Molecular structure, FT-IR, FT-Raman, NBO, HOMO and LUMO, MEP, NLO and molecular docking study of 2-[(E)-2-(2-bromophenyl)ethenyl]quinoline-6-carboxylic acid

Article abstract of DOI:10.1016/j.saa.2015.06.077

The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of 2-[(E)-2-(2-bromophenyl)ethenyl]quinoline-6-carboxylic acid have been investigated experimentally and theoretically using Gaussian09 software package. Pot

Full text of DOI:10.1016/j.saa.2015.06.077

Accepted Manuscript
Molecular structure, FT-IR, FT-Raman, NBO, HOMO and LUMO, MEP, NLO
and molecular docking study of 2-[(E)-2-(2-bromophenyl)ethenyl]quinoline-6-
carboxylic acid
Rajeev T. Ulahannan, C. Yohannan Panicker, Hema Tresa Varghese, Robert
Musiol, Josef Jampilek, Christian Van Alsenoy, Javeed Ahmad War, S.K.
Srivastava
PII:
S1386-1425(15)30014-7
http://dx.doi.org/10.1016/j.saa.2015.06.077
SAA 13847
DOI:
Reference:
Spectrochimica Acta Part A: Molecular and Biomo-
lecular Spectroscopy
To appear in:
Received Date:
Revised Date:
Accepted Date:
10 November 2014
20 June 2015
22 June 2015
Please cite this article as: R.T. Ulahannan, C. Yohannan Panicker, H.T. Varghese, R. Musiol, J. Jampilek, C. Van
Alsenoy, J.A. War, S.K. Srivastava, Molecular structure, FT-IR, FT-Raman, NBO, HOMO and LUMO, MEP, NLO
and molecular docking study of 2-[(E)-2-(2-bromophenyl)ethenyl]quinoline-6-carboxylic acid, Spectrochimica
Acta Part A: Molecular and Biomolecular Spectroscopy (2015), doi: http://dx.doi.org/10.1016/j.saa.2015.06.077
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Molecular structure, FT-IR, FT-Raman, NBO, HOMO and LUMO, MEP, NLO and
molecular docking study of 2-[(E)-2-(2-bromophenyl)ethenyl]quinoline-6-carboxylic acid
Rajeev T.Ulahannana, C.Yohannan Panickera*, Hema Tresa Vargheseb, Robert Musiolc, Josef
Jampilekd, Christian Van Alsenoye, Javeed Ahmad Warf, S.K.Srivastavaf
aDepartment of Physics, TKM College of Arts and Science, Kollam, Kerala, India.
bDepartment of Physics, Fatima Mata National College, Kollam, Kerala, India.
cInstitute of Chemistry, University of Silesia, Szkolna 9, 40007 Katowice, Poland.
dDepartment of Chemical Drugs, Faculty of Pharmacy, University of Veterinary and
Pharmaceutical Sciences Brno, Palackeho 1/3, 61242 Brno, Czech Republic.
eUniversity of Antwerp, Chemistry Department, Universiteitsplein 1, B2610 Antwerp,
Belgium.
fDepartment of Chemistry, Dr.H.S.Gour Central University, Sagar, M.P. 470003, India.
*author for correspondence: email: cyphyp@rediffmail.com
Phone: 91 9895370968
Abstract
The optimized molecular structure, vibrational frequencies, corresponding vibrational
assignments of 2-[(E)-2-(2-bromophenyl)ethenyl]quinoline-6-carboxylic acid have been
investigated experimentally and theoretically using Gaussian09 software package. Potential
energy distribution of the normal modes of vibrations was done using GAR2PED program.
1H-NMR chemical shifts calculations were carried out by using B3LYP functional with SDD
basis set. The HOMO and LUMO analysis is used to determine the charge transfer within the
molecule. The stability of the molecule arising from hyper-conjugative interaction and charge
delocalization has been analyzed using NBO analysis. MEP was performed by the DFT
method and the predicted infrared intensities and Raman activities have also been reported.
The calculated geometrical parameters are in agreement with that of similar derivatives. The
title compound forms a stable complex with PknB as is evident from the binding affinity
values and the molecular docking results suggest that the compound might exhibit inhibitory
activity against PknB and this may result in development of new anti-tuberculostic agents.
Keywords: DFT; FT-IR; FT-Raman; quinoline; MEP; Molecular docking.
1.
Introduction
Quinoline derivatives fascinate much interest due to their anti-amoebic, antiviral [1,
2], anti-parasitic [3], antimicrobial [4] and anti-tubercular activities [5]. They possess anti-
proliferative [6], anti-neoplastic [7], and cytotoxic properties [8]. Quinolines have been
detected in meteorite extracts, and in general quinolines are of astrobiological interest, since
this class of molecule includes nucleo bases, basic components of nucleic acids [9, 10].
Quinoline derivatives could be used as dopants in the polymer-LED materials [11]. They
could generate a sharp green electroluminescence and have high quantum efficiency of
emission in the blue and the green region [12, 13]. Quinoline based dyes have developed with
the advent of technology and are applied to electroluminescence and photochromism as well
as the field of medication [14, 15]. Quinoline posses non-centro symmetry and hence they are
used in the synthesis of molecules having non-linear optical responses [16, 17]. They are
widely used in electrochemical sensing [18] and optical switching devices [19]. In the present
work, IR and Raman spectra of the title compound are reported both experimentally and
theoretically. NBO, molecular electrostatic potential, NMR studies, first and second
hyperpolarizability are also reported. Due to the different potential biological activity of the
title compound, molecular docking of the title compound is also reported.
2. Experimental details
2-Methylquinoline-6-carboxylic acid was obtained by the Skraup synthesis form 4-
aminobenzoic acid and crotonaldehyde. To a refluxing solution of 1.0 equiv of 4-
aminobenzoic acid, was added dropwise over three hour period 1.2 equiv of crotonaldehyde.
1

The resulting mixture was heated under reflux for 2 hour. After being cooled aqueous
ammonia was added to pH 3 and the mixture was extracted with CH2Cl2. The organic layer
was washed with brine, dried over magnesium sulfate and concentrated under vacuum. The
crude product was recrystallized from ethanol. This quinolinecarboxylic acid (10 mmol) was
thoroughly mixed with 2-bromobenzaldehyde (20 mmol) and exposed to microwave
irradiation for 6 min. After the reaction was completed the crude product was washed with
diethyl ether (15 ml). Recrystallization from ethanol yielded the target 2-[(E)-2-(2-
bromophenyl)ethenyl]quinoline-6-carboxylic acid [20, 21]. Scheme 1 is provided as
supporting material.
The FT-IR spectrum (Fig. 1) was recorded using KBr pellets on a DR/Jasco FT-IR
6300 spectrometer. The spectral resolution was 4cm-1. The FT-Raman spectrum (Fig. 2) was
obtained on a Bruker RFS 100/s, Germany. For excitation of the spectrum the emission of
Nd:YAG laser was used with excitation wavelength 1064 nm and maximal power 150 mW;
measurement were performed on solid samples. One thousand scans were accumulated with
a total registration time of about 30 min. The spectral resolution after apodization was 2 cm-1.
Raman spectrum in the ranges 1750-3250 cm-1 and 250-1550 cm-1 are provided as supporting
1
material Fig.S1 and Fig.S2. H-NMR spectra was recorded on a Bruker AM-500 (500 MHz
for 1H), Bruker BioSpin Corp., Germany. Chemicals shifts are reported in ppm (δ) to internal
Si(CH3)4, when diffused easily exchangeable signals are omitted.
3.
Computational details
Calculations of the title compound are carried out with Gaussian09 program [22] using
the B3PW91/6-31G(6D,7F), B3LYP/6-31G(6D,7F) and B3LYP/SDD quantum chemical
calculation methods to predict the molecular structure and vibrational wave numbers.
Molecular geometry was fully optimized by Berny’s optimization algorithm using redundant
internal coordinates. Harmonic vibrational wave numbers are calculated using the analytic
second derivatives to confirm the convergence to minima on the potential energy surface. The
DFT hybrid B3LYP functional and SDD methods tend to overestimate the fundamental
modes, therefore scaling factor of 0.9613 has to be used for all the theoretically obtained
wavenumbers for obtaining a considerably better agreement with experimental data [23]. The
Stuttgart/Dresden effective core potential basis set (SDD) was chosen particularly because of
its advantage of doing faster calculations with relatively better accuracy and structures [24,
25]. Then frequency calculations were employed to confirm the structure as minimum points
in energy. Parameters corresponding to optimized geometry (SDD) of the title compound
(Fig. 3) are given in Table 1. The absence of imaginary wavenumbers on the calculated
vibrational spectrum confirms that the structure deduced corresponds to minimum energy.
The assignments of the calculated wave numbers are aided by the animation option of
GAUSSVIEW program, which gives a visual presentation of the vibrational modes [26]. The
potential energy distribution (PED) is calculated with the help of GAR2PED software
package [27].
4. Results and Discussion
4.1. IR and Raman spectra
The calculated wavenumbers (scaled), observed IR and Raman bands and
assignments are given in Table 2. In the following discussion, experimental values are
compared with B3LYP/SDD values, since these values are in agreement with the
experimental data. The carboxylic group is characterized by the OH stretch, C=O stretch and
OH out-of -plane deformation and by the C-O stretch and OH in-plane deformation. For the
title compound, the OH stretching is assigned at 3522 cm-1 theoretically. The C=O stretching
vibration in the spectra of carboxylic acids give rise to a strong band in the region 1600-1700
cm-1 [28]. The band observed at 1634 cm-1 in Raman and 1627 cm-1 in SDD is assigned as
C=O stretching mode. The OH in-plane deformation, coupled to C-O stretching mode is
2

expected in the region 1390 55 cm-1 [28], and the band at 1323 cm-1 in IR, 1314 cm-1 in
Raman and 1308 cm-1 in SDD is assigned as the in-plane bending of OH group which is not
pure but contains contributions from other modes also. The C(=O)O stretching mode coupled
to OH in-plane bending exhibits a band in the region 1250 80 cm-1 and the band at 1272
cm-1 in SDD is assigned as this mode. The deformation modes, out-of-plane OH, in-plane
C=O and out of plane C=O are expected in the region 905 65,725 95 and 595 85 cm-1
respectively [29]. These bands are assigned at 900 cm-1 (SDD), 708 (IR) and 723 (SDD), 518
(SDD) respectively. Ulahannan et al. [30] reported the γOH mode at 926 and δC=O at 766
cm-1.
Benzene ring possesses six ring-stretching vibrations, of which the four with the
highest wavenumbers (occurring near 1600, 1580, 1490 and 1440 cm-1) are good group
vibrations. With heavy substituent, the bands tend to shift to somewhat lower wavenumbers.
In the absence of ring conjugation, the band at 1580 cm-1 is usually weaker than that at 1600
cm-1. The fifth ring-stretching vibration is active near 1315 65 cm-1, a region that overlaps
strongly with that of the CH in-plane deformation. The sixth ring-stretching vibration, or the
ring-breathing mode, appears as a weak band near 1000 cm-1 in mono-, 1,3-di- and 1,3,5-
trisubstituted benzenes. In the otherwise substituted benzenes, however, this vibration is
substituent sensitive and difficult to distinguish from the ring in plane deformation [28]. For
the tri-substituted benzene ring PhI, the ring stretching modes are observed at 1476, 1392,
1236 cm-1 in IR, 1593, 1500, 1385, 1239 cm-1 in Raman and 1600, 1527, 1474, 1383, 1234
cm-1 in SDD. This is in agreement with the expected values [28]. In the asymmetric tri-
substituted benzenes, when all the three substituent are light, the frequency interval of the
ring breathing mode is between 500 and 600 cm-1. When all the three substituent are heavy,
the frequency appears above 1100 cm-1. In the case of mixed substituent the frequency is
expected to appear between 600 and 750 cm-1 [28]. For the title compound the PhI ring
breathing mode is observed at 738 cm-1 in SDD. Mary et al. [31] reported the mode at 733
cm-1 in IR and 738 cm-1 theoretically.
For the ortho substituted benzene the PhII stretching modes are expected in the range
1620-1260 cm-1 [28] and in the present case, these modes at 1588, 1534, 1421, 1296 cm-1 in
IR, 1463, 1396 cm-1 in Raman and 1574, 1537, 1453, 1402, 1300 cm-1 in SDD. In ortho di-
substitution, the ring-breathing mode has three wavenumber intervals according to whether
both substituents are heavy, or one of them is heavy while the other is light, or both of them
are light. In the first case, the interval is 1100-1130 cm-1, in the second case it is 1020-1070
cm-1, while in the third case [32] it is 630-780 cm-1. In the present case, the band observed at
1098 cm-1 in IR and 1104 cm-1 in SDD is assigned as the ring breathing mode.
The C-H stretching occurs above 3000 cm-1 for benzene ring [33]. In the present case
the bands at 3130, 3106, 3091 cm-1 in SDD for 1,2,4 tri-substituted benzene and 3118, 3103,
3087, 3071 cm-1 for 1,2-di-substituted benzene are assigned as the C-H stretching modes.
The in-plane CH vibrations are expected in the range of 1010-1300 cm-1, 1290-1050 cm-1 for
ortho substituted benzenes [28] and 1,2,4 tri-substituted benzenes, respectively. The modes at
1123 cm-1 in IR, 1117 cm-1 in Raman and 1259, 1146, 1123 cm-1 in SDD are assigned as
δCH mode for 1,2,4 tri-substituted benzene. Also the modes at 1154, 1098, 1023 cm-1 in IR,
1158, 1023 cm-1 in Raman and 1272, 1160, 1104, 1031 cm-1 in SDD are assigned as δCH
mode for ortho substituted benzene. The C-H out-of-plane deformations are observed
between 1000 and 700 cm-1 [28]. The out-of-plane CH vibrations are determined by the
number of adjacent hydrogen atoms on the ring. 1,2,4-trisubstituted benzenes show a medium
absorption in the range 940-840 cm-1 and a strong band in the range 940-840 cm-1.
For the title compound we observed these modes at 852 cm-1 in IR, 929 cm-1 in
Raman and 990, 930, 852 cm-1 in SDD. The bands at 960, 745 cm-1 in IR, 965 cm-1 in
Raman and 993, 960, 868, 740 cm-1 in SDD are assigned as this mode. The CH stretching
3

modes outside the benzene rings are assigned at 3057 cm-1 in IR, 3045 cm-1 in Raman and
3147, 3115, 3079 3044 cm-1 in SDD. In the present case C=C and C-C stretching modes are
assigned at 1616, 1196 cm-1 (IR), 1618 cm-1 (Raman) and 1623, 1184 cm-1 (SDD).
The CBr stretching vibrations are expected in the range 635 85 cm-1 [28, 34]. The
band at 638 cm-1 in IR and 635 cm-1 in SDD is assigned as this mode. Varghese et al. [35]
reported this mode at 637 cm-1 (IR), 639 cm-1 (Raman) and 632 cm-1 (SDD). Varghese et al.
[35] reported the in-plane and out of plane bending of CBr at 207 cm-1 and 120 cm-1
respectively, where we assigned these modes at 227 cm-1 (Raman), 254 cm-1 (SDD) and 158
cm-1 (SDD) respectively.
For the quinoline ring, the stretching modes are assigned at 1563 cm-1 in IR
spectrum, 1560 cm-1 in Raman spectrum and 1568 cm-1 theoretically (C=C stretching mode),
1500 cm-1 in Raman spectrum and 1527 cm-1 theoretically (C=N stretching mode), 1281
cm-1 in IR spectrum, 1285 cm-1 in Raman spectrum and 1285 cm-1 theoretically (C-N
stretching mode), 1476 cm-1 in IR, 1205 cm-1 in Raman, 1204 and 1474 cm-1 theoretically
(C-C stretching modes). The in-plane bending of the ring is assigned at 942, 813, 622 cm-1 in
IR and 946, 803, 802, 621, 522 cm-1 in SDD. The other deformation modes of the phenyl and
quinoline rings are identified and assigned in the Table 2. Chowdhury et al. [36] reported the
ring vibrations of quinoline ring at 1245, 1383, 1434, 1470 ,1593,1621 cm-1 in the Raman
spectra and 760 cm-1 as the ring breathing mode; the in-plane bending was reported by them
at 526, 472, 508, 624, 829, 869 cm-1.
In order to investigate the performance of vibrational wavenumbers of the title
compound, root mean square (RMS) values of wavenumbers were calculated using the
ꢐ
ꢇꢁꢈꢉꢊꢋꢌꢊ − ꢈꢉꢍꢎꢏꢅ . The RMS error of the observed IR bands
ꢆꢑ
ꢉ
ꢂ
ꢀ
expression, RMS = ꢁꢃꢄꢂ
ꢅ
and Raman bands were found to be 12.47 (B3PW91/6-31G(6D, 7F)), 10.65 (B3LYP/6-
31G(6D, 7F)), 8.62 (B3LYP/SDD) and 13.78 (B3PW91/6-31G(6D, 7F)), 11.85 (B3LYP/6-
31G(6D, 7F)), 10.45 (B3LYP/SDD), respectively. The small difference between
experimental and calculated vibrational modes may be due to the fact that experimental
results belong to the solid phase and theoretical calculations belong to gaseous phase.
4.2. Optimised geometrical parameters
To best of our knowledge, no X-ray crystallographic data of the title compound have
yet been reported. However, the theoretical results (SDD) obtained are almost comparable
with the reported structural parameters of similar derivates. For the title compound the bond
length of C1-C6 is 0.0428Å less than that of C1-C2 (1.4290Å) because of the delocalisation of
electrons due to the presence of C(=O)OH group. The bond length of C4-C5 (1.3958 Å) is
also less than that of C3-C4 (1.4197Å) owing to the delocalisation of electrons. The bond
length of C2-C3 is 1.4418Å. This large value for the bond length is due to the delocalisation
of electron density due to the adjacent quinoline ring. The lesser bond length of C10=O11
(1.2452 Å) could assigned due to the double bond character of that bond. The reported values
of bond length for C1-C2, C1-C6, C2-C3, C4-C5 and C10-O11 are 1.4211, 1.3859, 1.4181, 1.4218
and 1.2311 Å [37]. For the title compound the bond length C26-C29, C26-Br34, C29-H32 are
1.4057, 1.9693, 1.0853 Å respectively while the reported values are 1.37, 1.92, 1.0853 Å [38-
40]. The bond angles C5-C10-O11, C5-C10-O12, O11-C10-O12 and C10-O12-H13 are 125.9, 112.9,
121.2 and 110.2° respectively which are in agreement with the reported values 124.1, 114.6,
121.3, 106.6° for the respective bond angles [39]. For the title compound the bond angles C2-
N15-C19, C14-C17-H18, C14-C17-C19, N15-C19-C17, C24-C26-Br34 and C29-C26-Br34 are 119.4,
120.1, 119.8, 121.5, 123.7, 114.2° respectively. The reported values for these bond angles are
118.6, 120.9, 118.0, 123.6, 120.9 and 118.4° respectively [39-42].
4.3. Frontier molecular orbitals
4

HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied
Molecular Orbital) are the very important parameters for quantum chemistry. The eigen
values of HOMO and LUMO and their energy gap reflect the biological activity of the
molecule. A molecule having a small frontier orbital gap is more polarisable and is generally
associated with a high chemical reactivity and low kinetic stability [43-45]. HOMO which
can be thought as the outer orbital containing electrons tends to give these electrons as an
electron donor and hence the ionization potential is directly related to the energy of the
HOMO. On the other hand, LUMO can accept electrons and the LUMO energy is directly
related to electron affinity (Fig. 4). Two important molecular orbital were examined for the
title compound, HOMO and LUMO which are given in Fig. 4. The chemical potential, global
hardness and electrophilicity will pave the way to understand the structure and reactivity of
the molecule, with the aid of DFT based descriptors. Using HOMO and LUMO orbital
energies, the ionization energy and electron affinity can be expressed as: I = -EHOMO, A = -
ELUMO, η = (-EHOMO + ELUMO)/2 and µ = (EHOMO + ELUMO)/2 [46]. Parr et al. [47] proposed the
global electrophilicity power of a ligand as ω = µ2/2η. This index measures the stabilization
in energy when the system acquired an additional electronic charge from the environment.
Electrophilicity encompasses both the ability of an electrophile to acquire additional
electronic charge and the resistance of the system to exchange electronic charge with the
environment. It contains information about both electron transfer (chemical potential) and
stability (hardness) and is a better descriptor of global chemical reactivity. The hardness η
and chemical potential µ are given by the following relations: η = (I- A)/2 and µ= -(I+A)/2,
where I and A are the first ionization potential and electron affinity of the chemical species
[48]. For the title compound, EHOMO = -8.57eV, ELUMO = -6.55eV, energy gap = ELUMO
-
EHOMO = 2.02eV, ionization potential I = 8.57eV, electron affinity A = 6.55 eV, global
hardness η = 1.01 eV, chemical potential µ = -7.56 eV and global electrophilicity ω = µ2/2 η
= 28.29eV. It is seen that the chemical potential of the title compound is negative and it
means that the compound is stable. They do not decompose spontaneously into the elements
they are made up of. The hardness signifies the resistance towards the deformation of
electron cloud of chemical systems under small perturbation encountered during the chemical
process. The principle of hardness works in chemistry and physics but it is not physically
observable. Soft systems are large and highly polarisable, while hard systems are relatively
small and much less polarisable.
4.4. Molecular Electrostatic Potential
MEP is related to the electron density (ED) and is a very useful descriptor in
understanding sites for electrophilic and nucleophilic reactions as well as hydrogen bonding
interactions [49, 50]. The electrostatic potential V(r) is also well suited for analyzing
processes based on the "recognition" of one molecule by another, as in drug-receptor, and
enzyme-substrate interactions, because it is through their potentials that the two species first
"see" each other [51,52]. To predict reactive sites of electrophilic and nucleophilic attacks for
the investigated molecule, MEP at the B3LYP/SDD optimized geometry was calculated. The
negative (red and yellow) regions of MEP were related to electrophilic reactivity and the
positive (blue) regions to nucleophilic reactivity (Fig.S3-supporting material).
4.5. Natural Bond Orbital Analysis
The Natural Bond Orbital (NBO) calculations were performed using NBO 3.1
program [53] as implemented in the Gaussian09 package at the B3LYP/SDD level in order to
understand various second-order interactions between the filled orbital of one subsystem and
vacant orbital of another subsystem, which is a measure of the inter-molecular delocalization
or hyper-conjugation. NBO analysis provides the most accurate possible ‘natural Lewis
structure’ picture of 'j' because all orbital details are mathematically chosen to include the
highest possible percentage of the electron density. A useful aspect of the NBO method is
5

that it gives information about interactions of both filled and virtual orbital spaces that could
enhance the analysis of intra and inter-molecular interactions. The second-order Fock-matrix
was carried out to evaluate the donor-acceptor interactions in the NBO basis. The interactions
result in a loss of occupancy from the localized NBO of the idealized Lewis structure into an
empty non- Lewis orbital. For each donor (i) and acceptor (j) the stabilization energy (E2)
associated with the delocalization i→j is determined as:
(F )2
i, j
E(2) = ∆Eij = qi
(Ej − Ei )
where, qi → donor orbital occupancy, Ei, Ej → diagonal elements and Fij → the off diagonal
NBO Fock matrix element.
In NBO analysis large E(2) value shows the intensive interaction between electron-
donors and electron- acceptors, and greater the extent of conjugation of the whole system, the
possible intensive interaction are given in Table 3. The second-order perturbation theory
analysis of Fock-matrix in NBO basis shows strong inter-molecular hyper-conjugative
interactions are formed by orbital overlap between n(O), n(Br) and σ*(C-O), σ*(C-C) bond
orbital which result in ICT causing stabilization of the system. These interactions are
observed as an increase in electron density in C-O and C-C orbital that weakens the
respective bonds. There occurs a strong inter-molecular hyper-conjugative interaction of C10-
→
O12 from O11 of n2(O11) σ*(C10-O12) which increases ED(0.11896e) that weakens the
respective bonds C10-O12 leading to stabilization of 32.30 kJ/mol and also the hyper-
→σ*(C
conjugative interaction of C10-O12 from O12 of n3(O12) 10-O12) which increases ED
(0.11896e) that weakens the respective bonds C10-O12 leading to stabilization of 7.62 kJ/mol.
→σ
Again a hyper-conjugative interaction of C24-C26 from Br34 of n3(Br34)
*(C24-262) which
increases ED (0.04050e) that weakens the respective bonds C24-C26 leading to stabilization of
8.33 kJ/mol. These interactions are observed as an increase in electron density (ED) in C-C
and C-O orbital that weakens the respective bonds. The increased electron density at the
oxygen atoms leads to the elongation of respective bond length and a lowering of the
corresponding stretching wave number. The electron density (ED) is transferred from the
n(O) to the bonding σ* orbital of the C-C and C-O bonds, explaining both the elongation and
the red shift [54]. The hyper-conjugative interaction energy was deduced from the second-
order perturbation approach. Delocalization of electron density between occupied Lewis-type
(bond or lone pair) NBO orbital and formally unoccupied (anti bond or Rydberg) non-Lewis
NBO orbital corresponds to a stabilizing donor–acceptor interaction. The COOH stretching
modes can be used as a good probe for evaluating the bonding configuration around the
atoms and the electronic distribution in the ring. Hence the title compound is stabilized by
these orbital interactions. The NBO analysis also describes the bonding in terms of the
natural hybrid orbital n2(O11), which occupy a higher energy orbital (-0.28112 a.u) with
considerable p-character (100.00%) and low occupation number (1.86239) and the other
n1(O11) occupy a lower energy orbital( -0.70643a.u) with p-character (35.75%) and high
occupation number (1.97615).The NBO analysis also describes the bonding in terms of the
natural hybrid orbital n2(O12), which occupy a higher energy orbital (-0.34311 a.u) with
considerable p-character (100.00%) and low occupation number (1.83339) and the other
n1(O12) occupy a lower energy orbital(-0.60506 a.u) with p-character (53.38%) and high
occupation number (1.97983). The NBO analysis also describes the bonding in terms of the
natural hybrid orbital n3(Br34), which occupy a higher energy orbital( -0.29284a.u) with
considerable p-character (100.00%) and low occupation number (1.93812) and the other
n1(Br34) occupy a lower energy orbital(-0.69299 a.u) with p-character (12.04%) and high
occupation number (1.99049).Thus, a very close to pure p-type lone pair orbital participates
in the electron donation to the σ*(C10-O12) orbital for n2(O11)→σ*(C10-O12), σ*(C10-O12)
6

orbital for n3(O12)→σ*(C10-O12), and σ*(C24-C26) orbital for n3(Br34)→σ*(C24-C26)
interaction in the compound. The results are tabulated in Table S1 (supporting material).
4.6. Nonlinear Optical Properties
Nonlinear optics deals with the interaction of applied electromagnetic fields in
various materials to generate new electromagnetic fields, altered in wavenumber, phase, or
other physical properties [55]. Organic molecules able to manipulate photonic signals
efficiently are of importance in technologies such as optical communication, optical
computing, and dynamic image processing [56, 57]. In this context, the dynamic first
hyperpolarizability and average second hyperpolarizability of the title compound is also
calculated in the present study. The first hyperpolarizability (β0) of this novel molecular
system is calculated using SDD method, based on the finite field approach. In the presence of
an applied electric field, the energy of a system is a function of the electric field. First
hyperpolarizability is a third rank tensor that can be described by a 3×3×3 matrix. The 27
components of the 3D matrix can be reduced to 10 components due to the Kleinman
symmetry [58]. The components of β are defined as the coefficients in the Taylor series
expansion of the energy in the external electric field. When the electric field is weak and
homogeneous, this expansion becomes
1
1
1
j
j
E = E0 − µi F i −
αij F i F −
βijk F i F j F k −
γ
ijkl F i F F k F l + ...
∑
∑
∑
∑
2
6
24
i
ij
ijk
ijkl
where E0 is the energy of the unperturbed molecule, Fi is the field at the origin, µi, αij, βijk and
γijkl are the components of dipole moment, polarizability, the first hyperpolarizability, and
second hyperpolarizability, respectively. The calculated first hyperpolarizability of the title
compound is 5.37×10-30 e.s.u which is 41 times that of standard NLO material urea (0.13 ×
10-30 e.s.u) [59]. The reported values of hyperpolarizability of quinoline derivatives are
2.24×10-30 and 2.39×10-30e.s.u [60, 61].
The molecular second hyperpolarizability value can aid in gaining information about
the physical properties of materials to understand the origin of third harmonic signals
generated in chemical and biological structures. Such knowledge is effective in the
development of optical devices including the application of optical communication, optical
switching, optical signal processing and optical computing [62]. Measurement of the second
hyperpolarizability values of compounds can provide insight into the molecular structural
requirements for enhancement of third harmonic generation signal which has many
application including Third harmonic generation microscopy for imaging biological structure
by using contrast based on changes in the third-order nonlinear susceptibility which is a
function of the molecular second hyperpolarizability [63, 64]. The average second
hyperpolarizability has been calculated by using the following expression.
γav= 1/5[γ xxxx + γ yyyy + γ zzzz + 2 γ xxyy + 2 γ xxzz + 2 γ yyzz
]
The amount of charge transfer for the molecule depends on the nature of the end group of the
molecule. Increase of π-conjugated chain length in organic molecules, in general, enhances
the magnitude of hyperpolarizability. The calculated value of γav for the title compound is
-2.833×10-36 esu. The larger component of second hyperpolarizability is associated with the
larger ground state polarization which leads to strong electronic coupling between the ground
and the low lying excited state. This can be attributed to the enhanced charge transfer
interaction taking place. Thus the present investigation provides a new route to design high
performance NLO materials.
4.7
Mulliken charges
The calculation of atomic charges plays an important role in the application of
quantum mechanical calculations to molecular systems. Mulliken charges are calculated by
determining the electron population of each atom as defined in the basis function. The charge
distributions calculated by the Mulliken [65] and NBO methods for the equilibrium geometry
7

of 2-[(E)-2-2 bromophenyl ethynyl] quinoline-6-carboxilic acid are given in Table S2
(supporting material). The charge distribution on the molecule has an important influence on
the vibrational spectra. Also we done a comparison of Mulliken charges obtained by different
basis sets and tabulated it in Table S3 (supporting material) in order to assess the sensitivity
of the calculated charges to changes in (i) the choice of the basis set; (ii) the choice of the
quantum mechanical method. The results can, however, better be represented in graphical
form as shown in Fig. S4 (supporting material). We have observed a change in the charge
distribution by changing different basis sets. Distribution of the charges in this compound is
also influenced by the carboxylic group and C26Br34. Based on the charge distribution
calculated by various ways (see Tables S2 and S3) it can be concluded that all the hetero
atoms showed significant electron density. An increased electron density (negative charge)
can be also found in the neighbourhood of C4, C17, O12, C25 and C26. Significantly positive
charges were predicted for C3 and C24. Therefore it can be concluded that electrophilic
substitution of the quinoline scaffold is more preferred than nucleophilic substitution.
Reactions based on the attack of a nucleophile are favoured especially on carboxyl carbons
C10 and C19.
4.8. 1H-NMR spectrum
The experimental spectrum data of title compound in DMSO is obtained at 500 MHz,
using TMS as internal standard, and is shown in Table 4. B3LYP/GIAO was used to calculate
the absolute isotropic chemical shielding of the title compound [66]. Relative chemical shifts
were then estimated by using the corresponding TMS shielding: σcalc (TMS) calculated in
advance at the same theoretical level as this paper. Numerical values of chemical shift δcalc
=
σcalc(TMS) - σcalc together with calculated values of σcalc (TMS), are reported in Table 4. The
chemical shift and the experimental 1H NMR data were in agreement. Thus, the results have
shown that the predicted proton chemical shifts were in good agreement with the
experimental data for the title compound.
4.8. Molecular docking
With time most microbes develop resistance against commercial antibiotics which
increases the demand for development of new antimicrobial drugs. Oxo derivatives of
Quinoline constitute a series of broad-spectrum antibacterial drugs [67]. In addition literature
survey reveals that quinoline derivatives in general are highly active against different
microbial strains [68-70]. Amongst the bacterial infections, tuberculosis (TB) is the leading
bacterial infection in the world [71]. With the hypothesis that the quinoline derivative under
study would be active against mycobacterium tuberculosis we decided to evaluate in silico
antibacterial activity of the title compound. In addition to other molecular targets, the protein
kinases have been recognized as effective molecular target in Mycobacterium tuberculosis
drug discovery. In Mycobacterium tuberculosis the protein kinases genome contains 11
serine/threonine protein kinases, including protein kinase A (PknA) and protein kinase B
(PknB), which play vital role in regulating cell shape and cell wall synthesis. PknB, is
essential for mycobacterium viability and is predominant in many more distantly related
gram-positive bacteria [72, 73]. PknB being an essential protein kinase has been established
as molecular target for antibiotics [74] was selected as molecular target for docking.
Molecular docking simulations were performed on AutoDock-Vina software [75].
The 3D crystal structure of M. tuberculosis PknB was obtained from Protein Data Bank (PDB
ID: 2FUM) [76]. The protein was prepared for docking by removing the co-crystallized
ligand, water molecules and co-factors. AutoDockTools (ADT) graphical user interface was
used to calculate Kollman charges and to add polar hydrogen. Ligand was prepared for
docking by minimizing its energy at B3LYP/SDD level of theory. Charges were calculated
by Geistenger method. Active site of the protein was defined in a way that it included
residues of the active site within the grid dimensions of 40Å×40Å×40Å. The most popular
8

algorithm, Lamarckian Genetic Algorithm (LGA) available in Autodock Vina was employed
for docking. Docking protocol was tested by redocking the co-crystallized inhibitor. Docking
protocol which we employed predicted the same conformation as was present in the PDB
crystal structure with RMSD value well within the reliable range of 2Å. Amongst the nine
docked conformations, one which binded with high affinity at the active site was visualized
for detailed ligand-protein interactions in Discover Studio Visualizer 4.0 and Pymol software.
The ligand binds at the catalytic site of substrate (Fig.S5-supporting material) by
weak non-covalent interactions most prominent of which are H-bonding and alkyl-π
interactions. Asp156 forms two H-bonds of 2.27Å and 2.06Å lengths respectively with
carboxylate oxygen. Met155, Ala38, Val25 Leu17 and Val95 hold the aromatic rings by
alkyl- π interactions (given as supporting information in Fig. S6). The inhibitor 2-[(E)-2-(2-
bromophenyl)ethenyl]quinoline-6-carboxylic acid forms a stable complex with PknB as is
evident from the binding affinity (∆G in kcal/mol) values (supplementary Table S4). These
preliminary results suggest that the compound might exhibit inhibitory activity against PknB.
This may result in development of new anti-tuberculostic agents. However biological tests
need to be done so as to validate computational predictions.
5.
Conclusion
The FT-IR and FT-Raman studies of the title compound in the ground state were
reported experimentally and theoretically. Potential energy distribution of normal modes of
vibrations was done using GAR2PED program. The ring stretching modes in IR and Raman
spectra are evidence for charge transfer interaction between the donor and the acceptor group
through the π system. The chemical reactivity is understood from chemical potential,
electrophilicity and global hardness. MEP predicts the most reactive part in the molecule.
Optimized geometrical parameters of the title compound are in agreement with that of similar
derivatives. The calculated first hyperpolarizability is comparable with the reported values of
similar quinoline derivatives and the study of second hyperpolarizability reveals it is an
1
attractive compound for future studies in non linear optics. The calculated H-NMR results
are in good agreement with the experimental data. The molecular docking results suggest that
the compound might exhibit inhibitory activity against PknB and this may result in
development of new anti-tuberculostic agents.
Acknowledgements
The authors are thankful to University of Antwerp for access to the university’s CalcUA
Supercomputer Cluster. RTU thanks University of Kerala for a research fellowship and JAW
would like to thank Department of Science and Technology, New Delhi, India for INSPIRE
fellowship.
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Figure Captions
Fig.1 FT-IR spectrum of 2-[(E)-2-(2-bromophenyl)ethenyl]quinoline-6-carboxylic acid
Fig.2 FT-Raman spectrum of 2-[(E)-2-(2-bromophenyl)ethenyl]quinoline-6-carboxylic acid
Fig.3 Optimized geometry (B3LYP/SDD) of 2-[(E)-2-(2-bromophenyl)ethenyl]quinoline-6-
carboxylic acid
Fig.4 HOMO and LUMO plots of 2-[(E)-2-(2-bromophenyl)ethenyl]quinoline-6-carboxylic
acid
12

Table 1. Optimized geometrical parameters (B3LYP/SDD) of 2ebq6c, atom labelling according to
Fig.3.
Bond lengths (Å)
C1-C2
Bond angles (˚)
C2-C1-C6
C2-C1-H7
C6-C1-H7
C1-C2-C3
C1-C2-N15
C3-C2-N15
C2-C3-C4
C2-C3-C14
C4-C3-C14
C3-C4-C5
C3-C4-H8
C5-C4-H8
C4-C5-C6
C4-C5-C10
C6-C5-C10
C1-C6-C5
C1-C6-H9
C5-C6-H9
C5-C10-O11
C5-C10-O12
O11-C10-O12
C10-O12-H13
C3-C14-H16
C3-C14-C17
H16-C14-C17
C2-N15-C19
C14-C17-H18
C14-C17-C19
H18-C17-C19
N15-C19-C17
N15-C19-C20
C17-C19-C20
C19-C20-H21
C19-C20-C22
H21-C20-C22
C20-C22-H23
C20-C22-C24
H23-C22-C24
C22-C24-C25
C22-C24-C26
C25-C24-C26
C24-C25-C27
Dihedral angles (˚)
C6-C1-C2-C3
C6-C1-C2-N15
H7-C1-C2-C3
H7-C1-C2-N15
C2-C1-C6-C5
C2-C1-C6-H9
H7-C1-C6-C5
H7-C1-C6-H9
C1-C2-C3-C4
C1-C2-C3-C14
N15-C2-C3-C4
N15-C2-C3-C14
C1-C2-N15-C19
C3-C2-N15-C19
C2-C3-C4-C5
C2-C3-C4-H8
C14-C3-C4-C5
C14-C3-C4-H8
C2-C3-C14-H16
C2-C3-C14-C1
C4-C3-C14-H16
C4-C3-C14-C17
C3-C4-C5-C6
C3-C4-C5-C10
H8-C4-C5-C6
H8-C4-C5-C10
C4-C5-C6-C1
C4-C5-C6-H9
C10-C5-C6-C1
C10-C5-C6-H9
C4-C5-C10-O11
C4-C5-C10-O12
C6-C5-C10-O11
C6-C5-C10-O12
1.4290
1.3862
1.0853
1.4418
1.3772
1.4197
1.4322
1.3958
1.0872
1.4317
1.4834
1.0843
1.2452
1.3912
0.9837
1.0876
1.3818
1.3499
1.0843
1.4423
1.4724
1.0817
1.3619
1.0903
1.4745
1.4287
1.4233
1.3991
1.088
120.6
117.7
121.8
119.1
118.6
122.3
119.5
117.2
123.3
120.3
120.5
119.1
120.3
118.2
121.5
120.2
121.0
118.7
125.9
112.9
121.2
110.2
119.4
119.8
120.7
119.4
120.1
119.8
120.1
121.5
114.8
123.6
112.8
125.0
122.1
116.8
131.7
111.4
114.8
129.7
115.4
123.1
0.0
-180.0
-180.0
0.0
C1-C6
C1-H7
C2-C3
C2-N15
C3-C4
C3-C14
C4-C5
C4-H8
C5-C6
0.0
180.0
-180.0
0.0
0.0
180.0
180.0
0.0
-180.0
0.0
C5-C10
C6-H9
C10-O11
C10-O12
O12-H13
C14-H16
C14-C17
N15-C19
C17-H18
C17-C19
C19-C20
C20-H21
C20-C22
C22-H23
C22-C24
C24-C25
C24-C26
C25-C27
C25-H28
C26-C29
C26-Br34
C27-C30
C27-H31
C29-C30
C29-H32
C30-H33
0.0
-180.0
180.0
0.0
180.0
0.0
0.0
-180.0
0.0
-180.0
180.0
0.0
0.0
180.0
180.0
0.0
1.4057
1.9693
1.4072
1.0865
1.4055
1.0853
1.0864
0.0
180.0
-180.0
0.0
C5-C10-O12-H13 -180.0
O11-C10-O12-H13 0.0
C3-C14-C17-H18
C3-C14-C17-C19
H16-C14-C17-H18 0.0
H16-C14-C17-C19 -180.0
180.0
0.0
C2-N15-C19-C17
C2-N15-C19-C20
0.0
-180.0
1

C24-C25-H28
C27-C25-H28
C24-C26-C29
C24-C26-Br34
C29-C26-Br34
C25-C27-C30
C25-C27-H31
C30-C27-H31
C26-C29-C30
C26-C29-H32
C30-C29-H32
C27-C30-C29
C27-C30-H33
C29-C30-H33
117.7
119.1
122.0
123.7
114.2
119.5
119.9
120.5
120.5
119.5
119.9
119.3
120.9
119.8
C14-C17-C19-N15 0.0
C14-C17-C19-C20 180.0
H18-C17-C19-N15 -180.0
H18-C17-C19-C20 0.0
C15-C19-C20-H21 0.0
C15-C19-C20-C22 -180.0
C17-C19-C20-H21 -180.0
C17-C19-C20-C22 0.0
C19-C20-C22-H23 0.0
C19-C20-C22-C24 180.0
H21-C20-C22-H23 -180.0
H21-C20-C22-C24 -0.0
C20-C22-C24-C25 -180.0
C20-C22-C24-C26 0.0
H23-C22-C24-C25 0.0
H23-C22-C24-C26 -180.0
C22-C24-C25-C27 180.0
C22-C24-C25-H28 0.0
C26-C24-C25-C27 -0.0
C26-C24-C25-H28 180.0
C22-C24-C26-C29 -180.0
C22-C24-C26-Br34 0.0
C25-C24-C26-C29 0.0
C25-C24-C26-Br34 -180.0
C24-C25-C27-C30 -0.0
C24-C25-C27-H31 -180.0
H28-C25-C27-C30 180.0
H28-C25-C27-H31 0.0
C24-C26-C29-C30
0.0
C24-C26-C29-H32 -180.0
Br34-C26-C29-C30 180.0
Br34-C26-C29-H32 -0.0
C25-C27-C30-C29
C25-C27-C30-H33
0.0
180.0
H31-C27-C30-C29 -180.0
H31-C27-C30-H33 -0.0
C26-C29-C30-C27 -0.0
C26-C29-C30-H33 180.0
H32-C29-C30-C27 180.0
H32-C29-C30-H33
0.0
--------------------------------------------------------------------------------------------------------------
2

Table 2. Calculated wavenumbers (Scaled), observed IR, Raman bands and assignments of 2-[(E)-2-(2-bromophenyl)ethenyl]
quinoline-6-carboxylic acid
B3PW91/6-31G(6D, 7F)
B3LYP/6-31G(6D, 7F)
B3LYP/SDD
υ(cm-1)
3522
IR
Raman
Assignmentsa
-
υ(cm-1)
IRI
RA
υ(cm-1)
IRI
RA
IRI
RA
υ(cm-1)υ(cm-1)
3661
87.33 331.69
1.67 23.42
2.54 161.71
3489
73.66 348.32
1.91 23.45
2.97 163.03
93.23 277.64
4.75 16.80
2.80 146.19
-
-
-
-
-
-
υOH(100)
υCH(99)
υCHI(82)
υCHII(17)
υCHII(75)
υCHII(19)
υCH(99)
υCHI(99)
υCHII(98)
υCHI(99)
υCHII(94)
υCH(98)
υCHII(94)
υCH(97)
υCO(74)
υC=C(49)
δCH(23)
3298
3169
3147
3265
3130
3130
3253
17.90 293.95
3117
16.82 266.02
3118
26.36 314.41
-
-
3245
3244
3239
3227
3224
3214
3207
3170
1739
1718
12.79 79.96
1.09 49.66
16.76 169.69
0.62 66.93
1.31 104.98
5.03 59.15
8.46 46.66
18.73 23.94
304.8 355.34
0.33 4876.9
3109
3108
3102
3094
3088
3078
3073
3039
1657
1641
13.89 81.50
1.73 51.55
21.69 219.06
0.99 67.89
8.39 114.32
5.39 56.58
9.23 50.80
18.16 22.49
293.58 377.29
1.07 5014.5
3115
3106
3103
3091
3087
3079
3071
3044
1627
1623
12.81 61.18
1.40 40.31
18.16 135.24
0.86 61.86
6.67 85.94
4.72 46.97
12.12 44.21
19.43 18.74
120.32 3539.9
175.26 1788.9
-
-
-
-
-
-
-
-
-
-
-
-
-
-
3057 3045
1634
1616 1618
-
1

1687
1664
1658
1626
1610
263.4 5486.0
6.55 1525.0
64.33 4397.3
8.02 490.21
19.79 174.08
1609
1586
1582
1551
1535
256.30 4779.9
14.01 803.36
62.27 5313.6
7.48 480.63
16.69 131.22
1600
1574
1568
1537
1527
347.22 7632.8
46.91 5.23
-
1593
υPhI(63)
υPhI(20
1588 -
υPhII(31)
υC=C(15)
υC=C(24)
υPhII(26)
υPhII(72)
δCHII(14)
υPhI(41)
υCC(15)
υC=N(24)
υPhI(42)
δCH(12)
υCC(21)
δCHII(22)
υPhII(42)
υPhI(12)
δCHI(20)
δCH(12)
υC=N(10)
δCHII(25)
υPhII(56)
29.47 6476.4
8.25 512.10
31.69 269.02
1563 1560
1534 -
-
1500
1557
91.80 149.58
1488
93.21 84.495
1474
111.83 234.94
1476 -
1542
1532
36.77 332.57
99.83 1689.2
1477
1467
19.00 688.69
100.38 1501.1
1453
1446
72.02 20.97
-
-
1463
35.40 2029.91
1437
1493
14.84 53.92
1434
14.82 39.98
1402
16.74 54.79
1421 1396
2

1459
17.11 730.73
1398
24.32 83.93
1383
23.57 830.11
1392 1385
δCH(16)
υPhI(51)
υPhI(67)
δCH(35)
υPhI(17)
υC=N(17)
υC=C(10)
δCH(10)
δOH(63)
δCHI(12)
δCH(11)
υPhII(80)
υCN(38),
υCO(25)
υCO(45)
δCHII(35)
υCN(14)
δCHI(35)
δRing(11)
δCHI(14)
υPhI(55)
1451
1428
17.26 902.45
6.25 1100.3
1377
1371
10.22 737.22
22.00 1875.8
1375
1356
17.47 971.10
24.09 1218.64
-
-
-
-
1420
1392
51.36 20.96
117.65 20.31
1354
1330
31.04 5.99
1341
1308
8.84 91.74
72.03 180.18
1345 1347
1323 1314
74.24 159.87
1379
1363
12.78 127.27
78.55 2797.5
1308
1303
0.85 46.53
121.39 3339.0
1300
1285
22.40 113.15
119.34 3397.33
1296 -
1281 1285
1348
1332
23.87 2.63
1291
1279
19.96 3.52
1272
1259
21.17 34.39
3.13 74.26
-
-
-
-
0.33 136.23
1.58 25.49
1299
14.84 60.56
1248
11.95 78.77
1234
19.53 155.16
1236 1239
3

1297
1274
7.25 3.56
1245
1213
3.52 22.16
25.49 208.68
1227
1204
12.89 36.12
4.52 168.50
-
-
-
δCHII(30)
δCH(35)
υCC(28)
υPhI(22)
δCH(11
2.36 171.23
1205
1255
19.04 1724.3
1200
78.77 1762.1
1184
12.94 1557.20
1196 -
υCC(34)
υPhII(25)
δCHII(20)
δCHII(69)
υPhII(10)
δCH(43)
δCHI(51)
δCHI(39)
υPhI(12)
δOH(10)
υPhII(54)
δCHII(41)
δOH(23)
υCC(12)
υCO(39)
δOH(17)
1224
1204
1184
2.30 84.34
56.38 353.14
152.00 129.03
1176
1159
1137
4.09 209.43
56.67 378.82
109.16 116.57
1160
1146
1123
6.53 234.58
34.36 274.77
107.94 150.20
1154 1158
-
-
1123 1117
1098 -
1171
1166
1107
11.54 12.73
200.19 48.44
252.21 96.00
1121
1118
1054
11.71 10.24
239.34 64.75
279.00 104.65
1104
1103
1032
20.22 9.27
116.03 66.70
349.46 133.32
-
-
1047 1045
4

1097
1065
1064
1054
4.19 51.31
30.09 0.99
33.81 253.15
14.80 5.02
1050
1026
1016
1009
4.67 49.41
35.35 0.16
33.89 284.19
3.31 6.33
1031
1006
1005
993
3.64 109.47
4.87 0.34
33.52 0.40
0.33 1.00
1023 1023
υPhII(22)
δCHII(60)
τC=O(31)
γCH(57)
υPhII(20)
δPhII(43)
γCHII(73)
τPhII(17)
γCHI(86)
γPhI(51)
γCH(28)
γCHII(72)
δRing(27)
δPhI(23)
γCHI(70)
τPhI(10)
γCH(51)
γCHII(26)
δPhI(17)
γOH(41)
υCC(10)
γCHII(68)
-
-
-
-
-
-
1037
1026
0.01 0.55
0.01 0.55
994
994
0.05 0.73
0.05 0.73
990
990
45.17 264.79
24.76 2.53
-
-
-
-
1013
985
1.78 7.60
6.32 2.26
969
944
2.53 8.59
8.21 3.92
960
946
0.30 0.22
17.86 3.28
960
942
965
-
981
980
957
16.42 1.83
1.30 32.61
7.72 58.06
942
939
915
15.13 4.20
0.37 30.32
10.12 63.59
930
911
900
9.47 4.53
0.00 23.12
14.44 72.46
-
929
912
-
-
-
921
0.47 2.40
882
0.49 2.43
868
34.83 0.36
-
-
5

908
2.96 24.79
870
3.72 25.64
865
4.60 2.58
-
-
δCC(21)
δPhII(20)
δCH(14)
υCC(12)
γCHI(69)
γCH(43)
γPhI(27)
δRing(39)
υPhI(16)
δRing(37)
τPhI(31)
τPhII(29)
γCHII(25)
γCC(11)
γCHII(51)
τPhII(22)
γCBr(11)
υPhI(33)
δPhI(10)
δC=O(36)
γCC(13)
τRing(12)
892
861
32.51 1.57
35.56 1.45
856
827
28.25 1.91
31.22 1.60
852
829
2.93 19.88
33.78 1.92
852
-
-
836
854
827
804
8.95 87.12
2.66 1.40
2.66 1.36
817
793
770
10.73 89.12
3.65 1.75
6.20 1.20
803
802
762
6.46 0.49
11.01 101.82
48.71 0.15
813
-
-
-
771
772
790
3.05 38.68
756
41.23 6.21
740
2.26 45.68
745
-
789
770
49.46 5.19
57.33 2.30
755
736
2.89 39.04
48.57 1.97
738
723
77.80 0.91
5.18 2.49
-
-
-
708
6

732
701
28.91 49.46
13.66 1.53
701
672
24.59 55.43
14.54 1.53
685
669
22.07 63.20
8.11 0.36
-
-
-
δPhI(29)
δCC(25)
τPhI(28)
τRing(14)
γCC(17)
δPhII(18)
υCBr(64)
δRing(41)
δPhI(16)
δPhII(14)
δCO(31)
δPhI(23)
δPhII(17)
τCO(62)
γCC(10)
τPhII(39)
γCC(22)
δRing(22)
δPhII(31)
δRing(42)
δPhI(27)
668
679
659
6.63 6.01
12.52 7.81
652
636
6.33 6.91
11.92 8.49
635
621
8.78 9.12
10.40 9.21
638
622
-
-
641
65.63 3.54
615
64.98 3.86
598
68.22 5.74
-
-
636
573
569
553
120.00 10.85
9.93 2.41
13.08 9.76
0.19 42.77
607
550
546
531
114.74 11.54
10.54 2.94
13.14 10.39
0.39 44.09
594
541
531
522
112.02 7.58
25.80 3.15
14.49 12.33
0.22 50.57
-
594
-
555
531
-
536
-
7

548
5.92 1.32
527
5.78 2.83
518
7.34 1.75
-
-
γCO(28)
δPhI(12)
δCC(12)
δPhI(36)
τPhII(22)
δCC(30)
δCO(17)
τCC(33)
τPhI(25)
τRing(28)
τPhII(54)
γCBr(22)
δPhI(43)
τRing(33)
δCC(30)
τPhI(22)
δPhI(22)
γCC(16)
τRing(14)
δCO(25)
δCBr(12)
541
511
507
11.09 1.44
2.73 1.40
1.48 0.36
520
491
488
12.48 1.90
2.81 1.34
0.70 0.38
514
489
483
12.58 1.54
1.95 0.29
3.14 1.80
503
-
500
-
480
474
479
418
4.06
367
10.69 0.09
1.97 3.29
0.42 6.32
5.61 0.77
460
404
389
353
8.90 0.10
1.82 3.33
0.47 6.24
5.11 0.87
448
400
381
347
11.98 0.84
1.92 2.36
0.38 6.91
5.66 0.20
439
417
-
-
405
-
-
-
359
10.52 2.23
344
10.59 2.65
337
12.34 2.97
-
312
8

309
287
269
5.68 11.26
0.14 7.29
0.71 1.85
293
277
258
5.35 11.11
0.11 7.73
0.79 2.13
286
267
254
5.11 12.31
0.07 2.57
0.92 2.01
-
-
-
-
δCBr(28)
τPhII(25)
τPhII(29)
γCBr(16)
δCBr(40)
δC=C(17)
δCC(13)
γCC(20)
τCC(26)
δCBr(28)
δCC(19)
τRing(42)
τPhI(24)
τCC(12)
δCBr(17)
δCC(25)
τPhII(24)
γCBr(40)
δCC(40)
δRing(13)
-
227
224
192
180
0.30 4.17
1.43 2.66
3.06 0.60
216
184
175
0.34 3.96
1.56 2.64
2.82 0.55
202
180
172
1.08 3.53
1.45 3.07
3.32 1.30
-
-
-
-
-
-
175
174
121
1.01 0.23
0.72 0.84
0.18 0.66
169
167
116
0.92 0.16
0.84 0.22
0.16 0.68
164
158
109
1.09 0.31
0.53 0.57
0.13 0.63
-
-
-
-
-
-
9

107
72
0.19 2.01
2.67 2.08
104
70
0.21 2.14
2.41 2.28
93
68
0.26 0.58
2.37 1.97
-
-
-
-
τPhI(22)
γCC(13)
τCC(11)
τCO(39)
τC=C(14)
τCC(10)
τCO(36)
τCC(12)
δC=C(33)
δCC(49)
τRing(22)
γCC(15)
τPhI(14)
τCC(32),
τPhI(24)
66
45
27
0.32 2.09
0.03 0.12
0.04 0.76
64
43
26
0.38 1.95
0.03 0.13
0.03 0.73
60
41
25
0.79 0.83
0.04 0.27
0.06 0.35
-
-
-
-
-
-
13
0.05
3.55
13
0.04 3.62
6
0.03 2.94
-
-
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------
aυ-stretching; δ-in-plane deformation; γ-out-of-plane deformation; τ-torsion; PhI- tri-substituted phenyl ring; PhII-1,2-substituted phenyl
ring; Ring-quinoline ring; In the assignment column the potential energy distributions are given in brackets.
10

Table 3. Second-order perturbation theory analysis of Fock matrix in NBO basis corresponding to the intra
molecular bonds of the title compound
Donor(i) Type ED/e
Acceptor(j) Type ED/e
E(2)a
1.53
1.95
1.44
3.65
4.44
2.26
2.32
2.01
2.71
3.96
1.23
1.37
2.18
1.33
3.15
2.41
1.88
1.80
5.46
2.73
1.14
1.32
2.13
5.25
3.04
2.25
2.24
4.78
E(j)-E(i)b
1.25
1.16
1.13
1.17
1.17
1.18
1.20
1.17
1.25
1.20
1.23
1.18
1.54
1.45
1.35
1.06
1.25
1.15
1.11
1.22
1.14
1.13
1.26
1.11
1.17
1.22
1.24
1.18
F(i,j)c
0.039
0.043
0.036
0.058
0.064
0.046
0.047
0.043
0.052
0.062
0.035
0.036
0.052
0.040
0.059
0.046
0.043
0.041
0.070
0.052
0.032
0.035
0.046
0.068
0.053
0.047
0.047
0.067
C1-C2
σ
-
1.97310
C1-C6
σ*
σ*
σ*
σ*
σ*
σ*
σ*
σ *
σ*
σ*
σ*
σ*
σ*
σ*
σ*
σ*
σ*
σ*
σ*
σ*
σ*
σ*
σ*
σ*
σ*
σ*
σ*
σ*
0.01245
0.04904
0.02251
0.02371
0.02000
0.02474
0.02066
0.02371
0.01245
0.02066
0.01952
0.02470
0.02470
0.06179
0.01952
0.11896
0.01106
0.02746
0.02251
0.01106
0.02000
0.04102
0.01430
0.02443
0.02443
0.02320
0.02358
0.02443
-
-
C2-C3
-
-
-
C2-N15
C3-C14
N15-C19
C1-C2
-
-
-
-
-
-
C2-C3
σ
-
1.97032
-
-
C3-C4
-
-
-
C3-C14
C1-C6
C5-C10
σ
-
1.97008
-
-
C3-C4
-
-
-
C4-C5
-
-
-
C5-C6
C10-O11
σ
-
1.99271
C5-C6
-
-
C5-C10
C4-C5
C10-O12
σ
-
1.96367
-
-
C10-O12
C14-C17
C19-C20
C2-N15
C14-C17
N15-C19
C17-C19
C20-C22
C22-C24
C22-C24
C24-C25
C26-C29
C22-C24
C17-C19
σ
-
1.97811
-
-
C19-C20
σ
-
1.96834
-
-
-
-
-
-
-
-
-
-
-
-
-
-
C24-C26
σ
-
1.97671
-
-
-
-
-
C26-C29
σ
1.98029
1