Vibrational spectroscopic investigation and theoretical calculations of (E)-3-phenyl-N-[4-(Phenyl-Amino) quinazoline-7-yl] acrylamide

Article abstract of DOI:10.1080/00387010.2011.650812

Optimized geometrical structure and harmonic vibration frequencies of prior synthesized (E)-3-phenyl-N-[4-(phenyl-amino) quinazoline-7-yl] acrylamide were computed by ab initio HF and DFT/B3LYP methods using both 6-31G* and 6-311G* basis sets and the Moll

Full text of DOI:10.1080/00387010.2011.650812

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Vibrational Spectroscopic Investigation and Theoretical
Calculations of (E)-3-Phenyl-N-[4-(Phenyl-Amino)
Quinazoline-7-yl] Acrylamide
Qing Zheng a , Yang Zhang b , Yong Dai a & Xiangyun Han a
a Department of Chemical and Biological Engineering , Yancheng Institute of Technology ,
Yancheng , China
b Department of Biological and Chemical Engineering , Jiaxing University , Zhejiang , China
Published online: 08 Oct 2012.
To cite this article: Qing Zheng , Yang Zhang , Yong Dai & Xiangyun Han (2012) Vibrational Spectroscopic Investigation
and Theoretical Calculations of (E)-3-Phenyl-N-[4-(Phenyl-Amino) Quinazoline-7-yl] Acrylamide, Spectroscopy Letters: An
International Journal for Rapid Communication, 45:7, 530-540, DOI: 10.1080/00387010.2011.650812
To link to this article: http://dx.doi.org/10.1080/00387010.2011.650812
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Spectroscopy Letters, 45:530–540, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0038-7010 print=1532-2289 online
DOI: 10.1080/00387010.2011.650812
Vibrational Spectroscopic Investigation and
Theoretical Calculations of (E)-3-Phenyl-N-
[4-(Phenyl-Amino) Quinazoline-7-yl]
Acrylamide
Qing Zheng1,
Yang Zhang2,
ABSTRACT Optimized geometrical structure and harmonic vibration
Yong Dai1,
and Xiangyun Han1
1Department of Chemical and
frequencies of prior synthesized (E)-3-phenyl-N-[4-(phenyl-amino) quinazo-
line-7-yl] acrylamide were computed by ab initio HF and DFT=B3LYP meth-
ods using both 6-31Gꢀ and 6-311Gꢀꢀ basis sets and the Moller–Plesset
second-order perturbation (MP2) method merely at the 6-31Gꢀ level. The
Biological Engineering,
Yancheng Institute of
infrared (IR) spectrum of the title compound has been measured in the
range of 400–4000 cmꢁ1. Complete vibrational assignments of the IR spectra
Technology, Yancheng, China
2Department of Biological and
were proposed. Moreover, the calculated wavenumbers of the title com-
pound were compared with the experimental data. The correlation analyses
indicate that good linearity relationships exist between the scaled theoretical
vibration frequencies and the experimental values. Additionally, the atoms
in molecules (AIM) method was applied to explore the possible intramol-
ecular interactions in the title compound.
Chemical Engineering, Jiaxing
University, Zhejiang, China
KEYWORDS atoms in molecules (AIM) method, B3LYP, HF, IR spectra, MP2,
(E)-3-phenyl-N-[4-(phenyl-amino) quinazoline-7-yl] acrylamide
INTRODUCTION
The 4-anilinoquinazoline derivatives have proven to be highly potent and
selective among the many reported classes of protein kinase inhibitors.[1–3]
These compounds have been identified as potential anticancer drugs since
they are inhibitors of the ErbB family of receptor tyrosine kinases (epidermal
growth factor receptor [EGFR], ErbB2 and ErbB4).[4–6] By restraining EGFR
produced via abnormal signal transduction owing to hyperactivation of tyro-
sine protein kinases as a result of overexpression or mutation, anticancer
activities against human squamous head and neck carcinomas, lung cancer,
and breast cancer are brought about.[7] Moreover, based on the 4-anilinoqui-
nazoline scaffold, three ErbB family-directed inhibitors (Tarceva, gefitinib,
and lapatinib) have been clinically approved for treating certain types of
cancer.
Received 11 October 2011;
accepted 14 December 2011.
Address correspondence to
Qing Zheng, Department of Chemical
and Biological Engineering,
Yancheng Institute of Technology,
Yancheng 224003, P. R. China. E-mail:
zhengqing0508@163.com
530

A considerable amount of studies have been con-
ducted on various properties of 4-anilinoquinazoline
derivatives. For example, Hennequin et al.[8] investi-
gated the structure–activity relationship of a novel
subseries of 4-anilinoquinazoline EGFR inhibitors
substituted at the C-6 position with carbon-linked
side chains. The binding mode of the 4-anilinoquina-
zoline class of protein kinase inhibitor has been
studied by Shewchuk et al.[9] Gayani and
co-workers[10] reported the design and synthesis of
a set of ‘‘clickable’’ 4-anilinoquinazoline kinase inhi-
bitors. Chandregowda et al.[11] synthesized a series of
6,7-dialkoxy-4-anilinoquinazolines and checked
their anticancer activities. Meanwhile, some three-
dimensional quantitative structure–activity rela-
tionships (3D-QSARs) for 4-anilinoquinazoline
compounds have also been presented.[12,13] How-
ever, there is little research on their vibration spectra,
which might be useful for the design of novel inhibi-
tors. Vibrational spectroscopy is of practical impor-
tance to confirm the identity of a completely new
molecule as well as to derivate the thermochemical
and kinetic information. This work can be of refer-
ence value to study spectral properties of similar
compounds.
Geometrical parameters, atomic charges, vibrational
wavenumbers, and modes of vibrations of the title
molecule were investigated using HF and DFT=
B3LYP methods with both 6-31Gꢀ and 6-311Gꢀꢀ basis
sets and the Moller–Plesset second-order pertur-
bation (MP2) method merely at the 6-31Gꢀ level.
The experimental IR spectrum of the title compound
was measured and analyzed. In addition, the experi-
mental values were compared with the theoretical
ones. Moreover, the atoms in molecules (AIM)
method was applied to investigate the possible intra-
molecular interactions in the title compound, which
might result in the shifts of vibrational frequencies.
EXPERIMENTAL DETAILS
Synthesis of the title compound involved the
following steps:
2-Amino-4-nitro-benzoic acid (0.005 mol, 0.91 g),
formamidine acetate (0.0075 mol, 0.78 g), and etha-
nol (20 mL) were mixed and heated to reflux for
24 hr. The reaction mixture was then left to cool
down. The formed precipitates were filtered to give
7-nitro-quinazoline-4-ketone (0.70 g). Yield: 73.3%.
7-Nitro-quinazoline-4-ketone (0.01 mol, 1.91 g),
thionyl chloride (20 mL), two drops of DMF, and
1,2-dichloroethane (4 mL) were mixed and heated
to reflux for 4 hr. After cooling to room temperature,
the reaction mixture was poured onto crushed ice.
The resulting suspension was filtered, washed with
water to neutrality, and dried with an infrared oven
to give 4-chloro-7-nitro-quinazoline (1.74 g). Yield:
82.58%.
Ab initio Hartree-Fock (HF) and density functional
theory (DFT)=B3LYP are at present widely used
methods for simulating molecular vibration spectra.
For instance, the HF and B3LYP calculations for
2-chlorotoluene and 2-bromotoluene showed excel-
lent agreement with the observed IR spectra.[14]
Ramoji et al.[15] reported that the simulated
vibrational spectra of 3-acetyl-6-bromocoumarin
and 3-acetyl-6-methylcoumarin with HF and B3LYP
methods were quite close to the corresponding
experimental frequencies. Nagabalasubramanian
et al.[16] further confirmed the success of the HF
and B3LYP methods in exploring the IR spectra for
1,5-methylnaphthalene. Furthermore, Møller–Plesset
perturbation theory (MP) is one of several quantum
chemistry post-Hartree–Fock ab initio methods in
the field of computational chemistry. It improves
on the Hartree–Fock method via adding electron cor-
relation effects by means of Rayleigh–Schro¨dinger
perturbation theory (RS-PT), usually to second (MP2)
order.
4-Chloro-7-nitro-quinazoline (0.01 mol, 2.10 g),
aniline (2.73 mL), and isopropyl alcohol (50 mL)
were mixed and heated to reflux for 2 hr. The
reaction mixture was then put into the fridge and
allowed to stand overnight. 4-Phenyl-amino-7-
nitro-quinazoline hydrochloride (2.06 g) was collec-
ted by filtration. Yield: 68.2%.
4-Phenyl-amino-7-nitro-quinazoline hydrochlor-
ide (0.002 mol, 0.61 g), ethanol (16 mL), water (12 mL),
iron (0.01 mol, 0.56 g), and glacial acetic acid (4 mL)
were mixed and heated to reflux at 81ꢂC for an hour.
The filtrate obtained by filtration of the reaction mix-
ture was concentrated, adjusted to pH ¼ 8 with
saturated aqueous sodium carbonate solution, and
then filtered. The resulting filter cake was dried
and recrystallized from a mixture of ethanol and
This paper is an attempt to thoroughly study the
IR spectrum of (E)-3-phenyl-N-[4-(phenyl-amino)
quinazoline-7-yl] acrylamide prepared in advance.
531
Vibrational Spectroscopic Investigation of (E)-3-phenyl-N-[4-(Phenyl-Amino) Quinazoline-7-yl] Acrylamide

water (1:1) to give 4-phenyl-amino-7-amino (0.34 g).
Yield: 71.7%.
The solid sample was dissolved in standard CDCl3
solvent. Then, the 1H NMR spectra were measured at
400 MHz on a Bruker Avance NMR spectrometer,
with TMS as the internal reference. The observed
1H NMR spectra is denoted in Fig. 1. The IR spectrum
was recorded on a Nexus 470 FT-IR spectro-
photometer in the range of 400–4000 cmꢁ1 at room
temperature using the KBr pellet technique. The
spectral resolution is ꢃ2 cmꢁ1.
Cinnamic acid (0.001 mol, 0.148 g) was dissolved
in pyridine (5 mL) under stirring at room tempera-
ture. Then, benzenesulfonyl chloride (0.001 mol,
0.127 mL) was dropwise added into the solution;
the temperature was controlled at 0ꢂC throughout
the whole process. The reaction mixture was stirred
for 15 min at room temperature until it became vis-
cous. After cooling to 0ꢂC with an ice bath, 4-phenyl-
amino-7-amino quinazoline (0.001 mol, 0.236 g) in
5 mL of pyridine and dimethylaminopyridine
(0.06 g) were added into the solution. The mixture
obtained was slowly stirred at room temperature.
The reaction endpoint was monitored by thin-layer
chromatography (TLC), with the reaction time being
1.5 hr. The reaction solution was then poured into
ice-cooled water under agitation. The resulting light
yellow suspension was filtered, washed with water
to neutrality, dried over anhydrous magnesium sul-
fate, and recrystallized from a mixture of methanol
and ethanol to give the crude product (0.125 g) as
buff amorphous powder. Yield: 34.1%, m.p. 266.8–
269.9ꢂC.
QUANTUM CHEMICAL
CALCULATIONS
The entire quantum chemical calculations were
performed with the Gaussian 03 program,[17] using
both the HF and B3LYP methods at the 6-31Gꢀ and
6-311Gꢀꢀ level of theories and the MP2 method
merely at the 6-31Gꢀ level. For the theoretical wave-
numbers, the scaling factors have been introduced to
compensate for the errors arising from vibrational
anharmonicity and basis set incompleteness. The
assignments of the vibrational frequencies have been
made on the basis of the Gaussview program.[18] In
addition, the AIM method was applied to study the
possible intramolecular interactions in the title com-
pound. The AIM analysis was performed with the
AIM2000 software,[19] using the wave function
obtained by the B3LYP=6-31Gꢀ method for an
example.
RESULTS AND DISCUSSION
Molecular Geometry
The optimized geometry with numbering of atoms
for the title compound is shown in Fig. 2. In the
current paper, phenyl rings of C1C2C3C4C5C6,
C12C14C15C16C17C13, and C23C24C25C26C27C28
are designated as PhI, PhII, and PhIII, respectively.
Qring stands for quinazoline ring. The structure
was found to be minimal on the potential energy
surface since there is no imaginary frequency. The
global minimum energy obtained by the HF, DFT,
and MP2 methods with the 6-31Gꢀ basis set for the
title molecule is ꢁ1174.151465, ꢁ1181.549309, and
ꢁ1174.140 a.u., respectively. At the 6-311Gꢀꢀ level,
the corresponding value with the HF and DFT meth-
ods is ꢁ1174.404218 and ꢁ1181.838810 a.u., respect-
ively. The selected theoretical structural parameters
FIGURE 1 Observed 1H-NMR spectrum of (E)-3-phenyl-N-
[4-(phenyl-amino) quinazoline-7-yl] acrylamide in CDCl3. (color
figure available online.)
Q. Zheng et al.
532

the AIM calculations by the other four methods
showed similar results.
Atomic charges affect dipole moment, molecular
polarizability, electronic structure, and other proper-
ties of molecules. As a result, it is necessary to con-
sider Mulliken atomic charges in applying quantum
chemical calculation to the molecular system. The
total atomic charges obtained by Mulliken popu-
lation analysis are listed in Table 2. From Table 2, it
is seen that the charge changes with basis set. For
example, the charge of O (11) atom is ꢁ0.377 e for
B3LYP=6-311Gꢀꢀ, ꢁ0.523 e for B3LYP=6-31Gꢀ,
ꢁ0.505 e for HF=6-311Gꢀꢀ, ꢁ0.624 e for HF=
6-31Gꢀ, and ꢁ0.649 e for MP2=6-31Gꢀ. Considering
all the methods and basis sets used in the atomic
charge calculation, hydrogen atoms exhibit positive
charge, which are acceptor atoms, whereas nega-
tively charged carbon atoms are donor atoms. The
negative values on N and O atoms lead to a redistri-
bution of electron density.
FIGURE 2 Optimized geometry with atomic numbering and
molecular graph of (E)-3-phenyl-N-[4-(phenyl-amino) quinazo-
line-7-yl] acrylamide. (color figure available online.)
(bond lengths, bond angles, and dihedral angles) are
summarized in Table 1. In this work, geometry opti-
mization parameters have been obtained by
assuming Cs point group symmetry. Obviously, the
corresponding structural parameters are almost
equal to each other with the same exchange func-
tion. For different exchange functions, bond angles
calculated by the three methods were almost consist-
ent with each other, but the bond lengths were
found to be slightly shorter in case of HF calculation
with respect to those of both the B3LYP and MP2
methods, due to the neglect of electron correlation.
Except for the two dihedral angles N21C18N20C23
and H40N20C23C24, the B3LYP method gave almost
the same dihedral angles as the HF method. Com-
pared with the other two methods, the MP2 calcula-
tions totally had large deviations in the prediction of
the dihedral angles; the cases of the C5C7C8C9 and
C7C8C9O11 dihedral angles were the two exceptions.
For the title compound, the electron density topo-
logical graph obtained on the optimized wave func-
tion by the B3LYP method at the 6-31Gꢀ level was
also illustrated in Fig. 2, in which the ring critical
points were represented with the yellow points,
while the bond critical points were denoted with
the red points. Obviously, there are four kinds of
intramolecular weak interactions in (E)-3-phenyl-N-
[4-(phenyl-amino) quinazoline-7-yl] acrylamide,
namely, N(21) ꢄ ꢄ ꢄ H(42), H(39) ꢄ ꢄ ꢄ H(40), O(11) ꢄ ꢄ ꢄ
H(37), and H(32) ꢄ ꢄ ꢄ H(35) interactions. Moreover,
Vibrational Analysis
Vibrational spectroscopy has proven to be effec-
tive in refining chemical structures and investigating
reaction kinetics of organic compounds.[20,21] The
experimental frequencies with their probable assign-
ments are given in Table 3. The observed IR spec-
trum is shown in Fig. 3. The detailed vibrational
assignments of (E)-3-phenyl-N-[4-(phenyl-amino)
quinazoline-7-yl] acrylamide are briefly illustrated
herein.
C–H Vibrations
The characteristic C–H stretching vibrations of the
phenyl ring are expected to appear in the range of
3100–3000 cmꢁ1.[22] The bands in this region are
not affected appreciably by the nature and position
of the substituents.[23] Two medium strong bands
observed at 3030 and 3056 cmꢁ1 in experimental IR
spectra are the results of the coupling of the C-H
stretching vibration of the phenyl ring I and C-H
stretching of H-C(7) ¼ C(8)-H.
The C–H in-plane bending vibrations usually
occur in the region 1000–1300 cmꢁ1 and are very
useful for the identifications of structural groups.[24]
One infrared band at 1248 cmꢁ1 with medium strong
intensity and two weak infrared bands at 994 and
533
Vibrational Spectroscopic Investigation of (E)-3-phenyl-N-[4-(Phenyl-Amino) Quinazoline-7-yl] Acrylamide

TABLE 1 Optimized Parameters of (E)-3-Phenyl-N-[4-(Phenyl-Amino) Quinazoline-7-yl] Acrylamide
Parameters
HF=6-31Gꢀ
HF=6-311Gꢀꢀ
B3LYP=6-31Gꢀ
B3LYP=6-311Gꢀꢀ
MP2=6-31Gꢀ
˚
Bond length (A)
R(4,5)
1.396
1.392
1.473
1.327
1.487
1.369
1.201
1.400
1.419
1.370
1.361
1.406
1.400
1.412
1.362
1.442
1.358
1.302
1.412
1.344
1.390
1.287
1.391
1.395
1.390
1.473
1.325
1.489
1.369
1.194
1.400
1.418
1.369
1.360
1.406
1.398
1.411
1.362
1.442
1.357
1.300
1.410
1.344
1.389
1.285
1.393
1.409
1.407
1.462
1.346
1.484
1.388
1.227
1.403
1.421
1.388
1.378
1.409
1.425
1.414
1.372
1.446
1.370
1.328
1.410
1.354
1.404
1.312
1.407
1.406
1.404
1.462
1.342
1.485
1.386
1.220
1.402
1.419
1.386
1.376
1.407
1.422
1.412
1.370
1.445
1.368
1.324
1.410
1.353
1.401
1.309
1.405
1.406
1.405
1.463
1.347
1.485
1.381
1.234
1.406
1.418
1.387
1.382
1.408
1.419
1.413
1.375
1.439
1.374
1.327
1.411
1.361
1.402
1.318
1.403
R(5,6)
R(5,7)
R(7,8)
R(8,9)
R(9,10)
R(9,11)
R(10,12)
R(12,13)
R(14,12)
R(13,17)
R(14,15)
R(15,16)
R(16,17)
R(15,19)
R(16,18)
R(18,20)
R(18,21)
R(20,23)
R(21,22)
R(23,24)
R(22,19)
R(23,28)
Bond angle (ꢂ)
A(4,5,6)
118.4
127.9
119.7
113.3
122.8
123.8
129.6
122.0
118.3
129.7
128.3
115.7
117.5
119.3
118.4
128.0
119.6
113.1
122.9
124.0
129.5
122.0
118.3
130.7
128.3
115.7
117.6
119.1
118.1
128.1
119.9
113.2
123.3
123.5
129.5
122.0
118.2
132.0
128.6
115.3
117.2
119.1
118.1
128.2
119.9
113.0
123.4
123.6
129.5
122.0
118.3
132.0
128.4
115.5
117.4
119.1
118.7
126.1
119.6
113.0
123.1
123.9
128.8
121.3
118.7
128.1
128.4
115.0
116.7
119.7
A(5,7,8)
A(7,8,9)
A(8,9,10)
A(8,9,11)
A(10,9,11)
A(9,10,12)
A(13,17,16)
A(15,16,17)
A(18,20,23)
A(19,22,21)
A(22,19,15)
A(22,21,18)
A(24,23,28)
Dihedral angle (ꢂ)
D(34,7,8,35)
D(5,7,8,9)
D(7,8,9,11)
D(4,5,7,34)
D(32,4,5,7)
D(8,9,10,12)
D(11,9,10,12)
D(10,12,13,37)
D(20,18,21,22)
D(21,18,20,23)
D(38,14,12,10)
D(40,20,23,24)
ꢁ179.9
180.0
0.0
ꢁ180.0
180.0
0.0
180.0
ꢁ180.0
0.0
ꢁ180.0
180.0
0.0
ꢁ177.3
ꢁ179.8
ꢁ0.3
ꢁ179.4
0.1
ꢁ179.9
0.0
ꢁ180.0
0.0
ꢁ180.0
0.0
ꢁ159.3
3.0
ꢁ179.8
0.2
ꢁ179.9
0.1
ꢁ180.0
0.0
ꢁ180.0
0.0
ꢁ178.2
2.3
ꢁ0.3
178.7
ꢁ2.7
0.1
ꢁ0.2
178.9
ꢁ2.1
0.1
0.0
0.0
1.5
180.0
0.0
ꢁ180.0
0.0
178.3
ꢁ4.1
0.0
0.0
ꢁ1.4
ꢁ158.1
ꢁ165.4
ꢁ180.0
180.0
ꢁ164.7
Q. Zheng et al.
534

TABLE 2 Mulliken Atomic Charges (e) of (E)-3-Phenyl-N-[4-(Phenyl-Amino) Quinazoline-7-yl] Acrylamide
Atoms
HF=6-31Gꢀ
HF=6-311Gꢀꢀ
B3LYP=6-31Gꢀ
B3LYP=6-311Gꢀꢀ
MP2=6-31Gꢀ
C1
ꢁ0.202
ꢁ0.193
ꢁ0.203
ꢁ0.204
0.020
ꢁ0.083
ꢁ0.089
ꢁ0.080
ꢁ0.084
ꢁ0.065
ꢁ0.080
0.031
ꢁ0.131
ꢁ0.123
ꢁ0.131
ꢁ0.171
0.169
ꢁ0.092
ꢁ0.078
ꢁ0.093
ꢁ0.051
ꢁ0.073
ꢁ0.060
ꢁ0.017
ꢁ0.230
0.454
ꢁ0.203
ꢁ0.194
ꢁ0.204
ꢁ0.205
0.012
C2
C3
C4
C5
C6
ꢁ0.216
ꢁ0.128
ꢁ0.359
0.845
ꢁ0.187
ꢁ0.153
ꢁ0.229
0.648
ꢁ0.211
ꢁ0.128
ꢁ0.355
0.851
C7
C8
ꢁ0.300
0.659
C9
N10
O11
C12
C13
C14
C15
C16
C17
C18
N19
N20
N21
C22
C23
C24
C25
C26
C27
C28
H29
H30
H31
H32
H33
H34
H35
H36
H37
H38
H39
H40
H41
H42
H43
H44
H45
H46
ꢁ0.956
ꢁ0.624
0.401
ꢁ0.601
ꢁ0.505
0.284
ꢁ0.761
ꢁ0.523
0.385
ꢁ0.476
ꢁ0.377
0.207
ꢁ0.954
ꢁ0.649
0.401
ꢁ0.245
ꢁ0.301
0.288
ꢁ0.110
ꢁ0.126
0.187
ꢁ0.160
ꢁ0.251
0.245
ꢁ0.088
ꢁ0.070
0.074
ꢁ0.252
ꢁ0.302
0.295
ꢁ0.116
ꢁ0.184
0.744
ꢁ0.212
ꢁ0.030
0.695
0.117
ꢁ0.161
ꢁ0.047
0.516
ꢁ0.108
ꢁ0.190
0.719
ꢁ0.223
0.537
ꢁ0.606
ꢁ0.953
ꢁ0.664
0.282
ꢁ0.490
ꢁ0.615
ꢁ0.550
0.265
ꢁ0.502
ꢁ0.782
ꢁ0.518
0.171
ꢁ0.346
ꢁ0.482
ꢁ0.406
0.138
ꢁ0.612
ꢁ0.936
ꢁ0.663
0.285
0.364
0.244
0.366
0.176
0.361
ꢁ0.202
ꢁ0.198
ꢁ0.212
ꢁ0.191
ꢁ0.263
0.211
ꢁ0.095
ꢁ0.079
ꢁ0.116
ꢁ0.076
ꢁ0.158
0.104
ꢁ0.147
ꢁ0.145
ꢁ0.128
ꢁ0.131
ꢁ0.209
0.139
ꢁ0.070
ꢁ0.102
ꢁ0.090
ꢁ0.097
ꢁ0.131
0.101
ꢁ0.203
ꢁ0.197
ꢁ0.215
ꢁ0.190
ꢁ0.266
0.211
0.210
0.105
0.138
0.101
0.212
0.209
0.102
0.138
0.099
0.210
0.207
0.093
0.131
0.090
0.210
0.217
0.099
0.142
0.098
0.218
0.250
0.134
0.171
0.119
0.255
0.193
0.093
0.127
0.090
0.197
0.402
0.244
0.338
0.232
0.406
0.286
0.160
0.195
0.143
0.291
0.218
0.096
0.137
0.092
0.219
0.207
0.081
0.129
0.075
0.213
0.407
0.243
0.346
0.233
0.404
0.207
0.102
0.143
0.104
0.212
0.249
0.140
0.183
0.133
0.252
0.204
0.100
0.132
0.096
0.204
0.201
0.096
0.127
0.092
0.200
0.203
0.098
0.130
0.093
0.204
0.196
0.086
0.120
0.083
0.195
1083 cmꢁ1 are assigned to C–H in-plane bending
vibrations. All these bands are in the expected range.
The highly informative C–H out-of-plane bending
vibrations are strongly coupled vibrations and
appear in the region 900–667 cmꢁ1.[25,26] Substitution
patterns on the ring can be judged from these bands.
The pure out-of-plane vibrations have shown as two
absorptions at 695 cmꢁ1 and 750 cmꢁ1.
535
Vibrational Spectroscopic Investigation of (E)-3-phenyl-N-[4-(Phenyl-Amino) Quinazoline-7-yl] Acrylamide

TABLE 3 Experimental and Calculated Frequencies (cmꢁ1) with General Mode Assignments for (E)-3-Phenyl-N-[4-(Phenyl-Amino) Qui-
nazoline-7-yl] Acrylamide
HF
B3LYP
MP2
6-31Gꢀ
6-311Gꢀꢀ
Scaledc
6-31Gꢀ
Scaledd
6-311Gꢀꢀ
Scalede
6-31Gꢀ
Scaledf
No.
Freq.a
Unscaled
Scaledb
Assignmentsg
=
1
2
—
325
448
291
401
292
400
287
397
289
399
290
372
b C O
—
c N(20)-H
c N(20)-H
3
—
496
444
449
460
462
416
4
—
538
482
485
479
479
444
c C-H I, c N(10)-H
c N(10)-H
c N(10)-H
v C(5)-C(7)
d-Ph III
5
511w
—
576
516
516
517
520
461
6
597
534
534
545
539
494
7
—
635
569
573
569
574
499
8
598w
—
678
607
612
609
614
524
9
679
608
613
609
615
559
d-Ph I
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
—
768
688
692
677
683
639
c C-H III
c C-H I
c C-H III
c C-H I
c C-H II, Qring c C C
v C(23)-N(20), v C(24) ¼ C(25)
c C-H III
695w
750 m
—
795
712
719
705
710
656
842
754
760
740
742
686
860
770
776
749
754
687
=
—
877
785
793
783
787
759
—
906
811
811
792
801
764
—
940
842
844
819
822
779
—
950
851
854
832
837
786
c C-H I
=
—
978
876
881
836
845
798
c -C CH
—
989
885
888
857
865
807
c C(14)-H
Qring trigonal breathing
c C-H III
Ph II trigonal breathing
c C-H I
Ph III trigonal breathing
Ph I trigonal breathing
c C-H III
c C(13)-H, c C(17)-H
c C-H I
v C(8)-C(9), v C(9)-N(10)
c C-H III
c C-H I
c C(22)-H
887w
—
999
894
902
878
887
813
1023
1032
1045
1089
1090
1094
1099
1100
1109
1120
1127
1129
1131
1133
1145
1166
1190
1194
1213
1221
1274
1295
1305
1306
1315
1320
1350
1384
916
920
890
897
825
—
924
928
895
901
829
—
936
939
925
929
839
—
975
978
926
941
842
—
976
980
928
942
846
—
979
987
931
950
847
—
984
987
951
959
872
—
985
994
959
973
904
—
993
997
960
975
920
—
1003
1009
1011
1013
1014
1025
1044
1065
1069
1086
1093
1141
1159
1168
1169
1177
1182
1209
1239
1006
1012
1014
1016
1021
1025
1045
1064
1071
1081
1089
1140
1160
1169
1170
1178
1180
1209
1243
976
981
951
—
977
983
964
—
991
990
969
994w
—
997
997
984
b C-H I, b C-H III
b C-H I, b C-H III
c C(7)-H
b C-H II, Q ring b C-H
b C-H I
1017
1018
1054
1072
1076
1113
1136
1149
1166
1169
1170
1192
1199
1230
1280
1017
1018
1054
1071
1074
1110
1131
1147
1163
1165
1167
1189
1195
1224
1278
1009
1010
1042
1064
1069
1107
1141
1149
1164
1166
1166
1187
1193
1228
1271
—
—
—
1083w
—
b C-H III
b C(25)-H, b C(26)-H
b C(1)-H, b C(2)-H
b C(13)-H, b C(14)-H
b C(13)-H, b C(17)-H
b C-H III
b C-H I
b C(1)-H, b C(2)-H
b C-H III
—
—
—
—
—
—
—
1248ms
—
b C-H I, b C(14)-H
v C(23)-N(20), b C-H III
(Continued )
Q. Zheng et al.
536

TABLE 3 Continued
HF
B3LYP
MP2
6-31Gꢀ
6-311Gꢀꢀ
Scaledc
6-31Gꢀ
Scaledd
6-311Gꢀꢀ
Scalede
6-31Gꢀ
Scaledf
No.
Freq.a
Unscaled
Scaledb
Assignmentsg
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
—
1434
1442
1471
1484
1491
1498
1534
1552
1611
1617
1664
1672
1674
1725
1739
1781
1799
1808
1812
1822
1857
1955
3345
3359
3372
3376
3377
3378
3389
3395
3458
3475
3880
3919
1284
1291
1317
1329
1335
1341
1373
1390
1442
1448
1490
1497
1499
1544
1557
1595
1611
1619
1621
1631
1663
1750
3044
3057
3069
3072
3073
3074
3084
3089
3147
3162
3531
3566
1285
1292
1320
1330
1335
1341
1376
1393
1443
1447
1493
1497
1499
1550
1559
1599
1615
1622
1625
1636
1665
1752
3009
3022
3032
3037
3038
3039
3049
3056
3122
3124
3530
3567
1301
1307
1317
1322
1323
1336
1381
1388
1435
1440
1480
1486
1487
1515
1529
1570
1571
1596
1600
1601
1627
1702
3029
3039
3051
3056
3062
3063
3076
3080
3141
3142
3452
3485
1294
1301
1311
1318
1320
1329
1378
1381
1431
1435
1477
1478
1479
1508
1524
1566
1567
1590
1594
1595
1623
1696
3012
3016
3031
3036
3042
3043
3057
3060
3113
3114
3462
3492
1292
1302
1311
1336
1375
1387
1397
1406
1424
1425
1468
1470
1475
1493
1519
1555
1559
1581
1582
1586
1628
1680
3002
3003
3018
3019
3022
3027
3043
3044
3092
3096
3391
3407
b C-H II
b C(7)-H
v C(22)-N(21), b C(22)-H
b C-H III
b C-H I
b C(8)-H
Ph II skeleton vibration
Qring skeleton vibration
Ph III skeleton vibration
Ph I skeleton vibration
Ph II skeleton vibration
Ph I skeleton vibration
Ph III skeleton vibration
v C(18)-N(20), b N(20)-H
b N(10)-H
Ph II skeleton vibration, b N(10)-H
Ph III skeleton vibration, b N(20)-H
Ph I skeleton vibration
Ph III skeleton vibration
Ph II skeleton vibration
—
—
—
—
—
1369ms
1401s
1443vs
—
1499vs
—
—
—
1524vs
1555vs
—
—
—
1599vs
1630vs
1670ms
—
=
v C C
=
v C O
v C(24)-H
=
3030ms
—
v C-H I, v -C CH
v C(17)-H
=
3056ms
—
v C-H I, v -C CH
v C(14)-H
v C(22)-H
v C-H III
v C-H I
—
—
—
—
v C(24)-H
v C(13)-H
v N-H amide
v N-H
—
3367ms
3455ms
avs: very strong; s: strong; ms: medium strong; m: medium; w: weak.
bWith the scale factor of 0.910 for calculated wavenumbers greater than 3000 cmꢁ1 and the scale factor of 0.8953 for lower wavenumbers.
cWith the scale factor of 0.910 for calculated wavenumbers greater than 3000 cmꢁ1 and the scale factor of 0.9051 for lower wavenumbers.
dWith the scale factor of 0.958 for calculated wavenumbers greater than 3000 cmꢁ1 and the scale factor of 0.9613 for lower wavenumbers.
eWith the scale factor of 0.958 for calculated wavenumbers greater than 3000 cmꢁ1 and the scale factor of 0.9682 for lower wavenumbers.
fWith the scale factor of 0.937 for calculated wavenumbers greater than 3000 cmꢁ1 and the scale factor of 0.9441 for lower wavenumbers.
gv: stretching; b: in-plane bending; c: out-of-plane bending; d: deformation.
Vibration Modes of C(7) ¼ c(8)
The characteristic C C stretching vibration of trans-
Amide Group Vibrations
=
Secondary amide shows only one N-H stretching
band between 3370 and 3170 cmꢁ1 in the infrared
olefin is expected to appear at about 1660 cmꢁ1.
Consequently, the very strong IR band observed
spectrum. Owing to Fermi resonance of 1550 cmꢁ1
,
at 1630 cmꢁ1 is attributed to the C C stretching
=
a weaker band may appear at about 3100 cmꢁ1 in
secondary amides. The precise location of this
mode.
537
Vibrational Spectroscopic Investigation of (E)-3-phenyl-N-[4-(Phenyl-Amino) Quinazoline-7-yl] Acrylamide

Ring Vibrations
Ring stretching vibrations are expected to occur in
the range 1000–1590 cmꢁ1. The bands with variable
intensities observed at 1369, 1401, 1443, 1499, and
1599 cmꢁ1 are assigned to ring stretching vibrations.
All bands appeared in the expected range. Moreover,
the very strong absorption at 1555 cmꢁ1 is assigned
to skeleton vibration of the phenyl ring II being
weakly coupled to N–H in-plane bending.
The frequencies occurring at 1000 cmꢁ1 are nor-
mally assigned as the trigonal ring breathing
vibration.[28] The weak IR band occurred at 887 cmꢁ1
and is ascribed to trigonal breathing of the quinazoline
ring. The ring deformation vibrations were observed
at 598 cmꢁ1.
Comparisons of the Experimental and
Theoretical Frequencies
Owing to the neglect of electron correlation
effects and basis set deficiencies, the calculated fre-
quencies are usually higher than the corresponding
FIGURE 3 The calculated and experimental IR spectra of (E)-3-
-phenyl-N-[4-(phenyl-amino) quinazoline-7-yl] acrylamide. (color
figure available online.)
vibration mode depends on the other groups adjac-
ent to the –CONH– skeleton.[27] Hence, the medium
strong band observed at 3367 cmꢁ1 in IR is assigned
to the N-H stretching.
There is competition for the lone pair of electrons
=
of the nitrogen between the C O and the phenyl ring
in the title molecule. The medium strong IR band
observed at 1670 cmꢁ1 is ascribed to the amide-I
=
band, C O stretching mode. We can see clearly from
Fig. 2 that there is a bond critical point between
2
O(11) and H(37), with q(r) being 0.019 andr q(r)
being ꢁ0.017. The resulting O(11) ꢄ ꢄ ꢄ H(37) intramol-
ecular interaction will influence the infrared frequ-
ency. Together with the conjugation of the adjacent
=
C C group, the O(11) ꢄ ꢄ ꢄ H(37) weak intramolecular
interaction makes the electron density of carbonyl
averaged, leading to a decline in force constant of
=
=
the C O bond. As a result, the C O bond is slightly
elongated. Finally, the absorption frequency shifts
to a lower wavenumber.
The peak at 1524 cmꢁ1 with very strong intensity
in IR is attributed to the amide-II band, N–H in-plane
bending mode. The N–H out-of-plane bending is
observed as a weak band at 511 cmꢁ1.
FIGURE 4 Correlation graphs between the experimental and
the theoretical wavenumbers. (color figure available online.)
Q. Zheng et al.
538

TABLE 4 Correlation Equations Between the Theoretical and the Experimental Absorption Frequencies
Calculation method
Correlation equations
n
R2
SE
HF=6-31Gꢀ
y ¼ 1.034x ꢁ28.913
y ¼ 1.0259x ꢁ16.764
y ¼ 1.0139x ꢁ15.772
y ¼ 1.011x ꢁ13.575
y ¼ 1.0093x ꢁ36.605
21
21
21
21
21
0.9987
0.9981
0.9996
0.9993
0.9990
33.3
40.1
19.1
24.9
29.2
HF=6-311Gꢀꢀ
B3LYP=6-31Gꢀ
B3LYP=6-311Gꢀꢀ
MP2=6-31Gꢀ
experimental quantities. Frequency overestimation
has been reported in several papers.[29,30] In order
to fit the calculated values with the experimental
ones, it is necessary to scale down the calculated
harmonic frequencies. Palafox et al.[31] described
the importance of quantum chemical scaling in the
calculation of the harmonic vibrational wavenum-
bers. The scaling factors recommended by Merrick
et al.[32] are used in this work. The unscaled and
scaled wavenumbers are also reported in Table 3.
After applying the scaling factors, the theoretical cal-
culations are in good agreement with the experi-
mental data. For visual comparison, the calculated
IR spectra are also shown in Fig. 3. By plotting the
computed versus the observed frequencies, the lin-
earity between them can be judged. The correlation
graph between the experimental and the theoretical
wavenumbers is adopted to vividly display the agree-
ment of the predictions with the observation (Fig. 4).
The correlation equations with sample number n
being 21 are summarized in Table 4. Generally, there
are good linearity relationships between the calculated
and experimental frequencies because all the corre-
lation coefficients are larger than 0.99. On the one
hand, DFT calculations, compared with the HF and
MP2 methods, gave values closer to the experimental
wavenumbers, since the correlation equations posses-
sing relatively lager R2 values and smaller SE values are
the two obtained at the B3LYP=6-31Gꢀ and B3LYP=
6-311Gꢀꢀ levels, with R2 being 0.9996 and 0.9993,
respectively, and SE being 19.1 and 24.9, respectively.
The superiority of the DFT method is reflected in this
aspect. On the other hand, the larger basis set does not
show evident improvement in the accuracy of the
vibration frequencies.
out. The molecular geometry and the wavenumbers
were calculated using HF, B3LYP, and MP2 methods
with the Gaussian 03 software. The scaled theoretical
vibration frequencies are in excellent agreement with
the experimental data. And frequencies calculated by
the DFT=B3LYP method are more consistent with the
experimental values than the HF method. The larger
correlation coefficients (R2 > 0.99) indicate that the
observed frequencies may be reproduced by the
computed values.
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