Synthesis of nanostructures based on 1,4- and 1,3,5-ethynylphenyl subunits with π-extended conjugation. Carbon dendron units

Article abstract of DOI:10.1021/jo034972b

Nanometer-sized conjugated 1,4- and 1,3,5-ethynylphenyl oligomers were synthesized starting from 3,5-di(trimethylsilylethynyl)phenylacetylene and p-[3,5-di(trimethylsilylethynyl)-1-ethynylphenyl]-phenyl acetylene by cross-coupling reaction with a convenient haloaryl derivative, catalyzed by palladium(II)/copper(I), in excellent yield. The terminal acetylenes were efficiently prepared by a specific protection-deprotection methodology. All ethynylphenyl homologues obtained show fluorescence emission, with the bathochromic shift of approximately 20 nm by each ethynylphenyl unit increasing the conjugate chain. Parallel conjugated ethynylphenyl chains were prepared through the insertion of a 1,5-naphthalene subunit, and the compounds exhibit fluorescence radiation emission.

Full text of DOI:10.1021/jo034972b

Syn th esis of Na n ostr u ctu r es Ba sed on 1,4- a n d 1,3,5-Eth yn ylp h en yl
Su bu n its w ith π-Exten d ed Con ju ga tion . Ca r bon Den d r on Un its
J . Gonzalo Rodr´ıguez,* J orge Esquivias, Antonio Lafuente, and Cristina D´ıaz†
Departamento Quı´mica Orga´nica and Departamento Qu´ımica F´ısica Aplicada, Facultad de Ciencias,
Universidad Auto´noma, Cantoblanco, 28049 Madrid, Spain
gonzalo.rodriguez@uam.es
Received J uly 7, 2003
Nanometer-sized conjugated 1,4- and 1,3,5-ethynylphenyl oligomers were synthesized starting from
3,5-di(trimethylsilylethynyl)phenylacetylene and p-[3,5-di(trimethylsilylethynyl)-1-ethynylphenyl]-
phenyl acetylene by cross-coupling reaction with a convenient haloaryl derivative, catalyzed by
palladium(II)/copper(I), in excellent yield. The terminal acetylenes were efficiently prepared by a
specific protection-deprotection methodology. All ethynylphenyl homologues obtained show fluo-
rescence emission, with the bathochromic shift of approximately 20 nm by each ethynylphenyl
unit increasing the conjugate chain. Parallel conjugated ethynylphenyl chains were prepared
through the insertion of a 1,5-naphthalene subunit, and the compounds exhibit fluorescence
radiation emission.
In tr od u ction
Conjugated systems integrated by 1,2-, 1,3-, 1,4-di-
ethynyl and 1,3,5-triethynylphenyl units have been used
in the preparation of aromatic monomers bearing mul-
tiple ethynyl groups with electroluminescence proper-
ties10 poly(phenylvinylene) with fluorescence properties,
as well as dendrimers11 with the poly(yne) chain.12 The
triple bonds play the role of a wire while the polyaromatic
systems behave as an energy relay subunit.
We now report the controlled synthesis of a novel
family of rigid conjugated nanostructures based on 1,4-
di(ethynylphenyl) and 1,3,5-tri(ethynylphenyl) units, which
serve to prepare stable and geometrically well-defined
nanostructures. The diethynyl or triethynyl substituted
benzene show a variety of geometric possibilities by their
hexagonal structure such as 1,4-linear, 1,3-trigonal and
1,2-closed angle structures (60°).
The synthesis and characterization of nanometer-sized
conjugated molecules of precise length and constitution
are of widespread interest, which is due to their inherent
synthetic flexibility that permits the design of molecular
architectures with important properties.1,2 Molecules
showing π-extended conjugation, in general, can present
electroconductive, magnetic, and optical properties.3
A variety of potential applications such as artificial
photosynthesis,4 photocatalysis,5 molecular photovoltaic
cells,6 molecular informatics,7 and optoelectronic de-
vices8,9 are beginning to emerge from this new field of
research.
† Departamento Qu´ımica F´ısica Aplicada.
(1) Tour, J . M. Chem. Rev. 1996, 96, 537.
(2) (a) Huang, S. S.; Tour, J . M. Polym. Prepr. 1998, 39, 525. (b)
Grosshenny, V.; Romero, F. M.; Ziessel, R. J . Org. Chem. 1997, 62,
1491. (d) Brad, W. W.; Brand, S. C.; Pak; J . J .; Haley, M. M. Chem.
Eur. J . 2000, 6, 2044.
(3) (a) Bunz, U. H. F. Chem. Rev. 2000, 100, 1605. (b) Irie, M. Chem.
Rev. 2000, 100, 1685. (c) Delaire, J . A.; Nakatani, K. Chem. Rev. 2000,
100, 1817. (d) Giesa, R. J . Macromol. Sci., Rev. Macromol. Chem. Phys.
1996, 36, 631.
(4) Capitosti, G. J .; Guerrero, C. D.; Binkley, D. E., J r.; Rajesh, C.
S.; Modarelli, D. A. J . Org. Chem. 2003, 68, 247.
(5) (a) Mclean, D. G.; Rogers, J . E.; Cooper, T. M. Proc. SPIE-Int.
Soc. Opt. Eng. 2002, 4462, 11. (b) Ziessel, R. In Photosensitization
and Photocatalysis Using Inorganic and Organometallic Compounds;
Kalyanasundaram, K., Gra¨tzel, M., Eds.; Kluwer Academic Publish-
ers: Dordecht, 1993; p 217.
Resu lts a n d Discu ssion
Nanostructure compounds were prepared by linking
conjugated subunits with the appropriate geometry. The
linear 1,2-di(p-iodophenyl)acetylene subunit (2)13 was
obtained in practically quantitative yield (98%), starting
with the corresponding E/ Z ethenyl mixture 1,14 by
bromine addition followed by dehydrobromination with
potassium tert-butoxide, at room temperature. The ethen-
yl derivative (1) was satisfactorily obtained (85%) by the
Wittig reaction between p-(iodophenyl)carboxaldehyde
and the p-(iodobenzyl)(triphenyl) phosphonium ylide,
prepared in situ, from the corresponding phosphonium
salt with potassium tert-butoxide in toluene. Scheme 1.
(6) (a) Guijum, Y.; Yuping, D.; Tingbing, C.; Shuming, Y.; Yip, J .
W. L.; Benzhong, T. J . Colloid Interface Sci. 2003, 257, 263. (b) Brabec,
C. J .; Sariciftci, N. S.; Hummelen, J . C. Adv. Funct. Mater. 2001, 11,
15. (c) Yu, G.; Gao, J .; Hummelen, J . C.; Wudl, F.; Heeger, A. J . Science
1995, 270, 1789.
(7) (a) Seminario, J . M.; Zacarias, A. G.; Tour, J . M. J . Am. Chem.
Soc. 1999, 121, 411. (b) Tour, J . M.; Kozaki, M.; Seminario, J . M. J .
Am. Chem. Soc. 1998, 120, 8486. (c) Barakat, M. T.; Dean, P. M. J .
Comput.-Aided Mol. Des. 1995, 9, 341.
(8) Nielsen, N. B.; Diederich, F. Chem. Rec. 2002, 2, 189.
(9) Barker, J . R. In Molecular Electronics; Petty, M. C., Bryce, M.
R., Bloor, D., Eds.; Edward Arnold: London, 1995; p 345.
(10) Anderson S. Chem Eur. J . 2001, 7, 4706.
(11) Deb S. K.; Maddux T. M.; Yu L. J . Am. Chem. Soc. 1997, 119,
9079.
(12) Gibtner, T.; Hampel F.; Gisselbrecht J -P.; Hirsch A. Chem. Eur.
J . 2002, 8, 409.
(13) Novikov, A. N.; Griguiev, M. G. Zh. Org. Khim. 1978, 14, 1790.
(14) Drefahl, G.; Schaaf, S. Chem. Ber. 1957, 90, 148.
10.1021/jo034972b CCC: $25.00 © 2003 American Chemical Society
Published on Web 09/26/2003
8120
J . Org. Chem. 2003, 68, 8120-8128

Ethynylphenyl-Based Nanostructures
SCHEME 1a
a
t
t
(i) BuOK, toluene, p-iodobenzaldehyde, (ii) Br2, CCl4, (iii) BuOK.
SCHEME 2a
a
(i) 2-Methyl-3-butyn-2-ol, Cl2Pd(Ph3P)2, CuI, NEt3, (ii) NaOH, toluene at reflux; (iii) trimethylsilylethyne, Cl2Pd(Ph3P)2, CuI, NEt3,
rt.
On the other hand, the synthesis of protected molecular
aqueous sodium hydroxide.19 Under the anhydrous condi-
tions, sodium hydroxide dissociation was avoided and
thus the sodium hydroxide can only behave as a basic
group abstracting the acid proton of the alcohol with
elimination of acetone. In contrast, in the presence of a
small amount of water or MeOH the sodium hydroxide
is partially dissociated and a nucleophilic attack of the
OR anion to the silicon atom takes place, with formation
of Me3Si-OR and the elimination of the trimethylsilyl-
ethyne groups.
Syn th esis of Ter m in a l Acetylen es w ith Tr igon a l-
Lin ea r Geom etr y. Following the specific deprotection
methodology, terminal acetylenes with trigonal-linear
geometry were synthesized. Thus, the heterocoupling
reaction of the terminal acetylene 7 with 4-(3-hydroxy-
3-methyl-1-butynyl)-1-iodobenzene,20 catalyzed by the
palladium/copper system, gives 8 in good yield, which by
the specific deprotection of the propargylic group affords
9, Scheme 3. Likewise, the heterocoupling reaction
between 9 and 4-(3-hydroxy-3-methyl-1-butynyl)-1-iodo-
benzene, in the presence of the palladium/copper system,
gives 10 in good yield, which by specific deprotection of
the propargylic group affords 11.
subunits with trigonal geometry was undertaken starting
with 1,3,5-tribromobenzene, Scheme 2. Thus, 1,3,5-[tris-
(3-hydroxy-3-methyl-1-butynyl)]benzene (3)15 was ob-
tained by heterocoupling of 1,3,5-tribromobenzene with
2-methyl-3-butyn-2-ol in the presence of the palladium/
copper catalyst system, in good yield (80%). However, 3,5-
[bis(3-hydroxy-3-methyl-1-butynyl)]-1-ethynylbenzene (4)
was isolated pure in low yield (12%) by deprotection with
powdered sodium hydroxide in dry toluene at reflux
temperature,16 Scheme 2.
Because of the low yield of the propargylic derivative
4, other synthetic methodology was applied. An alterna-
tive synthesis of a diprotected derivative involved the
heterocoupling reaction between 1,3,5-tribromobenzene
and 2-methyl-3-butyn-2-ol, in the presence of the pal-
ladium catalyst, to obtain the mono heterocoupled com-
pound 517 (80%), which was doubly heterocoupled with
trimethylsilylethyne in triethylamine with the palladium
catalyst, at reflux temperature, to give 6 in good yield
(85%). The specific deprotection of the propargylic group
was carried out with powdered sodium hydroxide in dry
toluene at reflux temperature, giving the doubly pro-
tected terminal acetylene 7 (colorless oil),18 Scheme 2.
Now, we can synthesize a new family of ethynylphenyl
nanostructures with π-extended conjugation along the
lineal axis, employing the terminal acetylenes 7, 9, and
11, Scheme 4. Thus, p-diiodobenzene as the linear
separator unit was doubly heterocoupled with 7 (or 9),
in the presence of the palladium/copper catalyst system,
giving 12 (or 13), Scheme 4.
The specific method for deprotection of 2-methyl-3-
butyn-2-ol in dry toluene, in the presence of the tri-
methylsilylethyne protecting group, requires rigorous
anhydrous conditions. There are many references for
trimethylsilyl deprotection with different bases such as
(15) McBride, M.; Hugh, J . A.; Kenneth, W. Synth. Commun. 1996,
26, 2309.
(16) Rodriguez, J . G.; Tejedor, J . L. J . Org. Chem. 2002, 67, 7631.
(17) Kaneko, T.; Horie, T.; Aoki, T.; Oikawa, E. Kobunshi Runbun-
shu 2000, 57, 672.
(19) (a) Manini, P.; Amrein, W.; Gramlich, V.; Diederich, F. Angew.
Chem., Int. Ed. 2002, 41, 4334. (b) Marshall, J . A.; Bourbeau, M. Org.
Lett. 2002, 4, 3931. (c) Dondoni, A.; Mariotti, G.; Marra, A. J . Org.
Chem. 2002, 67, 4475.
(20) Ha¨nniem, E.; Takalo, H.; J ouko K. Acta Chem. Scand. B 1988,
42, 614.
(18) Rodr´ıguez, J . G.; Esquivias, J . Tetrahedron Lett. 2003, 26, 4831.
J . Org. Chem, Vol. 68, No. 21, 2003 8121

Rodr´ıguez et al.
SCHEME 3a
a
(i) PdCl2(PPh3)2, CuI, NEt3, 4-(3-hydroxy-3-methyl-1-butyn)-1-iodobenzene, (ii) NaOH, toluene at reflux temperature.
SCHEME 4a
a
(i) PdCl2(PPh3)2, CuI, NEt3.
SCHEME 5a
a
(i) PdCl2(PPh3)2, CuI, NEt3, 1,5-diiodonaphthalene.
Moreover, a longer linear separator unit was used for
the preparation of the ethynylphenyl homologue com-
pound 14 (or 15). Thus, double heterocoupling between
1,2-di(p-iodophenyl)ethyne (2) and the terminal acetylene
7 (or 9), catalyzed by the palladium/copper system, gives
14 (or 15) in good yield, Scheme 4.
Syn th esis of Con ju ga ted P a r a llel Exten d ed Tr i-
gon a l-Lin ea r Na n ostr u ctu r es. The intercalation of the
1,5-naphthylethynyl structural module permits extension
of a parallel conjugated linear chain. The optical proper-
ties of the new nanostructure compounds were analyzed.
Our experience shows that the 1,5-disubstituted naph-
thylethynyl rings present π-extended conjugation.16
The synthesis of a parallel trigonal-linear growing
chain structure was undertaken for heterocoupling reac-
tion of the terminal acetylenes with 1,5-diiodonaphtha-
lene. Hence, the heterocoupling reaction between the
terminal acetylene 7 (or 9 or 11) and 1,5-diiodonaphtha-
lene, in the presence of the palladium/copper catalyst
system, gives 16 (or 17 or 18) in good to excellent yield
(85-95%), Scheme 5.
Syn th esis of 1,3-Bu ta d iyn e Con ju ga ted Na n o-
st r u ct u r es b y Oxid a t ive Dim er iza t ion . A practical
method to extend the conjugation of the ethynylphenyl
chains was the oxidative homocoupling of the corre-
sponding terminal acetylene by the Eglinton-Glaser reac-
8122 J . Org. Chem., Vol. 68, No. 21, 2003

Ethynylphenyl-Based Nanostructures
SCHEME 6a
a
(i) CuCl, O2, pyridine.
SCHEME 7a
TABLE 1. Wa velen gth s for F ir st Absor p tion a n d
F lu or escen ce Em ission Ma xim a for Com p ou n d s 12-15 in
CH2Cl2 a t Room Tem p er a tu r e
UV-vis
max, nm
fluorescence
max, nm
compd
λ
ꢀ (M-1 cm-1
44900 (67100)
)
λ
Φfa
12 (n ) 1) 326 (348, sh)
13 (n ) 3) 354 (375, sh) 103600 (74600)
76300 (61000)
355, 373
394, 413
376, 394
414, 435
0.65
0.72
0.68
0.77
14 (n ) 2) 344 (365, sh)
a
(i) Cl2Sn, AcOEt, reflux, (ii) NaNO2, H2SO4, 0 °C, (iii) KI, H2O.
15 (n ) 4) 360 (383, sh) 114000 (86700)
tion.21 The oxidative dimerization of terminal acetylene
7 (or 9, or 11) was catalyzed by a cuprous salt (chloride
or iodide) in pyridine, under oxygen atmosphere, to give
the corresponding 1,3-diyne 19 (or 20, or 21), Scheme 6.
Syn th esis of Eth yn ylp h en yl Den d r on s w ith a
1,3,5-Tr isu bstitu ted Ben zen e Cor e. The terminal
acetylene subunits were employed for the preparation of
the dendron base unit in 1,3,5-trisubstituted benzene
with a planar conjugated star disposition. However, the
heterocoupling reaction of 1,3,5-tribromobenzene with the
terminal acetylenes only provided the oxidative dimer-
ization to the corresponding 1,3-diynes, as the Eglinton-
Glaser behavior of the catalyst. The more reactive 1,3,5-
triiodobenzene was synthesized. The direct iodination of
benzene gives a mixture of products that results in low
yield and tedious purification.22,23 A new practical syn-
thesis of 1,3,5-triiodobenzene has been developed to
prepare 1,3,5-tri(ethynylphenyl)benzene derivatives.
The synthesis of 1,3,5-triidobenzene was carried out
by reduction of 1-iodo-3,5-dinitrobenzene with stannous
chloride in ethyl acetate, to obtain 1-iodo-3,5-diamino-
benzene (22)24 in practically quantitative yield (98%). The
diamino derivate 22 was transformed in 1,3,5-triiodo-
benzene (23) through the double diazonium salt with
successive potassium iodide treatment.16,25,26 Compound
23 was purely obtained as a white solid in good yield
(68%), Scheme 7.
a
Fluorescence quantum yield was determined in CH2Cl2 rela-
tive to 2-aminopyridine in 0.1 N H2SO4.
TABLE 2. Wa velen gth s for F ir st Absor p tion a n d
F lu or escen ce Em ission Ma xim a for Com p ou n d s 16-18 in
CH2Cl2 a t Room Tem p er a tu r e
UV-vis
fluorescence
max, nm
compd
λ
max, nm
ꢀ (M-1 cm-1
)
λ
Φfa
16
17
18
352 (368, sh)
365 (373, sh)
366 (389, sh)
33800 (27500)
65100 (57300)
97800 (73500)
377, 398
397, 418
418, 438
0.60
0.81
0.82
a
Fluorescence quantum yield was determined in dichloro-
methane relative to 2-aminopyridine in 0.1 N H2SO4.
the ethynylphenyl dendron unit 24 (or 25 or 26), in good
yield (80-93%), Scheme 8.
UV-vis a n d F lu or escen ce An a lysis of th e Con ju -
ga ted Com p ou n d s 12-26 in Dich lor om eth a n e. The
UV-vis absorption analysis of diluted solutions of the
conjugated compounds 12-26 was carried out in dichlo-
romethane. The maxima absorption wavelength (λmax
)
showed a strong bathochromic shift with the increasing
number n of repeated units, which is a characteristic for
short oligomers of conjugated systems. The corresponding
molar extinction coefficients ꢀmax also increase with n,
Tables 1-4.
The conjugated synthesized nanostructures 12-26,
exhibit high fluorescent emission radiation in solution
of dichloromethane. An analysis of the optical properties
of this family of compounds was carried out. Figure 1
shows the fluorescence spectra of the linear family of the
compounds 12-15.
Compounds 12-15 exhibit two emission bands, which
present a bathochromic shift of 20 nm for each ethynyl-
phenyl unit in the chain, while the quantum yield
shows a moderate increase (for an estimate error of
3%). This effect seems to be of analytically useful interest
to determine the number of ethynylphenyl units in a
polymer by means of the fluorescence analysis data.
Figure 2 shows the fluorescence spectra of the naph-
thylethynyl nanostructures 16-18. A bathochromic shift
of 20 nm between the naphthylethynyl homologues was
The heterocoupling reaction between the terminal
acetylene 7 (or 9 or 11) with 1,3,5-triiodobenzene gives
(21) (a) Glaser, G. Chem. Ber. 1869, 2, 422. (b) Glaser, G. Liebigs
Ann. Chem. 1870, 159.
(22) Scho¨berl, U.; Magnera, T. F.; Harrison, R. M.; Fleisher, F.;
Pflug, J . L.; Schwab, P. F. H.; Meng X.; Lipiak, D.; Noll, B. C.; Allured,
V. S.; Rudalevige, T.; Lee, S.; Michl, J . J . Am. Chem. Soc. 1997, 119,
3907.
(23) Mattern, D. L. J . Org. Chem. 1984, 49, 3051.
(24) Beltz, M. W.; Harris, F. W. High Perform. Polym. 1995, 1, 23.
(25) Hodgson, H. H. Whitehurst, J . S. J . Chem. Soc. 1947, 80.
(26) Curry, H. M.; Shechter, H.; Bossenbroek, B.; Sanders, D. C. J .
Am. Chem. Soc. 1969, 69, 371.
(27) (a) Ames, D. E.; Bull, D.; Takundwa, C. Synthesis 1981, 364.
(b) Rodr´ıguez, J . G.; Mart´ın-Villamil, R.; Cano, F. H.; Fonseca, I. J .
Chem. Soc., Perkin Trans. 1 1997, 709.
(28) Harthan, W. W.; Silloway, H. L. Organic Syntheses; Wiley: New
York, 1955; Collect. Vol. III, p 82.
J . Org. Chem, Vol. 68, No. 21, 2003 8123

Rodr´ıguez et al.
SCHEME 8a
a
(i) 1,3,5-Triiodobenzene, Cl2Pd(PPh3)2, CuI, NEt3.
TABLE 3. Wa velen gth s for F ir st Absor p tion a n d
F lu or escen ce Em ission Ma xim a for Com p ou n d s 19-21 in
CH2Cl2 a t Room Tem p er a tu r e
TABLE 4. Wa velen gth s for F ir st Absor p tion a n d
F lu or escen ce Em ission Ma xim a for Com p ou n d s 24-26 in
CH2Cl2 a t Room Tem p er a tu r e
UV-vis
fluorescence
max, nm
UV-vis
fluorescence
max, nm
compd
λ
max, nm
ꢀ (M-1 cm-1
)
λ
Φfa
compd
λ
max, nm
ꢀ (M-1 cm-1
)
λ
Φfa
19
20
21
314 (336, sh)
346 (375, sh)
369 (387, sh) 123900 (98500)
28200 (22800)
96000 (64800)
365, 388
386, 412
414, 438
<0.01
0.33
0.54
24
25
26
291 (308, sh)
329 (351, sh) 181200 (143700)
347 (366, sh) 187500 (156000)
89800 (87400)
353, 367
356, 377
377, 398
0.16
0.48
0.80
a
a
Fluorescence quantum yield was determined in dichloro-
methane relative to 2-aminopyridine in 0.1 N H2SO4.
Fluorescence quantum yield was determined in dichloro-
methane relative to 2-aminopyridine in 0.1 N H2SO4.
F IGURE 1. Normalized emission spectra for compounds 12-
15 in CH2Cl2 at room temperature.
F IGURE 2. Normalized emission spectra for compounds 16-
18 in CH2Cl2 at room temperature.
also observed, while high quantum yield values were
measured, 81% and 82% for 17 and 18, respectively,
Table 2.
Figure 3 shows the fluorescence spectra of the 1,3-diyne
family compounds 19-21. A bathochromic shift was also
observed, although the wavelength of the emission shows
variable increasing values closely to 20 nm for each
ethynylphenyl unit in the chain, Table 3.
Finally, Figure 4 shows the fluorescence spectra for the
conjugated 1,3,5-trisubstituted benzene dendron units
24-26. The bathochromic wavelength shift effect, in-
creasing by 20 nm, was only observed between com-
pounds 25 and 26, and this increase fails for the
compounds 24 (linked to the benzene core) and 25, in the
two emission bands. However, the quantum yield shows
8124 J . Org. Chem., Vol. 68, No. 21, 2003

Ethynylphenyl-Based Nanostructures
cence emission radiation, with a bathochromic shift of
20 nm for each ethynylphenyl unit increasing the con-
jugated chain. In general, the homologue compounds
show high quantum yields (65-82%), which increase
whith the conjugation.
Exp er im en ta l Section
Gen er a l P r oced u r es. Melting points were determined in
open capillaries and are uncorrected. IR spectra were recorded
using KBr pellets or NaCl plates, and only partial data is
reported. Proton nuclear magnetic resonance (1H NMR) spec-
tra were recorded at 300 MHz. Chemical shifts are reported
in delta (δ) units, parts per million (ppm) downfield from
trimethylsilane. Coupling constants are reported in hertz (Hz).
Carbon-13 nuclear magnetic resonance (13C NMR) spectra
were recorded at 75 MHz. Chemical shifts are reported in delta
(δ) units, parts per million (ppm) relative to the center of the
triplet at 77.00 ppm for deuteriochloroform. Mass spectra were
obtained at an ionizing potential of 70 eV and reported as m/e
(relative intensity). Accurate masses are reported for the
molecular ion (M + 1) or a suitable fragment ion. Flash
chromatography was performed on silica gel 60 (200-400
mesh) using the indicated solvents. The UV-vis spectra
F IGURE 3. Normalized emission spectra for compounds 19-
21 in CH2Cl2 at room temperature.
frequencies are given in nm and ꢀ in L mol-1 cm-1
.
3,5-[Bis(3-h yd r oxy-3-m eth yl-1-bu tyn yl)]-1-eth yn ylben -
zen e (4). Gen er a l P r oced u r e for Syn th esis of Ar yla cet-
ylen es.27 To a solution of 3 (1 g, 3.08 mmol) in anhydrous
toluene (30 mL) was added finely powdered sodium hydroxide
(37 mg, 9.26 mmol) under argon atmosphere. The mixture was
warmed at the reflux temperature for 3 h (monitored by TLC)
and then filtered. The solvent was removed, giving 4 as a pale
brown solid (98.3 mg, 12%), mp 95-97 °C. IR (KBr): cm-1 3302
(tC-H), 3270 (O-H), 2200 (CtC), 1580 and 1413 (CdC), 1160
(C-OH), 883 (1,3,5 trisubst). 1H NMR (CDCl3): δ 7.44 (br s,
3H), 3.06 (s, 1H), 1.52 (s, 12H). 13C NMR (CDCl3): δ 134.2,
123.2, 122.6, 94.8, 81.8, 80.5, 78.2, 65.5, 31.07. C18H18O2
(266.33): anal. calcd C 81.17, H 6.81; found C 81.32, H 6.51.
3,5-Bis(tr im eth ylsilyleth yn yl)-1-(3-h yd r oxy-3-m eth yl-
1-bu tyn yl)ben zen e (6). Gen er a l P r oced u r e of th e Heter o-
cou p lin g Rea ction . To a solution of compound 5 (1.0 g, 3.14
mmol), trimethylsilylethyne (1.11 mL, 7.85 mmol), and 2-meth-
yl-3-butyn-2-ol (3.17 g, 38.22 mmol) in freshly distilled tri-
ethylamine (30 mL) under argon atmosphere and at room
temperature, was added dichloro bis(triphenylphosphine)-
palladium (551 mg, 0.785 mmol) and a small amount of
cuprous iodide. The mixture was stirred at 60 °C for 15 h
(monitored by TLC) and then, the amine was removed under
reduced pressure. The crude residue was washed with a
saturated aqueous ammonium chloride solution with a small
amount of KCN and extracted with dichloromethane. The
extracts were dried on anhydrous sodium sulfate, and after
filtration the solvent was removed and the residue was purified
by silica gel column chromatography, eluting with hexane/
ethyl acetate (4:1). Compound 6 was isolated as a white solid
(939 mg, 85%), mp 85-86 °C. IR (KBr): cm-1 3312 (O-H), 2160
(CtC), 1581 and 1412 (CdC), 1250 (Si-CH3), 882 (1,3,5
trisubst.), 759 (C-Si). 1H NMR (CDCl3): δ 7.47 (t, 1H, J ) 1.4
Hz), 7.43 (d, 2H, J ) 1.4 Hz), 1.57 (s, 6H), 0.21 (s, 18H). 13C
NMR (CDCl3): δ 134.7, 134.5, 123.6, 123.2, 103.1, 95.5, 94.8,
80.4, 65.4, 31.3, -0.19. C21H28OSi2 (362.62): anal. calcd C
71.53, H 8.00; found C 71.59, H 7.93.
F IGURE 4. Normalized emission spectra for compounds 24-
26 in CH2Cl2 at room temperature.
high increasing with the number of the ethynylphenyl
units in the chain, Table 4.
Con clu sion s
This work describes a simple and useful synthetic
route to prepare 1,4- and 1,3,5-ethynylphenyl oligomers
by means of the specific deprotection of the terminal
acetylene bond. The Sonogashira cross-coupling reaction
between a convenient haloaryl derivative and a terminal
acetylene such as 3,5-di(trimethylsilylethynyl)phenyl-
acetylene or p-[3,5-di(trimethylsilylethynyl)-1-ethynyl-
phenyl]phenylacetylene, catalyzed by the palladium/
copper system, give the corresponding ethynylphenyl
oligomers in excellent yield. In the UV-vis spectra,
the maxima absorption wavelengths λmax show a batho-
chromic shift with the conjugated ethynylphenyl number
n of repeated units. The corresponding molar extinction
coefficients ꢀmax also increase with n. All the ethynyl-
phenyl homologue compounds obtained show a fluores-
3,5-Bis(t r im et h ylsilylet h yn yl)-1-et h yn ylb en zen e (7).
Following the general method used for the synthesis of 4, to a
solution of compound 6 (280 mg, 0.79 mmol) in anhydrous
toluene (40 mL) was added finely powdered sodium hydroxide
(3.16 mg, 0.079 mmol). The mixture was stirred for 4 h and
then filtered. The solvent was removed, giving 7 as colorless
oil18 (229 mg, 99%). IR (NaCl): cm-1 3302 (tC-H), 2162 (Ct
C), 1580 and 1413 (CdC), 1250 (Si-CH3), 883 (1,3,5 trisubst.),
1
760 (C-Si). H NMR (CDCl3): δ 7.53 (t, 1H, J ) 1.4 Hz), 7.50
(d, 2H, J ) 1.4 Hz), 3.06 (s, 1H), 0.23 (s, 18H). 13C NMR
J . Org. Chem, Vol. 68, No. 21, 2003 8125

Rodr´ıguez et al.
(CDCl3): δ 135.3, 135.0, 123.7, 122.6, 102.9, 95.5, 81.8, 78.2,
-0.19. C18H22Si2 (294.54): anal. calcd C 73.40, H 7.53; found
C 73.52, H 7.46.
ylphosphine)palladium (45 mg, 0.068 mmol), and triethylamine
(30 mL) was stirred for 15 h. Purification was carried out by
flash chromatography on a silica gel column, eluting with
hexane, giving 12 as a white solid (220 mg, 98%), mp 220-
221 °C. UV-vis (CH2Cl2), λmax (nm): 348 (sh, ꢀ, 44900), 326
(ꢀ, 67100), 270 (ꢀ, 142300). Fluorescence (CH2Cl2), λmax (nm):
373, 355 (φ ) 0.65). IR (KBr): cm-1 2158 (CtC), 1579 and
1508 (CdC), 1251 (Si-CH3), 840 (1,3,5 trisubst), 758 (C-Si).
1H NMR (CDCl3): δ 7.56 (d, 4H, J ) 1.6 Hz), 7.53 (t, 2H, J )
1.6 Hz), 7.46 (br s, 4H), 0.24 (s, 36H). 13C NMR (CDCl3): δ
134.9, 134.5, 131.6, 123.7, 123.4, 122.7, 103.1, 95.7, 89.9, 89.6,
-0.17. MS m/z (relative intensity): 662.1 (M+ 80), 559 (10),
316.2 (55). C42H46Si4 (663.16): anal. calcd C 76.07, H 6.99;
found C 76.15, H 6.91.
1-[(3,5-Bis-tr im eth ylsilyleth yn ylp h en yl)eth yn yl]-4-(3-
h yd r oxy-3-m eth yl-1-bu tyn yl)ben zen e (8). Following the
general method used for the synthesis of 6, a mixture of 4-(3-
hydroxy-3-methyl-1-butynyl)-1-iodobenzene20 (350 mg, 1.225
mmol), compound 7 (360 mg, 1.225 mmol), dichloro bis-
(triphenylphosphine)palladium (88 mg, 0.013 mmol), and
triethylamine (30 mL) was stirred for 12 h. Purification was
carried out by flash chromatography on a silica gel column,
eluting with hexane/ethyl acetate (4:1), providing 8 as a white
solid (498 mg, 90%), mp 95-97 °C. IR (KBr): cm-1 3356 (O-
H), 2157 (CtC), 1576 and 1506 (CdC), 1249 (Si-CH3), 1161
(C-OH), 840 (1,3,5 trisubst.), 758 (C-Si). 1H NMR (CDCl3):
δ 7.54 (d, 2H, J ) 1.6 Hz), 7.52 (t, 2H, J ) 1.6 Hz), 7.43 (d,
2H, J ) 8.5 Hz), 7.38 (d, 2H, J ) 8.5 Hz), 1.62 (s, 6H), 0.23 (s,
18H). 13C NMR (CDCl3): δ 134.9, 134.5, 131.6, 131.4, 123.7,
123.4, 122.9, 122.5, 103.1, 95.76, 96.7, 89.9, 89.6, 81.7, 65.6,
31.4, -0.17. C28H32OSi2 (452.73): anal. calcd C 76.93, H 7.12;
found C 77.02, H 7.06.
1-[(3,5-Bis-tr im eth ylsilyleth yn ylph en yl)eth yn yl]-4-eth -
yn ylben zen e (9). Following the general method used for the
synthesis of 4, a mixture of compound 8 (350 mg, 0.774 mmol),
anhydrous toluene (40 mL), and finely powdered sodium
hydroxide (3.2 mg, 0.0774 mmol) was stirred for 4 h and then
filtered. The solvent was removed, giving 9 as an orange solid
(302 mg, 99%), mp 80-83°C. IR (KBr): cm-1 3302 (tC-H),
2157 (CtC), 1576 and 1506 (CdC), 1249 (Si-CH3), 840 (1,3,5
trisubst.), 758 (C-Si). 1H NMR (CDCl3): δ 7.57 (d, 2H, J ) 1.6
Hz), 7.54 (t, 1H, J ) 1.6 Hz), 7.48 (d, 2H, J ) 8.5 Hz), 7.45 (d,
2H, J ) 8.5 Hz), 3.19 (s, 1H,), 0.26 (s, 18H). 13C NMR (CDCl3):
δ 135.0, 134.5, 132.1, 131.4, 123.7, 123.4, 123.1, 122.2, 103.1,
95.76, 89.9, 89.6, 83.1, 79.1, -0.17. C26H26Si2 (394.66): anal.
calcd C 79.13, H 6.64; found C 79.19, H 6.58.
1-{[(3,5-Bis-tr im eth ylsilyleth yn ylph en yl)eth yn ylph en yl]-
eth yn yl}-4-(3-h yd r oxy-3-m eth yl-1-bu tyn yl)ben zen e (10).
Following the general method used for the synthesis of 6, a
mixture of 4-(3-hydroxy-3-methyl-1-butynyl)-1-iodobenzene20
(181 mg, 0.642 mmol), compound 9 (250 mg, 0.642 mmol),
dichloro bis(triphenylphosphine)palladium (45 mg, 0.06 mmol),
and triethylamine (30 mL) was stirred for 15 h. Purification
was carried out by flash chromatography on a silica gel column,
eluting with hexane/ethyl acetate (4:1), providing 10 as a white
solid (312 mg, 88%), mp 214-215 °C. IR (KBr): cm-1 3355
(O-H), 2157 (CtC), 1580 and 1511 (CdC), 1250 (Si-CH3),
1161 (C-OH), 840 (1,3,5 trisubst), 758 (C-Si). 1H NMR
(CDCl3): δ 7.55 (d, 2H, J ) 1.6 Hz), 7.53 (t, 2H, J ) 1.6 Hz),
7.48 (br s, 4H), 7.46 (d, 2H, J ) 8.3 Hz), 7.39 (d, 2H, J ) 8.3
Hz), 1.62 (s, 6H), 0.24 (s, 18H). 13C NMR (CDCl3): δ 134.9,
134.5, 131.5, 131.4, 123.8, 123.4, 123.1, 122.8, 103.12, 96.12,
95.76, 90.9, 90.7, 90.0, 89.6, 65.6, 31.4, -0.22. C37H36OSi2
(552.85): anal. calcd C 80.38, H 6.56; found C 80.45, H 6.49.
1,4-Bis{(3,5-bis-tr im eth ylsilyleth yn ylp h en yl)eth yn yl-
p h en yl]eth yn yl}ben zen e (13). Following the general method
used for the synthesis of 6, a mixture of 1,4-diiodobenzene (100
mg, 0.303 mmol), compound 9 (239 mg, 0.61 mmol), dichloro
bis(triphenylphosphine)palladium (42.5 mg, 0.06 mmol), and
triethylamine (30 mL) was stirred for 12 h. Purification was
carried out by flash chromatography on a silica gel column,
eluting with hexane, providing 13 as a green solid (256 mg,
98%), mp 270-273 °C. UV-vis (CH2Cl2), λmax (nm): 375 (sh,
ꢀ, 74600), 354 (ꢀ, 103600), 269 (ꢀ, 86700), 255 (ꢀ, 82000), 240
(ꢀ, 84800). Fluorescence (CH2Cl2), λmax (nm): 413, 394 (φ )
0.72). IR (KBr): cm-1 2157 (CtC), 1578 and 1518 (CdC), 1249
1
(Si-CH3), 842 (1,3,5 trisubst), 758 (C-Si). H NMR (CDCl3):
δ 7.56 (d, 4H, J ) 1.6 Hz), 7.53 (t, 2H, J ) 1.6 Hz), 7.51-7.49
(m, 12H), 0.24 (s, 36H). 13C NMR (CDCl3): δ 134.9, 134.5, 131.6,
123.7, 123.4, 123.1, 123.0, 122.7, 103.0, 95.7, 91.0, 91.1, 90.0,
89.6, -0.17. MS m/z (relative intensity): 862.1 (M+ 100), 416.2
(66). C58H54Si4 (863.39): anal. calcd C 80.68, H 6.30; found C
80.79, H 6.21.
Di{4-[(3,5-b is-t r im et h ylsilylet h yn ylp h en yl)et h yn yl-
p h en yl]eth yn yl}eth yn e (14). Following the general method
used for the synthesis of 6, a mixture of compound 2 (50 mg,
0.12 mmol), compound 7 (68.41 mg, 0.24 mmol), dichloro bis-
(triphenylphosphine)palladium (16,3 mg, 0.024 mmol), and
triethylamine (30 mL) was stirred for 15 h. Purification was
carried out by flash chromatography on a silica gel column,
eluting with hexane providing 14 as a green solid (89.7 mg,
98%), mp 220-223 °C. UV-vis (CH2Cl2), λmax (nm): 365 (sh,
ꢀ, 61000), 344 (ꢀ, 76300), 266 (ꢀ, 68200), 254 (ꢀ, 75800), 240 (ꢀ,
75500). Fluorescence (CH2Cl2), λmax (nm): 394, 376 (φ ) 0.68).
IR (KBr): cm-1 2160 (CtC), 1578 and 1466 (CdC), 1250 (Si-
CH3), 878 (1,3,5 trisubst), 759 (C-Si). 1H NMR (CDCl3): δ 7.56
(d, 4H, J ) 1.6 Hz), 7.53 (t, 2H, J ) 1.6 Hz), 7.51 (d, 4H, J )
8.9 Hz), 7.47 (d, 4H, J ) 8.9 Hz), 0.24 (s, 36H). 13C NMR
(CDCl3): δ 134.9, 134.5, 131.6, 123.7, 123.4, 123.1, 122.7, 103.0,
95.7, 91.0, 90.0, 89.6, -0.19. MS m/z (relative intensity): 762.2
(M+ 100), 690.2 (5), 366.3 (55). C50H50Si4 (763.27): anal. calcd
C 78.68, H 6.60; found C 78.75, H 6.53.
Di{4-[((3,5-b is-t r im et h ylsilylet h yn ylp h en yl)et h yn yl-
p h en yl)eth yn ylp h en yl]eth yn yl}eth yn e (15). Following the
general method used for the synthesis of 6, a mixture of
compound 2 (109 mg, 0.254 mmol), compound 9 (200 mg, 0.507
mmol), dichloro bis(triphenylphosphine)palladium (19 mg, 0.02
mmol), and triethylamine (30 mL) was stirred for 15 h.
Purification was carried out by flash chromatography on a
silica gel column, eluting with hexane, providing 15 as a green
solid (208 mg, 85%), mp 273-275 °C. UV-vis (CH2Cl2), λmax
(nm): 383 (sh, ꢀ, 86700), 360 (ꢀ, 114000), 267 (ꢀ, 78500), 240
(ꢀ, 96000). Fluorescence (CH2Cl2), λmax (nm): 435, 414 (φ )
0.77). IR (KBr): cm-1 2160 (CtC), 1578 and 1466 (CdC), 1250
1-{[(3,5-Bis-tr im eth ylsilyleth yn ylph en yl)eth yn ylph en yl]-
eth yn yl}-4-eth yn ylben zen e (11). Following the general
method used for the synthesis of 4, a mixture of compound 10
(270 mg, 0.48 mmol), anhydrous toluene (40 mL), and finely
powdered sodium hydroxide (2 mg, 0.048 mmol) was stirred
for 4 h and then filtered. The solvent was removed giving 11
as an orange solid (235 mg 99%), mp 148-150 °C. IR (KBr):
cm-1 3302 (tC-H), 2157 (CtC), 1576 and 1506 (CdC), 1249
1
(Si-CH3), 840 (1,3,5 trisubst), 758 (C-Si). H NMR (CDCl3):
δ 7.57 (d, 2H, J ) 1.6 Hz), 7.55 (t, 2H, J ) 1.6 Hz), 7.51 (d,
2H, J ) 8.7 Hz), 7.48 (s a, 4H), 7.47 (d, 2H, J ) 8.7 Hz), 3.20
(s, 1H), 0.26 (s, 18H). 13C NMR (CDCl3): δ 134.9, 134.5, 132.0,
131.5, 131.4, 123.8, 123.5, 123.4, 123.0, 122.8, 122.1, 103.1,
95.76, 90.9, 90.8, 89.6, 83.2, 79.08, -0.17. C34H30Si2 (494.77):
anal. calcd C 82.54, H 6.11; found C 82.58, H 6.41.
1
(Si-CH3), 878 (1,3,5 trisubst), 759 (C-Si). H NMR (CDCl3):
δ 7.56 (d, 4H, J ) 1.6 Hz), 7.52-7.49 (m, 18H), 0.24 (s, 36H).
13C NMR (CDCl3): δ 134.9, 134.5, 131.6, 123.8, 123.5, 123.1,
123.0, 122.8, 103.1, 95.8, 91.0, 91.1, 90.0, 89.6, -0.17. MS m/z
(relative intensity): 962.2 (M+ 100), 663.2 (51). C66H58Si4
(963.51): anal. calcd C 82.27, H 6.07; found C 82.32, H 6.01.
1,4-Bis[(3,5-bis-tr im eth ylsilyleth yn ylp h en yl)eth yn yl]-
ben zen e (12). Following the general method used for the
synthesis of 6, a mixture 1,4-diiodobenzene (112 mg, 0.34
mmol), compound 7 (200 mg, 0.68 mmol), dichloro bis(triphen-
1,5-Bis[(3,5-bis-tr im eth ylsilyleth yn ylp h en yl)eth yn yl]-
n a p h th a len e (16). Following the general method used for the
8126 J . Org. Chem., Vol. 68, No. 21, 2003

Ethynylphenyl-Based Nanostructures
synthesis of 6, a mixture of 1,5-diiodonaphthalene16 (100 mg,
0.26 mmol), compound 7 (154.8 mg, 0.52 mmol), dichloro bis-
(triphenylphosphine)palladium (36.9 mg, 0.052 mmol) and
triethylamine (30 mL) was stirred for 12 h. Purification was
carried out by flash chromatography on a silica gel column,
eluting with hexane, providing 16 as a white solid (176.1 mg,
95%), mp 228-230 °C: UV-vis (CH2Cl2), λmax (nm): 368 (sh,
ꢀ, 27500), 352 (ꢀ, 33800), 268 (ꢀ, 80700), 254 (ꢀ, 80200), 243 (ꢀ,
95400). Fluorescence (CH2Cl2), λmax (nm): 398, 377 (φ ) 0.60).
IR (KBr): cm-1 2152 (CtC), 1583 and 1410 (CdC), 1250 (Si-
CH3), 843 (1,3,5 trisubst), 759 (C-Si). 1H NMR (CDCl3): δ 8.41
(d, 2H, J ) 8.61 Hz), 7.79 (d, 2H, J ) 6.5 Hz), 7.68 (d, 4H, J
) 1.6 Hz), 7.55-7.6 (m, 4H), 0.26 (s, 36H). 13C NMR (CDCl3):
δ 135.0, 134.5, 133.0, 131.2, 127.3, 126.3, 123.8, 123.7, 120.9,
103.1, 95.8, 93.0, 88.3, -0.14. MS m/z (relative intensity):
712.3 (M+ 100), 609.2 (8), 341.3 (50). C46H48Si4 (713.22): anal.
calcd C 77.46, H 6.78; found C 77.52, H 6.71.
1,5-Bis{[(3,5-bis-tr im eth ylsilyleth yn ylp h en yl)eth yn yl-
p h en yl]eth yn yl}n a p h th a len e (17). Following the general
method used for the synthesis of 6, a mixture of 1,5-diiodo-
naphthalene16 (100 mg, 0.26 mmol), compound 9 (204.8 mg,
0.52 mmol), dichloro bis(triphenylphosphine) palladium (36.9
mg, 0.052 mmol), and triethylamine (30 mL) was stirred for
12 h. Purification was carried out by flash chromatography
on a silica gel column, eluting with hexane, providing 17 as a
yellow solid (255.6 mg, 95%), mp 271-273 °C. UV-vis (CH2-
Cl2), λmax (nm): 373 (sh, ꢀ, 57300), 365 (ꢀ, 65100), 270 (ꢀ,
106600), 247 (ꢀ, 110500). Fluorescence (CH2Cl2), λmax (nm):
418, 397 (φ ) 0.81). IR (KBr): cm-1 2158 (CtC), 1579 and
1411 (CdC), 1250 (Si-CH3), 843 (1,3,5 trisubst), 757 (C-Si).
1H NMR (CDCl3): δ 8.45 (d, 2H, J ) 8.5 Hz), 7.83 (d, 2H, J )
6.5 Hz), 7.51-7.64 (m, 16H), 0.25 (s, 36H). 13C NMR (CDCl3):
δ 134.9, 134.5, 133.0, 131.69, 131.63, 131.113, 127.2, 126.2,
123.8, 123.8, 123.5, 123.3, 122.8, 121.1, 103.1, 95.8, 94.3, 90.0,
89.6, 89.3, -0.19. MS m/z (relative intensity): 912.5 (M+ 100),
441.4 (43), 207.0 (17). C62H56Si4 (913.45): anal. calcd C 81.52,
H 6.18; found C 81.60, H 6.10.
314 (ꢀ, 28200), 269 (ꢀ, 90000), 256 (ꢀ, 77100). Fluorescence
(CH2Cl2), λmax (nm): 388, 365 (φ < 0.01). IR (KBr): cm-1 2158
(CtC), 1577 and 1503 (CdC), 1249 (Si-CH3), 842 (1,3,5
1
trisubst), 758 (C-Si). H NMR (CDCl3): δ 7.55 (t, 2H, J ) 1.6
Hz), 7.52 (d, 4H, J ) 1.6 Hz), 0.24 (s, 36H). 13C NMR (CDCl3):
δ 135.8, 135.2, 123.8, 122.1, 102.7, 96.2, 80.1, 74.5, -0.22. MS
m/z (relative intensity): 586.1 (M+ 100), 483.1 (35), 278.2 (39),
73 (84). C36H42Si4 (587.06): anal. calcd C 73.65, H 7.21; found
C 73.70, H 7.17.
1,4-Di[4-(3,5-bis-tr im eth ylsilyleth yn ylp h en yl)eth yn yl-
p h en yl]bu ta d iyn e (20). Following the general method used
for the preparation of 19, a mixture of cuprous chloride (37.9
mg, 0.19 mmol) in dry pyridine (25 mL) and compound 9 (301.9
mg, 0.76 mmol) in dry pyridine (20 mL) was stirred for 1 h.
Purification was carried out by flash chromatography on a
silica gel column, eluting with hexane/dichloromethane (4:1),
providing 20 as a green solid (293.2 mg, 98%), mp 249-252
°C. UV-vis (CH2Cl2), λmax (nm): 375 (sh, ꢀ, 64800), 346 (ꢀ,
96000), 270 (ꢀ, 122100). Fluorescence (CH2Cl2), λmax (nm): 412,
386 (φ ) 0.33). IR (KBr): cm-1 2158 (CtC), 1577 and 1503
(CdC), 1249 (Si-CH3), 842 (1,3,5 trisubst), 758 (C-Si). 1H
NMR (CDCl3): δ 7.56 (d, 4H, J ) 1.6 Hz), 7.53 (t, 2H, J ) 1.6
Hz), 7.51 (d, 4H, J ) 8.5 Hz), 7.45 (d, 4H, J ) 8.5 Hz), 0.24 (s,
36H). 13C NMR (CDCl3): δ 135.0, 134.5, 132.4, 131.6, 123.8,
123.3, 121.7, 103.1, 95.8, 90.3; 89.8, 82.1, 75.7, -0.19. MS m/z
(relative intensity): 786.1 (M+ 100), 378.2 (48), 73 (54). C52H50
-
Si4 (787.30): anal. calcd C 79.33, H 6.40; found C 79.38, H
6.37.
1,4-Di{4-[(3,5-bis-tr im eth ylsilyleth yn ylp h en yl)eth yn -
ylp h en yl]eth yn ylp h en yl}bu ta d iyn e (21). Following the
general method used for the preparation of 19, a mixture of
cuprous chloride (22 mg, 0.11 mmol) in dry pyridine (25 mL)
and compound 11 (220 mg, 0.445 mmol) in dry pyridine (20
mL) was stirred for 1 h. Purification was carried out by flash
chromatography on a silica gel column, eluting with hexane/
dichloromethane (4:1), providing 21 as a green solid (217.5 mg,
99%), mp 253-255 °C. UV-vis (CH2Cl2), λmax (nm): 387 (sh,
ꢀ, 98500), 369 (ꢀ, 123900), 269 (ꢀ, 73300), 253 (ꢀ, 78100), 240
(ꢀ, 88400). Fluorescence (CH2Cl2), λmax (nm): 438, 414 (φ )
0.54). IR (KBr): cm-1 2160 (CtC), 1578 and 1502 (CdC), 1250
1,5-Bis{[((3,5-bis-t r im et h ylsilylet h yn ylp h en yl)et h yn -
ylp h en yl)eth yn ylp h en yl]eth yn yl}n a p h th a len e (18). Fol-
lowing the general method used for the synthesis of 6, a
mixture of 1,5-diiodonaphthalene16 (38.44 mg, 0.103 mmol),
compound 11 (100 mg, 0.205 mmol), dichloro bis(triphenylphos-
phine) palladium (10 mg, 0.02 mmol), and triethylamine (30
mL) was stirred for 12 h. Purification was carried out by flash
chromatography on a silica gel column, eluting with hexane,
providing 18 as a yellow solid (97.5 mg, 85%), mp 298-300
°C. UV-vis (CH2Cl2), λmax (nm): 389 (sh, ꢀ, 73500), 366 (ꢀ,
97800), 268 (ꢀ, 58900), 241 (ꢀ, 88100). Fluorescence (CH2Cl2),
λmax (nm): 438, 418 (φ ) 0.82). IR (KBr): cm-1 2159 (CtC),
1578 and 1411 (CdC), 1253 (Si-CH3), 843 (1,3,5 trisubst), 757
1
(Si-CH3), 841 (1,3,5 trisubst), 758 (C-Si). H NMR (CDCl3):
δ 7.56 (d, 4H, J ) 1.6 Hz), 7.53 (t, 2H, J ) 1.6 Hz), 7.52 (d,
4H, J ) 8.5 Hz), 7.51 (d, 4H, J ) 8.9 Hz), 7.47 (d, 4H, J ) 8.5
Hz), 7.45 (d, 4H, J ) 8.9 Hz), 0.24 (s, 36H). 13C NMR (CDCl3):
δ 135.0, 134.5, 132.4, 131.6, 123.9, 123.8, 123.5, 123.0, 122.9,
121.6, 103.1, 95.8, 91.8, 90.9, 90.0, 89.7, 82.1, 75.7, -0.17. MS
m/z (relative intensity): 986.1 (M+ 100), 478.2 (38), 73 (57).
C
68H58Si4 (987.53): anal. calcd C 87.70, H 5.92; found C 87.76,
H 5.88.
1,3,5-Tr is[(3,5-bis-tr im eth ylsilyleth yn ylph en yl)eth yn yl]-
1
(C-Si). H NMR (CDCl3): δ 8.45 (d, 2H, J ) 8.5 Hz), 7.83 (d,
ben zen e (24). Following the general method used for the
synthesis of 6, a mixture of 1,3,5-triiodobenzene (100 mg, 0.22
mmol), compound 7 (206 mg, 0.7 mmol), dichloro bis(triphen-
ylphosphine)palladium (49 mg, 0.07 mmol), and triethylamine
(30 mL) was stirred for 12 h. Purification was carried out by
flash chromatography on a silica gel column, eluting with
hexane, providing 24 as a white solid (195 mg, 93%), mp 118-
120 °C. UV-vis (CH2Cl2), λmax (nm): 308 (sh, ꢀ, 87400), 291
(ꢀ, 89800), 267 (ꢀ, 134500), 254 (ꢀ, 119800). Fluorescence (CH2-
Cl2), λmax (nm): 367, 353 (φ ) 0.16). IR (KBr): cm-1 2156 (Ct
C), 1587 and 1411 (CdC), 1250 (Si-CH3), 848 (1,3,5 trisubst),
2H, J ) 6.5 Hz), 7.47-7.66 (m, 24H), 0.25 (s, 36H). 13C NMR
(CDCl3): δ 135.0, 134.6, 133.1, 131.66, 131.16, 127.2, 126.2,
123.5, 123.3, 123.2, 123.1, 122.8, 121.1, 103.1, 95.8, 94.4, 91.1,
91.0, 90.0, 89.7, 89.3, -0.14. MS m/z (relative intensity)
FAB+: 1112.5 (M+ 100). C78H64Si4 (1113.68): anal. calcd C
84.12, H 5.79; found C 84.17, H 5.74.
1,4-Di(3,5-b is-t r im e t h ylsilyle t h yn ylp h e n yl)b u t a d i-
yn e (19) by Hom ocou p lin g Rea ction of Ar yla cetylen e.
Gen er a l P r oced u r e. To a solution of cuprous chloride (74
mg, 0.33 mmol) in dry pyridine (25 mL), under oxygen
atmosphere at 40°C, was added a solution of the arylacetylene
7 (400 mg, 1.35 mmol) in dry pyridine (10 mL), and the mixture
was stirred for 40 min. The solvent was removed, giving a
residual solid that was washed with ammonium hydroxide
until the blue color disappeared and then extracted with
dichloromethane. The organic layer was dried on anhydrous
magnesium sulfate, and after filtration and solvent evapora-
tion a brown solid was obtained, which was purified by silica
gel column chromatography, eluting with hexane/dichloro-
methane (4:1), giving 19 as a white solid (390 mg 98%), mp
198-201 °C. UV-vis (CH2Cl2), λmax (nm): 336 (sh, ꢀ, 22800),
1
758 (C-Si). H NMR (CDCl3): δ 7.58 (s, 3H), 7.56 (d, 6H, J )
1.6 Hz), 7.54 (t, 3H, J ) 1.6 Hz), 0.25 (s, 54H). 13C NMR
(CDCl3): δ 135.1, 134.6, 134.3, 123.8, 123.7, 123.1, 103.0, 95.9,
89.0, 88.5, -0.19. MS m/z (relative intensity): 954.0 (M+ 57),
73 (100). C60H66Si6 (955.68): anal. calcd C 75.41, H 6.96; found
C 75.46, H 6.89.
1,3,5-Tr is{[(3,5-bis-tr im eth ylsilyleth yn ylp h en yl)eth yn -
ylp h en yl]et h yn yl}b en zen e (25). Following the general
method used for the synthesis of 6, a mixture of 1,3,5-triiodo-
benzene (100 mg, 0.22 mmol), compound 9 (270 mg, 0.7 mmol),
dichloro bis(triphenylphosphine)palladium (49 mg, 0.07 mmol),
J . Org. Chem, Vol. 68, No. 21, 2003 8127

Rodr´ıguez et al.
and triethylamine (30 mL) was stirred for 12 h. Purification
was carried out by flash chromatography on a silica gel column,
eluting with hexane, providing 25 as a green solid (234.5 mg,
85%), mp 145-146 °C. UV-vis (CH2Cl2), λmax (nm): 351 (sh,
ꢀ, 143700), 329 (ꢀ, 181200), 270 (ꢀ, 106600), 255 (ꢀ, 102000).
Fluorescence (CH2Cl2), λmax (nm): 377, 356 (φ ) 0.48). IR
(KBr): cm-1 2156 (CtC), 1580 and 1411 (CdC), 1249
silica gel column, eluting with hexane, providing 25 as a yellow
solid (109.4 mg, 80%), mp 201-203 °C. UV-vis (CH2Cl2), λmax
(nm): 366 (sh, ꢀ, 156000), 347 (ꢀ, 187500), 268 (ꢀ, 105000), 254
(ꢀ, 123000). Fluorescence (CH2Cl2), λmax (nm): 398, 377 (φ )
0.80). IR (KBr): cm-1 2159 (CtC), 1580 and 1411 (CdC), 1250
1
(Si-CH3), 845 (1,3,5 trisubst), 759 (C-Si). H NMR (CDCl3):
δ 7.67 (s, 3H), 7.56 (d, 6H, J ) 1.6 Hz), 7.55-7.53 (m, 15H),
7.50 (d, 6H, J ) 8.6 Hz), 7.49 (d, 6H, J ) 8.6 Hz), 0.25 (s,
54H). 13C NMR (CDCl3): δ 135.0, 134.5, 134.2, 131.6, 123.9,
123.8, 123.5, 123.2, 123.1, 122.8, 122.7, 103.1, 95.8, 91.1, 91.0,
90.3, 90.0, 89.6, -0.17. MS m/z (relative intensity) FAB+:
1555.6 (M+ 80). C108H90Si6 (1536.38): anal. calcd C 83.34, H
5.83; found C 83.39, H 5.78.
1
(Si-CH3), 843 (1,3,5 trisubst), 759 (C-Si). H NMR (CDCl3):
δ 7.67 (s, 3H), 7.57 (d, 6H, J ) 1.6 Hz), 7.54 (t, 3H, J ) 1.6
Hz), 7.52 (d, 6H, J ) 8.9 Hz), 7.48 (d, 6H, J ) 8.9 Hz), 0.25 (s,
54H). 13C NMR (CDCl3): δ 135.0, 134.5, 134.2, 131.6, 123.9,
123.8, 123.5, 123.0, 122.8, 103.1, 95.8, 90.3, 89.9; 89.7, 89.6,
-0.17. MS m/z (relative intensity) FAB+: 1255.1 (M+ 100).
C84H78Si6 (1254.47): anal. calcd C 80.32, H 6.26; found C 80.39,
H 6.20.
Ack n ow led gm en t. J .G.R. will be always grateful to
his father Natalio Rodriguez Mene´ndez (deceased on
01/06/03) for ethical advice on life. We are grateful to
CICYT of Spain for financial support (project no.
PB97-0060).
1,3,5-Tr is{[((3,5-b is-t r im et h ylsilylet h yn ylp h en yl)et h -
yn ylp h en yl)eth yn ylp h en yleth yn yl}ben zen e (26). Follow-
ing the general method used for the synthesis of 6, a mixture
of 1,3,5-triiodobenzene (40 mg, 0.089 mmol), compound 11 (130
mg, 0.2 mmol), dichloro bis(triphenylphosphine)palladium (14
mg, 0.02 mmol), and triethylamine (30 mL) was stirred for 12
h. Purification was carried out by flash chromatography on a
J O034972B
8128 J . Org. Chem., Vol. 68, No. 21, 2003