3D-conjugated systems based on oligothiophenes and phosphorus nodes

Article abstract of DOI:10.1039/b806169f

3D-conjugated systems based on oligothiophene segments grafted on a phosphorus or on a phosphine oxide node have been synthesized. Under Stille coupling conditions, bromide terminated thienyl phosphine derivatives undergo a breaking of the phosphorus-carbon bond attributed to a ligand exchange with the Pd catalyst. The electronic properties of the new compounds have been analyzed by UV-vis and fluorescence spectroscopy and cyclic voltammetry.

Full text of DOI:10.1039/b806169f

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
3D-conjugated systems based on oligothiophenes and phosphorus nodes†
Philippe Leriche,* David Aillerie, Sophie Roquet, Magali Allain, Antonio Cravino, Pierre Fre`re and
Jean Roncali*
Received 11th April 2008, Accepted 28th May 2008
First published as an Advance Article on the web 11th July 2008
DOI: 10.1039/b806169f
3D-conjugated systems based on oligothiophene segments grafted on a phosphorus or on a phosphine
oxide node have been synthesized. Under Stille coupling conditions, bromide terminated thienyl
phosphine derivatives undergo a breaking of the phosphorus–carbon bond attributed to a ligand
exchange with the Pd catalyst. The electronic properties of the new compounds have been analyzed by
UV-vis and fluorescence spectroscopy and cyclic voltammetry.
phosphorus tribromide was reacted with the lithio-derivative of
Introduction
n-hexylterthiophene (3) and n-hexylthiophene-EDOT-thiophene7
Organic semiconductors (OSCs) are subject to a considerable
(4) to obtain the target compounds 1a and 2a in 35 and 25% yields
current interest motivated by the perspective of achieving large
respectively (Scheme 1).
area, low-cost, lightweight and flexible (opto)electronic devices.1
Many organic semiconductors used as active materials in organic
field effect transistors (OFETs) and photovoltaic cells derive from
linearly p-conjugated systems such as oligoacenes2 or thiophene-
based oligomers or polymers.3 However, due to their low dimen-
sionality, these materials present anisotropic optical and charge-
transport properties which can pose specific problems for device
fabrication and operation.4 In recent years, we and others have
undertaken the development of new classes of OSCs possessing
isotropic optical and charge-transport properties. Thus, it has
been recently shown that 3D architectures consisting of a silicon,5
twisted bithiophene6 or triphenylamine7 node functionalized with
oligothiophene conjugated segments can lead to interesting active
materials for organic solar cells, light emitting diodes (OLEDs)
and field-effect transistors. Several examples of p-conjugated
systems incorporating phosphorus8 have been described and
some of these compounds exhibit interesting properties as active
materials in OLED. However, there are few examples of molecular
architectures in which phosphorus is used as a node for connecting
linear conjugated segments.9 Me´tivier et al. have described a phos-
phorus oxide derivatized with three oligo(phenylacetylene) chains
and analyzed its photophysical properties.9 In our continuing
interest in p-conjugated systems of high-dimensionality, we report
here on the synthesis of compounds consisting of a phosphorus
node derivatized with short-chain oligothiophene branches.
Results and discussion
Synthesis
Fixation of aromatic systems on phosphorus is generally
achieved by addition of lithiated species or Grignard reagents
on phosphorus tribromide or trichloride.10 In the present case,
University of Angers, CNRS, CIMA, 2 Bd Lavoisier, 49045, Angers, France.
E-mail: philippe.leriche@univ-angers.fr, jean.roncali@univ-angers.fr
Scheme 1
† Electronic supplementary information (ESI) available: Detailed crystal-
In order to synthesize building blocks that could be useful
lographic data. CCDC reference numbers 684727 (6a) and 684728 (6b).
for the further synthesis of other symmetrical or unsymmetrical
systems, phosphine derivatives 5a and 6a with terminal bromine
For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/b806169f
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atom(s) have been prepared by treatment of 2,5-dibromothiophene
by n-BuLi followed by addition of phosphorus tribromide or
chorodiphenylphosphine (Scheme 2).
Scheme 2
All these compounds are stable in ambient conditions in
the solid state, however they undergo a more or less rapid
oxidation into the corresponding phosphorus oxides in solution.
The oxidation process is rather slow for 1a but extremely fast
for 2a. This difference can be related to the electron donating
properties of the branches and attributed to orbital interactions
between aromatics and phosphorus nodes.11 Oxidation performed
using hydrogen peroxide at room temperature in THF leads to
quantitative conversion for all compounds. (Scheme 3).
Fig. 1 ORTEP views of 6a (top) and 6b (bottom), ellipsoids drawn at
50% probability level.
Scheme 3
The X-ray structures of derivatives 6a and 6b are presented in
Fig. 1. Both derivatives crystallize in the P1 21/n space group.
Compound 6a presents a pyramidal geometry with thiophene–
phosphorus–thiophene angles of 99◦, 102◦ and 103◦ respectively.
The oxidation of phosphine into phosphorus oxide in 6b produces
an increase of the thiophene–phosphorus–thiophene angles to
104◦, 105◦ and 107◦. This phenomenon is logical if one consider
the decrease of the coulombic repulsions when passing from the
lone pair to the bonded oxygen atom.
In order to synthesize systems with longer conjugated branches,
compound 6a bearing three terminal bromine atoms was used
as reactant. Attempts to perform Suzuki or Kumada coupling
with the appropriate thienyl derivatives failed. A Stille coupling
with a stoichiometric amount of 2-tributylstannylthiophene in the
presence of Pd(PPh3)4 as catalyst allowed to isolate the target
compound 7a in 40% yield together with 20% of undesired
terthiophene 8. The formation of terthiophene 8 implies a side-
reaction with breaking of the C–P bond together with the expected
cleavage of the C–Sn bond in the reagent. This assumption is
confirmed by the use of an excess of stannic derivative which led
to terthiophene (8) as the unique product (60% yield, Scheme 4).
Aryl–aryl exchange reactions in Pd complexes12 involving C–P
bond breaking have been already discussed in the literature and
their influence on Suzuki13 or Stille14 coupling reactions is well
documented. However, phosphorus compounds are generally used
as ligands in the catalyst and not as reagent and the consequences
Scheme 4
of the observed exchanges are thus different. In the present case,
the cleavage of the C–P bond probably involves a ligand exchange
between the triphenylphosphine of the catalyst Pd(PPh3)4 and 6a.
In order to test this hypothesis, phosphorus oxides 5b and 6b
which are not subject to ligand exchange have been reacted with
the stannyl derivative of 3,4-ethylenedioxythiophene (EDOT) in
Stille conditions. In this case, the target compounds 9b and 10b
were isolated in 70 and 65% yield respectively without any evidence
of C–P bond cleavage (Scheme 5).
It is worth noting that after one week in refluxing toluene in
the presence of the stannyl derivative of thiophene or EDOT
and Pd(PPh3)4, compound 7a or debrominated 5a and 6a were
recovered unreacted and intact, thus demonstrating that the
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already observed for trianthrylphosphorus compounds16 has been
ascribed to the influence of the phosphorus lone pair and to
through-space interactions between chromophores that contribute
to fluorescence quenching. On the other hand, oxidation of
phosphine into phosphine oxide produces a significant increase
of φem, from 4 to 15%, between 2a and 2b.
In this case, the increase of the fluorescence may be due to
the absence of the phosphorus lone pair together with a decrease
of through-space interactions among the conjugated chains due
to the increase of thiophene–phosphorus–thiophene angles in
the oxyphosphorus derivatives as demonstrated by the X-ray
structures of 6a and 6b.
Conclusions
Star-shaped conjugated systems based on oligothiophenes grafted
on a phosphorus node have been synthesized by condensation
of lithiated species on halogenophosphorus nodes and by Stille
coupling reactions. In the latter case, the analysis of the reaction
conditions allowed us to identify an undesired reaction involving a
ligand exchange with the catalyst. However, this parasitic reaction
can be prevented when the phosphine node is oxidized into the
corresponding oxide.
Scheme 5
The electrochemical, UV-vis, fluorescence data together with X-
ray diffraction results provide a coherent picture suggesting that
in addition to electronic effects, the oxidation of the phosphorus
node indirectly affects the electronic properties of the conjugated
system through small geometrical changes.
presence of a bromine atom at the terminal position of the
thiophene is required for ligand exchange.
UV-vis absorption, fluorescence and cyclic voltammetry
Derivatives 1–4 undergo a non reversible oxidation process. Exam-
ination of the values of the anodic peak potential (Epa) recorded by
cyclic voltammetry (Table 1) shows that as expected, compounds
2 containing an EDOT unit are oxidized at lower potentials than
compounds 1. The non linear compounds 1–2 show slightly higher
Epa values than the corresponding individual branches 3 and 4.
The slight decrease of Epa observed for the phosphorus oxide
derivatives when compared with their phosphine analogues is
rather intriguing. Whereas this phenomenon could be related to
differences in diffusion coefficients,15 further work is needed to
clarify this point.
The UV-vis data show that the compounds 1b–2b based on
phosphine oxide nodes absorb practically at the same wavelength
as the corresponding phosphine based system 1a–2a (Table 1).
Comparison of the fluorescence quantum efficiencies (φem) of
compounds 1a and 2a to those of the corresponding terthienyls
shows that the passage from the individual chains to the non
linear molecules leads to a slight decrease of φem. Such an effect
Experimental
General
1
Solvents were purified and dried using standard protocols. H
NMR and 13C NMR spectra were recorded on a Bruker AVANCE
DRX 500 spectrometer operating at 500.13 and 125.7 MHz;
d are given in ppm (relative to TMS) and coupling constants
(J) in Hz. Matrix-assisted laser desorption ionization time-of-
flight (MALDI-TOF) mass spectra were recorded by a Bruker
Biflex-III, equipped with a N2 laser (337 nm). For the matrix,
dithranol in CH2Cl2 was used. High resolution mass spectra were
recorded under FAB mode on a Jeol JMS 700 spectrometer. UV-
visible optical data were recorded with a Perkin-Elmer Lambda
19 spectrophotometer. X-Ray diffraction experiments were carried
out in the h–2h reflection mode with a Bruker D500 diffractometer
equipped with a speed detector Vantec. Cyclic voltammetry was
performed with an EG & G PAR 273A potentiostat with a
standard three-electrode cell using platinum electrodes and a
Ag/AgCl reference electrode.
Table 1 UV-Vis Absorption, fluorescence emission and oxidation poten-
tials of the compounds
kmax/nma
kem/nma
φem (%)c
E
pa/Vc
b
Synthetic procedure
Compound
Tris(5ꢀꢀ-hexyl-5-terthienyl)phosphine 1a. To 3 g of 5-hexyl-
2,2ꢀ:5ꢀ,2ꢀꢀ-terthiophene (9 mmol) dissolved in 150 mL of THF
cooled at −70 ◦C, 6 mL (9 mmol) of tert-butyllithium 1.5 mol L−1
ar◦e slowly dropped. The mixture is stirred for 1 h 30 min at
1a
1b
2a
2b
3
392
391
404
404
354
379
445
459
462
464
434
411
6
10
4
15
6
1.16
1.10
0.96
0.92
1.08
0.80
◦
0 C and cooled again at −60 C after which 530 mg (2 mmol)
4
6
of phosphorus bromide are added. The mixture is stirred for
15 h at room temperature. The formed precipitate is dissolved
in methylene chloride and the organic layer is washed with an
a In CH2Cl2. b Versus anthracene as standard. c Pt electrodes, 0.10 M n-
Bu4NPF6–CH2Cl2, scan rate 100 mV s−1 ref. Ag/AgCl.
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aqueous saturated solution of ammonium chloride and then twice
with water. The organic layer is then dried on magnesium sulfate
and the solvent is evaporated. Chromatography on silica gel using
petroleum ether (PE)–methylene chloride (1 : 1) as eluent gives
1.1 g of an orange solid. Yield: 35%; mp = 155 ◦C; Rf = 0.9 (PE :
CH2Cl2 1 : 1); NMR 1H (CDCl3): 7.30 (dd, 1H, 3JH-H = 3.72 Hz;
3JH-P = 6.60 Hz, H4), 7.12 (dd, 1H, 3JH-H = 3.65 Hz; 4JH-P = 1.39 Hz,
H3), 7.08 (d, 1H, 3J = 3.79 Hz, H3ꢀꢀ ), 6.97 (m, 2H, H3ꢀ and H4ꢀ ), 6.70
(d, 1H, 3J = 3.75 Hz, H4ꢀꢀ ), 2.80 (t, 2H, 3J= 7.00 Hz, T-CH2), 1.70
(qt, 2H, 3J = 7.00 Hz, T-CH2-CH2), 1.40 (m, 6H, CH2-CH2-CH2-
CH3), 0.90 (t, 3H, 3J = 6.00 Hz, CH3); NMR 13C (CDCl3): 145.6,
143.7, 137.3, 136.6, 136.4, 136.3, 136.1, 134.4, 134.0, 124.7, 124.6,
123.3, 31.3, 29.9, 28.4, 22.3, 13.8; NMR 31P (CDCl3): −43.41; MS
Tris(3ꢀ,4ꢀ-ethylenedioxy-5ꢀꢀ-hexyl-5-terthienyl)phosphine oxide
2b. To 80 mg (0,067 mmol) of tris(3ꢀ,4ꢀ-ethylenedioxy-5ꢀꢀ-hexyl-
2-terthienyl)phosphine dissolved in 30 mL of tetrahydrofuran,
1 mL of hydrogen peroxide (35% in water) is added. The mixture
is stirred for 15 h after which 100 mL of methylene chloride are
added. The organic phase is washed with water and then dried
on magnesium sulfate. After evaporation of solvent, the residue
is chromatographed on silica gel using dichloromethane–ethyl
acetate (9 : 1) as eluent allowing 60 mg of 2b to be isolated as a
brown solid. Yield: 74%; mp = 70 ◦C; Rf = 0.35 (CH2Cl2 : AcOEt
9 : 1); NMR 1H (CDCl3): 7.52 (dd, 1H, 3JH-H = 3.85 Hz, 3JH-P
=
3
4
8.22 Hz, H4), 7.23 (dd, 1H, JH-H = 3.84 Hz, JH-P = 1.98 Hz,
ꢀꢀ
H3), 7.05 (d, 1H, J = 3.59 Hz, H3 ), 6.69 (d, 1H, J = 3.61 Hz,
3
3
ꢀꢀ
•
(Malditof) calcd for C54H57PS9: 1024; found: 1024 (M+ ); Anal. for
H4 ), 4.36 (m, 4H, O-CH2-CH2-O), 2.79 (t, 2H, J = 7.56 Hz,
3
3
C54H57PS9 Found (Calcd): C, 63.78 (63.24); H, 5.75 (5.60); S, 28.33
(28.14).
T-CH2), 1.67 (quint, 2H, J = 7.29 Hz, T-CH2-CH2), 1.34 (m,
2H, CH2-CH2-CH2-CH3), 1.30 (m, 4H, CH2-CH2-CH3), 0.88 (t,
3H, 3J = 6.80 Hz, CH3); NMR 13C (CDCl3): 145.7, 143.7 (JC-P
=
Tris(3ꢀ,4ꢀ-ethylenedioxy-5ꢀꢀ-hexyl-5-terthienyl)phosphine
2a.
10.5 Hz), 139.1, 137.1 (JC-P = 16.6 Hz), 136.8, 131.3, 124.4,
123.4, 122.9, 122.8, 112.1, 107.6, 65.1, 64.9, 31.6, 31.5, 30.1, 28.8,
22.6, 14.1; NMR 31P (CDCl3): 5.92; MS (Malditof) calcd for
C60H63O7PS9: 1214; found: 1215 (M + H)+.
To 2 g of 3ꢀ,4ꢀ-ethylenedioxy-5-hexyl-2,2ꢀ: 5ꢀ,2ꢀꢀ-terthiophene
(5.1 mmol) dissolved in 80 mL of THF cooled to −70 ◦C, 3.4 mL
(5.1 mmol) of tert-butyllithium 1.5 mol L−1 are slowly dropped.
The mixture is stirred for 1 h 30 min at 0 ◦C and cooled again to
−60 ◦C after which 310 mg (1.14 mmol) of phosphorus tribromide
are added. The mixture is stirred for 15 h at room temperature.
The formed precipitate is dissolved in methylene chloride and the
organic layer is washed with an aqueous saturated solution of
ammonium chloride and then twice with water. The organic layer
is then dried on magnesium sulfate and the solvent is evaporated.
Chromatography on silica gel using petroleum ether–methylene
chloride (2 : 1 and then 1 : 1) as eluent gives 520 mg of a yellow
solid. This compound is not ◦stable in solution as it rapidly
oxidizes. Yield: 25%; mp = 60 C; Rf = 0.7 (PE : CH2Cl2 1 : 1);
(5-Bromo-2-thienyl)(diphenyl)phosphine 5a. To 3 g of 2,5-
dibromothiophene (12.4◦mmol) dissolved in 50 mL of dry diethyl
ether and cooled at −50 C, 7.7 mL of n-butyllithium 1.6 mol L−1
(12.4 mmol) are added dropwise. The mixture is stirred for 1 h
30 min at 0 ◦C, cooled again at −50 ◦C and 2.7 g (11.2 mmol)
of chlorodiphenylphosphine are added. After 15 h at room
temperature and addition of methylene chloride (dissolution of
the formed precipitate), the organic layer is washed with an
aqueous saturated solution of ammonium chloride, with water
and dried on magnesium sulfate. After evaporation, the residue is
chromatographed on silica gel using petroleum ether as eluent to
afford 3.2 g of a pale yellow solid. Yield: 75%; mp = 79 ◦C; Rf =
1
NMR H (CDCl3): 7.27 (dd, 1H, 3J = 3.78 Hz, 3JH-P = 6.40 Hz,
H4), 7.17 (dd, 1H, 3J = 3.64 Hz, 4JH-P= 1.46 Hz, H3), 7.02 (d, 1H,
3J = 3.60 Hz, H3ꢀꢀ ), 6.68 (d, 1H, 3J = 3.59 Hz, H4ꢀꢀ ), 4.35 (m, 4H,
0.5 (PE); NMR 1H (CDCl3): 7.40 (m, 10H), 7.10 (dd, 1H, 3JH-P
=
3
3
3
6.50 Hz, JH-H = 3.75 Hz, H3), 7.05 (dd, 1H, JH-H = 3.75 Hz,
4JH-P = 1.00 Hz, H4); NMR 31P (CDCl3): −18.7; MS (Malditof)
calcd for C16H12BrPS: 345.9; found: 346.8 (M + H)+.
O-CH2-CH2-O), 2.78 (t, 2H, J = 7.61 Hz, T-CH2), 1.66 (quint,
2H, 3J = 7.47 Hz, T-CH2-CH2), 1.35 (m, 2H, T-CH2-CH2-CH2),
1.29 (m, 4H, CH2-CH2-CH3), 0.86 (m, 3H, CH3); MS (Malditof)
calcd for C60H63O6PS9: 1198; found: 1199 (M + H)+.
Tris(2-bromo-5-thienyl)phosphine 6a. To
2
g
of 2,5-
Tris(5ꢀꢀ-hexyl-5-terthienyl)phosphine oxide 1b. To 80 mg
(0,078 mmol) of tris(5ꢀꢀ-hexyl-2-terthienyl)phosphine dissolved in
30 mL of tetrahydrofuran, 1 mL of hydrogen peroxide (35% in
water) is added. The mixture is stirred for 15 h after which 100 mL
of methylene chloride are added. The organic phase is washed with
water and then dried on magnesium sulfate. After evaporation
of solvent, the residue is chromatographed on silica gel using
dichloromethane–ethyl acetate (9 : 1) as eluent giving 77 mg of
dibromothiophene (8.27 m◦mol) dissolved in 20 mL of dry
diethyl ether cooled at −50 C, 5.2 mL (1 eq.) of n-butyllithium
1.6 mol L−1 are slowly dropped. The solution is then stirred for
1 h 30 min at 0 ◦C and cooled again at −60 ◦C after which 0.22 eq.
of phosphorus bromide are added. The mixture is stirred for
15 h at room temperature. 20 mL of a saturated solution of
ammonium chloride in water are then added at 0 ◦C after which
the organic layer is washed twice with water. The organic layer is
then dried on magnesium sulfate and the solvent is evaporated.
Chromatography on silica gel using petroleum ether as eluent
affords 610 mg of a white solid. Monocrystals were obtained by
recrystallization in a methylene chl◦oride, petroleum ether mixture
◦
an orange solid. Yield: 95%; mp = 179 C; Rf = 0.75 (CH2Cl2 :
1
3
AcOEt 9 : 1); NMR H (CDCl3): 7.60 (dd, 1H, JH-H = 3.75 Hz;
3JH-P = 6.50 Hz, H4), 7.20 (dd, 1H, 3JH-H = 3.75 Hz, 4JH-P = 1.00 Hz,
H3), 7.10 (d, 1H, 3J = 3.75 Hz, H3ꢀ), 7.00 (2d, 2H, 3J = 3.75 Hz, H3ꢀꢀ
and H4ꢀ ), 6.70 (d, 1H, 3J = 3.75 Hz, H4ꢀꢀ ), 2.70 (t, 2H, 3J = 7.00 Hz,
1
(see ESI). Yield: 43%; mp = 93 C; Rf = 0.6 (PE); NMR H
3
T-CH2), 1.70 (qt, 2H, J = 7.00 Hz, T-CH2-CH2-), 1.30 (m, 6H,
3
3
(CDCl3): 7.10 (dd, 1H, JH-H = 3.50 Hz, JH-P = 6.50 Hz, H4),
CH2-CH2-CH2-CH3), 0.90 (t, 3H, 3J = 6.00 Hz, CH3); NMR 13
C
7.00 (dd, 1H, JH-H = 3.50 Hz, JH-P = 1.00 Hz, H3); NMR 31P
(CDCl3): −42; MS (Malditof) calcd for C12H6Br3PS3: 514; found:
516.
3
4
(CDCl3): 146.5 (JC-P = 6.1 Hz), 146.3, 138.8, 137.8 (JC-P = 9.9 Hz),
133.9, 133.5, 132.3, 131.2, 126.1, 125.0, 124.3 (JC-P = 13.8 Hz),
123.9, 123.7, 31.5, 30.2, 29.7, 28.7, 22.6, 14.1; NMR 31P (CDCl3):
4.55; MS (Malditof) calcd for C54H57OPS9: 1040; found 1041
(M + H)+.
(5-Bromo-2-thienyl)(diphenyl)phosphine oxide 5b. To 0.5 g
(1.44 mmol) of (5-bromo-2-thienyl)(diphenyl)phosphine dissolved
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in 50 mL of tetrahydrofuran, 2 mL of hydrogen peroxide (35%
in water) are added. The mixture is stirred for 20 h after which
100 mL of methylene chloride are added. The organic phase
is washed five times with 100 mL of water and then dried on
magnesium sulfate. After evaporation of solvent, the residue is
chromatographed on silica gel using dichloromethane and then
dichloromethane–ethyl acetate (9 : 1) as eluent giving 420 mg
of 5b as a white solid. Yield: 80%; mp = 117 ◦C; NMR 1H
(CDCl3): 7.72 (m, 4H, phenyl), 7.57 (m, 2H, phenyl), 7.48 (m,
4H, phenyl), 7.21 (dd, 1H, 3JH-P = 8.00 Hz, 3JH-H = 3.76 Hz), 7.13
0.81 g (1.82 mmol.) of 3,4-ethylenedioxy-2-tributylstannylthio-
phene and a catalytic amount of Pd(PPh3)4 are dissolved in
40 mL of degassed toluene. The mixture is refluxed under nitrogen
atmosphere for 24 h. After cooling the organic phase is washed
with brine and dried on magnesium sulfate. The solvent is
evaporated and the residue is chromatographed on silica gel using
dichloromethane and then dichloromethane–ethyl acetate (85 :
15) as eluent allowing the isolation of 130 mg of 10b as a yellow
◦
1
solid. Yield: 65%; mp (decomp.) ≈ 93 C; NMR H (CDCl3):
3
3
7.51 (dd, 1H, JH-P = 8.30 Hz, JH-H = 3.80 Hz), 7.17 (dd, 1H,
3JH-H = 3.80 Hz, 4JH-P = 2.20 Hz), 6.29 (s, 1H), 4.32 (m, 2H, CH2),
4.22 (m, 2H, CH2); NMR 13C (CDCl3): 144.0, 141.9, 138.9, 137.0,
132.2, 130.9, 111.1, 98.7, 65.1, 64.5; NMR 31P (CDCl3): 5.86; MS
(Malditof) calcd for C30H21O7PS6: 715.9; found: 715.7 (M)+.
3
4
(dd, 1H, JH-H = 3.82 Hz, JH-P = 1.96 Hz); NMR 31P (CDCl3):
20.94; MS (Malditof) calcd for C16H12BrOPS: 361.9; found: 363.0
(M + H)+.
Tris(2-bromo-5-thienyl)phosphine oxide 6b. To 0.5 g (0.97 mmol)
of tris(2-bromo-5-thienyl)phosphine dissolved in 50 mL of tetrahy-
drofuran, 5 mL of hydrogen peroxide (35% in water) are added.
The mixture is stirred for 4 h after which 100 mL of methylene
chloride are added. The organic phase is washed five times
with 100 mL of water and then dried on magnesium sulfate.
After evaporation of solvent, the residue is chromatographed on
silica gel using dichloromethane and then dichloromethane–ethyl
acetate (95 : 5) as eluent allowing the isolation of ◦440 mg of 6b
Crystallographic data
Data collection was performed at 293 K on a STOE-IPDS diffrac-
tometer for 6b and on a BRUKER KappaCCD diffractometer for
6a, bothequippedwithagraphitemonochromatorutilizingMoKa
˚
radiation (k = 0.71073 A). The structures were solved by direct
methods (SIR92) and refined on F2 by full matrix least-squares
techniques using the SHELX-97 package. All non-H atoms were
refined anisotropically and the H atoms were included in the
calculation without refinement. Absorption was corrected by the
Gaussian technique for 6b and by Sadabs program for 6a.
1
as white crystals (see ESI). Yield: 87%; mp = 155 C; NMR H
3
3
(CDCl3): 7.35 (dd, 1H, JH-H = 8.90 Hz, JH-P = 3.80 Hz), 7.17
3
4
(dd, 1H, JH-P = 3.80 Hz, JH-H = 2.30 Hz); NMR 31P (CDCl3):
1.94.
Crystal data for 6a. Colorless prism (0.56 × 0.18 × 0.14 mm3),
C12H6Br3P1S3, Mr = 517.05, monoclinic, space group P21/n, a =
Tris(5-bithienyl)phosphine 7a. To 100 mg (0.19 mmol) of tris-5-
(2-bromothienyl)phosphine dissolved in 20 mL of toluene, 240 mg
(0.63 mmol) of 2-tributylstannylthiophene and 30 mg of Pd(PPh3)4
are added under inert atmosphere. The mixture is refluxed for
12 h after which the organic layer is washed with brine and dried
on magnesium sulfate. The residue is chromatographed on silica
gel using petroleum ether–methylene chloride (4 : 1) as eluent
affording 40 mg of 7a isolated as a white solid. Yield: 40%; mp =
150 ◦C; Rf = 0.4 (PE : CH2Cl2 4 : 1); NMR 1H (CDCl3): 7.30 (dd,
1H, 3J = 3.75 Hz, 3JH-P = 6.50 Hz, H4), 7.22 (dd, 1H, 3J = 5.00 Hz,
4JH-P = 1.00 Hz, H5ꢀ ), 7.20 (d, 1H, 3J = 3.75 Hz, H3), 7.15 (dd, 1H,
3J = 3.75 Hz, 4J = 1.00 Hz, H3ꢀ ), 7.00 (dd, 1H, 3J = 5.00 Hz, 3J =
3.75 Hz, H4ꢀ ); MS (Malditof) calcd for C24H15PS6: 525.9; found:
525.6 (M)+.
◦
˚
˚
˚
9.563(1) A, b = 9.483(1) A, c = 18.527(3) A, b = 101.93(1) , V =
3
1643.9(4) A , Z = 4, qcalc = 2.089 g cm−3, l (MoKa) = 7.823 mm−1,
˚
F(000) = 984, hmin = 2.42◦, hmax = 25.02◦, 27411 reflections col-
lected, 2887 unique (Rint = 0.058), restraints/parameters = 0/172,
R1 = 0.0404 and wR2 = 0.0860 using 2162 reflections with I >
2r(I), R1 = 0.0680 and wR2 = 0.0960 using all data, GOF = 1.061.
Crystal data for 6b. Colorless prism (0.48 × 0.27 × 0.13 mm3),
C12H6Br3O1P1S3, Mr = 533.05, monoclinic, space group P21/n, a =
◦
˚
˚
˚
˚
9.8214(9) A, b = 9.4798(8) A, c = 18.488(2) A, b = 102.87(1) , V =
1678.1(3) A , Z = 4, qcalc = 2.110 g cm−3, l (MoKa) = 7.671 mm−1,
3
F(000) = 1016, hmin = 2.17◦, hmax = 25.89◦, 13628 reflections col-
lected, 3243 unique (Rint = 0.080), restraints/parameters = 0/181,
R1 = 0.0538 and wR2 = 0.1421 using 2192 reflections with I >
2r(I), R1 = 0.0803 and wR2 = 0.1546 using all data, GOF = 1.002.
(3ꢀ,4ꢀ-Ethylenedioxy-2ꢀ,5-bithiophene)(diphenyl)phosphine oxide
9b. 0.21
g (0.58 mmol) of (5-bromo-2-thienyl)(diphenyl)-
phosphine oxide, 0.75 g (1.74 mmol) of 3,4-ethylenedioxy-2-
tributylstannylthiophene and a catalytic amount of Pd(PPh3)4 are
dissolved in 50 mL of degassed toluene. The mixture is refluxed
under nitrogen atmosphere for 20 h. After cooling, the organic
phase is washed with brine and dried on magnesium sulfate.
The solvent is evaporated and the residue is chromatographed
on silica gel using dichloromethane and then dichloromethane–
ethyl acetate (9 : 1) as eluent allowing the isolation of 170 mg of
Acknowledgements
We thank Professor R. Re´au for fruitful discussions and Dr J.
Delaunay (SCAS Angers) for NMR analyses. The Re´gion des
Pays de la Loire is acknowledged for the PhD grant to SR.
1
9b as a yellow oil. Yield: 70%; NMR H (CDCl3): 7.74 (m, 4H),
References
7.57 (m, 2H), 7.53 (m, 4H), 7.45 (dd, 1H, 3JH-P = 7.60 Hz, 3JH-H
=
3.76 Hz), 7.23 (dd, 1H, 3JH-H = 3.81 Hz, 4JH-P = 1.98 Hz), 6.26 (s,
1H), 4.27 (m, 2H, CH2), 7.00 (m, 2H, CH2); NMR 31P (CDCl3):
22.01 (s).
1 C. D. Dimitrakopolous and P. Malenfant, Adv. Mater., 2002, 14, 99;
J. A. Rogers, Z. Bao, A. Dodabalapur, B. Crone, V. R. Raju, H. E. Katz,
V. Kuck, K. J. Ammundson and P. Drzaic, Proc. Natl. Acad. Eng., 2001,
98, 4817; F. Garnier, Acc. Chem. Res., 1999, 32, 209; G. Horowitz, Adv.
Mater., 1998, 10, 3; H. E. Katz, J. Mater. Chem., 1997, 7, 369; A. Kraft,
A. C. Grimsdale and A. B. Holmes, Angew. Chem., Int. Ed., 1998, 37,
402; U. Mitschke and P. Bauerle, J. Mater. Chem., 2000, 10, 1471.
Tris(3ꢀ,4ꢀ-ethylenedioxy-2ꢀ,5-bithiophene)phosphine oxide 10b.
0.15 g (0,28 mmol) of tris(2-bromo-5-thienyl)phosphine oxide,
3206 | Org. Biomol. Chem., 2008, 6, 3202–3207
This journal is
The Royal Society of Chemistry 2008
©

View Article Online
2 S. Yoo, B. Domerq and B. Kippelen, Appl. Phys. Lett., 2004, 85, 5427;
Y. Shao, S. Sista, C.-W. Chu, D. Sievers and Y. Yang, Appl. Phys. Lett.,
2007, 90, 103501.
8 T. Baumbartner and R. Re´au, Chem. Rev., 2006, 106, 5681; H.-C. Su,
O. Fadhel, C.-J. Yang, T.-Y. Cho, C. Fave, M. Hissler, C.-C. Wu and
R. Re´au, J. Am. Chem. Soc., 2006, 128, 983; M. Hissler and C. Lescop
Rre´au, J. Organomet. Chem., 2005, 690, 2482; M. Sebastien, M. Hissler,
C. Fave, J. Rault-Berthelot, C. Odin and R. Re´au, Angew. Chem., Int.
Ed., 2006, 45, 6152; Y. Dienes, M. Eggenstein, T. Neumann, U. Englert
and T. Baumbartner, Dalton Trans., 2006, 1424; T. Neumann, Y. Dienes
and T. Baumbartner, Org. Lett., 2006, 8, 495; S. Durben, Y. Dienes and
T. Baumbartner, Org. Lett., 2006, 8, 5893; Y. Diennes, S. Durben, T.
Karpati, T. Neumann, U. Englert, L. Nyulaszi and T. Baumgartner,
Chem.–Eur. J., 2007, 13, 7487.
9 R. Me´tivier, R. Armengual, I. Leray, V. Michelet and J.-P. Geneˆt,
Org. Lett., 2006, 6, 739; M. Fourmigue´ and P. Batail, J. Chem. Soc.,
Chem. Commun., 1991, 1370; N. Soh, T. Ariyoshi, T. Fukaminato, H.
Nakajima, K. Nakano and T. Imato, Org. Biomol. Chem., 2007, 5,
3762.
10 Y. L. Gol’dfarb, A. A. Dudinov, V. P. Litinov, D. S. Yurit and Y. T.
Struchkov, Chem. Heterocycl. Compd. (Engl. Transl.)., 1982, 18, 1021.
11 D. W. Allen and D. F. Ashford, J. Inorg. Nucl. Chem., 1976, 38,
1953.
12 K.-C. Kong and C.-H. Cheng, J. Am. Chem. Soc., 1991, 113, 6313;
V. V. Grushin, Organometallics, 2000, 19, 1888; F. Leca, M. Sauthier,
L. Toupet and R. Re´au, Chem.–Eur. J., 2003, 9, 3785.
3 Handbook of Conducting Polymers, ed. T. Skotheim and J. Reynolds,
CRC Press, Boca Raton, Florida, USA, 3rd edn, 2007.
4 J. Roncali, P. Leriche and A. Cravino, Adv. Mater., 2007, 19, 2045 and
references cited therein.
5 S. Roquet, R. de Bettignies, P. Leriche, A. Cravino and J. Roncali,
J. Mater. Chem., 2006, 29, 3040; see also: Y. Harima, D-H. Kim, Y.
Tsutitori, X. Jiang, R. Patil, Y. Ooyama, J. Oshita and A. Kunai, Chem.
Phys. Lett., 2006, 387; M. Fujitsuka, D. W. Cho, J. Ohshita, A. Kunai
and T. Majima, J. Phys. Chem. C, 2007, 111, 1993.
6 S. Karpe, A. Cravino, P. Fre`re, M. Allain, G. Mabon and J. Roncali,
Adv. Funct. Mater., 2007, 17, 1163; see also: B. S. Nehls, F. Galbrecht,
A. Bilge, D. J. Brauer, C. W. Lehmann, U. Scherf and T. Farrell, Org.
Biomol. Chem., 2005, 3, 3213; A. Bilge, A. Zen, M. Forster, H. Li, F.
Galbrecht, B. S. Nehls, T. Farrell, D. Neher and U. Scherf, J. Mater.
Chem., 2006, 16, 3177.
7 A. Cravino, S. Roquet, O. Ale´veˆque, P. Leriche, P. Fre`re and J. Roncali,
Chem. Mater., 2006, 18, 2584; S. Roquet, A. Cravino, P. Leriche, O.
Aleveˆque, P. Fre`re and J. Roncali, J. Am. Chem. Soc., 2006, 128, 3459;
A. Cravino, P. Leriche, O. Ale´veˆque, S. Roquet and J. Roncali, Adv.
Mater., 2006, 18, 3033; A. Cravino, S. Roquet, P. Leriche, O. Aleveˆque,
P. Fre`re and J. Roncali, Chem. Commun., 2006, 1416; P. Leriche, P.
Fre`re, A. Cravino, O. Ale´veˆque and J. Roncali, J. Org. Chem., 2007,
72, 8332; H. Choi, C. Baik, S. O. Kang, J. Ko, M-S. Kang, Md. K.
Nazeeruddin and M. Gra¨tzel, Angew. Chem., Int. Ed., 2007, 46, 1; Z.
Ge, T. Hayakawa, S. Ando, M. Ueda, T. Akiike, H. Miyamato, T. Kajita
and M-A. Kakimoto, Adv. Funct. Mater., 2008, 18, 584; J-C. Li, S-H.
Li, Y-B. Hahn, K-J. Kim, K. Zong and Y-S. Lee, Synth. Met., 2008,
158, 150; W. Xu, B. Peng, J. Chen, M. Liang and F. Cai, J. Phys. Chem.
C, 2008, 112, 874.
13 F. E. Goodson, T. I. Wallow and B. M. Novak, J. Am. Chem. Soc.,
1997, 119, 12441.
14 D. K. Morita, J. K. Stille and J. R. Norton, J. Am. Chem. Soc., 1995,
117, 8576; B. E. Segelstein, T. W. Butler and B. L. Chenard, J. Org.
Chem., 1995, 60, 12.
15 A. J. Bard and L. L. Faulkner, Electrochemical Methods, Fundamentals
and Applications, Wiley, New York, 1980.
16 S. Yamagushi, S. Akiyama and K. Tamao, J. Organomet. Chem., 2002,
277.
This journal is
The Royal Society of Chemistry 2008
Org. Biomol. Chem., 2008, 6, 3202–3207 | 3207
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