Experimental and density functional theory studies on (E)-2-[(2- (hydroxymethyl)phenylimino)methyl]benzene-1,4-diol

Article abstract of DOI:10.1016/j.molstruc.2011.03.055

The Schiff base compound (E)-2-[(2-(hydroxymethyl)phenylimino)methyl] benzene-1,4-diol has been synthesized and characterized by ¹H NMR, ¹³C NMR, IR, UV-Vis and single-crystal X-ray diffraction. Molecular geometry of the title compou

Full text of DOI:10.1016/j.molstruc.2011.03.055

Journal of Molecular Structure 995 (2011) 58–65
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Experimental and density functional theory studies on (E)-2-[(2-(hydroxymethyl)
phenylimino)methyl]benzene-1,4-diol
b
c
a
Yelda Bingöl Alpaslan a, Gökhan Alpaslan a, , Aysßen Alaman Ag˘ar , Nazan Ocak Iskeleli , Emin Öztekin
⇑
_
a Department of Physics, Faculty of Arts & Science, Ondokuz Mayıs University, 55139 Kurupelit, Samsun, Turkey
b Department of Chemistry, Faculty of Arts & Science, Ondokuz Mayıs University, 55139 Kurupelit, Samsun, Turkey
c Department of Science Education, Ondokuz Mayıs University, 55200 Atakum, Samsun, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
The Schiff base compound (E)-2-[(2-(hydroxymethyl)phenylimino)methyl]benzene-1,4-diol has been
synthesized and characterized by 1H NMR, 13C NMR, IR, UV–Vis and single-crystal X-ray diffraction. Molec-
ular geometry of the title compound in the ground state have been calculated using the density functional
method (DFT) with 6-31G(d) basis set and compared with the experimental data. The calculated results
show that the optimized geometry can well reproduce the crystal structure. By using TD-DFT method,
electronic absorption spectra of the compound have been predicted and a good agreement with the
TD-DFT method and experimental one is determined. The energetic behavior of the compound in solvent
media has been examined using B3LYP method with the 6-31G(d) basis set by applying the polarizable
continuum model (PCM). The total energy of the title compound decreases with increasing polarity of
the solvent. In addition, DFT calculations of the compound, molecular electrostatic potential (MEP),
natural bond orbital analysis (NBO) and non-linear optical (NLO) properties were performed at B3LYP/
6-31G(d) level of theory.
Received 13 December 2010
Received in revised form 23 March 2011
Accepted 23 March 2011
Available online 7 April 2011
Keywords:
Schiff base
DFT
NBO
Non-linear optical
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
the field of optoelectronic such as optical communication, optical
computing, optical switching, and dynamic image processing
Schiff bases are used as starting materials in the synthesis of
important drugs, such as antibiotics and antiallergic, antiphlogistic,
and antitumor substances [1–3]. They have been extensively used
as ligands in the field of coordination chemistry [4,5]. Schiff base
compounds display interesting photochromic and thermochromic
features in the solid state and can be classified in terms of these
properties [6]. Photo- and thermochromism arise via H-atom
transfer from the hydroxy O atom to the imine N atom [7,8]. Such
proton-exchanging materials can be utilized for the design of var-
ious molecular electronic devices [9,10].
In general, Schiff bases display two possible tautomeric forms,
the phenol-imine (OH) and the keto-amine (NH) forms. Depending
on the tautomers, two types of intramolecular hydrogen bonds are
observed in Schiff bases: OAHꢀ ꢀ ꢀN in phenol-imine [11,12] and
NAHꢀ ꢀ ꢀO in keto-amine [13,14] tautomers. Another form of the
Schiff base compounds is also known as zwitterion having an ionic
intramolecular hydrogen bond (N+AHꢀ ꢀ ꢀOꢁ) and this form is rarely
seen in the solid state [15,16].
[17,18]. Due to their high molecular hyperpolarizabilities, organic
materials display a number of significant non-linear optical prop-
erties. NLO materials were categorized as multilayered semi-
conductor structures, molecular based macroscopic assemblies,
and traditional inorganic solids. A variety of inorganic, organic
and organometallic molecular systems have been studied for NLO
activity [17–19].
By means of increasing development of computational chemis-
try in the past decade, the research of theoretical modeling of drug
design, functional material design, etc., has become much more
mature than ever. Many important chemical and physical proper-
ties of biological and chemical systems can be predicted from the
first principles by various computational techniques [20,21]. Cur-
rently, density functional theory (DFT) method has been accepted
as a popular post-HF approach for the computation of structural
characteristics, vibrational frequencies and energies of molecules
by the ab initio community [22] and for the efficiency and accuracy
with respect to the evaluation of a number of molecular properties
[23,24].
Non-linear optical materials (NLO) have been attractive in
recent years with respect to their future potential applications in
In this study, we report the synthesis, characterization and
crystal structure of
a new Schiff base, (E)-2-[(2-(hydroxy-
methyl)phenylimino)methyl]benzene-1,4-diol (Scheme 1). The
properties of the structure geometry, molecular electrostatic
potential (MEP), natural bond orbitals (NBO), and non-linear
⇑
Corresponding author. Tel.: +90 3623121919.
E-mail address: gokhana@omu.edu.tr (G. Alpaslan).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.03.055

Y.B. Alpaslan et al. / Journal of Molecular Structure 995 (2011) 58–65
59
scattering factors were taken from SHELXL-97 [26]. The molecular
graphics were done using Ortep-3 for Windows [27]. The data col-
lection conditions and parameters of refinement process are listed
in Table 1.
2.4. Computational procedures
The molecular geometry is directly taken from the X-ray diffrac-
tion experimental results without any constraints. In the next step,
the DFT calculations with a hybrid functional B3LYP (Becke’s three
parameter hybrid functional using the LYP correlation functional)
at 6-31G(d) basis set by the Berny method [28,29] were performed
with the Gaussian 03W software package [30] and Gaussview visu-
alization program [31]. The electronic absorption spectra were
calculated using the time-dependent density functional theory
(TD-DFT) method [32–35]. Also, it is calculated in ethanol solution
using the Polarizable Continuum Model (PCM) [36–39]. In order to
investigation the energetic and dipole moments behavior of the ti-
tle compound in solvent media, we also carried out optimization
calculations in three kinds of solvents (chloroform, ethanol and
water) by using PCM method. To investigate the reactive sites of
the title compound the molecular electrostatic potential was eval-
uated using the B3LYP/6-31G(d) method. The molecular electro-
static potential, V(r), at a given point r(x, y, z) in the vicinity of a
molecule, is defined in terms of the interaction energy between
the electrical charge generated by the molecule’s electrons and nu-
clei and a positive test charge located at r. For the system studied
the V(r) values were calculated as described previously using the
equation [40],
Scheme
(C14 H13NO3).
1. (E)-2-[(2-(hydroxymethyl)phenylimino)methyl]benzene-1,4-diol
optical (NLO) properties for the title compound at the DFT/B3LYP/
6-31G(d) level were studied. These studies are valuable for pro-
viding insight into molecular properties of Schiff base
compounds.
2. Experimental and computational method
2.1. Synthesis
The compound (E)-2-[(2-(hydroxymethyl)phenylimino)methyl]
benzene-1,4-diol was prepared by reflux a mixture of a solution con-
taining 2,5-dihydroxybenzaldehyde (0.05 g 0.36 mmol) in 20 ml
ethanol and a solution containing 2-aminobenzylalcohol (0.045 g
0.36 mmol) in 20 ml ethanol. The reaction mixture was stirred for
1 h under reflux. The crystals of (E)-2-[(2-(hydroxymethyl)phenyli-
mino)methyl]benzene-1,4-diol, suitable for X-ray analysis were
obtained from ethyl alcohol by slow evaporation (yield% 76; m.p.
167–169 °C). 13C NMR (d in ppm, CDCl3): 160.5 (C@N), 153.9,
151.6, 150.3, 135.5, 132.9, 129.1, 122.7, 121.5, 120.9, 120.1, 118.9,
116.9 (ArAC), 60.5 (ACH2 A). 1H NMR (d in ppm, CDCl3): 11.65–
9.49 [s, 2H,ArAOH], 8.92 [s, 1H,CH@N], 7.45–6.92 [m, 7H,ArA(CH)],
5.30 [s, 1H, CH2AOH], 4.71 [s, 2H, CH2].
Z
X
ZA
RA ꢁ r
q
ðr0Þ
VðrÞ ¼
ꢁ
dr0
ð1Þ
r0 ꢁ r
A
Table 1
Crystallographic data for the title compound.
Crystal data
Chemical formula
Crystal shape/color
Formula weight
Crystal system
C14H13NO3
Plate/red
243.25
Orthorhombic
P212121
Space group
Unit cell parameters
a = 4.6356(17) Å
b = 13.9188(7) Å
c = 18.700 (7) Å
1206.6(4) Å3
4
1.339
0.10
512
2.2. Instrumentation
Volume
The FT-IR spectrum of the title compound was recorded in the
4000–400 cmꢁ1 region by a Shimadzu FTIR-8900 spectrophotome-
ter using KBr pellets. 1H and 13C NMR spectra were recorded with a
Bruker AC 200 MHz spectrometer (TMS as internal standard). Elec-
tronic absorption spectra were measured on a Unicam UV–VIS
spectrophotometer in EtOH solvent.
Z
Dx (Mg cmꢁ3
)
l
(mmꢁ1
)
F000
Crystal size (mm3)
0.75 ꢂ 0.45 ꢂ 0.06
Data collection
Diffractometer/meas. meth
Absorption correction
STOE IPDS II/w-scan
Integration
2.3. X-ray crystallography
Tmin
0.950
Tmax
0.989
17,318, 1422, 1200
A
red crystal of the compound with dimensions of
No. of measured, independent and observed
0.75 ꢂ 0.45 ꢂ 0.06 mm was mounted on goniometer and data col-
reflections
Criterion for observed reflections
Rint
hmax
I > 2r(I)
0.040
26
lection was performed on a STOE IPDS II diffractometer by the w
scan technique using graphite monochromated Mo K
a radiation
(k = 0.71073 Å) at 296 K. The systematic absences and intensity
symmetries indicated the orthorhombic P212121 space group. A to-
tal of 17318 reflection (1422 unique) with [1.8° < h < 26°] were col-
lected in the w scan mode and cell parameters were determined by
Refinement
Refinement on
F2
R[F2 > 2
r
(F2)], wR, S
0.039, 0.87, 1.05
1422
167
w = 1/
[r
2(F20)+(0.0843P)2]
P = F20 + 2F2c )/3
0.13, ꢁ0.14
No. of reflection
No. of parameters
Weighting scheme
using X-AREA software [25]. Absorption correction (l )
= 0.1 mmꢁ1
was obtained by the integration method via X-RED32 software
[25]. The crystal structure was solved by direct methods using
SHELXS-97 [26]. The maximum peaks and deepest hole observed
D
qmax, D )
qmin (e Åꢁ3
in the final
D
q
map were 0.13 and ꢁ0.14 e Åꢁ3, respectively. The

60
Y.B. Alpaslan et al. / Journal of Molecular Structure 995 (2011) 58–65
where ZA is the charge of nucleus A, located at RA,
q
ðr0Þ is the elec-
The most remarkable discrepancy exists in the orientation of
the phenylmethanol ring in the title compound. The orientation
of the phenylmethanol ring is defined by torsion angles
C13AC8AN1AC7 [180.0(2)°] and C9AC8AN1AC7 [ꢁ0.3(4)°]. These
torsion angles have been calculated at ꢁ145.3° and 32.3° for
B3LYP/6-31G(d) level. According to X-ray studies, the dihedral an-
gle between the C1/C6 and C8/C13 rings is 2.55(7)°, whereas the
dihedral angle has been calculated at 37.91° for B3LYP.
tronic density function of the molecule, and r0 is the dummy integra-
tion variable. The linear polarizability and first hyperpolarizability
properties of the title compound were obtained from molecular
polarizabilities based on theoretical calculations. In addition, NBO
analysis was performed at B3LYP/6-31G (d) level by means of the
NBO 3.1 program within the Gaussian 03W package [41].
As seen from Table 3, the optimized bond lengths and the bond
angles are slightly different than the experimental values. We noted
that the experimental results belong to the solid phase and theoret-
ical calculations belong to the gas phase. In the solid state the
experimental results are related to molecular packing, but in the
gas phase the isolated molecules are considered in the theoretical
calculations. The maximum difference between the experimental
values and those obtained from the theoretical calculations is
0.027 Å for bond distances and 2.4° for bond angles. According to
these results, the biggest differences of bond lengths and bond an-
gles mainly occurs in the groups involved in the hydrogen bond [i.e.,
C2AO1, C7AN1AC8, C13AC8AN1] which can be also easily under-
stood taking into account the intra- and intermolecular hydrogen
bond interactions present in the crystal.
A logical method for globally comparing the structure obtained
with the theoretical calculation is by superimposing the molecular
skeleton with that obtained from X-ray diffraction, giving a RMSE
of 0.029 Å for B3LYP/6-31G(d) (Fig. 3). According to these results,
it may be concluded that the B3LYP calculation well reproduce
the geometry of the title compound.
3. Results and discussion
3.1. Description of the crystal structure
The title compound, an Ortep-3 view of which is shown in Fig. 1,
crystallizes in the orthorhombic space group P212121 with Z = 4 in
the unit cell. The asymmetric unit in the crystal structure contains
only one molecule. The C7AN1 and C6AO1 bonds of the title
compound are the most important indicators of the tautomeric
type. X-ray structure determinations reveal that the enol tautomer
is favoured over the keto tautomer. This is evident from the ob-
served C6AO1 bond distance of 1.351(3) Å, which is consistent
with the CAO single bond; similarly the C7AN1 distance of
1.271(3) Å is also consistent with the C@N double bonding. These
bond distances are comparable with those of compounds previ-
ously reported as enol-imine [11,42]. The molecular structure of
the title compound is approximately planar. The dihedral angle be-
tween the C1AC6 and C8AC13 rings is 2.55(7)°. The molecular
structure is stabilized by a O1AH1ꢀ ꢀ ꢀN1 intramolecular hydrogen
bond which generates an S(6) ring motif (Fig. 1) [43]. The sum of
the Van der Waals radius of the N and O atoms [3.07 Å] is signifi-
cantly longer than the intramolecular N1ꢀ ꢀ ꢀO1 [2.612 Å] hydrogen
bond length [44]. In the crystal structure, molecules are linked by
intermolecular OAHꢀ ꢀ ꢀO hydrogen bonds (Fig. 2), namely
O2AH21ꢀ ꢀ ꢀO3 (symmetry code: ꢁx + 2, y + 1/2) and O3AH3ꢀ ꢀ ꢀO2
(symmetry code: ꢁx + 3/2, ꢁy + 1, z ꢁ 1/2). The details of the
hydrogen bonds are summarized in Table 2.
3.3. IR spectroscopy
The IR spectrum of the title compound have some characteristic
bands of the stretching vibrations of the OH, CN and CO groups.
The experimental OAH stretching modes were observed at range
of 3478–3347 cmꢁ1. In addition, the stretching frequency observed
at 3019 cmꢁ1 in the compound shows the presence of OAHꢀ ꢀ ꢀN
intramolecular hydrogen bond [45]. The characteristic region of
1500–1700 cmꢁ1 can be used to identify the proton transfer of
3.2. Theoretical structure
The optimized parameters (bond length, angles, and dihedral an-
gles) of the title compound have been obtained by using the B3LYP/
6-31G(d) method. The obtained results are listed in Table 3. When
the X-ray structure of the title compound is compared with its opti-
mized counterpart (see Fig. 3), conformational discrepancies are ob-
served between them.
Schiff bases. The title compound shows a strong band at
1624 cmꢁ1 which is assigned to C@N stretching vibration. Another
characteristic region of the Schiff bases derivative spectrum is
1100–1400 cmꢁ1, which is attributed to CAO stretching vibrations.
The title compound with strong band at 1216 cmꢁ1 possesses high-
est percentage of enol-imine tautomer due to the stabilization of
Fig. 1. Ortep-3 diagram of the title compound. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. The
intramolecular hydrogen bond is shown as a dashed line.

Y.B. Alpaslan et al. / Journal of Molecular Structure 995 (2011) 58–65
61
Fig. 2. Packing diagram of the title compound.
Table 2
Table 3
Hydrogen-bond geometry (Å, °).
Selected molecular structure parameters.
DAHꢀ ꢀ ꢀA
DAH
Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA
DAHꢀ ꢀ ꢀA
Parameters Experimental
B3LYP/6-31G(d)
O1AH1ꢀ ꢀ ꢀN1
O2AH21ꢀ ꢀ ꢀO3i
O3AH3ꢀ ꢀ ꢀO2ii
0.82
0.82
0.82
1.89
1.84
1.99
2.612(3)
2.619(2)
2.724(2)
146
157
148
Bond lengths (Å)
C1AC2
C2AC3
C3AC4
C1AC7
C6AO1
C7AN1
C8AC13
C8AN1
C14AO3
1.391(3)
1.371(3)
1.383(3)
1.453(3)
1.351(3)
1.270(3)
1.393(3)
1.418(3)
1.423(3)
1.413
1.385
1.406
1.448
1.345
1.293
1.412
1.410
1.421
Symmetry codes: (i) ꢁx + 2, y + 1/2, ꢁz + 3/2; (ii) ꢁx + 3/2, ꢁy + 1, zꢁ1/2.
phenolic CAO bond [46]. The presence of OAH, C@N, and CAO
stretching vibrations strongly suggest that the title compound
has the enol-imine form in the solid state.
Bond angles (°)
C2AC1AC6
C2AC1AC7
O2AC3AC4
O1AC6AC5
O1AC6AC1
N1AC7AC1
C9AC8AN1
C13AC8AN1
C10AC9AC8
C7AN1AC8
3.4. Electronic absorption spectra
118.8(2)
119.2
119.3
117.0
118.5
122.4
122.6
122.2
118.0
120.6
120.9
120.0(2)
117.4(2)
118.9(2)
122.2(2)
121.8(2)
124.6(2)
115.9(2)
120.5(2)
123.3(2)
The UV–visible spectrum of o-hydroxylated Schiff bases that ex-
ist mainly as the phenol-imine structure indicate the presence of a
band at <400 nm, whereas compounds existing in the keto-amine
form show a new band, especially in polar and non-polar solvents
at >400 nm [47–49]. Electronic absorption spectra of the title com-
pound in the ethanol solvent show a band at 368 nm (log e = 4.037),
which corresponds to the enol-imine form. This value for related
compounds is similar to in the literature [50]. However, the com-
pound showed no absorption above 400 nm. This indicates that
the title compound is in the enol-imine form in ethanol solvent.
Electronic absorption spectra were calculated by using TD-DFT
method based on the B3LYP/6-31G(d) level optimized structure
in gas phase. The predicted absorption wavelength is at 372 nm
with the oscillator strength being 0.224 for TD-DFT calculation.
In addition to the results gas phase, TD-DFT calculations of the title
compound in ethanol solvent were performed by using PCM
model. The PCM calculations reveal that the calculated absorption
Torsion angles (°)
C7AC1AC6AO1
C2AC1AC7AN1
N1AC8AC13AC14
C1AC7AN1AC8
C9AC8AN1AC7
C13AC8AN1AC7
1.9 (3)
ꢁ178.9 (2)
ꢁ0.7 (3)
ꢁ0.1
ꢁ179.5
1.2
177.0
32.3
178.7 (2)
ꢁ0.3 (4)
180.0(2)
ꢁ145.3
band has a red shift with a value of 380 nm with an oscillator
strength of 0.270. The reason for the red shift is a solvent effect,

62
Y.B. Alpaslan et al. / Journal of Molecular Structure 995 (2011) 58–65
Table 4, we can conclude that the total molecular energies ob-
tained by PCM method decrease with the increasing polarity of
the solvent, while the dipole moments and hardness will increase
with the increase of the polarity of the solvent. According to these
results, the stability of the title compound increases in going from
the gas phase to the solution phase.
3.6. Molecular electrostatic potential
The molecular electrostatic potential (MEP) is related to the elec-
tronic density and is a very useful descriptor for determining sites
for electrophilic attack and nucleophilic reactions as well as hydro-
gen-bonding interactions [53–55]. The electrostatic potential V(r) is
also well suited for analysing processes based on the ‘recognition’ of
one molecule by another, as in drug–receptor and enzyme–
substrate interactions, because it is through their potentials that
the two species first ‘see’ each other [56,57]. Being a real physical
property, V(r) can be determined experimentally by diffraction or
by computational methods [58].
Fig. 3. Atom-by-atom superimposition of the calculated structure (red) over the X-
ray structure (black) for the title compound.
which can affect the geometry and electronic structure as well as
the properties of the molecule by inducing a lower energy
[50,51]. Comparing these values with the corresponding experi-
mental values, TD-DFT method for both in gas phase and solvent
media is useful to predict UV–Vis spectrum (Fig. 4).
According to the TD-DFT calculational electronic absorption
spectra, the maximum absorption wavelength corresponding to
the electronic transition is from the highest occupied molecular
orbital (HOMO) to the lowest unoccupied molecular orbital
(LUMO).
As seen from Fig. 5, while the HOMO is localized on hydroqui-
none fragment and benzene ring, the LUMO is localized on the
imine group and two benzene rings. Molecular orbital coefficients
analyses based on optimized geometry indicate that, for the title
compound, the frontier molecular orbitals are mainly composed
To predict reactive sites of electrophilic and nucleophilic attack
for the investigated molecule, the MEP at the B3LYP/6-31G(d) opti-
mized geometry was calculated. The negative (red1
) region of MEP
was related to electrophilic reactivity and the positive (blue) region
to nucleophilic reactivity as shown in Fig. 6. As can be seen from
the figure, this molecule has several possible sites for electrophilic
attack. Negative electrostatic potential regions (red color) are
mainly localized over the O1 atom, the O2 and O3 atoms. The neg-
ative V(r) values are ꢁ0.049 a.u. for O3 atom which is the most
negative region, ꢁ0.036 a.u. for O1 atom and ꢁ0.026 a.u. for O2
atom. However, a maximum positive region (blue color) is local-
ized on the O2AH21 bond with a value of 0.069 a.u., indicating a
possible site for nucleophilic attack.
According to these calculated results, the MEP map shows that
the negative potential sites are on oxygen atoms as well as the po-
sitive potential sites are around the hydrogen atoms. These sites
give information concerning the region from where the compound
can have metallic bondings and intermolecular interactions. So,
Fig. 6 confirms the existence of the intermolecular O2AH21ꢀ ꢀ ꢀO3
and O3AH3ꢀ ꢀ ꢀO2 interactions.
of
p-atomic orbitals, so the electronic transitions are mainly de-
rived from the contribution of bands
p ? .
pꢃ
3.5. Total energies in solvent media
In order to evaluate the energetic behavior of the title com-
pound in solvent media, we carried out calculations in gas phase
and three kinds of solvent (water, ethanol, chloroform). The calcu-
lated total, HOMO and LUMO energies, dipole moment and chem-
3.7. NBO analysis
ical hardness (g) using the PCM by B3LYP/6-31G(d) are listed in
Table 4. The chemical hardness is quite useful to rationalize the
relative stability and reactivity of chemical species. Hard species
having large HOMO–LUMO gap will be more stable and less reac-
tive than soft species having small HOMO–LUMO gap [52]. From
NBO analysis provides an efficient method for studying intra-
and intermolecular bonding and interaction among bonds, and also
provides a convenient basis for investigating charge transfer or
conjugative interaction in molecular systems [59]. The larger the
E(2) value, the more intensive is the interaction between electron
donors and electron acceptors, i.e., the more donating tendency
from electron donors to electron acceptors and the greater the ex-
tent of conjugation of the whole system. Delocalization of electron
density between occupied Lewis-type (bond or lone pair) NBO
orbitals and formally unoccupied (antibond or Rydgberg) non-
Lewis NBO orbitals correspond to a stabilizing donor–acceptor
interaction. In order to investigate the intra and intermolecular
interactions, the stabilization energies of the title compound were
performed by using second-order perturbation theory. For each
donor NBO(i) and acceptor NBO(j), the stabilization energy E(2)
associated with electron delocalization between donor and accep-
tor is estimated as [60,61]
2
ðFijÞ
Eð2Þ ¼ ꢁq
ð2Þ
i ej
ꢁ
ei
Fig. 4. UV–Vis spectra of title compound in ethanol solvent and the comparison of
calculated transitions in gas phase (vertical solid line) and ethanol solvent (vertical
dashed line) with the experimental spectra.
1
For interpretation of color in Figs. 1–3, 5, and 6, the reader is referred to the web
version of this article.

Y.B. Alpaslan et al. / Journal of Molecular Structure 995 (2011) 58–65
63
Fig. 5. HOMO and LUMO of the title compound.
Table 4
Calculated energies, dipole moments, frontier orbital energies and chemical hardness.
Gas phase
Chloroform
Ethanol
= 24.55)
Water
(e = 78.39)
(e
= 1) = 4.9)
(e
(
e
Etotal (Hartree)
EHOMO (eV)
ELUMO (eV)
ꢁ821.71678294
ꢁ5.513
ꢁ821.73558671
ꢁ5.467
ꢁ821.74327396
ꢁ5.465
ꢁ821.74525316
ꢁ5.464
ꢁ1.833
ꢁ1.749
ꢁ1.732
ꢁ1.725
g
(eV)
(D)
1.840
4.2814
1.859
5.5114
1.866
6.0874
1.869
6.2327
l
where qi is the donor orbital occupancy, ei, ej are diagonal elements
apparent that OAHꢀ ꢀ ꢀN and OAHꢀ ꢀ ꢀO interactions significantly
(orbital energies), and Fij is the off-diagonal NBO Fock matrix ele-
ment. The results of second-order perturbation theory analysis of
the Fock Matrix at B3LYP/6-31G(d) level of theory are presented
in Table 5.
influence crystal packing with this molecule.
3.8. Non-linear optical effects
NBO analysis revealed that the n(N1) ? r(O1AH1) interactions
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 [62]. Organic molecules with
give the strongest stabilization to the system of the title com-
pound by 24.04 kcal molꢁ1, and strengthen the intramolecular
O1AH1ꢀ ꢀ ꢀN1 hydrogen bond. The NBO interactions of the
n(O3) ?
r (O2AH21) and n(O2) ? r (O3AH3) imply the exis-
significant non-linear optical activity generally consist of a
p-
tence of OAHꢀ ꢀ ꢀO hydrogen bonds which have the total stabiliza-
electron conjugated moiety substituted by an electron donor group
on one end of the conjugated structure and an electron acceptor
tion energies 17.33 and 9.76 kcal molꢁ1, respectively. Thus, it is
Fig. 6. Molecular electrostatic potential map calculated at B3LYP/6-31G(d) level.

64
Y.B. Alpaslan et al. / Journal of Molecular Structure 995 (2011) 58–65
Table 5
demonstrates that the title compound can be used as a good
non-linear optical material.
Second-order perturbation theory analysis of the Fock matrix in NBO basis, calculated
at B3LYP/6-31G(d) level.
Donor orbital (i) Acceptor orbital (j) E(2)c
(kcal/mol)
ej–
ei (a.u.)a Fij (a.u.)b
Supplementary material
LP(1) N1
LP(1) O3
LP(2) O3
LP(1) O2
LP(1) O2
BD(1) O1AH1
BD(1) O2AH21
BD(1) O2AH21
BD(1) O3AH3
BD(1) O3AH3
27.27
2.39
14.94
9.54
0.78
1.00
0.86
1.08
0.80
0.133
0.044
0.102
0.093
0.012
Crystallographic data for the structure reported in this article
have been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication number CCDC 734185. Copies
of the data can be obtained free of charge on application to CCDC
12 Union Road, Cambridge CB21 EZ, UK (fax: +44 1223 336 033;
e-mail: data_request@ccdc.cam.ac.uk).
0.22
a
b
c
Energy difference between donor and acceptor i and j NBO orbitals.
Fij is the Fock matrix element between i and j NBO orbitals.
E(2) means energy of hyper conjugative interaction.
References
group on the other end, forming a ‘push–pull’ conjugated structure
[63].
The total static dipole moment (l), the linear polarizability (a)
and the first hyperpolarizability (b) using the x, y, z components
[1] D. Barton, W.D. Ollis, Comprehensive Organic Chemistry, Pergamon, Oxford,
1979.
[2] R.W. Layer, Chem. Rev. 63 (1963) 489.
[3] C.K. Ingold, Structure and Mechanism in Organic Chemistry, second ed., Cornell
Univ., Ithaca, 1969.
are defined as [24,64]:
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
[4] M. Calligaris, G. Nardin, L. Randaccio, Coord. Chem. Rev. 7 (1972) 385.
[5] A.D. Garnovski, A.L. Nivorozhkin, V.I. Minkin, Coord. Chem. Rev. 126 (1993)
1369.
[6] M.D. Cohen, G.M.J. Schmidt, S. Flavian, J. Chem. Soc. (1964) 2041.
[7] E. Hadjoudis, M. Vitterakis, I.M. Mavridis, Tetrahedron 43 (1987) 1345.
[8] X.X. Xu, X.Z. You, Z.F. Sun, X. Wang, H.X. Liu, Acta Crystallogr. C50 (1994) 1169.
[9] L. Feringa, W.F. Jager, B. De Lange, Tetrahedron 49 (1993) 8267.
[10] S.H. Alarcon, D. Pagani, J. Bacigalupo, A.C. Olivieri, J. Mol. Struct. 475 (1999)
233.
l
a
¼
¼
lx2
þ
ly2
þ
lz2
ð3Þ
ð4Þ
axx
þ
ayy
3
þ
azz
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
À
Á
À
Á
À
Á
2
2
2
b ¼
bxxx þ bxyy þ bxzz þ byyy þ bxxy þ byzz þ bzzz þ bxxz þ byyz
[11] Ç. Albayrak, B. Koßsar, S. Demir, M. Odabasßog˘lu, O. Büyükgüngör, J. Mol. Struct.
963 (2010) 211.
ð5Þ
[12] O. Sahin, O. Büyükgüngör, Ç. Albayrak, M. Odabasßog˘lu, Acta Cryst. E61 (2005)
o1288.
[13] B. Koßsar, Ç. Albayrak, M. Odabasßog˘lu, O. Büyükgüngör, Acta Cryst. E61 (2005)
The dipole moment (
hyperpolarizability (b) were calculated at the B3LYP/6-31G(d) level
using Gaussian 03W program package. The calculated dipole mo-
l
), linear polarizability (
a
) and the first
o1097.
_
[14] H. Petek, Ç. Albayrak, M. Odabasßog˘lu, I. Sßenel, O. Büyükgüngör, J. Chem. Cryst.
38 (2008) 901.
ment (l), polarizability (a) and first hyperpolarizability (b) for title
compound are 4.28 D, 25.06 Å3 and 4.1 ꢂ 10ꢁ30 cm5/esu
respectively.
[15] T.M. Krygowski, K. Wozniak, R. Anulewicz, D. Pawlak, W. Kolodziejski, E.
Grech, A. Szady, J. Phys. Chem. A 101 (1997) 9399.
[16] H. Petek, Ç. Albayrak, E. Ag˘ar, H. Kalkan, Acta Cryst. E62 (2006) o3685.
[17] D.R. Kanis, M.A. Ratner, T.J. Marks, Chem. Rev. 94 (1994) 195.
[18] P.N. Prasad, D.J. Williams, Introduction to Nonlinear Optical Effects in
Molecules and Polymers, Wiley, New York, 1991.
[19] M. Yavuz, H. Tanak, J. Mol. Struct. THEOCHEM 961 (2010) 9.
[20] Y. Zhang, Z.J. Guo, X.Z. You, J. Am. Chem. Soc. 123 (2001) 9378.
[21] H. Tanak, A. Ag˘ar, M. Yavuz, J. Mol. Mod. 16 (2010) 577.
[22] M. Kurt, T.R. Sertbakan, M. Ozduran, Acta A: Mol. Biomol. Spectrosc. 70 (2008)
664.
[23] C. Ravikumar, I.H. Joe, V.S. Jayakumar, Chem. Phys. Lett. 460 (2008) 552–558.
[24] R. Zhang, B. Du, G. Sun, Y. Sun, Spectrochim. Acta A 75 (2010) 1115.
[25] Stoe & Cie. X-AREA (Version 1.18) and X-RED32 (Version 1.04), Darmstadt,
Germany, 2002.
The calculated values of the title compound are greater than
those of urea (the
l, a
and b of urea are 1.3732 D, 3.8312 Å3 and
0.37289 ꢂ 10ꢁ30 cm5/esu obtained by B3LYP/6-31G(d) method)
[62]. Theoretically, the first-order hyperpolarizability of the title
compound is of 10.1 times magnitude of urea. These results indi-
cate that title compound is a good candidate of non-linear optical
material.
4. Conclusion
[26] G.M. Sheldrick, Acta Cryst. A64 (2008) 112.
[27] L.J. Farrugia, ORTEPIII for Windows, J. Appl. Cryst. 30 (1997) 565.
[28] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
(E)-2-[(2-(hydroxymethyl)phenylimino)methyl]benzene-1,4-diol
has been synthesized and characterized by 1H NMR, 13C NMR, IR,
UV–Vis and single-crystal X-ray diffraction. The X-ray, IR, NMR
and UV–Vis spectral data for the title compound show that the
compound exists in the enol-imine tautomeric form, which is
stabilized by the intramolecular OAHꢀ ꢀ ꢀN hydrogen bond. The
comparisons between the calculated results and the X-ray experi-
mental data indicate that B3LYP/6-31G(d) method shows a good
agreement with the experimental results. The TD-DFT calculations
lead to a very closer agreement with the experimental absorption
spectra both gas phase and solvent media. Molecular orbital coef-
ficient analyses suggest that the electronic spectrum corresponds
[29] C. Lee, W.T. Yang, R.G. Parr, Phys. Revi. B 37 (1988) 785.
[30] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
J.A. Montgomery Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox,
H.P. Hratchian, J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E.
Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y.
Ayala, K. Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S.
Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K.
Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J.
Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L.
Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M.
Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A.
Pople, Gaussian 03, Revision E.01 Gaussian, Inc., Wallingford, CT, 2004.
[31] R. Dennington II, T. Keith, J. Millam, GaussView, Version 4.1.2, Semichem, Inc.,
Shawnee Mission, KS, 2007.
to the
p ?
pꢃ electronic transition. The total energy of the title
compound decreases with increasing polarity of the solvent. The
MEP map shows that the negative potential sites are on oxygen
atoms as well as the positive potential sites are around the hydro-
gen atoms. These sites give information about the region from
where the compound can have intermolecular interactions and
[32] E. Runge, E.K.U. Gross, Phys. Rev. Lett. 52 (1984) 997.
[33] R.E. Stratmann, G.E. Scuseria, M.J. Frisch, J. Chem. Phys. 109 (1998) 8218.
[34] R. Bauernschmitt, R. Ahlrichs, Chem. Phys. Lett. 256 (1996) 454.
[35] M.E. Casida, C. Jamorski, K.C. Casida, D.R. Salahub, J. Chem. Phys. 108 (1998)
4439.
[36] S. Miertus, E. Scrocco, J. Tomasi, Chem. Phys. 55 (1981) 117.
[37] V. Barone, M. Cossi, J. Phys. Chem. A 102 (1998) 1995.
[38] M. Cossi, N. Rega, G. Scalmani, V. Barone, J. Comput. Chem. 24 (2003) 669.
[39] J. Tomasi, B. Mennucci, R. Cammi, Chem. Rev. 105 (2005) 2999.
[40] P. Politzer, J.S. Murray, Theor. Chem. Acc. 108 (2002) 134.
metallic bonding. The NBO analysis revealed that the n(N1) ?
r
(O1AH1) interaction gives the strongest stabilization to the
system. The predicted non-linear optical (NLO) properties of the
title compound are much greater than those of urea. This study

Y.B. Alpaslan et al. / Journal of Molecular Structure 995 (2011) 58–65
65
[41] E.D. Glendening, J.K. Badenhoop, A.E. Reed, J.E. Carpenter, F. Weinhold, NBO
[53] E. Scrocco, J. Tomasi, Adv. Quant. Chem. 11 (1979) 115.
[54] F.J. Luque, J.M. Lopez, M. Orozco, Theor. Chem. Acc. 103 (2000) 343.
[55] N. Okulik, A.H. Jubert, Int. Electron. J. Mol. Des. 4 (2005) 17.
Version 3.1. Theoretical Chemistry Institute, University of Wisconsin, Madison,
1995.
[42] Z.S. Sahin, S. Gümüßs, M. Macit, I. Sßamil, Acta Crystallogr. E65 (2009) o3022.
[43] J. Bernstein, R.E. Davies, L. Shimoni, N.L. Chang, Angew. Chem. Int. Ed. Engl. 34
(1995) 1555.
[56] P. Politzer, P.R. Laurence, K. Jayasuriya, J. McKinney, Environ. Health Perspect.
61 (1985) 191.
[57] E. Scrocco, J. Tomasi, Topics in Current Chemistry, vol. 7, Springer, Berlin,
1973.
[44] A. Bondi, J. Phys. Chem. 68 (1964) 441.
[45] H. Nazır, M. Yıldız, H. Yılmaz, M.N. Tahir, D. Ülkü, J. Mol. Struct. 524 (2000)
241.
[58] P. Politzer, D.G. Truhlar, Chemical Applications of Atomic and Molecular
Electrostatic Potentials, Plenum, New York, 1981.
[46] H. Unver, M. Yıldız, H. Özay, T.N. Durlu, Spectrochim. Acta A 74 (2009) 1095.
[47] S.R. Salman, N.A.I. Saleh, Spectrosc. Lett. 30 (1997) 1289.
[48] M. Yıldız, Z. Kılıç, T. Hökelek, J. Mol. Struct. 441 (1998) 1.
[49] H. Ünver, M. Yıldız, D.M. Zengin, S. Özbey, E. Kendi, J. Chem. Cryst. 31 (2001)
211.
[50] A. Ag˘ar, H. Tanak, M. Yavuz, Mol. Phys. 108 (2010) 1759.
[51] Z.C. Rong, L.Z. Jiang, C.Y. Hong, C.H. Shan, Y. Zhi Wu, Y.L. Hua, J. Mol. Struct.
THEOCHEM 899 (2009) 86.
[59] M. Snehalatha, C. Ravikumar, I. Hubert Joe, N. Sekar, V.S. Jayakumar,
Spectrochim. Acta A 72 (2009) 654.
[60] D.W. Schwenke, D.G. Truhlar, J. Chem. Phys. 82 (1985) 2418.
[61] M. Gutowski, G. Chalasinski, J. Chem. Phys. 98 (1993) 4728.
[62] Y.X. Sun, Q.L. Hao, W.X. Wei, Z.X. Yu, L.D. Lu, X. Wang, Y.S. Wang, J. Mol. Struct.
THEOCHEM 904 (2009) 74.
[63] D. Sajan, J. Binoy, I. Hubert Joe, V.S. Jayakumar, J. Zaleski, J. Raman Spectrosc.
36 (3) (2005) 221.
[52] N. Özbek, G. Kavak, Y. Özcan, S. Ide, N. Karacan, J. Mol. Struct. 919 (2009) 154.
[64] H. Tanak, J. Mol. Struct. THEOCHEM 950 (2010) 5.