Theoretical and experimental study on the effect of end chain length on ultraviolet absorption behavior and photostability of alkoxy benzoate based liquid crystals

Article abstract of DOI:10.13005/ojc/330317

Liquid crystals homologous of 4-(4-chlorobenzoyloxy)phenyl 4-(n-alkoxy)benzoate (n CBPAB: n=8,14,16, where n is the number of carbon atoms in the alkoxy chain) were prepared and investigated for their liquid crystalline properties. The geometrical paramet

Full text of DOI:10.13005/ojc/330317

ISSN: 0970-020 X
CODEN: OJCHEG
2017, Vol. 33, No. (3):
Pg.1190-1199
ORIENTAL JOURNAL OF CHEMISTRY
An International Open Free Access, Peer Reviewed Research Journal
www.orientjchem.org
Theoretical and Experimental Study on the Effect of End Chain
Length on Ultraviolet Absorption Behavior and
Photostability of Alkoxy Benzoate Based Liquid Crystals
AHMED M. EL DEFRAWY 1,2*, SAID Z. MOHAMMADY 1,3
MARWA G. ELGHALBAN 1,2 and HOSSA F. EL-SHARIEF1
1Department of Chemistry, Faculty of Applied Science, Umm Al-Qura University, Makkah, Saudi Arabia.
2Department of Chemistry, Faculty of Science, Mansoura University, Egypt.
3 Department of chemistry, Faculty of Science, Cairo University, Egypt.
*Corresponding author E-mail: ameldefrawy@gmail.com
http://dx.doi.org/10.13005/ojc/330317
(Received: February 01, 2017; Accepted: April 14, 2017)
ABSTRACT
Liquid crystals homologous of 4-(4-chlorobenzoyloxy)phenyl 4-(n-alkoxy)benzoate (n
CBPAB: n=8,14,16, where n is the number of carbon atoms in the alkoxy chain) were prepared and
investigated for their liquid crystalline properties. The geometrical parameters and atomic charge
distribution of the nCBPAB structures under investigation have been calculated using DFT level of
calculation applying the B3LYP/6-31G(d) basis set.TD-DFT calculations have been used to predict
the absorption spectra of the considered molecules. Furthermore, theoretically predicted molecular
descriptors have been used to correlate with the phase stability of these molecules. In addition to
that, the photo stability of these molecules has been investigated which provide valuable data for
experimental applications.
Keywords: liquid crystals, DFT, Photostability, ovality.
INTRODUCTION
and modify its technological properties such as in
temperature sensors, electrooptic displays etc. Most
mesogenic molecules consists of an aromatic core
attached to one or two alkyl chains4 that influence
the properties of these molecules such as transition
temperature5–8. The development of such a different
The research of investigating new liquid
crystal (LC) molecules has become one of the most
fascinating topics in chemistry and materials science
particularly. Thesematerials,whichareknowntoshow
properties that are an intermediate among solids and
liquids known as “mesophases,” are gaining a great
interest now a days 1-3.The motivation behind these
studies is to investigate its structure in order to tune
types and phase of liquid is closely related to
9,10
the molecular structure of these molecules
.
Subsequently, to correlate the molecular structure
with liquid crystal properties at the molecular level

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DEFRAWY et al., Orient. J. Chem., Vol. 33(3), 1190-1199 (2017)
remains a subtle objective. To investigate the key is. Differential scanning calorimetry (Perkin-Elmer
role of molecular interactions in these compounds, DSC-7) has been used for the transition temperature
several quantum mechanical studies have been led (TN) measurements. The molecular formula (i.e.,
out by several workers 11–27
.
abundance of H-atoms) of the prepared compounds
was confirmed by 1H NMR (Bruker, 400 MHz) and IR
The purpose of this work is to theoretically (1C-Schimadzu FTIR).The nano assemblies of liquid
calculate molecular properties of the chosen crystals were investigated by transmission electron
model liquid crystal molecules and correlate microscopy (TEM). The TEM image was obtained
them with experimentally measured properties. using Jeol JSM 6390 equipment.
Model molecules used in this study involve
4-(4-chlorobenzoyloxy)phenyl4-(n-alkoxy)benzoate Chemistry
homologous series. Quantum chemical calculations
The synthetic routes for many of the
were conducted utilizing TDDFT method using intermediates as well as the targeted compounds
DFT/ B3LYP level of calculations with 6-31G(d) basis are explained as indicated in sheme1
set in addition to semiemperical calculations using
the PM7 hamiltonian to acquire molecular properties Preparation Of Ethyl-4-N-Alkoxybenzoates (1)
and the electronic spectra for the molecules under
To a solution of ethyl-4-hydroxybenzoate
investigation. The results of theoretical study were ethyl and the appropriate 1-chloro-n-alkane was
reported here in and have been utilized to decipher added drop-wise while stirring until obtaining the
the liquid crystalline behavior obtained experimentally ester(1) 5.
for these molecules.
Preparation of 4-n-alkoxybenzoic acids(2)
EXPERIMENTAL AND THEORETICAL
METHODS
The ester obtained Ethyl-4-n-
alkoxybenzoates (1) was directly hydrolyzed by
adding potassium hydroxide and heating for two
hours.The cold solution is added with stirring to cold
Materials and methods
All the chemical ingredients used to dilute hydrochloric acid. After recrystallization, the
resulting acid (2) is TLC pure 28
.
prepare the LC molecules under investigation were
procured from Sigma Aldrich, USA and used as it
Fig .1: 1HNMR spectra for the C8 compound as a representative example for the series

DEFRAWY et al., Orient. J. Chem., Vol. 33(3), 1190-1199 (2017)
1192
Preparation of 4-n-alkoxybenzoyl chloride(3)
n-alkoxybenzoic acids(2)( 0.01 mol )
and thionylchloride (0.01 mol) are placed in dry a
250 ml flask then reflux till obtaining the product 4-n-
alkoxybenzoyl chloride(3), details of the procedure
can be found elsewhere28.
Preparation of 4-hydroxyphenyl-4’-n-alkoxy
benzoate (4)
Approximately (0.01 mol ) of 4-n-
alkoxybenzoyl chloride (3) was added to
(0.01 mol ) of hydroquinone in(50 ml) of dry benzene
with drops of triethyl amine. The reaction mixture
was stirred with reflux for 6 h.The crystalline product
(4) was separated by filtration; vacuum dried and
recrystallized using a proper solvent. The prepared
compounds have been characterized using infrared
spectral measurements for the function group
identification such as the carbonyl group that have
been well observed around 1730 cm-1.
Preparation of diester(5):4-(4-chlorobenzoyloxy)
phenyl 4-(octyloxy) benzoate(C8)
One molar equivalent of the 4-substituted
benzoyl chloride in dry pyridine was added drop-
wise with stirring to a solution of 4-hydroxyphenyl-
4’-octyloxy benzoate (0.01mol) in dry benzene
with drops of pyridine .The products, after being
crystallized twice from acetic acid, were TLC pure.
Fig. 2: Mid IR (2000-400 cm-1) spectra for the
molecules under investigation
Scheme1: Reagents and conditions for the preparation of the targeted compounds

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DEFRAWY et al., Orient. J. Chem., Vol. 33(3), 1190-1199 (2017)
The prepared compound have been characterized
using infrared and HNMR. The characteristics of
RESULTS AND DISCUSSIONS
1
the obtained compound are given below: dH(400
The first set of the compounds under
MHz DMSO)0.87(3H,t),1.32(-CH2,m),1.759(2H, investigation (Fig. 1) including the chloro derivative
quintet),4.10(2H,t), 7.1(2H,t), 7.39(4H,t), 7.70(2H,d), and the alkyl group of length 8, 14 and 16 carbon
8.15(4H,m);IR (KBr)/cm-1: 3110, 3067, 2968, 2926, atoms were prepared and subjected to some
2884,2854,1731,1604, 1509,1289,1187,1086, and experimental measurements concerning the IR
1010,756.
(Fig. 2) as well as the transition temperature (TN )
from the nematic to the isotropic phase.
The experimental procedure for the
preparation of compound4-(4-chlorobenzoyloxy)
In addition to that, this set of molecules
phenyl 4-(tetradecyloxy) benzoate (C14) and were subjected to a theoretical treatment using the
compound 4-(4-chlorobenzoyloxy)phenyl DFT level of calculations as mentioned previously
4-(hexadecyloxy)benzoate(C16)wasasdescribedfor and the following results were obtained as follows
the preparation of compound 4-(4-chlorobenzoyloxy)
phenyl 4-(octyloxy)benzoate (C8) except that the Ground state geometries and shape of the
4-hydroxyphenyl-4’-tetradecyloxy benzoate and molecules
4-hydroxyphenyl-4’-hexadecyloxy benzoate were
Many factors influence the actual liquid
used respectively instead of the corresponding crystal phase exhibited.It is usually believed that the
4-hydroxyphenyl-4’-octyloxy benzoate .
molecule geometrical shape mainly determines the
observed phase. However, other properties such
as intermolecular repulsions, attractive interactions
Theoretical calculation
Quantum Chemical calculations were and hydrogen bonds may play an important role.
performed in the gas phase using Density Functional The optimized parameters (bond lengths and bond
Theory (DFT) implemented in the GAUSSIAN angles) for compounds C8, C14 and C16 under
29
(09) program
in addition to the MOPAC 2016 investigation were obtained by using B3LYP/6-31G
semiempirical package 30 . We employed the B3LYP (d) level of calculation. The results are depicted in
(Becke three-parameter Lee–Yang–Parr) exchange Tables 1. It was found that the structural parameters
31,32
correlation functional
with 6-31G(d) basis sets of the molecules is not affected by the alkyl chain
using the Gaussian 09 program and the PM7 length, where by increasing the chain length there is
Hamiltonian using the MOPAC2016 software. Time no change in these parameters.The increase of the
dependent Density functional theory (TDDFT) chain length of these compounds leads to a change
calculation at the B3LYP/6-31G(d) level of theory in the dihedral angle (Table1) of the three rings A,
will be used to predict the absorption spectra for the B, and C (Fig. 3). This change in the dihedral angle
titled compounds.All calculations were conducted in obviously will affect the molecular interactions in
the liquid crystalline state. It is worthy to note that,
the gas phase.
Fig. 3: geometry model optimized at B3LYP/6-31G (d) level showing the atomic Numbering
and Ring Labeling for the compounds under investigation, where the alkyl group
chain (R) has been omitted for clarity

DEFRAWY et al., Orient. J. Chem., Vol. 33(3), 1190-1199 (2017)
1194
by changing the number of the carbon atoms in
the alkyl chain, the zigzag structure of the alkyl
chain length in all the liquid crystalline homologous
compounds show no change and the angles are
not affected. Thus, the discussion was centered on
the ring dihedrals with the different chain lengths.
The inspection of these data (Table1) reveals that
these compounds shows a non planar conformation
which is more underlined on both sides of benzene
ring number B (Fig.3), the values of these dihedral
angles are shown in Table 1.
Two dihedral angles will be considered for
the inspection of the effect of changing the alkyl
chain length on the molecular geometry. The first
angle ϴ (7-9-10-11) shows a consistent decrease
from -50.3 to -48.0 on going from compound C8 to
compound C14 to compound C16. On the other
hand, the second dihedral angles θ shows increase
in its value by increasing the alky chain length from
C8 to C14 then decrease from C14 to C16 again
( Table 1).
The intramolecular hydrogen bonding
between the HB1(H30-O8) and HB2(H31-O18)
values (Table 1) were also affected by the change
in the alkyl chain length. The bond length for the
HB1 shows a consistent decrease by increasing the
alkyl chain length, where as the HB2 bond lengths
show an increase then a decrease from C8 to C16
(Table 1). This could be attributed to the change in
the dihedral angle that affects the degree of out of
plane angles of the rings in the mesogenic part,
which affects the hydrogen bond length (Table 1).
Table 1: Selected optimized geometric
parameters for the mesogen molecules
calculated using the B3LYP/6-31G
(d) level of calculation
parameter
C8
C14
C16
Bond length
R(1-38)
R(4-7)
R(7-8)
R(7-9)
R(9-10)
R(13-16)
R(16-17)
R(17-18)
1.357
1.479
1.212
1.377
1.392
1.397
1.369
1.210
1.488
1.755
1.358
1.479
1.212
1.377
1.392
1.397
1.368
1.211
1.488
1.755
1.358
1.479
1.212
1.377
1.392
1.398
1.369
1.210
1.488
1.755
R(17-19)
R(24-25)
Hydrogen Bond
HB1(8-30)
HB2(18-31)
Angles
2.577
2.605
2.545
2.618
2.537
2.611
A(1-38-39)
A(4-7-8)
A(4-7-9)
119.1
125.2
111.4
123.4
120.6
120.6
122.7
116.3
124.2
111.3
124.6
117.6
122.8
120.4
125.2
111.3
123.5
120.0
121.0
123.1
116.0
124.2
111.2
124.5
117.6
122.9
120.4
125.2
111.3
123.5
121.0
120.5
123.0
116.0
124.1
111.3
124.6
117.5
122.9
A(8-7-9)
A(7-9-10)
A(13-16-17)
A(9-10-11)
A(9-10-15)
A(16-17-18)
A(16-17-19)
A(18-17-19)
A(17-19-20)
A(17-19-21)
Dihedral angle
Ф(7-9-10-11)
θ(12-13-16-17)
-50.3
-51.4
-48.9
-52.1
-48.0
-51.8
Fig. 4:The TEM and SAED images for the liquid
crystal molecules under investigation

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DEFRAWY et al., Orient. J. Chem., Vol. 33(3), 1190-1199 (2017)
The TEM images of the liquid crystal Ovality Index, (O), defined by
homologous are shown in Fig. 4. TEM image
shows a crystal size ranging from 20nm to 47nm.
To ascertain the crystalline nature of these liquid
O= (A/ 4p)/ (3V/4p)2/3
crystals, their selected area diffraction pattern A: area of the molecule
(SAED) were also recorded (Fig. 4). The diffraction V: volume of the molecule
patterns of the compounds under investigation show
diffraction fringes for the Liquid crystal C8 were as for
This property (ovality index) is an indicator
the C14 and C16 did not show any diffraction fringes, of how close is the molecule geometry to a sphere,
clearly ruling out their crystalline nature.
a cylinder or a disk. If O=1.0 it is a perfect sphere, if
Fig.5: Isodensity plots (isodensity contour = 0.02 a.u.) of the frontier orbitals
of the C8, C14 and C16 liquid crystal molecules calculated
by B3LYP /6-31G(d) level of calculation
Table 2: quantum chemical parameters for the different compounds as obtained from
B3LYP/6-31G (d) method and PM7 semi empirical method in the gas phase
Comp.
EHOMO
(ev)
ELUMO
(ev)
Dipole
moment
N
QC
QA
TN
(exp.)
Ovality
index*
Eb
C8
C14
C16
-6.22610 -1.62428
-6.19073 -1.62292
-6.18882 -1.62401
4.8944
5.0744
5.0641
8
14
16
-0.343
-0.347
-0.347
0.393
0.342
0.341
66.3
52.8
32.8
1.594
1.694
1.730
0.47
0.45
0.45
*Results obtained from the PM7 semiempirical method

DEFRAWY et al., Orient. J. Chem., Vol. 33(3), 1190-1199 (2017)
1196
O>1.0 it is a cylinder and if O<1.0 it is closer to a disk.
The data obtained from the PM7 semiemperical
calculation was used to compute the molecular
volume employed in the ovality formula. The values
of the ovality index for the three compounds under
investigation are depicted in Table 2. The order of
increasing the ovality index is following the order
C8< C14 < C16 and are all larger than 1. This
indicates that these molecules tend to be cylindrical
in shape (Fig. 4).
The molecular orbitals especially the
HOMO and the LUMO are of important factors in
obtaining the information concerning the electron
conductivity of the molecules33. As inferred fromTable
2 , the HOMO and LUMO energies did not change
significantly upon the change in the alkyl chain
length.Hence, the energy gap for the three molecules
gives almost equal values indicating nearly similar
electrical conductivity. The electron density plots
of the HOMO and LUMO (Fig.5) explain the above
mentioned discussion as it shows that the electron
density for both orbital are not localized on the alkyl
chain so it is not affected by its length.
Frontier Molecular Orbital Analysis
Molecular orbital and their properties, like
energy, are very useful for physicists and chemists
and their frontier electron density used for predicting
the most reactive position in p -electron systems
and also explained several types of reaction in
conjugated system. Our results indicate that the
energy differences between the lowest unoccupied
molecular orbit (LUMO) and the highest occupied
molecular orbit (HOMO) are predominantly not
affected too much by the alkyl chain length. Because
the energetically favored electron promotion is from
the HOMO to LUMO, the resulted absorption will be
located at about 270 nm. Thus, the absorption of
270 nm light renders these substances as colorless
compounds. The energy gap of HOMO–LUMO
(Table 2), in the compounds under investigation
explains the eventual charge transfer interaction
within these molecules. Fig. 4 shows the electron
density plots for frontier molecular orbitals of the
molecules under investigation.
Excitation binding energy (Eb) is a very important
parameter that governs the generation of the charge
in organic materials used in electronics 34
.
Eb = Eg – Evert
.
Where Eb is the excitation binding energy,
Eg is the band gap and Evert is the vertical transition
energy. The values of Eb are depicted in Table 2.
As inferred from Table 2, one can observe that the
values of the excitation binding energies for the three
liquid crystal molecules show close values. This
can be attributed to the insignificant discrepancies
between the obtained electronic energy levels for
the molecules under investigation when changing
the alkyl chain length, which in turn makes the Eb
value insignificantly changed (Table 2)34
.
Table 3:The UV – Vis absorption band, Electron transition, oscillator
strength (f) for the C8 , C14 and C16 liquid crystal molecules as
obtained from the TD-DFT calculation
Molecule Absorption Electron
Oscillator
Main transition
configuration
bands
transition strength (f)
C8
300
272
255
S0→S1
S0→S3
S0→S5
0.2347
0.3610
0.0983
H→L(68%)
H→L+1(73%)
H-6→L+1(37%)
C14
C16
301
272
255
S0→S1
S0→S3
S0→S5
0.2286
0.3990
0.1111
H→L(66%)
H→L+1(71%)
H-6→L+1(35%)
301
272
255
S0→S1
S0→S3
S0→S5
0.2307
0.3970
0.1041
H→L(66%)
H→L+1(72%)
H-6→L+1(35%)

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DEFRAWY et al., Orient. J. Chem., Vol. 33(3), 1190-1199 (2017)
estimated and analyzed in order to give important
Atomic Charges
One of the important factors that information that could be critical in the industrial
determine the mesophase stability is the electrostatic application of these molecules 35
interactions managed by the partial atomic charges
.
of the mesophase molecule. Mullikan population
In a recent study on the newly prepared 1,4
analysis has been obtained for the atoms constituting phenylene dibenzoate moiety36, three absorption
the molecules under investigation. Each molecule bands were observed at 342nm, 285nm and
has been divided into three parts, the first is the alkyl 280nm . The molecules under investigation, which
chain part and the second is the core part, which is are derivatives of these moiety exhibit also three
the rest of the molecule except the chlorine atom, bands as obtained from the TDDFT calculation at
which is the third part.
the B3LYP/6-31G(d) level of theory (Fig. 6). The UV
spectral data are depicted in Table 3.
The total charge on the alkyl chain part
(QA) and the core (QC) part are depicted in Table 2.
The C8 molecule (Fig.6) shows three
The charge on the chlorine atom for all the molecules prominent bands in the range from 255 nm to 300
under investigation was found to be 0.008. by careful nm in the UV region. The band (ë1) at 255 nm is
inspection ofTable 2, one can conclude that QC for all assigned as p- p* transition for the aromatic rings and
molecules possess a total negative charge , while the possessing an oscillator strength value of 0.098. The
QA for all molecules have positive charge value.This second band ( l2) appears at 272nm with a higher
will give an account for the phase stability of these oscillator strength of 0.361 and it is the strongest
molecules due to the strong interaction between them band in the spectra and can be assigned as p- p*
as well as with the chlorine atom. It is also worthy to transition for the carbonyl group in addition to a band
mention that, the largest difference between the QA predicted to be at 300 nm (l3) which is assigned
and QC is found in the C8 molecule. This accounts as the n- p* transition of the carbonyl group. The
for the higherTN value compared to the C14 and C16 contribution of the molecular orbitals to the different
molecule (Table 2).
UV spectral observed for this molecule are depicted
in Table 3.
Ultraviolet (UV) absorption spectra
The UV light affects the LC molecules in a
TheTDDFT predicted absorption spectra for
way that can reach to gradual degradation of these compounds C14 and C16 are shown in Fig.6. The
molecules and hence affects their properties. from simulated spectra for both compounds show three
this point, the UV absorption spectra should be bands which is in the same place as for compound
Table 4: Inter correlation matrix between different molecular descriptors and the transition
temperature
Variables EHOMO ELUMO
D
N
QC
QA
TN Ovality HB1
HB2
φ
ϴ
EHOMO
ELUMO
D
1
0.620
0.995 0.692
1
1
N
0.981 0.454 0.957
1
QC
QA
TN
-0.999 -0.655 -0.999 -0.971
-1.000 -0.642 -0.998 -0.975 1.000
-0.831 -0.078 -0.774 -0.924 0.805 0.815
1
1
1
Ovality
HB1
HB2
Ф
0.977 0.440 0.953 1.000 -0.967 -0.971 -0.930
-0.990 -0.500 -0.971 -0.999 0.982 0.985 0.903 -0.998
0.818 0.959 0.869 0.689 -0.843 -0.834 -0.359 0.678 -0.726
1
1
1
0.938 0.310 0.901 0.988 -0.922 -0.928 -0.972 0.990 -0.978 0.568
1
ϴ
-0.884 -0.915 -0.925 -0.775 0.904 0.897 0.474 -0.765 0.807 -0.992 -0.667 1

DEFRAWY et al., Orient. J. Chem., Vol. 33(3), 1190-1199 (2017)
1198
angles showing that the angle Ф(7-9-10-11) is
highly positive correlated to the dipole moment
which means as this angle increase the value of
the dipole moment increase. On the other hand, the
dihedral angle θ(12-13-16-17) shows a high negative
correlation with the dipole moment which means
inverse correlation to each other. The results show
the high dependence of the dipole moment value on
the dihedral angles. It is worthy to mention that, as
the dihedral angle decrease the value of the dipole
moment increase this could be attributed to the
increase in the conjugation in the mesogenic part.
As inferred from Table 4, the transition
temperature (TN)hasgood+vecorrelationcoefficients
with HB1, QC and QA. This means that as these
parameters increase the transition temperature
increase. Whereas, the transition temperature
Fig. 6: Simulated UV spectra for the liquid
crystal molecules under investigation
C8. The oscillator strength and main configuration
transitions are depicted inTable 3. The surface plots
for these compounds ( Fig.6) gives an indication that
the change in the alkyl chain length has no effect on
the electronic structure of these molecules as the
molecular orbitals contributing to these bands show
electron densities mainly on the core part with no
contribution of the alkyl chain part.
has good -ve correlation coefficients with EHOMO
,
Dipole moment, the number of carbon atoms
(N) , the dihedral angles (Ф) and the ovality index
(O) .This means that as these parameters increase
the transition temperature decrease. The Ovality
index (O) was found to be the highest correlated
parameter with R= -0.972 (Table 4) among the
studied parameters which shows the importance
of this parameter in the prediction of the transition
temperature (TN) of these molecules and similar
ones.
The S0→S1transition in all three molecules
corresponds mainly to H→L orbitals with 68%, 66%
and 66% for the C8, C14 and C16 respectively.
The oscillator strength value corresponds to this
transition in the C8 molecule shows the highest
value of 0.2347 among the three molecules (Table
3). This gives an indication that this molecule has
the highest flexibility for the electronic transition. All
of the molecules under investigation possess same
photo stability in the UV region.
CONCLUSION
In this work, electronic structure properties
for homologous 4(4-(4-chlorobenzoyloxy)phenyl 4
(n-alkoxy)benzoate(n =8,14,16) series have been
calculated using quantum chemical methods.
Relationships between these properties and
experimentally measured parameters related to the
liquid crystal behavior were established and used to
account for the photo stability of these molecules.
In the molecules studied here, the ovality was found
to be an important factor that could be used to
investigate the effect of structure on the transition
temperature.
Quantitative property relationship
Correlation coefficient matrix has been
obtained between the different molecular descriptors
and the transition temperature, and the results are
shown in Table 4. The dipole moment is another
important parameter of these compounds and
plays an important role in the stabilization of these
mesomorphic states. As the chain length increase,
the value of the dipole moment for the liquid crystal
homologous compounds under investigation found
to be changed.The value of the dipole moment was
found to be affected by the change of the dihedral
angles (Ф and θ). Table 4 shows the correlation
coefficients for the dipole moment with these dihedral
ACKNOWLEDGEMENT
The authors would like to thank the institute
of scientific research and Revival of Islamic Heritage
at Umm Al-Qura University, project ID (43405048)
for the financial support.

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