Electrochemistry and spectroelectrochemistry of a novel selenophene-based monomer

Article abstract of DOI:10.1016/j.electacta.2011.11.021

A stereocontrolled synthesis of a novel selenophene-based monomer namely (E,E)-1,4-dimethoxy-2,5-bis[2-(selenophen-2-yl)ethenyl]benzene has been successfully performed starting from 1,4-dimethoxybenzene. Its spectra, electrochemistry and polymerization ha

Full text of DOI:10.1016/j.electacta.2011.11.021

Electrochimica Acta 59 (2012) 567–572
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Electrochimica Acta
journal homepage: www.elsevier.com/locate/electacta
Electrochemistry and spectroelectrochemistry of a novel selenophene-based
monomer
Przemyslaw Dataa,b, Mieczyslaw Lapkowskia,b,∗, Radoslaw Motykaa, Jerzy Suwinskia
a Faculty of Chemistry, Silesian University of Technology, 44-100 Gliwice, Poland
b Center of Polymer and Carbon Materials, Polish Academy of Sciences, 41-819 Zabrze, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 July 2011
Received in revised form 3 November 2011
Accepted 4 November 2011
Available online 15 November 2011
A stereocontrolled synthesis of a novel selenophene-based monomer namely (E,E)-1,4-dimethoxy-
2,5-bis[2-(selenophen-2-yl)ethenyl]benzene has been successfully performed starting from 1,4-
dimethoxybenzene. Its spectra, electrochemistry and polymerization have been studied.
© 2011 Elsevier Ltd. All rights reserved.
Keywords:
Synthesis
Properties
Spectroelectrochemistry
X-ray analysis
1. Introduction
higher mobility than analog of polythiophenes (P3HT) [21,22]
Poly(9,90-n-dioctylfluorene-alt-biselenophene) (F8Se2) [23] and
In recent years there has been a rapid development of studies
related to the production of new materials for electrochromic
devices [1], electronic papers, sensors, radio frequency identifica-
tion tags [2], polymeric light emitting diodes, organic photovoltaic
devices [3,4], and organic single crystal field-effect transistors
[5]. An important group of compounds that may have potential
application are oligomers [6,7] or polymers of thiophene and
their derivatives [8]. Oligomers of thiophene are well known
to possess good electrodonating properties [9], considerable
mobility of charges and substantial crystallinity [10]. Surprisingly,
up to 2005 only little attention has been given to polymers of
selenophene and its derivatives even though selenophene has
lower oxidation potential in compare to its sulfur or oxygen
analogs. In the last few years a number of papers on polymers
bearing selenophene have grown rapidly [11–17] and first elec-
poly(5,50-bis(3-dodecylthiophene-2-yl)2-20-biselenophene)
(PDT2Se2) [24] revealed an order of magnitude larger field-effect
mobility than their sulfur analogs, when used as active layers
in OFETs. For this reason, in recent years an increasing interest
in oligomers, polymers and copolymers containing selenophene
moiety has been observed. Of the many compounds synthesized
and studied may be mentioned: 1,3-diarylbenzo[c]selenophenes
[25], benzo[1,2-b:4,5-b’]diselenophenes [26], selenopheno[3,2-
b]thiophene
benzo[c]thiophene/benzo[c]selenophene
[27]
or
9,9-dialkylfluorene
derivatives
capped
[28].
Attracted much interest: poly(3,4-ethylenedioxyselenophene)
(PEDOS; PEDOT analog) [29–31], poly(fluorene-co-selenophene)
[13] and poly(9,9ꢀ-dioctylfluorene-alt-biselenophene) [21]. Very
recent review on poly(selenophene) and its derivatives was done
by Patra and Bendikov [32]. Selenophene derivatives have a lower
oxidation potentials than the thiophenes but higher than tel-
lurophenes analogs in series Te < Se < S [33,34]. In comparison with
tellurophene analogs selenophene derivatives are more stable
[35,36].
trochromic device where
a selenophene-containing polymer
was used as an active layer was described in 2009 [18]. Few
years ago, regioregular poly(3-hexylselenophene) (P3HS) [19,20]
have been reported for organic electronic applications, with
Formerly, it was shown that monomers with conjugated system
of multiple bonds bearing two terminal residues of chalco-
gens (furan or thiophene) with free positions in C5 (Fig. 1,
structure 1) are able to electropolymerize leading to linear
PPV-type conducting systems that show strong electrolumines-
cence [37–40]. Now we present a synthesis and some properties
∗
Corresponding author at: Faculty of Chemistry, Silesian University of Technol-
ogy, 44-100 Gliwice, Poland.
E-mail address: mieczyslaw.lapkowski@polsl.pl (M. Lapkowski).
0013-4686/$ – see front matter © 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.electacta.2011.11.021

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P. Data et al. / Electrochimica Acta 59 (2012) 567–572
supplementary publication nos. CCDC 812456. Copies of the data
can be obtained, free of charge, on application to CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK (fax: +44 01223 336033 or e-mail:
deposit@ccdc.cam.ac.Uk).
2.2. Electrochemical measurement
The solutions of compound 2 with the concentration of 1.0 mM
were used for cyclic voltammperommetry measurements. Elec-
trochemical studies were conducted in 0.1 M solution of Bu4NBF4
(Sigma Aldrich 99%) in anhydrous dichloromethane at room tem-
perature. The electrochemical investigations were carried out
using Eco Chemie Company’s AUTOLAB potentiostat “PGSTAT20”.
The results were collected using GPES (General Purpose Electro-
chemical System) software. The electrochemical cell comprised
of platinum wire with 1 mm diameter of working area as work-
ing electrode, Ag wire – calibrated versus ferrocene/ferrocinium
redox couple – as a quasi-reference electrode and platinum coil as
auxiliary electrode. Cyclic voltammperometry measurements were
conducted at 50 mV/s potential rate.
Fig. 1. Structures of monomers with conjugated system of multiple bonds and two
terminal residues of furan (1a), thiophene (1b) or selenophene (2).
of compound 2 being (EE) selenophene analog of compounds
1.
2. Experimental
2.1. Synthesis
2.1.1. General
All solvents were dried and then distilled before the use. Other
commercial substances and reagents were used without purifica-
tion. Melting points (not corrected) were determined on Boetius
HMK apparatus. NMR spectra were taken in CDCl3 with TMS as
an internal reference by Varian XL-300 at 300 MHz for 1H and at
75.5 MHz for 13C. EA results were obtained using Perkin-Elmer CHN
automatic analyzer. X-ray structural data have been obtained on
the Gemini A Ultra diffractometer. The structures were determined
by means of direct methods and refined by the full-matrix least
squares technique.
3. Results and discussion
A
stereocontrolled three steps synthesis of
a
novel
selenophene-based monomer namely (E,E)-1,4-dimethoxy-2,5-
bis[2-(selenophen-2-yl)ethenyl]benzene (2) has been successfully
performed starting from 1,4-dimethoxybenzene (3) as it is shown
in Scheme 1. Compound 3 was treated with paraformaldehyde
and gaseous hydrogen chloride in the solution of glacial acetic acid
and concentrated hydrochloric acid to give 2,5-bis(chloromethyl)-
1,4-dimethoxybenzene (4). The latter compound on heating
at with ca 20% excess of triethoxyphosphine 150 ◦C afforded
2,5-bis(diethylphosphononomethyl)-1,4-dimethoxybenzene as a
white powder in 30% yield.
2.1.2. Preparation details
2.1.2.1. (E,E)-1,4-dimethoxy-2,5-bis[2-(selenophen-2-
yl)ethenyl]benzene
(2). This
compound
was
synthesized
following a slightly modified procedure known for the syn-
thesis of (E,E)-2,5-bis(2,5-dihexylstyryl)-1,4-dimethoxybenzene
[39,40]. Preparation procedures of intermediate materials
(selenophene-2-carboxyaldehyde and tetraethyl [2,5-dimethoxy-
1,4-bis(methylene)]diphosphonate) can be obtained on request
from authors as an supplementary additional material.
During our former work on preparation of several compounds
of type 1, we treated bis(chloromethyl)-1,4-dialkoxybenzenes with
triphenylphosphine (instead of triethoxyphosphine used here); the
respective substitution products obtained in form of salts, were
then condensed with appropriate 2-chalcogenecarbaldehydes.
Such method in all cases lead to mixtures of stereoisomers differing
in configuration of substituents at the double bonds. Separa-
tion of stereoisomers was always troublesome [37–41]. After all,
ZZ isomers were rather unstable and in solutions quickly iso-
merized to give equilibrium mixtures. All separated steroisomers
underwent electropolymerization showing two oxidation peaks.
For the stereoisomers, first oxidation peaks appeared at differ-
ent potentials decreasing in the following order ZZ, EZ, EE. Only
small differences in oxidation potentials could be spotted for the
second peaks what might suggest isomerization prior to oxida-
tion. Polymers obtained from the stereoisomers did not show
distinct differences what seemed to support the former sugges-
tion [39]. Therefore, a stereocontrolled condensation of 5 with
2-selenophenecarbaldehyde leading to the most stable EE isomer
was a method of choice for the synthesis of 2 even if yields achieved
would be lower in comparison with reaction using triphenylphos-
phine derivatives. Indeed, the reaction afforded the expected EE
isomer as the only product. Its structure was proved by 1H NMR
spectrum analysis (two doublets 2H J = 15.9 Hz at 7.13 and 7.33 cor-
responding to two pairs of vinyl groups of E configuration). This
finding was confirmed by X-ray crystallography of 2 monocrystal
(crystal dimensions 0.38 mm × 0.27 mm × 0.12 mm). 3058 reflec-
tions were collected using Cu K␣ radiation within 3 h 13 min at
100 K. Program used to solve structure was: SHELXS97 (Sheldrick
[42]); program used to refine structure: SHELXL97 (Sheldrick [43]).
ORTEP projection is shown in Fig. 2. The shape of molecules of
A
cold
2.28 mmol)
solution
of
and
selenophene-2-karboxyaldehyde
tetraethyl [2,5-dimethoxy-1,4-
(0.36 g,
bis(methylene)]diphosphonate (0.50 g, 1.14 mmol) in dry DMF
(5 mL) was added dropwise to a solution of t-BuOK (0.79 g,
7.05 mmol) in DMF (10 mL) at 0 ◦C. The mixture was stirred
without cooling for 2.5 h and then poured into cold water (50 mL)
acidified with conc. HCl (1 mL). The obtained solution was extracted
with dichloromethane (3 × 25 mL) and organic extracts were dried
over MgSO4. The solvents were evaporated under diminished
pressure and the residue purified by column chromatography
over silica gel using hexane:benzene (4:1) as eluent to give
(E,E)-1,4-dimethoxy-2,5-bis[2-(selenophen-2-yl)ethenyl]benzene
(0.15 g, 0.34 mmol, 30%) as orange crystals (m.p. 224–226 ◦C). 1H
NMR ı (300 MHz, CDCl3): 3.91 (6H, s, CH3); 7.04 (2H, s, ArH),
7.13 (2H, d, J = 15.9 Hz, CH vinyl); 7.20–7.24 (4H, m, C4H3Se, C4H,
C3H); 7.33 (2H, d, J = 15.9 Hz, CH vinyl); 7.83–7.85 (2H, m, C4H3Se,
C5H). 13C NMR (75 MHz, CDCl3): ı 56.42 (OCH3); 109.38 (Ar,
CH); 124.51 (C vinyl); 124.96 (C vinyl); 126.28 (ArCCH); 128.84
(C4H3Se, C5); 129.00 (C4H3Se, C4); 130.27 (C4H3Se, C3); 150.00
(C4H3Se, C2); 151.59 (Ar, COAlk). UV (CH2Cl2): ꢀ = 414.5 nm;
ε = (4.66 0.29) × 104;
ꢀ = 355.0 nm;
ε = (1.77 0.12) × 104;
ꢀ = 293.0 nm; ε = (0.82 0.07) × 104 [dm3/mol cm].
The structure of product was additionally proved by X-ray
measurements of
a monocrystal of (E,E)-1,4-dimethoxy-2,5-
bis[2-(selenophen-2-yl)ethenyl]benzene (2). Crystallographic data
(excluding structure factors) for the structure of 2 has been
deposited with the Cambridge Crystallographic Data Centre as

P. Data et al. / Electrochimica Acta 59 (2012) 567–572
569
Scheme 1. A stereocontrolled three steps synthesis of (E,E)-1,4-dimethoxy-2,5-bis[2-(selenophen-2-yl)ethenyl]benzene (2).
conventional factors R were based on F, with F set to zero for
negative F2. The following results were obtained: final R indices
[>2sigma(I)], R1 = 0.0449, wR2 = 0.1168 and final R indices (all data),
R1 = 0.0476, wR2 = 0.1211.
For the sample, Mo provided better data than Cu in terms
of R1 [>2sigma(I)]. R1 (all data) was similar in both cases while
the intensity of the Cu data was vastly greater than that for Mo,
with a value for I/sigma of 60 compared to 25. The ellipsoids
for the Mo data set were generally less well behaved than for
Cu.
The selenophene rings in the crystal of monomer 2 (Fig. 3)
are disordered over two orientations. Taking into account the
extent of disorder in this crystallographic structure of 2, a final
R1 of 4.49% is an excellent result. Similar phenomena disorders
in ring orientations were detected e.g., in structures of all 1,4-
dialkoxy-2,5-bis[2-(thiophene-2-yl)ethenyl]benzenes studied by
X-ray crystallography and thus can be consider as typical for com-
pounds of such type [37,41,44].
Synthesized compound 2 was oxidized during the multielectron
process shown in Fig. 4, with not clearly distinguishable individual
peaks, but coalescing ones to give a first maximum at 0.46 V and the
next, very broad at 0.95–1.05 V. During the reduction the increase of
current is observed in potential range 0.5–0.7 V indicating that the
process of catalytic polymerization showing a prominent peak for
the reduction of the forming polymer, showing up at the potential
Fig. 2. Molecular structure of (E,E)-1,4-dimethoxy-2,5-bis[2-(selenophen-2-yl)-
ethenyl]benzene (2) showing 50% probability displacement ellipsoids obtained by
ORTEP 3. A dominant conformation in the crystal is indicated by thicker lines.
monomer 2 allows relatively efficient crystal packing. The packing
mode is shown in Fig. 3 in a projection along the ˛-axis.
Refinement of F2 was calculated against all reflections. The
weighted R-factor wR and goodness of fit S were based on F2,
Fig. 4. Cyclic voltammograms of electropolymerization of compound 2 in wide oxi-
dation range. Measure conditions: scan rate 50 mV/s, Ag wire – calibrated versus
ferrocene/ferrocinium redox couple as a quasi-reference electrode.
Fig. 3. Crystal packing, shown in a projection along the crystallographic ˛-axis.

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P. Data et al. / Electrochimica Acta 59 (2012) 567–572
Fig. 5. Cyclic voltammograms of electropolymerization (a) of 2, doping–dedoping process of obtained polymeric film in monomer free medium (b) and redox process of
polymeric film in monomer free medium (c). Measure conditions: scan rate 50 mV/s, Ag wire – calibrated versus ferrocene/ferrocinium redox couple as a quasi-reference
electrode.
of 0.2 V. The next two scans shows the oxidation of the polymer
at potentials of 0.2 V prior to monomer oxidation peak, height of
which clearly increases confirming the autocatalytic effect of the
polymer formed on the electrode.
The best properties of the polymer were obtained by limiting
the potential of polymerization to approximately 0.6 V thus slightly
higher than the oxidation potential of monomer (2), as shown in
Fig. 5a. A regular increase of the polymer layer was observed when
the oxidation potential was 0.2 V and the reduction one equal to
0.18 V. The sharp reduction peak at the potential of −0.11 V is
responsible for a violent change of conductivity of the polymer at
the transition from the conductive phase to nonconductive one.
By transferring the electrode with deposited polymer layer into
an electrolyte solution without the monomer, voltammetric curve
shown in Fig. 5b was obtained. It is evident that the shape of
the polymer curve very well matches those obtained during the
polymerization what may suggest practically quantitative poly-
merization of monomer 2 with only very small amounts of possible
by-products. The rapid decrease in current after return of potential
Table 1
Electrochemical and optical band-gap.
Homo (eV)
Lumo (eV)
Eg El. (eV)
Eg Op. (eV)
Poly(1b)
Poly(2)
−5.26
−4.79
−3.33
−3.09
1.93
1.70
1.92
1.67
Fig. 6. A comparison of monomer 2 fluorescence spectra and excitation spectra.

P. Data et al. / Electrochimica Acta 59 (2012) 567–572
571
Fig. 7. UV–Vis spectra recorded during electrochemical oxidation of poly(2) film.
at 0.6 V demonstrates that the resulting polymer is characterized
by high electrical conductivity. Next voltammetric cycles run at the
same practical curves showing high electrochemical stability of the
polymers at the investigated range of potentials. In addition to the
oxidation, monomer 2 can also be reduced, as shown in Fig. 5c,
yielding reversible redox system located at the potential ca. −2.0 V.
This allowed us to determine so called electrochemical band gap,
which is equal to 1.70 eV. Comparing the results obtained here with
data for thiophene analog one can see that the energy gap width
for the thiophene polymer is higher amounting to 1.93 eV.
Monomer 2 readily undergoes electropolymerization to afford
product of excellent stability. Both monomer 2 and its polymer
exhibit photoluminescent properties what could enable them to
qualify for the group of materials of the potential applications in
optoelectronics.
Acknowledgments
X-ray measurements was performed courtesy of Oliver Presly,
Ph.D., Program Marketing Manager, XRD; Oxford Diffraction Ltd. –
now Agilent Technologies.
Fluorescence spectra of monomer
2
registered in
dichloromethane solution are illustrated in Fig. 6. These obser-
vations are consistent with the absorption spectroscopy data.
The monomers exhibited a strong peak at 467 and 492 nm when
excited by 385 (Fig. 6).
References
[1] P.M. Beaujuge, J.R. Reynolds, Chem. Rev. 110 (2010) 268.
[2] H. Klauk, Chem. Soc. Rev. 39 (2010) 2643.
In order to find relation between redox processes and UV–Vis
absorption the spectroelectrochemical properties of polymer of
2 prepared on ITO coated glass electrode was investigated. The
UV–Vis set of spectrum recorded during the polymer oxidation
revealed the absorption band (400–700 nm) correlated with the
polymer (Fig. 7), gradually losing its intensity as the applied poten-
tial is increased. In the same time, the new defined absorption
band occurred (700–1100 nm Fig. 7), owing the formation of radical
cation (polaron). Formation of other charge carriers (probably bipo-
laron band) occurs with absorption band formation from 950 nm to
beyond 1100 nm. Under oxidation polymers layer from gold color
turns to dark violet.
Thank to electrochemical characterization of polymers by ana-
lyzing oxidation and reduction processes it is possible to estimation
of electrochemical band-gap value. In correlation to the molecular
band, oxidation peak is related to the HOMO band and reduc-
tion peak is related to the LUMO band. Electrochemical band-gap
value is the range between those peaks (Table 1). The lowest
electrochemical and optical band-gap have polymer containing
biselenophene unit.
[3] H. Dong, C. Wang, W. Hu, Chem. Commun. 46 (2010) 5211.
[4] A.W. Hains, Z. Liang, M.A. Woodhouse, B.A. Gregg, Chem. Rev. 110 (2010) 6689.
[5] L. Jiang, H. Dong, W. Hu, J. Mater. Chem. 20 (2010) 4994.
[6] A.R. Murphy, J.M.J. Fréchet, Chem. Rev. 107 (2007) 1066.
[7] A. Mishra, C.Q. Ma, P. Baüerle, Chem. Rev. 109 (2009) 1141.
[8] S.S. Zade, N. Zamoshchik, M. Bendikov, Acc. Chem. Res. 44 (2011) 14.
[9] J. Heinze, B.A. Frontana-Uribe, S. Ludwigs, Chem. Rev. 110 (2010) 4724.
[10] R. LI, W. Hu, Y. Liu, D. Zhu, Acc. Chem. Res. 43 (2010) 529.
[11] T.T. Ong, S.C. Ng, H.S.O. Chan, Polymer 44 (2003) 5597.
[12] K. Takimiya, Y. Kunugi, Y. Konda, N. Niihara, T. Otsubo, J. Am. Chem. Soc. 126
(2004) 5084.
[13] R. Yang, R. Tian, Q. Hou, Y. Zhang, Y. Li, W. Yang, C. Zhang, Y. Cao, J. Polym. Sci.:
Part A: Polym. Chem. 43 (2005) 823.
[14] D.J. Crouch, P.J. Skabara, J.E. Lohr, J.J.W. McDouall, M. Heeney, I. McCulloch, D.
Sparrowe, M. Shkunov, S.J. Coles, P.N. Horton, M.B. Hursthouse, Chem. Mater.
17 (2005) 6567.
[15] K. Aydemir, S. Tarkuc, A. Durmus, G.E. Gunbas, L. Toppare, Polymer 49 (2008)
2029.
[16] Y. Arslan Udum, S. Tarkuc, L. Toppare, Synth. Met. 159 (2009) 361.
[17] M. Heeney, W. Zhang, D.J. Crouch, M.L. Chabinyc, S. Gordeyev, R. Hamilton, S.J.
Higgins, I. McCulloch, P.J. Skabara, D. Sparrowe, S. Tierney, Chem. Commun.
(2007) 5061.
[18] Z. Chen, H. Lemke, S. Albert-Seifried, M. Caironi, M.M. Nielsen, M. Heeney, W.
Zhang, I. McCulloch, H. Sirringhaus, Adv. Mater. 22 (2010) 2371.
[19] A.M. Ballantyne, L. Chen, J. Nelson, D.D.C. Bradley, Y. Astuti, A. Maurano, C.G.
Shuttle, J.R. Durrant, M. Heeney, W. Duffy, I. McCulloch, Adv. Mater. 19 (2007)
4544.
[20] M. Heeney, W. Zhang, D. Crouch, D. Sparrowe, R. Hamilton, S. Higgins, P.
Skabara, I. McCulloch, Chem. Commun. (2007) 5061.
[21] Y.M. Kim, E. Lim, I.-N. Kang, B.-J. Jung, J. Lee, B.W. Koo, L.-M. Do, H.-K. Shim,
Macromolecules 39 (2006) 4081.
[22] H. Kong, D.S. Chung, I.-N. Kang, J.-H. Park, M.-J.I.H. Jung, C.E. Park, H.-K. Shim, J.
Mater. Chem. 19 (2009) 3490.
[23] A.K. Mohanakrishnan, P. Amaladass, Tetrahedron Lett. 46 (2005) 7201.
[24] P. Gao, D. Beckmann, H.N. Tsao, X. Feng, V. Enkelmann, W. Pisulaz, K. Mullen,
Chem. Commun. (2008) 1548.
[25] H. Kong, Y.K. Jung, N.S. Cho, I.-N. Kang, J.-H. Park, S. Cho, H.-K. Shim, Chem.
Mater. 21 (2009) 2650.
[26] S.P. Mishra, A.E. Javier, R. Zhang, J. Liu, J.A. Belot, I. Osaka, R.D. McCullough, J.
Mater. Chem. 21 (2011) 1551.
[27] A.K. Mohanakrishnan, N.S. Kumar, P. Amaladass, Tetrahedron Lett. 49 (2008)
4792.
4. Conclusions
Presented results show that (E,E)-1,4-dimethoxy-2,5-bis[2-
(selenophen-2-yl)ethenyl]benzene (monomer 2) can be obtained
by condensation of 2-selenophenecarbaldehyde with tetraethyl
[2,5-dimethoxy-1,4-bis(methylene)]-diphosphonate as the solely
isolated isomer. Its structure as EE isomer can be proved both by
the presence of two doublets at 7.13 and 7.33 (with J = 15.9 Hz) cor-
responding to two pairs of E vinyl protons groups in analysis of 1
NMR spectrum and by analysis of X-ray measurements results of a
monocrystal of 2.
H

572
P. Data et al. / Electrochimica Acta 59 (2012) 567–572
[28] N.S. Kumar, A.K. Mohanakrishnan, Tetrahedron 66 (2010) 5660.
[29] A. Patra, Y.H. Wijsboom, S.S. Zade, M. Li, Y. Sheynin, G. Leitus, M. Bendikov, J.
Am. Chem. Soc. 130 (2008) 6734.
[37] R. Gabanski, K. Waskiewicz, J. Suwin´ ski, ARKIVOC V (2005) 58.
[38] K. Waskiewicz, R. Gabanski, J. Zak, M. Lapkowski, J. Suwinski, Electrochem.
Solid-State Lett. 8 (2005) E24.
[30] Y.H. Wijsboom, Y. Sheynin, A. Patra, N. Zamoshchik, R. Vardimon, G. Leitus, M.
Bendikov, J. Mater. Chem. 21 (2011) 1368.
[39] M. Lapkowski, K. Waskiewicz, R. Gabanski, J. Zak, J. Suwinski, Russ. J. Elec-
trochem. 42 (2006) 1267.
[31] Y.H. Wijsboom, A. Patra, S.S. Zade, Y. Sheynin, M. Li, L.J.W. Shimon, M. Bendikov,
Angew. Chem. Int. Ed. 48 (2009) 5443.
[32] A. Patra, M. Bendikov, J. Mater. Chem. 20 (2010) 422.
[33] A. Patra, Y.H. Wijsboom, G. Leitus, M. Bendikov, Org. Lett. 11 (2009) 1487.
[34] T. Otsubo, S. Inoue, H. Nozoe, T. Jigami, F. Ogura, Synth. Met. 69 (1995) 537.
[35] A.A. Jahnke, D.S. Seferos, Macromol. Rapid Commun. 32 (2011) 943.
[36] P. Data, M. Lapkowski, J. Suwinski, R. Motyka, Macromol. Chem. Phys. (2011),
doi:10.1002/macp.201100384.
[40] I. Brehm, S. Hinneschiedt, H. Meier, Eur. J. Org. Chem. 18 (2002) 3162.
[41] I. Fuks-Janczarek, A.H. Reshak, W. Kuznik, I.V. Kityk, R. Gabanski, M. Łapkowski,
R. Motyka, J. Suwinski, Spectrochim. Acta Part A 72 (2009) 394.
[42] G.M. Sheldrick, Acta Crystallogr. Sect. A (1990) 467.
[43] G.M. Sheldrick, Program for crystal structure refinement, University Gottingen,
Germany, 1997.
[44] H. Irngartinger, J. Lichtenhaler, R. Herpich, Struct. Cem. 5 (1994) 283.