Microwave-assisted selective synthesis of mono- and bistriazines with π-conjugated spacers and study of the optoelectronic properties

Article abstract of DOI:10.1021/jo500480r

A series of mono- and bistriazine derivatives were selectively prepared in high yields using microwave irradiation. Donor substituents were attached on the triazine ring, including pyrazolyl-substituted anilines and o-, m-, and p-phenylenediamine as π-conjugated spacers. This method was used to build σ-π-σ-A-σ-D systems for monotriazines and D-σ-A-σ-π-σ-A-σ-D systems for bistriazines. A study of the optoelectronic properties was performed by UV-vis and fluorescence spectroscopy and cyclic voltammetry. The monotriazines do not show any emission, but the bistriazines are blue emitters and show an interesting solvatochromic effect with large Stokes shifts of more than 10 000 cm^-1 in some cases and quantum yields up to 23%. The optoelectronic properties depend on the conjugation and the position and donor character of the substituents and spacers. Cyclic voltammetry was used to determine the energy levels (HOMO and LUMO) in the bistriazines. An increase in the energy of the HOMO and a decrease in the energy of the LUMO were observed upon extending the conjugation. The title compounds showed interesting properties for use in optoelectronic devices, especially as blue emitters.

Full text of DOI:10.1021/jo500480r

Article
pubs.acs.org/joc
Microwave-Assisted Selective Synthesis of Mono- and Bistriazines
with π‑Conjugated Spacers and Study of the Optoelectronic
Properties
A. Ruiz-Carretero,† O. Noguez,‡ T. Herrera, J. R. Ramírez, A. Sanchez-Migallon,* and A. de la Hoz*
́
́
́
Departamento de Química Organica, Facultad de Ciencias y Tecnologías Químicas, Universidad de Castilla-La Mancha, 13071
Ciudad Real, Spain
S
* Supporting Information
ABSTRACT: A series of mono- and bistriazine derivatives
were selectively prepared in high yields using microwave
irradiation. Donor substituents were attached on the triazine
ring, including pyrazolyl-substituted anilines and o-, m-, and p-
phenylenediamine as π-conjugated spacers. This method was
used to build σ−π−σ−A−σ−D systems for monotriazines and
D−σ−A−σ−π−σ−A−σ−D systems for bistriazines. A study of
the optoelectronic properties was performed by UV−vis and
fluorescence spectroscopy and cyclic voltammetry. The
monotriazines do not show any emission, but the bistriazines
are blue emitters and show an interesting solvatochromic effect
with large Stokes shifts of more than 10 000 cm−1 in some
cases and quantum yields up to 23%. The optoelectronic properties depend on the conjugation and the position and donor
character of the substituents and spacers. Cyclic voltammetry was used to determine the energy levels (HOMO and LUMO) in
the bistriazines. An increase in the energy of the HOMO and a decrease in the energy of the LUMO were observed upon
extending the conjugation. The title compounds showed interesting properties for use in optoelectronic devices, especially as
blue emitters.
strong electron-acceptor character of the triazine heterocycle
makes these systems comparable to D−A-substituted benzene
rings.
INTRODUCTION
■
π-Conjugated systems are key compounds in the field of
materials chemistry because of their interesting optical and
electronic properties, which result in a wide variety of
applications.1 The efficiency of optoelectronic devices based on
π-conjugated systems, such as light-emitting diodes (LEDs,
OLEDs, SMOLEDs), field-effect transistors (FETs), and
photovoltaic cells (PVs), is based on the appropriate choice of
the chemical structure, supramolecular aggregation, and
electronic properties. Therefore, the construction of π-
conjugated assemblies with controlled morphology and the
desired properties is crucial for the fabrication of such devices.2
An interesting strategy to boost light absorption and tune the
energy levels in π-conjugated systems is the incorporation of
electron donor (D) and electron acceptor (A) moieties in the
molecular design.1,3,4 Linear and star-shaped systems can be
found among the most interesting π-conjugated systems that
contain D and A groups. For example, linear D−π−A−π−D or
A−π−A−π−A structures have been described in systems that
include azobenzenes,5 pyridazines,6,7 1,2,4,5-tetrazines,8 squar-
ines,9 and ferrocene.9
Recently, some examples of star-shaped triazine derivatives
have been reported to show good optical and electronic
properties, and they have found applications in ionic liquids,14
magnetic materials,15 and blue-luminescent OLEDs.16 Some of
these materials were designed with a D−π−A17 or D−π−A−π−
D−π−A18 electronic arrangement. In particular, the latter system
has been shown to promote electron transport, and the
derivatives synthesized according to this design exhibit large
Stokes shifts, high thermal stability, and solvatochromism.19
π-Conjugated systems that contain only one triazine ring have
been investigated for many years.20,21 However, bis- and
bitriazine derivatives have received much less attention, despite
the fact that they have interesting chemical structures that can
result in new properties such as high acceptor capacity or the
ability to form chelates.22,23
In the work described here, a new series of mono- and
bistriazines was prepared using a rapid, clean, and selective
method based on the use of microwave irradiation and simple
purification procedures. A detailed study of the optoelectronic
properties of these materials is also described, and the results
In the case of star-shaped systems, highly functionalized
branches are included,1,10 and the most interesting examples are
the ones based on trisubstituted benzene rings and 1,3,5-
triazines.11−13 The introduction of nitrogen atoms has been used
to replace acceptor functional groups in the benzene ring. The
Received: February 27, 2014
Published: April 9, 2014
© 2014 American Chemical Society
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Table 1. Yields of Monotriazines 3−5
highlight the potential of these structures for use in the
fabrication of optoelectronic devices.
Scheme 1. Synthesis of Monotriazine 3a
RESULTS AND DISCUSSION
■
Efficient procedures were applied for the preparation of
bistriazine derivatives using microwave irradiation, which
resulted in short reaction times and the minimum amount of
solvent, with solvent-free conditions used in some cases.
Furthermore, simple purification procedures were employed to
obtain the final products.
The preparation of the bistriazine derivatives presented here
involved two steps. In the first step, monochlorotriazines24
1
were reacted with o-, m-, and p-phenylenediamines to yield
monotriazines 3−5 (see Scheme 1). The second step involved
the reaction of monotriazines 3−5 and chlorotriazines 1 to
obtain bistriazines 6−8 (see Scheme 2). This two-step procedure
allowed the preparation of symmetric and asymmetric
bistriazines as well as the isolation of monotriazines. It is
important to note that the third substitution in chlorotriazines
always requires harsher conditions,25 and microwave (MW)
irradiation is the best energy source reported to date to carry out
this substitution reaction successfully.
Monotriazines with a D−π−A−π−D structure were obtained
by attaching donor substituents to the triazine π-acceptor ring.
These substituents included pyrazole rings as π-donor hetero-
cycles in order to study their influence on the optical properties
and bearing in mind the interest in such compounds as ligands in
coordination chemistry. Pyrazolyl substituents were introduced
in different positions of the benzene ring (compounds c, d, and
e) and were also directly attached to the aminotriazine
(compounds f). Different donor moieties, such as p-methoxy
groups (compounds b), were also attached on the molecular
structure, and their effects on the optoelectronic properties were
explored.
with the aliphatic amine. Initially, solvent-free reactions were
carried out, but complex mixtures were obtained. Small amounts
of toluene, an apolar solvent that is transparent to MW
irradiation, were subsequently added to the reaction mixtures.
However, these conditions failed because of the low reactivity of
aromatic amines. As a consequence, a polar solvent with strong
MW absorption, DMSO (0.5 mL/meq), was added, and this gave
the best results. In this case, a homogeneous mixture and the
appropriate reaction temperature were obtained. The final
optimized conditions required an excess of p-phenylenediamine
(3 equiv) and DIPEA as the base. The reaction proved to be very
clean, and pure products were obtained by simple precipitation
and washing with water (Scheme 1).
The optimized conditions were applied to derivatives 3b−f,
and with the exception of 3b, these reactions required harsher
conditions (70 W) (Table 1). The optimized conditions were
also applied to the reactions with m-phenylenediamine (2b) and
o-phenylenediamine (2c) to give the corresponding mono-
triazines 4a,c−e and 5c−e, respectively, in excellent yields,
especially when o-phenylenediamine was used as the spacer
(Table 1).
Synthesis of Symmetric and Asymmetric Bistriazines
6−8. In this case, the conditions were optimized using the
reaction affording phenyl-substituted derivative 6a (Scheme 2).
The best conditions involved the use of DMSO as the solvent
(0.5 mL), DIPEA as the base, and a molar ratio of 1:1:1. The
conditions of time, power, and temperature used for the
preparation of monotriazines resulted in incomplete reactions,
and the best results were obtained when the reactions were
carried out at 170 °C for 15 min with an irradiation power of 80
Synthesis of Monotriazines 3−5. The reaction conditions
for the preparation of monotriazines 3−5 were optimized using
the reaction between monochlorotriazine 1a, which was
previously synthesized by our group,24 and p-phenylenediamine
(2a) to give monotriazine 3a (Scheme 1).
We previously described the reaction of chlorotriazines with 4-
aminobenzylamine.26 In this case, the different reactivity of
aliphatic and aromatic amines facilitated the selective reaction
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Scheme 2. Synthesis of Bistriazine 6a
Table 2. Yields of Bistriazines 6−8
W. The use of these conditions enabled compound 6a to be
obtained in 97% yield after precipitation and washing with water.
These conditions were extended to the preparation of
symmetric and asymmetric bistriazines, which were obtained in
excellent yields (Table 2). Reactions with m-phenylenediamine
required 20 min to reach total conversion in the case of
symmetric and asymmetric bistriazines (Table 2). Similarly,
reactions with o-phenylenediamine required slightly longer
reaction times (30 min) to obtain excellent yields of both
mono- and bistriazines (Table 2).
Structural Determination. All of the compounds were
characterized by NMR spectroscopy (1H, 13C, gHSQC, COSY).
The 1H NMR spectra at 25 °C show a complex pattern of broad
signals due to the restricted rotation of the Ctriazine−N bonds. The
free energy of activation has been determined by our group24,27
and others28 to be on the order of 50−80 kJ mol−1.
In the case of monotriazines, four rotamers are possible
(Figure S1 in the Supporting Information). However, this
number can rise to 16 in the case of the bistriazine derivatives.
This situation prevents the assignment and determination of the
free energy of activation of these compounds. As a consequence,
the NMR spectra were recorded at high temperatures (80−125
°C) using DMSO as the solvent. At these temperatures, rotation
is a rapid process and a single compound can be detected (Figure
S2 in the Supporting Information).
Optical Properties. The optical properties of the mono- and
bistriazines were studied in solution. The D−π−A−π−D
electronic arrangement makes them very attractive for the
development of compounds with interesting luminescence
properties.29
Absorption Properties. The UV−vis spectra of monotriazines
3−5, classified according to the spacer, are shown in Figure 1.
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Figure 1. Normalized absorption spectra of monotriazines. Spacers: (a) p-phenylenediamine; (b) m-phenylenediamine; (c) o-phenylenediamine.
The absorption maxima and comparative data for the parent
chlorotriazines are listed in Table 3.
with the spacer is allowed (compounds 3e−5e and 3c−5c), but
this effect is almost nonexistent in derivatives with pyrazolyl
substituents in the meta position (compounds 3d−5d).
The introduction of donor groups increases the energy of the
ground state. Similarly, the energy of the first excited state
decreases as a result of the presence of electron-withdrawing
groups. The combination of these two factors leads to a
reduction in the energy gap between the ground and excited
states, thus resulting in a bathochromic shift.
Table 3. Absorption Maxima of Monotriazines 3−5
The main band in the absorption spectra is the result of the
π−π* transition observed in π-conjugated systems. The band
with the smaller extinction coefficient, at around 400 nm, could
be assigned to an intramolecular charge transfer (ICT) band
from the donor nitrogen atoms of the free amino groups and the
pyrazolyl groups to the triazine (i.e., the acceptor).30 However,
despite the possibility that some degree of polarization may
occur, it is difficult to envisage a state with total charge
separation. On the other hand, it has previously been reported
that donor aromatic rings may form delocalized π systems that
are coplanar with other adjacent rings.31 Such a situation would
maximize the ICT and could explain the bathochromic shift.
The spectra are not consistent with an organized structure, as
only broad bands are observed. This indicates the presence of
monotriazine aggregates that can be formed by hydrogen
bonding and π−π stacking. As a consequence, para-substituted
monotriazines (e.g., 3e) show a broad band due to the higher
conjugation and planarity, a structure that may favor stacking. In
contrast, ortho-substituted monotriazines present two different
bands. In this case, the higher level of steric hindrance probably
reduces the planarity and consequently the stacking.
In the case of monotriazines, the phenylenediamine spacers
can be considered as donor moieties. Therefore, it can be stated
that the triazine ring (acceptor) is connected to three donor
substituents.
The introduction of the phenylenediamine spacers results in a
slight bathochromic shift in the absorption maximum, which
increases with the conjugation of the free amino group: para >
ortho > meta. The difference between the p- and o-phenylenedi-
amine spacers may be the result of the higher level of steric
hindrance of the ortho substituents, leading to a decrease in the
conjugation.
In derivatives f, the pyrazole ring is directly attached to the
aminotriazine ring, and this leads to a smaller bathochromic shift
as the electronic density must be shared between the triazine and
benzene rings.
The introduction of a methoxy group also led to a
bathochromic shift (shoulder at 282 nm) with respect to the
unsubstituted derivatives 3a−5a, but this shift was smaller than
the one found in the compounds that contain the pyrazolyl
The incorporation of pyrazolyl groups, which are donor π-
electron-rich heterocycles, as substituents on the phenyl ring
generally results in a bathochromic shift when good conjugation
Figure 2. Normalized absorption spectra of bistriazines. Spacers: (a) p-phenylenediamine; (b) m-phenylenediamine; (c) o-phenylenediamine.
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group. This effect is probably related to the donor capacity of the
two groups, which is higher for the pyrazole ring.32
The UV−vis spectra of the symmetric and asymmetric
bistriazines 6−8, classified according to the spacer, are shown
in Figure 2, and the absorption maxima are listed in Table 4. In
Table 5. Emission Maxima of Bistriazines 6−8
1,4 spacer
1,3 spacer
1,2 spacer
compd
λmax (nm)
compd
λmax (nm)
compd
λmax (nm)
b
6a
6b
6c
380/450
c
371 /434/490
385/479
7c
424
8c
438
Table 4. Absorption Maxima of Bistriazines 6−8
b
c
c
6d
6f
377/479
7d
343 /427
8d
325 /425
1,4 spacer
1,3 spacer
1,2 spacer
b
380/480
a
c
compd
λmax (nm)
compd
λmax (nm)
compd
λmax (nm)
6cd
381/485
7de
372 /408
a
b
6a
6b
6c
263
266
Emission maxima of the excimer band. Onset of the excimer band.
Shoulder.
c
245/288
264
7c
246/283
266
8c
245/285
263
6d
6f
7d
8d
287
groups were present as substituents, as in bistriazine 6b. Two
emission bands at 434 and 490 nm and a vibronic shoulder at 371
nm were observed.
6cd
254/275
7de
278
comparison to monotriazines, the extension of the conjugation in
bistriazines should lead to higher extinction coefficients, and a
bathochromic shift would not be expected as the distance
between donor and acceptor remains constant. Experimentally, a
small hypsochromic shift was observed (up to 12 nm). The main
difference between mono- and bistriazines is that monotriazines
have a free amino group that acts as a donor substituent. In
bistriazines, this amino group is attached to the second triazine
ring, which reduces its donor ability. The rest of the structural
features under investigation, such as the presence of pyrazole or
methoxy groups as donors, show the same trends as described
above for the monotriazine derivatives.
The emission spectra of bistriazines 7 and 8 present a different
pattern, and evidence for the formation of excimers was not
observed. These spectra contain featureless broad bands, which is
a sign of aggregation in the excited state.
The absorption and emission spectra do not show specular
symmetry in any case. This behavior is usual in π-conjugated
hydrocarbons, poly(p-phenylene vinylene)s, polythiophenes,
and poly(p-phenylene)s, and it has been related to higher
torsional mobility in the fundamental state compared with the
first excited state. This behavior is a deviation from the Franck−
Condon principle, which is applicable to the compounds
discussed above. Moreover, several studies of π-conjugated
polymers and oligomers have shown that restricted rotational
and vibrational movements in these aggregates can be
responsible for aggregation-induced emission (AIE) phenom-
ena.36
The asymmetric bistriazine 6cd shows a broad band with two
maxima at 254 and 275 nm. The nature of this spectrum could be
the result of the addition of bistriazines 6c and 6d with pyrazolyl
groups in the ortho and meta positions, respectively.
Emission Properties. Monotriazine derivatives 3−5 were
found to be very poor emitters in solution, with quantum yields
of less than 1%. This result can be explained by strong
intermolecular association formed by hydrogen bonding and π-
stacking that produces fluorescence quenching.
The fluorescence spectra of bistriazines 6−8, classified
according to the spacer, are shown in Figure 3, and the
absorption maxima are listed in Table 5. The spectroscopic
features of these derivatives are compared to those of the parent
chlorotriazines.
Para-substituted bistriazines 6 show an emission band at 380
nm and a second band at longer wavelengths. The latter band is
due to formation of excimers,33 which are favored by the planar
disposition of these compounds.34,35 The formation of excimers
is enhanced in the pyrazolyl-substituted bistriazines, but this
effect is less marked in the meta isomer 6d because of the lower
conjugation. A different pattern was observed when methoxy
Quantum Yields and Stokes Shifts. Additional data used for
the determination of the quantum yields (Φ) and Stokes shifts
are listed in Table 6. The quantum yields were modest, with a
maximum value of 23% in the case of bistriazine 6d, which has
pyrazoles at the meta position and p-phenylenediamine as the
spacer. It can be seen from Figure 3 that the formation of
excimers is minimal for this derivative, and hence, there is less
quenching than in the case of bistriazines 6c and 6cd. The Stokes
shifts of the bistriazines were determined to be higher than 50
000 cm−1 in all cases. This behavior is typical in systems that are
known to form intermolecular excimers with a high degree of
aggregation.37
Solvatochromism. The influence of different solvents
(CH2Cl2, CH3CN, and MeOH) on the absorption and emission
properties was studied for bistriazines 6a and 6c. Figure 4 shows
the absorption and emission spectra of 6c in these solvents, and
Table 7 lists the absorption and emission maxima for 6a and 6c.
Figure 3. Normalized emission spectra of bistriazines 6−8. Spacers: (a) p-phenylenediamine; (b) m-phenylenediamine; (c) o-phenylenediamine.
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Table 6. Additional Spectroscopic Data
spacer
1,4
compd
λabs (nm)
ε (105 M−1 cm−1
)
λem (nm)
Stokes shift (cm−1
)
Φ (%)
6a
263
266
0.47
2.06
1.34
0.43
0.53
1.02
2.32
2.46
2.6
380/450
434/490
385/479
381/450
380/450
381/485
424
85 470
44 642
103 092
85 470
107 520
94 339
56 179
62 111
76 923
51 813
68 027
4.4
6b
6c
0.38
4.1
245/288
264
6d
6e
23
287
7.3
4.5
0.77
2
6cd
7c
245/275
246/283
266
1,3
1,2
7d
7de
8c
339/427
372/408
438
278
1.8
0.68
3
245/285
278
1.98
2.2
8d
325/425
Interestingly, total quenching of the emission was found when
MeOH was used as the solvent, probably due to the formation of
hydrogen bonds between the solvent and the bistriazine
derivatives.
The same study with bistriazine 6a containing an unsub-
stituted benzene ring showed smaller effects, as expected, since
the absence of the pyrazolyl group reduces the push−pull effect.
These differences were observed in both the absorption and
emission spectra but were especially important in the absorption
spectra using methanol as the solvent. In this regard, the
formation of hydrogen bonds with the pyrazole nitrogens is
thought to be responsible for this dramatic effect.
It should be remarked that the quantum yields strongly
depend on the polarity of the solvent, and in particular, for
compound 6c Φ increases when the polarity of the solvent
increases, from only 4% in CH2Cl2 to 28% in CH3CN. The use of
CH2Cl2 promotes aggregation of these derivatives, as demon-
strated by the formation of excimers, and makes them less
emissive when this solvent is used.
Figure 4. (a) Absorption and (b) emission spectra of compound 6c in
different solvents.
Table 7. Absorption and Emission Maxima of Compounds 6a
and 6c in Different Solvents
absorption λmax (nm)
emission λmax (nm)
solvent
6a
6c
6a
6c
CH2Cl2
CH3CN
CH3OH
263
263
274
245/288
244/281
272/313
380/450
385
385/450
386
−
−
Electrochemical Properties. A cyclic voltammetry study of
the electrochemical properties of bistriazines 6−8 was performed
in order to determine the HOMO and LUMO energies. The
appropriate choice of donor and acceptor moieties can be used to
tune the emission of these molecules. For instance, the
attachment of a donor group at one end of the molecule may
enhance the efficiency of electronic devices by increasing the
energy of the HOMO and decreasing the band-gap energy.
The oxidation and reduction potentials for bistriazines 6−8,
the oxidation and reduction onsets, the HOMO and LUMO
energies, and the band-gap energies as determined from the UV
data (ΔEopt) (eq S2 in the Supporting Information) and the
cyclic voltammetry data (ΔE) are given in Table 8.
A positive solvatochromic effect was observed in the
absorption spectra in going from CH2Cl2 to MeOH. A
bathochromic shift was observed in the two absorption bands,
showing some degree of polarization in the fundamental state.38
MeOH can form hydrogen bonds with the bistriazine derivatives,
favoring the charge separation and reducing the energy gap
between the fundamental and excited states. However, this effect
was not observed with an aprotic polar solvent, as from CH2Cl2
to CH3CN a slight hypsochromic shift was observed.
Regarding the emission properties, no shifts in the emission
maxima were found when the spectra were recorded in CH2Cl2
and CH3CN. However, excimer formation was much higher with
CH2Cl2, a solvent that promotes the aggregation of the
bistriazines studied.
The ΔEopt data indicate that lower band-gap energies were
found when conjugation was more extended, as shown for
instance by comparison of compound 6c (pyrazole at the ortho
Table 8. Electrochemical Data for Bistriazines 6−8
compd
Eox(onset)/Eox(max)
Ered(onset)/Ered(max)
EHOMO (eV)
ELUMO (eV)
ΔE (eV)
ΔEopt (eV)
6a
6c
6d
6f
0.85/1.133
1.01/1.208
0.83/1.124
0.79/0.94
−0.76/−1.57
−0.8/−1.10
−0.42/−0.74
−
5.25
5.41
5.23
5.19
5.10
5.14
5.21
5.25
4.73
3.64
3.60
3.98
−
3.93
3.99
3.65
4
1.61
1.81
1.25
−
1.17
1.15
1.56
1.25
1.72
2.49
2.47
2.50
2.46
2.49
3.09
3.19
3.3
6cd
7c
7d
8c
8d
0.70/1.136
0.74/0.982
0.81/1.121
0.85/1.040
0.33/1.173
−0.47/−0.80
−0.51/−1.04
−0.75/−1.20
−0.40/−0.673, 1.164
−0.39/−0.74, 1.115
3.01
3.09
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Figure 5. Oxidation curves for bistriazines (a) 6a and (b) 6d.
position) with 6d (pyrazole at the meta position) or compound
6e (para substitution) with compounds 7d (meta substitution)
and 8c (ortho substitution).
Similarly, the HOMO energies were higher for triazines with
more extensive conjugation, where the oxidation process
requires more energy. When the substituent is at the meta
position or m-phenylenediamine is used as the spacer, the
conjugation is less extensive and the oxidation process occurs
more easily.
As far as the LUMO energies are concerned, derivatives with a
higher degree of conjugation had lower LUMO energies,
facilitating the reduction processes. LUMOs that are higher in
energy were calculated for derivatives with donor substituents in
the meta position or those in which m-phenylenediamine is the
spacer.
Compound 6a, which contains unsubstituted phenyl rings, has
HOMO and LUMO energies with intermediate values with
respect to the para- and meta-substituted derivatives.
The differences between the electrochemical and optical
values can be explained by the different solvents (acetonitrile vs
dichloromethane) and concentrations used in each technique.
Considering the possible electronic and photovoltaic
applications, compounds with a lower energy gap (lower
LUMO and higher HOMO) should be more appropriate.
Oxidation curves for bistriazines 6−8 were irreversible in all
cases. As an example, the oxidation curves for bistriazines 6a and
6d are shown in Figure 5. Only one maximum was observed for
compound 6a (phenyl-substituted), while for compound 6c (m-
pyrazolyl), a second band with lower intensity and at lower
oxidation potential was observed. The reduction curves were
irreversible in most cases, except for some derivatives such as
bistriazine 6d (Figure 6).
CONCLUSIONS
■
A series of mono- and bistriazine derivatives was prepared by
reaction of chlorotriazines with o-, m-, and p-phenylenediamine.
The reactions were performed selectively using microwave
irradiation, short reaction times, a minimum amount of solvent,
and simple purification procedures. This method is very versatile
and allows the selective preparation of monotriazines and
symmetric and asymmetric bistriazines.
These compounds showed interesting optoelectronic and
electrochemical properties, with clear differences observed
between the mono- and bistriazines, different spacers, and the
presence of donor substituents. The electronic properties
depend on the solvent used, and solvatochromism was observed.
This behavior was especially marked when methanol was used as
the solvent, resulting in a large bathochromic shift (200 nm) and
high quantum yields (28%). The interesting properties of these
mono- and bistriazine derivatives open the way to possible
applications in the field of optoelectronic devices.
EXPERIMENTAL SECTION
■
General. All of the reagents and solvents were commercial grade and
used without further purification. Melting points were obtained with an
SMP3 apparatus without correction. Thin-layer chromatograms were
obtained on AL silica gel 60 F254 from Merck. Reactions were
performed in a microwave monomode reactor (CEM, Discover) at
ambient pressure, and the reaction temperatures were measured with an
infrared pyrometer.
NMR spectra were recorded in DMSO-d6 on NMR spectrometers
operating at 499.980 and 299.98 MHz for 1H and at 125.423 and 75.42
MHz for 13C. IR spectra were recorded on an IR spectrophotometer
provided with an attenuated total reflectance (ATR) accessory. Mass
spectra were recorded with FAB ionization in the positive mode and a
magnetic sector mass analyzer (FAB-B). UV−vis and fluorescence
spectra were recorded at ambient temperature using spectroscopic grade
dichloromethane and a concentration of 5.5 × 10−6 M for absorbance
and 10−6 M for fluorescence. Cyclic voltammetry was carried out using a
platinum working electrode, a Ag/AgCl reference electrode, and a
platinum counter electrode. Degassed acetonitrile was used as the
solvent and a 0.1 mM solution of Bu4NPF6 as the supporting electrolyte.
The sweep speed was 100 mV/s.
Preparation of Monotriazines 3−5. The spacer (o-, m-, or p-
phenylenediamine), the appropriate chlorotriazine 2 (0.3 mmol), and
diisopropylethylamine (DIPEA) in a 3:1:1 ratio were dissolved in
anhydrous DMSO. The mixture was introduced into a microwave flask
fitted with a reflux condenser and a silica gel tube under argon. The
mixture was subjected to microwave irradiation at ambient pressure for
10 min (20 min with o-phenylenediamine) at 50 W (70 W for p-
methoxyphenyl) and 140 °C. The mixture was washed with water (3 × 2
mL) and filtered to give the pure product.
Figure 6. Reduction curves for bistriazine 6d.
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Article
N-4-Aminophenyl-N′,N″-diphenyl-1,3,5-triazine-2,4,6-triamine
(3a). From 6-chloro-N,N′-diphenyl-1,3,5-triazine-2,4-diamine (1a) (0.3
mmol, 0.0897 g), p-phenylenediamine (2a) (0.9 mmol, 0.097 g), DIPEA
(0.3 mmol, 0.039 g), and DMSO (0.5 mL). White solid, 0.100 g (98%),
mp 201−205 °C (decomp). 1H NMR (25 °C, 500 MHz, DMSO) δ 4.82
(bs, 2H), 6.55 (d, J = 7.8 Hz, 2H), 6.96 (t, J = 7.07 Hz, 2H), 7.26 (t, J =
6.55 Hz, 4H), 7.33 (d, J = 7.32 Hz, 2H), 7.80 (bs, 4H), 8.79 (bs, 1H),
9.08 (bs, 2H, NH). 13C NMR (25 °C, 125 MHz, DMSO) δ 113.8, 120.1,
121.7, 123.0, 128.3, 128.6, 140.2, 144.4, 164.1, 164.2. IR (neat) ν 3388,
3265, 1575, 1514, 1415 cm−1. UV λmax/nm (ε/105 mol L−1 cm−1) 274
(0.81). MS (FAB-B) m/z [M + H]+ calcd for C21H20N7 370.1780, found
370.1755.
2H), 7.26 (m, 4H), 7.5 (s, 4H), 7.73 (s, 4H), 7.82 (s, 2H), 8.56 (bs, 3H),
8.97 (bs, 2H). 13C NMR (125 MHz, 95 °C, DMSO) δ 113.8, 116.9,
117.5, 124.0, 124.8, 125.1, 128.3, 129.0, 133.2, 139.7, 144.5, 163.4, 165.0.
IR (neat) ν 3078, 1556, 1504, 1394 cm−1. UV λmax/nm (ε/105 mol L−1
cm−1) 298 (0.31). MS (FAB-B) m/z [M + H]+ calcd for C27H24N11
502.2216, found 502.2144.
N-3-Aminophenyl-N′,N″-diphenyl-1,3,5-triazine-2,4,6-triamine
(4a). From 6-chloro-N,N′-diphenyl-1,3,5-triazine-2,4-diamine (1a) (0.3
mmol, 0.0897 g), m-phenylenediamine (2b) (0.9 mmol, 0.097g),
DIPEA (0.3 mmol, 0.039 g), and DMSO (0.5 mL). White solid, 0.100 g
(98%), mp 107 °C (decomp). 1H NMR (500 MHz, 25 °C, DMSO) δ
4.88 (bs, 2H), 6.25 (d, J = 6.83 Hz, 1H), 6.9−7.0 (m, 5H), 7.28 (t, J =
8.05 Hz, 4H), 7.81 (d, J = 7.81 Hz, 4H), 8.95 (bs, 1H), 9.14 (s, 2H). 13C
NMR (125 MHz, 25 °C, DMSO) δ 106.8, 108.7, 109.2, 120.2, 121.8,
128.3, 128.6, 140.0, 140.2, 148.6, 164.1, 164.1. IR (neat) ν 3390, 3275,
1574, 1416 cm−1. UV λmax/nm (ε/105 mol L−1 cm−1) 272 (1.76). MS
(FAB-B) m/z [M + H]+ calcd for C21H20N7 370.1780, found 370.1767.
N-3-Aminophenyl-N′,N″-bis(2-pyrazol-1-ylphenyl)-1,3,5-triazine-
2,4,6-triamine (4c). From 6-chloro-N,N′-bis(2-pyrazol-1-ylphenyl)-
1,3,5-triazine-2,4-diamine (1c) (0.3 mmol, 0.128 g), m-phenylenedi-
amine (2b) (0.9 mmol, 0.097 g), DIPEA (0.3 mmol, 0.039 g), and
N-4-Aminophenyl-N′,N″-bis(4-methoxyphenyl)-1,3,5-triazine-
2,4,6-triamine (3b). From 6-chloro-N,N′-bis(4-methoxyphenyl)-1,3,5-
triazine-2,4-diamine (1b) (0.5 mmol, 0.178 g), p-phenylenediamine
(2a) (1.5 mmol, 0.162 g), DIPEA (0.5 mmol, 0.087 g), and DMSO (0.5
mL). White solid, 0.150 g (70%), mp 85−89.4 °C (decomp). 1H NMR
(500 MHz, 80 °C, DMSO) δ 3.75 (s, 6H), 4.59 (bs, 2H), 6.55 (d, J =
8.78 Hz, 2H), 6.86 (d, J = 9.27 Hz, 4H), 7.32 (d, J = 8.78 Hz, 2H), 7.63
(d, J = 9.27 Hz, 4H), 8.4 (bs, 1H), 8.62 (bs, 2H). 13C NMR (125 MHz,
80 °C, DMSO) δ 55.0, 113.3, 113.6, 121.8, 122.5, 128.8, 133.0, 143.8,
1
154.4, 164.0, 164.1. IR (neat) ν 3383, 1573, 1512, 1232 cm−1. UV λmax
/
DMSO (0.5 mL). White solid, 0.129 g (86%), mp 107−111 °C. H
nm (ε/105 mol L−1 cm−1) 253, 282 (8.3). MS (FAB-B) m/z [M + H]+
calcd for C23H24N7O2 430.1991, found 430.1983.
NMR (500 MHz, 25 °C, DMSO) δ 4.88 (bs, 2H), 6.24 (d, J = 7.32 Hz,
1H), 6.56 (bs, 2H), 6.78−6.86 (m, 2H), 6.88 (pseudo t, J = 7.81 Hz,
1H), 7.22 (t, J = 7.56 Hz, 2H), 7.39 (t, J = 7.56 Hz, 2H), 7.54 (d, J = 7.81
Hz, 2H), 7.88 (d, J = 1.4 Hz, 2H), 8.23 (d, J = 1.95 Hz, 2H), 8.29 (bs,
2H), 9.25 (s, 1H), 9.51 (bs, 2H). 13C NMR (125 MHz, 25 °C, DMSO) δ
106.5, 107.1, 108.8, 108.9, 123.7, 124.6, 127.4, 128.5, 130.6, 131.3, 131.7,
139.9, 141.0, 148.6, 164.1, 164.1. IR (neat) ν 3306, 1504, 1446, 1411
cm−1. UV λmax/nm (ε/105 mol L−1 cm−1) 244, 281 (1.68). MS (FAB-B)
m/z [M + H]+ calcd for C27H24N11 502.2216, found 502.2206.
N-4-Aminophenyl-N′,N″-bis(2-pyrazol-1-ylphenyl)-1,3,5-triazine-
2,4,6-triamine (3c). From 6-chloro-N,N′-bis(2-pyrazol-1-ylphenyl)-
1,3,5-triazine-2,4-diamine (1c) (0.3 mmol, 0.0897 g), p-phenylenedi-
amine (2a) (0.9 mmol, 0.097 g), DIPEA (0.3 mmol, 0.039 g), and
DMSO (0.5 mL). White solid, 0.09 g (95%), mp 107−111 °C. 1H NMR
(500 MHz, 80 °C, DMSO) δ 4.65 (bs, 2H), 6.52 (d, J = 8.29 Hz, 2H),
6.54 (t, J = 2.19 Hz, 2H), 7.18 (t, J = 7.56 Hz, 2H), 7.22 (d, J = 8.78 Hz,
2H), 7.35 (t, J = 7.56 Hz, 2H), 7.50 (dd, J = 8.29 and 1.22 Hz, 2H), 7.84
(d, J = 1.95 Hz, 2H), 8.16 (d, J = 2.44 Hz, 2H), 8.31 (d, J = 8.29 Hz, 2H),
8.85 (bs, 1H), 9.24 (bs, 2H). 13C NMR (125 MHz, 80 °C, DMSO) δ
106.6, 113.5, 122.3, 123.0, 123.4, 123.9, 127.0, 128.2, 130.1, 130.8, 131.9,
N-3-Aminophenyl-N′,N″-bis(3-pyrazol-1-ylphenyl)-1,3,5-triazine-
2,4,6-triamine (4d). From 6-chloro-N,N′-bis(3-pyrazol-1-ylphenyl)-
1,3,5-triazine-2,4-diamine (1d) (0.23 mmol, 0.098 g), m-phenylenedi-
amine (2b) (0.7 mmol, 0.075 g), DIPEA (0.23 mmol, 0.037 g), and
1
140.5, 144.0, 163.9, 163.9. IR (neat) ν 3311, 1504, 1415 cm−1. UV λmax
/
DMSO (0.5 mL). White solid, 0.105 g (91%), mp 111 °C. H NMR
nm (ε/105 mol L−1 cm−1) 245, 284 (0.5). MS (FAB-B) m/z [M + H]+
calcd for C27H24N11 502.2216, found 502.2214.
(500 MHz, 80 °C, DMSO) δ 4.7 (bs, 2H), 6.29 (d, J = 7.8 Hz, 1H), 6.5
(t, J = 1.95 Hz, 2H), 6.88 (t, J = 7.8 Hz, 1H), 6.95−6.98 (m, 2H), 7.34 (t,
J = 8.0 Hz, 2H), 7.43 (d, J = 7.8 Hz, 2H), 7.71 (d, J = 1.95 Hz, 2H), 7.82
(d, J = 8.3 Hz, 2H), 8.1 (d, J = 1.95 Hz, 2H), 8.26 (d, J = 2.44 Hz, 2H),
8.8 (s, 1H), 9.1 (bs, 2H). 13C NMR (125 MHz, 80 °C, DMSO) δ 107.0,
107.1, 108.9, 109.5, 110.5, 112.2, 118.1. 127.2, 128.2, 128.9, 139.7, 139.7,
140.3, 140.6, 148.2, 164.0, 164.1. IR (neat) ν 3388, 3288, 1583, 1409
cm−1. UV λmax/nm (ε/105 mol L−1 cm−1) 264 (0.88). MS (FAB-B) m/z
[M + H]+ calcd for C27H24N11 502.2216, found 502.2208.
N-4-Aminophenyl-N′,N″-bis(3-pyrazol-1-ylphenyl)-1,3,5-triazine-
2,4,6-triamine (3d). From 6-chloro-N,N′-bis(3-pyrazol-1-ylphenyl)-
1,3,5-triazine-2,4-diamine (1d) (0.1 mmol, 0.043 g), p-phenylenedi-
amine (2a) (0.3 mmol, 0.039 g), DIPEA (0.1 mmol, 0.0129 g), and
1
DMSO (0.5 mL). White solid, 0.099 g (99%), mp 107−110 °C. H
NMR (300 MHz, 80 °C, DMSO) δ 4.60 (s, 2H), 6.50−6.54 (m, 3H),
7.31 (t, J = 8.35 Hz, 4H), 7.41 (pseudo d, J = 8.13 Hz, 2H), 7.7 (d, J =
1.76 Hz, 2H), 7.79 (d, J = 8.13 Hz, 2H), 8.1 (t, J = 1.97 Hz, 2H), 8.21 (d,
J = 2.42 Hz, 2H), 8.61 (bs, 1H), 9.05 (bs, 2H). 13C NMR (75 MHz, 80
°C, DMSO) δ 107.1, 110.3, 112.0, 113.7, 117.9, 123.1, 127.2, 128.2,
128.8, 139.7, 140.2, 140.8, 144.2, 164.0, 164.2. IR (neat) ν 3284, 1581,
1514, 1413 cm−1. UV λmax/nm (ε/105 mol L−1 cm−1) 266 (0.8). MS
(FAB-B) m/z [M + H]+ calcd for C27H24N11 502.2216, found 502.2220.
N-4-Aminophenyl-N′,N″-bis(4-pyrazol-1-ylphenyl)-1,3,5-triazine-
2,4,6-triamine (3e). From 6-chloro-N,N′-bis(4-pyrazol-1-ylphenyl)-
1,3,5-triazine-2,4-diamine (1e) (0.1 mmol, 0.043 g), p-phenylenedi-
amine (2a) (0.3 mmol, 0.039 g), DIPEA (0.1 mmol, 0.0129 g), and
N-3-Aminophenyl-N′,N″-bis(4-pyrazol-1-ylphenyl)-1,3,5-triazine-
2,4,6-triamine (4e). From 6-chloro-N,N′-bis(4-pyrazol-1-ylphenyl)-
1,3,5-triazine-2,4-diamine (1e) (0.25 mmol, 0.1073 g), m-phenylenedi-
amine (2b) (0.75 mmol, 0.078 g), DIPEA (0.25 mmol, 0.039 g), and
1
DMSO (0.5 mL). White solid, 0.125 g (99%), mp 118−119 °C. H
NMR (500 MHz, 120 °C, DMSO) δ 4.57 (bs, 2H), 6.34 (dd, J = 1.46
and 6.34 Hz, 1H), 6.49 (dd, J = 1.95 and 2.44 Hz, 2H), 6.91−7.0 (m,
2H), 7.03 (m, 1H), 7.68 (d, J = 9.27 Hz, 6H), 7.88 (d, J = 9.27 Hz, 4H),
8.25 (d, J = 2.44 Hz, 2H), 8.52 (bs, 1H), 8.87 (bs, 2H). 13C NMR (125
MHz, 120 °C, DMSO) δ 106.5, 107.1, 108.9, 109.5, 118.4, 120.7, 126.7,
127.9, 134.3, 137.8, 139.6, 139.7, 147.9, 163.9, 164.1. IR (neat) ν 3389,
1581, 1524, 1410 cm−1. UV λmax/nm (ε/105 mol L−1 cm−1) 275 (0.37).
MS (FAB-B) m/z [M + H]+ calcd for C27H24N11 502.2216, found
502.2196.
1
DMSO (0.5 mL). White solid, 0.099 g (99%), mp 135−138.2 °C. H
NMR (500 MHz, 80 °C, DMSO) δ 4.66 (bs, 2H), 6.49 (t, J = 1.95 Hz,
2H), 6.59 (d, J = 8.29 Hz, 2H), 7.32 (d, J = 8.29 Hz, 2H), 7.69 (m, 6H),
7.9 (d, J = 8.78 Hz, 4H), 8.31 (d, J = 2.44 Hz, 2H), 8.61 (bs, 1H), 9.02
(bs, 2H). 13C NMR (125 MHz, 80 °C, DMSO) δ 107.0, 113.7, 118.5,
120.6, 123.0, 127.0, 128.4, 134.1, 138.2, 140.0, 144.2, 163.9, 164.2. IR
(neat) ν 1575, 1487, 1409 cm−1. UV λmax/nm (ε/105 mol L−1 cm−1) 279
(1.5). MS (FAB-B) m/z [M + H]+ calcd for C27H24N11 502.2216, found
502.2209.
N-2-Aminophenyl-N′,N″-bis(2-pyrazol-1-ylphenyl)-1,3,5-triazine-
2,4,6-triamine (5c). From 6-chloro-N,N′-bis(2-pyrazol-1-ylphenyl)-
1,3,5-triazine-2,4-diamine (1c) (0.14 mmol, 0.06 g), o-phenylenedi-
amine (2c) (0.42 mmol, 0.045 g), DIPEA (0.14 mmol, 0.026 g), and
1
DMSO (0.5 mL). White solid, 0.065 g (97%), mp 107−111 °C. H
NMR (500 MHz, 25 °C, DMSO) δ 4.85 (s, 2H), 6.56 (m, 3H), 6.73 (d, J
= 7.81 Hz, 1H), 6.91 (t, J = 7.81 Hz, 1H), 7.18 (pseudo t, J = 6.10 Hz,
3H), 7.28 (m, 2H), 7.49 (d, J = 8.78 Hz, 2H), 7.87 (s, 2H), 8.21 (s, 2H),
8.28 (m, 2H), 8.62 (s, 1H), 9.43 (s, 2H). 13C NMR (125 MHz, 25 °C,
DMSO) δ 107.2, 115.6, 115.9, 123.3, 123.6, 123.7, 124.1, 125.8, 126.9,
127.4, 131.4, 131.9, 141.0, 142.9, 164.1, 165.2. IR (neat) ν 3290, 1574,
N-4-Aminophenyl-N′,N″-bis(1-phenyl-1H-pyrazol-4-yl)-1,3,5-tria-
zine-2,4,6-triamine (3f). From 6-chloro-N,N′-bis(1-phenyl-1H-pyra-
zol-4-yl)-1,3,5-triazine-2,4-diamine (1f) (0.23 mmol, 0.1 g), p-phenyl-
enediamine (2a) (0.7 mmol, 0.075 g), DIPEA (0.23 mmol, 0.04 g), and
DMSO (0.5 mL). White solid, 0.099 g (86%), mp 131−134.5 °C. H
NMR (500 MHz, 95 °C, DMSO) δ 4.71 (bs, 2H), 6.64 (d, J = 8.29 Hz,
1
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Article
1704, 1414 cm−1. UV λmax/nm (ε/105 mol L−1 cm−1) 241, 273 (0.2). MS
(FAB-B) m/z [M + H]+ calcd for C27H24N11 502.2216, found 502.2203.
N-2-Aminophenyl-N′,N″-bis(3-pyrazol-1-ylphenyl)-1,3,5-triazine-
2,4,6-triamine (5d). From 6-chloro-N,N′-bis(3-pyrazol-1-ylphenyl)-
1,3,5-triazine-2,4-diamine (1d) (0.23 mmol, 0.098 g), o-phenylenedi-
amine (2c) (0.7 mmol, 0.075 g), DIPEA (0.23 mmol, 0.037 g), and
9.36 (bs, 4H). 13C NMR (125 MHz, 80 °C, DMSO) δ 106.6, 120.4,
123.3, 123.4, 124.2, 127.0, 130.5, 130.8, 131.7, 134.0, 140.5, 163.9, 164.0.
IR (neat) ν 3286, 1726, 1658, 1523 cm−1. UV λmax/nm (ε/105 mol L−1
cm−1) 245, 288 (1.34). MS (FAB-B) m/z [M + H]+ calcd for C48H39N20
895.3667, found 895.3678.
N,N′-Bis[4,6-bis(3-pyrazol-1-ylphenylamino)-1,3,5-triazin-2-yl]-p-
phenylenediamine (6d). From N-4-aminophenyl-N′,N″-bis(3-pyrazol-
1-ylphenyl)-1,3,5-triazine-2,4,6-triamine (3d) (0.13 mmol, 0.063 g), 6-
chloro-N,N′-bis(3-pyrazol-1-ylphenyl)-1,3,5-triazine-2,4-diamine (1d)
(0.13 mmol, 0.056 g), DIPEA (0.13 mmol, 0.016 g), and DMSO (0.5
mL). White solid, 0.110 g (95%), mp 165−168 °C (decomp). 1H NMR
(500 MHz, 80 °C, DMSO) δ 6.49 (t, J = 1.95 Hz, 4H), 7.34 (t, J = 8.05
Hz, 4H), 7.42 (d, J = 8.29 Hz, 4H), 7.65 (s, 4H), 7.70 (d, J = 1.46 Hz,
4H), 7.83 (d, J = 7.32 Hz, 4H), 8.12 (d, J = 1.95 Hz, 4H), 8.25 (d, J = 2.44
Hz, 4H), 9.02 (bs, 2H), 9.22 (bs, 4H). 13C NMR (125 MHz, 80 °C,
DMSO) δ 107.1, 110.6, 112.2, 118.1, 120.9, 127.2, 128.9, 134.2, 139.7,
140.3, 140.7, 164.0, 164.1. IR (neat) ν 3400, 3277, 1583, 1487, 1408
cm−1. UV λmax/nm (ε/105 mol L−1 cm−1) 264 (0.43). MS (FAB-B) m/z
[M + H]+ calcd for C48H39N20 895.3667, found 895.3666.
N,N′-Bis[4,6-bis(1-phenyl-1H-pyrazol-4-ylamino)-1,3,5-triazin-2-
yl]-p-phenylenediamine (6f). From N-4-aminophenyl-N′,N″-bis(1-
phenyl-1H-pyrazol-4-yl)-1,3,5-triazine-2,4,6-triamine (3f) (0.19 mmol,
0.099 g), 6-chloro-N,N′-bis(1-phenyl-1H-pyrazol-4-yl)-1,3,5-triazine-
2,4-diamine (1f) (0.19 mmol, 0.082 g), DIPEA (0.19 mmol, 0.034 g),
and DMSO (0.5 mL). White solid, 0.165 g (97%), mp 117−121 °C
(decomp). 1H NMR (500 MHz, 120 °C, DMSO) δ 7.24 (t, J = 6.8 Hz,
4H), 7.45 (t, J = 7.06 Hz, 8H), 7.74 (m, 12H), 7.88 (s, 4H), 8.58 (s, 4H),
8.9−9.1 (m, 6H). 13C NMR (125 MHz, 120 °C, DMSO) δ 117.1, 117.5,
121.4, 124.5, 125.0, 128.7, 133.4, 134.4, 139.6, 163.5, 164.47. IR (neat) ν
3408, 3284, 1556, 1495, 1396 cm−1. UV λmax/nm (ε/105 mol L−1 cm−1)
287 (20.53). MS (FAB-B) m/z [M + H]+ calcd for C48H39N20 895.3667,
found 895.3678.
N-[4,6-Bis(3-pyrazol-1-ylphenylamino)-1,3,5-triazin-2-yl]-N′-[4,6-
bis(2-pyrazol-1-ylphenylamino)-1,3,5-triazin-2-yl]-p-phenylenedi-
amine (6cd). From N-4-aminophenyl-N′,N″-bis(3-pyrazol-1-ylphen-
yl)-1,3,5-triazine-2,4,6-triamine (3d) (0.12 mmol, 0.06 g), 6-chloro-
N,N′-bis(2-pyrazol-1-ylphenyl)-1,3,5-triazine-2,4-diamine (1c) (0.12
mmol, 0.051 g), DIPEA (0.12 mmol, 0.015 g), and DMSO (0.5 mL).
White solid, 0.08 g (75%), mp 120.3−122 °C (decomp). 1H NMR (500
MHz, 80 °C, DMSO) δ 6.47−6.54 (m, 4H), 7.21 (t, J = 7.56 Hz, 2H),
7.3−7.44 (m, 6H), 7.5−7.7 (m, 8H), 7.76−7.88 (m, 4H), 8.1−8.2 (m,
4H), 8.22−8.32 (m, 4H), 9.0−9.4 (m, 6H). 13C NMR (125 MHz, 80 °C,
DMSO) δ 106.7, 107.2, 110.5, 112.2, 118.1, 120.4, 121.0, 123.3, 123.5,
124.3, 127.0, 127.2, 129.0, 130.5, 130.9, 131.7, 134.1, 134.1, 139.8, 140.3,
140.5, 140.7, 163.9, 164.0, 164.1. IR (neat) ν 3395, 3304, 1580, 1485,
1408 cm−1. UV λmax/nm (ε/105 mol L−1 cm−1) 254, 275 (1.02). MS
(FAB-B) m/z [M + H]+ calcd for C48H39N20 895.3667, found 895.3684.
N,N′-Bis[4,6-bis(2-pyrazol-1-ylphenylamino)-1,3,5-triazin-2-yl]-
m-phenylenediamine (7c). From N-3-aminophenyl-N′,N″-bis(3-pyr-
azol-1-ylphenyl)-1,3,5-triazine-2,4,6-triamine (4c) (0.12 mmol, 0.06 g),
6-chloro-N,N′-bis(2-pyrazol-1-ylphenyl)-1,3,5-triazine-2,4-diamine
(1c) (0.12 mmol, 0.051 g), DIPEA (0.12 mmol, 0.015 g), and DMSO
(0.5 mL). White solid, 0.08 g (75%), mp 138−139 °C. 1H NMR (500
MHz, 80 °C, DMSO) δ 6.5 (t, J = 2.19 Hz, 4H), 7.15 (m, 7H), 7.31 (t, J =
7.57 Hz, 4H), 7.5 (dd, J = 8.29 and 1.22 Hz, 4H), 7.81 (d, J = 1.46 Hz,
4H), 8.02 (t, J = 1.95 Hz, 1H), 8.11 (d, J = 2.44 Hz, 4H), 8.27 (d, J = 7.69
Hz, 4H), 9.14 (bs, 2H), 9.34 (bs, 4H). 13C NMR (125 MHz, 80 °C,
DMSO) δ 106.6, 113.7, 115.0, 123.2, 123.3, 124.1, 126.9, 127.4, 130.4,
130.7, 131.6, 139.0, 140.4, 163.9, 164.0. IR (neat) ν 3277, 1504, 1447,
1408 cm−1. UV λmax/nm (ε/105 mol L−1 cm−1) 246, 283 (2.32). MS
(FAB-B) m/z [M + H]+ calcd for C48H39N20 895.3667, found 895.3678.
N,N′-Bis[4,6-bis(3-pyrazol-1-ylphenylamino)-1,3,5-triazin-2-yl]-
m-phenylenediamine (7d). From N-3-aminophenyl-N′,N″-bis(3-pyr-
azol-1-ylphenyl)-1,3,5-triazine-2,4,6-triamine (4d) (0.21 mmol, 0.105
g), 6-chloro-N,N′-bis(3-pyrazol-1-ylphenyl)-1,3,5-triazine-2,4-diamine
(1d) (0.21 mmol, 0.09 g), DIPEA (0.21 mmol, 0.03 g), and DMSO
(0.5 mL). White solid, 0.186 g (98%), mp 104−105 °C (decomp). 1H
NMR (500 MHz, 95 °C, DMSO) δ 6.48 (bs, 4H), 7.08 (t, J = 8.29 Hz,
1H), 7.33 (m, 5H), 7.41 (d, J = 8.29 Hz, 4H), 7.48 (d, J = 7.81 Hz, 1H),
7.69 (bs, 4H), 7.81 (d, J = 8.29 Hz, 4H), 8.02 (s, 1H), 8.09 (s, 4H), 8.23
1
DMSO (0.5 mL). White solid, 0.113 g (98%), mp 105−106 °C. H
NMR (500 MHz, 80 °C, DMSO) δ 4.75 (bs, 2H), 6.49 (t, J = 2.19 Hz,
2H), 6.56 (t, J = 6.83 Hz, 1H), 6.77 (d, J = 7.32 Hz, 1H), 6.93 (t, J = 7.32
Hz, 1H), 7.28 (t, J = 8.05 Hz, 3H), 7.39 (d, J = 8.29 Hz, 2H), 7.69 (d, J =
1.46 Hz, 2H), 7.76 (d, J = 7.81 Hz, 2H), 8.10 (s, 2H), 8.17 (bs, 2H), 8.27
(s, 1H), 9.14 (s, 2H). 13C NMR (75 MHz, 80 °C, DMSO) δ 107.1,
110.2, 112.0, 115.6, 116.1, 117.8, 123.9, 125.6, 126.7, 127.2, 128.8, 139.6,
140.2, 140.7, 142.8, 164.1, 165.1. IR (neat) ν 3290, 1580, 1504, 1414
cm−1. UV λmax/nm (ε/105 mol L−1 cm−1) 262 (1.37). MS (FAB-B) m/z
[M + H]+ calcd for C27H24N11 502.2216, found 502.2216.
N-2-Aminophenyl-N′,N″-bis(4-pyrazol-1-ylphenyl)-1,3,5-triazine-
2,4,6-triamine (5e). From 6-chloro-N,N′-bis(4-pyrazol-1-ylphenyl)-
1,3,5-triazine-2,4-diamine (1e) (0.25 mmol, 0.1073 g), o-phenylenedi-
amine (2c) (0.75 mmol, 0.078 g), DIPEA (0.25 mmol, 0.039 g), and
1
DMSO (0.5 mL). White solid, 0.115 g (92%), mp 154 °C. H NMR
(500 MHz, 95 °C, DMSO) δ 4.68 (bs, 2H), 6.48 (t, J = 2.19 Hz, 2H),
6.65 (t, J = 7.56 Hz, 1H), 6.82 (d, J = 8.29 Hz, 1H), 6.97 (t, J = 7.2 Hz,
1H), 7.31 (d, J = 7.81 Hz, 1H), 7.64 (d, J = 8.78 Hz, 4H), 7.68 (d, J = 1.95
Hz, 2H), 7.87 (d, J = 8.78 Hz, 4H), 8.14 (bs, 1H), 8.27 (d, J = 2.44 Hz,
2H), 8.99 (bs, 2H). 13C NMR (125 MHz, 95 °C, DMSO) δ 106.7, 115.6,
116.1, 118.4, 120.5, 124.1, 125.4, 126.7, 126.8, 134.1, 138.1, 139.8, 142.7,
164.0, 165.2. IR (neat) ν 3396, 3286, 1521, 1487, 1410 cm−1. UV λmax
/
nm (ε/105 mol L−1 cm−1) 294 (1.05). MS (FAB-B) m/z [M + H]+ calcd
for C27H24N11 502.2216, found 502.2196.
Preparation of Bistriazines 6−8. The synthesis of bistriazines was
similar to the preparation of monotriazines, using the appropriate
chlorotriazine 1, monotriazine 3−5, and diisopropylethylamine
(DIPEA) in a 1:1:1 ratio and anhydrous DMSO (0.5 mL) as the
solvent. The mixture was irradiated under argon for 15 min for 6, 20 min
for 7 and 30 min for 8 at 170 °C and 80 W. The crude product was
washed with water (2 × 3 mL) and filtered to give the pure product.
N,N′-Bis[4,6-bis(phenylamino)-1,3,5-triazin-2-yl]-p-phenylenedi-
amine (6a). From N-4-aminophenyl-N′,N″-diphenyl-1,3,5-triazine-
2,4,6-triamine (3a) (0.5 mmol, 0.185 g), 6-chloro-N,N′-diphenyl-
1,3,5-triazine-2,4-diamine (1a) (0.5 mmol, 0.148 g), DIPEA (0.5 mmol,
0.065 g), and DMSO (0.5 mL). White solid, 0.306 g (97%), mp 150 °C
(decomp). 1H NMR (500 MHz, 25 °C, DMSO) δ 6.98 (t, J = 7.32 Hz,
4H), 7.28 (t, J = 7.81 Hz, 8H), 7.72 (s, 4H), 7.82 (d, J = 6.83 Hz, 8H),
9.17 (s, 2H), 9.20 (s, 4H). 13C NMR (125 MHz, 25 °C, DMSO) δ 120.2,
120.7, 121.9, 128.3, 134.5, 140.0, 164.0, 164.1. IR (neat) ν 3402, 3287,
1574, 1493, 1410 cm−1. UV λmax/nm (ε/105 mol L−1 cm−1) 263 (0.47).
MS (FAB) [M + H]+ m/z calcd for C36H31N12 631.2795, found
631.2828.
N,N′-Bis[4,6-bis(4-methoxyphenylamino)-1,3,5-triazin-2-yl]-p-
phenylenediamine (6b). From N-4-aminophenyl-N′,N″-bis(4-methox-
yphenyl)-1,3,5-triazine-2,4,6-triamine (3b) (0.23 mmol, 0.1 g), 6-
chloro-N,N′-bis(4-methoxyphenyl)-1,3,5-triazine-2,4-diamine (1b)
(0.23 mmol, 0.08 g), DIPEA (0.23 mmol, 0.036 g), and DMSO (0.5
mL). White solid, 0.146 g (85%), mp 111−114 °C (decomp). 1H NMR
(500 MHz, 80 °C, DMSO) δ 3.74 (s, 12H), 6.86 (d, J = 8.78 Hz, 8H),
7.64 (m, 12H), 8.72 (s, 4H), 8.78 (s, 2H). 13C NMR (75 MHz, 80 °C,
DMSO) δ 55.0, 113.4, 120.4, 122.0, 132.8, 134.2, 154.6, 163.9, 164.0. IR
(neat) ν 3404, 1574, 1495, 1410 cm−1. UV λmax/nm (ε/105 mol L−1
cm−1) 266 (2.06). MS (FAB-B) m/z [M + H]+ calcd for C40H39N12O4
751.3217, found 751.3218.
N,N′-Bis[4,6-bis(2-pyrazol-1-ylphenylamino)-1,3,5-triazin-2-yl]-p-
phenylenediamine (6c). From N-4-aminophenyl-N′,N″-bis(2-pyrazol-
1-ylphenyl)-1,3,5-triazine-2,4,6-triamine (3c) (0.18 mmol, 0.09 g), 6-
chloro-N,N′-bis(2-pyrazol-1-ylphenyl)-1,3,5-triazine-2,4-diamine (1c)
(0.18 mmol, 0.077 g), DIPEA (0.18 mmol, 0.026 g), and DMSO (0.5
1
mL). White solid, 0.127 g (80%), mp 170−172.5 °C (decomp). H
NMR (500 MHz, 80 °C, DMSO) δ 6.54 (t, J = 2.19 Hz, 4H), 7.21 (t, J =
7.81 Hz, 4H), 7.37 (t, J = 8.5 Hz, 4H), 7.53 (m, 8H), 7.84 (d, J = 1.95 Hz,
4H), 8.17 (d, J = 2.44 Hz, 4H), 8.3 (d, J = 8.29 Hz, 4H), 9.2 (bs, 2H),
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Article
(bs, 4H), 8.89 (s, 2H), 9.15 (bs, 4H). 13C NMR (125 MHz, 95 °C,
DMSO) δ 107.1, 110.7, 111.5, 112.3, 115.5, 118.2, 127.2, 127.3, 128.9,
139.3, 139.8, 140.3, 140.5, 164.1. IR (neat) ν 3397, 3290, 1583, 1454,
1408 cm−1. UV λmax/nm (ε/105 mol L−1 cm−1) 266 (2.46). MS (FAB-B)
m/z [M + H]+ calcd for C48H39N20 895.3667, found 895.3656.
Present Addresses
†A.R.-C.: Institute of Science and Supramolecular Engineering
(ISIS), University of Strasbourg, 8 Allee Gaspard Monge,
Strasbourg Cedex 67083, France.
‡O.N.: Facultad de estudios superiores Cuautitlan
Nacional Autonoma de Mexico (UNAM), 54740 Cuautitlan
Izcali, Mexico.
Notes
́
́
, Universidad
N-[4,6-bis(3-pyrazol-1-ylphenylamino)-1,3,5-triazin-2-yl]-N′-[4,6-
bis(4-pyrazol-1-ylphenylamino)-1,3,5-triazin-2-yl]-m-phenylenedi-
amine (7de). From N-3-aminophenyl-N′,N″-bis(3-pyrazol-1-ylphen-
yl)-1,3,5-triazine-2,4,6-triamine (4d) (0.19 mmol, 0.085 g), 6-chloro-
N,N′-bis(4-pyrazol-1-ylphenyl)-1,3,5-triazine-2,4-diamine (1e) (0.19
mmol, 0.10 g), DIPEA (0.19 mmol, 0.027 g), and DMSO (0.5 mL).
White solid, 0.081 g (95%), mp 104−105 °C (decomp). 1H NMR (500
MHz, 80 °C, DMSO) δ 6.49−6.51 (m, 4H), 7.18 (t, J = 8.08 Hz, 1H),
7.33 (t, J = 8.05 Hz, 2H), 7.41 (d, J = 9.27 Hz, 2H), 7.46 (d, J = 8.79 Hz,
1H), 7.50 (pseudo t, J = 6.83 Hz, 1H), 7.6−7.75 (m, 8H), 7.84 (d, J =
8.29 Hz, 2H), 7.91 (d, J = 8.78 Hz, 4H), 8.2−8.14 (m, 3H), 8.2−8.36 (m,
4H), 8.94 (bs, 1H), 9.03 (bs, 1H), 9.12 (bs, 2H), 9.19 (bs, 2H). 13C
NMR (125 MHz, 80 °C, DMSO) δ 106.9, 106.9, 107.2, 107.3, 107.3,
110.6, 111.2, 112.2, 113.0, 114.1, 118.1, 118.4, 118.4, 118.5, 118.6, 120.8,
120.9, 126.9, 127.0, 127.2, 127.3, 127.7, 128.9, 129.1, 129.2, 134.3, 137.9,
139.3, 139.7, 139.8, 140.0, 140.0, 140.3, 140.4, 140.5, 140.6, 163.9, 164.1,
164.1. IR (neat) ν 3404, 3289, 1582, 1494, 1410 cm−1. UV λmax/nm (ε/
105 mol L−1 cm−1) 278 (2.6). MS (FAB-B) m/z [M + H]+ calcd for
C48H39N20 895.3667, found 895.3648.
́
́
́
́
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Financial support from the DGCYT of Spain through Project
CTQ2011-22410/BQU is acknowledged.
REFERENCES
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7.14 Hz, 4H), 7.48 (d, J = 7.69 Hz, 4H), 7.66 (m, 2H), 7.78 (d, J = 1.76
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N,N′-Bis[4,6-bis(3-pyrazol-1-ylphenylamino)-1,3,5-triazin-2-yl]-o-
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(0.16 mmol, 0.06 g), DIPEA (0.12 mmol, 0.015 g), and DMSO (0.5
mL). White solid, 0.127 g (94%), mp 108 °C (decomp). 1H NMR (300
MHz, 80 °C, DMSO) δ 6.48 (t, J = 2.20 Hz, 4H), 7.1 (m, 2H), 7.27 (t, J =
8.02 Hz, 4H), 7.39 (d, J = 7.25 Hz, 4H), 7.68 (d, J = 1.76 Hz, 4H), 7.74
(pseudo d, J = 5.93 Hz, 6H), 8.06 (t, J = 1.98 Hz, 4H), 8.18 (d, J = 2.42
Hz, 4H), 8.49 (bs, 2H), 9.29 (bs, 4H). 13C NMR (75 MHz, 80 °C,
DMSO) δ 107.1, 110.6, 112.2, 118.0, 124.2, 124.4, 125.4, 127.1, 128.8,
131.8, 139.6, 140.2, 140.3, 140.4, 164.1, 164.5. IR (neat) ν 3379, 3290,
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MS (FAB-B) m/z [M + H]+ calcd for C48H39N20 895.3667, found
895.3654.
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ASSOCIATED CONTENT
■
S
* Supporting Information
Dynamic behavior by NMR spectroscopy; determination of
quantum yields; and NMR, UV−vis, fluorescence, and IR
spectra. This material is available free of charge via the Internet at
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AUTHOR INFORMATION
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Corresponding Authors
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X. Chem.Eur. J. 2013, 19, 12853−12858.
*E-mail: Antonio.Hoz@uclm.es.
*E-mail: Ana.Smigallon@uclm.es.
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