Carbon dendron nano-chains with π-extended conjugation based on end-capped N,N-dimethylamino in linear 1,4-phenylethynyl or in 1,5-naphthylethynyl subunits: Fluorescence analysis

Article abstract of DOI:10.1016/j.tet.2004.12.054

The synthesis of dendrons with the end-capped 5-(N,N-dimethylamino) naphthyl-1-ethynyl unit connected to conjugated naphthylethynyl or p-phenylethynyl chains, as the branches of the 1,3,5-substituted benzene core, have been undertaken by heterocoupling re

Full text of DOI:10.1016/j.tet.2004.12.054

Tetrahedron 61 (2005) 2047–2054
Carbon dendron nano-chains with p-extended conjugation based
on end-capped N,N-dimethylamino in linear 1,4-phenylethynyl or
in 1,5-naphthylethynyl subunits: fluorescence analysis
*
J. Gonzalo Rodrıguez and J. Luis Tejedor
´
´
´
´
Departamento de Quımica Organica, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid, Spain
Received 17 November 2004; revised 20 December 2004; accepted 22 December 2004
Available online 21 January 2005
Abstract—The synthesis of dendrons with the end-capped 5-(N,N-dimethylamino)naphthyl-1-ethynyl unit connected to conjugated
naphthylethynyl or p-phenylethynyl chains, as the branches of the 1,3,5-substituted benzene core, have been undertaken by heterocoupling
reaction between 1,3,5-triiodobenzene and the convenient end-capped 5-(N,N-dimethylamino)naphthylacetylene or 5-(N,N-dimethylami-
no)naphthylethynylphenylacetylene in the presence of the palladium–copper catalyst system, in excellent yields. The influence of the
alternating naphthylethynyl–phenylethynyl chains on the fluorescence emission radiation, in the dendron structures, has been analyzed.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
potential applications such as artificial photosynthesis,13
photocatalysis,14 molecular photovoltaic cells,15 molecular
informatics,16 and optoelectronic devices,17,18 are beginning
to emerge from this new field of research.
Hyperbranched polymers and dendrimers are highly
branched macromolecules that have received considerable
attention.1–5 Dendrimers are synthesized by multistep
reactions requiring tedious purification, whereas hyper-
branched polymers are prepared by one-step polymerization
resulting in less regular structures. An undesirable feature of
the one-step polymerization is the loss of control in
molecular weight, accompanied by broad molecular weight
distributions6 and possible intramolecular cyclization.7
Conjugated systems integrated by 1,4-diethynyl or 1,3,5-
triethynylphenyl units have been used in the preparation of
aromatic oligomers bearing multiple ethynyl groups that
exhibit electroluminescence properties,19 poly(phenyl-
vinylene) with fluorescence properties as well as dendri-
mers20 with poly(yne) chain.21 The triple bond play the role
of a wire while the polyaromatic system behaves as an
energy relay subunit.
The convergent method for synthesizing dendrons and
´
8
dendrimers had been reported by Hawker and Frechet, and
We now report the controlled synthesis of a novel family of
rigid conjugated dendron nanostructures with a controlled
geometry and the fluorescence properties.
this appeared to be the best method for making well-defined
structures.
The area of highly conjugated, all-carbon and carbon-rich
macromolecules continues to be of intense attention.9 The
synthesis and characterization of nanometer-sized conju-
gated molecules of precise length and constitution are of
wide-spread interest, which is due to their inherent synthetic
flexibility which permits the design of molecular archi-
tectures with important properties.10,11 Molecules showing
p-extended conjugation, in general, can present electro-
conductive, magnetic and optical properties.12 A variety of
2. Results and discussion
The syntheses of the end-capped 5-(N,N-dimethylamino)-
naphthylacetylenes (1, 2 and 3) designed as the branches of
the 1,3,5-benzene dendron structures were carried out by
the heterocoupling between the terminal naphthylacetylene
and 4-(5-iodo-1-naphthyl)-2-methyl-3-butyn-2-ol,22 in
presence of PdCl2(PPh3)2 and Cu2I2 catalyst system, in
NEt3, Scheme 1.
Keywords: 1,3,5-Tri(naphthylethynyl)benzene; 1,3,5-Tri(p-phenylethy-
nyl)benzene; Dendron base units; Sonogashira reaction.
* Corresponding author. Tel.: C34 914974715; fax: C34 914973966;
e-mail: gonzalo.rodriguez@uam.es
Compound 1 was obtained by heterocoupling reaction
between 5-iodo-N,N-dimethylnaphthalen-1-amine and
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.12.054

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2048
Scheme 1. (i) Cl2Pd(PPh3)2, Cu2I2, NEt3, 4-(5-iodo-1-naphthyl)-2-methyl-3-butyn-2-ol. (ii) NaOH, toluene, at the reflux temperature.
2-methyl-3-butyn-2-ol in NEt3, catalyzed by the palladium–
copper system to give the propargyl intermediate, which by
treatment with a catalytic amount of powdered NaOH in
toluene, at the reflux temperature, gives 1 as a dark amber
solid, in practically quantitative yield.
decreasing for compound 2. These dual fluorescence and
fast intramolecular charge transfer (ICT) effect were
observed in N,N-dialkylaminophenyl24 or naphthyl25
derivatives.
The end-capped 5-(N,N-dimethylamino)naphthalenes con-
necting with p-phenylethynyl chains as 5 and 7 were
designed as the branches of the 1,3,5-benzene dendron
structures. The synthesis was carried out by the hetero-
coupling between the appropriate terminal acetylene and
4-(p-iodophenyl)-2-methyl-3-butyn-2-ol,26 Scheme 2.
The naphthylacetylene homologue 2 was satisfactory
obtained by the heterocoupling between the terminal
acetylene 1 and 4-(5-iodo-1-naphthyl)-2-methyl-3-butyn-
2-ol in NEt3, catalyzed by the palladium–copper system,
under a rigorous carbon dioxide atmosphere,23 to give the
propargyl intermediate, which by treatment with a catalytic
amount of powdered NaOH in toluene at the reflux
temperature gives 2, as a yellow solid, in practically
quantitative yield. Under the palladium catalytic conditions,
compound 1 was really sensitive to the homocoupling
reaction to give the 1,3-diyne derivative, which was avoided
by use of a compatible carbon dioxide atmosphere.23
Thus, 5-[(4-ethynyl-1-phenyl)ethynyl]-N,N-dimethyl-
naphthalen-1-amine (5) was obtained in excellent yield,27
by the heterocoupling between the terminal acetylene 1 and
4-(p-iodophenyl)-2-methyl-3-butyn-2-ol in NEt3, in the
presence of the palladium–copper system, under a rigorous
carbon dioxide atmosphere,23 to give 4-(4-{[5-(N,N-
dimethylamino)-1-naphthyl]ethynyl}-1-phenyl)-2-methyl-
3-butyn-2-ol (4), which was treated with a catalytic amount
of powdered NaOH in toluene, at the reflux temperature.
Compound 3 was obtained by the heterocoupling between
the terminal acetylene 2 and 4-(5-iodo-1-naphthyl)-2-
methyl-3-butyn-2-ol, in NEt3 under argon atmosphere,
catalyzed by the palladium–copper system, giving the
propargyl intermediate, which by catalytic treatment with
powdered NaOH, in toluene at the reflux temperature
affords 3 in quantitative yield.
The naphthylacetylene 7 was satisfactory obtained by the
heterocoupling between the terminal acetylene 5 and 4-(p-
iodophenyl)-2-methyl-3-butyn-2-ol in NEt3, under argon
atmosphere, catalyzed by the palladium–copper system,
yielding the propargyl intermediate 6, followed the treat-
ment with a catalytic amount of powdered NaOH in toluene,
at the reflux temperature.
The end-capped 5-(N,N-dimethylamino)naphthylacetylenes
(1–3) show fluorescence emission spectra with an important
quantum yield in dichloromethane, Table 1.
The ultraviolet–visible absorption and fluorescence emis-
sion spectra of the end-capped 5-(N,N-dimethylamino)-
naphthalenes with p-phenylethynyl chains (5 and 7) are
summarized in Table 2.
The analysis of the fluorescence emission spectra allows to
some remarkable facts: (i) compounds 1 and 2 show only a
broad emission band while 3 shows two bands; (ii) the
emission bands of the compound 2 and the first band of 3
show a normal Stokes shift for conjugated naphthalene
rings, while 1 and the second band of 3 show a large
anomalous Stokes shift; (iii) the fluorescence quantum
yields are considerable though a significant slight
In contrast with the naphthylacetylenes 1, 2 and 3 the
conjugated naphthylethynylphenyl acetylenes 5 and 7 show
fluorescence emission radiation with a large anomalous
Stokes shift and the quantum yields strongly decreases.
Table 1. UV–vis and fluorescence spectra of compounds 1, 2 and 3
Compound
UV–visa (CH2Cl2) lmax, nm
3 (MK1 cmK1
)
Fb (CH2Cl2) lmax, nm
Ff
1
2
3
336
343
363
2200
23,100
26,600
463
397
398 and 414
0.63c
0.55d
0.65d
a At room temperature.
b At room temperature and [c]y10K8 M.
c Fluorescence quantum yield in dichloromethane relative to quinine sulfate in 1 N H2SO4.
d Fluorescence quantum yield was in dichloromethane relative to 2-aminopyridine in 0.1 N H2SO4.

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2049
Scheme 2. (i) Cl2Pd(PPh3)2, Cu2I2, NEt3, 4-(p-iodophenyl)-2-methyl-3-butyn-2-ol, CO2 atmosphere. (ii) NaOH, toluene, at the reflux temperature. (iii)
Cl2Pd(PPh3)2, Cu2I2, NEt3, 4-(p-iodophenyl)-2-methyl-3-butyn-2-ol.
Table 2. UV–vis and fluorescence spectra of compound 5 and 7
Compound
UV–visa (CH2Cl2) lmax, nm
3 (MK1 cmK1
)
Fb (CH2Cl2) lmax, nm
Ffc
5
7
354
364
18,300
32,800
510
529
0.32
0.23
a At room temperature.
b At room temperature and [c]y10K8 M.
c Fluorescence quantum yield in dichloromethane relative to quinine sulfate in 1 N H2SO4.
Moreover, the quantum yield also decreases with the
number of the ethynylphenyl units (5 and 7).
The ultraviolet–visible absorption and fluorescence emis-
sion spectra of the end-capped 5-(N,N-dimethylamino)-
naphthylethynyl dendrons with 1,3,5-trisubstituted benzene
core and naphthylethynyl or p-phenylethynyl chains are
summarized in Table 3.
Now, the synthesis of the end-capped 5-(N,N-dimethyl-
amino)naphthylethynyl dendrons with 1,3,5-trisubstituted
benzene core and naphthylethynyl or p-phenylethynyl
chains were satisfactory carried out by heterocoupling
between the terminal naphthylacetylenes (1, 2 and 3) or
phenylacetylenes (5 and 7) and 1,3,5-triiodobenzene,28 in
NEt3 under argon atmosphere, in the presence of the
palladium–copper catalyst system.
The conjugated compounds 8–12 show fluorescence emis-
sion radiation with a large anomalous Stokes shift as their
terminal acetylene parents 1, 2, 3, 5 and 7. The quantum
yields of the naphthylethynyl–naphthyl or naphthylethynyl–
phenyl dendron families decrease with the conjugated size
chain 8–10 and 11–12. It has been postulated in N,N-
dialkylaminophenyl or N,N-dialkylaminonaphthylderiva-
tives, that the dimethylamino group undergoes an important
twist relative to the conjugated system, giving large
anomalous Stokes shift with quantum yield decreasing.24,
25 Hence the anomalous Stokes shift observed are due to an
intramolecular charge transfer (ICT) or a twisted ICT
(TICT) produced by the presence of the donor N,N-
dimethylamino group.
Thus, the heterocoupling reaction between the terminal
acetylenes (1–3) with 1,3,5-triiodobenzene affords 5-(N,N-
dimethylamino)naphthylethynyl dendron nanostructures
8–10, as orange solids: compound 8 (nZ0) (85%) and
compound 9 (nZ1) (81%). Only for the heterocoupling
between 1 and 1,3,5-triiodobenzene was necessary a
rigorous carbon dioxide atmosphere, to avoid the homo-
coupled 1,3-butadiyne product,23 while, the heterocoupling
between the terminal acetylene 3 and 1,3,5-triiodobenzene
was carried out under argon atmosphere, in pyridine at
reflux temperature, giving 10 (nZ2) in modest yield (30%),
Scheme 3.
3. Conclusions
The synthesis of extended chain conjugated naphthyl-
ethynyl and phenylethynyl dendron structures have
been designed to improve the fluorescent properties. The
end-capped 5-(N,N-dimethylamino)naphthyl-1-ethynyl
connected to conjugated phenylethynyl units show a
constant quantum yield with the increasing of the number
of phenylethynyl units.
On the other hand, the synthesis of the end-capped 5-(N,N-
dimethylamino)naphthylethynylphenylethynyl dendrons,
with the more sterically alleviate p-phenylethynyl chains,
was satisfactory carried out by heterocoupling between the
terminal naphthylethynylphenylacetylenes (5 and 7) and
1,3,5-triiodobenzene, in NEt3 under argon atmosphere, in
the presence of the palladium–copper catalyst system.
Compounds 11 (nZ1, 79%) and 12 (nZ2, 62%) were
isolated as dark yellow solids, Scheme 4.
An efficient divergent–convergent synthesis methodology
for the preparation of dendrons with the end-capped 5-(N,N-
dimethylamino)naphthyl-1-ethynyl moiety connected to

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2050
Scheme 3. (i) 1,3,5-Triiodobenzene, Cl2Pd(PPh3)2, Cu2I2, NEt3.
Scheme 4. (i) 1,3,5-Triiodobenzene, Cl2Pd(PPh3)2, Cu2I2, NEt3.
conjugated naphthylethynyl or p-phenylethynyl chains
as the branches of the 1,3,5- substituted benzene core,
have been carried out by the heterocoupling reaction
between 1,3,5-triiodobenzene and the corresponding
end-capped 5-(N,N-dimethylamino)naphthylacetylene or
5-(N,N-dimethylamino)naphthylethynylphenylacetylene
in the presence of the palladium–copper catalyst system,
in excellent yields. The naphthylethynyl–naphthyl and
naphthylethynyl–phenyl conjugated families show fluor-
escence properties with a large anomalous Stoke shift
due to a ICT or TICT effect due to the presence of the
donor N,N-dimethylamino group. The quantum yields of
the fluorescence emission radiation of the N,N-
(dimethylamino)naphthylethynyl chains show an import-
ant decreasing with the conjugated size chain in the
dendron structures.

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2051
Table 3. UV–vis and fluorescence spectra of the dendron structures 8, 9, 10, 11 and 12
Compound
UV–visa (CH2Cl2) lmax, nm
3 (MK1 cmK1
)
Fb (CH2Cl2) lmax, nm
Ffc
8
9
10
11
12
356
364
370
365
353
81,400
10,650
96,800
98,200
119,900
504
527
530
530
531
0.43
0.21
0.08
0.20
0.19
a At room temperature.
b At room temperature and [c]y10K8 M.
c Fluorescence quantum yield in dichloromethane relative to quinine sulfate in 1 N H2SO4.
1
4. Experimental
1165, 791. H NMR (CDCl3): d 8.24 (d, 1H, JZ8.7 Hz),
7.99 (d, 1H, JZ8.7 Hz), 7.63 (d, 1H, JZ6.9 Hz), 7.47 (t,
1H, JZ8.1 Hz), 7.41 (dd, 1H, JZ6.9, 8.7 Hz), 7.11 (d, 1H,
JZ7.8 Hz), 2.89 (s, 6H), 1.73 (s, 6H). 13C NMR (CDCl3): d
151.24, 134.64, 130.32, 128.58, 126.61, 125.01, 124.28,
120.75, 120.52, 114.49, 98.48, 80.69, 65.85, 45.29, 31.64.
C17H19NO (253.34). Anal. Calcd C 80.60, H 7.56, N 5.53.
Found: C 80.74, H 7.44, N 5.68.
4.1. General
Melting points were determined in open capillaries using a
Buchi or Reichert hot stage microscope and are uncorrected.
IR spectra of solids were recorded as KBr pellets and IR
spectra of oils were recorded as thin films on NaCl plates
with a Bruker Vector 22 spectrophotometer, and the wave
numbers are given in cmK1. 1H NMR spectra and 13C NMR
spectra were recorded at 300 and 75 MHz respectively on a
Bruker Aspect spectrometer. Chemical shifts are given in d
with TMS as an internal reference and constants coupling J
are given in Hz, the solvent is CDCl3. Mass spectra were
recorded on a VG AutoSpec spectrometer at 70 eV and the
MALDI-TOF spectra were recorded on a Bruker Reflex III
spectrometer. The UV–vis spectra were recorded on a
Hewlett–Packard 8453 spectrometer, frequencies are given
in nm and 3 in L molK1 cmK1. All fluorescence spectra
were recorded at room temperature at 10K8 M on a SLM
Aminco Bowman series 2, the fluorescence quantum yield
was determined in dichloromethane on freshly prepared
samples (air-equilibrated) with absorbances at the excitation
wavelength (365 nm for the standard quinine sulfate). The
samples quinine sulfate in 1 N H2SO4 and 2-aminopyridine
in 0.1 N H2SO4 were employed as a standard (FfZ0.55 and
0.66, respectively) to measure the fluorescence quantum
yields, which were corrected taking into account the
refractive indices of the solvents used. Yields are given
after chromatography column separation on silica gel 60
(200–400 mesh) using the indicated solvents or solvent
crystallization.
4.1.1.2. (b) 5-Ethynyl-N,N-dimethylnaphthalen-1-
amine (1). General procedure for arylacetylenes. To a
solution of 1a (700 mg, 2.8 mmol) in anhydrous toluene
(40 mL) was added finely powdered NaOH (12 mg,
0,28 mmol), under argon atmosphere, and the mixture was
warmed at the reflux temperature for 10 h (monitored by
TLC), and then filtered. The solvent was removed at
reduced pressure and the solid residue was purified by silica
gel column chromatography, eluting with hexane/dichloro-
methane (1:2) giving 1 as a dark amber solid, mp 50–51 8C,
545 mg (100%) yield. UV–vis (CH2Cl2), lmax (nm): 229 (3,
12,300), 254 (3, 4800), 336 (3, 2200). Fluorescence
(CH2Cl2), lmax (nm): 463 (fZ0.63). IR (KBr, cmK1):
3299, 2294, 1402, 791. 1H NMR (CDCl3): d 8.46 (d, 1H, JZ
9.0 Hz), 8.31 (d, 1H, JZ8.4 Hz), 7.93 (d, 1H, JZ7.2 Hz),
7.64 (t, 1H, JZ7.8 Hz), 7.56 (dd, 1H, JZ9.0, 7.2 Hz), 7.21
(d, 1H, JZ7.5 Hz), 3.65 (s, 1H), 2.89 (s, 6H). 13C NMR
(CDCl3): d 151.15, 134.81, 131.05, 128.44, 126.77, 125.44,
124.10, 120.63, 119.92, 114.50, 82.21, 81.82, 45.06. COSY
(1H/1H): 8.46/7.56/7.93/, 8.31/7.64/7.21. HETCORR
(13C/1H): 131.05/7.93, 126.77/7.64, 125.44/8.46, 124.10/
7.56, 120.63/8.31, 114.50/7.21. MS (70 eV): 195 (MC, 100),
194 (43), 179 (7), 165 (3), 152 (31). C14H13N (195.26). Anal.
CalcdC86.12, H6.71, N 7.17. Found: C85.92, H6.86, N 7.02.
4.1.1. 5-Ethynyl-N,N-dimethylnaphthalen-1-amine (1).
4.1.1.1. (a) 4-[5-(N,N-Dimethylamino)-1-naphthyl]-2-
methyl-3-butyn-2-ol (1a). General procedure for the
cross-coupling reaction. To a solution of 5-iodo-N,N-
dimethylnaphthalen-1-amine (1 g, 3.4 mmol) and 2-methyl-
3-butyn-2-ol (314 mg, 3.74 mmol) in freshly distilled
NHEt2 (or NEt3) (40 mL), under argon atmosphere and
at room temperature, was added PdCl2(PPh3)2 (24 mg,
0.034 mmol) and Cu2I2 (0.5 mg, 0.003 mmol). The mixture
was stirred 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 little amount of KCN, and extracted with
dichloromethane. The extracts were dried on anhydrous
sodium sulfate and after filtration, the solvent was removed
to give a brown solid, which was purified by silica gel
column chromatography, eluting with hexane/ethyl acetate
(3:1). Compound 1a was isolated as a dark amber oil,
840 mg (98%) yield. IR (film, cmK1): 3398, 2220, 1409,
4.1.2. 5-[(5-Ethynyl-1-naphthyl)ethynyl]-N,N-dimethyl-
naphthalen-1-amine (2).
4.1.2.1. (a) 4-(5-{[5-(N,N-Dimethylamino)-1-naphthy-
l]ethynyl}-1-naphthyl)-2-methyl-3-butyn-2-ol (2a).
General procedure for the cross-coupling reaction in
CO2 atmosphere. A dispersion of the components in dry
triethylamine was placed in a Schlenk: compound 1
(100 mg, 0.51 mmol), 4-(5-iodo-1-naphthyl)-2-methyl-3-
butyn-2-ol (171 mg, 0.51 mmol), NEt3 (30 mL), PdCl2-
(PPh3)2 (36 mg, 0.051 mmol) and Cu2I2 (1 mg,
0.0051 mmol). Then, carbonic dry-ice rods were added
and maintained in slow sublimation until a white dense
cloud was formed. The carbonic anhydride atmosphere was
slowly displaced with an external stream of carbonic
anhydride, bubbled through the dry triethylamine solution.
The mixture was stirred at room temperature for 15 h
(monitored by TLC) and then, the amine was removed under
reduced pressure. The crude residue was washed with a

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2052
saturated aqueous ammonium chloride solution with a little
amount of KCN, and extracted with dichloromethane. The
extracts were dried on anhydrous sodium sulfate and after
filtration, the solvent was removed to give a brown solid,
which was purified by silica gel column chromatography,
eluting with hexane/ethyl acetate (2:1). Compound 2a was
isolated as a pale yellow solid, mp 120–121 8C, 180 mg
(87%) yield. IR (KBr, cmK1): 3280, 2224, 1418, 1152, 782.
1H NMR (CDCl3): d 8.57 (d, 1H, JZ8.4 Hz), 8.34 (d, 1H,
JZ7.5 Hz), 8.32 (d, 1H, JZ7.8 Hz), 8.26 (d, 1H, JZ
8.7 Hz), 7.92 (d, 1H, JZ6.9 Hz), 7.88 (d, 1H, JZ7.5 Hz),
7.72 (d, 1H, JZ7.2 Hz), 7.62–7.49 (m, 4H), 7.16 (d, 1H, JZ
7.5 Hz), 2.93 (s, 6H), 1.76 (s, 6H). 13C NMR (CDCl3): d
151.41, 134.65, 133.18, 133.07, 130.99 (2C), 130.61,
128.75, 127.15, 126.87, 126.80, 126.19, 126.09, 125.30,
124.50, 121.67, 121.09, 120.99, 120.82, 114.65, 99.19,
93.37, 91.90, 80.10, 65.76, 45.34, 31.50. C29H25NO
(403.52). Anal. Calcd C 86.32, H 6.24, N 3.47. Found: C
86.49, H 6.34, N 3.56.
1H, JZ8.4 Hz), 8.29 (d, 1H, JZ7.8 Hz), 7.97 (d, 2H, JZ
6.3 Hz), 7.96 (d, 1H, JZ6.6 Hz), 7.91 (d, 1H, JZ7.2 Hz),
7.76 (d, 1H, JZ7.5 Hz), 7.70–7.51 (m, 6H), 7.19 (d, 1H, JZ
6.9 Hz), 2.96 (s, 6H), 1.77 (s, 6H). 13C NMR (CDCl3): d
151.49, 134.73, 133.24 (3C), 133.07, 131.23, 131.19,
131.12, 131.07, 130.66, 128.56, 127.45 (2C), 127.09 (2C),
126.92, 126.41, 126.31 (2C), 126.22, 125.39, 124.52,
121.86, 121.45 (2C), 121.15, 121.00, 120.95, 114.70,
99.28, 93.51, 92.67, 92.59, 91.90, 80.10, 65.94, 45.39,
31.68. C41H31NO (553.70). Anal. Calcd C 88.94, H 5.64, N
2.53. Found: C 89.02, H 5.50, N 2.78.
4.1.3.2. (b) 5-({5-[(5-Ethynyl-1-naphthyl)ethynyl]-1-
naphthyl}ethynyl)-N,N-dimethylnaphthalen-1-amine
(3). Following the general method used for the synthesis of
1, a mixture of compound 3a (200 mg, 0.36 mmol),
anhydrous toluene (40 mL), and finely powdered NaOH
(1.4 mg, 0.036 mmol) was stirred for 10 h and then filtered.
The residual solid was purified by silica gel column
chromatography, eluting with hexane/dichloromethane
(1:3) giving 3 as a pale orange solid, mp 210–211 8C,
177 mg (100%) yield. UV–vis (CH2Cl2), lmax (nm): 235 (3,
55,800), 363 (3, 26,600). Fluorescence (CH2Cl2), lmax (nm):
398, 414 (fZ0.65). IR (KBr, cmK1): 3293, 2219, 2083,
4.1.2.2. (b) 5-[(5-Ethynyl-1-naphthyl)ethynyl]-N,N-
dimethylnaphthalen-1-amine (2). Following the general
method used for the synthesis of 1, a mixture of compound
2a (100 mg, 0.25 mmol), anhydrous toluene (50 mL), and
finely powdered NaOH (1 mg, 0.03 mmol) was stirred for
5 h and then filtered. The residual solid was purified by
silica gel column chromatography, eluting with hexane/
dichloromethane (1:1) giving 2 as a yellow solid, mp 145–
147 8C, 86 mg (100%) yield. UV–vis (CH2Cl2), lmax (nm):
235 (3, 65,500), 343 (3, 23,100). Fluorescence (CH2Cl2),
lmax (nm): 397 (fZ0.55). IR (KBr, cmK1): 3293, 2188,
1
1420, 790. H NMR (CDCl3): d 8.63 (d, 1H, JZ8.4 Hz),
8.60 (d, 1H, JZ8.4 Hz), 8.59 (d, 1H, JZ8.4 Hz), 8.44 (d,
1H, JZ8.4 Hz), 8.33 (d, 1H, JZ8.7 Hz), 8.27 (d, 1H, JZ
8.4 Hz), 7.96 (d, 2H, JZ7.2 Hz), 7.95 (d, 1H, JZ7.2 Hz),
7.89 (d, 1H, JZ7.5 Hz), 7.83 (d, 1H, JZ7.2 Hz), 7.68–7.50
(m, 6H), 7.18 (d, 1H, JZ7.5 Hz), 3.53 (s, 1H), 2.93 (s, 6H).
13C NMR (CDCl3): d 151.57, 134.74, 133.52, 133.22 (2C),
133.04, 131.90, 131.25 (2C), 131.17, 130.70, 128.82,
127.63, 127.49, 127.10, 127.05, 126.93, 126.44 (2C),
126.32, 126.18, 125.36, 124.56, 121.89, 121.50, 121.44,
121.16, 121.07, 120.42, 114.74, 93.53, 92.75, 92.53, 91.93,
82.47, 81.60, 45.42. MS (70 eV): 495 (MC, 100), 494 (9),
441 (15), 316 (12), 277 (7), 247 (22). C38H25N (495.62).
Anal. Calcd C 92.09, H 5.08, N 2.83. Found: C 91.02, H
5.34, N 2.78.
1
2099, 1402, 787. H NMR (CDCl3): d 8.61 (d, 1H, JZ
8.4 Hz), 8.42 (d, 1H, JZ8.4 Hz), 8.32 (d, 1H, JZ8.7 Hz),
8.26 (d, 1H, JZ8.1 Hz), 7.93 (d, 1H, JZ6.9 Hz), 7.88 (d,
1H, JZ7.5 Hz), 7.82 (d, 1H, JZ7.5 Hz), 7.64–7.49 (m, 4H),
7.17 (d, 1H, JZ7.8 Hz), 3.52 (s, 1H), 2.93 (s, 6H). 13C NMR
(CDCl3): d 151.40, 134.65, 133.43, 133.01, 131.80, 131.05,
130.61, 128.79, 127.68, 126.88, 126.82, 126.37, 126.03,
125.34, 124.49, 121.69, 121.07, 120.95, 120.26, 114.66,
93.43, 91.78, 82.39, 81.56, 45.36. HMQC (1H/13C): 8.61/
127.68, 8.42/126.82, 8.32/125.34, 8.26/120.95, 7.93/131.05,
7.88/130.61, 7.82/131.80, 7.61/126.37, 7.58/126.03, 7.56/
126.88, 7.52/124.49, 7.17/114.66. COSY (1H/1H): 8.61/
7.58/7.82, 8.42/7.61/7.93, 8.32/7.52/7.88, 8.26/7.56/7.17.
MS (70 eV): 345 (MC, 100), 344 (19), 328 (10), 300 (21),
172 (12), 150 (18). C26H19N (345.44). Anal. Calcd C 90.40,
H 5.54, N 4.05. Found: C 90.48, H 5.28, N 4.89.
4.1.4. 4-{4-[(4-{[5-(N,N-Dimethylamino)-1-naphthyl]-
ethynyl}-1-phenyl)ethynyl]-1-phenyl}-2-methyl-3-butyn-
2-ol (6). Following the general method used for the
synthesis of 1a, a mixture of PdCl2(PPh3)2 (24 mg,
0.034 mmol), Cu2I2 (0.7 mg, 0.003 mmol), compound 5
(100 mg, 0.34 mmol), 4-(p-iodophenyl)-2-methyl-3-butyn-
2-ol) (97 mg, 0.34 mmol), and NEt3 (40 mL) was stirred for
12 h. A flash chromatography on silica gel, eluting with
hexane/ethyl acetate (2:1) giving 6 as a yellow solid, mp
163–165 8C, 135 mg (88%) yield. IR (KBr, cmK1): 3424,
2925, 2227, 1409, 1162, 838, 786. 1H NMR (CDCl3): d 8.27
(d, 1H, JZ8.4 Hz), 8.12 (d, 1H, JZ8.7 Hz), 7.76 (d, 1H,
JZ7.2 Hz), 7.62 (d, 2H, JZ8.4 Hz), 7.54 (d, 2H, JZ
8.4 Hz), 7.50 (dd, 1H, JZ8.7 Hz, JZ7.5 Hz), 7.49 (d, 2H,
JZ8.4 Hz), 7.48 (dd, 1H, JZ7.2, 8.2 Hz), 7.41 (d, 2H, JZ
8.4 Hz), 7.14 (d, 1H, JZ7.5 Hz), 2.90 (s, 6H), 1.63 (s, 6H).
13C NMR (CDCl3): d 151.32, 134.61, 131.55 (3C), 131.46,
130.49, 128.68, 126.76, 125.31, 124.41, 123.59, 122.89,
122.75 (2C), 120.86 (2C), 114.64, 95.67, 93.70, 90.91,
90.81, 90.15, 81.82, 65.54, 45.35, 31.28. C33H27NO
(453.58). Anal. Calcd C 87.38, H 6.00, N 3.09. Found: C
87.49, H 5.85, N 3.30.
4.1.3. 5-({5-[(5-Ethynyl-1-naphthyl)ethynyl]-1-naphthyl}-
ethynyl)-N,N-dimethylnaphthalen-1-amine (3).
4.1.3.1. (a) 4-{5-[(5-{[5-(N,N-Dimethylamino)-1-
naphthyl]ethynyl}-1-naphthyl)ethynyl]-1-naphtyl}-2-
methyl-3-butyn-2-ol (3a). Following the general method
used for the synthesis of 1a, a mixture of PdCl2(PPh3)2
(173 mg, 0.25 mmol), Cu2I2 (5 mg, 0.025 mmol), com-
pound 2 (850 mg, 2.46 mmol), 4-(5-iodo-1-naphthyl)-2-
methyl-3-butyn-2-ol (826 mg, 2.46 mmol), and NEt3
(200 mL) was stirred for 20 h. A flash chromatography on
silica gel, eluting with hexane/ethyl acetate (2:1) giving 3a
as an orange solid, mp 238–240 8C, 1.2 g (88%) yield. IR
(KBr, cmK1): 3287, 2274, 2217, 1421, 1151, 780. 1H NMR
(CDCl3): d 8.65 (d, 1H, JZ8.1 Hz), 8.61 (d, 1H, JZ7.8 Hz),
8.58 (d, 1H, JZ8.4 Hz), 8.38 (d, 1H, JZ8.4 Hz), 8.34 (d,

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J. G. Rodrıguez, J. L. Tejedor / Tetrahedron 61 (2005) 2047–2054
2053
4.1.5. 5-({4-[(4-Ethynyl-1-phenyl)ethynyl]-1-phenyl}-
ethynyl)-N,N-dimethylnaphthalen-1-amine (7). Follow-
ing the general method used for the synthesis of 1, a mixture
of compound 6 (100 mg, 0.22 mmol), anhydrous toluene
(40 mL), and finely powdered NaOH (0.9 mg, 0.022 mmol)
was stirred for 3 h and then filtered. The residual solid was
purified by silica gel column chromatography, eluting with
hexane/dichloromethane (1:2) giving 7 as a yellow-green
solid, mp 151–152 8C, 86 mg (100%) yield. UV–vis
(CH2Cl2), lmax (nm): 232 (3, 35,200), 264 (3, 17,400), 337
(3, 44,800), 364s (3, 32,800). Fluorescence (CH2Cl2), lmax
(nm): 529 (fZ0.23). IR (KBr, cmK1): 3196, 2925, 2208,
2095, 1406, 839, 784. 1H NMR (CDCl3): d 8.27 (d, 1H, JZ
8.4 Hz), 8.12 (d, 1H, JZ8.4 Hz), 7.76 (d, 1H, JZ6.9 Hz),
7.63 (d, 2H, JZ8.1 Hz), 7.55 (d, 2H, JZ8.4 Hz), 7.52 (dd,
1H, JZ8.4, 7.2 Hz), 7.50 (s, 4H), 7.47 (dd, 1H, JZ6.9,
8.4 Hz), 7.14 (d, 1H, JZ7.2 Hz), 3.20 (s, 1H), 2.90 (s, 6H).
13C NMR (CDCl3): d 151.34, 134.60, 132.09, 131.60 (2C),
131.47, 130.51, 128.69, 126.79, 125.33, 124.54, 123.64,
123.51, 122.67, 122.05, 120.85 (2C), 114.64, 93.68, 91.12,
90.65, 90.13, 83.23, 79.03, 45.34. MS (70 eV): 395 (MC,
100), 394 (9), 352 (8), 197 (18).C30H21N (395.50). Anal.
Calcd C 91.11, H 5.35, N 3.54. Found: C 91.28, H 5.54, N
3.38.
(CDCl3): d 151.44, 134.67, 134.29, 133.19 (2C), 131.32,
131.90, 130.67, 128.82, 127.68, 126.94, 126.48, 126.26,
125.37, 124.54, 124.32, 121.86, 121.13, 121.01 (2C),
120.90, 114.68, 93.53, 93.03, 91.87, 88.88, 45.40. MS
(FABC): 1108 (MC, 100). C84H57N3 (1108.39). Anal.
Calcd C 91.03, H 5.18, N 3.79. Found: C 90.92, H 5.31, N
3.62.
4.1.8.
1,3,5-Tri{[5-({5-[(5-{N,N-dimethylamino}-1-
naphthyl)ethynyl]-1-naphthyl}ethynyl)-1-naphthyl]-
ethynyl}benzene (10). Following the general method used
for the synthesis of 1a, a mixture of PdCl2(PPh3)2 (42 mg,
0.06 mmol), Cu2I2 (1.2 mg, 0.006 mmol), compound 3
(100 mg, 0.20 mmol), 1,3,5-triiodobenzene (30 mg,
0.07 mmol), and pyridine (40 mL) was stirred for 40 h at
reflux. A flash chromatography on silica gel, eluting with
hexane/dichloromethane (1:4) giving 6 as a pale orange
solid, mp 212–214 8C, 93 mg (30%) yield. UV–vis
(CH2Cl2), lmax (nm): 232 (3, 193,400), 370 (3, 96,800).
Fluorescence (CH2Cl2), lmax (nm): 530 (fZ0.08). IR (KBr,
1
cmK1): 2223, 2200, 1420, 967, 780. H NMR (CDCl3): d
8.82 (d, 3H, JZ8.4 Hz), 8.65 (d, 3H, JZ8.7 Hz), 8.54 (d,
3H, JZ8.4 Hz), 8.32 (d, 3H, JZ8.1 Hz), 8.30 (d, 3H, JZ
8.1 Hz), 8.26 (d, 3H, JZ8.1 Hz), 8.02 (d, 3H, JZ7.2 Hz),
8.01 (d, 3H, JZ7.2 Hz), 7.96 (d, 6H, JZ6.6 Hz), 7.89 (d,
3H, JZ7.2 Hz), 7.75 (d, 3H, JZ7.2 Hz), 7.72–7.50 (m,
18H), 7.17 (d, 3H, JZ7.8 Hz), 2.93 (s, 3H). 13C NMR
(CDCl3): d 151.52, 134.73, 133.26 (2C), 132.92 (2C),
132.46, 132.03, 131.71, 131.45, 131.19, 130.69, 128.88,
128.12, 127.84, 126.91, 126.78, 126.55, 126.29, 125.95
(2C), 125.90, 125.46, 124.52, 122.23, 122.04 (2C), 121.07
(2C), 120.97, 117.64, 114.73, 93.80, 93.68 (2C), 91.79 (2C),
91.46, 45.39. MS (FABC): 1557 (MC, 100). C120H75N3
(1558.93). Anal. Calcd C 92.46, H 4.85, N 2.70. Found: C
92.39, H 4.97, N 2.53.
4.1.6. 1,3,5-Tri[(5-{N,N-dimethylamino}-1-naphthyl)-
ethynyl]benzene (8). Following the general method used
for the synthesis of 2a, a mixture of PdCl2(PPh3)2 (36 mg,
0.051 mmol), Cu2I2 (1 mg, 0.005 mmol), compound 1
(100 mg, 0.51 mmol), 1,3,5-triiodobenzene (77 mg,
0.17 mmol), and NEt3 (30 mL) was stirred for 15 h. A
flash chromatography on silica gel, eluting with hexane/
dichloromethane (1:6) giving 8 as a dark orange solid, mp
193–195 8C, 95 mg (85%) yield. UV–vis (CH2Cl2), lmax
(nm): 232 (3, 180,940), 256s (3, 111,500), 310 (3, 85,500),
356 (3, 81,400). Fluorescence (CH2Cl2), lmax (nm): 504
(fZ0.43). IR (KBr, cmK1): 2208, 1400, 990, 789. 1H NMR
(CDCl3): d 8.33 (d, 3H, JZ8.7 Hz), 8.22 (d, 3H, JZ7.8 Hz),
7.93 (s, 3H), 7.83 (d, 3H, JZ6.9 Hz), 7.58 (t, 3H, JZ
8.1 Hz), 7.51 (dd, 3H, JZ8.7, 6.9 Hz), 7.17 (d, 3H, JZ
7.5 Hz), 2.93 (s, 18H). 13C NMR (CDCl3): d 151.35, 134.66,
134.02, 130.65, 128.69, 126.89, 125.46, 124.40, 120.89,
120.62 (2C), 114.67, 92.50, 89.34, 45.30. MS (70 eV): 657
(MC, 100), 643 (3), 328 (13).C48H39N3 (657.85). Anal.
Calcd C 87.64, H 5.98, N 6.39. Found: C 87.50, H 6.11, N
6.51.
4.1.9. 1,3,5-Tri({4-[(5-{N,N-dimethylamino}-1-naphthyl)-
ethynyl]-1-phenyl}ethynyl)benzene (11). Following the
general method used for the synthesis of 1a, a mixture of
PdCl2(PPh3)2 (24 mg, 0.011 mmol), Cu2I2 (0.7 mg,
0.0013 mmol), compound 5 (100 mg, 0.34 mmol), 1,3,5-
triiodobenzene (155 mg, 0.11 mmol), and NEt3 (30 mL)
was stirred for 72 h. A flash chromatography on silica gel,
eluting with hexane/dichloromethane (1:2) giving 11 as an
dark yellow solid, mp 85–86 8C, 86 mg (79%) yield. UV–
vis (CH2Cl2), lmax (nm): 230 (3, 122,900), 262s (3, 57,500),
337 (3, 106,500), 365 (3, 98,200). Fluorescence (CH2Cl2),
lmax (nm): 530 (fZ0.20). IR (KBr, cmK1): 2924, 2206,
4.1.7. 1,3,5-Tri({5-[(5-{N,N-dimethylamino}-1-naphthyl)-
ethynyl]-1-naphthyl}ethynyl)benzene (9). Following
the general method used for the synthesis of 1a, a mixture
of PdCl2(PPh3)2 (93 mg, 0.13 mmol), Cu2I2 (3 mg,
0.013 mmol), compound 2 (250 mg, 0.73 mmol), 1,3,5-
triiodobenzene (100 mg, 0.22 mmol), and NEt3 (40 mL)
was stirred for 20 h. A flash chromatography on silica gel,
eluting with hexane/dichloromethane (1:4) giving 9 as an
orange solid, mp 237–238 8C, 198 mg (81%) yield. UV–vis
(CH2Cl2), lmax (nm): 239 (3, 18,100), 364 (3, 10,650). IR
(KBr, cmK1): 2206, 1435, 984, 783. Fluorescence
1
1407, 961, 834, 786. H NMR (CDCl3): d 8.29 (d, 3H, JZ
8.9 Hz), 8.14 (d, 3H, JZ8.1 Hz), 7.77 (d, 3H, JZ6.9 Hz),
7.70 (s, 3H), 7.64 (d, 6H, JZ8.5 Hz), 7.57 (dd, 3H, JZ8.1,
6.8 Hz), 7.55 (d, 6H, JZ8.5 Hz), 7.49 (dd, 3H, JZ8.9,
6.9 Hz), 7.15 (d, 3H, JZ6.8 Hz), 2.91 (s, 18H). 13C NMR
(CDCl3): d 151.33, 139.78, 134.56, 131.58 (2C), 130.52,
128.65, 126.78, 125.36, 124.41, 123.91, 122.21 (2C),
120.81, 120.73, 114.63, 93.59, 91.03, 90.30, 88.66, 45.32.
MS (MALDI-TOF): 957.0. C72H51N3 (958.21). Anal. Calcd
C 90.25, H 5.36, N 4.39. Found: C 90.14, H 5.51, N 4.24.
1
(CH2Cl2), lmax (nm): 527 (fZ0.21). H NMR (CDCl3): d
8.63 (d, 3H, JZ8.4 Hz), 8.54 (d, 3H, JZ8.4 Hz), 8.32 (d,
3H, JZ8.4 Hz), 8.27 (d, 3H, JZ8.7 Hz), 7.96 (d, 3H, JZ
5.7 Hz), 7.95 (s, 3H), 7.89 (d, 3H, JZ7.2 Hz), 7.71–7.50 (m,
12H), 7.17 (d, 3H, JZ6.6 Hz), 2.93 (s, 18H). 13C NMR
4.1.10. 1,3,5-Tri{[4-({4-[(5-{N,N-dimethylamino}-1-
naphthyl)ethynyl]-1-phenyl}ethynyl)-1-phenyl]ethynyl}-
benzene (12). Following the general method used for the
synthesis of 1a, a mixture of PdCl2(PPh3)2 (6 mg,

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J. G. Rodrıguez, J. L. Tejedor / Tetrahedron 61 (2005) 2047–2054
2054
Materials: The Oligomer Approach; Mu¨llen, K., Wegner, G.,
Eds.; Wiley-VCH: Weinheim, 1998.
0.008 mmol), Cu2I2 (0.2 mg, 0.0006 mmol), compound 7
(100 mg, 0.25 mmol), compound 1,3,5-triiodobenzene
(37 mg, 0.08 mmol), and NEt3 (40 mL) was stirred for
72 h. A flash chromatography on silica gel, eluting with
hexane/dichloromethane (1:2) giving 12 as an dark yellow
solid, mp 209–210 8C, 65 mg (62%) yield. UV–vis
(CH2Cl2), lmax (nm): 232 (3, 94,500), 353 (3, 119,900).
Fluorescence (CH2Cl2), lmax (nm): 531 (fZ0.19). IR (KBr,
cmK1): 2924, 2207, 1407, 962, 835, 787. 1H NMR (CDCl3):
d 8.28 (d, 3H, JZ8.9 Hz), 8.13 (d, 3H, JZ8.5 Hz), 7.76 (d,
3H, JZ6.9 Hz), 7.68 (s, 3H), 7.64 (d, 6H, JZ8.9 Hz), 7.55–
7.44 (m, 24H), 7.14 (d, 3H, JZ7.3 Hz), 2.91 (s, 18H). 13C
NMR (CDCl3): d 151.38, 139.28, 134.626, 131.64 (4C),
130.52, 128.76, 126.78, 125.39, 124.44, 123.94, 122.71
(4C), 120.90 (2C), 114.65, 93.71, 90.31, 90.86, 90.36,
90.19, 86.63, 45.35. MS (MALDI-TOF): 1258. C96H63N3
(1258.57). Anal. Calcd C 91.62, H 5.05, N 3.34. Found: C
91.45, H 5.20, N 3.19.
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