Synthesis, optical, and spectroscopic characterisation of substituted 3-phenyl-2-arylacrylonitriles

Article abstract of DOI:10.2478/s11696-010-0075-x

The Knoevenagel condensation between aldehydes and substrates with active methylene groups was applied to synthesise a series of 3-(4-substituted phenyl)-2-arylacrylonitriles (aryl = phenyl or pyridyl). Chloro-, fluoro-, or dimethylamino-substituted aryls

Full text of DOI:10.2478/s11696-010-0075-x

Chemical Papers 65 (1) 42–51 (2011)
DOI: 10.2478/s11696-010-0075-x
ORIGINAL PAPER
Synthesis, optical, and spectroscopic characterisation of substituted
3-phenyl-2-arylacrylonitriles
M. Judith Percino*, Víctor M. Chapela, Enrique Pérez-Gutiérrez,
Margarita Cerón, Guillermo Soriano
Centro de Química, Instituto de Ciencias, Universidad Autónoma de Puebla, Complejo de Ciencias, ICUAP,
Edif. 194, 22 Sur y San Claudio, C.P. 72570 Puebla, México
Received 26 April 2010; Revised 2 August 2010; Accepted 4 August 2010
The Knoevenagel condensation between aldehydes and substrates with active methylene groups
was applied to synthesise a series of 3-(4-substituted phenyl)-2-arylacrylonitriles (aryl = phenyl or
pyridyl). Chloro-, fluoro-, or dimethylamino-substituted aryls and a cyano group attached to the
double bond of acrylonitrile were studied. Previous studies showed that the condensation prod-
ucts were E isomers. The compounds synthesised were: 3-(4-chlorophenyl)-2-phenylacrylonitrile,
3-(4-chlorophenyl)-2-(pyridin-2-yl)acrylonitrile, 3-(4-chlorophenyl)-2-(pyridin-3-yl)acrylonitrile, 3-
(4-chlorophenyl)-2-(pyridin-4-yl)acrylonitrile, 3-(4-fluorophenyl)-2-phenylacrylonitrile, 3-(4-fluoro-
phenyl)-2-(pyridin-2-yl)acrylonitrile, 3-(4-fluorophenyl)-2-(pyridin-3-yl)acrylonitrile, 3-(4-fluorophe-
nyl)-2-(pyridin-4-yl)acrylonitrile, 3-(4-dimethylaminophenyl)-2-phenylacrylonitrile, 3-(4-dimethyl-
aminophenyl)-2-(pyridin-2-yl)acrylonitrile, 3-(4-dimethylaminophenyl)-2-(pyridin-3-yl)acrylonitrile,
and 3-(4-dimethylaminophenyl)-2-(pyridin-4-yl)acrylonitrile. Structures were confirmed by IR, MS,
and NMR spectral data. Molar absorption coefficient, absorbance, and fluorescence emission spectra
were compared in order to evaluate the effects of substituents on phenyl and the position of nitrogen
in pyridine moiety on the electronic properties of acrylonitrile derivatives prepared.
c
ꢀ 2011 Institute of Chemistry, Slovak Academy of Sciences
Keywords: solvent-free synthesis, Knoevenagel condensation, propenenitrile, 4-dimethylaminophe-
nyl derivatives, phenylpyridylacrylonitriles
Introduction
(Maruyama et al., 1998; Gómez et al., 1999; Segura
et al., 1999).
Unsaturated nitriles play a key role in several path-
ways proposed in the synthesis of prebiotic biologi-
cal molecules (Guillemin et al., 1998). Arylacryloni-
triles are important in the synthesis of biologically
active molecules such as perfumes (Fraysse, 1980),
flavonoid pigments (Fringuelli et al., 1994), sexual
pheromones, and vitamin A. Arylacrylonitriles were
also directly implicated as plant growth regulators
for increasing soybean yield (Mori, 1979), and as in-
hibitors of prostaglandin synthetase (Peat & Jeffcoat,
1982; Michel et al., 1984). Recently, they were used in
the field of organic materials to obtain high-electron
affinity polymers, which can be used to produce light-
emitting diodes (LEDs) with air stable electrodes
The traditional preparation of arylacrylonitriles in-
volves the reaction of aromatic aldehydes with arylace-
tonitriles, the Knoevenagel reaction (Knoevenagel,
1896), and the Meyer and Frost reaction (Frost, 1889).
The reaction is performed under basic conditions in
a polar solvent (NaOH, KOH, NaOEt, K2CO3 in
MeOH, EtOH, or THF) (D’Sa et al., 1998; Guillot
et al., 2005). In recent years, attention has been fo-
cused on the use of natural inorganic solids, includ-
ing alumina, amino groups immobilised on silica gel,
zinc, magnesium and aluminium oxides, resins, mag-
nesium phosphate, and phosphate impregnated with
sodium nitrate to catalyse organic reactions in het-
erogeneous media (Wang & Cheng, 2004). For ex-
*Corresponding author, e-mail: jpercino@siu.buap.mx

M. J. Percino et al./Chemical Papers 65 (1) 42–51 (2011)
43
3
5
2
4
NC
6
NC
O
1
7
8
5'
13
Z
W
X
Z
9
W
X
+
6'
10
12
Y
Y
I
11
II
II
a
b
c
III
I
a
W
X
C
C
N
C
Y
Z
Z
Cl
F
III
W
X
Y
C
C
C
N
C
C
C
N
C
C
N
C
C
C
C
C
N
a
b
c
C
N
C
C
C
N
C
C
C
C
C
N
C
C
C
N
C
C
Cl
Cl
Cl
Cl
F
F
F
F
b
c
N(CH3)2
d
d
e
f
g
h
i
N(CH3)2
N(CH3)2
N(CH3)2
N(CH3)2
j
k
l
N
C
C
C
N
C
C
C
N
Fig. 1. Synthesis of (E)-3-(4-chlorophenyl)-2-phenylacrylonitrile (IIIa), (E)-3-(4-chlorophenyl)-2-(pyridin-2-yl)acrylonitrile (IIIb),
(E)-3-(4-chlorophenyl)-2-(pyridin-3-yl)acrylonitrile (IIIc), (E)-3-(4-chlorophenyl)-2-(pyridin-4-yl)acrylonitrile (IIId), (E)-
3-(4-fluorophenyl)-2-phenylacrylonitrile (IIIe), (E)-3-(4-fluorophenyl)-2-(pyridin-2-yl)acrylonitrile (IIIf ), (E)-3-(4-fluoro-
phenyl)-2-(pyridin-3-yl)acrylonitrile (IIIg), (E)-3-(4-fluorophenyl)-2-(pyridin-4-yl)acrylonitrile (IIIh), (E)-3-(4-dimethyl-
aminophenyl)-2-phenylacrylonitrile (IIIi), (E)-3-(4-dimethylaminophenyl)-2-(pyridin-2-yl)acrylonitrile (IIIj), (E)-3-(4-di-
methylaminophenyl)-2-(pyridin-3-yl)acrylonitrile (IIIk), and (E)-3-(4-dimethylaminophenyl)-2-(pyridin-4-yl)acrylonitrile
(IIIl).
ample, the Knoevenagel condensation between alde-
hydes and substrates that contain active methylene
groups has been conducted in ethanol at room tem-
perature, in the presence of potassium phosphate, to
produce asymmetrical olefins. These condensation re-
actions have been shown to produce only E isomers
with yields higher than 80 %. Moreover, it was found
that heterocyclic products were formed when salicy-
laldehyde was used under these conditions (Al-Shihry,
2004). In recent years, efforts have been made to pre-
pare a solid catalyst with basic properties. This could
offer a cleaner synthesis (Bigi et al., 2000) and an effi-
cient environment-friendly procedure for the conden-
sation of malononitrile with aromatic, heteroaromatic,
and aliphatic aldehydes in water. Within 1 h, ylidene-
malononitriles were synthesised with high yields (84–
98 %) in distilled water at 65◦C without the addition
of a catalyst. Recently, solvent-free procedures were
developed that used neat powdered base KOH at room
temperature in the reaction of phenylacetonitrile with
4-methoxybenzaldehyde to yield the Z and E acry-
lonitrile isomers which were accompanied by a com-
pound resulting from the Michael addition (Loupy et
al., 2005). An efficient method for the Knoevenagel
condensation was developed using anhydrous ferric
sulphate (Fe2(SO4)3) to produce electrophilic alkenes
within a short time with an excellent yield (Gill
et al., 2008). The α-benzylbenzimidazoleacetonitriles
are useful intermediates/subunits in the synthesis of
molecules of pharmaceutical or biological interest;
they can be combined with aromatic aldehydes in the
presence of basic alumina under solvent-free condi-
tions (Dubey et al., 2007).
Our group previously studied the syntheses of
styrylpyridine and stilbenes using the Knoevenagel
condensation under solvent-free conditions without
a catalyst (Percino et al., 2006, 2007, 2008). Re-
cently, this method has been used to synthesise sev-
eral compounds, including various acrylonitrile deriva-
tives (Percino et al., 2010). In the present work, we
used the Knoevenagel condensation applying catalyst-
free conditions. Phenylpyridylacrylonitrile derivatives
—
with the CN group attached to the C C bond were
—
synthesised, and their absorption and emission proper-
ties determined. A correlation between the electronic
properties of these structures and Cl, F, and dimethy-
lamino substituents and the position of nitrogen atom
in pyridine moiety was also investigated.
Experimental
Phenylacetonitrile, 2-pyridylacetonitrile, 3-pyridyl-
acetonitrile hydrochloride 4-pyridylacetonitrile, 4-fluo-
robenzaldehyde, 4-chlorobenzaldehyde, and 4-dime-
thylaminobenzaldehyde acquired from Aldrich Chem-
ical Co. (Mexico) were purified before use. The IR
spectra were recorded with a Vertex model 70 Bruker
750 FT-IR spectrophotometer by ATR. 1H (400 MHz)
and 13C (125 MHz) NMR spectra were obtained with
a Varian NMR spectrometer using CDCl3 as a sol-

44
M. J. Percino et al./Chemical Papers 65 (1) 42–51 (2011)
Table 1. Reaction temperature (T), time (t), yields, and properties of compounds IIIa–IIIl
Compound
T/◦C
t/h
Yield/%
72
Appearance
M.p./◦C
99–100
Soluble in
IIIa
140
24
colourless crystals
toluene, CHCl3, THF, EtOH, MeOH,
DMSO
IIIb
IIIc
140
140
24
24
37
13
beige powder
beige powder
68–78
CHCl3, THF, Me2CO, MeOH, DMSO
108–110
toluene, THF, Me2CO, EtOH, MeOH,
DMSO
IIId
IIIe
IIIf
IIIg
120
120
140
140
24
48
48
48
33
53
23
20
yellow powder
colourless crystals
colourless crystals
beige crystals
97–97
106–107
91
toluene, CHCl3, THF, EtOH, MeOH,
DMSO
toluene, CHCl3, THF, EtOH, MeOH,
DMSO
toluene, CHCl3, THF, EtOH, MeOH,
DMSO
110–114
toluene, CCl4, CHCl3, THF, Me2CO,
EtOH, MeOH, DMSO
IIIh
IIIi
120
100
24
28
55
51
yellow powder
yellow powder
151–152
132–133
CHCl3, THF, EtOH, MeOH
CHCl3, THF, Me2CO, EtOH, MeOH,
DMSO
IIIj
100
33
51
yellow powder
115
CHCl3, THF, Me2CO, EtOH, MeOH,
DMSO
IIIk
IIIl
100
100
28
24
12
65
orange powder
yellow powder
118
168
CHCla3, DMSO
CCla4 , CHCl3a, THFa, Me2COa,
DMSOa
a) Soluble only when heated.
vent. The EI mass spectra were acquired with a Jeol
MStation 700-D instrument. UV-VIS absorption spec-
tra were recorded at room temperature in CHCl3 with
an Ocean Optics SD2000 spectrometer equipped with
the light source UV-VIS DT 1000 CE from Analyti-
cal Instrument System, using 1 cm quartz cell. The
molar absorption coefficient (ε) was calculated ac-
cording to the Beer–Lambert law: A = εlc where c
= 5 × 10−5 M (in CHCl3). Photoluminescence spec-
tra were recorded using the above spectrometer and
a Mineralight UVGL-58 UV lamp as the excitation
source. Melting points (0–300◦C; uncorrected) were
determined with an SEV apparatus.
33 h) in the absence of a solvent. In the course of the
reaction, the mixtures were of an oily appearance with
a brown to red colour. The mixtures were neutralised
with an aqueous HCl solution and more water was
added to precipitate the products as powders. These
products were purified by recrystallisation from hex-
ane, chloroform, or cyclohexane, and characterised by
1
IR, H, 13C NMR, UV, and fluorescence spectroscopy
and EI mass spectrometry.
Results and discussion
In obtaining the target compounds, the tempera-
ture, reaction time, presence of the substituents (F,
Cl, and N(CH3)2), and the ortho-, meta-, and para-
positions of the pyridine played important roles in the
product formation. Table 1 shows the yields and prop-
erties of all compounds. We used the same reaction
conditions in the synthesis of compounds IIIa–IIIh;
best yields were obtained in case of IIIa and IIIe, and
poorest for IIIc and IIIg, with chloro- and fluoroben-
zaldehyde. We compared these yield results with those
obtained recently (Percino et al., 2010) under the same
conditions in the reactions of phenylacetonitrile with
benzaldehyde, 2-pyridineacetonitrile with benzalde-
hyde, 3-pyridineacetonitrile with benzaldehyde, and
phenylacetonitrile with pyridinealdehyde. The results
reported indicated that the aromatic aldehyde might
play a more important role than the cyanomethy-
lene group (CH2CN). This may be explained by the
high reactivity of benzaldehyde possessing an electron-
withdrawing group in the para position (F and Cl).
Synthesis of compounds IIIa–IIIl
Compounds IIIa–IIIh were prepared by the con-
densation reaction of the corresponding acetonitrile
and 4-chloro or 4-fluorobenzadehyde (Fig. 1). The
mole ratio of the acetonitrile to 4-chlorobenzaldehyde
was 2 : 1 and acetonitrile to 4-fluorobenzaldehyde
1 : 1. The mixtures were allowed to react under re-
flux (140◦C for 24 h) in the absence of any con-
densing agent or solvent, with the exception of IIId
and IIIh where DMF was used as a solvent. In the
course of the reaction, the mixtures were of an oily
appearance with a brown to red colour. The mixtures
were treated with 2 M NaOH solution to precipitate
the products as powders. To prepare compounds IIIi–
IIIl, mixtures of the corresponding arylacetonitrile, 4-
dimethylaminobenzaldehyde, and piperidine of 1 : 1
: 6 mole ratio were heated under reflux (100◦C, 24–

M. J. Percino et al./Chemical Papers 65 (1) 42–51 (2011)
45
H
H
Ar
H
Ar
H
Ar
Ar
+
H2O
+
H2C
CH
OH
O
H
OH
Ph
CN
NC
Ph
Ph
NC
NC
Ph
Fig. 2. Temperature-dependent mechanism of the condensation reaction.
The results led us to investigate the mechanism
underlying the reaction of the production of IIIa and
IIIe, compounds similar to 2,3-diphenylacrylonitrile
which was obtained within a shorter reaction time due
to change in temperature (Percino et al., 2010). A sub-
stance that could act as a base was not included in
either of the reactions. However, according to a mech-
anism reported recently (Boucard, 2001), a base is
necessary for the Knoevenagel condensation reaction.
Boucard (2001) described the Knoevenagel condensa-
tion mechanism but had no direct proof as to the in-
tervention of a carbanion. She reported that, based
on proton and carbon NMR, the first step did not in-
volve a carbanion, but a particular ionised species in
methanol (no data were provided).
compounds, even at higher temperatures. Therefore,
these compounds were only obtained when the piperi-
dine catalyst was used, as recommended for this sort
of reaction. This could be explained by the low re-
activity of an aromatic aldehyde possesing dimethy-
lamino group, which is a strong electron donor, in the
molecule. Another interesting observation as regards
the reactivity of the reagents and their effect on the
yield was the position of N in the ring; as expected, a
lower reactivity was observed for N in the meta posi-
tion to the aldehyde group.
FTIR and NMR characteristics
FTIR spectra of compounds IIIa–IIIh showed sim-
Recent studies have described the Knoevenagel
condensation (Taha et al., 2008) in the synthesis of
several substituted stilbenes derived from weak acidic
substrates, 4-nitrotoluene (pKa = 20.49) or pheny-
lacetonitrile (pKa = 21.9) that reacted with benzalde-
hyde using tetrabutylammonium bromide (TBAB) or
18-crown 6 as phase transfer catalysts. The authors
stated that the competitive Cannizzaro reaction oc-
curred concurrently with the Knoevenagel condensa-
tion.
Solid potassium carbonate as a base and crown-
ether as the phase transfer catalyst proved best in
the reaction of phenylacetonitrile and benzaldehyde,
even though the former was a weak acid. In the Can-
nizzaro reaction, the base induced a disproportiona-
tion of the aldehyde which lacked a hydrogen atom in
the α-position. The inhibiting role of the competing
Cannizzaro reaction was shown to be more significant
when benzaldehydes of higher elecrophilic character
were used. For example, when 4-nitrobenzaldehyde re-
acted with 4-nitrotoluene under the same conditions,
no stilbene was formed at all, and only the Canniz-
zaro products (4-nitrobenzyl alcohol and sodium 4-
nitrobenzoate) were observed.
On the basis of the results from solvent-free reac-
tions without a base catalyst, it is interesting to note
that some reactions do not require a base to catal-
yse the reaction. Thus, it can be proposed that either
the phenylacetonitriles are dissociated or the carbonyl
could be responsible for extracting a proton to initiate
the reaction (Fig. 2).
The reactivity of the aromatic aldehyde was accen-
tuated when 4-dimethylaminobenzaldehyde was used
in the synthesis of compounds IIIi–IIIl. Conditions
that lacked a catalyst and solvent did not yield these
ilar characteristic bands in the region of 1645–1675
cm−1 (Table 2). These were assigned to the ν(C C)
—
—
vibrations of the alkene double bond which is con-
jugated with an aromatic ring and nitrile group
(Williams & Fleming, 1980; Yang et al., 2002).
The bands at 761 cm−1, 778 cm−1, 774 cm−1
,
and 775 cm−1 for compounds IIIa–IIId, repectively,
and the bands at 757 cm−1, 777 cm−1, 774 cm−1
,
and 771 cm−1 for compounds IIIe–IIIh, respectively,
were assigned to the δ(C—H) vibrations of C—H ad-
jacent to the double bond. The bands at 2203–2219
cm−1 were due to the C N stretching vibrations.
—
—
—
The bands at 1227 cm−1 and 822 cm−1 were assigned
to the ν(C—F) and ν(C—Cl) vibrations, respectively.
FTIR spectra of compounds IIIi–IIIl showed similar
characteristic bands, but the peaks assigned to the
—
ν(C C) vibrations of the alkene double bond con-
—
jugated with an aromatic ring were shifted to 1610
cm−1, 1613 cm−1, 1613 cm−1, and 1611 cm−1, respec-
—
—
tively. This indicates that, even with the C N group
—
attached to the alkene double bond, the presence of an
electron-donor group such as N(CH3)2 in the para po-
sition induced a strong conjugation. The bands at 763
cm−1, 785 cm−1, 772 cm−1, and 785 cm−1 were as-
signed to the δ(C—H) vibrations of C—H adjacent to
a double bond in IIIi—IIIl, respectively. Analogously,
the bands at 2199 cm−1, 2205 cm−1, 2202 cm−1, and
2010 cm−1 were assigned to the stretching vibrations
—
—
of C N group (Table 2).
—
From 1H NMR data, the principal evidence (Sil-
verstein & Webster, 1997) of the structure of all the
compounds prepared was the singlet at δ in the range
of 7.01–8.54 due to the proton attached to the dou-
ble bond. These values indicated that the effect of the
pyridine ring located in the ortho position in relation

46
M. J. Percino et al./Chemical Papers 65 (1) 42–51 (2011)
Table 2. Spectral characterisation of compounds IIIa–IIIl
Compound
Spectral characterizationa
—
IR (KBr), ν˜/cm−1: 3088 (w), 3057 (m), 3034 (s), 2219 (s, C N), 1652 (w, C C), 1590 (s), 1492 (s), 829 (s, C—Cl),
—
—
—
—
IIIa
—
761 (s, C—H in C CH)
—
3
3
1H NMR (CDCl3), δ: 7.82–7.80 (d, 2H, J(5,6)
= ꢀ ꢀ =
3J(5 ,6 ) = 8.4 Hz, H-5, H-5ꢀ), 7.66–7.64 (dd, 2H, J(9,10)
4
3J(13,12) = 8.1 Hz, J(9,11)
=
4J(13,11) = 1.5 Hz, H-9, H-13), 7.46 (s, 1H, H-3), 7.44–7.38 (m, 3H, H-10, H-11,
H-12), 7.43–7.40 (d, 2H, H-6, H-6ꢀ)
13C NMR (CDCl3), δ: 140.6 (C-3), 136.4 (C-7), 134.2 (C-4), 132.2 (C-8), 130.5 (C-5), 129.5 (C-9), 129.5 (C-13),
129.4 (C-10), 129.4 (C-12), 129.2 (C-11), 126.0 (C-6), 117.7 (C-1), 112.3 (C-2)
MS, m/z (Ir/%): 239 (63.5) (M+), 238 (7.1), 204 (100), 203 (74.6), 177 (18.3), 176 (14.7), 151 (7.0), 102 (18.3), 93
(27.1), 18 (15.1)
—
—
—
IIIb
IR (KBr), ν˜/cm−1: 3098 (m), 3071 (m), 3048 (m), 2217 (s, C N), 1645 (w, C C), 1584 (s), 1492 (s), 822 (s,
—
—
—
C—Cl), 778 (m, C—H in C CH)
—
1H NMR (CDCl3), δ: 8.67–8.66 (dd, 1H, J(12,11) = 4.8 Hz, J(12,10) = 1.2 Hz, H-12), 8.54 (s, 1H, H-3), 7.97–7.95
3
4
3
3
3
(d, 2H, J(5,6)
= ꢀ ꢀ
3J(5 ,6 ) = 8.4 Hz, H-5, H-5ꢀ), 7.88–7.84 (m, 2H, J(9,10) = 8.0 Hz, J(10,11) = 7.2 Hz, H-9, H-10),
7.48–7.46 (d, 2H, H-6, H-6ꢀ), 7.36–7.33 (m, 1H, H-11)
13C NMR (CDCl3), δ: 151.0 (C-8), 149.5 (C-12), 144.3 (C-3), 138.0 (C-7), 137.5 (C-4), 132.0 (C-5), 131.4 (C-10),
129.5 (C-6), 123.9 (C-11), 121.7 (C-9), 117.0 (C-1), 111.2 (C-2)
MS, m/z (Ir/%): 240 (80.7) (M+), 239 (100), 203 (13.5), 177 (10.0), 151 (4.6), 102 (13.2), 79 (11.4), 78 (7.1), 52
(5.7), 28 (10), 18 (18.5)
—
IR (KBr), ν˜/cm−1: 3080 (w), 3051 (m), 3017 (m), 2214 (s, C N), 1651 (w, C C), 1588 (s), 1493 (s), 821 (s,
—
—
—
—
IIIc
—
C—Cl), 774 (m, C—H in C CH)
—
1H NMR (CDCl3), δ: 8.99 (s, 1H, H-13), 8.67–8.66 (d, 1H, J(11,10) = 4.8 Hz, H-11), 8.06–8.04 (d, 1H, J(9,10)
=
3
3
3
8.0 Hz, H-9), 7.89–7.86 (d, 2H, J(5,6)
= ꢀ ꢀ
3J(5 ,6 ) = 8.4 Hz, H-5, H-5ꢀ), 7.60 (s, 1H, H-3), 7.50–7.49 (m, 1H, H-10),
7.49–7.47 (d, 2H, H-6, H-6ꢀ)
13C NMR (CDCl3), δ: 150.1 (C-13), 146.9 (C-11), 142.6 (C-3), 137.6 (C-7), 133.9 (C-8), 131.7 (C-4), 130.9 (C-5),
130.6 (C-6), 129.6 (C-9), 124.0 (C-10), 117.1 (C-1), 107.0 (C-2)
MS, m/z (Ir/%): 240 (13.3) (M+), 239 (19.0), 205 (6.6), 177 (4.9), 75 (5.6), 51 (10.2), 39 (100), 38 (25.3), 18 (16.1)
—
—
—
IIId
IR (KBr), ν˜/cm−1: 3053 (m), 3025 (w), 2213 (s, C N), 1675 (w, C C), 1588 (s), 1550 (m), 1495 (s), 819 (s,
—
—
—
C—Cl), 775 (s, C—H in C CH)
—
1H NMR (CDCl3), δ: 8.66–8.65 (d, 2H, J(10,9)
= =
3J(12,13) = 4.8 Hz, H-10, H-12), 7.84–7.82 (d, 2H, J(5,6)
3
3
3J(5 ,6 ) = 8.4 Hz, H-5, H-5ꢀ), 7.62 (s, 1H, H-3), 7.53–7.52 (d, 2H, H-9, H-13), 7.44–7.42 (d, 2H, H-6, H-6ꢀ)
ꢀ
ꢀ
13C NMR (CDCl3), δ: 150.7 (C-10), 150.7 (C-12), 143.7 (C-3), 141.7 (C-8), 137.9 (C-4), 131.4 (C-7), 131.1 (C-6),
129.7 (C-5), 120.1 (C-9), 120.1 (C-13), 116.8 (C-1), 107.1 (C-2)
MS, m/z (Ir/%): 240 (100) (M+), 239 (76.2), 205 (69.4), 204 (5.7), 177 (20.1), 151 (13.6), 139 (5.0), 102 (9.3), 75
(8.6), 44 (11.5), 28 (37.0), 18 (54.6)
—
—
—
IIIe
IIIf
IR (KBr), ν˜/cm−1: 3103 (w), 3059 (m), 3039 (s), 2220 (s, C N), 1652 (w, C C), 1599 (s), 1447 (s), 1238 (s,
—
—
—
C—F), 757 (s, C—H in C CH)
—
1H NMR (CDCl3), δ: 7.92–7.90 (d, 2H, J(5,6)
= ꢀ ꢀ =
3J(5 ,6 ) = 8.4 Hz, H-5, H-5ꢀ), 7.68–7.66 (d, 2H, J(9,10)
3
3
3J(13,12)= 7.6 Hz, H-9, H-13), 7.50 (s, 1H, H-3), 7.47–7.40 (m, 3H, H-10, H-11, H-12), 7.16–7.14 (d, 2H, H-6, H-6ꢀ)
13C NMR (CDCl3), δ: 162.2 (C-7), 141.0 (C-3), 134.5 (C-8), 131.6 (C-5), 130.2 (C-4), 129.4 (C-9), 129.4 (C-13),
129.3 (C-10), 129.3 (C-12), 126.1 (C-11), 118.1 (C-1), 116.5 (C-6), 112.0 (C-2)
MS, m/z (Ir/%): 223 (100) (M+) 222 (60.9), 208 (27.8), 196 (9.8), 195 (12.6), 183 (6.5), 98 (9.1), 28 (11.6), 18 (29.9)
—
IR (KBr), ν˜/cm−1: 3084 (w), 3049 (m), 2215 (s, C N), 1658 (w, C C), 1592 (s), 1507 (s), 1234 (s, C—F), 777
—
—
—
—
—
(m, C—H in C CH)
—
1H NMR (CDCl3), δ: 8.65–8.64 (m, 1H, J(12,11) = 4.8 Hz, J(12,10) = 1.2 Hz, H-12), 8.46 (s, 1H, H-3), 8.02–8.00
3
4
3
3
(d, 2H, J(5,6)
= ꢀ ꢀ
3J(5 ,6 ) = 8.4 Hz, H-5, H-5ꢀ), 7.81–7.79 (m, 2H, 3J(9,10) = 8.8 Hz, J(10,11) = 7.2 Hz, H-9,
H-10), 7.32–7.30 (m, 1H, H-11), 7.20–7.18 (d, 2H, H-6, H-6ꢀ)
13C NMR (CDCl3), δ: 151.0 (C-8), 149.6 (C-12), 144.2 (C-3), 137.9 (C-4), 137.0 (C-10), 132.5 (C-6), 132.4 (C-5),
123.8 (C-9), 123.8 (C-11), 121.5 (C-7), 117.2 (C-1), 108.3 (C-2)
MS, m/z (Ir/%): 224 (25.3) (M+), 223 (100), 198 (4.2), 169 (2.4), 112 (2.5), 79 (3.8), 32 (11.9), 28 (35.9), 18 (57.0),
17 (11.9)
—
—
—
IIIg
IR (KBr), ν˜/cm−1: 3043 (m), 2214 (s, C N), 1668 (m, C C), 1599 (s), 1510 (s), 1230 (s, C—F), 774 (s, C—H in
—
—
—
C
CH)
—
1H NMR (CDCl3), δ: 8.98 (s, 1H, H-13), 8.67–8.66 (d, 1H, J(11,10) = 3.6 Hz, H-11), 8.05–8.03 (d, 1H, J(9,10)
=
3
3
3
6.4 Hz, H-9), 7.96–7.93 (d, 2H, J(5,6)
= ꢀ ꢀ
3J(5 ,6 ) = 8.8 Hz, H-5, H-5ꢀ), 7.60 (s, 1H, H-3), 7.47–7.46 (m, 1H, H-10),
7.22–7.20 (d, 2H, H-6, H-6ꢀ)
13C NMR (CDCl3), δ: 166.0 (C-7), 149.4 (C-13), 146.4 (C-11), 142.9 (C-3), 134.3 (C-9), 132.0 (C-5), 131.8 (C-8),
129.5 (C-4), 124.1 (C-10), 116.7 (C-6), 116.4 (C-1), 108.0 (C-2)
MS, m/z (Ir/%): 224 (66.5) (M+), 223 (100), 203 (4.9), 195 (7.0), 169 (6.3), 144 (3.1), 109 (4.2), 18 (13.3)

M. J. Percino et al./Chemical Papers 65 (1) 42–51 (2011)
47
Table 2. (continued)
Compound
Spectral characterizationa
—
—
—
IIIh
IIIi
IIIj
IIIk
IR (KBr), ν˜/cm−1: 3056 (m), 2927 (w), 2214 (s, C N), 1674 (w, C C), 1594 (s), 1515 (m), 1419 (s), 1249 (s,
—
—
—
C—F), 771 (s, C—H in C CH)
—
1H NMR (CDCl3), δ: 8.73–8.71 (d, 2H, J(10,9)
= =
3J(12,13) = 4.8 Hz, H-10, H-12), 7.99–7.97 (d, 2H, J(5,6)
3
3
3J(5 ,6 ) = 8.4 Hz, H-5, H-5ꢀ), 7.70 (s, 1H, H-3), 7.60–7.59 (d, 2H, H-9, H-13), 7.23–7.21 (d, 2H, H-6, H-6ꢀ)
ꢀ
ꢀ
13C NMR (CDCl3), δ: 162.0 (C-7), 150.6 (C-10), 150.6 (C-12), 144.1 (C-3), 142.0 (C-8), 132.2 (C-9), 132.2 (C-13),
129.0 (C-4), 120.2 (C-5), 117.0 (C-1), 116.8 (C-6), 109.0 (C-2)
MS, m/z (Ir/%): 224 (100) (M+), 223 (95.6), 205 (13.7), 197 (18.0), 196 (12.9), 169 (10.8), 140 (23.8), 123 (36.1),
109 (12.2), 95 (15.5), 28 (27.4), 18 (49.8)
—
IR (KBr), ν˜/cm−1: 3086 (m), 3065 (m), 3031 (m), 2900 (m), 2821 (m), 2199 (s, C N), 1610 (s, C C), 1578 (s),
—
—
—
—
—
1529 (s), 1376 (s, C—N), 763 (m, C—H in C CH)
—
3
1H NMR (CDCl3), δ: 7.87–7.85 (d, 2H, J(5,6)
=
3J(5 ,6 )
ꢀ
ꢀ
= 8.8 Hz, H-5, H-5ꢀ), 7.64–7.63; 7.64–7.62 (dd,
4
2H, 3J(9,10)
=
3J(13,12) = 7.2 Hz, J(9,11)
=
4J(13,11) = 1.6 Hz, H-9, H-13), 7.41 (s, 1H, H-3), 7.43–7.29 (m,
3H, H-10, H-11, H-12), 6.74–6.71 (d, 2H, H-6, H-6ꢀ), 3.06 (s, 6H, 2 × CH3)
13C NMR (CDCl3), δ: 151.6 (C-7), 142.7 (C-3), 135.7 (C-8), 131.5 (C-13), 131.5 (C-9), 129.1 (C-10), 129.1 (C-12),
128.2 (C-11), 127.3 (C-5), 125.7 (C-4), 119.6 (C-1), 112.1 (C-6), 105.0 (C-2), 40.5 (2 × CH3)
MS, m/z (Ir/%): 248 (100) (M+), 247 (67.2), 204 (4.2), 203 (3.5), 178 (2.8), 153 (2.8), 18 (4.2)
—
IR (KBr), ν˜/cm−1: 3081 (w), 3003 (w), 2907 (m), 2858 (m), 2818 (m), 2205 (s, C N), 1613 (s, C C), 1585 (s),
—
—
—
—
—
1558 (m), 1526 (s), 1372 (s, C—N), 785 (s, C—H in C CH)
—
1H NMR (CDCl3), δ: 8.60–8.59 (dd, 1H, J(12,11) = 4.5 Hz, J(12,10) = 1.5 Hz, H-12), 8.33 (s, 1H, H-3), 7.99–7.96
3
4
3
3
3
(d, 2H, J(5,6)
= ꢀ ꢀ
3J(5 ,6 ) = 8.7 Hz, H-5, H-5ꢀ), 7.73–7.71 (m, 2H, J(9,10) = 7.8 Hz, J(10,11) = 7.2 Hz, H-9, H-10),
7.20–7.17 (m, 1H, H-11), 6.74–6.72 (d, 2H, H-6, H-6ꢀ), 3.08 (s, 6H, 2 × CH3)
13C NMR (CDCl3), δ: 152.5 (C-8), 152.1 (C-7), 149.3 (C-12), 145.2 (C-3), 137.1 (C-10), 132.3 (C-11), 122.1 (C-4),
121.2 (C-9), 120.4 (C-5), 119.4 (C-1), 111.5 (C-6), 104.9 (C-2), 40.0 (2 × CH3)
MS, m/z (Ir/%): 249 (87.3) (M+), 248 (100), 232 (20.4), 223 (4.9), 205 (9.1), 125 (6.3), 28 (7.0), 18 (22.5)
—
IR (KBr), ν˜/cm−1: 3092 (w), 3049 (w), 3026 (w), 2906 (m), 2823 (m), 2202 (s, C N), 1613 (s, C C), 1579 (s),
1530 (m), 1480 (m), 1379 (s, C—N), 772 (s, C—H in C CH)
1H NMR (CDCl3), δ: 8.93–8.92 (d, 1H, J(11,10) = 1.6 Hz, H-11), 8.56–8.55 (m, 1H, J(10,9) = 5.2 Hz, H-10),
—
—
—
—
—
—
3
3
3
3
8.10–8.07 (m, 1H, J(11,9) = 1.6 Hz, H-9), 7.91–7.89 (d, 2H, J(5,6)
H-3), 6.74–6.72 (d, 2H, H-6, H-6ꢀ), 3.09 (s, 6H, 2 × CH3)
= ꢀ ꢀ
3J(5 ,6 ) = 9.2 Hz, H-5; H-5ꢀ), 7.43 (s, 1H,
13C NMR (CDCl3), δ: 153.5(C-3), 150.0 (C-13), 149.6 (C-11), 148.8 (C-7), 133.7 (C-9), 131.6(C-8), 127.3 (C-5),
124.7 (C-4), 123.8 (C-10), 118.8 (C-1), 114.2 (C-6), 99.6 (C-2), 40.3 (2 × CH3)
MS, m/z (Ir/%): 249 (100) (M+), 248 (50.7), 234 (25.3), 206 (20.7), 205 (15.8), 177 (4.9), 151 (4.2), 124 (3.8), 28
(5.6), 18 (14.7)
—
IIIl
IR (KBr), ν˜/cm−1: 3143 (w), 3083 (w), 3051 (m), 3022 (m), 2987 (m), 2895 (m), 2814 (m), 2210 (s, C N), 1611
—
—
—
—
(s, C C), 1579 (s), 1526 (m), 1490 (s), 1371 (s, C—N), 785 (s, C—H in C CH)
—
—
3
3
1H NMR (CDCl3), δ: 8.61–8.60 (d, 2H, J(10,9)
3J(5 ,6 ) = 8.8 Hz, H-5, H-5ꢀ), 7.01 (s, 1H, H-3), 7.59–7.58 (d, 2H, H-9, H-13), 6.74–6.72 (d, 2H, H-6, H-6ꢀ), 3.11 (s,
6H, 2 × CH3)
= =
3J(12,13) = 4.8 Hz, H-10, H-12), 7.94–7.92 (d, 2H, J(5,6)
ꢀ
ꢀ
13C NMR (CDCl3), δ: 152.4 (C-7), 152.4 (C-10), 152.4 (C-12), 144.9 (C-3), 143.0 (C-8), 132.2 (C-4), 120.6 (C-9),
120.6 (C-13), 119.3 (C-5), 118.5 (C-1), 111.5 (C-6), 101.0 (C-2), 40.0 (2 × CH3)
MS, m/z (Ir/%): 249 (100) (M+), 248 (59.8), 234 (12.6), 206 (12.6), 205 (11.9), 177 (4.9), 151 (4.5), 28 (19.0), 18
(19.0)
a) Atom numbering corresponds to the numbering in Fig. 1.
to the double bond was stronger than the effect of CN
group. The 13C NMR spectra exhibited signals at δ
116.4–119.6 assigned to the C1 atom of nitrile group.
These values are in good accordance with those re-
cently reported for some nitriles (Gatial et al., 2004;
Vida et al., 2007; Gróf et al., 2007). It has also been es-
found for propenenitrile derivatives by Gatial et al.
(2004).
UV-VIS and fluorescence spectra
UV absorption spectra for compounds IIIa–IIId are
shown in Fig. 3a. The wavelengths of maximum ab-
sorbance (λmax) were 319 nm, 319 nm, 326 nm, and
319 nm which are typical of the π–π* transition of
3
tablished that vicinal coupling constants J(C,H) (be-
tween olefinic hydrogen and cyano carbon) are about
5 Hz for cis and 10 Hz for trans positions of H and
CN, respectively. The values of 14.1 Hz, 9.9 Hz, and
13.5 Hz of vicinal coupling constants 3J(C,C) (between
olefinic carbon and cyano carbon) observed in cou-
pled and decoupled 13C NMR spectra of compounds
IIIa, IIIf, and IIIi, respectively, indicate that E iso-
mers are present in the solution. Similar values were
2
2
—
the conjugated RRC CR R segments (Williams &
—
Fleming, 1980). The molar absorptivity ε shown in
Fig. 3b is used to compare the spectra of different com-
pounds because it is considered an intrinsic property
of a species. All these compounds displayed strong ab-
sorbance (ε > 10000) but little difference was observed

48
M. J. Percino et al./Chemical Papers 65 (1) 42–51 (2011)
b
a
3
1.5
1.0
0.5
0.0
2
1
ε
0
300
400
500
300
400
500
Wavelength/nm
Wavelength/nm
Fig. 3. Absorbance (a) and molar absorptivity ε (b) of compounds IIIa (solid line), IIIb (dashed line), IIIc (dotted line), and IIId
(dot–dashed line) in chloroform.
3
1.5
b
a
2
1
0
1.0
0.5
0.0
ε
300
400
500
600
300
400
500
600
Wavelength/nm
Wavelength/nm
Fig. 4. Absorbance (a) and molar absorptivity ε (b) of compounds IIIe (solid line), IIIf (dashed line), IIIg (dotted line), and IIIh
(dot–dashed line) in chloroform.
between isomers IIIa–IIId. Fig. 4 shows the λmax of
315 nm, 324 nm, 314 nm, and 315 nm, respectively
for compounds IIIe–IIIh. However, the comparison of
ε of these compounds revealed that the compounds
with Cl substituent exhibited a stronger absorbance.
On the other hand, the position of the N atom in the
ring had only a small effect, as shown by the similar-
ity of ε values for the three compounds differing in the
position of N atom.
The absorbance of the conjugated system in com-
pounds IIIi–IIIl displayed a significant bathochromic
effect due to the N(CH3)2 substituent, and a small
influence due to the presence of nitrogen atom in
the ring (Fig. 5). The bathochromic effect shifted
the λmax of IIIi–IIIl to 381 nm, 395 nm, 389 nm,
and 406 nm, respectively. Fig. 5 also shows the ε
values indicating a stronger absorbance for IIIi; all
other compounds had ε values lower than 30000
mol−1 mL−1. Compound IIIi was comparable with
the N,N-dimethyl-4-styrylaniline (Yang et al., 2002)
obtained by using a palladium catalyst to form
an aromatic carbon–nitrogen bond (Wolfe et al.,
1998).
Therefore, for the 3-(4-dimethylaminophenyl)-2-
pyridylacrylonitrile derivatives, the push-pull effect
was strongest in IIIl because it showed a higher
bathochromic effect than in IIIi, IIIj, and IIIk; how-
ever, the ε values showed that compound IIIi was the
most efficient.
On the other hand, the CN group attached to
the double bond in compounds IIIa–IIIl did not show
any important effect on their absorption spectra. The
spectra of compounds IIIa–IIId were compared with
the spectra of similar compounds bearing aromatic
rings at double bond in the trans position (Percino
et al., 2010) including (E)-2-(4-fluorostyryl)pyridine,
(E)-2-(4-chlorostyryl)pyridine, and (E)-4-(4-chloro-
styryl)pyridine, exhibiting λmax values in the range
of 311–318 nm. In comparison with λmax values of
309 nm for 2,3-diphenylacrylonitrile and 324 nm for
3-phenyl-2-(pyridin-2-yl)acrylonitrile, it is clear that
the presence of the CN group in the structure does
not cause any appreciable bathochromic shift.
Emission spectra of compounds IIIa–IIIh were
measured at an excitation wavelength of 368 nm
(Fig. 6). Photoluminescence spectra exhibited strong

M. J. Percino et al./Chemical Papers 65 (1) 42–51 (2011)
49
2.0
1.5
1.0
0.5
0.0
a
b
3
2
1
ε
0
300
400
500
600
300
400
500
600
Wavelength/nm
Wavelength/nm
Fig. 5. Absorbance (a) and molar absorptivity ε (b) of compounds IIIi (solid line), IIIj (dashed line), IIIk (dotted line), and IIIl
(dot–dashed line) in chloroform.
1.0
0.8
0.6
0.4
0.2
0.0
a
b
1.0
0.8
0.6
0.4
0.2
0.0
300
400
500
600
700
300
400
500
600
700
Wavelength/nm
Wavelength/nm
Fig. 6. Photoluminescence emission spectra of compounds: (a) IIIa (solid line), IIIb (dashed line), IIIc (dotted line), and IIId
(dot–dashed line), (b) IIIe (solid line), IIIf (dashed line), IIIg (dotted line), and IIIh (dot–dashed line) in chloroform.
b
a
1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.8
0.6
0.4
0.2
0.0
450
500
550
600
650
700
500
600
700
Wavelength/nm
Wavelength/nm
Fig. 7. Photoluminescence emission spectra of compounds: (a) IIIi (solid line), IIIj (dashed line), IIIk (dotted line), and IIIl
(dot–dashed line), (b) IIId (solid line) and IIIh (dashed line) in solid state.
emissions with maxima at 485 nm (IIIa), 496 nm
(IIIb), 485 nm (IIIc), 496 nm (IIId), 492 nm (IIIe),
479 nm (IIIf ), 467 nm (IIIg), and 492 nm (IIIh). No
significant differences were observed in emissions of
isomers of the IIIa–IIId or IIIe–IIIh series.
maximum emissions at 507 nm, 542 nm, 580 nm,
and 616 nm, respectively. These compounds displayed
significant differences in electronic spectra due to
the electron-donating functional group attached. The
emission spectra could be measured only in a solid
state because these compounds did not exhibit fluo-
Fluorescence spectra of IIIi–IIIl (Fig. 7) showed

50
M. J. Percino et al./Chemical Papers 65 (1) 42–51 (2011)
rescence under the conditions applied to compounds
IIIa–IIIh in CHCl3.
Salzer, R. (2004). The vibrational and NMR spectra and con-
formations of methoxymethylene- and 1-methoxyethylidene-
propanedinitrile including solvent effect calculations. Asian
Chemistry Letters, 8, 169–186.
Gill, C., Pandhare, G., Raut, R., Gore, V., & Gholap, S.
(2008). Knoevenagel condensation in neutral media: A sim-
ple and efficient protocol for the synthesis of electrophillic
alkenes catalyzed by anhydrous ferric sulphate with remark-
able reusability. Bulletin of the Catalysis Society of India, 7,
153–157.
Fig. 7 shows that the fluorescence spectra of some
compounds exhibit one broad absorption peak with
a red-shift maximum. The red shift suggests that the
π-conjugation of the main chain of the compound was
influenced by meta linkages. These linkages caused the
reduction in the π-conjugation length.
Gómez, R., Segura, J. L., & Martín, N. (1999). New optically
active polyarylene vinylenes: control of chromophore separa-
tion by binaphthyl units. Chemical Communications, 1999,
619–620. DOI: 10.1039/a809405e.
Conclusions
A series of highly soluble phenylarylacrylonitrile
derivatives were prepared by the reaction of halogen-
substituted benzaldehyde with phenyl- and pyridy-
lacetonitrile applying the Knoevenagel method with-
out a solvent or catalyst. The results showed the dif-
ferent reactivity of aldehydes with arylacetonitriles.
It was proposed that the inclusion of a base catalyst
in the reaction mechanism was not necessary. Also,
the optical results showed that the electronegativity
of the chromophores can be tuned by attaching dif-
ferent electron-withdrawing groups to the para posi-
tion of the ring without any significant change in elec-
tronic spectra. In addition, in comparison with the
N(CH3)2 group, the CN substituent on the vinylene
moiety causes a weak bathochromic shift.
Gróf, M., Polovková, J., Gatial, A., Milata, V., Černuchová,
P., Prónayová, N.,
& Matějka, P. (2007). Isomers and
conformers of two push–pull hydrazines studied by NMR
and vibrational spectroscopy and by ab initio calculations.
Journal of Molecular Structure, 834–836, 284–293. DOI:
10.1016/j.molstruc.2006.10.018.
Guillemin, J.-C., Breneman, C. M., Joseph, J. C., & Ferris, J.
P. (1998). Regioselectivity of the photochemical addition of
ammonia, phosphine, and silane to olefinic and acetylenic ni-
triles. Chemistry – A European Journal, 4, 1074–1082. DOI:
10.1002/(SICI)1521-3765(19980615)4:6<1074::AID-CHEM
1074>3.0.CO;2-B.
Guillot, R., Loupy, A., Meddour, A., Pellet, M.,
& Pe-
tit, A. (2005). Solvent-free condensation of arylacetoni-
trile with aldehydes. Tetrahedron, 61, 10129–10137. DOI:
10.1016/j.tet.2005.07.040.
Knoevenagel, E. (1896). Ueber eine Darstellungsweise des Ben-
zylidenacetessigesters. Berichte der Deutschen Chemischen
Gesellschaft, 29, 172–174. DOI: 10.1002/cber.18960290133.
Loupy, A., Pellet, M., Petit, A., & Vo-Thanh, G. (2005).
Solvent-free condensation of phenylacetonitrile and nonanen-
itrile with 4-methoxybenzaldehyde: optimization and mech-
anistic studies. Organic & Biomolecular Chemistry, 3, 1534–
1540. DOI: 10.1039/b418156e.
Maruyama, S., Tao, X.-T., Hokari, H., Noh, T., Zhang, Y.,
Wada, T., Sasabe, H., Suzuki, H., Watanabe, T., & Miy-
ata, S. (1998). A cyclic carbazole oligomer for electrolumi-
nescence applications. Chemistry Letters, 27, 749–750. DOI:
10.1246/cl.1998.749.
Acknowledgements. The authors wish to acknowledge the fi-
nancial support received from VIEP-BUAP and assistance with
EI mass spectrometry received from M. C. Vladimir Carranza.
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