Synthesis and optoelectronic properties of nanometer-sized and highly soluble homocoupled oligodiacetylenes

Article abstract of DOI:10.1002/chem.200801119

A new series of pure, nanometer-sized and highly-soluble homocoupled oligodiacetylenes (HODA) consisting of two symmetrical oligodiacetylene units was synthesized with high yield and on a multi-milligram scale under mild, catalytic Sonogashira conditions.

Full text of DOI:10.1002/chem.200801119

DOI: 10.1002/chem.200801119
Synthesis and Optoelectronic Properties of Nanometer-Sized and Highly
Soluble Homocoupled Oligodiacetylenes
Gregor S. Pilzak,[a] Jacob Baggerman,[a] Barend van Lagen,[a] Maarten A. Posthumus,[a]
Ernst J. R. Sudhçlter,[a, b] and Han Zuilhof*[a]
Abstract: A new series of pure, nano-
meter-sized and highly-soluble homo-
coupled oligodiacetylenes (HODA)
consisting of two symmetrical oligodi-
thin drop-casted films. An additional
red-shifted absorption is observed in
the solid state and in solution at low
temperatures, which is caused by aggre-
gation. The lmax of the fluorescence
emission increases with the chain
length and reaches 492 nm for the lon-
gest oligomer. The fluorescence quan-
tum yield has its maximum for the
shortest oligomer and decreases rapidly
for the longer ones. A similar trend is
found for the fluorescence lifetime
with a maximum of 100 ps for the ho-
mocoupled monomer. The rotational
correlation time shows a linear increase
with the oligomer length. This reveals a
significant persistence length and indi-
cates that the HODA molecules are
fully stretched molecular rods (up to
8.2 nm).
ACHTUNGTRENNUNGacetylene units was synthesized with
high yield and on a multi-milligram
scale under mild, catalytic Sonogashira
conditions. The lmax and the emax of ab-
sorption for these HODAs show an in-
crease with the chain elongation. The
lmax converges to 450 nm for the lon-
gest members of the series at micromo-
lar concentration and to 462 nm for
Keywords: absorption · conjugated
oligomers · fluorescence · nano-
structures · polydiacetylenes
Introduction
ties of the corresponding polymeric materials. However, the
synthesis of long p-conjugated oligomers is often difficult,
owing to the low solubility of the molecules, possible limita-
tions of the synthetic route (specifically for longer oligo-
mers), or purification problems.[9] Novel methods for the
preparation of conjugated oligomers are thus frequently re-
quired to obtain series of soluble monodisperse oligomers.[10]
Oligomers based on repeating enyne units, such as oligo-
diacetylenes, act as models of polydiacetylene (PDA) for un-
derstanding the influence of the precise conjugation length
on the electronic properties.[11–15] Recently, we have pub-
lished an iterative approach to construct a new series of
The development of nanometer-sized conjugated molecules,
which play a crucial role in a wide variety of photoinduced
processes, has attracted a lot of scientific interest in the last
decade.[1–4] Various potential applications in optoelectronic
devices, such as photo-voltaic cells,[5] light-emitting diodes,[6]
and field-effect transistors[7] are emerging from this.[8] The
design of accurately defined p-conjugated oligomers is im-
portant, as this provides information about the evolution of
the electronic, optical, thermal, and morphological proper-
ACHUTNGERNoNUG ligoACHTUNGTERNdNUGN iacetylenes ranging from monomer up to octamer
bearing 17 conjugated double and triple bonds. In this study
we extend our method[15] to produce nanometer-sized mate-
rials reaching up to 30 conjugated double and triple bonds
with an estimated length of ꢀ8 nm.
[a] G. S. Pilzak, Dr. J. Baggerman, B. van Lagen, Dr. M. A. Posthumus,
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)317-484-914
We describe the synthesis of a new series of highly soluble
homocoupled oligodiacetylenes (HODAs), which consist of
two symmetrical oligodiacetylene units. The series ranges
from monomer 1-1 (C34H50O2 and Mr =490.38) to heptamer
1-7 (C166H242O2 and Mr =2267.67, Figure 1), synthesized in
high purity (ꢁ99%) and with high yields (80–90%), which
allows the isolation of significant amounts of these oligo-
mers. We report on the optical properties of these materials
E-mail: Han.Zuilhof@wur.nl
[b] Prof. Dr. E. J. R. Sudhçlter
Present address: Delft University of Technology
Department of DelftChemTech
Laboratory of Nano-organic Chemistry
Julianalaan 136, 2628 BL Delft (The Netherlands)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200801119.
2296
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 2296 – 2304

FULL PAPER
ambient air conditions. Essential for this palladium-cata-
lyzed homocoupling is the presence of both a copper(I) salt
and an amine, which results in the formation of Cu(I) acety-
lides from terminal acetylenes in situ. This can be effectively
used to induce the desired homocoupling.[11a] As reported by
Elangovan et al.[16] the use of tetrakis(triphenylphosphine)
palladium(0) under an oxygen atmosphere generates a PdII
catalyst in situ, which is the active catalyst for the homocou-
pling of terminal acetylenes. To increase the rate of the reac-
tion and to minimize formation of side products, the concen-
tration of the tetrakis(triphenylphosphine)palladium catalyst
and Cu(I) cocatalyst was kept slightly higher (>5 mol%)
than used previously; in the case when the crosscoupled So-
nogashira product was the target.[15] Under such optimized
conditions the homocoupling of long oligomers proceeded
almost quantitatively (>90% isolated yields) and all cou-
pling reactions were completed within 3 h.
Figure 1. Series of novel HODAs 1-n under present study (n=1–7).
by using both steady-state and picosecond time-resolved
techniques.
Results and Discussion
Steady-state absorption in solution: The high solubility of
the synthesized HODAs is the direct result of the laterally
attached asymmetrical alkyl side-chains, and allows us to
study the optical properties of HODAs both with and with-
out aggregation. The ground-state optical absorption of the
1-n series was measured both in solution and as a drop-
casted thin film. The absorption of the HODA series 1-n up
to n=7 as a monodisperse solution in n-hexane is depicted
in Figure 3. Similar spectra were obtained in 1,2-dichloro-
ethane (DCE).
Synthesis of HODAs: A series of soluble oligodiacetylenes
bearing two different endcaps and asymmetrical alkyl side
chains 2-n, ranging from monomer up to heptamer, was syn-
thesized according to our previously reported approach.[15]
The protodesilylation of oligodiacetylene 2-n using a mild
alkaline method proceeded quantitatively and resulted in
the formation of terminal acetylenes 3-n, as shown in
Figure 2.
Figure 3. Electronic absorption spectra of methoxy-endcapped oligo
AHCTUNGTRENGNaUN cetylenes 1-n (n=1–7) in n-hexane.
ACHTUNGTRENNUNGdi-
The steady-state absorption spectra recorded in both sol-
vents show the expected red-shift of the absorption maxi-
mum (lmax) and an increase of the extinction coefficient
(emax) with an increasing conjugation length. This bathochro-
mic shift is similar to literature data reported for shorter
enyne-based oligomer series reported by others[13,17,18] and
us,[12,15] and becomes smaller with chain elongation: Dlmax
decreases from ꢀ0.34 eV going from 1-1 to 1-2 (in both n-
Figure 2. Homocoupling of ODAs to yield homocoupled elongated ana-
logs. Reagents: a) K2CO3, catalytic H2O, MeOH/THF, b) [Pd
CuI, Et2NH, THF.
ACHTUNGTRNE(NUNG PPh3)4],
The homocoupling of the terminal oligodiacetylene 3-n
was performed by means of a mild catalytic reaction under
Chem. Eur. J. 2009, 15, 2296 – 2304
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2297

H. Zuilhof et al.
hexane and DCE) to ꢀ0.02 eV in n-hexane and ꢀ0.04 eV in
DCE going from 1-6 to 1-7 (Table 1).
Table 1. Absorption data of HODAs 1-n (n=1–7) in n-hexane and DCE.
1-n (CL[a]
)
lmax [nm] ([eV])
emax [ꢁ103 dm3 molꢂ1 cmꢂ1
]
n-hexane
DCE
n-hexane
DCE
1-1 (6)
339 (3.66)
374 (3.32)
412 (3.01)
429 (2.89)
432 (2.87)
437 (2.84)
440 (2.82)
344 (3.60)
380 (3.26)
419 (2.96)
436 (2.84)
441 (2.81)
447 (2.77)
450 (2.76)
36.2
61.1
93.8
124.7
154.8
180.7
218.2
30.1
54.3
83.2
104.2
133.2
160.3
186.6
1-2 (10)
1-3 (14)
1-4 (18)
1-5 (22)
1-6 (26)
1-7 (30)
[a] Conjugation length as sum of number of double and triple bonds.
The lmax and the emax for the homocoupled oligomers
matches rather closely the corresponding values of lmax for
2-n of similar conjugation length. The optical properties of
HODAs are dominated by the C2h symmetry that is present
in fully stretched, planar oligomers. To the degree that this
is correct, based on both the analogy with oligodiacetylenes
and the fluorescence quantum yields and time-resolved fluo-
rescence anisotropy data reported below, their absorption
Figure 4. Extinction coefficient maxima of HODA series 1-n (n=1–7) in
*
n-hexane (&) and DCE ( ) solution at micromolar concentrations (2ꢁ
10ꢂ6 m) versus CL. c: y=7001x/R2 =0.991, g: y=6060x/R2 =0.993).
the structural differences between both oligomeric series.
The 2-n series have only one tert-OMe endcap, which in
ACHTUNGTRENNUNGduc-
!
spectrum is associated with a S
2A
S0A
(11Ag) transi-
ACHTUNGTRENNUNG
tion.[11b,12,15,19,20]
tert-OMe end groups are placed exactly at the opposite site
of the oligodiacetylene chain. This results in structural sym-
metry of the 1-n series and thus a low (negligible) dipole
moment.
The dominant solvent effect is the polarization shift,
which is attributed to the difference in solvent refractive
index.[21] A bathochromic effect is observed upon changing
the solvent from n-hexane (refractive index, nr =1.375; em-
pirical solvent polarity parameter, ET(30)=31.0) to DCE
(nr =1.445; ET(30)=41.3).[22,23] This relatively small shift (
ꢀ0.06 eV for all oligomers) is in line with previously report-
ed data for long oligodiacetylene series.[15] This shows that
the excited-state dipole moment me of HODAs 1-n is only
marginally larger than the ground-state dipole moment mg.
The extinction coefficient depends on the solvent polarity
and conjugation length (CL), defined as the sum of the
number of double and triple bonds with CL=4n + 2, as de-
picted in Figure 4.
The absorption maximum of the oligomers (expressed in
eV) displays a linear relation with the reciprocal conjugation
length (1/CL) as shown in Figure 5 together with literature
data points for the 2-n series[15] (CL=3–17) and oligo
N
ACHTUNGTRENNUNGacet-
AHCTUNGTRENNUNG
2.56 eV (484 nm) for a PDA polymer with n=8 in n-hexane
is obtained, whereas in DCE a value of 2.51 eV (494 nm) is
calculated. These extrapolated values match almost exactly
The emax increases linearly with CL in both solvents, which
shows that the S2–S0 energy gap is evenly decreasing during
the extension of the conjugated p–p systems, and results in
a more probable absorption. This observation of linearity in-
dicates that the charge delocalization in the extended chro-
mophoric system is not significantly hampered by kinks or
torsions,[24,25] as those would have scaled with the number of
possible conformations, which increases exponentially with
the chain length and would thus have yielded a less than
linear increase.[26] For the HODAs the difference between
the emax in n-hexane and DCE is approximately 20% in
favor of the nonpolar solvent. This observation is similar to
the molar extinction decrease for non-polar and dipole-less
b-carotene[27] with an increase of solvent polarity. However,
this is in contrast with the previously reported solvent de-
pendence of emax for the 2-n series, which showed an in-
crease of the extinction maximum upon an increase of sol-
vent polarity.[15] Apparently, this phenomenon results from
Figure 5. lmax of the absorption versus 1/CL and its linear fits of HODA
series 1-n (n=1–7) and 2-n[15] (CL=3–17) in n-hexane and DCE solution
at micromolar concentrations (2ꢁ10ꢂ6 m) compared to oligotriacetylenes
(OTA)[28] with CL=3–48 in CHCl3 solution at room temperature.
2298
www.chemeurj.org
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 2296 – 2304

Synthesis and Properties of Oligodiacetylenes
FULL PAPER
the lmax values reported by us previously for the 2-n series
up to octamer, that is, 2.55 eV (487 nm) in n-hexane and
2.48 (500 nm) in DCE.[15]
The absorption maximum of the longest HODA (1-7) in
solution is 440 and 450 nm in n-hexane and DCE, respec-
tively. Compared with the 2-n series (no absorptionꢁ
500 nm) the absorption spectrum for 1-7 reaches higher,
that is, up to 535 nm (see Figure 3). This value is still signifi-
cantly lower than the reported values for longer-wavelength
absorptions (lmax up to 700 nm) of PDA chains, the most
closely related class of conjugated polymers.[29] For plots like
these, it is known that for extended oligomers they start to
deviate from linearity, and curve horizontally near the y-
axis.[30,31] This was previously observed for the highly analo-
gous oligo-triacetylenes (OTAs),[28] for which truncation ef-
fects on the conjugation are already noticeable for the oligo-
mers with more than 24 conjugated bonds. However, for the
HODAs with the elongation of the conjugation length line-
arity of the plot is retained. This phenomenon is illustrated
in Figure 5 in which no flattening of the curve towards the
y-axis is observed. This observation, together with the line-
arity of the emax and lmax of absorption with CL and 1/CL,
respectively, clearly shows the continuously increased conju-
gation in the 1-n series up to 30 double and triple bonds.
Steady-state optical absorption in thin films: The optical ab-
sorption of oligomer 1-3 to 1-7 in thin-solid films is depicted
in Figure 6a. The color change between the millimolar solu-
tion and the solid state of the conjugated oligomer 1-7 is
clearly visible to the naked eye (Figure 6b).
To investigate whether this bathochromic shift should be
attributed to aggregation or concentration effects, the opti-
cal absorption of the 1-n series in the solid state was investi-
gated in drop-casted thin films. The absorption spectrum is
recorded 12 h after the start of the solvent evaporation from
the quartz plate that contains the solid material prepared by
means of drop-casting. The solid-state absorption spectra of
the HODA series 1-n show a bathochromic shift of the ab-
sorption maxima with ꢀ0.07 eV relatively to the absorption
maxima of 1-n solutions in DCE (Table 1). These data
match rather closely the values that were observed for the
Figure 6. Steady-state optical absorption of HODAs: a) normalized ab-
sorption spectra of drop-casted 1-n series (n=3–7); b) Color change
upon solvent evaporation of 1-7 solution in n-hexane (left) versus the 1-7
in thin solid film (right). Normalized absorption spectra of c) HODA 1-3
and d) 1-7 in solution versus thin solid film.
both media with a closely matching extrapolated lmax of
2.50 eV (496 nm) in thin film and 2.51 eV (494 nm) in DCE
solution. As the absorption maxima in solid films consistent-
ly occur at lower energies than observed in solution, where-
as in solution the HODAs were shown to be largely planar
(vide supra), this suggests that the differences in lmax be-
tween solid and solution phase are largely medium effects.
In contrast, the appearance of an additional absorption at
long wavelength in the solid-state measurements is attribut-
ed to intermolecular interactions, that is, p–p stacking.
These interactions are dominant in the solid state, but do
not manifest itself in monodisperse solutions (up to 3 mm) at
room temperature, where the steric hindrance from lateral
alkyl chains is dominant. This aggregation leads to substan-
tial long-wavelength absorption for longer oligomers, and
for example, 1-7 the absorption >550 nm is clearly not a
result of the properties of isolated oligomer chains. These
findings are supported by our previous measurements of
bathochromic shift of solid 2-n oligodiacetylenes
(
ꢀ0.10 eV) of similar CL.[15] Furthermore, the spectra are
characterized by an additional electronic transition appear-
ing at lower energy, ꢀ0.23 eV below the main absorption
maxima, followed by a significant absorption increase in the
range of 550–800 nm. This characteristic pattern for all solid
oligomers under study was also reported previously by us
for the 2-n absorption in thin films.[15] Figure 6c and Fig-
ure 7d display a comparison between solution and thin-film
absorption for the shortest 1-3 and longest 1-7 solid oligo-
mers. The solid-state absorption data of the solid HODAs
are summarized in Table 2.
The correlation between the reciprocal value of the CL
and the absorption maximum (expressed in eV) is depicted
in Figure 7 for the maxima of both the solid state films and
the solutions in DCE. We see a similar linear dependence in
Chem. Eur. J. 2009, 15, 2296 – 2304
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2299

H. Zuilhof et al.
Figure 8. Absorption spectra of HODA 1-7 in methylcyclohexane at
293 K (b), 210 K (g) and 150 K (c); data at more intermediate
temperatures available in the Supporting Information.
Figure 7. lmax of the absorption of HODA series 1-n (n=3–7) in DCE
) solution at micromolar concentrations (2ꢁ10ꢂ6 m) compared to lmax
*
(
~
of the absorption of drop-casted films ( ) and lmax additional electronic
transition (ꢁ) as function of 1/CL. a: y=6.76x+2.51 (494 nm/R2 =
0.984), c: y=5.45x+2.50 (496 nm/R2 =0.991), c: y=5.53x+2.25
(551 nm/R2 =0.998).
criminate between these two effects the concentration de-
pendence of the absorption change was studied. The absorp-
tion change at 513 nm upon cooling and subsequent heating
of solutions of 1-7 in methylcyclohexane with concentrations
of ꢀ4 ꢁ10ꢂ6 m and ꢀ5 ꢁ10ꢂ7 m is shown in Figure 9.
Table 2. Solid state absorption data of HODAs 1-n (n=3–7)
shoulder
1-n (CL[a]
)
lmax [nm] ([eV])
lmax
[nm] ([eV])
1-3 (14)
1-4 (18)
1-5 (22)
1-6 (26)
1-7 (30)
430 (2.88)
441 (2.81)
453 (2.74)
459 (2.70)
462 (2.68)
468 (2.65)
486 (2.55)
495 (2.51)
503 (2.47)
509 (2.44)
[a] Conjugation length as sum of number of double and triple bonds.
longer members of 2-n series.[15] It is important to emphasize
that this systematic study of the optical properties of this
series of oligomers makes it possible to distinguish intra-
and intermolecular effects on the optical absorption of ex-
tended conjugated systems.
Figure 9. Absorption of HODA 1-7 in methylcyclohexane at 513 nm
upon cooling and heating between 293 K and 150 K measured for two
Temperature-dependent absorption in solution: More in-
sight in the origin of the spectral differences between solu-
tion and solid state was obtained by measuring the absorp-
tion spectra of HODA 1-7 in methylcyclohexane at lower
temperatures (Figure 8). The absorption band at 440 nm
shifts upon cooling initially towards the red and a shoulder
appears at 470 nm. This is probably owed to restriction of
the conformational motion at lower temperatures, resulting
in higher population of the lower vibrational levels of the
ground state and an slight increase of conjugation. Similar
effects were observed by Giesa et al. for short oligodiacety-
lenes in methyltetrahydrofuran.[18]
Upon further cooling an additional absorption band ap-
pears around 513 nm, which matches with the additional
peak observed in the solid state. Similar thermochromic be-
havior has been observed for polydiacetylenes in solution[32]
and other conjugated oligomers[33] and polymers,[34,35] and
this has been attributed to either intramolecular conforma-
tional changes or intermolecular aggregation effects. Yet, for
polymers these are frequently difficult to distinguish. To dis-
ꢂ7
solutions with concentrations of ꢀ4ꢁ10ꢂ6 m ( ) and ꢀ5ꢁ10 m ( ) with
~
*
sigmoidal curves fitted to the data.
The temperature at which the absorption change takes
place is dependent on the concentration of the oligomer.
The data was fitted to a sigmoidal curve from which the
transition temperature was obtained. The transition temper-
ature is the temperature at which the value of the absorp-
tion change is half of the maximum absorption change. In a
solution of 1-7 with a concentration of ꢀ4 ꢁ10ꢂ6 m the tran-
sition temperature upon cooling is 198 K, whereas for a so-
lution of ꢀ5 ꢁ10ꢂ7 m the transition takes place at 180 K.
The concentration dependence of the chromatic transition
shows that the additional absorption band at 513 nm arises
as a result of intermolecular p–p stacking interactions and is
not owed to conformational changes. The system shows sig-
nificant hysteresis upon heating of the sample. The transi-
tion temperatures shift to 224 K and 214 K for the solutions
with concentrations of respectively 4 ꢁ10ꢂ6 m and 5 ꢁ10ꢂ7 m.
2300
www.chemeurj.org
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 2296 – 2304

Synthesis and Properties of Oligodiacetylenes
FULL PAPER
This suggests that the aggregation process is relatively slow.
Similar hysteresis was found for polydiacetylenes in 1,2-di-
chloroethane by Wenz et al.[36] These experiments strongly
suggest that the thermochromism of polydiacetylenes in so-
lution is not solely caused by a conformational coil-to-rod
transition but that intermolecular interactions play an im-
portant role in the absorption change.
this series of HODAs up to CL=30 we do not see any satu-
ration in the evolution of lmax of the emission as function of
the chain length. In other words: Up to this length no evi-
dence is observed for truncation of the C-C conjugation as
would be suggested by the concept of effective conjugation
length.
The values of the lmax emission are of higher energy com-
pared to the literature data for 2-n, that is, 1-7 with CL=30
has the lmax emission of 492 nm compared to 520 nm for the
shorter 2-8 with 17 conjugated double and triple bonds. Ap-
parently, the chromophore of HODAs is different from that
of the 2-n series and deserves future spectroscopic and theo-
retical studies. The 0–0 transition is not detectable for this
series, which was also the situation for the low emitting 2-n
of similar CL. Therefore, it is not possible to study the evo-
lution of the Stokes shift for this series. The fluorescence
quantum yield is only marginal (ꢃ0.012) for the HODAs
having CLꢁ6, which is even lower than the values reported
for 2-n. The Ff decreases down to 0.001 for the longest
member of this series. This tendency is in line with the ob-
servation that PDA polymers show marginal fluorescence
quantum yields, mostly lower than 0.001.[29,38]
Steady-state fluorescence in solution: Emission spectra mea-
sured for millimolar solutions of the HODA series were re-
corded in n-hexane (Figure 10). The maximum fluorescence
Fluorescence lifetimes and anisotropy: Picosecond time-re-
solved single photon counting with lex =372 nm was used to
determine the fluorescence lifetimes (tF) of the oligomers
series 1-n. The observed lifetimes in the HODA series mea-
sured in n-hexane are shown in Table 4.
Figure 10. Fluorescence spectra of HODAs 1-n (n=1–7) in n-hexane;
inset: Emission maxima of HODA solutions in n-hexane versus 1/CL.
Table 4. Fluorescence lifetimes tF, their relative amplitudes A, and the
average lifetimes tAVG in n-hexane.
[b,c]
1-n (CL[a]
)
t1 (A1)[b]
t2 (A2)[b]
tAVG
quantum yield (Ff) is observed for the homocoupled mono-
mer 1-1 (Ff =0.041; see Table 3), and decreases with in-
creasing chain length. The emission maximum (expressed in
eV) decreases with an increasing chain length n and shows a
linear relation with the reciprocal value of the conjugation
length (Figure 10 inset), analogous to data previously report-
ed for 2-n.[15] This supports a continuously increasing conju-
gation of these oligomers, without major distortions or con-
formational changes in line with data for the absorption
maximum versus 1/CL (Figure 5 and Figure 7). The extrapo-
lated value for the lmax of the emission for the polymer (n=
8) is 2.43 eV (510 nm; Figure 10 bottom). In addition, for
1-1 (6)
1-2 (10)
1-3 (14)
40 (71)
54 (49)
19 (94)
252 (29)
126 (51)
576 (6)
101
91
55
[a] conjugation length as number of double and triple bonds. [b] tF [ps]
(relative amplitudes). [c] calculated using Equation (1).
The decay curves of 1-1 to 1-3 required fitting with two
exponentials; the marginal decays determined for 1-4 up to
1-7 (lifetimes, tꢃ10 ps) required only one exponent. The
average lifetime tAVG was calculated according to Equa-
tion (1):
A1
A1 þ A2
A2
A1 þ A2
ð1Þ
tAVG
¼
t1 þ
t2
Table 3. Emission data of HODAs 1-n (n=1–7) in n-hexane.
1-n (CL[a]
)
lmax [nm] ([eV])
Quantum yield Ff
[b,c]
1-1 (6)
430 (2.88)
457 (2.71)
464 (2.67)
484 (2.56)
487 (2.55)
490 (2.53)
492 (2.52)
0.041
0.012
0.008
0.006
0.005
0.003
0.001
for which A1 and A2 are the contributions of the decays
obtained from the curve fitting. The data in Table 4 indicate
that the excited-state lifetimes of oligomers are in line with
the trend shown for the fluorescence quantum yield: tF de-
creases rapidly with increasing chain length. Moreover, the
longest lifetimes are recorded for the shortest oligomers 1-1
and 2-2, which have the conjugation length of CL=6 and
10, respectively. This tendency is in line with the previously
presented data for 2-n[15] which showed the tAVG maximum
1-2 (10)
1-3 (14)
1-4 (18)
1-5 (22)
1-6 (26)
1-7 (30)
[a] Conjugation length as number of double and triple bonds.
[b] Quantum yield determined by comparison with quinine bisulfate in
0.1m H2SO4: Ff =0.535.[37] [c] Experimental error ꢄ0.002.
Chem. Eur. J. 2009, 15, 2296 – 2304
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2301

H. Zuilhof et al.
for the trimer with CL=7.
Fluorescence depolarization (r) of the HODAs under
present study was determined by picosecond time-resolved
fluorescence anisotropy measurements.[39] The resulting an-
ACHTUNGTRENNUNGisoACHTUNGTRENNUNGtropy lifetime is determined by the shape, size, and flexi-
bility of the rotating molecule. This technique has proven to
be useful in our recent investigations of the conformational
behavior of rod-shaped 2-n. Based on the experiments that
reveal extended conjugation (vide supra) it is assumed that
the HODAs also possess a relatively large axial ratio, and
that their rotation around the longitudinal axis progresses
much faster than the rotation around the short, perpendicu-
lar axes. Therefore, the observed anisotropy decay kinetics
r(t) of HODAs are indeed mono-exponential and character-
ized by an initial anisotropy value r0 and one rotation corre-
lation time (tR) according to Equation (2):[37]
Figure 11. Anisotropy lifetimes vs. the estimated length of HODA series
1-n with n=1–7 up to 8.2 nm. y=540.6x/R2 =0.97.
rðtÞ ¼ r0 ꢅ expðꢂt=tRÞ
ð2Þ
in which r0 is determined by the angle g between the ab-
sorption and emission transition moment [Eqn. (3)]:
molecule in its fully extended shape provides clear evidence,
that there are no significant geometrical changes of HODA
structures within this series, because otherwise tR would
have increased less than linearly with conjugation length CL
or the length of the fully extended system. Therefore, we
conclude that the long HODAs up to 30 double and triple
bonds do behave like conformationally rigid, molecular
rods.[41]
r0 ¼ ð3 cos2gꢂ1Þ=5
ð3Þ
The recorded initial anisotropy value r0 for the HODAs
series was 0.3, which indicates a small angle (ꢀ158) between
absorption and emission transition moments. This tendency
is analogous to the trends shown for long oligodiacetylene
oligomers 2-n[15] and the trimeric oligodiacetylenes investi-
gated previously.[12,20,29] The rotation correlation times tR for
HODAs recorded in n-hexane are listed in Table 5. Because
longer oligomers display a marginal emission the experimen-
tal error for these measurements was relatively high.
Conclusion
A novel, nanometer-sized, and highly soluble HODA series
was synthesized on a multi-milligram scale through a mild,
catalytic coupling under ambient conditions with high yields
and purity. The series ranges up to 30 conjugated double
and triple bonds with an estimated length of 8.2 nm and,
therefore, is one of the longest synthesized, fully conjugated
series of aromatic-free molecular wires.
The absorption and emission of HODAs show a batho-
chromic shift upon chain elongation. Furthermore, the thin-
film absorption measurements show an additional high-
wavelength absorption for all solid HODAs, which we att-
Table 5. The rotation correlation time tR of 1-n (n=1–7).
1-n (CL[a]
)
tR [ps]
1-1 (6)
1.25ꢁ102 (ꢄ 0.20ꢁ102)
1.94ꢁ102 (ꢄ 0.20ꢁ102)
2.6ꢁ102 (ꢄ 0.3ꢁ102)
3.0ꢁ102 (ꢄ 0.3ꢁ102)
3.2ꢁ102 (ꢄ 0.4ꢁ102)
3.7ꢁ102 (ꢄ 0.5ꢁ102)
4.3ꢁ102 (ꢄ 0.5ꢁ102)
1-2 (10)
1-3 (14)
1-4 (18)
1-5 (22)
1-6 (26)
1-7 (30)
[a] Conjugation length as number of double and triple bonds.
ACHUTNGRENrNUG ibACHUTNGTRENuNNGU te to the intermolecular stacking of p-p systems. In solu-
tion at room temperature, the steric hindrance from lateral
alkyl chains of the HODA backbone prevents this aggrega-
tion up to millimolar concentration. However, cooling of
solutions of HODA 1-7 gives rise to formation of aggregates
with absorption spectra similar to those of the solid HODA.
The dependency of the maxima of both the absorption
and the emission on the reciprocal conjugation length is
found to be linear and is similar with the correlation report-
ed for the 2-n series. Moreover, this linearity is also ob-
served for the emax of the absorption in n-hexane and DCE.
These observations are in line with the linear correlation
found for the rotational correlation times as a function of
the oligomer length. These patterns evidently show the con-
The anisotropy lifetimes showed an increase with the olig-
ACHTUNGTRENNUNGomer length indicating an increased rotation time around
perpendicular axis for longer oligomers. This is illustrated in
Figure 11 in which a linear dependence for tR and the length
of the oligomer is depicted. Such linearity has recently also
been reported by us[15] and others[40] for largely fully stretch-
ed species of similar sizes in which, under simplifying condi-
tions,[37] tR =hV/RT, and the molecular volume Vꢀlr2 (h=
viscosity, l=length of the molecule, and r=molecular diam-
eter). In other words: The tR values are proportional to the
molecular length l. The observed correlation of tR with the
2302
www.chemeurj.org
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 2296 – 2304

Synthesis and Properties of Oligodiacetylenes
FULL PAPER
in which
I
and IR are the integrated emission intensities of the
tinuously increased conjugation in the 1-n series up to 30
double and triple bonds.
oligodiacetACTHNUTRGNEyUNG lene and quinine bisulfate solutions, respectively, OD refers
to the optical densities of the respective solutions and n is the refractive
index.
Lifetime of fluorescence and fluorescence anisotropy in solution: The
fluorescence lifetime and anisotropy were recorded by using a FLS920P
Spectrometer (Edinburgh Instruments) for time correlated photon count-
ing (TCSP) (time set up: 5 or 10 ns, 4096 channels, 10000 counts for 1-1
to 1-4, 1000 counts for 1-5 to 1-7). Pulsed diode lasers (372 nm, FWHM:
54 ps; 444 nm, FWHM: 63 ps) and pulsed LEDꢃs (283 nm, FWHM:<
500 ps; 304 nm, FWHM:<350 ps) from PicoQuant were used as light
sources. The anisotropy measurements were performed by using vertical
and horizontal polarizations. All spectroscopic measurements were car-
ried out under magic-angle conditions unless stated otherwise, to avoid
the possible influence of rotational motions of the probe molecules.
Experimental Section
Solvents and reagents: For all dry reactions performed under a steady
stream of argon (or reductive atmosphere of argon/hydrogen mixture 1:1
v/v) the equipment was dried in an oven at 1508C for several hours and
allowed to cool down in an atmosphere of dry nitrogen or argon. Pure,
dry, and degassed ether and tetrahydrofuran were obtained by distillation
of the commercial material over sodium particles. CH2Cl2 was distilled
and dried over calcium hydride or sodium hydride. Dry DMF was pur-
chased from Sigma–Aldrich and stored under argon. All other specified
chemicals were commercially purchased (Aldrich, Fluka or Riedel-de
Haꢂn) and used without further purification.
General method for synthesis of (1-n) series via a) protodesilylation of
oligodiacetylenes (2-n) followed by b) catalytic homocoupling of oligo-
diacetylenes (3-n) under Sonogashira conditions, as illustrated in
Figure 2: The synthesis of the crosscoupled oligodiacetylene (2-n) is per-
formed according to the procedure described elsewhere.[15] a) A solution
of (2-n) (1 eq) in THF/MeOH (1:1, 5 mLmmolꢂ1) is stirred in round-bot-
tomed flask. H2O (3 dropsmmolꢂ1) and K2CO3 (2 eq) is added to the so-
lution and stirred for 3 h. After working up following the general proce-
dure, the terminal acetylene (3-n) is submitted to the catalytic homocou-
General work up and purification procedure: Reaction monitoring and
reagents visualization was performed on silica gel or reversed-phase silica
gel plates with UV-light (254 and 366 nm) combined with GC/MS. Usual-
ly the reaction mixture was diluted with water and extracted 3ꢁ with an
organic solvent (petroleum ether 40–60, hexane, or ethyl acetate). The
combined organic extracts were washed with brine and dried over anhy-
drous sodium sulfate prior to filtration and evaporation of the solvent
under reduced pressure. Flash chromatography was performed on com-
mercially available silica gel (0.035–0.070 nm pore diameter) and mix-
tures of freshly distilled petroleum ether 40/60 and ethyl acetate or re-
versed-phase silica gel (0.04–0.06 nm pore diameter, Screening Devices)
with freshly distilled mixtures of acetonitrile and ethyl acetate. Final pu-
rification was performed on Shimadzu preparative HPLC using a C18
column (Alltech Alltima 250 mmꢁ22 mm; 5m) with HPLC-grade water,
acetonitrile and ethylacetate mixture.
pling step (b). b) A mixture of terminal acetylene (3-n), PdACHTUNGTRENNUNG(PPh3)4 (7
mol%), CuI (8 mol%), distilled diethyl amine (2 mLmmolꢂ1) and THF
(5 mLmmolꢂ1) is placed in a round-bottomed flask, equipped with a mag-
netic stirrer. The mixture is stirred for 3 h at 258C under ambient atmo-
AHCTUNGERTGsNNUN phere, concentrated and filtrated over a short silica gel column (5%
Et3N solution in petroleum ether 40/60). The residue is pre-purified on
reversed phase silica (ACN/EtOAc) and finally purified on preparative
HPLC to give pure (99.5%) HODA (1-n).
Nuclear magnetic resonance spectroscopy and mass spectroscopy:
1H NMR and 13C NMR spectra were determined at room temperature by
using a Bruker CXP 400 NMR-spectrometer. The samples were prepared
in CDCl3 solutions unless indicated otherwise. Chemical shifts are report-
ed in ppm downfield relative to tetramethylsilane (d=0 ppm for 1H) or
based on the solvent peak (CDCl3) (d=77.00 ppm for 13C NMR) as an
internal standard. HRMS was performed by using a Finnigan Mat95 mass
spectrometer. MALDI-TOF MS analysis was performed by using a Ul-
traFlex TOF (Bruker Daltonics Bremen).
AHCTUNGTERG(NNUN 5E,11E)-5,12-dibutyl-2,15-dimethoxy-2,15-dimethyl-6,11-dipropylhexa-
deca-5,11-dien-3,7,9,13-tetrayne (1-1): Pale yellow liquid (1.00 mmol,
0.490 g, 96%) from (2-1) (2.08 mol, 0.662 g); 1H NMR (300 MHz,
CDCl3): d=0.91–0.96 (m, 12H), 1.30–1.43 (m, 4H), 1.50 (12H), 1.50–1.65
(8H), 2.37–2.47 (8H), 3.38 ppm (6H) 13C NMR (75 MHz, CDCl3): d=
13.57, 13.92, 21.74, 22.00, 28.34, 30.58, 34.96, 36.75, 51.74, 71.18, 82.17,
83.50, 83.60, 102.23, 128.09, 133.33 ppm; HRMS: m/z: observed
(490.3815); calculated (490.3811).
(5E,9E,15E,19E)-5,9,16,20-tetrabutyl-2,23-dimethoxy-2,23-dimethyl-
6,10,15,19-tetrapropyltetracosa-5,9,15,19-tetraen-3,7,11,13,17,21-hexayne
(1-2): Pale yellow liquid (0.29 mmol, 0.231 g, 85%) from (2-2) (0.69 mol,
0.322 g); 1H NMR (300 MHz, CDCl3): d=0.88–0.96 (m, 24H), 1.29–1.41
(m, 8H), 1.51 (s, 12H), 1.49–1.66 (m, 16H), 2.41–2.52 (m, 16H),
3.39 ppm (s, 6H); 13C NMR (75 MHz, CDCl3): d=13.59, 13.93, 13.99,
21.75, 21.89, 22.06, 22.22, 28.41, 29.70, 30.67, 30.75, 34.96, 35.13, 36.94,
37.08, 51.72, 71,20, 82.93, 83.90, 84.58, 97.88, 100.46, 100.69, 127.77,
129.23, 129.59, 133.97 ppm; HRMS: m/z: observed (786.6318); calculated
(786.6315).
Steady-state absorption and fluorescence: Absorption spectra of the
oligoACHTUNGTRENNUNGdiacetylenes in n-hexane (spectrophotometric grade, Riedel-de
Haꢂn) and DCE (spectrophotometric grade, Sigma-Aldrich) were record-
ed by using a Cary 100 UV-Vis spectrophotometer (scan range: 200–
800 nm, scan rate: 300 nmminꢂ1, date interval 0.5 nm) and steady-state
fluorescence by using a FLS920P Spectrometer (slit exc.: 2 nm, slit em.:
2 nm, step: 1.0, dwell: 0.2 s). Absorption spectra of oligodiacetylenes in
film by means of drop casting were recorded by using a Cary 50 UV-Vis
spectrophotometer (scan range 200–850 nm, scan rate 300 nmminꢂ1, data
interval 0.5 nm). Absorption spectra at low temperatures in methylcyclo-
hexane (spectrophotometric grade, Sigma-Aldrich) were obtained by
using an LP920 spectrophotometer (Edinburgh Instruments Limited)
fitted with a 450 W Xe arc lamp as probe-light source, a red-sensitive
photomultiplier (R928, Hamamatsu) as detector and a cryostat (Optistat
DN; Oxford Instruments, UK) with temperature controller (ITC 503S;
Oxford Instruments, UK) as sample holder.
(5E,9E,13E,19E,23E,27E)-5,9,13,20,24,28-hexabutyl-2,31-dimethoxy-
2,31-dimethyl-6,10,14,19,23,27-hexapropyldotriaconta-5,9,13,19,23,27-
hexaen-3,7,11,15,17,21,25,29-octayne (1-3): Yellow liquid (0.46 mmol,
0.499 g, 84%) from (2-3) (1.10 mol, 0.677 g); 1H NMR (300 MHz,
CDCl3): d=0.88–0.97 (m, 36H), 1.28–1.42 (m, 12H), 1.51 (s, 12H), 1.51–
1.68 (m, 24H), 2.42–2.53 (m, 24H), 3.39 ppm (s, 6H); 13C NMR (75 MHz,
CDCl3): d=13.59, 13.61, 13.93, 13.99, 21.74, 21.91, 22.07, 22.23, 22.28,
28.42, 29.69, 30.68, 30.77, 30.83, 34.94, 35.13, 36.97, 37.10, 37.27, 51.71,
71.21, 83.08, 83.98, 84.74, 98.34, 98.63, 99.00, 100.46, 101.05, 127.79,
128.94, 129.13, 129.40, 129.74, 130.31, 134.01 ppm; HRMS: m/z: observed
(1082.8840); calculated (1082.8819).
Determination of fluorescence quantum yield in solution: In order to
evaluate the fluorescence quantum yield (FF) of the oligodiacetylenes so-
lution in n-hexane and DCE, the areas of the corrected emission spectra
were compared to a spectrum of a reference solution of quinine bisulfate
in H2SO4 (0.1m) measured at 366 nm having FR =0.535.[37] The fluores-
cence quantum yields of the oligodiacetylenes were determined using the
Equation (4):
(5E,9E,13E,17E,23E,27E,31E,35E)-5,9,13,17,24,28,32,36-octabutyl-2,39-
dimethoxy-2,39-dimethyl-6,10,14,18,23,27,31,35-octapropyltetraconta-
5,9,13,17,23,27,31,35-octaen-3,7,11,15,19,21,25,29,33,37-decayne
(1-4):
Yellow solid (0.29 mmol, 0.400 g, 80%) from (2-4) (0.72 mol, 0.550 g);
1H NMR (300 MHz, CDCl3): d=0.87–0.97 (m, 48H), 1.27–1.41 (m, 16H),
1.51 (s, 12H), 1.51–1.70 (m, 32H), 2.41–2.53 (m, 32H), 3.39 ppm (s, 6H);
13C NMR (75 MHz, CDCl3): d=13.59, 13.62, 13.94, 13.99, 21.75, 21.92,
I ODR n2
ð4Þ
FF ¼ F
R IR OD nR
2
Chem. Eur. J. 2009, 15, 2296 – 2304
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2303

H. Zuilhof et al.
22.08, 22.23, 22.29, 28.42, 29.70, 30.69, 30.78, 30.85, 34.93, 35.10, 35.14,
36.98, 37.11, 37.30, 51.71, 71.21, 83.10, 84.01, 84.78, 98.44, 98.78, 98.80,
99.09, 99.60, 100.39, 101.15, 127.80, 128.98, 129.12, 129.45, 129.86, 129.93,
130.37, 134.02 ppm; HRMS: m/z: observed (1379.1306); calculated
(1379.1323); MALDI-TOF-MS: m/z: observed (1379.01).
[7] Y. Zhu, A. Babel, S. A. Jenekhe, Macromolecules 2005, 38, 7983–
7991.
[8] S. A. Jenekhe, Chem. Mater. 2004, 16, 4381–4382.
[9] J. M. Tour, Chem. Rev. 1996, 96, 537–553.
[10] R. E. Martin, F. Diederich, Angew. Chem. 1999, 111, 1440–1469;
Angew. Chem. Int. Ed. 1999, 38, 1350–1377.
(5E,9E,13E,17E,21E,27E,31E,35E,39E,43E)-
[11] a) M. Polhuis, C. C. J. Hendrikx, H. Zuilhof, E. J. R. Sudhçlter, Tet-
rahedron Lett. 2003, 44, 899–901; b) G. S. Pilzak, B. van Lagen,
C. C. J. Hendrikx, E. J. R. Sudhçlter, H. Zuilhof, Tetrahedron Lett.
2008, 49, 4949–4952.
[12] C. C. J. Hendrikx, M. Polhuis, A. Pul-Hootsen, R. B. M. Koehorst,
A. Hoek van, H. Zuilhof, E. J. R. Sudhçlter, Phys. Chem. Chem.
Phys. 2005, 7, 548–553.
[13] Y. Takayama, C. Delas, K. Muraoka, F. Sato, Org. Lett. 2003, 5,
365–368.
[14] Y. Takayama, C. Delas, K. Muraoka, M. Uemura, F. Sato, J. Am.
Chem. Soc. 2003, 125, 14163–14167.
5,9,13,17,21,28,32,36,40,44-decabutyl-2,47-dimethoxy-2,47-dimethyl-
6,10,14,18,22,27,31,35,39,43-decapropyloctatetraconta-
5,9,13,17,21,27,31,35,39,43-decaen-3,7,11,15,19,23,25,29,33,37,41,45-dodec-
ayne (1-5): Yellow/orange solid (0.097 mmol, 0.163 g, 81%) from (2-5)
(0.24 mol, 0.219 g); 1H NMR (300 MHz, CDCl3): d=0.83–0.98 (m, 60H),
1.27–1.42 (m, 20H), 1.51 (s, 12H), 1.51–1.70 (m, 40H), 2.43–2.52 (m,
40H), 3.39 ppm (s, 6H); 13C NMR (75 MHz, CDCl3): d=13.59, 13.62,
13.93, 13.99, 21.75, 21.92, 22.08, 22.23, 22.30, 28.43, 29.35, 29.69, 30.69,
30.79, 30.86, 34.93, 35.11, 35.14, 36.98, 37.11, 37.30, 51.71, 71.21, 83.11,
84.02, 84.79, 98.48, 98.74, 98.80, 99.20, 99.24, 99.39, 99.69, 100.37, 101.17,
127.81, 128.94, 128.99, 129.16, 129.17, 129.46, 129.50, 129.71, 129.81,
129.92, 130.38, 134.02 ppm; HRMS: m/z: observed (1675.3814); calculat-
ed (1675.3827); MALDI-TOF-MS: m/z: observed (1675.25).
[15] G. S. Pilzak, B. van Lagen, C. C. J. Hendrikx, E. J. R. Sudhçlter, H.
Zuilhof, Chem. Eur. J. 2008, 14, 7939–7950.
[16] A. Elangovan, Y.-H. Wang, T.-I. Ho, Org. Lett. 2003, 5, 1841–1844.
[17] F. Wudl, S. P. Bitler, J. Am. Chem. Soc. 1986, 108, 4685–4687.
[18] R. Giesa, R. C. Schulz, Polym. Int. 1994, 33, 43–60.
[19] B. E. Kohler, D. E. Schilke, J. Chem. Phys. 1987, 86, 5214–5215.
[20] G. M. Balkowski, M. Groeneveld, H. Zhang, C. C. J. Hendrikx, M.
Polhuis, H. Zuilhof, W. J. Buma, J. Phys. Chem. A 2006, 110, 11435–
11439.
[21] N. S. Bayliss, E. G. McRae, J. Phys. Chem. 1954, 58, 1002–1006.
[22] C. Reichardt, Solvents and Solvent Effects in Organic Chemistry,
Wiley-VCH, 2003.
[23] D. V. Matyushov, R. Schmid, B. M. Ladanyi, J. Phys. Chem. B 1997,
101, 1035–1050.
[24] H. Kuhn, J. Chem. Phys. 1949, 17, 1198–1212.
[25] H. Kuhn, J. Chem. Phys. 1958, 29, 958–959.
[26] N. Li, K. Jia, S. Wang, A. Xia, J. Phys. Chem. A 2007, 111, 9393–
9398.
[27] N. E. Craft, J. H. Scares Jr, J. Agric. Food Chem. 1992, 40, 431–434.
[28] R. E. Martin, U. Gubler, J. Cornil, M. Balakina, C. Boudon, C. Bos-
shard, J.-P. Gisselbrecht, F. Diederich, P. Gꢄnter, M. Gross, J.-L.
Brꢅdas, Chem. Eur. J. 2000, 6, 3622–3635.
[29] H. Zuilhof, H. M. Barentsen, M. Dijk van, E. J. R. Sudhçlter,
R. J. O. M. Hoofman, L. D. A. Siebbeles, M. P. de Haas, J. M.
Warman in Supramolecular Photosensitive and Electroactive Materi-
als (Ed. H. S. Nalwa), Academic Press, San Diego, San Francisco,
New York, Boston, London, Sydney, Tokyo, 2001, pp. 339–437.
[30] J. Gierschner, J. Cornil, H. Egelhaaf, J. Adv. Mater. 2007, 173–191.
[31] S. S. Zade, M. Bendikov, Org. Lett. 2006, 5243–5246.
[32] B. Chu, R. L. Xu, Acc. Chem. Res. 1991, 24, 384–389.
[33] J. J. Apperloo, R. A. J. Janssen, P. R. L. Malenfant, J. M. J. Frechet,
Macromolecules 2000, 33, 7038–7043.
(5E,9E,13E,17E,21E,25E,31E,35E,39E,43E,47E,51E)-
5,9,13,17,21,25,32,36,40,44,48,52-dodecabutyl-2,55-dimethoxy-2,55-dimeth-
yl-6,10,14,18,22,26,31,35,39,43,47,51-dodecapropylhexapentaconta-
5,9,13,17,21,25,31,35,39,43,47,51-dodecaen-
3,7,11,15,19,23,27,29,33,37,41,45,49,53-tetradecayne (1-6): Orange solid
(0.049 mmol, 0.097 g, 82%) from (2-6) (0.12 mol, 0.127 g); 1H NMR
(300 MHz, CDCl3): d=0.85–0.98 (m, 72H), 1.27–1.42 (m, 24H), 1.51 (s,
12H), 1.51–1.69 (m, 48H), 2.45–2.55 (m, 48H), 3.39 ppm (s, 6H);
13C NMR (75 MHz, CDCl3, 258C): d=13.59, 13.63, 13.94, 14.00, 21.74,
21.92, 22.07, 22.23, 22.30, 28.41, 29.69, 30.68, 30.77, 30.85, 34.92, 35.09,
35.12, 36.96, 37.10, 37.31, 51.71, 71.20, 83.08, 84.01, 84.82, 98.47, 98.52,
98.70, 98.79, 99.26, 99.34, 99.48, 99.71, 100.32, 101.17, 127.81, 128.91,
129.22, 129.47, 129.66, 129.76, 129.93, 130.38, 134.01 ppm; MALDI-TOF-
MS: m/z: observed (1971.41); calculated (1971.63).
(5E,9E,13E,17E,21E,25E,29E,35E,39E,43E,47E,51E,55E,59E)-
5,9,13,17,21,25,29,36,40,44,48,52,56,60-tetradecabutyl-2,63-dimethoxy-
2,63-dimethyl-6,10,14,18,22,26,30,35,39,43,47,51,55,59-tetradecapropylte-
trahexaconta-5,9,13,17,21,25,29,35,39,43,47,51,55,59-tetradecaen-
3,7,11,15,19,23,27,31,33,37,41,45,49,53,57,61-hexadecayne (1-7): Orange/
red solid (0.040 mmol, 0.091 g, 79%) from (2-7) (0.10 mol, 0.119 g);
1H NMR (300 MHz, CDCl3): d=0.87–0.98 (m, 84H), 1.27–1.41 (m, 28H),
1.51 (s, 12H), 1.51–1.68 (m, 56H), 2.45–2.55 (m, 56H), 3.39 ppm (s, 6H);
13C NMR (75 MHz, CDCl3): d=13.59, 13.63, 13.93, 14.00, 21.75, 21.93,
22.08, 22.23, 22.31, 28.42, 29.69, 30.69, 30.79, 30.87, 34.93, 35.10, 35.14,
36.98, 37.11, 37.31, 37.33, 51.71, 71.22, 83.12, 84.03, 84.80, 98.49, 98.71,
98.82, 98.85, 99.26, 99.27, 99.31, 99.38, 99.42, 99.51, 99.71, 99.74, 100.39,
101.17, 127.81, 128.92, 129.00, 129.18, 129.21, 129.24, 129.47, 129.71,
129.77, 129.93, 130.38, 134.02 ppm; MALDI-TOF-MS: m/z: observed
(2267.67); calculated (2267.88).
[34] F. J. M. Hoeben, P. Jonkheijm, E. W. Meijer, A. Schenning, Chem.
Rev. 2005, 105, 1491–1546.
[35] N. Lebouch, S. Garreau, G. Louarn, M. Belletete, G. Durocher, M.
Leclerc, Macromolecules 2005, 38, 9631–9637.
[36] G. Wenz, M. A. Mꢄller, M. Schmidt, G. Wegner, Macromolecules
1984, 17, 837–850.
[37] J. R. Lakowicz, Principles of Fluorescence Spectroscopy, Kluwer
Academic/Plenum Publishers, 1999, 420–421.
[38] R. Lecuiller, J. Berrehar, C. Lapersonne-Meyer, M. Schott, Phys.
Rev. Lett. 1998, 80, 4068–4071.
Acknowledgements
The authors thank the Dutch Technology Foundation STW for generous
funding of this research (projectno. WPC 5740), and Dr. Jan Kroon
(ECN), Dr. Herman Schoo (TNO), Dr. Joost Smits (Shell) and Prof.
Wybren Jan Buma (Univ. of Amsterdam) for helpful discussions.
[39] P. Kapusta, R. Erdmann, U. Ortmann, M. Wahl, J. Fluoresc. 2003,
13, 179–183.
[40] N. Aratani, Z. S. Yoon, D. Kim, A. Osuka, J. Chin. Chem. Soc. 2006,
53, 41–46.
[41] Theoretical studies that further clarify this effect are currently ongo-
ing in our laboratories.
[1] M. Surin, R. Lazzaroni, W. J. Feast, A. P. H. J. Schenning, E. W.
Meijer, P. Leclere, Synth. Met. 2004, 147, 67–72.
[2] J. G. Rodriguez, J. L. Tejedor, J. Org. Chem. 2002, 67, 7631–7640.
[3] A. Aviram, M. A. Ratner, Chem. Phys. Lett. 1974, 29, 277–283.
[4] A. Pron, P. Rannou, Prog. Polym. Sci. 2002, 27, 135–190.
[5] N. Tessler, D. J. Pinner, P. K. H. Ho, Opt. Mater. 2001, 17, 155–160.
[6] J. H. Burroughes, C. A. Jones, R. H. Friend, Nature 1988, 335, 137–
141.
Received: June 9, 2008
Revised: October 18, 2008
Published online: January 20, 2009
2304
www.chemeurj.org
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 2296 – 2304