Concise syntheses, polymers, and properties of 3-arylthieno[3,2- b ]thiophenes

Article abstract of DOI:10.1021/ma301604e

Thieno[3,2-b]thiophenes (TT), having para-substituted phenyl groups at C-3, have been synthesized through a ring closure reaction, using P ₄S₁₀, in moderate to high yields. Their absorbance studies displayed that the TT, having nitro

Full text of DOI:10.1021/ma301604e

Article
pubs.acs.org/Macromolecules
Concise Syntheses, Polymers, and Properties of
3‑Arylthieno[3,2‑b]thiophenes
Asli Capan,† Hojat Veisi,‡ Ahmet C. Goren,§ and Turan Ozturk†,§,*
†Department of Chemistry, Faculty of Science, Istanbul Technical University, Maslak, Istanbul 34469, Turkey
‡Department of Chemistry, Payame Noor University, 19395-4697 Tehran, I. R. of Iran
§Chemistry Group, Organic Chemistry Laboratory, TUBITAK UME, PBox 54, 41470, Gebze-Kocaeli, Turkey
S
* Supporting Information
ABSTRACT: Thieno[3,2-b]thiophenes (TT), having para-substituted
phenyl groups at C-3, have been synthesized through a ring closure
reaction, using P4S10, in moderate to high yields. Their absorbance studies
displayed that the TT, having nitrophenyl group had the most red shift
absorbance at 365 nm, which also showed the lowest optical band gap of
2.92 eV; the rest of the TTs had the absorbance between 300 and 302 nm.
Cyclic voltammetry studies indicated that while all the TTs had the
oxidation potentials above 1.0 V, the TT with dimethylaminophenyl
group had the lowest oxidation potential of 1.33 V. The rest had the oxidation potentials between 1.6 and 1.99 V. The TTs were
both electropolymerized and copolymerized with thiophene through Suzuki coupling reaction. Electropolymerized polymers
indicated that while the polymer having strong electron donating dimethylaminophenyl group had the lowest oxidation potential
of 0.97 V, the rest of the polymers displayed the potentials between 1.09 and 1.39 V. Their electronic band gaps varied between
1.86 and 2.46 eV. The CV−UV studies of the polymers, electro-deposited on ITO, showed absorbance maxima between 431 and
468 nm, and the lowest optical band gap was observed with the polymer having methoxyphenyl group (1.99 eV). The rest of the
polymers had the optical band gaps between 2.05 and 2.19 eV. Regarding the copolymers, the one with methoxyphenyl group
had the lowest oxidation potential of 0.75 V. They displayed absorption and emission maxima between 325 and 445 and 454−
564 nm, respectively. Their optical and electronic band gaps varied between 2.0 and 2.5 eV. As the copolymer having strong
electron donating methoxyphenyl group had the highest quantum yield, 0.64 eV, the one with strong electron withdrawing
nitrophenyl group had the lowest quantum yield of 0.003 eV.
(2), thieno[3,4-b]thiophene (3), and thieno[3,4-c]thiophene
(4), among which the TT (1) has the lowest band gap and
ionization potential.14e This is due to the orientation of the
fused rings, which lead to a better conjugation in TT.
Moreover, when (1) was copolymerized with thiophene, a
lower HOMO energy level was observed compared with
poly(3-hexylthiophene).14e,7 This was explained that the flow of
electrons from the TT is less favorable than a thiophene ring as
TT has a larger resonance stabilization energy. One of the
reasons for polythiophenes being susceptible to various
oxidation mechanisms is having a very rich electron system.15
INTRODUCTION
■
Organic electronic materials have been the focus of an
increasing attention particularly in chemistry and physics.1−4
This is due to their possible applications in electronics and
optoelectronics, such as organic light-emitting diodes
(OLED),5 field-effect transistors (FET),4,6 lasers,7 photo-
diodes,8 and solar cells.9 Among them, thiophene-based π-
conjugated materials have been holding a particular interest,
owing to their environmental stability, high charge carrier
mobility, low cost and flexibility.10 One of the important
advantages of using thiophene in designing organic materials is
easy modification for tuning the electronic properties of the
materials such as electron affinity, ionization potential,
absorption and emission.11 Such tuning could also be
performed by fusing thiophene rings,12 among which
thienothiophenes (TT) play an important role as their core
skeleton consists of two fused rigid thiophene rings to limit the
rotational disorder between the rings and create a better π-
conjugation.12b,13 Recently various applications incorporating
TT into conjugated oligomers or polymers to improve their
electronic and optoelectronic properties have appeared in the
literature.14
Reports on the syntheses of TTs have been concentrated on
thieno[3,2-b]thiophene (1), as it has the most attractive
chemical structure.12b Leriche and co-workers achieved the
Received: July 30, 2012
As two fused thiophenes, thienothiophenes have four
isomers, thieno[3,2-b]thiophene (1), thieno[2,3-b]thiophene
Revised: September 16, 2012
Published: September 28, 2012
© 2012 American Chemical Society
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Article
viscometer, was conducted to measure the absolute molecular weights
(Mn,TDGPC and Mw,TDGPC) in THF with a flow rate of 0.5 mL/min at 35
°C. Three detectors were calibrated with a PS standard having a
narrow molecular weight distribution (Mn = 115 000 g/mol, Mw/Mn =
1.02, [η] = 0.519 dL/g at 35 °C in THF, dn/dc = 0.185 mL/g),
provided by Viscotek company.
synthesis in five steps through the ring closure of 3-
(carboxymethylsulfanyl)thiophene.16 Henssler and Matzger
reported that the reaction of 3-(2,2-diethoxy-ethylsulfanyl)-
thiophene in the presence of sulfonic acid resin gave (1) in high
yield.17 Thermal decomposition of thieno[3,2-b]thiophene-2-
carboxylic acid by Fuller and co-workers, which was synthesized
in three steps, in the presence of Cu in quinoline at 260 °C,
produced TT (1).18 Various substituted TTs and analogues of
TT, such as 2,3,5,6-tetrabromothieno[3,2-b]thiophene, 3,6-
dibromothieno[3,2-b]thiophene, 3-bromothieno[3,2-b]-
thiophene,18 3,6-dialkylthieno[3,2-b]thiophene,14b,17 5-bromo-
3-chlorothieno[3,2-b]thiophene-2-carbonyl chloride, 6-bromo-
3,5-dichlorothieno[3,2-b]thiophene-2-carbonyl chloride,19 2-
(6-bromo-5-methyl-3-(trifluoromethyl)thieno[3,2-b]thiophen-
2-yl)benzo[d]thiazole, 3-chloro-6-methoxy-carbonylnaphtho-
[2′,1′:2,3-b]thieno[4,5-d]thiophene-2-carboxylic acid chloride,
benzo[b]thieno[3,2-b]thiophene-2-carboxylic acid, 3a,5-di-
methyl-3aH-6,7,8,9-tetrahydrobenzo[c]thieno[3,2-b]thiophene,
2,3:5,6-bis(ethylenedithio)thieno[3,2-b]thiophene, thieno-
[2′,3′:4,5]thieno[2,3-c]quinoline, and 2,5-bis(3,5-di-tert-butyl-
4-oxocyclohexa-2,5-dien-2-ylidene)-2,5-dihydro-1,4-dithiapen-
talene were reported.20
As a continuation of our research on the synthesis of fused
thiophene derivatives,12a,21 we report here a concise syntheses
of thieno[3,2-b]thiophenes, having phenyl moiety (PhTT) (5)
at C-3, substituted with various groups such as methoxy
(MPhTT) (6), nitro (NPhTT) (7), bromine (BrPhTT) (8),
amine (APhTT) (9), and dimethylamine (DMAPhTT) (10).
Their electropolymerizations and polymerizations with thio-
phene through Suzuki coupling were conducted and their
properties were investigated.
1-Phenyl-2-(thiophen-3-ylthio)ethanone (13). To a solution of
3-bromothiophene (11) (11.83 mmol, 1.15 mL, 97%) dissolved in dry
diethyl ether (50 mL) was added n- butyllithium (11.83 mmol, 7.4 mL,
1.6 M) at −78 °C under nitrogen atmosphere and the mixture was
stirred for 1 h at the same temperature. Than, S8 (11.83 mmol, 0.38 g)
was added and the mixture was stirred for 1 h, after which it was placed
into an ice bath and 2-bromoacetophenone (12) (14.2 mmol, 2.83 g)
was introduced into the mixture portion wise. Stirring was continued
for 3 h and the reaction was quenched with water (10 mL). The
solution was extracted with diethyl ether and the organic layer was
washed with NaHCO3 (10%) and water. Organic layer was dried over
Na2SO4, filtered and the solvent was evaporated under reduced
pressure. The residue which remained in the reaction flask was washed
with dichloromethane, and the organic layer was extracted with
NaHCO3 (10%) and water. The organic layer was dried over Na2SO4
and filtered, and the solvent was evaporated under reduced pressure.
The crude products were combined and the residue was separated by
column chromatography eluting with hexane/CH2Cl2 (3/1) to give
the title compound (13) (1.13 g, 41%) as light yellow powder, mp
38−40 °C. IR (ATR, diamond) 3096, 2898, 1672, 1580, 1592, 772,
1
682 cm−1; H NMR (600 MHz, acetone-d6) δ (ppm) 8.02 (d, J = 8.2
Hz, 2H), 7.63 (t, J = 8.2 Hz, 1H), 7.52 (t, J = 8.2 Hz, 2H), 7.49 (dd, J
= 5.3, 2.9 Hz, 1H), 7.36 (dd, J = 2.9, 1.2 Hz, 1H), 7.08 (dd, J = 5.3, 1.2
Hz, 1H), 4.43 (s, 2H); 13C NMR (150 MHz, CDCl3) δ (ppm) 194.2,
135.4, 133.5, 130.3, 129.8, 128.7, 126.5, 126.4, 42.1; HRMS m/z calcd
for C12H10OS2+Na 257.0065, found 257.007.
The following were similarly prepared.
1-(4-Methoxyphenyl)-2-(thiophen-3-ylthio)ethanone (14).
The crude product was separated by column chromatography eluting
with hexane/CH2Cl2 (3/1) to give the title compound (14) (1.6 g,
53%) as white powder, mp 69−71 °C. IR (ATR, diamond) 3099,
2976, 1660, 1600, 1572, 1508, 856, 833, 818, 632 cm−1; 1H NMR (600
MHz, acetone-d6) δ (ppm) 8.00 (d, J = 8.78 Hz, 2H), 7.50 (dd, J = 4.9
Hz, 3.0 Hz, 1H), 7.36 (dd, J = 3.0 Hz, 1.2 Hz, 1H), 7.08 (dd, J = 4.9
Hz, 1,2 Hz, 1H), 7.03 (d, J = 8.78, 2H), 4.38 (s, 2H), 3.89 (s, 3H); 13C
NMR (150 MHz, CDCl3) δ (ppm) 192.9, 163.8, 131.0, 130.3, 130.0,
128.4, 126.3, 126.2, 113.8, 55.5, 41.9; HRMS m/z calcd for
C13H13O2S2 265.0357, found 2265.035.
1-(4-Nitrophenyl)-2-(thiophen-3-ylthio)ethanone (15). The
crude product was separated by column chromatography eluting
with hexane/CH2Cl2 (3/1) to give the title compound (15) (2.76 g,
84%) as yellow powder, mp 99−100 °C. IR (ATR, diamond) 3100,
1
2889, 1680, 1519, 1345, 854, 842, 741, 684 cm−1; H NMR (600
EXPERIMENTAL DETAILS
■
MHz, acetone-d6) δ (ppm) 8.35 (d, J = 8.8 Hz, 2H), 8.24 (d, J = 8.8
Hz, 2H), 7.51 (dd, J = 4.7 Hz, 3.0 Hz, 1H), 7.38 (dd, J = 3.0 Hz, 1.1
Hz, 1H), 7.09 (dd, J = 4.7 Hz, 1.1 Hz, 1H), 4.49 (s, 2H); 13C NMR
(150 MHz, CDCl3) δ (ppm) 192.5, 150.4, 139.9, 130.4, 129.8, 128.6,
127.8, 126.9, 123.9, 42.1; HRMS m/z calcd for C12H8N1O3S2
277.9951, found 277.9940.
1-(4-Bromophenyl)-2-(thiophen-3-ylthio)ethanone (16). The
crude product was separated by column chromatography eluting with
hexane/CH2Cl2 (3/1) to give the title compound (16) (2.1 g, 57%) as
yellow powder, mp 79−82 °C. IR (ATR, diamond) 3096, 2888, 1672,
1581, 1395, 1193, 856, 812 cm−1; 1H NMR (600 MHz, acetone-d6) δ
(ppm) 7.94 (d, J = 8.2 Hz, 2H), 7.71 (d, J = 8.2 Hz, 2H), 7.50 (dd, J =
5.3 Hz, 3.0 Hz, 1H), 7.37 (dd, J = 3.0 Hz, 1.2 Hz, 1H), 7.09 (dd, J =
5.3 Hz, 1.2 Hz, 1H), 4.41 (s, 2H); 13C NMR (150 MHz, CDCl3) δ
(ppm) 193.2, 134.1, 132.0, 130.4, 130.2, 129.3, 128.7, 127.0, 126.6,
41.9; MS m/z = 314.87 (M + 1). Anal. Calcd fof C12H9BrOS2: C, 46.0;
H, 2.90. Found: C, 46.20; H, 2.82.
Materials. 3-bromothiophene, 97%, (Across), phosphorus decasu-
lfide, 2-bromoacetophenone, 2-bromo-4′-methoxyacetophenone, 2-
bromo-4′-nitroacetophenone, 2,4′-dibromoacetophenone, n-butyl-
lithium, dichloromethane (Aldrich), diethyl ether, toluene, and sodium
bicarbonate (Merck) were used without further purification except for
diethyl ether and THF, which was dried over metallic sodium.
Methods. CH-Instruments Model 400A was used as a potentiostat
for the CV studies. FTIR spectra were recorded on a Thermo Nicolet
6700 FT-IR spectrometer. UV measurements were studied on
HITACHI U-0080D. H and 13C NMR spectra were recorded on a
1
Varian model NMR (500 and 600 MHz). Proton and carbon chemical
shifts are reported in ppm downfield from tetramethylsilane (TMS).
Mass spectra were recorded on Bruker MICROTOFQ and Thermo
LCQ-Deca ion trap mass instruments. Thermal analyses (TA) of the
polymers were conducted by PerkineElmer Thermal Analyzer System
equipped with Pyris 6 model thermogravimetry and Jude Differential
Scanning calorimetry (DSC) systems. A triple detection GPC (TD-
GPC) setup with an Agilent 1200 model isocratic pump, four Waters
Styragel columns (guard, HR 5E, HR 4, HR 3, and HR 2) and a
Viscotek TDA 302 triple detector, including RI, dual laser light
scattering (λ = 670 nm, at 90° and 7°) and a differential pressure
3-Phenylthieno[3,2-b]thiophene (5). A mixture of 13 (0.5 g, 2.1
mmol), P4S10 (1.83 g, 4.1 mmol), and p-toluenesulfonic acid (1.9 g,
10.3 mmol) dissolved in toluene (80 mL) was refluxed for 3 h. The
mixture was then extracted with dichloromethane and the organic layer
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was washed with NaHCO3 (10%), brine, water and the organic layer
was dried over Na2SO4, filtered and the solvent was evaporated under
reduced pressure. The crude product was separated by column
chromatography eluting with hexane/CH2Cl2 (7/1) to give the title
compound (5) (0.43 g, 94%) as white powder, mp 47−49 °C. IR
(ATR, diamond) 3095, 3028, 1601, 1509, 1446, 1355, 840, 753, 688,
654 cm−1; 1H NMR (600 MHz, CDCl3) δ (ppm) 7.76 (d, J = 7.3 Hz,
2H), 7.5 (s, 1H), 7.46 (t, J = 7.3 Hz, 2H), 7.42 (d, J = 5.3 Hz, 1H),
7.34 (t, J = 7.3 Hz, 1H), 7.30 (d, J = 5.3 Hz, 1H); 13C NMR (150
MHz, CDCl3) δ (ppm) 139.6, 137.9, 134.8, 134.4, 128.9, 127.6, 127.2,
126.4, 122.6, 119.8; HRMS m/z calcd for C12H8N1O3S2 217.0146,
found 217.015.
757, 699 cm−1; 1H NMR (600 MHz, acetone-d6) δ (ppm) 7.69 (d, J =
8.8 Hz, 2H), 7.65 (dd, J = 5.3 Hz, 1.5 Hz, 1H), 7.61 (d, J = 1.5 Hz,
1H), 7.45 (d, J = 5.3 Hz, 1H), 6.88 (d, J = 8.8 Hz, 2H), 3.01 (s, 6H);
13C NMR (150 MHz, CDCl3) δ (ppm) 139.3, 137.9, 134.5, 128.0,
127.9, 127.2, 127.0, 120.0, 119.8, 113.0, 40.8; MS m/z = 260.13 (M +
1). Anal. Calcd for C14H13NS2: C, 64.80; H, 5.03. Found: C, 64.99; H,
4.86.
2,5-Dibromo-3-phenylthieno[3,2-b]thiophene (17). To a
solution of 3-phenylthieno[3,2-b]thiophene (5) (0.558 g, 2.58
mmol), dissolved in DMF (100 mL), was added N-bromosuccinimide
(1.01 g, 5.67 mmol) in DMF (50 mL) by syringe at −10 °C in dark.
After stirring for 3 h at the same temperature, the reaction mixture was
poured into water (100 mL). The precipitated solid was filtrated and
purified by column chromatography eluting with hexane to give the
title compound (17) (0.59 g, 61%) as a white solid, mp 104−106 °C.
IR (ATR, diamond) 3093, 3043, 2919, 2874, 1597, 1575, 1518, 1485,
1461, 1439, 1339, 1308, 1260, 1182, 1074, 1005, 871, 802, 759, 695,
575, 520, 466 cm−1; 1H NMR (600 MHz, CDCl3) δ (ppm) 7.64 (d, J
= 7.4 Hz, 2H), 7.48 (t, J = 7.4 Hz, 2H), 7.42 (t, J = 7.4 Hz. 1H), 7.21
(s, 1H); 13C NMR (150 MHz, CDCl3) δ (ppm) 136.1, 133.3, 128.9,
128.8, 128.6. 128.5, 128.3, 128.2, 122.1, 113.7; MS m/z =374.87 (M +
1).
The following were similarly prepared.
3-(4-Methoxyphenyl)thieno[3,2-b]thiophene (6). The crude
product was separated by column chromatography eluting with
hexane/CH2Cl2 (7/1) to give the title compound (6) (0.34 g, 80%) as
yellow powder, mp 85−88 °C. IR (ATR, diamond) 3096, 1605, 1523,
1
1245, 1029, 829, 706, 655 cm−1; H NMR (600 MHz, CDCl3) δ
(ppm) 7.70 (d, J = 8.8 Hz, 2H), 7.43 (d, J = 5.3, 1H), 7.4 (s, 1H), 7.30
(d, J = 5.3 Hz, 1H), 7.01 (d, J = 8.8 Hz, 2H), 3.85 (s, 3H); 13C NMR
(150 MHz, CDCl3) δ (ppm) 159.2, 139.5, 137.9, 135.1, 127.6, 127.6,
127.1, 121.2, 119.9, 114.3, 55.4; MS m/z = 247.27 (M + 1). Anal.
Calcd for C13H10OS2: C, 63.32; H, 4.10. Found: C, 63.46; H, 3.97.
3-(4-Nitrophenyl)thieno[3,2-b]thiophene (7). The crude prod-
uct was separated by column chromatography eluting with hexane/
CH2Cl2 (7/1) to give the title compound (7) (0.37 g, 91%) as yellow
powder, mp 128−130 °C. IR (ATR, diamond) 3114, 1591, 1503,
The following were similarly prepared.
2,5-Dibromo-3-(4-methoxyphenyl)thieno[3,2-b]thiophene
(18). 18 was obtained (0.41 g, 65%) as a yellow solid, mp 102−103
°C. IR (ATR, diamond) 3076, 2933, 2833, 1604, 1528, 1487, 1463,
1339, 1287, 1244, 1177, 1110, 1031, 905, 828, 776, 695, 623, 580, 523,
450 cm−1; 1H NMR (600 MHz, CDCl3) δ (ppm) 7.58 (d, J = 8.4 Hz,
2H), 7.21 (s, 1H), 7.02 (d, J = 8.4 Hz, 2H), 3.87 (s, 3H); 13C NMR
(150 MHz, CDCl3) δ (ppm) 156.6, 139.2, 135.8, 133.13, 133.11,
129.6, 125.6, 122.2, 114.2, 109.1, 103.2, 55.3; MS m/z = 404.98 (M +
1).
1
1322, 1109, 844, 704, 643 cm−1; H NMR (600 MHz, CDCl3) δ
(ppm) 8.34 (d, J = 8.2 Hz, 2H), 7.91 (d, J = 8.2 Hz, 2H), 7.70 (s, 1H),
7.50 (d, J = 5.3 Hz, 1H), 7.35 (d, J = 5.3 Hz, 1H); 13C NMR (150
MHz, CDCl3) δ (ppm) 146.8, 140.9, 140.2, 137.4, 132,2, 127.8, 126.8,
125.6, 124.5, 119.9; MS m/z = 261.20 (M + 1). Anal. Calcd for
C12H7NO2S2: C, 55.10; H, 2.68. Found: C, 55.22; H, 2.58.
2,5-Dibromo-3-(4-nitrophenyl)thieno[3,2-b]thiophene (19).
19 was obtained (0.41 g, 68%) as a white solid, mp. 121−123 °C.
IR (ATR, diamond) 3090, 2923, 2848, 1592, 1512, 1342, 1184, 1104,
1008, 902, 843, 706, 574 cm−1; 1H NMR (600 MHz, CDCl3) δ (ppm)
8.36 (d, J = 8.8 Hz, 2H), 7.84 (d, J = 8.8 Hz, 2H) 7.25 (s, 1H); 13C
NMR (150 MHz, CDCl3) δ (ppm) 147.3, 140.3, 138.1, 137.6, 131.4,
129.4, 126.9, 124.1, 119.6, 111.9; MS m/z = 419.87 (M + 1).
2,5-Dibromo-3-(4-aminophenyl)thieno[3,2-b]thiophene
(20). A mixture of 19 (0.31 g, 0.74 mmol), Fe powder (0.165 g, 2.96
mmol), and HCl (0.1 mL) was refluxed in ethanol (50 mL, 79%) for 3
h. The mixture was then extracted with dichloromethane, washed with
NaHCO3 (10%) and water. The organic layer was dried over Na2SO4
and filtered, and the solvent was evaporated under reduced pressure.
The crude product was separated by column chromatography eluting
with hexane/CH2Cl2 (2/1) to give the title compound (20) (0.185 g,
43%) as white solid, mp 170−172 °C. IR (ATR, diamond) 3430, 3324,
3194, 2920, 2851, 1619, 1533, 1490, 1464, 1337, 1282, 1177, 1082,
3-(4-Bromophenyl)thieno[3,2-b]thiophene (8). The crude
product was separated by column chromatography eluting with
hexane/CH2Cl2 (7/1) to give the title compound (8) (0.39 g, 85%) as
white powder, mp 101−103 °C. IR (ATR, diamond) 3096, 1508,
1480, 1345, 1218, 1075, 1006, 845, 824, 721, 653 cm−1; 1H NMR (600
MHz, CDCl3) δ (ppm) 7.62 (d, J = 8.5 Hz, 2H), 7.59 (d, J = 8.5 Hz,
2H), 7.49 (s, 1H), 7.45 (d, J = 5.3 Hz, 1H), 7.31 (d, J = 5.3 Hz, 1H);
13C NMR (150 MHz, CDCl3) δ (ppm) 139.8, 133.7, 133.3, 132.1,
129.8, 127.9, 127.4, 122.9, 121.5, 119.9; MS m/z = 295.07 (M + 1).
Anal. Calcd for C12H7BrS2: C, 48.79; H, 2.35. Found: C, 48.66; H,
2.29.
3-(4-Aminophenyl)thieno[3,2-b]thiophene (9). A mixture of 7
(0.1 g, 0.38 mmol), Fe powder (1 g, 17.8 mmol), and HCl (0.5 mL)
was refluxed in ethanol (50 mL, 79%) for 2 h. The mixture was then
extracted with dichloromethane, washed with NaHCO3 (10%) and
water. Organic layer was dried over Na2SO4, filtered and the solvent
was evaporated under reduced pressure. The crude product was
separated by column chromatography eluting with hexane/CH2Cl2
(3/1) to give the title compound (9) (84 mg, 83%) as brownish
viscous liquid. IR (ATR, diamond) 3447, 3369, 3096, 1619, 1532,
1488, 1350, 1282, 1184, 1085, 945, 823, 729, 653 cm−1; 1H NMR (600
MHz, CDCl3) δ (ppm) 7.57 (d, J = 8.2 Hz, 2H), 7.42 (dd, J = 5.3, J =
1.8 Hz, 1H), 7.34 (d, J = 1.8 Hz, 1H) 7.29 (d, J = 5.3 Hz, 1H) 6.77 (d,
2H, J = 8.2). 13C NMR (150 MHz, CDCl3) δ (ppm) 145.9, 139.2,
137.8, 129.4, 127.4, 127.0, 120.2, 119.8, 115.3, 115.0. m/z = 233.02 (M
+ 1).
3-(4-N,N-Dimethylaminophenyl)thieno[3,2-b]thiophene
(10). To a mixture of 9 (74 mg, 0.319 mmol) and K2CO3 (44 mg,
0.319 mmol) in DMF (50 mL) was added iodomethane (99 mg, 0.7
mmol) by syringe and the mixture was stirred at 100 °C for 3 h. DMF
was evaporated under reduced pressure. Water was added and the
mixture was extracted with dichloromethane. Organic layer was dried
over Na2SO4, filtered and the solvent was evaporated under reduced
pressure. The crude product was separated by column chromatog-
raphy eluting with hexane/CH2Cl2 (3:1) to give the title compound
(10) (54 mg, 65%) as a white powder, mp 120−123 °C. IR (ATR,
diamond) 3093, 2920, 1609, 1533, 1489, 1357, 1224, 1061, 946, 813,
1
1018, 806, 736, 574, 525, 459 cm−1; H NMR (600 MHz, CDCl3) δ
(ppm) 7.45 (d, J = 8.5 Hz, 2H), 7.19 (s, 1H), 6.78 (d, J = 8.5 Hz, 2H)
3.85 (bs, 2H); 13C NMR (150 MHz, CDCl3) δ (ppm) 149.3, 136.1,
132.1, 125.9, 124.8, 124.2, 122.8, 117.6, 116.0, 111.2; MS m/z =
389.87 (M + 1).
2,5-Dibromo-3-(4-N,N-dimethylaminophenyl)thieno[3,2-b]-
thiophene (21). To a mixture of (20) (129 mg, 0.331 mmol) and
K2CO3 (95 mg, 0.69 mmol) in DMF (20 mL) was added iodomethane
(62 μL, 0.99 mmol) by syringe, and the mixture was stirred at 100 °C
for 3 h. The solvent was evaporated under reduced pressure, and the
mixture was extracted with dichloromethane. Organic layer was dried
over Na2SO4, filtered and the solvent was evaporated under reduced
pressure. The crude product was separated by column chromatog-
raphy, eluting with hexane to give the title compound (21) (50 mg,
36%) as yellow solid, mp 95−98 °C. IR (ATR, diamond) 3093, 3020,
2919, 2850, 1734, 1609, 1536, 1493, 1355, 1205, 1153, 1016, 946, 814,
734, 579, 463 cm‑1; 1H NMR (500 MHz, CDCl3) δ (ppm) 7.55 (d, J =
8.2 Hz, 2H), 7.19 (s, 1H), 6.83 (d, J = 8.2 Hz, 2H), 3.03 (s, 6H); 13C
NMR (125 MHz, CDCl3) δ (ppm) 138.2, 134.6, 132.4, 128.1, 125.1,
121.1, 118.3, 112.3, 111.3, 107.0, 28.6; MS m/z = 417.87 (M + 1).
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4,4,5,5-Tetramethyl-2-(thiophene-2-yl)-1,3,2-dioxaborolane
(22). A 1.223 g (14.53 mmol) sample of thiophene dissolved in 50 mL
dry THF. At −78 °C and under nitrogen atmosphere 6.4 mL (15.9
mmol) 2.5 M n-butyllithium was added. After stirring 20 min, 3.26 mL
(15.9 mmol) 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane was
added. It was stirred at room temperature and under nitrogen
atmosphere overnight. The solvent was removed under vacuum and
the crude product was dissolved in dichloromethane and washed with
HCl solution (5 N). The organic layer was dried over Na2SO4 and
filtered, and the solvent was evaporated under reduced pressure. The
crude product was separated by column chromatography eluting with
hexane/dichloromethane (3/1) to give the title compound (22) (2.44
mg, 81%) as a white solid, mp. 64−67 °C. IR (ATR, diamond) 3098,
2976, 2926, 1519, 1422, 1360, 1328, 1295, 1267, 1209, 1133, 1055,
placed into a three-component CV cell filled with TBABF4 or
NaClO4/LiClO4 (1:1) solutions in ACN, as a supporting electrolyte.
Measurements were performed at room temperature.
RESULTS AND DISCUSSIONS
■
Syntheses of thienothiophenes (TT), PhTT (5), MPhTT (6),
NPhTT (7), and BrPhTT (8), having substituted phenyl
moiety at C-3 were achieved in two steps by applying the
method developed for the syntheses of dithienothiophenes.21
Lithiation of 3-bromothiophene (11) with n-butyllithium at
−78 °C was followed by addition of elemental sulfur and then
α-bromoketones (12), which led to the production of the
corresponding α-thioketones (13−16) in 41−84% yields
(Scheme 1). Ring closure reaction of the ketones in the
1
1017, 1001, 956, 848, 777, 722, 686, 663, 576, 518, 429 cm−1; H
NMR (600 MHz, CDCl3) δ (ppm) 7.66 (dd, J = 3.9 Hz, J = 1.1 Hz,
1H), 7.64 (dd, J = 4.8 Hz, J = 1.1 Hz, 1H), 7.19 (dd, J = 4.8 Hz, J = 3.9
Hz, 1H), 1.35 (s, 12H) ; 13C NMR (150 MHz, CDCl3) δ (ppm)
137.1, 132.3, 128.2, 84.1, 24.7 (the signal of the carbon next to
tetravalent boron was not observed due to quadrupolar broadening);22
MS m/z = 211.07 (M + 1).
Scheme 1. Syntheses of Thienothiophenes
2,5-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane-2-yl)-
thiophene (23). To a solution of 2,5-dibromothiophene (0.95 g, 3.95
mmol), dissolved in dry THF (50 mL), was added n-butyllithium
(5.18 mL, 8.3 mmol, 1.6 M) at −78 °C under nitrogen atmosphere.
After stirring for 1 h, 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxabor-
olane (4.03 mL, 19.75 mmol) was added by syringe, and the stirring
was continued for further 1 h at −78 °C, after which the mixture was
left stirring at room temperature overnight. The crude product was
poured into water, extracted with ethyl acetate and washed with brine.
The organic layer was dried over Na2SO4 and filtered, and the solvent
was evaporated under reduced pressure. The crude product was
dissolved in minimum amount of dichloromethane and precipitated in
hexane to give the title compound (23) (1.245 mg, 93%) as a white
solid, mp 210−212 °C. IR (ATR, diamond) 2973, 2924, 2849, 1521,
presence of P4S10 in refluxing toluene gave the corresponding
thienothiophenes (5−8) in 80−94% yields.23 It is important to
note that the purity of P4S10 is crucial to have higher yields of
the products. Pure P4S10 does not have any or has very low
smell and its color is very light yellow. The nitro group on the
phenyl moiety of the NPhTT (7) was reduced to amine with
Fe/HCl to yield the APhTT (9) in 83%, which was noticed not
to be stable enough for long-standing. It was then methylated
with methyl iodide to obtain the DMAPhTT (10), having
dimetylaminophenyl group in 65% yield.
The TTs, 5−8 and 10, were both electropolymerized and
polymerized via Suzuki coupling with 2,5-bis(4,4,5,5-tetrameth-
yl-1,3,2-dioxaborolane-2-yl)thiophene 23 to obtain the poly-
mers 24−27 (Scheme 2). For the Suzuki coupling polymer-
izations, initially, the TTs 5−7 were dibrominated with NBS to
obtain the 2,5-dibromoTTs 17−19 in 61−68% yields.
Reduction of the nitro group of the 2,5-dibromoTT 19 to
amino 20 was achieved using Fe/HCl in 43% yield. Use of
excess Fe powder, like in the reduction of the nitro group of 7
to the amino 9, caused the loss of one of the bromines on the
ring; around 1:2 mol ratio of nitro 19/Fe was found to be the
ideal. As it was noticed that the aminoTT 20 is not stable
enough, which goes brownish in couple of hours, it was
methylated with methyl iodide to obtain the dimethylaminoTT
21 in 36%. Four dibromoTTs, 17−19 and 21, were then
subjected to polymerizations with 2,5-diborolaneylthiophene
23, reactions of which were terminated by using 2-
bromothiophene and 2-borolaneylthiophene 22 to give the
polymers 24−27.
1
1369, 1320, 1259, 1134, 1040, 957, 851, 666, 578, 518, 423 cm−1; H
NMR (600 MHz, CDCl3) δ (ppm) 7.66 (s, 2H), 1.34 (s, 24H) ; 13C
NMR (150 MHz, CDCl3) δ (ppm) 137.6, 84.1, 24.7 (The signal of the
carbon next to tetravalent boron was not observed due to quadrupolar
broadening);22 MS m/z = 337.5 (M + 1).
Poly(3-phenyl-2-(thiophen-2-yl)thieno[3,2-b]thiophene)
(24). In a Schlenk tube, bis(triphenylphosphine)palladium(II)chloride
(14 mg, 0.021 mmol) was degassed under high vacuum. A mixture of
2,5-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane-2-yl)thiophene (23)
(0.143 g, 0.427 mmol) and 2,5-dibromo-3-phenylthieno[3,2-b]-
thiophene (17) (0.160 g, 0.427 mmol), dissolved in THF (50 mL)
and degassed with nitrogen, and a solution of K2CO3 (1.5 mL, 2 M),
degassed with nitrogen, were added to the Schlenk tube under
nitrogen atmosphere. The mixture was stirred at 70 °C for 3 days.
Then, a solution of 2-bromothiophene (12 μL, 0.125 mmol) dissolved
in THF (1 mL) and degassed with nitrogen was added and the mixture
was left stirring for 1 day. A solution of 4,4,5,5-tetramethyl-2-
(thiophene-2-yl)-1,3,2-dioxaborolane (22) (32.6 mg, 0.137 mmol)
dissolved in THF (1 mL) and degassed with nitrogen was added and
stirred for overnight. After the mixture was filtrated through Celite, the
solution was concentrated under vacuum and the polymer was
precipitated in cold methanol: Mw 55213, Mn 47926, Mw/Mn 1.15, and
dn/dc 0.25 mL/g (THF, 35 °C).
The following were similarly prepared.
Poly(3-(4-methoxyphenyl)-2-(thiophen-2-yl)thieno[3,2-b]-
thiophene) (25) [Mw 262751, Mn 68470, Mw/Mn 3.83, and dn/dc
0.178 mL/g (THF, 35 °C)], poly(3-(4-nitrophenyl)-2-(thiophen-2-
yl)thieno[3,2-b]thiophene) (26) [Mw 264163, Mn 62726, Mw/Mn 4.21,
and dn/dc: 0.09 mL/g (THF, 35 °C)], and poly(3-(4-N,N-
dimethylaminophenyl)-2-(thiophen-2-yl)thieno[3,2-b]thiophene)
(27) [Mw 14360, Mn 6051, Mw/Mn 2.37, and dn/dc: 0.10 mL/g (THF,
35 °C)].
Electronic absorption spectra of the TTs were examined in
dichloromethane (DCM) (Figure 1). While the TTs having Ph
(5), 4-MeOPh (6), 4-BrPh (8), and 4-(CH3)2N groups showed
absorption maxima between 300 and 302 nm, the TT with 4-
Cyclic Voltammetry (CV) Mesurements. Electropolymerizations
of the monomers were studied by CV. Ag wire as the reference
electrode and Pt wires as both counter and working electrodes were
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Electrochemistry of the TTs 5−8 and 10 were conducted in
a cyclic voltammetry (CV), using Pt wires as working and
counter electrodes and Ag wire as a reference electrode.
Electrolytes (TBA)PF6 (0.1 M) for 5, 7, and 8, (TBA)BF4 (0.1
M) for 6, and NaClO4 (0.1 M)/LiClO4 (0.1 M) for 10 were
employed. The TT concentrations were 1 × 10−3 M and the
scan rate for the measurements was kept as 100 mV/s. As the
compounds PhTT (5), MPhTT (6), NPhTT (7), and BrPhTT
(8) displayed one semireversible oxidation potential above 1 V,
i.e., 1.68, 1.60, 1.99, and 1.85, respectively, DMAPhTT (10)
had two oxidation potentials of 0.74 and 1.33 V, irreversible
and semireversible, respectively (Figure 2). The lowest
Scheme 2. Syntheses of TT-Thiophene Polymers
Figure 1. UV measurements of the TTs in DCM.
NO2Ph displayed a red shift up to 365 nm, which is not
surprising as nitrobenzene has a strong absorption at 270 nm
compare with the strong absorption peak of aniline at 229 nm
(Figure 1, Table 1).24 In parallel, optical band gap calculations
of the TTs (5), (6), (8) and (10) had a comparable manner
between 3.54 and 3.75 eV, except the TT having nitro group
(7), which had the lowest band gap of 2.92 eV. It could be
concluded that the groups on the phenyl moiety can make
some effects on the TT ring, such as red shift on absorption
and lowering the band gap when they provide π-extension to
the ring.
Figure 2. Cyclic voltammograms of the TTs. Conditions: 1 × 10−3
M
solutions of 5, 7, and 8 in acetonitrile, 0.1 M Bu4NPF6; 6 in
acetonitrile, 0.1 M Bu4NBF4; 10 in acetonitrile, NaClO4/LiClO4 (0.1
M) (1/1). 100 mV/s scan rate, Pt wires as working and counter
electrodes, and Ag wire as a reference electrode.
Table 1. Electrochemical, Optical and Electronic Properties of the TTs and the Polymers
c
h
h
TT Eox (V) polymer Eox (V) polymer Ered (V) polymer Eg (eV)
TT λ (nm)
polymer λ (nm)
TT Egopt (eV) polymer Egopt (eV)
a
b
b
b
a
b
b
b
b
b
d
e
e
e
e
e
f
f
g
5
1.68
1.39 /1.04
−1.54 /−1.42
2.46
1.86
1.98
2.35
2.27
300 /329
328 /460 /600
3.75
3.70
2.92
3.68
3.54
2.05
1.99
2.16
2.19
2.01
a
a
d
f
f
g
6
1.60
1.36 /0.89
−1.27 /−0.97
302 /334
318 /439 /619
a
a
d
f
f
g
g
g
7
1.99
1.09 /1.04
−1.22 /−0.94
365 /424
331 /442 /572
b
a
d
f
f
8
1.85
1.12/0.92
−1.67 /−1.43
302 /336
324 /431 /563
a
b
a
d
f
f
10
0.74/1.33
0.97 /0.73
−1.77 /−1.54
302 /349
317 /468 /615
a
b
c
Oxidation and reduction maxima. Onsets of oxidation and reduction. From the difference between the onsets of the oxidation and the reduction
d
e
f
g
processes. Absorption maxima in DCM. Onset of the absorption in DCM. Absorption maxima of the polymer films coated on ITO. Onset of the
absorption coated on ITO. From the onsets of the absorptions.
h
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Figure 3. Electropolymerization of the TTs. One ×10−3 M solutions of (5), (7) and (8) in acetonitrile, 0.1 M Bu4NPF6; (6) in acetonitrile, 0.1 M
Bu4NBF4; (10) in acetonitrile, NaClO4/LiClO4 (0.1 M) (1/1). 100 mV/s scan rate, Pt wires as working and counter electrodes and Ag wire as a
reference electrode.
oxidation peak at 0.74 might be due to the dimethylaniline
moiety of the molecule. The highest oxidation/reduction peaks
were observed with the NPhTT (7), having strong electron
withdrawing nitrophenyl group. The general trend indicated
that the nature of the substituted groups has some effects on
the oxidation/reduction potentials of the TTs. Electron
donating groups, like dimethylamino and methoxy, make the
TT rings electron rich and then reduce their oxidation/
reduction potentials. On the other hand, electron withdrawing
groups, like nitro and bromine make the TT rings electron poor
and increase their oxidation/reduction potentials.
The TTs were electropolymerized by repetitive-cycling over
their redox-active peaks, using Pt wires as working and counter
electrodes and Ag wire as a reference electrode in CH3CN.
Bu4NPF6 for 5, 7, and 8, Bu4NPF4 for 6, and the mixture of
NaClO4/LiClO4 for 10 were applied as electrolytes. Their
polymerizations were observed by means of deposition of the
polymers on Pt electrode surface and as an increase of
oxidation and reduction peaks (Figure 3).
Electrochemistries of the poly-TTs, i.e. p(PhTT), p-
(MPhTT), p(NPhTT), p(BrPhTT), and p(DMAPhTT),
were investigated with their films on Pt disk electrode in a
monomer-free CH3CN solution, containing Bu4NPF6 as a
supporting electrolyte (Figure 4). Before the experiments, each
polymer was dedoped to its neutral state by repetitive cycling in
a region of no electroactivity. While the p(PhTT) and
p(MPhTT) featured reversible and quasi-reversible oxidation
waves, respectively, the rest of the polymers, p(NPhTT),
p(BrPhTT) and p(DMAPhTT) displayed irreversible oxidation
waves. Although the lowest oxidation peak was observed with
the polymer p(DMAPhTT) with 0.97 V, having strong electron
donating dimethylamino groups, there is no clear conclusion
for the effect of the substituted groups on the TT polymer
Figure 4. Cyclic voltammograms of the polymer films on Pt disk
electrode in acetonitrile, 0.1 M Bu4NPF6, 100 mV/s scan rate.
chains for the rest of the polymers, oxidation peaks of which
varied between 1.09 and 1.39 V, i.e., 1.09 V for p(NPhTT),
1.12 V for p(BrPhTT), 1.36 V for p(MPhTT), and 1.39 V for
p(PhTT). Such a result could be attributed to the factor of the
morphology of the polymer films and interchain interactions.
Regarding the reduction of the polymers, while the polymer,
p(DMATT), had the most negative potential (−1.77 V), the
polymer p(NPhTT), having the most electron withdrawing
nitro group had the least negative potential (−1.22 V).
Electronic band gaps of the polymers varied between 1.86
and 2.46 V (Table 1).
Optical behaviors of the polymers were examined by UV
measurements. The TTs were electrochemically polymerized
on indium−tin−oxide (ITO) coated glass electrodes (20 mC)
and washed with a monomer free solution to remove the
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Figure 5. CV−UV measurments of the polymers coated on ITO, 0−1.8 V. Conditions: 5, 7, and 8 in acetonitrile, 0.1 M Bu4NPF6; 6 in acetonitrile,
0.1 M Bu4NBF4; 10 in acetonitrile, NaClO4/LiClO4 (0.1 M) (1/1), 5 mV/s scan rate, Pt wire as counter electrode, and Ag wire as a reference
electrode.
unreacted monomers. Absorbance measurements of the
polymers on ITO indicated that all the polymers had two
general absorbance maxima between 317 and 331 nm and at
431−468 nm, possibly due to the phenyl moieties and the TT
backbones, respectively. Interestingly, contrary to the absorp-
tions of the monomers, among which the monomer NPhTT
(7) showed the longest absorption maximum (365 nm) and the
longest onset of absorption (424 nm), the polymers displayed a
regular trend of onsets of absorptions. As the polymers having
electron donating groups had the longest onsets, the polymers
having electron withdrawing groups had the shortest onsets.
Then, their absorption onsets and, in connection, their optical
band gaps could be summarized in the order of p(MPhTT)
(619 nm) > p(DMAPhTT) (615 nm) > p(PhTT) (600 nm) >
p(NPhTT) (572 nm) > p(BrPhTT) (563 nm) and p(MPhTT)
(1.99 eV) < p(DMAPhTT) (2.01 eV) < p(PhTT) (2.05 eV) <
p(NPhTT) (2.16 eV) < p(BrPhTT) (2.19 eV), respectively
(Table 1). It looks like the effect of the conjugation of the nitro
group with the TT ring was suppressed by long conjugation in
the polymer chain.
Figure 6. Absorbance and emission spectra of the polymers 24−27.
nitro group 26 had the lowest quantum yield (0.003), the one
with methoxy group 25 had the highest yield (0.64) (Table 2),
which are expected results as the strong electron withdrawing
nitrobenzene group decreases the quantum yield.25 Optical
band gaps of the polymers were calculated to be between 2.28
and 2.57 eV from their absorption onsets.
Spectroelectrochemistry of the polymers was investigated
(Figure 5). The polymer coated glasses were introduced into
UV cuvettes as working electrodes, filled with monomer free
electrolyte solution. Pt and Ag wires were used as counter and
reference electrodes, respectively. For all the polymers
p(PhTT), p(MPhTT), p(NPhTT), p(BrPhTT), and p-
(DMAPhTT), the changes in their absorbance were measured
in situ as a function of potential change starting from 0 V,
which was gradually increased up to 2.2 V. The alterations of
the absorbances were observed through stepwise UV measure-
ments. In overall appearance of the five polymers, as a result of
the electrochemical doping, their absorption peaks at neutral
states, decreased in intensity, while new polaron and bipolaron
peaks were formed around 700 and 1000 nm (Figure 5).
The polymers 24−27, obtained by Suzuki coupling of the
dibromoTTs 17−19 and 21 with 2,5-diborolaneylthiophene 23
(Scheme 2) displayed absorbance and emission bands between
413 and 445 and at 454−564 nm, respectively (Figure 6, Table
2). Their quantum yields indicated that as the polymer having
Cyclic voltammetry behaviors of the polymers 24−27 were
investigated in dry and degassed acetonitrile, having Bu4NPF6
as electrolyte, under nitrogen atmosphere, by drop-coating onto
Pt disk electrode from their dichloromethane solutions (Figure
7, Table 2). Pt and Ag wires were applied as counter and
reference electrodes. The polymers were scanned between −2
and +2 V and their electronic bandgaps were calculated to be
between 2.07 and 2.43 eV from the differences between the
onsets of oxidation and reduction peaks.
Thermal gravity analyses of the polymers 24−27 displayed
the start of exothermic weight lose at 248, 261, 255, and 301
°C, respectively, which was supported by decomposition peaks
obtained from DSC measurements at the same temperatures
(see Supporting Information).
CONCLUSIONS
■
In this work, a concise synthesis of thieno[3,2-b]thiophene
(TT) derivatives, having substituted phenyl groups at C-3, have
been reported, which involved two steps with overall moderate
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Table 2. Electrochemical, Optical and Electronic Properties of the Copolymers 24−27
c
d
Eox (V)
Ered (V)
Eg (eV)
UVmax λ (nm)
UVonset λ (nm)
Egopt (eV)
Em, max λ (nm)
ΦF
a
b
b
b
a
b
b
b
b
e
24
25
26
27
1.31 /0.82
−1.73 /−1.61
2.43
2.31
2.29
2.07
445
413
325
541
509
481
538
2.28
2.42
2.57
2.29
561
537
454
564
0.47
a
a
e
0.93 /0.75
−1.78 /−1.56
0.64
a
a
f
1.27 /0.88
−1.51 /−1.41
0.003
a
b
a
e
1.2 /1.02
−1.15 /−1.05
445
c
0.41
a
b
Oxidation and reduction maxima. Oxidation and reduction onsets. From the difference between the onsets of the oxidation and the reduction
processes. From the onsets of the absorptions. Fluorescein was used as a reference. 9,10-Diphenylanthracene was used as a reference.
d
e
f
Figure 7. Cyclic voltammograms of the polymers 24−27 on Pt disk electrode in acetonitrile, 0.1 M Bu4NPF6, and 100 mV/s scan rate.
to high yields. As the syntheses of TTs, having functional
groups at C-3, is a difficult task, the method reported here is a
convenient one. Their polymers were prepared by both
electrochemistry and Suzuki coupling with thiophene. Proper-
ties of the TTs and their polymers were characterized by
absorption and fluorescence spectroscopies, CV and CV−UV−
vis spectroelectrochemistry. The longest absorption band and
the lowest band gap were displayed by the TT having 4-
nitrophenyl group at 365 nm and as 2.92 eV, respectively.
Regarding the polymers coated on ITO, the polymer with 4-
methoxyphenyl had the longest red edge and the lowest band
gap of 1.99 eV. The copolymers of the TTs with thiophene
displayed band gaps and emissions between 2.0 and 2.50 eV
and 454−564 nm, respectively. The highest quantum yield was
obtained as 0.64 with TT, having a methoxy group on the
phenyl moiety. The most important part of the resultant TTs is
that their functional groups such as nitrophenyl, aniline,
bromophenyl and methoxyphenyl, could easily be further
functionalized to synthesize new building blocks for new
organic materials. Currently, our investigation has been focused
on the syntheses of such materials, incorporating the TTs
presented in this study.
ASSOCIATED CONTENT
■
S
* Supporting Information
1H and 13C NMR spectra, HRMS and MS of the new
compounds, and TGA curves of the polymers. This material is
available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*Telephone: 90 212 285 6994. Fax: 90 212 285 6386. E-mail
ozturktur@itu.edu.tr.
Author Contributions
The manuscript was written through the contributions of all
authors. All authors have given approval to the final version of
the manuscript.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank Prof Mehmet S. Eroglu of Marmara University for
TGA and DSC analyses, Istanbul Technical University, Turkey,
for a grant to A.C. (Ph.D.) and Unsped Global Logistic for
financial support.
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(20) Litvinov, L. P. Russ. Chem. Rev. (Engl. Transl.) 2005, 74, 217−
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NOTE ADDED AFTER ASAP PUBLICATION
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