Hybrid conjugated organic oligomers consisting of oligodiacetylene and thiophene units: Synthesis and optical properties

Article abstract of DOI:10.1002/chem.200900893

Novel and highly soluble hybrid conjugated organic oligomers consisting of oligodiacetylene and thiophene units have been synthesized in high purity through iterative and divergent approaches based on a sequence of Sonogashira reactions. The series of thiophene-containing oligodiacetylenes (ThODAs) and homocoupled ThODAs (HThODAs) show-both in solution and in the solid state-a strong optical absorption, which is progressively red shifted with increasing chain length. The linear correlation of the absorption maximum (λ^Amax) with the inverse of conjugation length (CL = number of double and triple bonds) shows that the effective conjugation length of this system is extended up to at least CL = 20. Furthermore, absorption measurements of dropcast thin films display not only a bathochromic shift of the absorption maxima but also a higher wavelength absorption, which is attributed to increased π-π interactions. The wavelength of the maximum fluorescence emission (λ^Emax) also increases with CL, and emission is maximal for oligomers with CL = 7-12 (fluorescence quantum yield φ_F = ～0.2). Both longer and shorter oligomers display marginal emission. The calculated Stokes shifts of these planar materials are relatively large (0.4 eV) for all oligomers, and likely due to excitation to the S₂ state, thus suggesting that the presence of enyne moieties dominates the ordering of the lowest excited states. The fluorescence lifetimes (τ_F) are short (τ_F'max =Le; 1ns) and closely follow the tendency obtained for the fluorescence quantum yield. The anisotropy lifetimes show a near-linear increase with CL, in line with highly rigid oligomers.

Full text of DOI:10.1002/chem.200900893

FULL PAPER
DOI: 10.1002/chem.200900893
Hybrid Conjugated Organic Oligomers Consisting of Oligodiacetylene and
Thiophene Units: Synthesis and Optical Properties
Gregor S. Pilzak, Kitty van Gruijthuijsen, Reindert H. van Doorn, Barend van Lagen,
Ernst J. R. Sudhçlter, and Han Zuilhof*[a]
Abstract: Novel and highly soluble
hybrid conjugated organic oligomers
consisting of oligodiacetylene and thio-
phene units have been synthesized in
high purity through iterative and diver-
gent approaches based on a sequence
of Sonogashira reactions. The series of
thiophene-containing oligodiacetylenes
(ThODAs) and homocoupled ThODAs
(HThODAs) show—both in solution
and in the solid state—a strong optical
absorption, which is progressively red
shifted with increasing chain length.
The linear correlation of the absorption
maximum (lAmax) with the inverse of
conjugation length (CL=number of
double and triple bonds) shows that
the effective conjugation length of this
system is extended up to at least CL=
20. Furthermore, absorption measure-
ments of dropcast thin films display not
only a bathochromic shift of the ab-
sorption maxima but also a higher
wavelength absorption, which is attrib-
uted to increased p–p interactions. The
wavelength of the maximum fluores-
cence emission (lEmax) also increases
with CL, and emission is maximal for
oligomers with CL=7–12 (fluorescence
quantum yield FF =~0.2). Both longer
and shorter oligomers display marginal
emission. The calculated Stokes shifts
of these planar materials are relatively
large (0.4 eV) for all oligomers, and
likely due to excitation to the S2 state,
thus suggesting that the presence of
enyne moieties dominates the ordering
of the lowest excited states. The fluo-
rescence lifetimes (tF) are short
(tF,max =!1 ns) and closely follow the
tendency obtained for the fluorescence
quantum yield. The anisotropy life-
times show a near-linear increase with
CL, in line with highly rigid oligomers.
Keywords: fluorescence
·
hybrid
materials · oligomerization · optical
absorption · pi interactions · Stokes
shift
Introduction
physical study that clarified the optical properties of poly-
diacetylenes.[6–8]
Structurally well-defined p-conjugated oligomers such as oli-
gothiophenes, oligoarylvinylenes, and oligodiacetylenes have
attracted considerable attention as promising nanoscale can-
didates for organic electronic devices.[1–4] To study the evolu-
tion of the optoelectronic properties of these materials as a
function of the chain length, a new series of monodisperse
oligomers were designed as model compounds.[5] Recently,
we developed novel methods for the synthesis of oligodiace-
tylene-based materials that have allowed a detailed photo-
The development of new oligodiacetylene-based materials
is often hampered by their low solubility and a laborious
and troublesome synthesis of significantly elongated oligo-
mers.[9,10] Although extensive studies based on oli-
goenes,[11,12]
oligoarylenevinylenes,[13,14]
oligotriacety-
lenes,[15–21] and oligothiophenes,[22–28] are known, analogous
studies centered around the diacetylene functionality as
present in polydiacetylenes are rather scarce. This lack of
study is a shortcoming given several of the unique properties
of polydiacetylenes, such as nonlinear optical (NLO) proper-
ties and chromic properties, that arise due to its p-conjugat-
ed system.[4,29–34] Furthermore, few examples of the structur-
al modulation of such p-oligomeric chains by incorporation
of an aromatic moiety are reported.[35–37] Such an approach
provides a new and versatile way to explore and optimize
the optoelectronic properties of conjugated oligomers.
Moreover, the use of a bifunctional aromatic moiety as a
central unit provides a new and rapid divergent synthetic
approach to the preparation of long conjugated oligomers.
[a] G. S. Pilzak, K. van Gruijthuijsen, R. H. van Doorn, B. van Lagen,
Prof. Dr. E. J. R. Sudhçlter, Prof. Dr. H. Zuilhof
Laboratory of Organic Chemistry
Wageningen University
Dreijenplein 8, 6703 HB Wageningen (The Netherlands)
Fax : (+31)317-484914
E-mail: han.zuilhof@wur.nl
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200900893.
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As a result, we have set out to develop new synthetic routes
toward thiophene-containing enyne-based oligomers and
study their photophysical behavior in detail. Herein, we de-
scribe the synthesis of a novel series of highly soluble thio-
phene-containing oligodiacetylenes (ThODAs) and homo-
coupled ThODAs (HThODAs; Scheme 1).
end groups. The banana-shaped ThODAs are constructed in
a new, divergent way. A central thiophene molecule is used
to couple two oligodiacetylene building blocks, thus result-
ing in a rapid extension of the oligomeric chain conjugation.
Series 4-n is equipped with two thiophene end caps, whereas
the 5-n series has two CACHTNUGTRNEUGN(CH3)2OMe endgroups. The homo-
coupled ThODAs 6-n consist of two symmetric ThODA sub-
units. All these novel oligomers with oligodiacetylene subu-
nits up to a trimer are synthesized in high purity (ꢀ99%)
and moderate-to-high yields (30–90%). These yields allow
the isolation of significant amounts of all members of these
series (including the longest ThODA 4-3 with 20 conjugated
p–p bonds) and the systematic study of their optical proper-
ties. Therefore, we also report in detail an investigation of
the optical properties by using both steady-state and pico-
second time-resolved optical spectroscopic analysis.
Results and Discussion
Synthesis of ThODAs and HThODAs: The ThODA and
HThODA series were prepared according to the synthetic
route illustrated in Scheme 2. The synthesis of oligodiacety-
lene building block 1 has been reported by us previously.[6]
The 2-ethynyl-5-methylthiophene used to introduce
a
second thiophene end cap was synthesized from 2-carboxyl-
5-methylthiophene through a short sequence including bro-
mination of the carboxyl group and reduction of 2-(2,2-di-
bromovinyl)-5-methylthiophene. This thiophene end cap is
introduced through a Sonogashira coupling of the iodoenyne
1 with the 2-ethynyl-5-methylthiophene and results in the
formation of 1-1. Compound 1-1 was protodesilylated under
alkaline conditions and subjected to a catalytic coupling
with 2-iodo-5-methylthiophene in a reductive atmosphere to
afford 2-1 bearing two thiophene end caps. The use of a 1:1
mixture of H2/Ar and a large excess of iodothiophene pro-
vided suppression of the homocoupling of terminal acety-
lenes down to 15%. However, a negative side effect of this
approach is slow poisoning of the catalyst by the thiophene
moiety, which resulted in somewhat lower yields compared
to the analogous reaction with oligodiacetylenes.[6] Similar
reaction conditions (10 equiv of 1 and a reductive atmos-
phere) were chosen for the catalytic elongation of the
ThODA backbone. Iodoenyne 1 was recovered quantitative-
ly after each step, which justified the use of this large excess.
This chain extension is performed up to a trimer through a
sequence of protodesilylation of 1-n followed by a Sonoga-
shira coupling with 1. After each step, a second thiophene
end cap is introduced to yield 2-n.
Scheme 1. Series of novel ThODAs and HThODAs studied herein in
which n=1–3.
The synthesis of the banana-shaped 4-n and 5-n series was
performed through a Sonogashira coupling of two 1-n or 3-n
building blocks, respectively, and a central 2,5-di-iodothio-
phene moiety. To achieve completion of this transformation,
an excess of the oligodiacetylene moiety is used, which un-
fortunately, results in slightly lower yields compared to the
catalytic reaction of similar oligodiacetylenes due to an in-
creased degree of homocoupling.
In our approach, the thiophene moiety is positioned
either as a conjugation-extending end cap, a central anchor
unit, or both. The linear ThODA series 1-n is end capped
with a trimethylsilyl (TMS) moiety and a thiophene group,
whereas the 2-n series has two thiophene end caps, in con-
trast to 3-n, which has been synthesized by us previously[6]
and is equipped with a TMS unit and tert-CACTHNUGTRNEUNG(CH3)2OCH3
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Photophysical Properties of Oligodiacetylene-Based p-Conjugated Oligomers
FULL PAPER
Scheme 2. Synthesis of the ThODA and HThODA series based on a sequence of Sonogashira couplings.i) [Pd
ii) K2CO3 cat. H2O, MeOH/THF.
ACHTNUGTNERN(NUG Ph3)4], CuI, Et2NH, THF, RT, H2/Ar;
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H. Zuilhof et al.
The synthesis of HThODAs
6-n is performed quantitatively
by
a mild catalytic reaction
under ambient air conditions:
two protodesilylated building
blocks 1-n are coupled symmet-
rically to yield the correspond-
ing HThODAs 6-n up to a ho-
mocoupled trimer with two
thiophene end caps. The use of
tetrakis(triphenylphosphine)-
palladium(0) in an oxygen at-
mosphere generates a PdII cata-
lyst in situ, which is the active
catalyst for the homocoupling
of terminal acetylenes.[8] To in-
crease the rate of the reaction
and to minimize the formation
of the cross-coupled side prod-
uct, the concentration of the
tetrakis(triphenylphosphine)-
palladium catalyst and CuI
cocatalyst is kept higher
(>5 mol%) than when a cross-
coupled Sonogashira product
was targeted. Under these opti-
mized conditions, the homocou-
pling of long ThODAs proceed-
ed almost quantitatively (~90%
yield of isolated products)
within 3 h.
Figure 1. Electronic absorption spectra of the oligomers measured in n-hexane (the 3-n series has been report-
ed previously[6]). e=extinction coefficient.
Steady-state optical absorption
in solution: The high solubility
Table 1. Absorption data of the studied oligomers in n-hexane, toluene,
of the synthesized ThODAs and HThODAs that result from
the asymmetric laterally attached alkyl side chains and polar
end caps, allowed us to study their optical properties in solu-
tion. The ground-state optical absorption of all series was
measured both in solution and as a dropcast thin film (see
Figure 1 for the absorption of these series in n-hexane). Ad-
ditionally, Table 1 shows an overview of the optical absorp-
tion characteristics of these oligomers measured in solutions
of n-hexane, toluene, and methanol.
and methanol.
Oligomer (CL)[a]
lAmax [nm] ([eV])
emax [ꢃ103 molꢁ1
dm3 cmꢁ1
methanol n-hexane
]
n-hexane toluene
1-1 (5)
1-2 (7)
1-3 (9)
2-1 (7)
327 (3.79) 332 (3.73) 327 (3.79) 20.0
360 (3.44) 365 (3.40) 360 (3.44) 23.1
386 (3.21) 393 (3.16) 386 (3.21) 49.4
355 (3.49) 360 (3.44) 355 (3.49) 25.4
380 (3.26) 386 (3.21) 380 (3.26) 32.4
396 (3.13) 403 (3.08) 395 (3.14) 57.8
403 (3.08) 410 (3.02) 402 (3.08) 61.4
419 (2.96) 426 (2.91) 417 (2.97) 71.4
2-2 (9)
2-3 (11)
4-1 (12)
4-2 (16)
4-3 (20)
5-1 (8)
5-2 (12)
5-3 (16)
6-1 (10)
6-2 (14)
6-3 (18)
The steady-state absorption spectra recorded in all sol-
vents show the expected red shift of the maximum absorp-
tion peak (lAmax) with an increase in the conjugation length
(CL=number of double and triple bonds). A similar de-
pendence is observed for the extinction coefficient (emax) de-
termined in n-hexane. The evolution of the maximum ab-
429 (2.89) 433 (2.86) [b]
100.4
373 (3.32) 378 (3.28) 372 (3.33) 34.9
407 (3.05) 412 (3.01) 404 (3.07) 54.4
421 (2.95) 427 (2.90) 418 (2.97) 94.2
377 (3.29) 385 (3.22) 382 (3.25) 50.4
412 (3.01) 419 (2.96) 410 (3.02) 81.9
sorption peak shows that the bathochromic shift (DlA
)
max
426 (2.91) 434 (2.86) [b]
153.1
decreases slightly with an increasing CL for all solvents, in
line with observed trends for oligodiacetylenes,[6] homocou-
pled oligodiacetylenes,[8] and oligothiophenes[3] and as ex-
pected from simple ꢁparticle-in-a-boxꢂ considerations.
[a] Conjugation length is the total number of the conjugated double and
triple bonds. [b] Not obtained due to low solubility in methanol.
Changing the solvent induces a small shift of the maxi-
mum absorption peak as well. The bathochromic shift
ranges from DlAmax =0.03 eV for 4-3 up to DlAmax =0.10 eV
for 1–2 upon changing the solvent from n-hexane (refractive
index=1.375; ET(30)=31.0 kcalmolꢁ1)[38] to toluene (refrac-
tive index=1.50; ET(30)=33.9 kcalmolꢁ1).[38] This observa-
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Photophysical Properties of Oligodiacetylene-Based p-Conjugated Oligomers
FULL PAPER
tion shows the stabilizing effect of an aromatic solvent on
the excited state of these molecules. This red shift in the
maximum absorption resembles those values determined
previously for oligodiacetylenes[6] and homocoupled oligo-
diacetylenes[8] and is analogous to data reported for shorter
diacetylene-based oligomers.[7,10,39–41] The shortest ThODA
series 1-n displays similar absorption maxmia in both
hexane and methanol. The shift of the maximum absorption
peak going from n-hexane to methanol (refractive index=
1.33; ET(30)=55.4 kcalmolꢁ1)[38] for the other oligomers
under study is marginal. We observed a small blue shift in
the maximum absorption (DlAmax =~0.2 eV), which is
caused by destabilization of the excited state of these oligo-
mers by a smaller solvent refractive index.[38,42,43]
glet states (S1 and S2; Figure 3), but these are accessed with
different ease.
Figure 3. Schematic depiction of the electronic transitions in the oligo-
thiophenes[46,47] and oligodiacetylenes[45] upon one-photon excitation.
Plots of the maximum absorption, expressed in energy
units versus 1/CL for the oligomers under study are depicted
in Figure 2 together with reported linear fits for oligodiace-
From the Ag ground state in planar conjugated oligomers,
such as oligodiacetylenes, only the transition to the excited
singlet state Bu is allowed; excitation to the second 2Ag sin-
glet state is symmetry forbidden.[41,48] Because of these sym-
metry reasons, for the diacetylene-based oligomers only the
transition to the S2 state is allowed.[6–8,41,48] For the oligothio-
phenes, electronic excitation is to the S1 state.[3,46] As a
result, mixing the thiophene moieties into an oligodiacety-
lene-based framework can qualitatively be expected to lead
to higher excitation energies when compared to pure oligo-
thiophenes, as is indeed observed. The absorption maxima
of the thiophene-containing compounds generally resemble
those of diacetylene-based oligomers with a similar CL (see
Figures 4, 6 and below). Whereas for all the ThODA series,
the presence of thiophene moieties causes a marginal blue
shift of the absorption, lAmax of the HThODA series matches
almost exactly the values reported for the rod-like homo-
coupled oligodiacetylenes with identical CL. Obviously, in
these materials, the thiophene moiety, which is positioned at
the end of the homocoupled oligodiacetylene structure, re-
sults in an extension of the conjugation that is similar to
chain prolongation with one oligodiacetylene unit. In com-
parison with, for example, series 4-n, which also features ter-
minal thiophene moieties, it is seen that the excited-state
character is significantly affected by the central unit (thio-
phene or diacetylene) within the molecule.
Figure 2. Energy of maximum absorption versus 1/CL of the ThODAs
and HThODAs in n-hexane at micromolar concentrations (2ꢃ10ꢁ6 m)
and room temperature, together with linear fits of the corresponding
data reported for oligodiacetylenes,[6] homocoupled oligodiacetylenes,[8]
and oligothiophenes.[3]
tylenes,[6] homocoupled oligodiacetylenes,[8] and oligothio-
phenes for comparison.[3] For each of the five current series,
a linear correlation was observed, with r2 ꢀ0.99, although
the curves will of course flatten eventually upon further in-
crease of CL (decrease of 1/CL).[5]
The optical absorption maxima for ThODAs and HThO-
DAs are almost parallel to those of the diacetylene-based
series. The extrapolated value of the absorption for the poly-
mers (1/CL!0) is nearly identical for all the thiophene-con-
taining series (between lAmax =2.61 and 2.41 eV) and is basi-
cally identical to values derived from oligodiacetylenes and
homocoupled oligodiacetylenes (lAmax =2.55 and 2.56 eV, re-
spectively). However, the values reported for the oligothio-
phenes are slightly lower (lAmax =2.23 eV).[3] This outcome is
revealing in terms of the nature of the excited singlet states
to which the oligomers are excited upon photon absorption.
Both oligothiophenes (nonplanar)[44] and oligodiacetylenes
(C2h symmetry)[41,45] have two low-lying, planar excited sin-
The linear relation of the energy of the maximum absorp-
tion with 1/CL up to CL=20 indicates that the elongation
of the conjugation length in the thiophene-containing oligo-
diacetylenes is preserved for all the compounds in the pres-
ent study. The conjugation in ThODA and HThODA oligo-
meric chains is therefore not significantly decreased by
kinks or torsions in the backbone.[6–8] The effective conjuga-
tion length (ECL) for these oligomers is therefore at least
20 and most likely >20 conjugated double and triple bonds.
Steady-state optical absorption in thin films: The optical ab-
sorption in the solid state of the members of the ThODA
and HThODA series that are solids at room temperature
was investigated by using dropcast thin films. The absorption
spectrum was recorded 12 hours after the start of the solvent
evaporation from the quartz plate containing the solid mate-
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H. Zuilhof et al.
higher-wavelength absorption from l=550 nm upwards. The
liquid-to-solid red shift of the absorption maxima of the 4-n
series and 5-3 is approximately DlAmax =0.15 eV and is
slightly larger compared to the reported shift (DlA
=
max
~0.10 eV) for the oligodiacetylene 3-n series.[6] The HThO-
DAs show an even larger liquid-to-solid red shift that ranges
from DlAmax =0.17 to 0.25 eV for 6-3 and 6-1 compared to
DlAmax =0.07 eV observed for homocoupled oligodiacety-
lenes.[8] The available data are used for a correlation be-
tween the reciprocal value of CL and the absorption
maxima for both liquids and solids and are compared to the
reported values for oligodiacetylenes[6] and homocoupled
oligodiacetylenes[8] as dropcast films (Figure 5).
Figure 4. Normalized absorption spectra of 4-n and 6-n in solution (l)
versus thin solid film (s).
rial prepared through dropcasting. (Unfortunately, the short-
er oligomers such as the 1-n and 2-n series and 5-1 and 5-2
are liquids, thus hampering such studies.) The absorption
plots of the dropcast thin films of 4-n and 6-n compared to
solution plots are shown in Figure 4 (the plot of 5-3 is simi-
lar and is given in the Supporting Information). The solid-
state absorption data of the studied solid oligomers are sum-
marized in Table 2.
The solid-state absorption of ThODAs and HThODAs is
characterized by three features: 1) a red-shifted maximum
absorption relative to the absorption maxima in solution;
2) a clearly visible red-shifted shoulder, and 3) an additional
Figure 5. The absorption maximum (lAmax) of 4-n, 5-3 (top), and 6-n
(bottom) in n-hexane (2ꢃ10ꢁ6 m) (l) and dropcast films (s) with addition-
al electronic transitions (lmax) compared to reports of dropcast films of
oligodiacetylenes[6] and homocoupled oligodiacetylenes[8] as a function of
1/CL.
Table 2. Solid-state absorption data of the 4-n, 5-3, and 6-n series.
The trends for the 4-n series and 5-3 are similar to that
observed for (homocoupled) oligodiacetylenes, thus pointing
to a dominant effect of the ODA moieties in determining
this liquid-to-solid effect. For the 6-n series, it may tentative-
ly be concluded that extension to an infinite polymer would
yield a further decrease in the excitation energy in compari-
son to the analogous homocoupled oligodiacetylenes (i.e.,
from lAmax =2.5 to 2.3 eV). Furthermore, we observe an ad-
ditional electronic transition that appears at lower energy
Oligomer (CL)
lmax
lmax (right shoulder)
[nm] ([eV])
[nm] ([eV])
4-1 (12)
4-2 (16)
4-3 (20)
5-3 (16)
6-1 (12)
6-2 (14)
6-3 (18)
421 (2.95)
441 (2.81)
455 (2.73)
444 (2.79)
408 (3.04)
437 (2.84)
455 (2.73)
466 (2.66)
484 (2.56)
498 (2.49)
492 (2.52)
446 (2.78)
479 (2.59)
496 (2.50)
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Photophysical Properties of Oligodiacetylene-Based p-Conjugated Oligomers
FULL PAPER
(lAmax =~0.26 eV) below the main absorption maxima, fol-
lowed by a significant absorption increase in the range l=
550–800 nm. This red-shifted shoulder positioned at a higher
wavelength region is already present for shorter oligomers
in solution, such as ThODAs 1-n, 2-1, 2-2, and 5-1
(Figure 1), but is absent in solutions of longer hybrid oligo-
mers. We interpret this outcome to mean that for short
ThODAs without a central thiophene unit, the flat oligomer-
ic geometry (C2h-like) is dominant, as reported for rod-like
oligodiacetylene chains.[41,45] For longer oligomers, entropic
reasons might also allow other geometries to play a role
emission of diacetylene-based oligomers,[6,8] in which no dis-
tinguishable shoulder at the high-energy side of the fluores-
cence band was visible for these oligomers with CLꢀ6. For
the linear ThODAs series 1-n and 2-n, the maximum fluo-
rescence quantum yield is observed for dimers 1-2 and 2-2,
whereas the monomers display this maximum in the linear
ꢁ
(e.g., with slight rotations around the C C bonds), and the
resulting peak broadening may make the lowest-energy
transition invisible as a separate shoulder. In the solid state,
interchain interactions may force planarity, and thus bring
back the shoulder. Moreover, the significantly increased
long-wavelength absorption (above l=550 nm for longest
studied oligomers) is caused by the intermolecular stacking
of p orbitals in the solid state, which is absent in diluted so-
lution. Due to steric repulsion from the alkyl side chains,
these oligomers do not show aggregation even in concentrat-
ed solution up to 5 mm.
Steady-state fluorescence in solution: Emission spectra mea-
sured for homogeneous millimolar solutions of the ThODA
and HThODA series were recorded in n-hexane, methanol,
and toluene. Table 3 summarizes the characteristic features
Table 3. Emission data of the studied oligomers in n-hexane.
Oligomer
(CL)
lE [nm]
([eV])
Quantum yield
Stokes shift
[eV]
max
(FF)[a,b]
1-1 (5)
1-2 (7)
1-3 (9)
2-1 (7)
370 (3.35)
407 (3.05)
441 (2.81)
397 (3.12)
431 (2.88)
452 (2.74)
457 (2.71)
478 (2.59)
490 (2.53)
415 (2.99)
461 (2.69)
480 (2.58)
438 (2.83)
468 (2.65)
482 (2.57)
0.003
0.170
0.005
0.110
0.140
0.002
0.100
0.003
0.002
0.210
0.006
0.002
0.067
0.001
0.001
0.422
0.446
0.426
0.370
0.386
0.388
0.364
0.365
0.360
0.336
0.357
0.362
0.458
[c]
2-2 (9)
2-3 (11)
4-1 (12)
4-2 (16)
4-3 (20)
5-1 (8)
5-2 (12)
5-3 (16)
6-1 (10)
6-2 (14)
6-3 (18)
[c]
[a] Quantum yield is determined by comparison with tryptophan: FF =
0.13.[49] [b] Experimental error=ꢃ0.002. [c] Not determined due to an
absence of a visible 0–0 transition.
of the steady-state fluorescence of these oligomers measured
in n-hexane (similar features were observed in methanol
and toluene and are given in the Supporting Information).
These marked features are 1) a clear red shift of the emis-
sion maxima (lEmax) with increasing CL and 2) a sharp maxi-
mum of the fluorescence quantum yield (FF,max) for the olig-
omers where CLꢂ12 and 3, which arises from a resolved 0–
0 transition (Figure 6). This last feature differs from the
Figure 6. Fluorescence spectra of ThODAs and HThODA measured in n-
hexane (because of the marginal emission all the spectra, except 1-2, 2-1,
2-2, 4-1, 5-1, and 6-1 are multiplied by a factor of five).
Chem. Eur. J. 2009, 15, 9085 – 9096
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9091

H. Zuilhof et al.
HThODAs 6-n and the banana-shaped 4-n and 5-n ThODAs
series. Upon further chain elongation, the fluorescence
quantum yield becomes marginal, likely as a result of highly
efficient internal conversion.[45]
Changing the solvent from n-hexane to toluene induces a
red shift of emission maxima. This red shift is rather small
for ThODAs in toluene (between DlEmax =0.05 and
0.07 eV), but becomes slightly larger for the HThODA
series (DlE
ranging from 0.07 eV up to 0.13 eV). Increas-
max
ing the polarity even more by changing the solvent to meth-
Figure 7. Planar geometry of the ThODA oligomer 2-1 (front and side
view; optimized at the B3LYP/6-311GACTHNUTRGNEUNG(d,p) level of theory).
anol results, only for the 1-n series, in a relatively large red
E
shift of lE
( l
ranging from 0.08 to 0.17 eV. For all
~
max
max
E
~
other studied oligomers, this shift is smaller ( l
ꢂ 0.04
max
E
~
eV for 2-n, 4-n, and 5-n) or similar ( l max ꢀ0.08 eV for 1-
n) compared to the red shift in p-electron-rich toluene. In
line with this pattern, the emission maxima for ThODAs
and HThODAs are highest in toluene, except for the 1-n
series. For oligomers, such as 1-n and 3-n with two different
endgroups, the solvent polarity plays an important role. For
oligomers without a (significant) dipole, the possibilities for
increased p–p interactions with the solvent (as in toluene)
are obviously more important.
plays the planarity of this species, which implies that – in
contrast to oligothiophenes – the observed large Stokes shift
of the these hybrid materials is likely not due to large geo-
metrical changes, such as rotations, upon excitation, but to
excitation to a higher excited state, in line with Figure 3
(right). In other words, the order of the Bu and 2Ag states
seems fixed by the presence of the enyne moieties, even in
molecules, such as 2-1, with two thiophene moieties and
only one enyne unit.
The emission quantum yield is highly dependent on CL.
We observe a sharp maximum for the fluorescence quantum
yield (FF) in all solvents for relatively short ThODAs, that
is, the fluorescence quantum yield in n-hexane is highest for
1-2 (FF =0.17, CL=7), 2-2 (FF =0.14, CL=9), and similar
to an oligodiacetylene trimer (FF =0.16, CL=7).[6] For the
longer series 4-n, 5-n, and 6-n, the maximum fluorescence
quantum yield is recorded for the monomers 4-1 (FF =0.10,
CL=12), 5-1 (FF =0.21, CL=8), and 6-1 (FF =0.07, CL=
10). These values are—for 5-1—five times larger than the
marginal emission reported for oligodiacetylenes with such
Fluorescence lifetimes and anisotropy: Picosecond time-re-
solved single-photon counting at five different excitation
wavelengths (l=295, 360, 380, 400, and 410 nm) was used to
determine the fluorescence lifetimes (tF) of the studied oli-
gomer series. The observed lifetimes for the ThODA and
HThODA series measured in n-hexane are shown in Table 4
and fall typically in the range tF =100–900 ps. The decay
curves of the compounds with lifetimes of tF >200 ps could
all be fitted with one exponent. The compounds with mar-
ginal fluorescence displayed more complex decay kinetics,
thus requiring a sum of two or three exponentials. In that
CL values[6] or for homocoupled oligodiacetylenes (FF,max
=
0.041, reported for the monomer with CL=6[8]). This phe-
nomenon shows that incorporation of the thiophene moiety
into an oligodiacetylene framework increases the fluores-
cence quantum yield, which is further increased in toluene.
This behavior clearly indicates that an aromatic solvent sta-
bilizes the intramolecular charge transfer in the excited state
of the hybrid oligomers, which results not only in a fluores-
cence emission at longer wavelengths but effects also an in-
creased efficiency thereof.
From the absorption and emission data, the Stokes shifts
in n-hexane were obtained (Table 3; see the Supporting In-
formation for similar data in toluene and methanol). These
values are rather large (0.30–0.45 eV) and similar to those
of oligodiacetylenes[41] but slightly smaller than reported for
oligothiophenes (~0.6 eV).[50,51] For oligothiophenes, the
large Stokes shift is attributed to significant differences in
geometry of the nonplanar ground state and the planar ex-
cited state.[44,51,52] In contrast, the S2 excitation in oligodiace-
tylenes causes this large shift, which is followed by rapid in-
ternal conversion to the S1 state and fluorescence from
there (Figure 3).[45] For the studied hybrid systems, the pla-
narity was investigated by DFT calculations (B3LYP/6-
Table 4. Fluorescence lifetimes (tF), relative amplitudes (A), average
lifetimes (tavg), and rotation correlation times (tR) of the ThODA and
HThODA series in n-hexane.
Oligomer
(CL)
t1
t 2
t
t
t
2
(A1) [ps]
(A2) [ps]
(A2) [ps]
150 (5)
[a] [ps]
[b] [ps]
avg
R
1-1 (5)
1-2 (7)
1-3 (9)
2-1 (7)
2-2 (9)
2-3 (11)
4-1 (12)
4-2 (16)
4-3 (20)
5-1 (8)
5-2 (12)
10 (66)[c]
781 (100)
13 (9)[c]
200 (100)
839 (100)
7 (49)[c]
41 (29)
26
50
119
200
205
250
321
218
643
910
380
204 (91)
187
94 (51)
51
551 (100)
6 (49)[c]
300 (21)
514 (9)
793 (30)
742 (12)
304
49
3 (91)[c]
304 (100)
20 (92)
678 (8)
73
5-3 (16)
6-1 (10)
6-2 (14)
13 (100)
280 (100)
6 (72)[c]
731
151
441
84 (16)
107
[a] Calculated by using Equation (1). [b] Experimental error=ꢂ50 ps.
[c] Values not accurate because the instrument response time was ap-
proximately 400 ps.
311G
ACHTUNGTRENNUNG(d,p)) on 2-1 (Figure 7). The resulting geometry dis-
9092
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Chem. Eur. J. 2009, 15, 9085 – 9096

Photophysical Properties of Oligodiacetylene-Based p-Conjugated Oligomers
FULL PAPER
case, the average fluorescence lifetime (tF,avg) was calculated
according to Equation (1):
enyne moieties and for all the studied compounds a 2Ag
state. These oligomers show a clear linear increase in ab-
sorption maxima for the p–p* transition with the conjuga-
tion length both in solution and the dropcast solid-state
film. Optical absorption studies of the drop-cast films dis-
play a second red-shifted absorption maximum and higher-
wavelength absorption, which are attributed to molecular
planarization and aggregation, respectively. A more efficient
p-electron delocalization along the oligodiacetylene back-
bone is obtained upon introduction of electron-rich-thio-
phene moieties, which result in a red-shifted maximum emis-
sion compared to the oligodiacetylenes. This modulation
also results in a significant increase of the quantum yield of
emission up to a factor of 5, in comparison to oligodiacety-
lenes and homocoupled oligodiacetylenes of the same conju-
gation length.
A1
A2
A3
tF;AVG
¼
t1 þ
t2 þ
t3
A1 þ A2 þ A3
A1 þ A2 þ A3
A1 þ A2 þ A3
ð1Þ
where A1, A2, and A3 are the contributions of the decays ob-
tained from the curve fitting. The evolution of fluorescence
lifetime with increasing oligomeric chain length closely fol-
lows the trend shown for the fluorescence quantum yield
(Table 3).
We determined the rotation correlation times (tR) for
ThODAs and HThODAs in n-hexane (Table 4).[49] Because
the longer oligomers display marginal emission, the experi-
mental error for these measurements was relatively high.
The anisotropy lifetimes show an increase with the CL, thus
indicating an increased rotation time around the perpendic-
ular axis for the longer oligomers. This behavior is illustrat-
ed in Figure 8, in which a linear dependence of the rotation
Experimental Section
Solvents and reagents: For all dry reactions performed under a steady
stream of argon (or a reductive atmosphere of argon/hydrogen (1:1)), the
equipment was dried in an oven at 1508C for several hours and allowed
to cool in an atmosphere of dry nitrogen or argon. Pure, dry, and de-
gassed ether and THF were obtained by distillation of the commercial
material over sodium particles. CH2Cl2 was distilled and dried over calci-
um hydride or sodium hydride. Dry DMF was purchased from Sigma–Al-
drich and stored under argon. All the other specified chemicals were
commercially purchased (Aldrich, Fluka, or Riedel-de Haꢄn) and used
without further purification.
General workup and purification procedure: Reaction monitoring and re-
agent visualization was performed on silica gel or reversed-phase silica
gel plates with UV light (l=254 and 366 nm) combined with GCMS.
Usually the reaction mixture was diluted with water and extracted three-
fold with an organic solvent (petroleum ether 40/60, hexane, or ethyl ace-
tate). The combined organic extracts were washed with brine, dried over
anhydrous sodium sulfate prior to filtration, and the solvent was removed
by evaporation under reduced pressure. Flash chromatography was per-
formed on commercially available silica gel (pore diameter: 0.035–
0.070 nm) and with mixtures of freshly distilled petroleum ether 40/60
and ethyl acetate or on reversed-phase silica gel (pore diameter: 0.04–
0.06 nm; Screening Devices) with mixtures of freshly distilled acetonitrile
and ethyl acetate. Final purification was performed on Shimadzu prepa-
rative HPLC using a C18 column (250ꢃ22 mm; 5 m; Alltech Alltima)
with HPLC-grade water, acetonitrile, and ethyl acetate mixture.
NMR spectroscopic and mass-spectrometric analysis: 1H and 13C NMR
spectra were determined on a Bruker CXP 300 NMR spectrometer in a
solution of CDCl3, unless indicated otherwise. Chemical shifts are report-
ed in ppm downfield relative to tetramethylsilane (TMS; d=0 ppm for
1H NMR) or the solvent peak (CDCl3; d=77.00 ppm for 13C NMR) as an
internal standard. HRMS was performed on Finnigan Mat95 mass spec-
trometer.
Figure 8. Anisotropy lifetimes versus the CL of the ThODA and
HThODA series.
correlation time and CL of the oligomers is depicted. This
outcome is as expected for conjugated oligomers with a
linear increase in the distance between the terminal atoms
going from one member of the series to the next, thus show-
ing the rigidity of even the longest oligomers in the present
study.
Conclusion
Steady-state absorption and fluorescence: Absorption spectra of the oli-
godiacetylenes in n-hexane (spectrophotometric grade; Riedel-de Haꢄn)
and 1,2-dichloroethane (DCE; spectrophotometric grade; Sigma–Al-
drich) were recorded on a Cary 100 UV/Vis spectrophotometer (scan
range (l)=200–800 nm, scan rate=300 nmminꢁ1, date interval=0.5 nm)
and steady-state fluorescence using a FLS920P Spectrometer (slit excita-
tion=2 nm, slit emission=2 nm, step=1.0, dwell=0.2 s). The absorption
spectra of oligodiacetylenes in film through dropcasting were recorded
on a Cary 50 UV/Vis spectrophotometer (scan range (l)=200–850 nm,
scan rate=300 nmminꢁ1, data interval=0.5 nm).
Novel series of highly soluble oligodiacetylenes with thio-
phene moieties as an end cap and/or a central unit were syn-
thesized in high purity. These oligomers display photophysi-
cal properties in between those of oligodiacetylenes and ho-
mocoupled oligodiacetylenes on the one hand and oligothio-
phenes on the other. Whereas the presence of the thiophene
units affects the energy of the excited states and the relaxa-
tion thereof, the nature of the lowest-excited state of these
hybrid materials (Ag or Bu) is determined by the presence of
Determination of fluorescence quantum yield in solution: To evaluate
the fluorescence quantum yield (FF) of solutions of oligodiacetylenes in
Chem. Eur. J. 2009, 15, 9085 – 9096
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9093

H. Zuilhof et al.
n-hexane, toluene, and methanol, the areas of the corrected emission
spectra were compared to a spectrum of a reference molecule. A diluted
solution of tryptophan in water was used, and a value of FR =0.13 was
obtained at 258C measured at l=280 nm.[49] The relevant fluorescence
quantum yields of the oligodiacetylenes were determined from the rela-
tionship given in Equation (2):
equalized dropping funnel containing the terminal acetylene (1 equiv).
The terminal ThODA 1-n or 3-n[6] was added slowly over 6 h to the
stirred mixture under a constant flow of argon/hydrogen (1:1). The reac-
tion mixture was further stirred overnight at 258C, concentrated, and fil-
trated over a short column of silica gel (5% ethyl acetate in petroleum
ether 40/60). The residue was prepurified on reversed-phase silica gel
(MeCN/EtOAc) and finally purified on preparative HPLC to give pure
(99%) elongated ThODA 4-n or 5-n, respectively.
I ODR n2 Rclexc;R
ð2Þ
FF ¼ F
R IR OD
Rclexc
nR2
Catalytic homocoupling of protodesilylated members of ThODA series
3-n under Sonogashira conditions: A mixture of terminal acetylene 3-n,[6]
[PdACHTNURTGNEUGN(PPh3)4] (7 mol%), CuI (8 mol%), distilled diethyl amine
where I and IR are the integrated emission intensities of solutions of oli-
godiacetylene and tryptophan, respectively, OD is the optical density of
the respective solutions, and n is the refractive index. The ratio of Rclexc
is a correction factor for the lamp spectrum due to the different excita-
tion wavelength used for the determination of the OD and I values of
the studied compound and solution of tryptophan.
(2 mLmmꢁ1), and THF (5 mLmmꢁ1) was placed in a round-bottomed
flask equipped with a magnetic stirrer. The reaction mixture was stirred
for 3 h at 258C under ambient atmosphere, concentrated, and filtrated
over a short column of silica gel (5% ethyl acetate in petroleum ether
40/60). The residue was prepurified on reversed-phase silica gel (MeCN/
EtOAc) and finally purified on preparative HPLC to give pure (99.5%)
HThODA 6-n.
Time-resolved fluorescence measurements: The fluorescence lifetime and
anisotropy were recorded using a FLS920P spectrometer (Edinburgh In-
struments) for time-correlated photon counting (TCSP; time setup=5 or
10 ns, channels=4096, counts=10000 for 1-1–1-4, 1000 for 1-5–1-7).
Pulsed diode lasers (l=372 nm, FWHM=54 ps; l=444 nm, FWHM=
63 ps) and pulsed LEDs (l=283 nm, FWHM=<500 ps; l=304 nm,
FWHM=<350 ps; PicoQuant) were used as the light source. The aniso-
tropy measurements were performed by using vertical and horizontal po-
larizations. All other conditions and setup parameters were reported ear-
lier by Van Hoek and co-workers.[53–55]
2-Ethynyl-5-methylthiophene:
2-Thiophenecarbaldehyde
(40 mmol,
4.48 g) was added in portions to a stirred and cooled (08C) solution of
PPh3 (100 mmol, 26.2 g) and CBr4 (50 mmol, 16.6 g) in anhydrous di-
chloromethane (200 mL) in an argon atmosphere. After completion of
the reaction (monitored by GCMS and TLC analysis), the crude reaction
mixture was extracted as usual (see the general procedure) and purified
by column chromatography on silica gel (petroleum ether 40/60). 2-(2,2-
Dibromovinyl)-5-methylthiophene was obtained as light-brown solid
(38.3 mmol, 10.8 g, 94%). A solution of nBuLi (4.27 mmol, 2.51 mL,
1.7m in hexanes) was added dropwise to a stirred and cooled (ꢁ788C) so-
lution of 2-(2,2-dibromovinyl)-5-methylthiophene (2.13 mmol, 0.6 g) in
anhydrous diethyl ether (30 mL) in an argon atmosphere. After stirring
for 30 min, the reaction mixture was allowed to warm to room tempera-
ture. After completion (monitored by GCMS and TLC analysis), the re-
action mixture was extracted as usual (see the general procedure) to
yield 2-ethynyl-5-methylthiophene as a pale-brown liquid (1.87 mmol,
0.22 g, 88%). 1H NMR: d=2.48 (s, 3H), 3.30 (s, 1H), 6.64 (dq, 1H, J=3
and 6 Hz), 7.10 ppm (d, 1H, J=6 Hz); 13C NMR: d=15.32, 22.62, 80.37,
119.52, 125.15, 133.33, 142.36 ppm; HRMS: m/z: calcd: 122.0191; found:
122.0195.
General method for the protodesilylation of the (Th)ODA series prior to
the catalytic chain-elongation process (Scheme 2): A solution of oligodia-
cetylene (1 equiv) in THF/MeOH (1:1, 5 mLmmꢁ1) was stirred in round-
bottomed flask. Water (3 dropsmmolꢁ1) and K2CO3 (2 equiv) were added
to the solution and stirred for 3 h. After the workup, following the gener-
al procedure given above, the terminal (Th)ODA was submitted to the
catalytic chain-elongation step.
Catalytic Sonogashira coupling of terminal (Th)ODAs 1-n or 3-n[6] with
iododiacetylene (1): A mixture of ((E)-4-iodo-3-propyloct-3-en-1-ynyl)tri-
methylsilane (1; 10 equiv), [PdACHTNUGTRNEUNG(PPh3)4] (5 mol%), CuI (2 mol%), and
dry, degassed diethylamine (2 mLmmꢁ1) and THF (5 mLmmꢁ1) were
placed anaerobically in a dried, brown two-necked round-bottomed flask
equipped with a magnetic stirrer, an argon/hydrogen in- and outlet, and a
pressure-equalized dropping funnel containing terminal acetylene
(1 equiv). The terminal (Th)ODA 1-n or 3-n was added slowly over 6 h
to the stirred mixture under a constant flow of argon/hydrogen (1:1). The
reaction mixture was further stirred overnight at 258C, concentrated, and
filtrated over a short column of silica gel (5% Et3N in petroleum ether
40/60). The residue was prepurified on reversed-phase silica gel (MeCN/
EtOAc) and finally purified on preparative HPLC to give pure (99%)
elongated (Th)ODA 1-n or 3-n,[6] while iododiacetylene (1) was recov-
ered quantitatively.
(E)-{3-Butyl-4-[2-(5-methylthiophen-2-yl)ethynyl]hept-3-en-1-ynyl}trime-
thylsilane (1-1): Colorless oil (0.57 mmol, 0.197 g, 95%) obtained from 1.
1H NMR: d=0.22 (s, 9H), 0.97 (t, 3H, J=7.2 Hz), 0.98 (t, 3H, J=
7.4 Hz), 1.38 (sextet, 2H J=7.3 Hz), 1.53–1.69 (m, 4H), 2.42 (t, 2H, J=
7.4 Hz), 2.45–2.55 (m, 5H), 6.66 (m, 1H,), 7.00 ppm (d, 1H, J=3.5 Hz);
13C NMR: d=0.0, 13.6, 13.9, 15.4, 21.7, 22.1, 30.5, 34.5, 36.8, 92.2, 92.3,
103.6, 104.7, 121.2, 125.4, 128.9, 130.8, 131.6, 142.2 ppm; HRMS: m/z:
calcd: 342.1838; found: 342.1840.
AHCTUNGTERG{NNUN (3E,7E)-4,7-Dibutyl-8-[2-(5-methylthiophen-2-yl)ethynyl]-3-propylunde-
ca-3,7-dien-1,5-diynyl}trimethylsilane (1-2): Pale-yellow oil (0.22 mmol,
1
0.106 g, 88%) obtained from 1–1; H NMR: d=0.23 (s, 9H), 0.96 (t, 6H,
Catalytic Sonogashira coupling of protodesilylated members of ThODA
J=7.4 Hz), 0.99 (t, 6H, J=7.9 Hz), 1.31–1.48 (m, 4H), 1.52–1.74 (m,
8H), 2.42 (t, 2H, J=7.4 Hz), 2.45–2.58 (m, 9H), 6.67 (m, 1H), 7.01 (d,
1H, J=3.6 Hz); 13C NMR: d=0.0, 13.6, 13.9, 14.0, 15.4, 21.7, 21.8, 22.1,
22.3, 22.4, 30.5, 30.8, 32.0, 34.8, 34.8, 37.0, 37.2, 92.2, 92.7, 98.5, 99.0,
103.8, 104.9, 121.3, 125.2, 125.5, 128.8, 129.2, 131.3, 131.6, 131.9, 142.2;
HRMS: m/z: calcd: 490.3090; found: 490.3089.
series 1-n with 2-iodo-5-methylthiophene: A mixture of 2-iodo-5-methyl-
thiophene (3 equiv), [Pd
gassed diethyl amine (2 mLmmꢁ1) and THF (5 mLmmꢁ1) was placed
anaerobically in dried, brown two-necked round-bottomed flask
ACHTUNGTERN(NUNG PPh3)4] (5 mol%), CuI (2 mol%), and dry, de-
a
equipped with a magnetic stirrer, an argon/hydrogen in- and outlet, and a
pressure-equalized dropping funnel containing the terminal acetylene
(1 equiv). The terminal ThODA 1-n was added slowly over 6 h to the
stirred mixture under a constant flow of argon/hydrogen (1:1). The reac-
tion mixture was further stirred overnight at 258C, concentrated, and fil-
trated over a short column of silica gel (petroleum ether 40/60). The resi-
due was prepurified on reversed-phase silica gel (MeCN/EtOAc) and fi-
nally purified on preparative HPLC to give pure (99%) elongated
ThODA 2-n.
Trimethyl-{(3E,7E,11E-3,8,11-tributyl-12-[2-(5-methylthiophen-2-yl)-
A
(1-3):
Pale-yellow oil (0.06 mmol, 0.036 g, 85%) obtained from 1-2. 1H NMR:
d=0.23 (s, 9H), 0.91–1.02 (m, 18H), 1.32–1.48 (m, 6H), 1.52–1.71 (m,
12H), 2.37–2.58 (m, 15H), 6.67 (m, 1H, J=3.6 Hz), 7.01 ppm (d, 1H, J=
3.6 Hz); 13C NMR: d=0.4, 13.6, 13.9, 14.0, 14.0, 15.4, 21.7, 21.8, 21.9,
22.1, 22.3, 22.3, 30.5, 30.8, 34.7, 34.8, 35.1, 37.0, 37.2, 37.3, 92.3, 92.8, 98.7,
99.1, 99.1, 103.8, 104.9, 121.3, 125.5, 128.8, 129.2, 129.3, 129.7, 131.3,
131.6, 142.2 ppm; HRMS: m/z: calcd: 638.4342; found: 638.4337.
Catalytic Sonogashira coupling of protodesilylated members of ThODA
series 1-n or 3-n with 2,5-diiodothiophene: A mixture of 2,5-diiodothio-
phene (3 equiv), [Pd
(PPh3)4] (5 mol%), CuI (2 mol%), and dry, degassed
(E)-2-Methyl-5-{4-[2-(5-methylthiophen-2-yl)ethynyl]-3-propyloct-3-en-1-
ynyl}thiophene (2-1): Yellow oil (0.74 mmol, 0.217 g, 68%) obtained
from 1-1. 1H NMR: d=0.96 (t, 3H, J=6.9 Hz), 0.98 (t, 3H, J=6.9 Hz),
1.45 (sextet, 2H, J=7.3 Hz), 1.56–1.77 (m, 4H), 2.50 (s, 6H), 1.47–2.60
9094
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Chem. Eur. J. 2009, 15, 9085 – 9096

Photophysical Properties of Oligodiacetylene-Based p-Conjugated Oligomers
FULL PAPER
(m, 4H), 6.67 (m, 2H), 6.98 (d, 1H, J=3.5 Hz), 6.99 ppm (d, 1H, J=
3.5 Hz); 13C NMR: d=13.7, 14.0, 15.4, 21.9, 22.2, 30.7, 34.6, 36.9, 92.1,
92.6, 92.7, 121.3, 125.5, 128.8, 129.3, 131.6, 142.2 ppm; HRMS: m/z:
calcd: 366.1476; found: 366.1474.
2,5-Bis((3E,7E,11E)-3,8,11-tributyl-15-methoxy-15-methyl-4,7,12-tripro-
pylhexadeca-3,7,11-trien-1,5,9,13-tetraynyl)thiophene (5-3): Yellow/
brown solid (0.02 mmol, 0.190 g, 66%) obtained from 3-3.[6] 1H NMR:
d=0.90–1.00 (m, 36H), 1.30–1.49 (m, 12H), 1.52 (s, 12H), 1.53–1.70 (m,
24H), 2.41–2.56 (m, 24H), 3.40 (s, 6H), 7.06 ppm (s, 2H); 13C NMR: d=
13.6, 13.6, 14.0, 14.0, 21.8, 21.9, 21.9, 22.1, 22.2, 22.3, 28.4, 30.7, 30.7, 30.8,
34.9, 35.0, 35.1, 36.9, 37.1, 37.3, 51.7, 71.2, 84.0, 91.5, 94.9, 98.4, 98.8, 99.7,
100.4, 125.0, 128.2, 129.0, 129.1, 129.4, 130.0, 131.0, 131.4 ppm; HRMS:
m/z: calcd: 1164.8696; found: 1164.8670.
2-{(3E,7E)-4,7-Dibutyl-8-[2-(5-methylthiophen-2-yl)ethynyl]-3-propylun-
deca-3,7-dien-1,5-diynyl}-5-methylthiophene (2-2): Yellow oil (0.07 mmol,
0.034 g, 53%) obtained from 1-2. 1H NMR: d=0.92–1.04 (m, 12H), 1.43
(sextet, 4H, J=7.2 Hz), 1.54–1.74 (m, 8H), 2.46–2.58 (m, 14H), 6.67 (m,
2H), 7.00 (d, 1H, J=3.5 Hz), 7.01 ppm (d, 1H, J=3.5 Hz); 13C NMR:
d=13.7, 14.0, 14.0, 15.4, 21.9, 21.9, 22.2, 22.3, 22.6, 30.8, 30.9, 34.8, 34.9,
37.0, 37.2, 92.3, 92.3, 92.8, 92.8, 98.9, 99.0, 121.3, 125.5, 128.8, 129.2, 129.3,
129.7, 131.6, 142.2 ppm; HRMS: m/z: calcd: 514.2727; found: 514.2727.
2-{(3E,9E)-4,9-Dibutyl-10-[2-(5-methylthiophen-2-yl)ethynyl]-3-propyltri-
deca-3,9-dien-1,5,7-triynyl}-5-methylthiophene (6-1): Yellow/brown solid
(0.59 mmol, 0.320 g, 95%) obtained from 1-1. 1H NMR: d=0.97 (t, 6H,
J=7.3 Hz), 0.99 (t, 6H, J=7.3 Hz), 1.41 (sextet, 4H, J=7.4 Hz), 1.55–
1.72 (m, 8H), 2.43–2.65 (m, 14H), 6.67 (d, 1H, J=3.5 Hz), 6.68 (d, 1H,
J=3.5 Hz), 7.03 ppm (d, 2H, J=3.7 Hz); 13C NMR: d=13.6, 13.9, 15.4,
21.8, 22.1, 30.7, 34.8, 36.8, 82.9, 84.4, 92.4, 94.2, 120.9, 125.6, 127.8, 132.0,
133.6, 142.7 ppm; HRMS: m/z: calcd: 538.2728; found: 538.2729.
2-{(3E,7E,11E)-4,7-Dibutyl-12-[2-(5-methylthiophen-2-yl)ethynyl]-3,8,11-
tripropylhexadeca-3,7,11-trien-1,5,9-triynyl}-5-methylthiophene
(2-3):
Yellow oil (0.03 mmol, 0.019 g, 40%) obtained from 1-3. 1H NMR: d=
0.87–1.04 (m, 18H), 1.32–1.48 (m, 6H), 1.51–1.73 (m, 12H), 2.44–2.58 (m,
18H), 6.67 (d, 2H, J=3.6 Hz), 7.00 (d, 1H, J=3.5 Hz), 7.01 ppm (d, 1H,
J=3.5 Hz); 13C NMR: d=13.6, 14.0, 14.0, 14.0, 15.4, 21.9, 21.9, 22.1, 22.3,
22.3, 30.7, 30.9, 34.8, 34.9, 35.1, 37.0, 37.2, 37.3, 92.3, 92.3, 92.8, 92.9, 99.1,
99.2, 121.3, 125.5, 128.8, 129.2, 129.2, 129.3, 129.7, 129.8, 131.6,
142.2 ppm; HRMS: m/z: calcd: 662.3979; found: 662.3977.
2-Methyl-5-{(3E,7E,13E,17E)-4,7,14,17-tetrabutyl-18-[2-(5-methylthio-
phen-2-yl)ethynyl]-3,8,13-tripropylhenicosa-3,7,13,17-tetraen-1,5,9,11,15-
pentaynyl}thiophene (6-2): Dark-orange solid (0.28 mmol, 0.230 g, 90%)
obtained from 1-2. 1H NMR: d=0.80–1.03 (m, 24H), 1.40 (sextet, 8H,
J=7.3 Hz), 1.55–1.72 (m, 16H), 2.43–2.65 (m, 22H), 6.67 (m, 2H),
7.02 ppm (d, 2H, J=3.7 Hz); 13C NMR: d=13.6, 13.6, 13.9, 14.0, 15.4,
21.8, 21.9, 22.1, 22.3, 30.8, 30.8, 34.9, 35.2, 37.0, 37.2, 83.1, 84.7, 92.7, 92.7,
98.5, 100.9, 121.2, 125.5, 127.8, 129.0, 129.9, 131.7, 134.0, 142.4 ppm;
HRMS: m/z: calcd: 834.5232; found: 834.5227.
2,5-Bis{(E)-3-butyl-4-[2-(5-methylthiophen-2-yl)ethynyl]hept-3-en-1-
ynyl}thiophene (4-1): Yellow solid (0.26 mmol, 0.164 g, 40%) obtained
from 1-1. 1H NMR: d=1.01 (t, 6H, J=7.2 Hz), 1.04 (t, 6H, J=7.2 Hz),
1.45 (sextet, 4H, J=7.3 Hz), 1.59–1.77 (m, 8H), 2.51 (s, 6H), 2.52–2.62
(m, 8H), 6.69 (m, 2H), 7.04 (d, 1H, J=3.5 Hz), 7.05 (d, 1H, J=3.5 Hz),
7.08 ppm (s, 2H); 13C NMR: d=13.7, 14.0, 15.5, 21.9, 22.1, 22.2, 22.5,
29.7, 30.8, 30.9, 31.7, 34.8, 36.8, 91.6, 92.8, 92.9, 94.8, 121.1, 125.0, 125.6,
128.3, 130.6, 131.4, 132.0, 142.5 ppm; HRMS: m/z: calcd: 620.2605;
found: 620.2599.
2-{(3E,7E,11E,17E,21E,25E)-4,7,12,17,22,25-Hexabutyl-26-[2-(5-methyl-
thiophen-2-yl)ethynyl]-3,8,11,18,21-pentapropylnonacosa-3,7,11,17,21,25-
hexaen-1,5,9,13,15,19,23-heptaynyl}-5-methylthiophene (6-3): Orange/
brown solid (0.10 mmol, 0.110 g, 89%) obtained from 1-3. 1H NMR: d=
0.88–1.03 (m, 36H), 1.33–1.44 (m, 12H), 1.50–1.70 (m, 24H), 2.43–2.65
(m, 30H), 6.67 (m, 2H), 7.01 ppm (d, 2H, J=3.7 Hz); 13C NMR: d=13.6,
13,9, 14.0, 14.0, 15.4, 21.8, 21.9, 22.1, 22.3, 22.3, 30.8, 30.8, 34.8, 35.1, 37.0,
37.2, 37.3, 83.1, 84.8, 92.4, 92.8, 98.8, 99.0, 99.5, 101.1, 121.2, 125.5, 127.8,
129.0, 129.2, 129.4, 130.4, 131.6, 134.0, 142.3 ppm; HRMS: m/z: calcd:
1130.7736; found: 1130.7749.
2,5-Bis
ACHTUNGTRENNUNG{(3E,7E)-4,7-dibutyl-8-[2-(5-methylthiophen-2-yl)ethynyl]-3-pro-
ACHTUNGTRENNUNGpylundeca-3,7-dien-1,5-diynyl}thiophene (4-2): Yellow–brown solid
(0.02 mmol, 0.019 g, 30%) obtained from 1-2. 1H NMR: d=0.98 (t, 6H,
J=7.3 Hz), 0.99 (t, 6H, J=6.9 Hz), 1.00 (t, 6H, J=7.3 Hz), 1.02 (t, 6H,
J=6.9 Hz), 1.34–1.48 (m, 8H), 1.54–1.74 (m, 16H), 2.46–2.59 (m, 22H),
6.67 (m, 2H), 7.02 (d, 2H, J=3.5 Hz), 7.06 ppm (s, 2H); 13C NMR: d=
13.7, 14.0, 14.0, 15.4, 21.9, 22.0, 22.2, 22.3, 29.7, 30.8, 30.9, 34.9, 35.0, 36.9,
37.2, 91.5, 92.5, 92.8, 94.9, 98.8, 99.6, 121.2, 125.0, 125.5, 128.2, 129.1,
129.6, 131.0, 131.4, 131.7, 142.3 ppm; HRMS: m/z: calcd: 916.5109;
found: 916.5116.
Acknowledgements
2,5-Bis{(3E,7E,11E)-3,8,11-tributyl-12-[2-(5-methylthiophen-2-yl)ethyn-
yl]-4,7-dipropylpentadeca-3,7,11-trien-1,5,9-triynyl}thiophene
(4-3):
The authors thank the Dutch Technology Foundation STW for generous
funding of this research (project no. WPC 5740), Dr. Jan Kroon (ECN)
and Dr. Joost Smits (Shell) for helpful discussions, Dr. M. A. Posthumus
for performing HRMS experiments, Dr. Jacob Baggerman for the quan-
tum-chemical calculation of 2-1, and Ing. E. J. Bakx for performing
MALDI-TOF mass-spectrometric experiments.
Orange/brown solid (0.02 mmol, 0.028 g, 30%) obtained from 1-3.
1H NMR: d=0.92–1.04 (m, 36H), 1.33–1.49 (m, 12H), 1.54–1.74 (m,
24H), 2.45–2.59 (m, 30H), 6.67 (d, 2H, J=3.7 Hz), 7.02 (d, 2H, J=
3.6 Hz), 7.06 ppm (s, 2H); 13C NMR: d=13.7, 14.0, 14.0, 14.0, 15.4, 21.9,
22.0, 22.1, 22.3, 22.4, 30.8, 30.9, 30.9, 34.9, 35.0, 35.1, 36.9, 37.2, 37.3, 91.5,
92.4, 92.8, 95.0, 99.0, 99.1, 99.3, 99.8, 121.3, 125.0, 125.5, 128.2, 129.1,
129.3, 130.1, 131.0, 131.4, 131.7, 142.3 ppm; MALDI-TOF-MS: m/z:
calcd: 1212.76; found: 1212.71.
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ACHTUNGTRENNUNGthiophene (5-1): Pale-yellow oil (0.27 mmol, 0.157 g, 49%) obtained from
3-1.[6] 1H NMR: d=0.94 (t, 6H, J=7.3 Hz), 0.95 (t, 6H, J=7.4 Hz), 1.37
(sextet, 4H, J=7.3 Hz), 1.52 (s, 12H), 1.52–1.63 (m, 8H), 2.44 (t, 4H, J=
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13C NMR: d=13.6, 14.0, 21.8, 22.1, 28.4, 30.6, 34.8, 36.7, 51.8, 71.2, 83.7,
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572.3688; found: 572.3691.
2,5-BisACHTUNGTRENNUNG((3E,7E)-4,7-dibutyl-11-methoxy-11-methyl-3,8-dipropyldodeca-
3,7-dien-1,5,9-triynyl)thiophene (5-2): Yellow/orange oil (0.03 mmol,
0.262 g, 46%) obtained from 3-2.[6] 1H NMR: d=0.89–1.02 (m, 24H),
1.29–1.49 (m, 8H), 1.52 (s, 6H), 1.53–1.72 (m, 22H), 2.39–2.57 (m, 16H),
3.40 (s, 6H), 7.05 ppm (s, 2H); 13C NMR: d=13.6, 13.6, 14.0, 14.0, 21.8,
21.9, 22.1, 22.2, 22.7, 28.4, 30.7, 30.7, 34.9, 35.0, 36.9, 37.1, 51.7, 71.2, 84.0,
91.4, 94.8, 98.1, 99.1, 100.5, 125.0, 128.2, 129.3, 129.3, 131.0, 131.4 ppm;
HRMS: m/z: calcd: 868.6192; found: 868.6197.
Chem. Eur. J. 2009, 15, 9085 – 9096
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Published online: July 27, 2009
9096
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