N′-(2-methoxy-benzylidene)-N-[4-(3-methyl-3-phenyl-cyclobutyl) -thiazol-2-yl]-chloro-acetic hydrazide: X-ray structure, spectroscopic characterization and DFT studies

Article abstract of DOI:10.1016/j.molstruc.2012.05.059

In this work, the structure of N′-(2-methoxy-benzylidene)-N-[4-(3- methyl-3-phenyl-cyclobutyl)-thiazol-2-yl]-chloro-acetic hydrazide, (C ₂₄H₂₄ClN₃O₂S), was characterized by X-ray single crystal diffraction technique, IR-NMR spectroscopy and quantum chemical computational methods as both experimental and theoretically. The compound crystallizes in the orthorhombic space group P na2₁ with a = 14.4170 (4) A, b = 11.5441 (4) A, c = 27.8420 (8) A and Z = 8. X-ray study shows that crystal has two independent molecules in the asymmetric unit. The molecular geometry was also optimized using density functional theory (DFT/B3LYP) method with the 6-311G(d,p) basis set and compared with the experimental data. To determine conformational flexibility, molecular energy profile of the tittle compound was obtained by semi-empirical (AM1) with respect to selected degree of torsional freedom, which was varied from -180° to +180° in steps 10°. From the optimized geometry of the molecule, vibrational frequencies, gauge-independent atomic orbital (GIAO) ¹H and ¹³C NMR chemical shift values, molecular electrostatic potential (MEP) distribution, non-linear optical properties, frontier molecular orbitals (FMOs) of the title compound have been calculated in the ground state theoretically.

Full text of DOI:10.1016/j.molstruc.2012.05.059

Journal of Molecular Structure 1026 (2012) 117–126
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
N0-(2-methoxy-benzylidene)-N-[4-(3-methyl-3-phenyl-cyclobutyl)-thiazol-2-yl]-
chloro-acetic hydrazide: X-ray structure, spectroscopic characterization
and DFT studies
a,
a
b
b
⇑
_
Ersin Inkaya , Muharrem Dinçer , Öner Ekici , Alaaddin Cukurovali
a Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University, Kurupelit, 55139 Samsun, Turkey
b Department of Chemistry, Faculty of Science Fırat University, 23200 Elazıg˘, Turkey
h i g h l i g h t s
"
"
"
IR-NMR spectroscopy and X-ray single crystal diffraction.
Cyclobutane, DFT(B3LYP)/6-311G(d,p).
Non-linear optical properties of the title compound have been calculated.
a r t i c l e i n f o
a b s t r a c t
In this work, the structure of N0-(2-methoxy-benzylidene)-N-[4-(3-methyl-3-phenyl-cyclobutyl)-thiazol-
2-yl]-chloro-acetic hydrazide, (C24H24ClN3O2S), was characterized by X-ray single crystal diffraction tech-
nique, IR-NMR spectroscopy and quantum chemical computational methods as both experimental and
theoretically. The compound crystallizes in the orthorhombic space group P na21 with a = 14.4170
(4) Å, b = 11.5441 (4) Å, c = 27.8420 (8) Å and Z = 8. X-ray study shows that crystal has two independent
molecules in the asymmetric unit. The molecular geometry was also optimized using density functional
theory (DFT/B3LYP) method with the 6-311G(d,p) basis set and compared with the experimental data. To
determine conformational flexibility, molecular energy profile of the tittle compound was obtained by
semi-empirical (AM1) with respect to selected degree of torsional freedom, which was varied from
ꢀ180° to +180° in steps 10°. From the optimized geometry of the molecule, vibrational frequencies,
gauge-independent atomic orbital (GIAO) 1H and 13C NMR chemical shift values, molecular electrostatic
potential (MEP) distribution, non-linear optical properties, frontier molecular orbitals (FMOs) of the title
compound have been calculated in the ground state theoretically.
Article history:
Received 7 February 2012
Received in revised form 23 May 2012
Accepted 23 May 2012
Available online 31 May 2012
Keywords:
X-ray structure determination
IR and NMR spectroscopy
DFT calculations
Cyclobutane
Non-linear optical properties
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
p-conjugated, exhibit interest as materials for wide spectrum
applications, particularly as corrosion inhibitors [9], catalyst carri-
ers [10,11], thermo-stable materials [12–14], a metal ion complex-
ing agents [15] and in biological systems [16–18]. The Schiff base
compounds have been also under investigation during last years
because of their potential applicability in optical communications
and many of them have NLO behavior [19,20].
Due to the developments in computational chemistry over the
past decade, research into the theoretical modeling of drug design,
functional material design, etc., has become much more mature.
Many important chemical and physical properties of biological
and chemical systems can be predicted from first principles using
various computational techniques [21]. In recent years, density
functional theory (DFT) has been a shooting star in theoretical
modeling. The development of better and better exchange–correla-
tion functional has made it possible to calculate many molecular
properties with accuracy comparable to traditional correlated ab
The chemistry of aminothiazoles and their derivatives has at-
tracted the attention of chemists, because they exhibit important
biological activity in medicinal chemistry [1], such as antibiotic,
anti-inflammatory, antihelmintic, or fungicidal properties [2–4].
2-Aminothiazoles are known mainly as biologically active com-
pounds with a broad range of activities and as intermediates in
the synthesis of antibiotics, well-known sulfa drugs, and some dyes
[5,6]. In addition, it has been shown that 3-substituted cyclobutane
carboxylic acid derivatives exhibit anti-inflammatory and antide-
pressant activities [7] and also liquid crystal properties [8].
Azomethines (known as Schiff-bases), having imine groups
(CH@N) and benzene rings in the main chain alternately, and being
⇑
Corresponding author. Tel.: +90 362 3121919/5256; fax: +90 362 4576081.
E-mail address: ersin.inkaya@oposta.omu.edu.tr (E. Inkaya).
_
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.05.059

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118
E. Inkaya et al. / Journal of Molecular Structure 1026 (2012) 117–126
Table 1
initio methods, at more favorable computational cost [22].
A survey of the literature revealed that DFT has great accuracy in
reproducing the experimental values for the geometry, dipole mo-
ment, vibrational frequency, etc. [23–29].
Crystal data and structure refinement parameters for the title compound.
Color/shape
Light brown
C24H24ClN3O2S
453.97
Chemical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell parameters
a, b, c (Å)
In this paper, we report the synthesis, characterization and
296
crystal structure of N0-(2-methoxy-benzylidene)-N-[4-(3-methyl-
0.71073 Mo K
Orthorhombic
P na21
a
3-phenyl-cyclobutyl)-thiazol-2-yl]-chloro-acetic hydrazide, (C24
-
H24ClN3O2S), as well as theoretical studies using the DFT/B3LYP/
6-311G(d,p) method. The aim of the present work was to describe
and characterize the molecular structure, vibrational properties
and chemical shifts of the title compound, both experimentally
and theoretically. A comparison of the experimental and theoreti-
cal spectra can be very useful in making correct assignments and
understanding the basic chemical shift-molecular structure rela-
tionship. Molecular electrostatic potential (MEP), frontier molecu-
lar orbitals (FMOs), conformational flexibility and nonlinear optical
properties of the title compound were studied at the B3LYP/6-
311G(d,p) level. We also make comparisons between experimental
and calculated values.
14.4170 (4), 11.5441 (4), 27.8420 (8)
4633.8 (2)
8
1.302
0.28
1904
Volume (Å3)
Z
Dcalc (g/cm3)
l
(mmꢀ1
)
F(000)
Crystal size (mm3)
Diffractometer/measurement
method
0.78 ꢁ 0.49 ꢁ 0.11
STOE IPDS 2/x scan
Index ranges
ꢀ17 6 h 6 17, ꢀ14 6 k 6 14,
ꢀ33 6 l 6 33
h Range for data collection (°)
Reflections collected
Independent/observed reflections
Rint
1.5 6 h 6 25.6
32,624
4469/3266
0.080
2. Experimental and theoretical methods
Refinement method
Full-matrix least-squares on F2
4469/1/559
Data/restraints/parameters
Goodness-of-fit on F2
1.00
2.1. Experimental
R indices [I > 2
R indices (all data)
qmin (e/Å3)
CCDC deposition no.
r
(I)]
R1 = 0.0430, wR2 = 0.0814
R1 = 0.0650, wR2 = 0.0886
0.14, ꢀ0.13
2.1.1. General remarks
D
qmax, D
The melting points were determined in open capillary tubes on
a digital Gallenkamp melting point apparatus and are uncorrected.
The IR spectrum of the tittle compound was recorded in the range
4000–400 cmꢀ1 using a Mattson 1000 FT-IR spectrometer with KBr
pellets. The 1H and 13C nuclear magnetic resonance (NMR) spectra
were recorded on a Varian-Mercury-Plus 400 MHz spectrometer
using TMS as internal standard and CDCl3 (chloroform) as solvent.
815,994
using SHELXL-97 [31], implemented in the WinGX [32] program
suite. Non-hydrogen atoms were refined with anisotropic displace-
ment parameters. All H atoms were located in a difference Fourier
map and were refined isotropically. Data collection: Stoe X-AREA
[33], cell refinement: Stoe X-AREA [33], data reduction: Stoe X-
RED [33]. The general-purpose crystallographic tool PLATON [34]
was used for the structure analysis and presentation of the results.
The structure was refined to Rint = 0.080 with 3266 observed reflec-
2.1.2. Synthesis
A solution of 0.3775 g (1 mmol) of N-(2-methoxybenzylidene)-
N0-[4-(3-methyl-3-phenyl-cyclobutyl)-thiazol-2-yl]-hydrazine was
dissolved in 20 mL 1,4-dioxane containing 1 mmol triethylamine.
tions using I > 2r(I) threshold. The programs DIAMOND [35] and
ORTEP-3 [32] for Windows were used preparation of the figures.
Details of the data collection conditions and the parameters of
the refinement process are given in Table 1.
To this solution, 90 lL (1 mmol) chloro acetyl chloride in 10 mL
1,4-dioxane was added dropwise for 2-h period at the room tem-
perature with stirring. The compound thus precipitated was fil-
tered, washed with copious water, and crystallized from ethanol.
The shiny crystals suitable for X-ray analysis was obtained by slow
evaporation from its alcoholic solution. Yield: 63% M.p.: 395 K
(Fig. 1).
2.2. Theoretical
The molecular structure of the compound in the ground state
(in vacuo) was optimized using density functional theory (DFT/
B3LYP) method with the 6-311G(d,p) basis set. All the calculations
were performed without specifying any symmetry for the title
molecule by using Gauss View molecular visualization program
[36] and Gaussian 03 program package [37]. For modeling, the ini-
tial guess of the compound was first obtained from the X-ray coor-
dinates. The harmonic vibrational frequencies were calculated at
the same level of theory for the optimized structure A and the ob-
tained frequencies were scaled by 0.9669 [38]. The geometry of the
compound, together with that of tetramethylsilane (TMS), was
fully optimized. 1H and 13C NMR chemical shifts were calculated
using the standard GIAO/B3LYP/6-311G(d,p) (Gauge-Independent
Atomic Orbital) approach [39,40] with the Gaussian 03 program
package. The predicted 1H and 13C NMR chemical shifts were de-
2.1.3. Crystallography
The single-crystal X-ray data were collected on a STOE IPDS II
image plate diffractometer at 296 K. Graphite-monochromated
Mo Ka radiation (k = 0.71073 Å) and the w-scan technique were
used. The structure was solved by direct methods using SHELXS-
97 [30] and refined through the full-matrix least-squares method
rived from the equation d = R0
ꢀ
R, where d is the chemical shift,
R
is the absolute shielding and R0 is the absolute shielding of
the standard (TMS), whose values are 31.99 and 184.79 ppm for
B3LYP/6-311G(d,p). The effect of solvent on the theoretical NMR
parameters was included using the default model IEF-PCM
(Integral-Equation-Formalism Polarizable Continuum Model) [41]
provided by Gaussian 03. Chloroform was used as solvent.
Fig. 1. The structure of the title compound.

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E. Inkaya et al. / Journal of Molecular Structure 1026 (2012) 117–126
119
In order to describe conformational flexibility of the title molecule,
the selected torsion angles u1 (C6AC1AC7AC9) and u2 (S1A
C14AN2AN3), was varied from ꢀ180° to ꢀ180° in every 10° and
the molecular energy profile as a function of the selected torsional
degree of freedom is obtained by performing single point
calculations on the calculated potential energy surface, and the
molecular energy profile was obtained at the AM1 calculations.
For the calculation of MEP [42,43], the same level theory B3LYP/
6-311G(d,p) were used. The mean linear polarisability and mean
first hyperpolarisability properties of the title compound were ob-
tained using molecular polarisabilities based on theoretical
calculations.
There are two obviously different CAN bond distances in the
thiazole rings. One of them N1AC14 bond lengths are indicative
of a significant double bond character for molecules A and B. Addi-
tionally, the C12AC13 bond distances are 1.347 (6) Å and 1.359
(6) Å for both molecules, respectively. According to this results,
C12AC13 bonds characterizing a C@C double bond. The S1AC13
and S1AC14 bond lengths are shorter than the accepted value for
an SACsp2 single bond (1.76 Å; [46]), resulting from the conjuga-
tion of the electrons of atom S1 with atoms C13 and C14.
In the molecular structure of the title compound, the inter-
atomic distance between thiophene atom S1 and the carboxyl
atom O2 are 2.681 Å and 2.608 Å for both molecules, which are less
than the sum of the atomic van der Waals radii for sulfur and
oxygen, 1.80 and 1.52 Å, respectively [47]. The directionality of
3. Results and discussion
the
r-hole bonds is quite evident; the CASAO angle is about
159.3°, putting the oxygens approximately on the extension of
the CAS bond [48].
3.1. Crystal structure
Perspective view of the crystal packing in the unit cell is shown
The title compound, a DIAMOND view of which is shown in
Fig. 2, is a crystallizing in the orthorhombic space group P na21
with eight molecules in unit cell. The asymmetric unit contains
two independent molecules (A and B). The tittle molecule com-
posed of a central thiazole ring, with chloro-acetic hydrazide and
N0-(2-methoxy-benzylidene) groups connected 2-position of the
ring and a (3-methyl-3-phenyl-cyclobutyl) group in the 4-position,
for both independent molecules.
in Fig. 3. The crystal structure does not exhibit intermolecular,
stacking (face-to-face) interactions. There are, however, one
-ring) intermolecular
p–p
CAHꢂ ꢂ ꢂN intramolecular and one CAHꢂ ꢂ ꢂCg (
p
interactions, details of which is given in Table 2. An intramolecular
C17AH17ꢂ ꢂ ꢂN1 contact leads to the formation of a six-membered
ring with graph-set descriptor S(6) [49]. In addition, atom C13A
at (x,y,z) forms a CAHꢂ ꢂ ꢂCg (
p-ring) contact, via atom H13, with
the centroid of the C1BAC6B ring. The packing is further stabilized
The thiazole rings are planar with a maximum deviation of
0.0075 (24) Å for atom C13A and ꢀ0.0008 (25) Å for atom C13B.
In the crystal structure, the phenyl and thiazole rings are in cis
positions with respect to the cyclobutane ring, for both indepen-
dent molecules. The dihedral angles between the thiazole planes
(S1/N1/C12-C14) with the benzene planes (C1-C6) and the cyclo-
butane planes (C7, C9-C11) are 74.47°, 37.26° and 88.86°, 48.59°,
respectively for molecule A and B. Although close to being planar,
the cyclobutane ring is puckered. The C10/C11/C9 plane forms a
dihedral angle of 28.08 (5)° with the C9/C7/C10 plane for molecule
A and 25.16 (4)° for molecule B. This values is significantly longer
than those in the literatures; 23.5 [44], 25.74 (6) [45]. However,
when the bond lengths and angles of the cyclobutane rings in
the title compound are compared with these, it is seen that there
are no significant differences.
by van der Waals forces.
3.2. Optimized structures
The first task for the computational work is to determine the
optimized geometry of the tittle compound. The starting coordi-
nates were those obtained from the X-ray structure determination.
The optimized parameters (bond lengths, bond angles and dihedral
angles) of the title compound were obtained using the B3LYP/6-
311G(d,p) method for both independent molecules. The results
are listed in Table 3 and compared with the experimental data
for the title compound.
The most notable discrepancies are found in the orientation
of the 3-phenyl-cyclobutyl group of the title compound. The
Fig. 2. A view of the title compound showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 40% probability level and H atoms are shown as small
spheres of arbitrary radii. Hydrogen bonds are indicated by broken lines.

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E. Inkaya et al. / Journal of Molecular Structure 1026 (2012) 117–126
Table 3
Experimental and optimized geometrical parameters of the title compound.
Parameters
Experimental
Calculated
B3LYP/6-311G(d,p)
A
B
A
B
Bond lengths (Å)
Cl1AC16
N1AC14
N2AC15
N3AC17
O1AC15
O2AC23
O2AC24
S1AC13
S1AC14
C1AC2
1.771 (4)
1.301 (5)
1.389 (5)
1.269 (4)
1.208 (5)
1.347 (5)
1.429 (5)
1.698 (5)
1.732 (4)
1.379 (7)
1.381 (8)
1.362 (9)
1.347 (6)
1.777 (4)
1.295 (4)
1.382 (4)
1.262 (4)
1.206 (4)
1.349 (5)
1.433 (5)
1.718 (5)
1.734 (3)
1.382 (6)
1.373 (7)
1.339 (7)
1.359 (5)
1.7968
1.2992
1.4052
1.2847
1.2073
1.3614
1.4219
1.7378
1.7674
1.3994
1.3930
1.3929
1.3601
1.7969
1.2993
1.4052
1.2847
1.2074
1.3614
1.4220
1.7379
1.7675
1.3995
1.3930
1.3931
1.3602
C2AC3
C3AC4
C12AC13
Bond angles (°)
C15AN2AN3
C17AN3AN2
N1AC12AC11
C23AO2AC24
N1AC14AN2
N1AC14AS1
O1AC15AN2
N2AC15AC16
O2AC23AC22
C13AS1AC14
C10AC7AC9
C9AC11AC10
111.8 (3)
122.3 (3)
118.4 (4)
118.6 (3)
122.2 (3)
115.5 (3)
121.5 (4)
113.7 (3)
125.4 (3)
87.9 (2)
112.9 (3)
113.001
123.436
117.846
119.045
123.031
114.355
121.510
114.734
116.291
87.782
113.002
123.436
117.851
119.045
123.031
122.613
121.511
114.734
116.293
87.7825
87.8533
88.6142
121.9 (3)
117.1 (3)
118.0 (3)
123.2 (3)
114.8 (3)
121.3 (3)
114.6 (3)
125.1 (4)
88.12 (18)
87.3 (3)
86.2 (3)
87.6 (4)
87.850
88.610
88.2 (3)
Dihedral angles (°)
N3AN2AC14AS1
N2AN3AC17AC18
N3AN2AC15AO1
C13AS1AC14AN2
ꢀ165.3 (3)
176.8 (3)
174.6 (4)
ꢀ179.2 (4)
176.6 (3)
178.4 (3)
ꢀ179.458
179.896
179.954
179.593
ꢀ179.430
179.885
179.941
179.590
ꢀ179.6 (4)
ꢀ179.9 (3)
the experimental results are for the solid phase and the theoretical
calculations are for the gas phase. In the solid state, the existence of
a crystal field along with the intermolecular interactions connect
the molecules together, which results in the differences in bond
parameters between the calculated and experimental values [50].
A global comparison was performed by superimposing the
molecular skeletons obtained from X-ray diffraction and the theo-
retical calculations atom by atom (Fig. 4), obtaining RMSE values of
0.973 and 1.715 Å for A and B, respectively. According to this re-
sult, the smallest RMSE value is obtained for molecule A and the
geometry obtained from this molecule coincides better with the
crystalline structure than molecule B. For that reason, we used
the geometry from molecule A, while calculate other parameters
such as vibrational frequencies, molecular electrostatic potential
(MEP), frontier molecular orbitals (FMOs) and conformational
flexibility.
Fig. 3. Packing diagram of the title compound.
Table 2
Hydrogen bonding geometry for the title compound.
DAHꢂ ꢂ ꢂA
DAH (Å)
Hꢂ ꢂ ꢂA (Å)
Dꢂ ꢂ ꢂA (Å)
DAHꢂ ꢂ ꢂA (°)
123
128
139
C17AAH17Aꢂ ꢂ ꢂN1A
C17BAH17Bꢂ ꢂ ꢂN1B
C13AAH13ꢂ ꢂ ꢂCg7i
0.93
0.93
0.93
2.21
2.08
2.98
2.831 (5)
2.757 (5)
3.733
B3LYP/6-311G(d,p)
C17AAH17Aꢂ ꢂ ꢂN1A
C17BAH17Bꢂ ꢂ ꢂN1B
1.08
1.08
2.08
2.08
2.80
2.81
121.69
121.70
Symmetry code: (i) ꢀx + 1/2, y + 1/2, z ꢀ 1/2. Cg7: Centroid of the C1BAC6B.
3.3. Vibrational spectra
orientation of the 3-phenyl-cyclobutyl group for A and B are de-
fined by a torsion angles C6AC1AC7AC10 of 127.3 (5)° and 127.2
(5)° for the X-ray structure and 141.15° and 141.06° for B3LYP,
respectively. The dihedral angles between the thiazole planes
(S1/N1/C12-C14) with the benzene planes (C1-C6) and the cyclo-
butane planes (C7, C9-C11) for the independent molecule A and
B are 74.47°, 37.26° and 88.86°, 48.59° in the X-ray structure,
and in the optimized structures the corresponding angles are
75.81°, 46.74° and 75.82°, 46.61°, respectively.
It is well known that the calculated harmonic frequencies are
usually higher than the corresponding experimental quantities
and tend to overestimate vibrational frequencies. After scaling,
the error distributions match well with the experimental frequen-
cies and the calculated vibrations are in good agreement with the
experimental results. DFT calculations on harmonic frequencies
have provided excellent vibrational frequencies for organic com-
pounds if a proper scaling factor is used to correct the calculated
frequencies to compensate for the approximate treatment of elec-
tron correlation, for the anharmonicity effects and for basis set
deficiencies [51]. So, in this work, the theoretical harmonic
frequencies have been scaled by the classical factor of 0.9669
As seen from Table 3, most of the optimized bond lengths are
slightly longer than the experimental values and the bond angles
are slightly different from the experimental angles. We note that

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E. Inkaya et al. / Journal of Molecular Structure 1026 (2012) 117–126
121
Fig. 4. Atom-by-atom superimposition of the calculated structures (red) on the X-ray structures (black) for molecules A and B.
Fig. 5. Experimental FT-IR spectra (a) From 3200 to 2700 cmꢀ1 and (b) From 1800 to 500 cmꢀ1
.
according to [37] in order to correct the theoretical error. The
vibrational bands assignments have been made by using Gauss
View molecular visualization program [36].
tal data, and obtained a correlation coefficient of 0.99617 for
B3LYP/6-311G(d,p). As we can see from the correlation graphs in
Fig. 6, the experimental fundamentals are found to have a good
correlation with the calculations.
The experimental and theoretical simulated FT-IR spectra are
shown in Figs. 5a and b, and 6a and b, where the experimental
and calculated infrared intensities are plotted against the vibra-
tional frequencies. As a whole, the calculated spectra are more reg-
ular than the observed FT-IR and some bands found in the
predicated IR spectra were not observed in the experimental spec-
tra, as shown in Fig. 4 and Table 4. This is due to the fact that many
vibrations presenting in condensed phase lead to strong perturba-
tion of infrared intensities of many other modes.
In the higher frequency region, almost all of the vibrations be-
long to CAH3 and ring CAH and CAH2 stretching vibrations. The
CAH, CAH2 and CAH3 symmetrical and asymmetrical stretching
vibrations are observed at 2649–3104 cmꢀ1 range and theoreti-
cally these frequencies have been calculated at 2908–3141 cmꢀ1
3.4. NMR spectra
The characterization of the compound was further enhanced by
the use of 1H and 13C NMR spectroscopy. The 1H and 13C NMR spec-
tra of the tittle compound recorded using TMS as an internal stan-
dard and chloroform (CDCl3) as solvent. GIAO 1H and 13C chemical
shift values (with respect to TMS) were calculated using the B3LYP
method with the 6-311G(d,p) basis set and compared with exper-
imental 1H and 13C chemical shift values. The results of this calcu-
lation are shown in Table 5 together with the experimental values.
We have calculated 1H chemical shift values (with respect to
TMS) of 11.44–1.56 ppm at the B3LYP/6-311G(d,p) level, however,
the experimental results were observed to be 9.14–1.59 ppm. In
the 1H NMR spectra of the compound, the chemical shift values
of CAH3 protons were observed to be 1.59ꢃ (H8ꢃ) and 3.66ꢃ
(H24ꢃ) ppm, respectively. These signals have been calculated as
1.56ꢃ and 4.02ꢃ ppm for B3LYP methods with the 6-311G(d,p) level,
respectively. The CAH2 signals of cyclobutane ring are observed
2.53ꢃ and 2.64ꢃ ppm while they appeared 2.61ꢃ and 2.55ꢃ ppm in
theoretical calculation. The CH hydrogen of the thiazole ring ap-
pears at 6.92 ppm, and is determined computationally at
9.45 ppm. The chemical shift of an azomethine CH@N hydrogen
calculated at 9.14 ppm and is observed to be 11.44 ppm in the
experimental spectra.
region for B3LYP. Two different mC@N stretching vibrations are ap-
peared in the tittle molecule. One of them is observed at 1612 cmꢀ1
band in thiazole ring whereas the other appeared at 1535 cmꢀ1 in
azomethine group. These bands have been calculated at 1604 and
1518 cmꢀ1 for B3LYP/6-311G(d,p), respectively. Another character-
istic region of the thiazole derivative spectrum is 1535–1160 cmꢀ1
,
which is attributed to
tittle compound shows a strong band at 1715 cmꢀ1 which is as-
signed to C@O stretching. The stretching C@O vibration gives
rise to
mC@N and mCAS stretching vibrations. The
m
m
a
band in the experimental infrared spectrum at
1715 cmꢀ1, and the calculated value is predicted to be 10 cmꢀ1
higher at 1725 cmꢀ1. The other calculated vibrational frequencies
can be seen in Table 4.
13C NMR spectra of tittle compound show signal at 167.57 and
159.05 ppm, respectively, due to the C14 and C15 atoms of thiazole
and carboxyl groups. These signals were calculated at 166.16 and
To make a comparison with experimental observations, we
studied the correlation between the calculated and the experimen-

_
122
E. Inkaya et al. / Journal of Molecular Structure 1026 (2012) 117–126
Table 4
Comparison of the observed and calculated vibrational spectra of the title compound.
Assignment
Experimental IR with KBr (cmꢀ1
)
Calculated (cmꢀ1) B3LYP/6-311G(d,p)
Scaled freq.
I (km/mol)
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
c
c
CAH(thiazole)
CAH(azomethine)
sCAH(phenyl)
asCAH(phenyl)
sCAH(phenyl)
asCAH(phenyl)
asCAH(phenyl)
asCAH(phenyl)
asCAH2(chl. act. acid)
asCAH3
3104
–
–
3057
–
3141
3113
3105
3097
3082
3081
3071
3064
3063
3034
3010
3003
2982
2967
2945
2944
2908
1725
1604
1568
1518
1473
1454
1446
1394
1371
1342
1296
1278
1256
1235
1212
1147
1145
1135
1020
1010
999
1.25
12.30
9.70
11.32
21.90
16.18
35.53
10.16
1.04
18.10
15.75
33.36
52.61
33.31
38.94
8.58
59.30
292.09
76.46
2.04
3025
–
–
–
–
sCAH2(chl. act. acid)
asCAH2(cyclobutane)
asCAH3
2963
2960
–
asCAH3
–
–
sCAH2(cyclobutane)
CAH(cyclobutane)
sCAH3
2866
2649
1715
1612
1580
1535
–
1500
–
1430
–
1365
–
1270
–
1200
1160
1075
–
C@O
C@N(azomethine)
C@C(phenyl)
+ mCAC(phenyl)
C@C(thiazole)
CAH(phenyl)
CAH2(cyclobutane)
+
+
m
a
C@N(thiazole)
CAH3
CAH3
54.12
117.76
24.25
2.33
14.36
9.45
+
a
a
a
a
CAH3
CAH2(chl. act. acid)
CAH(azomethine)
cCAH(cyclobutane)
3.83
x
x
CAH2(chl. act. acid)
CAH2(cyclobutane)
CAH2(chl. act. acid)
+
m
m
CAN
CAC
109.84
40.23
37.11
249.90
247.69
17.58
0.78
14.61
34.20
7.80
+
m
m
m
c
CAN(thiazole)
CAOAC
CANAN + mCAS
CAH(phenyl)
+
a
dCAH2(chl. act. acid)
dCAH2(cyclobutane)
+
cCAH(thiazole)
–
960
–
–
–
m
m
CAO + h(phenyl)
CAN(thiazole)
+
cCAH(thiazole)
bCAH(azomethine)
CAC(cyclobutane)
7.66
2.41
m
982
bCAH(phenyl)
–
967
0.14
h(cyclobutane)
940
–
733
–
720
–
701
644
–
933
903
780
755
742
723
707
693
4.66
7.72
c
m
CAH2(chl. act. acid)
CACl(chl. act. acid)
29.47
26.66
64.43
26.22
100.25
47.60
7.47
bCAH(phenyl)
bCAH(phenyl)
bCAH(thiazole)
mSACAN(thiazole)
+
mCAC(chl. act. acid)
bCAH(phenyl)
h(thiazole)
603
bCAH(phenyl)
566
538
13.66
Vibrational modes: m, stretching; a, scissoring; c, rocking; x, wagging; d, twisting; b, in-plane bending; h, ring breathing. Abbreviations: s, symmetric; as, asymmetric.
Fig. 6. Theoretical FT-IR spectra (a) from 3200 to 2700 cmꢀ1 and (b) from 1800 to 500 cmꢀ1
.

_
E. Inkaya et al. / Journal of Molecular Structure 1026 (2012) 117–126
123
Table 5
Experimental and theoretical 13C and 1H isotropic chemical shifts (ppm) for the title
compound.
Atom Experimental (ppm) (CDCl3)
Calculated (ppm) B3LYP/6-311G(d,p)
C1
C2
C3
C4
C5
C6
C7
C8
147.86
125.02
126.71
125.56
126.71
125.02
39.01
29.72
41.12
41.12
31.11
152.01
111.52
167.57
159.05
43.89
155.60
121.09
128.37
122.08
132.73
112.51
157.15
55.67
6.98
160.95
130.91
134.39
131.38
134.25
130.64
45.91
34.04
40.57
46.09
36.15
161.15
117.31
166.16
174.37
56.91
152.09
128.71
131.18
125.89
139.66
114.79
167.6
57.01
7.48
C9
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C22
C23
C24
H2
Fig. 7. Correlation graphic of calculated and experimental frequencies of title
compound.
H3
7.02
7.64
H4
7.14
7.48
H5
7.10
7.58
H8a
H9a
H10a
H11
H13
H16a
H17
H19
H20
H21
H22
H24a
1.59a
1.56a
2.53a
2.61a
2.64a
2.55a
3.81
4.02
6.92
6.78
4.84a
5.13a
9.14
7.92
7.02
7.26
11.44
8.25
7.32
7.75
6.92
6.99
3.66a
4.02a
Note: The atom numbering according to Fig. 2 used in the assignment of chemical
shifts.
a
Average.
174.37 ppm, respectively. The existence of the intramolecular
hydrogen bond owing to the azomethine (CH@N) atom is con-
firmed at ꢄ155.60 ppm. Due to this interaction, the experimental
and theoretical chemical shift difference for atom C17. The ali-
phatic CH2 (C9, C10 and C16) carbons are observed at 41.12 and
43.89 ppm and the C atoms (C8 and C24) of methyl groups are ob-
served at 29.72 and 55.67 ppm, respectively.
To make comparison with experimental observations, we pres-
ent correlation graphs in Fig. 7 based on the calculations. As can be
seen from the correlation graphs, 1H and 13C the correlation coeffi-
cients are 0.99069 and 0.96643 for B3LYP, respectively. As can be
seen from Table 5, the theoretical 1H and 13C chemical shift results
for the title compound are generally closer to the experimental 1H
and 13C shift data.
3.5. Molecular electrostatic potential
Fig. 8. Correlation graphics between the experimental and theoretical NMR
chemical shift values of the title compound.
The molecular electrostatic potential (MEP) is related to the
electronic density and is a very useful descriptor in understanding
sites for electrophilic attack and nucleophilic reactions as well as
hydrogen-bonding interactions [52–54]. The electrostatic potential
V(r) are also well suited for analyzing processes based on the ‘‘rec-
ognition’’ of one molecule by another, as in drug–receptor, and en-
zyme-substrate interactions, because it is through their potentials
that the two species first ‘‘see’’ each other [55,56]. Being a real
physical property V(r) can be determined experimentally by dif-
fraction or by computational methods [57].

_
124
E. Inkaya et al. / Journal of Molecular Structure 1026 (2012) 117–126
Fig. 9. Molecular electrostatic potential map calculated at B3LYP/6-311G(d,p) level.
Fig. 10. Molecular orbital surfaces and energy levels given in parentheses for the HOMO ꢀ 1, HOMO, LUMO and LUMO + 1 of the title compound computed at B3LYP/6-
311G(d,p) level.
To visually consider the most probable sites of the title mole-
cule for an interaction with electrophilic and nucleophilic species,
MEP was calculated at the B3LYP/6-311G(d,p) optimized geometry.
While electrophilic reactivities visualized by red* color which indi-
cate the negative regions of the molecule, the nucleophilic reactivi-
ties colored by blue, indicating the positive regions of the molecule
as shown Fig. 8.
As can be seen in from Fig. 8, there is one possible site on the
title compound for electrophilic attack. The negative regions are
mainly over the O1 atom. But chlorine also is negative, with the
characteristic negative ring and a less negative region on the
extension of the bond to the chlorine atom (the
is more positive as the partner in the covalent bond is more elec-
tron withdrawing. Thus, as shall be seen, in thiazole -hole on
r-hole). A r-hole
r
the extension of an SAC bond is more positive than that on the
extension of an OAC bond [58]. The maximum values of negative
and positive regions are ꢀ0.057 and 0.033 a.u., respectively. These
results provide information concerning the region where the
⁄
For interpretation of color in Figs. 4 and 8, the reader is referred to the web
version of this article.

_
E. Inkaya et al. / Journal of Molecular Structure 1026 (2012) 117–126
125
compound can have intra- or intermolecular interaction and
metallic bonding. So, the MEP map confirms the existence of intra-
and intermolecular interactions observed in the solid state.
3.6. Frontier molecular orbitals
The frontier molecular orbitals play an important role in the
electric and optical properties, as well as in UV–Vis spectra and
chemical reactions [59]. By examining the frontier orbitals of a
molecule the optical properties and the steps to react with other
molecules can be determined. The calculations indicate that the
tittle compound has 119 occupied molecular orbitals.
Fig.
9 shows the distributions and energy levels of the
HOMO ꢀ 1, HOMO, LUMO and LUMO + 1 orbitals computed at
the B3LYP/6-311G(d,p) level for the title compound. Both the high-
est occupied molecular orbitals (HOMOs) and the lowest-lying
unoccupied molecular orbitals (LUMOs) are mainly located at the
rings and mostly the
p-antibonding type orbitals. The value of
the energy separation between the HOMO and LUMO is 7.84 eV.
This large HOMO–LUMO gap automatically means high excitation
energies for many of the excited states, good stability and a large
chemical hardness for the title compound.
3.7. Conformational analysis
Based on B3LYP/6-311 G(d,p) optimized geometry for molecule
A, the total energy of the title compound has been calculated by
this method, which is ꢀ2102.39172692 a.u. In order to define the
preferential position of the benzene ring with respect to cyclobu-
tane ring and the preferential position of 2-chloro-N0-(2-methoxy-
benzylidene)acetohydrazide fragment with respect to thiazole
ring, respectively, a preliminary search of low-energy structures
was performed using AM1 computation as a function of selected
torsion angles u1 (C6AC1AC7AC9) and u2 (S1AC14AN2AN3).
The respective values of the selected degrees of torsional freedom,
u1 (C6AC1AC7AC9) and u2 (S1AC14AN2AN3), are 127.3° and
ꢀ165.3° in the X-ray structure, whereas the corresponding values
in optimized geometries are 141.15° and ꢀ179.45° for B3LYP/6-
311G(d,p).
Fig. 11. Molecular energy profile of the optimized counterpart of the tittle
compound versus selected degrees of torsional freedom.
been explained in detail previously [65], and DFT has been exten-
sively used as an effective method to investigate the organic NLO
Molecular energy profiles with respect to rotations about
selected torsion angles are presented in Fig. 10. According to the
materials [66]. The total molecular dipole moment (
polarizability ( tot) and first-order hyperpolarizability (btot) of the
title compound were calculated at the B3LYP/6-311G(d,p) level.
ltot), linear
a
results the low energy domains for
u1 (C6AC1AC7AC9) are located
at ꢀ40° and 140° having energy of 0.115501 and 0.115502 a.u.,
respectively, while they are located at ꢀ110° and 100° having
energy of 0.112093 and 0.114418 a.u., respectively, for u2
(S1AC14AN2AN3). The energy difference between the most
favorable and most unfavorable conformers, which arises from
the rotational potential barrier calculated with respect to the se-
lected torsion angle, was calculated as 0.00343 a.u. for u1
(C6AC1AC7AC9) and as 0.01039 a.u. for u2 (S1AC14AN2AN3),
when both selected degrees of torsional freedom are considered
(see Fig. 11).
The calculated values of ltot
, atot and btot are 7.8192 D,
49.9846 Å3 and 1.9312 ꢁ 10ꢀ30 cm5/esu. Urea is one of the proto-
typical molecules used in the study of the NLO properties of molec-
ular systems. Therefore it was used frequently as a threshold value
for comparative purposes. The values of ltot, atot and btot of urea are
3.53 D, 4.1446 Å3 and 0.5883 ꢁ 10ꢀ30 cm5/esu obtained at the
same level. Theoretically, the first-order hyperpolarizability of
the title compound is of 3.2 times magnitude of urea. According
to these results, the title compound is a good candidate of NLO
material.
3.8. Non-linear optical effects
4. Conclusions
Non-linear optical (NLO) effects arise from the interactions of
electromagnetic fields in various media to produce new fields al-
tered in phase, frequency, amplitude or other propagation charac-
teristics from the incident fields [60]. NLO is at the forefront of
current research because of its importance in providing the key
functions of frequency shifting, optical modulation, optical switch-
ing, optical logic, and optical memory for the emerging technolo-
gies in areas such as telecommunications, signal processing, and
optical interconnections [61–64].
In this study, N0-(2-methoxy-benzylidene)-N-[4-(3-methyl-3-
phenyl-cyclobutyl)-thiazol-2-yl]-chloro-acetic hydrazide, (C24H24
-
ClN3O2S), was synthesized and characterized by spectroscopic
(FT-IR and NMR) and structural (single-crystal X-ray diffraction)
techniques. To support the solid state structure, the geometric
parameters, vibrational frequencies and 1H and 13C NMR chemical
shifts of the title compound have been calculated using the density
functional theory (DFT/B3LYP) method with the 6-311G(d,p) basis
set, and compared with the experimental findings. The MEP map
shows that the negative potential sites are on electronegative
The calculations of the mean linear polarizability (
atot) and the
mean first hyperpolarizability (btot) from the Gaussian output have

_
126
E. Inkaya et al. / Journal of Molecular Structure 1026 (2012) 117–126
[26] G.E. Scuseria, J. Chem. Phys. 97 (1992) 7528.
atoms and the positive potential sites are around the hydrogen
atoms. These sites provide information concerning the region from
where the compound can undergo intra- and intermolecular inter-
actions. The value of the energy separation between the HOMO and
LUMO is very large and this energy gap gives significant informa-
tion about the title compound. The predicted nonlinear optical
(NLO) properties of the title compound are much greater than
those of urea. The title compound is a good candidate as second-or-
der nonlinear optical material.
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CCDC 815994 contains supplementary crystallographic data
(excluding structure factors) for the structure reported in this arti-
cle. These data can be obtained free of charge via http://www.ccdc.
cam.ac.uk/data_request/cif, by e-mailing data_request@ccdc.
cam.ac.uk or by contacting The Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223
336033.
Acknowledgments
I wish to thank Prof. Dr. Orhan Büyükgüngör for his help with
the data collection and acknowledge the Faculty of Arts and Sci-
ences, Ondokuz Mayıs University, Turkey, for the use of the STOE
IPDS II diffractometer (purchased under Grant No. F-279 of the
University Research Fund).
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