Monodisperse oligo(2,5-dipropoxy-1,4-phenyleneethynylene)s

Article abstract of DOI:10.1002/1099-0690(200208)2002:16<2808::AID-EJOC2808>3.0.CO;2-U

Oligo(phenyleneethynylene)s 1 are rod-like compounds with undisturbed conjugation. In supplementation of the previously described members of this series 1a-e, with repeating units of up to n = 5, this work contains the preparation of higher oligomers 1f-i

Full text of DOI:10.1002/1099-0690(200208)2002:16<2808::AID-EJOC2808>3.0.CO;2-U

FULL PAPER
Monodisperse Oligo(2,5-dipropoxy-1,4-phenyleneethynylene)s
Dirk Ickenroth,[a] Silke Weissmann,[a] Norbert Rumpf,[a] and Herbert Meier*[a]
Keywords: Absorption / Alkynes / Conjugation / Fluorescence / Oligomers
Oligo(phenyleneethynylene)s 1 are rod-like compounds with
fluorescence bands showed convergence for increasing
undisturbed conjugation. In supplementation of the previ- values of n, reaching limiting values at the effective conjuga-
ously described members of this series 1a−e, with repeating
units of up to n = 5, this work contains the preparation of
higher oligomers 1f−i (n = 6, 7, 8, 10) through the use of the
Sonogashira−Hagihara reaction. Both the absorption and the
tion length of nECL = 10.
( Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany,
2002)
Introduction
Results and Discussion
Conjugated oligomers represent interesting compounds
for many applications in materials science.[1Ϫ31] Moreover,
their properties as Ϫ for example Ϫ electrical semi-
conductors, photoconductors, electroluminophores, and
materials for nonlinear optics (NLO) make them model
compounds for the corresponding conjugated polymers,
which have compared to the oligomers some advantages in
processing. In this context we decided to synthesize a series
of monodisperse oligo(2,5-dipropoxy-1,4-phenyleneethynyl-
ene)s (OPEs) 1aϪi. The first five members of the series (n ϭ
1Ϫ5) and their astonishingly high second order hyperpolar-
izabilities γ were described recently.[31] We have now ex-
tended the study to the convergence of the electronic prop-
erties for n Ǟ ϱ: that means, to the ideal, defect-free poly-
mer.
In the previous paper,[31] which dealt with the prepara-
tion of the OPEs 1aϪe, the synthetic strategy was based on
SonogashiraϪHagihara reactions between iodo- or bro-
moarenes and ethynylarenes. Important features of the Pd0-
catalyzed C(sp2)ϪC(sp) coupling reactions were the higher
reactivity of the iodo compounds relative to the bromo
compounds and a selective protecting group technique on
the ethynyl side. A set of building blocks serving for the
preparation of 1aϪe was thus obtained, and this starter kit
could now be applied for the formation of the higher oligo-
mers 1fϪi.
The preparation of the hexamer 1f made use of the di-
bromo compound 2 and the half-protected diethynyl com-
pound 3. In a double coupling reaction, the pentamer 4
with two triisopropylsilyl end groups was obtained. Depro-
tection with tetrabutylammonium fluoride provided the
pentamer 5, which, on coupling with the iodobenzene 6 on
both sides, gave OPE 1f.
The preparation of the heptamer 1g began with the
trimer 7. Coupling with the iodo compound 8 yielded the
tetramer 9, which was deprotected to afford the ethynyl sys-
tem 10. In addition, 7 was coupled with 11 to give the
trimer 12. The bromo substituent was maintained intact un-
der the mild conditions and could then be used for the final
coupling 10 ϩ 12 Ǟ 1g.
Scheme 1. Oligo(2,5-dipropoxy-1,4-phenyleneethynylene)s (OPEs)
1aϪi
Scheme 4 illustrates the production of the octamer 1h
and the decamer 1i. The dibromo compound 13 was
coupled with two equivalents of the trimer 7 and gave OPE
1h, while the diiodo compound 15 furnished OPE 1i
through coupling with the pentamer 14. The yields ob-
tained in SonogashiraϪHagihara reactions tend to be lower
with bromo components than with iodo compounds, be-
cause the reaction rate with bromoarenes is lower and side
reactions can take place. One especially has to take care to
ensure oxygen-free reaction media, so that the competing
Propoxy chains confer sufficient solubility and pro-
cessability. Moreover, they shift the absorption and the
fluorescence to longer wavelengths.
[a]
Institut für Organische Chemie der Johannes Gutenberg-
Universität Mainz,
Duesbergweg 10Ϫ14, 55099 Mainz, Germany
Fax: (internat.) ϩ49-(0)6131/3925396
E-mail: hmeier@mail.uni-mainz.de
2808
 WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 1434Ϫ193X/02/0816Ϫ2808 $ 20.00ϩ.50/0 Eur. J. Org. Chem. 2002, 2808Ϫ2814

Monodisperse Oligo(2,5-dipropoxy-1,4-phenyleneethynylene)s
FULL PAPER
Scheme 4. Synthesis of octamer OPE 1h and decamer OPE 1i
for all members of the series. Moreover, more highly
charged ions M3ϩ, M4ϩ, etc. were also detected for the
longer chains (n Ն 4). The short systems 1aϪd showed ad-
ditional peaks [2 M]ϩ of dimeric aggregates.
Scheme 2. Synthesis of the hexamer OPE 1f
Because of the symmetry of the molecules, the FTϪIR
spectra of the oligomers 1aϪi did not exhibit CC triple
bond stretching vibrations. The most intense bands were
found at (1509 Ϯ 7) cmϪ1 for the aromatic stretching vibra-
tions, at (1432 Ϯ 5) cmϪ1 for the CH2 deformation vibra-
tions, and at (1273 Ϯ 3) cmϪ1 and (1210 Ϯ 8) cmϪ1 for the
stretching vibrations of the CO single bonds.
The most important spectroscopic characterization of the
oligomers 1aϪi concerned UV/Vis and fluorescence spec-
troscopy. Unlike the IR and NMR spectra, which both pre-
dominantly reflected the data for the repeating units, the
electronic spectra depended on the length of the chromoph-
ores. Since there were no special steric or push-pull ef-
fects[32] present in 1aϪi, a monotonous bathochromic shift
of the absorption and fluorescence bands with increasing n
was to be expected. The convergence of the energies E(n) of
the electronic transitions for n Ǟ ϱ can be quantitatively
described by exponential functions.[33] Apart from the valid-
ity for the 0 Ǟ 0 transitions, the absorption and fluores-
cence maxima can be taken in the majority of conjugated
series.[33] If the vibrational structure does not allow the 0
Ǟ 0 transitions to be determined, one can also use the ab-
sorption edges λ0.1, where ε is 1/10 of εmax. Table 2 sum-
marizes the absorption and emission data of the oligomers
1aϪi.
Scheme 3. Synthesis of the heptamer OPE 1g
oxidative coupling is reduced to a minimum (this cannot be
completely avoided because of the presence of PdII).
The NMR spectroscopic characterization of the oligo-
The λmax values of the UV/Vis absorption bands of 1aϪi
mers 1aϪi revealed that the terminal benzene rings Ϫ irre- at most depended only to a very small extent on the concen-
spective of the number of repeat units n Ϫ gave signals that trations of the solutions in CHCl3. Such dependence was
could be distinguished from the signals of the inner seg- observed for n ϭ 4, 5, and 6. We attributed this result to
ments. A pronounced anisotropy effect in the inner parts of aggregation, and compared it to the strong influence of
the rigid conjugated chain gave rise to low-field shifts for concentration on the fluorescence spectra. Figure 1 depicts
the aromatic protons, the aromatic methine carbon atoms, three selected examples: the emissions of 1b (n ϭ 2, λexc
and for the acetylenic carbon atoms. Table 1 summarizes 378 nm), 1d (n ϭ 4, λexc ϭ 412 nm), and 1h (n ϭ 8, λexc
ϭ
ϭ
the NMR spectroscopic data of the compounds 1aϪi.
435 nm). Each spectrum showed two different bands, the
The field desorption technique proved suitable for mass ratio of the intensities of the two bands changing markedly
spectrometry of the oligomers 1aϪi. In addition to the (pro- with the concentration. The broad bands at longer wave-
tonated) molecular ions Mϩ, the M2ϩ peaks could be found lengths decreased with decreasing concentration; we there-
Eur. J. Org. Chem. 2002, 2808Ϫ2814
2809

D. Ickenroth, S. Weissmann, N. Rumpf, H. Meier
FULL PAPER
1
Table 1. H/13C NMR spectroscopic data of the oligomer OPEs 1aϪi (δ values in CDCl3, TMS as internal standard)
Group
Position in the chain
Terminal phenylethynyl segment
Inner phenylene-ethynylene segment
H2COϪC-2
H2COϪC-5
HC-3
HC-4
HC-6
3.97 Ϯ 0.10/71.3 Ϯ 0.2
3.86 Ϯ 0.01/70.2 Ϯ 0.1
6.81 Ϯ 0.01/114.4 Ϯ 0.3
6.81 Ϯ 0.01/116.6 Ϯ 0.3
7.01 Ϯ 0.03/118.5 Ϯ 0.3
Ϫ/114.3 Ϯ 0.2
3.97 Ϯ 0.10/71.3 Ϯ 0.2
3.97 Ϯ 0.10/71.3 Ϯ 0.2
7.01 Ϯ 0.03/117.7 Ϯ 0.8
Ϫ/Ϫ
7.01 Ϯ 0.03/117.7 Ϯ 0.8
Ϫ/114.5 Ϯ 0.4
Cq
CqO
Ϫ/152.9 Ϯ 0.3
Ϫ/154.3 Ϯ 0.3
Ϫ/153.5 Ϯ 0.3
Ϫ/153.5 Ϯ 0.3
C(sp)
Ϫ/89.8 Ϯ 0.2
Ϫ/91.5 Ϯ 0.3
Table 2. Oligo(1,4-phenyleneethynylene)s 1aϪi
Repeating units
n
Absorption in CHCl3
Fluorescence
in CHCl3
λmax [nm]
Absorption
in polystyrene
λmax [nm]
[a]
[b]
1
λmax
[nm]
λ0.1
10Ϫ3 εmax
[nm]
[L·molϪ1·cmϪ1
]
a
b
c
d
e
f
g
h
i
1
2
3
4
5
6
7
8
338
378
399
412
419
424
430
434
438
367
410
436
452
460
466
469
471
475
15.9
39.0
54.7
371
411
437
453
462
466
469
471
475
335
377
394
410
417
423
427
430
Ϫ
80.6
112.1
132.0
156.2
180.0
202.2
10
[a]
[b]
The average εmax/n amounts to 20.35·103 L·molϪ1·cmϪ1
.
The excitation wavelengths used for the fluorescence measurements corre-
sponded to the absorption maxima (λmax Ϯ 1.0) nm.
fore attributed this emission to an aggregate. (The other the convergence (n Ǟ ϱ). Figure 2 shows the corresponding
compounds of the 1 series displayed the same behavior.) plots based on exponential functions:[33]
For compound 1d, the maximum of the aggregate emission
was higher than the maximum of the monomer emission
even in the 10Ϫ4  solution. Lowering of the concentration
to 10Ϫ5  and 10Ϫ6  resulted here Ϫ as in all other cases
Ϫ in an intensity decrease. The effect was more pronounced
for the higher oligomers such as 1h than for the lower oligo-
mers.
λ(n) ϭ λϱ Ϫ (λϱ Ϫ λ1)eϪb(nϪ1)
(1)
Table 3 summarizes the values for the fit to parameter b,
the extrapolated wavelength λϱ, the total effect of conjuga-
tion[33]
How is it possible to explain the fact that absorption did
not show a concentration effect Ϫ except for some medium
oligomers (n ϭ 4, 5, 6) Ϫ while fluorescence displayed very
strong dependence on the concentration for all oligomers
1aϪi?
(2)
Either the strong aggregation tendency could be present
only in the first excited singlet state S1, so that we would
see a kind of excimer fluorescence, or the aggregates could
also be formed in the ground state S0, but the geometrical
arrangement might be such that monomer absorption and
aggregate absorption would differ either not at all or very
little. The latter precondition would be ideally fulfilled for
an arrangement between J and H aggregation with parallel
and the effective conjugation length
(3)
It turned out that 1i (n ϭ 10) just reached the conver-
but laterally shifted chains in the so-called ‘‘magic angle’’ gence limits both of the absorption and of the fluorescence.
arrangement. The average lifetime of the S1 states would The total effect of conjugation ∆E gave an answer to the
certainly be sufficient for a geometrical change resulting in question of how much the absorption and the fluorescence
a different emission.
would be shifted on going from the very first member of
Nevertheless, all λmax values of the absorption and the the series (1a) to the infinitely long chain. The values for
fluorescence bands could be used for the determination of nECL and ∆E in the OPE series 1 were somewhat smaller
2810
Eur. J. Org. Chem. 2002, 2808Ϫ2814

Monodisperse Oligo(2,5-dipropoxy-1,4-phenyleneethynylene)s
FULL PAPER
Figure 1. Fluorescence spectra (uncorrected) of 1b, 1d, and 1h in CHCl3; concentration: top 10Ϫ4 , middle 10Ϫ5 , bottom 10Ϫ6

than those found in the series of the oligo(2,5-
dipropoxyphenylenevinylene)s, with trans configured
double bonds instead of the triple bonds.[33] Although steric
hindrance caused torsions along the chain in the OPV
series, impairing the conjugation, the effect of conjugation
was higher for the olefinic systems. This result can be ex-
plained by the resonance integrals, which were less different
in the OPV series because the bond lengths were less differ-
ent than in the OPE series.
Summary and Conclusions
In supplementation of the previously described oligo(2,5-
dipropoxy-1,4-phenyleneethynylene)s 1aϪe (n ϭ 1Ϫ5),[31]
we report here on the preparation of the higher members
1fϪi (n ϭ 6Ϫ8, 10) of the OPE series. The monotonous
bathochromic shifts of the absorption and fluorescence
maxima of the whole series 1aϪi now permit the extrapola-
tion (n Ǟ ϱ), giving limiting values λϱ of 438 and 475 nm,
respectively. The effective conjugation length was reached
for nECL ϭ 10. Longer defect-free segments of polymer
chains PPE would not change the extrapolated values un-
less special end groups were present.[32] Whereas the ab-
sorption spectra of 1aϪi in chloroform were independent
of concentration Ϫ with slight exceptions for n ϭ 4Ϫ6 Ϫ
the fluorescence spectra exhibited, together with the mono-
mer bands, second bands at longer wavelengths, the intens-
ities of which decreased with decreasing concentration and
were therefore attributed to aggregate emission (excimer
emission).
Figure 2. Convergence of the λmax values of the absorption and the
fluorescence for increasing numbers n of repeat units in the series
1 measured in CHCl3. (The exponential fit function (1) is specified
by the parameters given in Table 3.)
Table 3. Convergence data of the long-wavelength absorption and
the monomer emission of 1aϪi
Absorption
Fluorescence
b
0.468 Ϯ 0.027
438 Ϯ 3
100 Ϯ 3
0.837
0.502 Ϯ 0.012
475 Ϯ 3
104 Ϯ 3
0.732
λϱ [nm]
(λϱ Ϫ λ1) [nm]
∆E [eV]
nECL
Experimental Section
General: Melting points (uncorrected): Büchi apparatus. NMR:
Bruker AM 400 and ARX 400, CDCl3 as solvent unless otherwise
10
10
Eur. J. Org. Chem. 2002, 2808Ϫ2814
2811

D. Ickenroth, S. Weissmann, N. Rumpf, H. Meier
FULL PAPER
stated, TMS as internal standard. MS: Varian MAT CH7A and
Finnigan MAT 95. UV/Vis: Zeiss MCS 320/340 and PerkinϪElmer
Lambda 20, chloroform as solvent. Fluorescence: PerkinϪElmer
LS 50 B (chloroform). FT-IR: PerkinϪElmer GX, KBr pellets.
H]2ϩ and [M ϩ 2 H]3ϩ. C96H114O14(1492.0): calcd. C 77.29, H 7.70;
found C 77.31, H 7.76.
1-[2,5-Dipropoxy-4-(2,5-dipropoxyphenylethynyl)phenylethynyl]-4-
[2,5-dipropoxy-4-(triisopropylsilylethynyl)phenylethynyl]-2,5-
1,4-Bis{2,5-dipropoxy-4-[2,5-dipropoxy-4-(triisopropylsilylethynyl)- dipropoxybenzene (9): Triphenylphosphane (100 mg, 0.38 mmol),
phenylethynyl]phenylethynyl}-2,5-dipropoxybenzene (4): Triphenyl-
phosphane (0.10 g, 0.38 mmol), CuI (0.07 g, 0.38 mmol), and
Pd(PPh3)2Cl2 (0.13 g, 0.19 mmol) were added to a degassed solu-
CuI (74 mg, 0.39 mmol), and Pd(PPh3)2Cl2 (134 mg, 0.19 mmol)
were added to a degassed solution of 7[31] (5.0 g, 7.68 mmol) and
8[31] (4.04 g, 8.07 mmol) in 120 mL of piperidine. The mixture was
tion of 2[31] (3.0 g, 3.82 mmol) and 3[31] (3.6 g, 9.03 mmol) in stirred under argon at 50 °C for 1 h and at 20 °C for 72 h. The
100 mL of toluene/50 mL of piperidine. After the mixture had been
stirred for 16 h under nitrogen, the solvent was removed, and the
residue was dissolved in 100 mL of CH2Cl2, washed with 50 mL of
solvent was removed, and the residue was treated with 150 mL of
CH2Cl2. After extraction with 50 mL of NH4Cl, 50 mL of water,
and 50 mL of NaHCO3, the solvent was evaporated and the residue
NH4Cl, 50 mL of water, and 50 mL of NaHCO3, and dried over was filtered through 10 ϫ 5 cm SiO2 with CHCl3. Column chroma-
Na2SO4. Column chromatography (30 ϫ 3 cm SiO2, toluene)
tography (50 ϫ 3 cm SiO2, toluene and then toluene/cyclohexane
yielded yellow crystals (2.1 g, 39%), which melted at 195 °C. 1H 10:1) yielded yellow crystals (6.57 g, 84%), which melted at 112 °C.
NMR (CDCl3): δ ϭ 1.06 (m, 72 H, CH3 and CH and CH3 of 1H NMR (CDCl3): δ ϭ 1.05 (m, 45 H, CH3, CH(CH3)2], 1.83 (m,
Si[CH(CH3)2]3), 1.82 (m, 20 H, CH2), 3.94 (m, 20 H, OCH2), 6.92/
6.94 (2 s, 2 H and 2 H, arom. H of outer benzene rings), 7.00 (s, 6
H, arom. H of inner benzene rings) ppm. 13C NMR (CDCl3): δ ϭ
16 H, CH2), 3.87 (m, 4 H, OCH2), 3.99 (m, 12 H, OCH2), 6.81 (m,
2 H, arom. H), 6.93Ϫ7.03 (m, 7 H, arom. H) ppm. 13C NMR
(CDCl3): δ ϭ 10.5, 10.6 (CH3), 11.4 (CH of isopropyl), 18.7 (CH3
10.4 (CH3), 11.3 (CH of isopropyl), 18.6 (CH3 of isopropyl), 22.6, of isopropyl), 22.6, 22.7, 22.8 (CH2), 70.2, 70.9, 71.2, 71.4, 71.5
22.7 (CH2), 70.9, 71.2, 71.4 (OCH2), 91.3, 91.5, 96.4, 103.0 (acetyl. (OCH2), 89.8, 91.4, 91.6, 96.5, 103.1 (acetyl. C), 114.0, 114.1, 114.4,
C), 114.1, 114.4, 116.8, 117.5, 118.1 (arom. C), 153.2, 153.5, 154.3 114.7, 116.6, 116.8, 117.5, 117.6, 118.0, 118.7 (arom. C), 152.9,
(CqO) ppm.[34] MS (FD): m/z (%) ϭ 1421 [M ϩ H]ϩ, 711 [M ϩ 153.3, 153.5, 154.0, 154.4 (CqO) ppm.[34] MS (FD): m/z (%) ϭ 1024
H]2ϩ, 474 (1) [M ϩ H]3ϩ. C90H122O10Si2 (1420.1): calcd. C 76.12, (100) [M ϩ H]ϩ, 512 (31) [M ϩ H]2ϩ. C65H86O8Si (1023.5): calcd.
H 8.66; found C 76.08, H 8.63.
C 76.28, H 8.47; found C 76.13, H 8.61.
1,4-Bis{2,5-dipropoxy-4-[2,5-dipropoxy-4-(ethynyl)phenylethynyl]-
1-[2,5-Dipropoxy-4-(2,5-dipropoxyphenylethynyl)phenylethynyl]-4-
(2,5-dipropoxy-4-ethynylphenyl)-2,5-dipropoxybenzene (10): Com-
pound 9 (6.25 g, 6.11 mmol) in 70 mL of THF was treated with
(C4H9)4NϩFϪ (2.89 g, 9.16 mmol). The yellow solution immedi-
ately turned red-brown. After 5 min stirring, the solvent was re-
moved, and the residue was dissolved in 100 mL of chloroform and
phenylethynyl}-2,5-dipropoxybenzene (5): Compound
4 (0.56 g,
0.39 mmol) was dissolved in THF (25 mL) and treated with
(C4H9)4NϩF (0.19 g, 0.59 mmol). After 15 min the solvent was re-
moved, and the residue was dissolved in 50 mL of CH2Cl2 and
extracted with 50 mL of water. The organic phase was dried with
Na2SO4, concentrated, and purified by column chromatography extracted with 100 mL of water. The organic layer was dried over
(30 ϫ 3 cm SiO2, CH2Cl2). Yellow crystals (0.44 g, 96%) were ob- Na2SO4 and concentrated. Column chromatography (80 ϫ 2 cm
1
tained, and these melted at 173 °C. H NMR (CDCl3): δ ϭ 1.07
SiO2, toluene) yielded yellow crystals (3.51 g, 66%), which melted
1
(m, 30 H, CH3), 1.83 (m, 20 H, CH2), 3.33 (s, 2 H, acetyl. H), 3.97 at 126 °C. H NMR (CDCl3): δ ϭ 1.07 (m, 24 H, CH3), 1.84 (m,
(m, 20 H, OCH2), 6.96/6.98 (2 s, 2 H and 2 H, arom. H of the
outer benzene rings), 7.00 (s, 6 H, arom. H of the inner benzene
16 H, CH2), 3.33 (s, 1 H, acetyl. H), 3.83 (t, 2 H, OCH2), 3.98 (m,
14 H, OCH2), 6.81 (m, 2 H, arom. H), 6.96Ϫ7.03 (m, 7 H, arom.
rings) ppm. 13C NMR (CDCl3): δ ϭ 10.4, 10.5 (CH3), 22.6, 22.7 H) ppm. 13C NMR (CDCl3): δ ϭ 10.4, 10.5, 10.6 (CH3), 22.6, 22.7,
(CH2), 71.2, 71.3, 71.4 (OCH2), 91.3, 91.6, 91.7 (acetyl. C), 112.9,
22.8 (CH2), 70.2, 71.1, 71.2, 71.3, 71.4 (OCH2), 80.1, 82.3, 89.8,
114.4, 114.6, 114.7, 115.3, 117.4, 117.7, 118.3 (arom. C), 153.5, 91.2, 91.4, 91.6, 91.7 (acetyl. C), 112.6, 114.1, 114.2, 114.4, 114.6,
153.6, 154.3 (CqO) ppm.[34] MS (FD): m/z (%) ϭ 1107 (100) [M]ϩ,
554 (36) [M]2ϩ. C72H82O10 (1107.4): calcd. C 78.09, H 7.46; found
C 77.95, H 7.51.
114.7, 115.1, 116.7, 117.2, 117.5, 118.1, 118.6 (arom. C), 152.9,
153.3, 153.4, 154.0, 154.1 (CqO) ppm.[34] MS (FD): m/z (%) ϭ 867
(100) [M ϩ H]ϩ, 434 (8) [M ϩ H]2ϩ. C56H66O8 (867.1): calcd. C
77.57, H 7.67; found C 77.18, H 7.97.
Hexamer OPE 1f: Triphenylphosphane (15 mg, 0.057 mmol), CuI
(11 mg, 0.057 mmol), and Pd(PPh3)2Cl2 (20 mg, 0.029 mmol) were 1-(4-Bromo-2,5-dipropoxyphenylethynyl)-4-[2,5-dipropoxy-4-(2,5-
added to a degassed solution of 5 (300 mg, 0.27 mmol) and 6[31]
(260 mg, 0.81 mmol) in 20 mL of THF/20 mL of piperidine. After
the mixture had been stirred under argon for 19 h, the solvent was
evaporated and the residue was dissolved in 100 mL of CH2Cl2.
dipropoxyphenylethynyl)phenylethynyl]-2,5-dipropoxybenzene (12):
Triphenylphosphane (20.1 mg, 0.077 mmol), CuI (14.6 mg,
0.077 mmol), and Pd(PPh3)Cl2 (27.0 mg, 0.039 mmol) were added
to a degassed solution of 7[31] (1.0 g, 1.54 mmol) and 11[31] (0.75 g,
The solution was extracted with 50 mL of NH4Cl, 50 mL of water, 1.85 mmol) in 120 mL of piperidine. After the mixture had been
and 50 mL of NaHCO3. The organic layer was dried over Na2SO4,
concentrated, and subjected to column chromatography [30 ϫ 3 cm
SiO2, CH2Cl2/cyclohexane (50:1)]. Yellow crystals (120 mg, 30%)
that melted at 190 °C were obtained. FT-IR (KBr): ν˜ ϭ 2961, 2928,
stirred under nitrogen at 50 °C for 4 h and at 20 °C for 12 h, the
solvent was removed and the residue was treated with 200 mL of
CH2Cl2. The solution was extracted with 100 mL of NH4Cl,
100 mL of water, and 100 mL of NaHCO3 and dried over Na2SO4,
2875, 1515, 1464, 1429, 1387, 1275, 1211 cmϪ1. 1H NMR (CDCl3): and the solvents were evaporated. Twofold column chromatography
δ ϭ 1.07 (m, 42 H, CH3), 1.87 (m, 28 H, CH2), 3.86 (t, 4 H, OCH2), (15 ϫ 4 cm SiO2/toluene and then 30 ϫ 2 cm SiO2/toluene/cyclo-
3.98 (m, 24 H, OCH2), 6.81 (s, 4 H, arom. H), 7.01 (s, 12 H, arom.
H) ppm. 13C NMR (CDCl3): δ ϭ 10.4, 10.5 (CH3), 22.6, 22.7, 22.8 at 130 °C. H NMR (CDCl3): δ ϭ 1.06 (m, 24 H, CH3), 1.82 (m,
(CH2), 70.3, 71.3, 71.5 (OCH2), 89.9, 91.4, 91.6 (acetyl. C), 114.2, 16 H, CH2), 3.86 (t, 2 H, OCH2), 3.98 (m, 14 H, OCH2), 6.81 (m,
114.3, 114.5, 114.6, 114.9, 116.7, 117.7, 117.8, 118.8 (arom. C), 2 H, arom. H), 7.00Ϫ7.08 (m, 7 H, arom. H) ppm. 13C NMR
153.0, 153.6, 154.1 (CqO) ppm.[34] MS (FD): m/z (%) ϭ 1494 (96),
(CDCl3): δ ϭ 10.6 (CH3), 22.6, 22.7, 22.8 (CH2), 70.2, 71.1, 71.2,
747 (100), 498 (3); the peaks correspond to [M ϩ 2 H]ϩ, [M ϩ 2 71.4, 71.5, 71.6 (OCH2), 89.8, 90.6, 90.8, 91.4, 91.6 (acetyl. C),
hexane (5:1) yielded yellow crystals (540 mg, 38%), which melted
1
2812
Eur. J. Org. Chem. 2002, 2808Ϫ2814

Monodisperse Oligo(2,5-dipropoxy-1,4-phenyleneethynylene)s
113.1, 113.3, 114.0, 114.1, 114.2, 114.4, 114.5, 114.7, 116.6, 117.4,
FULL PAPER
on SiO2 (20 ϫ 3 cm) with CHCl3 was followed by further column
117.5, 117.9, 118.3, 118.6 (arom. C), 149.5, 152.9, 153.5, 154.0 chromatography (30 ϫ 3 cm SiO2) with a toluene/CH2Cl2 gradient
(CqO) ppm.[34] MS (FD): m/z (%) ϭ 921/923 (100) [M ϩ H]ϩ, Br
isotope pattern, 462/461 (7) [M ϩ H]2ϩ· C54H65BrO8 (922.0): calcd.
C 70.35, H 7.11; found C 70.48, H 7.08.
from 1:1 to 1:3. Yellow crystals (48 mg, 22%) were obtained, and
these did not melt below 220 °C, but started to decompose at this
temperature. FTϪIR (KBr): ν˜ ϭ 2964, 2934, 2876, 1512, 1427,
1388, 1275, 1212 cmϪ1 1H NMR (CDCl3): δ ϭ 1.07 (m, 66 H,
.
Heptamer OPE 1g: The catalyst, consisting of triphenylphosphane
(3.0 mg, 0.011 mmol), CuI (2.2 mg, 0.012 mmol), and Pd(PPh3)3Cl2
(4.0 mg, 0.006 mmol), was added to a degassed solution of 10
(200 mg, 0.228 mmol) and 12 (260 mg, 0.282 mmol) in 70 mL of
piperidine. After the mixture had been stirred under argon at 50
°C for 1 h and at 20 °C for 28 h, the solvent was removed, and the
residue was dissolved in 50 mL of chloroform and extracted with
25 mL of NH4Cl, 25 mL of water, and 25 mL of NaHCO3. The
organic phase was dried over Na2SO4, filtered through SiO2 (10 ϫ
5 cm) with chloroform, and purified by column chromatography
(50 ϫ 2 cm SiO2) with a solvent gradient changing from CH2Cl2/
toluene 5:1 via CH2Cl2/cyclohexane 5:1 to toluene/cyclohexane 1:1.
Yellow crystals (20 mg, 5%) were isolated, and these melted at 204
°C. FT-IR (KBr): ν˜ ϭ 2963, 2934, 2876, 1515, 1428, 1387, 1275,
CH3), 1.84 (m, 44 H, CH2), 3.87 (t, 4 H, OCH2), 4.00 (m, 40 H,
OCH2), 6.81 (s, 4 H, arom. H), 7.01 (s, 20 H, arom. H) ppm. 13C
NMR (CDCl3): δ ϭ 10.6 (CH3), 22.7, 22.8 (CH2), 70.3, 71.2, 71.4
(OCH2), 89.8, 91.4, 91.6 (acetyl. C), 114.0, 114.4, 114.7, 117.5,
118.7 (arom. C), 152.9, 153.5, 154.0 (arom. CqO) ppm.[34] MS
(FD): m/z (%) ϭ 2359 (100), 1180 (69), 787 (26), 590 (4); the peaks
correspond to [M ϩ 3 H]ϩ, [M ϩ 3 H]2ϩ, [M ϩ 3 H]3ϩ and [M ϩ
3 H]4ϩ. C152H178O22 (2357.1): calcd. C 77.46, H 7.61; found C
76.86, H 8.00.
Acknowledgments
We are grateful to the Deutsche Forschungsgemeinschaft and the
Fonds der Chemischen Industrie for financial support.
1
1211 cmϪ1. H NMR (CDCl3): δ ϭ 1.07 (m, 48 H, CH3), 1.84 (m,
32 H, CH2), 3.86 (t, 4 H, OCH2), 3.99 (m, 28 H, OCH2), 6.81 (s,
4 H, arom. H), 7.01 (s, 14 H, arom. H) ppm. 13C NMR (CDCl3):
δ ϭ 10.6 (CH3), 22.7 (CH2), 70.3, 71.2, 71.4 (OCH2), 89.8, 91.4,
91.6 (acetyl. C), 114.0, 114.1, 114.4, 114.7, 117.4, 117.5, 118.7
(arom. C), 152.9, 153.5, 154.0 (arom. CqO) ppm. MS (FD): m/z
(%) ϭ 1710 (36), 855 (100), 570 (16), 428 (1); the peaks correspond
[1]
H.-H. Hörhold, M. Helbig, D. Raabe, J. Opfermann, U. Scherf,
R. Stockmann, D. Weiß, Z. Chem. 1987, 27, 126Ϫ137.
[2]
H. Meier, Angew. Chem. 1992, 104, 1425Ϫ1446; Angew. Chem.
Int. Ed. Engl. 1992, 31, 1399Ϫ1420.
[3]
K. Müllen, Pure Appl. Chem. 1993, 65, 89Ϫ96.
to [M ϩ 2 H]ϩ, [M ϩ 2 H]2ϩ, [M ϩ 2 H]3ϩ and [M ϩ 2 H]4ϩ
.
[4]
˚
W. R. Salaneck, I. Lundström, B. R Anby, Conjugated Poly-
mers and Related Materials, Oxford University Press, Oxford,
1993.
C110H130O16 (1708.2): calcd. C 77.34, H 7.67; found C 77.04,
H 7.63.
[5]
M. Moroni, J. Le Moigne, Macromolecules 1994, 27, 562Ϫ571.
[6]
Octamer OPE 1h: Triphenylphosphane (16 mg, 0.064 mmol), CuI
(12 mg, 0.064 mmol), and Pd(PPh3)2Cl2 (22 mg, 0.033 mmol) were
added to a degassed solution of 13[31] (1.0 g, 1.28 mmol) and 7[31]
(1.9 g, 2.92 mmol) in 20 mL of toluene/8 mL of piperidine. The
mixture was stirred under argon at 50 °C for 18 h, the solvent was
removed, and the residue was treated with 50 mL of CH2Cl2. The
solution was extracted with 50 mL of NH4Cl, 50 mL of water, and
50 mL of NaHCO3. The dried (Na2SO4) and concentrated organic
phase was subjected to column chromatography (20 ϫ 2 cm SiO2;
CH2Cl2/toluene, 5:1 with a gradient to 10:1). The raw product was
dissolved in 3 mL of CH2Cl2, to which 50 mL of cyclohexane were
then added, so that the pure compound 1h started to crystallize.
Yellow crystals (80 mg, 3%) were obtained, and these melted at 202
°C. FTϪIR (KBr): ν˜ ϭ 2964, 2936, 2876, 1512, 1473, 1427, 1388,
J. S. Schumm, D. L. Pearson, J. M. Tour, Angew. Chem. 1994,
106, 1445Ϫ1448; Angew. Chem. Int. Ed. Engl. 1994, 33,
1360Ϫ1363.
[7]
V. A. Solomin, W. Heitz, Macromol. Chem. Phys. 1994, 195,
303Ϫ314.
J. M. Tour, L. Jones, II, D. L. Pearson, J. J. S. Lamba, T. P.
Burgin, G. M. Whitesides, D. L. Allara, A. N. Parikh, S. V.
Atre, J. Am. Chem. Soc. 1995, 117, 9529Ϫ9534.
T. Mangel, A. Eberhardt, U. Scherf, U. H. F. Bunz, K. Müllen,
Macromol. Rapid Commun. 1995, 16, 571Ϫ580.
J. M. Tour, Chem. Rev. 1996, 96, 537Ϫ553.
O. Lavastre, L. Ollivier, P. H. Dixneuf, S. Sibandhit, Tetrahed-
[8]
[9]
[10]
[11]
ron 1996, 52, 5495Ϫ5504.
[12]
C. Weder, M. S. Wrighton, Macromolecules 1996, 29,
5157Ϫ5165.
[13]
R. Giesa, J. Macromo. Sci., Rev. Macromol. Chem. Phys. 1996,
C36, 631Ϫ670.
K. Weiss, A. Michel, M. E. Auth, U. H. F. Bunz, T. Mangel,
1274, 1211 cmϪ1 1H NMR (CDCl3): δ ϭ 1.05 (m, 54 H, CH3),
.
1.85 (m, 36 H, CH2), 3.86 (t, 4 H, OCH2), 4.00 (m, 32 H, OCH2),
6.81 (s, 4 H, arom. H), 7.02 (s, 12 H, arom. H) ppm. 13C NMR
(CDCl3): δ ϭ 10.4, 10.5 (CH3), 22.6, 22.7, 22.8 (CH2), 70.3, 71.3,
71.5 (OCH2), 89.8, 91.4, 91.6 (acetyl. C), 114.2, 114.3, 114.5, 114.6,
114.9, 117.6, 117.7, 118.8 (arom. C), 152.9, 153.5, 154.0 (arom.
CqO) ppm.[34] MS (FD): m/z (%) ϭ 1926 (76), 963 (100), 642 (33),
482 (3); the peaks correspond to [M ϩ 2 H]ϩ, [M ϩ 2 H]2ϩ, [M ϩ
2 H]3ϩ and [M ϩ 2 H]4ϩ. C124H130O16 (1924.5): calcd. C 77.39, H
7.65; found C 77.28, H 7.60.
[14]
K. Müllen, Angew. Chem. 1997, 109, 522Ϫ525; Angew. Chem.
Int. Ed. Engl. 1997, 36, 506Ϫ509.
[15]
U. Ziener, A. Godt, J. Org. Chem. 1997, 62, 6137Ϫ6134.
[16]
L. Jones, II, J. S. Schumm, J. M. Tour, J. Org. Chem. 1997,
62, 1388Ϫ1410.
[17]
D. Steiger, P. Smith, C. Weder, Macromol. Rapid Commun.
1997, 18, 643Ϫ649.
[18]
R. H. Grubbs, D. Kratz, Chem. Ber./Recueil 1997, 126,
149Ϫ157.
[19]
V. Francke, T. Mangel, K. Müllen, Macromolecules 1998, 31,
2447Ϫ2453.
L. Kloppenburg, D. Song, U. H. F. Bunz, J. Am. Chem. Soc.
Decamer OPE 1i: Pd(PPh3)2Cl2 (2.8 mg, 0.0054 mmol), CuI
(2.0 mg, 0.0105 mmol), and triphenylphosphane (2.4 mg,
0.0107 mmol) were added to a degassed solution of 14[31] (260 mg,
0.240 mmol) and 15[31] (48 mg, 0.108 mmol) in 50 mL of piperidine.
The yellow solution was stirred under argon at 50 °C for 3 h and
then at 20 °C for 48 h. The solvent was removed and the residue
was dissolved in chloroform. After extraction with 20 mL of
NH4Cl, 20 mL of water, and 20 mL of NaHCO3, the organic phase
was dried over Na2SO4 and concentrated. Column chromatography
[20]
1998, 120, 7973Ϫ7974.
[21]
R. Fiesel, U. Scherf, Macromol. Rapid Commun. 1998, 19,
427Ϫ431.
[22]
A. Kraft, A. C. Grimsdale, A. B. Holmes, Angew. Chem. 1998,
110, 416Ϫ443; Angew. Chem. Int. Ed. 1998, 37, 403Ϫ428.
[23]
K. Müllen, G. Wegner, Electronic Materials: The Oligomer Ap-
proach, Wiley-VCH, Weinheim, 1998.
Eur. J. Org. Chem. 2002, 2808Ϫ2814
2813

D. Ickenroth, S. Weissmann, N. Rumpf, H. Meier
FULL PAPER
[24]
[31]
[32]
U. Scherf, Top. Curr. Chem. 1999, 201, 163Ϫ222.
H. Meier, D. Ickenroth, U. Stalmach, K. Koynov, A. Bahtiar,
C. Bubeck, Eur. J. Org. Chem. 2001, 4431Ϫ4443.
H. Meier, J. Gerold, H. Kolshorn, W. Baumann, M. Bletz, An-
gew. Chem. 2002, 114, 302Ϫ306; Angew. Chem. Int. Ed. 2002,
41, 292Ϫ295.
[25]
R. E. Martin, F. Diederich, Angew. Chem. 1999, 111,
1440Ϫ1469; Angew. Chem. Int. Ed. 1999, 38, 1350Ϫ1377.
[26]
H. Kukula, S. Veit, A. Godt, Eur. J. Org. Chem. 1999,
277Ϫ286.
[27]
[33]
[34]
U. H. F. Bunz, V. Enkelmann, L. Kloppenburg, D. Jones, K.
H. Meier, U. Stalmach, H. Kolshorn, Acta Polym. 1997, 48,
D. Shimizu, J. B. Claridge, H.-C. zur Loye, G. Lieser, Chem.
Mater. 1999, 11, 1416Ϫ1424.
L. Kloppenburg, D. Jones, U. H. F. Bunz, Macromolecules
379Ϫ384.
The number of the carbon signals is lower than the number of
nonequivalent carbon atoms because of superimposition of sig-
nals.
[28]
1999, 32, 4194Ϫ4203.
[29]
U. H. F. Bunz, Chem. Rev. 2000, 100, 1605Ϫ1644.
Received March 7, 2002
[30]
J. L. Segura, N. Martin, J. Mater. Chem. 2000, 10, 2403Ϫ2435.
[O02121]
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