From model compounds to extended π-conjugated systems: Synthesis and properties of dithieno[3,2-b:2′3′-d]phospholes

Article abstract of DOI:10.1002/chem.200500152

To explore their suitability for applications in molecular optoelectronics and as sensory materials, novel dithieno[3,2-b:2′,3′-d]phospholes have been synthesized and their reactivity and properties investigated. An efficient two-step synthesis allowed fo

Full text of DOI:10.1002/chem.200500152

FULL PAPER
From Model Compounds to Extended p-Conjugated Systems:
Synthesis and Properties of Dithieno[3,2-b:2’,3’-d]phospholes
Thomas Baumgartner,*[a] Werner Bergmans,[a] Tamµs Kµrpµti,[b] Toni Neumann,[a]
Martin Nieger,[c] and Lµszló Nyulµszi*[b]
Abstract: To explore their suitability
for applications in molecular optoelec-
tronics and as sensory materials, novel
dithieno[3,2-b:2’,3’-d]phospholes have
been synthesized and their reactivity
and properties investigated. An effi-
cient two-step synthesis allowed for a
modular assembly of differently func-
tionalized compounds. The dithie-
no[3,2-b:2’,3’-d]phosphole system ex-
hibits extraordinary optoelectronic
properties with respect to wavelength,
intensity, and tunability. Owing to the
nucleophilic nature of the central phos-
phorus atom, its significant electronic
influence on the conjugated p system
can be altered selectively by chemically
facile modifications such as oxidation
or complexation with Lewis acids or
transition metals. All the dithieno-
phosphole species presented show very
strong blue photoluminescence with
excellent quantum yield efficiencies
supporting their potential utility as
blue-light emitting components in or-
ganic light emitting diodes (OLEDs).
Furthermore, depending on the elec-
tronic nature of the phosphorus center,
the materials exhibit distinctive optoe-
lectronic properties suggesting that the
dithieno[3,2-b:2’,3’-d]phosphole system
may be useful as sensory material. The-
oretical calculations, including time-de-
pendent DFT methods, revealed the
excellent predictability of the struc-
tures and optoelectronic properties of
the functionalized dithienophospholes
allowing the design of future dithie-
no[3,2-b:2’,3’-d]phosphole-based mate-
rials to be ”stream-lined”. By using tin-
functionalized dithienophosphole mon-
omers, a strategy, which involves Stille
coupling, towards extended p-conjugat-
ed materials with significantly redshift-
ed optoelectronic properties is also
presented.
Keywords: density functional calcu-
lations · luminescence · molecular
electronics
· optical properties ·
phosphorus heterocycles
Introduction
The incorporation of phosphorus centers into oligomeric or
macromolecular materials is currently receiving increasing
amounts of interest.[1] The versatile reactivity and electronic
nature of phosphorus offers interesting opportunities for the
development of new materials with novel properties. Phos-
phole-containing systems are of particular interest in molec-
ular electronics as materials that possess the structurally re-
lated pyrrole and thiophene moieties are already well-estab-
lished in this field.[2] The corresponding phosphole-contain-
ing materials have great potential for applications in elec-
tronic devices such as photovoltaic cells, organic or polymer
light-emitting diodes (OLEDs or PLEDs), polymeric sen-
sors, and organic thin-film transistors (OTFTs).[3] Recently,
RØau and co-workers, who incorporated the phosphole
moiety into extended thiophene-containing p-conjugated
systems (P1), demonstrated the advantageous electronic fea-
tures of these phosphorus-containing systems which allow
selective fine-tuning of the electronic structure of the mate-
[a] Dr. T. Baumgartner, W. Bergmans, T. Neumann
Institute of Inorganic Chemistry, RWTH-Aachen University
Landoltweg 1, 52074 Aachen (Germany)
Fax : (+49)241-809-2644
E-mail: thomas.baumgartner@ac.rwth-aachen.de
[b] Dr. T. Kµrpµti, Prof. L. Nyulµszi
Department of Inorganic Chemistry
Technical University of Budapest
1521 Budapest GellØrt tØr 4 (Hungary)
Fax : (+36)1463-3462
E-mail: nyulaszi@mail.bme.hu
[c] Dr. M. Nieger
Institut für Anorganische Chemie, Universität Bonn
Gerhard-Domagk-Strasse 1, 53121 Bonn (Germany)
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author. It contains tables
of relevant bond lengths for 10b, 11, and 13 determined by single-
crystal X-ray structure studies, selected bond lengths and Bird indices
for the investigated species (S2b, T1–T4) calculated at the B3LYP/6-
31G* level of theory and TD-DFT-calculated optical spectroscopy
data.
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DOI: 10.1002/chem.200500152
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rials.[1f,4] Owing to the pyramidal nature of the tricoordinate
phosphorus center, an efficient interaction of its lone-pair
orbital with the conjugated p system is inhibited resulting in
only a small amount of lone-pair delocalization. A weak in-
teraction can, however, be observed between the p* LUMO
based systems (P7), on the other hand, had been completely
unknown until recently.
As part of our research into the development of processi-
ble, electronically active, macromolecular inorganic materi-
als we focused our attention on the novel dithieno[3,2-
*
and the exocyclic sPC orbital. Therefore, the lone pair at the
phosphorus atom functions as a kind of dopant in the p
system rather than being an integral part of the aromatic
system. Conveniently, the electronic structure of the p-con-
jugated system can be efficiently controlled by simple chem-
ical modifications, such as the oxidation or complexation of
the phosphorus center.[1f,4] Although these intriguing fea-
tures, in addition to theoretical calculations,[5] strongly sup-
port the advantages of the incorporation of phosphole moi-
eties into extended oligomeric or macromolecular systems,
only a few examples of phosphole-containing systems have
been reported to date: The first oligomeric phosphole-con-
taining materials P2 and P3 were reported by Mathey and
co-workers in the early 1990s,[6] whereas the first example of
a macromolecular phosphole system P4 was only reported
in 1997 by Mao and Tilley.[7a] Recently, RØau and co-work-
ers accessed the bithiophene-bridged phosphole polymer
P5a by electropolymerization[1f] and Chujo and co-workers
reported the phenylene(ethynylene)-linked material P5b.[7b]
b:2’,3’-d]phosphole moiety P7.[16] In this system, the molecu-
lar framework of the bithienyl moiety is rigidified by a phos-
phorus bridge to give a new anellated ring system. This
system should possess a smaller HOMO–LUMO gap than
any of its component rings, as has been observed for related
sulfur-bridged thiophene materials.[17] Furthermore, the
HOMO–LUMO gap is reduced by the interaction of the p*
*
LUMOwith the sPC orbital and the presence of the phos-
phorus atom allows selective tuning of the electronic proper-
ties of the material by its functionalization. Like almost no
other element, trivalent phosphorus is particularly suited for
the bridging position in the dithieno system owing to its nu-
cleophilic nature. Its ability to react with oxidizing agents,
its Lewis basicity, which allows reactions with Lewis acids, in
addition to its potential for coordination to transition metals
allows the electronic properties of the dithienophosphole
materials to be modified by a unique variety of synthetically
facile methods. Note that in this context the incorporation
of a phosphole unit into a benzo-anellated ring system has
been found to further reduce the lone-pair delocalization[18]
largely because the benzene subunits tend to retain their ar-
omatic character. Therefore, (di)benzophospholes (P8), or
dithienophospholes (P7) for that matter, cannot be consid-
ered classic phospholes; they represent an independent class
of compound.[19]
Recently we reported that the novel dithieno[3,2-b:2’,3’-
d]phosphole species 1 (a: R=Ph; b: R=4-tBuPh) and the
corresponding polymeric materials 2 (a: E=lone pair; b:
E=O; TBDMS =tert-butyldimethylsilyl) possessed very ad-
vantageous properties with respect to wavelength, intensity,
tunability, as well as optical and thermal stability.[16a] The
dithieno[3,2-b:2’,3’-d]phosphole moiety is a very efficient
emitter of blue light suggesting potential applications in op-
toelectronic devices such as PLEDs or polymeric sensory
materials.
As already indicated, careful consideration of the
HOMO–LUMO gap, which strongly influences the optical
and electronic properties of materials, is essential for their
utility in molecular electronics.[8] In this context, Ohshita
and co-workers have shown, for example, that the incorpo-
ration of a silicon bridge into a bithienyl moiety reduces the
HOMO–LUMO gap of the material (S1) significantly owing
to the formation of an extended planar p-conjugated
system. This feature could allow the material to be used as a
hole-transport material in electroluminescent (EL) devices.[9]
However, the number of different dithieno systems is very
limited and the only known examples include boron (S2a,
E=BR),[10] carbon (S2b, E=CR2),[11] nitrogen (S2c, E=
In this paper we report in detail on the synthesis and op-
toelectronic properties of the dithieno[3,2-b:2’,3’-d]phos-
phole system including theoretical calculations. We will dis-
cuss the possibilities of tuning the electronic structure of the
[14]
NR),[12] silicon (S1),[13] and sulfur (S2d–f, E=S(=O)0,1,2
)
as bridging elements. The use of phosphorus has only been
reported in compound P6,[15] whereas s3,l3-phosphorus-
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Synthesis and Properties of Dithienophospholes
FULL PAPER
dithieno[3,2-b:2’,3’-d]phospholes 6–9 as off-white waxy
solids in good yields after filtration through neutral alumina.
All four compounds exhibit 31P NMR chemical shifts (6: d=
À25.0 ppm; 7: d=0.3 ppm; 8: d=À27.4 ppm; 9: d=
À28.2 ppm) that are significantly shifted upfield relative to
those of the phospholes reported by RØau et al. (d31P=11–
45 ppm),[1f] but in the same range as the non-silyl-functional-
ized dithienophospholes 1a and 1b (cf. 1a: d31P=
À21.5 ppm; 1b: d=À22.5 ppm)[16a] indicating that these si-
lyldithienophospholes are related to dibenzophosphole (cf.
d31P=À12.8 ppm for P8; R=Ph)[21] rather than to classic
phospholes. The slight upfield shift of the 31P NMR resonan-
ces of the aryl-substituted, silyl-functionalized systems rela-
tive to their nonfunctionalized congeners supports the fur-
ther extended p-conjugated system induced by the electron-
system by various chemical modifications and thus probe
the potential of the dithienophosphole system for use as sen-
sory materials. Furthermore, a route to extended p-conju-
gated systems containing the dithieno[3,2-b:2’,3’-d]phos-
phole moiety is discussed as well.
1
accepting silicon centers in 6–9. The H and 13C NMR data
for 6–9 show the same trends as those observed for the re-
lated dithieno systems[9,12] and for the previously reported
dithienophospholes.[16]
Results and Discussion
Synthesis and characterization of dithieno[3,2-b:2’,3’-
d]phospholes: By taking into account the properties of the
systems described by Ohshita[9,13] and RØau[1f,4] and their co-
workers it seemed necessary for us to incorporate an elec-
tron acceptor into the dithienophosphole system in order to
further optimize the HOMO–LUMO separation. We decid-
ed to use silyl groups since they can be easily introduced
and exhibit suitable acceptor properties through negative
hyperconjugation.[20]
Derivatization of the dithieno[3,2-b:2’,3’-d]phosphole
system: As mentioned earlier, the unique ability of phos-
phorus to react with oxidizing agents, its Lewis basicity,
which allows reactions with Lewis acids, in addition to its
potential for coordination to transition metals, enables a
broad range of synthetically facile chemical modifications to
be made to tune the electronic properties of the dithieno-
phosphole materials. Note that exploitation of the nucleo-
philicity of the s3,l3-phosphorus atom gives rise to a signifi-
cant increase in the acceptor properties of this center.
Reaction of 6 with oxidizing agents such as H2O2 or sulfur
in THF at room temperature resulted in the clean formation
of the phosphole oxide 10a and the phosphole sulfide 11, re-
spectively (Scheme 2). The 31P NMR spectrum of the oxi-
dized species 10a exhibits a signal at d=17.2 ppm, which, as
expected for a phosphane oxide, is at a low field relative to
that of 6. However, the value of the chemical shift for 10a is
still upfield-shifted relative to related bis(thienyl)phosphole
oxide systems (d31Pꢀ45 ppm),[1f,4] supporting the high
degree of p conjugation in the dithieno subunits in 10a. The
same is true for the sulfurized species 11 which has a 31P
NMR resonance at d=23.6 ppm (cf. d31Pꢀ53 ppm for bis-
By applying synthetic variations of the strategy by Ohshi-
ta et al. for the synthesis of dithienosiloles[9a] to our system,
we were able to access novel dithieno[3,2-b:2’,3’-d]phos-
pholes with the desired silyl functionality. Starting from
3,3’,5,5’-tetrabromobithiophene 3, the silyl groups were in-
troduced by reaction with n-butyllithium followed by the ad-
dition of the corresponding chlorosilanes (Me3SiCl, tBuMe2-
SiCl) at À788C in THF to afford the silyl-functionalized bi-
thiophenes 4[9a] and
5 in almost quantitative yields
(Scheme 1). Subsequent lithiation of 4 and 5 with two equiv-
alents of n-butyllithium followed by the addition of RPCl2
(R=Ph, 4-tBuPh, tBu) in the presence of N,N,N’,N’-tetra-
methyl-1,2-ethanediamine (TMEDA) cleanly afforded the
Scheme 1. Synthesis of dithieno[3,2-b:2’,3’-d]phospholes 6–9.
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T. Baumgartner, L. Nyulµszi et al.
À
and C4A C5A (1.454(3) Š) bonds between the two thio-
phene units are in accordance with the enhanced electron-
acceptor properties of the phosphorus center in 10b com-
pared with 1a.[16a] Additional delocalization of the p-conju-
gated system through the phosphorus center should be pos-
À
sible in 10b leading to elongation of the C4(A) C5(A)
bond as well as the aforementioned bond lengths of the di-
thieno ring system thus suggesting increased aromatic char-
acter in the phosphole subunit (vide infra). These structural
features indicate that substitution of the phosphorus center
can indeed have an effect on the degree of p conjugation,
which is potentially interesting in terms of the optoelectron-
ic properties of the material.
In the case of 11, one of the molecules in the unit cell ex-
hibits some disorder in the dithienophosphole ring unit and
at one silyl group,[23] whereas the other molecule is some-
what disordered at one silyl group only allowing for discus-
sion of some of the structural features of 11 in the solid
state (Figure 2). Similar to the observations made for 1a[16a]
and 10b, the high degree of p conjugation in the dithieno-
phosphole system is apparent in the elongated double bonds
Scheme 2. Functionalization of dithieno[3,2-b:2’,3’-d]phospholes 6 and 8.
(thienyl)phosphole sulfides[1f,4]).
The 1H and 13C NMR data
show the same trend and corre-
late with the data observed for
non-silyl-functionalized dithie-
nophospholes.[16]
We were able to obtain single
crystals suitable for X-ray crys-
tal structure studies of 10b[22]
and 11 from concentrated solu-
tions of them in pentane and
hexane, respectively, at room
temperature. The structural
data for both compounds show
two independent molecules
each of 10b and 11 in the unit
cells. The single-crystal X-ray
diffraction analysis of 10b con-
firmed the expected planar ge-
Figure 1. Molecular structure of 10b (50% probability level) in the solid state. Hydrogen atoms are omitted
ometry of the rigid tricyclic di-
thienophosphole, with the two
thiophene moieties and the
phosphole unit in an anti con-
figuration (see Figure 1). The
À
À
À
À
for clarity. Selected bond lengths (Š): C1 C2: 1.380(3); C2 C3: 1.413(3); C3 C4: 1.385(3); C4 C5: 1.455(3);
À
À
À
À
À
À
C5 C6: 1.380(3); C6 C7: 1.412(3); C7 C8: 1.378(3); P1 C3: 1.811(2); P1 C6: 1.812(2); P1 C31: 1.809(3);
À
À
Si1 C1: 1.864(3); Si2 C8: 1.867(2).
high degree of p conjugation is apparent in the short single
bonds as well as in the elongated double bonds of the fused
ring systems. However, the bond shortening/elongation is
slightly more pronounced in 10b than in 1a[16a] presumably
due to the presence of the electron-accepting silyl groups in
10b and the oxygen substituent on the phosphorus atom.
The high degree of p conjugation is further supported by
the elongated bonds between the silicon atoms and the
and the shortened single bonds of the ring system, as well as
the elongated bonds between the silicon atoms and the
À
carbon atoms of the thiophene ring (Si1A C1A: 1.874(3) Š:
À
Si2A C8A: 1.870(4) Š). The slightly elongated bond be-
À
tween the two thiophene units (C4A C5A: 1.461(4) Š; cf.
1.440(2) Š for 1a[16a]), which is comparable to that in 10b, as
À
well as the shortened P C bonds, supports the electron-ac-
cepting nature of the phosphorus atom in 11.
À
carbon atoms of the thiophene ring (Si1 C1: 1.864(3) Š,
Reaction of 6 with the Lewis acid BH3 (used as
BH3·SMe2) in dichloromethane at room temperature afford-
ed the Lewis acid–base adduct 12 in quantitative yield.
À
À
À
Si1A C1A: 1.867(3) Š, Si2 C8: 1.867(2) Š, Si2A C8A:
À
1.873(2) Š). The somewhat elongated C4 C5 (1.455(3) Š)
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Synthesis and Properties of Dithienophospholes
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Figure 2. Molecular structure of 11 (50% probability level) in the solid
state. Hydrogen atoms and the second, more disordered, molecule are
Figure 3. Molecular structure of 13 (50% probability level) in the solid
state. Hydrogen atoms and three toluene solvent molecules are omitted
À
omitted for clarity. Selected bond lengths (Š): C1A C2A: 1.377(4);
À
À
for clarity. Selected bond lengths (Š): Pd1 Cl1: 2.3036(5); Pd1 P1:
À
À
À
À
C2A C3A: 1.406(4); C3A C4A: 1.381(4); C4A C5A: 1.461(4); C5A
À
À
À
À
2.3080(5); C2 C6; 1.382(3); C7 C11: 1.380(3); C6 C7: 1.448(3); C2 C3/
À
À
À
C6A: 1.378(4); C6A C7A: 1.413(4); C7A C8A: 1.375(4); Si1A C1A:
À
À
À
À
C10 C11: 1.415(3); C3 C4: 1.373(3); C9 C10: 1.377(3); C4 Si4:
À
À
À
1.874(3); Si2A C8A: 1.870(4); P1A C3A: 1.804(3); P1A C6A: 1.803(3);
À
À
À
À
1.875(2); C9 Si9: 1.879(2); P1 C2: 1.809(2); P1 C11: 1.8183(2); P1
C12: 1.822(2).
À
P1A C31A 1.810(3).
Again, the 31P NMR resonance is shifted downfield (d31P=
12.1 ppm) as a result of an increase in the acceptor proper-
ties of the phosphorus center, but not as much as that ob-
served for the phosphorus(v) species 10 and 11 in accor-
dance with the electronic nature of the Lewis adduct.[16a] The
11B NMR spectrum exhibits a resonance at d=À39.4 ppm
ment of the ring systems. The palladium atom exhibits a
À
near-perfect square-planar geometry and the Pd Cl
À
(2.3036(5) Š) and Pd P (2.3080(5) Š) bond lengths surpris-
ingly are almost similar. Whereas in known palladium-
À
À
phosphole complexes the Pd Cl and Pd P bonds usually
differ significantly[25–28] for steric reasons, a combination of
electronic and steric effects may cause the bond lengths in
13 to be similar. The phosphorus atom adopts a slightly dis-
torted tetrahedral geometry similar to related phosphole
complexes.[25–28] Consistent with the dithienophospholes
1
that is typical of phosphane–borane adducts[24] and the H
and 13C NMR data are comparable to related dithienophos-
pholes.[16a]
In order to investigate the ligand properties of the dithie-
nophosphole system, we reacted two equivalents of 6 with
one equivalent of [Pd(cod)Cl2] (cod=1,5-cyclooctadiene) in
CHCl3 at room temperature. The 31P NMR spectrum of 13
revealed the presence of two different species at d31P=1.5
and 8.9 ppm suggesting the generation of two isomers
(trans/cis) in a ratio of 3:1. By comparison with related bis-
phosphane palladium complexes, the low-field resonance
can be attributed to a cis-configured complex whereas the
1a,[16a] 10b, and 11, the lengths of the C C bonds of the
À
À
phosphole moiety show similar trends; that is, the C2 C6
À
(1.382(3) Š) and the C7 C11 bonds (1.380(3) Š) are again
elongated whereas the C6 C7 bond (1.448(3) Š) is short-
ened. The same is true for the bond lengths of the thiophene
À
À
À
subunits; the C2 C3/C10 C11 bonds of 1.415(3) Š each and
À
À
the C3 C4/C9 C10 bonds of 1.373(3)/1.377(3) Š correspond
to those of 1a,[16a] 10b, and 11, which supports the expected
degree of p conjugation in 13. The relatively long exohedral
1
high-field species correlates to the trans isomer.[25,26] The H
NMR data are unexceptional, but the 13C NMR data show a
noteworthy feature: most of the signals in the 13C NMR
spectrum exhibit a pseudotriplet splitting due to coupling to
two different phosphorus centers located on the same and
the adjacent dithienophosphole ligand.
Orange-red crystals of 13 suitable for an X-ray diffraction
study were obtained from a concentrated toluene solution at
room temperature. Similar to an earlier observation,[26] the
C Si bonds of 1.875(2) Š (C4 Si4) and 1.879(2) Š (C9 Si9)
again suggest extension of the p system to the silicon atoms,
supporting the importance of acceptor substituents in the
optimized electronic structures of the dithienophospholes.
À
À
À
À
À
The endohedral P C bond lengths of 1.809(2) Š for P1 C2
and 1.8183(2) Š for P1 C11 correspond to those observed
for 10b and 11 and reflect the change in the electronic
nature of the phosphorus atom now displaying a strong ac-
ceptor center.
À
structural data revealed
a
trans-complex geometry
(Figure 3), even though cis-[Pd(cod)Cl2] was used as the
starting material, supporting the NMR data for 13 in solu-
tion. Owing to an inversion center at the central palladium
atom, the two dithienophosphole ligands exhibit an anti con-
figuration (nearly C2h symmetry) with a coplanar arrange-
Optoelectronic properties: Dithienophospholes 6–13 exhibit
a strong blue photoluminescence. This feature has many po-
tential applications since the detection of fluorescence is
rapidly becoming the method of choice in materials science
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T. Baumgartner, L. Nyulµszi et al.
and optoelectronics and also in medical and environmental
studies.[29,30] Owing to its highly sensitive, selective, and safe
nature it allows, for example, the observation of living pro-
cesses and electronic transitions. Luminescence in materials
can reflect the delocalization and polarization of the elec-
tronic structure.[31] Therefore, changing the electronic struc-
ture of a material should affect its luminescence properties.
Any structural changes can easily be detected in the fluores-
cence phenomena and would allow dithienophospholes to
be used as sensory materials once a library for different de-
rivatives has been created.
lex =338 nm, lem =415 nm; 1b: lex =338 nm, lem =
408 nm),[16a] which reflects the effect of acceptor components
present in the system.
Oxidation of the phosphorus atom with oxygen or sulfur
increases the electron-accepting ability of the phosphorus
atom resulting in a redshift of about 30 nm for lex and about
40 nm for lem (10a/11: lex =374 nm, lem =460 nm). The
phosphole–borane adduct 12 shows maximum wavelengths
for excitation at 354 nm and emission at 432 nm, which lie
between the values for the s3,l3 species 6 and the oxidized
s4,l5 compounds 10a and 11, consistent with the electronic
nature of the Lewis acid–base pair and as anticipated from
31P NMR spectroscopy. The wavelength maxima for the pal-
ladium complex 13 show the strongest redshift (lex =384 nm,
lem =470 nm) which can be attributed to the electronic inter-
actions between the dithienophosphole ligand and the tran-
sition-metal center. Note that photoluminescence is only sig-
nificant when 13 is irradiated at the maximum excitation
wavelength (lex =384 nm). Irradiation at 365 nm results in
an almost negligible emission at 470 nm indicating a very
narrow window for the photoluminescence of 13.
Owing to the similar nature of oxygen and sulfur, com-
pounds 10a and 11 exhibit similar lex and lem. However, the
relative intensities of their emissions are significantly differ-
ent (ratio of ca. 8:1 for 10a/11) suggesting that fluorescence
is noticeably quenched by the soft sulfur substituent. This in-
dicates that the relative emission intensities detected by
fluorescence spectroscopy may well prove helpful to distin-
guish between closely related compounds. The relative emis-
sion intensities (with concentrations) of 6 and 10a–13 are
shown in Figure 4. By using compound 11 as a standard, the
intensity of the emission from 13 (at lex =384 nm) and 6 is
seen to be almost six times higher whereas compound 10a
shows much stronger fluorescence that amounts to approxi-
mately eight times the intensity of 11. The borane adduct 12
exhibits the strongest emission intensity being almost twelve
times stronger than that for 11. Note also that the photolu-
For this reason we have investigated the photolumines-
cence (PL) properties of eight representative systems involv-
ing a s3,l3-phosphorus center (6–9), one of two different
s4,l5-phosphorus centers (10a, 11),
a Lewis acid–base
adduct (12), or a transition-metal-substituted phosphorus
center (13). As expected, species with structurally different
phosphorus centers have different maximum wavelengths
for excitation (lex) and emission (lem) reflecting the elec-
tronic nature of the respective systems. Surprisingly, the
maximum wavelengths for emission from the s3,l3-phospho-
rus-containing systems 6–9 all appear at lem =422 nm,
whereas the wavelengths for excitation/absorption are signif-
icantly affected by different substituents. As a result lex ex-
periences a redshift upon introduction of a tert-butyl group
at the silyl centers (lex =364 nm for 8, lex =365 nm for 9; cf.
lex =344 nm for 6) which is consistent with the stronger +I
effect of the tert-butyl unit compared with the methyl
moiety. This effect is even more pronounced in 7 in which
the tert-butyl group is connected directly to the phosphorus
center with lex =372 nm (see Table 1). Complete removal of
the silyl functionalities, as in dithienophospholes 1a,b, on
the other hand, leads to a significant blueshift in the maxi-
mum wavelengths for excitation as well as emission (1a:
Table 1. Optical and electrochemical data for 1a,b, 6–13, 15, 16, and 18.
[c]
Compound lex
[nm][a]
lem
[nm][b]
lg(e/ dm3 molÀ1 cmÀ1
)
fPL
EPA
[V][d]
1a
338
336
334
344
350
372
364
365
374
374
374
397
355
358(0.41)
384
357
379
415
408
4.38
4.50
0.779 1.20
0.881 1.22
1b[e]
calcd
6
(0.2)[f]
4.26
422
0.604 1.35
calcd
7
8
(0.44)[f]
4.39
4.51
422
422
422
460
0.724 1.24
0.794
0.730
–
–
9
4.46
10a
calcd
11
calcd
12
calcd
13
15
4.09
0.556 1.59
(0.34)[f]
4.00
460
432
0.556 1.55
(0.1)[f]
4.10
0.545 1.54
[f]
470
427
463
4.03
4.42
4.40
–
0.614 1.42, 1.58
0.687
0.572
–
–
–
–
16
18
456, 502 555
[a] lmax for excitation in CH2Cl2. [b] lmax for emission in CH2Cl2. [c] Fluo-
rescence quantum yield (Æ10%) relative to quinine sulfate (0.1m H2SO4
solution); excitation at 365 nm. [d] Measured in CH2Cl2 versus SCE.
[e] See ref. [16a]. [f] Relative intensity.
Figure 4. Fluorescence emission spectra of 6 (c=5”0À5 m), 10a (c=1”
10À4 m), 11 (c=1”10À4 m), 12 (c=1”10À4 m), and 13 (c=3”10À5 m) with
the relative intensities shown.
4692
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Chem. Eur. J. 2005, 11, 4687 – 4699

Synthesis and Properties of Dithienophospholes
FULL PAPER
minescence quantum yields of all the investigated dithieno-
phosphole species are extraordinarily high ranging between
54 and almost 90% which is unprecedented for phos-
pholes[1f] or dithieno systems.[9,12,14] This behavior is possibly
related to the rigid structure of the anellated ring system
which reduces the probability of internal conversions.
These results strongly underline the supposition that the
dithienophosphole system is an excellent candidate for use
as optoelectronic material because it allows its electronic
properties to be fine-tuned in multiple ways to accommo-
date the needs of certain applications: Manipulation of the
electronic nature of the phosphorus center affords the most
significant shifts in the absorption and emission wavelengths
allowing the luminescence properties of the material to be
adjusted over a relatively broad range (~50 nm). In addi-
tion, functionalization of the thiophene unit, for example, as
shown here with silyl groups, represents another valuable
tool to further tune the luminescence properties of the
system—other functional groups could also be considered.
Very importantly, the optoelectronic properties can even be
fine-tuned by variation of the substituents at the phosphorus
and silicon centers. In this way only the maximum wave-
length for excitation (lex) can be tweaked to adjust the
Stokes shift of the material selectively since the wavelength
for emission (lem) remains unaffected in this case.
Figure 5. Frontier orbitals of the parent dithieno[3,2-b:2’,3’-d]phosphole
(top) and dithieno[3,2-b:2’,3’-d]cyclopentadiene (bottom).
thieno[3,2-b:2’,3’-d]phosphole should be described as an
entity. While the HOMO has a nodal plane through the
phosphorus atom and its substituent, the LUMOhas some
Theoretical calculations: To gain a deeper understanding of
the effects that influence the electronic structure of the di-
thieno[3,2-b:2’,3’-d]phospholes investigated, we have carried
out quantum chemical calculations. In order to study the
substituent effects systematically we have considered not
only the synthesized compounds, but we have also attached
the substituents to the ring system T in a stepwise manner.
À
contribution from the s*(P R1) orbital, and it is clear that it
will be affected by chemical modifications to this atom. The
À
LUMOof S2b has a smaller contribution from the s*(C
R1) orbital than its phosphorus analogue T1 (Figure 5). This
orbital is responsible for the tuning of the optoelectronic
properties that results from modification of the substituents
at the phosphorus atom.
The calculated structural parameters match the available
X-ray structural data closely. The data obtained for the
parent dithieno[3,2-b:2’,3’-d]phosphole are in accordance
with expectations. The bond lengths of the bithienyl frame-
work are similar to those of dithieno[3,2-b:2’,3’-d]cyclopen-
tadiene (S2b, E=CH2), indicating that the replacement of
the CH2 group by a PH unit results in only small changes to
À
The HOMO and LUMO of T1 are shown in Figure 5
(top). Both orbitals can easily be derived from the frontier
orbitals of both phosphole and thiophene and are also simi-
lar to the orbitals of dithieno[3,2-b:2’,3’-d]cyclopentadiene
(S2b, E=CH2) (Figure 5, bottom). The HOMO is an anti-
bonding combination of the thiophene moleculeꢁs HOMOs,
and at the phosphole ring, it is very similar to the phosphole
moleculeꢁs HOMO. The LUMO is a bonding combination
of the thiophene moleculeꢁs LUMOs, with some contribu-
the structure. In the C C framework the formal single
bonds in each ring shorten to 1.440 and 1.424 Š (cf. 1.459
and 1.430 Š for the phosphole and thiophene rings, respec-
tively), while the formal double-bond lengths increase to
1.385 Š each (cf. 1.356 and 1.367 Š for the phosphole and
the thiophene rings, respectively).
To assess the delocalization in the ring systems we have
calculated the Bird indices (BI)[32] which are used to mea-
sure the aromaticity in the ring, as judged by the alternation
of the bond lengths in all the T1–T4 derivatives. The maxi-
mum value of this index is set to 100 (e.g., in the case of
benzene in which there is no bond-length alternation).
Phosphole itself has a low Bird index of 47, while the thio-
phene BI value is 68. The Bird indices are somewhat higher
in the anellated system for both the phosphole (BI=53) and
*
tion from the sPH-MO, similar to the phosphole LUMO at
the central five-membered ring. The fact that both frontier
orbitals can easily be derived from the orbitals of the con-
stituent rings shows that the p system is well delocalized
over the entire molecule. Thus, none of the subunits of the
ring system dominates the electronic structure and the di-
Chem. Eur. J. 2005, 11, 4687 – 4699
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4693

T. Baumgartner, L. Nyulµszi et al.
thiophene (BI=71) rings, indicating that the delocalization
is extended in the dithieno[3,2-b:2’,3’-d]phospholes in agree-
ment with the previous conclusions obtained from the mo-
lecular orbitals. The Bird index of the cyclopentadienyl ring
in S2b (E=CH2) is lower than that of the phosphole ring
(BI=41), while it remains unaltered in the thienyl rings
(BI=72).
Phenyl substitution at the phosphorus atom of the phos-
phole ring results in negligible structural changes with the
calculated bond lengths matching the X-ray data almost ex-
actly.[16a] Silyl substitution at the thienyl rings also results in
only small structural changes. The effect of oxo and thiono
groups at the phosphorus atom is somewhat larger; the
exhibit semiconducting properties that would open up even
greater possibilities for applications in molecular electronics.
In order to probe the access to the desired extended p-
conjugated systems we initially targeted a synthetic protocol
that involves Stille coupling, which has successfully been uti-
lized in the synthesis of thiophene-containing polymers
before.[33] The required tin functionalization of the mono-
mers was achieved by reaction of 3,3’,5,5’-tetrabromo-2,2’-bi-
thiophene (3) with two equivalents each of nBuLi and tribu-
tyltin chloride in THF at À788C in a similar procedure to
that used in the synthesis of silyl-substituted species 4 and 5.
3,3’-Dibromo-5,5’-bis(tributyltin)-2,2’-bithiophene (14) was
obtained in 88% yield and can be treated with another two
equivalents of nBuLi in Et2Oat À788C in the presence of a
five-fold excess of TMEDA. The tin-functionalized dithieno-
phosphole 15 was obtained in fair yields (ca. 65%) after ad-
dition of PhPCl2 and subsequent filtration through neutral
alumina. Note, that one of the major byproducts of this re-
action is tetrabutyltin, which is presumably generated by nu-
cleophilic attack by nBuLi at the tin centers of 14. This side-
reaction can be suppressed to some extent by the addition
of TMEDA, which coordinates to the tin centers and thus
reduces the access of nBuLi. This observation, however, un-
derlines the leaving-group character of the tin group and
could be beneficial for the generation of extended p-conju-
gated moieties. The dithienophosphole 15 exhibits a 31P
NMR chemical shift at d=À28.0 ppm, which is in the same
range as those observed for the silyl-functionalized conge-
À
length of the C C bond opposite the phosphorus atom in
the five-membered ring is slightly lengthened upon oxida-
tion of the phosphorus atom either by oxygen (e.g., 1.454 Š
for T1=O) or sulfur (e.g., 1.451 Š for T1=S), while the exo-
À
cyclic P C bond lengths are shortened (e.g., 1.827 Š for
T1=O and 1.829 Š for T1=S), increasing somewhat the aro-
matic character of the phosphole ring (e.g., T1=O: BI=57;
À
T1=S: BI=56). (The increased bond order of the P C
bonds compensates the decrease in the bond order of the
À
C C bond.)
While the structural parameters of the substituted dithie-
no[3,2-b:2’,3’-d]phospholes investigated are similar, the
time-dependent (TD)-DFT-calculated optoelectronic prop-
erties show a much larger variance. This is in accordance
with the fact that substituents on the phosphorus atom have
a direct effect on its contribution to the LUMO. In accord-
1
ners 6, 8, and 9. The same is true for the H and 13C NMR
*
ance with the involvement of the sPH orbital in the dithie-
data of the tin-functionalized dithienophosphole 15.
no[3,2-b:2’,3’-d]phosphole LUMO, the calculated excitation
energy of T1 (324 nm) is lower than that of S2b (310 nm).
Further substitution by phenyl (at the phosphorus atom)
and by the trimethylsilyl groups lowers the excitation
energy. An even larger effect is caused by oxygen or sulfur
substitution at the phosphorus center; these substituents
lower the LUMOenergy considerably. The TD-DFT-calcu-
lated excitation energies show surprisingly good agreement
with the observed band maxima for all compounds for
which experimental data are available (see Table 1). Thus,
such computations are extremely helpful in predicting the
optoelectronic properties of dithieno[3,2-b:2’,3’-d]phos-
pholes.
However, the Stille-coupling protocol generally requires a
palladium catalyst, but the dithienophosphole system itself
is a suitable ligand for a palladium center (see 13) that
could potentially poison the catalyst and inhibit the catalytic
process. We therefore anticipated that it would be necessary
to protect the phosphorus center of the dithienophosphole
in order to achieve the desired cross-coupling reaction. We
decided to test the corresponding phosphole oxide 16, which
was synthesized by a similar procedure to that described for
the corresponding silyl-functionalized dithienophospholes
10a,b. The observed trend in the multinuclear NMR data of
16 corresponds to that of its silyl relatives with a 31P NMR
chemical shift at d31P=14.7 ppm, which is slightly shifted
upfield relative to that of 10a,b. The same is true for the op-
toelectronic properties of 15 and 16, which have wavelength
maxima that are almost similar to those of the silyl-function-
alized derivatives with a significant redshift of Dlex ꢀ20 nm
Synthesis of extended p-conjugated dithienophosphole sys-
tems: It would be of great advantage for future materials
applications to be able to exploit the favorable properties
possessed by macromolecules in terms of their processibility
(i.e., their ability to form thin films) as recently shown by
our group.[16a] For this reason, the intriguing results obtained
from the investigation of the optoelectronic properties of
the dithienophosphole monomers/model compounds stimu-
lated us to further explore the incorporation of the dithieno-
phosphole moiety into extended oligomeric or polymeric
materials. In this context, the synthesis of materials with an
exclusively p-conjugated backbone is of particular interest
as the resulting oligomers/polymers might be expected to
and Dlem ꢀ40 nm for 16 relative to 15 (lex =357 nm; lem
=
427 nm, see Table 1).
Preliminary cross-coupling reactions following a typical
Stille protocol were then performed by treating 16 in THF
or N-methylpyrrolidinone (NMP) with a mixture of [Pd-
(PPh3)4] and CuI as catalysts using 1,4-diiodo-2,5-bis-
(octyloxy)benzene 17 as the aryl halide component
(Scheme 3). The alkyloxy substituents of the diiodobenzene
were anticipated to aid the necessary solubility of the target-
ed materials. In the course of our work NMP was found to
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Chem. Eur. J. 2005, 11, 4687 – 4699

Synthesis and Properties of Dithienophospholes
FULL PAPER
379 nm; lem =463 nm). These
preliminary findings suggest
that extended p-conjugated di-
thienophosphole materials are
accessible by this route and
therefore optimization of the
reaction conditions is currently
undergoing detailed investiga-
tion.
Conclusions
Scheme 3. Synthesis and polymerization of tin-functionalized dithieno[3,2-b:2’,3’-d]phospholes.
In conclusion, we have synthe-
sized a novel class of phospho-
rus-based materials that are po-
be the solvent of choice for these experiments owing to its
high boiling point which allowed the cross-coupling reaction
to be performed at around 2008C, which is apparently es-
sential for the formation of longer chains. After two days, a
reddish-brown material was obtained after evaporation of
the solvent and precipitation from THF in hexane. The 31P
NMR spectrum of 18 revealed one very broad resonance at
d31P~14 ppm. This indicated the presence of only one phos-
phorus species and correlates well with a dithienophosphole
oxide. The formation of the desired product is further sup-
tentially very useful in molecular electronics. The very flexi-
ble protocol for the synthesis of the dithieno[3,2-b:2’,3’-
d]phosphole system allows access to a wide variety of differ-
ently functionalized species with intriguing optoelectronic
properties with respect to wavelength and intensity. Chemi-
cally facile modifications to the central phosphorus atom
allow the electronic structure of the system to be tuned very
efficiently. Further fine-tuning can be accomplished by the
proper choice of exocyclic substituents, which allows, for ex-
ample, selective manipulation of the absorption properties
of the material while the emission properties remain unaf-
fected thus modifying the Stokes shift in an efficient way.
The versatile tunability of the material opens up a multitude
of potential applications for dithienophospholes in molecu-
lar electronics, for example, as blue-light emitter material in
OLEDs/PLEDs, as sensory material, and as organic transis-
tor material (OTFT).
The theoretical investigations of the dithieno[3,2-b:2’,3’-
d]phosphole system have shown that this system has a
unique electronic structure that is derived from bithiophene,
but which is significantly influenced by the phosphorus
atom. Furthermore, the results emphasize the fact that struc-
tural changes to the system are governed by the occupied
orbitals. While these remain more or less unchanged, the op-
tical properties can be significantly influenced by the unoc-
cupied orbitals, particularly by the LUMO, which is sensitive
to substitution at the phosphorus center. Following from
this, several properties of the system can be simulated very
efficiently. Especially noteworthy is the ability of the time-
dependent DFT calculations to match the experimentally
observed UV absorptions almost perfectly. Hence this type
of theoretical calculation can be used to predict the opto-
electronic properties of unknown dithienophosphole species,
resulting in the “stream-lined” design of dithienophosphole
materials for use in molecular electronics.
1
ported by the H and 13C NMR spectra of 18 which exhibit
(broad) resonances due to the aryl and the alkyloxy moiet-
ies. Owing to the reduced solubility of the extended p-conju-
gated material in THF, we were unable to obtain an exact
molecular weight for 18 by GPC analysis, but the formation
of dithienophosphole-containing chains with a broad molec-
ular weight distribution is supported by the data. The suc-
cess of the cross-coupling step is further supported by the
optoelectronic properties of the material (see Figure 6). The
Figure 6. Normalized fluorescence spectra (excitation and emission) of 15
(b) and 18 (g) in CH2Cl2.
Our initial results obtained by using the Stille cross-cou-
pling protocol clearly indicate that it should be possible to
generate long chain, exclusively p-conjugated dithieno-
phosphole oligomers/polymers by this route. However, fur-
ther studies need to be performed to find the optimized re-
action conditions for this cross-coupling step. Functionalities
strongly extended p conjugation of 18 is evident in a very
significant redshift of the maximum wavelength for excita-
tion (lex =456, 502 nm) and an emission at lem =555 nm in
the yellow-green region of the optical spectrum (cf. 16: lex =
Chem. Eur. J. 2005, 11, 4687 – 4699
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4695

T. Baumgartner, L. Nyulµszi et al.
Table 2. Crystal data and structure refinement for 10b, 11, and 13.[a]
that enhance the solubility of
the material are required if the
targeted polymeric materials
10b
11
13·3C7H8
formula
C26H37OPS2Si2
516.83
C20H25PS3Si2
448.73
C40H50Cl2P2PdS4Si4·3C7H8
1287.04
123(2)
are to be analyzed comprehen- Mr
T [K]
110(2)
110(2)
sively. Good solubility (i.e.,
processability) is as important
for prospective applications in
organic or polymer-based light-
emitting diodes (OLED/PLED)
as a broad molecular weight
distribution. We are therefore
currently looking to vary the
l [Š]
0.71073
0.71073
triclinic
P1 (no.2)
10.839(2)
11.454(2)
19.428(4)
96.41(3)
0.71073
triclinic
crystal system
space group
a [Š]
b [Š]
c [Š]
monoclinic
P(2)1/c (no.14)
14.411(5)
12.392(4)
32.359(11)
90
¯
¯
P1 (no.2)
8.6369(2)
12.7335(3)
15.2681(4)
99.497(1)
99.985(1)
94.185(1)
1622.11(7)
1.318
a [8]
b [8]
g [8]
97.101(9)
90
94.33(3)
91.16(3)
aryl halide component and V [Š3]
5734(4)
1.197
2389.2(8)
1.248
1calcd [MgmÀ3
]
other solubilizing groups as
well as investigating the Suzuki
cross-coupling protocol as an
alternative way to access these
intriguing materials.
Z
8
4
1
m [mmÀ1
F(000)
]
0.342
2208
0.481
944
0.657
670
crystal size [mm3]
q range [8]
index ranges
0.41”0.37”0.13
1.27–27.60
À18ꢁhꢁ18
À12ꢁkꢁ16
À41ꢁlꢁ42
43144
13228 (R(int)=0.0515)
27.60 (99.6%)
empirical
0.959/0.937
13228/0/577
1.047
0.44”0.17”0.06
1.06–28.38
À14ꢁhꢁ14
À15ꢁkꢁ15
À25ꢁlꢁ25
30361
11887 (R(int)=0.0434)
28.38 (99.2%)
empirical
0.9717/0.8163
11887/72/469
1.037
0.50”0.40”0.30
2.75–25.00
À9ꢁhꢁ10
À15ꢁkꢁ15
À18ꢁlꢁ18
19257
5709 (R(int)=0.0317)
25.00 (99.8%)
none
reflections collected
independent reflections
completeness to q [8]
absorption correction
max./min. transmission
data/restraints/parameters
GOF on F2
Experimental Section
Calculations: Theoretical calculations
were carried out at the B3LYP/6-31G*
level by using the Gaussian 98 suite of
programs:[34] This level of theory has
provided satisfactory results for the
phosphole–thiophene oligomers befor-
e.[1f] The geometries were fully opti-
mized and second derivatives were cal-
culated for the resulting structures.
Only positive eigenvalues of the Hessi-
an matrix were obtained, proving that
all the structures obtained are real
–
5709/60/322
1.060
final R indices [I>2s(I)]
R indices (all data)
largest diff. peak/hole [eŠ
[a] The refinement method was full-matrix least-squares on F2 for all three compounds.
R1 =0.0478, wR2 =0.1124 R1 =0.0601, wR2 =0.1487 R1 =0.0270, wR2 =0.0704
R1 =0.0683, wR2 =0.1261 R1 =0.0912, wR2 =0.1673 R1 =0.0328, wR2 =0.0725
À3
]
0.518/À0.316
1.158/À0.921
1.047/À0.688
methods (SHELXTL) and refined on F2 by full-matrix least-squares tech-
niques. Hydrogen atoms were included by using a riding model.
minima on the potential-energy hypersurface. The vertical excitation en-
ergies were calculated for the optimized structures by the time-depen-
dent (TD) density functional method by using the B3LYP functional and
the 6-31G* basis set.
CCDC 263187 (10b), 263186 (11), and 262991 (13) contain the supple-
mentary crystallographic data for this paper. These data can be obtained
free of charge from the Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
The Bird index was calculated according to the original procedure of
Bird.[32] However, when the Gordy equation[35] was used to obtain bond
orders from the calculated bond lengths we used the “a” and “b” con-
stants developed from the B3LYP/6-31G* optimized single- and double-
bonded molecules (e.g., for the C C bond we used ethane and ethylene
with bond orders of one and two, respectively).
Synthesis of 5: nBuLi (8 mL, 20 mmol) was added dropwise to a solution
of 3 (4.82 g, 10 mmol) in THF (100 mL) at À788C. The solution was stir-
red for 15 min at À788C and tert-butyldimethylsilyl chloride (3.01 g,
20 mmol) dissolved in THF (10 mL) was added dropwise to the reaction
mixture at that temperature. The reaction mixture was allowed to warm
slowly to room temperature and the solvent was subsequently removed
under vacuum. The residue was taken up in pentane (ca. 60 mL) and fil-
tered through neutral alumina. Evaporation of the solvent under vacuum
provided 5 as beige solid (5.1 g, 93% yield).
1H NMR (500 MHz, CDCl3): d=7.15 (s; Ar-H), 0.95 (s, 18H; Si-tBu),
0.31 ppm (s, 12H; SiMe3); 13C{1H} NMR (125.7 MHz, CDCl3): d=140.7
(s; Ar-Ar), 137.0 (s; Ar-H), 134.2 (s; Ar-Si), 112.8 (s; Ar-Br), 26.3 (s; SiC-
(CH3)3), 16.0 (s; SiC(CH3)3), À5.2 ppm (s; SiMe2); MS (70 eV, EI): m/z
(%): 552 (30) [M+], 495 (100) [M+ÀC4H9], 73 (25) [SiMe3+].
Synthesis of 6 and 7: nBuLi (4 mL, 10 mmol) was added dropwise to a so-
lution of 4 (2.34 g, 5 mmol) in Et2O(50 mL) at À788C. The solution was
stirred for 1 h before the temperature was raised to approximately
À308C. Subsequently, RPCl2 (R=Ph: 0.90 g, 5 mmol; R=tBu: 0.80 g,
5 mmol), dissolved in Et2O(5 mL), was added slowly to the reaction mix-
ture which was allowed to warm quickly to room temperature. The sol-
vent was then removed under vacuum, and the residue taken up in n-
hexane (ca. 50 mL) and filtered through neutral alumina to remove LiCl
and some brown impurities. The filtrate was evaporated to dryness and 6
À
General procedures: Reactions were carried out in dry glassware and
under inert atmosphere of purified argon by using Schlenk techniques.
Solvents were dried over appropriate drying agents and then distilled.
nBuLi (2.5m in hexane), H2O2 (30% in H2O), sulfur, BH3·SMe2 (1m in
CH2Cl2), and tBuMe2SiCl were used as received. Liquid reagents
(PhPCl2, Bu3SnCl, and TMEDA) were freshly distilled prior to use.
3,3’,5,5’-Tetrabromo-2,2’-bithiophene (3),[36] 5,5’-bis(trimethylsilyl)-3,3’-di-
bromo-2,2’-bithiophene (4),[9a] RPCl2 (R=tBu[37] and 4-tBuC6H4[38]), [Pd-
(cod)Cl2],[39] and 1,4-diiodo-2,5-bis(octyloxy)benzene (18)[40] were pre-
pared by methods reported in the literature. 1H, 13C, 31P, and 11B NMR
spectra were recorded with a Bruker DRX 400, Varian Mercury 200 or
Unity 500 MHz-spectrometer. Chemical shifts are referenced to external
85% H3PO4 (31P), BF3·Et2O (11B) or TMS (13C, 1H). Electron ionization
(70 eV) mass spectra were recorded with a Finnigan 8230 spectrometer.
Elemental analyses were performed by the Microanalytical Laboratory
of the Institut für Anorganische und Analytische Chemie, Johannes Gu-
tenberg-Universität, Mainz. Crystal data and details of the data collection
are provided in Table 2. Diffraction data for 10a and 11 were collected
with a Bruker SMART D8 goniometer with an APEX CCD detector and
for 13 on a Nonius KappaCCD. The structures were solved by direct
4696
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2005, 11, 4687 – 4699

Synthesis and Properties of Dithienophospholes
FULL PAPER
and 7 were obtained as off-white solids (R=Ph: 1.50 g, 72% yield; R=
tBu: 1.43 g, 72% yield).
MS (70 eV, EI): m/z (%): 432 (100) [M+], 417 (55) [M+ÀMe], 73 (40)
[SiMe3+]; elemental analysis calcd (%) for C20H25OPS2Si2 (432.7): C
55.52, H 5.82, S 14.82; found: C 55.63, H 5.82, S 15.51.
1
Compound 6: 31P{1H} NMR (162 MHz, CDCl3): d=À25.0 ppm; H NMR
Compound 10b: 31P{1H} NMR (80.9 MHz, CDCl3): d=14.9 ppm; 1H
NMR (400 MHz, CDCl3): d=7.67 (dd, 3J(H,P)=13.5, 3J(H,H)=7.5 Hz,
2H; o-Ph), 7.45 (td, 3J(H,H)=7.5, 4J(C,P)=1.9 Hz, 1H; p-Ph), 7.36 (td,
(400 MHz, CDCl3): d=7.34 (br, 2H; o-Ph), 7.26 (br, 2H; m-Ph), 7.25 (br,
1H; p-Ph), 7.20 (s, 2H; Ar-H), 0.30 ppm (s, 18H; Si(CH3)3); 13C{1H}
NMR (100.6 MHz, CDCl3): d=148.6 (d, 2J(C,P)=9.6 Hz; Ar), 146.7 (br;
Ar), 142.6 (d, J(C,P)=2.1 Hz; Ar), 133.9 (d, 1J(C,P)=15.5 Hz; ipso-Ph),
133.0 (d, 2J(C,P)=18.3 Hz; o-Ar), 132.4 (d, 2J(C,P)=20.3 Hz; o-Ar),
3
2
3J(H,H)=7.8, J(H,P)=3.3 Hz, 2H; m-Ph), 7.12 (d, J(H,P)=2.2 Hz, 2H;
Ar-H), 0.83 (s, 18H; Si-tBu), 0.20 (s, 6H; SiMe2), 0.19 ppm (s, 6H;
SiMe2); 13C{1H} NMR (100.6 MHz, CDCl3): d=150.9 (d, J(C,P)=
23.7 Hz; Ar), 142.8 (d, J(C,P)=10.7 Hz; Ar), 139.5 (d, 1J(C,P)=
108.3 Hz; ipso-Ar), 133.2 (d, 2J(C,P)=13.7 Hz; o-Ar), 132.2 (d, 4J(C,P)=
3.8 Hz; p-Ph), 130.9 (d, J(C,P)=11.4 Hz; m-Ar), 130.1 (d, 1J(C,P)=
105.3 Hz; ipso-Ph), 128.7 (d, 2J(C,P)=13.7 Hz; o-Ar), 26.3 (s; SiC-
(CH3)3), 16.9 (s; SiC(CH3)3), À4.8 (s; SiMe), À4.9 ppm (s; SiMe); ele-
mental analysis calcd (%) for C26H37OPS2Si2 (516.9): C 60.42, H 7.11, S
12.41; found: C 60.73, H 7.13, S 12.85.
3
129.0 (s; p-Ph), 128.5 (d, J(C,P)=7.8 Hz; m-Ph), À0.2 ppm (s; SiC3); MS
(70 eV, EI): m/z (%): 416 (80) [M+], 73 (100) [SiMe3+]; elemental analy-
sis calcd (%) for C20H25PS2Si2 (416.7): C 57.65, H 6.05, S 15.39; found: C
57.68, H 5.93, S 15.40.
Compound 7: 31P{1H} NMR (162 MHz, CDCl3): d=0.3 ppm; 1H NMR
(400 MHz, CDCl3): d=7.16 (s, 2H; Ar-H), 1.03 (d, 3J(H,P)=13.7 Hz,
9H; C(CH3)3), 0.31 ppm (s, 18H; Si(CH3)3); 13C{1H} NMR (100.6 MHz,
CDCl3): d=147.3 (d, 2J(C,P)=15.9 Hz; Ar), 147.0 (d, 1J(C,P)=35.4 Hz;
Ar), 141.6 (d, J(C,P)=3.7 Hz; Ar), 133.3 (d, 2J(C,P)=16.4 Hz; o-Ar),
32.3 (d, 1J(C,P)=12.4 Hz; CMe3), 27.5 (d, 2J(C,P)=14.3 Hz; C(CH3)3),
À0.1 ppm (s, SiC3); elemental analysis calcd (%) for C20H25PS2Si2 (396.7):
C 54.50, H 7.37, S 16.17; found: C 55.80, H 7.60, S 15.78.
Synthesis of 11: Elemental sulfur (100 mg, 3.1 mmol) was added to a solu-
tion of 6 (1.25 g, 3 mmol) in THF (20 mL) at room temperature and the
reaction mixture was stirred for 16 h. Subsequently, the solvent was re-
moved under vacuum and the residue taken up in warm hexane (10 mL).
Slow evaporation of the solvent provided 11 as yellow crystals (1.24 g,
92% yield).
Synthesis of 8 and 9: nBuLi (4 mL, 10 mmol) was added dropwise to a
solution of 5 (2.78 g, 5 mmol) and TMEDA (1.51 mL, 10 mmol) in Et2O
(50 mL) at À788C. The solution was stirred for 1 h before the tempera-
ture was raised to ca. À308C. Subsequently, RPCl2 (R=Ph: 0.90 g,
5 mmol; R=4-tBuPh: 1.18 g, 5 mmol), dissolved in Et2O(10 mL), was
added slowly to the reaction mixture and the resulting mixture was al-
lowed to warm quickly to room temperature. The solvent was then re-
moved under vacuum, the residue taken up in pentane (ca. 60 mL) and
filtered to remove LiCl. The filtrate was concentrated and left to crystal-
lize at À308C. Compounds 8 and 9 were obtained as white amorphous
solids (8: 2.0 g, 81% yield; 9: 2.2 g, 78% yield).
Compound 8: 31P{1H} NMR (80.9 MHz, CDCl3): d=À27.4 ppm; 1H
NMR (500 MHz, CDCl3): d=7.38 (m, 2H; o-Ph), 7.30 (m, 3H; Ph-H),
7.26 (s, 2H; Ar-H), 0.94 (s, 18H; Si-tBu), 0.32 (s, 6H; SiMe2), 0.31 ppm
(s, 6H; SiMe2); 13C{1H} NMR (125.7 MHz, CDCl3): d=148.7 (d, 1J
(C,P)=9.7 Hz; ipso-Ar), 147.0 (d, J(C,P)=3.2 Hz; Ar), 139.8 (d, J(C,P)=
4.3 Hz; Ar), 134.3 (d, 2J(C,P)=18.3 Hz; o-Ar), 134.2 (d, 1J(C,P)=
15.0 Hz; ipso-Ph), 132.5 (d, 2J(C,P)=20.4 Hz; o-Ar), 129.1 (s; p-Ph),
128.5 (d, 3J(C,P)=8.6 Hz; m-Ph), 26.4 (s; SiC(CH3)3), 17.0 (s; SiC(CH3)3),
À4.9 ppm (s; SiMe2); elemental analysis calcd (%) for C26H37PS2Si2
(500.9): C 62.35, H 7.45, S 12.80; found: C 62.75, H 7.28, S 12.76.
Compound 9: 31P{1H} NMR (80.9 MHz, CDCl3): d=À28.2 ppm; 1H
NMR (500 MHz, CDCl3): d=7.30 (br, 2H; Ar-H), 7.27 (br, 2H; Ar-H),
7.24 (br, 2H; Ar-H), 1.26 (s, 9H; C(CH3)3), 0.92 (s, 18H; Si-tBu), 0.29 (s,
6H; SiMe2), 0.28 ppm (s, 6H; SiMe2); 13C{1H} NMR (125.7 MHz,
CDCl3): d=152.3 (s; p-Ar), 148.8 (d, J(C,P)=10.7 Hz; Ar), 146.8 (d, J
(C,P)=2.1 Hz; Ar), 139.5 (d, J(C,P)=4.3 Hz; Ar), 134.5 (d, 2J(C,P)=
18.3 Hz; o-Ar), 132.3 (d, 2J(C,P)=21.5 Hz; o-Ar), 130.4 (d, 1J(C,P)=
14.0 Hz; ipso-Ar), 125.7 (d, 3J(C,P)=6.4 Hz; m-Ar), 34.1 (s; CMe3), 31.2
(s; C(CH3)3), 26.4 (s; SiC(CH3)3), 17.0 (s; SiCMe3), À4.8 (s; SiMe),
À4.9 ppm (s; SiMe); elemental analysis calcd (%) for C30H45PS2Si2
(557.0): C 64.70, H 8.14, S 11.51; found: C 65.03, H 8.96, S 10.76.
31P{1H} NMR (162.0 MHz, CDCl3): d=23.6 ppm; 1H NMR (400 MHz,
CDCl3): d=7.78 (br, 2H; o-Ph), 7.47 (br, 1H; p-Ph), 7.38 (br, 2H; m-
Ph), 7.17 (d, 2J(H,P)=2.3 Hz, 2H; Ar-H), 0.28 ppm (s, 18H; Si(CH3)3);
13C{1H} NMR (100.6 MHz, CDCl3): d=148.9 (d, J(C,P)=21.1 Hz; Ar),
145.9 (d, J(C,P)=11.1 Hz; Ar), 143.2 (d, 1J(C,P)=90.8 Hz; ipso-Ar),
4
2
131.8 (d, J(C,P)=3.2 Hz; p-Ph), 131.3 (d, J(C,P)=14.1 Hz; o-Ar), 130.7
(d, 2J(C,P)=12.4 Hz; o-Ar), 129.9 (d, 1J(C,P)=84.0 Hz; ipso-Ph), 128.6
(d, 3J(C,P)=13.4 Hz; m-Ph), À0.4 ppm (s; SiC3); MS (70 eV, EI): m/z
(%): 448 (100) [M+], 433 (10) [M+ÀMe], 371 (85) [M+ÀPh], 73 (30)
[SiMe3+]; elemental analysis calcd (%) for C20H25PS3Si2 (448.8): C 53.53,
H 5.62, S 21.44; found: C 53.52, H 5.52, S 21.09.
Synthesis of 12: BH3·SMe2 (3.3 mL, 3.3 mmol) was added to a solution of
6 (1.25 g, 3 mmol) in CH2Cl2 (20 mL) at room temperature and the reac-
tion mixture was stirred for 1 h. Subsequently, all volatile materials were
removed under vacuum to provide 12 as yellowish crystals (1.28 g, 99%
yield).
31P{1H} NMR (162.0 MHz, CDCl3): d=12.1 ppm (br); 11B{1H} NMR
(128.4 MHz, CDCl3): d=À39.4 ppm; 1H NMR (400 MHz, CDCl3): d=
7.60 (dd, 3J(H,P)=11.7, 3J(H,H)=7.5 Hz, 2H; o-Ph), 7.50 (brt, 3J
(H,H)=7.5 Hz, 1H; p-Ph), 7.36 (brt, 3J(H,H)=7.5 Hz, 2H; m-Ph), 7.17
(d, 3J(H,P)=1.1 Hz, 2H; Ar-H), 1.1 (very broad, 3H; BH3), 0.30 ppm (s,
18H; Si(CH3)3); 13C{1H} NMR (100.6 MHz, CDCl3): d=149.7 (d,
J
(C,P)=11.5 Hz; Ar), 145.4 (d, J(C,P)=8.7 Hz; Ar), 140.5 (d, 1J(C,P)=
59.6 Hz; ipso-Ar), 132.1 (d, 2J(C,P)=14.3 Hz; o-Ar), 131.8 (d, 2J(C,P)=
10.9 Hz; o-Ar), 131.6 (s; p-Ph), 130.1 (d, 1J(C,P)=94.1 Hz; ipso-Ar),
128.8 (d, 3J(C,P)=10.6 Hz; m-Ph), À0.3 ppm (s; SiC3); MS (70 eV, EI):
m/z (%): 430 (8) [M+], 416 (100) [M+ÀBH3], 73 (25) [SiMe3+]; elemen-
tal analysis calcd (%) for C20H28BPS2Si2 (430.5): C 55.80, H 6.56, S 14.90;
found: C 55.92, H 6.57, S 14.89.
Synthesis of 13: [Pd(cod)Cl2] (0.12 g, 0.4 mmol) was added to a solution
of 6 (0.34 g, 0.8 mmol) in CHCl3 (30 mL) at room temperature and stir-
red for another 30 min. Subsequent evaporation of all volatiles under
vacuum provided 13 as a yellow powder in quantitative yield (0.40 g,
99%). Recrystallization from toluene provided orange crystals suitable
for X-ray structure analysis.
31P{1H} NMR (162.0 MHz, CDCl3): d=1.5 ppm (8.9 (0.3 equiv)); 1H
NMR (400 MHz, CDCl3): d=7.78 (brm, 2H; o-Ph), 7.69 (br, 2H; m-Ph)
(6.70 (0.3 equiv)), 7.33–7.22 (brm, 3H; Ar), 0.30 ppm (s, 18H; Si(CH3)3)
(0.24 (0.3 equiv)); 13C{1H} NMR (100.6 MHz, CDCl3): d=148.7 (t, 2J
(C,P)=7.5 Hz; Ar), 143.3 (br; Ar), 139.9 (t, J(C,P)=26.5 Hz; Ar), 135.8
(t, 1J(C,P)=5.6 Hz; Ar), 132.9 (dd, 1J(C,P)=311.9, 17.1 Hz; ipso-Ar),
132.7 (d, J(C,P)=7.2 Hz; Ar), 130.6 (s; p-Ph), 128.6 (t, 3J(C,P)=5.6 Hz;
m-Ph), À0.2 ppm (s; SiC3); elemental analysis calcd (%) for
C40H50Cl2P2PdS4Si4 (1010.7): C 47.53, H 4.99, S 12.69; found: C 47.65, H
4.94, S 13.14.
Synthesis of 10: Hydrogen peroxide (0.5 g, 3.3 mmol, 30% solution in
H2O) was added to a solution of 6 (1.25 g, 3 mmol) or 8 (1.50 g, 3 mmol)
in THF (20 mL) at room temperature. The reaction mixture was stirred
for 16 h. Subsequently, all volatile materials were removed under vacuum
and the residue taken up in warm hexane (10 mL). Slow evaporation of
the solvent provided 10a as light yellow crystals and 10b as colorless
crystals (10a: 1.23 g, 95% yield; 10b: 1.50 g, 97% yield).
Compound 10a: 31P{1H} NMR (162.0 MHz, CDCl3): d=17.2 ppm; 1H
NMR (400 MHz, CDCl3): d=7.73 (dd, 3J(H,P)=13.4, 3J(H,H)=7.4 Hz,
2H; o-Ph), 7.50 (td, 3J(H,H)=7.4, 4J(C,P)=2.0 Hz, 1H; p-Ph), 7.40 (td,
3
2
3J(H,H)=7.8, J(H,P)=3.1 Hz, 2H; m-Ph), 7.16 (d, J(H,P)=2.1 Hz, 2H;
Ar-H), 0.28 ppm (s, 18H; Si(CH3)3); 13C{1H} NMR (100.6 MHz, CDCl3):
d=150.6 (d, J(C,P)=24.9 Hz; Ar), 145.5 (d, J(C,P)=11.0 Hz; Ar), 140.7
(d, 1J(C,P)=108.6 Hz; ipso-Ar), 132.1 (s; p-Ph), 132.0 (d, 2J(C,P)=
13.0 Hz; o-Ar), 130.8 (d, 3J(C,P)=11.4 Hz; m-Ph), 129.9 (d, 1J(C,P)=
2
107.5 Hz; ipso-Ph), 128.6 (d, J(C,P)=13.0 Hz; o-Ar), À0.3 ppm (s; SiC3);
Chem. Eur. J. 2005, 11, 4687 – 4699
www.chemeurj.org
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4697

T. Baumgartner, L. Nyulµszi et al.
Synthesis of 14: nBuLi (8 mL, 20 mmol) was added dropwise to a solu-
tion of 3,3’-5,5’-tetrabromobithiophene (3) (4.82 g, 10 mmol) in THF
(100 mL) at À788C. The solution was stirred for 15 min at À788C and
then tributyltin chloride (6.51 g, 20 mmol) was added dropwise to the re-
action mixture at that temperature. The reaction mixture was allowed to
warm slowly to room temperature and the solvent was subsequently re-
moved under vacuum. The residue was taken up in pentane (ca. 60 mL)
and filtered through neutral alumina. Evaporation of the volatiles under
vacuum at elevated temperatures provided 14 as an orange oil (7.2 g,
88% yield).
hexane and the residue dried under vacuum to yield 18 as a reddish
brown powder (1.1 g).
31P{1H} NMR (202.3 MHz, C2D2Cl4): dꢀ14 ppm; 1H NMR (500 MHz,
C2D2Cl4): d=7.64–6.90 (br; Ar-H), 3.95 (br; OCH2), 1.71–0.88 ppm
(brm; alkyl-H); 13C{1H} NMR (125.6 MHz, C2D2Cl4): d=155.6, 144.0,
142.1, 130.5, 128.4 (br; CAr), 69.6 (br; OCH2), 31.6, 29.1, 26.6, 26.1, 22.5,
14.1, 13.5 ppm (Calkyl).
1H NMR (500 MHz, CDCl3): d=7.04 (s/d, 2J(H,Sn117/119)=21.4 Hz, 2H;
Ar-H), 1.58 (m, 12H; CH2), 1.35 (m, 12H; CH2), 1.13 (m, 12H; CH2-Sn),
0.91 ppm (t, 18H; CH3Bu); 13C{1H} NMR (125.6 MHz, CDCl3): d=139.7
(s; Ar-Ar), 138.1 (s/d, 2J(C,Sn117/119)=21.1 Hz; Ar-H), 134.6 (s; Ar-Sn),
112.8 (s; Ar-Br), 28.9 (s/d, J(C,Sn117/119)=21.1 Hz; CH2), 27.2 (s/d,
J(C,Sn117/119)=59.5 Hz; CH2), 13.6 (s; CH3), 11.0 ppm (s/d, J(C,Sn117/119)=
348.0 Hz; CH2Sn); MS (70 eV, EI): m/z (%): 902 (25) [M+], 844 (60)
[M+ÀBu], 313 (100) [C8H18BrSn+], 57 (50) [Bu+].
Synthesis of 15: nBuLi (1.6 mL, 4 mmol) was added dropwise to a solu-
tion of 14 (1.80 g, 2 mmol) and TMEDA (1.51 mL, 10 mmol) in Et2O
(50 mL) at À788C. Subsequently, PhPCl2 (0.36 g, 2 mmol), dissolved in
Et2O(10 mL), was slowly added to the reaction mixture and the resulting
suspension was allowed to warm quickly to room temperature. The sol-
vent was then removed under vacuum, and the residue taken up in pen-
tane (ca. 60 mL) and filtered through neutral alumina to remove LiCl
and some brown impurities. The filtrate was evaporated to dryness at ele-
vated temperatures and 15 was obtained as orange-brown oil (1.05 g,
62% yield).
31P{1H} NMR (80.9 MHz, CDCl3): d=À28.0 ppm; 1H NMR (500 MHz,
CDCl3): d=7.39 (br, 2H; o-Ph), 7.28 (br, 3H; m,p-Ph), 7.17 (s/d,
2J(C,Sn117/119)=20.7 Hz, 2H; Ar-H), 1.55 (m, 12H; CH2), 1.34 (m, 12H;
CH2), 1.13 (m, 12H; CH2Sn), 0.90 ppm (t, 18H; CH3); 13C{1H} NMR
(125.6 MHz, CDCl3): d=148.0 (d, 1J(C,P)=10.5 Hz; ipso-Ar), 147.5 (d,
2J(C,P)=2.5 Hz; Ar-Ar), 138.7 (d, 3J(C,P)=2.8 Hz; Ar-Sn), 134.6 (d, s/d,
3J(C,P)=18.2, 2J(C,Sn117/119)=18.4 Hz; Ar-H), 134.9 (d, 1J(C,P)=16.3 Hz;
ipso-Ph), 132.5 (d, 1J(C,P)=18.2 Hz; o-Ph), 128.7 (s; p-Ph), 128.6 (d, 4J
(C,P)=6.7 Hz; m-Ph), 29.0 (s; CH2), 27.3 (s; CH2), 13.7 (s; CH3),
11.0 ppm (s; CH2Sn); 119Sn{1H} NMR (186.3 MHz, CDCl3): d=
À36.7 ppm; elemental analysis calcd (%) for C38H61PS2Sn2 (850.4): C
53.67, H 7.23, S 7.54; found: C 53.28, H 7.17, S 8.56.
Acknowledgements
The authors would like to thank Prof. Dr. J. Okuda for his generous sup-
port of this work. Financial support from the Fonds der Chemischen In-
dustrie, BMBF, and from OTKA (Grant No. T 034675 and D 042216) is
gratefully acknowledged. We thank Prof. Dr. U. Englert for the X-ray
data collection and helpful discussions, Prof. Dr. U. Kçlle for his assis-
tance with the cyclovoltammetry, and A. Bartole-Scott (University of
Toronto) for the GPC analyses. T.K. and L.N. acknowledge the generous
allocation of computer time from NIIF/Hungary.
[1] a) F. Mathey, Angew. Chem. 2003, 115, 1616; Angew. Chem. Int. Ed.
2003, 42, 1578; b) Z. Jin, B. L. Lucht, J. Organomet. Chem. 2002,
653, 167; c) C.-W. Tsang, M. Yam, D. P. Gates, J. Am. Chem. Soc.
2003, 125, 1480; d) C.-W. Tsang, B. Baharloo, D. Riendl, M. Yam,
D. P. Gates, Angew. Chem. 2004, 116, 5800; Angew. Chem. Int. Ed.
2004, 43, 5682; e) R. C. Smith, J. D. Protasiewicz, J. Am. Chem. Soc.
2004, 126, 2268; f) C. Hay, M. Hissler, C. Fischmeister, J. Rault-Ber-
thelot, L. Toupet, L. Nyulµszi, R. RØau, Chem. Eur. J. 2001, 7, 4222.
[2] See, for example: a) Handbook of Oligo- and Polythiophenes (Ed.:
D. Fichou), Wiley-VCH, Weinheim, 1998; b) Conjugated Conducting
Polymers, Vol. 102 (Ed.: H. Kiess), Springer, New York, 1992.
[3] G. Tourillion, “Polythiophene and its Derivatives” in Handbook of
Conducting Polymers (Ed.: T. A. Skotheim), Marcel Dekker, New
York, 1986.
[4] a) C. Hay, C. Fischmeister, M. Hissler, L. Toupet, R. RØau, Angew.
Chem. 2000, 112, 1882; Angew. Chem. Int. Ed. 2000, 39, 1812; b) C.
Hay, D. Le Vilain, V. Deborde, L. Toupet, R. RØau, Chem.
Commun. 1999, 345; c) C. Fave, T.-Y. Cho, M. Hissler, C.-W. Chen,
T.-Y. Luh, C.-C. Wu, R. RØau, J. Am. Chem. Soc. 2003, 125, 9254;
d) C. Fave, M. Hissler, T. Kµrpµti, J. Rault-Berthelot, V. Deborde, L.
Toupet, L. Nyulµszi, R. RØau, J. Am. Chem. Soc. 2004, 126, 6058.
[5] a) D. Delaere, M. T. Nguyen, L. G. Vanquickenborne, Phys. Chem.
Chem. Phys. 2002, 4, 1522; b) D. Delaere, M. T. Nguyen, L. G. Van-
quickenborne, J. Phys. Chem. A 2003, 107, 838; c) J. Ma, S. Li, Y.
Jiang, Macromolecules 2002, 35, 1109.
[6] a) E. Deschamps, L. Ricard, F. Mathey, Angew. Chem. 1994, 106,
1214; Angew. Chem. Int. Ed. Engl. 1994, 33, 1158; b) M.-O. BØv-
ierre, F. Mercier, L. Ricard, F. Mathey, Angew. Chem. 1990, 102,
672; Angew. Chem. Int. Ed. Engl. 1990, 29, 655.
[7] a) S. S. H. Mao, T. D. Tilley, Macromolecules 1997, 30, 5566; b) Y.
Morisaki, Y. Aiki, Y. Chujo, Macromolecules 2003, 36, 2594.
[8] J. Roncali, Chem. Rev. 1997, 97, 173.
[9] a) J. Ohshita, M. Nodono, H. Kai, T. Watanabe, A. Kunai, K. Koma-
guchi, M. Shiotani, A. Adachi, K. Okita, Y. Harima, K. Yamashita,
M. Ishikawa, Organometallics 1999, 18, 1453; b) J. Ohshita, T.
Sumida, A. Kunai, A. Adachi, K. Sakamaki, K. Okita, Macromole-
cules 2000, 33, 8890; c) J. Ohshita, H. Kai, T. Sumida, A. Kunai, A.
Adachi, K. Sakamaki, K. Okita, J. Organomet. Chem. 2002, 642,
137.
Synthesis of 16: Hydrogen peroxide (0.5 g, 3.3 mmol, 30% solution in
H2O) was added to a solution of 15 (2.55 g, 3 mmol) in THF (20 mL) at
room temperature. The reaction mixture was stirred for 3 h. Subsequent-
ly, all volatile materials were removed under vacuum and the residue
taken up in pentane and filtered through neutral alumina. Evaporation
of the solvent under vacuum provided 16 as a yellow oil (2.36 g, 91%
yield). 31P{1H} NMR (80.9 MHz, CDCl3): d=14.7 ppm; 1H NMR
(500 MHz, CDCl3): d=7.76 (dd, 3J(H,P)=14.0, 3J(H,H)=7.4 Hz, 2H; o-
Ph), 7.52 (td, 3J(H,H)=7.6, 4J(C,P)=2.4 Hz, 1H; p-Ph), 7.42 (td, 3J
(H,H)=7.6, 3J(H,P)=3.4 Hz, 2H; m-Ph), 7.12 (d/dd, 3J(H,P)=2.1,
2J(C,Sn117/119)=19.6 Hz, 2H; Ar-H), 1.54 (m, 12H; CH2), 1.31 (m, 12H;
CH2), 1.10 (m, 12H; CH2Sn), 0.89 ppm (t, 18H; CH3); 13C{1H} NMR
(125.6 MHz, CDCl3): d=151.5 (d, 1J(C,P)=30.0 Hz; ipso-Ar), 141.8 (d,
2
2J(C,P)=12.5 Hz; Ar-Ar), 140.6 (s; Ar-Sn), 133.4 (d, J(C,P)=12.5 Hz; o-
Ar), 132.0 (d, 1J(C,P)=2.9 Hz; p-Ph), 132.0 (d, 1J(C,P)=69.9 Hz; ipso-
Ph), 131.0 (d, 2J(C,P)=11.5 Hz; o-Ar), 128.7 (d, 4J(C,P)=13.4 Hz; m-
Ph), 28.9 (s; CH2), 27.2 (s; CH2), 13.6 (s; CH3), 11.0 ppm (s, CH2Sn); ele-
mental analysis calcd (%) for C38H61OPS2Sn2 (866.4): C 52.68, H 7.10, S
7.40; found: C 51.86, H 7.02, S 6.96.
Synthesis of 18: Catalytic amounts of [Pd(PPh3)4] and CuI were added to
a solution of dithienophosphole 16 (1.73 g, 1.5 mmol) and 1,4-diiodo-2,5-
bis(octyloxy)benzene 17 (0.88 g, 1.5 mmol) in NMP (80 mL). The light-
yellow reaction mixture was then stirred for 48h at 2008C after which
time the color changed to orange-red. The solution was then cooled to
room temperature, the solvent evaporated under vacuum, and the result-
ing amorphous solid taken up in a small amount of THF (ca. 5 mL). The
suspension was then filtered through a filter paper, precipitated into
[10] S. Kim, K.-H. Song, S. O. Kang, J. Ko, Chem. Commun. 2004, 68.
[11] T. Benincori, V. Consonni, P. Grammatica, T. Pilati„ S. Rizzo, F.
Pannicolo, R. Todeschini, G. Zotti, Chem. Mater. 2001, 13, 1665.
[12] a) D. D. Kenning, K. Ogawa, S. D. Rothstein, S. C. Rasmussen,
Polym. Mater. Sci. Eng. 2002, 86, 59; b) K. Ogawa, S. C. Rasmussen,
J. Org. Chem. 2003, 68, 2921.
[13] J. Ohshita, M. Nodono, T. Watanabe, Y. Ueno, A. Kunai, Y. Harima,
K. Yamashita, M. Ishikawa, J. Organomet. Chem. 1998, 553, 487.
4698
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www.chemeurj.org
Chem. Eur. J. 2005, 11, 4687 – 4699

Synthesis and Properties of Dithienophospholes
FULL PAPER
[14] G. Barbarella, L. Favaretto, G. Sotgiu, L. Antolini, G. Gigli, R. Cin-
golati, A. Bongini, Chem. Mater. 2001, 13, 4112.
[28] P. B. Koster, F. van Bolhuis, G. J. Visser, Acta Crystallogr. 1970, 26,
1932.
[15] J.-P. Lampin, F. Mathey, J. Organomet. Chem. 1974, 71, 239.
[16] a) T. Baumgartner, T. Neumann, B. Wirges, Angew. Chem. 2004,
116, 6323; Angew. Chem. Int. Ed. 2004, 43, 6197; b) T. Baumgartner,
Macromol. Symp. 2003, 196, 279.
[17] a) M. Pomerantz in Handbook of Conducting Polymers, 2nd ed.,
(Eds.: T. A. Skotheim, R. L. Elsenbaumer, J. R. Reynolds), Marcel
Dekker, New York, 1998, pp. 277–309; b) X. Zhang, A. J. Matzger,
J. Org. Chem. 2003, 68, 9813; c) S. Y. Hong, J. M. Song, J. Chem.
Phys. 1997, 107, 10607.
[29] B. Valeur, Molecular Fluorescence, Principles and Applications,
Wiley-VCH, Weinheim, 2002.
[30] G. Barbarella, Chem. Eur. J. 2002, 8, 5073.
[31] D. T. McQuade, A. E. Pullen, T. M. Swager, Chem. Rev. 2000, 100,
2537.
[32] C. W. Bird, Tetrahedron 1985, 41, 1409.
[33] Z. Bao, W. K. Chan, L. Yu, J. Am. Chem. Soc. 1995, 117, 12426.
[34] Gaussian 98 (Revision A.5), M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, V. G. Zakrzewski,
J. A. Montgomery, Jr., R. E. Stratmann, J. C. Burant, S. Dapprich,
J. M. Millam, A. D. Daniels, K. N. Kudin, M. C. Strain, O. Farkas, J.
Tomasi, V. Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli,
C. Adamo, S. Clifford, J. Ochterski, G. A. Petersson, P. Y. Ayala, Q.
Cui, K. Morokuma, D. K. Malick, A. D. Rabuck, K. Raghavachari,
J. B. Foresman, J. Cioslowski, J. V. Ortiz, B. B. Stefanov, G. Liu, A.
Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, R. L. Martin,
D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara,
C. Gonzalez, M. Challacombe, P. M. W. Gill, B. G. Johnson, W.
Chen, M. W. Wong, J. L. Andres, M. Head-Gordon, E. S. Replogle,
J. A. Pople, Gaussian, Inc., Pittsburgh, PA, 1998.
[18] a) A. N. Hughes, D. Kleemola, J. Heterocycl. Chem. 1976, 13, 1;
b) W. Egan, R. Tang, G. Zon, K. Mislow, J. Am. Chem. Soc. 1971,
93, 6205.
[19] F. Mathey, Chem. Rev. 1988, 88, 429.
[20] A. Reed, P. von R. Schleyer, J. Am. Chem. Soc. 1990, 112, 1434.
[21] T. K. Miyamoto, Y. Matsuura, K. Okude, H. Ichida, J. Organomet.
Chem. 1989, 373, C8.
[22] Obtained in a similar manner as 10a by using 8 as the starting mate-
rial.
[23] The observed disorder can be attributed to molecular motions—
even at 110 K—within the crystal which lead to the displaced thio-
phene and silyl units.
[35] W. Gordy, J. Chem. Phys. 1947, 15, 305.
[24] H. Nçth, B. Wrackmeyer, Nuclear Magnetic Resonance Spectroscopy
of Boron Compounds, Springer, New York, 1978.
[25] a) J. J. MacDougall, J. H. Nelson, F. Mathey, J. J. Mayerle, Inorg.
Chem. 1980, 19, 709; b) J. Hydrio, M. Gouygou, F. Dallemer,
G. G. A. Balavoine, J.-C. Daran, J. Organomet. Chem. 2002, 643-644,
19.
[36] H. Meng, W. Huang, J. Org. Chem. 2000, 65, 3894.
[37] M. Fild, O. Stelzer, R. Schmutzler, Inorg. Synth. 1973, 14, 4.
[38] E. P. Kyba, J. Am. Chem. Soc. 1976, 98, 4805.
[39] D. Drew, J. R. Doyle, Inorg. Synth. 1972, 13, 52.
[40] C. Weder, M. S. Wrighton, Macromolecules 1996, 29, 5157.
[26] M. Ogasawara, K. Yoshida, T. Hayashi, Organometallics 2001, 20,
1014.
[27] W. L. Wilson, J. Fischer, R. E. Wasylishen, K. Eichele, V. J. Catalano,
J. H. Frederik, J. H. Nelson, Inorg. Chem. 1996, 35, 1486.
Received: February 11, 2005
Published online: May 25, 2005
Chem. Eur. J. 2005, 11, 4687 – 4699
www.chemeurj.org
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4699