4-arylvinyl-2,6-di(pyridin-2-yl)pyrimidines: Synthesis and optical properties

Article abstract of DOI:10.1021/jo200204u

A series of 4-arylvinyl-2,6-di(pyridin-2-yl)pyrimidines have been efficiently prepared by a double cross-coupling reaction between 2,4-dichloro-6-methylpyrimidine and 2-(tributylstannyl)pyridine, followed by aldol condensation with the appropriate aromatic aldehyde substituted with electron-donating, electron-withdrawing, dendritic, or water-soluble groups. The effect of different protic and aprotic solvents on the optical absorption and emission properties of these systems was studied. Compounds with electron-donating groups display strong emission solvatochromism, suggesting the formation of an intramolecular charge-separated emitting state. The solvatochromic behavior depends not only on the solvent polarity but also on the hydrogen bonding parameters of the solvent. The effect of protonation was also studied, and the abilities of some of these molecules to function as colorimetric and luminescent pH sensors were demonstrated with dramatic color changes and luminescence switching upon the introduction of acid.

Full text of DOI:10.1021/jo200204u

ARTICLE
pubs.acs.org/joc
4-Arylvinyl-2,6-di(pyridin-2-yl)pyrimidines: Synthesis and
Optical Properties
Caroline Hadad, Sylvain Achelle, Joaquín C. García-Martinez,* and Juliꢀan Rodríguez-Lꢀopez*
Facultad de Química, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain
S Supporting Information
b
ABSTRACT: A series of 4-arylvinyl-2,6-di(pyridin-2-yl)-
pyrimidines have been efficiently prepared by a double cross-
coupling reaction between 2,4-dichloro-6-methylpyrimidine
and 2-(tributylstannyl)pyridine, followed by aldol condensation
with the appropriate aromatic aldehyde substituted with elec-
tron-donating, electron-withdrawing, dendritic, or water-solu-
ble groups. The effect of different protic and aprotic solvents on
the optical absorption and emission properties of these systems
was studied. Compounds with electron-donating groups display
strong emission solvatochromism, suggesting the formation of an intramolecular charge-separated emitting state. The solvato-
chromic behavior depends not only on the solvent polarity but also on the hydrogen bonding parameters of the solvent. The effect of
protonation was also studied, and the abilities of some of these molecules to function as colorimetric and luminescent pH sensors
were demonstrated with dramatic color changes and luminescence switching upon the introduction of acid.
’ INTRODUCTION
influence on the luminescence properties of the resulting supra-
molecular assemblies.9
Over the past decade, there has been considerable interest in
the synthesis and characterization of conjugated organic com-
pounds due to their applications in a wide range of electronic and
optoelectronic devices. Indeed, such compounds are used as
liquid crystals,1 components for light-emitting devices (OLEDs)
for displays and lighting,2 as field effect transistors (OFETs),3
and in single molecular electronics.4 Fluorescent chromophores,
which are generally known to have planar and rigid π-conjugated
systems, are also of interest as functional materials in molecular
probes.5 Molecular fluorescence enables high sensitivity in
detection, “ONꢀOFF” switchability, subnanometer spatial re-
solution, and submillisecond temporal resolution.6
Since the late 1990s, fluorescent oligopyridines have been of
considerable interest as tunable fluorophores through intermo-
lecular interactions. The parent oligopyridines (2,20-bipyridine,
2,20:60,200-terpyridine, and 1,10-phenanthroline) possess extre-
mely low fluorescence quantum yields and undesirable short
emission wavelengths. However, the introduction of electron-
donating moieties leads to an enhancement in quantum yields
and a shift to the visible region of the emission wavelength.7
2,20:60,200-Terpyridine is well-known for its good coordination
ability due to its suitably arranged ring nitrogens. Among the
unique properties of terpyridines, their luminescent properties
upon coordination with metal ions are particularly attractive due
to the high potential for technological applications such as light-
emitting devices and probes over a large spectral range.8 The
assembly of these useful materials is based on the large binding
constants between the terpyridine ligand and various metal ions.
To date, many complexes have been investigated, and it has been
widely demonstrated that the choice of ligand has a marked
More recently, pyrimidine has also been used in the above
context. Thus, conjugated 2,4,6-trisubstituted pyrimidine deri-
vatives have shown important fluorescence properties,10 as well
as self-assembly properties,10e,11 and 2,4-diarylvinylpyrimidines
have also been described as good fluorophores,12 pH sensors,13
and two-photon absorption chromophores.14 Functionalization
of pyrimidine with two 2-pyridyl groups in positions 2 and 4 leads
to an effective tridentate ligand for metal cations (similar to a
2,20:60,200-terpyridine) that can generate various useful materials.
For example, a dinuclear ruthenium complex with this ligand was
described as a near IR-emitting Ru(II) complex that exhibits the
longest-lived emission and highest quantum yield reported to
date.15 The additional nitrogen of the pyrimidine ring is respon-
sible for a less efficient nonradiative pathway, thus providing a flat
bridging acceptor ligand that can lead to a large delocalized π
surface. Therefore, the synthesis of new pyrimidine analogues of
terpyridine is a good option to obtain high emission efficiency as
well as new emission colors.
Dendrons are monodisperse wedge-shaped dendrimer sec-
tions with multiple terminal groups and a single reactive function
at the focal point.16 Among their unique properties,17 it has been
demonstrated that dendritic arms can function as light harvesting
antennae.18 Conjugated dendrimers with poly(phenylenevinylene)
(PPV) and poly(phenyleneethynylene) scaffolds19 and poly-
(benzyl ether) dendrimers (also called Frꢀechet-type den-
drimers)20 represent two important groups within this class of
Received: January 27, 2011
Published: April 04, 2011
r
2011 American Chemical Society
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Table 1. Preparation of Di(pyridin-2-yl)pyrimidines
Scheme 1. Synthesis of the AꢀπꢀDꢀπꢀA Compound 3
In this contribution, we describe the synthesis and character-
ization of a novel series of fluorescent 2,6-di(pyridin-2-yl)-
pyrimidines functionalized with phenylenevinylene arms bearing
either electron-donating or electron-withdrawing groups. These
highly conjugated molecules have an AꢀπꢀD or AꢀπꢀA
structure (A = acceptor, D = donor) because of the strong
electron-withdrawing character of the 2,6-di(pyridin-2-yl)-
pyrimidine unit. The influence of the nature of the electroactive
substituents on the optical absorption and emission properties
was examined along with the fluorosolvatochromism and pH
sensitivity. The incorporation of Frꢀechet and PPV dendritic
structures on the di(pyridin-2-yl)pyrimidine unit was also as-
sessed in an effort to combine the properties of both types of
chromophores.
Additionally, the potential behavior of the 2,6-di(pyridin-2-
yl)pyrimidine moiety as a ligand can also be used to modulate the
optoelectronic properties of these molecules. An in-depth study
into the complexation of these compounds with various metal
cations will be published elsewhere.
’ RESULTS AND DISCUSSION
Preparation of 2,6-Di(pyridin-2-yl)pyrimidines. The target
compounds 2aꢀj were prepared in two steps from commercially
available 2,4-dichloro-6-methylpyrimidine (Table 1). The first
step was a double cross-coupling reaction with 2-(tributyl-
stannyl)pyridine under Stille conditions.22 The second step
involved the aldol condensation between aromatic aldehydes
and the methylpyrimidine derivative 1 in boiling aqueous 5 M
NaOH (1 M for 2f) using Aliquat 336 as a phase-transfer catalyst
in the absence of an organic solvent.23 The experimental protocol
is straightforward and offers easy access, in moderate to good
yields, to a wide variety of di(pyridin-2-yl)pyrimidines containing
electron-withdrawing and -donating groups, as well as PPV and
Frꢀechet-type dendrons.
A similar protocol gave the AꢀπꢀDꢀπꢀA derivative 3, which
contains two pushꢀpull systems, in moderate yield (57%) after a
double condensation reaction between 4,40-diformyltriphenylamine
and the methylpyrimidine drivative 1 (Scheme 1).
All new compounds were soluble in THF, chloroform, and
dichloromethane (2j was also soluble in water) and were
characterized using a variety of analytical techniques. The overall
purities of these products were confirmed by elemental analysis.
NMR experiments proved very useful to confirm the structures
of the compounds (see Experimental Section and Supporting
Information). The selectivity of the aldol reactions was suffi-
ciently high to generate all-trans isomers within the limits of
NMR detection. The stereochemistry of the double bonds was
materials. Terpyridine ligands have been successfully attached
to the focal point of phenylacetylene dendrons.21 Such
binding-ligand anchored dendrons exhibited broad absorption,
large molar extinction coefficients, and high fluorescence
quantum yields. However, di(pyridin-2-yl)pyrimidine deriva-
tives bearing artificial light-harvesting dendritic systems with a
cascade-type energy gradient have not been investigated in
detail.
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Table 2. UV/vis and Photoluminescence (PL) Data
compda
UV/vis λmax, nm (ε, Mꢀ1 cmꢀ1
)
PL λmax, nm
ΦF
Stokes shift, cmꢀ1
3
2a
2b
2c
2d
2e
2f
283 (31400), 335 (24600)
283 (32400), 339 (31000)
278 (22400), 413 (21300)
282 (31000), 416 (31300)
407
484
540
540
461
423
505
430
425
494
544
<0.01b
<0.01b
0.22c
0.52c
0.15c
<0.01b
0.05b
0.02b
0.02b
0.22c
5281
9215
5695
5520
5455
6571
10319
6329
6056
7867
4387
280 (41600), 357 (35900), 369 (36100)
281 (31300), 331 (20300)
293 (57000), 332 (79900)
282 (26300), 338 (22200)
281 (31900), 339 (21500)
279 (15400), 355 (16800)
280 (48000), 439 (37100)
2g
2h
2i
2j
3
0.46d
a All spectra were recorded in CH2Cl2 solutions at room temperature at c = 1.0 ꢁ 10ꢀ5 M to 3.0 ꢁ 10ꢀ5 M for UV/vis spectra and 1.0 ꢁ 10ꢀ6 to 3.0 ꢁ
10ꢀ6 M for PL spectra. b Fluorescence quantum yield ((10%) determined relative to quinine sulfate in 0.1 M H2SO4 as standard (ΦF = 0.54); excitation
c
at 340 nm. Fluorescence quantum yield ((10%) determined relative to anthracene in ethanol as standard (ΦF = 0.27); excitation at 356 nm.
d Fluorescence quantum yield ((10%) determined relative to rhodamine 101 in ethanol as standard (ΦF = 0.92); excitation at 526 nm.
unequivocally established on the basis of the coupling constant
for the vinylic protons in the 1H NMR spectra (J ∼ 16 Hz).
These materials are perfectly stable in the solid state and could
be stored without the need for any special precautions. Only
compound 2j underwent partial cisꢀtrans isomerization when
it was allowed to stand in chloroform solution at room
temperature.
UV/vis and PL Spectroscopy. The optical properties of the
prepared structures were investigated by UV/vis and photolu-
minescence (PL) spectroscopy in CH2Cl2 solutions at room
temperature and at low concentration (1.0 ꢁ 10ꢀ5 to 3.0 ꢁ 10ꢀ5
M for UV/vis spectra and 1.0 ꢁ 10ꢀ6 to 3.0 ꢁ 10ꢀ6 M for PL
spectra). Under these conditions, aggregation or self-absorption
effects were not observed. The data obtained are summarized in
Table 2. All compounds were photostable and did not undergo
cisꢀtrans isomerization under the analysis conditions. As an
example, the spectra for derivatives 2g and 3 are shown in
Figure 1. UV/vis and emission spectra of compounds 2g and 3.
Figure 1.
The UV/vis spectra showed strong absorption bands at λmax
=
331ꢀ439 nm, and these were accompanied in all cases by a
second or even a third band at higher energy. The materials are
also fluorescent and emit light when irradiated, showing a typical
response in the visible region (407ꢀ544 nm). In comparison
with di(pyridin-2-yl)pyrimidine 2a (model compound), deriva-
tives 2bꢀe exhibited red-shifted absorption and fluorescence
emission spectra that are consistent with an increase in the
electron-donating character of the substituent in the aromatic
ring. In contrast, compound 2f, which contains an electron-
withdrawing group (R = p-CF3ꢀC6H4ꢀ), showed a lower
energy absorption band and a small red-shift in the emission
band. The introduction of electron-donating groups also led to
an increase in the value of the fluorescence quantum yield (ΦF).
The AꢀπꢀDꢀπꢀA derivative 3 has a higher λabs value, a similar
λems value, and a lower quantum yield than the analogous
AꢀπꢀD compound 2d.
di(pyridin-2-yl)pyrimidine unit in the ground state. On the other
hand, when compounds 2h and 2i were excited in the dendron
absorption band at 282 and 281 nm, respectively, the fluores-
cence of the benzyl ether dendrons (λmax ∼ 345 nm) was
totally quenched, and this was accompanied by an increase in
the fluorescence intensity of the arylvinyl-2,6-di(pyridin-2-yl)-
pyrimidine moiety (λmax = 430 and 425 nm, respectively). These
results show that an efficient energy transfer from the Frꢀechet-
type dendrons to the arylvinyl-2,6-di(pyridin-2-yl)pyrimidine
unit takes place. Analogously, excitation of compound 2g also
led to quenching of the fluorescence of the dendritic wedge
(λmax ∼ 410 nm). In this case, a band at a maximum wavelength
of 505 nm was observed in the spectrum. The ability of both PPV
and Frꢀechet-type dendrons to act as extremely efficient light-
harvesting antennae that are capable of transferring light energy
has been well documented.18
As far as the dendritic materials are concerned, the UV/vis
spectra of compounds 2gꢀi consist of a simple superposition of
the absorptions due to the independent chromophores. The
spectra exhibited insignificant red shifts in the absorption bands,
indicating a negligible intramolecular interaction between
the donor dendritic wedges and the acceptor arylvinyl-2,6-
In general, larges Stokes shifts were obtained for the com-
pounds under investigation. As observed in related structures,13
this phenomenon is especially relevant for dendritic com-
pound 2g and indicates large differences (vibrational, electro-
nic, geometric) between the FranckꢀCondon state and the
excited state.
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Table 3. Optical Properties of 2,6-Di(pyridin-2-yl)pyrimidines 2bꢀd, 2f, and 2g in Various Aprotic Solvents
n-hexane
THF
CH2Cl2
DMSO
ΔET(30) = 59.0
UV/vis
ΔET(30)a = 0.0
ΔET(30) = 27.2
ΔET(30) = 42.7
UV/vis
PL
UV/vis
PL
UV/vis
PL
PL
compd
λmax, nm
λmax, nm
λmax, nm
λmax, nm
λmax, nm
λmax, nm
λmax, nm
λmax, nm
2b
2c
2d
2f
281, 339
276, 395
279, 399
279, 328
285, 329
410, 432
435, 458
441, 463
433
281, 341
280, 409
281, 411
281, 331
291, 331
445
531
517
421
480
283, 339
278, 413
282, 416
281, 331
293, 332
484
540
540
423
505
285, 346
278, 422
283, 418
283, 334
291, 334
506
598
575
423
553
2g
412, 428
a DimrothꢀReichardt polarity parameter, J molꢀ1
.
3
The optical properties of the water-soluble derivative 2j were
also measured in water and compared to those obtained in
CH2Cl2. Whereas changes were not observed in the absorbance
spectrum (λabs = 280 and 355 nm), a red-shifted emission band
(λem = 535 nm) that led to a high Stokes shift (9650 cmꢀ1) was
obtained, and this was accompanied by a decrease in the value of
the fluorescence quantum yield (ΦF < 0.01).
Solvatochromic Behavior. We investigated the absorbance
and emission behaviors of di(pyridin-2-yl)pyrimidines 2bꢀd, 2f,
and the dendritic derivative 2g in different aprotic solvents (n-
hexane, THF, CH2Cl2, and DMSO). The corresponding spec-
troscopic data are collected in Table 3. The slight, irrelevant
changes observed in the absorption spectra again reveal an
insignificant intramolecular interaction between donor and ac-
ceptor groups in the ground state. In contrast, the emission
spectra exhibit distinct solvent dependence. Broad structureless
emissions and larger Stokes shifts were observed on increasing
the solvent polarity along with a decrease in the fluorescence
intensity (see Supporting Information, Figures S1ꢀS5). The
correlation of the emission maxima with the solvent-dependent
ΔET(30) DimrothꢀReichardt polarity parameter is represented
in Figure 2 and was found to be positively linear for di(pyridin-2-
yl)pyrimidines 2bꢀd and 2g. This is typical solvatochromic
behavior for compounds that undergo an internal charge transfer
upon excitation, leading to a highly polar, charge-separated
emitting state stabilized by polar solvents.13,24 Indeed, the
presence of strong electron-donating substituents such as di-
methylamine (2c) or diphenylamine (2d) gave rise to larger
slopes (Figure 2) compared to moderate electron-donating
substituents (2b or 2g), indicating a stronger influence of the
solvent polarity. As expected, compound 2f, which contains an
electron-withdrawing group, did not show a red-shift in either
absorbance or emission because formation of the charge transfer
state was unfeasible.
Nevertheless, when methanol was used as solvent, the results
could not be explained on the basis of the solvent polarity,
suggesting that hydrogen bonding may play an important role.
Consequently, the solvatochromic behavior of compounds 2b,
2d, and 2g was also studied in polar, protic solvents such as
2-propanol, ethanol, and methanol (Table 4). Similar UV/vis
spectra were obtained for these compounds on increasing the
polarity and the hydrogen bonding values of the solvents (see
Supporting Information, Figures S6ꢀS8). The absorption spec-
tra are also comparable with those obtained in aprotic solvents.
Thus, polar solvents do not seem to induce significant changes in
Figure 2. Emission wavelength (λmax) as a function of Dimrothꢀ
Reichardt polarity parameter for compounds 2bꢀd, 2f, and 2g.
Table 4. Optical Properties of 2,6-Di(pyridin-2-yl)pyrimidines
2b, 2d, and 2h in Polar, Protic Solvents
2-propanol
ΔET(30)a = 82.8
Rb = 0.76
ethanol
ΔET(30) = 87.9
R = 0.86
methanol
ΔET(30) = 103.0
R = 0.98
UV/vis
PL
UV/vis
PL
UV/vis
PL
compd λmax, nm λmax, nm λmax, nm λmax, nm λmax, nm λmax, nm
2b
2d
2g
284, 341
282, 416
291, 327
415
557
535
284, 342 425
283, 417 574
284, 342
283, 416
327
431
590
410
327 440, 550
a DimrothꢀReichardt polarity parameter, J molꢀ1
.
b Hydrogen bond-
3
ing parameter.
the ground state. The lack of correlation of the emission maxima
with the solvent polarity can be explained by the presence of a
good hydrogen bond acceptor (the pyrimidine ring). The excited
states are definitely changed by hydrogen bonding interactions
and become more energetic. A solvent-induced red-shift of the
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Figure 3. Normalized emission spectra of 2b (left) and 2d (right) in protic solvents. Inset: wavelength as a function of DimrothꢀReichardt polarity
parameter. For a UVꢀvis version, see Supporting Information, Figures S6 and S7.
Figure 5. Top: Change in color of THF solutions of several di(pyridin-
2-yl)pyrimidines (c = 6.3 ꢁ 10ꢀ6 to 1.3 ꢁ 10ꢀ5 M) in the presence of
10ꢀ2 M p-TSA. Bottom: Change in color of THF solutions of 3 with
increasing p-TSA concentration.
Figure 4. Normalized emission spectra of 2g in protic solvents. For a
UVꢀvis version, see Supporting Information Figure S8.
compounds 2bꢀe underwent significant color changes in the
presence of p-TSA (para-toluenesulfonic acid, 10ꢀ2 M)
(Figure 5). This color change was found to be fully reversible
by neutralization with a base such as Et3N.
The changes in the UVꢀvis spectra of 2b upon addition of
acid are illustrated in Figure 6. The spectra show the progressive
attenuation of the absorption band for the neutral compound on
increasing the concentration of acid, whereas a new red-shifted
band corresponding to the protonated species appeared. This is
a general behavior except for di(pyridin-2-yl)pyrimidine 2c
(Table 5, see Supporting Information for spectra of the other
compounds), for which a blue-shifted band could be observed—
probably due to the protonation of the more strongly basic
dimethylamino group.
As far as the PL spectra are concerned, only compounds 2b
and 2e remained slightly emissive after protonation, and these
showed a red-shifted fluorescence (Table 5 and Figure 6). In
contrast, di(pyridin-2-yl)pyrimidines 2cꢀd and 3 became none-
missive upon addition of p-TSA. In these cases, not only the
pyrimidine ring but also the dimethyl and diphenylamino groups
can be protonated, and therefore their ability to donate electrons
is significantly attenuated.
emission maxima was found for derivatives 2b and 2d on
increasing the polarity, once again suggesting the formation of
a charge transfer emitting state (Figure 3). The positive linear
correlation between the emission maxima and the ΔET(30)
DimrothꢀReichardt polarity parameter indicates that the effect
of hydrogen bonding is comparable for all alcoholic solvents. In
contrast, this effect is not comparable for all alcohols in the
dendritic compound 2g. In this case, the emission maximum was
totally dependent on the hydrogen bonding parameter: i.e., as the
hydrogen bonding ability increased, the excited state also in-
creased in energy (see Figure 4).
Protonation Studies. In a previous study,13 we demonstrated
the ability of related 4,6-bis(arylvinyl)pyrimidines to function as
colorimetric and luminescent pH sensors due to the basic
character of the nitrogen atoms of the pyrimidine ring. From
this point of view, we decided to evaluate the effect of proton-
ation on the optical properties of several of the prepared di-
(pyridin-2-yl)pyrimidines (2bꢀe and 3). In an analogous way to
their bis(arylvinyl)pyrimidine counterparts, THF solutions of
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Figure 6. Changes in the absorption (left) and emission (right) spectra of 2b (2.0 ꢁ 10ꢀ5 M in THF) upon addition of p-TSA (7.5 ꢁ 10ꢀ5 M to a large
excess).
in an effort to tune their optoelectronic properties, will be
reported elsewhere.
Table 5. Optical Properties of Di(pyridin-2-yl)pyrimidines
2bꢀe and 3g upon Addition of p-TSA
UV/vis (p-TSA 10ꢀ2 M in THF)
PL (THF)
Stokes shift
cmꢀ1
’ EXPERIMENTAL SECTION
compda
λmax, nm (ε, Mꢀ1.cmꢀ1
)
λmax, nm
General. In air- and moisture-sensitive reactions, all glassware was
flame-dried and cooled under Ar. NMR spectra were acquired at 25 °C.
Chemical shifts are given in parts per million relative to TMS (1H, 0.0
ppm), CDCl3 (13C, 77.0 ppm), and CFCl3 (19F, 0.0 ppm). IR spectra
were recorded on an FT-IR spectrophotometer equipped with an ATR
accessory. UV/vis and fluorescence spectra were recorded using stan-
dard 1 cm quartz cells. Compounds were excited at their absorption
maxima (band of lowest energy) for recording the emission spectra
(uncorrected); however, different wavelengths were used to determine
fluorescence quantum yields in cases where compounds and standards
absorbed significantly. All solutions were measured with optical densities
below 0.1. Stokes shifts were calculated considering the lowest energetic
absorption band. MALDI-TOF mass spectra were registered in positive
reflection mode using dithranol as the matrix material. Melting
points are uncorrected. 3,4,5-Tris(2,5,8,11-tetraoxatridecan-13-yloxy)-
benzaldehyde, used for the synthesis of 2j, was prepared according to the
literature.25
2b
2c
2d
2e
3
372 (14700)
542
--b
--b
8432
--
359 (13100)
297 (34800), 470 (19000)
420 (16100)
--
540
--b
5291
--
303 (33800), 521 (23700)
a All spectra were recorded at room temperature at c = 6.3 ꢁ 10ꢀ6 M to
1.3 ꢁ 10ꢀ5 M. b No fluorescence.
’ CONCLUSIONS
In summary, a new series of 2,6-di(pyridin-2-yl)pyrimidines
functionalized with phenylenevinylene groups at the 4-position
has been efficiently prepared by a straightforward two-step
synthetic methodology. The protocol permits not only the
incorporation of electron-donating and electron-withdrawing
groups at the end of the π-conjugated system but also functio-
nalization with water-soluble groups and dendritic wedges. The
resulting compounds were characterized using a variety of
techniques. The optical properties were studied and were found
to be comparable to those of the bis(arylvinyl)pyrimidine
counterparts previously reported by us.13 Thus, all of the
molecules present absorption wavelengths in the UV or visible
region and emit light with significant Stokes shifts. The results of
solvatochromism studies support the formation of very polar
excited intramolecular charge transfer states with terminal electron-
donating groups. Likewise, these 4-arylvinyl-2,6-di(pyridin-2-
yl)pyrimidines display a dramatic and reversible color change and
luminescence switching upon addition of acid. This phenomenon is
due to the protonation of the nitrogen atoms of the pyrimidine ring.
This behavior indicates that this type of material is also valuable for
the development of colorimetric and luminescent pH sensors.
Nevertheless, in contrast to bis(arylvinyl)pyrimidines, the pre-
sence of the 2,6-di(pyridin-2-yl)pyrimidine moiety enables the
coordination of different families of metal cations. An in-depth
study into the ability of these molecules to act as binding ligands,
4-Methyl-2,6-di(pyridin-2-yl)pyrimidine (1). A solution of
tetrakis(triphenylphosphine)palladium (338 mg, 0.293 mmol), 2-(tri-
butylstannyl)pyridine (90%) (2 g, 4.89 mmol), and 2,4-dichloro-6-
methylpyrimidine (318 mg, 1.95 mmol) in toluene (25 mL) was heated
under reflux for 48 h under argon. The mixture was allowed to cool, and
water (30 mL) was added. The mixture was filtered, and the aqueous
phase was extracted with ethyl acetate (3 ꢁ 30 mL). The combined
organic extracts were dried over MgSO4, filtered, and evaporated under
reduced pressure. The residue was purified by column chromatography
(alumina, eluent: hexanes to ethyl acetate) to give 394 mg (81%) of the
1
title compound as a beige solid. Mp 90ꢀ92 °C. H NMR (500 MHz,
CDCl3) δ 2.78 (s, 3H), 7.41ꢀ7.45 (m, 2H), 7.88ꢀ7.92 (m, 2H), 8.26 (s,
1H), 8.66 (d, 1H, J = 8.5 Hz), 8.69 (d, 1H, J = 8.0 Hz), 8.74ꢀ8.75 (m,
1H), 8.88ꢀ8.90 (m, 1H). 13C NMR and DEPT (125 MHz, CDCl3) δ
24.9 (CH3), 115.9 (CH), 122.1 (CH), 123.8 (CH), 124.7 (CH), 125.4
(CH), 136.9 (CH), 137.1 (CH), 149.5 (CH), 150.1 (CH), 154.1 (C),
155.2 (C), 162.8 (C), 163.2 (C), 169.5 (C). IR (ATR) ν 1578, 1565,
1466, 1435, 1369, 993, 806, 761 cmꢀ1. MALDI-TOF m/z 248.4 [Mþ].
Anal. Calcd for C15H12N4: C, 72.56; H, 4.87; N, 22.57. Found: C, 72.37;
H, 4.89; N, 22.43.
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ARTICLE
(E)-2,4-Di(pyridin-2-yl)-6-styrylpyrimidine (2a). Aliquat 336
(20 mg, 0.049 mmol), benzaldehyde (60 mg, 0.570 mmol), 4-methyl-
2,6-di(pyridin-2-yl)pyrimidine 1 (118 mg, 0.475 mmol), and aqueous 5
M NaOH (10 mL) were placed in a 50 mL round-bottomed flask. The
reaction mixture was heated under reflux with stirring for 6 h. The
mixture was allowed to cool and was diluted with water (50 mL) and
extracted with ethyl acetate (3 ꢁ 20 mL). The combined organic extracts
were dried (MgSO4), filtered, and evaporated under reduced pressure.
The residue was purified by column chromatography (alumina, eluent:
hexane/ethyl acetate, 3:7) to give 117 mg (73%) of 2a as a beige solid.
Mp 170ꢀ171 °C. 1H NMR (500 MHz, CDCl3) δ 7.35ꢀ7.46 (m, 6H),
7.77 (d, 2H, J = 7.5 Hz), 7.92 (dt, 2H, J = 2.0 and 8.0 Hz), 8.04 (d, 1H, J =
16.5 Hz), 8.53 (s, 1H), 8.70 (dt, 1H, J = 1.0 and 8.0 Hz), 8.74 (dt, 1H, J =
1.0 and 8.0 Hz), 8.78 (dq, 1H, J = 1.0 and 4.5 Hz), 8.92 (dq, 1H, J = 1.0
and 5.0 Hz). 13C NMR and DEPT (125 MHz, CDCl3) δ 112.8 (CH),
122.2 (CH), 124.0 (CH), 124.7 (CH), 125.4 (CH), 127.0 (CH), 127.7
(CH), 128.9 (CH), 129.3 (CH), 135.9 (C), 136.8 (CH), 137.1 (CH),
137.5 (CH), 149.4 (CH), 150.1 (CH), 154.2 (C), 155.4 (C), 163.4 (C),
163.5 (C), 165.1 (C). IR (ATR) ν 1639, 1576, 1556, 1523, 1367, 972,
808, 767 cmꢀ1. MALDI-TOF m/z 336.7 [Mþ]. Anal. Calcd for
C22H16N4 (336.14): C, 78.55; H, 4.79; N, 16.66. Found: C, 78.30; H,
4.92; N, 16.36.
(E)-4-(4-Methylstyryl)-2,6-di(pyridin-2-yl)pyrimidine (2b).
This compound was prepared from Aliquat 336 (46 mg, 0.113 mmol),
4-methylbenzaldehyde (176 mg, 1.47 mmol), and 4-methyl-2,6-di-
(pyridin-2-yl)pyrimidine 1 (280 mg, 1.23 mmol) using the same
procedure described for 2a. The reaction mixture was heated under
reflux with stirring for 2 h. The residue was purified by crystallization
from a mixture of EtAcO/hexanes (10 mL, 1/1) to give 275 mg (64%) of
2b as a beige solid. Mp 142ꢀ144 °C. 1H NMR (500 MHz, CDCl3) δ
2.39 (s, 3H), 7.23 (d, 2H, J = 8.0 Hz), 7.38 (d, 1H, J = 16.0 Hz),
7.42ꢀ7.46 (m, 2H), 7.57 (d, 2H, J = 8.0 Hz), 7.91 (td, 2H, J = 1.5 and 7.5
Hz), 8.01 (d, 1H, J = 16.0 Hz), 8.51 (s, 1H), 8.70 (dt, 1H, J = 1.0 and 7.5
Hz), 8.73 (dt, 1H, J = 1.0 and 7.5 Hz), 8.77 (br d, 1H, J = 4.5 Hz), 8.91
(br d, 1H, J = 4.5 Hz). 13C NMR and DEPT (125 MHz, CDCl3) δ 21.4
(CH3), 112.7 (CH), 122.1 (CH), 123.9 (CH), 124.7 (CH), 125.4
(CH), 126.0 (CH), 127.7 (CH), 129.6 (CH), 133.1 (C), 136.9 (CH),
137.1 (CH), 137.5 (CH), 139.6 (C), 149.4 (CH), 150.1 (CH), 154.2
(C), 155.4 (C), 163.4 (C), 163.5 (C), 165.0 (C). IR (ATR) ν 1633,
1577, 1564, 1557, 1520, 1368, 968, 826, 764 cmꢀ1. MALDI-TOF m/z
350.5 [Mþ]. Anal. Calcd for C23H18N4: C, 78.83; H, 5.18; N, 15.99.
Found: C, 78.50; H, 4.92; N, 15.76.
procedure described for 2a. The reaction mixture was heated under reflux
with stirring for 2 h. The residue was purified by column chromatography
(alumina, eluent: hexane/ethyl acetate, 1:1) to give 295 mg (60%) of 2d as a
yellow solid. Mp 181ꢀ182 °C. 1H NMR (500 MHz, CDCl3) δ 7.04ꢀ7.11
(m, 4H), 7.12ꢀ7.18 (m, 4H), 7.27ꢀ7.34 (m, 5H), 7.40ꢀ7.46 (m, 2H),
7.52 (d, 2H, J = 8.5 Hz), 7.91 (td, 2H, J = 2.0 and 8.0 Hz), 7.99 (d, 1H, J =
16.0 Hz), 8.49 (s, 1H), 8.69 (br d, 1H, J = 8.0 Hz), 8.73 (br d, 1H, J = 8.0
Hz), 8.76 (br d, 1H, J = 4.5 Hz), 8.91 (br d, 1H, J = 4.5 Hz). 13C NMR and
DEPT (125 MHz, CDCl3) δ 112.4 (CH), 122.1 (CH), 122.2 (CH), 123.7
(CH), 123.9 (CH), 124.6 (CH), 124.7 (CH), 125.2 (CH), 125.3 (CH),
128.7 (CH), 129.2 (C), 129.4 (CH), 136.8 (CH), 137.0 (CH), 137.1
(CH), 147.1 (C), 149.0 (C), 149.4 (CH), 150.1 (CH), 154.3 (C), 155.5
(C), 163.2 (C), 163.5 (C), 165.2 (C). IR (ATR) ν 1627, 1575, 1562, 1519,
1487, 1469, 1369, 1269, 748 cmꢀ1. MALDI-TOF m/z 504.5 [M þ Hþ].
Anal. Calcd for C34H25N5 (503.21): C, 81.09; H, 5.00; N, 13.91. Found: C,
80.99; H, 5.26; N, 14.07.
(E)-4-[2-(6-Methoxynaphthalen-2-yl)vinyl]-2,6-di(pyridin-
2-yl)pyrimidine (2e). This compound was prepared from Aliquat 336
(26 mg, 0.064 mmol), 6-methoxy-2-naphthaldehyde (122 mg, 0.650
mmol), and 4-methyl-2,6-di(pyridin-2-yl)pyrimidine 1 (162 mg, 0.652
mmol) using the same procedure described for 2a. The reaction mixture
was heated under reflux with stirring for 6 h. The residue was washed
with ethanol to give 143 mg (52%) of 2e as a yellow solid. Mp
185ꢀ187 °C. 1H NMR (500 MHz, CDCl3) δ 3.95 (s, 3H),
7.15ꢀ7.20 (m, 2H), 7.42ꢀ7.46 (m, 3H), 7.61ꢀ7.83 (m, 3H),
7.85ꢀ8.10 (m, 3H), 8.20 (d, 1H, J = 16.5 Hz), 8.56 (s, 1H), 8.73 (d,
1H, J = 8.0 Hz), 8.77 (d, 1H, J = 8.0 Hz), 8.79 (br d, 1H, J = 4.5 Hz), 8.95
(br d, 1H, J = 4.0 Hz). 13C NMR and DEPT (125 MHz, CDCl3) δ 55.4
(CH3), 106.0 (CH), 112.9 (CH), 119.3 (CH), 122.2 (CH), 124.0
(CH), 124.3 (CH), 124.8 (CH), 125.5 (CH), 126.1 (CH), 127.5 (CH),
128.9 (C), 129.0 (CH), 130.0 (CH), 131.3 (C), 135.2 (C), 137.1 (CH),
137.2 (CH), 137.8 (CH), 149.4 (CH), 149.9 (CH), 154.2 (C), 155.2
(C), 158.5 (C), 163.3 (C), 163.5 (C), 165.0 (C). IR (ATR) ν 1622,
1575, 1556, 1519, 1467, 1371, 1259, 1174, 848, 780, 740, 675, 663 cmꢀ1
.
MALDI-TOF m/z 415.8 [Mþ]. Anal. Calcd for C27H20N4O (416.47):
C, 77.87; H, 4.84; N, 13.45. Found: C, 77.56; H, 4.72; N, 13.34.
(E)-2,4-Di(pyridin-2-yl)-6-(4-trifluoromethylstyryl)pyrimidine
(2f). This compound was prepared from Aliquat 336 (16 mg, 0.039 mmol),
4-(trifluoromethyl)benzaldehyde (102 mg, 0.586 mmol), 4-methyl-2,6-di-
(pyridin-2-yl)pyrimidine 1(97 mg, 0.391 mmol), and an aqueous solution of
sodium hydroxide (1 M, 15 mL) using the same procedure described for 2a.
The reaction mixture was heated under reflux with stirring for 20 h. The
residue was purified by column chromatography (alumina, eluent: hexane/
ethyl acetate, 1:1) to give 65 mg (41%) of 2f as a pale yellow solid. Mp
96ꢀ98 °C. 1H NMR (500 MHz, CDCl3) δ 7.45ꢀ7.47 (m, 2H), 7.47 (d,
1H, J = 16.5 Hz), 7.67 (d, 2H, J = 8.0 Hz), 7.76 (d, 2H, J = 8.0 Hz),
7.92ꢀ7.94 (m, 2H), 8.07 (d, 1H, J= 16.5 Hz), 8.54 (s, 1H), 8.71 (dd, 1H, J=
1.0and8.0Hz), 8.75(dd, 1H,J=1.0and8.0Hz),8.77(brd, 1H,J=4.5Hz),
8.93 (br d, 1H, J = 4.0 Hz). 13C NMR and DEPT (125 MHz, CDCl3) δ
113.3 (CH), 122.2 (CH), 124.0 (q, J = 270.2 Hz, CF3), 124.0 (CH), 124.9
(CH), 125.6 (CH), 125.8 (q, J = 3.7 Hz, CH), 127.7 (CH), 129.2 (CH),
130.7 (q, J = 32.6 Hz, C), 135.7 (CH), 137.0 (CH), 137.2 (CH), 139.2 (C),
149.5 (CH), 150.1 (CH), 153.9 (C), 155.0 (C), 163.5 (C), 163.9 (C), 164.1
(C). 19F NMR (282 MHz, CDCl3) δ ꢀ63.1. IR (ATR) ν 1555, 1369, 1379,
1163, 1109, 1065, 763 cmꢀ1. MALDI-TOF m/z 403.8 [Mþ]. Anal. Calcd
for C23H15F3N4 (404.12): C, 68.31; H, 3.74; N, 13.85. Found: C, 68.01; H,
3.83; N, 13.50.
(E)-4-(4-Dimethylaminostyryl)-2,6-di(pyridin-2-yl)pyrimidine
(2c). This compound was prepared from Aliquat 336 (52 mg, 0.126 mmol),
4-(dimethylamino)benzaldehyde (227 mg, 1.52 mmol), and 4-methyl-2,6-
di(pyridin-2-yl)pyrimidine 1 (315 mg, 1.27 mmol) using the same proce-
dure described for 2a. The reaction mixture was heated under reflux with
stirring for 2 h. The residue was washed with a hot ethanol to give 281 mg
(58%) of2c as a red solid. Mp 182ꢀ184 °C. 1H NMR (500 MHz, CDCl3) δ
3.04 (s, 6H), 6.74 (d, 2H, J = 9.0 Hz), 7.22 (d, 1H, J = 16.0 Hz), 7.41ꢀ7.45
(m, 2H), 7.57 (d, 2H, J = 8.0 Hz), 7.91 (td, 2H, J = 2.0 and 8.0 Hz), 7.98 (d,
1H, J = 16.0 Hz), 8.45 (s, 1H), 8.70 (br d, 1H, J = 8.5 Hz), 8.71 (br d, 1H, J =
8.5 Hz), 8.77 (br d, J = 4.0 Hz, 1H), 8.91 (br d, J = 4.0 Hz, 1H). 13C NMR
and DEPT (125 MHz, CDCl3) δ 40.2 (CH3), 112.0 (CH), 112.1 (CH),
122.1 (CH), 122.3 (CH), 123.9 (CH), 124.0 (C), 124.5 (CH), 125.2
(CH), 129.2 (CH), 136.6 (CH), 137.1 (CH), 138.0 (CH), 149.4 (CH),
150.1 (CH), 151.2 (C), 154.5 (C), 155.6 (C), 162.9 (C), 163.4 (C), 165.7
(C). IR (ATR) ν 1602, 1556, 1508, 1359, 1182, 974, 810, 764, 740 cmꢀ1
.
(E,E,E)-4-{3,5-Bis[4-(hexyloxy)styryl]styryl}-2,6-di(pyridin-2-yl)-
pyrimidine (2g). This compound was prepared from Aliquat 336 (12 mg,
0.029 mmol), 3,5-bis[4-(hexyloxy)styryl]benzaldehyde (165 mg, 0.323
mmol), and 4-methyl-2,6-di(pyridin-2-yl)pyrimidine 1 (73 mg, 0.294
mmol) using the same procedure described above for 2a. The residue
was dissolved in hot ethyl acetate and precipitated with cold ethanol to give
120 mg (55%) of 2g as a yellow solid. Mp 80ꢀ82 °C. 1H NMR (500 MHz,
MALDI-TOF m/z 380.4 [M þ Hþ]. Anal. Calcd for C24H21N5 (379.18):
C, 75.97; H, 5.58; N, 18.46. Found: C, 75.64; H, 5.46; N, 18.17.
(E)-4-(4-Diphenylaminostyryl)-2,6-di(pyridin-2-yl)pyrimidine
(2d). This compound was prepared from Aliquat 336 (40 mg, 0.098 mmol),
4-(diphenylamino)benzaldehyde (346 mg, 1.27 mmol), and 4-methyl-2,6-
di(pyridin-2-yl)pyrimidine 1 (242 mg, 0.975 mmol) using the same
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ARTICLE
CDCl3) δ 0.88ꢀ0.85 (m, 6H), 1.32ꢀ1.40 (m, 8H), 1.45ꢀ1.53 (m, 4H),
1.81 (m, 4H), 4.00 (t, 4H, J = 7.5 Hz), 6.93 (d, 4H,J = 8.5 Hz), 7.02 (d, 2H,
J = 16.0 Hz), 7.17 (d, 2H, J = 16.0 Hz), 7.42ꢀ7.46 (m, 2H), 7.48ꢀ7.55 (m,
5H), 7.57 (s, 1H), 7.68 (s, 2H), 7.92 (dt, 2H, J = 1.0 and 7.5 Hz), 8.04 (d,
1H, J = 16.0 Hz), 8.59 (s, 1H), 8.72 (d, 1H, J = 8.0 Hz), 8.74 (d, 1H, J = 8.0
Hz), 8.79 (br d, 1H, J = 5.0 Hz), 8.94 (br d, 1H, J = 5.0 Hz). 13C NMR and
DEPT (125 MHz, CDCl3) δ 14.0 (CH3), 22.6 (CH2), 25.7 (CH2), 29.2
(CH2), 31.6 (CH2), 68.1 (CH2), 112.7 (CH), 114.8 (CH), 122.2 (CH),
124.0 (CH), 124.1 (CH), 124.7 (CH), 125.3 (CH), 125.4 (CH), 125.7
(CH), 127.5 (CH), 127.8 (CH), 129.2 (CH), 129.7 (C), 136.5 (C), 136.8
(CH), 137.1 (CH), 137.4 (CH), 138.6 (C), 149.5 (CH), 150.2 (CH),
154.2 (C), 155.4 (C), 159.1 (C), 163.6 (C), 164.8 (C). IR (ATR) ν 1633,
1576, 1508, 1369, 1244, 1172, 958 cmꢀ1. MALDI-TOF m/z 741.3 [M þ
Hþ]. Anal. Calcd for C50H52N4O2 (740.41): C, 81.05; H, 7.07; N, 7.56.
Found: C, 80.75; H, 6.79; N, 7.34.
(E)-4-[3,5-Bis-(benzyloxy)styryl]-2,6-di(pyridin-2-yl)pyri-
midine (2h). This compound was prepared from Aliquat 336 (24 mg,
0.059 mmol), 3,5-dibenzyloxybenzaldehyde (187 mg, 0.588 mmol),
and 4-methyl-2,6-di(pyridin-2-yl)pyrimidine 1 (146 mg, 0.588 mmol)
using the same procedure described for 2a. The reaction mixture was
heated under reflux with stirring for 6 h. The reaction mixture was
extracted with CH2Cl2 (3 ꢁ 20 mL). The residue was washed with a
mixture of EtOH/hexanes and then with MeOH to give 210 mg (65%)
of 2h as a white solid. Mp 154ꢀ156 °C. 1H NMR (500 MHz, CDCl3)
δ 5.09 (s, 4H), 6.65 (t, 1H, J = 2.0 Hz), 6.92 (d, 2H, J = 2.0 Hz),
7.36ꢀ7.44 (m, 13H), 7.91 (br t, 2H, J = 8.0 Hz), 7.93 (d, 1H, J = 16.0
Hz), 8.52 (s, 1H), 8.70 (d, 1H, J = 8.0 Hz), 8.73 (d, 1H, J = 8.5 Hz),
8.77 (br d, 1H, J = 4.0 Hz), 8.91 (br d, 1H, J = 4.5 Hz). 13C NMR and
DEPT (125 MHz, CDCl3) δ 70.1 (CH2), 103.7 (CH), 106.6 (CH),
112.8 (CH), 122.1 (CH), 124.0 (CH), 124.7 (CH), 125.4 (CH), 127.5
(CH), 127.6 (CH), 128.0 (CH), 128.6 (CH), 136.7 (C), 136.9 (CH),
137.1 (CH), 137.4 (CH), 137.8 (C), 149.4 (CH), 150.1 (CH), 154.1
(C), 155.3 (C), 160.2 (C), 163.5 (C), 163.6 (C), 164.7 (C). IR (ATR)
ν 1639, 1591, 1575, 1562, 1519, 1435, 1371, 1160, 1043, 968, 821, 738,
678 cmꢀ1. MALDI-TOF m/z 570.2 [M þ Naþ]. Anal. Calcd for
C36H28N4O2 (548.63): C, 78.81; H, 5.14; N, 10.21. Found: C, 78.50;
H, 4.93; N, 9.99.
(E)-4-{3,5-Bis[3,5-bis(benzyloxy)benzyloxy]styryl}-2,6-
di(pyridin-2-yl)pyrimidine (2i). This compound was prepared
from Aliquat 336 (14 mg, 0.033 mmol), 3,5-bis[3,5-bis(benzyloxy)ben-
zyloxy]benzaldehyde (248 mg, 0.334 mmol), and 4-methyl-2,6-di-
(pyridin-2-yl)pyrimidine 1 (83 mg, 0.588 mmol) using the same
procedure described for 2h. The residue was washed with a mixture of
EtOH/hexanes and then with MeOH to give 148 mg (48%) of 2i as a
white solid. Mp 157ꢀ159 °C. 1H NMR (500 MHz, CDCl3) δ 5.04 (s,
4H), 5.06 (s, 8H), 6.59 (t, 2H, J = 2.5 Hz), 6.62 (t, 1H, J = 2.0 Hz), 6.72
(d, 4H, J = 2.5 Hz), 6.92 (d, 2H, J = 2.0 Hz), 7.28ꢀ7.48 (m, 23H), 7.91
(td, 2H, J = 1.5 and 7.5 Hz), 7.98 (d, 1H, J = 16 Hz), 8.54 (s, 1H), 8.74
(br d, 1H, J = 7.5 Hz), 8.76 (br d, 1H, J = 4.0 Hz), 8.81 (br d, 1H, J = 8.0
Hz), 8.96 (br d, 1H, J = 4.5 Hz). 13C NMR and DEPT (125 MHz,
CDCl3) δ 70.0 (CH2), 70.1 (CH2), 101.7 (CH), 103.7 (CH), 106.3
(CH), 106.8 (CH), 113.2 (CH), 122.4 (CH), 124.1 (CH), 125.0 (CH),
125.5 (CH), 127.5 (CH), 127.6 (CH), 128.0 (CH), 128.6 (CH), 136.8
(C), 137.2 (CH), 137.6 (CH), 137.8 (C), 139.1 (C), 149.4 (CH), 149.5
(CH), 154.0 (C), 154.6 (C), 160.1 (C), 160.2 (C), 162.8 (C), 163.8
(C), 164.7 (C). IR (ATR) ν 1591, 1444, 1371, 1149, 1049, 825, 736,
694 cmꢀ1. MALDI-TOF m/z 973.0 [Mþ]. Anal. Calcd for C64H52N4O6
(973.12): C, 78.99; H, 5.39; N, 5.76. Found: C, 78.63; H, 5.31; N, 5.56.
(E)-2,4-Di(pyridin-2-yl)-6-[3,4,5-tris(2,5,8,11-tetraoxatridecan-
13-yloxy)styryl]pyrimidine (2j). This compound was prepared from
Aliquat 336 (17 mg, 0.042 mmol), 3,4,5-tris(2,5,8,11-tetraoxatridecan-13-
yloxy)benzaldehyde (0.303 mg, 0.419 mmol), and 4-methyl-2,6-di-
(pyridin-2-yl)pyrimidine 1 (104 mg, 0.419 mmol) using the same
procedure described above for 2a. The reaction mixture was heated under
reflux with stirring for 2 h. The residue was purified by precipitation from a
mixture of hexane/ether (10 mL, 1:1) to give 131 mg (33%) of 2j as a
1
yellow oil. H NMR (500 MHz, CDCl3) δ 3.37 (s, 6H), 3.38 (s, 3H),
3.52ꢀ3.60 (m, 6H), 3.62ꢀ3.70 (m, 24H), 3.73ꢀ3.76 (m, 6H), 3.81 (t,
2H, J = 5.5 Hz), 3.89 (t, 4H, J = 5.5 Hz), 4.19ꢀ4.25 (m, 6H), 6.92 (s, 2H),
7.30 (d, 1H, J = 16.0 Hz), 7.43ꢀ7.46 (m, 2H), 7.89 (d, 1H, J = 16.0 Hz),
7.90ꢀ7.94 (m, 2H), 8.53 (s, 1H), 8.71 (d, 1H, J = 8.0 Hz), 8.73 (d, 1H, J =
8.0 Hz), 8.77 (br d, 1H, J = 5.5 Hz), 8.92 (br d, 1H, J = 5.0 Hz). 13C NMR
and DEPT (125 MHz, CDCl3) δ 59.0 (CH3), 68.8 (CH2), 69.7 (CH2),
70.5 (CH2), 70.5 (CH2), 70.6 (CH2), 70.6 (CH2), 70.6 (CH2), 70.6
(CH2), 70.7 (CH2), 70.8 (CH2), 71.9 (CH2), 72.4 (CH2), 107.1 (CH),
112.5 (CH), 122.1 (CH), 124.0 (CH), 124.7 (CH), 125.4 (CH), 126.4
(CH), 131.2 (C), 136.9 (CH), 137.1 (CH), 137.2 (CH), 139.6 (C), 149.4
(CH), 150.1 (CH), 152.8 (C), 154.2 (C), 155.3 (C), 163.4 (C), 163.5
(C), 164.8 (C). IR (ATR) ν 1634, 1576, 1562, 1327, 1246, 1097,
768 cmꢀ1. MALDI-TOF m/z 955.1 [M þ Hþ]. Anal. Calcd for
C49H70N4O15: C, 61.62; H, 7.39; N, 5.87. Found: C, 61.32; H, 7.13;
N, 5.71.
4-{(E)-2-[2,6-Di(pyridin-2-yl)pyrimidin-4-yl]vinyl}-N-(4-{(E)-
2-[2,6-di(pyridin-2-yl)pyrimidin-4-yl]vinyl}phenyl)-N-phe-
nylaniline (3). This compound was prepared from Aliquat 336
(12 mg, 0.029 mmol), 4,40-diformyltriphenylamine (87 mg, 0.288
mmol), and 4-methyl-2,6-di(pyridin-2-yl)pyrimidine 1 (150 mg, 0.604
mmol) using the same procedure described above for 2a after 14 h
under reflux. The residue was washed with ethanol to give 126 mg
(57%) of 3 as an orange solid. Mp 184ꢀ186 °C. 1H NMR (500 MHz,
CDCl3) δ 7.15 (d, 5H, J = 9.0 Hz), 7.20 (d, 2H, J = 8.0 Hz), 7.32 (d,
2H, J = 16.5 Hz), 7.35 (t, 2H, J = 8.5 Hz), 7.44 (m, 4H), 7.57 (d, 4H, J =
9.0 Hz), 7.89ꢀ7.95 (m, 4H), 7.99 (d, 2H, J = 16.5 Hz), 8.50 (s, 2H),
8.70 (d, 2H, J = 8.0 Hz), 8.77 (d, 2H, J = 8.0 Hz), 7.77 (br d, 2H, J = 4.5
Hz), 8.92 (br d, 2H, J = 5.0 Hz). 13C NMR and DEPT (125 MHz,
CDCl3) δ 112.6 (CH), 122.2 (CH), 123.6 (CH), 1 24.0 (CH), 124.4
(CH), 124.7 (CH), 125.2 (CH), 125.4 (CH), 125.8 (CH), 128.8
(CH), 129.6 (CH), 130.3 (C), 136.9 (CH), 137.1 (CH), 146.6 (C),
148.3 (C), 149.4 (CH), 150.0 (CH), 154.3 (C), 155.4 (C), 163.3 (C),
163.4 (C), 165.1 (C). IR (ATR) ν 1556, 1504, 1367, 1274, 1177,
764 cmꢀ1. MALDI-TOF m/z 784.0 [M þ Naþ]. Anal. Calcd for
C50H35N9: C, 78.82; H, 4.63; N, 16.55. Found: C, 78.53; H, 4.30;
N, 16.32.
’ ASSOCIATED CONTENT
1
Supporting Information. Copies of H NMR and 13C
S
b
NMR spectra for all compounds and absorption and emission
spectra in various solvents and with increasing p-TSA concentra-
tion. This material is available free of charge via the Internet at
http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: joaquinc.garcia@uclm.es; julian.rodriguez@uclm.es.
’ ACKNOWLEDGMENT
Financial support from the Junta de Comunidades de Castilla-
La Mancha (JCCM, project PCI08-0033) is gratefully acknowl-
edged. C. H. also thanks the JCCM and Fondo Social Europeo
for a postdoctoral fellowship.
’ REFERENCES
(1) (a) Tschierske, C. J. Mater. Chem. 2001, 11, 2647–2671. (b)
Tschierske, C. Annu. Rep. Prog. Chem., Sect. C 2001, 97, 191–267.
3844
dx.doi.org/10.1021/jo200204u |J. Org. Chem. 2011, 76, 3837–3845

The Journal of Organic Chemistry
ARTICLE
(2) (a) Kraft, A.; Grimsdale, A. C.; Holmes, A. B. Angew. Chem., Int. Ed.
1998, 37, 402–428. (b) Mitschke, U.; B€auerle J. Mater. Chem. 2000,
10, 1471–1509. (c) Lo, S.-C.; Burn, P. L. Chem. Rev. 2007, 107,
1097–1116.
(f) Li, L.; Tian, Y.; Yang, J.; Sun, P.; Kong, L.; Wu, J.; Zhou, H.; Zhang, S.;
Jin, B.; Tao, X.; Jiang, M. Chem. Commun. 2010, 46, 1673–1675.
(15) Polson, M. I. J.; Loiseau, F.; Campagna, S.; Hanan, G. S. Chem.
Commun. 2006, 1301–1303.
(3) (a) Fichou, D. J. Mater. Chem. 2000, 10, 571–589. (b) Kim,
D. H.; Park, Y. D.; Jang, Y.; Yang, H.; Kim, Y. H.; Han, J. I.; Moon, D. G.;
Park, S.; Chang, T.; Chang, C.; Joo, M.; Ryu, C. Y.; Cho., K. Adv. Funct.
Mater. 2005, 15, 77–82. (c) Funahashi, M.; Zhang, F.; Tamaoki, N. Adv.
Mater. 2007, 19, 353–358.
(16) (a) Newkome, G. R.; Moorefield, C. N.; V€ogtle, F. Dendrimers
and Dendrons; Wiley-VCH: Weinheim, 2001. (b) Dendrimers and other
Dendritic Polymers; Frꢀechet, J. M. J., Tomalia, D. A., Eds.; Wiley:
Chichester, 2001. (c) Grayson, S. M.; Frꢀechet, J. M. Chem. Rev. 2001,
101, 3819–3867.
(4) (a) Tour, J. M. Acc. Chem. Res. 2000, 33, 791–804. (b) Tour, J. M.
Chem. Rev. 1996, 96, 537–554. (c) Wang, C.; Batsanov, A. S.; Bryce,
M. R.; Sage, I. Org. Lett. 2004, 6, 2181–2184. (d) Elbing, M.; Ochs,
R.; Koentopp, M.; Fisher, M.; von H€anisch, C.; Weigend, F.; Evers, F.;
Weber, H. B.; Mayor, M. Proc. Natl. Acad. Sci. U.S.A. 2005, 102,
8815–8820.
(5) (a) de Silva, A. P.; Gunaratne, H. Q. N.; Gunnlaugsson, T.;
Huxley, A. J. M.; McCoy, C. P.; Rademacher, J. T.; Rice, T. E. Chem. Rev.
1997, 97, 1515–1566. (b) Callan, J. F.; de Silva, A. P.; Magri, D. C.
Tetrahedron 2005, 61, 8551–8588.
(17) Astruc, D.; Boisselier, E.; Ornelas, C. Chem. Rev. 2010, 110,
1857–1959.
(18) (a) Burn, P. L.; Lo, S.-C.; Samuel, I. D. W. Adv. Mater. 2007,
19, 1675–1688. (b) Lo, S.-C.; Burn, P. L. Chem. Rev. 2007,
107, 1097–1116. (c) Adronov, A.; Frꢀechet, J. M. J. Chem. Commun.
2000, 1701–1710. (d) Stuart, G. M.; Fox, M. A. J. Am. Chem. Soc. 1996,
118, 4354–4360.
(19) García-Martínez, J. C.; Díez-Barra, E.; Rodríguez-Lꢀopez, J. Curr.
Org. Synth. 2008, 5, 267–290.
(20) (a) Hawker, C. J.; Frꢀechet, J. M. J. J. Am. Chem. Soc. 1990,
112, 7638–7647. (b) Hawker, C. J.; Frꢀechet, J. M. J. J. Chem. Soc., Chem.
Commun. 1990, 1010–1013.
(6) Bryan, A. J.; de Silva, A. P.; de Silva, S. A.; Rupasinghe, R. A. D.
D.; Sandanayake, K. R. A. S. Biosensors 1989, 4, 169–174.
(7) (a) Ajayagosh, A.; Carol, P.; Sreejith, S. J. Am. Chem. Soc. 2005,
127, 14962–14963. (b) Goodall, W.; Williams, J. A. G. Chem. Commun.
2001, 2514–2515. (c) Loren, J. C.; Siegel, J. S. Angew. Chem., Int. Ed.
2001, 40, 754–757. (d) Raw, S. A.; Taylow, R. J. K. Chem. Commun.
2004, 508–509. (e) Kozhevnikov, V. N.; Shabunina, O. V.; Kopchuk,
D. S.; Ustinova, M. M.; K€onig, B.; Kozhevnikov, D. N. Tetrahedron 2008,
64, 8963–8973. (f) Han, F.-S.; Higushi, M.; Kurth, D. G. Tetrahedron
2008, 64, 9108–9116.
(8) For recent reviews: (a) Cooke, M. W.; Hanan, G. S. Chem. Soc.
Rev. 2007, 36, 1466–1476. (b) Constable, E. C. Chem. Soc. Rev. 2007,
36, 246–253. (c) Kurth, D. G.; Higushi, M. Soft Mater. 2006, 2, 915–927.
(d) Andres, P. R.; Schubert, U. S. Adv. Mater. 2004, 16, 1043–1068.
(9) See for example: (a) Cooke, M. W.; Hanan, G. S.; Loiseau, F.;
Campagna, S.; Watanabe, M.; Tanaka, Y. J. Am. Chem. Soc. 2007,
129, 10479–10488. (b) Camerel, F.; Ziessel, R.; Donnio, B.; Bourgogne,
C.; Guillon, D.; Schmutz, M.; Iacovita, C.; Bucher, J. P. Angew. Chem., Int.
Ed. 2007, 46, 2659–2662. (c) Carlsson, C. N.; Kuehl, C. J.; Da-Re, R. E.;
Veautier, J. M.; Schelter, E. J.; Milligan, A. E.; Scott, B. L.; Bauer, E. D.;
Thompson, J. D.; Morris, D. E.; John, K. D. J. Am. Chem. Soc. 2006,
128, 7230–7241. (d) Coppo, P.; Duati, M.; Kozhevnikov, V. N.;
Hofstraat, J. W.; De Cola, L. Angew. Chem., Int. Ed. 2005, 44, 1806–1810.
(10) (a) Itami, K.; Yamazaki, D.; Yoshida, J.-i. J. Am. Chem. Soc. 2004,
126, 15396–15397. (b) Achelle, S.; Ramondenc, Y.; Marsais, F.; Plꢀe, N.
Eur. J. Org. Chem. 2008, 3129–3140. (c) Achelle, S.; Ramondenc, Y.;
Dupas, G.; Plꢀe, N. Tetrahedron 2008, 64, 2783–2791. (d) Bagley, M. C.;
Lin, Z.; Pope, S. J. A. Tetrahedron Lett. 2009, 50, 6818–6822. (e) Achelle,
S.; Plꢀe, N.; Kreher, D.; Attias, A.-J.; Arfaoui, I.; Charra, F. Tetrahedron
Lett. 2009, 50, 7055–7058.
(21) Pan, Y.; Lu, M.; Peng, Z.; Melinger, J. S. Org. Biomol. Chem.
2003, 1, 4465–4470.
(22) (a) Stille, J. K. Angew. Chem., Int. Ed. Engl. 1986, 25, 508–524.
(b) Espinet, P.; Echavarren, A. M. Angew. Chem., Int. Ed. 2004,
43, 4707–4734.
(23) Vanden Eynde, J. J.; Pascal, L.; Van Haverbeke, Y.; Dubois, P.
Synth. Commun. 2001, 31, 3167–3173.
(24) (a) Katan, C.; Terenziani, F.; Mongin, O.; Werts, M. H. V.;
Porrꢁes, L.; Pons, T.; Metz, J.; Tretiak, S.; Blanchard-Desce, M. J. Phys.
Chem. A 2005, 109, 3024–3037. (b) Lartia, R.; Allain, C.; Bordeau, G.;
Schmidt, F.; Fiorini-Debuischert, C.; Charra, F.; Teulade-Fichou, M.-P.
J. Org. Chem. 2008, 73, 1732–1744. (c) Achelle, S.; Saettel, N.; Baldeck,
P.; Teulade-Fichou, M.-P.; Maillard, P. J. Porphyrins Phthalocyanines
2010, 14, 877–884. (d) Lincker, F.; Kreher, D.; Attias, A.-J.; Do, J.; Kim,
^
E.; Hapiot, P.; Lemaitre, N.; Geffroy, B.; Ulrich, G.; Ziessel, R. Inorg.
Chem. 2010, 49, 3991–4001.
(25) Zheng, Q.; Bonoiu, A.; Ohulchanskyy, T. Y.; He, G. S.; Prasad,
P. N. Mol. Pharmaceutics 2008, 5, 389–398.
(11) Lin, Y.-C.; Lai, C. K.; Chang, Y.-C.; Liu, K.-T. Liq. Cryst. 2002,
29, 237–242.
(12) (a) Pascal, L.; Vanden Eynde, J.-J.; Van Haverbeke, Y.; Dubois,
P.; Rant, U.; Zojer, E.; Leising, G.; Lazzaroni, R.; Cornil, J.; Brꢀedas, J.-L.
Synth. Met. 2001, 119, 183–184. (b) Pascal, L.; Vanden Eynde, J.-J.; Van
Haverbeke, Y.; Dubois, P.; Michel, A.; Rant, U.; Zojer, E.; Leising, G.;
Van Dorn, L. O.; Gruhn, N. E.; R.; Cornil, J.; Brꢀedas, J.-L. J. Phys. Chem. B
2002, 106, 6442–6450.
(13) Achelle, S.; Nouira, I.; Pfaffinger, B.; Ramondenc, Y.; Plꢀe, N.;
Rodríguez-Lꢀopez, J. J. Org. Chem. 2009, 74, 3711–3717.
(14) (a) Liu, B.; Hu, X.-L.; Liu, J.; Zhao, Y.-D.; Huang, Z.-L.
Tetrahedron Lett. 2007, 48, 5958–5962. (b) Liu, Z.; Chen, T.; Liu, B.;
Huang, Z.-L.; Huang, T.; Li, S.; Xu, Y.; Qin, J. J. Mater. Chem. 2007,
17, 4685–4689. (c) Liu, Z.; Shao, P.; Huang, Z.; Liu, B.; Chen, T.; Qin, J.
Chem. Commun. 2008, 2260–2262. (d) Li, L.; Tic-an, Y.-P.; Yang, J.-X.;
Sun, P.-P.; Wu, J.-Y.; Zhou, H.-P.; Zhang, S.-Y.; Jin, B.-K.; Xing, X.-J.;
Wang, C.-K.; Li, M.; Cheng, G.-H.; Tang, H.-H.; Huang, W.-H.; Tao,
X.-T.; Jiang, M.-H. Chem. Asian J. 2009, 4, 668–680. (e) Akdas-Kilig, H.;
Roisnel, T.; Ledoux, I.; Le Bozec, H. New. J. Chem. 2009, 33, 1470–1473.
3845
dx.doi.org/10.1021/jo200204u |J. Org. Chem. 2011, 76, 3837–3845