Structural and computational studies of 2,5-diarylpenta-2,4-dienenitriles

Article abstract of DOI:10.1016/j.molstruc.2011.03.060

2,5-Diarylpenta-2,4-dienenitriles 1-9 were synthesized and characterized by the high resolution ¹H, ¹³C, ¹H-¹H COSY and ¹H-¹³C COSY spectra. Spectral data indicate the trans arrangement of

Full text of DOI:10.1016/j.molstruc.2011.03.060

Journal of Molecular Structure 995 (2011) 78–90
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Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Structural and computational studies of 2,5-diarylpenta-2,4-dienenitriles
⇑
A. Manimekalai , A. Balamurugan
Department of Chemistry, Annamalai University, Annamalainagar, Tamilnadu 608 002, India
a r t i c l e i n f o
a b s t r a c t
2,5-Diarylpenta-2,4-dienenitriles 1–9 were synthesized and characterized by the high resolution 1H, 13C,
1H–1H COSY and 1H–13C COSY spectra. Spectral data indicate the trans arrangement of the side chain pro-
tons H(3), H(4) and H(5) and trans orientation of H(3) proton with respect to cyano group in 1–9. Com-
putational calculations were carried out for some possible structures and they support the conformation
in which all side chain protons are trans to each other and H(3) proton is trans to CN group. Moreover, syn
orientation of NO2 group with respect to H(5) proton in 4–6 is revealed by computational calculations
and chemical shift data. From the favored conformations, geometrical parameters, HOMO–LUMO ener-
gies, dipole moment, polarizabilities and first order hyperpolarizabilities were determined theoretically.
The highest btot is observed for the nitrile 9 where electron releasing substituent (OCH3) and electron
withdrawing substituent (NO2) are present at the opposite ends of the conjugated system and hence it
is the best NLO candidate. The NLO character decreases according to the order 9 > 3 > 5 > 4
> 7 > 8 > 6 > 2 > 1. The 1H and 13C chemical shifts in gaseous state as well as in solution were also deter-
mined theoretically by DFT method and they are in agreement with the experimental values. NBO anal-
yses were further carried out for the minimum energy conformer. From 1H and 13C chemical shifts, the
effect of introduction of substituents (NO2, OCH3, Cl) in the phenyl ring on the chemical shifts of the side
chain protons [H(3), H(4) and H(5)] and carbons [C(3), C(4) and C(5)] were analyzed in detail.
Ó 2011 Elsevier B.V. All rights reserved.
Article history:
Received 16 January 2011
Received in revised form 27 March 2011
Accepted 28 March 2011
Available online 1 April 2011
Keywords:
2,5-Diarylpenta-2,4-dienenitriles
Theoretical
Spectral studies
1. Introduction
emitting diodes (LEDs) with air stable electrodes [15–17]. Synthe-
sis, characterization and photophysical properties of novel tri-
Organic molecules with conjugated
p-electron system are
phenylamine derivatives containing a,b-diarylacrylonitriles were
known to exhibit extremely large optical non-linear responses in
terms of their molecular hyperpolarizabilities with application in
many current areas of interest, such as second harmonic genera-
tion (SHG) and linear electro-optimization (LEO) [1–3]. Both theo-
retical and experimental studies have shown that large
hyperpolarizabilities generally arise from a combination of a strong
electron donor and acceptor positioned at opposite ends of a suit-
able conjugation path. The values obtained are dependent not only
on the strength of the donor and acceptor group but also on the
path length between them. Large molecular hyperpolarizability b
studied in detail by Yue et al. [18]. They are found to be efficient
green emitters at room temperature in solution and in solid state.
Considerable work has been carried out on the synthesis and
biological aspects of arylacrylonitriles derived from several substi-
tuted aromatic, heteroaromatic and aliphatic carbonyl compounds
[8–11,19]. The present investigation focuses on the synthesis and
theoretical investigation of the molecular structures and their
NBO analysis of arylacrylonitriles with extended conjugation i.e.,
heavily substituted 2,5-diarylpenta-2,4-dienenitriles derived from
several cinnamaldehydes and arylacetonitriles and their stereo-
chemical investigation through NMR studies. HOMO–LUMO ener-
gies, dipole moment, polarizability and first hyperpolarizabilites
were determined by DFT method and compared. The 1H and 13C
chemical shifts were also determined theoretically and compared
with the observed values.
arises due to the delocalization of p-electronic clouds [4–7]. In or-
der to enhance the intermolecular charge transfer, most of the
molecules developed as NLO materials are equipped with apparent
donor and/or acceptor substituents such as nitro-, amino-, azo-,
halo-, cyano-, and hydroxyl. Unsaturated nitriles play important
role in biological system [8–11] and serve as versatile intermedi-
ates in the synthesis of a variety of products [12–14]. Recently they
were used in the field of organic materials in order to obtain high-
electron affinity polymers, which can be used to produce light
2. Experimental
2.1. Preparation of 2,5-diarylpenta-2,4-dienenitriles 1–9
⇑
To a mixture of appropriate cinnamaldehyde (0.01 mol) and
potassium hydroxide (0.01 mol) in 50 mL ethanol, appropriate aryl
Corresponding author. Tel.: +91 9486283468.
E-mail address: profmeka1@gmail.com (A. Manimekalai).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.03.060

A. Manimekalai, A. Balamurugan / Journal of Molecular Structure 995 (2011) 78–90
79
acetonitrile (0.01 mol) was added and the solution was stirred for
5 min at room temperature. The solid obtained was separated,
dried, and then recrystallized from absolute ethanol. The physical
and mass spectral data of all the synthesized compounds are dis-
played in Table 1.
approach using B3LYP/6-31G⁄ basis set available in Gaussian-03
package. The 1H and 13C chemical shifts were determined theoret-
ically by DFT method in gaseous state as well as in CDCl3 [SCRF-
PCM model] using the basis set B3LYP/6-311+G(2d,p) Giao. NBO
calculations were determined theoretically by DFT method using
the basis set B3LYP/6-31G(d) and B3LYP/6-311+G(d,p).
2.2. Spectral measurements
3. Results and discussion
Mass spectra were recorded on VARIAN Saturn 2200 mass spec-
trometer with a sensitivity of 0.3 ng at 70 eV with a direct inlet sys-
tem and the inlet temperature was maintained at 70 °C. Proton
spectra at 500 MHz and proton decoupled 13C NMR spectra at
125 MHz were recorded at room temperature on DRX 500 NMR
spectrometer using 10 mm sample tubes. Samples were prepared
by dissolving about 10 mg of the sample in 0.5 mL of chloroform-
d containing 1% TMS for 1H and 0.5 g of the sample in 2.5 mL of
chloroform-d containing a few drops of TMS for 13C. The solvent
chloroform-d also provided the internal field frequency lock signal.
Proton spectrum has the following experimental parameters: num-
ber of scans 32; spectral width 6009 Hz; acquisition time 2.73 s.
The experimental parameters for 13C NMR spectra are: spectral
width 32,768 Hz; number of scans ranges from 64 to 468; acquisi-
tion time 1.20 s.
2,5-Diphenylpenta-2,4-dienenitrile (1), 2-(p-chlorophenyl)-
5-phenylpenta-2,4-dienenitrile (2), 2-(p-nitrophenyl)-5-phenyl-
penta-2,4-dienenitrile (3), 5-(o-nitrophenyl)-2-phenylpenta-2,
4-dienenitrile (4), 2-(p-chlorophenyl)-5-(o-nitrophenyl)penta-2,4-
dienenitrile
(5),
2-(p-nitrophenyl)-5-(o-nitrophenyl)penta-2,
4-dienenitrile (6), 5-(p-methoxyphenyl)-2-phenylpenta-2,4-diene-
nitrile (7), 2-(p-chlorophenyl)-5-(p-methoxyphenyl)penta-2,
4-dienenitrile (8) and 2-(p-nitrophenyl)-5-(p-methoxyphenyl)-
penta-2,4-dienenitrile (9) were synthesized according to the
Scheme 1 and the high resolution 1H, 13C, 1H–1H COSY and
1H–13C COSY NMR spectra have been recorded in CDCl3 and ana-
lyzed. The 1H and 13C NMR spectra reveal the presence of only
one isomer in solution. The signals in the 1H NMR spectra were as-
signed based on their positions, integrals and multiplicities and
confirmed by the correlations observed in the COSY spectra. In
13C NMR spectra quaternary carbon can be easily distinguished
from other carbons based on small intensities. Assignments of
the aromatic ring carbons and side chain carbons made on the ba-
sis of cross peaks observed in 1H–13C COSY spectra. For example
the assignments of signals in the nitrile 1 are made as follows.
The 1H–1H COSY spectra were performed on a DRX-500 NMR
spectrometer at 500 MHz using the standard pulse sequences
employing the TPPI method to obtain pure absorption mode spec-
tra. For 1H–1H COSY spectra the experimental parameters are:
number of scans 16, acquisition time 0.15 s, spectral width
6666 Hz. 1H–13C COSY spectra were obtained on a DRX-500
NMR spectrometer using standard parameters: the number of
scans 16; number of data points 2048; acquisition time 0.15 s
and spectral width 6666 Hz.
CN
OHC CH
CH2
CH
Z
+
2.3. Computational study
Geometry optimizations were carried out according to Density
Functional Theory available in Dmol3 [hybrid functional BLYP with
the basis set dnp] [20] and Gaussian-03 package [B3LYP/6-
31G(d,p) basis set] [21] for all the structures of nitriles 1–9. The
electric dipole moment, polarizabilities and hyperpolarizabilities
were determined from the DFT optimized structures by finite field
Y
KOH
X
55
Z
54
56
Table 1
Physical and mass spectral data of 1–9.
N 6
H4
4
53
51
Compounds Physical data
Colour Yield m.p.
(%) (C)
167– 231.9 [M+1], 231.0 [M]+, 230.1,
168 152.9, 91.0, 51.1
144– 267.9 [M+2], 266.0 [M]+, 266.8
Mass spectral data (m/z)
5
C
52
1
C
C
Y
2
C
3
C
H5
1
2
Greenish 84
yellow
Greenish 82
yellow
22
21
H3
145
[M+1], 265.1, 231.2, 230.2, 115.1,
51.1
23
26
3
4
Greenish 82
yellow
142– 278 [M+2], 277 [M+1], 247.1,
X
Y
H
H
H
NO2
NO2
Z
143
132.1, 115.0
24
25
1
2
3
;
;
;
H
Cl
H
H
Green
78
176– 275.8 [M]+, 275.0 [Mꢀ1], 247.1,
X
177
242.2, 222.2, 204.1, 156.0, 132.0,
119.0, 117.4, 115.2, 92.0, 83.0
NO2
H
Cl
NO2 NO2
H
Cl
NO2
H
H
H
H
OCH3
OCH3
OCH3
5
6
7
8
9
Green
Green
77
78
200– 309.7 [M]ꢁ+, 308.9, 292.8, 258.1,
4
;
5
;
6
;
7
;
8
;
9
;
201
104– 323.2, 322.0 [M+2], 319.6 [M]+,
105 105.1, 77.0, 51.0
144– 262.1 [M+1], 261.0 [M]+, 246.3,
145 184.1, 121.2, 51.0
167– 298.0, 296.0 [M+1], 295.1 [M]+,
168 260.3, 245.2, 144.8, 50.1
144– 308.0 [M+2], 307.0 [M+1], 306.0
145
[M]+, 54.9
257.2, 131.9, 119.8, 92.0, 75.8
Greenish 85
yellow
Greenish 84
yellow
Greenish 84
yellow
H
H
H
Scheme 1. Structures of 1–9.

80
A. Manimekalai, A. Balamurugan / Journal of Molecular Structure 995 (2011) 78–90
13C NMR spectrum of 1 shows signals at 141.58, 141.23, 135.79,
in 1H–13C COSY spectrum. In a similar manner assignments were
done for 2–9. The various chemical shifts and coupling constants
determined in this manner for 1–9 are reported in the Tables 2
and 3.
133.28, 129.55, 129.07, 128.94, 127.53, 125.63, 125.19, 116.95 and
113.22 ppm. Based on small intensities the signals at 135.79,
133.28, 116.95 and 113.22 ppm are assigned to the quaternary car-
bons. Among quaternary carbon signals, the signals at 135.79 and
133.28 ppm should be due to ipso carbons of phenyl ring. The
remaining signals at 113.22 and 116.95 ppm are due to carbon pos-
sessing cyano group (CCN) and cyano carbon (CN) respectively and
this assignments is based on the expectation that the cyano bear-
ing carbon resonates at lower frequency compared to cyano carbon
[22]. From the comparison of chemical shifts of the ipso carbons in
nitrile 1 (135.79 and 133.28 ppm) with those nitriles 2 and 3. It is
concluded that the signal at 135.79 ppm is due to ipso carbon of
phenyl ring at C5 (C51). Obviously the remaining signal at
133.28 ppm is due to ipso carbon of phenyl ring at C2 (C21). The
remaining signals are assigned based on the correlations observed
3.1. Conformation of 2,5-diarylpenta-2,4-dienenitriles
3.1.1. Spectral studies
It is seen from Table 2 that the two couplings associated with
H(4) signal in 4–9 are in the range 11 and 15 Hz (J3,4 and J4,5).
The large magnitude suggest that the two nearby protons H(3)
and H(5) must be trans to the side chain proton H(4). There are
two possible ways of attaching the cyano and aryl groups at C-2,
(i) cyano group is anti to H(3) [A] i.e., Z configuration and (ii) cyano
group is syn to H(3) [B] i.e., E configuration as shown in Scheme 2.
Previously it has been established that in 3-aryl-2-phenylacrylo-
Table 2
1H chemical shifts (ppm) of 1–9.
Compounds H(3)
H(4)
H(5)
Aromatic protons
C(2)
C(5)
1
2
3
4
7.45–7.35
7.45–7.35
7.03 [dd, 2.91 (J3,5), 7.64 (d, 7.46 Hz) [H(22), H(26)]
11.54 (J4,5) Hz] 7.45–7.35 [H(23), H(24), H(25)]
7.03 [dd, 3.17 (J3,5), 7.54 (d, 8.41 Hz) [H(22), H(26)]
11.14 (J4,5) Hz] 7.33–7.40 [H(23), H(25)]
7.56 (d, 7.05 Hz) [H(52), H(56)] 7.45–7.35 [H(53),
H(54), H(55)]
7.54 (d, 8.41 Hz) [H(52), H(56)] 7.33–7.40 [H(53),
H(54), H(55)]
7.40–7.33
7.63–7.55
7.40–7.33
7.45–7.40
7.16 [dd, 4.50 (J3,5), 7.79 (d, 8.95 Hz) [H(22), H(26)] 8.29 7.63–7.55 [H(52), H(56)] 7.45–7.40 [H(53, H(54),
15.25 (J4,5) Hz]
7.55 [d, 15.15 (J4,5
(d, 8.90 Hz) [H(23), H(25)]
7.65–7.68 [H(22), H(26)] 7.41–7.51
[H(23), H(24), H(25)]
H(55)]
7.48 [d,
11.30 (J3,4
Hz]
7.46 [d,
11.20 (J3,4
Hz]
7.64 [d,
11.10 (J3,4
Hz]
7.39 [d,
11.25 (J3,4
Hz]
7.35 [d,
10.80 (J3,4
Hz]
7.55 [d,
11.20 (J3,4
Hz]
7.37 [dd, 15.23
(J4,5), 11.18 (J3,4) Hz] Hz]
)
)
)
)
)
)
8.01 (dd, 8.20, 1.05 Hz) [H(53)] 7.41–7.51 [H(54)]
7.65–7.68 [H(55)] 7.83 (d, 7.40 Hz) [H(56)]
)
)
)
)
5
6
7
8
9
7.35 [dd, 15.13
(J4,5), 11.13 (J3,4) Hz] Hz]
7.57 [d, 14.95 (J4,5
7.59 (d, 8.55 Hz) [H(22), H(26)] 7.42 8.02 (d, 8.15 Hz) [H(53)] 7.51 [H(54)], 7.67 [H(55)]
(d, 8.60 Hz) [H(23), H(25)]
7.83 (d, 7.75 Hz) [H(56)]
7.39 [dd, 15.20 (J4,5), 7.71 [d, 15.15 (J4,5
11.20 (J3,4) Hz]
7.838 (d, 8.80 Hz) [H(22), H(26)]
8.32 (d, 8.80 Hz) [H(23), H(25)]
8.07 (d, 8.20 Hz) [H(53)] 7.56 [H(54)], 7.73 [H(55)]
7.844 (d, 7.33 Hz) [H(56)]
Hz]
7.27 [dd, 15.23
(J4,5), 11.23 (J3,4) Hz] Hz]
6.97 [d, 15.20 (J4,5
7.61 (d, 7.60 Hz) [H(22), H(26)] 7.41 ꢂ7.50 [H(52), H(56)] ꢂ6.91 [H(53), H(55)]
[H(23), H(25)] 7.34 [H(24)]
7.23 [dd, 15.18
(J4,5), 11.23 (J3,4) Hz] Hz]
6.97 [d, 15.15 (J4,5
7.52 (d, 8.60 Hz) [H(22), H(26)] 7.36 7.49 (d, 8.70 Hz) [H(52), H(56)] 6.91 (d, 8.70 Hz)
(d. 8.40 Hz) [H(23), H(25)]
)
)
[H(53), H(55)]
7.29 [dd, 15.30 (J4,5), 7.12 [d, 15.25 (J4,5
11.30 (J3,4) Hz]
7.76 (d, 8.90 Hz) [H(22), H(26)]
8.27(d, 8.90 Hz) [H(23), H(25)]
7.54 (d, 8.65 Hz) [H(52), H(56)] 6.94 (d, 8.75 Hz)
[H(53), H(55)]
Hz]
Values within parentheses are observed coupling constants derived from the particular signal.
Table 3
13C chemical shifts (ppm) of 1–9.
Compounds C(3)
C(4)
C(5)
CCN
CN
ipso carbons
Other carbons
C(2) aromatic
C(5) aromatic
1
2
3
4
5
6
7
8
9
141.58 125.19 141.23 113.22 116.95 135.79 [C(51)] 133.28 [C(21)]
125.63 [C(22), C(26)] 129.07
[C(23), C(24), C(25)]
126.75 [C(22), C(26)] 129.24
[C(23), C(25)]
126.20 [C(22), C(26)] 124.40
[C(23), C(25)]
125.86 [C(22), C(26)] 129.16
[C(23), C(25)] 129.62 [C(24)]
127.07 [C(22), C(26)] 129.72
[C(23), C(25)]
126.58 [C(22), C(26)] 124.43
[C(23), C(25)]
125.46 [C(22), C(26)] 129.01
[C(23), C(25)] 128.79 [C(24)]
126.60 [C(22), C(26)] 129.19
[C(23), C(25)]
127.53 [C(52), C(56)] 128.94
[C(53), C(55)] 129.55 [C(54)]
127.57 [C(52), C(56)] 128.93
[C(53), C(55)] 129.71 [C(54)]
127.96 [C(52), C(56)] 129.10
[C(53), C(55)] 130.42 [C(54)]
125.03 [C(53] 129.55 [C(54)]
133.41 [C(55)] 128.49 [C(56)]
125.08 [C(53)] 129.72 [C(54)]
133.47 [C(55)] 128.53 [C(56)]
125.16 [C(53)] 130.24 [C(54)]
133.60 [C(55)] 128.67 [C(56)]
129.09 [C(52), C(56)] 114.42
[C(53), C(55)] 55.38 [OCH3]
129.19 [C(52), C(56)] 114.44
[C(53), C(55)] 55.37 [OCH3]
129.67 [C(52), C(56)] 114.58
[C(53), C(55)] 55.48 [OCH3]
141.90 124.87 141.85 111.86 116.62 135.56 [C(51)] 131.73 [C(21)]
135.01 [C(24)]
145.04 124.63 144.41 110.86 116.09 135.24 [C(51)] 139.44 [C(21)]
147.68 [C(24)]
140.45 129.73 135.08 115.92 116.51 131.29 [C(51)] 132.67 [C(21)]
148.05 [C(52)]
140.81 129.42 135.73 111.24 116.21 131.22 [C(51), C(24)] 131.22
[C(21)] 148.07 [C(52)]
143.98 128.90 138.25 113.56 115.66 131.59 [C(51)] 148.13 [C(24)]
148.13 [C(52)] 138.74 [C(21)]
142.08 123.15 141.00 111.65 117.23 133.47 [C(21)] 128.61 [C(51)]
160.88 [C(54)]
142.39 122.87 141.62 110.33 116.90 131.99 [C(21)] 134.65 [C(24)]
161.01 [C(54)] 128.43 [C(51)]
145.52 122.56 144.29 109.16 116.43 139.70 [C(21)] 147.33 [C(24)]
128.07 [C(51)] 161.56 [C(54)]
125.91 [C(22), C(26)] 124.33
[C(23), C(25)]

A. Manimekalai, A. Balamurugan / Journal of Molecular Structure 995 (2011) 78–90
81
H
C
H
C
H
C
H
C
CN
Ar
Ar
C
H
C
Ar
C
C
Ar
H
CN
A
B
Scheme 2. Possible configurations of cyano group.
H
C
C
CN
10a
; X = H
10b
10c
; X = F
; X = CH3
10d
; X = OCH3
X
Fig. 3. ORTEP and close packed structures of 1.
Fig. 1. Structure of nitrile 10.
nitriles (10a–10d) (Fig. 1), the two aryl rings are occupying trans
arrangement and the side chain CH protons resonate in the region
7.40–7.54 ppm [22–24]. The chemical shifts of H(3) in the nitriles
4–9 are closer to the values reported in 10a–10d and hence in 4–9
also H(3) protons must be trans to CN group. The chemical shifts of
H(3) in 1–3 are closer to 4–9 and hence one can expect that H(3)
protons must be trans to CN group in 1–3 also. Therefore, the fa-
vored structures of 2,5-diarylpenta-2,4-dienenitriles 1–9 are pre-
dicted to be A in which all the side chain protons are trans to
each other and H(3) protons are trans to CN group (Fig. 2). For 1
single crystal measurements were also made [25] and it reveals
the geometry A in which all the side chain protons are trans to each
other. The molecule belongs to the monoclinic crystal lattice (C2/c).
The ORTEP and the close packed structures are given in Fig. 3.
3.1.2. Theoretical studies
In order to predict the favored conformation of penta-2,4-
dienenitriles 1–9 in gaseous state, theoretical studies were also
performed in the present study. Since trans-cinnamaldehyde was
used as one of the starting materials for the synthesis of nitriles
all the side chain protons must be trans to each other in 1–9 and
only two isomers possible for the nitriles 1–3 and 7–9 as shown
in Scheme 2. In the isomer A the cyano group is anti to H(3)
whereas in B it is syn to H(3). For the nitrile derivatives derived
from o-nitrocinnamaldehyde i.e., 4–6 there are two more struc-
tures as shown in Scheme 3 are possible. In isomers A and B the
nitro group adopts syn orientation with respect to H(5) proton
whereas in structures C and D the nitro group adopts anti orienta-
tion with respect to H(5). In structures A and C, cyano group is anti
to H(3) whereas in structures B and D the cyano group is syn to
H(3).
Computational calculations were carried out according to Den-
sity Functional Theory available in Dmol3 and Gaussian-03 package
for all the structures shown in Schemes 2 and 3. Table 4 reports the
energies of nitriles 1–9 according to these methods. Calculations
reveal that Z isomer [A] is thermodynamically favored over the E
isomer [B] in all the nitriles and nitro group prefers syn orientation
with respect to H(5) in nitriles 4–6. The spectral studies also pre-
dict the same geometries. Thus, the geometries predicted in solu-
tion (NMR study) are in agreement with the geometries
predicted in the gaseous state.
Crystal data
C17H13
N
V = 2456.42(13) Å3
Z = 8
Mr = 231.28
Monoclinic, C2/c
a = 16.9390(5) Å
b = 7.5869(2) Å
c = 19.3809(6) Å
b = 92.521(3)°
Cu K
l
a radiation
= 0.56 mmꢀ1
T = 110 K
0.53 ꢃ 0.36 ꢃ 0.29 mm
H
C
H
C
The DFT [B3LYP/6-31G(d,p)] optimized structures of 1–9 are
reproduced in Fig. 4. The geometric parameters derived from the
favored conformations according to Dmol3 and Gaussian methods
are reported in Table 5. In most of the cases there is a good
agreement between the values. Only slight variation in the geo-
metric parameters (bond lengths and bond angles) by varying
the basis set are observed in the present study. Deviations are
observed only in some torsional angles. The torsional angles C4–
C5–C51–C52 and C4–C5–C51–C56 in 4–6 around 156° and 28°
indicate that the o-nitrophenyl ring at C-5 is tilted from the plane
Ar
Ar
C
H
C
CN
A
Fig. 2. Favored conformations of 1–9.

82
A. Manimekalai, A. Balamurugan / Journal of Molecular Structure 995 (2011) 78–90
X
H
C3
H
H
H
NO2
NO2
C5
C3
CN
C5
C4
H
C2
C4
H
C2
CN
B
A
X
X
H
C3
H
H
H
C5
C5
C3
CN
C4
C2
CN
C4
C2
H
H
NO2
NO2
X
D
C
4
;
5
;
6
;
H
Cl
NO2
X
Scheme 3. Possible conformations of nitro group.
Table 4
the phenyl ring at C-2 also. HOMO–LUMO energies were also cal-
culated and the values are listed in Table 6. The electric dipole mo-
ment, polarizabilities and first order polarizabilities were also
calculated by DFT method using the basis set B3LYP/6-31G⁄ avail-
able in Gaussian-03 package and these values are listed in Tables 7
and 8.
HOMO and LUMO orbitals are stabilized by the introduction of
chloro and nitro substituents at the para position of the phenyl ring
at C-2 and nitro substituent at the ortho position of phenyl ring at
C-5 whereas electron releasing para-methoxy substituent at C-5
destabilizes both HOMO and LUMO orbitals. From Table 7, it is seen
that the introduction of chloro and nitro substituent at the para
position of phenyl ring at C-2 and methoxy substituent at the para
position of phenyl ring at C-5 increases both the dipole moments
and polarizabilities. However, the introduction of nitro substituent
at the ortho position of phenyl ring at C-5 decreases dipole moment
but increases polarizability values.
DFT energies of possible isomers of nitriles 1–9.
Compounds
Isomers
Energy (hartrees)
Dmol3
Gaussian-03
1
2
3
4
A
B
ꢀ710.3261829
ꢀ710.3224585
ꢀ1169.9556548
ꢀ1169.9516894
ꢀ914.9180623
ꢀ914.9134514
ꢀ914.9093353
ꢀ914.9041518
ꢀ914.9026229
ꢀ914.9005451
ꢀ1374.5371179
ꢀ1374.5336127
ꢀ1374.5317713
ꢀ1374.5301577
ꢀ1119.4995644
ꢀ1119.4945854
ꢀ1119.4932249
ꢀ1119.4911207
ꢀ824.8693374
ꢀ824.8656181
ꢀ1284.4990757
ꢀ1284.4951218
ꢀ710.3808157
ꢀ710.3769114
ꢀ1169.974859
ꢀ1169.9708903
ꢀ914.8802554
ꢀ914.8756887
ꢀ914.8727347
ꢀ914.8681545
ꢀ914.8647505
ꢀ914.8643782
ꢀ1374.4664979
ꢀ1374.4618194
ꢀ1374.4586084
ꢀ1374.4583501
ꢀ1119.3709499
ꢀ1119.3660786
ꢀ1119.3633093
ꢀ1119.3625873
ꢀ824.9074083
ꢀ824.9035803
ꢀ1284.5016459
ꢀ1284.4977103
A
B
A
B
A
B
C
D
5
6
A
B
C
D
Second order NLO calculations and comparison of the NLO
properties of various substituted systems reveal that the presence
of NO2 group enhances the second order NLO properties of the
molecules [4–7,26,27]. Large first order hyperpolarizability is
expected for the 2,5-diarylpenta-2,4-dienenitriles 1–9 since exten-
sive delocalization is present in this system. Table 8 reveals that
A
B
C
D
7
8
9
A
B
first order hyperpolarizability is dominated by the component bxxx
.
A
B
The highest btot is observed for the nitrile 9 where electron
releasing substituent (OCH3) and electron withdrawing substituent
(NO2) are present at the opposite ends of the conjugated system.
Among the nitriles, the best NLO candidate is 9. The NLO character
decreases according to the following order:
A
B
ꢀ1029.4622544
ꢀ1029.4573121
ꢀ1029.4075938
ꢀ1029.4030247
9 > 3 > 5 > 4 > 7 > 8 > 6 > 2 > 1:
containing the side chain moiety in 4–6. This is further supported
by the torsional angles H5–C5–C51–C52 (ꢂ23°) and H5–C5–C51–
C56 (ꢂ152°). The torsional angles C22–C21–C2–C3, C22–C21–C2–
C1, C26–C21–C2–C3 and C26–C21–C2–C1 indicate the tilting of
The macroscopic susceptibility in the condensed phase assuming
the electric fields to be the same is directly proportional to the
microscopic (hyper) polarizabilities. The electric field experienced

A. Manimekalai, A. Balamurugan / Journal of Molecular Structure 995 (2011) 78–90
83
Fig. 4. Optimized structures of favored conformations of 1–9.
Table 5
Selected geometric parameters [bond lengths (Å), bond angles (°) and torsional angles (°)] in 1–9.
Geometric
parameters
1
2
3
4
5
6
7
8
9
XRD
Theor.
Bond lengths
C1–C2
1.445
1.354
1.442
1.345
1.465
1.484
1.149
–
1.435
(1.437)
1.368
(1.379)
1.435
(1.431)
1.356
(1.366)
1.459
(1.458)
1.481
(1.484)
1.165
(1.171)
–
1.435
(1.436)
1.368
(1.380)
1.435
(1.431)
1.357
(1.367)
1.459
(1.458)
1.480
(1.483)
1.165
(1.171)
1.756
(1.766)
–
1.435
(1.437)
1.370
(1.381)
1.433
(1.429)
1.358
(1.368)
1.457
(1.456)
1.478
(1.479)
1.165
(1.171)
–
1.436 (1.438) 1.436 (1.438) 1.436
1.435
(1.436)
1.369
(1.380)
1.434
(1.430)
1.358
(1.368)
1.454
(1.454)
1.481
(1.484)
1.165
(1.171)
–
1.434 (1.436) 1.435
(1.436)
1.369 (1.381) 1.371
(1.384)
1.433 (1.429) 1.430
(1.426)
1.359 (1.369) 1.361
(1.371)
1.454 (1.453) 1.451
(1.450)
1.480 (1.483) 1.477
(1.478)
1.165 (1.171) 1.165
(1.171)
(1.438)
1.366 (1.380) 1.367 (1.380) 1.367
(1.380)
1.438 (1.432) 1.437 (1.431) 1.436
(1.432)
1.355 (1.367) 1.355 (1.369) 1.356
(1.366)
1.465 (1.460) 1.465 (1.462) 1.465
(1.462)
1.480 (1.481) 1.479 (1.480) 1.479
(1.480)
1.165 (1.173) 1.165 (1.171) 1.164
(1.170)
C2–C3
C3–C4
C4–C5
C5–C51
C2–C21
C1–N6
C24–Cl
C24–N
C52–N
C54–O
–
1.755 (1.763)
–
1.757 (1.757)
–
–
–
–
–
1.468
(1.481)
–
–
–
1.469
–
–
–
–
1.466
(1.467)
–
(1.486)
–
–
–
1.474 (1.490) 1.474 (1.503) 1.474
(1.491)
–
–
–
–
–
1.360
(1.376)
1.359 (1.359) 1.357
(1.373)
Bond angles
C21–C2–C3
125.3
126.2
121.4
127.2
116.6
118.1
124.6
(125.1)
126.0
(126.2)
122.4
(122.9)
127.6
(127.5)
117.0
(117.0)
118.4
124.6
(125.0)
126.0
(126.5)
122.3
(122.4)
127.6
(127.9)
117.0
(116.9)
118.5
124.4
(124.8)
126.0
(126.3)
122.1
(122.4)
127.6
(127.7)
117.1
(117.1)
118.5
124.6 (125.2) 124.6 (125.2) 124.6
124.5
(125.1)
126.2
(126.5)
122.4
(122.7)
127.7
(127.8)
117.0
(117.0)
118.4
124.5 (125.0) 124.4
(124.7)
126.1 (126.6) 126.0
(126.5)
122.3 (122.5) 122.1
(122.3)
127.7 (127.7) 127.6
(127.9)
117.0 (117.0) 117.1
(117.2)
118.5 (118.0) 118.4
(118.1)
(125.1)
125.6 (125.9) 125.6 (125.7) 125.6
(125.6)
122.3 (122.3) 122.2 (122.1) 122.0
(122.3)
124.5 (125.8) 124.5 (126.0) 124.5
(125.6)
117.1 (117.2) 117.0 (117.0) 117.0
(117.2)
C2–C3–C4
C3–C4–C5
C4–C5–C51
C21–C2–C1
C3–C2–C1
118.3 (117.7) 118.4 (117.8) 118.4
(117.8)
(117.9)
(118.0)
(118.1)
(117.9)
Torsional angles
C1–C2–C3–C4
C2–C3–C4–C5
ꢀ2.7
ꢀ2.0 (ꢀ0.6) ꢀ2.1 (ꢀ0.5) ꢀ1.8 (ꢀ0.7) 2.3 (0.8)
2.4 (0.6)
ꢀ179.0
ꢀ1.8 (0.3)
179.8
(180.0)
ꢀ2.1 (ꢀ0.6) ꢀ2.1 (ꢀ0.4)
ꢀ1.8 (ꢀ0.6)
177.4
179.2
179.1
179.1
ꢀ178.9
179.0
179.0 (179.0) 178.9
(178.3)
ꢀ179.9
(179.9)
0.3 (ꢀ3.3)
(178.5)
180.0
(ꢀ179.7)
(178.4)
179.9
(179.8)
(ꢀ180.0)
(ꢀ179.6)
(178.2)
179.9
(178.4)
180.0
C3–C4–C5–C51
C4–C5–C51–C56
177.5
177.8 (179.0) 178.0 (179.7) 177.9
(179.0)
ꢀ189.0
(179.8)
0.0 (ꢀ2.7)
(ꢀ179.5)
ꢀ0.4 (ꢀ2.2)
(ꢀ179.9)
ꢀ15.2
ꢀ0.4 (ꢀ2.7) ꢀ0.3 (ꢀ3.4) ꢀ27.0
(ꢀ14.7)
ꢀ27.3 (ꢀ3.6)
ꢀ27.8
ꢀ0.4 (ꢀ2.5)
(ꢀ16.1)
(continued on next page)

84
A. Manimekalai, A. Balamurugan / Journal of Molecular Structure 995 (2011) 78–90
Table 5 (continued)
Geometric
parameters
1
2
3
4
5
6
7
8
9
XRD
165.3
Theor.
C4–C5–C51–C52
ꢀ179.7
179.7
(177.3)
0.0 (ꢀ0.1)
179.8
(176.8)
ꢀ0.0 (ꢀ0.2)
156.4 (168.5) 156.0 (177.3) 155.5
(167.3)
–
ꢀ180.0
179.6 (177.8) 179.6
(177.6)
0.0 (0.0)
(176.7)
(177.3)
C5–C51–C52–
H52
–
0.0 (ꢀ0.7)
–
–
0.0 (ꢀ0.1)
0.0 (0.1)
C5–C51–C56–
H56
–
0.0 (ꢀ0.4)
0.0 (ꢀ0.3)
0.0 (ꢀ0.3)
ꢀ0.1 (0.0)
ꢀ0.2 (0.4)
ꢀ0.2 (0.4)
0.0 (ꢀ0.3)
0.0 (ꢀ0.4)
ꢀ0.1 (ꢀ0.3)
C21–C2–C3–C4
177.8
179.0
(179.6)
179.0
179.5
(179.7)
162.3
(178.3)
ꢀ16.4
(ꢀ1.3)
163.5
(178.7)
ꢀ17.8
(ꢀ1.7)
ꢀ179.0
ꢀ178.8
179.7
(179.3)
163.8
(177.3)
ꢀ15.4
(ꢀ2.3)
164.4
179.0
(179.9)
159.5
(178.8)
ꢀ19.5
(ꢀ0.7)
160.5
(179.2)
ꢀ20.6
(ꢀ1.2)
179.0
179.4
(180.0)
163.2
(179.0)
ꢀ15.6
(ꢀ0.4)
(ꢀ179.8)
(ꢀ179.7)
ꢀ159.5
(ꢀ179.5)
(ꢀ179.8)
C22–C21–C2–C3
C22–C21–C2–C1
C26–C21–C2–C1
C26–C21–C2–C3
ꢀ176.4 179.0
160.3
160.6
(ꢀ179.8)
18.1 (0.2)
ꢀ160.4
(178.5)
(179.3)
ꢀ18.6 (0.0)
(ꢀ178.7)
19.2 (0.9)
(179.7)
4.1
ꢀ19.6
ꢀ18.5 (0.4)
(ꢀ1.4)
160.3
161.3
ꢀ160.8
160.8
161.4 (179.4) 164.3
(179.8)
ꢀ19.7 (ꢀ0.1)
(178.5)
ꢀ20.7
(179.8)
ꢀ19.7
(ꢀ0.4)
(ꢀ179.3)
20.4 (1.1)
(ꢀ179.5)
(177.9)
ꢀ16.4
(ꢀ2.5)
3.3
–
19.4 (0.5)
ꢀ17.0
(ꢀ1.7)
ꢀ2.9 (0.0)
(ꢀ0.8)
H26–C26–C21–
C2
ꢀ2.8 (ꢀ0.2) ꢀ2.7 (ꢀ0.1) 2.9 (0.0)
2.8 (ꢀ0.1)
ꢀ2.4 (ꢀ0.9) ꢀ2.8 (0.0)
ꢀ2.8 (ꢀ0.2)
ꢀ2.6 (ꢀ0.2)
C5–C51–C52–N
H22–C22–C21–
C2
–
–
–
–
–
ꢀ4.7 (ꢀ4.1)
ꢀ0.8 (ꢀ0.3)
ꢀ4.7 (ꢀ1.7)
ꢀ0.7 (0.5)
4.7 (ꢀ4.7)
–
–
–
0.7 (0.0)
0.73 (0.3)
0.7 (0.1)
0.5 (0.3)
0.7 (ꢀ0.1)
0.7 (0.4)
0.6 (0.2)
H3–C3–C4–H4
–
–
ꢀ179.9
ꢀ179.9
(179.3)
179.9
ꢀ179.8
(178.9)
179.9
(179.0)
0.1 (ꢀ1.5)
ꢀ178.3
ꢀ178.2
ꢀ177.6
ꢀ180.0
(179.1)
180.0
(179.0)
0.0 (ꢀ1.5)
ꢀ180.0
ꢀ179.9
(178.9)
(ꢀ178.5)
(ꢀ179.3)
(178.0)
(179.5)
(179.2)
H4–C4–C5–H5
ꢀ179.9
175.5 (176.5) 175.6 (179.0) 175.7
(176.5)
0.2 (0.2)
179.9 (179.2) 179.9
(179.0)
(179.1)
(179.2)
0.0 (ꢀ1.3)
H3–C3–C4–C5
H4–C4–C5–C51
H5–C5–C51–C56
–
–
–
0.1 (ꢀ1.6)
0.0 (ꢀ0.5)
ꢀ179.7
0.2 (0.4)
ꢀ3.6 (ꢀ0.6)
0.8 (0.5)
ꢀ3.8 (ꢀ2.6) 0.0 (ꢀ0.4)
ꢀ0.1 (ꢀ1.2)
0.0 (ꢀ1.3)
ꢀ0.1 (ꢀ0.2) ꢀ0.1 (ꢀ0.6)
ꢀ3.7 (ꢀ2.4)
ꢀ0.1 (ꢀ0.2)
ꢀ0.1 (ꢀ0.5)
179.6
179.7
(177.0)
153.7 (166.4) 153.4 (176.8) 152.7
(164.9)
ꢀ180.0
179.6 (178.4) 179.6
(178.0)
(177.1)
(177.8)
(177.8)
H5–C5–C51–C52
–
0.3 (ꢀ2.9)
ꢀ0.3 (ꢀ2.2) ꢀ0.3 (ꢀ2.9) ꢀ22.8
ꢀ23.2 (ꢀ2.4)
ꢀ23.9
0.0 (ꢀ2.2)
ꢀ0.4 (ꢀ1.7)
ꢀ0.4 (ꢀ1.9)
(ꢀ10.4)
(ꢀ11.8)
Values within parentheses are calculated values according to the Dmol3 structures.
by the individual molecules in a macroscopic sample is not the
same as the applied external electric field which would be
experienced by an isolated molecule in the gas phase. Instead the
molecule in a macroscopically applied field experiences a local field
Ewloc [28]. This field (not known) is different from the macroscopi-
cally applied field (used in experiment is well known) because of
polarization of surrounding molecules. Therefore, non-linear optical
properties of a molecule in solution or in solid state will be different
from that of isolated molecule due to polarization effects caused by
the surrounding molecules. Even though theoretical studies can be
performed in liquid phase it does not solve the issue of local field
effects. The hyperpolarizability b in solution can be theoretically
Table 6
Calculated HOMO–LUMO energies (eV) of nitriles of 1–9.
Compounds
LUMO
Dmol3
HOMO
Dmol3
Energy gap (
Dmol3
DE)
Gaussian-03
Gaussian-03
Gaussian-03
1
2
3
4
5
6
7
8
9
ꢀ2.975
ꢀ3.132
ꢀ3.709
ꢀ3.610
ꢀ3.836
ꢀ4.069
ꢀ2.784
ꢀ2.943
ꢀ3.537
ꢀ2.298
ꢀ2.455
ꢀ2.981
ꢀ2.823
ꢀ2.936
ꢀ3.286
ꢀ2.123
ꢀ2.281
ꢀ2.833
ꢀ5.088
ꢀ5.199
ꢀ5.598
ꢀ5.455
ꢀ5.556
ꢀ5.969
ꢀ4.806
ꢀ4.920
ꢀ5.274
ꢀ5.711
ꢀ5.820
ꢀ6.160
ꢀ6.078
ꢀ6.171
ꢀ6.556
ꢀ5.412
ꢀ5.520
ꢀ5.812
2.113
2.067
1.889
1.845
1.720
1.900
2.022
1.977
1.737
2.736
3.365
3.179
3.255
3.235
3.270
3.289
3.239
2.979
Table 7
The electric dipole moment
l
(D) and the polarizability of nitriles 1–9.
1
2
3
4
5
6
7
8
9
lx
ly
lz
lrot
axx
axy
ayy
axz
ayz
azz
0.75
2.48
7.57
0.26
0.79
1.18
1.20
0.31
1.71
506.896
ꢀ0.717
224.640
ꢀ8.766
0.578
76.855
269.463
39.934
6.86
1.24
1.56
7.14
501.572
ꢀ62.478
247.930
150.019
ꢀ2.408
130.800
293.434
43.487
2.76
4.68
10.13
ꢀ4.05
ꢀ3.81
ꢀ3.25
ꢀ5.54
ꢀ5.29
ꢀ4.71
ꢀ0.24
0.43
2.45
ꢀ1.01
0.37
1.07
3.16
4.12
4.56
8.60
1.31
6.20
7.15
11.62
416.623
ꢀ52.756
202.491
129.322
ꢀ5.006
106.762
241.958
35.858
465.094
ꢀ48.850
206.915
146.072
ꢀ3.056
117.741
263.250
39.014
500.727
ꢀ49.745
217.461
161.075
ꢀ2.014
125.129
281.105
41.660
495.605
7.803
222.031
ꢀ9.067
5.002
69.741
262.459
38.896
526.597
ꢀ18.212
199.708
ꢀ2.501
2.947
74.737
267.013
39.589
580.877
ꢀ25.863
207.780
ꢀ1.430
3.341
79.052
289.237
42.865
635.991
ꢀ28.493
219.185
ꢀ1.216
3.375
78.991
311.389
46.148
h
a
i(a.u)
1024
ꢃ
atot(esu)

A. Manimekalai, A. Balamurugan / Journal of Molecular Structure 995 (2011) 78–90
85
Table 8
The hyperpolarizability of nitriles 1–9.
1
2
3
4
5
6
7
8
9
bxxx
bxxy
bxyy
byyy
bxxz
bxyz
byyz
bxzz
ꢀ296.527
124.206
ꢀ32.365
ꢀ15.496
ꢀ93.284
29.709
528.785
251.305
ꢀ17.374
ꢀ10.253
216.269
89.203
ꢀ9986.423
ꢀ241.512
115.302
5196.632
154.621
245.122
ꢀ279.834
111.013
ꢀ43.191
31.950
6126.237
182.781
215.788
ꢀ267.568
83.790
ꢀ4137.768
ꢀ669.606
399.278
ꢀ436.751
ꢀ1687.208
ꢀ252.984
194.976
ꢀ5499.648
ꢀ24.368
70.700
ꢀ5424.822
451.511
106.152
ꢀ26.013
ꢀ23.647
ꢀ30.040
ꢀ5.226
ꢀ20983.499
ꢀ1111.729
89.079
ꢀ2.842
ꢀ40.240
ꢀ20.819
ꢀ3859.447
ꢀ85.579
14.277
41.456
ꢀ17.331
ꢀ28.677
ꢀ6.627
5.509
6.809
49.085
ꢀ5.184
ꢀ4.065
51.840
55.008
ꢀ29.222
ꢀ6.109
86.550
ꢀ1488.666
5.054
2.160
ꢀ678.206
36.328
34.105
byzz
bzzz
27.295
31.323
699.195
6040.553
ꢀ31.783
ꢀ0.646
ꢀ6.876
ꢀ97.025
ꢀ32.805
ꢀ34.610
ꢀ36.815
ꢀ10.029
388.001
3352.059
ꢀ575.059
12179.292
105218.287
ꢀ3.894
ꢀ5.776
ꢀ274.192
4906.687
42390.344
7.634
7.327
9.179
btot (a.u)
1033 ꢃ btot (esu)
5450.036
47084.494
6346.241
54827.080
5393.521
46596.226
5299.179
45781.193
20877.479
180366.800
evaluated and compared to the experimental values obtained by
EFISH and HRS measurement and several studies have been
reported in literature [28–31].
[SCRF-PCM model] using the basis set B3LYP/6-311+G(2d,p) Giao.
The shielding magnitude obtained from the computational calcula-
tions are converted into their corresponding chemical shifts using
the conversion factor 182.4656 [13C] and 31.8821 [1H]. The exper-
imental 13C chemical shifts are closer to the theoretical values and
The 1H and 13C chemical shifts were also determined theoreti-
cally by DFT method in the gaseous state as well as in CDCl3
Fig. 5. (a-i). Correlation between the experimental and theoretical 13C chemical shifts for 1–9.

86
A. Manimekalai, A. Balamurugan / Journal of Molecular Structure 995 (2011) 78–90
Table 9
Experimental and theoretical 1H NMR [SCRF-PCM model] spectral data (ppm) of nitriles 1–9 in CDCl3.
Protons
1
2
3
4
5
6
7
8
9
Exp.
Theor.
Exp.
Theor.
Exp.
Theor.
Exp.
7.48
Theor.
Exp. Theor.
Exp. Theor.
Exp.
7.39
Theor.
Exp. Theor.
Exp. Theor.
H(3)
7.45–
7.35
7.45–
7.35
7.85
(7.92)
7.80
(8.15)
7.35
(7.23)
8.03
(8.33)
7.84
(7.76)
7.75
(7.64)
7.80
(7.72)
8.00
(8.05)
7.71
(8.44)
7.79
(7.81)
7.79
(7.71)
7.85
7.40–
7.33
7.40–
7.33
7.82
(7.85)
7.77
(8.10)
7.38
(7.00)
7.97
(8.22)
7.71
(7.68)
–
7.63–
7.55
7.45–
7.40
8.08
(8.80)
7.83
(8.16)
7.57
(7.44)
8.14
(8.36)
8.78
(8.79)
–
7.98
(8.07)
7.82
(8.29)
8.23
(8.09)
8.08
(8.29)
7.87
(7.85)
7.83
(7.70)
7.84
(7.75)
8.04
7.46 7.96
(7.70)
7.35 7.79
(7.81)
7.57 8.26
(8.17)
7.59 8.02
(8.11)
7.64 8.22
(8.14)
7.39 7.80
(8.26)
7.71 8.44
(8.35)
7.84 8.21
(8.34)
7.81
(7.60)
7.58
(7.87)
7.29
(7.08)
7.99
(8.03)
7.83
(7.72)
7.72
(7.55)
7.75
(7.52)
7.89
7.35 7.78
(7.49)
7.23 7.55
(7.82)
6.97 7.32
(7.12)
7.52 7.93
(7.96)
7.55 8.02
(7.72)
7.29 7.61
(7.88)
7.12 7.73
(7.27)
7.76 8.09
(8.13)
H(4)
7.37
7.55
7.27
6.97
7.61
7.41
7.34
7.41
7.61
H(5)
7.03
7.03
7.16
H(22)
H(23)
H(24)
H(25)
H(26)
H(52)
H(53)
H(54)
H(55)
H(56)
7.64
7.54
7.79
8.29
–
7.65–
7.68
7.41–
7.51
7.41–
7.51
7.41–
7.51
7.65–
7.68
–
7.45–
7.35
7.45–
7.35
7.45–
7.35
7.64
7.33–
7.40
–
7.42 7.75
(7.68)
8.32 8.82
(8.84)
7.36 7.69
(7.65)
8.27 8.72
(8.70)
–
–
–
–
–
–
–
–
7.33–
7.40
7.54
7.67
(7.76)
7.88
(7.94)
7.69
(8.38)
7.81
(7.78)
7.84
(7.74)
7.83
(7.75)
8.27
(7.61)
8.29
7.79
8.74
(8.80)
7.57
(8.02)
7.78
(8.43)
7.86
(7.82)
7.89
(7.81)
7.89
(7.80)
8.39
(7.65)
7.42 7.73
(7.72)
7.59 8.00
(7.83)
8.32 8.78
(8.82)
7.84 8.13
(8.10)
7.36 7.65
(7.53)
7.52 7.84
(7.74)
7.49 7.65
(8.23)
6.91 7.10
(7.29)
8.27 8.70
(8.68)
7.76 8.00
(7.84)
7.54 7.73
(8.27)
6.94 7.14
(7.32)
(8.16)
–
(7.78)
7.56
7.54
7.63–
7.55
7.45–
7.40
7.45–
7.40
7.45–
7.00
–
–
–
–
ꢂ7.50 7.64
(8.27)
ꢂ6.91 7.09
(7.30)
7.45–
7.35
7.45–
7.35
7.45–
7.35
7.56
7.33–
7.40
7.33–
7.40
7.33–
7.40
7.54
8.01
8.71
(8.68)
7.89
(7.64)
8.14
(7.92)
8.16
8.02 8.70
(8.67)
7.51 7.92
(7.67)
7.67 8.14
(7.88)
7.83 8.15
(8.18)
8.07 8.74
(8.51)
7.56 7.99
(7.78)
7.73 8.18
(7.98)
7.84 8.17
(8.49)
7.41–
7.51
7.65–
7.68
–
–
–
–
–
–
ꢂ6.91 7.33
(6.84)
ꢂ7.50 8.20
(7.46)
6.91 7.34
(6.90)
7.49 8.19
(7.46)
6.94 7.37
(6.45)
7.54 8.24
(7.51)
(7.68)
8.34
(7.63)
7.63–
7.55
7.83
(8.45)
Values within parentheses are calculated values in gaseous state.
Table 10
Experimental and theoretical 13C NMR [SCRF-PCM model] spectral data (ppm) of nitriles 1–9 in CDCl3.
Carbons 1
Exp.
2
3
4
5
6
7
8
9
Theor.
Exp.
Theor.
Exp.
Theor.
Exp.
Theor.
Exp.
Theor.
Exp.
Theor.
Exp.
Theor.
Exp.
Theor.
Exp.
Theor.
C(3)
141.58 151.00 141.90 134.46 145.04 155.34 140.45 132.46 140.81 133.11 143.98 136.72 142.08 134.17 142.39 135.24 145.52 138.02
(147.29) (147.73) (151.70) (146.69) (147.07) (151.13) (149.79) (149.23) (152.31)
125.19 129.00 124.87 112.43 124.63 128.43 129.73 118.33 129.42 118.02 128.90 117.66 123.15 110.48 122.87 110.12 122.56 109.90
(132.31) (131.31) (130.76) (137.13) (135.03) (136.08) (128.83) (128.05) (127.64)
141.23 150.56 141.85 133.47 144.41 155.06 135.08 129.20 135.73 130.33 138.25 133.86 141.00 132.27 141.62 133.17 144.29 136.54
(148.92) (150.18) (153.64) (143.16) (146.45) (148.11) (147.31) (148.07) (151.61)
113.22 116.86 111.86 100.22 110.86 113.92 115.92 105.95 111.24 104.32 113.56 102.88 116.65 99.61 110.33 97.89 109.16 96.67
(119.64) (117.52) (116.49) (123.34) (121.26) (120.84) (117.30) (115.58) (114.16)
116.95 123.55 116.92 105.55 116.09 122.67 116.51 105.41 116.21 105.07 115.66 104.54 117.23 106.26 116.90 105.91 116.43 105.42
(123.53) (123.13) (122.60) (123.21) (122.05) (122.41) (123.06) (122.78) (122.18)
133.28 140.90 131.73 123.50 139.44 148.67 132.67 123.41 131.22 122.69 138.74 130.40 133.47 124.65 131.99 123.86 139.70 132.12
(141.72) (139.72) (148.02) (141.12) (139.41) (147.18) (142.62) (140.63) (148.80)
135.79 141.63 133.56 124.17 135.24 140.98 131.29 124.73 131.22 124.77 131.59 124.29 128.61 117.54 128.43 117.32 128.07 117.05
C(4)
C(5)
CCN
CN
C(21)
C(51)
C(52)
C(54)
C(24)
(144.27)
–
(143.64)
–
(143.04)
–
(140.90)
(141.70)
(140.04)
(135.11)
–
(134.79)
– –
(134.31)
–
–
–
–
–
–
–
–
148.05 138.52 148.07 138.45 148.13 138.76
–
–
(160.86)
–
(155.15)
–
(161.21)
– 160.88 150.31 161.01 150.58 161.56 151.82
–
–
–
–
–
–
–
–
(169.32)
–
(169.54)
134.65 130.13 147.33 1378.26
(149.06) (153.79)
(170.52)
135.01 130.87 147.68 154.16
(151.75) (157.18)
–
131.22 131.99 148.13 138.04
(151.52) (158.44)
–
Values within parentheses are calculated values in gaseous state.
the data are displayed in Table 10. The correlation between
experimental and theoretical 13C values of side chain carbons
and ipso carbons are indicated in Fig. 5(a-i). However, theoretically
determined 1H chemical shifts are generally higher when com-
pared to experimental values and large deviations are observed
in the nitriles 4–6 containing o-nitrophenyl ring at C-5 and the
data are displayed in Table 9.
and the important second order perturbative estimates of do-
nor–acceptor interactions are displayed in Table 11. The occupan-
cies and the energies of the orbitals involved in primary
delocalization are
reported in Table 12. The labelling of atoms followed in the NBO
analysis are indicated in Fig. 6. The presence of cyano group is
expected to cause delocalization of electrons from C5–C4 bond
to C3–C2 bond instead of C5–C4 bond to C52–C51/C56–C51
bonds and this expectation is supported by the delocalization
NBO analyses at two levels of calculations [B3LYP/6-31G(d)
and B3LYP/6-311+G(d,p)] were carried out for the nitriles 1–9

A. Manimekalai, A. Balamurugan / Journal of Molecular Structure 995 (2011) 78–90
87
Table 11
NBO analysis of nitriles 1–9 by DFT method [B3LYP/6-311+G(d,p)].
Donor NBO
BD(2)
Acceptor NBO
BD⁄(2)/LP
1
2
3
4
5
6
7
8
9
C5–C4
C52–C51/C56–
C51⁄
13.08
(13.34)
20.03
(21.18)
20.13
(20.08)
19.62
(19.14)
19.02
(19.24)
20.82
(21.05)
18.20
(18.70)
20.11
(20.28)
16.80
(17.49)
13.43
(14.27)
18.83
(19.41)
12.26
12.98
(13.16)
20.46
(21.72)
20.17
(20.18)
19.59
(19.18)
18.92
(19.19)
20.98
(21.27)
18.17
(18.74)
19.94
(20.10)
17.04
(17.88)
13.24
(13.92)
18.88
(19.52)
12.65
12.62
(13.02)
21.89
(22.95)
20.29
(20.36)
19.16
(19.07)
18.79
(18.93)
21.39
(21.75)
18.52
(18.65)
19.53
(19.67)
18.52
(18.49)
12.49
(13.49)
18.88
(19.44)
14.23
11.24
(15.30)
19.11
(20.09)
(18.07)
11.10
(10.91⁄)
19.43
(19.45)
–
10.70
(12.53⁄)
20.48
(21.63)
–
12.74
(12.58)
20.89
(20.66)
21.35
(21.21)
16.31
(16.13)
14.99
(15.26)
22.77
(22.78)
19.51
(19.71)
18.09
(18.01)
18.34
(18.05)
13.09
(13.30)
19.13
(18.99)
12.49
12.68
(12.92)
21.26
(21.52)
21.32
(21.36)
16.28
(16.73)
14.92
(15.52)
23.00
(22.48)
19.46
(19.78)
17.98
(18.73)
18.61
(18.72)
12.97
(13.56)
19.19
(19.44)
12.91
12.57
(13.11)
22.66
(23.66)
21.41
(21.27)
16.13
(16.31)
14.64
(15.11)
23.58
(23.12)
19.37
(19.35)
17.80
(18.56)
19.39
(19.89)
12.52
(13.60)
19.24
(19.81)
14.74
C5–C4
C3–C2
C56–C55
C56–C55
C54–C53
C54–C53
C52–C51
C52–C51
C54–C53
C52–C51
C56–C55
C52–C51
C56–C55
C54–C53
C5–C4
(20.45)
(19.68)
(19.65)
(15.80)
(20.47)
–
–
–
–
–
–
–
–
–
–
C52–C51/C56–
C51⁄
10.42
(11.94)
13.31
(14.22)
18.28
(18.53)
11.95
(13.43)
–
10.48
10.68
(10.54⁄)
(12.56⁄)
C3–C2
C5–C4
13.11
12.50
(13.18)
18.33
(18.24)
12.32
(12.20)
13.92
(13.74)
18.49
(19.01)
13.82
(15.24)
13.18
C3–C2
C1–N6
C3–C2
C22–C21
C3–C2
(14.05)
13.51
(14.43)
13.52
(15.90)
12.89
(12.32)
–
(13.14)
13.43
(16.33)
12.94
C22–C21
C22–C21
C22–C21
C23–C24
C23–C24
C25–C26
C25–C26
C56–C51
C56–C51
C55–C54
C55–C54
C53–C52
C53–C52
C53–C52
N10–O12
C23–C24
N7–O9
(15.75)
20.13
(20.24)
19.25
(19.26)
20.62
(20.92)
20.22
(20.34)
19.57
(19.21)
19.46
(19.29)
–
(15.34)
22.09
(22.91)
19.82
(19.78)
18.79
(18.63)
19.22
(19.58)
18.71
(18.53)
19.86
(19.59)
–
(14.48)
23.92
(24.42)
17.16
(17.21)
17.73
(17.90)
20.72
(20.86)
20.79
(20.26)
18.73
(18.43)
–
(13.82)
21.75
(21.97)
19.71
(19.73)
19.15
(19.25)
18.93
(19.08)
18.75
(18.60)
20.13
(19.90)
21.46
(21.35)
19.36
(19.25)
20.38
(20.48)
24.30
(24.18)
20.41
(20.25)
17.05
(17.15)
25.09
(24.41)
12.22
(12.49)
–
(14.75)
23.37
(23.77)
17.23
(17.29)
17.99
(18.17)
20.54
(20.63)
20.88
(20.41)
19.07
(18.94)
21.00
(21.00)
19.35
(19.33)
20.58
(21.47)
24.01
(24.13)
20.37
(19.64)
17.05
(17.27)
24.70
(24.53)
12.22
(13.61)
25.59
(27.05)
12.23
(13.73)
22.32
(23.19)
19.82
(20.11)
18.61
(18.53)
19.35
(19.89)
18.74
(19.02)
19.77
(19.88)
–
(14.48)
24.24
(24.80)
17.05
(17.11)
17.58
(17.80)
20.78
(20.91)
20.71
(20.15)
18.51
(18.22)
–
C23–C24
C25–C26
C22–C21
C25–C26
C22–C21
C23–C24
C55–C54
C53–C52
C56–C51
C53–C52
C56–C51
C55–C54
N10–O12
LP(3) O11
N7–O9
19.71
(19.46)
19.14
(18.86)
21.02
(21.12)
19.92
(19.65)
19.61
(18.84)
19.75
(19.34)
21.59
20.32
(20.35)
19.23
(19.36)
20.48
(20.58)
20.36
(20.39)
19.56
(19.36)
19.35
(19.32)
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
19.37
20.32
24.40
20.41
17.07
25.20
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
12.21
(12.35)
–
26.24
(28.24)
12.12
26.67
(28.72)
12.05
LP(3) O8
(12.74)
(12.89)
(12.66)
LP
LP(1)N6
BD⁄/RY⁄
RY⁄(1) Cl
17.41
17.36
17.59
17.58
17.56
17.53
17.46
17.66
17.66
(16.84)
11.38
(12.02)
(16.79)
11.39
(12.05)
(16.74)
11.39
(12.12)
160.85
(179.85)
11.87
(11.83)
18.84
(19.12)
11.52
(16.87)
11.48
(12.67)
(17.11)
11.47
(12.61)
(16.75)
11.48
(12.14)
161.51
(181.14)
11.70
(12.11)
18.83
(19.10)
11.66
(17.17)
11.43
(12.53)
(17.07)
11.35
(11.95)
(16.75)
11.31
(12.11)
160.22
(179.18)
11.48
(11.74)
18.84
(19.09)
11.43
LP(1)N6
LP(3)O8
LP(2)O9
LP(2)O9
LP(2)O8
LP(2)O8
BD⁄(1) C2–C1
BD⁄(2)N7–O9
BD⁄(1)C24–N7
BD⁄(1)N7–08
BD⁄(1)C24–N7
BD⁄(1)N7–O9
(11.76)
18.77
(19.02)
(12.03)
18.77
(19.04)
(11.66)
18.77
(18.99)
(continued on next page)

88
A. Manimekalai, A. Balamurugan / Journal of Molecular Structure 995 (2011) 78–90
Table 11 (continued)
Donor NBO
BD(2)
Acceptor NBO
BD⁄(2)/LP
1
2
3
4
5
6
7
8
9
LP(2)O12
LP(2)O11
LP(2)O11
LP(3)O11
LP(2)O12
LP(2)O13
LP(3)Cl 7
LP(3)O11
BD⁄(1)C52–N10
11.97
(12.04)
10.90
(11.32)
18.99
(18.49)
155.25
(155.67)
18.71
12.01
(12.91)
10.91
(11.89)
18.98
(19.34)
155.05
(159.28)
18.73
12.12
(12.40)
10.90
(11.51)
18.95
(19.04)
154.46
(172.88)
18.79
BD⁄(1) C52–
N10
BD⁄(1)N10–O12
BD⁄(2)N10–O12
BD⁄(1) N10–
O11
BD⁄(2)C54–C53
(18.47)
(19.24)
(19.28)
31.16
(32.22)
31.40
(33.29)
12.44
32.00
(32.41)
BD⁄(2)C23–C24
BD⁄(1)N10–O11
12.58
(12.11)
12.80
(12.42)
(12.36)
10.67
Values within parentheses are calculated values according to the basis set B3LYP/6-31G(d).
Table 12
Energies, occupancies of primary donor and acceptor orbitals and their delocalization energies in nitriles 1–9 by DFT method [B3LYP/6-311+G(d,p)].
Nitriles Donor NBO
Occupancy
Energy (a.u)
Acceptor NBO
Occupancy
Energy (a.u)
E2
(kcal molꢀ1
)
1
2
3
4
5
6
7
8
9
BD(2) C54–C53/BD(2)
C5–C4
BD(2) C22–C21
1.65235
(1.80293)
1.62337
(1.62056)
1.45207
(1.43744)
1.44655
(1.43553)
1.44667
(1.44166)
1.44626
(1.43366)
1.83058
ꢀ0.26202
(ꢀ0.27198)
ꢀ0.26793
(ꢀ0.26098)
ꢀ0.2912
(BD⁄(2) C52–C51 (BD⁄(2)
C3–C2)
BD⁄(2) C23–C24
0.38516
(0.23634)
0.38917
(0.39017)
0.63206
(0.65804)
0.62360
(0.61790)
0.62253
(0.62260)
0.61950
(0.65399)
0.38977
(0.39308)
0.38891
(0.39991)
0.63418
(0.66048)
0.01609 (0.01648)
20.82 (21.18)
22.09 (22.91)
ꢀ0.00236
(ꢀ0.00417)
ꢀ0.15225
LP(3)O8
LP(3)O11
LP(3)O11
LP(3)O8
LP(2)O13
LP(2)O13
LP(3)O8
BD⁄(2) N7–O9
BD⁄(2) N10–O12
BD⁄(2) N10–O12
BD⁄(2) N7–O9
BD⁄(2) C54–C53
BD⁄(2) C54–C53
BD⁄(2) N7–O9
160.85
(179.85)
155.25
(155.67)
155.05
(159.28)
154.46
(ꢀ0.28142)
ꢀ0.30016
(ꢀ0.28300)
ꢀ0.30266
(ꢀ0.28492)
ꢀ0.30913
(ꢀ0.28668)
ꢀ0.33037
(ꢀ0.31556)
ꢀ0.33264
(ꢀ0.32045)
ꢀ0.28858
(ꢀ0.27788)
(ꢀ0.16372)
ꢀ0.15150
(ꢀ0.13649)
ꢀ0.15376
(ꢀ0.13543)
ꢀ0.15953
(ꢀ0.16853)
0.00923 (0.02196)
(181.14)
31.16 (32.22)
(1.82817)
1.82903
(1.82697)
1.45430
0.00654 (0.00637)
31.40 (33.29)
ꢀ0.14878
160.22
(179.18)
(1.43950)
(ꢀ0.16044)
Values within parentheses are calculated values according to the basis set B3LYP/6-31G(d).
energies in Table 11. Moreover, the introduction of substituents
in the phenyl ring attached to C2 carbon (cyanomethylene car-
bon) enhances this delocalization energy whereas the introduc-
tion of nitro group in the cinnamylidene (phenyl ring attached
to C5 carbon) ring lowers this delocalization energy. The delocal-
ization energies corresponding to the transfer of electrons from
C3–C2 bond to C1–N6 bond also support this conclusion. The en-
ergy corresponding to the delocalization of electrons from C52–
C51/C56–C51 bond to C5–C4 bond is increased by the presence
of substituents attached to the phenyl ring at C-2 and by the
methoxy substituent attached to the para position of phenyl ring
at C-5. However, the presence of ortho nitro group in the phenyl
ring at C-5 lowers this delocalization energy. This is due to the
tilting of o-nitrophenyl ring from the plane of the side chain moi-
ety. The introduction of substituents in the phenyl rings attached
to C2 and C5 carbons decreases the delocalization of electrons
from C22–C21 bond to C3–C2 bond.
delocalized onto the antibonding orbitals of N7–O9 bond. Compar-
ison of delocalization energies of nitriles 6 and 9 with that of 3 re-
veals that the introduction of electron releasing methoxy
substituent at the para position of phenyl ring attached to C5 car-
bon lowers this delocalization energy whereas the electron with-
drawing nitro substituent at the ortho position of the phenyl ring
attached to C5 carbon enhances this delocalization energy. In ortho
nitro derivatives 4 and 5 primary delocalization occurs from the
lone pair of electrons available on oxygen atom (O11) to the anti-
bonding orbital of N10–O12 bond and this delocalization is
enhanced by the presence of chloro substituent at the para position
of phenyl ring at C-2 [E2(5) > E2(4)]. In methoxy derivatives 7 and
8 delocalization occurs from the lone pair of electrons available on
oxygen atom of the methoxy group (O13) to the nearby antibond-
ing orbital of C54–C53 bond and this delocalization energy is high-
er for p-chloro derivative 8 compared to unsubstituted derivative
7. In nitrile 1 without ring substituent primary delocalization
occurs from the bonding orbital of C(54)–C(53) to antibonding
orbital of C(52)–C(51) according to higher basis set and from the
bonding orbital of C(5)–C(4) to antibonding orbital of C(3)–C(2)
(with the lower basis set). In p-chloro derivative 2 primary delocal-
ization occurs within the orbitals of p-chlorophenyl ring and the
From Table 12, it is seen that in nitro derivatives primary delo-
calization occurs within the orbitals of the nitro group attached to
the para position of the phenyl ring at C-2 (3, 6 and 9) and ortho
position of the phenyl ring at C-5 (4 and 5). In nitro derivatives
3, 6 and 9 the lone pair of electrons available on oxygen (O8) is

A. Manimekalai, A. Balamurugan / Journal of Molecular Structure 995 (2011) 78–90
89
55
Z13
δ
H
NO2
H
54
56
C5
δ
C3
Ar
N 6
H4
53
51
C4
H
C
4
C
5
C
52
1
C
CN
Y10
2
3
C
C
H5
22
21
Fig. 7. Steric polarization interaction in nitro derivatives.
H3
23
26
C(3) and C(5) carbons but deshields C(4) carbon. The shielding
magnitude observed on C(5) is considerably higher (ꢀ6.15 ppm)
than that on C(3) (ꢀ1.13 ppm). Such large deshielding magnitude
observed on H(5) proton and shielding magnitude observed on
C(5) suggest that the nitro group must be syn to the H(5) proton
in 4–6 as shown in Fig. 7. In this orientation, the nitro group expe-
riences severe steric interaction with H(5) proton. As a result of
this interaction C(5)–H bond is polarized and the H(5) proton
24
25
X7
X
Y
Z
1
;
2
;
3
;
H
H
H
H
H
H
H
Cl(7)
N(7)
acquires
a slight positive charge and corresponding carbon
O(8)
O(9)
acquires a slight negative charge.
In order to find out the influence of the methoxy substituent
on the side chain protons and the side carbons, the chemical
shifts of 1–3 have been compared with those of 7–9. There is
no appreciable change in the chemical shifts H(3) and H(5) pro-
tons and C(3) and C(5) carbons by the introduction of methoxy
substituent at the para position of the phenyl ring at C-5 in 1–
3. However, H(4) protons and C(4) carbons are found to be
slightly shielded due to the introduction of methoxy substituent
at para position of the phenyl ring at C-5. The mesomeric interac-
tion of the electron releasing methoxy substituent places a small
amount of negative charge on C(4) carbon and this negative
charge is transmitted to the corresponding hydrogen and hence
H(4) protons and C(4) carbons are shielded due to the presence
of methoxy substituent in 7–9.
O(11)
N(10)
N(10)
N(10)
4
;
5
;
6
;
H
H
H
H
O(12)
O(11)
Cl(7)
O(12)
O(11)
O(8)
O(9)
N(7)
O(12)
7
8
;
;
H
Cl(7)
H
H
O(13)
O(13)
−
CH3(14)
−
CH3(14)
O(8)
O(9)
9
;
N(7)
H
O(13)
−
CH3(14)
4. Conclusion
Fig. 6. Labelling of atoms in 1–9.
2,5-Diarylpenta-2,4-dienenitriles 1–9 were synthesized and
characterized by spectral studies. From the coupling constants,
chemical shifts and computational calculations the favored confor-
mation is predicted to be the one in which all side chain protons
are trans to each other and H(3) proton is trans to CN group.
Further, syn orientation of NO2 group with respect to H(5) proton
in 4–6 is revealed by computational calculations and chemical
shifts. HOMO–LUMO energies, dipole moment, polarizabilities
and first order hyperpolarizabilities were determined theoretically.
The highest btot is observed for the nitrile 9 hence it is the best NLO
candidate among the nitriles 1–9. The 1H and 13C chemical shifts
were also determined theoretically by DFT method and they are
in agreement with the experimental values. NBO analysis were car-
ried out and analyzed. The effect of introduction of substituents in
the phenyl ring on the chemical shifts of the side chain protons and
their carbons were analyzed in detail.
bonding pair of electrons in C22–C21 bond is delocalized onto the
antibonding orbital of C24–C23 bond.
3.2. Analysis of chemical shifts
The chemical shifts of p-chlorophenyl derivatives 2, 5 and 8 and
p-nitrophenyl derivatives 3, 6 and 9 have been compared with
those of 1, 4 and 7. Such comparison reveals that there is no appre-
ciable change in the chemical shifts of the side chain protons H(3),
H(4) and H(5) and the side chain carbons C(3), C(4) and C(5) by the
introduction of chloro group at the para position of the phenyl ring
at C-2. However, the introduction of nitro substituent in the para
position of phenyl ring at C-2 slightly deshields the H(3) and
H(5) protons and C(3) and C(5) carbons due to electron withdraw-
ing nature of nitro group.
Comparison of the chemical shifts of side chain protons H(3),
H(4) and H(5) in 1 and 4 reveals that the introduction of the nitro
substituent at the ortho position of the cinnamaylidene moiety
causes no change in the chemical shifts of H(3) and H(4) protons
but deshields H(5) proton appreciably (+0.52 ppm). Similar desh-
ielding magnitude has also been observed in 5 (+0.54 ppm) and 6
(+0.55 ppm) due to the presence of nitro substituent at the ortho
position of the phenyl ring of the cinnamylidene moiety (i.e., phe-
nyl ring at C-5). The introduction of the nitro substituent at the
ortho position of phenyl ring in cinnamylidene moiety shields
Acknowledgement
The authors thank the NMR Research Centre, Indian Institute of
Science, Bangalore for recording the NMR spectra.
Appendix A. Supplementary material
Mass fragmentation schemes (Schemes S1 and S2) and the cor-
responding table (Table S1) for the nitriles 1–9 are provided. Sup-

90
A. Manimekalai, A. Balamurugan / Journal of Molecular Structure 995 (2011) 78–90
(1994) 1679–1687;
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