Experimental and density functional theory (DFT) studies on (E)-2-Acetyl-4-(4-nitrophenyldiazenyl) phenol

Article abstract of DOI:10.1016/j.molstruc.2010.11.009

A suitable single crystal of (E)-2-Acetyl-4-(4-nitrophenyldiazenyl) phenol, formulated as C₁₄H₁₁N₃O₄, (I), reveals that the structure is adopted to its E configuration and molecules are linked by C?H?O hydrogen bonds. The title compound which has been characterized by IR, UV and single crystal X-ray diffraction analysis at 150 K crystallizes in the monoclinic space group C 2/c with a = 12.8640(8) ?, b = 7.3264(3) ?, c = 26.9330(17) ?, α = 90°, β = 93.052(5)°, γ = 90°, Z = 7. The molecular structure and geometry have also been optimized using B3LYP density functional theory method employing the 6-31G (d, p) basis set. To acquire lowest- energy molecular conformation of the title molecule, the selected torsion angle is varied every 10° and molecular energy profile is calculated from -180° to +180°. Furthermore, the molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis, nonlinear optical properties (NLO) and thermodynamic properties for the title molecule are also described from the computational process.

Full text of DOI:10.1016/j.molstruc.2010.11.009

Journal of Molecular Structure 985 (2011) 292–298
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Experimental and density functional theory (DFT) studies
on (E)-2-Acetyl-4-(4-nitrophenyldiazenyl) phenol
b
a
a
a
Serap Yazıcı a, , Çig˘dem Albayrak , Ismail Gümrükçüog˘lu , Ismet Sßenel , Orhan Büyükgüngör
⇑
_
_
a Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University, 55139 Kurupelit-Samsun, Turkey
b Faculty of Education, Sinop University, 57000 Sinop, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 October 2010
Received in revised form 3 November 2010
Accepted 3 November 2010
Available online 3 December 2010
A suitable single crystal of (E)-2-Acetyl-4-(4-nitrophenyldiazenyl) phenol, formulated as C14H11N3O4, (I),
reveals that the structure is adopted to its E configuration and molecules are linked by CAHꢀ ꢀ ꢀO hydrogen
bonds. The title compound which has been characterized by IR, UV and single crystal X-ray diffraction
analysis at 150 K crystallizes in the monoclinic space group
C 2/c with a = 12.8640(8) Å,
b = 7.3264(3) Å, c = 26.9330(17) Å, = 90°, b = 93.052(5)°, = 90°, Z = 7. The molecular structure and
a
c
geometry have also been optimized using B3LYP density functional theory method employing the 6-
31G (d, p) basis set. To acquire lowest- energy molecular conformation of the title molecule, the selected
torsion angle is varied every 10° and molecular energy profile is calculated from ꢁ180° to +180°. Further-
more, the molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis, nonlinear
optical properties (NLO) and thermodynamic properties for the title molecule are also described from
the computational process.
Keywords:
Diazenyl
X-ray analysis
Nonlinear optical properties
Frontier molecular orbitals
Density functional theory (DFT)
Molecular Electrostatic potential (MEP)
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
structure and geometry, FMOs, MEP, total molecular energies, di-
pole moments, NLO and thermodynamic properties have also been
Azo compounds are the oldest and largest class of industrial
synthesized organic dyes due to their versatile application in vari-
ous fields, such as dyeing textile fiber, biomedical studies, ad-
vanced application in organic synthesis and high technology
areas such as laser, liquid crystalline displays, electro-optical de-
vices and ink-jet printers [1–3]. All of azo compounds contain at
least one azo (AN@NA) group, which links two sp2–hybridized C
atoms in the structures. Almost all colours have been obtained
by increasing number of azo groups and attaching substitute
groups to aromatic rings that linked to azo groups [4]. Further-
more, azo compounds are a model of the photochromic com-
pounds that display cis and trans isomerism [5,6]. The trans-to-
cis isomerization occurs by photoirradiation with UV light and
cis-to-trans isomerization proceeds with blue light irradiation or
by heating. It is generally accepted that their trans forms are ther-
modynamically more stable than their cis form [7,8].
studied using the DFT/ B3LYP employing the 6-31G (d, p) basis set.
The results obtained from theoretical calculations and experiments
are compared in this study.
2. Experimental
2.1. Synthesis
The compound was prepared by reflux a mixture of a solu-
tion containing 4-nitroaniline (1.08 g, 7.8 mmol), water (20 ml)
and concentrated hydrochloric acid (1.97 ml, 23.4 mmol) was
stirred until a clear solution was obtained. This solution was
cooled down to 0–5 °C and
a solution of sodium nitrite
(0.75 g, 7.8 mmol) in water was added dropwise while the tem-
perature was maintained below 5 °C. The resulting mixture was
stirred for 30 min in an ice bath. 2-Hydroxyacetophenone
In this paper, we report the molecular and crystal structure of
(E)-2-Acetyl-4-(4-nitrophenyldiazenyl) phenol, together with the
IR, UV and single crystal X-ray diffraction studies. The conforma-
tional analysis of the title molecule with respect to the selected
torsion angle is achieved by DFT. Besides these, the molecular
(1.067 g, 7.8 mmol solution (pH 9) was gradually added to
a
cooled solution of 4-nitrobenzenediazonium chloride, prepared
as described above, and the resulting mixture was stirred at
0–5 °C for 2 h in ice bath. The product was recrystallized from
acetic acid to obtain solid (E)-2-Acetyl-4-(4-nitrophenyldiazenyl)
phenol. Crystals of (E)-2-Acetyl-4-(4-nitrophenyldiazenyl) phenol
(Fig. 1) were obtained after one day by slow evaporation from
DMSO (yield 88%, m.p. = 452–454 K).
⇑
Corresponding author. Fax: +90 0362 4576092.
E-mail address: yserap@omu.edu.tr (S. Yazıcı).
0022-2860/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2010.11.009

S. Yazıcı et al. / Journal of Molecular Structure 985 (2011) 292–298
293
2.4. Computational procedures
The molecular structure of the title molecule is optimized by
the DFT calculations with a hybrid functional B3LYP (Becke’s Three
parameter Hybrid Functional using the LYP Correlation Functional)
at 6-31G (d, p) basis set [11,12] and all of the calculations were car-
ried out using Gaussian 03 program package [13]. The vibrational
frequencies for optimized molecule have also been calculated at
the same level of the theory and achieved frequencies were scaled
by 0.9627 [14]. The electronic absorption spectra for optimized
molecule calculated with the time dependent density functional
theory (TD-DFT) at B3LYP/6-31G (d, p) level. To elucidate confor-
mational features of the molecule, the selected degree of torsional
freedom, T (C2AC1AN1AN2), was varied from ꢁ180° to +180° in
every 10° and the molecular energy profile was obtained with
the B3LYP/6-31G (d, p) method. In addition, FMO, MEP, NLO and
thermodynamic properties were performed with the same level
of theory.
Fig. 1. Chemical diagram of (E)-2-Acetyl-4-(4-nitrophenyldiazenyl) phenol.
2.2. Instrumentation
The FT-IR spectrum of the title compound was recorded in the
4000–400 cmꢁ1 region with a Bruker Vertex 80 V FT-IR spectrom-
eter using KBr pellets. Absorbtion spectra were determined on Uni-
cam UV–Vis spectrometer.
3. Results and discussion
2.3. X-ray crystallography
3.1. Description of the crystal structure
A brown crystal of size 0.420 ꢂ 0.317 ꢂ 0.130 mm3 was picked
for the crystallographic study. All diffraction measurements were
performed at low temperature (150 K) using graphite monochro-
mated Mo Ka radiation (k = 0.71073 Å) with a STOE IPDS II diffrac-
tometer. The systematic absences and intensity symmetries
The molecular structure, an ORTEP 3 [15] view of which is
shown Fig. 2, crystallizes in the monoclinic space group C2/c with
seven molecules in the unit cell. The compound has two aromatic
rings and an azo moiety. In the molecule, the aromatic rings which
adopt (E) configuration with respect to the N@N double bond, are
almost coplanar with a dihedral angle of 2.62(2)°. In the azo group,
while the N1AC1 and N2AC7 bond distances are 1.419(1) Å and
1.421(1) Å, respectively, the N1@N2 bond length is 1.262(1) Å
and these values are satisfactory agreement with found of those
in the literature [16–18]. N3AC10, N3AO1 and N3AO2 bond dis-
tances in the molecule are compared well with the values reported
previously [19]. The C13AO4 bond which has distance of
1.234(1) Å is also consistent with the value of the C@O double
bond in carbonyl compounds [20]. As a result of the delocalization
of the electron density in the azo bridge, C1AN1AN2AN7,
C2AC1AN1AN2 and N1AN2AC7AC8 torsion angles are
ꢁ179.4(1)°, 178.8(1)° and ꢁ179.1(1)°, respectively.
indicated the monoclinic C2/c space group. Correction for absorp-
tion
l = 0.11, by comparison of the intensities of equivalent reflec-
tions, was applied using X-RED software [9] and cell parameters
were determined by using X-AREA software [9]. The structure
was solved by direct methods using SHELXS 97 [10] and refined
by a full-matrix least-squares method using the program SHELXL
97 [10]. All non-hydrogen atoms were refined anisotropically and
the positions of H atoms, except for O-bound H atom, were ob-
tained from difference Fourier map of electron density in the unit
cell (CAH distance of 0.96 Å for methyl and hydroxyl groups,
0.93 Å for aromatic groups). The Uiso(H) values were fixed to
1.2Ueq(C) (for aromatic CH) and 1.5Ueq(C) (for CH3 and OH). Details
of crystal data, data collection, structure solution, and refinement
are listed in Table 1.
As can be seen in Fig. 2, atom H3 bonded to O3 forms a strong
intramolecular hydrogen bond with atom O4 [Dꢀ ꢀ ꢀA = 2.551(1) Å]
and this hydrogen bond generates an S(6) ring motif. The sum of
the van der Waals radii of two O atoms (3.04 Å) is significantly
longer than the intramolecular Oꢀ ꢀ ꢀO hydrogen bond length [21].
The crystal packing of the title molecule is stabilized by two inter-
molecular CAHꢀ ꢀ ꢀO hydrogen bonds, one of them is between the
atom C9 and oxygen of the carbonyl group (O4) and the other is be-
tween the atom C8 and oxygen of the nitro group (O2). These inter-
molecular interactions link neighbouring molecules in three
dimensions (Fig. 3) (Table 2). In addition to these interactions,
van der Waals forces should be effective on the crystal packing of
the title azo dye.
Table 1
Crystal data and structure refinement parameters for the title compound.
Chemical formula
Colour/shape
Formula weight
Temperature
C14H11N3O4
Brown/plate
285.25
150 K
Crystal system
Space group
Monoclinic
C 2/c
Unit cell parameters
a = 12.8640(8) Å
b = 7.3264(3) Å
c = 26.9330(17) Å
a
= 90°
b = 93.052(5)°
c
= 90°
Volume
Z
2534.8(3) Å3
7
3.2. Theoretical structure and conformation analysis
Density
Absorption coefficient
Tmin, Tmax
Diffractometer/meas. meth.
h range for data collection
Unique reflections measured
Independent/observed reflections
Data/restraints/parameters
Goodness of fit on F2
1.495 g/cm3
0.11 mmꢁ1
0.930, 0.993
STOE IPDS 2 /
1.51–26.76°
6261
2456/1919
1919/0/194
1.024
Some structural parameters obtained experimentally and calcu-
lated theoretically by B3LYP/6-31G (d, p) are given in Table 3 for
comparison. The differences observed between the experimental
and calculated parameters are due to the ignored effects. These ef-
fects are the intermolecular interactions which the theoretical
methods cannot take into account. While the experimental results
belong to the solid state, the calculated results belong to the iso-
lated gaseous phase. The maximum difference between the exper-
imental observation and those obtained from the theoretical
--scan
Final R indices [I > 2
R indices (all data)
r(I)]
R1 = 0.0364, wR1 = 0.0970
R2 = 0.0477, wR2 = 0.1013

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S. Yazıcı et al. / Journal of Molecular Structure 985 (2011) 292–298
Fig. 2. Ortep three diagram for (E)-2-Acetyl-4-(4-nitrophenyldiazenyl) phenol, with the atom numbering scheme.
Fig. 3. A partial packing diagram of (E)-2-Acetyl-4-(4-nitrophenyldiazenyl) phenol.
calculations is 0.0264 Å for bond distances and 1.7497° for bond
Table 2
angles. Besides these, in the optimized molecule, dihedral angle be-
tween the hydroxyl attached ring and NO2 attached ring is 0.018°.
Namely, the optimized geometry with B3LYP is preferred more pla-
nar conformation than X-ray geometry.
In order to define conformational flexibility of the title mole-
cule, the energy profile as a function of C2AC1AN1AN2 torsion an-
gle was achieved with B3LYP/6-31G (d, p) method (Fig. 4).
According to X-ray crystallographic study T (C2AC1AN1AN2) is
178.8(1)° and 180.0° for DFT. The conformational energy profile
shows two maxima near 90° and ꢁ90°. The aromatic rings are
nearly perpendicular at these values of selected torsion angle.
The energy barriers may be due to the steric interactions between
Hydrogen-bond geometry (Å, °).
DAHꢀ ꢀ ꢀA
DAH
Hꢀ ꢀ ꢀA
1.65(2)
2.57
Dꢀ ꢀ ꢀA
2.5509(15)
3.4856(17)
3.3199(16)
DAHꢀ ꢀ ꢀA
154(2)
170
O3AH3ꢀ ꢀ ꢀO4
C9AH9ꢀ ꢀ ꢀO4a
C8AH8ꢀ ꢀ ꢀO2b
0.96(3)
0.93
0.93
2.49
149
a
Symmetry code: x, 1 ꢁ y, ꢁ1/2 + z.
Symmetry code: x, 1 + y, z.
b
Table 3
Selected molecular structure parameter for the title compound.
the
p electrons of the two aromatic rings. It is clear from Fig. 5,
X-ray
DFT
X-ray
DFT
there are three local minima observed at 180°, 0° and ꢁ180° for
T (C2AC1AN1AN2) and these are most stable conformers for this
torsion angle. The DFT optimized geometry of the crystal structure
is coplanar at these values of selected torsion angle.
Bond lengths (Å)
C1AN1
N1AN2
N2AC7
O3AC4
O4AC13
C3AC13
C13AC14
C10AN3
N3AO1
Bond angles (°)
1.419(1)
1.262(1)
1.421(1)
1.341(1)
1.234(1)
1.477(1)
1.486(2)
1.463(1)
1.220(1)
1.224(1)
1.405 C1AN1AN2
1.264 N1AN2AC7
1.417 N2AC7AC8
1.330 O3AC4AC5
1.241 O3AC4AC3
1.473 O4AC13AC3
1.512 C3AC13AC14
1.470 C10AN3AO1
1.231 C10AN3AO2
1.231 O1AN3AO2
113.4(1) 115.2
114.4(1) 114.3
114.9(1) 115.3
117.4(1) 118.1
122.6(1) 122.2
119.4(1) 120.6
120.1(1) 120.3
118.2(1) 117.7
118.6(1) 117.7
123.1(1) 124.6
3.3. Vibrational spectra
The harmonic vibrational frequencies for (E)-2-Acetyl-4-(4-
nitrophenyldiazenyl) phenol have been calculated by using DFT
method at 6-31G (d, p) level. There are no imaginary values for
any frequencies, indicating that is the minimum energy structure
at this level of theory. In order to compare the theoretical results
with experimental values of those, all of the calculated frequencies
are scaled by 0.9627 for B3LYP/6-31G (d, p). Some characteristic IR
N3AO2
Torsion angles (°)
C2AC1AN1AN2 178.8(1)
180.0 O3AC4AC3AC13
ꢁ1.7(1)
0.0
0.0
0.0
C7AN2AN1AC1 ꢁ179.4(1) 180.0 O1AN3AC10AC9
4.4(2)
N1AN2AC7AC8 ꢁ179.1(1) 180.0 O2AN3AC10AC11 4.3(1)

S. Yazıcı et al. / Journal of Molecular Structure 985 (2011) 292–298
295
In the IR spectral data of the molecule which obtained from
2-hydroxy acetophenone two bands are extremely characteristic.
These are m(C@O) and m(N@N) stretching bands. While the exper-
imental N@N and C@O stretching modes were observed at 1424
and 1647 cmꢁ1 [22],respectively. The same bands were calculated
as 1451 and 1651 cmꢁ1, respectively. The nitro group in the stud-
ied molecule was denoted two very strong absorbtion bands in the
experimental and theoretical IR spectral analysis. These bands that
attributed to antisymmetric and symmetric NO2 stretching vibra-
tions were observed at 1524, 1342 cmꢁ1 for experimental that
have been calculated with B3LYP at 1603, 1553 cmꢁ1, respectively.
Because of the participation of the carbonyl group in hydrogen
bonding, the experimental frequencies were shifted towards lower
frequencies than the theoretical values of those. Due to the same
reason, while OAH stretching band experimentally located at the
region 2000–3000 cmꢁ1
, its theoretical value calculated as
3078 cmꢁ1. The above conclusions are in good agreement with
the literature values [23,24].
Fig. 4. Molecular energy profile using DFT against the selected torsional degree of
freedom.
3.4. Electronic absorption spectra
The electronic absorption bands which have azo groups ob-
tained from UV–Vis spectroscopy. The UV–Vis electronic absorp-
tion spectra of the title compound in different solvents had been
recorded in the previous study [22]. We have also calculated elec-
tronic absorption spectra of (E)-2-Acetyl-4-(4-nitrophenyldiaze-
nyl) phenol in three different solvents (DMSO, EtOH and CHCl3)
using TD-DFT at B3LYP/6-31G (d, p) level by adding the polarizable
continuum model (PCM). The theoretical and experimental absorp-
tion wavelengths are compared in Table 5. In the evaluation of the
results was based on the oscillator strengths (f-value) which great-
er than 0.1. It is well known that
p ?
pꢃ transition is shifted to long
wavelength with increasing the solvent polarity. The reason of this
shifting, the dipole moment of solvent is produced dipole moment
over the solute matter. Consequently, the energy of the pꢃ orbital is
decreased. As can be seen from Table 5, while excitation energies
decrease absorption wavelengths increase with increasing polarity
of the solvents in the title molecule too. In the calculated UV–Vis
spectrum of the title molecule absorption bands occur at
421.13 nm for DMSO, 417.59 nm for EtOH and 415.64 nm for
CHCl3, arising from HOMO ? LUMO transition.
3.5. Frontier molecular orbitals (FMOs)
Fig. 5. Correlation graphic of calculated and experimental frequencies of the title
compound.
The highest occupied molecular orbitals (HOMOs) and the low-
est-lying unoccupied molecular orbitals (LUMOs) are named as
frontier molecular orbitals (FMOs). The FMOs play an important
role in the electric and optical properties, as well as in UV–Vis
spectra and chemical reactions [25]. The distributions of the
HOMO-1, HOMO, LUMO and LUMO+1 orbitals computed at the
B3LYP/6-31G (d, p) level for the title molecule are illustrated in
Fig. 6. The calculations indicate that the title compound have 74
occupied MOs. While the HOMO and LUMO are localized on almost
the whole molecule, HOMO-1 and LUMO+1 are localized on the azo
bridge and the carbonyl attached ring, respectively. Both the
bands for the title azo dye has given in Table 4 and the correlation
graphic which described harmony between the calculated and
experimental frequencies is plotted (Fig. 5). As can be seen from
Fig. 5, experimental fundamentals have a better correlation with
B3LYP.
Table 4
HOMOs and the LUMOs are mostly
p-antibonding type orbitals.
Characteristic IR absorption bands of the title molecule.
Since the HOMO–LUMO energy separation has been used as a sim-
ple indicator of kinetic stability it can be said that the title mole-
cule which has a large HOMO–LUMO gap, 3.399 eV, implies high
kinetic stability and low chemical reactivity [26,27].
Assignments
Experimental (cmꢁ1
)
Calculated (cmꢁ1
)
OAH str.
C@O str.
N@N str.
CAO str.
2000–3000
1647
1424
1206
1318
1370
1342
1524
3078
1651
1451
1301
1567
1340
1553
1603
OAH bend.
3.6. Molecular electrostatic potential
CAN (nitro) str.
NAO (Symm) str.
NAO (asymm) str.
The molecular electrostatic potential isosurface superimposed
onto the total electronic density. The value of the molecular elec-
trostatic potential, V(r), created by a molecular system at a point
str.: stretching, bend.: bending.

296
S. Yazıcı et al. / Journal of Molecular Structure 985 (2011) 292–298
Table 5
Theoric and experimental absorbtion wavelengths for the title compound.
Oscillator strengths (f)
Theoretical wavelengths (k), nm
Experimental wavelengths (k), nm
Excitation energies, eV
Chloroform (
Ethanol ( = 24.55)
DMSO ( = 46.7)
e
= 4.9)
1.0334
0.9920
1.0221
415.64
417.59
421.13
366
365
373
2.9830
2.9690
2.9441
e
e
Fig. 7. Molecular electrostatic potential map calculated at B3LYP/6-31G (d, p).
Fig. 6. Molecular orbital surfaces and energies for the HOMO-1, HOMO, LUMO and
LUMO+1 of the title compound.
polarization effects in the polar solvents the dipol moment in-
creases with the polarity of the solvent. Furthermore, the energy
gap (DE) between the HOMO and LUMO of the title compound de-
creases with increasing polarity of the solvent.
r gives the electrostatic energy on a unit positive charge located at
r. The molecular electrostatic potential (MEP) is a useful property
to study reactivity given that an approaching electrophile will be
attracted to negative regions (particularly to points with most neg-
ative values), where the electron distribution effect is dominant.
Experimental V(r) computed with electron densities obtained from
X-ray diffraction data has been used to explore the electrophilicity
of hydrogen bonding functional groups [28]. In the majority of the
MEPs, while the maximum positive region which preferred site for
nucleophilic attack indications as blue colour, the maximum nega-
tive region which preferred site for electrophilic attack indications
as red colour. The study of experimental and theoretical V(r) shows
that H-donor and H-acceptor properties of molecules are revealed
by positive and negative regions, respectively, so that the forma-
tion of a H-bond can be regarded as the consequence of a comple-
mentarity between the electrostatic potentials [28].
3.8. Nonlinear optical effects
Nonlinear 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. The search of new materials
exhibiting efficient nonlinear optical (NLO) properties has been of
great interest in the recent years because of their potential applica-
tions in telecommunication, data storage and optical signal pro-
cessing [30–36]. It is known that the magnitude of the
polarizability and the first static hyperpolarizability of push–pull
molecular systems is dependent on the efficiency of electronic
communication between donor and the acceptor groups as that
will be the key to intra molecular charge transfer [37].
The polar properties of the title molecule were calculated at the
B3LYP/6-31G (d, p) level using the Gaussian 03 W program pack-
In the present study, the molecular electrostatic potential of (E)-
2-Acetyl-4-(4-nitrophenyldiazenyl) phenol depicted in Fig. 7. Neg-
ative regions are associated with O1, O2, O3 and O4 with values
around ꢁ0.047, ꢁ0.047, ꢁ0.026 and ꢁ0.029 a.u., respectively. So,
it is expected that the most preferred region for electrophilic attack
is that around O1 and O2. However, the most maximum positive
region is localized on atom C14 which a member of methyl group
with a value of 0.035 a.u. Therefore, it would be predicted that the
preferred site for nucleophilic attack will be C14.
age. The calculated values of electronic dipole moment,
l, polariz-
ability, , and the first hyperpolarizability, b for the title compound
a
which including NO2 as the donor group are, 3.9493 Debye,
34.7592 Å3 and 70.9379 ꢂ 10ꢁ30 cm5/esu, respectively. It is well
known that the substituents influence the polarity of the mole-
cules. The high value of the first hyperpolarizability of the title
compound can be seen a result of the resonance effect of nitro
group.
3.7. Energies and dipol moments
3.9. Thermodynamic properties
In order to evaluate the energetic behavior of the title
compound in solvent media, we carried out calculations in vacuo
and in various organic solvents (chloroform, ethanol and dimethyl-
sulfoxide, DMSO). The calculated total molecular energies, frontier
orbital energies and dipol moments using the PCM (polarizable
continuum model) [29] by B3LYP/6-31G (d, p) are listed in
Table 6. As seen in table, with the rising polarity of the solvent total
molecular energy of the title molecule diminishes and so the
stability of the structure increases. Due to the inductive solvent
In order to determinate the thermodynamic behavior of the title
compound, in the light of vibrational analysis and statistical
thermodynamics, the standard thermodynamic functions: molar
ꢀ
ꢁ
ꢀ
ꢁ
ꢀ
ꢁ
heat capacities Cp0;m , entropies Sm0 and enthalpies H0m , were
reached at the same level of theory and listed in Table 7. As seen
from Table 7, the standard thermodynamic functions increase at
any temperature from 100.00 to 500.00 K, due to the intensities
of molecular vibration increase as temperature increases. The

S. Yazıcı et al. / Journal of Molecular Structure 985 (2011) 292–298
297
Table 6
Calculated energies, dipole moments and frontier orbital energies for the title compound.
Gas phase (
e
= 1)
Chloroform (
e
= 4.9)
Ethanol (
e
= 24.55)
DMSO (e = 46.7)
ETOTAL (eV)
EHOMO (eV)
ELUMO (eV)
ꢁ27352.11496402
ꢁ6.4383
ꢁ27352.47387169
ꢁ6.3062
ꢁ27352.56739034
ꢁ6.2701
ꢁ27352.56753293
ꢁ6.2693
ꢁ3.0397
ꢁ3.0156
ꢁ3.0137
ꢁ3.0156
D
E (eV)
3.399
3.291
3.256
3.254
l
(D)
3.9521
4.5126
4.6659
4.6853
Table 7
Thermodynamic properties at different temperatures at the B3LYP/6-31G (d, p) level
for the title compound.
H0m (kcal/mol)
C0p;m (cal/mol K)
S0m (cal/mol K)
T (K)
100
150
200
250
298.150
300
350
400
450
1.989
3.738
6.012
28.459
38.356
48.670
59.187
66.900
69.556
79.434
88.579
96.876
104.314
90.987
105.189
118.199
130.632
139.906
142.707
154.485
165.964
177.118
187.927
8.808
11.650
12.127
15.954
20.257
24.996
30.129
500
Fig. 9. Correlation graphic of entropy and temperature for the title molecule.
Fig. 8. Correlation graphic of enthalpy and temperature for the title molecule.
correlation equations between these thermodynamic properties as
a function of the temperature T are as follows and the correlation
graphics of those show in Figs. 8–10.
C0p;m ¼ 4:66575 þ 0:23844T ꢁ 7:56983 ꢂ 10ꢁ5 T2
Fig. 10. Correlation graphic of heat capacity and temperature for the title molecule.
ðR2 ¼ 0:99941Þ
S0m ¼ 63:38186 þ 0:28802T ꢁ 7:83966 ꢂ 10ꢁ5 T2
ðR2 ¼ 0:99991Þ
the experimental results. Although there are some differences be-
tween the theoretical and experimental frequencies, due to the
participation of the carbonyl group in hydrogen bonding we can
generally say that there is a good linear correlation between them.
Molecular electrostatic potential map shows several possible sites
for electrophilic attack and shows a possible site for nucleophilic
attack. These sites may provide information about the possible
reaction regions for the title structure. The total molecular energy
of the title compound decreases with increasing polarity of the sol-
vent and the stability of the molecule increases. The correlations
between the statistical thermodynamics and temperature are also
obtained. It was seen that the heat capacities, entropies and enthal-
pies increase with the increasing temperature owing to the inten-
sities of the molecular vibrations increase with increasing
temperature. This study also demonstrates that the effect of the
H0m ¼ ꢁ0:06797 þ 0:01025T þ 1:00681 ꢂ 10ꢁ4 T2
ðR2 ¼ 0:99979Þ
4. Conclusion
In the present work, the synthesis, FT-IR and UV–Vis, crystal
and molecular structure determined by single crystal X-ray diffrac-
tion as well as DFT calculations, of (E)-2-Acetyl-4-(4-nitro-
phenyldiazenyl) phenol are reported. The comparisons between
the calculated results and the X-ray experimental data indicate
that B3LYP/6-31G (d, p) method shows a good agreement with

298
S. Yazıcı et al. / Journal of Molecular Structure 985 (2011) 292–298
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presence of a nitro group in the material enhances the nonlinear
optical property.
Supplementary data
CCDC 751379 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge via
www.ccdc.cam.ac.uk/data_request/cif, by emailing data_re-
quest@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallo-
graphic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK;
fax: +44 1223 336033.
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