Rod-like conjugated molecules with ethynylene linkage and pyridazine moieties: Synthesis and light emitting properties

Article abstract of DOI:10.3987/COM-10-11934

In this paper, we describe the synthesis of various rod-like conjugated molecules with ethynyl and vinylpyridazines units. The key steps involve Sonogashira cross-coupling and condensation reactions. The light-emitting properties of some molecules are inv

Full text of DOI:10.3987/COM-10-11934

HETEROCYCLES, Vol. 81, No. 6, 2010
1445
HETEROCYCLES, Vol. 81, No. 6, 2010, pp. 1445 - 1457. © The Japan Institute of Heterocyclic Chemistry
Received, 27th February, 2010, Accepted, 8th April, 2010, Published online, 9th April, 2010
DOI: 10.3987/COM-10-11934
ROD-LIKE CONJUGATED MOLECULES WITH ETHYNYLENE
LINKAGE AND PYRIDAZINE MOIETIES: SYNTHESIS AND LIGHT
EMITTING PROPERTIES
Caroline Hadad, Catherine Fiol-Petit, Anne-Sophie Cornec, Georges Dupas,
Yvan Ramondenc, and Nelly Plé*
L. C. O. F. H. Laboratory, UMR 6014-CNRS, INSA and University of Rouen,
IRCOF, 76821 Mont-Saint-Aignan Cedex, France
E-Mail: nelly.ple@insa-rouen.fr
Abstract – In this paper, we describe the synthesis of various rod-like conjugated
molecules with ethynyl and vinylpyridazines units. The key steps involve
Sonogashira cross-coupling and condensation reactions. The light-emitting
properties of some molecules are investigated in terms of absorption and emission
spectra.
INTRODUCTION
Linear arylethynyl molecules with extended -conjugation have received a considerable research interest
due to their potential applications as molecular wires,1 liquid crystals,2 components of organic light
emitting devices (OLEDs) for displays and lighting,3 non-linear optical materials,4 and more particularly
for two-photon absorption (TPA).5 Incorporation of one -deficient heterocycle such as pyridine,6
1,3,5-triazine7 or diazine8-10 into the backbone of such molecules gives rise to new materials with
interesting properties of electron conductivity and transport compared to their phenylene analogues.
Ethynyl moieties added in the backbone lead to ethynyl aromatic/heteroaromatic systems which are
versatile rigid-rod molecules. The main advantage of them compared to their arylenevinylene
counterparts is the lack of possible Z/E photoisomerization which is important (because the TPA
materials are photoexcited by the two-photon process) and their higher stability.11
With the aim to synthesize new conjugated structures containing ethynyl aromatic/heteroaromatic
moieties, a highly electronegative pyridazine ring was utilized as the dipolar moiety for incorporation into
the conjugated backbone. We report therein the synthesis of a new family of rod-like chromophores of the
A-π-D, A-π-D-π-A and D--A--D types with donors (D) and pyridazines units (A) linked by a
conjugated bridge (Scheme 1).

1446
HETEROCYCLES, Vol. 81, No. 6, 2010
N
N
N N
D
D
N
N
Type A--D--A
Type A--D
N
N
N
N
D
D
D
D
Type D--A--D
Scheme 1
Such molecules could present several interesting applications; we report here the light emitting properties
of some of them. This study is a part of our work dedicated to take advantages of diazines as building
blocks for the synthesis of organic molecular materials.12
RESULTS AND DISCUSSION
The ethynylene moiety could be introduced using Sonogashira coupling reactions with chloro, triflate and
iodo derivatives as starting materials.13 Among these methods, iodopyridazines were the most efficient
and convenient starting materials chosen to react with trimethylsilylacetylene under modified
Sonogashira conditions (Pd[PPh3]2Cl2, CuI, triethylamine in THF).14 Moreover, due to the -deficient
character of the pyridazine ring, the iodo derivatives can be easily obtained by nucleophilic substitution of
a chlorine atom by an iodine one starting from commercially available chloro derivatives.15 This
methodology was used to access to mono and bisalkynylpyridazines from the corresponding
3-iodo-6-methylpyridazine16 (1) (Scheme 2).
a
b
Me
I
I
Me
Me
N
N
N
N
N
N
4
52%
1
3 95%
c
d
Me
N
OC8H17
N
N
5
83%
Me
Me
N
N
N
N
C8H17O
6 36%
(a) i: trimethylsilylacetylene, Pd(PPh3)2Cl2, CuI, Et3N, THF, rt, 15h, ii: KOH, THF/ MeOH;
(b) 1,4-diiodobenzene, Pd(PPh3)2Cl2, CuI, Et3N, THF, rt, 48h;
(c) Julolidinylacetylene, Pd(PPh3)2Cl2, CuI, Et3N, THF, rt, 15h;
(d) 1,4-diethynyl-2,5-bis(octyloxy)benzene, Pd(PPh3)2Cl2, CuI, Et3N, THF, rt, 72h.
Scheme 2

HETEROCYCLES, Vol. 81, No. 6, 2010
1447
Starting from the 3,6-diiodopyridazine17 (2) and using double Sonogashira coupling reactions,
centrosymmetric dialkynylpyridazines 7, 8 were obtained in moderate yields. A further coupling reaction
of the julolidinylacetylene18 with the iodo compound 4 led to 9, which compared to the compound 5
presents a longer conjugated system (Scheme 3).
N
N
N N
a
I
Ar
Ar
I
Ar
Me
Me
N
2
7 Ar =
8 Ar =
53%
67%
N
N
N
N
N
N
a
Me
N
Me
I
N
9 86%
4
a) Pd(PPh3)2Cl2, CuI, Et3N, THF, rt, 48h
Scheme 3
The synthetic ways used allowed us to access to chromophores of type A-π-D for 5 and 9 and
chromophores of type A-π-D-π-A for 6 and D--A--D for 8. For this last compound, to appreciate the
effect of the conjugation on the photophysical properties, it would be interesting to modify the nature of
one of the conjugated linker by replacement of the ethynylene bridge by a vinylene one. In general,
ethynylene-linked (-CC-) systems are less conjugated than the corresponding vinylene-linked (-C=C-)
systems, because there are π- π and π*- π* energy mismatches at C(sp1)-C(sp2) connections.5
To incorporate a vinylene bridge in the backbone, a condensation reaction could be envisaged between
the methyl group of the pyridazine ring and various commercially available aldehydes, providing an
efficient synthetic way under environmentally friendly conditions.
The compound 5 substituted by a julolidinyl group, known to be an efficient electron-donating group D,
has been chosen as a starting material. Condensation reaction was carried out in boiling aqueous 5M
aqueous NaOH using Aliquat® 336 as a phase transfer agent, according to a previously reported
procedure19a-d (Scheme 4).
ArCHO
N
N
NaOH 5M
N
N
N
N
Ar
AliquatR 336
5
10 Ar = p-Br-Ph
11 Ar = p-N(Me)2Ph
38%
70%
12 Ar = p-C8H17O-Ph 61%
13 Ar = julolidinyl 17%
Scheme 4

1448
HETEROCYCLES, Vol. 81, No. 6, 2010
The compound 12 possessing a terminal alkoxy group with a long chain reveals a liquid crystal behavior
with a transition phase at 102 °C and a clearing temperature at 200 °C.
Geometrical, electronic and spectral properties
Geometry
We performed quantum mechanics calculations of the geometries and electronic structures using the
ab-initio DFT method at the B3LYP level of theory20 with the 6-31G* basis set21 for compounds 5, 8, 9,
11-13. In all cases, the computed geometry reveals a null dihedral angle between the pyridazine ring and
the vinylene or ethynylene chains; allowing a high charge transfer between the electron-withdrawing
pyridazine ring and the alkoxy, dimethylamino or julolidinyl electron-donating groups (Table 1).
Comparison of compounds 5 and 9 of type A-π-D highlights that incorporation in the chain of a phenyl
group which induces a -extended conjugation provides a lowering of the LUMO level. Comparison of
data for compounds 5, 8, 11, 12, 13 clearly shows that incorporation of an electron donating group results
in a decreasing of the HOMO-LUMO gap. The observed values for the alkyloxy (3.135), dimethylamino
(3.124) and julolidinyl (3.057) groups are in good agreement with the generally admitted order of electron
donating abilities and might correspond to a slight increasing of the absorption wavelengths (see further
explanations related to Table 2).
Table 1. HOMO/LUMO energy levels from DFT calculations
HOMO (eV)
- 4.899
- 4.792
- 4.809
- 4.598
- 4.771
- 4.451
LUMO (eV)
-1.240
HOMO-LUMO gap (eV)
Compound
5
8
3.659
3.377
3.081
3.124
3.135
3.057
-1.415
9
-1.728
11
12
13
-1.475
-1.636
-1.395
UV/Vis and PL Spectroscopy
The optical properties of some of the synthesized compounds were investigated by UV/Vis and
photoluminescence (PL) spectroscopy in CH2Cl2 at room temperature. The data obtained are summarized
in Table 2 and their absorption and emission spectra in Figure 1.

HETEROCYCLES, Vol. 81, No. 6, 2010
1449
Table 2. Absorption and emission properties
UV/ Visa
absmax (nm) (M-1.cm-1) emmax (nm)
PL
Stokes Shift
(cm-1)
8064
Compound
b
F
5
8
9
374
432
24913
13090
20720,
20685
16028
24930,
30983
12527
535
528
557
0.02
0.20
0.14
4209
300, 393
7492
11
12
425
537
562
0.23
0.09
4907
7144
335, 401
13
439
554
0.06
4728
a All spectra were recorded at room temperature at c = 1.10-6 to 20.10-6 M, in DCM. b Fluorescence quantum yield (±10%) in
DCM determined using harmane in 0.1 M H2SO4 ( = 0.83) as standard,22 excitation at 360 nm.
Figure 1. Absorption and photoluminescence spectra of compounds 5, 8, 9, 11-13.
Compounds 5 and 9 of type A-π-D have their absorption wavelengths (abs) located in UV (374-393 nm)
and their emission wavelengths (em) in visible. Both compounds exhibit a high Stokes Shift (7492- 8064
cm-1) and for 9, possessing the most conjugated backbone, we observed a red shift in agreement with the
lower calculated HOMO-LUMO gap (Table 1). The other compounds of type D--A--D with a larger
number of  electrons (8, 11-13) have their absorption wavelengths (abs) located in blue (401-439 nm)
and their em (528-562 nm) in visible. Comparison of compounds 11-13 allows us to appreciate the
influence of the electron-donating groups on the phenyl ring. Replacement of an alkoxy group by an
amino group (dimethylamino or julolidinyl) increases the absorption and emission wavelengths (abs, em),

1450
HETEROCYCLES, Vol. 81, No. 6, 2010
the highest bathochromic effect being observed for the julolidinyl group which is prone to have a stronger
donating effect. Comparison of compounds 8 and 13 allows us to appreciate the relative influence of a
vinylene or an ethynylene linker. No significant influence is observed on the absorption wavelengths,
whereas the vinyl compound 13 has the highest em and Stokes shifts but the centrosymmetric compound
8 exhibits the best quantum yield (F).
CONCLUSION
The synthesis of various rod-like conjugated molecules with ethynyl and vinylpyridazines units has been
performed using as key steps Sonogashira cross-coupling and aldol condensations reactions. These
compounds have interesting light-emitting properties which are investigated in terms of absorption and
emission spectra and high Stokes shifts. Presence of vinylene or ethynylenbridges allows an internal
charge transfer along these molecules making them good candidates for two-photons dyes.
EXPERIMENTAL
Melting points were determined on a Kofler hot-stage with a 2 degrees accuracy (± 2 °C). The 1H and 13C
NMR spectra were recorded on a Bruker AC 300 (300 MHz 1H, 75 MHz 13C) instrument. Microanalyses
were performed on a Carlo Erba CHNOS 1160 apparatus, measurement accuracy is about ± 0.4% on
carbon. The IR spectra were obtained as potassium bromide pellets with a Perkin-Elmer Paragon 500
spectrometer. Mass spectra were recorded on a GCMS-QP2010 Shimazu spectrometer. UV-Visible
spectra were obtained on a Varian Can 50 scan spectrophotometer. Fluorescence spectroscopic studies
were performed in a semi-micro fluorescence cell (Hellma®, 104F-QS, 10 x 4 mm, 1400 µL) with a
Varian Cary Eclipse spectrophotometer. Tetrahydrofuran (THF) and diethyl ether (Et2O) were distilled
from benzophenone sodium and used immediately. Water content of the solvent was estimated by the
modified Karl Fisher method (less than 60 ppm of water). Toluene, dichloromethane (DCM),
dimethylformamide (DMF) and triethylamine (NEt3) were distilled on CaH2. All reagents were purchased
from Aldrich chemical Co., Acros or Alpha Aeser.
3-((4-Iodophenyl)ethynyl)-6-methylpyridazine (4)
To a solution of diiodobenzene (372 mg, 1.13 mmol), PdCl2(PPh3)2 (28 mg, 0.04 mmol) and CuI (14 mg,
0.07 mmol) in Et3N (7 mL) was added 3-ethynyl-6-methylpyridazine (3) (160 mg, 1.36 mmol). The
reaction mixture was stirred under argon for 48 h at room temperature. The crude product was filtered
over Celite and evaporated under reduced pressure. The residue was purified by silica gel column
chromatography (eluent: petroleum ether/EtOAc 1/1) to give 188 mg (52%) of 4 as a dark orange solid.

HETEROCYCLES, Vol. 81, No. 6, 2010
1451
mp 179 °C. 1H NMR (CDCl3):  2.66 (s, 3H, CH3), 7.22-7.28 (m, 3H, 3  CH), 6.44 (d, 1H, J = 8.5 Hz,
CH), 7.64 (d, 2H, J = 8.5 Hz, 2  CH). 13C (CDCl3):  22.5 (CH3), 87.2 (Cq), 92.1 (Cq), 95.9 (Cq), 121.2
(Cq), 126.3 (CH), 129.2 (CH), 133.5 (2  CH), 137.7 (2  CH), 145.9 (Cq), 158.6 (Cq). IR: 2221, 1576,
1538, 1482, 1412, 1388, 1087, 1055, 1006, 844, 812, 515 cm-1. Anal. Calcd for C13H9IN2 (319.89): C,
48.77; H, 2.83; N, 8.75. Found: C, 48.66; H, 2.90; N, 8.89. CI-MS (isobutane). Calcd for C13H9IN2:
[M]+ = 320. Found: 321 [M+1].
3-(9-(Julolidinyl)ethynyl)-6-methylpyridazine (5)
To a solution of 3-iodo-6-methylpyridazine (1) (102 mg, 0.463 mmol), PdCl2(PPh3)2 (12 mg, 0.016
mmol) and CuI (6 mg, 0.030 mmol) in Et3N (3 mL) was added ethynyljulolidine18 (120 mg, 0.603 mmol).
The reaction mixture was stirred under argon for 8 h at 95 °C. After cooling, the crude product was
filtered over Celite and evaporated under reduced pressure. The residue was purified by silica gel column
1
chromatography (eluent: DCM/EtOAc 1/1) to give 80 mg (59%) of 5 as a brown solid. mp 124 °C. H
NMR (CDCl3):  1.93 (m, 4H, 2  CH2), 2.63-2.78 (m, 7H, CH3 and 2  CH2), 3.19 (t, 4H, J = 5.7 Hz, 2
 CH2), 7.04 (s, 2H, 2  CH), 7.23 (d, 1H, J = 8.7 Hz, CH), 7.42 (d, 1H, J = 8.7 Hz, CH). 13C (CDCl3): 
21.6 (2  CH2), 22.4 (CH3), 27.6 (2  CH2), 49.9 (2  CH2), 84.2 (Cq), 96.2 (Cq), 106.7 (Cq), 121.0 (2 
Cq), 126.1 (CH), 129.2 (CH), 131.0 (2  CH), 141.9 (Cq), 146.9 (Cq), 157.3 (Cq). IR: 2932, 2850, 2185,
1600, 1577, 1519, 1458, 1401, 1341, 1312, 1239, 1203, 1138, 1088, 1047, 885, 834 cm-1. CI-MS
(isobutane). Calcd for C19H19N3: [M]+ = 289. Found: 290 [M+1].
1,4-Bis((6-methylpyridazin-3-yl)ethynyl)-2,5-dioctyloxybenzene (6)
To
a
solution
of
3-iodo-6-methylpyridazine
(1)
(63
mg,
0.287
mmol)
and
1,4-diethynyl-2,5-dioctyloxybenzene (50 mg, 0.130 mmol) in Et3N (3 mL) were added PdCl2(PPh3)2 (6
mg, 0.009 mmol) and CuI (3 mg, 0.013 mmol). The reaction mixture was stirred under argon for 3 days at
room temperature. Water (20 mL) was added and the aqueous phase was extracted with DCM (3  20
mL). The combined organic extracts were dried over anhydrous MgSO4, filtered and evaporated under
reduced pressure. The residue was purified by silica gel column chromatography (eluent: petroleum
1
ether/EtOAc 1/1) to give 23 mg (36%) of 6 as a yellow solid. mp 150-151 °C. H NMR (CDCl3): 
0.72-0.86 (m, 6H, 2  CH3), 1.16-1.52 (m, 20H, 10  CH2, 5  CH), 1.85 (m, 4H, 2  CH2), 2.70 (s, 6H, 2
 CH3), 3.96 (t, 4H, J = 6.6 Hz, 2  CH2), 7.08 (s, 2H, 2  CH), 7.22 (d, 2H, J = 8.7 Hz, 2  CH), 7.44 (d,
2H, J = 8.7 Hz, 2  CH). 13C (CDCl3):  14.3 (2  CH3), 22.4 (2  CH3), 22.8 (2  CH2), 26.0 (2  CH2),
29.3 (2  CH2), 29.4 (2  CH2), 29.5 (2  CH2), 31.9 (2  CH2), 69.7 (2  CH2), 89.8 (2  Cq), 91.5 (2 
Cq), 113.6 (2  Cq), 117.3 (2  CH), 126.2 (2  CH), 129.7 (2  CH), 146.2 (2  Cq), 154.1 (2  Cq),

1452
HETEROCYCLES, Vol. 81, No. 6, 2010
158.4 (2  Cq). IR: 2947, 2922, 2217, 1505, 1471, 1401, 1389, 1282, 1219, 864, 724 cm-1. CI-MS
(isobutane). Calcd for C36H46N4O2: [M]+ = 566. Found : 567 [M+1].
3,6-Bis((4,6-dimethylpyrimidin-2-yl)ethynyl)pyridazine (7)
To a solution of 3,6-diiodopyridazine (2) (118 mg, 0.358 mmol) and 2-ethynyl-4,6-dimethylpyrimidine
(102 mg, 0.770 mmol) in a mixture of Et3N and DMSO (2.5/1 mL) were added PdCl2(PPh3)2 (9 mg,
0.012 mmol) and CuI (3 mg, 0.012 mmol). The reaction mixture was stirred under argon for 48 h at room
temperature. Solvents were evaporated under reduced pressure and DCM (20 mL) was added. The
organic phase was extracted with water (2  20 mL), dried over anhydrous MgSO4, filtered and
evaporated under reduced pressure. The residue was purified by silica gel column chromatography
1
(eluent: DCM/MeOH 9/1) to give 65 mg (53%) of 7 as a brown solid. mp 224-226 °C. H NMR
(CDCl3):  2.51 (s, 12H, 4  CH3), 7.05 (s, 2H, 2  CH), 7.71 (s, 2H, 2  CH). 13C (CDCl3):  24.0 (4 
CH3), 81.6 (2  Cq), 93.0 (2  Cq), 120.2 (2  CH), 129.4 (2  CH), 145.4 (2  Cq), 151.5 (2  Cq), 167.5
(4  Cq). IR: 2226, 1587, 1530, 1437, 1408, 1385, 1369, 1352 cm-1. CI-MS (isobutane). Calcd for
C20H16N6: [M]+ = 340. Found: 341 [M+1].
3,6-Bis(9-julolidinylethynyl)pyridazine (8)
To a solution of 3,6-diiodopyridazine (2) (108 mg, 0.325 mmol) and ethynyljulolidine18 (141 mg, 0.715
mmol) in a mixture of Et3N (2.5 mL) and DMSO (1 mL) were added PdCl2(PPh3)2 (8 mg, 0.011 mmol)
and CuI (3 mg, 0.011 mmol). The reaction mixture was stirred under argon for 48 h at room temperature.
Solvents were evaporated under reduced pressure and DCM (20 mL) was added. The organic phase was
extracted with water (2  20 mL), dried over anhydrous MgSO4, filtered and evaporated under reduced
pressure. The residue was purified by silica gel column chromatography (eluent: petroleum ether/EOAct
1/1) to give 102 mg (67%) of 8 as a dark orange solid. mp 200-202 °C. 1H NMR (CDCl3):  1.95 (m, 8H,
4  CH2), 2.76 (t, 8H, J = 6.4 Hz, 4  CH2), 3.22 (t, 8H, J = 5.7 Hz, 4  CH2), 7.07 (s, 4H, 4  CH), 7.42
(s, 2H, 2  CH). 13C (CDCl3):  21.7 (4  CH2), 27.7 (4  CH2), 50.0 (4  CH2), 84.9 (2  Cq), 98.3 (2 
Cq), 106.6 (2  Cq), 121.0 (4  Cq), 128.2 (2  CH), 132.1 (4  CH), 144.1 (2  Cq), 145.8 (2  Cq). IR:
2936, 2190, 1651, 1601, 1527, 1481, 1435, 1376, 1319, 1239, 1142, 888, 839, 768 cm-1. Anal. Calcd for
C32H30N4 (470.25): C, 81.67; H, 6.43; N, 11.91. Found: C, 81.56; H, 6.27; N, 11.75.
[4-(6-Methylpyrazin-3-yl)phenyl]julolidinylacetylene (9)
To a solution of 3-((4-iodophenyl)ethynyl)-6-methylpyridazine (4) (166 mg, 0.519 mmol), PdCl2(PPh3)2
(13 mg, 0.018 mmol) and CuI (6 mg, 0.034 mmol) in Et3N (3 mL) was added ethynyljulolidine (153 mg,

HETEROCYCLES, Vol. 81, No. 6, 2010
1453
0.777 mmol). The reaction mixture was stirred under argon at 95 °C for 48 h. The crude product was
filtered over Celite and evaporated under reduced pressure. The residue was purified by silica gel column
chromatography (eluent: petroleum ether/EtOAc 1/1) to give 174 mg (86%) of 9 as an orange-brown solid.
mp 207 °C. 1H NMR (CDCl3):  1.96 (q, 4H, J = 5.4 Hz, 2  CH2), 2.64-2.80 (m, 7H, 2  CH2 and CH3),
3.19 (t, 4H, J = 5.4 Hz, 2  CH2), 6.98 (s, 2H, 2  CH), 7.31 (d, 1H, J = 8.7 Hz, CH), 7.40-7.58 (m, 5H, 5
 CH). 13C (CDCl3):  21.8 (2  CH2), 22.6 (CH3), 27.7 (2  CH2), 50.0 (2  CH2), 86.8 (Cq), 87.2 (Cq),
93.3 (Cq), 94.4 (Cq), 108.2 (Cq), 120.2 (Cq), 121.1 (2  Cq), 125.9 (Cq), 126.3 (CH), 129.6 (CH), 130.5
(2  CH), 131.2 (2  CH), 132.1 (2  CH), 143.4 (Cq), 146.2 (Cq), 158.4 (Cq). CI-MS (isobutane). Calcd
for C27H23N3: [M]+ = 389. Found: 390 [M+1].
3-[4-(9-Julolidinylethynyl)phenyl]-6-(4-bromostyryl)pyrazine (10)
In a 25 mL round-bottomed flask were added Aliquat 336 (7 mg, 0.016 mmol),4-bromobenzaldehyde (34
mg, 0.181 mmol), [4-(6-methylpyrazin-3-yl)phenyl]julolidinylacetylene (9) (41 mg, 0.140 mmol) and
sodium hydroxide aqueous solution (5 M, 5 mL). The reaction vessel was heated to reflux under stirring
for 24 h. After cooling, water (30 mL) was added and the aqueous phase was extracted with DCM (3  20
mL). The combined organic extracts were dried over anhydrous MgSO4, filtered and evaporated under
reduced pressure. The residue was purified by silica gel column chromatography (eluent: petroleum
ether/EtOAc 6/4) to give 24 mg (38%) of 10 as a yellow solid. mp 215-217 °C. 1H NMR (CDCl3):  1.95
(m, 4H, 2  CH2), 2.72 (t, 4H, J = 6.4 Hz, 2  CH2), 3.22 (t, 4H, J = 5.7 Hz, 2  CH2), 7.08 (s, 2H, 2 
CH), 7.36 (d, 1H, J = 16.4 Hz, CH), 7.42-7.59 (m, 7H, 7  CH). Anal. Calcd for C26H22BrN3 (455.10): C,
68.43; H, 4.86; N, 9.21. Found C, 68.29; H, 4.56; N, 8.95.
3-[4-(9-Julolidinylethynyl)phenyl]-6-(4-dimethylaminostyryl)pyrazine (11)
In
a
25 mL round-bottomed flask were added Aliquat 336 (5 mg, 0.013 mmol
4-N,N-(dimethylamino)benzaldehyde (26 mg, 0.174 mmol), [4-(6-methylpyrazin-3-yl)phenyl]julolidiny
lacetylene (9) (39 mg, 0.135 mmol) and sodium hydroxide solution (5 M, 6 mL). The reaction vessel was
heated to reflux under stirring for 24 h. After cooling, water (30 mL) was added and the aqueous phase
was extracted with DCM (3 x 20 mL). The combined organic extracts were dried over anhydrous MgSO4,
filtered and evaporated under reduced pressure. The residue was purified by silica gel column
chromatography (eluent: petroleum ether/EtOAc 1/1) to give 39 mg (70%) of 11 as a dark red solid. mp
1
260 °C. H NMR (CDCl3):  1.95 (m, 4H, 2  CH2), 2.75 (t, 4H, J = 6.2 Hz, 2  CH), 3.01 (s, 6H, 2 
CH3), 3.21 (t, 4H, J = 5.7 Hz, 2  CH2), 6.0 (d, 2H, J = 8.4 Hz, 2  CH), 7.07 (s, 2H, 2  CH), 7.20 (d, 1H,
13
J = 16.4 Hz), 7.41-7.55 (5H, 5  CH). C (CDCl3):  21.7 (2  CH2), 27.7 (2  CH2), 40.4 (2  CH3),

1454
HETEROCYCLES, Vol. 81, No. 6, 2010
50.0 (2  CH2), 85.0 (Cq), 98.8 (Cq), 107.0 (Cq), 112.2 (2  CH), 120.6 (CH), 121.0 (2  Cq), 122.2 (CH),
124.3 (Cq), 128.8 (2  CH), 129.0 (CH), 131.1 (2  CH), 135.2 (CH), 143.8 (Cq), 146.2 (Cq), 151.0 (Cq),
156.3 (Cq). IR: 2927, 2835, 2181, 1599, 1518, 1459, 1430, 1349, 1307, 1241, 1187, 1161, 1143, 970, 887,
839, 811 cm-1. CI-MS (isobutane). Calcd for C28H28N4: [M]+ = 420. Found: 421 [M+1].
3-[4-(9-Julolidinylethynyl)phenyl]-6-(4-octyloxystyryl)pyrazine (12)
In a 25 mL round-bottomed flask were added Aliquat 336 (6.5 mg, 0.016 mmol),
4-(octyloxy)benzaldehyde (50 mg, 0.211 mmol), [4-(6-methylpyrazin-3-yl)phenyl]julolidinylacetylene
(9) (47 mg, 0.163 mmol) and aqueous sodium hydroxide solution (5 M, 6 mL). The reaction vessel was
heated to reflux under stirring for 24 h. After cooling, water (30 mL) was added and the aqueous phase
was extracted with DCM (3  20 mL). The combined organic extracts were dried over anhydrous MgSO4,
filtered and evaporated under reduced pressure. The residue was purified by silica gel column
chromatography (eluent: petroleum ether/EtOAc 6/4) to give 50 mg (61%) of 12 as an orange solid mp
200-202 °C. 1H NMR (CDCl3):  0.82-0.96 (m, 3H, CH3), 1.20-1.51 (m, 10H, 5  CH2), 1.79 (q, 2H, J =
6.6 Hz, CH2), 1.95 (q, 4H, J = 6.4 Hz, 2  CH2), 2.73 (t, 4H, J = 6.4 Hz, 2  CH2), 3.21 (t, 4H, J = 5.8 Hz,
2  CH2), 3.99 (t, 2H, J = 6.6 Hz, CH2), 6.91 (d, 2H, J = 8.7 Hz, 2  CH), 7.08 (s, 2H, 2  CH), 7.26 (d,
13
1H, J = 16.4 Hz, CH), 7.40-7.57 (5H, 5  CH). C (CDCl3):  14.2 (CH3), 21.7 (CH2), 22.8 (2  CH2),
26.1 (CH2), 27.7 (2  CH2), 29.3-29.4 (4  CH2), 31.9 (CH2), 50.0 (2  CH2), 68.3 (CH2), 84.9 (Cq,), 97.3
(Cq,), 106.8 (Cq), 114.9 (2  CH), 121.0 (2  Cq), 122.6 (CH), 122.9 (CH), 128.7 (Cq), 129.0 (2  CH),
129.1 (CH), 131.1 (2  CH), 134.6 (CH), 144.0 (Cq), 146.7 (Cq), 155.7 (Cq), 160.1 (Cq). IR: 2926, 2853,
2198, 1667, 1631, 1603, 1573, 1510, 1466, 1425, 1344, 1309, 1252, 1174, 1104, 1031, 976, 839 cm-1.
Anal. Calcd for C35H39N3O (505.31): C, 80.75; H, 7.77; N, 8.31. Found C, 80.47; H, 7.56; N, 8.18.
3-[4-(9-Julolidinylethynyl)phenyl]-6-julolidinyl)pyrazine (13)
In a 25 mL round-bottomed flask were added Aliquat 336 (5 mg, 0.012 mmol),julolidinylaldehyde (37
mg, 0.185 mmol), [4-(6-methylpyrazin-3-yl)phenyl]julolidinylacetylene (9) (36 mg, 0.124 mmol) and
aqueous sodium hydroxide solution (5 M, 6 ml). The reaction vessel was heated to reflux under stirring
for 24 h. After cooling, water (30 mL) was added and the aqueous phase was extracted with DCM(3  20
mL). The combined organic extracts were dried over anhydrous MgSO4, filtered and evaporated under
reduced pressure. The residue was purified by silica gel column chromatography (eluent: petroleum
1
ether/EtOAc 6/4) to give 10 mg (17%) of 13 as an orange solid. mp > 260 °C decomposition. H NMR
(CDCl3):  1.88-2.02 (m, 8H, 4  CH2), 2.27-2.81 (m, 8H, 4  CH2), 3.21 (t, 8H, J = 5.7 Hz, 4  CH2),
7.02-7.08 (m, 4H, 4  CH), 7.12 (d, 1H, J = 16.4 Hz), 7.36 (d, 1H, J = 7.0 Hz, CH), 7.39-7.51 (m, 2H, 2 

HETEROCYCLES, Vol. 81, No. 6, 2010
1455
CH). IR: 2920, 2842, 2206, 1651, 1479, 1435, 1374, 1263, 1199, 969, 768 cm-1. HRMS (ESI) calcd for
[C32H32N4+H]: 473.2705. Found: 473.2722.
REFERENCES
1. a) J. M. Tour, Acc. Chem. Res., 2000, 33, 791; b) J. M. Tour, Chem. Rev., 1996, 96, 537; c) J. M.
Lehn, ’Supramolecular Chemistry: Concepts and Perspectives’ VCH: Weinheim 1995; d) C. Wang,
A. S. Batsanov, and M. R. Bryce, J. Org. Chem., 2006, 71, 108.
2. a) G. W. Gray, M. Hird, and K. J. Toyne, Mol. Cryst. Liq. Cryst., 1991, 195, 221; b) L. K. M. Chan,
G. W. Gray, D. Lacey, T. Shrithanratana, and K. J. Toyne, Mol. Cryst. Liq.Cryst., 1987, 150B, 335;
c) L. K. M. Chan, G. W. Gray, D. Lacey, and K. J. Toyne, Mol. Cryst. Liq. Cryst., 1988, 158B, 209;
d) G. W. Gray, M. Hird, D. Lacey, and K. J. Toyne, J. Chem. Soc., Perkin Trans. 2, 1989, 2041; e) M.
Hird, K. J. Toyne, G. W. Gray, D. G. McDonnel, and I. C. Sage, Liq. Cryst., 1995, 18, 1.
3. a) A. Kraft, A. C. Grimsdale, and A. B. Holmes, Angew. Chem. Int. Ed., 1998, 37, 402; b) U.
Mitschke and P. Bäuerle, J. Mater. Chem., 2000, 10, 1471.
4. a) M. Albota, D. Beljonne, J.-L. Brédas, J. E. Erhlich, J.-Y. Fu, A. A. Heikel, S. E. Hess, T. Kogej, M.
D. Levin, S. R. Marder, D. McCord-Maughon, J. W. Perry, H. Röckel, M. Rumi, G. Subramaniam,
W. W. Webb, X.-L. Wu, and C. Xu, Science, 1998, 281, 1653; b) A. Hayek, F. Bolze, J.-F. Nicoud, P.
L. Baldeck, and Y. Mély, Photochem. Photobiol. Sci., 2000, 5, 102; c) F. Cherioux, A.-J. Attias, and
H. Maillotte, Adv. Funct. Mater., 2002, 12, 20; d) A.-L. Roy, M. Chavarot, E. Rose, F. Rose-Munch,
A.-J. Attias, D. Kréher, J.-L Fave, and C. Kamierszky, C. R. Chimie, 2005, 8, 1256.
5. M. Pawlicki, H. A. Collins, R. G. Denning, and H. L. Anderson, Angew. Chem. Int. Ed., 2009, 48,
3244.
6. a) J. K. Kim, J. W. Yu, J. M. Hong, H. N. Cho, D. Y. Kim, and C. Y. Kim, J. Mater. Chem., 1999, 9,
2171; b) J. A. Irvin, C. J. Dubois, and J. R. Reynolds, Chem. Commun., 1999, 2121; c) A. P.
Monkman, L.-O. Pålsson, R. W. T. Higgins, C. Wang, M. R. Bryce, and J. A. K. Howard, J. Am.
Chem. Soc., 2002, 124, 6049.
7. a) J. M. Lupton, L. R. Hemingway, I. D. W. Samuel, and P. L. Burn, J. Mater. Chem., 2000, 10, 867;
b) J. Pang, Y. Tao, S. Freiberg, X.-P. Yang, M. D’Iorio, and S. Wang, J. Mater. Chem., 2002, 12,
206.
8. a) G. Hugues, C. Wang, A. S. Batsanov, M. Fern, S. Frank, M. R. Bryce, I. F. Perepichka, A. P.
Monkman, and P. Lyons, Org. Biomol. Chem., 2003, 1, 3069; b) K. T. Wong, T. S. Hung, Y. Lin,
C.-C. Wu, G.-H. Lee, S.-M. Peng, C.H. Chou, and Y. O. Su, Org. Lett., 2002, 4, 513; c) C. C. Wu, Y.
T. Lin, H. H. Chiang, T. Y. Cho, C. W. Chen, K. T. Wong, Y. L. Liao, G. H. Lee, and S. M. Peng,
Appl. Phys. Lett., 2002, 81, 577.

1456
HETEROCYCLES, Vol. 81, No. 6, 2010
9. L. Zhao, I. F. Perepichka, F. Türsksoy, A. S. Batsanov, A. Beeby, K. S. Findlay, and M. R. Bryce,
New J. Chem., 2004, 28, 912.
10. S. Achelle, N. Plé, D. Kreher, F. Mathevet, A. Turck, and A.-J. Attias, Heterocycles, 2008, 75, 357.
11. W. J. Yang, C. H. Kim, M. Y. Jeong, S. K. Lee, M. J. Piao, S. J. Jeon, and B. R. Cho, Chem. Mater.,
2004, 16, 2783.
12. a) V. Gautheron Chapoulaud, N. Plé, A. Turck, and G. Quéguiner, Tetrahedron, 2000, 30, 5499; b) F.
Toudic, A. Heynderickx, N. Plé, A. Turck, and G. Quéguiner, Tetrahedron, 2003, 59, 6375; c) A.
Busch, V. Gautheron Chapoulaud, J. Audoux, N. Plé, and A. Turck, Tetrahedron, 2004, 60, 5373; d)
S. Achelle, N. Plé, A. Turck, J.-P. Bouillon, and C. Portella, J. Heterocycl. Chem., 2006, 43, 1243; e)
A. Busch, A. Turck, K. Nowicka, A. Barcella, C. Andraud, and N. Plé, Heterocycles, 2007, 71, 1723;
f) N. Hebbar, Y. Ramondenc, G. Plé, G. Dupas, and N. Plé, Tetrahedron, 2009, 65, 4190.
13. a) Y. Abe, A. Ohsawa, H. Arai, and H. Igeta, Heterocycles, 1978, 9, 1397; b) A. Ohsawa, Y. Abe,
and H. Igeta, Chem. Lett., 1979, 241; c) G. Heinisch and W. Holzer, Can. J. Chem., 1991, 69, 972; d)
D. Tousaint, J. Suffert, and C. G. Wermuth, Heterocycles, 1994, 38, 1273; e) D. S. Chekmarev, A. E.
Stepanov, and A. N. Kasatkin, Tetrahedron Lett., 2005, 46, 1303; f) B. U. W. Maes, P. Tapolcsányi,
C. Meyers, and P. Mátyus, Curr. Org. Chem., 2006, 10, 377.
14. T. L. Draper and T. R. Bailey, J. Org. Chem., 1995, 60, 748.
15. a) P. Coad, R. A. Coad, S. Clough, J. Hyepock, R. Salisbury, and C. Wilkins, J. Org. Chem., 1963,
28, 218; b) M. S. Shin, Y. J. Kang, H. A. Chung, J. W. Park, D. H. Kweon, W. S. Lee, Y. J. Yoon,
and S. K. Kim, J. Heterocycl. Chem., 1999, 36, 1135.
16. a) N. K. Basu and F. L. Rose, J. Chem. Soc., 1963, 5660; b) M. Ogata, Chem. Pharm. Bull., 1963, 11,
1522.
17. G. Heinisch and W. Holzer, Can. J. Chem., 1991, 69, 972.
18. N. Hebbar, Ph.D. University of Rouen 2008.
19. a) J. J. Vanden Eynde, L. Pascal, Y. Van Haverbeke, and P. Dubois, Synth. Commun., 2001, 31,
3167; b) L. Pascal, J. J. Vanden Eynde, Y. Van Haverbeke, and P. Dubois, Lett. Org. Chem., 2004, 1,
112; c) M. Mainil, L. Pascal, Vanden Eynde, Y. Van Haverbeke, and P. Dubois, e-Polymers, 2003,
056; d) D. M. Brown and A. A. R. Kon, J. Chem. Soc., 1948, 2147.
20. a) A. D. Becke, J. Chem. Phys., 1993, 98, 5648; b) C. T. Lee, W. T. Yang, and R. G. Parr, Phys. Rev.
B, 1988, 97, 785.
21. Gaussian 03, Revision C.02, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb,
J. R. Cheeseman, J. A. Montgomery, Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S.
Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A. Petersson, H.
Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.

HETEROCYCLES, Vol. 81, No. 6, 2010
1457
Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, C. Adamo, J.
Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W.
Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzewski,
S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J.
B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A.
Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng,
A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez,
and J. A. Pople, Gaussian, Inc., Wallingford CT, 2004.
This package has been implemented on a power-575 IBM cluster. We thank the Centre de Ressources
Informatiques de Haute-Normandie (CRIHAN) for software optimization and technical support.
22. a) S. Fery-Forgues and D. Lavabre, J. Chem. Educ., 1999, 76, 1260; b) R. Rusakowicz and A. C.
Testa, J. Phys. Chem., 1968, 72, 2680; c) A. Pardo, D. Reyman, J. M. L. Poyato, and F. Medina, J.
Lumin., 1992, 51, 269; d) Q. Umberger and V. K. LaMer, J. Am. Chem. Soc., 1945, 67, 1099.