Experimental and computational studies on (Z)-1-((4-phenylamino) phenylamino)-methylene)naphthalen-2(1H)-one

Article abstract of DOI:10.1007/s11224-011-9745-8

The Schiff base compound (Z)-1-((4-phenylamino)phenylamino)methylene) naphthalen-2(1H)-one has been synthesized and characterized by IR, UV-Vis, and X-ray single-crystal determination. Molecular geometry from X-ray experiment of the title compound in the ground state have been compared using the Hartree-Fock (HF) and density functional method (B3LYP) with 6-31G(d,p) basis set. Calculated results show that density functional theory DFT and HF can well reproduce the structure of the title compound. Using the time-dependent density functional theory (TD-DFT) and Hartree-Fock (TD-HF) methods, electronic absorption spectra of the title compound have been predicted and a good agreement with the TD-DFT method and experimental ones is determined. The energetic behavior of the title compound in solvent media has been examined using B3LYP method with the 6-31G(d,p) 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 title compound, molecular electrostatic potential (MEP), natural bond orbital analysis (NBO), and non-linear optical (NLO) properties were performed at B3LYP/6-31G(d,p) level of theory. Springer Science+Business Media, LLC 2011.

Full text of DOI:10.1007/s11224-011-9745-8

Struct Chem (2011) 22:681–690
DOI 10.1007/s11224-011-9745-8
ORIGINAL RESEARCH
Experimental and computational studies on (Z)-1-((4-
phenylamino)phenylamino)-methylene)naphthalen-2(1H)-one
•
Gokhan Alpaslan Mustafa Macit
•
¨
Ahmet Erdonmez Orhan Buyukgungor
•
¨
¨ ¨
¨
¨
Received: 26 November 2010 / Accepted: 20 January 2011 / Published online: 4 February 2011
Ó Springer Science+Business Media, LLC 2011
Abstract The Schiff base compound (Z)-1-((4-phenyla-
mino)phenylamino)methylene)naphthalen-2(1H)-one has
been synthesized and characterized by IR, UV–Vis, and
X-ray single-crystal determination. Molecular geometry
from X-ray experiment of the title compound in the ground
state have been compared using the Hartree–Fock (HF) and
density functional method (B3LYP) with 6-31G(d,p) basis
set. Calculated results show that density functional theory
DFT and HF can well reproduce the structure of the title
compound. Using the time-dependent density functional
theory (TD-DFT) and Hartree–Fock (TD-HF) methods,
electronic absorption spectra of the title compound have
been predicted and a good agreement with the TD-DFT
method and experimental ones is determined. The ener-
getic behavior of the title compound in solvent media has
been examined using B3LYP method with the 6-31G(d,p)
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 title compound, molecular electrostatic
potential (MEP), natural bond orbital analysis (NBO), and
non-linear optical (NLO) properties were performed at
B3LYP/6-31G(d,p) level of theory.
Introduction
Schiff base compounds have received special attention due
to their interesting thermochromism and/or photochromism
[1, 2], biological properties [3, 4], as well as a variety of
potential applications, e.g., for optical data storage [1, 2, 5],
as nonlinear optical materials [6, 7], anticorrosive materials
[8], or anticancer medicines [9–11]. Tautomerism and
isomerism phenomena for these compounds are of particular
chemical and theoretical interest in the context of their
photochromic and thermochromic properties [2, 12]. Photo-
and thermochromism due to a change in the p-electron
configuration induced by proton transfer [13, 14] Such pro-
ton exchanging materials can be utilized for the design of
various molecular electronic devices [15]. In general, Schiff
bases display two possible tautomeric forms, the phenol-
imine (or benzenoid) and the keto-amine (or quinoid) forms.
Depending on the tautomers, two types of intramolecular
hydrogen bonds are observed in Schiff bases: O–HꢀꢀꢀN in
phenol-imine [16, 17] and N–HꢀꢀꢀO in keto-amine [18–20]
tautomers. Another form of Schiff base compounds is their
zwitterionic tautomer, which is rarely seen for hydroxy
derivatives. The characteristic property of this form is the
presence of ionic N?–HꢀꢀꢀO- hydrogen bond [21]. Investi-
gation of structural stability of compounds by both experi-
mental techniques and theoretical methods has been of great
interest. Functional material design, theoretical modeling of
drug design and so on, has become possible as results of the
development of the computational techniques. Many
important properties such as molecular orbitals, electrostatic
potentials, dipole moment, non-linear optical properties, and
vibrational frequencies can be predicted by various compu-
tational techniques [22, 23].
Keywords Schiff base ꢀ DFT ꢀ HF ꢀ NBO ꢀ
Non-linear optical
¨
¨ ¨
¨
¨
G. Alpaslan (&) ꢀ A. Erdonmez ꢀ O. Buyukgungor
Department of Physics, Faculty of Arts & Science, Ondokuz
Mayıs University, 55139 Kurupelit-Samsun, Turkey
e-mail: gokhana@omu.edu.tr
M. Macit
Department of Chemistry, Faculty of Arts & Science, Ondokuz
Mayıs University, 55139 Kurupelit-Samsun, Turkey
In this work, we reported the synthesis, characterization
and crystal structure of the Schiff base compound (Z)-1-
123

682
Struct Chem (2011) 22:681–690
were collected in the w scan mode and cell parameters
were determined by using X-AREA software [24].
Absorption correction (l = 0.08 mm-1) was obtained by
the integration method via X-RED32 software [24]. The
crystal structure was solved by direct methods using
SHELXS-97 [25]. The absolute configuration could not be
determined from X-ray data, as no strong anomalous
scatterer is present, 1588 Friedel pairs were merged before
the final refinement. The maximum peaks and deepest hole
-3
Scheme 1 (Z)-1-((4-Phenylamino)phenylamino)methylene)naphtha-
len-2(1H)-one (C23H18N2O)
˚
observed in the final Dq map were 0.12 and -0.13 e A
,
respectively. The scattering factors were taken from
SHELXL-97 [24]. The molecular graphics were done
using Ortep-3 for Windows [26]. The data collection
conditions and parameters of refinement process are listed
in Table 1.
((4-phenylamino)phenylamino)methylene)naphthalen-2(1H)-
one (Scheme 1) as well as the theoretical studies on it using
the HF/6-31G(d,p) and DFT/B3LP/6-31G(d,p) methods.
The properties of the structural geometry, molecular elec-
trostatic potential (MEP), natural bond analysis (NBO), and
non-linear optical properties for the title compound at
B3LP/6-31G(d,p) level were studied. These studies are
valuable for providing insight into molecular properties of
Schiff base compounds.
Table 1 Crystallographic data for the title compound
Crystal data
Chemical formula
Crystal shape/color
Formula weight
Crystal system
C23H18N2O
Shapeless/red
338.39
Orthorhombic
Pna21
Experimental and computational method
Space group
˚
a = 13.0688(8) A
Unit cell parameters
Synthesis
˚
b = 22.5362(13) A
˚
c = 6.0975(3) A
3
The compound (Z)-1-((4-phenylamino)phenylamino)meth-
ylene)naphthalen-2(1H)-one was prepared by reflux a mix-
ture of a solution containing 2-hydroxy-1-naphthaldehyde
(17.2 mg; 0.1 mmol) in 30 ml ethanol and a solution con-
taining N-phenyl-p-phenylenediaminediamine (18.4 mg,
0.1 mmol) in 20 ethanol. The reaction mixture was stirred for
2 h under reflux. The crystals of (E)-1-((4-chlorophenyli-
mino)methyl)naphthalen-2-ol for X-ray analysis were
obtained from ethyl alcohol by slow evaporation (yield 72%;
m.p. 385–388 K). The IR spectrum was recorded in the
4000–400 cm-1 region using KBr pellet on a Schmadzu
FTIR-8900 spectrophotometer. Electronic absorption spec-
trum was measured on a Unicam UV–VIS spectrophotom-
eter in ethanol.
˚
1795.84(17) A
Volume
Z
4
Dx (Mg cm-3
l (mm-1
)
1.252
)
0.08
F000
712
Crystal size (mm3)
Data collection
Diffractometer/meas. meth
Absorption correction
Tmin
0.37 9 0.19 9 0.03
STOE IPDS II/w-scan
Integration
0.978
Tmax
0.996
No. of measured, independent and 12,478, 1,940, 798
observed reflections
Criterion for observed reflections
Rint
I [ 2r(I)
0.138
26
Crystal data for the title compound
hmax
Refinement
A red crystal of the compound with dimensions of
0.37 9 0.19 9 0.03 mm was mounted on goniometer and
data collection was performed on a STOE IPDS II dif-
fractometer by the w scan technique using graphite
Refinement on
F2
R[F2 [ 2r (F2)], wR, S
No. of reflections
No. of parameters
Weighting scheme
0.055, 0.087, 0.86
1,940
242
˚
monochromated Mo Ka radiation (k = 0.71073 A) at
w = 1/[r2(F20) ? (0.0843P)2]
P = (F20 ? 2F2c)/3
0.12, -0.13
296 K. The systematic absences and intensity symmetries
indicated the monoclinic Pna21 space group. A total of
12,478 reflections (1,940 unique) with 1.8° \ h \ 26°
-3
)
˚
Dqmax, Dqmin (e A
123

Struct Chem (2011) 22:681–690
Computational methods
683
performed at B3LYP/6-31G (d,p) level by means of the
NBO 3.1 program within the Gaussian 03 W package [40].
The molecular geometry is directly taken from the X-ray
diffraction experimental results without any constraints. In
the next step, the DFT calculations with a hybrid func-
tional B3LYP (Becke’s three parameter hybrid func-
tional using the LYP correlation functional) with the
6-31G(d,p) basis set and Hartree–Fock calculations with
the 6-31G(d,p) basis set using Berny method [27, 28]
were performed with the Gaussian 03W software package
[29] and Gaussview visualization program [30]. The
electronic absorption spectra were calculated using the
time-dependent density functional theory (TD-DFT) and
Hartree–Fock (TD-HF) methods [31–34]. Also, it is cal-
culated in ethanol solution using the polarizable contin-
uum model (PCM) [35–38]. In order to investigate the
energetic and dipole moment behavior of the title com-
pound in solvent media, we also carried out optimization
calculations in three kinds of solvents (chloroform, etha-
nol, and water) by using PCM method. To investigate the
reactive sites of the title compound the molecular elec-
trostatic potential was evaluated using the BLYP/6-
31G(d,p) method. The molecular electrostatic potential,
V(r), at a given point r(x, y, z) in the vicinity of a mol-
ecule, is defined in terms of the interaction energy
between the electrical charge generated by the molecule’s
electrons and nuclei and a positive test charge located at
r. For the system studied the V(r) values were calculated
as described previously using the equation [39],
Results and discussion
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 Pna21
with Z = 4 in the unit cell. The asymmetric unit in the
crystal structure contains only one molecule. The C11–N1
and C2–O1 bonds of the title compound are the most
important indicators of the tautomeric type. X-ray structure
determinations reveal that the keto tautomer is favoured
over the enol tautomer. This is evident from the observed
˚
C11–N1 bond distance of 1.319(7) A, which is consistent
with the C–N single bond; similarly the C2–O1 distance of
˚
1.297(2) A is also consistent with the C=O double bonding.
These bond distances are comparable with those of com-
pounds previously reported as keto-amine [41–43]. In
addition to these, the shortened C3–C4 naphthalene ring
˚
bond distance of 1.347 (8) A suggests a quinoidal effect
and confirms that the O1–C2 bond is not a pure single
bond. The imine N1 atom is sp2 hybridized and displays
coplanarity of the naphthaldimine fragment [44].
The dihedral angles between the naphthalene plane
A (C1–C10), the benzene plane B (C12–C17), and the other
benzene plane C (C18–C23) are 4.33(14)° (A/B), 30.21°
(A/C), and 29.68° (B/C). It is also known that Schiff bases
may exhibit photochromism depending on the planarity or
non-planarity, respectively [45]. The molecular structure is
stabilized by a N1–H1ꢀꢀꢀO1 intramolecular hydrogen bond
(Table 2) which generates an S(6) ring motif (Fig. 1)
[46] The sum of the Van der Waals radius of the N and O
Z
X
ZA
qðr0Þ
VðrÞ ¼
ꢁ
dr0
ð1Þ
RA ꢁ r
r0 ꢁ r
A
where ZA is the charge of nucleus A, located at RA, q(r0) is
the electronic density function of the molecule, and r0 is the
dummy integration 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
˚
atoms [3.07 A] is significantly longer than the intramo-
˚
lecular N1ꢀꢀꢀO1 [2.521(7) A] hydrogen bond length [47].
In the crystal structure, molecules are linked into
Fig. 1 Ortep-3 diagram of the
title compound. Displacement
ellipsoids are drawn at the 40%
probability level and H atoms
are shown as small spheres of
arbitrary radii. The
intramolecular hydrogen bond is
shown as a dashed line
123

684
Struct Chem (2011) 22:681–690
˚
Table 3 Selected molecular structure parameters
Table 2 Hydrogen-bond geometry (A, °)
Parameters
Experimental
HF/
6-31G(d,p)
B3LYP/
6-31G(d,p)
D–HꢀꢀꢀA
D–H
HꢀꢀꢀA
DꢀꢀꢀA
D–HꢀꢀꢀA
N1–H1ꢀꢀꢀO1
0.74(5)
0.98(5)
1.96(6)
1.93(5)
2.521(7)
2.897(6)
133(7)
168(5)
˚
Bond lengths (A)
N2–H2ꢀꢀꢀO1i
Symmetry code (i): x - 1/2, -y ? 1/2, z ? 1
C1–C2
1.422(7)
1.443(8)
1.439(8)
1.297(7)
1.347(8)
1.420(7)
1.407(9)
1.409(8)
1.351(9)
1.401(8)
1.376(8)
1.398(7)
1.406(8)
1.319(7)
1.416(7)
1.376(6)
1.376(7)
1.409(7)
1.411(7)
1.370(8)
1.384(7)
1.371(7)
1.405(7)
1.391(7)
1.362(10)
1.353(9)
1.370(9)
1.376(9)
1.384(8)
1.463
1.473
1.464
1.221
1.331
1.454
1.397
1.404
1.373
1.391
1.376
1.403
1.371
1.328
1.409
1.384
1.385
1.387
1.394
1.378
1.390
1.401
1.402
1.394
1.380
1.386
1.382
1.386
1.390
0.076
0.0043
1.464
1.461
1.452
1.262
1.355
1.441
1.409
1.425
1.383
1.403
1.386
1.413
1.395
1.335
1.403
1.403
1.384
1.407
1.406
1.388
1.402
1.395
1.400
1.406
1.391
1.396
1.395
1.393
1.405
0.043
0.0038
C1–C10
C2–C3
C2–O1
C3–C4
C4–C5
C5–C6
C5–C10
C6–C7
C7–C8
C8–C9
C9–C10
C1–C11
C11–N1
N1–C12
C12–C13
C13–C14
C14–C15
C15–C16
C16–C17
C17–C12
C15–N2
Fig. 2 Packing diagram of the title compound
N2–C18
one-dimensional polymeric C(11) chains along the a-axis
by intermolecular N2–H1ꢀꢀꢀO1 hydrogen bonds (Fig. 2).
C18–C19
C19–C20
C20–C21
C21–C22
C22–C23
C18–C23
Max. dif.
RMSE
Optimized geometries
The optimized parameters (bond lengths, bond angles, and
dihedral angles) of the title compound have been obtained
at HF and B3LYP methods with the 6-31G(d,p) basis set.
The calculated results are listed in Table 3. When the
X-ray structure of the title compound is compared with its
optimized counterparts (see Fig. 3), conformational dis-
crepancies are observed between them. The dihedral angles
between A, B, and C planes are calculated at 39.17° (A/B),
20.30° (A/C), 59.26° (B/C) for HF, and 11.82° (A/B),
54.92° (A/C), 43.87 (B/C) for B3LYP, respectively. The
orientation of the three rings is defined by the torsion
angles C1–C11–N1–C12 [-180°], C16–C15–N2–C18
[-16.4(10)°] and C14–C15–N2–C18 [160.4(7)°] which have
been calculated as 178.4°, -22.7°, and 160.1° for B3LYP,
and -176.9°, -52.8°, and 130.2° for HF, respectively.
As seen from Table 3, most of the calculated bond
lengths and the bond angles are slightly different from the
experimental ones. We noted that the experimental results
belong to the solid phase and theoretical calculations
belong to the gas phase. In the solid state the experimental
Bond angles (°)
C11–C1–C2
C11–C1–C10
C2–C1–C10
O1–C2–C1
O1–C2–C3
C1–C2–C3
C4–C3–C2
C3–C4–C5
C6–C5–C10
C6–C5–C4
C10–C5–C4
C7–C6–C5
C6–C7–C8
C9–C8–C7
119.1(6)
120.6(5)
120.3(6)
122.6(6)
118.9(6)
118.5(6)
119.9(6)
123.7(7)
120.0(6)
121.8(7)
118.2(6)
121.7(7)
118.1(7)
121.9(7)
118.7
121.1
120.1
122.9
119.8
117.1
121.3
122.9
120.6
119.8
119.4
121.1
118.6
120.8
118.2
121.3
120.3
122.6
119.9
117.3
121.5
122.4
120.2
120.3
119.1
121.3
118.9
120.7
123

Struct Chem (2011) 22:681–690
685
which can also easily be understood taking into account the
intra- and intermolecular hydrogen bond interactions
present in the crystal.
Table 3 continued
Parameters
Experimental
HF/
6-31G(d,p)
B3LYP/
6-31G(d,p)
In order to compare the theoretical results with the
experimental values, root mean square error (RMSE) is
used and the values which for the bond lengths and bond
C8–C9–C10
120.3(6)
117.9(6)
122.7(6)
119.5(6)
122.0(6)
118.2(5)
124.9(5)
116.7(5)
120.7(6)
128.8(5)
126.8(6)
120.3(7)
121.3(7)
117.6(8)
123.3(8)
118.2(7)
125.7(6)
116.0(6)
122.1(6)
119.2(8)
117.1(6)
126.6(6)
116.2(6)
120.6(6)
122.0(6)
121.5
117.1
124.0
118.8
126.5
118.8
122.3
118.8
120.3
125.9
125.2
120.1
121.0
118.8
120.6
118.8
123.2
117.9
120.7
120.5
120.4
121.2
118.2
120.6
121.0
5.4
121.6
117.2
123.9
118.9
123.1
118.2
123.6
117.9
120.4
129.5
128.0
120.0
121.1
118.9
120.5
118.7
122.8
118.4
121.2
120.6
118.6
123.3
117.9
120.5
121.4
3.3
C9–C10–C5
C9–C10–C1
˚
angles are calculated as 0.0043 A and 0.0289° for HF
C5–C10–C1
˚
method, and 0.0038 A and 0.0207° for B3LYP method,
N1–C11–C1
respectively. A logical method for globally comparing the
structures obtained with the theoretical calculations is by
superimposing the molecular skeleton with the obtained
˚
X-ray diffraction, giving a RMSE of 0.0136 A for B3LYP
˚
and 0.0483 A for method HF, respectively (Fig. 3).
C13–C12–C17
C13–C12–N1
C17–C12–N1
C12–C13–C14
C15–N2–C18
C11–N1–C12
C22–C23–C18
C21–C22–C23
C20–C21–C22
C21–C20–C19
C23–C18–C19
C23–C18–N2
C19–C18–N2
C16–C17–C12
C20–C19–C18
N2–C15–C14
N2–C15–C16
C14–C15–C16
C17–C16–C15
C13–C14–C15
Max. dif.
According to these results, it may be concluded that the
B3LYP calculation well reproduce the geometry of the title
compound.
IR spectroscopy
FT-IR spectrum of the title compound was recorded in the
4000–400 cm-1 region using KBr pellet on a Schmadzu
FT-IR 8900 spectrophotometer. The some characteristic
bands of the stretching vibrations of the NH, N–HꢀꢀꢀO, CN,
and CO groups were observed. The IR spectrum of the title
compound shows two bands at 3300 and 3112 cm-1 due to
N–H stretching vibrations. These differences between N–H
stretching vibration frequencies are because of the intra-
molecular N–HꢀꢀꢀO hydrogen bonding which leads a shift
to lower wave-number. The weak bands in the range
3033–3000 cm-1 correspond to the symmetric and asym-
metric stretching vibrations of aromatic CH bonds. The
characteristic region of 1500–1700 cm-1 can be used to
identify the proton transfer of Schiff bases [48]. The title
compound shows a strong band at 1620 cm-1 which is
assigned to C=O stretching vibration [49]. In addition to
these, the C–N stretching vibration was observed at
1315 cm-1. The absorption bands in the 1550–1590 cm-1
region must be related to the keto structure (C=C external
double bond). In other words, these bands occur only if
there is a considerable amount of the keto-tautomer [50].
The presence of N–H, C=O, and C–N stretching vibrations
strongly suggest that the title compound has keto-amine
tautomeric character in the solid state.
RMSE
0.0289
0.0207
Torsion angles (°)
C2–C1–C11–N1
C1–C11–N1–C12
C16–C15–N2–C18
N1–C12–C17–C16
C11–C1–C2–O1
C19–C18–N2–C15
1.9(9)
1.7
-176.9
-52.8
179.9
0.3
178.4
-22.7
179.9
0.8
-180
-16.4(10)
179.3(6)
-2.5(10)
163.8(7)
-3.2
168.9
155.0
results are related to molecular packing, but in the gas
phase the isolated molecules are considered in the theo-
retical calculations. The greatest differences of the bond
lengths between experimental and the predicted values are
Electronic absorption spectra
˚
found at C20–C21 bond with the difference being 0.043 A
˚
for B3LYP method, and C2–O1 bond with a value 0.076 A
The UV–Vis electronic absorption spectrum of the title
compound was recorded within 200–600 nm range on a
Unicam UV–Vis spectrophotometer in EtOH solvent.
The observed spectrum showed three bands at 466 nm
(log e = 4.093), 316 nm (log e = 3.839), and 256 nm
(log e = 4.126), which correspond to keto-amine and
phenol-imine forms, respectively. These values are similar
for HF method. For the bond angles, the biggest differences
occur at N2–C15–C16 bond angle, with the different values
being 3.3° for B3LYP method and 5.4° for HF method.
According to these results, the biggest differences of bond
lengths and bond angles mainly occurs in the groups
involved in the hydrogen bond [i.e., C2–O1, N2–C15–C16]
123

686
Struct Chem (2011) 22:681–690
Fig. 3 Atom-by-atom
superimposition of the
structures calculated (a DFT,
b HF) over the X-ray structures
(blue) for the title compound
(Color figure online)
Fig. 4 Molecular orbital
surfaces and energy levels given
in parentheses for the LUMO?1
(-0.612 eV), LUMO (-1.921
eV), HOMO-1 (-5.673 eV),
and HOMO (-4.885 eV) of the
title compound computed at
B3LYP/6-31G(d,p) level
to those found in related compound. [21] The electronic
absorption spectra of 2-hydroxy Schiff bases which exist
mainly as phenol-imine structure indicate the presence of a
band at \400 nm, whereas compounds that existing in the
keto-amine form show a new band, especially in polar and
nonpolar solvents at[400 nm [50–53]. According to these
results, the keto-amine character is dominant in ethanol
solvent which has absorption band at 466 nm.
calculated absorption bands have red shift at 472, 323, and
281 nm when compared with the gas-phase calculations of
TD-DFT method. The reason for this red shift is solvent
effect which can affect the geometry and electronic struc-
ture as well as the properties of the molecule as solvent
effects induce the lower energy of the molecules, and
generate more significant red shift for absorption bands
[54, 55]. Comparing these values with the corresponding
experimental values, TD-DFT method for both in gas-
phase and solvent media is useful to predict UV–Vis
spectrum.
Electronic absorption spectra of the title compound were
calculated by TD-DFT and TD-HF methods based on the
structure gas phase, respectively. For the TD-HF calcula-
tions, the absorption wavelengths are obtained at 294, 241,
and 175 nm. It is obvious that these bands are not consis-
tent of the experimental results. Besides that, the TD-DFT
theoretical absorption band calculations obtained at 438,
309, and 238 nm and it can be seen that these values are
corresponding to the experimental absorption ones. 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
According to the investigation on the frontier molecular
orbital (FMO) energy levels of the title compound, we can
find that the corresponding electronic transfer happened
between the highest occupied molecular orbital (HOMO)
and the lowest unoccupied molecular orbital (LUMO),
HOMO and LUMO?1, HOMO-1 and LUMO?1 orbitals,
respectively. Figure 4 shows the distributions and energy
levels of the FMOs computed at the B3LYP/6-31G(d,p)
level for the title compound.
123

Struct Chem (2011) 22:681–690
687
Table 4 Calculated energies, dipole moments, and frontier orbital energies
Gas phase (e = 1)
Chloroform (e = 4.9)
Ethanol (e = 24.55)
Water (e = 78.39)
Etotal (Hartree)
EHOMO (eV)
ELUMO (eV)
DE (eV)
-1072.0617547
-4.935
-1072.07841139
-4.892
-1072.08560718
-4.885
-1072.08836333
-4.872
-1.833
-1.889
-1.921
-1.908
3.102
3.002
2.964
2.961
l (D)
4.0564
5.4584
6.0996
6.3201
As seen from Fig. 4, in the LUMO?1 and LUMO,
electrons are mainly delocalized naphthalene ring and the
atoms of imine group; in the HOMO-1 and HOMO,
electrons are delocalized on the whole structure. Molecular
orbital coefficients analyses based on optimized geometry
indicate that, for the title compound, the frontier molecular
orbitals are mainly composed of p-atomic orbitals, so the
electronic transitions are mainly derived from the contri-
bution of bands p–p*.
The negative (red) region of MEP was related to electro-
philic reactivity and the positive (blue) region to nucleo-
philic reactivity (see Fig. 5). Negative region is chiefly on
the O1 atom. The negative V(r) value is -0.0572 a.u. for
O1 atom. However, a maximum positive region is localized
on the N2–H2 bond with a value of ?0.0572 a.u., indi-
cating a possible site for nucleophilic attack. These sites
give information concerning the region from where the
compound can have metallic bondings and intermolecular
interactions. The MEP is best suited for identifying sites for
intra- and intermolecular interactions [62]. So, Fig. 5
confirms the existence of the intermolecular N2–H2ꢀꢀꢀO1
interactions.
Total energies in solvent media
In order to evaluate the energetic behavior of the title
compound in solvent media, we carried out calculations in
three kinds of solvent (water, ethanol, chloroform). Total
molecular energies, frontier molecular orbital energies and
dipole moments have been calculated in solvent media with
B3LYP/6-31G(d,p) level using PCM model and the results
are presented in Table 4. According to Table 4, we can infer
that obtained total molecular energies and energy gap (DE)
between the HOMO–LUMO of the title compound by PCM
method decreases with the increasing polarity of the solvent
and while the dipole moments will increase with the increase
of the polarity of the solvent. Solvent effects improve the
charge delocalized in the molecules, therefore, inducing the
dipole moments to be raised. Ground-state dipole moment is
an important factor in measuring solvent effect a large
ground-state dipole moment gives rise to strong solvent
polarity effects [56, 57].
NBO analysis
NBO analysis provides an efficient method for studying
intra- and intermolecular bonding and interaction among
bonds, and also provides a convenient basis for investi-
gating charge transfer or conjugative interaction in
molecular systems [63]. 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
extent 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 investi-
gate the intra and intermolecular interactions, the stabil-
ization 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
acceptor is estimated as [64, 65]
Molecular electrostatic potential
MEP is related to the electronic density and is a very useful
descriptor in determining sites for electrophilic and nucle-
ophilic reactions as well as hydrogen bonding interactions
[58, 59]. The electrostatic potential V(r) is also well suited
for analyzing 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 [60, 61].
2
ðFijÞ
Eð2Þ ¼ ꢁqi
ð2Þ
ej ꢁ ei
where qi is the donor orbital occupancy, ei, ej are diagonal
elements (orbital energies), and Fij is the off-diagonal NBO
Fock matrix element. The results of second-order pertur-
bation theory analysis of the Fock Matrix at B3LYP/6-
31G(d,p) level of theory are presented in Table 5.
To predict reactive sites of electrophilic and nucleo-
philic attack for the investigated molecule, the MEP at the
B3LYP/6-31G(d,p) optimized geometry was calculated.
123

688
Struct Chem (2011) 22:681–690
Fig. 5 Molecular electrostatic
potential map calculated at
B3LYP/6-31G(d,p) level
(Color figure online)
Table 5 Second-order perturbation theory analysis of the Fock matrix in NBO basis, calculated at B3LYP/6-31G(d,p) level
Donor orbital (i)
Acceptor orbital (j)
E(2)a (kcal/mol)
ej - ebi (a.u.)
Fcij (a.u.)
LP(1) O1
LP(2) O1
LP(1) O1
LP(2) O1
LP(3) O1
a
BD(1) N1–H1
BD(1) N1–H1
BD(1) N2–H2
BD(1) N2–H2
BD(1) N2–H2
6.26
28.92
3.71
1.06
0.73
1.17
0.76
0.74
0.074
0.131
0.059
0.021
0.031
0.67
1.23
E(2) means energy of hyper conjugative interactions
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
NBO analysis revealed the n(O1) ? r(N1–H1) interac-
optical interconnections [67–70]. Organic molecules
that exhibit extended p conjugation, in particular, show
enhanced second-order NLO properties [71].
tions give the strongest stabilization to the system of the title
compound by 35.18 kcal mol-1, and strengthen the intra-
molecular N1–H1ꢀꢀꢀO1 hydrogen bond. The lone pairs of O1
also donate its electrons to r-type antibonding orbital for
N2–H2. The total stabilization energy of N2–H1ꢀꢀꢀO1
intermolecular hydrogen bonding is 5.61 kcal mol-1. Thus,
it is apparent that N–HꢀꢀꢀO intermolecular hydrogen bond
significantly influence crystal packing in this molecule.
The total static dipole moment (l), the linear polariz-
ability (a), and the first hyperpolarizability (b) using the x,
y, z components are defined as [72, 73]:
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
l ¼ l2x þ l2y þ l2z
ð3Þ
ð4Þ
axx þ ayy þ azz
a ¼
3
Non-linear optical effects
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
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
Non-linear optical (NLO) effects arise from the interac-
tions of electromagnetic fields in various media to produce
new fields altered in phase, frequency, amplitude, or other
propagation characteristics from the incident fields [66].
NLO is at the forefront of current research because of its
importance in providing the key functions of frequency
shifting, optical modulation, optical switching, optical
logic, and optical memory for the emerging technologies in
areas such as telecommunications, signal processing, and
ð5Þ
The dipole moment (l), linear polarizability (a), and the
first hyperpolarizability (b) were calculated at the B3LYP/
6-31G(d,p) level using Gaussian 03W program package.
The calculated dipole moment (l), polarizability (a),
and first hyperpolarizability (b) for title compound
3
-30
˚
are 4.0564 D, 49.54 A , and 100.029 9 10
respectively. The calculated values of first hyperpolarizability
cm5/esu,
123

Struct Chem (2011) 22:681–690
689
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and polarizability are greater than that of 4-(2,3,4-
trihydroxybenzylideneamino)antipyrine [66] and 2-methyl-
6-[2-(trifluorormethyl)phenyl-iminomethyl]phenol [73]. These
results indicate that title compound is a good candidate of
nonlinear optical material.
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(Z)-1-((4-Phenylamino)phenylamino)methylene)naphtha-
len-2(1H)-one has been synthesized and characterized by
IR, UV–Vis, and X-ray single-crystal diffraction. The
X-ray, IR, and UV–Vis spectral data for the title compound
show that the compound exists in the keto-amine tauto-
meric form, which is stabilized by the intramolecular
N–HꢀꢀꢀO hydrogen bond. The comparisons between the
calculated results and the X-ray experimental data indicate
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geometric parameters. The TD-DFT calculations lead to a
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spectra both gas phase and solvent media. Molecular
orbital coefficient analyses suggest that the electronic
spectrum corresponds to the p ? p* electronic transition.
The total energy of the title compound decreases with
increasing polarity of the solvent. The MEP map shows
that the negative potential site is on oxygen atom while the
positive potential sites are around the hydrogen atoms.
These sites give information about the region from where
the compound can have intermolecular interactions and
metallic bonding. The NBO analysis revealed that the
n(O1) ? r (N1–H1) interaction gives the strongest sta-
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intermolecular O1ꢀꢀꢀN2 contact is n(O1) ? r (N2–H2).
This study also demonstrates that the title compound can be
used as a good nonlinear optical material.
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CCDC-795577 contains the supplementary crystallographic
data for the compound reported in this paper. These data
can be obtained free of change at www.ccdc.cam.ac.uk/
conts/retrieving.html [or from the Cambridge Crystallo-
graphic Data Centre (CCDC), 12 Union Road, Cambridge
CB2 1EZ,UK; fax: ?44 1223 336033; e-mail: deposit@
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