π-Conjugated polymers exhibiting a novel doping based on redox of side chains

Article abstract of DOI:10.1021/ma025833j

Novel polyphenylene and polythiophene derivatives that have N,N′-diphenyl-1,4-phenylene-diamine (PDA) units were synthesized using the palladium-catalyzed Suzuki coupling or cross coupling. Each obtained polymer has good redox activity, and the polyphenylene derivatives have two redox couples in acetonitrile that contain 1 M trifluoroacetric acid, whereas the polythiophene derivatives show only one redox couple under the same conditions. The electronic conductivity of the polythiophene derivatives was dramatically enhanced (0.1 S/cm) by the one-electron oxidation of the PDA unit (0.4 V, vs Ag/Ag⁺), because of the injection of a radical cation into the main chain from the PDA unit. Spectroelectrochemistry showed that the radical cation of the thiophene-substituted PDA was more delocalized than the phenylene-substituted unit. Electrochemical analysis of the model compounds revealed that the injection of radical monocation radical carriers into the main chain is based on electron communication between the intramolecular PDAs.

Full text of DOI:10.1021/ma025833j

Macromolecules 2003, 36, 6325-6332
6325
π-Conjugated Polymers Exhibiting a Novel Doping Based on Redox of
Side Chains
Toyoh ik o Nish iu m i, Ma sa yosh i Higu ch i, a n d Kim ih isa Ya m a m oto*
Kanagawa Academy of Science and Technology (KAST) and Department of Chemistry,
Faculty of Science and Technology, Keio University, Yokohama 223-8522, J apan
Received November 15, 2002; Revised Manuscript Received J uly 3, 2003
ABSTRACT: Novel polyphenylene and polythiophene derivatives that have N,N′-diphenyl-1,4-phenylene-
diamine (PDA) units were synthesized using the palladium-catalyzed Suzuki coupling or cross coupling.
Each obtained polymer has good redox activity, and the polyphenylene derivatives have two redox couples
in acetonitrile that contain 1 M trifluoroacetric acid, whereas the polythiophene derivatives show only
one redox couple under the same conditions. The electronic conductivity of the polythiophene derivatives
was dramatically enhanced (0.1 S/cm) by the one-electron oxidation of the PDA unit (0.4 V, vs Ag/Ag+),
because of the injection of a radical cation into the main chain from the PDA unit. Spectroelectrochemistry
showed that the radical cation of the thiophene-substituted PDA was more delocalized than the phenylene-
substituted unit. Electrochemical analysis of the model compounds revealed that the injection of radical
monocation radical carriers into the main chain is based on electron communication between the
intramolecular PDAs.
1. In tr od u ction
that have PDA units exhibit two reversible redox
couples, such as PDA, but the polythiophene derivatives
exhibit only a single redox couple, because of their
electron communication between the PDA units through
the π-conjugated backbone. The electronic conductivity
of the polythiophene derivatives is dramatically en-
hanced by oxidation of the PDA unit, which is based on
the injection of a radical cation into the main chain. The
communication occurs through the electron transfer via
a coupling group. Electrochemical analysis of the model
compounds has revealed the existence of an electronic
interaction between the intramolecular PDAs.
The electrochemical properties of π-conjugated poly-
mers are significantly influenced by electron com-
munication between their redox-active1-4 sites, through
the π-conjugated backbone. The relationship between
this electron communication and their electrochemical
properties has not been sufficiently investigated, even
though many π-conjugated polymers that have redox-
active side groups, such as benzoquinone or ferrocene,
have been studied. There have been no attempts to
introduce two-electron-transfer redox-active molecules
with a very stable radical cation as a mixed valence
state with an intervalence charge-transfer (IV-CT)
band,5 because of the delocalization of electrons in which
a rapid electron transfer occurs between the redox sites,
to the π-conjugated polymers. The stable and delocalized
electron that is formed at the side chains could act as a
carrier in the π-conjugated chain through injection into
the backbone of the polymer. N,N′-Diphenyl-1,4-phen-
ylenediamine6 (PDA) derivatives were employed as the
stable two-electron redox moiety; these PDA derivatives
possess a mixed valence state with an IV-CT band. PDA
is the minimum redox unit of polyaniline,7 which is a
π-conjugated polymer with excellent redox properties
that are due to proton doping, and is widely applied to
materials that require a quick response, such as light-
weight secondary batteries,8 sensors,9 catalysts,10 and
electrochromic displays.11 We report herein the basic
electrochemical properties of the π-conjugated polymers
that have PDA units, focusing on the electron com-
munication between the PDA units of their model
compounds.12 To investigate the electron communication
between the redox-active units in the π-conjugated
polymer, we synthesized novel π-conjugated polyphen-
ylene and polythiophene derivatives that have PDA
units via the palladium-catalyzed Suzuki coupling13-15
or Stille coupling.16-20 The poly-p-phenylene derivatives
2. Exp er im en ta l Section
2.1. Ch em ica ls. Aniline was purchased from Aldrich
Chemical Co., Inc., and 2,5-dibromo-1,4-benzoquinone
was purchased from Tokyo Kasei Co., Ltd.; all other
chemicals were purchased from Kantoh Kagaku Co.,
Inc. (reagent grade), and were used without further
purification. The supporting electrolyte (TBABF4) was
recrystallized from a mixture of ethyl acetate and
hexane before use. The following compounds were
prepared according to literature procedures: benzene-
1,4-diboronic acid,15 4,4′-biphenyldiboronic acid bis-
(neopentylglycol),15 2,5-bis(tributylstannyl)thiophene,19
5,5′-bis(tributylstannyl)-2,2′-bithiophene,20 2a ,21 3a ,21
and B.21
2.2. Sp ectr oscop ic Mea su r em en ts. UV-Vis spec-
tra were obtained using a spectrometer (Shimadzu,
model UV-2400PC) with an indium-tin oxide (ITO)
electrode. Infrared (IR) spectra were obtained from a
potassium bromide (KBr) pellet using another spec-
trometer (J ASCO, model FT-IR-460Plus). NMR spectra
were recorded using a J EOL model J MN400 FT-NMR
spectrometer (400 MHz) in CDCl3, THF-d8, or a DMSO-
d6 + TMS internal standard solution. Matrix-assisted
laser desorption ionization-time-of-flight (MALDI-
TOF) mass spectra were obtained using a Shimadzu/
Kratos model KOMPACT MALDI mass spectrometer
(positive mode, with a matrix of dithranol). EI mass
* Author to whom correspondence should be addressed.
E-mail: yamamoto@chem.keio.ac.jp.
10.1021/ma025833j CCC: $25.00 © 2003 American Chemical Society
Published on Web 07/30/2003

6326 Nishiumi et al.
Macromolecules, Vol. 36, No. 17, 2003
+
spectra were obtained using a mass spectrometer (Hi-
tachi, model M-80B). CHNS elemental analysis was
performed using a Elementar Vario EL system. Elemen-
tal analysis for bromine was performed using the
combustion flask method, with a Mettler model Metro-
hm 682 apparatus for the potentiometric titration. Gel
permeation chromatography (GPC) was performed with
a Shimadzu model CLASS-LC10 apparatus (with a
Shodex model GPC-KD804 column (pore size, 200 Å;
bead size, 7 µm; exclusion limit, 4 × 105; 8.0 mm inner
diameter × 30 cm length) and a Shodex model GPC-
KD802 column (pore size, 60 Å; bead size, 6 µm;
exclusion limit, 5 × 103; 8.0 mm inner diameter × 30
cm length)) at 40 °C with a UV-Vis detector (Shimadzu,
model SPD-M10AVP). Tetrahydrofuran (THF) was used
as the eluent, at a flow rate of 1.0 mL/min. Molecular
weights were calculated against polystyrene standards.
(C-H), 697 (C-H), 502. EI-MS: 416, 418, 420 [M]
.
Anal. Calcd for C18H18Br2N2: C, 51.71; H, 3.37; N, 6.70.
Found: C, 51.80; H, 3.35; N, 6.73.
2.5. Syn th esis of Com p ou n d A Su bstitu ted by a n
Octyl Gr ou p (C). 4-n-Octyl-aniline (10.8 g 52.6 mmol)
was dissolved in chlorobenzene (20 mL) under nitrogen,
and titanium(IV) tetrachloride (1.07 g, 5.64 mmol) was
added dropwise at 90 °C. The addition funnel was then
rinsed with chlorobenzene (5 mL). 2,5-Dibromo-1,4-
benzoquinone (1.00 g, 3.76 mmol) that had been dis-
solved in chlorobenzene (50 mL) was added dropwise
to the mixture over a period of 15 min. The mixture was
stirred in an oil bath at 135 °C for 48 h. The precipitate
was removed by filtration and washed with chloroben-
zene (10 mL). The filtrate was concentrated, and
compound C (1.98 g, 82%, pale yellow wax) was isolated
by silica gel chromatography (1:1 hexane:dichloromethane
1
ratio). The analysis of C was as follows. H NMR (400
2.3. Electr och em ical Measu r em en ts. Electrochemi-
cal analyses were performed using an electrochemical
work station (BAS Co., Ltd., model ALS-660 or ALS-
701a) under the following conditions. Cyclic voltamme-
try (CV) and differential pulse voltammetry (DPV) were
performed under a N2 atmosphere after N2 bubbling for
15 min. A glassy carbon (GC) disk electrode (0.071 cm2)
was used as the working electrode and was polished
with 30-µm alumina before the experiments. The aux-
iliary electrode was a coiled platinum wire. The refer-
ence electrode was a commercial Ag/Ag+ electrode,
which was placed in the main cell compartment. The
formal potential of the ferrocene/ferrocenium couple was
0.076 V, versus this reference electrode in acetonitrile.
All potentials are quoted with respect to this Ag/Ag+
reference electrode. The potential was normalized to the
ferrocene/ferrocenium couple in acetonitrile. The scan
rate was 100 mV/s. The amplitude for the DPV mea-
surement was 50 mV. The in situ conductivity measure-
ments were obtained as follows. The polymer films were
prepared by casting onto an interdigitated platinum
microelectrode (length, 2 mm; width, 10 µm; interval, 5
µm). The conductivity of the resulting polymers was
measured between -0.1 V and 0.8 V in an acetonitrile-
TBABF4 electrolyte (0.2 M) that contained trifluoroace-
tic acid (TFA) (1 M) using CV (the counter electrode
accounted for 0.1 V of the constant drain voltage).
MHz, CDCl3, TMS standard, ppm): δ 7.39 (s, 2H, C6H2-
Br2), 7.11 (d, J ) 8.3 Hz, 4H, m-C6H5), 6.97 (d, J ) 8.3
Hz, 4H, o-C6H5), 5.67 (s, 2H, NH), 2.56 (t, J ) 7.8 Hz,
4H, Ph-CH2CH2-), 1.59 (p, J ) 4.8, 2.4 Hz, 4H, Ph-
CH2CH2-), 1.32-1.28 (m, 20H, -(CH2)5-CH3), 0.88 (t,
J ) 6.3 Hz, 6H, -CH3). 13C NMR (100 MHz, CDCl3 TMS
standard, ppm): δ 139.8 (NH-CC5H4), 137.0 (NH-
C[(CH)2(CBr)2]C), 135.7 (C8H17-CC5H4), 129.3 (m-
C6H4), 120.9 (C(CH)2(CBr)2C), 119.3 (o-C6H4), 112.6
(Br-C), 35.4 (Ph-CH2-), 32.0 (CH2), 31.7 (CH2), 29.6
(CH2), 29.4 (CH2), 29.4 (CH2), 22.8 (CH2), 14.2 (CH3).
IR (KBr, cm-1): 3415 (N-H), 2956 (CH2), 2920 (CH2),
2846 (CH2), 1614 (C-N), 1529 (C-N), 1459 (CdC), 1314,
1049, 892, 810 (C-H), 515. EI-MS: 644, 642, 640 [M]+.
Anal. Calcd for C34H46Br2N2: C, 63.55; H, 7.22; N, 4.36.
Found: C, 63.81; H, 7.13; N, 4.35.
2.6. Syn th esis of Dip h en yl P DA (1a ). A mixture
that contained A (0.042 g, 0.10 mmol), benzeneboronic
acid (73 mg, 0.6 mmol), and 5 mol % tetrakis(tri-
phenylphosphine) palladium(0) (0.012 g, 0.01 mmol)
that had been dissolved in dimethylether (DME) (2 mL)
and 2 M aqueous sodium carbonate (1 mL) was stirred
at 80 °C for 12 h under nitrogen. The mixture then was
poured into water. The organic layer was washed with
a saturated sodium hydrogen carbonate and separated
off, and the aqueous layer was extracted with dichlo-
romethane (3 times). The combined organic layers were
dried over anhydrous sodium sulfate and filtered. The
filtrate was concentrated, and compound 1a (36 mg,
87%, white powder) was isolated by silica gel chroma-
tography (1:1 hexane:dichloromethane ratio). The analy-
2.4. Syn th esis of Dibr om o-Su bstitu ted P DA (A).
Aniline (10.3 g, 111 mmol) was dissolved in chloroben-
zene (40 mL) under nitrogen, and titanium(IV) tetra-
chloride (2.14 g, 11.3 mmol) was added dropwise at 90
°C. The addition funnel was then rinsed with chloroben-
zene (10 mL). 2,5-Dibromo-1,4-benzoquinone (2.07 g,
7.79 mmol) that had been dissolved in chlorobenzene
(100 mL) was added dropwise over 15 min to the
mixture. The mixture was stirred in an oil bath at 135
°C for 12 h. The precipitate was removed by filtration
and washed with chlorobenzene (20 mL). The filtrate
was concentrated, and compound A (2.11 g, 65%, white
powder) was isolated by silica gel chromatography (1:1
hexane:dichloromethane ratio). The analysis of A was
1
sis of 1a was as follows. H NMR (400 MHz, THF-d8,
30 °C, TMS standard, ppm): δ 7.47 (d, J ) 7.4 Hz, 4H,
m-C6H5), 7.35 (s, 2H, C6H2), 7.33 (dd, J ) 7.4, 7.4 Hz,
4H, m-C6H5), 7.24 (t, J ) 7.4 Hz, 2H, p-C6H5), 7.09 (dd,
J ) 7.3, 8.3 Hz, 4H, m-C6H5NH), 6.91 (d, J ) 8.3 Hz,
4H, o-C6H5NH), 6.68 (t, J ) 7.3 Hz, 2H, p-C6H5NH),
6.36 (s, 2H, NH). 13C NMR (100 MHz, THF-d8): δ 145.9
(NH-CC5H6), 139.4 (C-CC5H6), 135.0 (NH-C[(CH)2-
(C-Ph)2]C), 134.3, 128.9 (m-Ph), 128.8 (m-Ph), 128.2,
126.9, 124.4, 118.6 (p-C6H5NH), 115.5 (o-C6H5NH). IR
(KBr, cm-1): 3393 (N-H), 1601 (C-N), 1528 (C-N),
1497 (CdC), 1477, 1401, 1317, 1256, 768 (C-H), 746
(C-H), 704 (C-H), 694 (C-H). EI-MS: 412 [M]+. Anal.
Calcd for C30H24N2: C, 87.35; H, 5.86; N, 6.79. Found:
C, 87.27; H, 6.06; N, 6.89.
1
as follows. H NMR (400 MHz, CDCl3, TMS standard,
ppm): δ 7.47 (s, 2H, C6H2Br2), 7.30 (dd, J ) 7.8, 7.2
Hz, 4H, m-C6H5), 7.04 (d, J ) 7.8 Hz, 4H, o-C6H5), 7.00
(t, J ) 7.2 Hz, 2H, p-C6H5), 5.76 (s, 2H, NH). 13C NMR
(100 MHz, CDCl3, 30 °C, TMS): δ 142.1 (NH-CC5H5),
135.4 (NH-C[(CH)2(CBr)2]C), 129.4 (m-C6H5), 121.9 (p-
C6H5), 121.5 (C(CH)2(CBr)2C), 118.6 (o-C6H5), 113.1 (Br-
C). IR (KBr, cm-1): 3399 (N-H), 1598 (C-N), 1523 (C-
N), 1469 (CdC), 1374, 1276, 1050, 887, 868 (C-H), 747
2.7. Syn th esis of Dith ien yl-Su bstitu ted P DA (1b).
A mixture that contained A (0.105 g, 0.25 mmol),
2-(tributylstannyl)thiophene (0.187 g, 0.5 mmol), and 2

Macromolecules, Vol. 36, No. 17, 2003
π-Conjugated Polymers Exhibiting a Novel Doping 6327
mol % tetrakis(triphenylphosphine) palladium(0) (0.012
g, 0.01 mmol) that had been dissolved in dioxane (3 mL)
was stirred at 100 °C for 24 h and cooled to room
temperature, and a solution of KF (2 mL, 1.0 M) was
added. The mixture was poured into water. The organic
layer was washed using saturated sodium hydrogen
carbonate and separated off, and the aqueous layer was
extracted with dichloromethane (3 times). The combined
organic layers were dried over anhydrous sodium sul-
fate, and compound 1b (0.098 g, 92%, yellow powder)
was isolated by silica gel chromatography (1:2 hexane:
dichloromethane ratio). The analysis of 1b was as
follows. 1H NMR (400 MHz, THF-d8, TMS standard, 30
°C, ppm): δ 7.57 (s, 2H, C6H2Th2), 7.32 (d, J ) 5.1 Hz,
2H, R-Th), 7.31 (d, J ) 3.9 Hz, 2H, â-Th), 7.12 (dd, J )
7.3, 7.3 Hz, 4H, m-C6H5), 6.99 (dd, J ) 3.9, 5.1 Hz, 2H,
â′-Th), 6.88 (d, J ) 7.3 Hz, 4H, o-C6H5), 6.71 (t, J ) 7.3
Hz, 2H, p-C6H5), 6.67 (s, 2H, NH). 13C NMR (100 MHz,
THF-d8): δ 145.8 (NH-CC5H5), 140.0 (C6H2-CC3H3S),
135.3 (NH-C[(CH)2(CTh)2]C), 128.8 (p-C6H5), 128.4 (â-
Th), 126.8 (NH-C[(CH)2(CTh)2]C), 125.7 (R-Th), 125.6
(â′-Th), 124.5, 118.8, 115.5 (o-C6H5). IR (KBr, cm-1):
3384 (N-H), 1601 (C-N), 1536 (C-N), 1518, 1497
(CdC), 1445, 1396, 1320, 1252, 845, 743 (C-H), 695
(C-H). EI-MS: 424 [M]+. Anal. Calcd for C26H20N2S2:
C, 73.55; H, 4.75; N, 6.60; S, 15.10. Found: C, 73.57; H,
4.84; N, 6.42.
washed using saturated sodium hydrogen carbonate and
brine and then was separated off, and the aqueous layer
was extracted with dichloromethane (3 times). Com-
pound 3b (0.315 g, 89%), a yellowish-brown powder, was
isolated by silica gel chromatography (1:1 hexane:
dichloromethane ratio). The analysis of 3b was as
follows. 1H NMR (400 MHz, THF-d8, 30 °C, TMS
standard, ppm): δ 7.45 (s, 2H, Th-CH-NH), 7.19 (s,
2H, Me-CH-NH), 7.15 (d, J ) 3.9 Hz, 2H, Th), 7.12
(dd, J ) 7.3, 7.3 Hz, 4H, m-C6H5), 7.10 (dd, J ) 7.3, 7.3
Hz, 4H, m-C6H5), 7.01 (d, J ) 3.9 Hz, 2H, Th), 6.83 (d,
J ) 7.3 Hz, 4H, o-C6H5), 6.82 (d, J ) 7.3 Hz, 4H, o-C6H5),
6.71 (t, J ) 7.3 Hz, 2H, p-C6H5), 6.68 (t, J ) 7.3 Hz,
2H, p-C6H5), 6.61 (s, 2H, NH), 6.58 (s, 2H, NH), 2.18 (s,
6H, CH3). 13C NMR (100 MHz, THF-d8, 30 °C, TMS
standard, ppm): δ 146.2 (NH-CC5H5), 145.9 (NH-
CC5H5), 139.6, 137.5, 137.1, 134.5, 131.6, 128.7, 126.9,
126.5, 125.8, 123.1, 121.9, 118.6, 118.4, 115.6, 115.3,
17.1. IR (KBr, cm-1): 3394 (N-H), 3368 (N-H), 3041
(CH3), 1598 (C-N), 1517 (C-N), 1496, 1399, 1292, 802
(C-H), 745 (C-H), 692 (C-H). TOF-MS: 710 [M]+.
Anal. Calcd for C46H38N4S2: C, 77.71; H, 5.39; N, 7.88;
S, 9.02. Found: C, 77.96; H, 5.36; N, 7.82.
2.10. P olym er iza tion of P P -P DA Com p lexes. A
typical polymerization procedure is as follows. A mixture
that contained A (0.105 g, 0.25 mmol), benzene-1,4-
diboronic acid (0.0414 g, 0.25 mmol), and tetrakis-
(triphenylphosphine) palladium(0) (0.0058 g, 0.005 mmol)
that had been dissolved in DME (2 mL) and aqueous
sodium carbonate (2 M, 1 mL) was stirred at 80 °C for
48 h under nitrogen, The reaction mixture was repre-
cipitated in methanol.
2.8. Syn th esis of P DAs Cou p led th r ou gh Th io-
p h en e (2b). Under nitrogen, a mixture that contained
B (0.353 g, 0.50 mmol), 2,5-bis(tributylstannyl)thio-
phene (0.331 g, 1.00 mmol), and tetrakis(triphenylphos-
phine) palladium(0) (0.0231 g, 0.02 mmol) that had been
dissolved in dioxane (7 mL) was stirred at 100 °C for
24 h and cooled to room temperature, and a solution of
KF (5 mL, 1.0 M) was added to quench the reaction.
The mixture was poured into water. The organic layer
was washed using saturated sodium hydrogen carbonate
and brine and then was separated off, and the aqueous
layer was extracted with dichloromethane (3 times). The
combined organic layers were dried over anhydrous
sodium sulfate and filtered. Compound 2b (0.245 g, 78%,
yellow powder) was isolated by silica gel chromatogra-
phy (1:2 hexane:dichloromethane ratio). The analysis
2.10.1. P P -P DA. P P -P DA (89%, green powder) was
obtained after collection via filtration and washing with
water. The analysis of P P -P DA was as follows. GPC:
1
Mn ) 1800, Mw/Mn ) 1.2. H NMR (400 MHz, DMSO-
d6, 30 °C, TMS standard, ppm): δ 7.44 (4H, C6H4), 7.22
(2H, C6H2), 7.08 (6H, m-C6H5, NH), 6.84 (4H, o-C6H5),
6.66 (2H, p-C6H5). 13C NMR (100 MHz, THF-d8, 30 °C,
TMS standard, ppm): δ 146.6 (NH-CC5H5), 137.9,
135.9, 134.7, 129.7, 128.6, 1255, 119.4, 116.3. IR (KBr,
cm-1): 3391 (N-H), 1600 (C-N), 1496 (CdC), 1386,
1307, 1257, 745 (C-H), 693 (C-H). TOF-MS: 1753
[(C24H18N2)4C18H14Br2N2]+.
1
of 2b was as follows. H NMR (400 MHz, THF-d8, 30
°C, TMS standard, ppm): δ 7.40 (s, 2H, Th-CH-NH),
7.17 (s, 2H, Me-CH-NH), 7.13 (s, 2H, â-Th), 7.11 (dd,
J ) 7.3, 7.3 Hz, 4H, m-C6H5), 7.08 (dd, J ) 7.3, 7.3 Hz,
4H, m-C6H5), 6.81 (d, J ) 7.3 Hz, 4H, o-C6H5), 6.79 (d,
J ) 7.3 Hz, 4H, o-C6H5), 6.70 (t, J ) 7.3 Hz, 2H, p-C6H5),
6.67 (t, J ) 7.3 Hz, 2H, p-C6H5), 6.57 (s, 2H, NH), 6.48
(s, 2H, NH), 2.16 (s, 6H, CH3). 13C NMR (100 MHz, THF-
d8): δ 146.8 (NH-CC5H5), 146.6 (NH-CC5H5), 141.2,
138.0, 135.3, 132.0, 129.5, 127.6, 126.7, 126.0, 123.0,
119.3, 119.1, 116.4, 116.1, 17.9. IR (KBr, cm-1): 3382
(N-H), 3044 (CH3), 1598 (C-N), 1496 (CdC), 1398,
1304, 1243, 745, 692. TOF-MS: 628 [M]+. Anal. Calcd
for C42H36N4S: C, 80.22; H, 5.77; N, 8.91; S, 5.10.
Found: C, 79.95; H, 5.76; N, 8.79.
2.10.2. P P 2-P DA. The analysis of P P 2-P DA (100%
yield, green powder) was as follows. GPC: Mn ) 2100,
Mw/Mn ) 2.0. 1H NMR (400 MHz, DMSO-d6, 30 °C, TMS
standard, ppm): δ 7.50 (4H, C6H4), 7.31 (4H, C6H4), 7.22
(2H, C6H2), 7.10 (6H, m-C6H5, NH), 6.88 (4H, o-C6H5),
6.65 (2H, p-C6H5). 13C NMR (100 MHz, DMSO-d6, 30
°C, TMS standard, ppm): δ 146.5 (NH-CC5H5), 137.8,
137.2, 133.6, 128.9, 128.8, 128.7, 126.1, 118.2, 115.3,
114.1. IR (KBr, cm-1): 3395 (N-H), 1599 (C-N), 1495
(CdC), 1473, 1438, 1254, 880, 822 (C-H), 744 (C-H),
691 (C-H), 503. Anal. Calcd for (C30H22N2)4C18H14
-
Br2N2: C, 80.45; H, 4.99; Br, 7.76; N, 6.80. Found: C,
79.97; H, 4.88; Br, 7.84; N, 6.04. TOF-MS: 1234
[(C30H22N2)2C18H14Br2N2]+.
2.9. Syn th esis of P DAs Cou p led th r ou gh Bith io-
p h en e (3b). A mixture that contained B (0.353 g, 0.50
mmol), 2,5-bis(tributylstannyl)thiophene (0.372 g, 1.00
mmol), and tetrakis(triphenylphosphine) palladium(0)
(0.0231 g, 0.02 mmol) that had been dissolved in dioxane
(7 mL) was stirred at 100 °C for 24 h under nitrogen
and cooled to room temperature, and a solution of KF
(5 mL, 1.0 M) was added to quench the reaction. The
mixture was poured into water. The organic layer was
2.10.3. octP P -P DA. The analysis of octP P -P DA
(98% yield, green powder) was as follows. GPC: Mn )
4400, Mw/Mn ) 1.8. 1H NMR (400 MHz, THF-d8, 30 °C,
TMS standard, ppm): δ 7.49 (4H, C6H4(backbone)), 7.30
(2H, C6H2), 6.98 (4H, m-C6H4), 6.87 (4H, o-C6H4), 6.45
(2H, NH), 2.49 (4H, CH2(C7H15)), 1.56 (4H, CH2CH2-
(C6H13)), 1.30 (20H, C2H4(CH2)5CH3), 0.88, CH3). 13C
NMR (100 MHz, THF-d8, 30 °C, TMS standard, ppm):
δ 144.3 (NH-CC5H4), 137.6, 136.0, 134.1, 129.6, 129.5,

6328 Nishiumi et al.
Macromolecules, Vol. 36, No. 17, 2003
124.1, 117.0, 36.0, 32.8, 32.7, 32.6, 30.4, 30.2, 23.5, 14.4.
IR (KBr, cm-1): 3392 (N-H), 2923 (CH2), 2851 (CH2),
1612 (C-N), 1513 (CdC), 1461, 1383, 1260, 824 (C-
H). TOF-MS: 2870 [(C40H50N2)4C34H46Br2N2]+.
Calcd for (C38H48N2S)6C34H46Br2N2: C, 78.1; H, 8.35; Br,
3.96; N, 4.86. Found: C, 77.5; H, 7.92; Br, 3.66; N, 4.86.
2.11.4. octP T2-P DA. The analysis of octP T2-P DA
(100% yield, orange powder) was as follows. GPC: Mn
1
2.10.4. octP P 2-P DA. The analysis of octP P 2-P DA
(98% yield, green powder) was as follows. GPC: Mn )
7400, Mw/Mn ) 2.7. 1H NMR (400 MHz, THF-d8, 60 °C,
TMS standard, ppm): δ 7.62 (d, 4H, J ) 8.3 Hz, C6H4-
(backbone)), 7.53 (d, 4H, J ) 8.3 Hz, C6H4(backbone)),
7.35 (s, 2H, C6H2), 6.93 (d, 4H, J ) 7.8 Hz, m-C6H4),
6.87 (d, 4H, J ) 7.8 Hz, o-C6H4), 6.27 (s, 2H, NH), 2.45
(t, 4H, J ) 7.8 Hz, CH2(C7H15)), 1.59 (m, 4H, J ) 4.8,
2.4 Hz, CH2CH2(C6H13)), 1.27-1.25 (m, 20H, C2H4-
(CH2)5CH3), 0.84 (t, 6H, J ) 6.7 Hz, CH3). 13C NMR (100
MHz, THF-d8, 30 °C, TMS standard, ppm): δ 143.5
(NH-CC5H4), 139.4, 138.5, 135.2, 133.3, 133.2, 129.4,
128.7, 126.7, 123.5, 116.0, 35.2, 32.0, 31.9, 29.6, 29.5,
29.4. IR (KBr, cm-1): 3407 (N-H), 2923 (CH2), 2851
(CH2), 1611 (C-N), 1511 (CdC), 1466, 1388, 1254. Anal.
Calcd for (C46H54N2)3C34H46Br2N2: C, 81.10; H, 8.23; N,
4.40. Found: C, 80.72; H, 7.76; N, 3.94.
) 6300, Mw/Mn ) 1.5. H NMR (400 MHz, THF-d8, 60
°C, TMS standard, ppm): δ 7.52 (2H, C6H2), 7.21 (2H,
Th), 7.06 (2H, Th), 6.99 (4H, m-C6H4), 6.84 (4H, o-C6H4),
6.40 (2H, NH), 2.27 (4H, CH2(C7H15)), 1.59 (4H, CH2CH2-
(C6H13)), 1.30 (20H, C2H4(CH2)5CH3), 0.88 (6H, CH3).
13C NMR (100 MHz, THF-d8, 60 °C, TMS standard,
ppm): δ 144.0 (NH-CC5H4), 140.0, 138.4, 136.6, 134.6,
129.6, 128.6, 127.3, 124.3, 124.1, 117.2, 36.0, 32.8, 32.5,
30.4, 30.2, 30.1, 23.4, 14.3. IR (KBr, cm-1): 3396 (N-
H), 2921 (CH2), 2850 (CH2), 1598 (C-N), 1510 (CdC),
1435, 790 (C-H), 693 (C-H). TOF-MS: 3231 [(C42H50N2-
S2)4C34H46Br2N2]+.
3. Resu lts a n d Discu ssion
3.1. Syn th esis of Novel P olyp h en ylen e a n d P oly-
th iop h en e Der iva tives Th a t Ha ve P DA Un its a n d
Mod el Com p ou n d s. The 2,5-dibromo- and 2-bromo-5-
methyl-substituted PDA derivatives (A, B,21 and C)
were synthesized via dehydration of the 2,5-dibromo-
or 2-bromo-5-methyl-benzoquinone with aniline or 4-n-
octyl-aniline in the presence of TiCl4 in yields of 65%,
56%, and 82%.22 (See Scheme 1.) The simplest pal-
ladium-catalyzed cross-coupling reactions were used for
the polymerization of the poly-p-phenylene or poly-
thiophene derivatives.23 Compounds 2a ,21 3a ,21 2b, and
3b were also synthesized through the coupling of 2
equimol of B with the difunctional phenylene15 or
thiophene19,20 derivatives in yields of 80%, 77%, 78%,
and 89%, respectively. The solubility of these compounds
was sufficient in THF. Novel polyphenylene or poly-
thiophene derivatives that had PDA units were obtained
via the coupling of the oligo phenylene or oligo thiophene
in good yields (79%-100%). The solubility of the non-
octyl-substituted polymers (P P -P DA, P P 2-P DA, P T-
P DA, and P T2-P DA) was poor, the polymerizations
proceeded nonuniformly, and the obtained THF-soluble
portion of these polymers was precipitated into acetone
to remove the oligomers. The octyl-substituted polymers
(octP P -P DA, octP P 2-P DA, octP T-P DA, and oct-
P T2-P DA) were soluble in common organic solvents
such as dichloromethane, chloroform, and THF. The
results of the characterization of the polymers are listed
in Table 1. The weight-average molecular weights (Mw)
of the non-octyl-substituted polymers of the THF-soluble
portionand of the octyl-substituted polymers were 2100-
4100 and 7900-20000, with a polydispersity of 1.2-2.0
and 1.7-2.7, respectively, as determined by GPC (using
THF as the eluent, based on polystyrene as the stan-
dard). The UV-Vis absorption spectra of the polymers
in dilute solutions of THF were measured and classified
into three categories, on the basis of the backbone
arrangement. The UV-Vis absorption maxima of the
poly-p-phenylene derivatives (P P -P DA, P P 2-P DA,
oct P P -P DA, and oct P P 2-P DA), poly(thienylene)
derivatives that include the mono-thiophenyl group
(P T-P DA and octP T-P DA), and poly(thienylene)
derivatives that include the dithienyl group (P T2-P DA
and octP T2-P DA) appeared at 291-304, 306-310,
and 442-460 nm, respectively. Because the absorption
maxima are mainly determined by the backbone ar-
rangement of the polymers, there are no effects of the
substitute and molecular weight on the UV-Vis absorp-
tion maxima.
2.11. P olym er iza tion of P T-P DA Com p lexes. A
typical polymerization procedure is as follows. A mixture
that contained A (0.105 g, 0.25 mmol), 2,5-bis(tributyl-
stannyl)thiophene (0.166 g, 0.25 mmol), and tetrakis-
(triphenylphosphine) palladium(0 (0.0058 g, 0.005 mmol)
that had been dissolved in dioxane (5 mL) was stirred
at 100 °C for 48 h under nitrogen and cooled to room
temperature, and a solution of KF (5 mL, 1.0 M) was
added to quench the reaction. The reaction mixture was
reprecipitated in methanol.
2.11.1. P T-P DA. P T-P DA (79% yield, orange pow-
der) was obtained after collection via filtration and
washing with water. The analysis of P T-P DA was as
1
follows. GPC: Mn ) 2100, Mw/Mn ) 1.5. H NMR (400
MHz, THF-d8, 60 °C, TMS standard, ppm): δ 7.52 (2H,
C6H2), 7.21 (2H, Th), 7.10 (4H, m-C6H5), 6.83 (4H,
o-C6H5), 6.72 (2H, p-C6H5), 6.50 (2H, NH). 13C NMR (100
MHz, THF-d8, 60 °C, TMS standard, ppm): δ 145.5
(NH-CC5H5), 140.5, 135.4, 128.8, 128.3, 126.0, 124.0,
119.1, 115.9. IR (KBr, cm-1): 3381 (N-H), 1599 (C-
N), 1495 (CdC), 1394, 1303, 1248, 744 (C-H), 691 (C-
H). TOF-MS: 1442 [(C22H16N2S)3C18H14Br2N2]+.
2.11.2. P T2-P DA. The analysis of P T2-P DA (100%
yield, orange powder) was as follows. GPC: Mn ) 2200,
1
Mw/Mn ) 1.4. H NMR (400 MHz, THF-d8, 60 °C, TMS
standard, ppm): δ 7.58 (2H, C6H2), 7.24 (2H, Th), 7.14
(6H, m-C6H5, Th), 6.89 (4H, o-C6H5), 6.73 (2H, p-C6H5),
6.62 (2H, NH). 13C NMR (100 MHz, THF-d8, 60 °C, TMS
standard, ppm): δ 146.8 (NH-CC5H4), 138.8, 136.7,
129.9, 129.7, 129.6, 127.6, 125.2, 124.6, 120.1, 116.8. IR
(KBr, cm-1): 3381 (N-H), 1598 (C-N), 1495 (CdC),
1394, 1303, 796 (C-H), 744 (C-H), 690 (C-H). TOF-
MS: 1687 [(C26H18N2S2)3C18H14Br2N2]+.
2.11.3. octP T-P DA. The analysis of octP T-P DA
(79% yield, orange powder) was as follows. GPC: Mn )
8200, Mw/Mn ) 1.7. 1H NMR (400 MHz, THF-d8, 50 °C,
TMS standard, ppm): δ 7.47 (2H, C6H2), 7.19 (2H, Th),
6.95 (4H, m-C6H4), 6.78 (4H, o-C6H4), 6.36 (2H, NH),
2.51 (4H, CH2(C7H15)), 1.57 (4H, CH2CH2(C6H13)), 1.31
(20H, C2H4(CH2)5CH3), 0.87 (6H, CH3). 13C NMR (100
MHz, THF-d8, 50 °C, TMS standard, ppm): δ 143.9
(NH-CC5H4), 141.3, 136.2, 134.3, 129.5, 128.3, 126.6,
123.9, 117.2, 36.0, 32.8, 32.6, 30.4, 30.2, 30.1, 23.4, 14.3.
IR (KBr, cm-1): 3392 (N-H), 2923 (CH2), 2851 (CH2),
1612 (C-N), 1513 (CdC), 1461, 1383, 1260, 824 (C-
H). TOF-MS: 3470 [(C38H48N2S)5C34H46Br2N2]+. Anal.

Macromolecules, Vol. 36, No. 17, 2003
π-Conjugated Polymers Exhibiting a Novel Doping 6329
Sch em e 1
Ta ble 1. P a lla d iu m -Ca ta lyzed P olym er iza tion a
yieldb
Mw
Mw/Mn
c
c
E°e (V)
d
polymer
(%)
solvent
(g/mol)
(g/mol)
λmax (nm)
P P -P DA
89
98
100
100
79
93
100
100
DME, H2Of
DME, H2Of
DME, H2Of
DME, H2Of
dioxaneg
2100
7900
4100
20000
3100
14000
3100
9500
1.2
1.8
2.0
2.7
1.5
1.7
1.4
1.5
291
294
302
304
306, 436
310, 437
442, 303
460, 311
0.28, 0.48
0.29, 0.44
0.29, 0.46
0.27, 0.41
0.40
0.36
0.40
0.33
octP P -P DA
P P 2-P DA
octP P 2-P DA
P T-P DA
octP T-P DA
P T2-P DA
octP T2-P DA
dioxaneg
dioxaneg
dioxaneg
a
All polymerizations were conducted for 48 h with 1 mol % palladium(0) catalysts. b Methanol-insoluble part. c Soluble portion, estimated
by GPC (THF, PS). In THF. e Redox potential of the polymer films on a GC electrode. Conditions: acetonitrile solution that contained
d
TBABF4 (0.2 M) and TFA (1 M). f A 2:1 mixture, with a concentration of 0.08 M at a temperature of 80 °C. Concentration of 0.05 M at
g
a temperature of 100 °C.
The IR spectra of all polymers showed absorptions at
in the NMR. All signals were clearly detected, and the
ratios of the integrated intensity of the amine were
consistent with the expected polymers. These polymers
are quite stable in air at room temperature.
∼3400 cm-1, which indicate a N-H stretching vibration.
1
Typical examples of the H NMR spectra of octP P 2-
1
P DA and octP T-P DA are shown in Figure 1. The H
NMR spectra of octP P 2-P DA and octP T-P DA in
THF-d8 each showed a sharp singlet, centered at 6.22
and 6.36 ppm, respectively, that was derived from the
amine of the PDA units. No separated signals of the
leaving group (such as the boronic acid, boronic acid,
dimethylpropyl ester, or tributyltin groups as an end
3.2. Electr och em istr y a n d Sp ectr oelectr och em -
istr y. The redox properties of the model compounds
(PDA, 1a , and 1b) were confirmed by cyclic voltammetry
(CV) (see Figure 2). These compounds underwent a two-
step oxidation, from the amine to the radical cation to
the imine forms. In the absence of TFA, the second redox
couple was not reversible, because the oxidative half-
reaction of the second couple involves the loss of one
electron and two protons, whereas the cathodic half-
reaction entails the gain of one electron and two
1
group) were identified, and the H NMR chemical shift
of the end groups, which have a bromine leaving group,
had almost the same value as that of the backbone, and
almost no end groups in these polymers were observed

6330 Nishiumi et al.
Macromolecules, Vol. 36, No. 17, 2003
Ta ble 2. E1/2 P oten tia ls (V, vs Ag/Ag+) of Mod el
Com p ou n d s (P DA, 1a , 1b) in Aceton itr ile Th a t Con ta in ed
TBABF 4 (0.2 M) a n d Tr iflu or oa cetic Acid (0.2 M)
Potential (V)
Wavelength (nm)
a
b
d
e
compound
E°1
E°2
∆Ec
λmax1
λmax2
PDA
1a
1b
0.27
0.27
0.30
0.55
0.50
0.45
0.28
0.23
0.15
698
717
751
518
545
551
a
b
For a 0/1+ couple. For a 1+/2+ couple. c ∆E ) E°2 - E°1.
For the radical monocation. e For the dication.
d
Ta ble 3. Electr och em ica l P a r a m eter s of Mod el
Com p ou n d s (1a -3a a n d 1b-3b)
a
c
∆Ei/4
∆Eb
(mV)
∆E(amine)
(mV)
compound
(mV)
1a
2a
3a
1b
2b
3b
67
72
74
67
89
87
42
48
50
42
63
61
228
220
221
170
155
132
a
∆Ei/4 is the full width at three-fourths-maximum current of
b
DPV. Potential splitting based on the interaction between PDA
units via the linking group. c Potential splitting based on the
interaction between amines within a single PDA unit.
the smallest magnitude, because of the radical mono-
cation delocalization into the thienyl group. These
results were supported by the spectroelectrochemical
measurement. The λmax values of 698, 717, and 751 nm
of the radical monocation were found for P DA, 1a , and
1b, respectively, meaning that the enhancement of the
radical cation delocalization is expected to vary in the
following order: P DA < 1a < 1b. The most broadened
absorption band was exhibited by 1b. These results
show that the delocalization of the radical monocation
expanded into the thiophene group via π-conjugation.
F igu r e 1. 1H NMR spectra of (a) octP P 2-P DA and (b)
octP T-P DA in THF-d8. Peaks marked with an asterisk (*)
are assigned to the solvent (THF).
3.3. Electr on Com m u n ica tion via a Ba ck bon e. To
determine the potential difference between the PDA
units exactly, the first redox waves of the compounds
that have two PDA units (2a , 3a , 2b, and 3b) were
compared to the compounds that have one PDA unit,
using the differential pulse voltammetry24 (DPV) mea-
surement (see Table 3 and Figure 3). Two oxidation
peaks were observed in the case of the dimeric com-
pounds of 2a , 3a , 2b, and 3b, despite them having four
redox sites. Some electrochemical interactions, such as
the coulombic repulsion, results in more splitting or
broadening of the DPV oxidation waves, according to
the electron communication intensity. Both the first and
second oxidation waves of 2a and 3a or 2b and 3b show
broadened peaks, compared to that of 1a or 1b. The full
width at three-fourths maximum current (∆Ei/4) of DPV
values of 2a and 3a were 72 and 74 mV, respectively,
which are similar to that of 1a . On the other hand, the
∆Ei/4 values of 2b and 3b are 89 and 87 mV, respec-
tively, which are 15 mV higher than that of 1b (63 mV,
which possesses nonelectron communication). These
results support the existence of the intramolecular
interaction between the two PDA units through the
linking group in 2b and 3b. In addition, the potential
difference between the two redox waves (∆E(amine)) in
2b and 3b is smaller than that in 1b, because the
electronic communication between two PDA units re-
duces the coulombic repulsion within each PDA unit.
The overlapping on the oxidation potential of the
thiophene group (∼0.6 V, vs Ag/Ag+) and the PDA units
is considered to allow the electronic communication
F igu r e 2. Cyclic voltammograms of model PDA compounds,
1a , and 1b (1 mM) for (a) an aprotic solution and (b) a solution
that contained trifluoroacetic acid (1 M) in an acetonitrile. The
electrolyte is TBABF4 (0.2 M), and the scan rate is 100 mV/s.
protons.6 In the presence of 1 M TFA, the cyclic
voltammograms of PDA, 1a , and 1b each show two
reversible redox waves at E°1 and E°2 (see Table 2).
The potential splitting, ∆E (E°2 - E°1), of 1b showed

Macromolecules, Vol. 36, No. 17, 2003
π-Conjugated Polymers Exhibiting a Novel Doping 6331
F igu r e 5. (a) Cyclic voltammograms of a cast film of octP T2-
P DA on a GC electrode (0.071 cm2) in an acetonitrile solution
that contained TBABF4 (0.2 M) and TFA (1 M) with a sweep
range of 0.0-0.7 V, vs Ag/Ag+. Scan rates of 5, 10, 20, 50, 100,
and 200 mV/s were used. Inset (labeled b) shows the redox
activity of (O) octP T-P DA and (b) octP T2-P DA polymers
on a GC electrode (0.071 cm2) in an acetonitrile solution that
contained TBABF4 (0.2 M) and TFA (1 M). This inset figure
F igu r e 3. Differential pulse voltammograms of (a) 1a , 2a ,
and 3a (1 mM) in an acetonitrile solution that contained
TBABF4 (0.2 M) and TFA (1 M), and (b) 1b, 2b, and 3b in an
acetonitrile solution that contained TBABF4 (0.2 M) and TFA
(5 M). Amplitude of DPV measurement is 50 mV.
shows the relationship between the oxidation peak current (ipa
)
and the scan rate in the cyclic voltammogram.
F igu r e 6. (a) UV-Vis spectra of the oxidation of 1b (s) to
the radical cation at a potential of 0-0.35 V, vs Ag/Ag+, and
(---) to the dication at a potential of 0.4-0.9 V, vs Ag/Ag+. (b)
UV-Vis spectra of P T-P DA film on an ITO electrode (0.2-
0.6 V, vs Ag/Ag+).
F igu r e 4. Cyclic voltammograms of cast films of P P -P DA,
P P 2-P DA, P T-P DA, and P T2-P DA on a GC electrode
(0.071 cm2) in an acetonitrile solution that contained TBABF4
(0.2 M) and TFA (1 M) with a sweep range of 0.0-0.8 V, vs
Ag/Ag+. Scan rate is 100 mV/s.
the poly-p-phenylene derivatives. The octyl-substituted
polymer films have redox potentials that are lower than
those of the others. The octyl-substituted thiophene
backbone polymers showed a good redox activity, and
the plot of the oxidation peak current (ipa) versus the
scan rate (v) of the oct P T-P DA and oct P T2-P DA
followed a straight line, with correlation coefficients of
0.993 and 0.991, respectively (see Figure 5).
From the spectroelectrochemical analysis of 1b, two
types of spectral changes that are based on two one-
electron oxidations were confirmed at a potential of 0.0-
0.8 V (see Figure 6, a). The absorption at ∼751 nm and
a potential of 0.35 V is assigned to the radical cation,
which was formed by the one-electron oxidation per PDA
unit, and that at ∼551 nm and a potential of 0.6 V is
assigned to the dication. These results show the char-
acter of the radical cation of only one PDA unit and the
between the PDA units in 2b and 3b. In contrast, the
higher oxidation potential of the phenyl group than that
of the PDA units makes it difficult to have an interaction
between the two PDA units.
3.4. Electr och em ica l P r op er ty of th e P olym er s.
The redox properties of the resulting polymer films were
confirmed by CV. The results of the redox waves were
different between the poly-p-phenylene derivatives and
the polythiophene derivatives. The typical results of the
obtained polymer (P P -P DA, P P 2-P DA, P T-P DA,
and P T2-P DA) are shown in Figure 4, and the redox
potentials are listed in Table 1. The polymer films of
the poly-p-phenylene derivatives show two reversible
redox couples, similar to the model compounds. How-
ever, that of the polythiophene derivatives showed only
one reversible redox couple, at the center potential of

6332 Nishiumi et al.
Macromolecules, Vol. 36, No. 17, 2003
The polythiophene derivatives that have a PDA show a
strong interaction between the intramolecular PDAs,
and the radical cation that was formed at the amine of
the PDA was delocalized. The electron transfer between
the PDAs through the backbone of the thiophene was
investigated.
Ack n ow led gm en t. This work was partially sup-
ported by a Grant-in-Aid for Scientific Research (Nos.
15036262, 15655019, 15350073) and the 21st COE
program (Keio-LCC) from the Ministry of Education
Science Foundation Culture, and a Grant-in-Aid for
Evaluative Technology (12407) from the Science and
Technology Agency, and Kanagawa Academy Science
and Technology Research Grant (Project No. 23).
F igu r e 7. (s) Cyclic voltammogram and (‚‚‚) in situ conduc-
tivity measurement) of P T-P DA films. Conditions: acetoni-
trile solution that contained TBABF4 (0.2 M) and TFA (1 M),
with a sweep range of 0.0-0.8 V, vs Ag/Ag+, scan rate of 100
mV/s; cast film on a GC electrode (0.071 cm2), scan rate of 100
mV/s for CV; cast film on platinum interdigitated array
electrode, scan rate of 10 mV/s for conductivity measurement.
Refer en ces a n d Notes
(1) Yamamoto, K.; Asada, T.; Nishide, H.; Tsuchida, E. Bull.
Chem. Soc. J pn. 1990, 63, 1211.
(2) Yamamoto, T.; Kimura, T.; Schiraishi, K. Macromolecules
Sch em e 2
1999, 32, 8886.
(3) Tan, L.; Curtis, M. D.; Francis, A. H. Macromolecules 2002,
35, 4628.
(4) Zotti, G.; Schiavon, G.; Zecchin, S.; Morin, J . F.; Leclerc, M.
Macromolecules 2002, 35, 2122.
(5) Nishikitani, Y.; Kobayashi, M.; Uchida, S.; Kubo, T. Electro-
chim. Acta 2001, 46, 2035.
(6) Mammone, R. J .; Binder, M. J . J . Electrochem. Soc. 1988,
135, 1057.
(7) Wolf, J . F.; Forbes, C. E.; Gould, S.; Shacklette, L. W. J .
Electrochem. Soc. 1989, 136, 2887.
(8) McQuade, D. T.; Pullen, A. E.; Swager, T. M. Chem. Rev.
2000, 100, 2537.
(9) Yamamoto, K.; Taneichi, D. Chem. Lett. 2000, 1, 4.
(10) Higuchi, M.; Ikeda, I.; Hirao, T. J . Org. Chem. 1997, 62, 1072.
(11) Gomes, M. A. B.; Goncalves, D.; Desouza, E. C. P.; Valla, B.;
Aegerter, M. A.; Bulhoes, L. O. S. Electrochim. Acta 1992,
37, 1653.
(12) Nishiumi, T.; Higuchi, M.; Yamamoto, K. Electrochemistry
2002, 70, 668.
(13) Miyaura, N.; Yanagi, T.; Suzuki, A. Synth. Commun. 1981,
11, 513.
(14) Lamba, J . J . S.; Tour, J . M. J . Am. Chem. Soc. 1994, 116,
11723.
(15) Kim, S.; J ackiw, J .; Robinson, E.; Schanze, K. S.; Reynolds,
J . R.; Baur, J .; Rubner, M. F.; Boils, D. Macromolecules 1998,
31, 964.
(16) Stille, J . K. Angew. Chem., Int. Ed. Engl. 1986, 25, 508.
(17) Bao, Z.; Chan, W. K.; Yu, L. Chem. Mater. 1993, 5, 2.
(18) Bao, Z.; Chan, W. K.; Yu, L. J . Am. Chem. Soc. 1995, 117,
12426.
example of no interaction between the two PDA units,
similar to the model compounds 2a and 3a and the poly-
p-phenylene derivatives. Only one redox wave was
observed in the cyclic voltammograms of the films that
contained the polythiophene derivatives. In the spec-
troelectrochemical analysis of the P T-P DA film, a
broad absorption at ∼750 nm and potentials of 0.5 V or
higher is assigned to the radical cation, and the absorp-
tion did not disappear at a potential higher than 0.6 V
(see Figure 6b). These results show that the radical
cation formed in the polythiophene derivatives is sta-
bilized by π-conjugation, expanded through the poly-
thiophene backbone.
(19) Seitzg, D. E.; Lee, S. H.; Hanson, S. H.; Bottaro, J . C. Synth.
Commun. 1983, 13, 121.
(20) Miller, L. L.; Yu, Y. J . Org. Chem. 1995, 60, 6813.
(21) Yamamoto, K.; Higuchi, M.; Nishiumi, T.; Takai, H. Bull.
Chem. Soc. J pn. 2002, 75, 1827.
(22) It should be noted that compounds A, B, and C were obtained
in a reduced state, because an excess amount of aniline
worked as a reductant and their yields were dependent on
their reductive efficiency to the products.
(23) As a coupling reaction for the introduction of a phenyl group,
we employed one of the typical Pd(0)(PPh3)4 cross-coupling
conditions. The cross coupling of PDA with a thiophene group
was performed using a Stille coupling agent without CuI. The
PDA unit would be oxidized in the palladium-catalyzed cycle,
but model compounds of the polymers, 2,5-diphenyl- (1a ) or
2,5-dithienyl- (1b) PDAs, were obtained in a reduced state
through palladium-catalyzed Suzuki coupling or cross cou-
pling of A with benzeneboronic acid or 2-(tributylstannyl)-
thiophene in yields of 87% and 92%, respectively.
(24) Richardson, D. E.; Taube, H. Inorg. Chem. 1981, 20, 1278.
(25) Thackeray, J . W.; White, H. S.; Wrighton, M. S. J . Phys.
Chem. 1985, 89, 5133.
The conductivities of P T-P DA and P T2-P DA were
measured using an interdigitated array electrode that
was modified with a polymer by casting.25-27 P T-P DA
and P T2-P DA exhibited conductivities of 0.10 and
0.067 S/cm, respectively, by the one-electron oxidation
of the PDA unit at 0.4 V, because of the formation of
polarons in the main chain (see Figure 7 and Scheme
2).
4. Con clu sion
(26) Ofer, D.; Crooks, R. M.; Wrighton, M. S. J . Am. Chem. Soc.
1990, 112, 7869.
(27) Zhu, S. S.; Swager, T. M. J . Am. Chem. Soc. 1997, 119, 12568.
Novel π-conjugated polymers and model compounds
that have N,N′-diphenyl-1,4-phenylenediamine (PDA)
units which act as two-electron redox units were syn-
thesized and their redox properties were investigated.
MA025833J