Synthesis and electrochemical investigations of crown-ether- functionalised bipyrroles

Article abstract of DOI:10.1039/a902333j

The synthesis of crown-ether-functionalised 2,2'-bipyrroles leads to a new class of electrochemically polymerisable monomers. The monomers and corresponding polymers were characterised by spectroscopy and cyclic voltammetry. In the presence of alkali metal ions the oxidation potentials of the polymers are altered and according to cyclic voltammetry, the observed shifts are at least partially reversible.

Full text of DOI:10.1039/a902333j

J O U R N A L O F
Synthesis and electrochemical investigations of crown-ether-
functionalised bipyrroles
Matthias Peters, Manfred L. Hallensleben* and Marc van Hooren
Institut fur Makromolekulare Chemie, Universitat Hannover, Am Kleinen Felde 30, D-30167
¨
¨
C H E M I S T R Y
Hannover, Germany
Received 23rd March 1999, Accepted 16th April 1999
The synthesis of crown-ether-functionalised 2,2∞-bipyrroles leads to a new class of electrochemically polymerisable
monomers. The monomers and corresponding polymers were characterised by spectroscopy and cyclic
voltammetry. In the presence of alkali metal ions the oxidation potentials of the polymers are altered and according
to cyclic voltammetry, the observed shifts are at least partially reversible.
Introduction
t
1.
2.
KBu
Br
1. ButLi
2. NiCl2
N
N
N
Functionalised electrically conductive polymers have received
much attention and have been proposed as a source of new
intelligent materials.1,2 One method to obtain functionalised
conducting polymers is via the polymerisation of monomers
that already contain functional groups. Conjugated conducting
polymers substituted with crown ether units have recently been
suggested as sensor materials for alkali metal ions.
OTHP
N
H
O
O
O
O
O
O
1
2
Poly(pyrrole)s substituted in the 3-position by azacrown
ethers were the first conducting polymers to display an ion-
specific voltammetric response towards alkali metal ions.3 For
derivatised poly(thiophene)s with remotely attached crown
ether functionalities complexation of ions causes an increase
in the oxidation potential of the polymer.4 This effect was
obtained even though the crown ether and the polymer back-
bone were electronically decoupled. Crown-ether-func-
tionalised poly(bithiophene)s with a poly(oxyethylene) bridge
connecting the 3- and 3∞-positions were synthesised to induce
twisting of the polymer backbone upon ion complexation.5
These polymers show ionochromic responses towards alkali
metal ions.
p-TosOH
N
N
1. 2 equiv. NaH
2. TosO
OTos
N
N
O
x
O
O
O
OH
HO
3
O
x
4 x = 1 5 x = 2
6 x = 3 7 x = 4
Here we report the synthesis and investigations of a new
monomeric system consisting of crown-ether-substituted 2,2∞-
bipyrrole units. The use of bipyrroles permits the establishment
of the crown ether functionality via the 1- and 1∞-positions. In
contrast to systems based on pyrroles or thiophenes, the
electrochemical polymerisation of these monomers can be
examined under mild conditions at low oxidation potentials
leading to polymers with intact functionalities and uniform
and regular structure. The resulting polymers combine a
conductive backbone with the complexing properties of crown
ether functionalities.6 This procedure can lead to new sensory
materials.3–7
Overall yields:
4 = 5% 5 = 5%
6 = 4% 7 = 3%
Scheme 1 Synthetic route to crown-ether-functionalised bipyrroles.
final step is the establishment of the crown ether functionality
via a dialkylation reaction of 3 with a derivative of oligo(ethy-
lene glycol)-di-p-tosylate. The corresponding sodium dial-
coholate is generated by deprotonation of 3 with 2 equiv. of
NaH. A nucleophilic substitution reaction of the sodium
dialcoholate with oligo(ethylene glycol)-di-p-tosylate results
in the formation of the crown ether ring. The size of the ring
depends on the number of ethylene glycol units in the oligo-
(ethylene glycol)-di-p-tosylate. In this manner we successfully
synthesised the new compounds 4, 5, 6 and 7 containing four,
five, six or seven oxygen atoms, respectively, in the crown
ether functionality.
Results and discussion
A four-step procedure was adopted in the synthesis of the new
crown-ether-substituted 2,2∞-bipyrrole monomers (Scheme 1).
The first step involves the alkylation at the 1-position by
deprotonation with KBut followed by reaction with 1-
bromo(2-tetrahydropyran-2-yl)ethane yielding 1, a derivative
of (pyrrol-2-yl)ethanol with a protected hydroxy group, the
THP ether function acting as the protecting functionality. The
dimer 2 was obtained by the oxidative coupling of the car-
All monomers were characterised by cyclic voltammetry and
show irreversible behaviour (Fig. 1), leading to the formation
of polymers. For 4 the first oxidation potential E 1 is at
pa
0.37 V (Table 1). The value of E 1 decreases as the number
pa
of oligo(ethylene glycol) units increases reaching a minimum
banions upon addition of NiCl after the deprotonation of 1
at the 2-position with ButLi.8 The cleavage of the protecting
group is achieved in polar solvents under acidic conditions.9
The presence of p-toluenesulfonic acid in a methanolic solution
of 2 leads to the fast and quantitative formation of 3. The
of 0.33 V for compounds 6 and 7, respectively. This effect can
be attributed to the torsion angle between the two pyrrole
rings, which is expected to be slightly reduced as the size of
the crown ether ring is extended, leading to a higher degree of
2
flexibility and a lower E 1. In contrast to this, the absorption
pa
J. Mater. Chem., 1999, 9, 1465–1469
1465

Fig. 3 Cyclic voltammogram of polymer P5 in MeCN–0.1 M TBAPF
(T =20 °C; v=100 mV s−1).
Fig. 1 Typical cyclic voltammogram of crown-ether-functionalised
bipyrrole 5 in CH Cl –0.1 M TBAPF (T =20 °C; v=100 mV s−1).
6
2
2
6
dimethyl-2,2∞-bipyrrole] and is traced back to structure relax-
ation effects.12,13 For practical applications measurements in
aqueous media are necessary. The stability of the polymer
films is demonstrated by the fact that these polymers can be
cycled in water (Fig. 4). There is only a small loss of charge
capacity during the first scans and in further scans no decompo-
sition of the polymer is observed.
Table 1 Peak potentials vs. Fc/Fc+ and absorption maxima for the
crown-ether functionalised bipyrroles and corresponding polymers
l
nm
/
Polymer
/V
Polymer
l /nm
max
Compound
x
E
1/V
E
pa
pa
max
4
5
6
7
1
2
3
4
0.37
0.36
0.33
0.33
252
253
253
253
0.24
0.19
0.16
0.14
298
300
300
300
In bulk electrolysis experiments free-standing films can be
deposited potentiostatically in MeCN–NBu PF on platinum
4
6
electrodes. These films show electrochromic behaviour being
blue–violet in the oxidised state and yellow in the neutral
state. The conductivity data show no significant trends and all
investigated polymers reveal conductivities in the range of
10−4 S cm−1, values typical for 1-substituted poly(pyrrole)s.12
FTIR spectra of the polymers show that there is no loss of
functionalisation, over-oxidation or branching, indicating a
uniform and regular structure. The UV–VIS spectra of all of
the investigated polymers show an absorption maximum at
300 nm (298 nm for the polymer P4). For comparison, studies
on oligo(1-methylpyrrole)s show only a small shift of the
absorption maximum with longer chain length and beyond
the pentamer there is only an infinitesimal bathochromic shift
of the p–p* transition.12,14 Extrapolation of the dependence
observed for the oligomers to an infinite degree of polymeris-
ation gives an expected absorption maximum of ca. 290 nm
for the ideal neutral polymer.12 The higher values of 300 nm
that we achieved for the crown ether functionalised poly(2,2∞-
bipyrrole)s seem to be due to at least partial planarisation of
the main chain in the solid state. This effect is very important
for the structure of the polymers. Such planarisation is a
requirement for a good transmission of a sensor signal and
one reason why we investigated these materials as sensory
materials for alkali metal ions.
maximum in the UV–VIS spectra is almost the same for all
monomers. The trace crossing of the first cycle in the
voltammograms is typical for compounds forming conducting
polymers and is viewed as proof of initiation of electropolym-
erisation.10,11 In multisweep cyclic voltammograms polymeris-
ation is indicated by the new oxidation peak in the second
scan in front of the E 1 signal (Fig. 2). The strongly drifting
pa
cathodic peaks from −1.0 to −1.26 V are due to protons
eliminated during the process of rearomatisation of the
polymer.
Corresponding polymers can be deposited potentiostatically
at 0.45 V vs. Fc/Fc+ in CH Cl or MeCN, with NBu PF as
2
2
4
6
electrolyte on a platinum disc electrode. CV measurements of
the polymers show a sharp oxidation and reduction peak
indicating a uniform and regular structure (Fig. 3). For the
polymer P4 the E is 0.24 V (Table 1) and decreases as the
pa
number of oligo(ethylene glycol) units increases reaching a
minimum of 0.14 V for the polymer P7, analogous to the
monomers. With extension of the crown ether unit, the torsion
angle between the two pyrrole rings should be reduced. In
addition, larger crown ether units will lead to a higher degree
of flexibility in the polymer leading to lower oxidation poten-
tials. In front of the oxidation peak there is a shoulder at
0.00 V. The appearance of this pre-peak was also observed in
cyclic voltammograms of poly(1-methylpyrrole) and poly[1,1∞-
The presence of alkali metal ions causes a change in the
cyclic voltammogramms of the corresponding polymers of
crown-ether-functionalised bipyrroles (Table 2).
For polymer P4 (Fig. 5) the presence of alkali metal ions
results in a decrease of E . Similar effects were observed for
pa
Fig. 2 Multisweep cyclic voltammogram of crown-ether-functionalised
bipyrrole 5 in CH Cl –0.1 M TBAPF (T =20 °C; v=100 mV s−1).
Fig. 4 Cyclic voltammogram of polymer P6 in H O–0.1 M LiClO
(T =20 °C; v=100 mV s−1).
2
4
2
2
6
1466
J. Mater. Chem., 1999, 9, 1465–1469

Table 2 Electrochemical response of the polymers towards the presence
of alkali metal ions
DE/mV
Polymer
E
/V
Li+
Na+
K+
pa
P4
P5
P6
P7
0.24
0.19
0.16
0.14
−10
26
28
−13
36
43
−12
31
18
11
31
28
polymers with sterically very demanding complexing
groups.15,16 The E of polymer P4 is higher and the l
pa
max
lower than those of the other investigated polymers indicating
that the compound with the smallest crown ether unit is the
sterically most demanding system. Thus complexation of alkali
metal ions by polymer P4 seems to cause a decrease of the
torsion angle between the pyrrole rings resulting in a higher
effective conjugation and in a lower oxidation potential of the
polymer. The size of Li+ should be ideal for complexation by
crown ethers with four oxygen atoms yet it causes the smallest
shift of the oxidation potential (10 mV). The presence of Na+
or K+ results in shifts of 13 and 12 mV, respectively. The
reason for the small shifts may be that for polymer P4 two
effects are directed against each other. Complexation should
cause an increased p-overlap in the conductive polymer back-
bone, resulting in a decrease of the oxidation potential.
However, complexation of cations leads to the formation of a
Coulomb barrier because of the concentration of positive
charges close to the conductive backbone which would lead
to an increase of the oxidation potential. The measured shifts
of the oxidation potential are therefore the result of two
competing effects and this explains why they are of small
magnitude.
Fig. 6 Cyclic voltammogram of polymer P6 in the absence and
presence of Na+, MeCN–0.1 M TBAPF (T =20 °C, v=100 mV s−1).
6
would be less accessible for complexation. With the formation
of, for example, sandwich complexes it would mainly be the
outer-sphere oxygens that would take part in complexation so
that different cation and crown ether sizes would have similar
small effects on the conductive polymer backbone.
Crystallographic studies of the monomer ligands and their
complexes should provide clues as to complexation behaviour:
such studies are in progress and will be published elsewhere.
In further cyclic voltammetric experiments we investigated
the degree of reversibility of complexation. After a polymer
film was subjected to cyclic voltammetry in the presence of
alkali ions the film was washed, dried and transferred into a
cell in the absence of akali metal ions and the oxidation
potential was remeasured. For Li+, for all investigated poly-
mers a complete return of the oxidation potential to its original
value measured in the absence of Li+ was observed. For Na+
and K+, however, degrees of reversibility of 92 and 79%,
respectively, were obtained. The lower degree of reversibility
for Na+ and K+ in comparison to Li+ can be explained in
terms of ionic radii since for larger ions (especially K+)
diffusion into and out of the polymer is hindered. Since the
shifts of the oxidation potential in response to the presence,
and the return of the shift in the absence of ions, are of small
magnitude the values of reversibilities are subject to a loss of
accuracy. To obtain a more exact impression on the nature
and effects of complexation by the polymers, additional investi-
gations such as spectroelectrochemical or XPS measurements
are necessary, and these will be published elsewhere.
For the other investigated polymers the presence of alkali
metal ions causes a shift of the oxidation potentials towards
higher values (Table 2, Fig. 6). It seems that complexation
causes an increase of the torsion angle between the pyrrole
rings so that the effective conjugation length is decreased.
Moreover the Coulomb barrier tends to cause an increase in
the oxidation potential. The presence of Na+ causes the largest
shift of the oxidation potential of all the polymers examined.
Because of its large ionic radius, the diffusion of K+ into the
polymer, and its mobility inside the polymer, in comparison
to Na+, should be more difficult resulting in a smaller shift
of E .
It can be concluded for crown-ether-functionalised bipyr-
roles that a new class of electrochemically polymerisable
monomers can be synthesised. Electrochemical polymerisation
leads to conductive polymers of regular structure, intact func-
tionality and high stability towards aqueous media. In CV
measurements the oxidation potential of the polymers shift in
the presence of alkali metal ions. For Li+ this shift is com-
pletely reversible, whereas for Na+ and K+ it is only partially
reversible.
pa
The reason for absence of selectivity could be the structure
of the polymer film with its lack of flexibility allowing only
partial complexation by the crown ether units. The planaris-
ation of the conductive polymer backbone seems to dominate
the polymer structure leading to a lack of flexibility. As a
result the inner-sphere oxygens close to the polymer backbone
Further investigations will focus on why the magnitudes of
the shifts of the oxidation potential are low in the presence of
metal ions. For example we hope to obtain information about
the distribution of ions in the polymer and the ion5ligand
ratio by XPS measurement.
Experimental
Melting points are uncorrected. IR spectra were taken on a
Bruker Equinox 55 FTIR spectrometer. NMR spectra were
recorded in CDCl on a Bruker AM 400 (400 MHz). Chemical
3
shifts are reported in parts per million (d) using tetramethylsil-
ane as internal standard. Mass spectra were recorded on a
Finnegan MAT 312 spectrometer. UV–VIS spectroscopy was
performed in MeCN using a Perkin-Elmer model Lamda 5
Fig. 5 Cyclic voltammogram of polymer P4 in the absence and
presence of Li+, MeCN–0.1 M TBAPF (T =20 °C, v=100 mV s−1).
6
J. Mater. Chem., 1999, 9, 1465–1469
1467

instrument. Cyclic voltammetry measurements were performed
in a Kiesele-type cell equipped with an integrated drying tube
for the electrolyte (0.1 mol L−1 NBu PF in superdry CH Cl
(m, 12H). 13C NMR (CDCl ): d 124.11, 122.07, 111.13,
3
107.38, 98.47, 66.97, 61.74, 46.45, 30.36, 25.29, 19.09. IR (KBr
film, cm−1): 2942, 2871, 2360, 2341, 1454, 1441, 1352, 1314,
1281, 1201, 1136, 1123, 1078, 1036, 981, 871, 814, 718. MS:
m/z 388 (M+), 288, 287, 204, 203, 187, 173, 159, 144, 132,
106, 85, 67; HRMS: m/z calc. 388.236208, found: 388.235870.
4
6
2 2
or MeCN or in ultrapure H O, c
=1×10−3 mol L−1).
2
monomer
In investigations of the electrochemical response towards the
presence of alkali ions [c
=0.1 mol L−1 (LiClO , NaClO
alkali
4
4
or KBF ], the working electrode was a platinum disk, the
UV–VIS (MeCN): l =256 nm.
4
max
counter electrode a platinum wire and the reference electrode
an AgCl-covered silver wire. All potentials measured in CH Cl
2
2
1,1∞-Bis(2-hydroxyethyl)-2,2∞-bipyrrole 3
and MeCN were calibrated against ferrocene [E0(Fc/Fc+)=
0.35 V vs. Ag/AgCl]. Cyclic voltammograms were recorded
using a computer-linked Heka PG 285 potentiostat with the
LabVIEW-Software package from National Instruments.
Bulk electrolysis experiments were performed in an one-
compartment cell employing an AgCl-covered silver wire as
reference electrode and platinum foils (A=2.25 cm−2) as
working and counter electrodes. The electrolyte consisted of
5×10−2 mol L−1 NBu PF in purified MeCN and the concen-
p-Toluenesulfonic acid (0.1 g) was added to a solution of 2
(1.94 g, 5 mmol) in 250 mL dry methanol and stirred at room
temperature for 3 h, the mixture changing from colourless to
dark red. The solution was slowly saturated with KOH,
washed with water (3×100 mL) and dried over Na SO .
2
4
Removal of the solvent under reduced pressure and purification
of the dark red oil by column chromatography (SiO , diethyl
2
ether, R =0.18) afforded colourless crystals of 3 (0.96 g,
4
6
f
tration of the given oligomer was 2.5×10−2 mol L−1.
4.36 mmol, 87%). 3: 1H NMR (CDCl ): d 6.94 (t, 2H), 6.34
3
Purification of CH Cl and MeCN was performed according
(t, 2H), 6.30 (dd, 2H), 4.04 (t, 4H), 3.74 (t, 4H), 2.79 (s,
2
2
to the literature.17 Conductivities were measured by a standard
four-probe method at room temperature on films, using
osmium contacts.
2H). 13C NMR (CDCl ): d 124.32, 121.90, 111.98, 107.70,
3
62.24, 48.96; IR (KBr, cm−1): 3166, 2928.6, 2721, 2300, 2251,
1719, 1645, 1485, 1430, 1388, 1359, 1318, 1281, 1260, 1233,
1217, 1172, 1086, 1047, 1016, 990, 959, 782, 730. MS: m/z 220
(M+), 201, 189, 176, 171, 157, 145, 132, 117, 104, 80. HRMS:
m/z calc. 220.121178, found 220.120911. UV–VIS (MeCN):
1-(2-Tetrahydropyran-2-yloxyethyl)pyrrole 1
A
solution of 4.03 g freshly distilled pyrrole (4.17 mL,
l
=253 nm, mp 72 °C.
60 mmol) in 100 mL dry toluene was cooled to 0 °C under
argon. A mixture of 6.95 g (62 mmol) KOBut and 0.4 g
(1 mmol) dibenzo-18-crown-6 in 100 mL dry toluene was
added and the resulting mixture was refluxed for 1 h. After
cooling to 0 °C a solution of 12.54 g (60 mmol) of 2-bromo(-
tetrahydropyran-2-yl)ethane in 80 mL dry THF was added
under vigorous stirring and the mixture was refluxed for 12 h.
The crude reaction mixture was diluted with diethyl ether and
the organic phases were washed with water (3×150 mL) and
dried over Na SO . The solvent was removed under reduced
max
General procedure for the synthesis of crown-ether-containing
bipyrroles
A solution of 3 (0.5 g, 2.27 mmol) in 100 mL dry THF was
added to NaH (104 mg, 5.54 mmol of a dispersion in mineral
oil) previously activated by washing with dry diethyl ether
(2×25 mL) and dry THF (1×25 mL). The resulting mixture
was refluxed under argon for 1 h and cooled to 0 °C prior to
the addition of the oligo(ethylene glycol)-di-p-tosylate
(2.27 mmol) in 100 mL dry THF and further refluxed for 14 h.
The mixture was poured into diethyl ether/water
(200 mL/200 mL) washed with water (2×200 mL) and dried
over Na SO . The solvent was removed under reduced pressure
2
4
pressure and the resulting dark liquid was purified by column
chromatography [SiO , light petroleum–diethyl ether (1051),
2
R =0.27]. Compound 1 was obtained as a yellow oil (7.61 g,
f
39 mmol, 65%). 1: 1H NMR (CDCl ): d 6.69 (t, 2H), 6.12 (t,
2H), 4.50 (t, 1H), 3.98 (m, 4H), 3.62 (m, 2H), 1.47–1.78 (m,
3
2
4
and the resulting brown oil was purified by column
chromatography.
6H). 13C NMR (CDCl ): d 120.86, 107.89, 98.45, 67.07, 61.66,
3
49.44, 30.34, 25.24, 29.98. IR (KBr film, cm−1) 2943, 1500,
1441, 1352, 1286, 1200, 1124, 1074, 1036, 980, 923, 871, 815,
724. MS: m/z 195 (M+), 139, 122, 110, 95, 85, 80, 78, 67.
HR-MS: m/z calc. 195.125929, found 195.126583.
1,1∞-(3,6,9,12-Tetraoxatetradecane-1,14-diyl)-2,2∞-bipyrrole 4.
Compound 4 (SiO , ethyl acetate, R =0.46) was obtained
2
f
as a pale yellow oil (0.37 g, 1.1 mmol, 49%). 1H NMR
1,1∞-Bis(2-tetrahydropyran-2-yloxyethyl)-2,2∞-bipyrrole 2
(CDCl ): d 6.80 (dd, 2H), 6.14 (m, 4H), 4.12 (m, 4H),
3
3.52–3.87 (m, 16H). 13C NMR (CDCl ): d 124.33, 121.58,
tert-Butyllithium (33 mL, 1.5 M solution in pentane) was
added to a vigorously stirred solution of 1 (9.75 g, 50 mmol)
in 100 mL degassed dry THF at −80 °C. The reaction mixture
was stirred for 30 min maintaining the temperature at −80 °C
and then allowed to reach room temperature. The resulting
solution, containing carbanions of 1 was added, using a
3
110.83, 107.49, 70.75, 70.67, 70.61, 70.57, 46.64; IR (KBr
film, cm−1): 3100, 2869, 1956, 1735, 1639, 1514, 1451, 1355,
1313, 1281, 1238, 1192, 1121, 994, 938, 890, 843, 790, 719,
617. MS: m/z 334 (M+), 290, 203, 185, 173, 157, 146, 132,
117, 104, 93, 79. HRMS: m/z calc. 334.189258, found
334.188171. UV–VIS (MeCN): l =252 nm; E 1=0.37 V
double-ended needle, to a suspension of NiCl (9.72 g,
max
pa
2
vs. Fc/Fc+.
75 mmol) in 50 mL degassed dry THF at −80 °C. The reaction
mixture was allowed to reach room temperature during which
it changed from yellow to black caused by the formation of
colloidal nickel. Stirring at room temperature for 12 h was
followed by removal of the nickel powder by filtration and
extraction with diethyl ether (3×100 mL). The combined
organic phases were washed with water (2×200 mL) and dried
over Na SO . The solvent was removed under reduced pressure
1,1∞-(3,6,9,12,15-Pentaoxaheptadecane-1,17-diyl)-2,2∞-
bipyrrole 5. Compound 5 [SiO , ethyl acetate–triethylamine
2
(2051), R =0.38] was obtained as a pale yellow oil (0.49 g,
f
1.30 mmol, 57%). 1H NMR (CDCl ): d 6.87 (dd, 2H), 6.21
(t, 2H), 6.17 (dd, 2H), 4.09 (m, 2H), 3.86 (m, 2H), 3.48–3.70
3
(m, 20H); 13C NMR (CDCl ): d 124.36, 121.60, 111.00,
2
4
3
and the resulting dark-brown liquid was purified by column
107.47, 70.79, 70.75, 70.70, 70.62, 70.51, 46.58; IR (KBr
chromatography (SiO , light petroleum–diethyl ether (1051),
film, cm−1): 3101, 2868, 1736, 1598, 1515, 1451, 1354, 1281,
1177, 1120, 926, 818, 720, 664, 616. MS: m/z 378 (M+), 348,
335, 304, 275, 247, 231, 203, 189, 173, 159, 146, 132, 117, 104,
93, 79. HRMS: m/z calc. 378.215472, found 378.214661.
UV–VIS (MeCN): l =253 nm. E 1=0.36 V vs. Fc/Fc+.
2
R =0.06). Compound 2 was obtained as a bright yellow oil
f
which slowly crystallised at −40 °C (2.14 g, 5.52 mmol, 22%).
2: 1H NMR (CDCl ): d 6.95 (t, 2H), 6.24 (dd, 4H), 4.55 (t,
3
2H), 4.05 (t, 2H), 3.85 (m, 2H), 3.30–3.70 (m, 8H), 1.50–1.90
max
pa
1468
J. Mater. Chem., 1999, 9, 1465–1469

1,1∞-(3,6,9,12,15,18-Hexaoxaeicosane-1,20-diyl)-2,2∞-
References
bipyrrole 6. Compound 6 (SiO , ethyl acetate, R =0.15) was
2
f
1
H. S. Nalwa, Handbook of Conductive Molecules and Polymers,
obtained as a pale yellow oil (0.42 g, 1.0 mmol, 44%). 1H
Wiley & Sons, Inc., New York, 1997.
NMR (CDCl ): d 6.87 (dd, 2H), 6.18 (dd, 2H), 6.15 (dd,
3
2
3
F. Garnier, Adv. Mater. (Weinheim), 1989, 1, 529.
H. K. Youssoufi, M. Hmyene, F. Garnier and D. J. Delabouglise,
J. Chem. Soc., Chem. Commun., 1991, 1550.
2H), 3.97 (m, 4H), 3.51–3.69 (m, 24H). 13C NMR (CDCl ):
3
d 124.18, 121.82, 110.90, 107.36, 70.71, 70.64, 70.61, 70.56,
70.50, 70.46, 46.47; IR (KBr film, cm−1): 3100, 2868, 2362,
1736, 1514, 1450, 1352, 1313, 1281, 1248, 1191, 1121, 940,
847, 790, 720, 616. MS: m/z 422 (M+), 392, 247, 203, 185,
173, 157, 146, 132, 117, 104, 93. HRMS: m/z calc. 422.241687,
found 422.242798. UV–VIS (MeCN): l =253 nm. E 1=
4
5
P. Bauerle and S. Scheib, Acta Polym., 1995, 46, 124.
T. M. Swager and M. J. Marsella, J. Am. Chem. Soc., 1993, 115,
12214.
C. J. Pedersen, J. Am. Chem. Soc., 1967, 89, 2495.
T. M. Swager and M. J. Marsella, Adv. Mater. (Weinheim), 1994,
6, 595.
T. Kauffmann and H. Lexy, Chem. Ber., 1981, 114, 3674.
T. W. Greene, Protective Groups in Organic Synthesis, Wiley &
Sons, Inc., New York, 1981, pp.21–22.
¨
6
7
max
pa
0.33 V vs. Fc/Fc+.
8
9
1,1∞-(3,6,9,12,15,18,21-Heptaoxatricosane-1,23-diyl)-2,2∞-
10 S. Asavapiriyanont, G. K. Chandler, G. A. Gunawardena and
D. J. Pletcher, Electroanal. Chem., 1984, 177, 245.
11 M. Dietrich, J. Heinze, G. Heywang and F. J. Jonas, Electroanal.
Chem., 1994, 369, 87.
12 N. Rohde, M. Eh, U. Geißler, M. L. Hallensleben, B. Voigt and
M. Voigt, Adv. Mater. (Weinheim), 1995, 7, 401.
13 N. Rohde, U.Geißler and M. L. Hallensleben, GDCh Monogr.,
1995, 2, 453.
14 T. Kauffmann, Angew. Chem., 1979, 91, 1.
15 M. J. Marsella, R. J. Newland, P. J. Carroll and T. M. Swager,
J. Am. Chem. Soc., 1995, 117, 9842.
16 M. J. Marsella, P. J. Carroll and T. M. Swager, J. Am. Chem.
Soc., 1996, 117, 9832.
bipyrrole 7. Compound 7 [SiO , ethyl acetate–triethylamine
2
(2051), R =0.34] was obtained as a colourless oil (0.33 g,
f
0.71 mmol, 31%). 1H NMR (CDCl ): d 6.86 (dd, 2H), 6.17
3
(dd, 2H), 6.14 (dd, 2H), 3.89 (m, 4H), 3.48–3.73 (m, 28H).
13C NMR (CDCl ): d 124.22, 121.87, 110.97, 107.47, 70.84,
3
70.71, 70.68, 70.66, 70.54, 70.51, 70.47, 46.45; IR (KBr
film, cm−1): 3101, 2870, 2360, 2341, 1943, 1648, 1597, 1514,
1451, 1400, 1355, 1281, 1248, 1189, 1177, 1117, 1019, 925,
818, 779, 721, 666. MS: m/z 466 (M+), 437, 423, 247, 203,
185, 173, 157, 146, 117, 132, 93. HRMS: m/z calc. 466.267902,
found 466.268341. UV–VIS (MeCN): l =253 nm. E 1=
max
pa
0.33 V vs. Fc/Fc+.
17 U. Geißler, M. L. Hallensleben and N. Rohde, Macromol. Chem.
Phys., 1996, 197, 2565.
Acknowledgements
The financial support from Deutsche Forschungsgemeinschaft
and from Fonds der Chemischen Industrie for this project is
appreciated.
Paper 9/02333J
J. Mater. Chem., 1999, 9, 1465–1469
1469