Synthesis and Solid-State Polymerization of 4-(Dimethylamino) phenylbutadiyne Derivatives and Their Charge-Transfer Complexes

Article abstract of DOI:10.1080/15421406.2013.804753

(Five urethane derivatives of 8-[4-(dimethylamino)phenyl]octa-5,7-diyn-1-ol were synthesized. They could be polymerized in the solid state to give conjugated backbones although structural regularity seemed to be not so high. Formability of chargetransfer

Full text of DOI:10.1080/15421406.2013.804753

This article was downloaded by: [University of Birmingham]
On: 28 January 2015, At: 00:55
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Molecular Crystals and Liquid Crystals
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/gmcl20
Synthesis and Solid-State Polymerization
of 4-(Dimethylamino)phenylbutadiyne
Derivatives and Their Charge-Transfer
Complexes
a
a
a
a
Shinji Ishii , Shota Kaneko , Yoko Tatewaki & Shuji Okada
a
Graduate School of Science and Engineering , Yamagata
University , Yonezawa , Japan
Published online: 11 Sep 2013.
To cite this article: Shinji Ishii , Shota Kaneko , Yoko Tatewaki & Shuji Okada (2013) Synthesis
and Solid-State Polymerization of 4-(Dimethylamino)phenylbutadiyne Derivatives and Their
Charge-Transfer Complexes, Molecular Crystals and Liquid Crystals, 580:1, 64-68, DOI:
10.1080/15421406.2013.804753
To link to this article: http://dx.doi.org/10.1080/15421406.2013.804753
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the
“
Content”) contained in the publications on our platform. However, Taylor & Francis,
our agents, and our licensors make no representations or warranties whatsoever as to
the accuracy, completeness, or suitability for any purpose of the Content. Any opinions
and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sources
of information. Taylor and Francis shall not be liable for any losses, actions, claims,
proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or
howsoever caused arising directly or indirectly in connection with, in relation to or arising
out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &
Conditions of access and use can be found at http://www.tandfonline.com/page/terms-
and-conditions

Mol. Cryst. Liq. Cryst., Vol. 580: pp. 64–68, 2013
Copyright © Taylor & Francis Group, LLC
ISSN: 1542-1406 print/1563-5287 online
DOI: 10.1080/15421406.2013.804753
Synthesis and Solid-State Polymerization
of 4-(Dimethylamino)phenylbutadiyne Derivatives
and Their Charge-Transfer Complexes
SHINJI ISHII, SHOTA KANEKO, YOKO TATEWAKI,
∗
AND SHUJI OKADA
Graduate School of Science and Engineering, Yamagata University,
Yonezawa, Japan
Five urethane derivatives of 8-[4-(dimethylamino)phenyl]octa-5,7-diyn-1-ol were syn-
thesized. They could be polymerized in the solid state to give conjugated backbones
although structural regularity seemed to be not so high. Formability of charge-
transfer (CT) complex of one of the urethane derivatives and bis[4-(dimethylamino)
phenyl]butadiyne as a reference compound with acceptors, such as 1,4-benzoquinone,
2
,4,7-trinitrofluorenone etc., were investigated by solution mixing and powder co-
grinding methods. In some cases, the CT complex formability was changed by the
preparation method.
Keywords Charge-transfer complex; conjugated polymer; donor; polydiacetylene;
solid-state polymerization
1. Introduction
Conjugated polymers are often recognized as conducting polymers. However, polydiacety-
lene obtained by solid-state polymerization of butadiyne monomers [1] has been exception
because its high crystallinity avoids immersing dopant molecules into the crystals and
effective doping is difficult [2]. On the other hand, charge-transfer (CT) complexes such
as tetrathiafluvalene-tetracyanoquinodimethane (TTF-TCNQ) have high crystallinity and
high conductivity [3]. Thus, if we combine these two systems, i.e., conjugated polymers
and CT complexes, interesting electronic properties may appear. Our strategy is as follows:
First, butadiyne derivatives with a donor (or an acceptor) moiety directly bound to the bu-
tadiynyl group are synthesized. Second, the monomers are mixed with acceptor (or donor)
molecules to form the CT complexes. Finally, the CT-complex monomers are polymerized
in the solid state. However, synthesis of solid-state polymerizable butadiyne monomers
directly substituted by one or two aromatic groups is quite difficult, and several attempts
should be required for the final goal. In this study as one step of this approach, we syn-
thesized butadiyne derivatives directly substituted by a 4-(dimethylamino)phenyl group as
donor-attached monomers. Their solid-state polymerizability and CT-complex formability
with acceptors were investigated.
∗
Address correspondence to Shuji Okada, Department of Organic Device Engineering, Graduate
School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510, Japan.
E-mail: okadas@yz.yamagata-u.ac.jp
[316]/64

4-(Dimethylamino)phenylbutadiyne Derivatives
[317]/65
Figure 1. Synthesis scheme of 4-(dimethylamino)phenylbutadiyne derivatives.
2
. Experimental
-(Dimethylamino)phenylbutadiyne derivatives 5a–5e and the reference compound 6 were
synthesized according to Fig. 1. The monomer melting points measured by a SII DSC
220 differential scanning calorimeter are also shown in Fig. 1. Their structures were
4
6
1
13
identified by H- and C-NMR spectra, IR spectra and elemental analyses. NMR spectra
were obtained using JEOL ECX-400 spectrometers, and IR spectra were recorded on a
Horiba FT-210 spectrometer. The data for 5a as a representative compound are as follows:
1
H-NMR (CDCl3, δ) 0.94 (3H, t, J = 7.2 Hz), 1.38 (2H, tq, J = 7.5, 7.2 Hz), 1.59–1.68
(
(
4H, m), 1.77 (2H, m), 2.40 (2H, t, J = 7.0 Hz), 2.97 (6H, s), 3.96 (2H, d, J = 5.0 Hz), 4.12
2H, t, J = 6.3 Hz), 4.16 (2H, t, J = 6.6 Hz), 5.15 (1H, broad t), 6.59 (2H, d, J = 9.0 Hz),
13
7
4
1
1
.35 (2H, d, J = 9.0 Hz); C-NMR (CDCl3, δ) 13.59, 18.97, 19.27, 24.79, 28.06, 30.50,
0.01, 42.68, 64.66, 65.26, 66.13, 72.21, 76.51, 82.65, 108.20, 111.61, 133.69, 150.36,
56.44, 170.09; IR (KBr) 3273, 3153, 2962, 2871, 2239, 2133, 1743, 1720, 1604, 1522,
−1
437, 1358, 1333, 1198, 1161, 1066 cm ; Found: C, 69.32; H, 7.67; N, 6.92%. Calcd for
C23H30N2O4: C, 69.32; H, 7.59; N, 7.03%.
Solid-state polymerization was examined by UV irradiation at 254 nm from a 4-W
lamp (UVP, UVG-11). Conversion to the polymer by UV irradiation for 3 h was estimated
from heat of melt, measured using DSC, for the monomer contained in the polymerized
samples. The CT complexes were prepared by two methods, i.e., solution mixing and
powder co-grinding [4]. In the solution mixing method, monomer solution was mixed
with acceptor solution, and solvent was evaporated. Solvent used were chloroform or THF
or acetonitrile. In the powder co-grinding method, monomer and acceptor crystals were
mixed and well ground using agate mortar and pestle. Mixing molar ratios of monomer
and acceptor molecules were 1:1 for 5a and 1:2 for 6. UV-visible-NIR diffuse reflectance
spectra of the solid samples were recorded using a Jasco V-570 spectrophotometer with an
integrated sphere (ILN-472).
3. Results and Discussion
Monomers 5a–5e were all polymerizable in the solid state by UV irradiation. Introduc-
tion of a urethane group for intermolecular hydrogen bonding increases probability of

66/[318]
S. Ishii et al.
Figure 2. Change in UV-visible diffuse reflectance spectra of 5a and 5e depending on irradiation
time of UV at 254 nm.
solid-state polymerization [5, 6]. Figure 2(a) shows the diffuse reflectance spectral change
of 5a during photopolymerization as a typical example. Absorption increase in the visible
region indicates formation of π-conjugated backbones. However, the excitonic absorption
band, which was observed for 27-[4-(dimethylamino)phenyl]heptacosa-24, 26-diynoic acid
at about 680 nm [7], was unclear except 5e, and the backbone structure seemed to be dis-
torted. Only for 5e, a weak excitonic peak appeared at around 660 nm as shown in Fig.
2(b). Conversion of 5a, 5b, 5c, 5d and 5e was obtained to be 11%, 9%, 4%, 9% and 17%,
respectively. On the other hand, photopolymerization of 6 was not observed.
CT complex formation of 5a was confirmed by satisfying the following conditions:
i) Color darkening due to appearance of the CT bands and (ii) no change in NMR
(
spectra, i.e., spectra assigned to be summation of the original components after mixing
indicates no new covalent bonds due to the reaction. Since it has been reported that [4-
(dimethylamino)phenyl]acetylene derivatives reacted with tetracyanoethylene (TCNE) or
TCNQ through [2 + 2] cycloaddition and the following ring opening [8, 9], other acceptors
such as 1,4-benzoquinone (BQ), chloranil, 2,4,7-trinitrofluorenone (TNF) and 2,3-dichloro-
5,6-dicyano-1,4-benzoquinone (DDQ) were combined. In the solution mixing method, TNF
and DDQ showed color change of the mixed solution. Diffuse reflectance spectra after sol-
vent evaporation of the mixture of 5a with TNF or DDQ are shown in Figs. 3(a) and (b).
Although both of them showed broad absorption in visible region, the CT sites were dif-
ferent. From the NMR study, DDQ was found to give a [2 + 2] adduct with 5a, i.e., a C≡C
bond next to the 4-(dimethylamino)phenyl group of the butadiyne monomers and a C C
bond substituted by two cyano groups in DDQ reacted to form a cyclobutene ring. Similar
[
2 + 2] cycloaddition reaction between acetylene and DDQ has been recently reported
[10]. Thus, the broad visible absorption for the mixture of 5a and DDQ was concluded to
be intramolecular CT in the adduct. On the other hand, condition (ii) was satisfied for TNF.
Namely, the CT complex formation was confirmed for the mixture of 5a and TNF, and
the broad visible absorption was assigned to intermolecular CT. Reaction of TNF with the
donor monomers seems to be unfavorable because aromaticity of the compounds will be
lost after the reaction like the case of DDQ. For weaker acceptors of BQ and chloranil, clear
color change of the mixed solution was not observed. However, by powder co-grinding,
in which effective concentration of the components increased, both of BQ and chloranil
showed color change due to CT-complex formation with 5a. Diffuse reflectance spectra of
these CT complexes are displayed in Figs. 3(c) and (d). For the reference compound 6, the
same behaviors toward acceptors as 5a were observed. Namely, the 1:1 adduct via [2 + 2]
cycloaddition was isolated for DDQ, and other acceptors afforded CT complexes by the

4-(Dimethylamino)phenylbutadiyne Derivatives
[319]/67
Figure 3. UV-visible-NIR diffuse reflectance spectra of the mixtures of 5a with (a) TNF, (b) DDQ,
c) BQ and (d) chloranil. Preparation conditions of the mixtures are described in the text.
(
same method used for 5a. Thus, we found three types of donor-acceptor interactions be-
tween 4-(dimethylamino)phenylbutadiyne derivatives and acceptors, i.e., adduct formation,
CT-complex formation even in the mixed solution and CT-complex formation by mixing
in the solid state.
4. Conclusion
A series of 4-(dimethylamino)phenylbutadiyne derivatives 5a–5e and 6 were synthesized,
and 5a–5e were found to be photopolymerizable in the solid state. Since these monomers
are good donors, CT-complex formability of 5a and 6 with some acceptors was investigated.
DDQ gave the [2 + 2] adducts while TNF formed the CT complexes in the mixed solution.
Although BQ and chloranil did not form the CT complexes in the mixed solution, they could
be prepared by powder co-grinding. Further studies on structures and properties, including
solid-state polymerizability and conductivity, of the CT complexes are in progress.
Acknowledgment
This work was supported by a Grant-in-Aid for Challenging Exploratory Research (No.
21655048) from Japan Society for the Promotion of Science.
References
[
[
[
1] Wegner, G. (1969). Z. Naturforsch., 24b, 824.
2] Nakanishi, H., Matsuda, H., & Kato, M. (1984). Mol. Cryst. Liq. Cryst., 105, 77.
3] Ferraris, J., Cowan, D. O., Walatka, Jr., V., & Perlstein, J. H. (1973). J. Am. Chem. Soc., 95, 948.

68/[320]
S. Ishii et al.
[4] Kuroda, R., Sato, T., & Imai, Y. (2008). Cryst. Eng. Comm., 10, 1881.
[5] Sarkar, A., Okada, S., Nakanishi, H., & Matsuda, H. (1998). Macromolecules, 31, 9174.
[6] Shibuya, T., Tatewaki, Y., & Okada, S. (2012). Mol. Cryst. Liq. Cryst., 568, 93.
[7] Okada, S., Matsuda, H., Otsuka, M., Nakanishi, H., & Kato, M. (1994). Bull. Chem. Soc. Jpn.,
67, 483.
[8] Michinobu, T., May, J. C., Lim, J. H., Boudon, C., Gisselbrecht, J.-P., Seiler, P., Gross, M.,
Biaggio, I., & Diederich, F. (2005). Chem. Commun., 737.
[9] Kivala, M., Boudon, C., Gisselbrecht, J.-P., Seiler, P., Gross, M., & Diederich, F. (2007). Chem.
Commun., 4731.
[10] Trofimov, B. A., Sobenina, L. N., Stepanova, Z. V., Ushakov, I. A., Sinegovskaya, L. M.,
Vakul’skaya, T. I., & Mikhaleva, A. I. (2010). Synthesis, 470.