Donor-linker-acceptor (D-π-A) diazine chromophores with extended π-conjugated cores: Synthesis, photophysical and second order nonlinear optical properties

Article abstract of DOI:10.1039/c5ra05736a

The synthesis of a series of push-pull pyrimidine and quinoxaline chromophores with extended π-conjugated cores is reported. Starting from a bromoarylvinyldiazine derivative, the key step in the preparation of the chromophores consists of a Sonogashira cr

Full text of DOI:10.1039/c5ra05736a

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Page 1 of 26
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DOI: 10.1039/C5RA05736A
diazine
Donor-Linker-Acceptor
(D--A)
chromophores with extended -conjugated core:
synthesis, photophysical and second order
nonlinear optical properties.
Sylvain Achelle,1* Alberto Barsella,2 Bertrand Caro,1 and Françoise Robin-le Guen.1
1 Institut des Sciences Chimiques de Rennes UMR CNRS 6226, IUT de Lannion, rue Edouard
Branly, BP 30219, F22302 Lannion Cedex, France
2
Département d’Optique ultra-rapide et Nanophotonique, IPCMS-CNRS, 23 Rue du Loess,
BP 43, 67034 Strasbourg Cedex 2, France
Corresponding author: sylvain.achelle@univ-rennes1.fr tel : (33) (0)2 96 46 94 46
Synopsis TOC
__________________________________________________________________________
Extended
-conjugated core
D
N
N
D = NR2, OMe
Increased 2nd Order
NLO response
High Fluorescence
quantum yield
Important emission
solvatochromism
The synthesis and photophysical properties of a series of push-pull pyrimidine and
quinoxaline chromophores with an extended -conjugated core are reported.
__________________________________________________________________________________

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DOI: 10.1039/C5RA05736A
Abstract
The synthesis of a series of push-pull pyrimidine and quinoxaline chromophores with an
extended -conjugated core is reported. Starting from a bromoarylvinyldiazine derivative, the
key step in the preparation of the chromophores consists of a Sonogashira cross-coupling
reaction. The photophysical properties of the compounds are described. A strong positive
emission solvatochromism, typical for dyes presenting Intramolecular Charge Transfer (ICT),
is observed, in particular for amino substituted derivatives with larger solvatochromic range
than known analogous chromophores with smaller -conjugated core. The second order non
linear optical (NLO) properties were investigated for some of the compounds and a
comparison with the NLO responses of already described diazine chromophores exhibits a
significant enhancement of the NLO properties by extension of the -conjugated core.
Key words: Pyrimidine ; Quinoxaline ; Push-Pull ; Non-linear Optics ; Fluorescence
Introduction
During the past decades, push-pull structures composed of a -conjugated core
substituted by electron-donating (D) and electron-attracting (A) groups were extensively
studied in materials chemistry.1 Indeed ICT in such D--A structure leads to polarization of
the chromophore and generation of molecular dipole.2 Push-pull molecules have found
applications as sensitizers for dye sensitized solar-cells (DSSCs),3 emitters for organic light
emitting diodes (OLEDs)4 and various fluorescent sensors.5 D--A is also the typical structure
of second-order NLO chromophores6 with applications in green lasers obtained from infrared
sources through frequency doubling, second harmonic generation microscopy or in terahertz
wave generation.7

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Diazines consist of six-membered aromatics with two nitrogen atoms. Three different
DOI: 10.1039/C5RA05736A
structures can be distinguished according to the relative positions of the nitrogen atoms:
pyridazine (1,2-diazine),8 pyrimidine (1,3-diazine),9 and pyrazine (1,4-diazine).10 The
(benzo)diazines with their highly π–deficient aromatic character are good candidates to be
incorporated as electron-withdrawing groups into push-pull scaffolds favoring ICT. The use
of diazine rings in the structure of π–conjugated materials has been recently reviewed.11
During the past decade, we have described a large library of (benzo)diazine chromophores
with fluorescent sensing applications and NLO properties.12 In the literature, there are only
few examples of diazine chromophores with second-order NLO properties.13 Among them we
have described a series of 4-arylvinylpyrimidine and 2-arylvinylquinoxaline derivatives that
exhibit moderate second-order NLO responses.14
Photophysical properties of push-pull molecules can be easily tuned by varying
various parameters.15 In particular, two design strategies were described for increasing their
second-order NLO polarizability.16 The first one consists in increasing the strength of the
donor and /or the acceptor. Recently, we have described the N-methylation and the
complexation of pyrimidine push-pull chromophores resulting in a dramatic increase of the
second-order NLO response.17 The second strategy consists in the elongation of the
conjugation pathway.
In this context, the aim of the present article is to describe the synthesis of seventeen
new diazine chromophores with extended -conjugated core. Indeed, we thought that it would
be of interest to study the influence of the nature of the -conjugated linker on the linear and
second-order NLO properties on diazine push-pull chromophores.
Results and discussion.
Preparation of chromophores. Halogenated starting materials were obtained by
condensation of 4-methylpyrimidine or 2-methylquinoxaline with the corresponding aromatic

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aldehydes in boiling aqueous 5M NaOH using aliquat 336 as a phase-transfer catalyst
DOI: 10.1039/C5RA05736A
according to the conditions initially described by Vanden Eynde (Schemes 1-2).18 As
previously observed, this synthetic protocol led to the selective formation of E-configured
vinylene bridges,12a,b,f,14,19 compounds 1a-c and 2 where obtained with moderate to good
yield.
Z
X
CHO
N
N
N
N
Z
Aliquat 336(cat.)/NaOH aq
X

1a Z = C=C, X = Br 78%
1b Z = C=C, X = I 84%
1c Z = S, X = Br
79%
Scheme 1 : Synthesis of compounds 1a-c
N
N
4-bromobenzaldehyde
N
Aliquat 336(cat.)/NaOH aq
N

Br
2 55%
Scheme 2 : Synthesis of compound 2
In order to compare the reactivity of bromo (1a) and iodo (1b) derivatives in Sonogashira
cross-coupling reaction, the two compounds were tested with phenylacetylene using
diisopropylamine as solvent in a pressure tube at 80°C, according to the conditions initially
described on chloropyrimidines (Scheme 3).20 In these conditions, compound 3a was obtained
with similar yield when starting from 1a or 1b. It should be noted that compound 3a can be
also obtained at room temperature in a mixture of triethylamine and THF starting from iodo
compound 1b with a correct yield (64%), which is not possible with bromo compound 1a.
Nevertheless, due to the high cost of 4-iodobenzaldehyde, we decided to start from bromo
derivatives for all the following reactions.

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Ph
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DOI: 10.1039/C5RA05736A
Pd(PPh3)2Cl2, CuI
N
N
N
N
HN(iPr)2, , 15h
3a
X
1a X = Br
1b X = I
X = Br 72%
X = I 68%
Scheme 3: Synthesis of compounds 3a
Similar conditions were used to obtain compounds 3, 4 and 5 starting from bromo derivatives
1a, 1c and 2 respectively and a variety of alkynes (Tables 1-3). In case of compounds 3e, 4e
and 5e, the trimethylsilyl group can be cleaved with potassiun hydroxide in methanol to
obtain the corresponding terminal alkynes 3f, 4f and 5f. These compounds appear as
interesting building blocks for the synthesis of more complex structures.
Table 1: Sonogashira Cross-coupling reaction with compound 1a
R
N
N
Pd(PPh3)2Cl2 CuI
N
N
HN(iPr)2,  15h
1a
Br
3a-f
R
Compd
R
Isolated yield (%)
72
3a
OMe
NMe2
NPh2
56
59
3b
3c
81
57
3d
3e
SiMe3
H
3fa
83
a : obtained by deprotection of compound 3e (KOH/MeOH rt, 15 min)
Table 2: Sonogashira Cross-coupling reaction with compound 1c
R
N
N
Pd(PPh3)2Cl2 CuI
N
N
S
S
R
Br
HN(iPr)2,  15h
1c
4a-f
Compd
R
Isolated yield (%)
69
4a
OMe
54
4b

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DOI: 10.1039/C5RA05736A
NMe2
NPh2
79
4c
89
Non isolated
56b
4d
4e
SiMe3
H
4fa
a : obtained by deprotection of compound 4e (KOH/MeOH rt, 15 min) b: over two steps
Table 3: Sonogashira Cross-coupling reaction with compound 2
R
N
N
N
N
Pd(PPh3)2Cl2 CuI
HN(iPr)2,  15h
2
Br
5a-f
R
Compd
R
Isolated yield (%)
95
5a
OMe
NMe2
NPh2
83
68
5b
5c
72
75
84
5d
5e
SiMe3
H
5fa
a : obtained by deprotection of compound 5e (KOH/MeOH rt, 15 min)
All new compounds are readily soluble in THF, chloroform and dichloromethane and were
characterized using a variety of analytical techniques (1H and 13C NMR, high-resolution mass
spectrometry, UV-visible and fluorescence spectrometry). NMR experiments proved very
useful to confirm the structures of the compounds (see Experimental Section and Supporting
Information). The selectivity of the Knoevenagel reactions was sufficiently high to generate
all-E isomers within the limits of NMR detection. The stereochemistry of the double bonds
was unequivocally established on the basis of the coupling constant for the vinylic protons in
the 1H NMR spectra (J ≈ 16 Hz).
These materials are perfectly stable in the solid state and could be stored without the need for
special precautions. However, it should be noted that some samples underwent partial E-Z
isomerization when allowed to stand in CDCl3 solution under sunlight at room temperature
for several days as observed by NMR.

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UV/Vis and PL Spectroscopy. The UV-Vis and photoluminescence (PL)
DOI: 10.1039/C5RA05736A
spectroscopic data of various oligomers measured in dichloromethane and in toluene at 25°C
are presented in tables 4 and S40. Analyses have been carried out using low concentration
solutions (1.0 x 10-5 to 3.0 x 10-5 M for UV/Vis spectra and 1.0 x 10-6 to 3.0 x 10-6 M for PL
spectra). As an example, the spectra for derivatives 3c, 4d and 5b in dichloromethane are
shown in Figure 1. Under these conditions, self-absorption effects were not observed. All
compounds are photostable and did not undergo E-Z isomerization under the analysis
conditions.
In dichloromethane, all compounds show absorption wavelengths (max) in the UV or visible
region (347-419 nm). In some cases, a second or even a third absorption band of higher
energy attributed to -* transition can be observed. All compounds are luminescent with, in
some cases, high quantum yield (up to 0.8). Very large Stokes shifts, in some case superior to
9000 cm-1 were observed, indicating large differences (vibrational, electronic, geometric)
between the Franck-Condon state and the excited state.
For the three series of compounds an important substituent effect is observed. For instance for
compounds 3, non-substituted compound 3a exhibits an emission maxima in CH2Cl2 at 420
nm this maxima is shifted to 612 nm in case of dimethylamino substituted compound 3c.
Compounds 3 and 5 are red-shifted in absorption and emission when compared with
corresponding 4-arylvinylpyrimidines and 2-arylvinylquinoxalines.14,21 Whereas 4-
(phenylvinyl)pyrimidine and 4-(p-methoxyphenylvinyl)pyrimidine are slighltly fluorescent,
extention of the conjugation leads to a dramatic increase of the fluorescence quantum yield. It
should be noted however that in the case of quinoxaline derivatives 5c-d the extension of the
-conjugated core leads to a diminution of the fluorescence quantum yield in
dichloromethane, nevertheless these values are much higher in toluene. Comparison of
compounds 3b-d with corresponding bisphenylenevinylene pyrimidine indicates that the

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introduction of a triple bond between the two phenyl rings also leads to red-shifted spectra.
DOI: 10.1039/C5RA05736A
This tendency is less significant with quinoxaline derivatives.
Comparison of quinoxaline derivatives 5 with pyrimidine derivatives 3 showed a
bathochromic shift of absorption and emission spectra in case of quinoxaline derivatives.
Concerning pyrimidine derivatives, when the -conjugated core includes a thienyl ring
(compounds 4) instead of a phenyl ring (compounds 3), a red shift in absorption and emission
is clearly observed in toluene. This tendency is not observed in dichloromethane for the most
electron-donating amino groups.
Table 4. UV/Vis and photoluminescence (PL) data in CH2Cl2
PL
Stokes shift
cm–1
UV/vis max, nm
(,mM–1·cm–1)
Compda
b

max, nm
420
F
347 (33.0)
355 (28.5)
0.11
0.51
0.54
0.41
<0.01
0.04
0.80
0.79
0.39
0.77
0.07
0.37
5009
3a
460
612
590
462
489
607
583
447
480
647
630
6429
9236
8432
4465
5660
7392
6886
3875
5276
9174
8941
3b
3c
3d
4a
4b
4c
4d
5a
5b
5c
5d
312 (18.8), 391 (25.0)
314 (32.9), 394 (34.4)
278 (10.1), 383 (34.1)
383 (36.1)
328 (16.7), 419 (31.5)
305sh (22.3), 342 (26,4), 416 (43.3)
308 (22.9), 381 (38.1)
302 (17.3), 383 (30.6)
321 (26.1), 406 (33.7)
306 (27.2), 333 (27.5), 403 (35.7)

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a
–5
–5
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DOI: 10.1039/C5RA05736A
All spectra were recorded at room temperature at c = 1.0  10 M to 3.0  10 M for absorption and
b
c = 1.0  10–6 M to 3.0  10–6 M for emission. Fluorescence quantum yield (10%) determined
relative to 9,10-Bis-phenylethynyl-anthracene in cyclohexane (F = 1.00).22
Figure 1: Normalized UV/Vis (solid line) and emission spectra (brocken line) of
compounds 3c, 4d and 5b.
In an effort to gain further insight into the photophysical process within these push-
pull molecules, we investigated their emission behavior in different aprotic solvents. The
results of these investigations are summarized in table 5. For all compounds, a bathochromic
shift of the emission band is observed with increasing solvent polarity as predicted by the
Dimroth–Reichardt polarity parameter (ET(30)).23 In contrast, the absorption wavelength is
not significantly shifted. Broad structureless emission and larger Stokes shifts were observed
for polar solvents. This solvatochromic behavior, which results from the stabilization of the
highly polar emitting state by polar solvents, is typical for compounds exhibiting an internal
charge transfer upon excitation and has been fully documented with donor-acceptor
fluorophores.24 It should be noted that in low polar solvents (hexane and sometimes toluene)
two well developed emission bands are observed, which may be due to the partial aggregation
of the chromophores. As an example the PL spectra for compound 4d and color change under
UV irradiation for compound 4c are shown in figures 2-3.
Table 5. Emission solvatochromism of diazines chromophores in various aprotic solvents

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Hexane
Toluene
THF
CH2Cl2
Acetone
MeCNView Article OnlineDMSO
DOI: 10.1039/C5RA05736A
ET(30)a = 30.9 ET(30)a = 33.9 ET(30)a = 37.4
ET(30)a = 40.7 ET(30)a = 42.2 ET(30)a = 45.6 ET(30)a = 45.1
Compd
max nm
376, 398
393, 412
459
max nm
390, 407
414, 427
501
max nm
407
445
590
554
453
479
600
557
430
459
634
584
max nm
420
460
612
590
462
489
607
583
447
480
647
630
max nm
421
max nm
422
max nm
423
3a
3b
3c
3d
4a
4b
4c
4d
5a
5b
5c
5d
474
485
493
b
b
659
-
-
434, 451
417, 440
427, 451
496
476
620
653
465
497
679
649
448
508
660
475
507
448
455
459
490
b
526
650
-
468, 491
414, 436
425
496
621
658
453
511
426
446
440
484
b
b
b
464
518
-
-
-
b
b
458
490
671
-
-
a Dimroth–Reichardt polarity parameter,kJmol–1. b no signal detected
Figure 2: Normalized emission of compound 4d in various solvents
Figure 3: Color of solution of 4c in various solvents (Hexane, Toluene, CHCl3, THF,
CH2Cl2) (c = 10-5 M).
All the amino substituted derivatives exhibit extended solvatochromic range. The highest
range between hexane and dichloromethane is observed for compound 5c ( = 183 nm, 

Page 11 of 26
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-1
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DOI: 10.1039/C5RA05736A
= 6095 cm ). It should be noted however that the red-shift observed, when the polarity is
increased, is associated with a dramatic decrease of the fluorescence intensity. As shown in
tables 6 and S41, extension of the -conjugated core leads to a dramatic increase of the
solvatochromic range.
For all of the compounds, the emission maxima were plotted versus ET(30) (see supporting
information S42-S43). A good linearity was obtained for all the compounds. The slopes of the
corresponding regression lines (SP) are good indications of the intensity of the ICT into the
chromophores. When comparing the SP values for pyrimidine derivatives 3 and quinoxaline
derivatives 5, a more intense solvatochromism is observed for the quinoxaline derivatives 5.
When comparing compounds 3 and 4, replacing a 1,4-phenylene linker by a 2,5-thienylene
one decreases the intensity of the solvatochromism.
Table 6: Solvatochromic range between hexane/heptane and dichloromethane for
compounds 3b-d and their analogues
N
N

D
(cm-1)
Compd
D
 (nm)

34a
2118a
OMe
48
2533
4500a
5447
3562b
4710b
5224
3b
OMe
NMe2
NMe2
NPh2
NPh2
NPh2
116a
153
83b
3c
104b
139
3d
a : data from ref 20 b : data from ref 13

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DOI: 10.1039/C5RA05736A
Second Order Non Linear Optical Properties.
Nonlinearities of the selected dyes 3c,d, 4b-d and 5c,d were evaluated by measuring the µ
coefficients by means of the Electric Field Induced Second Harmonic Generation (EFISH)
technique, at 1907 nm fundamental wavelength. The obtained values are reported in Table 7
and can be considered not affected by resonance effects, being the second harmonic signal
generated from chloroform solutions of these dyes (953.5 nm) far beyond the range of linear
absorption, as it can be evinced from UV-Visible spectra.
Table 7. µ values for compounds 3c,d, 4b-d, and 5c,d.
3c
560
3d
280
4b
150
4c
440
4d
400
5c
280
5d
200
µ [10-48 esu]a
a: µβ (2) at 1900 nm in CHCl3. Molecular concentrations used for the measurements were in
the range 10-3 to 10-2 M. µβ  10%.
All the µ values, reported in table 7 are positive and range from 150 to 560  10-48 esu.
These values which are lower or similar to the common benchmark of organic NLO
chromophores Disperse Red 1, indicate the occurrence of more polarized Frank-Condon
excited states than the ground states. As exemplified in table 7, the µ values are slightly
influenced by structural or electronic changes. The pyrimidine derivative 4b gave the lower
NLO response, as expected from the modest donor strength of the methoxy group. For more
polarized compounds bearing an amino donor group, it appears that the pyrimidine derivatives
3 exhibits higher µ values than the quinoxaline derivatives 5. The µ value difference is
more pronounced for the dimethylamino derivatives (3c, 5c). A similar tendency for
pyrimidine or quinoxaline push-pull dimethylaminophenylvinyl chromophores has been
observed previously.14 Except for compounds 4c and 4d which gave quasi-similar µ values,
dimethylamino derivatives are better NLO chromophores than their diphenylamino analogues.

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17
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These results are in agreement with the better donor capacity of the dimethylamDinOoI: 1g0.r10o3u9/pC.5RA05736A
Concerning the replacement of a 1,4-phenylene ring by a 2,5-thienylene unit in the spacer,
two opposite variations are observed: an increase of µ for the diphenylamino derivatives 3d,
4d (µ4d/µ3d =1.43) and a decrease of µ for the dimethylamino derivatives 3c, 4c (µ4c/µ3c
=0.78). This result does not agree with the bathochromic shift observed upon thienyl
substitution for the ICT band. For similar dialkylamino and diphenylamino push-pull
compounds bearing various acceptor groups, it has been shown that substitution of a 1,4-
phenylene linker for a 2,5-thienylene bridge slightly (for modest acceptors) or widely (for
stronger acceptors) increases the µ values.25 This is due to the lower resonance energy of the
thiophene ring which allows a better charge redistribution than the benzene ring.26 For the
dimethylamino compounds 3c and 4c, the decrease of µ upon phenyl-thienyl change may be
explained in terms of relation between  and the extent of ground-state polarization in the
molecule.25d Other experimental and theoretical investigations would be necessary to clarify
this point.
Finally, comparison with analogous derivatives with phenylenevinylene or
biphenylenevinylene -conjugated core14,17 indicates that the extension of the -conjugated
linker increases the µ value of pyrimidine derivatives. Inclusion of a carbon-carbon triple
bond between the two phenyl rings in 4-(p-dimethylaminobiphenylvinyl)pyrimidine
chromophore (compound 3c) is, however, less effective in term of µ enhancement than
adding a phenyl ring in 4-(p-dimethylaminophenylvinyl)pyrimidine.14 It should be noted that
the influence of the -conjugated linker is lower than the influence of methylation or
complexation of the diazine electron-attracting group or of electron-donating part.
Interestingly, the NLO response is not proportional to the solvatochromic range described
above.

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DOI: 10.1039/C5RA05736A
Conclusions
In conclusion, we have successfully synthesized ad characterized a series of push-pull
diazines derivatives with extended -conjugated core. These compounds exhibit absorption
maxima in the UV or visible region and are highly fluorescent. For amino substituted
derivatives, strong emission solvatochromism was also observed in a variety of nonpolar
solvents, a finding that supports the formation of very polar excited ICT states when terminal
amino electron-donating groups are present in the molecule. The solvatochromic ranges
observed are larger than for analogue structures with smaller -conjugated core. Extension of
the -conjugated linker results also in a moderate increase of the 2nd order NLO response.
Experimental Section
General. Compounds 1a and 2 were synthesized according to reported procedure.14 In air and
moisture-sensitive reactions, all glassware was flame-dried and cooled under nitrogen. NMR
spectra were acquired at room temperature. Chemical shifts are given in parts per million
relative to TMS (1H, 0.0 ppm) and CDCl3 (13C, 77.0 ppm). Acidic impurities in CDCl3 were
removed by treatment with anhydrous K2CO3. UV/vis and fluorescence spectra were recorded
using standard 1 cm quartz cells. Fluorescence spectra were corrected. Compounds were
excited at their absorption maxima (band of lowest energy) for recording the emission spectra;
however different wavelengths were used to determine fluorescence quantum yields in cases
where compounds and standards absorbed significantly. All solutions were measured with
optical densities below 0.1. Stokes shifts were calculated considering the lowest energetic
absorption band. Experimental details for EFISH techniques are given elsewhere.13g
General procedure for the synthesis of 4-Arylvinylpyrimidines : A stirred mixture of 4-
methylpyrimidine (470mg, 5 mmol) and the corresponding aldehyde (5 mmol) in aqueous
sodium hydroxide (5 M, 20 mL) containing Aliquat 336 (215 mg, 0.5 mmol) was heated

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under reflux for 2 h. The mixture was allowed to cool, and the precipitate wasDfOilI:t1e0r.1e0d39o/Cf5fR,A05736A
washed with water, and purified recrystallization from n-heptane/CH2Cl2.
General procedure for Sonogashira Cross-coupling reactions : A suspension of bromo
derivative (0.5 mmol), Pd(PPh3)2Cl2 (35 mg, 0.05 mmol), and CuI (5mg, 0.025 mmol) in
diisopropylamine (5 mL) was degazed three times in a pressure tube. The acetylene derivative
(0.6 mmol) was then added. The mixture was heated at 80°C overnight. The suspension was
then diluted with a mixture of water and dichloromethane (1:1, 30 mL) and the organic layer
was extracted with dichloromethane (2  30 mL). The combined organic extracts were dried
over MgSO4, filtered, and evaporated.
General procedure for trimethylsilyl group deprotection:
A
mixture of
trimethylsilylethynyl derivativ (1 mmol) and a solution of potassium hydroxyde in methanol
(1M, 10 mL) was stirred at room temperature for 15 min. The solution was then neutralized
with 1 M aqueous HCl and extracted with dichloromethane (3 x 20 mL). The combined
organic extracts were dried over MgSO4, filtered, and evaporated.
4-[2-(4-Iodophenyl)-vinyl]-pyrimidine (1b): cream solid ; 1.29 g; yield 84%; mp : 173-
175°C; 1H NMR (500 MHz, CDCl3)  7.09 (d, 1H, J = 16 Hz, Hvinyl), 7.34 (d, 2H, J = 8 Hz,
HPh), 7.38 (d, 1H, J = 5 Hz, H5pyrim), 7.76 (d, 2H, J = 8 Hz, HPh), 7.91 (d, 1H, J = 16 Hz,
Hvinyl), 8.72 (d, 1H, J = 5 Hz, H6pyrim), 9.19 (s, 1H, H2pyrim); 13C NMR and JMOD (125 MHz,
CDCl3)  161.9 (C), 158.9 (CH), 157.6 (CH), 138.1 (CH), 136.3 (C), 135.0 (CH), 129.2 (CH),
126.2 (CH), 118.9 (CH), 95.5 (C). Anal. Calcd for C12H9IN2 : C, 46.78; H, 2.94; N, 9.09.
Found C, 47.08; H, 2.91; N, 8.81.
4-[2-(5-Bromothiophen-2-yl)-vinyl]-pyrimidine (1c): pale yellow solid ; 1.06 g; yield 79%;
mp: 116-118°C; 1H NMR (300 MHz, CDCl3)  6.73 (d, 1H, J = 16 Hz, Hvinyl), 7.01 (d, 1H, J
= 3.9 Hz, Hthio), 7.01 (d, 1H, J = 3.9 Hz, Hthio), 7.23 (d, 1H, J1 = 5.1 Hz, J2 = 1.2 Hz, H5pyrim),

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7.93 (d, 1H, J = 16 Hz, Hvinyl), 8.67 (d, 1H, J = 5.1 Hz, H6pyrim), 9.14 (s, 1H, H2pyrim); C
DOI: 10.1039/C5RA05736A
NMR and JMOD (75 MHz, CDCl3)  161.5 (C), 158.8 (CH), 157.5 (CH), 142.6 (C), 131.0
(CH), 129.9 (CH), 129.4 (CH), 124.8 (CH), 118.8 (CH), 114.7 (C); HRMS (ESI/ASAP) m/z
79
calculated for C10H8N2 BrS [M+H]+: 266.9592, found 266.9590.
4-[2-(4-Phenylethynyl-phenyl)-vinyl]-pyrimidine (3a): Pale yellow solid; obtained
according to general procedure and purified by column chromatography (SiO2, Petroleum
1
Ether/EtOAc 7/3); yield 72% (101 mg), mp: 190-192°C; H NMR (500MHz, CDCl3)  7.08
(d, 1H, J = 16.0 Hz, Hvinyl), 7.32 (dd, 1H, J1 = 5.0 Hz, J2 = 1.0 Hz, H5pyrim), 7.37-7.35 (m, 3H,
HPh), 7.60-7.54 (m, 6H, HPh), 7.89 (d, 1H, J = 16.0 Hz, Hvinyl), 8.69 (d, 1H, J = 5.0 Hz,
H6pyrim), 9.18 (s, 1H, H2pyrim); 13C NMR and JMOD (125 MHz, CDCl3)  89.2 (C), 91.4 (C),
118.9 (CH), 123.1 (C), 124.4 (C), 126.2 (CH), 127.7 (CH), 128.4 (CH), 128.5 (CH), 131.7
(CH), 132.1 (CH), 135.4 (C), 136.7 (CH), 157.5 (CH), 159.0 (CH), 162.0 (C). HRMS
(ESI/ASAP) m/z calculated for C20H15N2 [M+H]+: 283.1230, found 283.1227.
4-{2-[4-(4-Methoxyphenylethynyl)-phenyl]-vinyl}-pyrimidine (3b): Orange solid; obtained
according to general procedure and purified by column chromatography (SiO2, Petroleum
Ether/EtOAc 1/1); yield 56% (87 mg), mp: 191-193°C; 1H NMR (300MHz, CDCl3)  3.86 (s,
3H, HOMe), 6.91 (d, 2H, J =8.7 Hz, HPh), 7.08 (d, 1H, J = 15.9 Hz, Hvinyl), 7.33 (dd, 1H, J1 =
5.0 Hz, J2 = 1.0 Hz, H5pyrim), 7.50 (d, 2H, J =8.7 Hz, HPh), 7.55 (d, 2H, J =8.7 Hz, HPh), 7.60
(d, 2H, J =8.7 Hz, HPh), 7.91 (d, 1H, J = 15.9 Hz, Hvinyl), 8.70 (d, 1H, J = 5.0 Hz, H6pyrim),
13
9.20 (s, 1H, H2pyrim); C NMR and JMOD (75 MHz, CDCl3)  55.3 (CH3), 88.0 (C), 91.5
(C), 114.1 (CH), 115.2 (C), 118.8 (CH), 124.8 (C), 126.0 (CH), 127.6 (CH), 131.9 (CH),
133.2 (CH), 135.0 (C), 136.4 (CH), 157.5 (CH), 158.9 (CH), 159.9 (C), 162.1 (C). HRMS
(ESI/ASAP) m/z calculated for C21H17N2O [M+H]+: 313.1335, found 313.1338.

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4-{2-[4-(4-N,N-dimethylaminophenylethynyl)-phenyl]-vinyl}-pyrimidine (3cD)O:I: 10O.10r3a9n/Cg5eRA05736A
solid; obtained according to general procedure and purified by column chromatography (SiO2,
1
Petroleum Ether/EtOAc 1/1); yield 59% (96 mg), mp: 261-263°C; H NMR (300MHz,
CDCl3)  3.02 (s, 6H, HNMe2), 6.68 (d, 2H, J =8.7 Hz, HPh), 7.06 (d, 1H, J = 15.9 Hz, Hvinyl),
7.33 (d, 1H, J = 5.0 Hz, H5pyrim), 7.44 (d, 2H, J =8.7 Hz, HPh), 7.53 (d, 2H, J =8.7 Hz, HPh),
7.58 (d, 2H, J =8.7 Hz, HPh), 7.89 (d, 1H, J = 15.9 Hz, Hvinyl), 8.70 (d, 1H, J = 5.0 Hz,
H6pyrim), 9.18 (s, 1H, H2pyrim); 13C NMR and JMOD (75 MHz, CDCl3)  40.1 (CH3), 87.4 (C),
93.0 (C), 109.7 (C), 111.8 (C), 118.7 (CH), 125.5 (C), 125.6 (CH), 127.6 (CH), 131.7 (CH),
132.8 (CH), 134.5 (C), 136.9 (CH), 150.3 (C), 157.4 (CH), 158.9 (CH), 162.2 (C). HRMS
(ESI/ASAP) m/z calculated for C21H17N2O [M+H]+: 326.1652, found 326.1650.
4-{2-[4-(4-N,N-diphenylaminophenylethynyl)-phenyl]-vinyl}-pyrimidine (3d): Orange
solid; obtained according to general procedure and purified by column chromatography (SiO2,
1
Petroleum Ether/EtOAc 7/3); yield 81% (181 mg), mp: 185-187°C; H NMR (300MHz,
CDCl3)  7.13-7.00 (m, 9H, HPh+Hvinyl), 7.31-7.27 (m, 5H, HPh+H5pyrim), 7.38 (d, 2H, J =8.7
Hz, HPh), 7.53 (d, 2H, J =8.7 Hz, HPh), 7.58 (d, 2H, J =8.7 Hz, HPh), 7.88 (d, 1H, J = 15.9 Hz,
Hvinyl), 8.68 (d, 1H, J = 5.0 Hz, H6pyrim), 9.17 (s, 1H, H2pyrim); 13C NMR and JMOD (75 MHz,
CDCl3)  88.6 (C), 91.9 (C), 115.7 (C), 118.8 (CH), 122.2 (CH), 123.7 (CH), 124.8 (C), 125.1
(CH), 126.0 (CH), 127.6 (CH), 129.4 (CH), 131.9 (CH), 132.6 (CH), 135.0 (C), 136.8 (CH),
147.2 (C), 148.2 (C), 157.5 (CH), 158.9 (CH), 162.1 (C). HRMS (ESI/ASAP) m/z calculated
for C32H24N3 [M+H]+: 450.1970, found 450.1972.
4-[2-(4-Trimethylsilylethynyl-phenyl)-vinyl]-pyrimidine (3e): Beige solid; obtained
according to general procedure and purified by column chromatography (SiO2, Petroleum
1
Ether/EtOAc 9/1 then EtOAc); yield 57% (79 mg), mp: 125-127°C; H NMR (300MHz,
CDCl3)  0.25 (s, 9H, HSiMe3), 7.00 (d, 1H, J = 15.9 Hz, Hvinyl), 7.25 (d, 1H, J = 5.0 Hz,

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H5pyrim), 7.45 (broad s, 4H, HPh) 7.82 (d, 1H, J = 15.9 Hz, Hvinyl), 8.65 (d, 1H, DJOI=: 105.1.0039/HC5zR,A05736A
H6pyrim), 9.14 (s, 1H, H2pyrim); 13C NMR and JMOD (75 MHz, CDCl3)  0.0 (CH3), 96.4 (C),
104.8 (C), 118.9 (CH), 124.2 (C), 126.4 (CH), 127.5 (CH), 132.5 (CH), 135.6 (CH), 136.6
(C), 157.5 (CH), 158.9 (CH), 161.9 (C). HRMS (ESI/ASAP) m/z calculated for C17H19N2Si
[M+H]+: 279.1312, found 279.1312.
4-[2-(4-Ethynylphenyl)-vinyl]-pyrimidine (3f): Beige solid; obtained according to general
1
procedure for deprotection of trimethylsilyl group; yield 83% (170 mg), mp: 154-156°C; H
NMR (300MHz, CDCl3)  3.18 (s, 1H, HCCH), 7.05 (d, 1H, J = 15.9 Hz, Hvinyl), 7.30 (d, 1H,
J = 5.0 Hz, H5pyrim), 7.50 (d, 2H, J =8.7 Hz, HPh), 7.55 (d, 2H, J =8.7 Hz, HPh), 7.85 (d, 1H, J
= 15.9 Hz, Hvinyl), 8.69 (broad s, 1H, H6pyrim), 9.17 (s, 1H, H2pyrim); 13C NMR and JMOD (75
MHz, CDCl3)  78.9 (CH), 83.3 (C), 118.9 (CH), 123.1 (C), 126.5 (CH), 127.5 (CH), 132.6
(CH), 135.9 (C), 136.6 (CH), 157.3 (CH), 158.7 (CH), 162.0 (C). HRMS (ESI/ASAP) m/z
calculated for C14H11N2 [M+H]+: 207.0917, found 207.0916.
4-[2-(5-Phenylethynyl-thiophen-2-yl)-vinyl]-pyrimidine (4a): Pale yellow solid; obtained
according to general procedure and purified by column chromatography (SiO2, Petroleum
Ether/EtOAc 7/3); yield 69% (97 mg), mp: 114-116°C; 1H NMR (300MHz, CDCl3)  6.80 (d,
1H, J = 15.6 Hz, Hvinyl), 7.14 (d, 1H, J = 3.3 Hz, Hthio), 7.23-7.29 (m, 2H, Hthio+ H5pyrim),
7.38-7.33 (m, 3H, HPh), 7.53-7.50 (m, 2H, HPh), 7.96 (d, 1H, J = 15.6 Hz, Hvinyl), 8.64 (broad
s, 1H, H6pyrim), 9.13 (s, 1H, H2pyrim); 13C NMR and JMOD (75 MHz, CDCl3)  82.7 (C), 95.5
(C), 118.8 (CH), 122.5 (C), 125.0 (C), 125.2 (CH), 128.4 (CH), 128.8 (CH), 129.6 (CH),
129.8 (CH), 131.5 (CH), 132.8 (CH), 142.2 (C), 157.4 (CH), 158.8 (CH), 161.5 (C). HRMS
(ESI/ASAP) m/z calculated for C18H13N2S [M+H]+: 289.0800, found 289.0796.
4-{2-[5-(4-Methoxyphenylethynyl)-thiophen-2-yl]-vinyl}-pyrimidine (4b): Orange solid;
obtained according to general procedure and purified by column chromatography (SiO2,

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DOI: 10.1039/C5RA05736A
Petroleum Ether/EtOAc 1/1); yield 54% (86 mg), mp: 115-117°C; H NMR (300MHz,
CDCl3)  3.83 (s, 3H, HOMe), 6.79 (d, 1H, J =15.6 Hz, Hvinyl), 6.88 (d, 2H, J =8.7 Hz, HPh),
7.13 (d, 1H, J =3.9 Hz, Hthio), 7.16 (d, 1H, J =3.9 Hz, Hthio), 7.22 (dd, 1H, J1 = 5.0 Hz, J2 = 1.0
Hz, H5pyrim), 7.46 (d, 2H, J =8.7 Hz, HPh), 7.95 (d, 1H, J =15.6 Hz, Hvinyl), 8.64 (d, 1H, J = 5.0
Hz, H6pyrim), 9.13 (s, 1H, H2pyrim); 13C NMR and JMOD (75 MHz, CDCl3)  55.3 (CH3), 81.5
(C), 95.6 (C), 114.1 (CH), 114.6 (C), 118.7 (CH), 124.9 (CH), 125.5 (C), 129.7 (CH), 129.6
(CH), 132.3 (CH), 133.0 (CH), 141.8 (C), 157.4 (CH), 158.8 (CH), 160.1 (C), 161.6 (C).
HRMS (ESI/ASAP) m/z calculated for C19H15N2OS [M+H]+: 319.0905, found 319.0900.
4-{2-[5-(4-N,N-dimethylaminophenylethynyl)-thiophen-2-yl]-vinyl}-pyrimidine
(4c):
yellow solid; obtained according to general procedure and purified by column
chromatography (SiO2, Petroleum Ether/EtOAc 1/1); yield 79% (131 mg), mp: 158-160°C;
1H NMR (300MHz, CDCl3)  3.00 (s, 6H, HNMe2), 6.65(d, 2H, J =8.7 Hz, HPh), 6.77(d, 1H, J
=15.6 Hz, Hvinyl), 7.12 (s, 2H, Hthio), 7.21 (d, 1H, J = 5.0 Hz, H5pyrim), 7.39 (d, 2H, J =8.7 Hz,
13
HPh), 7.95 (d, 1H, J =15.6 Hz, Hvinyl), 8.64 (broad s, 1H, H6pyrim), 9.12 (s, 1H, H2pyrim); C
NMR and JMOD (75 MHz, CDCl3)  40.1 (CH3), 80.9 (C), 97.3 (C), 109.0 (C), 111.8 (CH),
118.7 (CH), 124.5 (CH), 126.4 (C), 129.9 (CH), 130.0 (CH), 131.7 (CH), 132.7 (CH), 141.2
(C), 150.4 (C), 157.4 (CH), 158.8 (CH), 161.7 (C). HRMS (ESI/ASAP) m/z calculated for
C20H18N3S [M+H]+: 332.1221, found 332.1223.
4-{2-[5-(4-N,N-diphenylaminophenylethynyl)-thiophen-2-yl]-vinyl}-pyrimidine
(4d):
orange solid; obtained according to general procedure and purified by column
chromatography (SiO2, Petroleum Ether/EtOAc 1/1) followed by crystallization from
1
CH2Cl2/n-heptane; yield 89% (202 mg), mp: 177-179°C; H NMR (300MHz, CDCl3)  6.79
(d, 1H, J =15.6 Hz, Hvinyl), 7.00 (d, 2H, J =8.7 Hz, HPh), 7.16-7.05 (m, 9H, HPh + Hthio
+
H5pyrim), 7.37-7.28 (m, 6H, HPh), 7.97 (d, 1H, J =15.6 Hz, Hvinyl), 8.67 (broad s, 1H, H6pyrim),

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13
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DOI: 10.1039/C5RA05736A
9.15 (s, 1H, H2pyrim); C NMR and JMOD (75 MHz, CDCl3)  82.0 (C), 96.1 (C), 115.0 (C),
121.9 (CH), 123.8 (CH), 125.0 (CH), 125.2 (CH), 125.6 (C), 129.5 (CH), 128.8 (CH), 129.9
(CH), 132.3 (CH), 132.5 (CH), 141.8 (C), 147.1 (C), 148.5 (C), 157.4 (CH), 161.6 (C).
HRMS (ESI/ASAP) m/z calculated for C30H22N3S [M+H]+: 456.1534, found 456.1535.
4-[2-(5-Ethynylthiophen-2-yl)-vinyl]-pyrimidine (4f): Beige solid; obtained according to
general procedure for deprotection of trimethylsilyl group; yield 56% (59 mg), mp: 136-
1
138°C; H NMR (300MHz, CDCl3)  3.40 (s, 1H, HCCH), 6.74 (d, 1H, J = 15.9 Hz, Hvinyl),
7.03 (d, 1H, J = 3.9 Hz, Hthio), 7.13 (d, 1H, J = 3.9 Hz, Hthio), 7.15 (d, 1H, J = 5.0 Hz, H5pyrim),
13
7.87 (d, 1H, J = 15.9 Hz, Hvinyl), 8.59 (d, 1H, J = 5.0 Hz, H6pyrim), 9.06 (s, 1H, H2pyrim); C
NMR and JMOD (75 MHz, CDCl3)  76.8 (CH), 83.4 (C), 118.9 (CH), 123.4 (C), 125.6
(CH), 129.3 (CH), 129.4 (CH), 134.0 (CH), 142.5 (C), 157.5 (CH), 158.8 (CH), 161.4 (C).
HRMS (ESI/ASAP) m/z calculated for C12H9N2 [M+H]+: 213.0486, found 213.0484.
2-[2-(4-Phenylethynyl-phenyl)-vinyl]-quinoxaline (5a): yellow solid; obtained according to
general procedure and purified by column chromatography (SiO2, Petroleum Ether/EtOAc
1
3/7); yield 95% (157 mg), mp: 163-165°C; H NMR (300MHz, CDCl3)  7.37-7.28 (m, 4H,
HPh + Hvinyl), 7.66-7.56 (m, 6H, HPh), 7.78-7.72 (m, 2H, H6,7quinox), 7.87 (d, 1H, J =15.6 Hz,
13
Hvinyl), 8.09 (d, 2H, J =8.7 Hz, H5,8quinox), 9.04 (s, 1H, H2quinox); C NMR and JMOD (75
MHz, CDCl3)  89.3 (C), 91.2 (C), 123.1 (C), 124.0 (C), 126.0 (CH), 127.4 (CH), 128.4 (CH),
128.5 (CH), 129.18 (CH), 129.22 (CH), 129.4 (CH), 130.4 (CH), 131.7 (CH), 132.1 (CH),
135.5 (CH), 135.8 (C), 141.7 (C), 142.5 (C), 144.5 (CH), 150.4 (C). HRMS (ESI/ASAP) m/z
calculated for C24H17N2 [M+H]+: 333.1386, found 333.1386.
2-{2-[4-(4-Methoxyphenylethynyl)-phenyl]-vinyl}-quinoxaline (5b): yellow solid; obtained
according to general procedure and purified by column chromatography (SiO2, Petroleum
1
Ether/EtOAc 3/7); yield 83% (150 mg), mp: 163-165°C; H NMR (300MHz, CDCl3)  3.86

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(s, 3H, HOMe), 6.90 (d, 2H, J =8.7 Hz, HPh), 7.41 (d, 1H, J =15.6 Hz, Hvinyl), 7.51 (d, 2H, J
DOI: 10.1039/C5RA05736A
=8.7 Hz, HPh), 7.57 (d, 2H, J =8.7 Hz, HPh), 7.81-7.73 (m, 2H, H6,7quinox), 7.88 (d, 1H, J
13
=15.6 Hz, Hvinyl), 8.09 (d, 2H, J =8.7 Hz, H5,8quinox), 9.04 (s, 1H, H2quinox); C NMR and
JMOD (75 MHz, CDCl3)  55.3 (CH3), 88.1 (C), 91.4 (C), 114.1 (CH), 115.2 (C), 124.5 (C),
125.8 (CH), 127.4 (CH), 129.2 (CH), 129.4 (CH), 130.4 (CH), 131.9 (CH), 133.1 (CH), 135.5
(C), 135.7 (CH), 141.7 (C), 142.5 (C), 144.5 (CH), 150.5 (C), 159.8 (C). HRMS (ESI/ASAP)
m/z calculated for C25H19N2O [M+H]+: 363.1497, found 363.1498.
2-{2-[4-(4-N,N-dimethylaminophenylethynyl)-phenyl]-vinyl}-quinoxaline (5c): orange
solid; obtained according to general procedure and purified by column chromatography (SiO2,
1
Petroleum Ether/EtOAc 3/7); yield 68% (127 mg), mp: 199-201°C; H NMR (300MHz,
CDCl3)  3.00 (s, 6H, HNMe2), 6.67 (d, 2H, J =8.7 Hz, HPh), 7.38 (d, 1H, J =15.6 Hz, Hvinyl),
7.43 (d, 2H, J =8.7 Hz, HPh), 7.54 (d, 2H, J =8.7 Hz, HPh), 7.62 (d, 2H, J =8.7 Hz, HPh), 7.79-
7.68 (m, 2H, H6,7quinox), 7.85 (d, 1H, J =15.6 Hz, Hvinyl), 8.08 (d, 2H, J =8.7 Hz, H5,8quinox),
13
9.03 (s, 1H, H2quinox); C NMR and JMOD (75 MHz, CDCl3)  40.2 (CH3), 87.5 (C), 92.8
(C), 109.8 (C), 111.8 (C), 125.1 (C), 125.5 (CH), 127.4 (CH), 129.2 (CH), 129.3 (CH), 130.3
(CH), 131.7 (CH), 132.8 (CH), 135.0 (C), 135.8 (CH), 141.6 (C), 142.5 (C), 144.5 (CH),
150.3 (C), 150.6 (C). HRMS (ESI/ASAP) m/z calculated for C26H22N3 [M+H]+: 376.1808,
found 376.1806.
2-{2-[4-(4-N,N-diphenylaminophenylethynyl)-phenyl]-vinyl}-quinoxaline (5d): yellow
solid; obtained according to general procedure and purified by column chromatography (SiO2,
1
Petroleum Ether/EtOAc 3/7); yield 72% (180 mg), mp: 213-215°C; H NMR (300MHz,
CDCl3)  7.14-7.00 (m, 8H, HPh), 7.31-7.26 (m, 4H, HPh), 7.42-7.37 (m, 3H, HPh + Hvinyl),
7.55 (d, 2H, J =8.7 Hz, HPh), 7.63 (d, 2H, J =8.7 Hz, HPh), 7.79-7.68 (m, 2H, H6,7quinox), 7.87
(d, 1H, J =15.6 Hz, Hvinyl), 8.09-8.05 (m, 2H, H5,8quinox), 9.04 (s, 1H, H2quinox); 13C NMR and

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JMOD (75 MHz, CDCl3)  88.6 (C), 91.7 (C), 115.8 (C), 122.2 (CH), 123.6 (CH), 124.5 (C),
DOI: 10.1039/C5RA05736A
125.1 (C), 125.8 (CH), 127.4 (CH), 129.2 (CH), 129.3 (CH), 129.4 (CH), 130.3 (CH), 131.9
(CH), 132.6 (CH), 135.5 (C), 135.7 (CH), 141.7 (C), 142.5 (C), 144.5 (CH), 147.2 (C), 148.1
(C), 150.5 (C). HRMS (ESI/ASAP) m/z calculated for C36H26N3 [M+H]+: 500.2121, found
500.2119.
2-[2-(4-Trimethylsilylethynyl-phenyl)-vinyl]-quinoxaline (5e): Beige solid; obtained
according to general procedure and purified by column chromatography (SiO2, Petroleum
Ether/EtOAc 7/3); yield 75% (123 mg), mp: 123-125°C; 1H NMR (300MHz, CDCl3)  0.26
(s, 9H, HSiMe3), 7.37 (d, 1H, J = 16.2 Hz, Hvinyl), 7.51 (d, 2H, J = 8.4 Hz, HPh), 7.59 (d, 2H, J =
8.4 Hz, HPh), 7.79-7.68 (m, 2H, H6,7quinox), 7.84 (d, 1H, J =16.2 Hz, Hvinyl), 8.09-8.04 (m, 2H,
13
H5,8quinox), 9.02 (s, 1H, H2quinox); C NMR and JMOD (75 MHz, CDCl3)  0.0 (CH3), 96.3
(C), 104.9 (C), 123.9 (C), 126.2 (CH), 127.3 (CH), 129.2 (CH), 129.3 (CH), 129.5 (CH),
130.4 (CH), 132.5 (CH), 133.2 (CH), 135.6 (CH), 136.1 (C), 141.7 (CH), 142.6 (C), 144.5
(CH), 150.4 (C). HRMS (ESI/ASAP) m/z calculated for C21H21N2Si [M+H]+: 329.1469, found
329.1469.
2-[2-(4-Ethynylphenyl)-vinyl]-quinoxaline (5f): Beige solid; obtained according to general
1
procedure for deprotection of trimethylsilyl group; yield 84% (215 mg), mp: 123-125°C; H
NMR (300MHz, CDCl3)  3.19 (s, 1H, HCCH), 7.38 (d, 1H, J = 16.2 Hz, Hvinyl), 7.54 (d, 2H,
J = 8.4 Hz, HPh), 7.62 (d, 2H, J = 8.4 Hz, HPh), 7.79-7.70 (m, 2H, H6,7quinox), 7.85 (d, 1H, J
13
=16.2 Hz, Hvinyl), 8.09-8.06 (m, 2H, H5,8quinox), 9.03 (s, 1H, H2quinox); C NMR and JMOD
(75 MHz, CDCl3)  72.2 (CH), 78.8 (C), 122.8 (C), 126.3 (CH), 127.3 (C), 129.2 (CH), 129.5
(CH), 130.4 (CH), 132.6 (CH), 135.4 (CH), 136.4 (C), 141.4 (C), 142.5 (C), 144.5 (CH),
150.3 (C). HRMS (ESI/ASAP) m/z calculated for C18H13N2 [M+H]+: 257.1073, found
257.1075.

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DOI: 10.1039/C5RA05736A
1
Supporting Information Available: copies of H NMR and 13C NMR spectra for all
compounds, UV/Vis and PL data in toluene, solvatochromic range between hexane/heptane
and dichloromethane for compounds 5c and 5d and their analogues as well as plots of
emission maxima versus ET(30).
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