oxides due to their some advantages[9–12], functional conjugated polymers have also been widely employed as electrochromic mate-rials in electrochromic devices[13–15]. These advantages include not only multicolors and high contrast ratio but also include fast switching capability and long cycle times. Furthermore, these properties can be tuned via structural tailoring of the starting materials. Thus, signiﬁcant effort has been devoted to the design and synthesis of new polymeric electrochromics based on conju-gated polymers[16]. Among various conjugated polymers, polyt-hienylpyrroles, having 2,5-di(2-thienyl)pyrrole (SNS) repeating units, have been extensively investigated since functionalization of the monomer structure prior to polymerization is possible via N-substitution. This functionalization allows easy tuning of opto-electronic properties of the resulting conjugated polymer. Ferraris et al. reported the electrochemical and optical properties of various

N-substituted polythienylpyrroles and obtained soluble polymers via alkyl group substitution on the central pyrrole unit[17–20]. Otero et al. investigated the electrochemical polymerization and electrodissolution process of SNS in acetonitrile using various elec-trolytes[21,22]. Synthesis of a large number of soluble conjugated polymers from substituted SNS derivatives and their device appli-cations were also reported by Toppare et al.[23–26]. In addition, Cihaner et al. reported the formation of soluble polymers from sev-eral SNS derivatives, exhibiting electrochromic and ﬂuorescence properties[27–30]. We have also investigated the electrochemical polymerization and optoelectronic properties of phthalonitrile, phthalocyanine and luminol substituted SNS derivatives[30–33].

After Otero et al. reported the electrochemical polymerization of SNS in acetonitrile[17,18], Ferraris et al. investigated the elec-trochemical and optical properties of various N-substituted polyt-hienylpyrroles and obtained soluble polymers via alkyl group substitution on the central pyrrole unit [19–22]. Synthesis of a large number of soluble conjugated polymers from substituted SNS derivatives and their device applications were also reported by Toppare et al.[22–26]. In addition, Cihaner et al. reported the formation of soluble polymers from several SNS derivatives, exhib-iting electrochromic and ﬂuorescence properties[27–30]. We have also investigated the electrochemical polymerization and optoelec-tronic properties of phthalonitrile, phthalocyanine and luminol substituted SNS derivatives[30–33].

Herein, we report the electrochemical polymerization of a new monomer, 2,5-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1-phenyl-1H-pyrrole (ENE) bearing 3,4-ethylenedioxythiophene (EDOT) side groups. EDOT is a widely used analog of thiophene http://dx.doi.org/10.1016/j.jelechem.2014.07.005

1572-6657/Ó 2014 Published by Elsevier B.V.

⇑ Corresponding authors. Present address: Department of Energy Systems Engineering, Karamanog˘lu Mehmetbey University, 70100 Karaman, Turkey (B.B. Carbas).

E-mail addresses: bcarbas@kmu.edu.tr (B.B. Carbas), aonal@metu.edu.tr

(A.M. Önal).

1

Present address: Department of Chemistry, Yüzüncü Yıl University, 65080 Van, Turkey.

Contents lists available atScienceDirect

Journal of Electroanalytical Chemistry

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and it is expected that the replacement of thiophene side groups in SNS scaffold will not only lower the oxidation potential of the cor-responding monomer but also prevents the side reactions during the electrochemical polymerization, leading to formation of regio-regular conjugated polymers[7,33–35]. The monomer, ENE, was polymerized via potential cycling and the electrochromic proper-ties of the resulting polymer, P(ENE), was investigated via in situ spectroelectrochemical techniques. An electrochromic device, switching from 1.0 V at neutral state to 1.8 V at oxidized state, was also prepared by utilizing P(ENE) and PEDOT as anodically and cathodically coloring electrochromic materials.

2. Experimental

2.1. Electropolymerization and characterization

All chemicals were purchased from Aldrich and Merck chemical companies and used without any further puriﬁcation. Prior to elec-trochemical polymerization, redox behavior of the monomer, ENE, was investigated using cyclic voltammetry (CV) in acetonitrile (ACN) solution containing 0.1 M LiClO4and NaClO4in the ratio of

1:1 on platinum electrode. The monomer was successfully elec-tropolymerized via potentiodynamic or potentiostatic methods using three-electrode system containing a platinum disc (0.02 cm2_{) and a platinum wire as working and counter electrodes,}

respectively, as well as Ag/AgCl electrode (in 3 M NaCl (aq) solu-tion) as a reference electrode. Prior to spectroelectrochemical investigations, the polymer ﬁlm was switched between its neutral and doped state several times in order to equilibrate redox behav-ior in monomer-free electrolytic solution. For electro-optical stud-ies, indium-tin oxide (ITO, Delta Tech. 8–12 X, 0.7 cm 5 cm) electrodes were coated by the polymer ﬁlm. The coated electrode was dipped into a rectangular UV quartz cuvette (light path length = 1.0 cm, purchased from Sigma–Aldrich) together with Pt wire and Ag wire as counter and reference electrodes, respectively. In situ spectroelectrochemical studies were performed using Hewlett–Packard 8453A diode array spectrometer. A Pt wire was used as a counter electrode and an Ag wire as a pseudo-reference electrode which was calibrated externally using 5 mM solution of ferrocene/ferrocenium couple in the electrolytic solution. Electro-analytical measurements were performed using a Gamry PCI4/ 300 potentiostat–galvanostat. FTIR spectra were recorded on a Bru-ker Vertex 70 Spectrophotometer.

2.2. Fabrication of electrochromic device

For a dual type electrochromic device (ECD) fabrication, PEDOT as a cathodically coloring polymer was electropolymerized onto a 1.25 cm2 _{ITO glass surface from an ACN solution containing}

2 103_{M EDOT and 0.1 M TBAPF}

6via constant potential

electrol-ysis at 1.2 V. After coating PEDOT onto the ITO-glass surface, the ﬁlm was rinsed with ACN to remove all the unreacted monomers on the electrode surface. P(ENE) was also electropolymerized using CV method in ACN solution containing 0.1 M LiClO4 and

NaClO4 in the ratio of 1:1 on Pt electrode. The device was

con-structed using the electrochromic electrodes stacked face-to-face separated by gel electrolyte (TBABF4; ACN; poly(methyl

methacry-late); polycarbonate in the ratio of 3:70:7:20)[23,25]. The electro-chromic device was allowed to dry for 48 h at room temperature under atmospheric pressure. The electro-optical properties of the device were recorded in situ under various applied potentials. Finally, square wave potential method was used to perform switching between the colored states.

2.3. Synthesis of 2,5-bis-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1-phenyl-1H-pyrrole (ENE)

2.3.1. Synthesis of N-phenylpyrrole (3)

This compound was prepared from iodobenzene (1) according to a literature procedure[36]. To a stirred solution of iodobenzene (1) (2.850 g, 14 mmol), CuI (0.133 g, 0.7 mmol), n-Bu4NBr (0.225 g,

0.7 mmol) and NaOH (1.120 g, 28 mmol) in dry toluene (15 mL)

Scheme 1. Synthesis of 2,5-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1-phenyl-1H-pyrrole (ENE).

Fig. 1. Repetitive cyclic voltammograms of 2 mM ENE in 0.1 M LiClO4/NaClO4/ACN

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was added pyrrole (2) (0.938 g, 14 mmol), and the resulting solution was allowed to stir 100 °C under argon for 22 h. After the reaction was over, saturated NH4Cl solution (50 mL) was added

at room temperature and the organic layer was extracted with ethyl acetate (3 50 mL). The combined organic layers were washed with brine (50 mL), dried over MgSO4, ﬁltered and

concen-trated under reduced pressure. The residue was puriﬁed by ﬂash column chromatography on silica gel using ethyl acetate/hexane (1:9, v/v) as the eluent, affording N-phenylpyrrole (3) (1.813 g,

90%). 1_{H NMR (CDCl} 3, 400 MHz): d 7.57 (m, 4H), 7.56 (m, 1H), 7.29 (s, 2H), 6.59 (s, 2H) ; 13_{C NMR (CDCl} 3, 100 MHz): d 140.9, 129.8, 125.8, 120.6, 119.5, 110.7. 2.3.2. Synthesis of 2,5-dibromo-1-phenyl-1H-pyrrole (4)

This compound was prepared from N-phenylpyrrole (3) accord-ing to a modiﬁed literature procedure[37]. N-Phenylpyrrole (3) (0.715 g, 5 mmol) was dissolved in 20 mL of THF and cooled in an ice bath. N-Bromosuccinimide (1.780 g, 10 mmol) was added and the resulting mixture was stirred for a short time. Then, ice-bath was removed, and the mixture was stirred at room tempera-ture for 3 h. When reaction was over, the solvent was removed under reduced pressure. The crude 2,5-dibromo-1-phenyl-1H-pyr-role (4) was not so stable and immediately subjected to next step (see below). When necessary, it was stored at 18 °C to prevent decomposition.1_{H NMR (CDCl}

3, 400 MHz): d 7.50–7.35 (m, 3H),

7.20–7.10 (m, 2H), 6.25 (s, 2H).

2.3.3. Synthesis of ENE by Stille coupling method

To a solution of 2,5-dibromo-1-phenyl-1H-pyrrole (4) (0.301 g, 1 mmol) and (2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)tributylst-annane (0.864 g, 2 mmol) in a round-bottomed ﬂask in toluene (10 ml) was added PdCl2(PPh3)2(0.070 g, 0.1 mmol) under Argon.

The solution was stirred under reflux for 24 h. After the mixture was concentrated under reduced pressure, the resulting crude product was purified by flash chromatography on silica gel eluting with hexane/ethyl acetate (1:4, v/v), giving ENE (0.191 g, 45%).1_H

NMR (CDCl3, 400 MHz): d 7.35–7.15 (m, 5H), 6.59 (s, 2H), 6.01 (s,

2H), 4.01 (m, 4H), 3.94 (m, 4H); 13_{C NMR (CDCl}

3, 100 MHz): d

141.1, 138.2, 129.9, 128.8, 128.3, 128.1, 126.4, 110.9, 109.1, 98.2, 64.5, 64.4.

3. Results and discussion 3.1. Synthesis of ENE

In the present study, ENE was synthesized from 2,5-dibromo-1-phenyl-1H-pyrrole by using palladium-catalyzed Stille coupling reaction (Scheme 1). Initially, N-phenylpyrrole (3) was prepared from pyrrole and iodobenzene by using a literature procedure

[36]. When iodobenzene was allowed to react with pyrrole in the presence of CuI and base in toluene, the desired N-phenylpyrrole (3) was obtained in a good yield. After isolation of N-phenylpyrrole

Fig. 2. (a) p-Type doping behavior of P(ENE) ﬁlm (b) relationship of anodic (iac) and

cathodic current (icc) peaks at various scan rates and (c) comparison of charge and

discharge amounts during p-type doping of P(ENE) ﬁlm at various scan rates as a function of scan rate in 0.1 M LiClO4/ACN on Pt electrode.

Fig. 3. Optical absorption spectra of P(ENE) ﬁlm on ITO electrode in 0.1 M LiClO4/

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(3), bromination reaction was carried out to afford 2,5-dibromo-1-phenyl-1H-pyrrole (4). Note that 2,5-dibromo-1-phenyl-1H-pyr-role (4) was not so stable that it was immediately subjected to a palladium-catalyzed Stille coupling reaction with (2,3-dihydrothi-eno[3,4-b][1,4]dioxin-5-yl)trimethylstannane. When Stille cou-pling reaction was performed in the presence of Pd(PPh3)Cl2

(10 mol%) in dry toluene at reﬂuxing conditions for 24 h, the expected product was obtained in 45% yield.

3.2. Electrochemical behavior of ENE and its electropolymerization Electrochemical behavior of ENE was investigated in ACN using 0.1 M LiClO4and NaClO4(1:1) as supporting electrolytes. One

irre-versible oxidation peak at 0.45 V vs. Ag/AgCl was observed during

the anodic scan. During the reverse scan, a reduction peak was also observed which is accompanied with an oxidation peak (Fig. 1) at around 0.30 V. Upon successive anodic scans, this reversible peak gained intensity, which indicates the deposition of conducting polymer ﬁlm with increasing thickness on the working electrode surface.

After 25 repeated scans, the polymer coated working electrode was removed from the monomer solution, and in order to remove the oligomeric species and the electrolyte, it was rinsed with ACN. The electrochemical behavior of the polymer ﬁlm was investigated in 0.1 M LiClO4/ACN solution. The polymer ﬁlm was found to

exhi-bit three reversible redox couple representing the doping and de-doping of the polymer film at 0.20 V, 0.50 V, 0.85 V. (Fig. 2(a)). It was found that both anodic and cathodic peak currents increase linearly with increasing scan rate, which clearly indicates that the redox process is non-diffusional and the polymer film is well-adhered to the working electrode (Fig. 2(b)). The changes in the amounts and ratios of charge and discharge of p-type doped polymer film as a function of scan rate were also depicted in

Fig. 2(c). There is no appreciable change in charge/discharge amounts and their ratios (close to 1) especially at higher scan rates as shown inFig. 2(c). It indicates that the doping and de-doping processes occur easily and equally for polymer ﬁlm.

3.3. Spectroelectrochemical behavior of P(ENE)

Polymer ﬁlm was deposited on ITO and its transition between the neutral (de-doped) and oxidized (doped) states was studied in 0.1 M LiClO4/ACN solution.Fig. 3shows the in situ absorption

spectra of the polymer recorded at various applied potentials in terms of the reversible redox couple of P(ENE) between 0.3 V and 1.0 V in 0.1 M LiClO4/ACN. In the neutral state, polymer ﬁlm

exhibits an absorption band at 422 nm due to the

p

–

p

*_transition.

From the beginning of the low energy end of the

p

–

p

*_transition

band in the neutral state, the band gap value of 2.0 eV was found. This value is slightly lower than that of its thiophene analog, poly(1-phenyl-2,5-di(2-thienyl)-1H-pyrrole(P(PTP)) [23], due to greater donor effect of EDOT. Upon electrochemical doping, the evolution of the spectra shows a simultaneous increase of the absorbance at around 810 nm indicating polaron formation. As fur-ther doped (beyond 0.4 V), this band shifts to 750 nm and a new broad band centered at 920 nm starts to intensify indicating bipo-laron formation. These changes in the electronic absorption spec-trum was accompanied with electrochromic response and the color of the P(ENE) ﬁlm changes from dark orange to yellow. 3.4. Electrochromic switching of P(ENE) ﬁlm in solution

Since the ability of a polymer ﬁlm to switch rapidly between its redox states with an appreciable color change is important for elec-trochromic applications, we have also evaluated the switching ability of P(ENE) by monitoring the change in transmittance at 422, 745 and 919 nm. Square wave potential step method was cou-pled with optical spectroscopy for this purpose. The polymer ﬁlm coated on ITO was reversibly switched between 0.3 V and 1.0 V vs. Ag-wire for each 10 s. During the oxidation of the polymer P(ENE), 22.0%, 14.0% and 22.3% of percent transmittance changes were observed for the absorption bands at 422, 745 and 919 nm, respectively (Fig. 4).

The coloration efﬁciency (CE) for polymer is calculated from Eq.

(1)as described previously in[38]

CE ¼

D

OD=Qd ð1Þ

whereDOD is the change in optical density and Qdis the charge

passed during this process.DOD is determined from the percent

Fig. 4. Chronoabsorptometry experiments for P(ENE) on ITO in 0.1 M LiClO4/ACN

while the polymer was switched between 0.3 and 1.0 V with a switching time of 10 s at 422, 745 and 919 nm.

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transmittance (%T) before and after a full switch and is calculated using

D

OD ¼ logð%T of bleached state=%T of colored stateÞ ð2Þ

The data inTable 1give information about the spectroelectro-chemical behavior of the material. The time required to attain 95% of the total transmittance difference was found to be 1.4, 1.9 and 1.6 s from the neutral to oxidized states for 422, 745 and 919 nm, respectively. The multichromic behavior of the ﬁlm at dif-ferent applied voltages was also shown inTable 1.

3.5. P(ENE)/PEDOT electrochromic device

A dual type electrochromic device consisting of P(ENE) and PEDOT was constructed and its spectroelectrochemical behavior was investigated by recording the optical absorbance spectra at different applied potentials. Electrochromic device showed a reversible response in a potential range of 1.0 V (neutral) and 1.8 V (oxidized) as depicted inFig. 5. At 1.0 V, the polymer was reddish orange and PEDOT was transparent (light blue) in its oxi-dized state; therefore, the color of the device at 1.0 V was magenta. There was also an intermediate color with a gray-trans-parent color when 0.30 V was applied to the device. The color of the device at 1.8 V became dark blue. As the applied potential was increased, an absorption band at 600 nm was observed due to the neutral state of PEDOT layer.

3.6. Switching of electrochromic device

In order to determine the response time needed to perform switching between the colored states and optical contrast of device, kinetic studies were done. Under a square potential input of 1.0 and 1.8 V with a residence time of 10, 5, 3 and 2 s at each potential, the optical response at 630 nm for the device was mon-itored as shown in Fig. 6. The switching time was calculated as 0.57 s at 95% of the maximum transmittance for oxidized state at 630 nm and the optical contrast was calculated as 40% for 630 nm. When compared to a similar device constructed from P(PTP) and PEDOT (switching time 2.1 s and optical contrast 13% at 617 nm) [23], P(ENE)/PEDOT device found to exhibit shorter switching time and higher optical contrast value. The optical mem-ory is an important parameter to characterize an electrochromic device. The optical memory was measured when the device retains its color under open circuit conditions. Device shows a quite good optical memory in the neutral state with almost no loss in trans-mittance and also device has a good optical memory in the oxi-dized state with a slow decrease in transmittance up to a certain value. For example, when polarized by an applied pulse for 10 s and then kept under open circuit conditions, the device keeps its blue color without signiﬁcant loss at 630 nm.

4. Conclusion

In this study, we have synthesized a new monomer, 2,5-bis-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1-phenyl-1H-pyrrole (ENE), including EDOT (3,4-ethylenedioxythiophene) units. It was found that the integration of EDOT units to the system not only procured facile electrochemical polymerization but also lower the band gap (2.0 eV) of the corresponding polymer P(ENE) when compared to its thiophene analog (2.2 eV) due to greater donor power of EDOT side groups. The polymer ﬁlm exhibited multicolor behaviors under applied external potentials: dark orange, brown, faded-green, greenish blue, and yellow upon moving from neutral state to oxidized state. Also, P(ENE) has a good material potential for electrochemical capacitor because it preserves approximately equal

Table 1

Spectroelectrochemical data for P(ENE).

Fig. 5. Optoelectrochemical spectrum of P(ENE)/PEDOT in the presence of 0.1 M LiClO4/ACN. Inset: Colors of P(ENE)/PEDOT between its various redox states. (For

interpretation of the references to colour in this ﬁgure legend, the reader is referred to the web version of this article.)

Fig. 6. Electrochromic switching and optical absorbance monitored for P(ENE) at 630 nm in the presence of 0.1 M LiClO4/ACN.

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amount of charging/discharging property both at lower and higher scan rates. Furthermore, the ﬁrst electrochromic device application of P(ENE) was studied and its spectroelectrochemical properties were investigated. The electrochromic device was found to have higher optical contrast and shorter switching time when compared to the device constructed utilizing thiophene analog, P(PTP) and PEDOT[23].

Conﬂict of interest

There is no any conﬂict of interest ﬁnancially as well as among authors.

References

[1]F. Zhang, W. Mammo, L.M. Andersson, S. Admassie, M.R. Andersson, O. Inganas, Adv. Mater. 18 (2006) 2169.

[2]S.E. Shaheen, C.J. Brabec, N.S. Sariciftci, F. Padinger, T. Fromherz, J.C. Hummelen, Appl. Phys. Lett. 78 (2001) 841.

[3]J.H. Burroughes, D.D.C. Bradley, A.R. Brown, R.N. Marks, K. Mackay, R.H. Friend, P.L. Burns, A.B. Holmes, Nature 347 (1990) 539.

[4]M. Berggren, G. Gustafsson, O. Inganäs, M.R. Andersson, O. Wennerström, T. Hjertberg, Adv. Mater. 6 (1994) 488.

[5]A. Gadisa, E. Perzon, M.R. Andersson, O. Inganas, Appl. Phys. Lett. 90 (2007) 113510.

[6]O.R. Miranda, C.C. You, R. Phillips, I.B. Kim, P.S. Ghosh, U.H.F. Bunz, V.M. Rotello, J. Am. Chem. Soc. 129 (2007) 9856.

[7]B.B. Çarbasß, A. Kivrak, A.M. Önal, Electrochim. Acta 58 (2012) 223.

[8]V. Ibrahimova, M.E. Kocak, A.M. Önal, D. Tuncel, J. Polym. Sci. Part A: Polym. Chem. 51 (2013) 815.

[9]D.N. Buckley, L.D. Burke, J.K. Mukahy, Faraday Trans. 1 (72) (1976) 1896. [10]L.D. Burke, T.A.M. Thomey, D.P. Whelan, J. Electroanal. Chem. 107 (1980) 201. [11]W.C. Dautremont-Smith, Displays 3 (1982) 3.

[12]C.G. Granqvist, Sol. Energy Mater. Sol. Cells 60 (2000) 201.

[13]I. Schwendeman, R. Hickman, G. Sonmez, P. Schottland, K. Zong, D. Welsh, J.R. Reynolds, Chem. Mater. 14 (2002) 3118.

[14]H. Meng, D. Tucker, S. Chafﬁns, Y. Chen, R. Helgeson, B. Dunn, F. Wudl, Adv. Mater. 15 (2003) 146.

[15]A. Cihaner, F. Algı, Electrochim. Acta 53 (2007) 2574. [16]P.M. Beaujuge, J.R. Reynolds, Chem. Rev. 110 (2010) 268. [17]J.P. Ferraris, M.D. Newton, Polymer 33 (1992) 391. [18]J.P. Ferraris, G.D. Skiles, Polymer 28 (1987) 179.

[19]J.P. Ferraris, R.G. Andus, D.C. Hrncir, Steric effects on the optical and electrochemical properties of N-substituted pyrrole–thiophene monomers and polymers, J. Chem. Soc. Chem. Commun. (1989) 1318.

[20]J.P. Ferraris, T.R. Hanlon, Polymer 30 (1989) 1319.

[21]T.F. Otero, J. Carraco, A. Figuras, E. Brillas, J. Electroanal. Chem. 379 (1994) 231. [22]T.F. Otero, S. Villanueva, E. Brillas, J. Carrasco, Synthetic Met. 102 (1999) 1402. [23]S. Tarkuç, E. Sahmetliog˘lu, C. Tanyeli, I.M. Akhmedov, L. Toppare, Electrochim.

Acta 51 (2006) 5412.

[24]S. Varısß, M. Ak, C. Tanyeli, I.M. Akhmedov, L. Toppare, Eur. Polym. J. 42 (2006) 2352.

[25]E. Sßahin, E. Sahmetlioglu, I.M. Akhmedov, C. Tanyeli, L. Toppare, Org. Electron. 7 (2006) 351.

[26]S. Tarkuç, E. Sahmetliog˘lu, C. Tanyeli, I.M. Akhmedov, L. Toppare, Sensor. Actuat. B – Chem. 121 (2007) 622.

[27]F. Algı, A. Cihaner, Tetrahedron Lett. 49 (2008) 3530. [28]A. Cihaner, F. Algı, J. Electroanal. Chem. 614 (2008) 101. [29]A. Cihaner, F. Algı, Electrochim. Acta 53 (2008) 2574.

[30]A. Yavuz, B. Bezgin, A.M. Önal, J. Appl. Polym. Sci. 114 (2009) 2685. [31]A. Yavuz, B. Bezgin, L. Aras, A.M. Önal, J. Appl. Polym. Sci. 122 (2011) 1293. [32]A. Yavuz, B. Bezgin, L. Aras, A.M. Önal, J. Electroanal. Chem. 1–2 (2010) 116. [33]D. Asil, A. Cihaner, F. Algı, A.M. Önal, Electroanalysis 22 (2010) 2254. [34]E.E. Havinga, C.M.J. Mutsaers, L.W. Jenneskens, Chem. Mater. 8 (1996) 769. [35]G.A. Sotzing, J.R. Reynolds, P. Steel, Chem. Mater. 8 (1996) 882.

[36]J.W.W. Chang, X. Xu, P. Wai, H. Chan, Tetrahedron Lett. 48 (2007) 245. [37]H.M. Gilow, D.E. Burton, J. Org. Chem. 46 (1981) 2221.

[38]B.D. Reeves, C.R.G. Greiner, A.A. Argun, A. Cirpan, T.D. McCarley, J.R. Reynolds, Macromolecules 37 (2004) 7559.