Push-pull oligomers with 2,2-dicyanovinyl groups as electron acceptors

Article abstract of DOI:10.1002/ejoc.200600704

Three conjugated oligomer series with terminal donor-acceptor substitution were studied: oligo(1,4-phenylenevinylene)s DAOPVs 4a-d (n = 1-4), oligo(1,4-phenyleneethynylene)s DAOPEs 6a-d (n = 1-4) and oligo(2,5- thienyleneethynylene)s DAOTEs 8a-e (n = 1-5)

Full text of DOI:10.1002/ejoc.200600704

FULL PAPER
DOI: 10.1002/ejoc.200600704
Push-Pull Oligomers with 2,2-Dicyanovinyl Groups as Electron Acceptors
Herbert Meier,*[a] Bastian Mühling,[a] Jürgen Gerold,[a] Dominic Jacob,[b] and
Annette Oehlhof[a]
Keywords: Chromophores / Conjugation / Oligomers / Push-pull effect
Three conjugated oligomer series with terminal donor–ac-
ceptor substitution were studied: oligo(1,4-phenylenevinyl-
ene)s DAOPVs 4a–d (n = 1–4), oligo(1,4-phenyleneethyn-
ylene)s DAOPEs 6a–d (n = 1–4) and oligo(2,5-thienylene-
ethynylene)s DAOTEs 8a–e (n = 1–5). Dialkylamino or meth-
oxy groups served as electron donors and 2,2-dicyanovinyl
groups as strong electron acceptors. The push-pull effect po-
larizes the molecular chains – an effect which is documented
by the splitting of the 13C chemical shifts of two carbon atoms
of the double or triple bonds in the chain. For higher oligo-
mers (n Ն 3), the effect is mainly localized at the chain ends.
The long-wavelength absorption results in a charge-transfer
band which loses gradually its CT character since the intra-
molecular charge transfer (ICT) declines with increasing
numbers n of repeat units (increasing chromophore exten-
sion, increasing distance D–A). As a consequence, the
DAOPVs 4a–d and the DAOPEs 6a–d represent hypso-
chromic series, for which the λmax values decrease steadily
from n = 1 to n = 4. This is also true for the DAOTE series 8a–
e, but contrary to 4a–d and 6a–d the decrease is very small
in the beginning [λmax(1) – λmax(2) = 1 nm] and grows with
increasing n to λmax(4) – λmax(5) = 29 nm. Thus, series 8a–e
represents an until now unknown type of conjugated push-
pull oligomers.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
Introduction
Conjugated oligomers and polymers attract much atten-
tion because of their interesting properties in materials sci-
ence.[1] Push-pull systems having terminal donor–acceptor
substitution represent a special class of such oligomers.[2]
Their major applications are in the field of nonlinear op-
tics (NLO),[2,3] photorefractive materials (PR)[4] and two-
photon absorption (TPA).[5] Normally, conjugated oligo-
mers exhibit a monotonous bathochromic shift of the long-
wavelength band when the number n of repeat units is in-
creased. However, a terminal donor–acceptor substitution
can change this so that λmax(n) decreases monotonously
with increasing numbers n (hypsochromic effect), or is al-
most constant [λmax(n) ≈ λϱ], or goes through a maximum
for a certain nЈ before it approaches to λϱ. The specific be-
havior depends on the strength of donor D and acceptor
group A and to a certain extent also on the conjugated
chain of the repeat units [X]n (Scheme 1).[1v,2]
Scheme 1. Donor–acceptor-substituted conjugated oligomers
DAOPVs, DAOPEs and DAOTEs.
still unknown. We describe here oligomers 1 with composite
repeat
units,
namely
oligo(1,4-phenylenevinylene)s
(DAOPVs), oligo(1,4-phenyleneethynylene)s (DAOPEs)
and oligo(2,5-thienyleneethynylene)s (DAOTEs) bearing
2,2-dicyanovinyl groups as acceptor A and dialkylamino or
methoxy groups as donor groups D (Scheme 1).
Some time ago we started to study the effect of 2,2-dicya-
novinyl groups as very strong electron acceptors in push-
pull-substituted conjugated oligomers.[6] Simple series 1
having this acceptor, vinylene or 1,4-phenylene repeat units
X and alkoxy or dialkylamino as terminal donor groups are
Results and Discussion
Synthesis
[a] Institut für Organische Chemie der Johannes Gutenberg Uni-
versität,
It turned out that coupling reactions of Sonogashira–
Hagihara or Heck type are difficult with 2,2-dicyanovi-
nylbenzene derivatives. Therefore we decided to introduce
the desired acceptor group by condensation reactions of the
corresponding aldehydes and malononitrile. Scheme 2
Duesbergweg 10–14, 55099 Mainz, Germany
Fax: +49-6131-3925396
E-mail: hmeier@mail.uni-mainz.de
[b] Nirmala College, Muvattupuzha,
India
Eur. J. Org. Chem. 2007, 625–631
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
625

H. Meier, B. Mühling, J. Gerold, D. Jacob, A. Oehlhof
FULL PAPER
shows the reaction of oligo(1,4-phenylenevinylene)s 2a–
Scheme 4 demonstrates the preparation of the DAOTEs
d,[7,8] bearing terminal dialkylamino groups and formyl 8a–e. The aldehydes 7a–e[10] react with 3 to generate the
groups, and malononitrile 3. The yields of the target com- target compounds 8a–e. The yields are again high for the
pounds 4a–d are high for the shorter chains and somewhat lower members of the series and decrease with increasing
lower for the longer chains. The branched alkyl chains serve chain length. The solubilizing properties of the methoxy
as solubilizing groups. The dicyanovinyl group renders a group are comparably low, but the OTE chain provides a
much lower solubility than the formyl group. Therefore better solubility than the OPV and OPE chains. Therefore
100 MHz 13C NMR spectra with a reliable signal/noise ra- 1H NMR spectra of 8a–e and 13C NMR spectra of 8a–d
tio could only be obtained for 4a–c but not for 4d.
could be obtained in CDCl3.
Scheme 2. Preparation of the DAOPVs 4a–d.
Scheme 4. Preparation of the OTEs 8a–e having terminal donor–
acceptor substitution.
Scheme 3 shows the related procedure for the prepara-
tion of the DAOPEs 6a–d. The aldehydes 5a–d[9] and ma-
lononitrile (3) react to the target compounds 6a–d. The
yields are very high for the first members of the series and
decrease with increasing chain length. The didodecylamino
group serves as donor group and enhances the solubility.
Analogous to 4d, a 13C NMR spectrum of 6d could not be
obtained. Since 6d is even less soluble in CDCl3 than 4d,
the 1H NMR spectrum of 6d was measured in CDCl2–
CDCl2 at 60 °C.
Push-Pull Effect
The push-pull effect of the DAOVPs 4a–4d, DAOPEs
6a–6d and DAOTEs 8a–8e provokes a polarization of the
molecules in the ground state S0. This can be expressed by
the participation of dipolar resonance structures (valence
bond theory VB) or – in particular for the higher members
(n Ն 2) of the series – better by dipolar segments having
partial dipole moments µD and µA at the chain ends.[7,9]
Scheme 5 demonstrates the two models for series 8.
The double bonds in 4a and the triple bonds in 6a and
8a are strongly polarized. Scheme 6 demonstrates this in
comparison to the corresponding systems 10,[7] 11[9] and
12[10] which bear NO2 groups instead of dicyanovinyl
groups. 13C Chemical shifts are very sensitive toward
changes in the electron density. The donor groups cause a
high-field shift and the acceptor group a low-field shift –
each in the β-position of the multiple bonds. Thus, the ole-
finic carbon atoms in 4a have the δ values 129.0 + 5.1 =
134.1 and 129.0 – 7.2 = 121.8 ppm (Scheme 6); δ =
129.0 ppm is the 13C chemical shift for the unsubstituted
(E)-stilbene, 89.4 for tolane and 86.2 for dithienylacetylene.
The ∆δ values of the olefinic or acetylenic carbon atoms
listed in Scheme 6 indicate the polarization of the multiple
bonds. AM1 calculations of OPVs. and OPEs with the DA
combination N(CH3)2/NO2 revealed that the ∆δ values ob-
Scheme 3. Preparation of the DAOPEs 6a–d.
626
www.eurjoc.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2007, 625–631

Push-Pull Oligomers with 2,2-Dicyanovinyl Groups
FULL PAPER
tained for the double or triple bonds correlate exactly with
the charge differences ∆q for these bonds.[7,9] The effect of
the dicyanovinyl group is similar (4a/10, 6a/11) or even
stronger (8a/12) than the effect of the nitro group.
Extension of the chains 4, 6 and 8 leads in all cases to a
decrease of the ∆δ values with increasing numbers n. The
measured δ values for the terminal multiple bonds and their
differences ∆δ are listed in Table 1. The ∆δ values for exam-
ple in series 8a–d decline from 11.6 to 5.1 and 5.2, respec-
tively. The latter values are typical for purely donor or pu-
rely acceptor-substituted compounds;[7–10] that means the
push-pull effect disappears completely with increasing dis-
tance A–D.
Table 1. 13C NMR spectroscopic data of the terminal double/triple
bonds (δ values in CDCl3 related to TMS as internal standard, ∆δ
values indicating the polarization of the multiple bonds).
Scheme 5. Visualization of the push-pull effect of the DAOTEs 8:
a) VB model of 8a, b) model with terminal partial dipole moments
µA and µD for 8b–e.
n
δ(α)
δ(β)
∆δ
δ(α)
δ(β)
∆δ
4a
4b
4c
6a
6b
6c
8a
8b
8c
8d
1
2
3
1
2
3
1
2
3
4
134.1 121.3 12.8
129.9 122.7 7.2
129.2 123.0 6.2
121.3 134.1 12.8
125.7 133.1 7.4
127.0 133.0 6.0
98.4
94.0
93.4
95.7
89.7
88.9
88.7
87.4
86.9
87.0
84.1
83.5
83.6
83.6
11.0
7.1
6.4
11.6
6.2
5.3
87.4
89.7
90.1
84.1
86.4
88.4
88.2
98.4
95.2
94.7
95.7
92.0
93.4
93.4
11.0
5.5
4.6
11.6
5.6
5.0
5.1
5.2
The inner multiple bonds in 4c, 6c, 8c and 8d do not
exhibit a significant polarization (∆δ Ͻ 1.0). This result is
in accordance with the second model in Scheme 5. A DFT//
B3LYP/6-31G* study of a compound related to 8b, which
contains a 4-dimethylaminophenyl group instead of a 5-
methoxythien-2-yl group came to the corresponding result,
that the polarization induced by the push-pull effect is
mainly present in the chain ends but not in the center.[11]
UV/Vis Absorption
The long-wavelength electron transition of conjugated
systems is strongly influenced by push-pull effects. There
are several possibilities to estimate the strength of the push-
pull effect of terminal donor and acceptor groups on a con-
jugated chain.[12] A simple method consists of the energy
difference ∆E between the frontier HOMO (donor) and
LUMO (acceptor) in isolated individual molecules. The
smaller the |∆E| value is, the stronger is the push-pull ef-
fect.[12a] Dimethylaminobenzene and nitrobenzene give for
example a |∆E| value of 7.42 eV for DAOPV or DAOPE
series with terminal dimethylamino and nitro groups.[12a]
Since 2-cyanocinnamonitrile is a stronger acceptor com-
pound than nitrobenzene, the |∆E| value for the series 4a–d
and 6a–d should be even lower. More accurate methods
take the individual π-chain with its coupling to the frontier
orbitals of D and A into account. In particular this seems
Scheme 6. Polarization of the central double or triple bonds in 4,
6a and 8a compared to the effect of the corresponding nitro com-
pounds 10, 11 and 12 (δ values: 13C chemical shifts in CDCl3 re-
lated to TMS as internal standard, ∆δ: shift differences of the mul-
tiple bonds).
Eur. J. Org. Chem. 2007, 625–631
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
627

H. Meier, B. Mühling, J. Gerold, D. Jacob, A. Oehlhof
FULL PAPER
to be necessary for the OTE series 8a–e. According to ear- oligomers, in which the transition ergies ∆E(n) pass through
lier findings,[2] the intramolecular charge transfer (ICT), a minimum for a certain nЈ and then enter for higher n
which is involved in the long-wavelength absorption, is bet- values into a region of convergence to λϱ.[2] In series 8, this
ter fulfilled for 2,5-thienylenevinylene repeat units than for minimum is already reached for n = 1, but the region of
1,4-phenylenevinylene or 1,4-phenyleneethynylene units.
convergence is characterized by a high effective conjugation
The long-wavelength absorption maxima of three series length nECL. For the unsubstituted OTE series an nECL
4a–d and 6a–d and 8–e are visualized in Figure 1. The DA- value of 12 was estimated.[14] Certainly many more (than
OPVs 4a–d and the DAOPEs 6a–d are hypsochromic series; five) members of series 8 have to be studied in order to see
that means extension of the chromophore (increasing values the convergence region and the approach to λϱ.
n) leads to continous blue-shifts of the absorption bands.
The strong push-pull effect of the D/A-combination R2N/
CH=C(CN)2 or CH3O/CH=C(CN)2 causes a strong ICT
for the lowest members 4a, 6a and 8a (n = 1) of the three
series, where the distances D–A are small. Increasing values
n provoke a decreasing ICT. The red-shift caused by ICT is
then diminished. This leads to an overall hypsochromic ef-
fect because the extension of the chromophores can not
Conclusions
Conjugated oligomers 4a–d, 6a–d and 8a–e, having 1,4-
phenylenevinylene, 1,4-phenyleneethynylene or 2,5-thienyl-
eneethynylene repeat units [n = 1–4,(5)] and terminal do-
nor–acceptor substitution [R2N/CH=C(CN)2 or CH3O/
CH=C(CN)2] were obtained by Knoevenagel condensation
compensate the influence of the decreasing ICT on the
reactions of the corresponding aldehydes and malononitrile.
long-wavelength absorption. The charge-transfer band loses
The push-pull effect of the compounds leads to a polariza-
gradually its CT character.[2] Both series 4 and 6 should
tion of the chains, for n Ͼ 2 in particular of the chain ends.
An MO oriented model takes this better into account than
a VB model. An easy experimental proof of the polarization
is possible on the basis of the 13C chemical shift differences
∆δ of the two carbon atoms of each double or triple bond
in the chain.
approach to limiting values λϱ, whose prediction[2] would
demand the comparison with the corresponding series with-
out push-pull effect, which is unknown.
The intramolecular charge transfer (ICT) plays an out-
standing role for the long-wavelength absorption. It causes,
induced by the change of the electron correlation energy[2]
a red-shift which decreases with increasing numbers n of
repeat units, that means with increasing distance D–A. The
charge-transfer band loses gradually its character. Since the
extension of the conjugation can not compensate this effect,
all three discussed oligomer series are hypsochromic series.
Whereas the DAOPVs 4a–d and the DAOPEs 6a–d exhibit
this behavior in a mode reminiscent of some other recently
found[7–9] push-pull oligomers, the series DAOTE 8a–e be-
longs to a new type. Within the studied region of n = 1–5,
the λmax values are first almost constant and decrease then
more and more. Obviously, the extension of the conjugation
can nearly compensate the decrease of the ICT only up to
n = 3.
Figure 1. Long-wavelength absorption maxima of the OPVs 4a–d
(n = 1–4), OPEs 6a–d (n = 1–4) and OTEs 8a–e (n = 1–5) (measure-
ments in CDCl3).[13]
Experimental Section
General: The melting points were measured with a Büchi melting
point apparatus and are uncorrected. The UV/Vis spectra were ob-
tained with a Zeiss MCS 320/340 spectrometer. The 1H and 13C
Whereas the differences [λmax(n) – λmax(n+1)] decrease
with increasing numbers n for the two series DAOPV (4a– NMR spectra were recorded with the Bruker spectrometer AMX
400. CDCl3 served as solvent unless otherwise noted, and TMS
was used as the internal standard.
d) and DAOPE (6a–d), the OTE series 8a–e behaves oppo-
site in the measured range n = 1–5. The absorption maxima
for 8a (n = 1) and 8b (n = 2) are almost equal; that means
the extension of the chromophore from n = 1 to n = 2 can
nearly compensate the decrease of the ICT in the mutual
influence on the electron transition energy. Nevertheless,
series 8 must approach to a limiting value λϱ, too.[2] We
interpret the behavior of 8 in that way, that this series be-
The field desorption (FD) mass spectra were obtained with a Finni-
gan MAT 95 and the ESI (electrospray ionisation) mass spectra
with a Micromass/Waters QTOF Ultima 3 spectrometer. Elemental
analyses were performed in the microanalytical laboratory of the
Institute of Organic Chemistry of the University of Mainz.
General Procedure for the Knoevenagel Condensation Reaction of
longs to a special type of push-pull-substituted conjugated Aldehydes 2, 5, 7 and Malononitrile (3): A concentrated solution of
628 Eur. J. Org. Chem. 2007, 625–631
www.eurjoc.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Push-Pull Oligomers with 2,2-Dicyanovinyl Groups
FULL PAPER
m.p. 276 °C. H NMR (CDCl3): δ = 0.87 (t, 12 H, CH3), 1.24 (m,
1
aldehyde 2a–d, 5a–d or 7a–d (1.0–1.5 mmol) and 1.1 equiv. (1.1–
1.55 mmol) malononitrile (3) in 15–300 mL CH2Cl2 was stirred at 40 H, CH2), 1.83 (m, 2 H, CH), 3.21 (d, 4 H, NCH2), 6.62/7.35
room temperature in the presence of 85–130 mg (1.0–1.5 mmol) pi-
peridine. TLC control (SiO2, CH2Cl2) showed the progress of the
reaction. For the higher members of the series (n = 3–5) refluxing
of the solution was necessary to bring the reaction to the end (when
TLC indicated the total consumption of the aldehyde). The volatile
parts were evaporated and the residue purified by column
chromatography [(5ϫ40 cm SiO2), petroleum, b.p. 40–70 °C/
CH2Cl2, 1:1] and/or recrystallization from CH2Cl2, to which petro-
leum (b.p. 40–70 °C) was added in the heat till the solution became
turbid. (Only 4a is a viscous oil, which did not crystallize).
(AAЈMMЈ, 4 H, aromat. H, donor side), 6.86/7.04 (AB, 3J =
16.0 Hz, 2 H, olefin. H, donor side), 7.08–7.14 (m, 5 H, olefin.
H), 7.28 (d, J = 16.1 Hz, 1 H, olefin. H, acceptor side), 7.43/7.47
(AAЈBBЈ, 4 H, aromat. H), 7.50 (“s”, 4 H, aromat. H), 7.53 (“s”,
4 H, aromat. H), 7.62/7.89 (AAЈBBЈ, 4 H, aromat. H, acceptor
side), 7.68 [s, 1 H, CH=C(CN)2] ppm. FD MS: m/z (%) = 971 (100)
[M + H+]. UV/Vis (CHCl3): λmax = 441 nnm (logε ≈ 5.0). C70H87N3
(970.5): calcd. C 86.63, H 9.04, N 4.33; found C 86.36, H 9.23, N
4.11.
3
2-{4-[4-(Didodecylamino)phenylethynyl]benzylidene}malononitrile
1
2-[4-((E)-2-{4-[Bis(2-hexyloctyl)amino]phenyl}ethenyl)benzylidene]- (6a): Yield 593 mg, 98%, dark red crystals, m.p. 46 °C. H NMR
malononitrile (4a): Yield 578 mg, 87 %,[15,16] red oil. 1H NMR
(CDCl3): δ = 0.87 (t, 12 H, CH3), 1.24 (m, 40 H, CH2), 1.83 (m, 2
H, CH), 3.23 (d, 4 H, NCH2), 6.63/7.36 (AAЈMMЈ, 4 H, aromat.
(CDCl3): δ = 0.86 (t, 6 H, CH3), 1.24 (m, 36 H, CH2), 1.56 (m, 4
H, CH2), 3.26 (t, 4 H, NCH2), 6.56/7.36 (AAЈMMЈ, 4 H, aromat.
H, donor side), 7.54/7.84 (AAЈBBЈ, 4 H, aromat. H, acceptor side),
7.67 (s, 1 H, olefin. H) ppm. 13C NMR (CDCl3): δ = 14.1 (CH3),
22.6, 27.1, 27.2, 29.1, 29.3, 29.5, 29.6, 31.9 (CH2, partly superim-
posed), 50.9 (NCH2), 81.3, 158.6 [CH=C(CN)2], 87.4, 98.4 (alkyne
3
H, donor side), 6.86/7.22 (AB, J = 16.1 Hz, 2 H, olefin. H), 7.54/
7.84 (AAЈBBЈ, 4 H, aromat. H, acceptor side), 7.63 [s, 1 H,
CH=C(CN)2] ppm. 13C NMR (CDCl3): δ = 14.1 (CH3), 22.7, 26.4,
29.8, 31.6, 31.9 (CH2), 35.6 (CH), 56.7 (CH2N), 79.3, 158.7 C), 107.2, 129.1, 131.5, 148.7 (aromat. Cq), 111.2, 130.7, 131.7,
[CH=C(CN)2], 112.5, 126.5, 128.6, 131.6 (aromat. CH), 113.4, 133.5 (aromat. CH), 112.9, 114.0 (CN) ppm. FD MS: m/z (%) =
114.5 (CN), 121.3, 134.1 (olefin. CH), 123.1, 128.7, 145.5, 149.0
(aromat. Cq) ppm. FD MS: m/z (%) = 664 (100) [M+·]. UV/Vis
(CHCl3): λmax = 525 nm (logε = 4.50). C46H69N3 (664.1): calcd. C
83.20, H 10.47, N 6.33; found C 83.54, H 10.38, N 6.22.
606 (100) [M + H+]. UV/Vis (CHCl3): λmax = 489 nm (logε = 4.45).
C42H59N3 (606.0): calcd. C 83.25, H 9.81, N 6.93; found C 83.37,
H 9.82, N 6.85.
2-(4-{4-[4-(Didodecylamino)phenylethynyl]phenylethynyl}-
2-(4-{(E)-2-[4-((E)-2-{4-[Bis(2-hexyloctyl)amino]phenyl}ethenyl)-
phenyl]ethenyl}benzylidene)malononitrile (4b): Yield 659 mg, 86%,
benzylidene)malononitrile (6b): Yield 664 mg, 94 %, red crystals,
m.p. 89 °C. H NMR (CDCl3): δ = 0.86 (t, 6 H, CH3), 1.25 (m, 36
1
red crystals, m.p. 71 °C. 1H NMR (CDCl3): δ = 0.87 (t, 12 H, CH3), H, CH2), 1.53 (m, 4 H, CH2), 3.25 (t, 4 H, NCH2), 6.54/7.34
1.25 (m, 40 H, CH2), 1.83 (m, 2 H, CH), 3.22 (d, 4 H, NCH2), (AAЈMMЈ, 4 H, aromat. H, donor side), 7.47 (“s”, 4 H, aromat.
6.63/7.36 (AAЈMMЈ, 4 H, aromat. H, donor side), 6.86/7.07 (AB,
H), 7.62/7.87 (AAЈBBЈ, 4 H, aromat. H, acceptor side), 7.71 (s, 1
3J = 16.2 Hz, 2 H, olefin. H, donor side), 7.07/7.27 (AB, 3J =
H, olefin. H) ppm. 13C NMR (CDCl3): δ = 14.1 (CH3), 22.6, 27.1,
16.2 Hz, 2 H, olefin. H, acceptor side), 7.46/7.50 (AAЈBBЈ, 4 H, 27.2, 29.3, 29.5, 29.6, 31.7 (CH2, partly superimposed), 50.9
aromat. H), 7.61/7.88 (AAЈBBЈ, 4 H, aromat. H, acceptor side), (NCH2), 82.6, 158.4 [CH=C(CN)2], 86.9, 89.7, 94.0, 95.2 (alkyne
7.67 [s, 1 H, CH=C(CN)2] ppm. 13C NMR (CDCl3): δ = 14.1 C), 108.1, 120.6, 125.5, 130.2, 131.1, 148.2 (aromat. Cq), 111.2,
(CH3), 22.7, 26.4, 29.8, 31.9 (CH2), 35.6 (CH), 56.7 (CH2N), 80.7,
158.7 [CH=C(CN)2], 112.6, 126.3, 127.2, 127.5, 127.7, 131.5 (aro-
mat. CH), 113.1, 114.2 (CN), 122.7, 125.7, 129.9, 133.3 (olefin.
CH), 124.0, 129.7, 134.3, 139.3, 144.2, 148.3 (aromat. Cq) ppm. FD
130.6, 131.2, 132.4, 132.9, 137.7 (aromat. CH), 112.6, 113.7 (CN)
ppm. FD MS: m/z (%) = 706 (100) [M + H+]. UV/Vis (CHCl3):
λmax = 442 nm (logε = 4.56). C50H63N3 (706.1): calcd. C 85.06, H
8.99, N 5.95; found C 85.02, H 8.94, N 5.74.
MS: m/z (%) = 767 (100) [M + H+]. UV/Vis (CHCl3): λmax
=
2-[4-(4-{4-[4-(Didodecylamino)phenylethynyl]phenylethynyl}-
phenylethynyl)benzylidene]malononitrile (6c): Yield 709 mg, 88%,
red crystals, m.p. 178 °C. 1H NMR (CDCl3): δ = 0.86 (t, 6 H, CH3),
1.24 (m, 36 H, CH2), 1.53 (m, 4 H, CH2), 3.25 (t, 4 H, NCH2),
6.55/7.34 (AAЈMMЈ, 4 H, aromat. H, donor side), 7.45 (“s”, 4 H,
aromat. H), 7.51 (“s”, 4 H, aromat. H), 7.64/7.88 (AAЈBBЈ, 4 H,
494 nm (logε = 4.65). C54H75N3 (766.2): calcd. C 84.65, H 9.87, N
5.48; found C 84.20, H 9.94, N 5.36.
2-{4-[(E)-2-(4-{(E)-2-[4-((E)-2-{4-[Bis(2-hexyloctyl)amino]-
phenyl}ethenyl)phenyl]ethenyl}phenyl)ethenyl]benzylidene}-
malononitrile (4c): Yield 547 mg, 63%, red crystals, m.p. 167 °C. 1H
NMR (CDCl3): δ = 0.88 (t, 12 H, CH3), 1.25 (m, 40 H, CH2), 1.84 aromat. H, acceptor side), 7.72 (s, 1 H, olefin. H) ppm. 13C NMR
(m, 2 H, CH), 3.22 (d, 4 H, NCH2), 6.63/7.36 (AAЈMMЈ, 4 H, Ar-
(CDCl3): δ = 14.1 (CH3), 22.6, 27.1, 27.2, 29.3, 29.4, 29.5, 29.6,
31.9 (CH2, partly superimposed), 50.9 (NCH2), 82.8, 158.4
[CH=C(CN)2], 86.9, 88.5, 90.1, 90.2, 93.4, 94.7 (alkyne C), 108.2,
121.8, 124.2, 124.2, 124.5, 130.3, 131.5, 148.2 (aromat. Cq), 111.1,
130.6, 131.1, 131.4, 131.6, 131.8, 132.4, 132.9 (aromat. CH), 112.5,
113.6 (CN) ppm. FD MS: m/z (%) = 806 (100) [M + H+]. UV/Vis
H, donor side), 6.86/7.04 (AB, 3J = 16.0 Hz, 2 H, olefin. H, donor
3
side), 7.06/7.13 (AB, J = 16.4 Hz, 2 H, olefin. H), 7.09/7.26 (AB,
3J = 16.4 Hz, 2 H, olefin. H, acceptor side), 7.43/7.47 (AAЈBBЈ, 4
H, aromat. H), 7.51 (“s”, 4 H, aromat. H), 7.60/7.88 (AAЈBBЈ, 4
H, aromat. H, acceptor side), 7.65 [s, 1 H, CH=C(CN)2] ppm. 13C
NMR (CDCl3): δ = 14.1 (CH3), 22.6, 26.3, 29.8, 31.6, 31.9 (CH2), (CHCl3): λmax = 384 nm (logε = 4.75). C58H67N3 (806.2): calcd. C
35.6 (CH), 56.7 (NCH2), 80.9, 158.7 [CH=C(CN)2], 112.7, 126.2, 86.41, H 8.38, N 5.21; found C 86.62, H 8.51, N 5.23.
126.9, 127.2, 127.5, 127.6, 129.3, 131.5 (aromat. CH), 113.0, 114.1
2-{4-[4-(4-{4-[4-(Didodecylamino)phenylethynyl]phenylethynyl}-
(CN), 123.0, 126.3, 126.9, 127.0, 129.2, 133.0 (olefin. CH), 124.2,
phenylethynyl)phenylethynyl]benzylidene}malononitrile (6d): Yield
129.8, 135.2, 135.3, 138.2, 138.3, 143.9, 148.2 (aromat. Cq) ppm.
489 mg, 54 %, red crystals, m.p. Ͼ250 °C (recrystallization from
FD MS: m/z (%) = 869 (100) [M + H+]. UV/Vis (CHCl3): λmax
460 nm (logε = 4.88). C62H81N3 (868.4): calcd. C 85.76, H 9.40, N
4.84; found C 85.80, H 9.51, N 4.63.
=
1
CH2Cl2/CH3OH, 2:1). H NMR (CDCl2-CDCl2, 60 °C.): δ = 0.86
(t, 6 H, CH3), 1.24 (m, 36 H, CH2), 1.53 (m, 4 H, CH2), 3.25 (t, 4
H, NCH2), 6.55/7.35 (AAЈMMЈ, 4 H, aromat. H, donor side),
7.42–7.53 (m, 12 H, aromat. H), 7.65/7.89 (AAЈBBЈ, 4 H, aromat.
H, acceptor side), 7.73 (s, 1 H, olefin. H) ppm. FD MS: m/z (%) =
907 (100) [M + H+]. UV/Vis (CHCl3): λmax = 373 nm (logε = 4.94).
2-[4-((E)-2-{4-[(E)-2-(4-{(E)-2-[4-((E)-2-{4-[Bis(2-hexyloctyl)-
amino]phenyl}ethenyl)phenyl]ethenyl}phenyl)ethenyl]phenyl}ethenyl)-
benzylidene]malononitrile (4d): Yield 670 mg, 69 %, red crystals,
Eur. J. Org. Chem. 2007, 625–631
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
629

H. Meier, B. Mühling, J. Gerold, D. Jacob, A. Oehlhof
FULL PAPER
HRMS (ESI): calcd. for [C66H71N3 + H+] 906.5696; found:
906.5708.
1 H, olefin. H) ppm. FD MS: m/z (%) = 721 (100) [M + H+]. UV/
Vis (CHCl3): λmax = 424 nm (logε = 4.85). C39H16N2OS6 (720.9):
calcd. C 64.98, H 2.24, N 3.89, S 26.68; found C 64.82, H 2.28, N
3.92, S 26.79.
2-[5-(5-Methoxythiophen-2-ylethynyl)thiophen-2-ylmethylene]-
malononitrile (8a): Yield 275 mg, 93%, red crystals, m.p. 133 °C.
3
1H NMR (CDCl3): δ = 3.92 (s, 3 H, OCH3), 6.15/7.04 (AX, J =
3
4.1 Hz, 2 H, thienylene, donor side), 7.22/7.60 (AX, J = 3.5 Hz, 2
H, thienylene, acceptor side), 7.71 (s, 1 H, olefin. H) ppm. 13C
NMR (CDCl3): δ = 60.4 (OCH3), 77.4, 149.7 [CH=C(CN)2], 84.1,
95.7 (alkyne C), 104.9, 131.7, 133.3, 138.5 (CH), 107.3, 135.1,
135.2, 167.4 (Cq), 113.2, 113.9 (CN) ppm. FD MS: m/z (%) = 296
(100) [M+·]. UV/Vis (CHCl3): λmax = 470 nm (log ε = 4.53).
C15H8N2OS2 (296.0): calcd. C 60.79, H 2.72, N 9.45, S 21.64; found
C 60.65, H 2.51, N 9.71, S 21.48.
Acknowledgments
We are grateful to the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie, and the Center of Materials Sci-
ence of the University of Mainz for financial support.
[1] Selected monographs and reviews: a) W. R. Salaneck, I.
Lundström, B. R. Ranby, Conjugated Polymers and Related
Materials, Oxford University Press, Oxford, 1993; b) J. M.
Tour, Chem. Rev. 1996, 96, 537–553; c) R. Giesa, J. Macromol.
Sci., Rev. Macromol. Chem. Phys. 1996, 36, 631–670; d) J. S.
Moore, Acc. Chem. Res. 1997, 30, 402–413; e) L. Jones II, J. S.
Schumm, J. M. Tour, J. Org. Chem. 1997, 62, 1388–1410; f)
J. Roncali, Chem. Rev. 1997, 97, 173–205; g) A. Kraft, A. C.
Grimsdale, A. B. Holmes, Angew. Chem. 1998, 110, 416–443;
Angew. Chem. Int. Ed. 1998, 37, 403–428; h) Electronic Materi-
als: The Oligomer Approach (Eds.: K. Müllen, G. Wegner),
Wiley-VCH, Weinheim, 1998; i) T. M. Swager, Acc. Chem. Res.
1998, 31, 201–207; j) P. F. H. Schwab, M. D. Levin, J. Michl,
Chem. Rev. 1999, 99, 1863–1933; k) U. Scherf, Top. Curr. Chem.
1999, 201, 163–222; l) R. E. Martin, F. Diederich, Angew.
Chem. 1999, 111, 1440–1469; Angew. Chem. Int. Ed. 1999, 38,
1350–1377; m) J. J. Wolff, R. Wortmann, Adv. Phys. Org. Chem.
1999, 32, 121–217; n) U. H. F. Bunz, Chem. Rev. 2000, 100,
1605–1644; o) J. L. Segura, N. Martin, J. Mater. Chem. 2000,
10, 2403–2435; p) G. Hadziioannou, P. F. van Hutten, Semicon-
ductivity Polymers, Wiley-VCH, Weinheim, 2000; q) J. Roncali,
Acc. Chem. Res. 2000, 33, 147–156; r) J. M. Tour, Acc. Chem.
Res. 2000, 33, 791–804; s) U. H. F. Bunz, Acc. Chem. Res. 2001,
34, 998–1010; t) S. Tretiak, S. Mukamel, Chem. Rev. 2002, 102,
3171–3212; u) S. Szafert, J. A. Gladysz, Chem. Rev. 2003, 103,
4175–4205; v) H. Meier, in: Carbon-Rich Compounds (Eds.:
M. M. Haley, R. R. Tykwinski), Wiley-VCH, Weinheim, 2006,
476–528.
2-{5-[5-(5-Methoxythiophen-2-ylethynyl)thiophen-2-ylethynyl]-
thiophen-2-ylmethylene}malononitrile (8b): Yield 378 mg, 94%, red-
1
brown crystals, m.p. 155 °C. H NMR (CDCl3): δ = 3.92 (OCH3),
3
6.12/6.97 (AX, J = 4.1 Hz, 2 H, thienylene, donor side), 7.11/7.21
3
3
(AB, J = 4.0 Hz, 2 H, thienylene), 7.31/7.64 (AX, J = 4.1 Hz, 2
H, thienylene, acceptor side), 7.71 (s, 1 H, olefin. H) ppm. 13C
NMR (CDCl3): δ = 60.3 (OCH3), 78.3, 149.7 [CH=C(CN)2], 83.4,
86.4, 89.7, 92.0 (alkyne C), 104.4, 131.6, 131.9, 132.6, 133.7, 138.4
(CH), 108.4, 121.9, 126.5, 135.6, 135.8, 168.2 (Cq), 113.0, 113.1
(CN) ppm. FD MS: m/z (%) = 403 (100) [M + H+]. UV/Vis
(CHCl3): λmax = 469 nm (logε = 4.60). C21H10N2OS3 (402.5): calcd.
C 62.67, H 2.50, N 6.96, S 23.90; found C 62.53, H 2.79, N 6.73,
S 23.63.
2-(5-{5-[5-(5-Methoxythiophen-2-ylethynyl)thiophen-2-ylethynyl]-
thiophen-2-ylethynyl} thiophen-2-ylmethylene)malononitrile (8c):
1
Yield 453 mg, 89%, red crystals, m.p. 167 °C. H NMR (CDCl3):
3
δ = 3.89 (s, 3 H, OCH3), 6.10/6.96 (AX, J = 4.1 Hz, 2 H, thienyl-
ene, donor side), 7.08/7.15 (AB, 3J = 4.0 Hz, 2 H, thienylene), 7.17/
7.24 (AB, 3J = 4.0 Hz, 2 H, thienylene), 7.32/7.64 (AB, 3J = 4.1 Hz,
2 H, thienylene, acceptor side), 7.75 (s, 2 H, olefin. H) ppm. 13C
NMR (CDCl3): δ = 60.3 (OCH3), 78.4, 149.7 [CH=C(CN)2], 83.6,
86.4, 86.6, 88.4, 88.9, 93.4 (alkyne C), 104.3, 131.6, 131.7, 132.4,
132.7, 132.8, 133.7, 138.3 (CH), 108.4, 122.8, 123.1, 125.9, 126.4,
135.8, 136.0, 168.2 (Cq), 113.0, 113.7 (CN) ppm. FD MS: m/z (%)
= 509 (100) [M + H+]. UV/Vis (CHCl3): λmax = 466 nm (logε =
4.65). C27H12N2OS4 (508.7): calcd. C 63.76, H 2.38, N 5.51, S
25.21; found C 63.47, H 2.14, N 5.59, S 25.09.
[2] H. Meier, Angew. Chem. 2005, 117, 2536–2561; Angew. Chem.
Int. Ed. 2005, 44, 2482–2506 and references cited therein.
[3] See for example: K. Koynov, A. Bahtiar, C. Bubeck, B.
Mühling, H. Meier, J. Phys. Chem. B 2005, 109, 10184–10188.
[4] F. Würthner, R. Wortmann, K. Meerholz, ChemPhysChem
2002, 3, 17–31.
2-[5-(5-{5-[5-(5-Methoxythiophen-2-ylethynyl)thiophen-2-ylethynyl]-
thiophen-2-ylethynyl}thiophen-2-ylethynyl)thiophen-2-ylmethylene]-
malononitrile (8d): Yield 381 mg, 62%, red crystals, m.p. 174 °C.
[5] a) M. Albota, D. Beljonne, J.-L. Brédas, J. E. Ehrlich, J.-Y. Fu,
A. A. Heikal, S. E. Hess, T. Kogej, M. D. Levin, S. R. Marder,
D. McCord-Maughon, J. W. Perry, H. Röckel, M. Rumi, G.
Subramaniam, W. W. Webb, X.-L. Wu, C. Xu, Science 1998,
281, 1653–1656; b) B. A. Reinhardt, L. L. Brott, S. J. Clarson,
A. G. Dillard, J. C. Bhatt, R. Kannan, L. Yuan, G. S. He, P. N.
Prasad, Chem. Mater. 1998, 10, 1863–1874; c) K. D. Belfield,
D. J. Hagan, E. W. Van Stryland, K. J. Schafer, R. A. Negres,
Org. Lett. 1999, 1, 1575–1578; d) K. D. Belfield, K. J. Schafer,
W. Mourad, B. A. Reinhardt, J. Org. Chem. 2000, 65, 4475–
4481; e) R. Kannan, G. S. He, L. Yuan, F. Xu, P. N. Prasad,
A. G. Dombroskie, B. A. Reinhardt, J. W. Baur, R. A. Vaia, L.-
S. Tan, Chem. Mater. 2001, 13, 1896–1904; f) Z.-Q. Liu, Q.
Fang, D. Wang, G. Xue, W.-T. Yu, Z.-S. Shao, M.-H. Jiang,
Chem. Commun. 2002, 2900–2901; g) Z.-Q. Liu, Q. Fang, D.
Wang, D.-X. Cao, G. Xue, W.-T. Yu, H. Lei, Chem. Eur. J.
2003, 9, 5074–5084; h) D.-X. Cao, Z.-Q. Liu, Q. Fang, G.-B.
Xu, G. Xue, G.-Q. Liu, W.-T. Yu, J. Organomet. Chem. 2004,
689, 2201–2206; i) D.-X. Cao, Q. Fang, D. Wang, Z.-Q. Liu,
G. Xue, G.-B. Xu, W.-T. Yu, Eur. J. Org. Chem. 2003, 3628–
3636; j) J. Kawamata, M. Akiba, T. Tani, A. Harada, Y. In-
agaki, Chem. Lett. 2004, 33, 448–449; k) S. Kato, T. Matsum-
3
1H NMR (CDCl3): δ = 3.89 (s, 3 H, OCH3), 6.09/6.96 (AX, J =
3
4.1 Hz, 2 H, thienylene, donor side), 7.08/7.14 (AB, J = 4.0 Hz, 1
H, thienylene), 7.16–7.25 (m, 4 H, thienylene), 7.32/7.64 (AX, 3J =
4.2 Hz, 2 H, thienylene, acceptor side), 7.74 (s, 1 H, olefin. H) ppm.
13C NMR (CDCl3): δ = 60.3 (OCH3), 78.8, 149.7 [CH=C(CN)2],
83.6, 86.6, 86.7, 86.8, 87.6, 88.2, 88.7, 93.4 (alkyne C), 104.3, 131.6,
131.7, 132.3, 132.4, 132.5, 132.7, 132.8, 133.7, 138.3 (CH), 108.4,
122.3, 123.3, 123.9, 125.0, 125.6, 126.2, 136.0, 136.0, 168.2 (Cq),
113.0, 113.7 (CN) ppm. FD MS: m/z (%) = 615 (100) [M + H+].
UV/Vis (CHCl3): λmax = 453 nm (log ε = 4.72). C33H14N2OS5
(614.0): calcd. C 64.47, H 2.30, N 4.56, S 26.07; found C 64.66, H
2.46, N 4.51, S 25.98.
2-{5-[5-(5-{5-[5-(5-Methoxythiophen-2-ylethynyl)thiophen-2-ylethyn-
yl]thiophen-2-ylethynyl}thiophen-2-ylethynyl)thiophen-2-ylethynyl]-
thiophen-2-ylmethylene}malononitrile (8e): Yield 274 mg, 38%, red
1
crystals, m.p. 182 °C. H NMR (CDCl3): δ = 3.89 (s, 3 H, OCH3),
3
6.09/6.95 (AX, J = 4.1 Hz, 2 H, thienylene, donor side), 7.08/7.14
3
(AB, J = 4.0 Hz, 2 H, thienylene), 7.16–7.25 (m, 6 H, thienylene),
7.32/7.64 (AX, 3J = 4.2 Hz, 2 H, thienylene, acceptor side), 7.74 (s,
630
www.eurjoc.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2007, 625–631

Push-Pull Oligomers with 2,2-Dicyanovinyl Groups
FULL PAPER
oto, M. Shigeiwa, H. Gorohmaru, S. Maeda, T. Ishi-i, S. Ma-
taka, Chem. Eur. J. 2006, 12, 2303–2317.
[6] H. Meier, J. Gerold, D. Jacob, Tetrahedron Lett. 2003, 44,
1915–1918.
[7] H. Meier, J. Gerold, H. Kolshorn, B. Mühling, Chem. Eur. J.
2004, 10, 360–370.
[8] H. Meier, J. Gerold, H. Kolshorn, W. Baumann, M. Bletz, An-
gew. Chem. 2002, 114, 302–306; Angew. Chem. Int. Ed. 2002,
41, 292–295.
Wang, J. Chem. Soc., Faraday Trans. 1998, 94, 47–52; c) G. U.
Bublitz, R. Ortiz, S. R. Marder, S. G. Boxer, J. Am. Chem. Soc.
1997, 119, 3365–3376; d) S. R. Marder, C. B. Gorman, F. Mey-
ers, J. W. Perry, G. Bourhill, J.-L. Brédas, B. M. Pierce, Science
1994, 265, 632–635; e) S. M. Risser, D. N. Beratan, S. R.
Marder, J. Am. Chem. Soc. 1993, 115, 7719–7728; f) S. R.
Marder, D. N. Beratan, L.-T. Cheng, Science 1991, 252, 103–
106.
[13] The accuracy of the spectrometer is about 1 nm. For the sepa-
[9] H. Meier, B. Mühling, H. Kolshorn, Eur. J. Org. Chem. 2004,
ration of bands see ref.[9]
1033–1042.
[14] H. Meier, U. Stalmach, H. Kolshorn, Acta Polym. 1997, 48,
379–384.
[10] H. Meier, B. Mühling, A. Oehlhof, S. Theisinger, E. Kirsten,
Eur. J. Org. Chem. 2006, 405–413.
[11] M. C. Ruiz Delgado, V. Hernández, J. Casado, J. T. L. Navar-
rete, J.-M. Raimundo, P. Blanchard, J. Roncali, Chem. Eur. J.
2003, 9, 3670–3682.
[12] See for example: a) M. Dekhtyar, W. Rettig, Phys. Chem.
Chem. Phys. 2001, 3, 1602–1610; b) Y. Sheng, Y. Jiang, X.-C.
[15] An appreciable increase of the yield from 46[6] to 87% was
obtained by optimizing the reaction time (TLC control as de-
scribed).
[16] The yields in mg are always related to 1.0 mmol of aldehyde.
Received: August 11, 2006
Published Online: November 23, 2006
Eur. J. Org. Chem. 2007, 625–631
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
631