Synthesis and ionochromic properties of chelating conjugated polymers

Article abstract of DOI:10.1039/a905912a

Two types of conjugated copolymers functionalized by chelating subunits were prepared using the palladium catalysed coupling reaction of a dihalogenated substrate containing a coordinating unit and a bis(tributylstannyl) conjugated reagent. The ionochromic properties of the polymers containing crown ethers or bipyridine were studied.

Full text of DOI:10.1039/a905912a

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J O U R N A L O F
Synthesis and ionochromic properties of chelating conjugated
polymers
Mohammed Bouachrine, Jean-Pierre LeÁre-Porte, JoeÈl J. E. Moreau,*
FrancËoise Serein-Spirau and Christophe Torreilles
C H E M I S T R Y
HeÂteÂrochimie MoleÂculaire et MacromoleÂculaire, CNRS UMR 5076,
Ecole Nationale SupeÂrieure de Chimie, 8 rue de l'Ecole Normale,
34296 Montpellier Cedex 5, France. E-mail: jmoreau@cit.enscm.fr
Received 22nd July 1999, Accepted 12th October 1999
Two types of conjugated copolymers functionalized by chelating subunits were prepared using the palladium
catalysed coupling reaction of a dihalogenated substrate containing a coordinating unit and a
bis(tributylstannyl) conjugated reagent. The ionochromic properties of the polymers containing crown ethers or
bipyridine were studied.
Poly(p-phenylene-vinylene)s are of great interest for their
photophysics, charge transport and optoelectronic properties.1
Additionally, it has been shown more recently that some (2,2'-
bipyridyl-p-phenylene-vinylene) based polymers exhibit iono-
chromic properties in the presence of a wide variety of
transition metal ions.2 Moreover, their optoelectronic proper-
ties can be controlled by protonation±deprotonation pro-
cesses.3 Related chemoresponsive polymers are of interest for
the design of selective sensory materials.
thin ®lms on glass can be easily realized. In order to study their
potential applications as ion sensors, we introduced in the
polymer skeleton two types of chelating units: a crown ether for
the complexation of alkali or alkaline earth metal ions and a
2,2'-bipyridine unit which easily forms complexes with
transition metal ions.
Results and discussion
Substituted polythiophenes with side chains containing
crown ether4 or calix[4]arene5 also exhibit selective ionochro-
mism. Our current interest in the controlled synthesis of
thiophene-phenylene and thiophene vinylene copolymers6 has
led us to study the synthesis of polythiophene-phenylene
copolymers containing complexing units in the backbone of the
polymer. The optical properties of these copolymers where the
complexing unit is part of the polymer backbone are expected
to be strongly dependent on the ion.
Here, we report the synthesis and the ionochromic behavior
of [thienylene-p-(2,5-dialkoxy)-phenylene] copolymers which
contain chelating units in the polymer backbone. We earlier
showed that [thienylene-p-(2,5-dialkoxy)-phenylene] copoly-
mers have interesting luminescent and electrochromic proper-
ties.7 Moreover, owing to the presence of alkoxy substituents
1. Polymers synthesis
The synthesis of the two polymers was based on the Stille
coupling reaction between a dihalogeno aromatic substrate and
a bis(tributylstannyl) aromatic species in the presence of Pd(0)
as the catalyst. It has already proved to be an ef®cient route to
regioregular poly(3-alkylthiophene).8 Moreover, alternating
thienylene-phenylene copolymers9 have also been reported
using a polycondensation based on the Stille coupling reaction.
Polymers 1 were synthesized by a co-condensation reaction
using 2,5-bis(tributylstannyl)thiophene (3) with a known ratio
of 1,4-dibromo-2,5-di(2-butoxyethoxy)benzene (4) and of
4,4'(5')-dibromodibenzo-18-crown-6 ether (5). It gave soluble
conjugated polymers in THF or CHCl3 with alternating
conjugated unit and coordinating entities (Scheme 1).
Scheme 1 Synthesis of copolymers 1.
J. Mater. Chem., 2000, 10, 263±268
This journal is # The Royal Society of Chemistry 2000
263

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Fig. 1 1H NMR spectrum of coplymer 1d. The asterisks indicate
characteristic signals of the protons of the crown ether: a) aromatic
protons region; b) aliphatic protons region.
The structure of polymers 1 was studied by 1H NMR in
CDCl3. The relative intensities of the signals around d~7.2±
7.4 ppm and d~4±4.4 ppm allow estimation of the average
crown-ether content in the polymer chain. The values are very
close to the ratio of the two dibromo monomers 4 and 5 used in
the polycondensation with the tributyltin reagent (Scheme 1).
1
The H NMR spectrum of 1d is given as an example (Fig. 1).
This indicates that the two dibromo compounds 4 and 5
exhibit a similar reactivity towards the tin reagent 3 and their
incorporation in the polymer chain follows the initial
concentration ratio of the two monomers.
The molecular weights of polymers 1 were determined by size
exclusion chromatography (SEC) (THF as eluent) with an on-
line refractive index detector using polystyrene standards
calibration. The measured average molecular weights Mw
varied from 8.86103 to 146103 (Table 1). It suggested an
average degree of polymerization (Dpn) varying from 12 to 26.
The UV±Vis spectra were recorded from 10-4 M solutions in
CHCl3 and from thin ®lms on glass (Table 1).
The synthesis of polymer 2 is shown in Scheme 2.
The monomer 7 was synthesized in 63% yield by palladium(0)
(Pd(PPh3)4) catalysed coupling of 1,4-dibromo-2,5-di(octyl-
oxy)benzene (6) with 2-thienylzinc chloride.10 At 0 ³C 7 was
then metalated, in diethyl ether, using two equivalents of
n-butyllithium and treated with two mole-equivalents of
tributylstannyl chloride to give 8 in 60% yield. Finally, polymer
2 results from the palladium catalysed condensation between
Scheme 2 Synthesis of copolymer 2.
mism in the presence of alkali metals) are due to modi®cation
of the conformation of the coordinating side chain upon
interaction with the metal ion. It induces a cooperative twisting
of the main chain of the polymer and results in modi®cations of
the conjugation and optical properties of the polymer. Cyclic
voltammetry experiments performed with such conjugated
polymers having side chains containing coordinating units
showed variation in the oxidation potential when alkali metal
ions were added. Moreover these materials exhibited iono-
chromic properties.4,5b,12 We therefore examined the properties
of polymers 1.
A sample of polymer 1 was deposited on a platinum
electrode by evaporation of a saturated THF solution. Cyclic
voltammetry was then performed in MeCN (0.1 M Bu4NPF6;
50 mV s21). The observed variations of the oxidation potential:
z35 and z60 mV, when Liz or Kz were respectively added to
polymer 1d, were consistent with a weak coordination of these
ions to the crown ether unit (Fig. 2).
5,5'-diiodo-2,2'-bipyridine11
9 and the bis(tributylstannyl)
derivative 8. The structure of polymer 2 was studied in
1
CDCl3 solution by H NMR.
The molecular weight of polymer 2 was as previously
measured by SEC experiment in THF eluent and the value
refers to polystyrene standards: Mw~3477, Mw/Mn~1.12,
Dpn~5.
In the UV±Vis spectrum, the absorptions lmax of polymer 2
are 438 nm ꢀel ~23 250† in a 10-5 M solution in CHCl3 and
max
517 nm in a thin ®lm on glass.
2. Ion responsive properties
2.1 Polymer 1. It has been recently shown that poly(alk-
ylthiophene)s containing side chains functionalized with
oligo(oxyethylene) or crown ether have ionoresponsive proper-
ties.4,5b,12b,13,14 These ionoresponsive properties (e.g. ionochro-
However, we did not observe any ionochromic effect when
Liz or Kz ions were added to polymer 1 in a THF solution.
Table 1 Selected data for polymers 1
c
l
max/nm (emax
)
lmax/nm
Films on glass
a
Polymers of type 1
Mw
Mw/Mn
Dpnb
CHCl3 (1024 M)
1a
1b
1c
1d
14093
10515
8878
1.35
1.10
1.25
1.45
26
19
16
12
c
459 (26 010)
458 (24 560)
455 (24 304)
452 (23 346)
496
490
490
488
8795
aDetermined by SEC using polystyrene standards. bDegree of polymerisation. Measured in 1024 M CHCl3 solutions.
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Fig. 3 Modi®cation of the absorption spectrum of a 2 mL solution of
copolymer 2 (10 25 M) upon addition of increasing amounts of a
F3CCOOH solution (1 M) (each spectrum corresponds to the
successive addition of 20 mL of the acid solution): a) copolymer 2
alone; b) after addition to copolymer 2 of 400 mL of a F3CCOOH
solution (1 M).
units induces rotation of the two pyridyl rings, the planar
conformation of the protonated bipyridine unit leads to an
increase in the conjugation length of the polymer. In the
unprotonated form the 2,2'-bipyridyl units have more twisted
conformations and the mean conjugation length is lower.
The protonation±deprotonation cycle can be repeated at
room temperature without any noticeable degradation of the
®lm and without changes of its optical properties for at least
®ve cycles. Interestingly, the color of polymer 2 can change
continuously from yellow to pink in solution or from brown to
purple for thin ®lms in glass depending on the degree of
protonation without measurable degradation of ®lms during
more than ®ve cycles.
Fig. 2 Cyclic voltammetry of copolymer 1d. Shift of the oxidation
potential upon addition of Liz or Kz
.
The absence of the ionochromic effect could be attributed to
the structure of polymer 1. The coordinating unit is not the side
chain, but in the conjugated main chain. Complexation of
metal ions by the dibenzo-18-crown-6 unit probably occurred,
but it seems in this case that the interaction with the metal ion
did not modify the length of the conjugated segment. It is
possible that in this polymer, the change of the conformation of
the dibenzo-18-crown-6 ether affected only weakly the
conformation of the conjugated chain.
Transition metal ion responsive properties of polymer 2. The
ionochromic effect of polymer 2 was characterized by instant
color changes of the initially yellow solutions of polymer
(1025 M in CHCl3) upon the addition of solutions of metal
salts (1024 M in CHCl3). Fig. 4 shows the changes of color
from yellow (lmax~441 nm) to pink±purple according to the
nature of the ion. The absorption maxima varied from
2.2 Polymer 2. We therefore explored the ion responsive
properties of polymer 2 in which complexation of the
bipyridine unit was expected to strongly modify the conjuga-
tion properties of the material.
l
max~473 nm for Agz (AgBF4), lmax~516 nm for Cuz
Protonation±deprotonation. The protonation ability of
polymer 2 was ®rst observed in (10-5 M) CHCl3 solutions.
Addition of increasing amounts of a (1 M) CHCl3 solution of
tri¯uoroacetic acid (TFA) resulted in changes of the color of
the solution. The solution, originally yellow (lmax~425 nm),
became progressively pink (lmax~492 nm) (Fig. 3). After
addition of 400 mL of TFA (1 M) no further changes were
observed, the protonation of polymer 2 being completed.
Thin ®lms of polymer 2 on a glass substrate were realized by
slow evaporation of a saturated solution in CHCl3. The UV±vis
spectra showed an absorption maximum at lmax~438 nm. The
same value was observed using a poly(ethylene) support. As
previously observed with conjugated polymer,15 in comparison
to the solution behavior a red-shift of the absorption occurred
when the polymer was analysed in the solid state. Exposure of
the ®lm of polymer 2 to HCl or HCOOH vapors induced a
color change from brown to purple. It was characterized by a
bathochromic displacement of the absorption maxima of
Dlmax~86 nm (HCl vapor) and 33 nm (concentrated
HCOOH). The shifts of the absorption maximum depended
on the strength of the acid. When this purple ®lm was then
exposed to ammonia vapors, it turned brown again. These
color changes characterize the reversible protonation±depro-
tonation process of the 2,2'-bipyridyl units in the main chain of
polymer 2. This phenomenon is associated with differences in
the conformation of the 2,2'-bipyridyl unit in its protonated
and unprotonated form.3 The protonation of the 2,2'-bipyridyl
(Cu(CH3CN)4PF6), lmax~518 nm for Zn2z (ZnCl2) and
l
max~543 nm for Pd2z (PdCl2).
The ionochromic properties were also studied in the case of
thin ®lms. Thin orange ®lms of polymer 2 were laid on a glass
substrate upon slightly heating a few drops of a saturated
Fig. 4 Ionochromism of a solution of copolymer 2 in the presence of
transition metal ions: a) copolymer 2; b) with added Agz; c) with added
Cuz; d) with added Zn2z; e) with added Pd2z
.
J. Mater. Chem., 2000, 10, 263±268
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purple solution of polymer 2 in HCOOH. The IR spectrum of a
®lm deposited under these conditions showed a weak absorp-
tion band attributed to formate at n(CLO)~1598 cm21. It is
indicative of a partial protonation of polymer 2. It showed an
absorption maximum at lmax~447 nm. The samples were then
dipped into 10-4 M solutions of various metal salts in CHCl3. In
properties, copolymer 2 appears to be a good candidate for the
elaboration of ion sensory materials.
Experimental
CHCl3, THF, DMF and hexane (SDS) were dried by
distillation over phosphorus pentoxide, sodium benzophenone
ketyl and CaH2 respectively. 4,4'(5')-Dibromodibenzo-18-
crown-6 ether (Acros), 2-butoxyethanol and tributyltin chlor-
ide (Aldrich) were used without further puri®cation.
all cases, whatever the metal ion (Pd2z, Agz, Cd2z, Zn2z
,
Cuz), a slight red-shift of the absorption maximum was
recorded (lmax~460 nm). In the solid state, it showed a weak
and unselective coordination of the 2,2'-bipyridyl subunits
towards the metallic ions in polymer 2. It may be related to a
low accessibility of the bipyridine coordination site to the metal
ion or to the partial protonation of the 2,2'-bipyridine units.
We therefore studied a solvent of higher polarity than CHCl3 in
which metal ion salts are more soluble.
1H NMR spectra were recorded in CDCl3 at 200 MHz with a
Bruker AC 200 spectrometer, using residual CHCl3
(d~7.27 ppm) as the internal standard. 13C NMR spectra
were obtained at 50.32 MHz with a Bruker AC 200 spectro-
meter using CDCl3 (d~77.70 ppm) as the internal standard.
118Sn NMR spectra were recorded in CDCl3 at 93.27 MHz with
a Bruker AC 250 spectrometer. IR spectra were recorded with a
Perkin Elmer 1000 spectrometer. Melting points were measured
with an Electrothermal 9100 apparatus. Absorption spectra
were recorded on an MC2 Safas spectrometer and emission
spectra on an SLM-Aminco MC 200 spectrometer. SEC
measurements were realized on a Waters device equipped with
HR2 and HR3 Styragel columns. Cyclic voltammetry was
realised on an EGG potentiostat connected to a Kipp & Zonen
tracer.
A similar experiment was performed using more concen-
trated transition metal ion solutions (1 M) in MeOH. In the
absence of any metal ion a solvatochromism was observed since
in MeOH the absorption maximum of polymer 2 shifts to
lmax~478 nm. When orange ®lms of polymer 2 were
successively immersed in (1 M) solutions of metal salts in
MeOH, the polymer color became blue. The observed
absorption maxima were lmax~490 nm for Agz, 505 nm for
Pd2z, 520 nm for Zn2z and Cd2z and 530 nm for Cuz. In this
case, the ionochromism of polymer 2 appears even in the solid
state. The bathochromic shift of the absorption maximum is
indicative of an increase in the mean conjugation length of the
polymer.
Tetrakis(triphenylphosphine)palladium
This compound was prepared according to the literature.16
A lower value of Dlmax was however observed in the solid
state (Dlmax~50 nm) compared to the previous value in
solution (Dlmax~80 nm). This increase in the mean conjuga-
tion length is due to the planar conformation of the bidentate
coordinating bipyridyl subunits in the polymer in the presence
of transition metal ions.2 Even if the red-shift in the absorption
spectra due to conjugation enhancement is lower in a solid thin
®lm than in solution, the ®lms of polymer 2 appeared quite
responsive to transition metal ions.
2,5-Bis(tributylstannyl)thiophene (3)
This compound was prepared according to the literature.17
1,4-Dibromo-2,5-dioctoxybenzene (6)
This compound was prepared according to the literature.18
5,5'-Diiodo-2,2'-bipyridine (9)
Moreover, ®lms or solutions of polymer 2 containing
coordinated Zn, or Cu ions were also treated with a methanolic
ammonia solution (1.3 M). The polymer color changed
instantaneously, and turned back to its original color: orange
in the solid state and yellow when the sample is in solution.
Absorption wavelengths identical to the initial values of
around 440 nm for solutions and 480 nm for ®lms were
observed. Ammonia acts as a competitive ligand for metal ions
and removes the metal from the complexing site of the polymer.
The reversibility of the chelation properties of polymer 2 is an
important criterion for the use of this ionosensitive polymer as
a chemosensory material.
This compound was prepared according to the literature.11
1,4-Bis(2-butoxyethoxy)benzene (4a)
Under a nitrogen atmosphere, 2.07 g (0.090 mole) of sodium
metal were gradually introduced into a Schlenk tube containing
50 mL of 2-butoxyethanol. When the sodium had comple-
tely reacted, 7.07 g (0.030 mole) of p-dibromobenzene, 2.5 g
(0.032 mole) of copper(I) oxide and 0.1 g (0.003 mole) of
potassium iodide were quickly added. The mixture was heated
at 100 ³C for 24 h then a new portion of potassium iodide
(0.1 g; 0.003 mole) was introduced and the mixture was heated
again at 100 ³C for 24 h. The solution was ®ltered over Celite at
room temperature, hydrolysed and extracted three times with
diethyl ether. The organic layers were dried over magnesium
sulfate, concentrated under vacuum and the residual oil was
recrystallized in ethanol to give white crystals. Yield 20%, mp
28±29 ³C. Found: C, 69.67; H, 9.76; O, 20.59%. C18H30O4
requires C, 69.64; H, 9.74; O, 20.61%. dH (CDCl3): 0.92 (6 H, t,
2 CH3), 1.37 ( 4 H, m, 2 CH2), 1.55 (4 H, m, 2 CH2), 3.52 (4 H,
t, 2 CH2), 3.74 (4 H, t, 2 OCH2), 4.06 (4 H, t, 2 OCH2), 6.84 (4
H, s, 4 CHar). dC (CDCl3): 13.93 (2 CH3), 19.27, 31.72 (4 CH2),
68.08, 69.29, 71.37 (6 OCH2), 115.58 (4 CH), 153.15 (2 C).
Conclusion
We reported the preparation of two types of conjugated
alternating polymers containing in the main chain: chelating
subunits to introduce complexing properties and thienylene-p-
(2,5-dialkoxy)phenylene units to bring luminescent and elec-
trochromic properties. Additionally the presence of dialkoxy-
phenylenes provides the ability to realize ®lms on glass. The
coordinating properties of the copolymers were investigated.
When the chelating unit is a dibenzo-18-crown-6 ether, a weak
coordination of Liz or Kz ions was found and no
ionochromic properties were observed in the presence of
alkali metals. When 2,2'-bipyridyl is the coordinating entity,
the copolymer exhibits reversible ionochromic responses in the
presence of transition metal ions both in solution and in the
solid state. The ionochromic properties were also found upon
protonation±deprotonation of the copolymer in solution and in
the solid state. On the basis of observed enhanced ionochromic
1,4-Dibromo-2,5-bis(2-butoxyethoxy)benzene (4b)
1.88 g (0.0060 mole) of 4a in solution in 10 mL of carbon
tetrachloride were placed in a 100 mL magnetic stirred tricol
equipped with a condenser and an isobar dropping funnel. Br2
(0.62 mL, 0.0121 mole) was added dropwise from the funnel at
room temperature. The mixture was stirred for 3 h at room
temperature and then treated with 15 mL of a 20% solution of
KOH in water. After three extractions with diethyl ether, the
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organic layers were dried over magnesium sulfate, concentrated
in vacuo and the residual solid was recrystallized with ethanol
to give colorless plates. Yield 61%, mp 42.5±43.8 ³C. Found: C,
46.18; H, 6.04; O, 13.64%. C18H28O4Br2 requires C, 46.17; H,
6.02; O, 13.67%. dH (CDCl3): 0.90 (6 H, t, 2 CH3), 1.37 ( 4 H, m,
2 CH2), 1.59 (4 H, m, 2 CH2), 3.54 (4 H, t, 2 CH2), 3.77 (4 H, t,
2 OCH2), 4.10 (4 H, t, 2 OCH2), 7.15 (2 H, s, 2 CHar). dC
(CDCl3): 13.93 (2 CH3), 19.28, 31.79 (4 CH2), 69.06, 70.23,
71.52 (6 OCH2), 111.40 (2 C, C1, C4), 119.27 (2 CH, C3, C6),
150.38 (2 C, C2, C5).
was ®ltered, washed with acetone and dried in vacuo to give
0.427 g of 1a (Yield: 90%). Found: C, 66.4; H, 7.68; S, 8.24%.
dH (CDCl3): 0.92 (6 H, t, 2 CH3), 1.43 (4 H, m, 2 CH2), 1.63 (4
H, t, 2 CH2), 3.58 (4 H, t, 2 OCH2), 3.91 (4 H, t, 2 OCH2), 4.30
(4 H, t, 2 OCH2), 7.34 (2 H, s, 2 CHthienyl), 7.63 (2 H, s, CHar).
n
max(KBr)/cm21: 3067, 2956, 2930, 2866, 1602, 1542, 1491,
1458, 1405, 1263, 1216, 1122, 1060, 850, 797. Absorption: lmax
(CHCl3)/nm (emax/l mol21 cm21) 459 (26 010), lmax (®lm on
glass) 496 nm. Emission: lmax (CHCl3) 521 nm, lmax (®lm on
glass) 567 nm.
1,4-Bis(2-thienyl)-2,5-dioctoxybenzene (7)
Copolymer 1b
Under a nitrogen atmosphere, 7.14 mL (0.0178 mole) of a
2.5 M solution of n-butyllithium in hexane were slowly
introduced at 0 ³C, into a Schlenk tube containing thiophene
(1.008 g; 0.012 mole) dissolved in 20 mL of freshly distilled
THF. After stirring for 60 min at room temperature, the
obtained 2-thienyllithium solution was slowly added to a ZnCl2
(2.42 g; 0.0178 mole) suspension in 17 mL of THF and the
mixture was magnetically stirred at room temperature for 1 h.
This solution was then slowly added to a solution of 4b (3 g,
0.0061 mole) and Pd(PPh3)4 (0.14 g, 0.000122 mole) in 20 mL
of THF. When the addition was complete, the reaction mixture
was re¯uxed for 72 h. After cooling, the medium was
hydrolysed with a 1.5 M HCl solution. After three extractions
with diethyl ether, the organic layers were twice washed with
water and dried over MgSO4 and concentrated in vacuo before
recrystallisation from an ethanol±benzene mixture 3 : 1. Yield:
73%, mp 84-86 ³C. dH (CDCl3): 0.9 (6 H, t, 2 CH3), 1.33 (20 H,
m), 1.92 (4 H, t), 4.1 (4 H, t), 7.24 (2 H, s), 7.11 (2 H, m), 7.34 (2
H, d), 7.55 (2 H, d). dC (CDCl3): 14.12, 22.68, 26.24, 29.34,
29.4, 29.5, 31.84, 69.77, 112.9, 123.1, 125.2, 125.6, 126.7, 139.3,
149.3.
Copolymer 1b was prepared from 0.001 mole (0.6622 g) of 3,
9561025 mole (0.445 g) of 4b and 561025 mole (0.0259 g) of
5. Yield: 90% (0.428 g). Found: C, 67.5; H, 7.62; S, 8.16%. dH
(CDCl3): 0.92 (6 H, t, 2 CH3), 1.43 ( 4 H, m, 2 CH2), 1.63 (4 H,
t, 2 CH2), 3.58 (4 H, t, 2 OCH2), 3.91 (4 H, t, 2 OCH2), 4.30 (4
H, t, 2 OCH2), 7.34 (2 H, s, 2 CHthienyl), 7.63 (2 H, s, CHar).
n
max(KBr)/cm21: 3068, 2956, 2930, 2865, 1600, 1540, 1492,
1451, 1406, 1262, 1215, 1122, 1060, 846, 797. Absorption: lmax
(CHCl3)/nm (emax/l mol21 cm21) 458 (24 560), lmax (®lm on
glass) 490 nm. Emission: lmax (CHCl3) 520 nm, lmax (®lm on
glass) 570 nm.
Copolymer 1c
Copolymer 1c was prepared from 0.001 mole (0.6622 g) of 3,
90.961025 mole (0.426 g) of 4b and 9161026 mole (0.0466 g)
of 5. Yield: 90% (m~0.430 g). Found: C, 67.41; H, 7.54; S,
8.09%. dH (CDCl3): 0.92 (6 H, t, 2 CH3), 1.43 ( 4 H, m, 2 CH2),
1.63 (4 H, t, 2 CH2), 3.58 (4 H, t, 2 OCH2), 3.91 (4 H, t, 2
OCH2), 4.30 (4 H, t, 2 OCH2), 7.34 (2 H, s, 2 CHthienyl), 7.63 (2
H, s, CHar). nmax(KBr)/cm21: 3070, 2955, 2930, 2866, 1600,
1540, 1492, 1451, 1406, 1263, 1218, 1119, 1060, 847, 796.
Absorption: lmax (CHCl3)/nm (emax/l mol21 cm21
)
455
2',5'-Bis(tributylstannyl)[1,4-bis(2-thienyl)-2,5-dioctoxybenzene]
(8)
(24 304), lmax (®lm on glass) 490 nm. Emission: lmax (CHCl3)
520 nm, lmax (®lm on glass) 566 nm.
Under a nitrogen atmosphere, 3.7 mL (0.006 mole) of a 1.6 M
solution of n-butyllithium in hexane were introduced at 0 ³C,
into a Schlenk tube containing 7 (1.5 g; 0.003 mole) dissolved in
10 mL of freshly distilled diethyl ether. After stirring for two
hours at room temperature, Bu3SnCl (3.7 mL; 0.006 mole) in
10 mL of diethyl ether was slowly added at 0 ³C to the mixture
which was then stirred for one hour at room temperature. Ether
was evaporated and the residue was treated with pentane. The
solution was ®ltered and concentrated in vacuo; 3 was obtained
as a yellow oil. Yield: 60%. dH (CDCl3): 0.91 (24 H, t), 1.20
(12H, t), 1.26 (24 H, m), 1.34 (20 H, m), 1.9 (4 H, m), 4.06 (4 H,
T), 7.16 (2H, d), 7.25 (2 H, s), 7.67 (2 H, d). dC (CDCl3): 10.56,
13.70, 14.30, 22.5, 26.9, 29.1, 29.2, 29.3, 29.35, 31.7, 69.4, 112.6,
122.6, 126.1, 134.9, 137, 145, 148.9. dSn (CDCl3): 240.7.
Copolymer 1d
Copolymer 1d was prepared from 0.001 mole (0.6622 g) of 3,
83.361025 mole (0.3900 g) of 4b and 16.761025 mole
(0.0855 g) of 5. Yield: 90% (m~0.433 g). Found: C, 67.26;
H, 7.33; S, 8.01%. dH (CDCl3): 0.92 (6 H, t, 2 CH3), 1.43 ( 4 H,
m, 2 CH2), 1.63 (4 H, t, 2 CH2), 3.58 (4 H, t, 2 OCH2), 3.91 (16/
5 H, t, 8/5 OCH2), 3.99 (8/5 H, t, 4/5 OCH2), 4.19 (8/5 H, t, 4/5
OCH2), 4.30 (16/5 H, t, 8/5 OCH2), 6.63 (2/5H, s, Hcrown-ether),
7.13 (2/5H, d, Hcrown-ether), 7.20 (2/5H, d, Hcrown-ether), 7.34 (8/5
H, s, CHthienyl), 7.57 (2/5H, s, Hthienyl), 7.63 (2 H, s, CHar).
n
max(KBr)/cm21: 3067, 2955, 2926, 2861, 1600, 1538, 1494,
1453, 1451, 1403, 1263, 1216, 1122, 1042, 844, 795. Absorption:
lmax (CHCl3)/nm (emax/l mol21 cm21) 452 (24 304), lmax (®lm
on glass) 488 nm. Emission: lmax (CHCl3) 520 nm, lmax (®lm
on glass) 561 nm.
Copolymers 1
All copolymers 1 were synthesized according to the same
experimental procedure. The only changes that led to the four
different polymers of type 1 concern the relative ratios between
the two dibromo monomers engaged and the experimental
description is detailed in the case of 1a as an example.
Polymer 2
In a 100 mL Schlenk tube equipped with a condenser were
dissolved under a nitrogen atmosphere and at room tempera-
ture 0.022 g (2.1025 mole) of Pd(PPh3)4 in 20 mL of a THF±
DMF (50 : 50) solvent mixture. 0.002 mole (2.152 g) of 3 and
0.002 mole (0.816 g) of 9 were introduced by a syringe. The
reaction mixture was stirred at 80 ³C during three days.
Heating was then stopped and a red precipitate formed upon
adding methanol. The powder was ®ltered, washed with
acetone and dried in vacuo. dH (CDCl3): 0.07 (6 H, t, 2
CH3), 0.88 ( 4 H, m, 2 CH2), 1.32 (4 H, m, 2 CH2), 1.58 (4 H, m,
2 CH2), 4.17 (4 H, m, 2 OCH2), 7.29 (2 H, s, 2 CHthienyl), 7.44
(2 H, s, CHar), 8.5 (2 H, dd, Hpyr), 9 (1 H, d, Hpyr). nmax(KBr)/
cm21: 2915, 2848, 1601, 1572, 1535, 1502, 1454, 1406, 1262,
Copolymer 1a
In a 50 mL Schlenk tube equipped with a condenser were
dissolved under a nitrogen atmosphere and at room tempera-
ture 0.0115 g (1025 mole) of Pd(PPh3)4 in 10 mL of a THF±
DMF (50 : 50) solvent mixture. 0.001 mole (0.6622 g) of 3,
9861025 mole (0.4588 g) of 4b and 261025 mole (0.0103 g) of
5 were introduced by a syringe. The reaction mixture was
stirred at 80 ³C during three days. Heating was then stopped
and a red precipitate formed upon adding acetone. The powder
J. Mater. Chem., 2000, 10, 263±268
267

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and C. Torreilles, Synth. Met., 1999, 101, 588; (c) J.-P. LeÁre-Porte,
J. J. E. Moreau and C. Torreilles, Synth. Met., 1999, 101, 104.
(a) Z. Bao, W. K. Chan and L. Yu, J. Am. Chem. Soc., 1995, 117,
12426; (b) Z. Bao, R. Cai and L. Yu, Polym. Prepr., 1993, 34, 749;
(c) L. Yu, Z. Bao and R. Cai, Angew. Chem., Int. Ed. Engl., 1993,
32, 1345.
1211, 1089, 835, 794. Absorption: lmax (CHCl3)/nm (emax
l mol21 cm21) 438, lmax (®lm on glass) 517 nm.
/
9
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