Facile synthesis and characterization of symmetric n-[(phenylcarbonyl) carbamothioyl]benzamide thiourea: Experimental and theoretical investigations

Article abstract of DOI:10.21577/0103-5053.20180129

A thiourea derivative, N-[(phenylcarbonyl)carbamothioyl]benzamide, was synthesized and characterized by elemental analysis, thermal analysis, spectroscopic methods (Fourier transform infrared (FTIR), UV-Vis, Raman, matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF), tandem mass spectrometry (MS/MS) and nuclear magnetic resonance (NMR)) and quantum-chemical calculations. The synthetic route was simple and efficient, conducted just by one-step and no purification step was needed. The compound crystallizes in a non-centrosymmetric orthorhombic crystal system with a P212121 space group, with a = 5.06220(10) ?, b = 11.8623(3) ?, c = 21.9682(8) ?. The molecular conformation of the solid is stabilized by the N-H?O intramolecular hydrogen bond, which was present in the X-ray structure and was also found in the optimized geometry. The theoretical analysis showed that this strong interaction remains even when molecules are solvated, i.e., the rotation barrier and the hydrogen bond strength are greater than the solvent stabilization energy. In addition to this hydrogen bond effect, the relative position of phenyl groups has a certain influence on the chemical behavior of this thiourea and probably for other phenylthioureas.

Full text of DOI:10.21577/0103-5053.20180129

http://dx.doi.org/10.21577/0103-5053.20180129
J. Braz. Chem. Soc., Vol. 29, No. 12, 2502-2513, 2018
Printed in Brazil - ©2018 Sociedade Brasileira de Química
Article
Facile Synthesis and Characterization of Symmetric N-[(Phenylcarbonyl)
carbamothioyl]benzamide Thiourea: Experimental and Theoretical Investigations
Rafael G. Silveira,a,b Anderson J. L. Catão,a Beatriz N. Cunha,a,b Fernando Almeida,c
Rodrigo S. Correa,d Luan F. Diniz,e Juan C. Tenório,e Javier Ellena,e
Aleksey E. Kuznetsov,f Alzir A. Batista*,a and Edésio Alcântarag
aDepartamento de Química, Universidade Federal de São Carlos, 13565-905 São Carlos-SP, Brazil
bInstituto Federal Goiano, Campus Ceres, 76300-000 Ceres-GO, Brazil
cInstituto de Ciências Biomédicas, Universidade de São Paulo, 05508-900 São Paulo-SP, Brazil
dDepartamento de Química, Instituto de Ciências Exatas e Biológicas,
Universidade Federal de Ouro Preto, 35400-000 Ouro Preto-MG, Brazil
eInstituto de Física de São Carlos, Universidade de São Paulo, 13560-970 São Carlos-SP, Brazil
fInstituto de Química, Universidade de São Paulo, 05508-000 São Paulo-SP, Brazil
gInstituto de Química, Universidade Federal de Goiás, 74001-970 Goiânia-GO, Brazil
A thiourea derivative, N-[(phenylcarbonyl)carbamothioyl]benzamide, was synthesized and
characterized by elemental analysis, thermal analysis, spectroscopic methods (Fourier transform
infrared (FTIR), UV-Vis, Raman, matrix-assisted laser desorption-ionization time-of-flight
mass spectrometry (MALDI-TOF), tandem mass spectrometry (MS/MS) and nuclear magnetic
resonance (NMR)) and quantum-chemical calculations. The synthetic route was simple and
efficient, conducted just by one-step and no purification step was needed. The compound
crystallizes in a non-centrosymmetric orthorhombic crystal system with a P212121 space group,
with a = 5.06220(10) Å, b = 11.8623(3) Å, c = 21.9682(8) Å. The molecular conformation of
the solid is stabilized by the N–H···O intramolecular hydrogen bond, which was present in the
X-ray structure and was also found in the optimized geometry. The theoretical analysis showed
that this strong interaction remains even when molecules are solvated, i.e., the rotation barrier
and the hydrogen bond strength are greater than the solvent stabilization energy. In addition to
this hydrogen bond effect, the relative position of phenyl groups has a certain influence on the
chemical behavior of this thiourea and probably for other phenylthioureas.
Keywords: thioureas derivative, synthesis, intramolecular hydrogen bond
Introduction
among the most reactive compounds containing sulfur
atoms in the functional groups. Their reactivity has been
broadly reported to be used in catalysis for asymmetric
synthesis with high selectivity and yield, and several studies
have reported the coordination of thioureas with metal
centers, making them attractive to be used in the recovery
of precious metals.6,7
Molecules containing the thiocarbonyl group are
versatile synthetic intermediates and numerous synthetic
applications have been developed, which serve as basic
building blocks for the synthesis of heterocyclic compounds,
natural products, guanidines, aryl isothiocyanate,
acrylamide, and benzothiazole.8,9 Furthermore, their
Thioureas are a well-known class of organic compounds,
which have been studied for several decades.1,2 These
compounds have proved to be very attractive from the
synthetic point of view. Therefore, it is possible to use
thioureas for designing numerous compounds with
chemical groups of biological interest, thus producing
almost a limitless variety of structures with new physico-
chemical characteristics. This makes great contributions
to the knowledge of these compounds.3-5 Thioureas are
*e-mail: daab@ufscar.br

Vol. 29, No. 12, 2018
Silveira et al.
2503
properties have been explored from the biological point
of view: they are used as anticancer, antioxidant, anti-HIV,
anti-parasitic, anti-inflammatory, fungicide, herbicide,
antiviral, rodenticidal and plant growth regulator agents.10-13
Currently reported synthetic methodologies are still
based on classic approaches, despite the numerous studies
of thioureas and derivatives available so far.3,4,6,10 These
methodologies entail using reactants such as fluorescein
isothiocyanate, thiophosgene and thiocyanate salts,
which are highly toxic and harmful to the environment.
Thus, the search for new synthetic routes that provide the
minimization of the number of reaction steps and use less
toxic reactants, polluting the environment less, poses as
a considerable and promising challenge. Stimulated by
this challenge, here we report on a synthetic route for a
new symmetric thiourea derivative, N-[(phenylcarbonyl)
carbamothioyl]benzamide (BT), which is simple and
fast, producing a compound with high purity and high
yield, using just recrystallization as the purification
technique. We also present a complete characterization
of the BT compound by infrared (IR), UV-Vis, Raman,
X-ray diffraction, nuclear magnetic resonance (NMR)
260 nm (ε = 21732.3 mol-1 L cm-1), 308 nm
(ε = 11189.8 mol-1 L cm-1) and dimethyl sulfoxide
(DMSO) 264 nm (ε = 19564.2 mol-1 L cm-1), 312 nm
(ε = 9968.3 mol-1 L cm-1); m/z 285.07; IR (KBr) ν / cm-1
ν(NH) 3361, ν(C‑Har) 3057, ν(C=O) 1635, ν(C–N) 1300,
1
ν(C=S) 1227; H NMR (400.21 MHz, CD2Cl2) d 7.72
(m, 2H), 7.61 (m, 4H), 8.03 (m, 4H); 13C{1H} NMR
(400.21 MHz, CD2Cl2) d 128.15 (C2, C9), 129.6 (C3,
C10), 134.16 (C4, C11), 132.61 (C1, C8), 166.9(C6),
177.8 (C5, C7).
Thermal analysis
Differential scanning calorimetry (DSC) measurements
were performed using a Shimadzu DSC-60 instrument. The
sample (2.5 0.5 mg) was placed in an open aluminum
pan and heated under N2 flow (50 mL min-1) from 25 to
500 °C at a heating rate of 10 °C min-1. Thermogravimetric
(TGA) analysis was carried out with a Shimadzu TGA-60
thermobalance. Approximately 5.0 mg of the sample was
placed in an aluminum pan and heated at 10 °C min-1 under
a N2 atmosphere (50 mL min-1) from 25 to 500 °C. The
resulting data were analyzed using the Shimadzu TA-60
software (version 2.2).
13
(1H, C{1H}, distortionless enhancement by polarization
transfer (DEPT)-135, correlation spectroscopy (COSY),
heteronuclear single quantum correlation (HSQC)),
supported by detailed theoretical calculations.
Hot-stage polarized optical microscopy (HSM)
was performed using a Leica DM2500P microscope
connected to Linkam T95-PE hot-stage equipment under
air atmosphere. Data were visualized using Linksys 32
software for the hot-stage control. The single crystal of the
BT compound was placed in a 13 mm glass coverslip within
a 22 mm diameter silver heating block inside the stage.
The sample was heated at a ramp rate of 10 °C min-1 over a
temperature range from 30 °C until the crystal has melted.
Experimental
Material and methods
Procedure for synthesis of BT compound
All chemicals used were of analytical grade. The
benzoyl chloride and the thiourea were purchased from
Sigma-Aldrich® and used without further purification.
Thiourea (6.5 g, 0.085 mol) was stirred in acetone (20 mL)
in an ice bath and benzoyl chloride (21 mL, 0.18 mol) was
slowly added dropwise. The reaction was continued for
45 min and then the reaction mixture was transferred to a
rotatory evaporator until the solvent completely evaporated,
yielding a white solid. This product was further dissolved
in 20 mL of dichloromethane and 20 mL of 10% aqueous
solution of NaHCO3. The organic phase (dichloromethane)
was separated, MgSO4 was added and then filtered. The
filtrate was reduced to about 5 mL, added to 1 mL of
hexane and left in the refrigerator overnight. The crystals
formed were filtered without any purification by column
chromatography.
X-ray crystallography
Single crystals of BT were selected and the molecular
structures were resolved at 293 K using graphite
monochromated Mo Kα radiation (λ = 0.71073 Å). Data
were acquired on a Bruker APEX II CCD diffractometer
and the structures were resolved by direct methods using
SHELXS.14 Non-hydrogen atom positions were determined
by Fourier-difference map analyses with refinements carried
out with the SHELXL package using full-matrix least
squares on F2 with anisotropic displacement parameters.15
All H-atoms were stereochemically positioned and refined
with the riding model.16 Table 1 summarizes the selected
crystallography data.
Spectroscopies
Yield: 93%, yellow solid. Elementary analysis,
calcd. (exp.): C, 63.36(63.45)%; H, 4.25(3.96)%;
N, 9.85(10.12)%. UV-Vis, spectrum in dichloromethane,
Solvents used for spectroscopic studies were of the
spectroscopic grade. The IR spectrum was recorded
using an FTIR Bomem-Michelson 102 spectrometer in

2504
Facile Synthesis and Characterization of Symmetric N-[(Phenylcarbonyl) carbamothioyl]benzamide Thiourea
J. Braz. Chem. Soc.
Table 1. Crystal and structure refinement data for the BT compound
Autoflex speed smart-beam mass-spectrometer (Bruker
Daltonics) using FlexControl software (version 3.3,
Bruker Daltonics). Spectra were recorded in the positive
reflector mode (laser frequency, 500 Hz; extraction delay
time, 130 ns; ion source 1 voltage, 19.0 kV; ion source
2 voltage, 16.8 kV; lens voltage, 7.9 kV; reflector 1,
21.0 kV; reflector 2, 9.35 kV; mass range, 100 to
1000 Da). For each spectrum, 5000 shots, in 500-shot
steps, were summed from different positions of the
target, collected and analyzed. All spectra were calibrated
by using adrenaline [M + H]+ = 184.09682, caffeine
[M + H]+ = 195.08765, lisinopril [M + H]+ = 406.23365
and reserpine [M + H]+ = 609.28066.
For tandem mass spectrometry (MS/MS) experiments,
the instrument was set to LIFT mode (laser frequency,
200 Hz; extraction delay time, 120 ns; ion source 1 voltage,
6.0 kV; ion source 2 voltage, 5.3 kV; lens voltage, 3.0 kV;
reflector 1, 27.0 kV; reflector 2, 11.6 kV; lift 1, 19.0 kV;
lift 2, 4.40 kV), and 2000 shots were summed in 500-shot
steps for each acquired spectrum.
Empirical formula
Formula weight
Temperature / K
Wavelength / Å
Crystal system
C15H12N2O2S
284.33
293(2)
0.71073
orthorhombic
P212121
Space group
Unit cell dimensions
a = 5.0620(10) Å; α = 90°
b = 11.8620(3) Å; β = 90°
c = 21.9680(8) Å; γ = 90°
1319.08(6)
Volume / Å3
Z
4
Density (calculated) / (mg m-3)
Absorption coefficient / mm-1
F(000)
1.432
0.248
592
Theta range for data collection / degree
Reflections collected
3.269 to 26.255
1576
Independent reflections
Completeness to theta = 25.242° / %
Refinement method
1576 [R(int) = 0.055]
99.8
A sample of 10 µg mL-1 of the BT solution was prepared
in CH3OH/H2O (50:50, v/v) with 1% of trifluoroacetic
acid (TFA) and 1 µL was applied to a NALDI® target
(nanostructured laser desorption ionization targets,
Nanosys, Inc.), which does not require any kind of matrix
for the ionization of the analyte.
full-matrix least-squares on F2
1576 / 0 / 182
1.093
Data / restraints / parameters
Goodness-of-fit on F2
Final R indices [I > 2sigma(I)]
R indices (all data)
R1 = 0.0550, wR2 = 0.1376
R1 = 0.0731, wR2 = 0.1584
0.16(19)
Computational details
Absolute structure parameter
Extinction coefficient
All calculations were performed using the Gaussian 09
package.17 The study was done using the 6-311++G(2d,2p)
basis set.18-20 It was performed geometry optimizations
and frequency calculations using the B3LYP density
functional.21,22 B3PW91 and M062X functionals were also
used for comparison purposes.21-24 UV-Vis spectra were
computed using CAM-B3LYP functional, which takes
dispersion corrections into account.25 The BT molecule
was studied in the gas phase and with implicit solvent
effects in both acetone and DMSO. These two solvents
were employed as characteristic representatives of protic
and aprotic solvents (dielectric constants ε = 20.7 and 46.7,
respectively). Considering the implicit solvent effects, the
vibrational geometries and frequencies were calculated
using the self-consistent reaction field IEF-PCM (integral
equation formalism- polarizable continuum model) method
(the UFF default model used in the Gaussian 09 package,
with the electrostatic scaling factor α set to 1.0).26-28 We
also performed a relaxed scan around the H1–N1···N2–H2
dihedral angle at the same level of theory. The scan was
done in steps of 20° to complete 360°. The characteristics
of the O···H–N hydrogen bond was theoretically explored
and analyzed via natural bond orbital (NBO) and quantum
0.027(7)
Largest diff. peak and hole / e.Å-3
0.534 and –0.342
the 4000-400 cm-1 region using solid samples pressed
into KBr pellets. Raman spectra were obtained using a
Bruker FT-Raman spectrophotometer in the 4000-400 cm-1
region, model RFS/100/S, using a Nd:YAG laser with
power of 60 mW and wavelength of 1064 nm. UV-Vis
spectra were recorded using an HP8452A (diode array)
spectrophotometer. Solution with the concentration of
4.4 × 10-5 mol L-1 in dimethyl sulfoxide (DMSO) and quartz
cells of 1.0 cm path length were used in the analysis. The
1H, 13C, DEPT-135 and advanced 2D NMR techniques
such as gradient enhanced, H-1H COSY, H-13C HSQC
correlation were used. These analyses were performed in
CD2Cl2 as a solvent in a 5 mm sample tube at 293 K using
a BrukerAvance III DRX 400 spectrometer working at 400
and 100 MHz at 9.4 T, for 1H and 13C, respectively.
1
1
Mass spectrometry
The samples were analyzed with a matrix-assisted
laser desorption-ionization time-of-flight (MALDI-TOF)

Vol. 29, No. 12, 2018
Silveira et al.
2505
theory of atom in molecules (QTAIM).29,30 Electron density
distribution function ρ(r), electron localization function
(ELF) and the Laplacian of ρ(r) were calculated from wave
function data (B3LYP/6-311++G(2d,2p)) of the equilibrium
geometry for the cis- and trans-conformers of BT. All the
wave function analysis were performed using Multiwfn 3.6
software package.31,32
Results and Discussion
Synthesis of the BT compound
Figure 2. (a) TGA; (b) DSC curves and (c) HSM images of BT.
Theone-stepsynthesisofthioamideN-[(phenylcarbonyl)
carbamothioyl] benzamide (BT) is outlined in Figure 1.
peak characteristic of a melting process at 174.48 °C
(Tonset = 168.75 °C). This event is followed by another
endothermic peak at 199.3 °C, attributed to the first stage
of thermal decomposition. These events are in agreement
with the TGA curve, which shows that the BT compound
is thermally stable up to 176 °C before it starts to lose
mass. The thermal decomposition also appears in the
DSC curve as an exothermic peak at 344.72 °C and, as
expected, a gradual weight loss is observed in the TGA
curve at this temperature. Although HSM and DSC/TGA
experiments were performed under different atmospheres,
the interpretation of DSC/TGA results was successfully
confirmed by the HSM experiments. The HSM images
(Figure 2c) show that a single crystal of the compound
BT starts to melt at around 170 °C and, above 177 °C, it is
completely melted into a liquid droplet. No other thermal
event was observed before the melting.
In summary, thermal analysis shows the absence of
solvent molecules in the crystalline structure and reveals
that the compound decomposes in two steps over the
temperature range of 176-263 °C. The first decomposition
step is the most important stage and occurs with a mass
loss of 74.6%, consistent with the evolution of the two
benzoyl moieties and remaining thiourea group (loss of
weight calculated, 73.9%). The second step is compatible
with a mass loss of 15.61% and might be attributed to
decomposition of the thiourea group.
Figure 1. Synthetic route of BT.
The solid-state structure of the BT was established by
X-ray crystallography and the NMR data obtained from a
CD2Cl2 solution are consistent with the X-ray structure.
The synthetic methodology used here is easier and faster
than the traditional methodologies used for synthesis of
thioureas and/or benzamides.33-35 In general, the traditional
process is as follows: the reaction between the respective
organic chloride (benzyl, acyl chloride, etc.) and KSCN
followed by the addition of the amine with the functional
group of interest. After this step, generally a further
purification step is required per chromatographic column.
Our synthesis uses less amount of solvent and is
performed in a fewer number of reaction steps (atom
economy), i.e., without a purification step, generating fewer
residues to be treated. The reaction yield was 93%. High
purity was also achieved as shown in the characterization
sections. The final product is presented in the form of
needle-shaped yellow crystals and no purification by
column chromatography was required. The product,
which melting point is 175 °C, is soluble in acetone,
dichloromethane, DMSO, ethyl ether and insoluble in
water.
X-ray crystallography
The molecular structure of the compound was
confirmed by X-ray crystallography (Figure 3). The BT
crystals were obtained in the form of yellow needles.
One well-shaped prismatic crystal with dimensions of
0.069 × 0.207 × 0.319 mm was used to collect X-ray
data. The results show that the compound crystallizes in a
non-centrosymmetric orthorhombic space group P212121
with just one molecule per asymmetric unit. The molecule
possesses a quasi-planar configuration with the carbonyl
Thermal characterization
The thermal profile was assessed by a combination of
DSC, TGA and HSM techniques. TGA and DSC curves
of the BT compound are shown in Figures 2a and 2b,
respectively.
The structure was found to be stable between 30 and
ca. 170 °C. The DSC curve exhibits an endothermic

2506
Facile Synthesis and Characterization of Symmetric N-[(Phenylcarbonyl) carbamothioyl]benzamide Thiourea
J. Braz. Chem. Soc.
Table 2. Bond distances for the BT compound: theoretical and
experimental values obtained by X-ray diffraction and mean values from
Mogul program data for some selected fragments
groups in different orientations with respect to the sulfur
atom, where one is cis-oriented and the other one is trans-
oriented. In the literature, these two different conformations
are denoted as S and U (the letter reflects the position of
the C=O and C=S double bonds) relative to the N–H bond.
As can be seen, the S1–C1–N1–C2–O1 moiety adopts a U
conformation, while the S1–C1–N2–C9–O2 moiety occurs
in S conformation. This last conformation is stabilized by an
intramolecular N1–H1···O2 hydrogen bond, an interaction
often reported in the literature on benzoylthioureas type
compounds.36-38
Mean values
from Mogul
analysis / Å
Theoretical
value / Å
Experimental
value / Å
Fragment
C1–N1
C1–N2
C1–S1
1.368
1.411
1.688
1.384
1.238
1.261
1.409
1.495
1.406
1.396
1.397
1.399
1.391
1.405
1.485
1.404
1.393
1.398
1.398
1.392
1.405
1.363
1.402
1.632
1.379
1.205
1.231
1.397
1.506
1.374
1.398
1.381
1.376
1.388
1.389
1.495
1.387
1.386
1.390
1.391
1.385
1.397
1.388(17)
1.388(17)
1.675(25)
1.374(18)
1.228(21)
1.228(21)
1.374(18)
1.497(21)
1.389(16)
1.384(18)
1.377(23)
1.377(23)
1.384(18)
1.389(16)
1.497(21)
1.389(16)
1.384(18)
1.377(23)
1.377(23)
1.384(18)
1.389(16)
C9–N2
O1–C2
O2–C9
C2–N1
C3–C2
C4–C3
C5–C4
C6–C5
C6–C7
C7–C8
Figure 3. Crystal structure of the BT compound, with selected atoms
labeled and ellipsoids at 30% of probability.
C8–C3
C10–C9
C11–C10
C12–C11
C13–C12
C13–C14
C14–C15
C15–C10
The geometric parameter analyses of the compound
were carried out using Mogul, a valuable knowledge base
for analyzing the conformational and geometric features of a
molecule under study.39 Using the structure (BT) as a base, it
is possible to search for similar compounds or substructures
of thioureas deposited in the Cambridge Crystallographic
Data Centre (CCDC). Using the Mogul program, as
expected, all bond lengths and bond angle values agree
statistically with those found for similar compounds. Table 1
shows the parameters for refinement and Table 2 presents
selected fragment (theoretical and experimental) values with
the mean values expected from the Mogul program.
The angles S1–C1–N1 (127.62°) and S1–C1–N2
(119.26°) indicate the presence of sp2 carbon of thione.
The same trend is also observed for the angles involving
the carbon atoms of amide groups. The bond distances
N2–C1 and N2–C9 have values of 1.402(5) and 1.379(5)Å,
respectively, which are in good agreement with those
expected for amide derivatives.40 The bond length C1=S1
[1.634(4) Å] is consistent with C=S double bonds of
thiones. Furthermore, bond lengths C2–O1 [1.205 Å] and
C9=O2 [1.231Å] show values characteristic of the carbonyl
groups of amides. As can be seen, the C2–O1 bond is
slightly longer than the C9=O2 bond, indicating a pure
double bond character in the C9=O2 fragment. As can be
seen, the C2–O1 group is involved in a resonance-assisted
hydrogen bond (RAHB), with the O2–C9–N2–C1–N1–H1
forming a stable six-membered ring. The well-oriented
intramolecular N1–H1···O2 hydrogen bond (H1···O2 and
N1···O1 distances of 1.864 and 2.592 Å, respectively)
contributes mainly to stabilization of the molecular
conformation.
In the BT structure, intermolecular forces are very
important for crystal packing stabilization. The C2=O1
carbonyl group acts as an acceptor of the H2 atom of
N2‑H2 amine group to form a classical hydrogen bond,
which gives rise to an infinite one-dimensional ribbon along
the b axis (Figure 4). By analyzing the crystal packing,
we can see that the existence of C15–H15···O1 weak
interaction is largely influenced by the strong N2–H2···O1
hydrogen bond, forming a well orientated H15···O1 contact
with the distance of 2.324 Å. In addition, the C8‑H8···S1
(2.748Å) weak intermolecular hydrogen bond is observed.
The contributions of all intermolecular contacts have been
studied in detail using the Hirshfeld surfaces (HS).
Hirshfeld surface analysis
In recent years, we have explored intermolecular
contacts of thiourea derivatives using the Hirshfeld surfaces

Vol. 29, No. 12, 2018
Silveira et al.
2507
than the sum of van der Waals (vdW) radii, while blue
and white represent the situation involving intermolecular
contacts longer and equal to the sum of van der Waals
(vdW) radii, respectively (Figure 5a). Thus, according
to these dnorm values mapped onto the Hirshfeld surface,
the difference between the sums of van der Waals (vdW)
radii can be seen, clearly indicating the specific region
able to be involved in intermolecular contacts. As can be
seen on the Hirshfeld surfaces of the BT compound, the
most intense red regions occur around the C=O and C=S
groups, due to bifurcation of the N2–H2···O1 and C8–
H8···S1 hydrogen bonds, in which the O and S atoms act
as an H-bond acceptor. Moreover, red regions are observed
near the ortho C–H of both aromatic groups, which act as
H-donors for C15‑H15···O1 and C8–H8···S1 non-classical
hydrogen bonds. The fingerprint plot shows that the O···H,
S···H, C···H, and H···H intermolecular contacts with relative
contributions 13.5, 11.9, 24.8 and 33.9%, respectively, are
very important interactions to stabilize the crystal assembly.
Figure 4. Classical intermolecular hydrogen bonds stabilizing the crystal
packing along the [010] direction.
(HS) and fingerprints plots. In this study, the results of this
analysis are represented in Figure 5.
The Hirshfeld surface of the compound, representing
the 3D dnorm, illustrates regions which are more suitable
to be involved in intermolecular contacts. As depicted
by the HS, in the region of the surface shown in red, the
distances between internal and external atoms are shorter
1H and 13C{1H}, 1H-1H COSY, 1H-13C HSQC, NMR analyses
Theone(1D)andtwo-dimensional(2D)1Hand13CNMR
experiments were used to assign the N-[(phenylcarbonyl)
carbamothioyl]benzamide compound. 1D 1H and 13C NMR,
2D HSQC and 1H-1H-COSY in CD2Cl2 confirm the purity
and the proposed structure of BT. It was determined the
chemical shifts and all bound hydrogen positions related
to each carbon atom, shown in Figures 6-7 and Figures S2
and S3 (Supplementary Information (SI) section).
Figure 6. 1H NMR spectrum (400.21 MHz, CD2Cl2) of BT.
The BT 1H NMR spectrum is dominated by the protons
in the aromatic region (7.72-8.03), i.e., benzene ring
protons. The signal at 7.72 ppm, whose integral is 2H, is
attributed to the hydrogens bound to C6 and C13 atoms (see
Figure 3 for atoms numbering). The signal at 7.61 ppm,
Figure 5. (a) Hirshfeld surface and (b-f) fingerprint plots for the BT
compound. The full fingerprint is shown in (b), and graphs (c), (d) and
(e) illustrate the O···H, S···H and C···H, (f) H···H intermolecular contacts,
respectively.

2508
Facile Synthesis and Characterization of Symmetric N-[(Phenylcarbonyl) carbamothioyl]benzamide Thiourea
J. Braz. Chem. Soc.
Figure 7. 13C NMR spectrum (100 MHz, CD2Cl2) and the structure of BT
with chemical shifts of 1H (red) and 13C (black).
whose integral is 4H, is attributed to the hydrogen bound
to C5 (C12) and C7 (C14) atoms and the signal at 8.03 ppm
is attributed to the less shielded protons, which are near
carboxyl groups bound at C4 (C11) and C8 (C15) atoms. At
11.75 ppm, there is an enlarged signal corresponding to the
H atoms directly bound to nitrogen atoms.
In the 13C NMR spectrum, carbon atoms C3 and C10 are
assigned at 132.61 ppm, which is the region where aromatic
carbon atoms do not bind any protons. The less shielded
carbon atoms, C2 and C9 of carbonyls, were assigned at
166.09 ppm. At 177.8 ppm, the thiocarbonyl carbon C1 is
assigned. The location of C1, between two electronegative
nitrogen atoms and sulfur atom, increases the deshielding
of this carbon.
Figure 8.Assignment of the two main peaks obtained in the mass spectrum
of the compound BT.
Mass spectrometry
The BT compound [C15H12N2O2S] has a molecular
weight equal to 284.33 a.u., and mass spectrometry
experiments show two main signals (MALDI-TOF and
MS/MS mass spectra, Figures S4, S5 and S6, SI section),
one peak at m/z 285.207, which can be attributed to the
molecular ion peak [C15H12N2O2S]H+, and the most intense
peak at m/z 105.03 attributed to the detection of the benzoyl
group. Figure 8 shows the thiourea fragmentation pattern.
Figure 9. UV-Vis experimental spectrum of BT (black solid line)
in DMSO, and theoretical (red dashed lines) at CAM-B3LYP/6-
311++G(2d,2p)//B3LYP/6-311++G(2d,2p) level.
260 nm (ν = 19564.2 cm-1) and 312 nm (ν = 9968.3 cm-1),
attributed to the transitions of type n → π* and π → π*,
respectively.
UV-Vis spectroscopy
The first transition is an n → π* transition, which
tends to have lower molar absorptivity, since this
transition is symmetry-forbidden in the C2 geometry.
As the C2 symmetry is broken, it is expected that the
transition gains in strength, but it is still weak. Thus,
there is no significant special overlap between HOMO
(highest occupied molecular orbital) and LUMO (lowest
unoccupied molecular orbital), i.e., the transition from
The experimental and theoretical spectra of the BT
compound are reported in Figure 9. The experimental
spectrum was obtained in DMSO as a solvent (concentration
of 4.4 × 10-5 mol L-1), while the theoretical spectra were
calculated using the functional CAM-B3LYP in the gas
phase and in DMSO using the PCM. The maximum
absorptions in the experimental spectrum occurred at

Vol. 29, No. 12, 2018
Silveira et al.
2509
the π non-bonding molecular orbital (HOMO), basically
formed by px sulfur atomic orbital, to the π anti-bonding
molecular orbital (LUMO), basically formed by py carbon
atomic orbitals, is expected to be very weak and thus
does not appear in the experimental UV-Vis spectrum,
as its intensity is under the detection limit. Furthermore,
the fact that the solvent (acetone) is polar contributed
to the decrease in absorptivity, as the lone pair of sulfur
atom interacts strongly with the solvent. In the theoretical
spectrum, this transition has excitation energy of 416.80 nm
or 2.97 eV. However, this oscillator is very weak with an
oscillator strength f ca. 0.0003 and, therefore, has little
influence on the convolution curve.
The second transition is a more intense one at 301.80 nm
or 4.11 eV. It corresponds to a π → π* (LUMO) transition.
It involves larger contributions of HOMO-1 and HOMO-6,
both π bonding orbitals. HOMO-1 is formed mainly by the
pz orbital of sulfur atom and HOMO-6 by the pz orbitals of
carbon atoms from the phenyl group.
Figure 11. Raman experimental spectrum of BT (black upper line) and
theoretical (red bottom line) at B3LYP/6-311++G(2d,2p) level.
are shown in Table S2 (SI section). There are 31 stretching,
30 bending deformation, and 29 torsion modes according
to PDE analysis.
The most intense transition is at 253.95 nm or 4.88 eV.
It corresponds to a π → π* (LUMO) transition. It involves
contributions of HOMO-2 and HOMO-1 π-bonding
orbitals. HOMO-2 has large contributions of pz orbitals of
carbon atoms from the phenyl group.
The infrared spectra showed strong absorbance in
the range of 1200-1600 cm-1, which is mainly assigned
to the carbon nitrogen modes. The five most intense IR
frequencies are: 1588.61 cm-1 (ds HNC), 1254.36 cm-1
(νas CC + νas NC), 1341.57 cm-1 (νas NC + νas CC),
1517.50 cm-1 (ds HNC + ds HCC), 3396.13 cm-1 (νs NH).
The five most intense Raman frequencies are: 3261.29 cm-1
(νs CH), 3260.18 cm-1 (νs CH), 1670.64 cm-1 (νas CC),
1274.2 cm-1 (νs CC + νas NC + ρ HNC), 3461.41 cm-1
(νs NH). N–H stretching modes are decoupled due to the
different chemical environment, i.e., the hydrogen bond
formation. H1–N1 stretching (number 89 in Table S2, SI
section) is red-shifted. The hydrogen bond N1–H1···O2
weakens the H1–N1 bond, as some electronic density
is involved in the hydrogen bonding. This fact is also
seen at a lower frequency (lower force constant) when
compared to H2–N2 stretching (number 90 in Table S2,
SI section). A lower constant means a weaker bond and
thus a more acidic hydrogen. The same features can be seen
in the Raman spectrum. Experimental Raman spectrum
shows two very intense peaks, one at 1619.14 cm-1 and
the other at 1039.28 cm-1, which correspond to ds HNC
(mode 72) and ds CCC (mode 47), respectively. In the
theoretical IR spectrum of the compound with dihedral
angle H1–N1‑N2–H2 equal to 55° (minimum point, see
Figure 10), the stretchings of N–H are coupled and two
peaks (νs and νas) with almost the same intensity (oscillator
strength) appear around 3600 cm-1. In this structure,
there is no intramolecular hydrogen bond. Thiol groups
are characterized at 1094.54 and 816.05 cm-1, which are
assigned to the C–S stretching vibration. The experimental
band around 2400 cm-1 (IR spectrum) is related to air CO2
FTIR and Raman spectroscopy
The experimental and theoretical infrared (IR) and
Raman absorption spectra for BT are shown in Figures 10
and 11. DFT calculations showed no imaginary frequency,
meaning that the optimized configurations (quasi-planar
structures) were true minima on the respective potential
energy surfaces. The vibrational infrared and Raman modes
and the respective assignments using potential energy
distribution (PED) implemented in the VEDA program41
Figure 10. FTIR experimental spectrum (KBr) of BT (black solid line)
and theoretical (red dashed line) at B3LYP/6-311++G(2d,2p) level.

2510
Facile Synthesis and Characterization of Symmetric N-[(Phenylcarbonyl) carbamothioyl]benzamide Thiourea
J. Braz. Chem. Soc.
absorption and therefore does not appear in the theoretical
spectrum.
To investigate the configuration space and the
contribution of the intermolecular hydrogen bond to the
structure configuration, it was performed a scan of the
dihedral angle H1–N1···N2–H2 in the solvent environment.
This study was performed to verify the lower energy
conformer when the selected dihedral angle that generates
the cisoide and transoid configurations of the N–H groups
in relation to C=S varied, and the profile obtained is quite
similar in both acetone and DMSO. The energy profile is
quite similar for both solvents: acetone and DMSO.
From the scan in Figure 12, it can be observed that the
lowest energy configuration is the one with the hydrogen
bond, i.e., the hydrogen atoms of amide groups are oriented
differently; while one is syn-periplanar in relation to the
thiol group, the other is anti-periplanar. The latter is the
one that forms the hydrogen bond.
Computational analysis
All the geometry optimizations converged to a
quasi-planar structure, with an N1–H1···O2 bond length
around 1.8 Å and angle bond about 140°, which indicates
the presence of the intermolecular hydrogen bond. This
bond persists even in calculations with implicit solvents.
The optimized structure is similar to that in Figure 3 and
can be seen in the Supplementary Information (Figure S1).
The theoretical structural parameters are quite similar
to those obtained by X-ray crystallography, as shown in
Table 2. All principal structural properties calculated have
a relative error below 2%. Rings are out-of-plane by about
30° in the gas phase and a little more, by 45°, in the solvent
environment. The crystallographic structure value is 28°.
The HOMO and LUMO energies (EHOMO and ELUMO
)
and HOMO-LUMO gap (HLG) for the BT molecule in the
gas phase and also in acetone (implicit solvent model) are
presented in Table 3 for three different DFT functionals. It
should be mentioned that the B3LYP functional presented
better computational cost vs. accuracy.
Solvent medium stabilizes total molecular energy and
molecular orbitals energies. Stabilization is greater for the
HOMO, which has a large contribution of px orbital of sulfur
atom (i.e., the lone-pair orbital), than for the LUMO, which
has mainly contributions of pz orbitals of carbon atoms.
Such behavior is expected and might be related to the low
intensity of n → π* transition (HOMO-LUMO transition),
which is suppressed in the experimental UV-Vis spectrum
(see Figure 9), very likely by the detection limit of the
spectroscope. Figure S7 (SI section) shows HOMO and
LUMO representation and gap energy of the optimized
structure at the B3LYP/6-311++G(2d,2p) level.
Figure 12. Dihedral H1–N1–N2–H1 relaxed scan in acetone and DMSO
at B3LYP/6-311++G(2d,2p) level.
According to Figure 3, the most stable configuration
is achieved when dihedral angle H1–N1–N2–H2 is about
177° and benzyl rings have angle of 49° between each
Table 3. Energies (HOMO, LUMO and HLG), in vacuum and acetone, for the BT compound, calculated by DFT functional, B3LYP, M062X and B3PW91
programs
DFT functional
Total energy / hartree Dipole moment / debye
Vacuum
EHOMO / eV
ELUMO / eV
HLG / eV
B3LYP
M062X
B3PW91
–1237.29
–1236.92
–1236.90
6.23
6.10
6.24
–6.06
–7.55
–6.10
–2.56
–1.56
–2.57
3.50
5.99
3.53
Solvent (acetone)
B3LYP
M062X
B3PW91
–1237.30
–1236.93
–1237.30
8.91
8.62
8.86
–6.45
–7.94
–6.46
–2.68
–1.73
–2.69
3.77
6.21
3.77
HOMO: highest occupied molecular orbital; LUMO: lowest unoccupied molecular orbital; HLG: HOMO LUMO gap; DFT: density functional theory.

Vol. 29, No. 12, 2018
Silveira et al.
2511
other. The most unstable configuration has dihedral angle
H1‑N1–N2–H2 about 90° and the relative position of benzyl
rings about 120°.
The region with the highest negative charge density is
centered on atom O1 as atom O2 has hydrogen bonding
with H1, reducing the charge density on the O2 atom, which
is in agreement with the data obtained from the Hirshfeld
surface analysis.
The scans show two local minima: one with dihedral
angle H1–N1–N2–H2 equal to –40° and the symmetric
counterpart, 40°. The relative angle between the benzyl
groups in these structures is around 85°. Between these
configurations, there is a maximum point where the same
dihedral angle is almost 0°, which means that hydrogen
atoms from amide groups are aligned (anti-periplanar with
thiol group) and the benzyl groups are by 112° out-of-plane.
Therefore, the sulfur and oxygen atoms are also aligned
(syn-periplanar). Although those configurations are energy
minima, the difference between the global minimum is still
large, about 0.42 eV. This energy difference is by the order
of magnitude larger than the thermal energy kBT, which for
300 K equals to 0.04 eV. Of course, this comparison is rough,
but it at least gives an idea if the thermal energy would be
enough to overcome the rotation barrier at room temperature,
for example. It can be concluded that most of the molecules
assume the minimum configuration even in the solvent phase,
which means that the intermolecular hydrogen bond remains
when the molecules are solvated. Overall, it can be said that
two geometric parameters are relevant to the configuration
energy, i.e., stabilization, which is the relative position of
phenyl groups, and the formation of the intermolecular
hydrogen bond N1–H1···O2. The latter is related to the relative
position of amide hydrogens.
In order to verify the electronic densities distribution
by the NBO analysis, in the Tables S5 and S6 (SI section)
are shown the NBO charges of the atoms, considering
both structural forms cis and trans configurations of the
BT molecule (Figure S8, SI section), and a complete
analysis of the data is presented in the Supplementary
Information. The data indicate that the sulfur atom displays
the largest difference between these forms, which suggest
that the electronic charge are more localized in trans-BT
than in cis-BT form, which agrees with the experimental
data, as can be clearly seen by the topological analysis
of the structure of the BT molecule (Figures S9 and S10,
SI section). Such difference might be understood by the
breakdown of resonance structure of the S–C–N–C–O
system.
The strongest stabilization of the trans-BT molecule
is associated with the lone pair orbital of oxygen and
nitrogen atoms. In all cases, the π∗ antibonding orbitals of
these atoms participate as acceptors, while the lone pairs
of them act as donors in the intermolecular interaction,
natom → π* orbitals. As result, the occupation number of
these antibonding orbitals is fairly high. The NBO analysis
reveals that there is a strong intramolecular interaction of
charge transfer from oxygen lone pairs to the N1–H1, in an
antibonding orbital (nO2 → σ*N1–H1). As a consequence, the
Molecular electrostatic potential (MEP) surface
occupation number of these orbitals is quite lower (nO2 orbital
)
The molecular electrostatic potential (MEP) surface
was plotted on the optimized structure of BT in the gas
phase, and is a powerful tool for analyzing and recognizing
the donor and acceptor regions of electron density.42,43
Figure 13 shows the computationally obtained MEP surface
map with the point charges fitting to the electrostatic
potentialV(r) calculated for the BT, and shows the negative
regions (red) and the positive regions (blue).
and higher (σ*N1–H1) than those of the cis configuration, and
a significant decrease of this intramolecular interaction was
observed, which is in agreement with the experimental
observation, where only the trans-BT structure was
obtained.
Conclusions
The thiourea derivative, N-[(phenylcarbonyl)
carbamothioyl]benzamide, was synthesized and fully
characterized. A new synthetic route for the synthesis of
the symmetric thiourea derivatives, with high purity and
high yield, was presented. This route can be easily used to
produce other thioureas by simply changing the reactant,
i.e., the functional group of interest. The BT compound
crystallized in the centrosymmetric space group P212121
and the DFT analysis showed good agreement with the
X-ray results. Moreover, the vibrational FTIR and Raman
spectra of the compound were recorded and assigned using
experimental and computed vibrational wavenumbers.
Figure 13. The computationally obtained MEP surface maps for the BT.

2512
Facile Synthesis and Characterization of Symmetric N-[(Phenylcarbonyl) carbamothioyl]benzamide Thiourea
J. Braz. Chem. Soc.
Good agreement for both vibrational and electronic spectra
was obtained.
6. Serdyuk, O. V.; Heckel, C. M.; Tsogoeva, S. B.; Org. Biomol.
Chem. 2013, 11, 7051.
An important result is related to the presence of the
intramolecular hydrogen bond, which is a quite strong
interaction and might play a noticeable role even in
the liquid phase. Its relative strength was estimated by
geometry optimizations for several structures (relaxed scan)
where this hydrogen bond length was constantly varied. In
conclusion, the rotation barrier is too high to be overcome
by simple thermal energy.
In summary, a new methodology for obtaining
symmetric thioureas quickly and easily was proposed,
with high purity and high yield, and also the data presented
in this paper can help to better understand this class of
thioureas. We hope that the method described here will
be used by others, making the synthesis of this important
class of compounds more efficient, cheaper, and generating
less waste.
7. Lin, T. L.; Lien, H. L.; J. Mol. Struct. 2013, 14, 9834.
8. Mushtaque, M.; Jahan, M.; Ali, M.; Khan, M. S.; Khan, M. S.;
Preeti, S.; Kesarwani, A.; J. Mol. Struct. 2016, 1122, 164.
9. Schoultz, X.; Gerber, T. I. A.; Hosten, E. C.; Polyhedron 2016,
113, 55.
10. Stefanska, J.; Szulczyk, D.; Koziol, A. E.; Miroslaw, B.;
Kedzierska, E.; Fidecka, S.; Busonera, B.; Sanna, G.; Giliberti,
G.; La Colla, P.; Struga, M.; Eur. J. Med. Chem. 2012, 55, 205.
11. Venkatachalam, T. K.; Mao, C.; Uckun, F. M.; Bioorg. Med.
Chem. 2004, 12, 4275.
12. Karakus, S.; Kucukguzel, S. G.; Kucukguzel, I.; De Clercq, E.;
Pannecouque, C.;Andrei, G.; Snoeck, R.; Sahin, F.; Bayrak, O.
F.; Eur. J. Med. Chem. 2009, 44, 3591.
13. Yonova, P. A.; Stoilkova, G. M.; J. Plant Growth Regul. 1997,
23, 280.
14. Sheldrick, G. M.; Acta Crystallogr., Sect. A: Found. Adv. 2008,
64, 112.
Supplementary Information
15. Sheldrick, G. M.; SHELXL97, Program for Crystal Structure
Refinement; University of Göttingen, Germany, 1997.
16. Enraf-Nonius; COLLECT; Nonius BV, Delft, The Netherlands,
1997.
Crystallographic data for the structure (BT) reported
in this paper have been deposited with the Cambridge
Crystallographic Data Center, CCDC No. 1582900. Copies
of the data can be obtained, free of charge, on application
to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax:
+44 1223 336033; e-mail: deposit@ccdc.cam.ac.uk or
http://www.ccdc.cam.ac.uk).
17. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.;
Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.;
Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng,
G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.;
Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda,
Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery Jr., J. A.;
Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers,
E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand,
J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S.
S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.;
Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo,
J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A.
J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.;
Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.;
Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö.;
Foresman, J. B.; Ortiz, J.V.; Cioslowski, J.; Fox, D. J.; Gaussian
09, Revision A.02; Gaussian, Inc., Wallingford, CT, 2009.
18. Mehdi, A.; Adane, L.; Patel, D. S.; Bharatam, P. V.; J. Comput.
Chem. 2009, 31, 1259.
1
The data of H and 13C NMR, MS, representation
of HOMO and LUMO and vibrational assignments for
compound BT are available free of charge at http://jbcs.
sbq.org.br as PDF file.
Acknowledgments
The authors are grateful for the support provided by
CAPES and CNPq (A. E. Kuznetsov). R. S. Correa would
also like to thank CNPq for the financial support (project
403588/2016-2).
References
1. Andreae, S.; Schimtz, E.; J. Prakt. Chem. 1987, 329, 1008.
2. Gardner, J. O.; J. Org. Chem. 1980, 45, 3909.
19. McLean,A. D.; Chandler, G. S.; J. Chem. Phys. 1980, 72, 5639.
20. Frisch, M. J.; Pople, J. A.; Binkley, J. S.; J. Chem. Phys. 1984,
80, 3265.
3. Singh, G.; Saroa, A.; Rani, S.; Promila; Girdhar, S.; Sahoo, S.;
Choquesillo-Lazarte, D.; Polyhedron 2016, 112, 51.
4. Madabhushi, S.; Mallu, K. K.; Vangipuram, V. S.; Kurva, S.;
Poornachandra, Y.; Kumar, C. G.; Bioorg. Med. Chem. Lett.
2014, 24, 4822.
21. Becke, A. D.; J. Chem. Phys. 1993, 98, 5648.
22. Lee, C.; Yang, W.; Parr, R. G.; Phys. Rev. B: Condens. Matter
Mater. Phys. 1988, 37, 785.
5. Saeed, A.; Ashraf, S.; White, J. M.; Soria, D. B.; Franca, C. A.;
Erben, M. F.; Spectrochim. Acta, Part A 2015, 150, 409.
23. Parr, R. G.;Yang, W.; Density-Functional Theory of Atoms and
Molecules; Oxford University Press: New York, 1989.

Vol. 29, No. 12, 2018
Silveira et al.
2513
24. Zhao, Y.; Truhlar, D. G.; Theor. Chem. Acc. 2007, 120, 215.
36. Saeed, A.; Parvez, M.; Cent. Eur. J. Chem. 2005, 3, 780.
25. Yanai, T.; Tew, D. P.; Handy, N. C.; Chem. Phys. Lett. 2004,
393, 51.
37. Li, G.; Zhao, M. M.; Wang, L.;Yang,Y. H.; Zhang,Y. J.; Dong,
X. Y.; Asian J. Chem. 2013, 25, 4334.
26. Barone, V.; Cossi, M.; Tomasi, J.; J. Chem. Phys. 1997, 107,
3210.
38. Kaminsky, W.; Goldberg, K. I.; West, D. X.; J. Mol. Struct.
2002, 605, 9.
27. Reed, A. E.; Curtiss, L. A.; Weinhold, F.; Chem. Rev.
(Washington, DC, U. S.) 1988, 88, 899.
39. Bruno, I. J.; Cole, J. C.; Kessler, M.; Luo, J.; Motherwell, W. D.
S.; Purkis, L. H.; Smith, B. R.; Taylor, R.; J. Chem. Inf. Comput.
Sci. 2004, 44, 2133.
28. Schaftenaar, G.; Noordik, J. H.; J. Comput.-Aided Mol. Des.
2000, 14, 123.
40. Hung, W. W.; Kassim, M. B.; Acta Crystallogr., Sect. E:
Crystallogr. Commun. 2010, 66, 3182.
29. Glendening, E. D.; Reed, A. E.; Carpenter, J. E.; Weinhold, F.;
NBO, version 3.1; University of Wisconsin, Madison, WI, 2009.
30. Bader, R. W. F.; Chem. Rev. (Washington, DC, U. S.) 1991, 91,
893.
41. Jamróz, M. H.; Spectrochim. Acta, Part A 2013, 114, 220.
42. Afzali, R.; Vakili, M.; Boluri, E.; Tayyari, S. F.; Nekoei, A. R.;
Hakimi-Tabar, M.; Darugar,V.; Spectrochim. Acta, Part A 2017,
190, 15.
31. Becke,A. D.; Edgecombe, K. E.; J. Chem. Phys. 1990, 92, 5397.
32. Tian, C. F. W.; J. Comput. Chem. 2012, 33, 580.
33. Ballini, R.; Bosica, G.; Fiorini, D.; Maggi, R.; Righi, P.; Sartori,
G.; Sartorio, R.; Tetrahedron Lett. 2002, 42, 8445.
34. Qiao, L.; Huang, J.; Hu, W.; Zhang,Y.; Guo, J.; Cao, W.; Miao,
K.; Qin, B.; Song, J.; J. Mol. Struct. 2017, 1139, 149.
35. Rauf, M. K.; Zaib, S.; Talib, A.; Ebihara, M.; Badshah, A.;
Bolte, M.; Iqbal, J.; Bioorg. Med. Chem. 2016, 24, 4452.
43. Leela, J. S.; Hemamalini, R.; Muthu, S.; Al-Saadi, A. A.;
Spectrochim. Acta, Part A 2015, 146, 177.
Submitted: February 20, 2018
Published online: July 2, 2018
This is an open-access article distributed under the terms of the Creative Commons Attribution License.