Synthesis and investigation of the properties of novel azocalix[4]arenes

Article abstract of DOI:10.1016/j.saa.2015.01.132

The azocalix[4]arenes molecules such as methylphenylazocalix[4]aren (MPcalix[4]) and methoxyphenylazocalix[4]aren (MOPcalix[4]) have been synthesized and characterized by experimental FT-IR and ¹H NMR spectral analyses. The fundamental vibrational transitions have been addressed by experimental FT-IR (4000-400 cm^-1) technique and density functional theory (DFT) employing B3LYP level with the 6-31G(d) and 6-311G(d,p) basis sets. The ¹H NMR spectra of the studied compounds have been recorded in chloroform, and compared with computed data obtained by using gauge including atomic orbital (GIAO) method. Furthermore, thermodynamic properties (heat capacity, entropy, and enthalpy changes) and frontier molecular orbitals of the molecules in the ground state have been calculated by using the same method and basis sets. The non-linear optical properties such as the first order hyperpolarizability (β₀), related properties (α₀ and Δα) are also computed. Information about the charge density distribution of the molecules and its chemical reactivity has been studied by mapping molecular electrostatic potential surface (MEPs). The scaled vibrational frequency values have been compared with experimental FT-IR spectroscopic data. The correlations between the observed and calculated frequencies are in good agreement with each other as well as the correlation of NMR data. The linear polarizability and first hyperpolarizability of the studied molecules indicate that the compounds are a good candidate of nonlinear optical materials.

Full text of DOI:10.1016/j.saa.2015.01.132

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 146 (2015) 151–162
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis and investigation of the properties of novel azocalix[4]arenes
H.H. Kart a, A. Bayrakdar a, S. Elcin b, H. Deligoz b, M. Karabacak c,
⇑
a Department of Physics, Pamukkale University, 20017, Kinikli, Denizli, Turkey
b Department of Chemical Engineering, Pamukkale University, 20017, Kinikli, Denizli, Turkey
c Department of Mechatronics Engineering, H.F.T. Technology Faculty, Celal Bayar University, 45400, Turgutlu, Manisa, Turkey
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
The azocalix[4]arenes molecules such as methylphenylazocalix[4]aren (MPcalix[4] (a)) and
methoxyphenylazocalix[4]aren (MOPcalix[4] (b)) have been synthesized and characterized by using
the experimental techniques and the quantum chemical computational method such as DFT employing
B3LYP level with the 6-31G(d) and 6-311G(d,p) basis sets.
ꢀ
The methylphenylazocalix[4]aren and
methoxyphenylazocalix[4]aren have
been synthesized.
Spectroscopic features of the
compounds have been examined by
FT-IR, 1H and 13C NMR techniques and
DFT method.
ꢀ
OH
OH
OH
OH
OH
OH
HO
HO
ꢀ
Thermodynamic features, nonlinear
optical properties and frontier
molecular orbitals have been
calculated.
N
N
N
N
N
N
N
N
H3C
H3CO
CH3
OCH3
(a)
(b)
a r t i c l e i n f o
a b s t r a c t
Article history:
The azocalix[4]arenes molecules such as methylphenylazocalix[4]aren (MPcalix[4]) and methoxyphenylazo-
calix[4]aren (MOPcalix[4]) have been synthesized and characterized by experimental FT-IR and 1H NMR
spectral analyses. The fundamental vibrational transitions have been addressed by experimental FT-IR
(4000–400 cmꢁ1) technique and density functional theory (DFT) employing B3LYP level with the 6-
31G(d) and 6-311G(d,p) basis sets. The 1H NMR spectra of the studied compounds have been recorded
in chloroform, and compared with computed data obtained by using gauge including atomic orbital
(GIAO) method. Furthermore, thermodynamic properties (heat capacity, entropy, and enthalpy changes)
and frontier molecular orbitals of the molecules in the ground state have been calculated by using the
same method and basis sets. The non-linear optical properties such as the first order hyperpolarizability
Received 31 October 2014
Received in revised form 6 January 2015
Accepted 29 January 2015
Available online 28 February 2015
Keywords:
Calixarene
FT-IR and NMR spectra
DFT
HOMO–LUMO
NLO and MEP
(b0), related properties (a0 and Da) are also computed. Information about the charge density distribution
of the molecules and its chemical reactivity has been studied by mapping molecular electrostatic poten-
tial surface (MEPs). The scaled vibrational frequency values have been compared with experimental FT-IR
spectroscopic data. The correlations between the observed and calculated frequencies are in good agree-
ment with each other as well as the correlation of NMR data. The linear polarizability and first
hyperpolarizability of the studied molecules indicate that the compounds are a good candidate of nonlin-
ear optical materials.
Ó 2015 Elsevier B.V. All rights reserved.
⇑
Corresponding author. Tel.: +90 236 314 10 10.
E-mail address: mehmet.karabacak@cbu.edu.tr (M. Karabacak).
http://dx.doi.org/10.1016/j.saa.2015.01.132
1386-1425/Ó 2015 Elsevier B.V. All rights reserved.

152
H.H. Kart et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 146 (2015) 151–162
basis sets [35]. Therefore, some scaling factors are used to
Introduction
Calixarenes,
eliminate the systematic errors in the force constants and frequen-
cies and provide better agreement with the observed ones. The
geometry optimization of the molecules is an important factor to
determine the NMR chemical shifts [36].
a
well-known family of macrocyclic phenol
formaldehyde oligomers, have been attracting the interest of
chemists for more than three decades. As these compounds repre-
sent readily available and precisely defined three-dimensional
structures, they found numerous applications in supramolecular
chemistry [1,2]. The unproblematic derivatization of the calix[4]
arene skeleton together with the controllable shape of the cavity
makes this molecule an ideal molecular scaffold for the construc-
tion of various receptors. Due to their excellent complexation
abilities, calix[4]arenes are frequently used for the design of novel
selective complexation agents. Depending on the substitution
pattern and the conformation, calix[4]arenes bind cations [3–5],
anions [6,7] and/or neutral compounds [8] via non covalent
The purpose of this work is to study the synthesis, experimental
and theoretical characterization of the compounds of MPcalix[4]
and MOPcalix[4]. The molecular structure, thermodynamics data,
frontier molecular orbitals, molecular electrostatic potential
(MEP), non-linear optical (NLO) properties, vibrational and NMR
spectra of ones are calculated by using the ab initio quantum
chemical method based on DFT with the basis sets of 6-31G(d)
and 6-311G(d,p). The experimental and theoretical calculations
can be very useful to make the correct assignment and understand-
ing the basic vibrational, NMR spectra and molecular structure
relations. A discussion on the experimental and theoretical studies
of these chemical compounds leads ones to a better analyzing of
the insight of them. Moreover, the results predicted from in this
work can be helpful in further studies of the compounds.
The paper is organized as follows; synthesizes and character-
ization of MPcalix[4] and MOPcalix[4] are presented in
‘Experimental Section’ as well as experimental details. The theo-
retical method used this work are introduced and the computa-
tional details are given in ‘Computational details Section’. The
quantum chemical ab initio simulation results for structural,
electronic and vibrational properties of the compounds such as
MPcalix[4] and MOPcalix[4] considered in this study are presented
and discussed in ‘Results and discussion Section’. The results pre-
dicted from theoretical methods are compared with the whenever
available experimental data in ‘Results and discussion Section’.
Finally, ‘Conclusion Section’ deals with the summary and conclu-
sions arising from this work.
interactions (cation–
bonds, electrostatic interactions, coordination bonds, van der
Waals interactions, etc.).
p interactions, p–p interactions, hydrogen
Diazo coupling reactions of chromogenic calix[4]arene which has
within the molecule an azophenol moiety as a coloration site have
been studied by Morita et al. [9] and Shinkai et al. [10] and they have
described the resulting NMR spectra. Ab initio studies of NMR
chemical shifts for calix[4]arene and its derivatives have been done
by Kara et al. [11]. Kurt et al. [12] synthesized calix[4]arene derivate
molecule and investigated the spectroscopic features with FT-IR,
FT-Raman, dispersive Raman and NMR. In our recent work, we have
synthesized a vic-dioxime derivative of calix[n]arene and have
studied its complexes [13,14], polymeric calix[n]arene derivatives
and selective extraction of transition metal cations [15,16].
The experimental studies and theoretical calculations on the
structural and vibrational properties of the azocalix[4]arenes mole-
cules such as MPcalix[4] and MOPcalix[4] are insufficient in the
literature. In order to interpret the experimental studies on the
azocalix[4]arenes, it should be done the complete theoretical stud-
ies of the molecular structure, thermodynamics properties, frontier
molecular orbitals, molecular electrostatic potential, non-linear
optical properties, vibrational and NMR spectra of them. The theo-
retical studies of the compounds provide ones to get the important
information about the physical and chemical properties of them.
Ab initio methods such as DFT and Hartree–Fock (HF) in the
computational chemistry are important theoretical tools to predict
the physical and chemical properties of molecules [17,18]. The
solution of the electronic Schrodinger equation is essential to the
applications of these methods to chemical problems in the ab initio
calculations. The development of fast digital computers has opened
the possibility of solving the electronic Schrodinger equation while
utilizing approximations for interesting systems [19]. Theoretical
calculations can allow ones to suggest frequencies that can be used
as fingerprint for the compounds. They can also make the band
assignments as well as the understanding of the relationship
between the observed spectral features and the molecular struc-
ture [20]. HF and DFT methods based on quantum mechanics are
widely used to determine the molecular structure, thermodynamic
properties, frontier molecular orbitals, molecular electrostatic
potential, non-linear optical properties, fundamental vibrational
modes and NMR spectra for small and large sized chemical mole-
cules at low computational cost [21–32]. In our previous studies
[11,33,34], we have also used these methods to investigate
structural, vibrational and NMR properties of the calix[4]arenes,
azocalix[4]arenes and dithiophosphonates.
Experimental
Materials
All of the chemical reagents and solvents used in this work are
of analytical grade purity and used without further purification. All
aqueous solutions are prepared with deionized water purified by
Human Power Plus I + UV water purification system.
Equipment
The vibrational frequencies of the title compounds by using the
FT-IR spectroscopy are measured in this work. The FT-IR spectrum
is recorded by a Perkin–Elmer 2000 FT-IR spectrophotometer in the
range of 4000–400 cmꢁ1. The 1H NMR spectrum is recorded on a
Bruker AVANCE DRX 400 NMR spectrometer in the medium of
chloroform.
Synthesis
We have synthesized p-tert-butylcalix[4]arene as a starting
material through the base catalyzed condensation reaction [37].
Di-benzoyl-tetra-p-tert-butylcalix[4]arene, di-benzoyl-di-p-tert-butyl-
calix[4]arene, 11,23-di-p-tert-butylcalix[4]arene, 25,26,27,28-tetrahy-
droxy-11,23-di-(tert-butyl)-5,17-(4-methoxyphenylazo)calix[4]arene
and 25,26,27,28-tetrahydroxy-11,23-di-(tert-butyl)-5,17-(4-methyl-
phenylazo)calix[4]arene are synthesized (Scheme 1) as described
in our previous study [38].
The harmonic vibrational frequencies calculated from the
ab initio quantum chemistry methods are usually larger than the
ones of experimental measurements. It is well known that this is
due to the neglect of anharmonic effects in the methods used in
computational chemistry. Errors are also coming from the incom-
plete incorporation of electron correlation and using the finite
Computational details
To provide complete information regarding to the structural
parameters, the fundamental vibrational modes, the chemical

H.H. Kart et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 146 (2015) 151–162
153
O
C
O
+
Pyridine
+
NaOH
+
C
Cl
H
O
H
Reflux
Ice bath
HO
O
OH
OH
O
HO
OH
OH
OH
O
C
O C
AlCl
3
Phenol
Toluene
rt
R
R
NaOH
N
NaNO2 / HCl
N
N
N
DMF / THF
THF / Water / EtOH
Reflux
H2N
R
+
HO
O
O
OH
Ice bath
O
C
O C
HO
OH
OH
OH
HO
OH
OH
OH
a)
R=
b)
-CH3
-OCH3
Scheme 1. Synthesis of (a) MPcalix[4] and (b) MOPcalix[4].
shifts, electronic structure properties, nonlinear optical features
and thermodynamic calculations of the compounds to be studied
in this work we have performed quantum chemical calculations
in the framework of DFT and Becke’s three parameter hybrid
exchange functional with Lee–Yang–Parr correlation functional
(B3LYP) method with 6-31G(d) and 6-311G(d,p) basis sets [39,40].
The Gaussian 09 software package program [40] is used to be
employed for the quantum chemical calculations. DFT methods
including hybrid functions have been frequently used because they
are fast and cheaper methods for theoretical quantum mechanical
calculations. Especially, selection of the accurate hybrid functions
of DFT increases efficiently. Molecular structures of MPcalix[4]
and MOPcalix[4] are optimized to get the global minima at the
level of ab initio DFT/B3LYP with the basis sets of 6-31G(d) and
6-311G(d,p) by considering C1 symmetry point group.
After optimizing process, the same basis sets and computational
method are used to calculate the vibrational spectra of MPcalix[4]
and MOPcalix[4] by utilizing the optimized structural parameters.
There are no imaginary frequency modes calculated from the opti-
mized geometry for the title compounds. This is due to the fact that
there is a minimum energy configuration of them on the potential
energy surface. The vibrational frequency modes calculated from
ab initio methods are typically larger than the fundamental
observed ones. This is due to the neglect of anharmonic effects in
the theoretical calculations. Incomplete incorporation of electron
correlation and the basis sets used in the calculations result into
the systematic errors. The overestimation of the ab initio harmonic
vibrational frequencies is relatively uniform, and as a result generic
frequency scaling factors are generally applied to compare
theoretical and experimental frequencies [41]. Therefore, in this
work, the frequency values that are calculated theoretically by
6-31G(d) and 6-311G(d,p) basis sets are scaled by 0.9613 and
0.9679 scaling factor [36], respectively, in order to determine the
vibrational spectra of the molecule accurately. The fundamental
vibrational frequencies are observed via the Gauss-View 5.0.8
molecular visualization software program [42] and made for
assignments of the experimental band in details.
The calculation procedure is also used to predict the 1H and 13
C
NMR shielding constants by applying the GIAO-DFT method [40] in
the medium of chloroform and compared with the experimental
NMR spectra.
Frontier molecular orbitals (HOMO–LUMO) are analyzed so that
they give us the information about the charge transfer between
energy levels in the molecules. HOMO and LUMO energy levels
are calculated by DFT/B3LYP method with the basis sets of
6-31G(d) and 6-311G(d,p). To investigate the reactive sites of the
compounds, the MEP is evaluated by using the DFT method.
Thermodynamic properties of the title molecules are also deter-
mined with the vibrational frequency analyzes. NLO features such
as the static dipole moment (
l), the mean polarizability (
a0), the
anisotropy of the polarizability (
D
a
) and the mean first order
hyperpolarizability (b0) values of the title molecules are also
calculated by using the finite field approach by using the same
method and basis sets.
Results and discussion
Molecular geometry
The chemical structures of MPcalix[4] and MOPcalix[4] are
shown in Fig. 1(a) and (b), respectively. The optimized structures
of these chemical materials by utilizing DFT/B3LYP/6-311G(d,p)
method with atom numbering schemes are represented in
Fig. S1(a) and (b), respectively. The geometries of these compounds
are possessing C1 point group symmetry. These molecules consist
of 110 and 112 atoms and they have 324 and 330 fundamental
vibrational modes according to the 3N-6 rule, respectively.
Structural properties
The some structural parameters such as bond lengths, bond
angles of MPcalix[4] and MOPcalix[4] studied in this work
determined from DFT/B3LYP level with 6-31G(d) and 6-311G(d,p)

154
H.H. Kart et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 146 (2015) 151–162
OH
OH
OH
OH
OH
HO
OH
HO
N
N
N
N
N
N
N
N
(b)
(a)
H3C
H3CO
CH3
OCH3
Fig. 1. Chemical structures of (a) MPcalix[4] and (b) MOPcalix[4].
according to the relationships of thermodynamic function and esti-
mate direction of chemical reactions according to the second law of
thermodynamics in thermochemical field [43].
Table 1
Some selected optimized geometrical parameters of MPcalix[4] in the ground state.
Parameters via
Gaussian
Bond lengths (Å)
DFT/B3LYP/6-
31G(d)
DFT/B3LYP/6-
311G(d,p)
Analysis of frontier molecular orbitals
R(10–33)
R(17–36)
R(13–52)
R(20–51)
R(55–54)
R(67–53)
R(17–18)
R(85–86)
R(51–53)
R(52–54)
R(33–34)
R(36–37)
R(57–12)
R(107–110)
C10–O33
C17–O36
C13–N52
C20–N51
C55–N54
C67–N53
C17–C18
C85–C86
N51–N53
N52–N54
O33–H34
O39–H37
C57–H62
C107–H110
1.347
1.374
1.426
1.434
1.431
1.433
1.410
1.540
1.249
1.253
0.985
0.987
1.088
1.095
1.347
1.391
1.430
1.433
1.434
1.429
1.408
1.542
1.243
1.248
0.977
0.986
1087
1.094
The most important frontier molecular orbitals (FMOs) such as
highest occupied molecular orbital (HOMO) and lowest unoccu-
pied molecular orbital (LUMO) are important part in the chemical
stability of the molecule. The FMOs play an important role in the
optical and electric properties as well as in UV–vis spectrum and
chemical reactions [44]. The energy difference between HOMO
and LUMO orbital is called as an energy gap that is important for
the stability of structures [45] and reveals the chemical activity
of the molecule. The HOMO represents the ability to donate an
electron and LUMO as an electron acceptor represents the ability
of accept an electron [46]. The energy gap between the HOMO
and the LUMO also determines the chemical reactivity, optical
polarizability and chemical hardness–softness of a molecule [46].
The HOMO and LUMO energies are predicted at DFT/B3LYP level
with the 6-31G(d) and 6-311G(d,p) basis sets for the chemical
compounds of MPcalix[4] and MOPcalix[4] (see Table 3). The
distributions and energy levels of the HOMO and LUMO orbitals
and corresponding density of state (DOS) for the materials of
MPcalix[4] and MOPcalix[4] are shown in Figs. 2 and 3, respec-
tively. The energy differences between the HOMO and LUMO of
the MPcalix[4] and MOPcalix[4] molecules considered in this work
for the basis set of 6-311G(d,p) are found as 3.520 and 3.175 eV.
The energy gap between HOMO and LUMO describes the chemical
reactivity, optical polarizability, kinetic stability, and chemical
softness–hardness of a molecule. The chemical hardness is a good
indicator of the chemical stability. The molecules having a small
energy gap are known as soft and having a large energy gap are
known as hard molecules [20]. The chemical hardness value
(1.587 eV) of MOPcalix[4] is smaller than that of MPcalix[4], which
is (1.760 eV). As a result, MPcalix[4] is harder than MOPcalix[4].
Bond angles (°)
A(1–2–3)
A(1–6–5)
C1–C2–C3
C1–C6–C5
C2–C1–C6
123.0
121.9
117.3
119.8
122.9
113.0
119.3
122.6
124.9
117.4
108.6
109.2
108.3
112.7
114.9
107.4
122.7
119.3
117.0
120.3
117.4
120.6
117.2
125.2
124.1
123.3
122.2
122.2
108.7
112.5
112.5
109.0
A(2–1–6)
A(2–1–39)
A(6–1–39)
A(1–39–9)
A(1–6–35)
A(21–20–51)
A(67–53–51)
A(1–2–7)
A(1–39–40)
A(1–39–41)
A(6–35–84)
A(10–33–34)
A(17–36–37)
A(30–38–83)
C2–C1–C39
C6–C1–C39
C1–C39–C9
C1–C6–O35
C21–C20–N51
C67–N53–N51
C1–C2–H7
C1–C39–H40
C1–C39–H41
C6–O35–H84
C10–O33–H34
C17–O36–H37
C30–O38–H83
as basis sets are presented in Tables 1 and 2, respectively.
Experimental data on the geometric structure of the compounds
are not available in literature. Therefore, they cannot be compared
with the experimental data. As shown in Tables 1 and 2, the bond
lengths and bond angles of these compounds computed from DFT/
B3LYP level with both 6-31G(d) and 6-311G(d,p) basis sets are
compatible with each other.
Analysis of molecular electrostatic potential
The molecular electrostatic potential surface is very useful to
understand the relative polarity of the compounds [47]. It also
serves as useful quantity to explain hydrogen bonding, reactivity
and structure–activity relationship to the molecules [48]. The
MEPs at a point r in the space around a molecule (in atomic units)
can be expressed as;
Thermodynamic analysis
The thermodynamic parameters of the azocalix[4]arene mole-
cules such as MPcalix[4] and MOPcalix[4] have been computed
by using the DFT/B3LYP level with the basis sets of 6-31G(d) and
6-311G(d,p) and they are presented in Table S1. As shown in
Table S1, thermodynamic parameters such as zero point energy,
rotational constants, thermal energy, molar capacity at constant
volume and entropy are given. All the thermodynamic data supply
helpful information for further study on azocalix[4]arenes. They
can be used to compute the other thermodynamic energies
Z
0
X
~
ZA
q
ðr Þ
VðrÞ ¼
ꢁ
d3r0
A
0
~
~
~
~
jr ꢁ rj
jRA ꢁ rj
where ZA is the charge on nucleus A, located at RA and
q
ðr0Þ is
the electronic density function of the molecule, and r0 is the
dummy integration variable. The first and second terms represent

H.H. Kart et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 146 (2015) 151–162
155
Table 2
Some selected optimized geometrical parameters of MOPcalix[4] in the ground state.
Parameters via
Gaussian
Bond lengths (Å)
DFT/B3LYP/6-
31G(d)
DFT/B3LYP/6-
311G(d,p)
R(10–33)
R(17–36)
R(70–104)
R(105–104)
R(20–51)
R(67–53)
R(10–11)
R(17–22)
R(51–53)
R(36–37)
R(14–16)
R(91–92)
R(42–44)
R(105–106)
C10–O33
C17–O36
C70–O104
C105–O104
C20–N51
C67–N53
C10–C11
C17–C22
N51–N53
O36–H37
C14–H16
C91–H92
C42–H44
C105–H106
1.349
1.375
1.362
1.421
1.434
1.431
1.410
1.410
1.251
0.987
1.085
1.096
1.097
1.098
1.347
1.372
1.361
1.423
1.433
1.431
1.408
1.406
1.245
0.980
1.082
1.093
1.094
1.095
Bond angles (°)
A(1–2–3)
A(1–6–5)
A(2–1–6)
A(2–1–39)
A(6–1–39)
A(1–39–9)
A(1–6–35)
A(13–52–54)
A(20–51–53)
A(58–103–109)
A(70–104–105)
A(1–39–41)
A(1–39–40)
A(1–2–7)
A(17–36–37)
A(6–35–76)
A(10–33–34)
A(30–38–75)
C1–C2–C3
C1–C6–C5
C2–C1–C6
C2–C1–C39
C6–C1–C39
C1–C39–C9
C1–C6–O35
C13–N52–N54
C20–N51–N53
C58–O103–C109
C70–O104–C105
C1–C39–H41
C1–C39–H40
C1–C2–H7
C17–O36–H37
C6–O35–H76
C10–O33–H34
C30–O38–H75
123.0
121.9
117.3
119.9
122.8
114.0
119.4
126.4
124.5
118.3
118.3
108.9
108.5
117.4
114.8
108.2
112.6
107.4
122.8
119.6
117.2
119.9
117.4
120.4
117.3
126.7
125.1
118.4
118.6
122.0
122.4
123.0
115.2
108.6
113.0
107.8
Table 3
Frontier molecular orbital energies, ionization potential (I), electron affinity (A), global
electronegativity (
v
), total hardness (
g
), and global softness (S) of MPcalix[4] and
MOPcalix[4].
MPcalix[4]
MOPcalix[4]
B3LYP/6-
31G(d)
B3LYP/6-
311G(d,p)
B3LYP/6-
31G(d)
B3LYP/6-
311G(d,p)
EHOMO (eV)
ELUMO (eV)
ꢁ5.235
ꢁ1.923
3.312
5.235
1.923
3.579
1.656
0.302
ꢁ5.604
ꢁ2.084
3.520
5.604
2.084
3.844
1.760
0.284
ꢁ5.001
ꢁ1.849
3.152
5.001
1.849
3.425
1.576
0.317
ꢁ5.230
ꢁ2.056
3.175
5.230
2.056
3.643
1.587
0.317
D
E (eV)
I (eV)
A (eV)
v
g
(eV)
(eV)
S (eVꢁ1
)
Fig. 2. The frontier molecular orbital energies and corresponding DOS spectrum of
MPcalix[4].
the contributions to the potential due to the nuclei and electrons,
respectively. V(r) is the resultant electrical potential at each point
r, which is the electrostatic effect produced at the point r by both
the electrons and the nuclei of the molecule. GaussView 5.0.8
visualization program [42] has been used to construct the MEP
surface and the shape of the frontier molecular orbitals.
blue-electron deficient or partially positive charge; light blue-
slightly electron deficient region; yellow-slightly electron rich
region, respectively. These maps confirm the different negative
and positive potential sites of the molecules in accordance with
the total electron density surface. The iso-electron density and
MEPs clearly indicate the probable sites for the electrophilic and
nucleophilic reactions as well as hydrogen-bonding interaction
[49–51]. As can be seen from the MEP map of the title molecules,
the N@N atoms reflect the most electronegative region (red region)
and have excess negative charge, and the hydrogen atoms have
positive charge.
The total electron density surface mapped with electrostatic
potential for MPcalix[4] and MOPcalix[4] calculated from DFT level
with the basis set 6-311G(d,p) is shown in Figs. 4(a) and 5(a),
respectively. The molecular electrostatic potential surfaces and
the contour maps of molecular electrostatic potential surface of
MPcalix[4] and MOPcalix[4] molecules predicted from DFT/B3LYP
method with the basis set of 6-311G(d,p) are also given in
Figs. 4(b and c) and 5(b and c), respectively. The color scheme for
the MEPs is red-electron rich or partially negative charge;

156
H.H. Kart et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 146 (2015) 151–162
of b are defined as the coefficients in Taylor series expansion of
the energy in the external electric field. When the external electric
field is weak and homogeneous, the expansion is given as;
1
2
1
6
E ¼ E0 ꢁ laFa
ꢁ
aabFaFb ꢁ ba FaFbFc þ . . .
b
c
where, E0 is the energy of the unperturbed molecules, F the
a
field at origin, la
polarizability and first hyperpolarizability, respectively. The static
dipole moment ( ), the mean polarizability ( 0) the anisotropy of
the polarizability ( ) and the mean hyperpolarizability (b0) by
, aab and b are the components of dipole moment,
abc
l
a
Da
using x, y and z components are calculated. The mathematical details
used for the calculations were reported in our earlier publications
[53,54].
The values of the polarizabilities (a) and hyperpolarizability (b)
of the Gaussian 09 output are calculated in the atomic unit (a.u).
Therefore, the calculated values are converted into electrostatic
units (esu) (for
a
: 1 a.u. = 0.1482 ꢂ 10ꢁ24 esu; and for b: 1 a.u =
8.639 ꢂ 10ꢁ33 esu) and given in Table 4. The higher values of dipole
moment, molecular polarizability, and hyperpolarizability are
important for more active non-linear optic properties. The com-
puted dipole moment of MPcalix[4] is equal to 5.181 Debye (D)
and 4.081 Debye (D) for the 6-31G(d) and 6-311G(d,p) basis sets,
respectively. The highest value of dipole moment of MPcalix[4]
for the basis set of 6-31G(d) is observed for the component of ly
.
The computed dipole moments of MOPcalix[4] for the basis sets
of 6-31G(d) and 6-311G(d,p) are found as 6.829 D and 6.980 D,
respectively. It is observed that the component of ly of
MOPcalix[4] is also highest value for the 6-311G(d,p). The
calculated polarizability aa has non-zero and zero values and
b
dominated by diagonal components as seen in Table 4.
The total polarizability (a0) of MPcalix[4] is calculated as
84.39 ꢂ 10ꢁ24 esu for the basis set of 6-31G(d), 90.25 ꢂ 10ꢁ24 esu
for the basis set of 6-311G(d,p), respectively. The total polarizabil-
ity (a
0) of MOPcalix[4] is further found as 86.31 ꢂ 10ꢁ24 esu for the
basis set of 6-31G(d), 91.80 ꢂ 10ꢁ24 esu for the basis set of
6-311G(d,p), respectively. The calculation of the b component
provides us very useful information about the direction of
charge delocalization. The first hyperpolarizability values of (b0)
of MPcalix[4] and MOPcalix[4] molecules are computed as
12.52 ꢂ 10ꢁ30 esu, 11.10 ꢂ 10ꢁ30 esu, 4.31 ꢂ 10ꢁ30 esu, and
5.80 ꢂ 10ꢁ30 esu for the 6-31G(d) and 6-311G(d,p), respectively.
The first hyperpolarizability values of bxxx for MPcalix[4] and
MOPcalix[4] molecules are evaluated as 885.6 ꢂ 10ꢁ30 esu and
906.6 ꢂ 10ꢁ30 esu for the basis set of 6-31G(d), respectively. The
large value of particular component bxxx indicates charge delocal-
ization along this direction. The large value of hyperpolarizability
b0 is the meaning of the measurement of non-linear optical activity
of the molecular system. When comparing the hyperpolarizability
values of MPcalix[4] and MOPcalix[4], it is concluded that
MPcalix[4] molecule has more non-linear optical response. Also
the first hyperpolarizability of the title molecules, which are more
than bo of urea, indicates that MPcalix[4] and MOPcalix[4]
molecules possess nonlinear optical properties and are potential
candidates for nonlinear optical applications.
Fig. 3. The frontier molecular orbital energies and corresponding DOS spectrums of
MOPcalix[4].
Non-Linear optical properties
The non-linear optical parameters such as dipole moment,
polarizability, anisotropy polarizibity and first order hyperpolarizabil-
ity of MPcalix[4] and MOPcalix[4] molecules are calculated by
using DFT/B3LYP level with 6-31G(d) and 6-311G(d,p) basis sets.
The numerical values of mentioned parameters are listed in
Table 4. In the presence of an applied electric field, the energy of
a system is a function of electric field. The first hyperpolarizability
is a third rank tensor that can be described by a 3 ꢂ 3 ꢂ 3 matrix.
The 27 compounds of the 3D matrix can be reduced to 10
compounds due to the Kleinman symmetry [52]. The compounds
Analysis of vibrational spectra
The investigation of the vibrational frequencies via ab initio
computational methods is becoming increasingly important tools
in the area of chemistry. Theoretically predicted frequencies can
serve ones to determine the fingerprints of the chemical com-
pounds. In the present study, we have performed a frequency
calculation analysis to obtain the spectroscopic signatures of
MPcalix[4] and MOPcalix[4] molecules. They consist of 110 and
112 atoms, respectively. Therefore they have 324 and 330

H.H. Kart et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 146 (2015) 151–162
157
Fig. 4. (a) Total electron density surface mapped with electrostatic potential, (b) the
molecular electrostatic potential surface and (c) the contour map of molecular
electrostatic potential surface of MPcalix[4].
Fig. 5. (a) Total electron density surface mapped with electrostatic potential, (b) the
molecular electrostatic potential surface and (c) the contour map of molecular
electrostatic potential surface of MOPcalix[4].
vibrational normal modes for MPcalix[4] and MOPcalix[4], respec-
tively. Theoretical calculations of infrared spectrum from DFT/
B3LYP level with the basis sets of 6-31G(d) and 6-311G(d,p) for
MPcalix[4] and MOPcalix[4] molecules and their corresponding
experimental spectra are plotted in Figs. 6(a–c) and 7(a–c),
respectively.
Some specific and important vibrational modes of the theoreti-
cal data computed from DFT method and their corresponding
experimental values are given in Tables 5 and 6 along with the
assignments of fundemental vibration modes. Assignments of the
vibrational modes are made on the basis of observation of
molecules by using GaussView visualization program [42] and
interpreted by means of PED by using VEDA 4 program [55].
All calculated wavenumbers are scaled by using the scaling
factors as 0.9614 and 0.9679 for the basis sets of 6-31G(d) and
6-311G(d,p) [41], respectively, as shown in Tables 5 and 6.
Whenever available experimental results are also given in the
same table to compare them with the corresponding theoretical
results.
The correlation graphs of frequency between the experimental
and calculated wavenumbers for MPcalix[4] calculated from DFT/
B3LYP level with 6-31G(d) and 6-311G(d,p) basis sets are shown
in Fig. S2(a) and (b), respectively. The same graphs for
MOPcalix[4] molecule by using the same method with the same
basis sets are plotted in Fig. S2(c) and (d), respectively. The correla-
tion between the experimental and the calculated frequencies after
scaling are linear. The equalities for MPcalix[4] are found as
m
cal. = 1.01mexp. ꢁ 16.45 (R2 = 0.9733) and
mcal. = 0.99mexp. + 6.09
(R2 = 0.9997) by using the method of DFT/B3LYP with the basis sets
of 6-31G(d) and 6-311G(d,p), respectively. The equalities for

158
H.H. Kart et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 146 (2015) 151–162
Table 4
The first hyperpolarizability b0 (ꢂ10ꢁ33 esu), electric dipole l0 (Debye), average
polarizability a0 (ꢂ10ꢁ24 esu) of MPcalix[4] and MOPcalix[4] molecules.
MPcalix[4]
6-31G(d)
MOPcalix[4]
6-31G(d)
6-311G(d,p)
6-311G(d,p)
bxxx
bxxy
bxyy
byyy
bxxz
bxyz
byyz
bxzz
byzz
bzzz
b0
lx
ly
lz
l0
axx
axy
ayy
axz
ayz
azz
a0
885.6
398.2
ꢁ368.1
371.8
549.2
ꢁ49.7
99.7
ꢁ299.9
ꢁ59.9
274.7
906.6
293.9
ꢁ750.7
ꢁ341.7
355.7
ꢁ121.0
ꢁ22.8
ꢁ48.1
151.5
142.6
4.31
ꢁ1.818
6.414
ꢁ1.481
6.829
640.56
26.40
642.17
23.50
36.65
464.49
86.31
26.21
814.6
506.8
ꢁ759.9
ꢁ435.5
398.0
ꢁ101.8
ꢁ1.3
ꢁ193.1
635.2
ꢁ70.5
187.3
31.4
17.5
ꢁ43.2
141.6
240.4
5.80
226.4
256.8
12.52
ꢁ0.555
4.617
ꢁ2.284
5.181
631.97
18.61
600.49
25.61
33.92
475.91
84.39
21.18
ꢁ139.0
401.6
11.10
ꢁ3.778
ꢁ1.305
ꢁ0.825
4.081
686.09
40.43
611.60
ꢁ8.39
ꢁ38.20
529.19
90.25
ꢁ2.110
6.500
ꢁ1.440
6.980
674.07
20.93
684.01
18.34
36.94
500.13
91.80
26.54
D
a
20.15
Fig. 6. (a) Experimental, (b) and (c) the calculated infrared spectra of MPcalix[4] by
using B3LYP method with the basis sets of 6-31G(d) and 6-311G(d,p), respectively.
MOPcalix[4] are also predicted as
mcal. = 0.99m
exp + 13.78 (R2 =
0.9980) and
m
cal. = 1.01mexp ꢁ 6.23 (R2 = 0.9984) by using the
method of DFT/B3LYP with the basis sets of 6-31G(d) and
6-311G(d,p), respectively. It can be concluded that the frequency
values obtained from the basis set of 6-311G(d,p) for the molecules
studied in this work are closer to the experimental data than that
of obtained through the 6-31G(d) basis set, since the slope and the
intercept values in the case of 6-311G(d,p) basis set goes to unity
and zero, as shown in Fig. S2(b) and (d), respectively.
There are some important vibrations of MPcalix[4] to be
focused on it. For example, the aliphatic C–H stretching vibrations
(for CH, CH2, CH3) of the chemical material MPcalix[4] are mea-
sured in the range of 2954–3071 cmꢁ1. The values of the scaled
C–H stretching vibrations are computed in the ranges of 2941–
3072 cmꢁ1 and 2953–3072 cmꢁ1 by using DFT/B3LYP level with
the basis sets of 6-31G(d) and 6-311G(d,p), respectively. The strong
strecthing vibrations assigned to C@C is found at 1604 cmꢁ1. The
computed value of C@C stretching vibration is calculated at
1601 cmꢁ1 and at 1598 cmꢁ1 by using DFT/B3LYP method with
the basis sets of 6-31G(d) and 6-311G(d,p), respectively. A very
strong band at 1458 cmꢁ1 is experimentally observed in case of
N@N stretching vibration in FT-IR spectrum, which is in agreement
with the simulated results at 1525 cmꢁ1 (for 6-31G(d)) and
1534 cmꢁ1 (for 6-311G(d,p)), respectively. The values of the strech-
ing bands of O-H are measured from 3205 to 3421 cmꢁ1. The
corresponding theoretical data are found in the range of 3271–
3578 cmꢁ1 and from 3185 to 3338 cmꢁ1 by using DFT method with
the basis sets of 6-31G(d) and 6-311G(d,p), respectively. The some
vibrations of of MPcalix[4] are given in [40] with the theoretical
data predicted from DFT/B3LYP method with the basis sets of
6-31G(d) and 6-311G(d,p).
Fig. 7. (a) Experimental, (b) and (c) the calculated infrared spectra of MOPcalix[4]
by using B3LYP method with the basis sets of 6-31G(d) and 6-311G(d,p),
respectively.
using DFT/B3LYP/6-31G(d) method and at 1597 cmꢁ1 by using
DFT/B3LYP/6-311G(d,p) level. In case of N@N stretching vibration,
a very strong band at 1457 cmꢁ1 in FT-IR spectrum is attributed the
N@N stretching vibration, which is in agreement with the
simulated result at 1534 cmꢁ1 (for 6-31G(d)) and 1525 cmꢁ1 (for
6-311G(d,p)). The observed band at 1145 cmꢁ1 is assigned to
C–O stretching vibration. The corresponding theoretical data are
found as 1243 cmꢁ1 and 1231 cmꢁ1 for the band of C–O stretching
For the material of MOPcalix[4], the aliphatic C–H stretching
vibrations (CH, CH2, CH3) are observed in the region 2872–
2959 cmꢁ1. The scaled aliphatic C–H stretching vibrations in the
ranges of 2932–2966 cmꢁ1 and 2909–2952 cmꢁ1 are calculated
by using DFT/B3LYP level with the basis sets of 6-31G(d) and 6-
311G(d,p), respectively. There is
a strecthing vibration at
1601 cmꢁ1, assigned to C@C stretching vibration. The computed
data for C@C stretching vibration is calculated at 1613 cmꢁ1 by

H.H. Kart et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 146 (2015) 151–162
159
Table 5
Some selected vibrational wavenumbers (cmꢁ1) of MPcalix[4] obtained from B3LYP/6-31(d) and B3LYP/6-311(d,p), experimental frequencies (cmꢁ1) from FT-IR spectrum, IR
Intensities (km molꢁ1), and assignment with TED percentage in square brackets.
Mode no.
Exp.
B3LYP/6-31G(d) frequency
B3LYP/6-311G(d,p) frequency
Assignment P 10%
Unscaled
Scaled
IIR
Unscaled
Scaled
IIR
324
323
322
321
311
308
307
306
305
304
303
284
283
282
272
259
235
230
229
227
225
219
215
214
204
197
11
191
175
170
169
168
165
152
139
136
131
125
118
114
112
111
109
104
96
3421
3346
3228
3205
3071
3066
3061
3056
3037
3027
3007
2963
2958
2954
1604
1458
1438
1420
1406
1395
1388
1363
1340
1306
1275
1243
1218
1203
1120
1063
1053
1039
1014
944
3722
3494
3433
3403
3195
3183
3181
3179
3177
3132
3129
3065
3065
3059
1665
1586
1512
1468
1463
1458
1451
1425
1366
1357
1328
1281
1258
1243
1166
1128
1119
1075
1063
974
3578
3359
3301
3271
3072
3060
3058
3056
3055
3011
3009
2947
2946
2941
1601
1525
1454
1411
1406
1402
1395
1370
1313
1305
1277
1231
1209
1195
1121
1084
1076
1034
1022
936
53.33
509.78
1748.1
181.72
5.47
15.86
11.71
13.24
20.86
2.59
31.21
28.23
23.8
21.15
2.02
252.33
0.58
8.99
5.33
2.5
2.04
3.1
4.8
10.04
2.39
3449
3425
3357
3291
3174
3164
3160
3159
3159
3108
3103
3054
3052
3051
1651
1585
1487
1464
1459
1437
1433
1409
1398
1339
1318
1283
1258
1245
1155
1117
1109
1061
1048
975
3338
3315
3249
3185
3072
3062
3058
3058
3058
3008
3003
2956
2954
2953
1598
1534
1439
1417
1413
1391
1387
1364
1353
1296
1275
1242
1217
1205
1118
1081
1073
1027
1014
944
337.96
1455.25
2187
43.48
7.73
ˆOH(98)
ˆOH(99)
ˆOH(98)
ˆOH(99)
ˆCH(97)
ˆCH(92)
ˆCH(85)
ˆCH(90)
ˆCH(95)
ˆasymCH2(90)
ˆasymCH2(90)
ˆsymCH2(95)
ˆsymCH2(95)
ˆsymCH2(95)
ˆCCring(65), dCCHring(25)
ˆNN(65), ˆCCring(20), dCCHring(15)
dCH3(55), sCH2(20)
dCOH(40), ˆCCring(28), sCH2(18), dCCHring(13)
dCOH(35), ˆCCring(28), dCCHring(13)
sCH3(60), dCCHring(25)
dCH3(75)
dCH3(60)
dCH3(85)
tCH2(25), ˆCCring(20), dCCHring(15)
ˆCCring(40), dCCHring(35)
dCCHring(35), ˆCCring(25), dCOH(15)
dCCHring(30), ˆCCring(20), dCOH(15)
dCCHring(25), tCH2(25), ˆCO(20), ˆCCring(20)
dCCHring(30), ˆCCring(25), ˆCN(20)
ˆCCring(20), tCH2(20), dCCHring(15)
tCH2(25), ˆCCring(20), dCCHring(20)
8.31
14.3
20.02
12.26
11.9
15.26
20.05
22.83
25.58
2.35
72.53
42.13
18.42
4.42
1.00
4.58
0.13
5.54
1.49
2.08
1.34
1.24
11.97
5.91
2.32
11.77
58.08
58.97
20.67
0.02
29.36
6.12
18.2
8.57
20.5
xCH3(58)
xCH3(68)
xCH3(62)
0.18
3.25
0.06
1.77
900
887
875
825
785
760
739
725
712
676
618
608
938
925
901
850
806
773
754
741
725
696
633
625
902
889
867
818
775
743
725
713
697
669
608
601
931
917
904
846
808
783
765
754
732
698
642
613
901
888
875
819
782
758
740
730
708
675
622
610
34.87
12.68
35.17
3.53
65.42
62.46
7.43
0.93
5.07
3.3
5.56
c
c
c
c
c
c
CH2(30), dCOH(23)
10.78
16.42
6.32
12.24
13.82
15.25
10
CHring(35){
CHring(45){
CHring(90){
CHring(30){
CHring(25){
s
s
s
s
s
CCCH},
CCCH}
CCCH}
CCCH}, dCOH(25)
CCCH}, dCOH(22)
xCH2(10)
dCOH(22),
c
CH2(20),
c
CHring(15){
HCCH}, CH2(18)
HCCH}, dCOH(22)
sCCCH}
c
c
c
c
c
CHring(24){
s
s
s
s
CCCH,
CCCH,
s
s
c
4.51
CHring(28){
CHring(30){
CHring(20){
14.05
11.98
5.22
CCCH,} ˆ{C–CH3}(24)
CCCC, CCCH}, ˆsymCNN(18)
CCCH}, {C–CH3}(10)
s
95
2.44
CH2(22),
c
CHring(20){
s
c
92
88
85
600
560
536
601
561
542
578
540
521
1.59
4.71
2.11
606
573
556
587
554
538
1.59
1.62
3.22
ˆCCring(24), dCCHring(18), dCOH(17),
dCOH(16), ˆCCring(15), dCCHring(10)
dCOH(35), ˆCCring(20), dCCHring(20),
c
CH2(15)
c
CH2(15)
84
83
82
79
526
518
510
492
541
532
524
503
520
511
504
483
1.7
12.99
3.24
543
541
526
513
526
523
510
497
2.95
2.09
10.74
5.49
c
c
c
c
CHring(25){
CHring(34){
CHring(20){
CHring(25){
sCCCH,
sCCCH,
sCCCC,
sCCCC,
s
HCCH}, dCCN(18),
cCH3(10)
sHCCH}, CH3(10), dCCN(10)
c
sCCCH}, dCCN(20),
c
CH3(10), dCCN(10)
CH2(15), dCCN(10)
2.25
s
CCCH}, dCCN(20),
c
78
76
75
481
469
447
500
472
449
481
453
432
3.96
2.75
7.94
498
477
469
482
461
454
0.42
5.11
1.82
ˆCCring(20), dCCHring(20),
s
CCCC(15),
CCCN(20)
CHring(15){sCCCH}
sCCCH(10)
sCCCC(25),
CH3(20),
s
c
c
ˆ: Stretching, ˆsym: symmetric stretching, ˆsym: asymmetric stretching, d: deformation,
x: wagging, s: torsion, t: twisting, c: rocking, s: scissoring.
vibration by using DFT method with the basis sets of 6-31G(d) and
6-311G(d,p), respectively. The other observed vibrations of the
compound of MOPcalix[4] are explicitly given in Table 6 along with
the theoretical values computed from DFT/B3LYP level with the
basis sets of 6-31G(d) and 6-311G(d,p). The values of the streching
bands of O–H are measured in the range from 3178 cmꢁ1 to
3703 cmꢁ1. The corresponding theoretical data are found in the
range of 3303–3603 cmꢁ1 and from 3355 cmꢁ1 to 3684 cmꢁ1 via
DFT method with the basis sets of 6-31G(d) and 6-311G(d,p),
respectively.
this work. Therefore, it is shown that only characteristic vibration
bands for the materials studied in this work can be identified as
shown in Tables 5 and 6. But we added all frequencies in Tables
S2 and S3.
NMR Spectra
NMR study is an exceptional tool to elucidate structure and con-
formation of the molecules. 1H and 13C NMR spectroscopies are
used to characterize the compounds. In this work, the experimen-
tal 1H NMR spectroscopy is only used to characterize the chemical
compounds of MPcalix[4] and MOPcalix[4]. DFT shielding
It is to say that it is generally difficult to assign all bands due to
the complex of the vibrational bands of the molecules studied in

160
H.H. Kart et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 146 (2015) 151–162
Table 6
Some selected vibrational wavenumbers (cmꢁ1) of MOPcalix[4] obtained from B3LYP/6-31(d) and B3LYP/6-311G(d,p), experimental frequencies (cmꢁ1) from FT-IR Spectrum, IR
Intensities (km molꢁ1), and assignment with TED percentage in square brackets.
Mode no.
Exp.
B3LYP/6-31G(d) frequency
B3LYP/6-311G(d,p) frequency
Assignment P 10%
Unscaled
Scaled
IIR
Unscaled
Scaled
IIR
330
328
327
290
279
278
273
270
268
265
242
236
234
232
229
226
222
221
218
210
206
202
178
176
172
171
170
170
165
163
161
157
144
139
136
132
130
121
119
117
115
108
101
100
99
3703
3420
3178
2959
2872
1601
1582
1570
1560
1457
1438
1419
1406
1395
1388
1362
1339
1308
1294
1273
1252
1145
1120
1103
1066
1057
1032
1032
1006
979
964
942
902
888
876
839
818
786
761
740
726
676
618
608
598
550
3723
3447
3413
3065
3030
1666
1652
1636
1621
1584
1511
1481
1468
1462
1458
1427
1388
1365
1353
1330
1312
1293
1172
1146
1129
1122
1077
1077
1058
1025
1004
975
939
917
905
873
863
807
784
765
741
699
640
631
625
563
530
497
3603
3336
3303
2966
2932
1613
1599
1584
1569
1534
1463
1433
1421
1415
1412
1381
1343
1321
1310
1288
1270
1243
1135
1109
1093
1086
1043
1043
1024
992
972
944
908
888
876
845
835
781
758
741
717
677
619
611
605
545
51.71
1570.32
240.98
28.98
42.46
69.6
3.49
6.45
2.91
188.79
0.14
3807
3498
3466
3050
3006
1650
1637
1622
1606
1575
1484
1467
1454
1446
1432
1402
1374
1348
1335
1315
1296
1272
1162
1135
1116
1110
1060
1060
1046
1021
997
972
932
917
906
871
842
805
793
760
742
695
640
632
625
562
529
3684
3386
3355
2952
2909
1597
1584
1570
1555
1525
1437
1420
1407
1400
1386
1357
1330
1305
1292
1273
1254
1231
1125
1099
1081
1074
1026
1026
1012
988
965
941
902
888
877
843
815
779
768
735
718
673
620
612
605
544
76.44
1560.55
254.41
28.48
43.43
51.14
8.27
ˆOH(98)
ˆOH(99)
ˆOH(98)
ˆsymCH2(96)
ˆsymCH3(99)
ˆCCring(65), dCCHring(25)
ˆCCring(45), dCCHring(25), dCOH(25)
ˆCCring(40), dCOH(30), dCCHring(20)
ˆCCring(60), dCCHring(25)
ˆNN(65), ˆCCring(20), dCCHring(15)
dCH3(80)
dCOH(35), ˆCCring(28), sCH2(18), dCCHring(13)
dCOH(40), sCH2(20), ˆCCring(15), dCCHring(15)
dCCHring(45), ˆCCring(40), sCH2(20)
dCH3(75)
11.9
13.88
192.3
0.05
20
11.45
7.29
4.2
1.81
9.31
5.76
7.02
32.3
36.19
195.22
18.56
8.02
21.01
9.8
5.23
3.56
16.44
12.32
5.85
dCH3(70)
dCOH(55)
x
x
CH2(20), dCCHring(15), ˆCCring(10)
CH2(75)
4.23
41.19
39.21
157.29
21.36
6.99
59.01
13.93
46.34
46.34
0.53
dCCHring(25), ˆCCring(15)
dCCHring(25), ˆCCring(15), dCOH(15),
ˆOC(60), ˆCCring(20), dCCHring(15)
ˆCCring(26), dCCHring(24)
xCH2(10)
dCCHring(35), ˆCCring(20)
57.4
ˆCCring(20), dCCHring(20), tCH2(20),
ˆCCring(20), dCCHring(20), tCH2(15),
ˆOC(35), ˆCCring(25), dCCHring(25)
ˆOC(35), ˆCCring(25), dCCHring(25)
x
CH3(10)
22.77
49.46
49.46
0.49
0.19
1.14
0.65
4.23
12.75
9.75
46.86
49.63
80.08
13.25
71.35
25.43
14.34
8.03
16.86
10.19
14.59
7.08
xCH3(15)
x
CH3(68)
dCCHring(30), ˆCCring(25)
ˆCCring(20), ˆC–CH2(20), dCCHring(20),
0.07
3.06
0.06
0.51
x
CH3(10)
CH2(14), dCCN(13)
{C–CH3}(16), CH2(10)
{C–CH3}(15)
c
c
c
c
c
c
c
c
CHring(27){
CHring(25){
CHring(38){
CHring(42){
CHring(25){
CHring(35){
CHring(35){
CHring(31){
s
s
s
s
s
s
s
s
CCCH},
CCCH},
x
x
x
2.73
CCCH, HCCH},
s
c
11.23
65.18
25.09
16.29
4.63
71.86
11.59
112.24
7.86
11.85
5.12
14.71
2.65
CCCH, sHCCH}
CCCH}, dCNN(15), xCH2(10)
CCCH}, dCOH(32), dCNN(15)
CCCH}, dCOH(32), dCNN(15)
CCCH, sHCCH}, xCH2(20), dCOH(18)
dCOH(35), ˆCCring(20), dCCHring(20)
c
c
c
c
c
CHring(26){
CHring(28){
CHring(40){
CHring(40){
CHring(37){
sCCCH,
sCCCH,
sCCCH,
sCCCH,
sCCCH,
s
s
s
s
s
HCCH}, dCOC(16), ˆ{C–CH3}(13)
HCCH}, CH3(21), dCOC(16), dCCN(13)
HCCH}, dCCN(20)
x
HCCH},
HCCH},
c
c
CH2(20), dCCN(20)
CH2(15), {C–CH3}(13)
x
92
86
80
79
77
69
dCOH(33),
c
CHring(22){
s
CCCH}, dCCN(15)
HCCH}, CH3(20), dCOC(16), dCCN(13)
HCCH}, dCCO(16), CH3(14), dCCN(10)
526
479
457
442
513
481
461
444
512
480
460
442
c
c
c
c
c
CHring(36){
sCCCH,
sCCCH,
sCCCH,
sCCCH,
s
s
s
s
x
7.72
0.55
4.34
5.97
496
475
457
416
9.63
0.81
5.24
6.09
CHring(30){
CHring(27){
CHring(24){
x
476
458
416
HCCH}, dCCO(18), dCCN(14),
HCCH}, dCCO(21), dCCN(18)
xCH3(10)
403
402
403
CH3(20),
c
CHring(15){
sCCCH}
ˆ: Stretching, ˆsym: symmetric stretching, ˆsym: asymmetric stretching, d: deformation,
x: wagging,
s
: torsion, t: twisting,
c: rocking, s: scissoring.
calculations are also rapid and applicable to large molecular sys-
tems. The GIAO 1H and 13C chemical shift calculations with respect
to tetramethylsilane (TMS) are carried out by using the DFT/B3LYP
with the basis sets of 6-31G(d) and 6-31G(d,p) in the medium of
chloroform (CDCl3) for utilizing the optimized structures of the
title molecules. The computed NMR results of 1H and 13C NMR
shielding constants by applying the GIAO DFT/B3LYP method are
given in Table 7 and Table S4, respectively, along with the available
experimental data. 1H NMR spectrum of the compounds are
recorded in the medium of CDCl3. In addition, we have investigated
the correlation between the calculation and experiment for 1H
NMR spectra to compare the computed and experimental data.
The linear correlation coefficients (R2) are obtained by using the
experimental 1H NMR chemical shift values and the data for DFT/
B3LYP method. Linear regression is carried out by using the linear
equation of y = A + Bx, where A and B are fit constants. The graphs
of the linear correlation of 1H for DFT/B3LYP with the basis sets of
6-31G(d) and 6-311G(d,p) for the chemical materials of MPcalix[4]
and MOPcalix[4] are shown in Fig. S3, respectively. The correlation
values for 1H chemical shifts are computed as (R2 = 0.8764) and
(R2 = 0.9733) by using DFT/B3LYP level with the basis sets of
6-31G(d) and 6-311G(d,p), respectively, for the chemical material
of MPcalix[4]. For the chemical material of MOPcalix[4], the
correlation values are found as (R2 = 0.8676) and (R2 = 0.8657). It
is shown that the relationships between the experimental and
calculated 1H chemical shifts for the DFT/B3LYP level with the
6-31G(d) and 6-311G(d,p) basis sets for the materials of
MPcalix[4] and MOPcalix[4] are approximately compatible with
the each other in the solvent of CDCl3.
It will be good to explain the some 1H NMR spectrum of the
materials of MPcalix[4] and MOPcalix[4] at this point. 1H NMR data
show that MPcalix[4] and MOPcalix[4] exist in a cone conformation

H.H. Kart et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 146 (2015) 151–162
161
Table 7
compound in its cone conformation. As seen in Tables, it is known
that bridge methylene groups in the calix[4]arene have the same
environment, therefore, it is expected the same values of the
chemical shift. However, the experiments on the calix[4]arenes
have shown that axial (H41, H44, H46 and H49) and equatorial
protons (H43, H47, H40 and H50) of bridge methylene groups in
the calix[4]arene have different values of chemical shifts. This is
due to the axial protons which are affected by ring current causing
the resonance of the axial protons at the lower magnetic field as
explained in Ref. [57]. This situation is also proved by using density
functional method used in this work.
Experimental and calculated values of 1H NMR chemical shifts (ppm) in chloroform
for MPcalix[4] and MOPcalix[4].
MPcalix[4]
MOPcalic[4]
Atoms 6-31G(d) 6-311G(d,p) Exp. Atoms 6-31G(d) 6-311G(d,p) Exp.
H7
H8
6.44
6.07
7.71
6.12
7.02
5.65
7.05
6.74
8.89
8.20
2.43
4.13
2.84
3.43
3.86
3.29
3.99
3.31
6.81
7.18
7.01
5.97
7.13
7.38
5.86
6.49
1.80
2.15
1.89
1.91
1.92
2.26
7.59
2.97
0.66
0.59
0.65
1.08
0.91
0.55
0.83
1.30
0.66
6.96
6.50
7.83
6.05
7.61
6.05
7.60
7.27
10.39
10.54
2.82
3.84
3.09
3.97
4.31
3.61
4.19
3.62
6.16
7.11
7.64
7.74
7.56
7.89
5.88
6.51
1.73
2.37
2.23
2.26
2.14
2.57
9.91
9.53
0.66
0.67
0.99
1.15
0.80
0.58
0.88
1.15
0.70
0.93
1.36
1.37
1.52
0.81
0.98
1.06
0.97
1.49
7.17 H7
7.17 H8
6.45
6.12
7.44
6.26
6.97
5.65
7.00
6.77
8.63
8.09
2.57
4.15
2.85
3.46
3.87
3.27
4.04
3.27
7.15
6.74
6.24
6.07
6.54
7.52
5.96
5.96
7.61
3.01
0.74
0.52
0.65
1.01
0.90
0.72
0.76
1.14
0.64
0.72
1.05
1.17
1.16
0.57
0.81
6.70
6.43
8.10
6.61
7.58
6.09
7.38
7.13
9.54
9.21
2.81
4.56
3.09
3.88
4.23
3.55
4.37
3.56
7.64
7.35
6.73
6.42
6.98
8.09
6.37
6.51
8.54
3.06
0.94
0.63
0.74
1.03
0.94
0.67
0.82
1.25
0.68
0.87
1.18
1.31
1.28
0.60
0.90
1.01
0.92
1.42
3.62
4.01
3.69
3.48
4.00
3.94
7.17
7.17
7.61
7.61
7.61
7.61
7.17
7.17
10.28
10.28
3.65
4.31
3.65
4.31
4.31
3.65
4.31
3.65
7.77
6.95
6.95
7.77
6.95
6.95
7.77
7.77
10.28
10.28
1.24
1.24
1.24
1.24
1.24
1.24
1.24
1.24
1.24
1.24
1.24
1.24
1.24
1.24
1.24
1.24
1.24
1.24
3.84
3.84
3.84
3.84
3.84
3.84
H15
H16
H23
H24
H31
H32
H34
H37
H40
H41
H43
H44
H46
H47
H49
H50
H61
H62
H63
H64
H71
H72
H73
H74
H76
H77
H78
H80
H81
H82
H83
H84
H87
H88
H89
H91
H92
H93
H95
H96
H97
7.63 H15
7.63 H16
7.63 H23
7.63 H24
7.17 H31
7.17 H32
10.29 H34
10.29 H37
3.65 H40
4.32 H41
3.65 H43
4.32 H44
4.32 H46
3.65 H47
4.32 H49
3.65 H50
7.67 H61
7.24 H62
7.24 H63
7.67 H64
7.24 H71
7.67 H72
7.67 H73
7.24 H74
2.38 H75
2.38 H76
2.38 H79
2.38 H80
2.38 H81
2.38 H83
10.29 H84
10.29 H85
1.23 H87
1.23 H88
1.23 H89
1.23 H92
1.23 H93
1.23 H94
1.23 H96
1.23 H97
1.23 H98
Conclusion
The experimental and theoretical characterizations of the azo-
calix[4]arene (MPcalix[4] and MOPcalix[4]) molecules are success-
fully carried out by using FT-IR, NMR spectra and quantum
chemical calculations. In conclusion, the following results arising
from this work can be summarized as:
1. DFT calculations on MPcalix[4] and MOPcalix[4] molecules are
presented for the first time in this work.
2. Structural properties such as bond lengths and angles of azo-
calix[4]arene molecules are investigated.
3. Thermodynamic properties (heat capacity, entropy, and
enthalpy changes) and frontier molecular orbitals of the title
molecules in the ground state have been calculated by using
DFT method.
4. The first order hyperpolarizability (b0) and related properties (b,
a0 and
Da) are also computed by using DFT calculations.
Information about the charge density distributions of the mole-
cules and its chemical reactivity has been studied by mapping
molecular electrostatic potential surface.
5. The recorded FT-IR and the calculated vibrational wavenumbers
of MPcalix[4] and MOPcalix[4], along with their relative inten-
sities and probable assignments are given in Tables. Assignments
proposed here for the fundamental bands observed in the
experimental vibration spectra of the compounds studied in
this work, which are based on the computed and scaled
wavenumbers via DFT/B3LYP/6-311G(d,p), are consistent with
literature.
H100 0.73
H101 1.09
H102 1.17
H104 1.15
H105 0.56
H106 0.81
H108 0.92
H109 0.88
H110 1.36
1.23 H100 0.91
1.23 H101 0.86
1.23 H102 1.31
1.23 H106 3.39
1.23 H107 3.69
1.23 H108 3.47
1.23 H110 3.30
1.23 H111 3.70
1.23 H112 3.64
6. The harmonic frequencies calculated from DFT based on quan-
tum mechanics deviate from the frequencies, slightly. The
observed disagreement between the theoretical and experi-
mental results could be a consequence of the anharmonicity
and of the general tendency of the quantum chemical methods
to overestimate of the force constants at the exact equilibrium
geometry. Furthermore, the one reason of discrepancy between
the observed and the calculated frequencies is that the experi-
mental results belong to solid phase while the theoretical
calculations have been calculated in the gaseous phase. The
another one is that the calculations have been actually
performed on a single molecule contrary to the experimental
values recorded in the presence of intermolecular interactions.
7. The correlation equalities of the frequency for the compound of
due to the appearance of ArCH2Ar as a typical AB type proton signal
at 3.65, 4.32 ppm and 3.65, 4.31 ppm (J = 13 Hz), respectively.
Moreover, two signals at 1.23 and 1.24 ppm in 1H NMR each for
18 protons of the molecules of MPcalix[4] and MOPcalix[4] as
shown in Table 7 show the presence of t-butyl groups having
different environment, i.e., two of the p-tert-butylphenolic rings
are substituted with bulky groups and the other two have got
hydroxyl groups. All these results are in agreement with the litera-
ture reports as a proof for cone conformation [56]. Moreover, the
results of 1H NMR could be correlated with each other. For
instance, 1H NMR spectrum of MPcalix[4] could be correlated with
the signal at the pair of doublets at 3.65 and 4.32 ppm (J = 13 Hz)
for ArCH2Ar protons. Similarly, singlet at 7.17 ppm for ArHpara pro-
tons observed in 1H NMR spectrum correlated well with the signal.
This specific correlation pattern indicates that 4 is a symmetrical
MPcalix[4] are predicted as
m
cal. = 1.01mexp. ꢁ 16.45 (R2 = 0.9733)
and cal. = 0.99m
m
exp. + 6.09 (R2 = 0.9997) by using the method of
DFT/B3LYP with the basis sets of 6-31G(d) and 6-311G(d,p),
respectively. The correlation equalities for MOPcalix[4] are also
predicted as mcal. = 0.99m mcal. = 1.01-
exp + 13.78 (R2 = 0.9980) and
mexp ꢁ 6.23 (R2 = 0.9984) by using the method of DFT/B3LYP
with the basis sets of 6-31G(d) and 6-311G(d,p), respectively.
It is shown that the values of the frequency obtained from the
basis set of 6-311G(d,p) for the molecules are closer to the
experimental data.

162
H.H. Kart et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 146 (2015) 151–162
8. The 1H and 13C NMR chemical shifts have been calculated by
using the DFT/B3LYP level with the basis sets of 6-31G(d) and
6-311G(d,p). The 1H NMR chemical shifts are compatible with
the experimental data in the solvent of CDCl3.
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