Bistriazine-based streptocyanines. Preparation, structural determination and optoelectronic properties

Article abstract of DOI:10.1016/j.dyepig.2016.04.016

A series of bistriazine-based streptocyanines has been selectively prepared. A variety of substituents has been introduced into the triazine ring with p-phenylenediamine as a conjugated spacer between the triazine and the streptocyanine moieties. Fukui in

Full text of DOI:10.1016/j.dyepig.2016.04.016

Dyes and Pigments 131 (2016) 307e319
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Bistriazine-based streptocyanines. Preparation, structural
determination and optoelectronic properties
a
,
,
b
a
a, **
Fernando Leon b, Patricia Elizalde a , Pilar Prieto , Ana Sanchez-Migallon
,
ꢀ
ꢀ
ꢀ
Antonio M. Rodríguez a c, Antonio de la Hoz a
Departamento de Química Organica, Facultad de Ciencias y Tecnologías Químicas, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain
,
, *
a
ꢀ
b
ꢀ
ꢀ
ꢀ
ꢀ
Departamento de Química Organica, Universidad Nacional Autonoma de Mexico, Facultad de Química, 04510 Mexico, Distrito Federal, Mexico
c Department of Chemical Sciences, University of Naples Federico II, 80126 Naples, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of bistriazine-based streptocyanines has been selectively prepared. A variety of substituents has
been introduced into the triazine ring with p-phenylenediamine as a conjugated spacer between the
triazine and the streptocyanine moieties. Fukui indices have been used to explain the different sequential
reactivity of the chlorine atoms in the triazine ring. 1D- and 2D-DNMR spectroscopy and computational
calculations have been carried out to explain the dynamic behavior of these complex systems, which can
be explained by the presence of a Cl … H bond. This method was used to build conjugated systems and to
show the interaction between the triazine part, the spacer, and the streptocyanine moiety. A study of the
optoelectronic properties has been performed by UVevis and fluorescence spectroscopy. Streptocyanine-
based bistriazines are violet-blue emitters and large Stokes shifts of more than 6000 cmꢀ1 were
observed. The title compounds showed interesting properties which have potential for use in opto-
electronic devices.
Received 4 January 2016
Received in revised form
1 April 2016
Accepted 6 April 2016
Available online 7 April 2016
Keywords:
Triazine
Streptocyanine
Computational calculations
DNMR
Luminescence
Microwave
© 2016 Elsevier Ltd. All rights reserved.
1. Introduction
that contain D and A groups.
Triazine derivatives have been used for the construction of star-
p-Conjugated molecular structures are among the most inves-
shaped derivatives. Some examples of star-shaped triazine de-
tigated systems in the field of molecular materials due to their
interesting optical and electronic properties [1]. However, the ef-
rivatives with a Dꢀ
p
ꢀA [5] or Dꢀ
p
ꢀAꢀ
p
ꢀDꢀ ꢀA [6] electronic
p
arrangement have found applications in solar cells [7], magnetic
materials [8], and blue-luminescent OLEDs [9]. In particular, the
later type of 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
ficiency of optoelectronic devices based on
not only highly depended on the chemical structure but also on the
supramolecular aggregation. Therefore, the construction of
p-conjugated systems is
p-
conjugated assemblies with controlled morphology and the desired
properties is crucial for the fabrication of the aforementioned de-
vices [2].
The choice of a good material for a specific application is hin-
dered by the complex structureeproperty relationship. An inter-
esting approach to tune the absorption in p-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
[10]. p-Conjugated systems that contain only one triazine ring have
been investigated for many years [11,12] but bistriazines have
received much less attention [13].
We recently described the preparation of mono- and bis-
triazines with phenylenediamine spacers with interesting opto-
electronic properties. The electronic properties depend on the
solvent and, in methanol, large bathochromic shifts and high
quantum yields were observed [14].
systems are among the most interesting
p
-conjugated materials
According to the approach outlined above, we planned the
preparation of bistriazines with a streptocyanine spacer. Strepto-
* Corresponding author.
** Corresponding author.
E-mail addresses: Ana.Smigallon@uclm.es (A. Sanchez-Migallon), Antonio.Hoz@
uclm.es (A. de la Hoz).
cyanines are highly conjugated dyes with extended p-systems.
These dyes show absorptions at long wavelengths and have high
molar absorptivities. Streptocyanines with Donor and Acceptor
ꢀ
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http://dx.doi.org/10.1016/j.dyepig.2016.04.016
0143-7208/© 2016 Elsevier Ltd. All rights reserved.

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F. Leon et al. / Dyes and Pigments 131 (2016) 307e319
308
groups have been used as Push-Pull systems [15]. These materials
are classified as streptopolymethines, cationic hemicyanines,
anionic streptopolymethine oxonols, neutral merocyanines, and
cyanines based on zwitterionic squarines. Cyanines have found
following equation:
fþA ¼ PAðN þ 1Þ ꢀ PAðNÞ
Where P stands for the population of atom A in a molecule M. The
calculated values are collected in Table 1.
The Fukui indices confirm that increased substitution of the
triazine ring results in a decrease in the electrophilic character that
hinders nucleophilic substitution in the carbon atoms. For this
applications in Dye Sensitized Solar Cells (DSSC) [7] as donor-
p
bridge-acceptor systems and, in some cases, they show impressive
efficiency [16]. Many of these compounds are either blue emitters
or absorb in the NIR region [17].
Kawamura [11] synthesized a squarylium-triazine dyad as a
photoradical generator that absorbs strongly in the red region and
undergoes an intramolecular photodissociative electron-transfer
reaction.
reason, the calculated outcomes represent
method to interpret the selectivity observed.
a straightforward
The aim of this research is the preparation of a new series of
bistriazine-based streptocyanines in order to show the influence of
2.2. Disubstituted triazines
this remarkable p-deficient heterocycle, that can show all possible
supramolecular interactions, on the optoelectronic properties of
streptocyanine dyes.
The synthesis of disubstituted triazines was performed by
double substitution of cyanuric chloride according to the procedure
of Kolmatov [23] for aromatic amines. The reaction conditions and
yields were very dependent on the basicity of the amine. For
strongly basic amines an acetic acid/sodium acetate buffer was
used but for amines with low basicity only acetic acid was required
(Table 2). p-Anisidine, 1-naphthylamine and diphenylamine were
selected because they show interesting properties as fluorophores
in fluorescence spectroscopy [24].
The reaction with diphenylamine (pKa ¼ 0.79) required the use
of acetic acid and 60 h to produce the monosubstituted product 3c'
in good yield (85%). The use of solvent-free conditions at high
temperatures [25] enabled triple substitution to give 3c” in 74%
yield. Finally, preparation of the desired 6-chloro-4,6-bis(N,N-
diphenylamino)-1,3,5-triazine (3c) could be performed in basic
conditions (Disiopropylethylamine, DIPEA) under reflux in di(n-
butyl)ether (Scheme 2).
2. Results and discussion
2.1. Synthesis of streptocyanines 7
The synthesis of the streptocyanines was planned in three steps,
starting with cyanuric chloride (1), disubstitution with aliphatic
and aromatic amines (2), reaction with p-phenylene diamine (4) to
give the monofunctional product (5) and finally reaction with 3-
chloro-N,N,N0,N0-tetramethyl-1,5-diaza-1,3-pentadienium
fluorophosphate (6) (Scheme 1).
hexa-
Starting with cyanuric chloride it is possible to replace
sequentially the three chloro-substituents with nucleophiles [18].
The first substitution can be performed at 0 ꢁC, the second one at
room temperature while the third substitution requires higher
temperatures, usually under reflux in an appropriate solvent.
The Fukui indices in cyanuric chloride and the mono- and di-
substituted compounds were determined computationally in or-
der to explain the different reaction conditions in the sequential
substitution of the chloro-substituents in cyanuric chloride. In brief,
Fukui indices provide information about which atoms in a molecule
have a higher tendency to either lose or accept an electron.
2.3. Introduction of the spacer, p-phenylenediamine (4)
The third substitution, which required harsher conditions, was
performed under microwave irradiation in the minimum amount
of DMSO (Table 3), with simple purification procedures to give
compounds 5 in excellent yields [14].
In chemistry this information is used to identify the positions
that are more prone to undergo nucleophilic or electrophilic attack.
Therefore, in an attempt to rationalize the different reactivities of
the chloro-substituents in cyanuric chloride, the condensed Fukui
function for the nucleophilic attack (fþA) [19] on monosubstituted
and disubstituted derivatives was calculated at the reactive carbon
atoms of the triazine ring within the framework of Density Func-
tional Theory (DFT) [20], employing the functional B3LYP [21] and
6-311 þ G(d,p) [22] as the basis set. The electrophilicity of an atom
A in a molecule M (of N electrons) was calculated using the
2.4. Preparation of streptocyanines 7
Finally, the synthesis of the streptocyanines was performed by
reaction of triazines 5 with 3-chloro-N,N,N0,N0-tetramethyl-1,5-
diaza-1,3-pentadienium hexafluorophosphate (6) [26] in ethanol
under reflux (Table 4).
The new compounds were characterized by spectroscopic
methods, particularly MALDI-TOF mass spectrometry and NMR
spectroscopy. The most characteristic signals in the 1H- and 13C-
NMR spectra of compounds 7 are listed in Table 5. These dimeric
systems show complex NMR spectra that are consistent with the
structures and also with the wide range of dynamic processes that
these compounds undergo. Some NMR spectra were recorded at
353 K because broad signals were observed for most compounds at
Table 1
Fukui indices (fþA) of the highlighted atom.
fþA ¼ 0.065
fþA ¼ 0.048
fþA ¼ 0.039
Scheme 1. Synthesis of dimeric triazines with a streptocyanine spacer.

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F. Leon et al. / Dyes and Pigments 131 (2016) 307e319
309
Table 2
Table 5
Reaction of cyanuric acid with aromatic and aliphatic amines.
Characteristic signals in the 1H- and 13C-NMR spectra of compounds 7 (solvent
DMSO-d6,
d in ppm).
R1
R2
Conditions
Yield
3a
3b
3c
3c'
H
H
Ph
Ph
Ph
p-CH3OC6H4
1-Naphthyl
Ph
Ph
Ph
AcOH/AcONa 25 ꢁC, 24 h [23]
AcOH 25 ꢁC, 48 h
93%
32%
61%
85%
74%
71%
DIPEA, di(n-butyl)ether 150 ꢁC, 6 h
AcOH 25 ꢁC, 60 h
H-2,4
NH-200
NH-400,600 NH-1,5 C-3
C-200
C-400,600
[a]
[a]
3c”[a]
No solvent 180 ꢁC, 2 h [25]
DIPEA, acetone 25 ꢁC, 24 h [27,28]
7a 8.24
7b 8.99
7c 8.17
8.99
7.20
6.81
9.09
9.13
e
94.27 163.87 163.99
98.00 164.06 166.03
98.08 161.57 163.28
106.07 163.57 164.54
[a]
3d
CH2CH2OCH2CH2
9.1
9.0
a
See Scheme 2 for these structures.
7d 8.01, 8.26 9.02. 9.09
e
a
Not observed.
298 K. This broadening is especially significant in the 13C-NMR
spectra and some signals were not observed clearly even at high
temperatures. Due to the low solubility of the streptocyanines NMR
spectra were recorded in DMSO, this produced some decomposi-
tion of the diimines to the amine and enamine, when long exper-
iments were required.
The 1H-NMR spectra show the presence of three different NH
groups and the H-2,4 signal at low field. In the 13C-NMR spectra, the
most characteristic signals are an upfield signal for C-3 of the
streptocyanine chain (d ~ 100) and two different signals for the
carbon atoms of the triazine ring. Signals of C-2,4 are hardly
observed at 150 ppm as broad signals due to a dynamic process.
Protons 2 and 4 of the dienic system are equivalent by meso-
merism and they appear as broad signals at 298 K. In compound 7d,
however, two signals are observed (one as a singlet and the second
as a doublet) and the signals of the p-phenylene group are also split.
The NMR data and spectra of 7d in different solvents and
different temperatures are shown in Table 6 and Fig. 1. It is
remarkable that splitting is observed at 298 K in DMSO-d6 and
CDCl3 but not in solution in DMF-d7, for which splitting is only
observed at lower temperature (233 K).
Scheme 2. Reaction of cyanuric chloride (1) with diphenylamine (2c).
Table 3
Reaction of disubstituted triazines 3 with p-phenylenediamine (4).
The synthesized compounds can show a great variety of isomers
due to the occurrence of different processes such as restricted
rotation and configurational isomerism (Fig. 2).
It is known that aminotriazines show restricted rotation around
the aminotriazine bond that leads to four possible isomers [27], and
a similar process is observed in 1,5-diazapentadiene systems to give
three isomers [26]. These processes have been studied by us and
others and the free energy of activation has been determined by
variable temperature NMR experiments [28]. Finally, s-cis/s-trans
R1
R2
Conditions
Yield
5a
5b
5c
5d
H
H
Ph
p-CH3OC6H4
1-Naphthyl
Ph
140 ꢁC, 70 W, 15 min
140 ꢁC, 70 W, 20 min
140 ꢁC, 70 W, 15 min
130 ꢁC, 90 W, 60 min
98%
98%
99%
94%
CH2CH2OCH2CH2
Table 4
Preparation of dimeric streptocyanines 7.
R1
R2
Reflux time
Yield
7a
7b
7c
7d
H
H
Ph
p-CH3OC6H4
1-Naphthyl
Ph
4 h
7 h
60 h
4 h
20%
48%
44%
29%
CH2CH2OCH2CH2

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F. Leon et al. / Dyes and Pigments 131 (2016) 307e319
310
Table 6
1H-NMR data for compound 7d in DMSO-d6, CDCl3, and DMF-d7
(d, in ppm, J in Hz).
Solvent
DMSO
T (K)
298
N-CH2
H-20,60
H-30,50
H-2,4
NH-1,5
NH
3.60
3.67
3.66
3.71
3.70
3.76
3.71
3.77
3.66
7.02
7.19
6.94
7.13
7.44
7.61
7.58
7.51
8.01 d J ¼ 12.7
8.26 s
9.01 d J ¼ 12.7
9.02
9.09
6.65
6.69
9.28
CDCl3
DMF
DMF
DMF
298
298
353
233
7.39 d J ¼ 12.7
6.88 d J ¼ 12.7
8.04 s
7.90
7.76
7.84
8.69
7.23
8.18
8.69
7.15
7.45
8.35 d J ¼ 11.6
9.58
9.64
8.4 s
Fig. 1. 1H-NMR spectra of compound 7d in DMSO-d6, CDCl3, and DMF-d7 at 298 K.
with different stabilities (Table 6 and Fig. 1). This observation
prompted us to study the origin of this result by DNMR experi-
ments and computational calculations.
The coalescence temperature (270 K) and the chemical shift in
the slow process (233 K) were determined from 1H-NMR spectra of
samples in DMF. A Free Energy of Activation of 12.9 kcal molꢀ1 was
€
calculated according to Sandstrom (Equation S1) [30]. However,
similar experiments carried out in DMSO and CDCl3 did not lead to
coalescence of the NH groups. As a consequence, thermodynamic
parameters for the rotation process were determined by 2D-EXSY
experiments at 298 K, i.e., the temperature of a slow process, in
both solvents. Rate constants were deduced according equation S2
and Free Energies of Activation were calculated from the rate
Fig. 2. Isomers produced by rotation and isomerization.
and Z/E isomerism are possible in the diene system of the strep-
tocyanine moiety [29]. As a consequence, up to 72 isomers,
rotamers, and configurational isomers are possible.
However, the different multiplicities of the H-2,4 signals (d and
s) cannot be explained by these kinetic processes. The integral of
the split signals indicates the presence of a 1:1 ratio in all solvents
and this situation is unlikely to occur with two rotamers or isomers
€
constants according to Sandstrom [30] (Equation S3). The values
obtained were 17.48 kcal molꢀ1 in CDCl3 (Fig. 3) and
17.65 kcal molꢀ1 in DMSO-d6. It is remarkable that the doublet at
d
7.39 exchanges with the singlet at d 8.04 ppm in CDCl3.

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F. Leon et al. / Dyes and Pigments 131 (2016) 307e319
311
Fig. 3. 2D-EXSY (tm ¼ 1 s) of compound 7d in CDCl3 at 298 K.
Fig. 5. Most stable structure of isomer I (hexafluorophosphate) in DMSO.
Fig. 4. Selected isomers of 1,5-diphenyl-1,5-diaza-2,3-pentadiene that were analyzed.
Fig. 6. Most stable structure of isomer I (perchlorate) in DMSO.
Table 7
Relative energies of isomers I-VII in the gas phase and in solution.
Energy (kcal molꢀ1
)
Isomer
Gas phase
Solution (CHCl3)
Solution (DMSO)
I
II
5.60
8.31
6.75
9.30
7.90
0.00
8.27
3.39
5.94
5.17
7.66
6.03
0.00
5.99
2.44
4.91
4.49
7.00
5.14
0.00
5.07
III
IV
V
VI
VII
Fig. 7. Most stable structure of isomer I with a chlorine atom (hexafluorophosphate) in
DMSO.
to determine the main isomers and to compare the theoretical
results with those obtained by NMR spectroscopy. Calculations
were performed using B3LYP/6-31G(d,p) and the Density
2.5. Computational calculations
A computational study of bistriazines 7 was carried out in order

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F. Leon et al. / Dyes and Pigments 131 (2016) 307e319
312
Scheme 3. Possible equilibrium in bistriazines 7; nd: not detected.
In the second step the protonated species of isomers I-VII were
studied as the hexafluorophosphates (Table S1) and perchlorates
(Table S2).
Once again isomer VI was the most stable in the gas phase but in
solution isomer I was the most stable both in CHCl3 and DMSO, a
finding that is consistent with the NMR spectra - from which an E
configuration was predicted for the double bond [19]. The coun-
terion (PF-6) was located close to the diene and hydrogen bonds
were formed between the fluorine and NeH atoms (Fig. 5).
For the perchlorate derivatives isomer VI was found to be more
stable in the gas phase but in solution isomer I was the most stable
in DMSO and isomer V in CHCl3. The counterion (ClO-4) is again
located close to the diene protons and hydrogen bonds are formed
between an oxygen and the NeH atom (Fig. 6).
Introduction of substituents into the 1,5-diazapentadiene sys-
tem was performed in a third step. The introduction of a chlorine
atom into the diene did not lead to appreciable modifications. Once
again, isomer VI is the most stable in the gas phase and isomer I in
solution. However, the PF-6 anion is now located opposite to the
chlorine atom (Fig. 7).
Fig. 8. Rotamers obtained upon the introduction of the triazine moiety. Relative en-
ergy (kcal molꢀ1).
Functional Theory (DFT) in the gas phase and in solution (CHCl3 and
DMSO). In solution, Self-Consistent Reaction Field (SRCF) models
for solvation were used. These continuum models consider the
solvent as a continuum, dielectric, and polarizable medium and the
solute is included in a cavity. This continuum is characterized by the
dielectric constant (ε) of the solvent. In this case the Polarizable
Continuum Model (PCM) was employed [31].
A stepwise optimization was carried out in order to simplify the
calculations. First, we analyzed the central 1,5-diphenyl-1,5-
diazapentadiene nucleus. In this case, we have chosen seven iso-
mers from the sixteen possibilities, we have discarded the more
congested isomers (Fig. 4). The results obtained are collected in
Table 7. Then we proceeded to study the protonated species. Finally,
we introduced sequentially the rest of the molecule, i.e., chlorine
atom, triazine rings, and substituents.
The introduction of the triazine rings into isomer I, which is the
most stable in solution, leads to two rotamers with a small energy
difference between them (Fig. 8).
In these two rotamers four hydrogen bonds are formed, two
between the Cl and the NeH atoms and two more between the F
and CeH atoms.
Finally, the amino groups were introduced into the triazine ring.
The study was focused on the morpholino-substituted compound
7d in order to reduce the number of isomers and, consequently, the
computational cost. This advantage is due to the fact that rotation of
the morpholino groups does not lead to different isomers and also
because this compound was studied by NMR spectroscopy, in
which splitting of the signals was observed. As described above,
both rotamers have a very similar stability in solution (Fig. 9) and
the results are therefore consistent with the 1H-NMR data.
Bearing in mind the results of the computational calculations
and the electronegativity of chlorine, we propose the formation of a
hydrogen bond with the Nþ-H and a slow equilibrium between the
isomers represented in Scheme 3. This proposal was supported by
computational calculations. A signal for the NeH that participates
in the hydrogen bond with the chlorine atom is not observed and,
consequently, it is not coupled with H-2, which appears as a singlet.
The most stable isomer, both in the gas phase and in solution, is
isomer VI and this stability is due to the formation of an intra-
molecular hydrogen bond (N … H distance 1.93 Å). Isomer I is the
second most stable isomer in DMSO and CHCl3, with a difference of
2.44 and 3.39 kcal molꢀ1 respectively with respect to VI.
Table 8
Absorption maxima of bistriazines 7a-d and comparison with the starting materials
5a-d and 6.
CH2Cl2
CH3OH
DMF
lmax (nm) [log ε]
lmax (nm) [log ε]
lmax (nm) [log ε]
6
327 [5.07]
321 [3.32]
324 [4.52]
5a
7a
5b
7b
5c
7c
5d
7d
283 [4.60]
277 [4.93], 380 [4.63]
295 [4.67]
306 [4.67], 377 [4.59]
284 [4.97]
283 [4.30], 378 [4.08]
278 [4.27]
275 [3.76]
278 [4.92], 382 [4.53]
278 [4.59]
301 [4.70], 383 [5.50]
282 [4.70]
282 [4.34], 372 [3.91]
273 [4.21]
281 [4.85]
281 [5.07], 387 [4.80]
305 [4.28]
308 [4.83], 384 [4.70]
283 [4.60]
280 [4.30], 388 [5.75]
277 [4.45]
Fig. 9. Most stable isomers of compound 7d. Relative energy (kcal molꢀ1
) and
hydrogen bond distances.
285 [4.20], 383 [4.68]
285 [4.10], 382 [3.86]
386 [4.76]

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F. Leon et al. / Dyes and Pigments 131 (2016) 307e319
313
a)
b)
1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.8
0.6
0.4
0.2
0.0
250
300
350
400
450
500
250
300
350
400
450
500
Wavelength (nm)
Wavelength (nm)
Fig. 10. a) Normalized absorption spectra of bistriazine 7a (¡) and comparison with the starting materials 5a (¡) and 6 (¡). b) Normalized absorption spectra of bistriazines 7a (¡),
7b (¡), 7c (¡) and 7d (¡). Solvent CH2Cl2.
Table 10
In contrast, the second NeH group is coupled with H-4 and the
Emission maxima of bistriazines 7a-d and the starting materials 5a-d and 6.
signal for this proton is a doublet.
CH2Cl2
CH3OH
DMF
2.6. Optoelectronic properties
lmax (nm)
lmax (nm)
lmax (nm)
6
383
409
409, 432, 455
379
410, 435, 460
380
408, 433, 455
410
408, 432, 454
395
399
407, 430, 455
378
405, 430, 500
359
403, 428
374
404, 429, 455
382
298
409, 435, 500
379
406, 431, 460
374
455
376
410, 433, 455
2.6.1. Absorption properties
5a
7a
5b
7b
5c
7c
5d
7d
The absorption and emission spectra of the bistriazines were
recorded in solvents with different polarities (CH2Cl2, CH3OH and
DMF) at three different concentrations (10ꢀ5 M, 10ꢀ6 M and
10ꢀ7 M).
The use of
p-conjugated molecules in photoluminiscent mate-
rials was introduced by Tang and Van Slyke for OLED's [32] and
today the preparation of organic compounds that are red, green,
and especially blue emitters is one of the most active areas of
research [33]. Other applications include the fabrication of opto-
electronic devices such as solar cells sensitized with organic dyes
(DSSC) or organic transistors.
The absorption maxima of bistriazines 7a-d in the three solvents
used are listed in Table 8 along with those of the starting materials
5a-d and 6 in order to assess the influence of the spacer on the
spectroscopic properties. Similarly, the normalized absorption
spectra of 7a, 5a, and 6 are shown in Fig. 10.
Triazines 5a-d give rise to a band at 278e308 nm in CH2Cl2. The
position of this band depends on the nature of the substituent and
it is bathochromically shifted in compounds that contain 1-
naphthyl groups (5b, 294 nm) and hypsochromically shifted in
those with morpholino groups (5d, 278 nm). A band due to the
dienic system is observed at 327 nm for streptocyanine 6.
The UVevis spectra of bistriazines 7a-d show two maxima at
279e308 and 378e380 nm. The band around 280 nm can be
1.0
0.8
0.6
0.4
0.2
0.0
400
500
600
Wavelength (nm)
Fig. 11. Emission spectra of bistriazines 7a (¡), 7b (¡), 7c (¡) and 7d (¡). Solvent
CH2Cl2. Excitation, see Table 11.
associated with n-p* transition and the band around 380 nm are
assigned to * transition of the conjugated backbone, due to
p p
ꢀ
absorption spectra of these compounds. This methodology is a
useful way to design new compounds with selected optoelectronic
properties. For this purpose, TD-DFT (time-dependent density
functional theory) is certainly the most popular method due to its
remarkably small computational cost and to the availability of
analytical derivatives allowing for easy exploration of the excited-
state potential energy surface [34].
It was remarked the difficulty of setting up a theoretical protocol
to reproduce the absorption spectrum of streptocyanine de-
rivatives, probably due to the three possible limit configurations for
the streptocyanine system [35]. Considering these difficulties we
selected compound 7a, with a reduced number of rotamers, for this
study and we used different theory levels. The outcomes obtained
are collected in Table 9.
their high absorption coefficients [9c]. This band is red shifted by
60e70 nm as a result of the higher conjugation with the phenyl
groups. The relative intensities of both bands depend on the sub-
stitution of the triazine ring, with this effect being more intense in
aryl-substituted bistriazines 7a-c while the band at 380 nm is more
intense in the morpholino derivative 7d (Fig. 10b).
We have used theoretical models in order to reproduce the
Table 9
Wavelength (nm) of the vertical transitions the lowest excited-state for compound
7a, calculated with various theoretical levels.
TD methodology
Abs (nm)
B3LYP/6-311 þ G(d,p)//B3LYP/6-311 þ G(d,p)
469.71
457.14
466.66
469.32
394.92
The results indicate that the calculated absorption maxima are
highly dependent on the level of calculation. In our case, most
methods fail to accurately reproduce the experimental values and
result in a large overestimation of the wavelength. However, for this
M062x/6-311 þ G(d,p)//M062x/6-311 þ G(d,p)
PBE(D3BJ)/6e311þþG(2d,2p)//PBE(D3BJ)/6e311þþG(2d,2p)
PBE(D3BJ)/6e311þþG(2d,2p)//PBE0(D3BJ)/6e311þþG(2d,2p)
B3LYP/6-311 þ G(d,p)//CAM-B3LYP/6e311þþG(2d,2p)

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314
Table 11
Emission maxima of bistriazines 7a-d and the starting materials 5a-d and 6 in CH2Cl2.
lmax (nm) [log ε]
lflouresc (nm)
Stokes shift (cmꢀ1
)
lexct (nm)
FF (%)
6
327 [5.07]
283 [4.60]
277 [4.93], 380 [4.63]
295 [4.67]
306 [4.67], 377 [4.59]
284 [4.97]
283 [4.30], 378 [4.08]
278 [4.27]
285 [4.20], 383 [4.68]
4471
10886
9457, 3168
7628
6152, 3467
8895
10875, 3307
9233
8421, 2962
327
280
380
295
381
284
381
277
385
5a
7a
5b
7b
5c
7c
5d
7d
409
409, 432, 455
379
410, 435, 460
380
408, 432, 455
410
0.1
0.4
0.2
0.2
408, 432, 454
type of compound, calculations at the B3LYP/6-311 þ G(d,p)//CAM-
B3LYP/6e311þþG(2d,2p) level of theory gives an optimum corre-
lation between experimental and theoretical results. On the study
of excited states and transition between these, it is advisable to take
precautions since the underestimation of charge-transfer (CT)
excitation energies (especially in donoreacceptor systems) [36] is
one of most common problem that exchangeecorrelation func-
tionals suffer. This failure of the method is partly avoided using the
Coulomb-attenuated CAM-B3LYP functional, leading to a correction
that has been previously observed in the literature [37].
1.0
0.8
0.6
0.4
0.2
0.0
400
500
600
2.6.2. Emission properties
Wavelength (nm)
The emission maxima of bistriazines 7a-d were recorded with
irradiation at the two maxima in the absorption spectra and are
collected in Table 10 for the three solvents used along with those of
the starting materials 5a-d and 6. The emission spectra of 7a-d are
shown in Fig. 11 (a comparison with the starting materials is shown
in Fig. S3).
Fig. 13. Solvatocromism on the emission spectra of bistriazine 7a. Excitation at 380 nm
CH2Cl2 (¡), CH3OH (¡) and DMF (¡).
380 nm
Triazines 5 were poor emitters in solution and only compound
5d showed a medium intensity fluorescence [14]. Similarly, bis-
triazines 7 showed only a low intensity emission in the fluores-
cence spectra, with the exception of 7a in dichloromethane
(Fig. S4). The strong intermolecular association produced in amino
2
1
triazines can explain this result where hydrogen bonding and
p-
stacking produce fluorescence quenching. The highest fluorescence
was usually observed on excitation of the band at 380 nm.
These bistriazines show emission over a wide range of wave-
lengths with a maximum at 432 nm and two other maxima at 408
and 455 nm. They show also a shoulder at 500 nm that can be
ascribed to the formation of excimers [38], which are formed by the
planar disposition of these compounds. This effect is especially
important for compound 3b with 1-naphthyl groups.
379 nm
378 nm
0
375 nm
400
500
600
373 nm
Wavelength (nm)
Fig. 14. Absorption spectra of bistriazine 7a at different concentrations 4.8 ꢂ 10ꢀ7
(¡), 7.2 ꢂ 10ꢀ6 M (¡), 4.8 ꢂ 10ꢀ6 M (¡), 2.4 ꢂ 10ꢀ6 M (¡) and 4.8 ꢂ 10ꢀ5 M (¡).
M
Very large Stokes shifts were observed, higher than 6000 cmꢀ1
(Table 11). These large values are typical in known systems and
imply the formation of intermolecular excimers with a high degree
a)
b)
180
160
140
120
100
80
1000
800
600
400
200
0
60
40
20
0
400
500
600
-20
300
400
500
Wavelength (nm)
Wavelength (nm)
Fig. 12. Effect of concentration on the emission spectra of bistriazine 7a in CH2Cl2 2.4 ꢂ 10ꢀ6 M (¡), 4.8 ꢂ 10ꢀ6 (¡) and 7.2 ꢂ 10ꢀ6 (¡) a) Excitation at 380 nm b) Excitation at
280 nm.

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315
of aggregation [39]. Excited state intramolecular charge transfer
(ESIPT) have also been considered to explain the large Stokes shifts
[40]. In our case, this possibility implies previous Z/E isomerization
to adopt the conformation for the ESIPT or the participation of the
Chlorine group, that has not been previously reported (Scheme S1).
Quantum yields were low but they are in the range of those
described for cyanine dyes used for labelling of proteins that pre-
sent of larger conjugation [41].
In streptocyanine 6, triazines 5, and bistriazines 7 the fluores-
cence intensity increased as the concentration decreased. This ef-
fect confirms again the formation of excimers that produce a
quenching in the fluorescence at higher concentrations. The fluo-
rescence increased at higher dilution, i.e., as a lower association was
observed (Fig. 12). It is interesting to note that the on excitation at
280 nm the band at 380 nm disappears at higher concentrations.
constituent dye molecules [45].
In our products, a strong association is produced and the
monomeric species cannot be detected even in highly dilute
solutions.
3. Conclusions
A new series of bistriazine substituted streptocyanines has been
prepared by reaction of p-aminophenylaminotriazines 5 with 3-
chloro-N,N,N0,N0,-tetramethyl-1,5-diaza-1,3-pentadienium hexa-
fluorophosphate (6).
For the preparation of the starting triazines 5, we have
confirmed the differential sequential reactivity of the chloro-
substituents in cyanuric chloride by determination of the Fukui
constants. These results confirms that the increased substitution of
the triazine ring results in a decrease in the electrophilic character
of the triazine ring.
2.6.3. Solvatochromism
In the absorption spectra solvent effects are negligible in the
band at 280 nm whereas a small bathochromic shift in the band at
380 nm (maximum 9 nm) is observed in DMF and the intensity
increases in this solvent (Fig. S2).
In the emission spectra of 7a, the same pattern is observed in
different solvents but a wide band at 500 nm was observed in DMF
(Fig. 13). This band confirms again the formation of excimers [38]
and is observed in all bistriazines especially in DMF but also in
MeOH and CH2Cl2 (Fig. S4).
The structure of streptocyanines 7 was studied by computa-
tional calculations and NMR spectroscopy. These techniques pro-
vided evidence of an intramolecular hydrogen bond between the
chlorine atom and the NH groups of the streptocyanine moiety that
permits the differentiation of the two parts of the molecule.
The electronic spectra of streptocyanines 7 can be visualized, by
comparison with the starting materials, as the sum of the two parts
of the molecule, the triazine and the dienic structure. The strep-
tocyanine part shows a large red shift because of the conjugation
with the phenylene group. The new compounds show interesting
optoelectronic properties; they are blue emitters, they show large
Stokes shifts and a strong association in solution by formation of
2.6.4. Aggregation of bistriazines
Aggregation of bistriazines was qualitatively studied by
recording the UVevis spectra at various temperatures. The varia-
tion of the spectra with temperature is often considered to be more
appropriate than concentration effects. This is because, with a
single solution, it is possible to obtain a large number of data and to
determine the transition from the monomeric to the completely
assembled species and also to determine the mechanism of ag-
gregation and even the thermodynamic parameters [37]. However,
the effect observed was very small in the range of temperatures
used in chloroform and the degree of aggregation is probably very
high in these compounds. The low solubility of these compounds
prevented the use of solvent with higher boiling point.
hydrogen bond and p-stacking that is reflected in an increase in the
fluorescence intensity when the concentration is reduced.
4. Experimental
4.1. General
All the calculations included in this paper were performed using
Gaussian 09 suite of programs [46].
All reagents and anhydrous solvents were purchased from
commercial sources and used without further purification. 3-
Chloro-N,N,N0,N0,-tetramethyl-1,5-diaza-1,3-pentadienium hexa-
fluorophosphate (6) was prepared as previously described [47].
Reactions under microwave irradiation were performed in a CEM
Discover monomode reactor with a dynamic method (temperature
controlled). Temperature was measured with the IR pyrometer
included in the microwave reactor. Melting points were deter-
mined in capillary tubes using a Büchi M-565 apparatus and are
given corrected. IR spectra were obtained with a Thermo Nicolet-
IR-100 spectrophotometer provided with ATR and a ZnSe lens.
NMR spectra were recorded on Varian Inova 500 spectrometer with
TMS as the internal standard. Assignment of the 1H and 13C signals
was done with the aid of homo and heteronuclear 2D correlations
(gCOSY y gHSQC) using the standard pulse sequences form Varian.
The 2D exchange spectra (EXSY) were acquired in the phase-
sensitive mode using the States-Haberkorn method [48]. Typi-
cally, a 3.1 kHz spectral width, 16 transients of 2048 data points
were collected for each 400 t1 increments. A 1s relaxation delay, an
11s (908) pulse width and a 0.165s acquisition time were used. The
free induction decays were processed with square cosine-bell fil-
ters in both dimensions and zero filling was applied prior to double
Fourier transition. Determination of the kinetic parameters
required two experiments with mixing times of 1 s (optimized) for
the exchange experiment and 0.02 s for the non-exchange spectra,
respectively. The cross peak/diagonal ratio was determined by
integrating the volume under the peaks. Mass spectra were
Therefore, the best results to differentiate these systems were
obtained at different concentrations (Fig. 14).
An important point is that absorption depends on the concen-
tration. Increasing the concentration does not produce a similar
increase in the Amax values and a small shift in the lmax is observed.
In this situation, LamberteBeer's law is not valid. This effect has
been ascribed to an increase in the formation of aggregates that
have the character of J aggregates with higher lmax and lower εmax
[42].
Considering the results described by Meijer et al. [43], we can
tentatively propose an isodesmic mechanism for the self-
association of bisimines 7. In an isodesmic equilibrium every
monomer addition to the growing chain is governed by a single
equilibrium constant and there is a gradual increase in the number
and length of the aggregated species. In this situation, Meijer
deduced that it is only at high concentrations or for high association
constants that long nanometer-sized objects are formed [43].
Numerous streptocyanines have been reported to form J-ag-
gregates [44]. The aggregates in solution exhibit distinct changes in
the absorption band as compared to the monomeric species.
Various aggregation patterns of the dyes have been proposed from
the spectral shifts. The bathochromically shifted J-bands (J for Jel-
ley) and hypsochromically shifted H-bands (H for hypsochromic) of
the aggregates have been explained in terms of molecular exciton
coupling theory, i.e., coupling of transition moments of the

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316
recorded ion a Bruker Autoflex II MALDI TOF/TOF spectrometer
using DHB as the matrix. UVevis spectra were recorded on a Varian
Cary model 5000 UVeViseNIR spectrophotometer provided with
control of temperature from ꢀ10 to 100 ꢁC. Variable temperature
experiments were recorded with 1.038 ꢂ 10ꢀ6 M solutions at 5-
degree intervals and the temperature was stabilized for 5 min
before recording the spectra. Fluorescence spectra were recorded
on a Jasco FP-750 spectrophotometer. In both cases, standard
quartz cells of 1 cm width were used. Spectra were recorded using
solvents of spectroscopic grade in the conditions specified in
Table 6. Determination of quantum yields were carried out on an
Uvikon-XS spectrofluorimeter. Quantum yields for compounds 7
were determined experimentally using as standard a solution of
quinine sulfate in Dichloromethane (FF ¼ 0.54) and applying the
following equation [49].
(61%). m.p. 216e220 ꢁC (from ethanol) (Lit. 221e222 ꢁC [50]). 1H
NMR (DMSO-d6, 500 MHz)
(DMSO-d6, 125 MHz)
d
¼ 7.08 (m, 12H), 7.16 (m, 8H). 13C NMR
d
¼ 126.1, 127.4, 128.7, 142.6, 165.6, 169.9. IR:
nmax ¼ 3647, 2980, 1738, 1200, 798, 752 cmꢀ1. MS (MALDI-TOF,
DHB) calculated m/z, 449.1407, found, 450.027 [M þ H]þ.
4.2.4. 2,4-Dichloro-6-diphenylamino-1,3,5-triazine (3c')
Following the general procedure for arylamines using diphe-
nylamine (2c) (85%). m.p. 178e179 ꢁC (from 2-propanol) (Lit.
172e174 [26]). 1H NMR (DMSO-d6, 500 MHz)
d
¼ 7.35 (m, 12H), 7.45
(m, 8H). 13C NMR (DMSO-d6, 125 MHz)
d
¼ 127.4, 127.7, 129.5, 141.8,
165.7, 169.1. MS (MALDI-TOF, DHB) calculated m/z, 316.0283, found,
316.892 [M þ H]þ.
4.2.5. 2,4,6-Tris(diphenylamino)-1,3,5-triazine (3c”) [25]
FFsa
sa
¼
FFst*ðAst=AsaÞ*ðIsa=IstÞ*ðnsa=nstÞ2
In a round-bottomed flask fitted with a reflux condenser, a
mixture of cyanuric chloride (1) (1.00 g, 5.4 mmol) and diphenyl-
amine (2c) (4.86 g, 28.7 mmol) was heated under reflux
(180e190 ꢁC) with efficient stirring for 2 h. The crude mixture was
cooled to 140 ꢁC and poured into cold water (500 mL). The solid was
filtered off in vacuum, extracted with acetone (3 ꢂ 300 mL) and
recrystallized (74%). m.p. 294e296 ꢁC (from toluene) (Lit.
¼
sample; st
¼
standard (quinine sulfate in CH2Cl2);
A ¼ absorbance; I ¼ integration of corrected fluorescence spec-
trum; n ¼ refractive index of the solvent.
4.2. Synthesis of 2-chloro-4,6-bisarylamino-1,3,5-triazines 3a-c,d'.
General procedure
297e298 ꢁC [25]). 1H NMR (DMSO-d6, 500 MHz)
7.92 (br, 10H). 13C NMR (DMSO-d6, 125 MHz)
d
¼ 7.50 (br, 15H),
d
¼ 123.5, 126.5, 128.4,
In a round-bottomed flask fitted with an addition funnel, cya-
nuric chloride (1) (1.84 g, 9.97 mmol) was dissolved in glacial acetic
acid (30 mL). A solution of the appropriate amine (2) (24.94 mmol)
and sodium acetate (2.566 g, 31.3 mmol) in acetic acid (10 mL) and
water (10 mL) was added slowly with vigorous stirring. Efficient
stirring was continued at room temperature for 12 h. The solid was
filtered off and washed with hot water until the washing water gave
a pH ¼ 6 (ca. 400 mL) and the product was dried in vacuo in the
presence of phosphorus pentoxide.
134.1, 166.2. MS (MALDI-TOF, DHB) calculated 582.2532, found, m/z
583.361 [M þ H]þ.
4.2.6. 2-Chloro-4,6-bis(morpholino)-1,3,5-triazine (3d)
In a round-bottomed flask fitted with an addition funnel, cya-
nuric chloride (1) (2.160 g, 11.7 mmol) was dissolved in acetone
(20 mL) and cooled in an ice bath. A solution of morpholine (2d)
(2.3 mL, 25.8 mmol) and DIPEA (4.6 mL) in acetone (15 mL) was
added slowly keeping the temperature at 4e5 ꢁC and stirring was
continued for 3 h in the ice bath and for 24 h at room temperature.
The solid was filtered off, washed with acetone (3 ꢂ 10 mL) and the
solvent was removed in vacuum to give an oily residue, which was
dissolved in hot ethanol (100 mL) and crystallized on cooling (71%).
m.p. 158e159 ꢁC (Lit. 173 ꢁC [51]). 1H NMR (DMSO-d6, 500 MHz)
4.2.1. 2-Chloro-4,6-bis(4'-methoxyphenylamino)-1,3,5-triazine
(3a)
Following the general procedure for arylamines and using 4-
methoxyaniline (2a) (93%). m.p. 199e200 ꢁC (lit. 198e199 ꢁC
[23]). 1H NMR (DMSO-d6, 500 MHz, 353 K)
d
¼ 3.74 (s, 3H), 6.9 (br d,
¼ 3.61 (bs, 8H), 3.69 (bs, 8H). 13C NMR (DMSO-d6, 125 MHz)
¼ 43.5, 66, 164.8, 168.7. IR: nmax ¼ 3024, 2943, 1738, 1217,
2H), 7.5 (d, J ¼ 8.8 Hz, 2H), 10.06 (bs, 2H). 13C NMR (DMSO-d6,
d
d
125 MHz, 353 K)
d
¼ 55.32, 114.57, 123.08, 130.16, 156.76, 164.29. IR:
791 cmꢀ1
.
nmax ¼ 3360, 2907, 2833, 1744, 1612, 1260, 988, 827 cmꢀ1
.
4.2.2. 2-Chloro-4,6-bis(1-naphthylamino)-1,3,5-triazine (3b)
Following the general procedure for arylamines and using 1-
naphthylamine (2b), stirring was continued for 48 h and acetic
acid (150 mL) was added at 24 h (32%). m.p. 182e183 ꢁC (from
4.3. Synthesis of 2-(4-aminophenylamino)-4,6-bis(alkyl or
arylamino)-1,3,5-triazines (5). General procedure [14]
p-Phenylenediamine and the appropriate chlorotriazine
3
ethanol). 1H NMR (DMSO-d6, 500 MHz, 353 K)
d
¼ 7.35 (t, J ¼ 7.9 Hz,
(0.3 mmol), and diisopropylethylamine (DIPEA) in a 3:1:1 ratio
were dissolved in anhydrous DMSO (1 mL). The mixture was
introduced into a microwave flask fitted with a reflux condenser
and a silica gel tube under argon. The mixture was irradiated under
microwaves for 10 min at 70 W and 140 ꢁC. Water (10 mL) was
added to the crude mixture, submitted to ultrasounds for 15 min
and filtered to give the pure product.
2H), 7.47 (m, 2H), 7.50 (ABCD system, J ¼ 8.0, 8.0,1.6 Hz, 4H), 7.75 (d,
J ¼ 7.9 Hz, 2H), 7.90 (ABCD system, J ¼ 8.0, 1.6 Hz, 2H), 8.0 (ABCD
system, J ¼ 8.0, 1.6 Hz, 2H), 9.76 (bs, 2H). 13C NMR (DMSO-d6,
125 MHz, 353 K)
d
¼ 123.7, 124.0, 125.9, 126.6, 128.6, 129.7, 134.1,
134.5, 166.6, 169.6. IR: nmax ¼ 3431, 3217, 3055, 1584, 1492, 785,
768 cmꢀ1. MS (MALDI-TOF, DHB) calculated m/z, 397.1094, found,
397.809 [M þ H]þ.
4.2.3. 2-Chloro-4,6-bis(diphenylamino)-1,3,5-triazine (3c)
4.3.1. 2-(4-Aminophenylamino)-4,6-bis(4-methoxyphenylamino)-
1,3,5-triazine (5a)
In a round-bottomed flask fitted with a reflux condenser, a
mixture of cyanuric chloride (1) (3.688 g, 20 mmol), diphenylamine
(2c) (7.107 g, 42 mmol), DIPEA (8.1 mL) and di-n-butyl ether (20 mL)
was heated under reflux (150 ꢁC) for 6 h with efficient stirring. The
mixture was poured into a mixture of ethanol (5 mL) and water
(10 mL) in an ice bath and was crystallized at 4 ꢁC for 12 h. The solid
was filtered off in vacuum and washed with cold ethanol (100 mL)
Following the general procedure using compound 3a (98%). m.p.
87e89 ꢁC (Lit. 85e89 ꢁC [50]). 1H NMR (DMSO-d6, 500 MHz)
d
¼ 3.73 (s, 6H), 4.80 (bs, 2H), 6.50 (d, J ¼ 8.8 Hz, 2H), 6.80 (d,
J ¼ 8.8 Hz, 4H), 7.32 (bs, 2H), 7.70 (bs, 4H), 8.80 (bs, 1H), 8.95 (bs,
2H). IR: nmax ¼ 3734, 2999, 1734, 1614, 1217, 791, 731 cmꢀ1. UV: lmax
(CH2Cl2) 282 nm (ε 60000 dm3 mol cmꢀ1).

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317
4.3.2. 2-(4-Aminophenylamino)-4,6-bis(1-naphthylamino)-1,3,5-
triazine (5b)
Following the general procedure using compound 3b (98%). m.p.
103e106 ꢁC (decomp.). 1H NMR (DMSO-d6, 500 MHz)
4.4.2. 1,5-{N,N'-bis-4-[4,6-bis(1-naphthylamino)-1,3,5-triazin-2-yl]
aminophenyl}-3-chloro-1,5-diaza-1,3-pentanodienium
hexafluorophosphate (7b)
d
¼ 4.60 (s,
Following the general procedure using compound 5b, (48%).
2 H), 6.25 (d, J ¼ 8.8 Hz, 2H), 7.09 (d, J ¼ 8.8 Hz), 7.43 (t, J ¼ 8.1 Hz),
7.50 (ABCD system, J ¼ 8.0, 8.0, 1.6 Hz), 7.60 (d, J ¼ 7.3 Hz, 2H), 7.72
(d, J ¼ 8.2, 2H), 7.91 (ABCD system, J ¼ 8.0, 1.6 Hz, 2H), 8.02 (ABCD
system, J ¼ 8.0, 1.6 Hz, 2H), 8.55 (bs, 1H), 8.97 (bs, 2H). 13C NMR
m.p. 148e151 ꢁC (decomp.) (orange powder). 1H NMR (DMSO-d6,
500 MHz)
d
¼ 6.88 (bs, 4H), 7.20 (bs, 2H), 7.45 (m, 8H), 7.52 (ABCD
system, J ¼ 8.0, 8.0, 1.6 Hz, 8 H), 7.60 (d, J ¼ 7.2 Hz, 4H), 7.75 (d,
J ¼ 8.1 Hz, 4H), 7.95 (ABCD system, J ¼ 8.0, 1.6 Hz, 4H), 8.05 (ABCD
system, J ¼ 8.0, 1.6 Hz, 4H), 8.99 (bs, 2H), 9.13 (bs, 4H). 13C NMR
(DMSO-d6, 125 MHz)
d
¼ 113.0, 121.1, 123, 124.4, 125.1, 125.1, 125.3,
127.4, 128.7, 128.9, 133.3, 134.5, 143, 163.6, 165.5. IR: nmax ¼ 3395,
3046, 2980, 1738, 1587, 1479, 806, 791, 770 cmꢀ1. UV: lmax (CH2Cl2)
294 nm (ε dm3 105 mol cmꢀ1 110000). MS: (MALDI-TOF, DHB)
calculated m/z, 469.2015, found, 470.081 [M þ H]þ. Found: C, 74.47;
H, 4.75; N, 21.12. C29H23N7 requires C, 74.18; H, 4.94; N, 20.88%.
(DMSO-d6, 125 MHz)
d
¼ 98, 120.3, 123.5, 123.7, 125.1, 125.5, 125.6,
125.8, 127.9, 129.5, 133.8, 134.8, 164.1, 166. IR: nmax ¼ 3647, 2988,
1748, 1607, 839, 770 cmꢀ1. UV: lmax (CH2Cl2) 304, 373 nm
(ε/dm3 mol. cmꢀ1 60000, 50000). MS: (MALDI-TOF, DHB) calculated
m/z, 1009.3718, found, 1009.419 [M þ H]þ. Found: C, 63.50; H, 4.10;
N, 16.85. C61H46ClF6N14P requires C, 63.40; H, 4.01; N, 16.97%.
4.3.3. 2-(4-Aminophenylamino)-4,6-bis(diphenylamino)-1,3,5-
triazine (5c)
4.4.3. 1,5-{N,N'-bis-4-[4,6-bis(diphenylamino)-1,3,5-triazin-2-yl]
aminophenyl}-3-chloro-1,5-diaza-1,3-pentanodienium
hexafluorophosphate (7c)
Following the general procedure using compound 3c (99%). m.p.
162e164 ꢁC (decomp.). 1H NMR (DMSO-d6, 500 MHz)
d
¼ 4.59 (s,
Following the general procedure using compound 5c, (44%).
m.p. 245e248 ꢁC (decomp.) (orange powder). 1H NMR (DMSO-d6,
2 H), 6.17 (d, J ¼ 8.8 Hz, 2H), 7.00 (d, J ¼ 8.8 Hz, 2H), 7.14 (m, 2H),
7.22 (m, 4H), 7.29 (m, 4H), 8.72 (s, H). 13C NMR (DMSO-d6, 125 MHz)
500 MHz, 80 ꢁC)
d
¼ 6.81 (bs, 2H), 6.85 (d, J ¼ 9.1 Hz, 4H), 7.18 (d,
J ¼ 7.0 Hz, 8H), 7.2e7.4 (m, 32H), 7.31 (m, 4H), 8.17 (bs, 2H), 9.1 (bs,
2H). 13C NMR (DMSO-d6, 125 MHz, 80 ꢁC)
d
¼ 113.2, 120.3, 124.6, 127.2, 127.9, 129.1, 142.7, 143.4, 163, 165.3. IR:
nmax ¼ 3373, 3024, 2968, 1737, 802, 754, 689 cmꢀ1. UV: lmax
(CH2Cl2) 283 nm (ε/dm3 mol. cmꢀ1120000). MS: (MALDI-TOF, DHB)
calculated m/z, 521.6280, found, 522.372 [M þ H]þ. Found: C, 76.28;
H, 4.98; N, 18.62. C33H27N7 requires C, 75.99; H, 5.22; N, 18.80%.
d
¼ 98.1, 116.6, 119.9,
125.5, 127.8, 128.6, 129.1, 143.3, 157, 161.6, 163.3. nmax ¼ 3669, 3647,
3379, 1734, 1647, 1400, 837, 746, 696 cmꢀ1. UV: lmax (CH2Cl2) 279,
381 nm (ε/dm3 mol. cmꢀ1 30000, 20000). MS: (MALDI-TOF, DHB)
calculated m/z, 1113.4344, found, 1113.458 [M þ H]þ. Found: C,
65.70; H, 4.39; N, 15.65. C69H54ClF6N14P requires C, 65.79; H, 4.32;
N, 15.57%.
4.3.4. 2-(4-Aminophenylamino)-4,6-bis(morpholino)-1,3,5-triazine
(5d)
Following the general procedure using compound 3d. Micro-
4.4.4. 1,5-{N,N'-bis-4-[4,6-bis(N,N'-morpholino)-1,3,5-triazin-2-
yl]-aminophenyl}-3-chloro-1,5-diaza-1,3-pentanodienium
hexafluorophosphate (7d)
wave irradiation (130 ꢁC, 90 W) for 90 min (94%). m.p. 208e210 ꢁC
(decomp.). 1H NMR (DMSO-d6, 500 MHz)
d
¼ 3.58 (m, 8H), 3.63 (m,
8H), 4.70 (s, 2H), 6.50 (d, J ¼ 8 Hz, 2H), 7.2 (d, J ¼ 8 Hz, 2H), 8.59 (s,
1H). 13C NMR (DMSO-d6, 125 MHz)
Following the general procedure using compound 5d, (29%).
m.p. 234e237 ꢁC (decomp.) (yellow powder). 1H NMR (DMSO-d6,
d
¼ 43.7, 66.5,114.2, 122.3,129.7,
500 MHz, 80 ꢁC)
d
¼ 3.62 (m, 16H), 3.71 (m, 16H), 7.13 (d, J ¼ 8.8 Hz,
144.1, 164.4, 165.2. IR: nmax ¼ 3744, 2968, 1738, 1364, 1217,
802 cmꢀ1. UV: lmax (CH2Cl2) 275 nm (ε/dm3 mol. cmꢀ1 50000). MS:
(MALDI-TOF, DHB) calculated m/z, 357.1913, found, 358.005
[M þ H]þ. Found: C, 56.90; H, 6.61; N, 27.30. C17H23N7O2 requires C,
57.13; H, 6.49; N, 27.43%.
2H), 7.60 (d, J ¼ 8.8 Hz, 2H), 8.09 (bs, 2H), 8.70 (bs, 2H). 13C NMR
(DMSO-d6, 125 MHz, 80 ꢁC)
d
¼ 42.9, 66.5, 106.1, 115.5, 120.2, 163.6,
164.5. IR: nmax ¼ 3647, 2980, 1748, 1734, 1558, 1217, 1030, 825 cmꢀ1
.
UV: lmax (CH2Cl2) 377 nm (ε/dm3 mol. cmꢀ1 40000). MS: (MALDI-
TOF, DHB) calculated m/z, 785.3515, found, 785.185 [M þ H]þ.
Found: C, 47.78; H, 4.91; N, 21.15. C37H46ClF6N14O4P requires C,
47.72; H, 4.98; N, 21.06%.
4.4. Synthesis of streptocyanines (7). General procedure [47]
In a round-bottomed flask fitted with a reflux condenser, a
mixture of compounds 5 (0.378 mmol) and 6 (0.058 g, 0.189 mmol)
in dry ethanol (25 mL) was heated under reflux for 4 h. The solvent
was removed in vacuum to give the pure product after recrystalli-
zation from 2-propanol.
Acknowledgements
Financial support from the Spanish Ministerio de Ciencia e
ꢀ
Innovacion CTQ2011-22410, CTQ2014-54987-P and PEII-2014-
002A is gratefully acknowledged. F.L. acknowledges a predoctoral
ꢀ
grant from the Programa de Apoyos para la Superacion del Personal
ꢀ
Academico (PASPA) of the UNAM. We acknowledge M.A. Herrero
4.4.1. 1,5-{N,N'-bis-4-[(4,6-bis(4'-methoxyphenylamino)-1,3,5-
triazin-2-yl)-aminophenyl]}-3-chloro-1,5-diaza-1,3-
pentanodienium hexafluorophosphate (7a)
for recording the MALDI-TOF spectra and technical support from
the High Performance Computing Service of the Universidad de
Castilla-La Mancha.
Following the general procedure using compound 5a, (20%).
m.p. 185e187 ꢁC (decomp.) (orange powder). 1H NMR (DMSO-d6,
Appendix A. Supplementary data
500 MHz)
7.64 (bs, 8H), 7.83 (bs, 8H), 8.24 (bs, 2H), 8.99 (bs, 4H), 9.09 (bs, 2H).
13C NMR (DMSO-d6, 125 MHz)
d
¼ 3.75 (s, 12H), 6.88 (d, J ¼ 8.8 Hz, 8H), 7.26 (bs, 4H),
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.dyepig.2016.04.016.
d
¼ 55.2, 94.3, 113.5, 120.8, 122.1, 132,
140.2, 154.6, 163.9, 164. IR: nmax ¼ 3647, 2986, 1748, 1734, 1624,
1254, 1105, 837 cmꢀ1. UV: lmax (CH2Cl2) 278, 375 nm (ε/dm3 mol.
cmꢀ1 90000, 50000). MS: (MALDI-TOF, DHB) calculated m/z,
929.3515, found, 929.367 [M þ H]þ. Found: C, 54.68; H, 4.39; N,
18.30. C49H46ClF6N14O4P requires C, 54.73; H, 4.31; N, 18.23%.
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